What occurs when electrical impulses come from multiple foci in the atrium?

When electrical impulses originate from multiple foci in the atrium, it results in atrial fibrillation. This arrhythmia is characterized by a rapid and irregular heartbeat due to the chaotic electrical activity within the atria. Unlike atrial flutter, which typically involves a single focus creating a distinct reentrant circuit, atrial fibrillation features multiple ectopic atrial foci firing at variable rates, leading to an uncoordinated atrial contraction. This contributes to the quivering of the atria rather than an effective contraction, increasing the risk of blood clots and stroke due to stagnant blood flow.

The other options do not reflect the same underlying mechanism. Ventricular tachycardia pertains to rapid impulses originating in the ventricles rather than the atria. Sinus rhythm represents a normal heartbeat originating from the natural pacemaker of the heart, the sinoatrial node, where impulses are organized and consistent, unlike the disorganized impulses seen in atrial fibrillation. Atrial flutter also tends to maintain a relatively organized rhythm compared to the chaotic impulses seen in atrial fibrillation.