Abstract 3135: Relative accuracies of Vasodilator Myocardial Contrast Echocardiography and Radionuclide Single Photon Emission Computed Tomography for the diagnosis of Coronary Artery Disease in patients with Left Bundle Branch Block
Background Complete left bundle branch block (LBBB) may be associated with flow limiting coronary artery disease (CAD). Perfusion abnormalities have been noted to occur both at rest and during vasodilator stress on single photon emission computed tomography (SPECT) even in the absence of CAD, likely due to partial volume effect. We hypothesized that MCE, by virtue of its superior spatial resolution, will be more accurate for the detection of CAD compared to SPECT.
Methods Accordingly 53 patients (mean age 66 ± 8yrs, mean LVEF 43 ± 18%) with LBBB with symptoms suggestive of CAD and scheduled for coronary arteriography underwent simultaneous vasodilator 99mTc-sestamibi SPECT and MCE. Perfusion defects, both at rest and stress, were scored on a matching 17 segment left ventricular model for both imaging modalities. Coronary arteriography was performed within a median time of 96 days.
Results Of the 53 patients, 18 (33%) demonstrated CAD (≥ 50% diameter stenosis in a major artery) of which SPECT detected 16 and MCE 15 (89% and 83% respectively; p=ns). However, of the 35 patients with no CAD, SPECT detected perfusion defects in 17 (49%) patients whilst MCE did so only in 2 (6%) (p<0.0003). Similarly on the vascular territory level (anterior and posterior circulations), of the 27 vessels with CAD, SPECT detected 19 (71%) and MCE detected 23 (85%), p=ns. However, SPECT was significantly (p=0.001) less specific compared to MCE (68% vs. 90% respectively). Superior overall specificity and accuracy of MCE compared to SPECT is due to its superior specificity in the anterior territory.(Table⇓)
Conclusion MCE and SPECT demonstrate comparable sensitivity for detection of CAD in patients with LBBB. However, both specificity and accuracy of MCE are significantly superior to SPECT.