Impact of diabetic retinopathy on cardiac outcome after coronary artery bypass surgery in India

Kumar, S (2014) Impact of diabetic retinopathy on cardiac outcome after coronary artery bypass surgery in India. Doctoral thesis, Aravind Eye Hospital and Postgraduate Institute of Ophthalmology, Madurai.

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Abstract

Diabetic retinopathy(DR) is a frequent and early sign of microvascular complication of diabetes, and the risk of retinopathy is directly related to the degree and duration of hyperglycemia . Coronary artery disease is the leading cause of death in diabetics. Coronary artery bypass graft surgery (CABG) is the preferred strategy for coronary revascularization in patients with diabetes mellitus and multivessel coronary artery disease (MVD). However, even after CABG, the long-term outcome among diabetics is suboptimal as compared with among nondiabetics. This unfavorable prognosis is believed to be related to more rapid progression of atherosclerosis within native coronary arteries and grafts, a high prevalence of myocardial infarction (MI) and persistence or recurrence of congestive heart failure among diabetics who have undergone CABG. Recently, epidemiologic studies have reported that patients with severe DR have a high risk of death from coronary artery disease (CAD). Therefore diabetics with retinopathy could constitute some proportion of candidates for CABG. However, little is known about the prognostic value of DR among diabetics after CABG in Indian population. This study will attempt to assess the impact of DR on the longterm outcome of CABG among diabetics in Madurai, India. INTRODUCTION: Diabetes poses a major health problem throughout the world and is recognised as one of the top five leading causes of death in most developed countries. The developing countries also face this threat and by the year 2025, three-quarters of the world’s 300 million adults with diabetes will be from the developing countries1. India and China would contribute to one thirds of its morbidity. The reason for the diabetes epidemic experienced in India may be because of the genetic predisposition, rapid urbanization and changes in lifestyle – eventually leading to insulin resistance1. The contributing factor for increased insulin resistance may be the Asian Indian phenotype which is known for its propensity for higher rates of abdominal obesity and increased visceral fat. Diabetic retinopathy (DR) is a vascular disorder which affects the microvasculature of the retina. DR occurs both in type 1 and type 2 diabetes mellitus. While almost all type 1 individuals will develop some form of DR after 15 years of diabetes, 75 percent of type 2 individuals will develop the same under similar circumstances. Diabetic retinopathy is primarily classified into non proliferative DR (NPDR), formerly termed simple, or background retinopathy, and proliferative diabetic retinopathy (PDR). The mildest form of NPDR is characterized by increased vascular permeability. The moderate form is characterised by dot shaped haemorrhages and venous dilation while the severe form shows the beginning of vascular closure as characterised by intra retinal microvascular abnormalities, which is an increased risk for developing PDR , new vessels develop in the retina which will bleed , leading to vitreous haemorrhage and blindness. Visual impairment in diabetic retinopathy occurs due to diabetic macular edema (DME) and vitreous haemorrhage. DME is defined as retinal thickening/hard exudates within 500 microns of the centre of the macula and is due to increased permeability of retinal vessels leading to macular oedema and retinal thickening. Sudden vitreous haemorrhage from the unstable new vessels resulting in total or partial visual loss or from pre-retinal haemorrhage/fibrosis or traction at the macula is another cause for visual impairment. AIMS : To assess the impact of diabetic retinopathy on cardiac outcome after coronary artery bypass graft surgery. OBJECTIVES: To prospectively assess 18-month cardiac outcome after CABG in diabetics with various stages of retinopathy, as compared with those without retinopathy. RESULTS AND ANALYSIS: A total of 325 patients were referred to the Department of Cardiothoracic Surgery for CABG from January 1st 2011 to December 31st 2011 was 325.Of these, 218 patients were found to be diabetic, accounting for 67% of patients referred for CABG. Out of these, 126 diabetic patients (57%) who were willing to be a part of the study were recruited as participants in the study. Informed consent was obtained from the participants. Others declined to participate due to unwillingness to travel or family circumstances which did not allow them to participate in this study. DISCUSSION: In 1855, Eduard Jaeger, an Austrian physician, was the first to painstakingly portray the retinal findings associated with diabetes in his seminal work “Beitrage zur Pathologie des Auges”. With a newly developed direct ophthalmoscope, he produced one of the first atlases containing 21 color plates of fundus paintings and described a “roundish” or oval yellowish spots and full or partial thickness extravasations through the retina in the macular region of a diabetic patient. Jaeger findings of the association between diabetes and retinal changes were controversial and were not adopted by the medical community. The debate as to whether macular changes were directly related to diabetes or whether they were caused by atherosclerosis and hypertension was unresolved at the beginning of the 20th century, until Arthur James Ballantyne, suggested that diabetic retinopathy represents a unique form of vasculopathy and his work showed for the first time the role of capillary wall alterations in the development of diabetic retinopathy as well as the presence of deep waxy exudates in the outer plexiform layer. SUMMARY AND CONCLUSION: The analytical results pertain to 126 subjects who consented to participate in this study. Demographic data gathered included age, gender and height & weight (to enable calculation of BMI). Comprehensive medical history included prior myocardial infarction (MI), history of angina, smoking, hypertension and treatment with insulin and oral hypoglycemic agents. Clinical data of the study participants included fasting blood sugar level (mg/dl), post prandial blood sugar level (mg/dl), HbA1c, lipid profile (HDL,LDL, TGL), blood urea & serum creatinine, systolic & diastolic blood pressure was collected at baseline, 3 months, 6 months, 12 months and 18 months follow up. All the above mentioned data was collected from patients using a structured proforma. One week prior to CABG, the study subjects underwent a comprehensive ophthalmic evaluation at Aravind Eye Hospital, Madurai. Grading of retinopathy was done using the International Diabetic Retinopathy Disease Severity Scale. Those subjects in serious risk of losing vision due to proliferative diabetic retinopathy were first treated by the ophthalmologist and the CABG was postponed for a period of 2-3 weeks in such instances. RECOMMENDATIONS: A multidisciplinary approach involving screening of fundus in diabetic patients undergoing CABG would offer a better prognostic indicator. Conversely, the diabetics who undergo routine ophthalmological examination should be screened for cardiac status. In addition to appropriate vision care, the detection of retinopathy might now also warrant a fuller cardiac evaluation and closer follow-up to prevent the development of adverse cardiac outcome. Given that an ophthalmic fundus evaluation is an inexpensive, quick and non invasive way of prognosticating the outcome of CABG. It is recommended that diabetic patient undergoing CABG is advised to undergo the same. CONCLUSION: In this study in the initial 6 months follow up after CABG in patients with and without retinopathy, there were no adverse cardiac events. But, this study is planned for 18 months follow up, and we need to wait for that period to assess the influence of severity of diabetic retinopathy on cardiac outcome.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: Diabetic retinopathy; cardiac outcome; coronary artery bypass surgery; India
Subjects: MEDICAL > Ophthalmology
Depositing User: Devi S
Date Deposited: 14 Feb 2018 12:03
Last Modified: 14 Feb 2018 12:03
URI: http://repository-tnmgrmu.ac.in/id/eprint/5704

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