Can ECG Detect Myocardial Infarction?

ECG is a crucial diagnostic tool for detecting myocardial infarction (MI), and in most cases, it can help identify whether a patient is experiencing a heart attack. The ability to detect MI through ECG largely depends on the type of heart attack and the changes observed in the electrical activity of the heart. Here's a closer look at how ECG contributes to diagnosing myocardial infarction.

ST-Segment Elevation Myocardial Infarction (STEMI)

STEMI is one of the most recognizable types of heart attack on an ECG. In this case, specific changes in the ST segment — a part of the ECG waveform — indicate acute damage to the heart muscle. Doctors typically use a 12-lead ECG to identify which leads show abnormal activity, helping them determine the location of the infarction.

Common ECG Patterns in STEMI

If ST-segment elevation appears in leads II, III, and aVF, it suggests damage to the inferior (lower) wall of the heart — also known as the diaphragmatic surface. When ST elevation is observed in leads V1 through V5, it typically indicates an anterior wall myocardial infarction, which affects the front part of the heart. Additionally, ST elevation in leads I and aVL points to a lateral wall infarction involving the left ventricle's side. These distinct patterns allow medical professionals to quickly identify the affected area and initiate appropriate treatment.

Non-ST-Segment Elevation Myocardial Infarction (NSTEMI)

Unlike STEMI, NSTEMI does not always present with clear ST-segment elevation on an ECG. Instead, it may show other subtle changes, such as T-wave inversion or ST-segment depression. Because these findings are less definitive, doctors must rely on additional diagnostic markers to confirm the presence of a heart attack.

Combining ECG with Blood Tests

To diagnose NSTEMI, clinicians often combine ECG findings with blood tests that measure cardiac biomarkers, particularly troponin levels. Elevated levels of cardiac enzymes, along with ECG abnormalities, support the diagnosis of NSTEMI. This integrated approach ensures more accurate detection and timely intervention, even when ECG changes are not immediately obvious.

In summary, while ECG plays a vital role in identifying myocardial infarction, its effectiveness depends on the type of MI and the interpretation of both electrical and biochemical markers. Understanding these nuances can improve early diagnosis and lead to better patient outcomes.