3-dimensional Poincare plots of the QT intervals-an approach to nonlinear QT analysis

The Poincare plots-a simple graphical, nonlinear method was implemented to express 24-h QT interval changes. The group of 23 pts with hypertrophic cardiomyopathy was analyzed (11 pts. with higher and 12 with lower risk of sudden cardiac death). The control group consisted of 10 healthy subjects. 24-h Holter ECG recordings were analyzed and RR and QT intervals were measured beat by beat. 3 dimensional QT and RR plots were constructed in the time delay coordinates. Three main forms of QT plots were observed, highly different in cases with hypertrophic cardiomyopathy compared to normals. Different shapes of QT and RR plots revealed a complex nonlinear relation of the QT and RR intervals.