How diabetes and cardiovascular disease go hand in hand.
Some 160 million people across the world suffer from diabetes mellitus (DM). This number is likely to increase exponentially in the years to come. The rate of increase may be more in India than elsewhere owing to a certain ethnic predisposition in the Indian population. The expected pandemic scale may be accounted for by higher detection rates, newer diagnostic facilities, increasing longevity and better public awareness about it. Dietary indiscipline, urbanisation, global isation and the resultant stress are other contributing factors.
Diabetes mellitus is not only a metabolic disorder but a cardiovascular disorder (CVD). Approximately 40 per cent of diabetics have an associated CVD. It is evident from various Indian registries that 40 per cent of patients who are admitted for CVD conditions such as heart attacks, or are being treated with the aid of coronary artery bypass graft surgery (CABG) or balloon angioplasty (PTCA), have DM. CVD and DM often coexist and are like cousins. Diabetes mellitus often leads to cardiovascular diseases, manifesting as heart attacks, strokes or peripheral vascular diseases. “If winter comes, can spring be far behind?” wrote Shelley in ‘Ode To The West Wind.’ If diabetes comes, vascular disease usually follows.
By the time a diabetic person comes in for tests, the vascular, or blood vessel, damage has already begun. Depending on the sugar level and the associated risk status of a patient, vascular disease is detected at various stages of such damage. So what is actually obvious at presentation is the tip of the iceberg.
DM is the most common cause of heart attacks in those below 45 years of age. In pre-menopausal women, diabetes takes away the element of gender protection that is otherwise available. Primary prevention in diabetics should be similar to secondary prevention in non-diabetics. This means that diabetics who have not suffered heart attacks should be treated on the same lines as non-diabetic persons who have suffered a heart attack. DM and CVD have common antecedents such as genetic predisposition and environmental factors — the so-called “common coil” hypothesis.
Shakespeare wrote in Hamlet: “When sorrows come, they come not single spies, but in battalions.” This is apt in the case of diabetes as DM brings with it other risks such as high blood pressure and lipid abnormalities (elevated levels of bad cholesterol types such as LDL and triglycerides and total cholesterol, besides low levels of HDL, the good cholesterol). Such “clustering” of risk factors compound CVD risk. Diabetics have a higher tendency for clot formation and abnormal functioning of the inner smooth lining of blood vessels, or endothelial dysfunction.
Asymptomatic coronary artery disease (CAD), involving the blood vessels supplying the heart muscles, is more common in diabetics than in others. Patients may not have any premonitory symptoms of heart attacks, as the pain perception is affected due to nerve damage caused by DM.
Early detection can prevent or delay vascular complications. The root cause of vascular damage is insulin resistance, insulin being the hormone that controls the metabolism of sugar. Insulin resistance precedes manifest diabetes by several years. The “deadly pentad” constitutes obesity, DM, high blood pressure, lipid abnormalities and CVD.
In cases of longstanding and uncontrolled DM, coronary arteries develop multiple blocks, and diffuse disease involving the entire vessel. The disease affects predominantly the ends of the vessels. The vessel caliber becomes small. These vessels are more prone to calcification. There is a high tendency for cholesterol plaques to rupture in diabetic vessels with resultant clot formation in the lumen of the vessels, which could be life threatening. Because of impaired blood supply to it, the heart’s pumping capacity comes down.
Such features, characteristic of diabetic vascular disease, will impede chances of success after treatment by balloon angioplasty (PTCA) or CABG surgery. Many patients may not even be suitable candidates for either of these procedures if they present themselves to the physician too late.
The key steps are early detection and control of blood sugar levels. Public awareness should be ensured through the media. Periodic personal health check-ups are essential. Camps can help reach out to the population for whom medical facilities are inaccessible.
Diabetic camps often tend to be one-day affairs meant for publicity and may fail to solve the problem. It is better to adopt a village or a designated population, such as an industrial population, on a long-term basis and follow up continuously over years for detection, control and prevention of complications due to DM. Non-governmental organisations and public-private partnership arrangements could help in this.
Who should follow up the patients? Physician training is important. The number of diabetologists is low in comparison to the large population of diabetics. Cardiologists are busy with the tertiary care of patients already suffering cardiovascular complications. The result is the emergence of a new breed of physicians called “cardiodiabetologists,” who are interested both in clinical cardiology and diabetology and have the ability to deliver optimal care. General practitioners should also be trained to reach out and cater to the needs of diabetic patients in the semi-urban and rural areas. At the European Society of Cardiology meeting, one hall was seen to be dedicated to the field of “Cardiodiabetology.”
In a nutshell, India faces an epidemic of DM, because of the ethnic and genetic predisposition. A majority of the cases develop cardiovascular complications. Early detection, optimal control of blood sugar levels and anticipated detection and management of complications are important. Regular follow-up and control of co-morbid conditions such as hypertension and lipid abnormalities is essential. Public awareness, physician training and specialist supervision are mandatory. Through proper measures, cardiovascular complications can certainly be delayed in diabetics.
(Dr. I. Sathyamurthy, an interventional cardiologist, is Director, Department of Cardiology, Apollo Hospitals, Chennai. He received the Padma Shri in 2000 and the Dr. B.C Roy National Award in 2001. He was conferred a D.Sc. (Honoris Causa) by the Dr. MGR Medical University, Chennai, in 2008).