Dobutamine compared with dipyridamole stress PET myocardial perfusion imaging identifies coronary collaterogenesis after external counter pulsation in patients with chronic total coronary occlusion

1654 Objectives: External counterpulsation (ECP) is an FDA approved treatment for patients with refractory angina who are not candidates for interventional revascularization, such as those with chronic total occlusion (CTO). While ECP has been shown invasively to induce coronary collateralization (COL), there is no noninvasive method for assessing the presence or efficacy of coronary collateral vessels into the ischemic zone. The objective of our study was to identify coronary collaterogenesis using PET myocardial perfusion imaging in patients with CTO. Methods: We sought to identify COL by comparing myocardial perfusion during vasodilator stress with i.v. dipyridamole (DIP), which reduces supply side pressure into the ischemic zone at risk (ZAR) in the presence of CTO, revealing coronary steal, vs. demand ischemic stress with i.v. dobutamine/atropine (DOB), which maintains supply side pressure. Six patients with CTO were treated with 35 sessions of ECP, using the conventional clinical protocol, and studied with both DIP and DOB stress PET myocardial perfusion imaging. Coronary flow capacity (CFC), which integrates absolute rest and stress flow with coronary flow reserve on a per pixel basis, was measured objectively with FDA approved HeartSee software. Results: As shown in the Table, all 6 patients demonstrated a decrease in the size of the potentially ischemic ZAR defined as moderate or severely reduced CFC, when CFC with DIP was compared with DOB: 29.5% LV mass vs. 4.5%; p < 0.02. Four of six patients also demonstrated significant improvement in global CFC by Kolmogorov-Smirnoff analysis of whole heart frequency histograms of CFC under DIP vs. DOB stress. One of the two patients who did not improve global CFC underwent coronary arteriography demonstrating a new flow limiting stenosis in the supply side vessel, which was successfully stented. The Image shows the same patient status post ECP treatment studied with DIP and DOB stress. The DOB divided by DIP parametric images in the third and fourth rows depict a quantitative map of coronary collateral flow capacity. Conclusions: ECP treatment is associated with improved coronary collateralization in patients with CTO, which can be identified noninvasively with quantitative PET myocardial perfusion imaging.