What Does an ECG Look Like for Coronary Heart Disease

Coronary heart disease (CHD) does not always present with a distinct or characteristic electrocardiogram (ECG) pattern. The ECG findings can vary widely among individuals and may even appear completely normal in some cases. Below are some of the most commonly observed ECG presentations associated with CHD:

No Observable ECG Changes

In certain cases, especially when a patient is not experiencing angina or any acute cardiac event, the ECG may appear entirely normal. This does not rule out the presence of underlying coronary artery narrowing or disease. The absence of ECG abnormalities should not be interpreted as the absence of CHD, as the condition may still exist without producing detectable electrical changes in the heart.

Non-Specific ECG Alterations

Some patients may display non-specific changes such as T-wave inversion. Normally, T-waves are upright in most leads. When inversion occurs, particularly in conjunction with ST-segment depression, it may suggest myocardial ischemia. These changes are more significant when they are dynamic—meaning they appear during symptoms and resolve when symptoms subside. Such variability supports the possibility of ischemic heart disease even if the resting ECG appears normal.

Acute Myocardial Infarction Patterns

ST-Segment Elevation as a Key Indicator

In more severe cases, such as acute myocardial infarction (heart attack), ECG changes are more pronounced. ST-segment elevation in two or more contiguous leads is a hallmark sign of an acute ST-elevation myocardial infarction (STEMI). This elevation may evolve over time, followed by ST-segment depression, loss of the R wave, development of pathological Q waves, and persistent T-wave inversion. These progressive changes are strong indicators of coronary artery disease and myocardial damage.

Old Myocardial Infarction and Chronic Changes

In patients with a history of heart attack, especially those with complications like ventricular aneurysm, chronic ECG changes may persist. These include persistent ST-segment elevation and loss of R waves in the precordial leads (V1–V4). These findings are often indicative of scarred or non-functional myocardium and are important markers of past ischemic events.

Stress Testing and Additional Diagnostic Tools

While resting ECGs are useful, they are not always conclusive for diagnosing CHD. Exercise stress testing is a common diagnostic tool used to provoke ischemic changes. During the test, a drop in the ST segment of more than 1 mm in two adjacent leads, lasting for over a minute, is considered a positive result. This suggests the presence of significant coronary artery disease and warrants further investigation.

Limitations of ECG Alone in CHD Diagnosis

It is important to note that some ECG abnormalities, such as T-wave inversion or flattening, may be suggestive of ischemia or coronary disease but are not definitive. Some patients with abnormal ECGs may have normal coronary arteries upon angiographic evaluation. Therefore, ECG findings must be interpreted in the context of clinical symptoms, risk factors, and additional diagnostic modalities such as echocardiography, nuclear stress tests, or coronary angiography to make a definitive diagnosis.