Isolated very low QRS voltage predicts response to tilt-table testing in patients with neurally mediated syncope.

Abstract

A number of patients with neurally mediated syncope (NMS) have isolated QRS complexes of very low voltage (≤0.3mV) in the frontal plane leads on the 12-lead electrocardiogram (ECG). The aim of this study was to assess the importance of QRS voltage in predicting response to tilt-table testing (TTT) in patients with suspected NMS. We included 216 patients (age: 49±20 years, 103 men) with suspected NMS who had either a positive or negative response to TTT (n=91 TTT+, and n=125 TTT-). The QRS voltage was measured in mV on 12-lead ECGs performed within 3 days of the TTT. The lowest QRS voltage (QRSmin), as well as the voltage in each of the 12 leads was also determined. Very low voltage (QRSmin ≤ 0.3mV) in the frontal leads was significantly more prevalent in the TTT+ group than in the TTT- group (74vs 22%, respectively; P < .001). Patients in the TTT+ group had significantly lower QRSmin when compared to patients in the TTT- group. QRSmin predicted a positive tilt-table test in a multivariate model that also included patient gender, height, history of presyncope, QRS duration, and left ventricular end-diastolic diameter indexed to height. ROC analysis showed that QRSmin of≥0.3mV discriminated between TTT+ and TTT- patients with a sensitivity of 78% and specificity of 68%. Isolated very low QRS voltage in the frontal leads predicts a positive response to TTT in patients with suspected NMS.