RT Journal Article SR Electronic T1 Identifying Successful Coronary Collaterogenesis Using PET Myocardial Perfusion Imaging: Ischemic Zone Coronary Flow Capacity Improves in Patients with Chronic Total Occlusion Treated with External Counter Pulsation JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 3383 OP 3383 VO 63 IS supplement 2 A1 Merhige, Michael A1 Davis, Cory A1 Keppler, Julia A1 Wilson, Kevin A1 Knapp, Connor YR 2022 UL http://jnm.snmjournals.org/content/63/supplement_2/3383.abstract AB 3383 Introduction: FDA approved External Counterpulsation (ECP) therapy reduces angina and improves coronary collateral flow index, as measured invasively using intracoronary wedge pressure. However, there is no noninvasive way to measure coronary collateral flow capacity in patients with chronic total occlusion. <u>Hypothesis</u>: Coronary collateral flow capacity (CCFC) is enhanced by ECP and can be measured noninvasively with quantitative PET myocardial perfusion imaging, by comparing stress perfusion in the post-stenotic bed during vasodilator stress, which reduces supply side pressure revealing coronary steal, compared with demand ischemia, using iv dobutamine, which maintains supply side pressure.Methods: Ten patients with angiographically documented CTO underwent 35 one-hour sessions of ECP and were advised to exercise vigorously thereafter. Patients were studied in a Positron HZLR or Attrius-L PET camera using Rubidum-82 at rest, and at 6 minutes after completion of a 4-minute iv dipyridamole (DIP) infusion, or at one minute after regadenoson iv bolus injection. A separate rest / iv dobutamine +/- atropine (DBT) stress PET was performed on a subsequent day, with stress tracer injection at the usual endpoints of significant ischemic symptoms or ST depression, or achievement of 85% of predicted maximal heart rate.Using FDA approved HeartSee software, absolute coronary blood flow in ml/min/g was calculated, using the first 2 minutes of data after tracer injection for the arterial input function with regions of interest placed in left atrium and/or aorta. The last 5 minutes of the total 7-minute acquisition were used to measure myocardial uptake. Absolute myocardial perfusion was calculated on a per pixel basis and displayed as Mercator projections depicting each quadrant of the left ventricle, at rest, during peak hyperemia, and as a third set of images, their ratio, depicting per pixel coronary flow reserve (CFR).Thereafter, a fourth set of parametric images were displayed, obtained by plotting peak absolute stress perfusion against the corresponding CFR for each pixel, to produce coronary flow capacity images (CFC), divided into 5 individual, clinically relevant “band-widths” ranging from values seen in normal young volunteers, to those seen during vasodilator stress induced ischemia. Kolmogorov-Smirnov statistical analysis was used to compare the change in CFC obtained with vasodilator vs. demand ischemic stress.Results: The size of the potentially ischemic zone at risk, defined as per cent LV mass with potentially ischemic coronary flow capacity (blue and green on CFC maps) fell for all patients treated with ECP, revealing collateral flow capacity, when DIP stress was compared with demand ischemic stress using DBT ( 32.8% vs 4.5% p < 0.001 ). One patient demonstrated minimal improvement in CFC despite ECP therapy (not shown). He underwent coronary arteriography, which demonstrated a new flow limiting stenosis in the supply side vessel, which was successfully stented.All 10­­ ECP treated patients improved minimal whole heart and lowest quadrant mean perfusion: DIP vs. DBT = 0.5 vs 1.1 ml/mn/g, p<0.01, and 1.0 v 1.9 ml/mn/g, p<0.001, demonstrating improved absolute perfusion into the ischemic zone with demand ischemic stress compared with vasodilator stress, consistent with the presence of collateral vessel arteriogenesis into the ischemic CTO bed. Peak nonischemic perfusion was also higher with DBT compared with DIP stress: maximal whole heart and highest quadrant: 3.4 vs 2.2 and 2.5 vs.1.7 ml/mn/g p<0.002, suggesting DBT (with atropine) is at least as potent a stimulus for maximal coronary blood flow as DIP in these severely diseased patients.Conclusions: Successful coronary collaterogenesis can be identified and quantified noninvasively in patients with chronic total coronary occlusion using PET MPI.