Normally when blood supply to a portion of the heart muscle is inadequate (ischaemia) you will suffer from angina characterised by one of the following - • acute chest pain, • feeling tight in your chest or • pain radiating to your left arm, shoulder or neck. If the blood supply is cut off completely you will suffer a heart attack. These symptoms are well known to most of us and we will seek urgent medical help if it occurs. However, there are many in the world who suffer from ischemic episodes without realising it as they do not have symptoms normally attributed to angina. This is known as silent ischaemia. They may also suffer a heart attack with no warning. People who have had previous heart attacks or those with diabetes are especially at risk of developing silent ischemia. It is said that "silent" (asymptomatic) myocardial ischemia is the most common manifestation of coronary heart disease (CHD), accounting for more than 75 percent of ischemic episodes during life. Painless myocardial infarctions on the other hand vary a little from silent ischaemia or infarction. Although there may not be chest pain or radiating pain in painless myocardial infraction, other symptoms relating to the condition may be present. They are: • Profuse sweating • Palpitation (due to increased sympathetic activity) • Breathlessness (due to cardiac failure) • Feel faint (syncope due to hypotension) • Extreme fatigue (due to poor tissue perfusion) • Sometimes patients become unconscious because of severe cerebral hypoperfusion (not enough blood reaching the brain). Both silent ischaemia and painless ischaemia occur in poorly controlled diabetics and non-diabetics over the age of seventy. The reason is because the pain conducting nerve fibres are paralysed in diabetes and old age and hence you do not feel the pain. If any of the symptoms described above is seen, it is essential to have your heart checked urgently. Diabetics must be particularly warned about this. Investigations: • Urgent ECG will normally show changes relating to ischaemia or infarction. • Blood Test to check cardiac enzymes and proteins should be done even when the ECG appears normal. The blood test will measure the levels of enzymes and proteins that are linked with injury of the heart muscle. They include the enzyme creatine kinase (CK), and the proteins troponin I (TnI) and troponin T (TnT). Their levels will rise if the heart has suffered an injury. If the ECG and blood tests are inconclusive two further tests could be done to make sure your heart is healthy. Ambulatory Electrocardiogram: • I f your doctor is able to arrange this, a small recorder will be attached by a belt to your waist. The machine will be connected by wires to your chest. It will continuously record the electrical activity of your heart as you carry on with your normal activities over a period of 24 to 48 hours. If your heart is affected during this period your doctor will be able to pick this up through the recording on the machine. Stress ECG : • This will be the ultimate test to check if your heart is normal and healthy. Here you will be connected to the machine by a few leads. The ECG is then recorded while you are on a treadmill. The stress levels of your heart will be increased slowly by making you walk faster and if necessary with the treadmill at an upward incline. • This test should only be done with a cardiologist nearby as he will know when to stop the test if you are in trouble or will be able to resuscitate you immediately if you suffer from a cardiac episode. Complication and mortality are more often seen in painless infarction than when you have associated chest pain. The probable cause for high mortality is that patients normally ignore their symptoms when they have no chest pain. They usually continue with their routine activities, if symptoms are bearable. Continued activity in the presence of myocardial infraction will lead to complications like irregular heart beat, cardiac failure and death. This is very common in India compared to other countries. It is estimated that more than 900 Indians under the age of 30 die from it everyday. It is more difficult to identify someone with silent ischemia or infarction as they do not have any symptoms recognised as originating from the heart. High risk populations (diabetics and elderly) should be made aware of this and should be advised on regular health checks and how they should protect their heart. It is important that everyone becomes aware of this silent killer. If you have had any of the symptoms mentioned with no accompanied chest pain, do not assume that your heart is not the cause. Seek advice and have your heart checked. Prof. S. Vaithinathan, MD., DM Cardiology.