[The adenosine-5'-triphosphate (ATP) test: a diagnostic tool in the management of syncope of unknown origin. Basic and clinical aspects]

Symptoms during ATP-test under pacing: impact on syncope recurrence and prediction from the ATP-test without pacing

Syncope recurrence in patients with positive ATP-test who underwent permanent pacemaker implantation is suspected to be related to vagal vasodilatation. We studied symptoms during ATP-test in 38 temporary paced patients. Among patients with positive ATP-test who underwent permanent pacemaker implantation (N = 14), the only one patient who recurred during follow-up was symptomatic during the initial paced ATP-test. Symptoms during paced ATP-test were well predicted by a higher blood pressure (BP) drop during standard ATP-test (i.e. without pacing) (Area under ROC curves > 0.70 for all BP parameters except for relative diastolic BP drop). Moreover, BP drop during standard and paced ATP-test were significantly correlated (all p ≤ 0.03). Thus, a higher BP drop measured during ATP-test without pacing might help identify patients who would experience recurrences due to vasodilatation under permanent pacing.

Blood pressure drop and symptoms during ATP-test under pacing

We studied systolic blood pressure (SBP) behavior and symptoms during ATP-test in temporary paced patients. SBP drop during ATP-test is only partially prevented by pacing. During DDD paced ATP-test, SBP minimum was lower in symptomatic patients. Considering the role of endogenous adenosine in neurally-mediated syncope (NMS), our results are concurrent with a SBP fall resulting in NMS recurrence under permanent pacing.

Syncope in adults: terminology, classification, and diagnostic strategy

Syncope is a relatively common clinical syndrome that is a subset of a broader range of conditions that cause transient loss of consciousness (TLOC). Other TLOC conditions include seizures, concussions, and intoxications. However, despite frequent confusion in the medical literature, syncope is and should be clearly distinguished from those other causes of TLOC by virtue of its pathophysiology; specifically, syncope is the result of self-terminating inadequacy of global cerebral nutrient perfusion, while the other forms of TLOC have different etiologies. Unfortunately, the diagnostic evaluation of syncope remains for the most part poorly managed and inefficient. Careful history-taking, physical examination, and judicious use of tests can not only increase the diagnostic yield of the evaluation, but also increase patient safety and reduced overall healthcare costs.