Drugs for heart failure Flashcards
(9 cards)
Recognise that heart failure describes a condition in which the heart is not efficiently pumping blood. The physiological responses to lowered blood pressure, through sympathetic nervous system activation and activation of the renin-angiotensinaldosterone system, may be counterproductive through increased fluid retention, increased peripheral vascular resistance and changes in heart muscle (“remodelling”)
Describe how digoxin acts to increase cardiac contractility
Targets K+ and Na+ ATPase pump preventing appropriate removal of Na+ from the cell (cardiomyocyte).
This in turn interferes with the Na+/Ca+ exchange of Ca+ out of the cell causing an excess of calcium
increase availability of calcium to actin and myosin
Discuss the role of diuretics in countering the fluid retention that accompanies heart failure
Diuretics aim to decrease blood volume. They do this by reducing the reabsorption of Na+ in the kidneys, this decrease in sodium reabsorption disrupts osmolality in the kidneys and ensures water is retained in the filtrate and excreeted along with sodium
Some are aldosterone antagonists and some are Na+ channel blockers
Discuss the role of beta-adrenergic blocking drugs in countering the sympathetic induced cardiac remodelling that can occur in heart failure
Beta-blockers counter the effects of sympathetic stimulation by preventing the binding of noradrenaline form the sympathetic NS
Discuss the role of renin-angiotensin inhibitors in countering the adverse effects of activation of the renin-angiotensin-aldosterone system in heart failure
Discuss the role of coronary blood supply in meeting myocardial oxygen demand and recognise that myocardial oxygen demand is a function of heart work.
Coronary blood supply carries higher amounts of oxygen (8–>70ml02/min) when exercise to fuel the heart with oxygen and FA for energy to pump.
In a patient with angina this supply cannot be met
Recognise that angina occurs when coronary blood supply is limited by obstruction in the coronary arteries, leading to myocardial oxygen supply that is insufficient for demand
Describe drugs that reduce heart work, and thus myocardial oxygen demand, through reduced cardiac rate and contractility: (beta-adrenoceptor blockers and cardioselective
calcium channel blockers)
B-adrenoreceptor antagonists: decrease heart rate and contractility induced by the sympathetic NS
- Metoprolol
- Atenolol
- -Olol’s!
Cardioselective calcium channel blockers: decrease available calcium used for contractility by action and myosin
- verapamil
- Diltiazem
Describe drugs that reduce peripheral vascular resistance (vascular selective calcium channel blockers and nitrates)
Vascular calcium channel blockers: decrease available calcium from smooth muscle to prevent vasoconstriction
- Dihydropyridines
Nitrates:
