Alternans of ventricular gradient during percutaneous transluminal coronary angioplasty

We evaluated the influence of local myocardial ischemia induced by acute coronary occlusion during percutaneous transluminal coronary angioplasty (PTCA) on the ventricular gradients (VG) and investigated whether 2:1 alternans of VG occurs. Twenty-seven patients with angina pectoris, who had one-vessel coronary artery stenosis, were studied. The VG of each consecutive heartbeat before, during, and after PTCA over a 22-second interval was calculated using a microcomputer. The standard deviation and coefficient of variation of magnitude were used as indices of VG variability. Frequency-domain analysis of time series consisting of beat-to-beat VG magnitude for a 22-second interval was also performed by the maximum entropy method. The standard deviation and coefficient of variation of VG magnitude during PTCA were significantly greater than those before and after PTCA (P <.01, P <.01, respectively), and the indices before PTCA were also significantly greater than those after PTCA (P <.05). The maximum power spectrum peaks around 0.5 cycles/beat during PTCA were significantly greater than those after PTCA (P <.01); this suggests that the enhancement of VG alternans is reflected by 2:1 alternans of the action potential in the acute local ischemic myocardium during PTCA.