The Presence of Very Low QRS Voltage in Multiple Frontal Leads is a Powerful Predictor of Recurrent Neurally Mediated Syncope

Introduction: Isolated very low QRS voltage (VLV; ≤ 0.3mV) on frontal leads on the electrocardiogram (ECG) has been shown to predict recurrence of neurally mediated syncope (NMS). In most patients VLV occurs in only one isolated ECG lead, however a small number of patients have ≥ 2 leads with VLV (Figure A), the significance of this pattern being unknown. Hypothesis: The aim of the study was to explore the potential relationship between the number of frontal leads with VLV and NMS recurrence. Methods: We included 268 patients with NMS (age 48±20 years, 150 women), with a median of 3 syncopal episodes who were followed for a median of 12 months. Results: Very low voltage was present in one frontal lead in 98 patients (37%), in 2 leads in 16 patients (6%), and in 3 leads in 1 patient (0.4%). Patients with VLV in multiple frontal leads had significantly smaller left ventricular end diastolic diameter (LVEDD) and left ventricular systolic diameter (LVESD) than patients with no VLV (42.8±3.9mm vs. 45.6±5.2mm; p = 0.029, and 27.7±3.9mm vs. 30.3±5.0mm; p = 0.049, respectively). During follow-up 69 patients (26%) experienced recurrent syncope. The actuarial total syncope recurrence rate increased progressively with the number of frontal leads displaying VLV (log rank test chi 2 =34.78; p < 0.0001; Figure B). Multiple frontal leads with VLV was associated with a relative risk of syncope recurrence of 5.5 in univariate analysis. Multivariate Cox regression revealed that the number of frontal leads displaying VLV predicted recurrent syncope (HR 1.83, 95%CI 1.28-2.62) in a model that included history of presyncope and syncope (HR 3.43, 95%CI 1.77-6.65) and LVEDD (HR 0.94, 95%CI 0.89-0.99). Conclusions: Very low voltage in multiple frontal leads is rare. If this pattern occurs, it is associated with a high risk of recurrent NMS. This phenomenon, which appears to be related at least partially to a smaller LV cavity size, may help generate new diagnostic tools and insights into the pathogenesis of NMS.