Cardiovascular Disorders PDF

Cardiovascular Disorders 12 CH A P TE R Ashley B. Saunders...

Cardiovascular Disorders 12 CH A P TE R Ashley B. Saunders B. Backward: Congestive CARDIOVASCULAR PHYSIOLOGY C. Forward: Reduced cardiac output DEFINITIONS D. Left-sided: Results in pulmonary edema I. Afterload: The force or tension on the ventricular E. Right-sided: Results in hepatomegaly, ascites, myocardium during contraction pleural effusion, pericardial effusion II. Preload: The volume of blood present in the ventri- F. Neuroendocrine consequences of heart cle at the end of diastole failure III. Chronotropy: Heart rate 1. Activation of the renin angiotensin aldosterone A. Positive chronotropy designates an increase in system (RAAS): A decrease in cardiac output is heart rate detected by the kidneys. Renin is released and B. Negative chronotropy designates a decrease in converts angiotensinogen to angiotensin I in heart rate the liver. Angiotensin I is converted to angio- IV. Inotropy: Myocardial contractility tensin II in the lungs. Angiotensin II stimulates A. Positive inotropy designates an increase in constriction of vascular smooth muscle, and contractility increased blood volume. Angiotensin II stimu- B. Negative inotropy designates a decrease in lates aldosterone, which leads to increased contractility sodium chloride retention, and increased V. Systole: Contraction of the heart chambers blood volume VI. Diastole: Period of relaxation of the heart chambers 2. Activation of the sympathetic nervous system. VII. Cardiac output: The combination of stroke volume Norepinephrine levels increase in response to and heart rate a decrease in cardiac output and results in VIII. Systemic vascular resistance: Resistance to blood tachycardia and vasoconstriction flow through the systemic arterioles IX. Blood pressure: The combination of cardiac output DIAGNOSTIC TESTS and systemic vascular resistance X. Eccentric hypertrophy: Dilated atrial or ventricular I. Echocardiography: Ultrasound of the heart used to chambers with normal to decreased wall thickness evaluate structure and function caused by a volume overload. Examples of heart II. Electrocardiography: Records the electrical activity diseases that result in eccentric hypertrophy include of the heart for analysis of heart rate and rhythm, the following: conduction abnormalities, and chamber enlargement A. Dilated cardiomyopathy patterns B. Valvular endocardiosis III. Holter monitor: Records an electrocardiogram (ECG) C. Patent ductus arteriosus (PDA) over an extended period D. Ventricular septal defect IV. Thoracic radiographs: Used to evaluate heart size E. Atrial septal defect (ASD) and shape, to assess pulmonary and mediastinal XI. Concentric hypertrophy: Ventricular wall thickening structures, and to evaluate for congestive heart caused by a pressure overload. Examples of heart failure (CHF) diseases that result in concentric hypertrophy V. Blood pressure: Systolic; mean and diastolic include the following: systemic arterial pressure can be measured A. Systemic hypertension invasively (direct) or noninvasively B. Pulmonary hypertension (indirect) C. Pulmonic stenosis VI. Cardiac catheterization and angiography: Catheters D. Aortic stenosis placed into peripheral vessels are used to evaluate XII. Heart failure: Occurs when the hearts ability to hemodynamics and to perform contrast studies of supply adequate blood flow is reduced the heart and vessels A. Congestive: Occurs when reduced cardiac VII. Nuclear cardiology: First-pass nuclear angiocardiog- function results in elevated venous pressures raphy studies assess the direction and magnitude and fluid accumulates in organs or body of shunts, and gated radionuclide studies evaluate cavities ventricular function 165 166 SECTION II SMALL ANIMAL Table 12-1 Clinical Characteristics of the Most Common Congenital Heart Defects in Dogs Defect Murmur Location Murmur Timing Pulse Quality Patent ductus arteriosus Left base Continuous Bounding Pulmonic stenosis Left base Systolic Normal Subaortic stenosis Left base Systolic Normal to decreased F. Physical examination (Table 12-1) CONGENITAL HEART DISEASE 1. Systolic left basilar murmur I. The most common congenital heart diseases in 2. Diastolic left basilar murmur dogs are PDA, subaortic stenosis, and pulmonic 3. Normal to weak pulse quality stenosis 4. Dyspnea II. The most common congenital heart diseases in cats G. Diagnosis are septal defects (ASD, ventricular septal defect, 1. Echocardiogram endocardial cushion defect) and atrioventricular a. Left ventricular hypertrophy valvular dysplasia b. Left atrial enlargement III. Most common defects resulting in cyanosis c. Subvalvular narrowing A. Tetralogy of Fallot d. Poststenotic dilation of aorta B. Right-to-left shunting PDA. Creates differential e. Thickened aortic valve leaflets cyanosis, cyanosis of the caudal mucous f. Aortic regurgitation membranes g. Elevated transaortic velocities C. Right-to-left shunting ventricular septal defect 2. Electrocardiography IV. Aortic stenosis a. Tall R waves in lead II suggestive of left A. Most often occurs as a result of a ridge or ring of ventricular enlargement tissue below the aortic valve (subvalvular) b. Wide P wave in lead II suggestive of left B. Severity can increase until a dog reaches mature atrial enlargement body weight c. ST segment depression C. Heritable d. Ventricular arrhythmias D. Common breeds: Newfoundland, golden retriever, 3. Thoracic radiographs (Figure 12-1) Rottweiler, German shepherd, boxer, bull terrier a. Normal in dogs with mild disease E. Clinical signs: May be normal; exercise intoler- b. Left ventricular enlargement ance, lethargy, syncope, cough, dyspnea, sudden c. Left atrial enlargement death d. Poststenotic dilation of aorta A B Figure 12-1 Lateral (A) and dorsoventral (B) radiographs from a young dog with subaortic stenosis. Prominent bulge in the cranial waist on the lateral view and widening of the cranial mediastinum on the dorsoventral view are consistent with poststenotic dilatation of the ascending aorta. (From Ettinger, SJ, Feldman, EC. Textbook of Veterinary Internal Medicine, 2-Vol Set, 6th ed. Philadelphia, 2004, Saunders.)  CHAPTER 12 Cardiovascular Disorders 167 H. Treatment b. High degree of difficulty 1. Balloon valvuloplasty c. Requires special equipment a. Variable success rate d. Costly b. No additional benefit compared with e. Not readily available -blocker therapy alone 3. Medical management. Congestive right heart 2. Surgery failure a. Resection of subvalvular lesion and a. Oxygen replacement with patch graft b. Diuretics b. High degree of difficulty c. Positive inotropic support c. Requires special equipment d. ACE inhibitor d. Costly e. Pleurocentesis e. Not readily available f. Abdominocentesis 3. Medical management H. Prognosis a. -Blocker therapy 1. Small defects: Favorable; rarely develop b. Antibiotic therapy to prevent valvular clinical signs endocarditis during periods of bacteremia 2. Moderate to large defects: Develop clinical c. CHF signs, shortened life span without defect (1) Oxygen closure (2) Diuretics VI. PDA (3) Nitroglycerin ointment A. Common congenital heart defect in dogs (4) Angiotensin-converting enzyme (ACE) B. More common in females inhibitor C. Heritable I. Prognosis D. Results from a congenital lack of ductal smooth 1. Mild: Favorable; rarely develop clinical signs muscle 2. Moderate: Favorable; may develop clinical signs E. Typically left to right shunting 3. Severe: Develop clinical signs, shortened life F. Common breeds: Miniature poodle, Maltese, span, risk of sudden death German shepherd, Yorkshire terrier, Shetland V. ASD sheepdog, collie, Pomeranian, Labrador retriever, A. Occurs in dogs and cats bichon frise B. Typically shunts left to right G. Clinical signs: May be normal; exercise C. Common breeds: Boxer, standard poodle intolerance, lethargy, cough, dyspnea D. Clinical signs: May be normal; exercise intoler- H. Physical examination ance, lethargy, syncope, right heart-sided heart 1. Continuous left basilar murmur failure with large defects, ascites 2. Systolic left apical murmur of mitral regurgitation E. Physical examination 3. Increased (hyperkinetic) pulse quality results 1. Systolic left basilar murmur from a large difference in systolic and diastolic 2. Split second heart sound pulse pressure 3. Normal pulse quality 4. Dyspnea 4. Right-sided heart failure with large defects: I. Diagnosis Ascites, jugular venous distension, positive 1. Echocardiogram hepatojugular reflex a. Left ventricular enlargement F. Diagnosis b. Left atrial enlargement 1. Echocardiogram c. Continuous color flow within the main a. Right ventricular enlargement pulmonary artery b. Right atrial enlargement d. Visualization of the PDA. Typically funnel c. ASD shaped with narrowing at the pulmonary 2. Electrocardiography artery side a. Deep S waves in leads I, II, III, aVf are e. Mitral regurgitation suggestive of right ventricular enlargement 2. Electrocardiography b. Right axis deviation a. Tall R waves in lead II suggestive of left c. Tall P waves in lead II suggestive of right ventricular enlargement atrial enlargement b. Wide P waves in lead II suggestive of left 3. Thoracic radiographs atrial enlargement a. Normal in dogs with mild disease 3. Thoracic radiographs b. Right atrial enlargement a. Normal in dogs with mild disease c. Right ventricular enlargement b. Left atrial enlargement d. Main pulmonary artery dilation c. Left ventricular enlargement e. Pleural effusion d. Aneurysmal bulge of descending aorta G. Treatment e. Pulmonary overcirculation 1. Interventional catheterization. Device used to f. Pulmonary edema close large ASDs 4. Blood pressure 2. Surgery a. Normal systolic a. Patch graft b. Decreased diastolic 168 SECTION II SMALL ANIMAL J. Treatment D. Heritable 1. Interventional catheterization: Device implan- E. Common breeds: English bulldog, West tation (coil, vascular plug, ductal occluder) Highland white terrier, boxer, Chihuahua, 2. Surgery. Ligation mastiff, beagle 3. Medical management F. Clinical signs: May be normal; exercise intoler- a. CHF ance, lethargy, syncope, ascites, sudden death (1) Oxygen G. Physical examination (2) Diuretics 1. Systolic left basilar murmur (3) Positive inotropic support 2. Diastolic left basilar murmur with significant (4) Nitroglycerin ointment pulmonic valvular regurgitation (5) ACE inhibitor 3. Normal pulse quality K. Prognosis 4. Ascites 1. Small PDA: Favorable, might not develop 5. Jugular venous distension clinical signs 6. Positive hepatojugular reflex 2. Moderate to large PDA: Develop clinical signs, H. Diagnosis favorable with ductal occlusion-ligation; 1. Echocardiogram shortened life span without treatment a. Right ventricular hypertrophy L. Right-to-left shunting PDA b. Interventricular septal flattening 1. Attributed to increased pulmonary vascular c. Right atrial enlargement resistance d. Poststenotic dilation of main pulmonary 2. Patients develop hypoxemia, exercise intoler- artery ance, collapse, tachypnea, dyspnea, ascites e. Thickened pulmonic valve leaflets 3. Polycythemia results from hypoxemia and is f. Restricted motion of pulmonic valve leaflets managed with phlebotomy or hydroxyurea g. Pulmonic regurgitation 4. PDA closure is contraindicated and will result h. Elevated peak transpulmonic velocities in severe hypoxemia and death i. Hypoplastic pulmonic valve annulus 5. Prognosis is poor j. Aberrant coronary artery VII. Pulmonic stenosis 2. Electrocardiography A. Valvular pulmonic stenosis is a common congenital a. Deep S waves in leads I, II, III, aVf suggestive heart disease in dogs of right ventricular enlargement B. Severity can increase until a dog reaches mature b. Right axis deviation body weight c. Tall P waves in lead II suggestive of right C. Occasionally, an aberrant left coronary artery atrial enlargement encircles the right ventricular outflow tract and 3. Thoracic radiographs (Figure 12-2) pulmonic valve causing pulmonic stenosis. a. Normal in dogs with mild disease Occurs most often in the English bulldog and b. Right ventricular enlargement boxer c. Right atrial enlargement A B Figure 12-2 Lateral (A) and dorsoventral (B) thoracic radiographs from a dog with pulmonic stenosis. Rounding of the sternal border and a bulge in the cranial waist of the heart can be seen in the lateral view. Right heart enlargement and a bulge in the main pulmonary artery segment are seen in the dorsoventral view. Pulmonary vessels are diminished even in the absence of a right-to-left shunt. (From Ettinger SJ, Feldman EC. Textbook of Veterinary Internal Medicine: 2-Vol Set, 6th ed. Philadelphia, 2004, Saunders.)  CHAPTER 12 Cardiovascular Disorders 169 d. Poststenotic dilation of main pulmonary c. Right atrial enlargement artery d. Overriding aorta e. Enlarged caudal vena cava e. Ventricular septal defect I. Treatment f. Color flow from right ventricle into aorta 1. Balloon valvuloplasty g. Poststenotic dilation of main pulmonary a. For valvular pulmonic stenosis artery b. Prognosis improved if pressure gradient is h. Thickened pulmonic valve leaflets reduced to mild i. Restricted motion of pulmonic valve 2. Surgery leaflets a. Resection of stenotic area and replacement j. Pulmonic regurgitation with a patch graft k. Elevated peak transpulmonic velocities b. Conduit around stenosis, especially if 2. Electrocardiography aberrant coronary artery a. Deep S waves in leads I, II, III, aVf suggestive c. High degree of difficulty of right ventricular enlargement d. Requires special equipment b. Right axis deviation e. Costly c. Tall P waves in lead II suggestive of right f. Not readily available atrial enlargement 3. Medical management 3. Thoracic radiographs a. -Blocker therapy a. Right ventricular enlargement b. Congestive right-sided heart failure b. Decreased pulmonary vasculature (1) Oxygen c. Poststenotic dilation of main pulmonary (2) Diuretics artery (3) ACE inhibitor 4. Packed cell volume (PCV): To monitor (4) Pleurocentesis polycythemia (5) Abdominocentesis 5. Arterial blood gas: To monitor hypoxemia J. Prognosis J. Treatment 1. Mild: Favorable; rarely develop clinical signs 1. Balloon valvuloplasty: For severe or 2. Moderate: Favorable; may develop clinical signs symptomatic valvular pulmonic stenosis 3. Severe: Develop clinical signs; shortened life 2. Surgery span, risk of sudden death a. Resection of the pulmonic stenosis and VIII. Tetralogy of Fallot replacement with a patch graft A. Characterized by a ventricular septal defect, b. Patch graft of the ventricular septal pulmonic stenosis, overriding aorta and right defect ventricular hypertrophy c. Blalock Taussig shunt: Connects the left B. Pulmonic stenosis creates an obstruction subclavian artery to the pulmonary to blood flow into the pulmonary artery. artery to create a communication Deoxygenated blood is delivered to the between the pulmonary and systemic systemic circulation, resulting in circulation hypoxemia d. High degree of difficulty C. Most common cyanotic congenital heart defect e. Requires special equipment in dogs f. Costly D. May result in polycythemia g. Not readily available E. Inherited as a simple autosomal recessive 3. Medical management trait a. Phlebotomy. PCV should be maintained F. Common breeds: Keeshond, English bulldog below 60% to 65% G. Clinical signs: May be normal; exercise intolerance, b. Hydroxyurea. Side effects related to lethargy, syncope, seizures resulting from myelosuppression polycythemia, dyspnea resulting from hypoxemia, c. -Blockers to relieve hypoxemic episodes ascites associated with sympathetic drive H. Physical examination d. CHF 1. Cyanosis with and without exercise (1) Oxygen 2. Systolic left or right basilar murmur of (2) Diuretics pulmonic stenosis (3) ACE inhibitor 3. Might not have an audible murmur (4) Pleurocentesis 4. Normal pulse quality (5) Abdominocentesis 5. Ascites K. Prognosis 6. Jugular venous distension 1. Mild: Favorable; rarely develop clinical 7. Positive hepatojugular reflex signs 8. Dyspnea 2. Moderate: May develop clinical signs I. Diagnosis 3. Severe: Develop clinical signs; shortened life 1. Echocardiogram span, risk of sudden death a. Right ventricular hypertrophy IX. Atrioventricular valvular dysplasia b. Interventricular septal flattening A. Mitral and tricuspid valve dysplasia 170 SECTION II SMALL ANIMAL 1. Malformation of the valve leaflets, chordae ten- (3) Right axis deviation dinae or papillary muscles result in regurgita- (4) Tall P waves in lead II suggestive of tion of the valve, valvular stenosis, or both right atrial enlargement 2. Occurs in both dogs and cats (5) Supraventricular premature beats B. Common breeds (6) Atrial fibrillation 1. Tricuspid valve dysplasia: Great Dane, German c. Thoracic radiographs shepherd, golden retriever, Labrador retriever, (1) Normal with mild disease Weimaraner (2) Right atrial enlargement 2. Mitral valve dysplasia: Great Dane, German (3) Right ventricular enlargement shepherd, golden retriever, bull terriers, (4) Caudal vena cava enlargement numerous cat breeds (5) Pleural effusion C. Clinical signs 2. Mitral valve dysplasia 1. Tricuspid valve dysplasia a. Echocardiogram a. May be normal (1) Left atrial enlargement b. Exercise intolerance (2) Left ventricular enlargement c. Lethargy (3) Mitral valve apparatus d. Syncope (a) Thickened valve leaflets e. Right-sided heart failure, ascites (b) Short or elongated valve leaflets f. Sudden death with restricted motion 2. Mitral valve dysplasia (c) Atrophy, hypertrophy, or a. May be normal malpositioned papillary muscles b. Exercise intolerance (d) Thickened, short, or elongated c. Lethargy chordae tendinae d. Syncope (4) Mitral regurgitation e. Left-sided heart failure b. Electrocardiography (1) Cough (1) Tall R waves in lead II suggestive of left (2) Dyspnea ventricular enlargement f. Sudden death (2) Wide P waves in lead II suggestive of left D. Physical examination atrial enlargement 1. Tricuspid valve dysplasia (3) Supraventricular premature beats a. Systolic right-sided heart murmur (4) Atrial fibrillation b. Normal pulse quality c. Thoracic radiographs c. Ascites (1) Normal with mild disease d. Jugular venous distension (2) Left atrial enlargement e. Positive hepatojugular reflex (3) Left ventricular enlargement f. Arrhythmias (4) Pulmonary venous enlargement 2. Mitral valve dysplasia (5) Pulmonary edema a. Systolic left apical murmur F. Treatment b. Normal pulse quality 1. Balloon valvuloplasty. Tricuspid valve stenosis c. Dyspnea 2. Surgery d. Arrhythmias a. Valvular repair or replacement E. Diagnosis b. High degree of difficulty 1. Tricuspid valve dysplasia c. Requires special equipment a. Echocardiogram d. Costly (1) Right atrial enlargement e. Not readily available (2) Right ventricular enlargement 3. Medical management (3) Tricuspid valve displaced toward the a. CHF right ventricle (1) Oxygen (4) Tricuspid valve apparatus (2) Diuretics (a) Thickened valve leaflets (3) Positive inotropic support (b) Short septal leaflet with restricted (4) Nitroglycerin ointment motion (5) ACE inhibitor (c) Elongated mural leaflet (6) Pleurocentesis (d) Atrophy, hypertrophy, or malposi- (7) Abdominocentesis tioned papillary muscles b. Antiarrhythmic therapy (e) Thickened, short, or elongated G. Prognosis chordae tendinae 1. Mild: Favorable; rarely develop clinical signs (5) Tricuspid regurgitation 2. Moderate: Favorable; may develop clinical signs b. Electrocardiography 3. Severe: Develop clinical signs, shortened life (1) Splintered QRS complex span, risk of sudden death (2) Deep S waves in leads I, II, III, aVf X. Ventricular septal defect suggestive of right ventricular A. Perimembranous defects occur most often enlargement in dogs  CHAPTER 12 Cardiovascular Disorders 171 B. Spontaneous closure rarely occurs D. Diagnosed with thoracic radiographs, C. Typically shunt left to right angiography, or esophageal endoscopy D. Common breeds: English springer spaniel, English E. Treatment requires surgical ligation of the bulldog ligamentum arteriosum E. Clinical signs: May be normal; exercise intoler- F. Prognosis is good to guarded. Residual esopha- ance, lethargy, cough, dyspnea geal functional and structural damage may persist F. Physical examination 1. Systolic right sternal or left basilar murmur. ACQUIRED HEART DISEASE Loud murmurs are associated with small ventricular septal defects I. Myocardial disease 2. Diastolic left basilar murmur associated with A. Dogs aortic regurgitation if aortic valve leaflet 1. Dilated cardiomyopathy prolapses into USD 2. Arrhythmogenic right ventricular 3. Normal pulse quality cardiomyopathy G. Diagnosis 3. Hypertrophic cardiomyopathy 1. Echocardiogram B. Cats a. Left ventricular enlargement 1. Hypertrophic cardiomyopathy b. Left atrial enlargement 2. Dilated cardiomyopathy c. Ventricular septal defect 3. Restrictive cardiomyopathy d. Aortic insufficiency 4. Arrhythmogenic right ventricular 2. Electrocardiography cardiomyopathy a. Tall R waves in lead II suggestive of left C. Dilated cardiomyopathy in dogs ventricular enlargement 1. Heritable in some breeds (boxer, Doberman b. Wide P waves in lead II suggestive of left pinscher, Great Dane, Newfoundland) atrial enlargement 2. More common in male dogs 3. Thoracic radiographs 3. Preclinical: Denoted by the presence of left a. Normal in dogs with small septal defects ventricular dilation, left ventricular systolic b. Left atrial enlargement dysfunction, and ventricular arrhythmias in c. Left ventricular enlargement the absence of clinical signs d. Pulmonary overcirculation 4. Clinical: Left ventricular dilation, left ventricu- e. Pulmonary edema lar systolic dysfunction, and ventricular H. Treatment arrhythmias in the presence of clinical signs 1. Interventional catheterization: Device used to 5. Common breeds: Doberman pinscher, close large ventricular septal defects Newfoundland, Irish wolfhound, Great Dane, 2. Surgery Labrador retriever, cocker spaniel, boxer, Saint a. Pulmonary artery banding Bernard, Old English sheepdog, Dalmatian b. Patch graft 6. Causes (1) High degree of difficulty a. Tachycardia induced (2) Requires special equipment (1) Myocardial dysfunction resulting from (3) Costly a persistently fast heart rate (4) Not readily available (200 beats/min) 3. Medical management. Congestive left-sided (2) Enlargement of all four heart chambers heart failure (3) May resolve with appropriate heart rate a. Oxygen control b. Diuretics b. Toxic. Adriamycin (doxorubicin) c. Positive inotropic support (1) Patients present with arrhythmias and d. Nitroglycerin ointment myocardial failure e. ACE inhibitor (2) Dose dependent and reversible I. Prognosis (3) Cardiotoxicity occurs at cumulative 1. Small defects: Favorable; rarely develop doses of 250 mg/m2 clinical signs c. Infectious myocarditis 2. Moderate to large defects: Develop clinical (1) Toxoplasma gondii signs; shortened life span without defect (2) Trypanosoma cruzi closure (a) Vector is the reduvid bug XI. Vascular ring anomaly. Persistent right fourth aortic (b) Forms arch i. Trypomastigote in blood A. The esophagus is surrounded by the pulmonary ii. Amastigote in host tissue artery, ligamentum arteriosum, right aortic arch, (c) Presentation heart base, and trachea i. Ventricular arrhythmias and B. Common breeds: German shepherd, Irish setter, atrioventricular block Great Dane ii. Systolic dysfunction of primarily C. Clinical signs of regurgitation are attributed to the right ventricle esophageal obstruction iii. Heart failure 172 SECTION II SMALL ANIMAL (d) No reliable cure i. Hepatosplenomegaly (e) Treat symptomatically j. Jugular venous distension (3) Parvovirus k. Positive hepatojugular reflex (a) Affected puppies during the 1970s 9. Diagnosis and 1980s a. Echocardiogram (b) Not routinely encountered now (1) Left or right ventricular dilation that most dogs are appropriately (2) Decreased systolic function vaccinated (3) Normal to decreased left ventricular (4) Distemper virus: Uncommon given wall thickness that most dogs are appropriately (4) Left or right atrial enlargement vaccinated (5) Mitral or tricuspid regurgitation d. Endocrine (6) Normal to decreased transaortic (1) Hypothyroidism velocities (a) May contribute b. Electrocardiography (Figure 12-3) e. Nutritional (1) Tall R waves in lead II suggestive of left (1) Taurine deficiency ventricular enlargement (a) Cocker spaniels (2) Wide P waves in lead II suggestive of left (b) Golden retrievers atrial enlargement (2) Carnitine deficiency (3) Ventricular arrhythmias (a) Cocker spaniels (4) Supraventricular premature beats (b) Boxers (5) Atrial fibrillation f. Idiopathic. No identifiable cause c. Thoracic radiographs 7. Clinical signs (1) Normal in dogs with an early stage of a. May be normal the disease b. Exercise intolerance (2) Left atrial enlargement c. Lethargy (3) Left ventricular enlargement d. Left- and right-sided heart failure (4) Right atrial enlargement (1) Cough (5) Right ventricular enlargement (2) Dyspnea (6) Enlarged pulmonary veins (3) Ascites (7) Pulmonary edema (4) Syncope (8) Pleural effusion (5) Sudden death d. Plasma taurine levels (6) Anorexia e. Thyroid panel (thyroxine [T4], free T4 by (7) Weight loss equilibrium dialysis [ED], thyroid-stimulating 8. Physical examination hormone [TSH]) a. Systolic left or right heart murmur f. Chagas titer associated with atrioventricular valvular 10. Treatment: Medical management regurgitation a. Preclinical b. Gallop (1) ACE inhibitor c. Arrhythmia (2) The use of -blockers is under d. Normal to decreased pulse quality investigation e. Pulse deficits b. CHF f. Normal to pale mucous membrane color (1) Oxygen g. Dyspnea (2) Diuretics h. Ascites (3) Positive inotropic support Figure 12-3 Lead II electrocardiogram tracing from a dog indicating atrial fibrillation and left ventricular enlargement. Note the irregular rhythm, lack of P waves, and widened QRS complex. 50 mm/sec; 10 mm/mV. (From Tilley LP et al. Manual of Canine and Feline Cardiology, 4th ed. Philadelphia, 2007, Saunders.)  CHAPTER 12 Cardiovascular Disorders 173 (4) Nitroglycerin ointment 5. Therapy consists of antiarrhythmic medication (5) ACE inhibitor such as sotalol or mexilitine combined with (6) Pleurocentesis atenolol (7) Abdominocentesis 6. High risk of sudden death c. Antiarrhythmic therapy E. Hypertrophic cardiomyopathy in dogs d. Nutritional supplements: Taurine, 1. Characterized by idiopathic concentric L-carnitine, fish oil, coenzyme Q10 hypertrophy of the ventricle 11. Prognosis 2. Rarely occurs in dogs a. Tachycardia induced: Favorable with 3. Rule out secondary causes of ventricular adequate heart rate control hypertrophy b. Toxic: Favorable a. Aortic stenosis c. Infectious myocarditis: Poor b. Systemic hypertension d. Endocrine: Hypothyroidism. Favorable c. Significant dehydration with thyroid supplementation d. Infiltrative neoplasia e. Nutritional F. Hypertrophic cardiomyopathy in cats (1) Taurine deficiency. Favorable with 1. Characterized by concentric hypertrophy of taurine supplementation the ventricle (2) L-carnitine deficiency. Favorable with 2. Hypertrophic obstructive cardiomyopathy carnitine supplementation (HOCM) occurs when there is a dynamic ob- f. Idiopathic. Poor struction to blood entering the left ventricular 12. Breed-related variations outflow tract secondary to systolic anterior a. Boxer: Present primarily with arrhythmias motion of the mitral valve b. Cocker spaniels: Associated with taurine 3. Inheritance patterns: Autosomal dominant in and L-carnitine deficiency Maine coon cats c. Golden retriever 4. Common breeds: Maine coon, Persian ragdoll, (1) Canine X-linked muscular dystrophy American shorthair, domestic shorthair, (2) Myocardial lesions develop before domestic longhair 1 year of age 5. Secondary causes of ventricular hypertrophy (3) Prognosis is guarded to poor a. Aortic stenosis d. Great Dane: X-linked inheritance pattern b. Systemic hypertension e. Irish wolfhound c. Hyperthyroidism (1) Frequently present with atrial d. Significant dehydration fibrillation e. Infiltrative neoplasia (2) Often have biventricular heart f. Acromegaly failure 6. Clinical signs: May be normal; exercise intoler- f. Portuguese water dogs: juvenile onset, poor ance, lethargy, left-sided and right-sided heart prognosis failure (cough, dyspnea, ascites), syncope, sud- D. Arrhythmogenic right ventricular cardiomyopathy den death, weight loss, decreased appetite, in dogs sudden lameness 1. Characterized pathologically by fatty or 7. Factors that may result in clinical decompensa- fibrofatty infiltration of the right ventricle tion: Anesthesia, long-acting corticosteroids, 2. Familial in boxers stress 3. Inherited as an autosomal dominant trait 8. Physical examination 4. Characterized by syncope, ventricular a. Systolic sternal murmur arrhythmias with a right ventricular origin, b. Gallop and occasionally systolic dysfunction c. Arrhythmia (Figure 12-4) d. Normal pulse quality Figure 12-4 Lead II electrocardiogram tracing from a 7-year-old male, castrated boxer with arrhythmogenic right ventricular cardiomyopathy. Ventricular premature beats with left bundle-branch block morphology are a common finding in dogs with this condition. 25 mm/sec; 0.5 cm/mV. (From Tilley LP. Manual of Canine and Feline Cardiology, 4th ed. Philadelphia, 2007, Saunders.) 174 SECTION II SMALL ANIMAL e. Normal to pale mucous membrane color G. Dilated cardiomyopathy in cats f. Dyspnea 1. Characterized by increased ventricular size g. Crackles and a reduction in contractility h. Ascites 2. Causes: Nutritional, taurine deficiency, i. Hepatosplenomegaly idiopathic j. Jugular venous distension 3. Clinical signs: Cough, dyspnea, vomiting, k. Pale nail beds anorexia, lethargy, syncope, sudden lameness, l. Hypothermia sudden death 9. Diagnosis 4. Physical examination a. Echocardiogram a. Systolic sternal murmur (1) Global or focal left ventricular wall b. Gallop thickening (6 mm) c. Arrhythmia (2) Papillary muscle hypertrophy d. Normal to decreased pulse quality (3) Left and right atrial enlargement e. Normal to pale mucous membrane color (4) Mitral regurgitation f. Dyspnea (5) Systolic anterior motion of the mitral g. Crackles valve h. Ascites (6) Normal to increased left ventricular i. Hepatosplenomegaly outflow tract velocities j. Jugular venous distension (7) Diastolic dysfunction k. Pale nail beds (8) Pleural effusion l. Hypothermia (9) Pericardial effusion 5. Diagnosis b. Electrocardiography a. Echocardiogram (1) Tall R waves in lead II suggestive of left (1) Left ventricular dilation ventricular enlargement (2) Decreased fractional shortening (2) Wide P waves in lead II suggestive of left (3) Left and/or right atrial enlargement atrial enlargement (4) Mitral regurgitation (3) Ventricular arrhythmias (5) Pleural effusion (4) Supraventricular arrhythmias (6) Pericardial effusion c. Thoracic radiographs (Figure 12-5) b. Thoracic radiographs (1) Normal in cats with an early stage of (1) Cardiomegaly the disease (2) Pleural effusion (2) Generalized cardiomegaly (3) Enlarged pulmonary veins (3) Left and/or right atrial enlargement (4) Pulmonary edema (4) Left ventricular enlargement c. Plasma or whole blood taurine (5) Enlarged pulmonary veins concentration (6) Pulmonary edema 6. Treatment. Medical management (7) Pleural effusion a. Positive inotropic therapy d. Thyroid b. Taurine supplementation e. Blood pressure c. ACE inhibitor 10. Treatment. Medical management d. CHF a. -Blocker or calcium channel blocker (1) Oxygen b. ACE inhibitor (2) Diuretics c. CHF (3) Pleurocentesis (1) Oxygen (4) Abdominocentesis (2) Diuretics e. Antiarrhythmic therapy (3) ACE inhibitor f. Thromboembolism (4) Pleurocentesis (1) Aspirin, clopidogrel (5) Abdominocentesis (2) Pain medication d. Antiarrhythmic therapy (3) Physical therapy e. Thromboembolism 7. Prognosis: Favorable with taurine supplemen- (1) Aspirin, clopidogrel tation, poor if idiopathic (2) Pain medication H. Restrictive cardiomyopathy in cats (3) Physical therapy 1. Classified as normal to mildly increased ven- 11. Prognosis tricular wall thickness with atrial enlargement a. Highly variable depending on ventricular and evidence of diastolic dysfunction wall thickness, atrial enlargement, and 2. May be a result of myocarditis presence of clinical signs 3. Clinical signs: Similar to hypertrophic b. Mild: Favorable, rarely develop clinical cardiomyopathy signs 4. Physical examination: Similar to hypertrophic c. Moderate: May develop clinical signs cardiomyopathy d. Severe: Develop clinical signs, prognosis 5. Diagnosis is poor a. Echocardiogram  CHAPTER 12 Cardiovascular Disorders 175 A B C D Figure 12-5 Radiographic examples of feline hypertrophic cardiomyopathy. Lateral (A) and dorsoventral (B) views showing atrial and mild ventricular enlargement along with patchy interstitial pulmonary edema (arrowheads) in a male domestic shorthair cat with left-sided congestive heart failure. Lateral (C) and dorsoventral (D) views of a male Siamese cat with marked atrial enlargement, dilated pulmonary veins (arrowheads, C), and atrial fibrillation. (From Nelson RW, Couto CG. Small Animal Internal Medicine, 4th ed. St Louis, 2009, Mosby.) 176 SECTION II SMALL ANIMAL (1) Normal to mild left ventricular wall b. Electrocardiography. Ventricular thickening arrhythmias (2) Diastolic ventricular dysfunction c. Thoracic radiographs (3) Biatrial enlargement (1) Normal in cats with an early stage of (4) Mitral regurgitation the disease (5) Pleural effusion (2) Generalized cardiomegaly (6) Pericardial effusion (3) Pleural effusion b. Electrocardiography: Similar to hypertrophic 5. Treatment. Medical management cardiomyopathy a. Positive inotropic support c. Thoracic radiographs: Similar to b. ACE inhibitor hypertrophic cardiomyopathy c. CHF 6. Treatment. Medical management (1) Oxygen a. -Blocker or calcium channel blocker (2) Diuretics b. ACE inhibitor (3) Pleurocentesis c. CHF (4) Abdominocentesis (1) Oxygen d. Antiarrhythmic therapy (2) Diuretics 6. Prognosis poor (3) Pleurocentesis II. Valvular endocardiosis (4) Abdominocentesis A. Commonly acquired heart disease in middle-aged d. Antiarrhythmic therapy to older dogs e. Thromboembolism B. Occurs with less frequency in cats (1) Aspirin, clopidogrel C. Result of myxomatous degeneration of the (2) Pain medication atrioventricular valves (mitral valve more (3) Physical therapy frequently than tricuspid valve) 7. Prognosis D. Progression to heart failure is highly variable a. Mild: Favorable; rarely develop clinical signs E. Acute decompensation occurs with chordae b. Moderate: May develop clinical signs tendinae rupture, left atrial rupture, and the onset c. Severe: Develop clinical signs; prognosis of arrhythmias is poor F. More common in small breed dogs but does I. Arrhythmogenic right ventricular cardiomyopathy occur in large and giant breeds in cats G. Common breeds: Cavalier King Charles spaniel, 1. Characterized by fatty or fibrofatty infiltration dachshund, miniature poodle, cocker spaniel, of the right ventricle Pomeranian, Miniature schnauzer, Boston terrier, 2. Clinical signs Chihuahua a. May be normal H. Clinical signs: May be normal; exercise intoler- b. Exercise intolerance ance, lethargy, anorexia, weight loss, left or right c. Lethargy heart failure (cough, dyspnea, ascites), syncope, d. Right-sided heart failure: Cough, dyspnea, sudden death ascites I. Physical examination e. Syncope 1. Systolic left apical murmur with mitral f. Sudden death regurgitation g. Weight loss 2. Systolic right heart murmur with tricuspid h. Decreased appetite regurgitation 3. Physical examination 3. Mid-systolic click a. Systolic sternal murmur 4. Normal pulse quality b. Gallop 5. Arrhythmia c. Arrhythmia 6. Gallop d. Normal pulse quality 7. Dyspnea e. Normal to pale mucous membrane 8. Signs of right-sided heart failure if tricuspid color endocardiosis or pulmonary hypertension f. Dyspnea a. Ascites g. Crackles b. Positive hepatojugular reflex h. Ascites c. Jugular venous distension i. Hepatosplenomegaly J. Diagnosis j. Jugular venous distension 1. Echocardiogram k. Hypothermia a. Left atrial enlargement 4. Diagnosis b. Left ventricular enlargement a. Echocardiogram c. Normal, increased, or decreased systolic (1) Right ventricular enlargement function (2) Right atrial enlargement d. Normal left ventricular wall thickness (3) Tricuspid regurgitation e. Thickened valve leaflets (4) Pleural effusion f. Prolapse or flail of the valve leaflets (5) Pericardial effusion g. Mitral regurgitation  CHAPTER 12 Cardiovascular Disorders 177 h. Normal transaortic and transpulmonic 5. Antiarrhythmic therapy velocities 6. Surgery: Valvular repair or replacement; i. Signs of right heart enlargement with tricus- high degree of difficulty, requires special pid endocardiosis or pulmonary hypertension equipment, costly, not readily available (1) Right atrial enlargement L. Prognosis: Dependent on progression and sever- (2) Right ventricular enlargement ity of the disease. Cavalier King Charles spaniels (3) Tricuspid regurgitation may have a faster rate of progression (4) Pulmonic regurgitation III. Valvular endocarditis (5) Pulmonary artery enlargement A. Incidence is higher in large breed dogs and dogs 2. Electrocardiography with congenital heart disease (aortic stenosis and a. Sinus arrhythmia ventricular septal defects) b. Sinus tachycardia B. Most common valves affected are aortic, mitral c. Tall R waves in lead II suggestive of left C. Most common infectious organisms ventricular enlargement 1. Escherichia coli d. Wide P waves in lead II suggestive of left 2. Staphylococcus aureus atrial enlargement 3. Streptococcus spp. e. Tall P waves in lead II suggestive of right 4. Corynebacterium atrial enlargement 5. Bartonella vinsonii more common in f. Supraventricular or ventricular premature culture-negative endocarditis beats D. Embolism of the kidney, spleen, liver, gastrointesti- g. Atrial fibrillation or flutter nal (GI) tract, brain and limbs have been reported 3. Thoracic radiographs E. Clinical signs: May be normal; exercise intolerance, a. Normal in dogs with an early stage of the lethargy, left-sided heart failure (cough, dyspnea), disease syncope, sudden death, anorexia, weight loss b. Left ventricular enlargement F. Physical examination c. Left atrial enlargement 1. Systolic left apical murmur if mitral d. Mainstem bronchial compression regurgitation e. Enlarged pulmonary veins 2. Diastolic left basilar murmur if aortic f. Pulmonary edema regurgitation g. Signs of right-sided heart disease with 3. Systolic left basilar murmur if aortic stenosis tricuspid endocardiosis or pulmonary 4. Systolic right sternal murmur if ventricular hypertension septal defect (1) Right atrial enlargement 5. Gallop (2) Right ventricular enlargement 6. Arrhythmia (3) Pulmonary artery enlargement 7. Normal to increased pulse quality (4) Pleural effusion 8. Pulse deficits 4. Blood pressure 9. Normal to pale mucous membrane color a. Normal systolic pressure 10. Dyspnea b. May be decreased in severe cases with 11. Painful joints resulting from septic arthritis reduced cardiac output 12. Fever c. May be increased with comorbidities such G. Diagnosis as renal or endocrine disease 1. Echocardiogram 5. Serum biochemistry panel and electrolytes a. Left ventricular dilation K. Treatment. Medical management b. Left atrial enlargement 1. Preclinical c. Normal to increased left ventricular wall a. No medication shown to delay the progres- thickness. Increased with aortic stenosis sion of the disease d. Mitral regurgitation b. ACE inhibitors frequently prescribed e. Aortic regurgitation c. The use of -blockers is under investigation f. Normal to increased transaortic velocities 2. CHF g. Vegetative valvular lesions a. Oxygen h. Thickened aortic valve leaflets b. Diuretics 2. Electrocardiography c. Positive inotropic support a. Tall R waves in lead II suggestive of left d. Nitroglycerin ointment ventricular enlargement e. ACE inhibitor b. Wide P waves in lead II suggestive of left f. Pleurocentesis atrial enlargement g. Abdominocentesis c. Ventricular arrhythmias 3. Mainstem bronchial compression d. Supraventricular premature beats a. Cough suppressant such as hydrocodone, e. Atrial fibrillation butorphanol, or dextromethorphan 3. Thoracic radiographs b. Bronchodilator such as theophylline a. Normal in dogs with an early stage of the 4. Systemic hypertension: Afterload reducers such disease as hydralazine, amlodipine, or ACE inhibitors b. Left atrial enlargement 178 SECTION II SMALL ANIMAL c. Left ventricular enlargement C. Life cycle (Figure 12-6) d. Enlarged pulmonary veins 1. L1 microfilaria are ingested by a mosquito e. Pulmonary edema (Table 12-2) 4. Complete blood cell count (CBC) 2. Within the mosquito, the L1 becomes L2 and a. Anemia the L2 becomes L3. Maturation time in the mos- b. Leukocytosis with a left shift quito is dependent on ambient temperature c. Monocytosis 3. L3 larvae are transmitted by the mosquito to 5. Biochemistry panel a host a. Azotemia 4. L3 becomes L4 within the host tissue b. Hypoalbuminemia 5. L4 molts to L5 adults c. Hyperglobulinemia 6. The L5 enters the vasculature and migrates to 6. Blood culture. False-negative if there is prior the heart and pulmonary arteries antibiotic therapy or intermittent bacterial D. Occult heartworm disease means the patient has shedding adult heartworms without circulating microfilariae 7. Urine culture E. Heartworms can result in end-organ damage 8. Blood pressure 1. Kidneys: Deposition of antigen-antibody com- a. Normal to decreased systolic pressure plexes results in glomerulonephritis b. Decreased diastolic pressure 2. Lungs H. Treatment. Medical management a. Pulmonary damage from inflammation and 1. Antibiotic therapy thromboembolic events a. Based on culture and sensitivity b. Eosinophilic granulomas b. Broad spectrum 3. Aberrant worm migration to brain, kidneys, 2. CHF and eyes a. Oxygen F. Canine b. Diuretics 1. Prepatent period is 5 to 7 months c. Positive inotropic support 2. The life span of the adult heartworm is approxi- d. Nitroglycerin ointment mately 5 years e. ACE inhibitor 3. Microfilaria can be passed from a mother to 3. Antiarrhythmic therapy her offspring I. Prognosis: Guarded to poor 4. Clinical signs: May be normal; cough, dyspnea, IV. Heartworm disease exercise intolerance, lethargy, ascites, A. Caused by Dirofilaria immitis syncope, anorexia, weight loss, hemoptysis, B. Transmitted by mosquitoes sudden death Figure 12-6 Life cycle of dirofilaria immitis in the dog. (From Atkins CE. Heartworm disease. From Allen DG, ed. Small Animal Medicine. Philadelphia, 1991, JB Lippincott; pp 341-363.)  CHAPTER 12 Cardiovascular Disorders 179 Table 12-2 Criteria to Differentiate Dirofilaria Immitis Microfilaria from Acanthocheilonema Reconditum (Dipetalonema Reconditam) Using a Modified Knott’s Test (Acanthocheilonema Reconditum) Microfilaria Criteria Dirofilaria Immitis Dipetalonema Reconditum Head Tapered Blunt Body Straight Curved Motion Stationary Progressive Relative length Longer Shorter 5. Physical examination (3) Enlarged and tortuous caudal a. May be normal pulmonary arteries b. Cough (4) Blunting of the caudal pulmonary c. Abnormal bronchovesicular sounds arteries d. Systolic right heart murmur of tricuspid (5) Right ventricular enlargement regurgitation. Caused by elevated right (6) Bronchointerstitial to alveolar ventricular pressures secondary to pulmo- pulmonary pattern nary hypertension, the physical presence of e. Electrocardiography the heartworms across the tricuspid valve, (1) Deep S waves in leads I, II, III, aVf or tricuspid valve endocardiosis suggestive of right ventricular e. Arrhythmias enlargement f. Split-second heart sound (2) Right axis deviation g. Fever (3) Tall P waves in lead II suggestive of h. Right-sided heart failure right atrial enlargement (1) Ascites f. Echocardiogram (2) Positive hepatojugular reflex (1) May be normal (3) Jugular venous distension (2) Right ventricular enlargement 6. Caval syndrome occurs when the heartworms (3) Main pulmonary artery enlargement migrate into the right atrium, right ventricle (4) Tricuspid regurgitation and vena cava (5) Pulmonic regurgitation a. Patients may have port wine-colored urine (6) Heartworms within the right atrium, with hemoglobinuria ventricle, or pulmonary artery b. Patients often develop renal and hepatic g. CBC failure, congestive right heart failure, and (1) May be normal disseminated intravascular coagulation (2) Anemia 7. Diagnosis (3) Neutrophilia a. Heartworm antigen test: Detects antigen (4) Lymphopenia found in the uterus of female worms. Enzyme- (5) Eosinophilia linked immunosorbent assay (ELISA) tests (6) Basophilia are highly sensitive and specific (7) Circulating microfilaria b. Heartworm antibody test. Nonspecific and (8) Thrombocytopenia no longer used in dogs h. Biochemistry panel c. Microfilaria test such as Difil or modified (1) May be normal Knott (2) Elevated serum alanine transferase, se- (1) Microfilaria are present in 70% to 80% rum alkaline phosphatase of dogs (3) Hyperglobulinemia (2) Potential reasons for an absence of mi- (4) Azotemia crofilaria i. Urinalysis: Proteinuria (a) Testing within the prepatent period 8. Treatment (b) Low worm burden a. Microfilariacidal (c) All-male infection (1) Slow kill rate with preventative doses (d) Immunologic destruction by the host of ivermectin, milbemycin oxime, and (e) Receiving macrolide preventative selamectin d. Thoracic radiographs (2) Corticosteroids, antihistamines, or (1) May be normal both may be administered 1 hour before (2) Enlarged main pulmonary artery microfilaricide to decrease the chance (Figure 12-7) for adverse effects 180 SECTION II SMALL ANIMAL A B Figure 12-7 A, Lateral; B, dorsoventral (DV) radiographs from a German shepherd with advanced heartworm disease. Enlargement of pulmonary arteries is seen, especially on DV view (arrowheads, B). (From Nelson RW, Couto CG. Small Animal Internal Medicine, 4th ed. St Louis, 2009, Mosby.) b. Adulticidal and include cough, anorexia, and (1) Melarsomine (Immiticide) fever (a) Arsenic based compound (f) At home care (b) Safer than its predecessor, thiacet- i. Strict cage confinement for arsemide 4 weeks with the standard (c) Standard protocol protocol and 8 weeks with the i. Consists of two intramuscular split protocol (IM) injections 24 hours apart ii. Concurrent administration ii. Seroconversion to a negative of antiinflammatory antigen test reaches approxi- corticosteroids mately 75% iii. Aspirin therapy is not iii. May be selected in cases with recommended financial issues, or for dogs iv. Concurrent corticosteroid without clinical signs and with and nonsteroidal anti- essentially normal diagnostic inflammatory medication is tests (thoracic radiographs and contraindicated blood work) (g) Recheck heartworm antigen test (d) Split protocol—Preferred 4 to 6 months following treatment i. Consists of a single IM injection (2) Ivermectin followed in 4 to 6 weeks by two (a) Kills adult heartworms after approx- IM injections 24 hours apart imately 31 months of consecutive ii. Seroconversion to a negative monthly administration antigen test reaches approxi- (b) Not recommended routinely as mately 90% adulticide therapy because of ongo- iii. Recommended for dogs with ing pulmonary and myocardial dam- clinical signs and abnormal age and potential development of diagnostic tests caval syndrome iv. Associated with fewer adverse (c) May be selected in dogs with con- effects current renal or hepatic disease v. Requires added expense and a (3) Surgery longer period of cage confinement (a) The physical removal of heartworms (e) Adverse effects typically occur 5 to is recommended with caval syn- 7 days after melarsomine injection drome when the heartworms are  CHAPTER 12 Cardiovascular Disorders 181 present within the right atrium or b. Heartworm antigen test right ventricle resulting in a hemo- (1) Detects antigen found in the uterus of lytic crisis or an obstruction to gravid female heartworms blood flow (2) Not particularly sensitive for detecting (b) Dogs require melarsomine treatment heartworms in cats. Positive in less following surgical removal of the than 50% of heartworm-positive cats heartworms c. Microfilaria test such as Difil or modified 9. Prevention Knott. Circulating microfilaria are present in a. Begin prevention by 6 to 8 weeks of only approximately 20% of cats age, especially in heartworm endemic d. Thoracic radiographs locations (1) May be normal b. Macrolide lactones (2) Pulmonary artery enlargement (1) Derived from Streptomyces spp. (3) Bronchointerstitial to alveolar (2) Administered monthly pulmonary pattern (3) Microfilaricidal (4) Generalized heart enlargement (a) Ivermectin kills microfilaria gradually (5) Pleural effusion (b) Milbemycin kills microfilaria quickly, e. Echocardiogram creating a potential risk of adverse (1) May be normal reactions (2) Right ventricular enlargement (4) Ivermectin (Heartgard Plus) has adulti- (3) Main pulmonary artery enlargement cide effects after prolonged continuous (4) Tricuspid regurgitation monthly use (5) Heartworms within the right atrium, (5) Safe when used in collies at the ventricle, or pulmonary artery preventative dose (6) Considered a sensitive test for (6) Oral examples detecting the presence of heartworms (a) Ivermectin (Heartgard) in cats (b) Milbemycine oxime (Interceptor). f. CBC (7) Topical examples: Selamectin (1) May be normal (Revolution), moxidectin (2) Anemia (Advantage Multi) (3) Neutrophilia c. Diethylcarbamazine (4) Lymphopenia (1) Administered daily (5) Eosinophilia (2) Efficacious against L3 and early L4 (6) Basophilia larvae (7) Circulating microfilaria (3) Administration to microfilaremic dogs (8) Thrombocytopenia can result in an anaphylactic reaction g. Biochemistry panel and death (1) May be normal 10. Prognosis (2) Hyperglobulinemia a. Favorable in mild to moderate cases (3) Azotemia b. Guarded if severe disease with clinical signs h. Urinalysis: Proteinuria c. Guarded to poor with caval syndrome 8. Treatment G. Feline a. Microfilariacide 1. Increased risk in male cats (1) Microfilaria-positive cats are rarely 2. The prepatent period is 8 months encountered 3. The life span of an adult heartworm is less (2) Preventative dose of ivermectin or than 4 years milbemycine oxime 4. The heartworm burden is typically lower, in b. Adulticide the range of one to nine worms (1) Melarsomine: Not recommended 5. Clinical signs: May be normal; lethargy, because of an association with vomiting, cough, dyspnea, anorexia, syncope, important and life-threatening adverse sudden death effects 6. Physical examination (2) Medical management: Treat clinical a. May be normal signs with corticosteroids, bronchodila- b. Murmur tors, and oxygen as needed c. Arrhythmia (3) Caval syndrome: Surgical removal d. Gallop rhythm 9. Prognosis: Favorable to guarded e. Abnormal bronchovesicular sounds 10. Monthly prevention f. Dyspnea a. Oral examples g. Ascites (1) Ivermectin (Heartgard) h. Jugular venous distension (2) Milbemycine oxime (Interceptor) 7. Diagnosis b. Topical examples a. Heartworm antibody test: Indicates prior or (1) Selamectin (Revolution) current heartworm infection (2) Moxidectin (Advantage Multi) 182 SECTION II SMALL ANIMAL V. Pericardial disease ii. Slow rate of growth A. More common in dogs iii. Late metastatic rate B. Congenital disorders (c) Mesothelioma 1. Cysts: Rare in dogs. Presenting signs are simi- i. Diffuse neoplasia of the pericar- lar to pericardial effusion dium, pleura, and peritoneum 2. Peritoneopericardial diaphragmatic hernia ii. Difficult to diagnose without a. Occurs because of abnormal fusion of the pericardial biopsy and immuno- septum transversum and pleuroperitoneal histochemistry folds (d) Other: Lymphoma, thyroid carci- b. Liver is the most common herniated noma, myxoma abdominal organ (2) Idiopathic c. Common breeds (a) Typically middle-aged, large-breed (1) Dogs: Weimaraner dogs (2) Cats (b) Commonly reported breeds: (a) Persian Golden retriever, Saint Bernard, (b) Himalayan Great Dane d. Clinical signs frequently related to respira- (3) Infectious tory difficulty or GI upset (a) Bacterial e. Diagnosis (b) Fungal (coccidioidomycosis, (1) Thoracic radiographs nocardia, actinomyces) (a) Cardiomegaly (c) Viral (feline infectious peritonitis) (b) Silhouette between the heart and (4) Left atrial rupture secondary to diaphragm chronic degenerative mitral valve (c) Abdominal contents within the disease thorax (5) Rodenticide poisoning (2) ECG d. Most common causes in dogs (a) Sinus tachycardia (1) Idiopathic (b) Small QRS complexes (2) Neoplasia (3) Echocardiogram: Abdominal contents e. Most common causes in cats present with the pericardium and (1) CHF displacing the heart (2) Feline infectious peritonitis f. Treatment: Surgical repair in symptomatic 3. Clinical signs: Weakness, lethargy, anorexia, patients weight loss, ascites, syncope, sudden death g. Prognosis: Excellent unless adhesions 4. Physical examination complicate the surgical repair a. Highly suggestive of pericardial effusion C. Acquired disorders (1) Muffled heart sounds 1. Constrictive pericardial disease (2) Jugular venous distension a. Fibrosis of the pericardium leads to (3) Weak or varying pulse quality restriction of cardiac filling and a reduction b. Arrhythmia in cardiac output c. Pulse deficits b. Idiopathic or inflammatory d. Normal to pale mucous membrane color c. Difficult to diagnose e. Ascites d. Treatment consists of surgically stripping f. Dyspnea the pericardium from the myocardium and D. Diagnosis is associated with increased morbidity and 1. Types of effusion mortality a. Transudate 2. Pericardial effusion b. Modified transudate a. Results in impaired ventricular filling and c. Exudate decreased cardiac output d. Hemorrhagic b. Occurs more often in middle-aged to older, e. Chylous large-breed dogs 2. Echocardiogram c. Causes a. Preferably performed before pericardio- (1) Neoplasia centesis if patient is stable (a) Hemangiosarcoma b. Anechoic space between the heart and i. Originates from the right auricle pericardial sac representative of pericardial ii. Commonly reported breeds: effusion Golden retriever, German shepherd c.