Changes in the electrical axis of the heart during inspiration in patients with suspected chronic thromboembolic pulmonary disease

The use of simple functional tests can increase the electrocardiogram sensitivity for detecting pulmonary hypertension (PH). The aim of the work is to evaluate changes in the electrical axis of the heart (EAH) during inhalation in patients with proven chronic thromboembolic PH (CTEPH) or suspected CTEPH, referred for right heart catheterization (RHC). Materials and methods. The study included 80 patients who underwent RHC according to clinical indications: 25 men and 55 women aged 52 ± 13 years. EAH was assessed when recording electrocardiogram during quiet breathing and on deep inhalation. Results. CTEPH (mean pulmonary artery pressure >20 mm Hg) was present in 69 patients. In the group without PH, in all cases, the EAH shifted to the right during inhalation, and in the group with PH – to the right in 33 (48%) cases and to the left in 36 (52%) cases. The difference in the EAH values during free breathing and inhalation had direct correlations with systolic, diastolic and mean pulmonary artery pressure, systolic right ventricle pressure and pulmonary vascular resistance (r=0.6-0.7; p<0.0001) and inverse correlations with stroke volume and cardiac output (r=-0.3; -0.4; p<0.01). In ROC analysis, both the EAH values during free breathing (>92°) and its changes during inhalation (>-6°) allowed us to separate the subgroups with and without PH with a sensitivity of 62-65% and a specificity of 100% (area under the ROC curve ± standard error 0.88 ± 0.04). Conclusions. In patients with CTEPH/suspected CTEPH in the subgroup without PH, the EAH shifted to the right during inhalation, and in the group with PH in 33 cases (48%) – to the right, and in 36 cases (52%) – to the left. The difference in the EAH values during free breathing and inhalation had reliable direct correlations of moderate strength with the mean pulmonary artery pressure and pulmonary vascular resistance. The values of the EAH during free breathing and its changes during inhalation made it possible to separate subgroups with and without PH with a sensitivity of 62–65% and a specificity of 100%.