Relationship between changes in the electrical axis of the heart during inspiration and the structural and functional state of the heart according to echocardiography in patients with precapillary pulmonary hypertension

   Introduction. A deep breath causes a whole range of physiological effects that are reflected in the electrocardiogram.

   The purpose of the study is to assess the position of the electrical axis of the heart during deep inspiration compared to quiet breathing in patients with precapillary pulmonary hypertension and compare these data with echocardiographic characteristics of the structural and functional state of the heart.

   Materials and methods. The study included 40 patients with idiopathic pulmonary hypertension and 40 patients with chronic thromboembolic pulmonary hypertension. Echocardiography assessed the size of the heart chambers, systolic and diastolic function of the right and left ventricles, pulmonary artery pressure, pulmonary vascular resistance and indicators of cardiovascular coupling.

   Results. The values of the electrical axis of the heart during free breathing were 106° [84°; 123°], on inspiration – 89° [87°; 120°] (p = 0.68). In 50 (62.5 %) patients, during a deep inspiration, the electrical axis of the heart shifted to the left from the original one, and in 30 (37.5 %) patients – to the right. In patients with a displacement of the electrical axis of the heart to the left from the original, compared with the others, the end-diastolic size of the left ventricle, end-diastolic and end-systolic volumes of the left ventricle, stroke volume, cardiac output were statistically significantly lower, and the eccentricity index, pulmonary vascular resistance and effective aortic stiffness – significantly larger.

   Conclusion. In patients with precapillary pulmonary hypertension, two variants of changes of the heart electrical axis during deep inspiration were identified: a shift to the right from the original and to the left from the original. Patients with a displacement of the electrical axis to the left from the original were characterized by a significantly greater increase in pulmonary vascular resistance, a decrease in left ventricular volumes, stroke volume and cardiac output.

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