An electrocardiogram (EKG or ECG) is a non-invasive medical test that records the heart’s electrical activity. This article clarifies the EKG’s capabilities and limitations in detecting heart blockages.
What an EKG Measures
An EKG measures the electrical signals generated by the heart. These impulses trigger the heart’s muscle contractions. The EKG translates these signals into wavy lines on a graph, representing the heart’s electrical rhythm.
This diagnostic tool reveals aspects of heart function, including heart rate and rhythm, which can indicate conditions like arrhythmias. An EKG can also show evidence of past heart attacks by detecting damage to heart muscle tissue. It provides a snapshot of the heart’s electrical activity during the test.
EKG and Heart Blockages
An EKG cannot directly visualize or detect a blockage, such as plaque buildup in a coronary artery. However, it can reveal indirect signs if a blockage is causing reduced blood flow to the heart muscle. These signs appear as changes in the heart’s electrical activity.
For instance, an EKG can show signs of myocardial ischemia, a condition where the heart muscle receives insufficient blood flow, often due to narrowed or blocked arteries. This manifests as specific alterations in the ST segment or T waves. The EKG can also indicate if a heart attack is currently happening or has occurred in the past, as heart attacks are frequently caused by arterial blockages. However, it does not confirm the precise location or severity of the blockage itself.
Diagnosing Coronary Artery Blockages
To directly diagnose and assess coronary artery blockages, other methods are used. Stress tests, which can be exercise-induced or pharmacological, evaluate how the heart performs under increased demand and can uncover insufficient blood flow. During an exercise stress test, an EKG monitors heart activity while a person walks on a treadmill or rides a stationary bike.
Imaging tests offer a more direct view of the arteries. An echocardiogram uses sound waves to visualize blood flow and heart chamber movement. Cardiac CT angiography (CCTA) uses X-rays and often a contrast dye to create detailed images of the coronary arteries, revealing blockages or narrowing. Cardiac catheterization, also known as an angiogram, is a definitive method for identifying the exact location and severity of blockages. It involves inserting a thin tube with a contrast dye directly into the arteries for detailed imaging.