CHF Flashcards
DRUGS USED TO TREAT CHF
- RAAS inhibitors
a. ACEI
b. ARBs
dec afterload, dec preload, dec remodeling - Other vasodilators
a. hydralazine + isosorbide dinitrate
b. amlodipine
dec afterload, dec preload, less
effect on remodeling - B antagonists
- diuretics
- inotropic drugs
a. cardiac glycosides (digoxin) used chronically
b. B-agonists (dobutamine) used acutely
c. Phosphodiesterase inhibitors (inamrinone,
milrinone) used acutely
ACE INHIBITORS/ARBs moa
a. inhibit the vasoconstrictor effects of angiotensin II
inhibit the retention of sodium and water by
inhibiting aldosterone
prevent aldosterone-mediated cardiac remodeling;
aldosterone may act directly on cardiac muscle to
promote increased collagen deposition and fibrosis
Cardiovascular actions
induce venous as well as
arterial vasodilation
a. preload: preload is reduced by reducing salt and
water retention and also by increasing venous
capacitance
b. afterload: afterload is reduced by arterial
vasodilation and improves signs of mitral regurgitation
c. ACEI/ARBs reduce the long-term remodeling of
the heart and vessels and is likely responsible for the
reduction in morbidity and mortality
B-Antagonists
Metoprolol, Bisoprolol, and Carvedilol are the -blockers studied extensively in heart failure
- Clinical use: improve symptoms, exercise tolerance, and several measures of ventricular function; effective in patients with mild to moderate cardiomyopathies in combination with ACE inhibitors +/- diuretics +/- digoxin; effective at decreasing mortality
Dosage: dosing is critical for B-blockers used in CHF; start
with a low initial dose and titrate upwards for the next 4-6
weeks; high doses could be lethal
Diuretics
1. Mechanism: reduce extracellular fluid volume and ventricular filling pressures (preload) but usually do not affect cardiac output due to the flatness of the ventricular function curve in patients with heart failure
Loops = furosemide, torsemide, bumetanide;
Thiazides: hydrochlorothiazide
Spironolactone, Eplerenone
a. aldosterone receptor antagonists
b. not very potent as diuretics (K+ sparing)
c. although ACE inhibitors and ARBs block
aldosterone production, there is a benefit of using one
of them with aldosterone receptor blockers; the main
concern with that combination is K+ retention so K+
levels must be monitored closely
Hydralazine
a. is mainly an arterial vasodilator so it reduces
afterload
b. reduces renal vascular resistance and increases
renal blood flow to a greater degree than most other
vasodilators
c. may be a drug of choice in patients with renal
dysfunction who cannot tolerate ACE inhibitors
Isosorbide dinitrate
a. is a venodilator so it reduces preload
b. the combination of hydralazine with isosorbide
dinitrate is less effective than ACE inhibitors/ARBs at
reducing mortality
Calcium Channel Blockers
- Most calcium channel blockers actually worsen the
symptoms of systolic dysfunction and increase mortality
due to negative inotropic effects (verapamil and diltiazem
especially)
Amlodipine has less negative inotropic effects and
may be useful in CHF
Digitalis (cardiac glycosides)
a. a group of compounds derived from the plant digitalis (foxglove); these drugs increase the contractility of the heart (positive inotropic effect); includes the drug digoxin; this drugs has a low therapeutic index (
Digitalis (cardiac glycosides) effects on cardiac contractility
the cardiac glycosides inc the force of contraction and inc cardiac output which more closely resembles the normal heart; the net result is improved circulation -> dec sympathetic activity -> dec peripheral vascular resistance; Note: in the normal heart, the positive inotropic effect of digitalis is counteracted by compensatory autonomic reflexes
Digitalis (cardiac glycosides) use
patients in sinus rhythm with mild to moderate heart failure will often respond to treatment with ACE inhibitors, diuretics, and -blockers and do not require digoxin; digoxin is preferred in heart failure with concurrent atrial fibrillation or patients who have not responded to standard therapies
Digitalis (cardiac glycosides) kinetics & adverse
e. pharmacokinetics: digoxin has a half-life of 36-48 hrs and an onset of action of 20 minutes
f. adverse effects: digitalis toxicity is one of the most
commonly encountered adverse drug reactions; the major effect is severe arrhythmias which include complete heart block; v-tach and v-fib; anorexia, nausea vomiting, headache, fatigue, confusion, and blurred vision are common
factors predisposing to digitalis toxicity:
1) hypokalemia can precipitate serious arrhythmia and
the toxicity is treated with discontinuation of digoxin
and potassium supplementation; severe digitalis toxicity
is treated with antidigoxin antibodies; 2) drugs:
quinidine and verapamil can both displace digoxin from
plasma proteins; potassium depleting diuretics
(thiazide or loop) can enhance digoxin toxicity
digoxin has no net effect on
survival in CHF patients
B-Adrenergic agonists
B-agonists improve cardiac performance by positive
inotropic effects (1); only used short-term due to
tachyphylaxis (rapid tolerance)
b. dobutamine: has actions on 1 receptors to
enhance cardiac contractility (maybe some 1 antagonist)
c. dobutamine is given by i.v. infusion to treat acute
heart failure
