PANCE Blueprint Cardiology (13%)

Dilated cardiomyopathy is a disease of the heart in which the heart becomes weakened and enlarged, and is unable to pump blood efficiently throughout the body. Therefore, it is commonly described as a contractile or systolic dysfunction. This is the most common form of cardiomyopathy not due to ischemic causes. Although many cases are idiopathic, it is thought that dilated cardiomyopathy is related to damage of the myocardium produced by toxic, metabolic, or infectious agents. Common causes of dilated cardiomyopathy include chronic alcohol abuse, wet beriberi related to thiamine deficiency, coxsackie B infection, cocaine use, Chagas disease, doxorubicin toxicity, hemochromatosis and peripartum cardiomyopathy. On physical exam, an S3 heart sound can be appreciated, due to turbulent blood flow between the walls of the ventricles, as blood flows from the atria in the volume overloaded heart. Dilated cardiomyopathy is also characterized by eccentric hypertrophy in which cardiac sarcomeres are added in series as opposed to parallel.

Loop diuretics are a class of diuretics that inhibit the Na-K-2Cl symporter in the thick ascending limb of the loop of Henle. Furosemide is the generic name for one of the most commonly used loop diuretics and is also known by the trade name, Lasix. These drugs are sulfa drugs, as they contain a sulfonamide group and can cause allergic reactions in patients with sulfa allergies. Loop diuretics often also lead to electrolyte abnormalities, such as hypokalemia and hypocalcemia. Additionally, these drugs can reduce urate excretion, leading to hyperuricemia, and subsequently gout. Ototoxicity is also a serious, but rare adverse effect of loop diuretics.

Selective β₁ blockers are drugs that act to block β₁ adrenergic receptors and typically treat cardiovascular diseases. They work to block the actions of norepinephrine and epinephrine on cardiovascular contractility, chronotropy, and the body’s release of renin. These drugs can be remembered by having the “olol” suffix in their names, such as atenolol, esmolol, and metoprolol. Some β₁ blocking drugs also work as partial β agonists at high doses, such as acebutolol.

Nonselective β-blockers were the first generation β-blockers and have antagonistic effects at both β₁ (heart, kidney) and β₂ receptors (lung, peripheral blood vessels and skeletal muscle) thus preventing direct sympathomimetics such as norepinephrine and epinephrine from binding to these receptors.

ACE inhibitors are antihypertensive drugs that work by inhibiting the renin-angiotensin-aldosterone-system. They help to lower blood pressure by inhibiting angiotensin converting enzyme and decreasing the amount of angiotensin II and aldosterone. Effects of inhibiting this conversion are translated into lowered arteriolar resistance, and increased venous capacity. This drug class decrease cardiac output and index, and stroke volume. Furthermore, natriuresis is increased, while there is decreased resistance in the blood vessels of the kidney. A side effect of these drugs is increased bradykinin, which may display as a persistant dry cough in patients.