Objectives: The purpose of the present study was to assess whether brief, repeated coronary artery occlusions during balloon angioplasty induce a myocardial ischemic protective effect.
Background: In animals, brief coronary artery occlusions preceding a more prolonged occlusion result in reduced infarct size. Whether myocardial protection against ischemia could also occur in humans during angioplasty remains controversial.
Methods: Thirteen patients with a proximal left anterior descending coronary artery stenosis with no angiographic collateral circulation underwent percutaneous transluminal coronary artery balloon angioplasty. Three 120-s balloon inflations separated by a 5-min equilibration period were performed. For each inflation, intracoronary ST segment modifications, septal wall thickening (M-mode echocardiography), left ventricular pressures and time derivatives were measured at baseline and at 30, 60 and 90 s after balloon inflation and 120 s after balloon deflation.
Results: Intracoronary electrocardiographic analysis showed that the time course of the maximal ST segment elevation was identical at each inflation, as were wall motion changes assessed by the decrease in septal wall thickening. For the first and last inflations, peak positive dP/dt decreased significantly by 13 +/- 9% (mean +/- SD) and 14 +/- 13%, whereas peak negative dP/dt increased by 23 +/- 15% and 22 +/- 10%, respectively (all p < 0.01 from baseline values). The relaxation time constant, tau, was altered similarly during the different inflations, from 44 +/- 6 to 74 +/- 13 ms and from 57 +/- 13 to 77 +/- 13 ms (all p < 0.001) for the first and last inflations, respectively. Left ventricular end-diastolic pressure increased to the same level after each inflation. In contrast to other hemodynamic variables, tau and left ventricular end-diastolic pressure did not return to baseline values in between the inflations, which may be due to myocardial stunning.
Conclusions: In patients with proximal left anterior descending coronary artery stenosis and no evidence of collateral circulation, brief periods of ischemia, such as those used during routine coronary balloon angioplasty, do not provide any protection against myocardial ischemia.