CV IV - CHF Flashcards
What is congestive heart failure?
A condition where the heart is so weak it cannot pump enough blood to meet the needs of the body
CHF is generally progressive and has a very high mortality rate
CHF results from damage to the heart, lowering its ability to contract. Reduced contractility decreases cardiac output, which triggers mechanisms to improve CO.
List 5 causes of CHF
- Coronary artery disease
- Hypertension
- Cardiomyopathies
- Arrhythmias
- Other
Give the broad steps for the pathophysiology of congestive heart failure.
Increased preload takes a bad situation and makes it worse by signalling mechanisms to improve cardiac output.
β1 receptors signal to the brain to increase SNS activity.
- Vasoconstriction
- β1R in kidney: Renin angiotensin system (causing aldosterone secretion and vasoconstriction)
Elevated water and sodium retention from aldosterone leads to an every higher preload.
True or false? Heart failure can be left, right or bilateral.
True
What happens with left heart failure?
Pulmonary congestion (fluid in lungs)
What happens with right heart failure?
Systemic congestion (systemic fluid accumulation)
What are four general signs and symptoms of CHF?
- Fatigue
- Shortness of breath
- Increased HR
- Hypertrophy of surviving heart cells/tissue
- Heart remodeling (dilation, more connective tissue, apoptosis, increase in cells with fetal characteristics) leads to high mortality!
What are the three main strategies in treating CHF?
- Unload the heart
- Increase strength of contraction of the heart
- Block effects of the SNS and RAS (which increase preload)
Give the 4 drugs which are used to treat CHF
- Diuretics
- ACE inhibitors and angiotensin receptor blockers
- Cardiac glycosides (eg. digoxin)
- β blockers
How do ACE inhibitors and angiotensin receptor blockers treat CHF? (4)
- Reduce peripheral resistance and unloads heart (decreased afterload in arteries and decreased preload in veins)
- Decrease aldosterone secretion from adrenal glands, also unloading the heart.
- Decreases long term remodeling of ventricles caused by CHF (reducing mortality)
- Decrease bradykinin breakdown (hence, elevating bradykinin, a vasodilator!)
How do diuretics treat CHF? (4)
Often loop diuretics
- Reduce preload
- Reduce edema (fluid congestion), which unloads heart
- Reduces hypertrophy (less fluid filled cells)
K sparing diuretics are aldosterone antagonists and decrease mortality in heart failure by decreasing fibrosis in heart
How do cardiac glycosides treat CHF and what are they?
- Found in purple foxglove (digoxin) and used to treat ‘dropsy’
- Increases contractility of a failing heart
- Also used as n anti-arrhythmic drug by mimicing the effects of the PNS on the heart (slows conduction of action potentials through AV node)
Increased cardiac output does:
- Reduces RAS activity
- Decreases BP
- Reduces HR
- Decreases Na and water retention
- Reduces preload
Describe the cellular mechanism of action of digoxin
- Inhibiting the Na/k-pump on heart cells, effectively causing sodium to accumulate outside and calcium to come in through an exchanger (due to higher gradient), leading to stronger contraction (good for CHF)
List the toxic effects of digoxin
Why are these especially worrisome in elderly?
- AV-node block and cardiac arrest
- Increased calcium in cells can cause arrhythmia
- Narrow therapeutic index
Elderly
- Digoxin eliminated by kidneys, renal function declines with age
How can β blockers treat CHF?
They decrease high SNS activity
- β1 block: lowers HR, lowers renin, lowers contractility
- β2 block: not useful and can cause asthma problems (bronchoconstriction)
- α1 block: vasodilation lowers afterload
- Reduces signs and symptoms of CHF
- Slows CHF progression
- Decreases mortality and reduces remodeling
