Polarcardiographic study of inferior myocardial infarction: global projection of heart vector.

The sensitivity of electrocardiographic, vectorcardiographic and polarcardiographic criteria for inferior myocardial infarction was studied. ECG and Frank system VCG were recorded in 50 normal cases and 40 cases of inferior myocardial infarction, whose acute phase was documented by typical electrocardiographic and serum enzymatic changes. The records were made from one month to 16 years after acute attacks. Polarcardiograms were obtained by a specially-designed analogue computer from X, Y and Z signals of the VCG, and recorded at a paper speed of 1000 mm/sec by Mingograph. The polarcardiographic tracings were measured at every 5 msec after onset of the QRS wave, and plotted on the Aitoff's equal-area projection. In normal cases, the QRS vectors plotted on Aitoff's projection passed through the narrow area between 15 to 35 msec after the QRS onset. Electrocardioraphic diagnosis of myocardial infarction was correctly made in 22 cases (55%), and by VCG the sensitivity was improved to 32 cases (80%). Polarcardiographic diagnosis was made in 33 cases (82.5%). Global plots of heart vector on Aitoff's projection were a useful display to visualize the sequential changes of heart vector. In inferior myocardial infarction, the QRS vector passed through the more superior portion to normal, and the diagnosis was accurately made in 33 cases (82.5%).