Which ECG change is likely in patients suffering from a pulmonary embolism?

In the context of a pulmonary embolism (PE), sinus tachycardia is a common ECG finding. This occurs because when a pulmonary embolism blocks a pulmonary artery, it reduces blood flow to the lungs and increases the workload on the heart. The right side of the heart has to pump harder to move blood through the obstructed vessels, leading to an increased heart rate in an attempt to maintain adequate cardiac output and oxygen delivery to the body. This compensatory mechanism manifests as sinus tachycardia on the ECG.

Understanding the physiological response to a PE helps clarify why other options are less likely. Bradyarrhythmia, slow sinus rhythm, and first-degree AV block do not typically align with the body's compensatory response to the acute stress of a pulmonary embolism. In summary, sinus tachycardia is a direct reflection of the cardiovascular strain due to PE, making it the most likely ECG change in these patients.