Heart failure (HF) is a condition in which the pump function of the heart is decreased due to changes in preload, afterload or contractility. The heart is unable to pump enough blood to meet the body’s metabolic needs.
Cardiac and neurohumoral compensatory responses are triggered as a result of the decreased pump function and the resultant decreased organ perfusion. Initially, these responses maintain normal systemic perfusion. However, chronic compensation leads to oedema and elevated arterial pressure (and thus increased preload & afterload) which eventually cause progression of HF.
Left ventricular failure is the most common form of HF and the target of most drug interventions. It can be divided into two categories: systolic failure and diastolic failure.
- In systolic left ventricular failure, there is a decrease in ejection fraction, usually due to reduced contractility resulting from a dilated ventricle.
- In diastolic left ventricular failure, ventricular filling is reduced due to impaired relaxation, wall stiffness, or acute massive valve regurgitation. However, ejection fraction is not decreased.
Isolated right ventricular failure is a relatively rare situation where emptying is impaired, usually from pulmonary arterial hypertension.
Unfortunately, HF is a vicious cycle. Failure of the left ventricle causes congestion of the pulmonary vasculature. The right ventricle must work harder to increase pulmonary artery pressure to force blood through the lungs into the weakened left ventricle. The patient develops dyspnoea, fatigue, and exercise intolerance. Over time, the right ventricle cannot maintain these high pressures and right ventricle output decreases, giving rise to venous congestion in the systemic circuit. As a result, the venous return decreases, as does the left ventricular output. Organ perfusion is reduced, which activates the renin-angiotensin system in the kidneys. The blood volume is increased and complicates the venous congestion, causing more systemic oedema.
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Which of the following is NOT a symptom of left ventricular dysfunction
Extra info: Left ventricular dysfunction is associated with congestion in the pulmonary system. Therefore all symptoms except hepatojugular reflux can be expected.
The best way to differentiate systolic from diastolic dysfunction is to measure
Extra info: A Doppler echocardiogram is the best test for measuring ejection fraction. EF is based on changes in ventricular chamber size between diastole and systole.
A decrease in cardiac output leads to
Extra info: B is the wrong answer because an increase in sympathetic activity should be expected. C is the wrong answer because hypertrophy would increase oxygen demand. D is the wrong answer because a decrease in cardiac output cannot be expected to produce a decrease in left ventricular end-diastolic volume.