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Theoretical grounds of integral vectors of ventricular depolarization and repolarization and their sum, i.e., the spatial ventricular gradient, have been studied. A systematic description and biophysical interpretation of these parameters are presented based on the distribution of cardiomyocyte action potential parameters in the inhomogeneous bidomain model of the myocardium. Recent medical studies have shown high efficiency and predictive value of the ventricular gradient, its constituents and related parameters, such as the angle between the con-stituents, the acceleration of repolarization, etc. Simple examples for a myocardial strip clarify the relationship between the action potential parameters and the resulting ventricular gradient. An explanation with graphic illustration is given for the very informative decartogram of repolarization acceleration. The results obtained here are useful in the modeling of vectorcardiograms for various pathological conditions of the heart ventricles and for various characteristics of the cardiomyocyte action potential, which determine its shape.

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Introduction. The prevalence of arterial hypertension (AH) among the adult population of Russia is high; up to 48% of deaths are due to its complications. Recently, prognostic indicators of the electrocardiogram (ECG) have attracted the attention of researchers. One of them is the QRS-T spatial angle (sQRS-Ta).The aim of the work is to study what clinical, laboratory and echocardiographic parameters are associated with increased sQRS-Ta in patients with AH.Material and methods. The study included 240 AH patients (48% men), mean age 62 ± 11 years. The study did not include patients with valvular disease, bundle branch block, preexcitation and ventricular pacing. Orthogonal leads were synthesized from digital ECGs in 12 leads and sQRS-Ta was calculated as a spatial angle between the integral QRS and T vectors. sQRS-Ta ≥ 90° was considered enlarged. We assessed the associations sQRS-Ta ≥ 90° with the following indicators by the method of logistic regression: sex; the presence of cardiovascular diseases; 5 age groups; overweight, obesity; smoking; heart rate (HR); systolic blood pressure (SBP), diastolic blood pressure; pulse blood pressure; blood glucose; total cholesterol; end-diastolic dimension (EDD) of the left ventricle (LV), LV wall thickness, relative LV wall thickness, left ventricular myocardial mass (LVMM), LVMM/body surface area (BSA); LVMM/height in the degree of 2,7, the presence of LV diastolic dysfunction.Results. According to univariate logistic regression, sQRS-Ta ≥ 90° associations were found with age, SBP, obesity, heart rate, LV EDD, LVMM, LVMM/BSA, and LVMM/ height2,7. In multivariate logistic regression models, the contribution of SBP ≥ 140 mmHg (odds ratio (OR) 2,22, 95% CI 1,20–4,10; p=0.01), age 55–64 years (OR 1,87; 1,01–3,44; p=0 .04), increased LV EDD (OR 2,70; 95% CI 1,27–5,72; p=0.01) and HR (OR 2,27; 95% CI 1,10–6,05; p =0.01) was independent.Conclusions. According to multivariate analysis, independent predictors of an increase in sQRS-Ta in patients with AH were SBP ≥ 140 mm Hg, an increase in LV EDD, HR > 80 beats/min, and age 55–64 years.

Aim. To explore the features of vectorcardiograms (VCG) of patients with essential hypertension complicated by chronic heart failure with reduced left ventricular ejection fraction (CHFrLVEF). Materials and methods. We analyzed VCGs of 70 hypertensive patients with CHFrLVEF and 275 hypertensive patients without clinical signs of CHF and with LVEF50%. We assessed the presence of rhythm and conduction disturbances, and the parameters of the synthesized VCG, i.e., module of the maximum QRS vector, planarity index of the spatial QRS loop (P/S), and spatial angle between the integral QRS and T vectors (sQRS-Ta). Results. In hypertensive patients with CHF, certain conditions were detected more often as compared with hypertensive patients without CHF, i.e., atrial fibrillation (AF) in 52.9% vs 5.1%; p0.0001, and left bundle branch block (LBBB) in 38.6% vs 0.4%; p0.0001. The module of the maximum QRS vector and sQRS-Ta were significantly greater and P/S was significantly less in VCGs of patients with CHF. ROC-analysis showed that the presence of AF and LBBB just as VCG parameters assessed in this study provide clear discrimination between hypertensive patients with or without CHF both in the group as a whole and in the subgroups (1) without LBBB, (2) with sinus rhythm, and (3) with AF. sQRS-Ta was the most informative parameter (threshold 137, sensitivity 91%, specificity 92%). The P/S indicator at the optimal threshold value 0.92 was characterized by lower specificity (68%) with rather high sensitivity (79%). Conclusion. AF, LBBB, increased module of the maximum QRS vector and sQRS-Ta, and decreased P/S index are present in hypertensive patients with CHFrLVEF as compared with patients without CHF.

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