The effect of intrathoracic heart position on electrocardiogram autocorrelation maps.

We studied the influence of the heart position in the thorax on the autocorrelation (AC) maps consisting of correlation coefficients between each pair of instantaneous electrocardiogram potential distributions over a time interval. We used a thorax-shaped electrolytic-filled tank with an isolated and perfused dog heart placed at positions spanning 5 cm on each space direction. The correlation coefficient between QRST AC maps was in the range of 0.92 to 0.99, whereas the correlation coefficient between the corresponding QRST integral maps was in the range of 0.55 to 0.87, proving that AC maps are less influenced by the heart position than integral maps. Thus, diagnostic indexes computed from the AC maps can be expected to be more specific to phenomena taking place in the myocardium than to criteria based directly on electrocardiogram amplitudes in various leads.