New possibilities of electrocardiography: evaluation of the vectorcardiographic QRS loop planarity in patients with myocardial infarction

The aim of the work is to evaluate the planarity of the QRS loop and its relationship with systolic dysfunction of the left ventricle in patients in the subacute period of myocardial infarction (MI).Materials and methods. The ECG of 265 patients with a diagnosis of acute myocardial infarction were analyzed. The control group consisted of 55 healthy individuals. The planarity index was calculated as the ratio of the area of the QRS loop projection onto the plane (the polar vector of the QRS loop) and the true area of the QRS loop in space using a synthesized vectorcardiogram.Results. In patients with MI, the planarity index was significantly lower than in healthy individuals: 0,87 [0,71; 0,94] and 0,96 [0,93; 0,97], respectively, p < 0,0001. Weak but significant correlations between the planarity index and the left ventricular ejection fraction (LVEF, r = 0,41, p < 0,001) and with the number of affected segments of the left ventricle according to echocardiography (r = −0,43, p < 0,001) were found. In patients with MI, the planarity index was lower in the presence of pulmonary edema in the acute period of MI (0,68 [0,54; 0,86]; without pulmonary edema 0,88 [0,76; 0,94], p < 0,001), and in the presence of a history of chronic heart failure (0,79 [0,61; 0,88]; without chronic heart failure 0,88 [0,75; 0,94], p = 0,007). In patients with MI of both anterior and inferior localization, the planarity index was significantly lower with LV EF < 50% compared with LV EF ≥ 50%. The planarity index was significantly lower in anterior MI than in inferior MI. Conclusion. In patients in the subacute period of MI, there is a decrease in the QRS loop planarity index, which correlates with the volume of myocardial damage, a decrease in LV EF, and the presence of acute and chronic heart failure. The QRS loop planarity index was significantly lower in anterior MI than in inferior MI.