Significance of anterior Q waves in left anterior fascicular block—A clinical and noninvasive assessment

Background : Electrocardiographic (ECG) Q waves in V leads (V 2 or V 3 ) pose a diagnostic challenge in the presence of left anterior fascicular block (LAFB). Benign Q waves in the absence of coronary artery disease (CAD) primarily due to LAFB have been described. This study evaluates Q waves in the presence of LAFB. Hypothesis : Anterior Q waves in the presence of LAFB may not be indicative of myocardial infarction (MI). Methods : From 1990 to 1997, ECGs of 236 male patients with LAFB were analyzes for presence of Q waves in the V leads. Records were reviewed for evidence of CAD. Of 236 patients with LAFB, 61 (26%) had Q waves in the V leads. In this group, 31 patients were available for further analysis. Results : Of the 31 patients with Q waves in the V leads who were available for further study, LAFB was present in 22 patients (71%) and LAFB plus right bundle‐branch block (RBBB) were present in 9 (29%). Of 20 patients with Q waves due to MI, 13 (65%) had LAFB and 7 (35%) had LAFB plus RBBB. Of 11 patients with benign Q waves, 9 (82%) and 2 (18%) had LAFB and LAFB plus RBBB, respectively. Benign Q waves were noted in 5.3% (11/206) patients with LAFB. The mean duration of Q waves and Q‐wave location limited to V 2 and/or V 3 are 0.029 s and 64% versus 0.053 s and 15% in benign versus pathologic Q waves, respectively. Conclusion : Patients with LAFB in the absence of MI may have Q waves in the V leads that are approximately 0.02 s in duration and restricted to one or two leads. This anomaly may represent a variation of conduction in the initial 0.02 s QRS vector due to LAFB.