Abstract 2080: Differing Electromechanical Response to Dobutamine Stress Differentiates Ischaemic from Non-Ischaemic Cardiomyopathy
Background. Resting 2D wall motion abnormalities do not reliably distinguish ischemic from non-ischemic dilated cardiomyopathy (DCM). Dobutamine stress echocardiography (DSE) using wall motion score index (WMSI) identifies coronary artery disease (CAD) in DCM, but the technique is subjective and complicated by left bundle branch block (LBBB). Left ventricular long axis motion is sensitive to ischemia and activation. We compared electromechanical changes in long axis function with WMSI for detection of CAD in DCM, with or without LBBB.
Methods. 73 patients with DCM, 48 with CAD (16 LBBB), 25 without CAD (10 LBBB) were studied during DSE. Electromechanical delay (onset of QRS to onset of segmental shortening: q-OS) from long axis echograms were measured at rest and peak stress and compared with WMSI. Post-ejection shortening (PES) was measured as amplitude of shortening after end-ejection.
Results. In non-ischemic DCM: q-OS shortened with stress (from 113±7ms to 80±8ms), even when LBBB was present (from 158±5ms to 106±5ms). This earlier phase shift in segmental shortening was associated with reduction in PES (from 1.0±0.2mm to 0.4±0.1mm, all p<0.001). In ischemic DCM: q-OS failed to shorten with stress (from 124±4ms to 130±6ms, p=NS), even when LBBB was present (156±10ms to 168±11ms, p<0.05). Delayed segmental shortening was associated with increased PES during stress (from 0.9±0.1mm to 1.8±0.2mm, p<0.001). Failure to shorten q-OS (by 25ms) detected CAD with sensitivity 90% and specificity 88%, which was significantly greater than the sensitivity and specificity for changes in WMSI (67% and 76% respectively, p<0.001). Even in LBBB, failure to shorten q-OS (by 37ms) detected CAD with sensitivity 93% and specificity 96%.
Conclusions. Long axis DSE is a quantifiable non-invasive technique for assessing effects of stress in DCM. It differentiates ischemic from non-ischemic cardiomyopathy with high sensitivity and specificity. It may thus be a useful and simple adjunct to a standard dobutamine stress test for detecting CAD in patients with DCM, particularly with co-existing LBBB.