EXAM #2: CONGESTIVE HEART FAILURE Flashcards
What is preload?
Tension developed on the wall of the ventricles before the start of contraction
This is equal to the end diastolic volume, and EDV is equal to the atrial pressure
What is the Frank Starling Principle?
More preload = more contractility TO A POINT
What is afterload?
The pressure the ventricle has to push against i.e. arterial pressure/ peripheral vascular resistance
What is the relationship between afterload and contractility?
Increasing afterload increases contractility to a point
This is called the anrep phenomenon
What is the relationship between the contractility and heart rate?
Faster heart rate will be associated with increased contraction
This is called the Bowditch phenomenon*
Draw the relationship between ventricular EDV and stroke volume. How is this changed in HF?
N/A
Generally, in HF you need MORE preload to produce the same amount of WORK.
Draw the pathophysiology of Heart Failure and the major drug action sites.
N/A
What is the main cause of HF?
Cardiac remodeling
What is stage A Heart Failure?
High risk for developing HF
- HTN
- CAD
- DM
- FHX of Cardiomyopathy
What is stage B Heart Failure?
Asymptomatic HF
- S/p MI
- LV systolic dysfunction
- Asymptomatic valvular disease
What is stage C Heart Failure?
Symptomatic HF
- Known structural heart disease
- Dyspnea/ Fatigue
- Reduced exercise tolerance
What is stage D Heart Failure?
Refractory End-Stage HF
- Symptoms at rest despite max. medical therapy
What drugs classes are used to treat Stage A HF?
1) ACEI or ARB
What drugs classes are used to treat Stage B HF?
1) ACEI or ARB
2) Beta-blocker
What drugs classes are used to treat Stage C HF?
1) ACEI or ARB
2) Beta-blocker
3) Diuretics
What drugs classes are used to treat Stage D HF?
1) ACEI or ARB
2) Beta-blocker
3) Diuretics
4) Digoxin
5) Positive ionotrope
What is the effect of diuretics alone on the pathophysiology of HF?
Shift to lower cardiac filling pressure on the same ventricular function curve
What is the effect of ionotropes alone on the pathophysiology of HF?
Shift to higher ventricular function curve BUT increased workload
What is the effect of vasodilators alone on the pathophysiology of HF?
Shift to improved ventricular function curve AND reduce cardiac filling pressure
What is the effect of vasodilators and ionotropes on the pathophysiology of HF?
Shift to improved ventricular function curve AND sight reduction in cardiac filling pressure
What is the effect of vasodilators, diuretics, and ionotropes on the pathophysiology of HF?
Shift to improved ventricular function curve AND significant reduction in cardiac filling pressure
What are the effects of beta agonists on myocardial contractility?
- Gs stimulation
- Increased cAMP
- Phosphorylation of the Ca++ channel in the sarcolemma
- Increased Ca++ induced Ca++ release
Positive ionotropy
How can intrinsic myocardial activity be increased?
1) Increase cytosolic Ca++
2) Increased myocardial cAMP
3) Agonism of B1 receptors
4) Increase B1 density
What drugs increase cytosolic Ca++?
Cardiac Glycosides i.e. Digoxin
What drugs increase myocardial cAMP?
Phosphodiesterase inhibitors
What drugs agonise B1 receptors?
Isupreal Dobutamine DA Epi NE
What drugs increase B1 receptor denisty?
Beta-1 ANTAGONISTS
What is the mechanism of action of digoxin?
1) Block Na+/K+ ATPase
2) Accumulation of intracellular Na+
3) Reduction in Na+/Ca++ exchange
4) INFLUX of Ca++ from extracellular space
Net ionotropic effect
What are the cardiac effects of Digoxin?
1) Positive ionotropy
2) Direct vagal effect
3) Increased coronary blood flow
4) Proarrhythmic
Why is digoxin used in patients with A-fib w/ RVR?
Direct vagal effect decreases AV conduction
What EKG change is characteristic of Digoxin?
Hockey stick ST depression
What is the proarrhythmic effect of digoxin related to?
K+
What is the half-life of digoxin?
36-48 hours
How long does it take to achieve steady-state blood levels of digoxin?
7 days
How is digoxin excreted?
Kidney
What are the adverse effects of Digoxin?
1) Hypokalemia
2) Acid-base disbalance
3) Arrhythmia (AV block)
What are the first symptoms that patients complain of with digoxin that should be concerning to you?
Anorexia
Nausea
Vomiting
Visual distrubance
What is the role of Digoxin in the treatment of HF?
Used frequently in HF, especially in CHF and a-fib w/ RVR; however
- Improves quality of life but NOT all-cause mortality
How is Digoxin overdose reversed?
Cholestyramine
List the phosphodiesterase 3 inhibitors.
Inamrione
Milrinone
What is the mechanism of action of the phosphodiesterase 3 inhibitors?
- Type III Phosphodiesterase degrades cAMP
- inhibition INCREASES cAMP
What is the effect of cAMP in the heart?
Increased intracellular Ca++ leading to enhanced contractility
What are the cardiovascular effects of the phosphodiesterase 3 inhibitors?
- Positive ionotrope
- Positive lusotropy
- Balanced venous and arterial dilation
All increase CO
What setting are Inamrinone and Milrinone used in?
ICU i.e. only for short-term support of advanced CHF
