Abstract
Objectives: To determine the frequency of altered cardiac repolarization by measuring the heart rate corrected QT interval in COPD patients.
 Setting: Department of Medicine at LUMHS hospital Hyderabad/Jamshoro.
 Study Design: Descriptive Cross sectional study. 
 Duration of Study: 6 months from 01-03-2019 to 31-08-2019.
 Methods: A total of 232 patients with severe acute exacerbation of COPD were included in this study. A 12 lead ECG was performed. QT intervals were measured on a resting ECG tracing in lead II. The QT interval was measured manually from the starting point of the QRS complex to the terminal point of the down slope of the T wave.
 Results: A total of 232 patients with COPD were included in this study. Most of the cases were above 50 years of age. The average age of the patients was 53.74±4.35 years. There were 92.67% (215/232) male and 7.33% (17/232) female. Out of 232 patients, 21.14% were current smoker and 75.86% were ex-smoker. A QTc interval >0.44 seconds was considered abnormally prolonged. Frequency of altered cardiac repolarization by measuring the heart rate corrected QT interval in COPD patients was 31.47% (73/232). Rate of altered cardiac repolarization was not significant among different age groups (p=0.641). Rate of altered cardiac repolarization was significantly high in male as compare to female (33.5% vs. 5.9%; p=0.018). This was not significant between obese and non-obese groups (p=0.100). Rate of altered cardiac repolarization was significantly high in former smoker (p=0.0005) and those patients whose duration of COPD was above 15 years (p=0.0005).
 Conclusion: Patients with hypoxic chronic obstructive pulmonary disease (COPD) have evidence of a subclinical parasympathetic autonomic neuropathy, with apparent preservation of sympathetic function. Measuring heart rate corrected QT interval (QTc) test is repeatable, easy to perform and a sensitive indicator for autonomic dysfunction in breathlessness individuals with COPD.
Highlights
Chronic obstructive pulmonary disease (COPD) remains a major public health problem
Rate of altered cardiac repolarization was significantly high in former smoker (p=0.0005) and those patients whose duration of COPD was above 15 years (p=0.0005)
The chronic airflow limitation characteristic of COPD is caused by a mixture of small airway disease and parenchymal destruction, the relative contributions of which vary from person to person [1]
Summary
Chronic obstructive pulmonary disease (COPD) remains a major public health problem. It has significant extra pulmonary effects that may contribute to the severity in individual patients. The chronic airflow limitation characteristic of COPD is caused by a mixture of small airway disease (obstructive bronchiolitis) and parenchymal destruction (emphysema), the relative contributions of which vary from person to person [1]. Chronic obstructive pulmonary disease (COPD) is associated with an increased risk of cardiovascular morbidity and mortality [7,8,9]. Previous population-based studies suggested that patients with COPD have a two to three fold increased risk of sudden cardiac death (SCD) [10]. Altered cardiac repolarization may result in an increased risk of malignant ventricular arrhythmias and sudden cardiac death. They found that QT interval was prolonged in 31.9% of the COPD patients
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