Acute myocardial infarction in patients with concomitant hypothyroidism: clinical features and heart rate variability during inpatient treatment

Abstract

Objective: to evaluate the features of the clinical course, as well as heart rate variability (HRV) during inpatient treatment in patients with ST-segment elevation myocardial infarction (STEMI) and concomitant newly diagnosed hypothyroidism.Materials and methods: the study included 133 patients with STEMI aged 40 to 88 years who were admitted to the cardiology department. Depending on the presence of newly diagnosed hypothyroidism syndrome, all patients were divided into 3 groups: group 1 consisted of patients with STEMI without hypothyroidism syndrome (n=57), group 2A — patients with STeMI and subclinical hypothyroidism (n=42) and group 2B — patients with STeMI and manifest hypothyroidism (n=34). Clinical symptoms and complications in the acute period of MI were evaluated in all patients, and Holter ECG monitoring (XM ECG) was performed.Results: during hospital treatment, patients with concomitant manifest hypothyroidism showed more frequent development of cardiac arrhythmias such as paroxysmal atrial fibrillation (AF) (p<0.05), supraventricular extrasystole (NE), paroxysmal supraventricular tachycardia (LVT) (p<0,05). When assessing the risk of early complications in the acute period of MI, higher scores were recorded in patients with manifest hypothyroidism (p<0.05). The analysis of HRV indicators showed that in the studied patients with concomitant manifest hypothyroidism, despite the presence of an acute period of MI, activation of the parasympathetic link of the ANS (autonomic nervous system) prevails in the regulation of heart rhythm, unlike in patients of the control group and the group with subclinical hypothyroidism, in whom, on the contrary, the influence of the sympathetic link of the ANS prevails.Conclusion: during hospitalization, patients with manifest hypothyroidism were statistically significantly more likely to develop supraventricular cardiac arrhythmias, and a higher risk of cardiovascular complications in the acute period of MI was determined compared with both the control group and the group of patients with subclinical hypothyroidism. In patients with concomitant manifest hypothyroidism, the activation of the parasympathetic link of the ANS in the regulation of heart rhythm is more pronounced, in contrast to patients in the control group and the group with subclinical hypothyroidism, in whom, on the contrary, the influence of the sympathetic link of the ANS prevails.