An electrocardiogram, or EKG, is a non-invasive medical test that records the electrical activity of the heart. Small electrodes are placed on the skin of the chest, arms, and legs. These electrodes detect the heart’s electrical impulses, translating them into a wavy line pattern that healthcare providers can interpret. An EKG assesses heart health and identifies any irregularities in its electrical signals.
What an EKG Reveals
An EKG provides valuable insights into the heart’s electrical function, detecting several heart conditions. It can identify arrhythmias, which are irregular heart rhythms like beating too quickly (tachycardia), too slowly (bradycardia), or with an erratic pattern. An EKG helps pinpoint where these rhythm disturbances originate within the heart.
The test can also offer evidence of a past heart attack, even if symptoms were not noticeable. Damage to heart muscle tissue from a previous myocardial infarction alters normal electrical pathways, creating abnormal EKG patterns. These patterns help determine which part of the heart may have been affected.
An EKG can indicate changes in the heart’s structure, such as thickened or enlarged heart muscle chambers (ventricular hypertrophy). Such changes can occur due to conditions like high blood pressure or heart valve disorders. An EKG can also show how imbalances in electrolytes, such as potassium or calcium, affect heart rhythm.
While an EKG does not directly visualize blood flow, it can show signs of active ischemia, a lack of blood flow to the heart muscle, especially when a person experiences chest pain. Reduced blood flow causes specific changes in the heart’s electrical signals.
Factors Influencing EKG Readings
Several factors can influence the quality and interpretation of EKG readings. Patient-related elements play a significant role in EKG accuracy. Body habitus, such as obesity, can make it challenging to obtain clear electrical signals. Muscle tremors or patient movement during the test can introduce “noise” or distortions into the reading.
Certain medications can impact heart rhythm and electrical signals, affecting EKG results. Other underlying medical conditions, including lung disease or thyroid issues, might affect the heart’s electrical activity and alter EKG patterns. Skin conditions, excessive sweating, or oily skin can reduce electrode contact quality, impeding electrical conduction and leading to inaccurate readings.
Technical factors are another important consideration. Improper placement of electrodes is a common cause of inaccurate EKG interpretations. Even slight deviations from the correct position can create significant changes, potentially leading to misdiagnosis. Electrical interference from other medical equipment or external sources can disrupt EKG signals and compromise data integrity.
The timing of the EKG also impacts its ability to detect issues. Since an EKG captures heart activity at a specific moment, intermittent heart events, such as sporadic arrhythmias, might not be present during the brief testing period. In such cases, longer-term monitoring devices, like Holter monitors, may be used to capture these transient events.
When EKG Isn’t Enough
Despite its diagnostic utility, an EKG has limitations and cannot definitively diagnose all heart conditions. It cannot reliably detect blockages in coronary arteries unless there are active symptoms of ischemia or evidence of a past heart attack. An EKG does not directly visualize the arteries or the extent of any narrowing.
An EKG is not a predictive tool for assessing the risk of future heart attacks in individuals without symptoms. It is not a standalone predictor for future cardiac events, even if some research suggests EKG data might contribute to risk assessment. A normal EKG reading does not guarantee a person is free from the risk of a future heart attack.
The EKG also does not provide detailed images of the heart’s structure, such as its valves, chambers, or congenital defects. For visualizing these structural aspects, imaging tests like echocardiograms, which use sound waves to create pictures of the heart, are necessary. While an EKG can indicate the presence of a problem, it often does not quantify its severity. An EKG is often one component of a broader diagnostic approach, with other tests complementing its findings for a comprehensive assessment of heart health.