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

Abstract

Background A number of patients with neurally mediated syncope (NMS) have isolated QRS complexes of very low voltage (≤0.3 mV) in the frontal plane leads on the 12‐lead electrocardiogram (ECG). Hypothesis 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. Methods 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. Results Very low voltage (QRSmin ≤ 0.3 mV) in the frontal leads was significantly more prevalent in the TTT+ group than in the TTT− group (74 vs 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 ≥0.3 mV discriminated between TTT+ and TTT− patients with a sensitivity of 78% and specificity of 68%. Conclusion Isolated very low QRS voltage in the frontal leads predicts a positive response to TTT in patients with suspected NMS.

Usefulness of the Electrocardiogram in a Patient Presenting with Right-Sided Pneumothorax and Presyncope

“…There were marked phasic QRS voltage changes observed especially in lead V2 and lead III, with lower frequency modulation, which appeared to be timed with respiratory movements. The electrocardiogram also revealed isolated very low QRS voltage (<0.3 mV) in lead III (Figure 1 green arrow) [16].…”

Electrocardiographic Patterns in Patients with Neurally Mediated Syncope

“…VLV was defined as a voltage of ≤0.3 mV in frontal leads and of ≤0.7 mV in precordial leads. These aspects were first described starting from an empirical observation that some patients with NMS have low voltage QRS complex present in an isolated frontal ECG lead [ 43 ] ( Figure 5 ).…”

“…The lead displaying VLV was close to perpendicular to the QRS axis. The voltage in frontal leads was found to be significantly lower in the TTT-positive group of patients in comparison with the TTT-negative group [ 43 ].…”

“…The mechanism for this isolated QRS voltage reduction is not known. However, given the fact that there was a significant correlation between the QRS with lowest voltage and LV end-diastolic diameter, the authors hypothesized that the presence of isolated VLV is due at least in part to a specific LV geometry encountered in patients with NMS [ 43 ].…”

“…Patients with NMS have reductions in voltage not only in frontal leads, but also in the precordial leads [ 43 , 48 ]. VLV in precordial leads, defined as a QRS voltage of ≤ 0.7 mV, was present in 36% of the 135 patients with NMS enrolled in a prospective study, with lead V1 displaying this pattern in most of the cases.…”