When "electrical alternans" is seen on a patient's EKG, what will the echocardiogram most likely demonstrate?

When electrical alternans is observed on an EKG, it is typically indicative of a large pericardial effusion. This phenomenon occurs when there is significant fluid accumulation in the pericardial space, leading to changes in the position of the heart during each heartbeat. The resultant movement can cause variations in the electrical voltage recorded by the EKG, manifesting as alternating peaks in the QRS complex.

On echocardiography, a large pericardial effusion will show an anechoic (dark) space surrounding the heart, which correlates with the presence of fluid. The size of the effusion can be assessed, along with its impact on cardiac function, such as possible diastolic dysfunction due to the compression of the heart chambers.

This connection between electrical alternans and large pericardial effusion highlights the importance of integrating diagnostic modalities—like EKG and echocardiography—in evaluating cardiac conditions. Understanding this relationship can assist clinicians in timely management of patients presenting with such findings.