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43 Cards in this Set
- Front
- Back
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What classes of drugs are used to tx CHF? (broadly)
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Positive inotropic drugs
Diuretics ACE inhibs and Angiotensin blockers Vasodilators |
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What are the 3 classes of positive inotropic drugs?
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cardiac glycosides (digitalis)
Bipyridines (inamrinone, milrinone) Sympathomimetics (dobutamine, dopamine) |
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Two ACE inhibs used to tx CHF?
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captopril
lisinopril |
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Two angiotensin receptor blockers used to tx CHF?
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losartan
candesartan |
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What's the basic difficulty in heart failure?
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Weakened contractile force
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How does a failing heart compensate for it's impaired contractility?
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Increasing rate and size of heart and activating the renin-angiotensin system
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Name 6 consequences of heart failure.
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Increased pressure in main circuits (inc venous pressure/pulmonary pressure).
Dyspnea Cyanosis Edema Increased Heart Rate Increased Heart Size |
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Name 4 symptoms of heart failure.
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1. tachycardia
2. dec exercise tolerance 3. shortness of breath 4. peripheral and pulmonary edema |
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What are the major causes of left heart failure? (4)
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coronary artery disease
hypertension valvular myocardial infarction |
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What are the major causes of right heart failure? (4)
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secondary to left-sided failure
pulmonary emphysema pulmonary valve lesions tricuspid valve stenosis or insuffieciency |
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Biochem explanations for the impaired contractility seen in heart failure? (6)
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1. ↓ rate of Ca binding by SR
2. ↓ intracell levels of cyclic AMP 3. ↓ β-receptor density or coupling 4. ↓ Na/Ca exchange 5. ↓ content of myofibibrillar protein 6. ↓activity of actomyosin and/or myosin ATPase |
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What are the stages of heart failure?
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Asymptomatic dysfunction, compensated, decompensated, and refractory (sx not controlled with tx)
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Structural features of cardiac glycosides?
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a. Steroidal nucleus
b. Unsaturated lactone ring on C17 c. Combination of aglycone with 1 to 4 molecules of sugar via a glycoside linkage at C3. |
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Effects of Cardiac Glycosides on...inotropy? Excitability? Conduction Velocity?
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Inotropy: Positive (↑C.O. = ↓sx CHF).
Excitability: slight ↑ A>Ven Conduction Velocity: slightly ↑ in atria & ventricle/significantly ↓ in conducting tissue esp. A-V node and His-Purkinje System |
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Effects of Cardiac Glycosides on...Refractory Period? Automaticity? Heart Rate?
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Refractory Period: slightly ↑ in atria & nodal tissue/slightly ↓ in ventricles
Automaticity: can be greatly ↑ (esp ventricle) Heart Rate: ↓ due to vagal stimulation and, in CHF, improved hemodynamics |
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Effects of Cardiac Glycosides on...BP? Diuresis? (why?)
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BP: not important in CHF tx; ↑ PVR due to vasoconstrict.
Diuresis: slight ↑ primarily due to ↑ renal blood flow as a consequence of positive inotropic effect (↑ CO etc.) |
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Mechanism of action of Cardiac Glycosides?
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interacts with membrane-bound Na+-K+ ATPase (Na-K pump).
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Therapeutic uses of Cardiac Glycosides?
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1. CHF
2. CHF with by atrial fibrillation 3. Supraventricular arrhythmias |
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Toxicity of Cardiac Glycosides?
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Very narrow therapeutic index. Estimated that it requires 60% of the toxic dose for therapeutic effectiveness
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Early toxic symptoms of Cardiac Glycosides?
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distaste for food, nausea, vomiting, diarrhea, disturbance of vision. (nausea and vomiting are due to a central effect)
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Late toxic symptoms of Cardiac Glycosides?
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complete spectrum of cardiac arrhythmias may result including A-V block, vent extrasystoles and vent fibrillation
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What enhances the toxicity of Cardiac Glycosides?
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Hypokalemia
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How is severe glycoside toxicity treated?
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Cardiac pacemaker catheritization
Administration of digitalis antibodies |
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What's the onset of action, max effect and action regression times of digoxin?
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10-30min onset
1-5 hr max effect 10 hr regression (35 hr half life) 2-6 days action gone |
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What percent of digoxin is absorbed, what percent is bound to plasma proteins, and what percent is excreted daily?
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75% absorbed via GI
25% bound 30% excreted daily (renal) |
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Name 2 bipyridines. Route?
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Inamrinone
Milrinone Given IV |
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How do bipyridines work?
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Selective inhibitors of phosphodiesterase 3 that reduce cAMP degradation = direct stimulation of myocardial contractility and vessel dilation = decreased PVR and pulmonary resistance
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What are dobutamine and dopamine? What do they do?
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Beta agonists.
Both increase force of contraction. Dopamine also increases RBF. |
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What are the disadvantages of dobutamine and dopamine?
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Must be given IV
Tolerance can develop |
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What is the major benefit of diuretics in the tx of CHF?
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Counters increased sodium & water retention
Effects are additive with those of ACE inhibitors & β antagonists |
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What is the use of ACE inhibitors and angiotensin blockers in the tx of CHF?
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Counter increased sodium & water retention due to activation of the renin-angiotensin-aldosterone system associated with CHF
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What do ACE inhibitors do?
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Suppress Ang II and aldosterone production, decrease sympathetic nervous system activity, and potentiate the effects of diuretics
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Which vessels do ACE inhibitors work best on? What's the effect of this?
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Arteries
Reduces afterload = increased stroke volume and cardiac output |
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What's the effect of ACE inhibitors in CHF pts with reduced renal blood flow?
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They limit the kidney’s ability to regulate glomerular perfusion pressure due to their selective effects on efferent arterial tone
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What common precipitating event for CHF are ACE inhibitors useful for?
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MI is the leading cause of CHF. ACE inhibs reduce vent dysfunction and mortality after acute MI = may prevent adverse ventricular remodeling
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What does Hydralazine do?
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Causes direct relaxation of arterial smooth muscle and reduces right & left ventricular afterload by reducing pulmonary and systemic vascular resistance
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When is Hydralazine particularly useful in the tx of CHF?
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CHF patients with renal dysfunction who can not tolerate ACE inhibitors
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When is Hydralazine most effective?
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when combined with venodilating agents (eg. organic nitrates)
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How are β-Adrenergic blockers useful in the tx of CHF?
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May antagonize the sustained activation of sympathetic nerves in compensated CHF may contribute to the progression of contractile dysfunction
β-blockers have shown to reduce hospitalization and decrease mortality in patients with mild-to-moderate CHF. |
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What tx is recommended in stage A CHF? (high risk, no sx)
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Risk factor reduction
Education |
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What tx is recommended in stage B CHF? (structural disease, no sx)
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ACE inhibs or angiotensin 1 receptor blockers for all pts
Beta blockers for some |
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What tx is recommended in stage C CHF? (sx)
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ACE inhibs and beta blockers in all pts
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What tx is recommended in stage D CHF? (refractory sx)
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inotropes
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