The ventricles are the two powerful muscular pumping chambers in the lower half of the heart. They receive blood from the upper chambers (the atria) and pump it out under high pressure: the right ventricle to the lungs, and the left ventricle to the rest of the body.
The left ventricle is the heart’s main pump. It has thick, muscular walls (around 9 to 12mm) to generate the high pressures needed to drive blood around the systemic circulation. The right ventricle is less muscular because it only needs to pump blood to the nearby lungs against lower resistance. The two ventricles are separated by the interventricular septum.
Ventricular function is a key measure of cardiac health. The ejection fraction (EF) describes the proportion of blood the left ventricle ejects with each beat; normal is 55% or above. A reduced ejection fraction indicates that the ventricle is not contracting effectively, which can occur after heart attack, in dilated cardiomyopathy, or following cardiac arrest due to myocardial stunning.
Life-threatening arrhythmias originating in the ventricles include ventricular tachycardia (VT) and ventricular fibrillation (VF). In VF, the ventricular muscle quivers chaotically rather than contracting in a coordinated sweep, producing no effective pumping action and causing immediate cardiac arrest. Defibrillation (via an AED or ICD) is the only effective treatment for VF.
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