The relationship between development of retinopathy and heart rate turbulence in patients with diabetes mellitus

In spite of the fact that the overall mortality due to cardiovascular disease in the general population has decreased about 20% in the last decade, the mortality in patients with diabetes has increased with a similar percentage (190). Cardiovascular disease is the leading cause of death in diabetes (1). The benefits of screening for coronary atherosclerosis or silent myocardial ischemia is still controversial in clinically asymptomatic diabetic patients, although diabetes has been considered a coronary artery disease equivalent (4,44,55,78). Moreover, diabetes is known to be associated with a 2-4 fold increase in the risk of sudden cardiac death (5-8). This increase is, at least partly, due to cardiac events associated with diffuse coronary involvement of coronary artery disease and malignant arrhythmias associated with cardiac autonomic neuropathy. Therefore, the non-invasive techniques which will detect high risk individuals at early stage have become to a diagnostic requirement in diabetic patients. In this study, the relationship between heart rate turbulence as a noninvasive diagnostic method which has been shown to be associated with increased cardiovascular mortality, and diabetic retinopathy that could be determine as noninvasively is investigated. In the study, type-2 diabetes patients without overt clinical, electrocardiographic or echocardiographic heart disease were included. Patients with comorbid disease other than hypertension, and hyperlipidemia were excluded. Moreover, patients with stage 3 and 4 hypertensive retinopathy were excluded. A total of 60 diabetic patients included in the study, were divided into three sub-groups including non-retinopathic (n=22, 53.0±8.8 years, 68% female, 32% male), non-proliferative retinopathy (n=17, 56.0±9.0 years, 53% female, 47% male) and proliferative diabetic retinopathy (n=21, 55.9±8.5 years, 62% female, 38% male). Fundus examination was performed with slit-lamp method, results were confirmed by fundus fluorescein angiography. At least 24-hour Holter recordings were obtained from all subjects. There was no significant difference between the groups when TO and TS variables were evaluated in combination. However, TS was seen to be significantly decreased in patients with proliferative retinopathy, while TO was similar among all groups when evaluated separately with or without excluding the patients who have no ventricular premature beats.