Final answer:
For a patient with syncope suspected of having a cardiac cause, the next step is a detailed cardiovascular assessment including an ECG and other tests to identify the underlying condition.
Step-by-step explanation:
The next most appropriate step in management for a patient presenting with syncope where a cardiac etiology is suspected would be a detailed cardiovascular assessment, which includes but is not limited to an electrocardiogram (ECG), echocardiography, and possibly blood tests to evaluate for ischemia, arrhythmias, or structural heart disease.
Auscultation using a stethoscope may provide initial insights into the heart's function; however, where cardiac syncope is suspected, further diagnostic testing is crucial to identify the specific underlying heart condition that could be causing the syncope. Depending on the ECG findings, additional steps might include hospital admission for telemetry monitoring, the use of anticoagulants or beta blockers, or an urgent intervention such as a pacemaker implantation if bradycardia is an issue or controlled electric shock if an arrhythmia is present.