How does cardiac tamponade primarily affect the heart's function?

Cardiac tamponade occurs when fluid accumulates in the pericardial space, exerting pressure on the heart. This pressure prevents the heart from filling adequately during diastole, which is the phase of the cardiac cycle when the heart relaxes and fills with blood. Impaired diastolic filling directly limits the amount of blood that can be received by the ventricles, leading to decreased stroke volume and compromised cardiac output.

As a result, the heart struggles to pump effectively, which can lead to symptoms such as hypotension and decreased perfusion to organs. The accumulation of fluid may lead the body to increase the heart rate as a compensatory mechanism to maintain cardiac output, but this does not improve filling; rather, it may exacerbate the underlying problem by increasing oxygen demand.

While impaired diastolic filling is the primary way cardiac tamponade affects heart function, it does not inherently improve cardiac output as fluid accumulation does not support the heart's effective pumping ability. Arrhythmias may occur in response to the strained cardiac function and do not necessarily prevent arrhythmias, making it clear that the most direct impact of cardiac tamponade is the impairment of diastolic filling.