Cardiovascular System Introduction VMC 5110

• This presents an introduction to the examination of the cardiovascular system and VMC 5110 by Dr. C Hankanga Malombola

Cardiovascular Overview

• The pulmonary artery transports blood to the lungs, where it is oxygenated
• The pulmonary vein brings oxygenated blood from the lungs back to the heart
• The aorta distributes oxygenated blood to the body
• The Vena cava returns deoxygenated blood from the body to the heart

Heart Anatomy

• The heart is composed of the right atrium, the left atrium, the right ventricle, and the left ventricle
• Relevant components include the aortic arch, pulmonary artery, coronary vessels, and chordae tendineae

History and Signalment

• Information regarding age, breed, and sex is relevant
• Vaccination status?
• Any changes in diet and water intake?
• Where was the animal obtained?
• Is the pet housed indoors or outdoors?
• How much time is spent outside, supervised?
• Normal activity level?
• Any coughing, excessive panting, gagging, or vomiting?
• Any recent changes in urinary habits?
• Episodes of fainting or weakness?
• Are the tongue and mucous membranes always pink, especially during exercise?
• Recent changes in attitude and activity level?
• Current medications?
• Any medications used in the past, and were they effective?

Clinical signs of heart disease

• General clinical signs include coughing, dyspnea, exercise intolerance, syncope, murmurs, and pulse abnormalities even if the animal is not in heart failure
• Weakness and syncope occur when cardiac output is reduced due to heart disease or heart failure
• Exercise intolerance and tiring may be caused by reduced skeletal muscle perfusion

Syncope Defined

• Syncope indicates an abrupt and transient loss of consciousness and postural tone
• Syncope is caused by an inadequate supply of oxygen or glucose to the brain
• Syncope can be differentiated from intermittent weakness or seizures
• It is characterized by rear limb weakness, sudden collapse, lateral recumbency, stiffening of forelimbs, opisthotonus, micturition, and vocalization
• Tonic/clonic motion, facial fits, defecation aura, postictal dementia, and neurological deficits are not characteristic of syncope
• Cardiac, pulmonary, metabolic, hematological, and neurological issues can cause syncope or episodic weakness

Clinical Signs: Cough

• Cough is typically seen in both respiratory and cardiac disease

Differentiating Cough: Cardiac vs Respiratory

• Cardiac: Thin/weight loss, worse at night with soft cough, possible rare pink sputum
• Respiratory: Normal or obese, often caused by exercise, ± mucopurulent sputum, harsh, debilitating
• Lung sounds in cardiac are none, crackles, wheezes most common, in the respiratory, it is none, wheezes, crackles; wheezes most common
• Airway cytology is normal in cardiac, Inflammatory or neoplastic in the respiratory
• Diuretics are responsive in cardiac patients but unresponsive in respiratory
• Hemogram in cardiac is normal or stress, showing normal results or ± polycythemia in respiratory
• The heart rate/rhythm is usually rapid, sinus rhythm/tachycardia in cardiac vs normal to slow, sinus arrhythmia in respiratory

Observation and General Examination

• Assess attitude, posture, body condition, level of anxiety, and respiratory pattern during the general examination

Physical Exam: Mucous Membranes

• Mucous membranes and capillary refill time (CRT) are assessed to determine peripheral perfusion, using oral, ocular, prepuce, or vaginal areas

Abnormal Mucous Membrane Colors:

• Pale: Anemia or poor cardiac output/high sympathetic tone
• Injected/Brick-red: Polycythemia, sepsis, excitement, other causes of peripheral dilation
• Cyanotic: Pulmonary parenchymal disease, airway obstruction, pleural space disease, pulmonary edema, right to left shunting, hypoventilation, shock, cold exposure, or methemoglobinemia
• Differential cyanosis: Reversed PDA where the head and forelimbs receive oxygenated blood, and caudal parts receive desaturated blood via the ductus
• Icterus: Hemolysis, hepatobiliary disease, or biliary obstruction

Physical Exam: Jugular Veins

• Systemic and right heart filling pressures are reflected at the jugular veins
• Veins should not be distended when the animal is standing with its head in a normal position
• Persistent jugular distention associated with right-sided heart failure, compression of cranial vena cava, or jugular or caudal vena cava thrombosis
• Jugular pulsations extending more than one-third of the way up the neck from the thoracic inlet are abnormal
• To differentiate true pulse from carotid transmission, occlude the vein lightly below the area of the visible pulse; if the pulse disappears, then it is a true jugular pulse; if it continues, it is being transmitted from the carotid

Causes of Jugular Distension/Pulsation:

• Distension alone is caused by Pericardial effusion/tamponade, right atrial mass/inflow obstruction, dilated cardiomyopathy, cranial mediastinal mass, and jugular v./cranial vena cava thrombosis
• Pulsation+Distension include Tricuspid insufficiency of any cause, Pulmonic stenosis, heartworm disease, pulmonary hypertension, ventricular premature contractions, and complete heart block

Hepatojugular Reflux

• Hepatojugular reflux is due to impaired right ventricular filling or tricuspid regurgitation
• Positive test: Applies firm pressure to the cranial abdomen while the animal stands, in order to increase venous return and cause transient jugular distension

Arterial Pulses

• Arterial pulses must be assessed for their strength, regularity, and pulse rate
• The difference between the systolic and diastolic arterial pressure equals pulse pressure
• When the difference is wide, the pulse is strong on palpation (hyperkinetic)
• When the difference is small, the pulse is weak (hypokinetic)
• If the rise to maximum systolic pressure is prolonged in severe SAS, the pulse feels weak (pulsus parvus et tardus)
• Alternately weak and strong pulses may indicate severe myocardial failure (pulsus alterans)
• An exaggerated decrease in systolic pressure during inspiration may indicate cardiac tamponade (pulsus paradoxus)
• Pulses should be palpated and compared; the femoral pulse should be evaluated simultaneously with the direct heart rate
• Fewer femoral pulses than heart beats indicate pulse deficits
• Weak pulse is associated with Excitement, HCM (cats), and Fever/sepsis
• Strong Pulses are associated with Dilated Cardiomyopathy, Aortic Stenosis, Pulmonic Stenosis
• Very strong bounding pulses are associated with Fever/sepsis, Shock Dehydration, and PDA

Additional Assessment

• Precordium: Palpate both sides of the animal's chest, strongest beat is in the left 5th intercostal space near the costochondral junction
• The precordial impulse will be stronger on the left side
• A shifted precordial impulse may indicate cardiomegaly or thoracic mass
• Reduced intensity may indicate obesity, weak cardiac contractions, pericardial effusion, intrathoracic masses, pleural effusion, or pneumothorax
• Palpable vibrations may indicate loud murmurs

Evaluation for Fluid Accumulation

• Evaluation of fluid accumulation includes in the body cavities, subcutis in dependant areas, and pulmonary oedema through observing, palpating, and auscultating

Thoracic Auscultation

• Identify normal heart sounds.
• Determine presence or absence of abnormal sounds.
• Assess cardiac rhythm
• Evaluate pulmonary sounds

Auscultation: Heart Sounds & Murmurs

• Heart sounds created by turbulent blood flow and associated vibrations in adjacent tissue during the cardiac cycle.
• Transient sounds are short duration; cardiac murmurs are longer duration.
• Heart sounds are characterized by frequency, amplitude, duration and quality/timbre
• The point of maximum intensity PMI of any abnormal sound should be located
• S1 is associated with closure and tensing of AV valves at the onset of systole
• S2 is associated with closure of aortic and pulmonic valves
• S3 and S4 diastolic are not audible in normal dogs and cats
• Loud S1 indicates thin chest wall, high sympathetic tone, tachycardia, systemic arterial hypertension
• Muffled S1 indicates obesity, pericardial effusion, diaphragmatic hernia, DCM, hypovolemia/poor ventricular filling, or pleural effusion
• Loud S2 indicates pulmonary hypertension

Cardiac Murmurs

• Represent sounds of longer duration than transient heart sounds
• Cardiac Murmurs are caused by turbulent flow in the heart and adjacent blood vessels
• Innocent murmurs should disappear as the dog matures and are thought to be due to larger stroke volumes in puppies
• Described by timing, intensity, radiation, quality, and pitch

Additional Sound

• Gallop sounds describe when S3 and S4 are audible, when the heart may sound like a galloping horse (gallop rhythm)
• Low freq. sounds
• Audible S3 indicates a ventricular dilation with myocardial failure
• Audible S4 indicates increased ventricular stiffness and hypertrophy

Valve Location for Auscultation

• Mitral: Lift, within the 5th intercostal space at the costochondral junction
• Pulmonic: Left, Between 2nd and 4th intercostal spaces just above the sternum
• Aortic: Left, within the 4th intercostal space just above the costochondral junction
• Tricuspid: Right, between the 3rd and 5th near the costochondral junction

Murmur Shapes and Descriptions

• Holosystolic refers to plateau or regurgitant
• Crescendo-decrescendo refers to diamond-shaped ejection

GRADING HEART MURMURS

• Grade I is a very soft murmur, heard only in a quiet room
• Grade II is a soft murmur but easily heard
• Grade III is a moderate-intensity murmur that radiates somewhat
• Grade IV is a loud murmur but not accompanied by precordial thrill and radiates over a larger area than III
• Grade V is a loud murmur with palpable precordial thrill
• Grade VI is a very loud murmur that can be heard with a stethoscope off the chest wall and is accompanied by a precordial thrill

Describing Murmurs

• Intensity is based on grade
• Position and Duration in Cardiac Cycle: Systolic,diastolic,pan-, holo- ,early-, late- continuous
• Valve area corresponding to PMI: Pulmonic, Mitral, Aortic, Tricuspid
• Quality: Plateau, crescendo, decrescendo, or diamond
• Character/Pitch: Blowing, musical, honking, harsh, or noisy, etc

Auscultatory findings

• Sub (aortic stenosis: Timing is systolic, ejection (crescendo-decrendo), and PMI is in the left base
• Mitral valve dysplasia: Timing is systolic, regurgitant (holosystolic, and PMI is in the left apex
• PDA: Timing is continuous; the sound is machinery and PMI is in the left base
• Pulmonic Stenosis: Timing is systolic ejection crescendo-decrendo, PMI is in the left base
• Tetralogy of Fallot: Timing is systolic , ejection crescendo-decrendo, PMI is in the left base
• Tricuspid valve dysplasia: Timing is systolic, regurgitant holosystolic, PMI is in the right midprecordium
• VSD: Timing is systolic, regurgitant (holosystolic), PMI is in the right base
• Atrial septal defect: Timing is systolic (diastolic, the sound is ejection, PMI is in the left base

Listen to Murmurs

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Additional Testing - Radiography

• Radiography helps to differentiate pulmonary from cardiac disease, judge severity of oedema or pleural effusions
• Assess the size and shape of the heart in cardiac images
• Assess cardiac chamber and intrathoracic blood vessel enlargements
• Normal VHS: L + S = 8.5-10.5

Electrical Testing

• Atrial depolarization corresponds to the P Wave on the ECG
• PR interval in electrocardiography corresponds to AV node conduction
• Ventricular Depolarization corresponds to the QRS Complex
• Purkinje fibers play a role in Ventricular Depolarization
• Ventricular repolarization corresponds to the T Wave

Normal ECG Waveforms and Descriptions

• P Wave: Atrial muscle activation wave, normally positive in leads II and aVF
• PR Interval: Aka PQ interval, duration of atrial muscle activation, and conduction over the AV node, bundle of His, and Purkinje fibers, measure from the start of the P wave to the QRS complex
• QRS Complex: Ventricular muscle activation wave; Q is the first negative deflection, R is the first positive deflection, and S is the negative deflection after R
• J Point: Point after the QRS complex and ST-T
• ST Segment: Represents the period between ventricular depolarization and repolarization correlates with phase 2 of the action potential
• T Wave: Ventricular muscle repolarization wave
• QT interval: Total time of ventricular depolarization and repolarization and measures from QRS complex start to end of T wave

Electrocardiography

• ECG often run when rhythm disturbances are present
• Height and width of P and QRS complexes can reveal chamber enlargements
• Abnormal QRS complexes can show electrolyte imbalances
• It can diagnose specific arrhythmias

Additional testing

• Echocardiography is non-invasive, used to evaluate cardiac chamber size, wall thickness, wall motion, valve configuration and motion and the proximal great vessels
• Doppler can measure direction and velocity of blood flow ###Angiography
• Angiography is done by injection of radiopaque dye to identify anatomic abnormalities especially congenital heart disease as well as the path of blood flow
• Cardiac catheterisation involves the placement of specialized catheters to measure pressure, cardiac output, and blood oxygen in different areas of the heart and vasculature
• It is important in estimating the severity of cardiac defects

biochemical Markers

• Cardiac troponins regulatory proteins associated with the thin contractile filaments.
• Cardiac troponin I (cTnl and cardiac troponin T (cTnT increase within a few hours of acute myocardial injury or necrosis
• Myocardial-bound creatinine kinase is an indicator of cardiac muscle damage
• Atrial natriuretic peptide (ANP) and Brain natriuretic peptide (BNP)