Clinical and structural-functional characteristics of cardiac involvement in hypothyroidism and associated conditions

The dissertation examines the clinical and structural-functional characteristics of cardiac involvement in patients with hypothyroidism, including cases combined with associated conditions such as arterial hypertension, coronary heart disease, and obesity. Based on a clinical-statistical analysis, the study assesses the influence of isolated hypothyroidism and of concomitant diseases on morphofunctional parameters of cardiac activity, total cholesterol levels, and electrocardiographic indices. Structural and functional cardiac changes are compared in relation to the etiology, duration, severity, and compensation of hypothyroidism, the presence of prior thyrotoxicosis, and patient age. A mathematical model has been developed for calculating an integral indicator of the severity of cardiac involvement in hypothyroidism, which enables a differentiated approach to the management of such patients.

Relevance of the problem. In recent years, the incidence of thyroid insufficiency has increased worldwide. The prevalence of acquired hypothyroidism is 1–2% [162]. In 70–80% of patients with hypothyroidism, symptoms of cardiac involvement are observed, termed hypothyroid cardiomyopathy [42]. Numerous studies have examined cardiac activity in hypothyroidism. The majority of investigations into cardiac function in hypothyroidism have demonstrated an increase in left ventricular myocardial mass index, a decrease in ejection fraction and stroke index, thickening of the interventricular septum and posterior wall of the left ventricle, a reduction in the ratio of early diastolic flow velocity to atrial systolic flow velocity, and a prolongation of the isovolumic relaxation phase. In some cases, the development of hydropericardium has been noted [9, 63, 93, 205]. However, such studies have frequently included only patients of a particular age or sex. The majority of scholarly works have assessed systolic or diastolic myocardial function in isolation. Essentially all studies have been conducted in patients without concomitant cardiovascular pathology. In evaluating cardiac activity in patients with hypothyroidism, body weight, compensation status, disease duration, disease etiology, and a history of thyrotoxicosis have not been taken into account. Recent studies have established that in elderly patients with hypothyroidism, marked atherosclerosis of the aorta and major vessels, coronary heart disease (CHD), and angina pectoris frequently develop [154]. Some researchers have noted that arterial pressure elevation is characteristic of hypothyroidism [27]. There exist studies that have demonstrated that thyroid hormones regulate body weight and cholesterol levels [117, 144, 219]. However, the available literature provides insufficient data on the structural and functional characteristics of the myocardium in patients with hypothyroidism combined with CHD, arterial hypertension, and obesity. Of particular interest is the study of the influence of these factors, as well as of the severity, compensation, and etiology of hypothyroidism and of prior thyrotoxicosis on cardiac activity.

Aim of the study – to investigate the clinical and structural-functional characteristics of cardiac activity in patients with hypothyroidism in order to develop a system for the comprehensive assessment of the data obtained and to determine the severity of cardiac involvement.

Objectives of the study

1. To evaluate the clinical and structural-functional characteristics of cardiac activity in patients with hypothyroidism.

2. To identify the dependence of structural-functional indicators of cardiac activity on the etiology, duration, severity, and compensation of hypothyroidism, on prior thyrotoxicosis, and on patient age.

3. To investigate the influence of conditions associated with hypothyroidism (CHD, arterial hypertension, obesity) on the structural-functional indicators of cardiac activity in patients with hypothyroidism.

4. To develop a mathematical model for assessing the severity of cardiac involvement in hypothyroidism.

5. To investigate the influence of conditions associated with hypothyroidism (CHD, arterial hypertension, obesity) on total cholesterol levels.

Scientific novelty. For the first time, on the basis of a clinical-statistical analysis, it has been established that hypothyroidism without associated conditions causes the development of hydropericardium, hypercholesterolemia, and enlargement of the left atrial cavity. In hypothyroidism combined with associated conditions (arterial hypertension, CHD, obesity), an additional increase in left atrial size, left ventricular myocardial mass, and myocardial wall thickness, as well as the development of diastolic dysfunction, have been observed.

A direct dependence of left atrial size, left ventricular myocardial mass and wall thickness, and indices of diastolic function on age has been discovered. A direct dependence of left ventricular myocardial mass on the severity of hypothyroidism has been identified. An integral indicator for assessing the severity of cardiac involvement in hypothyroidism has been calculated. It has been established that CHD and arterial hypertension combined with hypothyroidism lead to an additional increase in total cholesterol levels.

Practical value. The assessment performed of the isolated influence of hypothyroidism and of its associated conditions (arterial hypertension, coronary heart disease, obesity) on cardiac structure and function makes it possible to identify the most important structural-functional indicators required for diagnosing the severity of cardiac involvement in hypothyroidism. The proposed method for calculating an integral indicator of the severity of cardiac involvement in hypothyroidism enables a differentiated approach to the management of patients with hypothyroidism.

Main statements defended.

1. Hypothyroidism without associated conditions causes the development of hydropericardium, hypercholesterolemia, and enlargement of the left atrial cavity.

2. In hypothyroidism combined with associated conditions (arterial hypertension, coronary heart disease, obesity), the development of left ventricular myocardial hypertrophy, left atrial dilatation, and diastolic dysfunction is observed.

3. Optimal assessment of the severity of cardiac involvement in hypothyroidism is possible by determining an integral indicator based on a mathematical model.