Treatment of CHF Flashcards
preload
the amount of stretch of the heart muscle prior to contraction
afterload
the amount of resistance the heart must overcome to push the blood volume out into the systemic circulation.
what happens in chf
The heart is unable to pump sufficient blood to meet the needs of the body, so an inadequate cardiac output and so less oxygen is needed by the body
there is an impaired ability of the heart to fill with or eject blood
which is accompanies with significant fluid retention
and its accompanied with abnormal increase in blood volume and intercostal fluid
what are the 4 causes of heart failure
coronary heart disease
hypertension
diabeted
mitral valve disease
3 symptoms of chf
fatigue
shortness of breath
oedema
what are the 3 compensatory physiological responses in CHF
increased sympathetic activity
activation of the renin-angiotensin system
myocardial hypertrophy
explain what happens in increased sympathetic activity
in sympathetic activity there is a decrease in blood pressure which means there is an increase rate of contraction and force, as well as vasoconstriction
this increases cardiac PRELOAD
it also increases the work the heart does and therefore cardiac function will decline
explain the activation of the renin-angiotensin system
there is an increase in blood volume and peripheral resistance
more blood is then required to be returned to the heart
if the heart isn’t pumping adequately, the venous pressure increases and oedema occurs
increases the work of contraction and contributes to further decline in heart function
explain myocardial hypertrophy
these are structural changes
due to the heart increases in size, there is an elongation of heart fibres and resulting in weaker contractions
3 treatment strategies in CHF
alleviate symptoms
slow disease progression
improve survival
what are the 7 classes of drugs used for CHF
Angiotensin converting enzyme (ACE) inhibitor
angiotensin antagonists
diuretics
B-adrenoreceptor blockers
digoxin
direct vasodilators
cardiac inotropic agents (dobutamine)
ACE inhibitors actions
reduction in arterial resistance (after load)
reduction in venous tension
reduction in aldosterone secretion
inhibiting cardiac and vascular remodelling
what are the 4 side effects of ACE inhibitors
postural hypotension
hyperkalemia
angioedema
persistent dry cough
Why are ACE inhibitors contraindicated in pregnant women
because of foetal toxicity
Diuretics - which are commonly used
loop diuretics like furosemide and bumetanide
which are used in mild cases only
thiazides sich as hydrochlorothiazide
how are diuretics useful in reducing symptoms of volume overload in CHF
they decrease extracellular volume
decrease the venous return to the heart (preload) by decreases plasma volume, reduces cardiac workload
what do loop diuretics and thiazides cause
hypokalaemia
what helps in reducing the hypokalaemia due to the diuretics
potassium sparing diuretics
what is another name for beta blockers
B1 adrenoreceptor antagonists
Give the 2 examples of drugs that are used for CHF in beta blockers and
how do they act
metoprolol and carvedilol
act by inhibiting the sympathetic nervous system and increase beta receptor activity
give the 2 examples of vasodilators and who are they given to
isosorbide denigrate and hydralazine
patients who can’t tolerate ACE inhibitors
how do vasodilators work
act by dilating venous blood vessels leading to decrease cardiac preload
arterial dilators reduce systemic arteriolar resistance and decrease after load
give an example of digitalis glycosides
digoxin
how does digoxin work
increase the contractility of the heart muscle (positive ionotropic action)
used as a first line drug with patients in CHF and in atrial fibrillation
Inhibition of Na/K ATPase pump increases intracellular sodium concentration – eventually increase cytosolic calcium.
This leads to an increase in the force of contraction of the heart, and hence cardiac output.
adverse effects of digoxin
Cardiac arrhythmia caused by a decrease in intracellular potassium
Anorexia, nausea and vomiting
Headache, fatigue, confusion, blurred vision
A decrease in intracellular potassium predisposes to digoxin toxicity.
Monitor serum levels of potassium.
Monitor digoxin levels in renal insufficiency.
dobutamine
inotropic agent
agonist
