Is the system underlying the electrical signal of the human heart a non-linear deterministic system?

Percutaneous transluminal coronary angioplasty (PTCA) is a unique clinical setup by which the effects of acute cardiac ischemia in humans may be investigated. The present study was designed to assess qualitative changes in ECG waveforms during acute ischemia induced by balloon inflation (BI). 16 patients underwent PTCA; we analyzed and compared the effect of BI on body surface ECG, as well as ECG derived phase planes, and the quality of distribution of the Poincare´ sections (PS). We found that only 50% of the ECG tracings demonstrate morphological changes during BI. In 12 of 16 patients (75%) the PS distribution was qualitatively changed during BI. We conclude that such a change implies of a nonlinear deterministic feature of the system underlying the electrical signal of the human heart