Angina vs Myocardial Infarction: Understanding The Key Differences

Angina and myocardial infarction (MI) are both cardiovascular conditions that result from reduced blood flow to the heart muscle, but they differ significantly in terms of underlying causes, severity, and treatment approaches. Understanding these distinctions is crucial for timely diagnosis and appropriate medical intervention.

1. Differences in Pathophysiology and Severity

Angina typically occurs due to partial blockage or narrowing of the coronary arteries caused by atherosclerosis. This restricted blood flow can lead to chest discomfort or pain—often described as pressure, squeezing, or burning—especially during physical exertion or emotional stress. The pain may radiate to the arms, neck, jaw, or back. In most cases, symptoms subside within 3–5 minutes after resting or using nitroglycerin.

In contrast, myocardial infarction involves a complete or near-complete blockage of a coronary artery, often triggered by the rupture of an atherosclerotic plaque. This rupture leads to the formation of a blood clot, which cuts off oxygen supply to part of the heart muscle, causing tissue death. Symptoms tend to be more intense and prolonged, lasting more than 20–30 minutes, and are not relieved by rest or nitroglycerin. Common signs include severe chest pain, shortness of breath, profuse sweating, nausea, and a sense of impending doom.

2. Variations in Electrocardiogram (ECG) Findings

During an episode of angina, typical ECG changes include ST-segment depression and T-wave inversion, which usually return to normal once the episode resolves. However, in the case of variant (Prinzmetal's) angina, transient ST-segment elevation may be observed due to coronary artery spasm.

On the other hand, in myocardial infarction, ECG changes are more pronounced and persistent. The most notable findings include significant ST-segment elevation (in ST-elevation myocardial infarction or STEMI), new left bundle branch block, or the development of pathological Q waves, all of which indicate damage to the heart muscle.

3. Biomarker and Cardiac Enzyme Changes

One of the key diagnostic differences lies in the presence of cardiac biomarkers. During angina, cardiac enzymes such as troponin and creatine kinase-MB (CK-MB) remain normal, indicating no permanent damage to the heart muscle.

Conversely, in myocardial infarction, there is a clear elevation in these cardiac enzymes, reflecting myocardial cell injury and necrosis. Elevated troponin levels, in particular, are considered the gold standard for confirming a heart attack.

Conclusion

While both angina and myocardial infarction share similar symptoms and underlying causes, they represent different points on the spectrum of coronary artery disease. Prompt recognition of symptoms and appropriate diagnostic testing are essential for distinguishing between the two and initiating life-saving treatment when necessary.