Diabetes is the fourth main cause of death in most countries.People with diabetes are three times more likely to require hospitalization than without this condition.Diabetes is the leading cause of death due to CVD and stroke.More than 3.2 million deaths worldwide are due to diabetes every year, i.e. more than 6 deaths every minute.
Nearly 65% of patients with diabetes die of cardiovascular/cerebrovascular disease.People with diabetes who walk two hours a day can lower their mortality risk as well as their risk of dying from CVD. Physical inactivity is estimated to cause about 16-20% cases of diabetes.One percent decrease in HbA1c results in 14% reduction in the incidence of ACS.Management of ACS with diabetes may be more difficult than management of ACS alone, since the complications associated with diabetes are difficult to treat. Mortality and morbidity due to ACS with diabetes is much more higher than ACS occuring alone.
The mortality and complications are much higher in patients continued on OADs with or without control than those treated with insulin when ACS ensues. IV insulin infusion should be commenced for acute management in first 24-48 hours. Patients with type 1 diabetes should continue their usual basal insulin daily to reduce the risk of diabetic ketoacidosis if IV insulin is interrupted.
Role of Insulin in ACS
Insulin reduces free radical generation and proinflammatory action and also decreases proinflammatory cytokines, TNF alpha concentration and increases anti-inflammatory cytokines and supresses Plasminogen activator inhibitor-1 (PAI-1) which facilitates clot dissolution in acute MI.
Insulin prevents adhesion circulating leucocytes by suppression of above mediators of inflammation and prevents apoptosis of myocardial tissue and improves lipid metabolism and thereby protects myocardium and improves its function.
Heart in Diabetes
Hyperglycemia increases circulating free fatty acids (FFAs), which are toxic to the myocardium and induce arrhythmias.It causes osmotic diuresis resulting in volume depletion and further compromise myocardial function.It increases blood viscosity and tendency for vascular thrombosis.
The myocardium depends on aerobic metabolism and, unlike skeletal muscle, must not develop an appreciable oxygen debt.The preferred fuel for the myocardium is free fatty acids (FFAs) during fasting, glucose postprandially, and lactate and FFAs during exercise.
If the myocardium switches to anaerobic metabolism, such as during ischaemia, the balance of substrate is disturbed, FFAs and their unoxidised products accumulate and may lead to myocardial cell death. Hence while treating ACS,Insulin is infused as a Dextrose-Normal Saline infusion unlike insulin-saline infusion in the treatment of hyperglycemic crisis.Insufficient insulin (qualitative/quantitative) with hyperglycemia reduces myocardial contractility, promotes cardiac failure and arryhthmias.
EFFECTS OF HYPERGLYCEMIA ON HEART
Management of Diabetes
Initial Management in first 24-48 hours
The protocol of insulin therapy is little different than in usual situations, otherwise in a patient who is already on insulin and develops ACS.
DIGAMI Protocol
INFUSION :
? 500ml 5% glucose with 80 IU of soluble insulin(1U/6ml).
? Start with 30ml/h.
? Check blood glucose after 1 hr.
? Adjust infusion rate according to the protocol and aim for a blood glucose level of 7-10mmol/litre (126- 180mg/dl)
? Blood glucose should be checked after 1hr if infusion rate has been changed, otherwise every 2hr.
If the initial decrease in blood glucose exceeds 30%, the infusion rate should be left unchanged if blood glucose is >11mmol/litre (198mg/dl).
| BLOOD GLUCOSE LEVELS | ACTION |
| 1) > 15mmol/litre (> 270 mg/dl) | Give 8U of insulin as intravenous bolus injection and increase infusion rate by 6ml/hr. |
| 2) 11 to 14.9 mmol/litre (198-268.2 mg/dl) | Increase infusion rate by 3ml/hr. |
| 3) 7 to 10.9 mmol/litre (126-196.2 mg/dl) | Leave infusion rate unchanged. |
| 4) 4-6.9 mmol/litre (72-124.2mg/dl) | Decrease infusion rate by 6ml/hr. |
| 5) < 4mmol/litre (<72mg/dl) | Stop infusion for 15mins. Then test blood glucose and continue testing every 15 mins until blood glucose is more than 7 mmol/litre (126mg/dl). |
| In the presence of symptoms of hypoglycemia, administer 20ml of 30% glucose intravenously. The infusion is restarted with infusion rate decreased by 6ml/hr when blood glucose is > 7mmol/litre (126mg/dl) |
Insulin should be continued for atleast 6 weeks before resuming to OAD s since the arrhythmias following myocardial infarction can be prevented if Insulin is used after discharge from CCU.
Insulin is always insulin and it always acts.Change over to insulin from OADs in ACS even though the blood glucose is within normal limits.
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