Significance of anterior Q waves in left anterior fascicular block--a clinical and noninvasive assessment.

BACKGROUND

Electrocardiographic (ECG) Q waves in V leads (V2 or V3) 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 V2 and/or V3 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.