Pharm PP Ch 6_Cardiac.ppsx

Chapter 6 Cardiovascular Pharmacology or How to keep that rhythm going https://youtu.be/61YY8 emngPU  OBJECTIVES Heart function and A&P Terminology: arrhythmia, inotrope, chronotrope, Cardiac output, preload, afterload Compensatory mechanisms...

Chapter 6 Cardiovascular Pharmacology or How to keep that rhythm going https://youtu.be/61YY8 emngPU  OBJECTIVES Heart function and A&P Terminology: arrhythmia, inotrope, chronotrope, Cardiac output, preload, afterload Compensatory mechanisms Treating heart failure Dietary management  STRUCTURE AND FUNCTION: THE HEART Review the heart’s electrical activity and anatomic structures to understand how it functions. Understanding how the heart normally functions will aid you in this journey of learning cardiovascular drugs and their effects. Drugs are used due to diseases of cardiac tissue and subsequent dysfunction. Dysfunction impacts a patient’s quality (and quantity) of life. Veterinary technicians will care for many cardiac disease patients; therefore, drug therapy knowledge is essential to patient outcome and welfare.  THE HEART The basic function of the CV system is to deliver O2, nutrients, and hormones to various parts of the body Myocardium Left Ventricle thicker Systole vs. Diastole  CARDIOVASCULAR SYSTEM: HEART, VESSELS, BLOOD Transportation of vital nutrients and hormones Removal of waste products (CO2, etc.) Transportation of white blood cells, antibodies, and proteins Thermoregulation pH of body fluids Controls the water content of cells Maintains circulation of oxygenated blood (RBCs, hemoglobin) HR is controlled primarily by Autonomic NS Parasympathetic NS ________ Sympathetic NS ________ * Each cell in the heart is capable of contracting spontaneously  CARDIAC CONDUCTION SYSTEM Structures: SA node = cardiac pacemaker Intercalated disks  CO = HR X SV Cardiac output amount of blood pumped by the heart per minute Preload of ventricular stretch at the end of diastole Afterload Resistance in the left ventricle when ejecting blood our of the ventricle  CARDIAC OUTPUT: HEART RATE Direct connection between HR and CO Heart rate increases = cardiac output increases Tachycardia to compensate for disease processes results in reduced diastolic period, reduced preload, and increased oxygen consumption. Abnormal heart rates = acute heart failure  BRADYCARDIA Bradycardia  signs of reduced cardiac output Hypotension Lethargy Syncope Edema Altered mentation  CARDIAC OUTPUT: PRELOAD Stretching of the myocardial cells during diastole just prior to contraction The “priming process” for the cardiac contraction or “pump” “Pump” dysfunction (increases in the preload) clinical signs: Ascites Jugular vein distention Hepatomegaly Elevated central venous pressure (CVP)  CARDIAC OUTPUT: AFTERLOAD Resistance the left Clinical Signs: ventricle experiences Abnormal blood pressure when it tries to eject blood Hypothermic extremities Syncope Damaged ventricles = Shock reduction in cardiac Reduced CRT output Arrhythmias Reduced mentation  CARDIAC OUTPUT: CONTRACTILITY Ability of the myocardium to contract Poor contraction = preload affected = poor oxygenation Remember that preload = “priming process” for the cardiac contraction or “pump”  COMPENSATORY MECHANISMS Increase HR Increase stroke volume Increase efficiency of heart muscle Physiologic heart enlargement (a.k.a. heart remodeling)  HEART DISEASE Valvular disease Tricuspid valve Mitral valve Cardiac arrhythmias Myocardial disease Hypertrophic cardiomyopathy (feline) Cardiomyopathy Other: congenital defects, heartworm  CONGESTIVE HEART FAILURE Heart is incapable of pumping an adequate volume of blood Leading to Pulmonary edema (fluid in the lungs), Ascites (abdomen and peripheral limbs) Common Clinical Signs: Pulmonary edema Ascites Coughing Syncope Weight loss Cyanosis Lethargy Dyspnea Difficulty exercising  ARRHYTHMIAS Irregular rhythm + increased rate = pathologic process A sinus arrhythmia is an irregular rhythm that occurs at a low or normal heart rate. Pulse deficits (or absence of a peripheral arterial pulse) may also be detected if the heart rate is irregular. PULMONARY EDEMA SECONDARY TO HEART DISEASE CYANOTIC MUCOUS MEMBRANES FORCE & RHYTHM Inotropic: alters force of muscle contractions Chronotropic: changes HR by changing rhythm CATEGORIES OF CV DRUGS Positive inotropic Antiarrhythmic Vasodilators Diuretics  CLASSES OF CARDIOVASCULAR DRUGS: POSITIVE INOTROPIC AGENTS Stimulate the heart and increase the strength of the cardiac muscle contractions (increase HR) Glycosides Treatment of heart failure, increase the contraction of the heart leading to decrease in HR, can be extremely toxic Ex: Digoxin Catecholamines Synthetic forms of naturally occurring neurotransmitters; act on the beta and adrenergic receptor sites (increase HR and BP, strength of contraction) Ex: Dobutamine, Dopamine, Epinephrine Benzimidazole pyridazinones Cause vasodilation and strengthen cardiac muscle contraction Pimobendan (Vetmedin®)  POSITIVE INOTROPIC DRUGS Glycosides Digoxin, from the plant Digitalis purpurea Improves cardiac contractility Decreases HR Antiarrhythmic Decreases dyspnea Treat CHF, A fib, Supraventicular Tachycardia POSITIVE INOTROPIC DRUGS Catecholamines Increase Force and rate of contraction Constrict peripheral blood vessel Short serum half life, used in extreme cases ONLY ex: Epinephrine, Dopamine, Dobutamine  POSITIVE INOTROPIC DRUGS Benzimidazole Inotropic mixed dilator Ex: Pimobendan (Vetmedin®) Used for Atrioventricular insufficiency and Dilated Cardiomyopathy Contraindicated in Hypertrophic cardiomyopathy and aortic stenosis  CLASSES OF CARDIOVASCULAR DRUGS: ANTIARRHYTHMICS Affect ion channels and correcting electrical disturbances within the nodes Correct irregular heartbeats and decrease abnormally rapid heart rates, restoring the normal rhythm Beta Blockers Block the action of the sympathetic nervous system of the heart Slow the heartbeat Decreases the force of the contractions of the heart muscles Reduce blood vessel contraction in the heart, brain, rest of the body  ANTIARRHYTHMIC DRUGS Arrhythmias result in reduced cardiac output by poorly coordinated pumping activity Factors that predispose the heart to arrhythmias: hypoxemia electrolyte imbalances increased levels or sensitivity to catecholamines inhalant anesthetics cardiac trauma or disease that results in altered cells Antiarrythmias drug ex: Lidocaine CLASSES OF CARDIOVASCULAR DRUGS: ACE INHIBITORS CHF  ACE  Narrowing of blood vessels = hypertension Angiotensin Converting Enzyme (ACE) Prevents Constricting of the blood vessels These drugs inhibit the activity of the enzyme ACE Decreases the production of angiotensin II Allowing for the blood vessels to dilate and blood pressure is reduced Enalapril malate (Encard®)  CLASSES OF CARDIOVASCULAR DRUGS: POTASSIUM CHANNEL BLOCKERS Aid in cell repolarization Repolarization of both the S-A and A-V nodes PCB binds to, block the K+ channels that are responsible for repolarization (delays repolarization) Used primarily for treatment of cardiac arrhythmias Ex: Sotaol  CLASSES OF CARDIOVASCULAR DRUGS: CALCIUM CHANNEL BLOCKERS Prohibit the entry of calcium into the muscle cells of the heart and the arteries. Causes a decrease of the contraction of the heart and dilation of the arteries. CCB are used for treating hypertension and arrhythmias. Slow the heart rate and treatment of atrial fibrillation. Amlodipine (Norvasc®)  VASODILATOR DRUGS Nitroglycerin venodilator that reduces preload as a result of pooling of blood in peripheral vessels Hydralazine Arterial dilator-reduces afterload  CLASSES OF CARDIOVASCULAR DRUGS: DIURETICS Increase the excretion of Disorders treated with water and salt through diuretics include: diuresis (increased urination) Hypertension Action depends on the drug Heart failure Fluid and electrolyte balances Edema Three types of diuretics: Liver disease Thiazide Kidney disease Loop Diabetes Potassium-sparing  DIURETICS Increase excretion of water and salt through diuresis or urination Hypokalemia an adverse effect May result with administration of diuretics Loss of K+ due to increase urination Muscle weakness, Electrical conduction system of the heart Indications: reduce the harmful effects of CHF (pulmonary edema, ascites, increased cardiac work) by reducing plasma volume ex: furosemide (Lasix®), spironolactone  WHEN USING DIURETICS Patient must always have water!!!*  DIETARY MANAGEMENT 2 goals: Na restriction Maintain healthy BW  ANCILLARY TX OF CHF Bronchodilators Oxygen therapy Sedation QUESTIONS?