Collateral recruitment and "warm-up" after first exercise in ischemic heart disease

Background Proposed mechanisms for "warm-up" after angina on first exercise include ischemic preconditioning and collateral recruitment. The aim of th is study was to determine whether patients with ischemic heart disease and well-developed coronary collateral vessels have a greater warm-up response than those with no visible collateral vessels. Methods and Results Fifteen patients with a total coronary occlusion and co llateral vessels and 18 patients with a single coronary artery stenosis and no angiographically visible collateral vessels were studied. Warm-up was m easured as the difference in ST depression on the second compared with the first of 2 sequential treadmill exercise tests separated by 10 minutes of r est. There was a trend for the duration of second exercise to increase more in patients with occlusion than in those with stenosis (+1.3 vs +0.54 minu tes, respectively, P = .087). In both groups, ST depression was less on sec ond exercise than on first exercise. The size of this decrease was greater in the occlusion group than in the stenosis group. ST depression at equival ent submaximal exercise decreased by 0.52 vs 0.19 mm, respectively (P = .04 9). The rate of increase in Si depression during exercise decreased by 1.08 versus 0.55 mm/min, respectively (P = .034). These differences were less a fter adjustment for ST depression on first exercise (P = .11 and P = .063, respectively). Conclusions The trend for a greater decrease in ST depression on second com pared with first exercise in the patients with total coronary occlusion sug gests that an increase in collateral flow is a mechanism for warm-up after first exercise in ischemic heart disease.