Tissue velocity imaging with dobutamine stress echocardiography--a quantitative technique for identification of coronary artery disease in patients with left bundle branch block.

BACKGROUND: Patients with left bundle branch block (LBBB) exhibit abnormal septal motion that may limit the interpretation of stress echocardiograms and persuade the results of myocardial scintigraphy.

OBJECTIVES: We sought to analyze whether the use of tissue velocity imaging during graded dobutamine infusion is useful to identify and predict coronary artery disease (CAD) in patients with complete LBBB.

METHODS: In all, 62 patients with LBBB (mean age 62 years, 34 men) with suggested CAD underwent dobutamine stress-tissue Doppler echocardiography within 6 weeks before coronary arteriography. Dobutamine infusion started at 5 micro/kg/min and increased up to 40 micro/kg/min with additional atropine during submaximal heart rate responses. In addition to wall-motion analysis, pulsed wave tissue Doppler sampling of mitral annulus at 5 corners was performed at rest in the apical 4-chamber plus aorta and 2-chamber apical views. The measurements were repeated at low dose (10-15 micro/kg/min) and at peak stress. Tissue Doppler echocardiography measurements included early peak systolic velocity (PSV), postsystolic shortening (PSS) velocity, peak early diastolic velocity (Ve), and peak late diastolic velocity. The results were compared with 20 healthy subjects as a control group. Patients were classified into two groups according to angiographic results: LBBB with CAD (n = 32) and LBBB without CAD (n = 30).

RESULTS: There was no significant difference between LBBB groups in global wall-motion score index at rest; the delta changes in each group were almost similar during peak stress test (P > .05). In the LBBB with CAD group, PSV increased during peak stress to a smaller extent (6.3 +/- 1.1-7.2 +/- 2.0 cm/s, approximately 24% P < .03) than in non-CAD group (6.8 +/- 1.0-9.6 +/- 2.7 cm/s, approximately 46% P < .01). Similarly, Ve increased to a lesser extent in CAD group (deltaVe 1.6 +/- 1.7 vs 2.8 +/- 1.7 cm/s, approximately 25% vs 42% P < .0001). There were no significant difference in delta late diastolic velocity between LBBB and control groups or between each of them. PSS could be recorded at rest in 24 of 32 patients (75%) in CAD group and 17 of 30 patients (57%) in non-CAD group. In LBBB with CAD group, PSS was developed and significantly augmented from 4.7 +/- 3.1 to 6.3 +/- 3.4 cm/s (P < .001) during stress. Increment less than 2.5 cm/s in PSV and Ve during peak stress identified CAD with 88% sensitivity (for each) and 90% and 87% specificity, respectively. The cut-off values of PSS velocity greater than 4 cm/s at peak stress have strong diagnostic power for prediction of obstructive CAD in patients with LBBB (82% accuracy).

CONCLUSION: Tissue Doppler echocardiography with dobutamine stress allows a diagnostic benefit in the detection of CAD in patients with LBBB. The magnitude of change of PSV and Ve in addition to PSS are quantitative parameters to identify CAD in patients with LBBB where subjective wall-motion analysis failed.