Test 2: Cardiovascular Drugs/Therapy – Flashcards
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What treatment options exist to manage a bradyarrhythmia such as "Sick Sinus Syndrome"?
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Propantholene orally Pacemaker surgery
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What is the mechanism of action for a class I antiarrhythmic drug?
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Sodium-channel blockade
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What is the mechanism of action for a class II antiarrhythmic drug?
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Beta-blockade
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What is the mechanism of action for a class III antiarrhythmic drug?
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Potassium-channel blockade
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What is the mechanism of action for a class IV antiarrhythmic drug?
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Calcium-channel blockade
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Why do excessively high heart rates have a deleterious impact on cardiac output?
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Do not allow for adequate ventricular filling
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What drug is most commonly used to manage atrial fibrillation when there is underlying myocardial disease?
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Digoxin
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What drug is most commonly used to convert idiopathic atrial fibrillation to a normal sinus rhythm, and what are its main toxicities?
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Quinidine Can worsen cardiac arrhythmias
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What is the initial drug of choice in treating nearly all PVC's (premature ventricular contractions) during hospitalization?
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Lidocaine
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How does the presence of "escape beats" impact the use of antiarrhythmics?
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Don't want to confuse escape beats in 3rd degree heart blocks with PVC's. Ventricular antiarrhythmics can cause cardiac arrest with escape beats
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2 drugs that only work on supraventricular arrhythmias
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Digoxin Quinidine
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2 drugs that work on both supraventricular and ventricular arrhythmias
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Amiodarone Sotalol
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2 drugs that only work on ventricular arrhythmias
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Lidocaine Procainamide
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Name the therapeutic goals in the management of hypertrophic cardiomyopathy (HCM) (4)
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Treat underlying cause Decrease LA and LV pressure Relax cardiac muscle Slow heart rate
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3 ways to decrease LA and LV pressure in HCM
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Oxygen Furosemide Low dose opioid (butorphanol)
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What drug do we give to relax cardiac muscle in HCM?
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Diltiazem
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What 3 drugs can we give to slow the heart rate in HCM?
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Diltiazem Beta blockers Nonselective beta blockers
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Contrast the merits of diltiazem verses atenolol use in HCM
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Diltiazem can cause adverse reactions, so atenolol may be better. If they'll tolerate it, use diltiazem
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In early congestive heart failure (systolic heart failure) physiologic changes occur that allow "compensated" heart failure to exist. Explain the physiological changes and how eventually over-exaggerated responses lead to decompensated heart failure
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Heart failure leads to reduced cardiac output leading to reduced BP. This causes an activation of the sympathetic NS and RAA system. This leads to increased salt and water retention (excessive preload) and systemic vasoconstriction/increased resistance (excessive after load)
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Name the therapeutic goals in the management of congestive heart failure (systolic heart failure) (5)
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Decrease preload Decrease afterload Increase force of contraction Slow heart rate Decrease pulmonary edema
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6 drugs that will decrease preload for treatment of congestive heart failure
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Nitrates Diuretics (furosemide, torsemide, thiazides, spironolactone, aldactazide)
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2 drugs that will decrease afterload for treatment of congestive heart failure
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Amlodipine Hydralazine
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3 drugs that will decrease both preload and afterload for treatment of congestive heart failure
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Nitroprusside ACE inhibitors Benazepril
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Salt restriction has historically been a method used in heart failure to reduce preload. What disadvantages might this pose?
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Activates the renin-angiotensin system too early
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Does nitroglycerin decrease afterload, preload, or both?
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Preload
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Furosemide decreases preload. What additional benefit does it provide when pulmonary edema is present?
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Used as a treatment for pulmonary edema
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For what group of cardiac drugs does tachyphylaxis limit the duration of their usefulness?
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Nitrates
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Why are hydrochlorothiazide or spironolactone seldom used as a sole diuretic in congestive heart failure, yet are commonly used as adjunct diuretics with furosemide, especially when pulmonary edema occurs despite furosemide treatment?
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Weak diuresis as the sole diuretic used
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Explain how an Angiotensin converting enzyme (ACE) inhibitor, by virtue of inhibiting conversion of angiotensin I to II, has a beneficial effect in congestive heart failure
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Leads to less vasoconstriction and decreases sodium retention (decreased aldosterone)
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How might NSAIDs interfere with ACE inhibitors?
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May inhibit vasodilatory PG thereby decreasing GFR and/or inhibits the release of natural PGs
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When might benazepril be preferred over enalapril as an ACE inhibitor?
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Renal failure patients
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Describe how renal function and body weight impact the dosing of digoxin
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Has a long half-life Dose on lean body weight, not total body weight. Therefore, make your best guess with an obese animal
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What benefit besides inotropy does digoxin provide in CHF?
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Sensitizes baroreceptors to increase parasympathomimetic effect to slow conduction at AV node which slows the heart rate
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Which electrolyte abnormality predisposes to digoxin toxicity?
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Hypokalemia
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Pimobendan is an oral inotrope. What other beneficial effect does it have?
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Vasodilator
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Compare and contrast dobutamine verses dopamine as to receptors stimulated, clinical indications, existence of a "holiday", and whether a "therapeutic window" exists. Dobutamine
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Stimulates B1 receptors Can cause tachycardia Accumulates in cardiac muscle to be residual and give a "dobutamine holiday"
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Compare and contrast dobutamine verses dopamine as to receptors stimulated, clinical indications, existence of a "holiday", and whether a "therapeutic window" exists. Dopamine
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Stimulate B1 and dopamine receptors Vasodilation of renal and splanchnic arteries Has a therapeutic window (higher dose stimulates alpha receptors)
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Why are opioids often beneficial in pulmonary edema other than for sedation?
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Decreases preload Desensitizes CO2 receptors
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What is the drug to use for this mitral valve disease progression? Left atrial enlargement with mild clinical signs
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Enalapril
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What is the drug to use for this mitral valve disease progression? Left ventricular enlargement with systolic impairment
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Pimobendan/digoxin
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What is the drug to use for this mitral valve disease progression? Atrial fibrillation with a high heart rate
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Diltiazem
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What is the drug to use for this mitral valve disease progression? Early pulmonary edema
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Furosemide Torsemide
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What is the drug to use for this mitral valve disease progression? Refractory pulmonary edema
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Thiazide Spironolactone
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What is the drug to use for this mitral valve disease progression? PCV's
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Procainamide Sotolol
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How do pulmonary vessels differ in their response to hypoxia verses other vessels in the body?
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Pulmonary vessels constrict in the presence of hypoxia
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What is considered the vasodilator of choice in the management of pulmonary hypertension?
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Oxygen Sildenafil (viagra)
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Which breed of dog may be more prone to digoxin toxicity?
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Dobermanns
