Profile of Electrocardiograph in Type 2 Diabetes Patients and Its Correlation to Cardiac Dysautonomia

INTRODUCTION: Diabetes mellitus is a multi-metabolic disorder that shares the common phenotype of hyperglycemia. Globally, Diabetes Mellitus is a major threat to human health. The number of people with Diabetes has increased alarmingly since 1985 and the rate of new cases is escalating. In 1985, an estimated 30 million people worldwide had diabetes; by 2003, it was estimated that approximately 194 million people had diabetes, and this figure is expected to rise to almost 350 million by 2025. Type 2 Diabetes is a major health problem in India. The WHO has highlighted that India currently holds the top spot for most no. of people with diabetes and would continue to hold the top position in future also. The estimated burden in India would be around 79.4 million by the year 2030. Autonomic dysfunction in diabetes is common. Abnormal cardiovascular test suggesting cardiovascular autonomic neuropathy is present in 16-40% of diabetic population. Patients with diabetic cardiac autonomic neuropathy are more prone for sudden cardiac death probably due to silent myocardial ischemia or infarction or due to primary malignant ventricular arrhythmias. The ECG, which reflects the electrical activity of heart, is liable to show abnormalities in diabetics more often than in non-diabetics by virtue of the more attendant factors that are more commonly seen in diabetics. In this context the factors that modify impulse generation, conduction, nervous control of heart, vascular supply of the myocardium, state of myocardium, all required to be considered individually. There is a higher prevalence of RBBB and AV block in diabetics that cannot accounted by the increased incidence of ischemic heart disease alone. Higher incidence of these blocks is seen independent of ischemic heart disease. Autonomic dysfunction is often asymptomatic. Hence diagnosing asymptomatic cardiac autonomic dysfunction, a precursor of symptomatic cardiac autonomic neuropathy will help in a long way in taking sufficient precaution to delay (or) arrest its progression by various measures. Recent observations noted that corrected QT interval (QTc) in surface ECG seems prolonged in diabetics with autonomic neuropathy and postulations are made that it may be one of the cause of sudden death or a compounding factor for the predisposition of malignant ventricular arrhythmias. This highlights the importance of simple noninvasive investigation like ECG in diagnosing asymptomatic cardiac autonomic dysfunction. This study is performed to study the various ECG abnormalities in type 2 Diabetic patients to estimate the prevalence of cardiac dysautonomia in type 2 Diabetic patients by various ECG markers and to compare with the age and sex matched controls. AIMS OF THIS STUDY: 1. To study the various ECG abnormalities in Type 2 Diabetes mellitus patients as compared to controls. 2. To study the prevalence of cardiac dysautonomia in type 2 diabetes mellitus patients by various ECG markers. MATERIALS AND METHODS: MATERIALS: Study Population: 1. Study group- 50 patients with type 2 diabetes mellitus. 2. Control group- 50 age and sex matched controls. Place of Study: Out patients department, Department of Medicine, Department of Diabetology, Stanley Medical College, Chennai-1. Period of Study: Feb 2008 to September 2009. METHODS: All the study population and controls were subjected for thorough physical examination. Blood samples were drawn and subjected to estimation of causal blood glucose and renal function tests. INCLUSION CRITERIA: Type 2 diabetes patients except the ones with the following exclusion criteria: EXCLUSION CRITERIA: 1. Age > 60 years, 2. Documented CAD/ischemic heart disease, 3. Documented valvular heart disease/congenital heart disease, 4. Hypertension, 5. Uremia, 6. Drugs-any drug which alters the sinus node impulse generation and AV conduction, 7. Features of hypo and hyperthyroidism, 8. Fever and features suggestive of infections, 9. Chronic obstructive pulmonary disease and other chronic lung disorders, 10. Parkinsonism and other movement disorders, 11. Dyselectrolytemia. RESULTS: 1. The mean resting heart rate of study (diabetics) group (84.2±12.86bpm) is significantly higher (p<0.05) than that of control group (75.2±10.65). 2. The R-R interval of study group (725.4±121.49msec) is significantly lower (p<0.05) than that of controls (815.4±114.41msec). 3. The PR interval of study group (162.4±11.67msec) is significantly (p<0.05) higher than that of control group (138.2±16.99msec). 4. The QRS duration is prolonged in study group (68.4±11.67msec) as compared to that of controls (65±8.69msec). But it is not statistically significant. (p>0.05). 5. The QRS axis of study group is more towards left (26.4±30.54 degrees) as compared to that of controls (67.6±27.82 degrees) which is statistically significant(p<0.05). 6. The QTc interval in study group (405.16±40.38 msec) is significantly prolonged (p<0.05) than the controls (365.38±25.3 msec). 7. The ECG changes of ischemia and infarction is significantly higher in the study group (26%&10% respectively) when compared to the control group (12%&6%). 8. Prevalence of asymptomatic heart disease in the study group (27.78%) is higher when compared to the control group (11.11%). 9. The prevalence of intraventricular conduction blocks in diabetics (8%) is higher than that of controls (2%). 10. 28% of study group have abnormal HRBD suggesting early parasympathetic dysfunction. 11. 6% of the study group show significant postural drop of SBP (>30 mm Hg) on standing which probably indicates sympathetic nervous system dysfunction. 12. There is a positive correlation between QTc prolongation and significant postural fall in SBP (>30 mm Hg). All the three patients had significant QTc prolongation. CONCLUSIONS: The following ECG manifestations were present in type 2 Diabetic patients compared to non-diabetic population. 1. High resting heart rate, 2. Prolongation of PR interval, 3. Increased prevalence of ischemia and infarction, 4. Increased incidence of asymptomatic IHD, 5. Left ward QRS axis, 6. No significant difference in QRS duration. Following manifestations suggestive of cardiac dysautonomia in type 2 Diabetics Were: 1. Abnormal HRBD≤10bpm, 2. Prolonged QTc interval (QTc>460 msec) in 8%, 3. Significant postural drop in SBP (>30 mm Hg) in 6%, 4. There is a positive linear correlation between QTc prolongation (QTc>460 msec) and postural drop on SBP (>30 mm Hg). Thus, the evaluation of various cardiovascular reflexes in type 2 diabetics gives an easy and feasible bedside technique to determine the presence of cardiac dysautonomia