PPT 13: CHF Flashcards
Exam 2
Define heart failure
Heart fails to meet the metabolic demands of tissues - CO inadequate
What is the most common cause of heart failure?
Coronary artery disease
Differentiate between systolic and diastolic heart failure
Systolic failure – reduced cardiac function
- Acute; heart walls thinned (less effective pumping)
↓ CO, ↓ Ejection fraction
Diastolic failure – reduced cardiac filling (can be peripheral)
- Chronic; heart more stiff/thicker walls (chronic HTN)
- ↓ CO, Normal Ejection fraction
- Does not respond well to positive inotropic drugs
Differentiate between symptoms of right vs left ventricular failure of CHF
Right ventricle – peripheral congestion
Left ventricle – pulmonary congestion
Heart failure where the normal CO not sufficient for demands of body
“High-output” failure (rare)
- Hyperthyroidism
- Beriberi
- Anemia
- Arteriovenous shunts
Responds poorly to inotropic agents – treat underlying cause
What are the 4 factors of cardiac performance?
CO = SV x HR
- Preload
- Afterload
- Contractility
- Heart Rate
Define the Frank-Starling Law
Strength of contraction increases when stretched (Rubber band analogy)
- End systolic volume (ESV)
- % of blood remains in ventricles
- ↑%, ↑ pressure
______ is the end diastolic pressure that stretches out ventricles
Preload
EDV =
Passive filling + atrial contraction + ESV
Stroke volume =
EDV – ESV
What is considered altered preload?
> 20-25 mm Hg – pulmonary congestion
What are ways to decrease preload?
salt restriction, diuretics, venodilation (Nitroglycerin)
_______ is the resistance against which heart must pump blood
Afterload
Afterload _____ as CO decreases
Increases
Describe the vicious spiral of progression of heart failure
Decreased CO
Increased NE, AII, ET
Increased Afterload
Decreased EF
(then back to top)
Contraction of myocytes is called
inotropy
What is the first compensatory mechanism to respond to decreased CO?
Increased HR
What increases CO? What decreases it?
Increases CO: increased preload, contractility, HR
Decreases CO: increased afterload
Discuss the compensatory responses of decreased cardiac output
What are the treatment targets for CHF?
- Correcting failure of cardiac contractility (inotropy)
- Reversing salt and water retention (diet)
- Unloading stressed myocardium (B-blockers, Ca++ Channel blockers, and diuretics)
Which drug therapies directed at non-cardiac targets may be more useful for long-term treatment of heart failure
- ACE inhibitors
- Angiotensin receptor blockers
- Aldosterone receptor antagonists
- Vasodilators
Discuss the normal control of cardiac contractility
- Trigger Ca++ enters cell
- depends on number of L type channels, duration of channel opening, and sympathetic stimulation - Binds to channel is SR, release stored Ca++
- depends on amount stored and amount of trigger Ca++ - Frees actin to interact with myosin
- Removal of Ca++
- SR Calcium ATPase
- Na+/Ca2+ antiporter – sodium gradient
- Na+/K+ ATPase: removes sodium
What are the medications used to treat CHF?
- Calcium (Ca-Chloride, Ca-gluconate)
- Cardiac Glycosides (digoxin, digitoxin)
- PDE Inhibitors (Milrinone)
- Catecholamines
Others:
- ACE inhibitors and ARBs
- Diuretics
- Calcium sensitizers (Levosimendan)
- Vasodilators
- Beta blockers
What are the 3 meds to avoid in heart failure? Why?
- NSAIDS (increases BP)
- Thiazolidinediones (fluid retention)
- Metformin (lactic acidosis)
What are the medications used to treat acute HF?
IV treatment:
- Diuretics
- Dobutamine
- Vasodilators
What is the option for treatment of HF with euvolemic hyponatremia?
Conivaptan – ADH inhibitor → removes water, not sodium via urine
What are the non-pharmaceutical interventions for HF?
- LV Reduction Surgery (Batista Procedure)
- Poor prognosis, discontinued - Skeletal Muscle Augmentation (Cardiomyoplasty)
- Invasive, high failure (23% mortality) - Chronic Biventricular Resynchronization
- Cellular Cardiomyoplasty
- Cardioverter-Defribrilator
- Heart Transplant
_______ is the only oral (+) inotropic agent for HF
Digoxin
Digoxin has a ________ therapeutic index
narrow
How does digoxin help treat HF?
Positive inotropic, cardiac glycoside
- inhibits Na+/K+ ATPase pump
What are the electrical effects of digoxin?
↑PR, ↓QT
- digitalis effect = downward schwoop of ST segment (Salvador Dali)
What are the EKG changes that occur with digoxin toxicity?
tachycardia, fibrillation, arrest
What are the pharmacokinetics of digoxin?
A: Well absorbed (Foral = 65-80%) - (may be inactivated by gut bacteria in some)
D: Wide in tissues and CNS
M: Not extensive in humans
(T1/2 = 36-40 hours)
E: 2/3 excreted unchanged by kidneys
Which electrolyte changes effect digoxin?
- Hyperkalemia
- Hypercalcemia
- Hypomagnesia
What effect does hyperkalemia have on digoxin effects?
- Potassium competes with digoxin
- Excess K+, decreased effect
What effect does hypercalcemia have on digoxin effects?
Increased risk of digoxin induced arrhythmias
What effect does hypomagnesia have on digoxin effects?
Increased risk of digoxin induced arrhythmias
How do phosphodiesterase inhibitors help treat HF?
Enzymes that inactivate cAMP and cGMP - positive inotropic effects, vasodilation
Increase contractility w/o inhibiting Na+/K+ ATPase (increase/prolong Ca++)
PDE3 specific
Which phosphodiesterase inhibitor helps treat HF?
Milrinone
What are the beta adrenergic stimulants used to treat HF?
β1 selective
- Dopamine
- Dobutamine most widely used (Increased CO and Decreased ventricular filling pressure)
What is the advantage of using beta adrenergic stimulants over digoxin?
Less arrythmogenic than digitalis
What are the positive inotropic drugs used to treat HF?
Digoxin, phosphodiesterase inhibitors, beta adrenergic stimulants, and calcium sensitizers
What are the drugs w/o positive inotropic effects used to treat HF?
Diuretics, ACE inhibitors and ARBs, vasodilators, and beta blockers
How are diuretics used to help treat HF?
Reduce salt and water retention
- Reduce preload
- Reduce edema
- Reduce cardiac size
- Improved efficiency of cardiac pump
How are ACE inhibitors and ARBs used to help treat HF?
Reduce compensatory responses to failure
How are vasodilators used to help treat HF?
- Reduction in preload
- Reduction in afterload
How are beta blockers used to help treat HF?
Decreases stress on heart (force of contraction) and reduction in mortality
- Can’t be used for severe CHF or acute HF
How are Ca++ sensitizers used to help treat HF?
- Positive inotropic - Bind troponin, stabilize Ca2+ bound conformation
- Vasodilatory - Open K+ channels (vasodilation)
(Not yet approved in USA)
