Abstract 4705: Detection of Significant Left Anterior Descending Coronary Artery Disease in Pacemaker Dependent Patients Utilizing Real Time Perfusion Imaging During Dobutamine Stress Echocardiography
Non-invasive methods of detecting left anterior descending (LAD) coronary artery disease (CAD) in patients who are pacemaker dependent (PD) are limited because of right ventricular (RV)-pacing induced left ventricular wall thickening (WT) abnormalities involving the septum and apex. Real time perfusion echocardiography (RTPE) analyzes myocardial blood flow (MBF) changes with high resolution (<2 mm) during intravenous (IV) infusions of ultrasound contrast, and can potentially identify whether significant LAD is present in PD patients during dobutamine stress (DS). 54 consecutive PD patients who were being evaluated for CAD using DS echocardiography with RTPE were identified. Dobutamine was infused to 30 u/kg/min, but had to be combined with incremental RV pacing to achieve 85% predicted maximum heart rate. Perfusion and WT in the septum and apex were assessed at rest and at peak DS. MBF in the LAD territory was considered abnormal if a >4 second delay in contrast replenishment occurred during a continuous 3% Definity infusion at rest, or >2 second delay at peak DS. Quantitative coronary angiography (QCA) was performed to assess for significant CAD (>50% diameter stenosis considered significant). Outcomes were analyzed by examining coronary events (death, non-fatal myocardial infarction, or need for coronary revascularization) at a median follow-up of 20 months post DS. WT abnormalities in the septum and apex due to RV pacing were noted in 43 of the patients (80%), while the remaining patients exhibited normal WT. Of those with pacing-induced WT abnormalities, 25 (58%) had a MBF abnormality at peak stress, while 18 (42%) had normal myocardial contrast enhancement. Overall, the positive predictive value (PPV) of abnormal MBF by RTPE for the detection of LAD CAD in PD patients was 85%. Patients with a MBF abnormality in the LAD territory by RTPE had a coronary event rate of 17 % at follow up, while patients with normal MBF responses during DS had no events at follow up (negative predictive value 100%). RTPE is helpful in detecting CAD in the LAD territory of patients who are PD. A normal MBF response predicts an excellent cardiac outcome, irrespective of WT responses.