Can an ECG miss a heart attack? Cardiologist explains how to detect silent heart attacks

TIMING OF HEART ATTACK

If an ECG is performed very early in a heart attack, before significant damage has occurred, it might not show the typical changes. In some cases, even with a heart attack, the ECG can appear normal, particularly if the damage is minor or if the ECG is taken at a time when the heart is not experiencing significant electrical disturbance.

TYPE OF HEART ATTACK

Some heart attacks may not always present with clear ECG changes. Especially silent heart attacks, which may have few or no noticeable symptoms, can be missed by ECG if they don’t cause significant electrical changes. That’s why in suspicious cases, where the patient is symptomatic but the ECG is not indicative, we keep the patient under observation for 12 to 24 hours and conduct serial ECGs.

WHAT ARE OTHER CONFIRMATORY TESTS

We also test troponin, which is a protein that is released into the bloodstream when heart muscle is damaged. In fact, we do a repeat troponin test after 90 minutes to reconfirm an attack. While troponin is a highly sensitive and specific marker for heart muscle damage, it also takes time to rise in the bloodstream after a heart attack. A single negative troponin test, especially soon after the onset of chest pain, may not be enough to rule out a heart attack. That’s why a repeat is necessary.

Other options are ultrasound, which can assess heart function and identify any damage or abnormalities. Coronary angiography, an invasive procedure, can visualise the coronary arteries and identify blockages.

WHAT ARE PREVENTIVE CHECKS

Be careful about tracking your hypertension, cholesterol and obesity from age 25. Check for a genetic disorder called familial hypercholesterolemia (FH), an inherited condition. Such people tend to have increased levels of LDL cholesterol regardless of their weight, diet, habits and exercise and may need better control methods through medication. Check for lipoprotein (a), high levels of which can be risky even if other cholesterol levels are within the normal range. They accelerate plaque deposition. An extended lipid profile test should give you their levels. Keep your LDL range less than 50 mg/dL, 30mg/dL for those with a family history. Keep triglycerides or blood fats low.

Take the calcium score test. This test involves a simple CT scan and does not need an invasive procedure with dyes. It measures the amount of calcified plaque in your arteries, which in turn leads to heart attacks and strokes. A high score puts you in the at-risk category but it doesn’t mean you will get a heart attack the next moment. It indicates a probability so that medical intervention with drugs and lifestyle modification can be started early.

(Dr Singh is chairman, cardiac sciences, Max Healthcare)