Assessment of ECG Changes in Hypothyroid Patients and Their Correlation with Serum TSH Levels

Hypothyroidism, a common endocrine disorder, is known to influence cardiovascular physiology, particularly through its effects on cardiac electrophysiology. Electrocardiographic (ECG) abnormalities, such as bradycardia, low-voltage complexes, and prolonged QT intervals, are frequently observed. The relationship between the severity of hypothyroidism, often measured by serum thyroid-stimulating hormone (TSH) levels, and the extent of ECG changes remains a subject of clinical relevance.

This cross-sectional observational study was conducted over a period of six months at a tertiary care hospital. A total of 100 hypothyroid patients (TSH > 5.0 µIU/mL) aged between 20 and 60 years were enrolled. Patients with known cardiac diseases, electrolyte imbalances, or on medications affecting cardiac conduction were excluded. ECG parameters, including heart rate, PR interval, QRS duration, QT interval, and presence of low-voltage complexes, were recorded. Serum TSH levels were measured using chemiluminescence immunoassay. Statistical analysis was performed using Pearson's correlation and Chi-square tests to assess the relationship between ECG findings and TSH levels.

Out of the 100 patients, 70% were females and 30% were males. The mean age was 38.4 ± 9.6 years. Bradycardia (heart rate < 60 bpm) was observed in 48% of patients, prolonged QTc in 36%, and low-voltage complexes in 22%. A significant positive correlation was found between serum TSH levels and QTc interval (r = 0.41, P = 0.002), and a negative correlation with heart rate (r = -0.53, P < 0.001). The incidence of ECG changes was significantly higher in patients with TSH levels above 10 µIU/mL (P < 0.05).

Hypothyroidism is associated with distinct ECG abnormalities, the severity of which correlates with rising TSH levels. Regular ECG monitoring in hypothyroid patients, especially those with elevated TSH, is essential for early detection of potential cardiac complications and timely intervention.