Congestive Heart Failure - Howlett 3 Flashcards
CHF
Heart is so weak it cannot pump enough blood to meet the needs of the body
Progressive
Very high mortality rate
Decrease CO, which triggers mechanisms to improve CO, which worsens the situation
Treatment is to dampen down reflex actions trying to compensate
Causes of CHF
Coronary artery disease
Hypertension
Cardiomyopathies
Arrhythmias
Pathology of CHF
Increased Na and water retention by increasing aldosterone to increase preload
Increased vasoconstriction to increase afterload
This further reduces CO as heart damage cannot keep up
Left heart failure
Pulmonary congestion and fluid build up
Right heart failure
Systemic congestion and systemic fluid build up
Symptoms of CHF
Fatigue Shortness of breath Increase HR Hypertrophy Remodelling
Strategies in treating CHF
Unload the heart
Increase the strength of contraction of the heart
Block the effect of the SNS and RAS (compensatory responses)
Drugs used to treat CHF
- Diuretics
- Drugs that inhibit RAS
- Cardiac glycosides
- Beta blockers
Diuretics
Decrease salt and water retention Decrease preload (decrease circulating volume) Decrease afterload Decrease edema 1. Loop diuretics 2. Aldosterone receptor antagonists
Loop diuretics
Loop of hence
Very powerful
Chance secretion of K into urine
Aldosterone receptor antagonists
K-sparing diuretics
Mild diuresis
Increased heart function
Aldosterone contributes to fibrosis
Drugs that inhibit the RAS
ACE inhibitors, A2 receptor blockers, renin inhibitors
Reduce total peripheral resistance, decrease aldosterone secretion, decreases long term remodelling of ventricles
ACE inhibitors
Decrease bradykinin breakdown
Bradykinin
Vasodilator peptide that is broken down by ACE
Cardiac glycosides
Found in purple foxglove
Modernly introduced to treat dropsy
Digoxin clinically
Increases contractility
Digoxin
Clinically used cardiac glycoside
Increases contractility of heart
Anti-arrhythmic drug
Mimics effects of PNS on heart
Slows conduction of AP throughout AV node
Inhibits Na/K ATPase
Less Ca removed due to decreased Na gradient (Na/Ca exchanger) which increases contraction
CO goes up which reduces compensatory actions in SNS
Toxic effects of digoxin
- AV node: can cause AV blockage and cardiac arrest by stopping impulses from travelling from atria to ventricles
- Ventricles: narrow therapeutic index, increases Ca which may trigger arrhythmia
Can be particularly bad in elderly as their kidneys are slower
Beta-blockers
Decrease SNS activity Metoprolol, carvedilol Highly secretive B1: decrease HR, renin B2: not useful, in airway A1L decreases afterload Reduces signs and symptoms of CHF Slows progression of CHF Decreases mortality Reduces remodelling
