Selective use of diagnostic tests inpatients with syncope of unknown cause

We sought to prospectively assess the diagnostic yielding of a protocol in which electrophysiologic studies (EPS), tilt-table tests (TTTs), and loop recorder implantation are selectively used.

The optimal strategy in the diagnosis of patients with syncope of unknown cause has not been defined.

A total of 184 consecutive patients with syncope of unknown cause were classified into two groups. Group A consisted of 72 patients fulfilling any of the following criteria: 1) presence of structural heart disease or family history of sudden death; 2) abnormal electrocardiogram; 3) significant non-symptomatic arrhythmia on Holter monitoring; and 4) paroxysmal palpitations immediately before or after syncope. These patients initially underwent an EPS and, if this study was negative, TTT. In the remaining 112 patients (group B), TTT was performed.

The EPS was positive in 32 patients (44%) in group A. The TTT was positive in 80 patients (71%) in group B. An additional patient had carotid sinus hypersensitivity. In patients of group A with a negative EPS, the TTT was positive in 23 (57%). A loop recorder was implanted in 15 patients from group A with negative conventional testing, and diagnostic activation was obtained in seven patients. Overall, a positive diagnosis was achieved in 143 patients (78%).

In patients with syncope of unknown cause, selective use of EPS or TTT leads to a positive diagnosis in >70% of the cases. An implantable loop recorder can be useful in non-diagnosed cases.