Impedance cardiography and beat-to-beat blood pressure monitoring in diagnosis of syncope in long-QT syndrome.

Abstract

Syncope represents a diagnostic challenge in patients affected by long-QT syndrome (LQTS). It is crucial for the therapeutic decision to distinguish between potentially life-threatening ventricular tachycardias (Torsadede-pointes) and-especially during adolescence-neurocardiogenic syncopes. This case report presents a patient with LQTS2 (mutation in the HERG gene) on medication with beta-blocker, in whom a head-up-tilt table test was performed after syncope of unknown origin. The test was chosen in order to reproduce the circumstances under which the syncope had happened. The monitoring device consisted of impedance cardiography as well as non-invasive beat-to-beat blood-pressure measurement. By these means it was possible to register a reduced peripheral vascular resistance after tilting the patient, a reduced cardiac output and bradycardia leading to syncope after four minutes of upright posture. This was suggestive for neurocardiogenic syncope as a cause for the spell experienced. Further non-invasive diagnostic methods were normal. As the patient's family history was negative for syncopes, Torsade-de-pointes seemed unlikely.In this special case the non-invasive monitoring system of cardiac output, peripheral vascular resistance and beat-to-beat blood pressure measurements was useful as a supplemental tool during evaluation of syncope and helpful in decision-making against implantation of an ICD and for a more intense treatment with betablockers. Such monitoring devices offer new insights into the orthostatic regulation in young patients.