Utility of Inferior Lead Q-waveforms in diagnosing Ventricular Tachycardia

Abstract

Background: Electrocardiogram (ECG) differentiation of wide complex tachycardia (WCT) into ventricular tachycardia (VT) and supraventricular tachycardia with aberration (SVT-A) is often challenging. Objective: To determine if the presence of Q-waveforms (QS, Qr, QRs) in the inferior leads (II, III, aVF) can differentiate VT from SVT-A in a WCT compared to Brugada algorithm. We studied 2 inferior lead criteria namely QWC-A where all the inferior leads had a similar Q wave pattern and QWC-B where only lead aVF had a Q-waveform. Methods: A total of 181 consecutive cases of WCT were identified, digitally separated into precordial leads and inferior leads and independently reviewed by 2 electrophysiologists. An electrocardiographic diagnosis of VT or SVT-A was assigned based on Brugada and inferior lead algorithms. Results were compared to the final clinical diagnosis. Results: VT was the final clinical diagnosis in 24.9% of ECG cohort (45/181); 75.1% (136/181) were SVT-A. QWC-A and QWC-B had a high specificity (93.3% and 82.8%) and accuracy (78.2% and 71.0%), but low sensitivity (33.3% and 35.6%) in differentiating VT from SVT-A. The Brugada algorithm yielded a sensitivity of 82.2% and specificity of 68.4%. Area under the curve in ROC analysis was highest with Brugada algorithm (0.75, 95% CI 0.69-0.81) followed by QWC-A (0.63, 95% CI 0.56-0.70) and QWC-B (0.59, 95% CI 0.52-0.67). Conclusion: QWC-A and QWC-B criteria had poor sensitivity but high specificity in diagnosing VT in patients presenting with WCT. Further research combining this simple criterion with other newer diagnostic algorithms can potentially improve the accuracy of the overall diagnostic algorithm.

Tachycardia origin prediction using point of care ultrasound (TOP-UP) - A novel technique

“…[ 3 4 ] The Basel algorithm, limb lead algorithm, and inferior lead Q-wave algorithm are the three newer ECG algorithms that have recently been proposed to differentiate VT from SVT in WCT. [ 7 8 9 ] The limitations of current existing algorithms are the complexity of algorithms, less diagnostic accuracy, and the chance of misdiagnosis of preexcited SVT/fascicular VT/wide complex atrial flutter.…”

Emergence of inferior Q‐waves during tachycardia

“…One more recent report describes a patient with remote anterior wall myocardial infarction and left bundle branch block where anterior Q‐waves appeared during VT 3 . Subramany et al reported that inferior Q‐waves during WCT—without reference to SR ECG—are specific, but insensitive signs of VT 4 …”

“… 1 Premature ventricular beats have long been shown to uncover pathologic Q‐waves after myocardial infarction that is otherwise not evident on the ECG. 2 One more recent report describes a patient with remote anterior wall myocardial infarction and left bundle branch block where anterior Q‐waves appeared during VT. 3 Subramany et al reported that inferior Q‐waves during WCT—without reference to SR ECG—are specific, but insensitive signs of VT. 4 …”