Intense Exercise and Native Collateral Function in Stable Moderate Coronary Artery Disease: Incidental, Causal, or Clinically Important?

1431 In the report by Möbius-Winkler et al in this issue of Circulation, 60 patients with coronary artery disease (CAD) by angiogram and fractional flow reserve (FFR) ≤0.75 were randomly assigned to supervised highor moderate-intensity exercise or a sedentary group for 4 weeks at specialized rehabilitation centers. At angiogram, a coronary artery was occluded by low-pressure balloon occlusion for 1 minute without therapeutic percutaneous coronary intervention (PCI). The coronary pressure beyond the occlusion as a ratio to aortic pressure is an index of collateral back perfusion distal to the occlusion termed the collateral flow index (CFI), although flow is not measured, only pressure. Both highand moderate-intensity training significantly improved CFI and exercise threshold for angina in comparison with the sedentary subjects. Although collaterals on angiogram were not expressly addressed, the moderate, nonocclusive stenosis did not cause reported visible collaterals on the angiogram, thereby implying improved native microcollaterals as the mechanism attributed to improved exercise performance.