Can tight control of blood sugar harm the heart?
Strict control of blood sugar in a diabetic is certainly good for the heart in the long run. It can reduce the risk of development of blocks in the blood vessels of the heart. Uncontrolled blood sugar levels for a long period can also damage the heart muscle (diabetic cardiomyopathy). Long term poorly controlled diabetes can harm the kidney (diabetic nephropathy). Kidney disease is now considered an important risk factor for development of blocks in the blood vessels of the heart (coronary artery disease) which can lead to heart attack.
Having said that, strict control of diabetes also carries a risk of blood sugar falling below normal levels (hypoglycemia) at certain times, especially if a meal is missed. A person with an unstable heart disease carries a risk of worsening when blood sugar falls below normal level. When the blood sugar falls below normal levels, the sympathetic nervous system is activated in an attempt to bring back the blood sugar to normal levels. Increased activity of sympathetic nervous system increases the heart rate and blood pressure. This in turn increases the workload of the heart, which can lead to worsening of heart function in a person who has pre-existing blocks in the blood vessels of the heart. The person may get chest pain, breathlessness and abnormalities of heart rhythm, all of which can be potentially dangerous. Hence, though good control of blood sugar is ideal for heart health in the long run, it is essential to avoid abrupt fall in blood sugar while aiming at optimal long term control of diabetes.