Lecture 2- Treatment Of Congestive Heart Failure

Question 1

Preload + Afterload

Answer 1

Preload= amount of stretch of the heart muscle prior to contraction

Afterload= amount of resistance the heart must overcome to push the blood volume out into systemic circulation

Question 2

What happens in CHF?

Answer 2

Heart is unable to pump sufficient blood to meet the needs of the body —> Inadequate cardiac output —-> Oxygen needed by the body

-impaired ability of the heart to adequately fill with/eject blood
-accompanied by significant fluid retention
-often accompanied by abnormal increases in blood volume + interstitial fluid

Question 3

Causes and symptoms of CHF

Answer 3

Causes= coronary artery disease, hypertension, diabetes + mitral valve disease

Common symptoms= shortness of breath, oedema + fatigue

Question 4

Compensatory physiological responses in CHF

Answer 4

*increased sympathetic activity;
-increase in rate of+ force of contraction of the heart in response to fall in bp + vasoconstriction= increase in cardiac preload= increases work of the heart and contributes to decline in cardiac function
*activation of the renin-angiotensin system
-results in increased PR + blood volume (more blood returned to the heart)
-if heart is unable to pump= venous pressure increases + oedema occurs = increase the work of the heart and can contribute to further decline in heart function
*myocardial hypertrophy= increase in the size of= excessive elongation of the heart fibres= weaker contractions

Question 5

Treatment strategies in CHF

Answer 5

-alleviate symptoms
-slow disease progression
-improve survival

Question 6

Drugs used in treating CHF

Answer 6

*ACE inhibitors
*Angiotensin antagonists
*Diuretics
*B-adrenoreceptor blockers
*Digoxin
*Direct vasodilators
*Other cardiac inotropic agents

Question 7

ACE inhibitors

Answer 7

captopril, lisinopril, enalapril + ramipril
Actions=
-reduction in Afterload, preload and aldosterone secretion
-inhibition of cardiac + vascular remodelling
Side effects=
-postural hypotension, hyperkalemia, angioedema + persistent dry cough
Contraindications=
-pregnant women due to foetal toxicity

Question 8

Diuretics

Answer 8

-useful in reducing symptoms if volume overload in CHF by; decreasing the extracellular volume and venous return to the heart by decreasing plasma volume = reduces cardiac workload
-loop diuretics like furosemide + bumetanide = most effect
-thiazides like hydrochlorothiazide= effective in mild cases only
^however both cause hypokalemia
-potassium sparing diuretics= reduce hypokalemia due to these diuretics

Question 9

Beta blockers (B2 adrenoreceptor antagonists)

Answer 9

-carvedilol + metoprolol = used for CHF amongst beta blockers
-beta blockers= inhibit the sympathetic nervous system + increase beta receptor activity

Question 10

Vasodilators

Answer 10

-isosorbide dinitrate + hyralazine= patients who cannot tolerate ACE inhibitors
-act by dilating venous blood vessels = decrease in cardiac preload
-arterial dilators = reduce systemic arteriolar resistance + decrease Afterload

Question 11

Digitalis glycosides- Digoxin

Answer 11

-derives from digitalis (foxglove plant)
-increase the contraction to of the heart muscle = positive inotropic action
-used as a first-line drug in patients with CHF who are in arterial fibrillation
-inhibition of Na/K ATPase pump = increases intracellular sodium concentration = increases cytosolic calcium = increases in the force of contraction of the heart

Question 12

Digoxin adverse effects

Answer 12

-cardiac arrhythmia= decrease in intracellular potassium (predisposes to digoxin toxicity) therefore serum levels of potassium ad digoxin levels in renal insufficiency must be monitored
-anorexia, nausea + vomitting
-headache, fatigue, confusion + blurred vision