Name a common diagnostic test for suspected arrhythmias.

A resting 12-lead ECG is a fundamental diagnostic tool used to evaluate suspected arrhythmias. This test captures the electrical activity of the heart from multiple angles and provides valuable information about heart rhythm, rate, and any abnormalities in conduction. The 12-lead ECG allows healthcare professionals to identify different types of arrhythmias, including atrial fibrillation, ventricular tachycardia, and other rhythm disturbances. It is non-invasive, readily available, and provides immediate results, making it the preferred initial assessment for patients presenting with symptoms suggestive of arrhythmias.

The other options—X-ray imaging, blood tests, and MRI—do not serve as primary diagnostic tools for arrhythmias. While they can provide useful information in diagnosing other cardiovascular conditions or determining the underlying causes of arrhythmias, they do not directly assess the heart's electrical activity as effectively as a 12-lead ECG.