An electrocardiogram (EKG or ECG) is a graphic recording of the electrical activity generated by the heart, used as a non-invasive screening tool for various heart conditions. The procedure involves placing small electrodes on the skin to detect the heart’s electrical impulses, which are translated into a traceable pattern. Physical factors related to the patient’s body size and composition can significantly influence the resulting trace. Large breast tissue can introduce what appear to be abnormalities on the EKG, known as artifacts, by causing physical interference that creates misleading patterns.
Understanding How Tissue Affects EKG Signal Integrity
The electrical signals the heart produces must travel through the chest cavity to reach the electrodes placed on the skin. Large amounts of dense tissue, particularly fatty tissue found in the breasts, act as a barrier to this electrical current. This effect is known as signal attenuation, where the tissue weakens the electrical signal before it reaches the surface. Attenuation reduces the amplitude of the recorded waves, often resulting in a low voltage reading on the EKG.
The physical presence of large tissue volume also leads to electrode displacement, a major source of EKG error. The weight and size of the breasts can physically push the precordial leads (V3 through V6) away from their intended anatomical positions over the heart. When electrodes are placed on top of or beneath displaced tissue, they no longer record electrical activity from the correct location. This misplacement can cause the tracing to mimic concerning cardiac patterns.
Signal attenuation and displacement can lead to poor R-wave progression in the precordial leads. This pattern, characterized by smaller-than-expected electrical waves, can be incorrectly interpreted as a sign of a past heart attack, such as an anterior wall myocardial infarction. Furthermore, the dampening effect of the tissue can falsely trigger the low voltage criteria. Low voltage is a potential sign of conditions like pericardial effusion, where fluid surrounds the heart.
Recognizing EKG Artifacts vs. True Cardiac Abnormalities
Distinguishing between an artifact caused by dense tissue and a genuine heart problem is a central challenge in EKG interpretation. Interpreting physicians rarely rely on the EKG trace alone; they always consider the patient’s full clinical context, including symptoms, medical history, and risk factors. An EKG finding that suggests a problem but does not align with an otherwise asymptomatic patient is often a strong indicator of an artifact.
Tissue interference can produce pseudo-infarct patterns—EKG changes that look like a heart attack but are not caused by actual cardiac damage. These patterns often involve changes in the R-wave or ST-T segments in the anterior or lateral leads. Unlike a real heart abnormality, which tends to show a consistent and rhythmic pattern, an artifact may appear irregular or inconsistent across different leads.
To confirm whether an abnormal reading is simply an artifact, physicians utilize other diagnostic tools. Comparing the current EKG to previous tracings is a powerful technique, as a new pattern in an otherwise healthy patient suggests a technical issue. An echocardiogram (an ultrasound of the heart) can also be used to rule out actual heart damage or structural issues, providing definitive proof that the electrical tracing was misleading.
Techniques for Obtaining Accurate EKG Measurements
Medical professionals use several practical techniques to overcome the interference caused by large breast tissue and ensure an accurate EKG reading. The most direct method involves manually repositioning the tissue to allow for optimal electrode placement. The technician may gently lift or displace the breast tissue, typically superiorly or laterally, to expose the underlying chest wall. This action allows the precordial electrodes to be placed directly on the skin over the correct anatomical landmarks.
When repositioning the tissue is necessary, the electrodes (particularly V4, V5, and V6) are often placed at the inframammary fold, the crease where the breast meets the chest wall. This placement ensures the electrodes maintain contact with the chest wall and are positioned close to the ideal horizontal plane, minimizing signal attenuation. In some cases, the patient may be asked to hold their own breast tissue up to aid in maintaining the correct positioning during the procedure.
The patient’s position during the test can also be adjusted to improve electrode contact and reduce artifact. Asking the patient to lie in a semi-recumbent position, slightly elevated, can sometimes help the tissue fall away from the placement area. The EKG technician must meticulously document the exact placement of the electrodes and any specific maneuvers performed, such as lifting the tissue. This documentation is crucial for the interpreting physician to understand the context of any unusual patterns and for future EKG comparisons.