An electrocardiogram, commonly called an EKG or ECG, is a non-invasive test that measures the electrical activity of the heart. This test involves placing electrodes on the skin to detect the electrical impulses that govern the heart’s rhythm and pumping action. The EKG machine translates this electrical data into a waveform tracing on paper or a screen, which a medical professional then interprets. When a result is flagged as “abnormal,” it means the recorded electrical pattern deviates from the expected standard. This finding is merely a starting point that requires further investigation to determine if the deviation is harmless or points to an underlying health concern.
Understanding the Technical Deviations
The EKG tracing is a sequence of waves and segments, each corresponding to a specific electrical event in the heart. The P-wave represents the electrical activation of the heart’s upper chambers, the atria, before they contract. An abnormal P-wave might indicate an issue with atrial enlargement or the way the electrical signal starts.
Following the P-wave is the QRS complex, a sharp spike representing the electrical activation of the ventricles. If the QRS complex is too wide, it suggests a delay in electrical conduction through the ventricles, such as a bundle branch block. The duration of this complex is typically between 0.06 and 0.10 seconds in a healthy adult.
The ST segment and T-wave follow the QRS complex, reflecting the period when the ventricles electrically reset themselves, known as repolarization. Elevation or depression of the ST segment often suggests the heart muscle is not receiving enough blood flow, a condition called ischemia. The T-wave’s shape and direction can also be altered by various cardiac issues or systemic conditions.
Abnormal results are also identified by measuring the heart’s overall rate and rhythm. A heart rate below 60 beats per minute (bradycardia) or above 100 beats per minute (tachycardia) is considered an abnormal rate. Beyond speed, the rhythm’s regularity is assessed, looking for inconsistent or chaotic timing between beats, which indicates an arrhythmia.
Common Heart Conditions Indicated
Deviations in the EKG tracing often point toward specific cardiac diagnoses, most commonly arrhythmias, or irregular heart rhythms. Atrial fibrillation, for instance, is characterized by the absence of distinct P-waves and an irregularly fast ventricular rhythm, signaling chaotic electrical activity in the atria. Bradycardia, a slower-than-normal rhythm, can result from an issue with the heart’s natural pacemaker or a delay in the electrical signal passing through the conduction system.
Changes in the ST segment and T-wave are strongly associated with conditions affecting blood supply to the heart muscle. An elevated ST segment can be a time-sensitive sign of an acute heart attack, indicating a complete blockage of a coronary artery. Conversely, depressed ST segments or inverted T-waves may indicate ischemia, where blood flow is restricted.
An abnormal EKG can also reveal structural changes in the heart muscle. Ventricular hypertrophy, a thickening of the heart walls often caused by long-standing high blood pressure, causes the QRS complexes to appear unusually large. This enlarged muscle mass alters the electrical signal’s strength and path. Furthermore, pathological Q waves, which are deep and wide, can be a lasting electrical scar, providing evidence that a heart attack occurred previously, even if the person is currently asymptomatic.
Non-Disease Factors That Influence EKG Results
An abnormal EKG does not always signify a primary cardiac disease. Several external or temporary factors can alter the heart’s electrical signals, mimicking a pathology. Electrolyte imbalances, particularly in potassium, calcium, and magnesium, affect the heart’s electrical stability. For example, low potassium levels can cause changes in the T-wave and the appearance of a U-wave on the tracing.
Certain prescription medications can also produce changes in the EKG pattern. Drugs used to manage high blood pressure or psychiatric conditions can slow the heart rate or prolong the time it takes for the heart to recharge, altering the T-wave or QT interval. A thorough review of a person’s medication list is a routine step in interpreting an abnormal EKG result.
Technical errors during the test procedure can also lead to a false abnormal reading. Improper placement of the electrodes or poor skin contact can distort the electrical waveforms, making the tracing appear irregular. Additionally, physiological variations, such as the slow heart rate and specific T-wave changes seen in highly conditioned endurance athletes, are considered normal for that individual but would be flagged as abnormal in the general population.
Necessary Follow-Up and Interpretation
Receiving an abnormal EKG result necessitates a comprehensive interpretation by a medical professional who considers the context of the individual’s symptoms and medical history. The next steps focus on gathering further evidence to confirm or rule out a diagnosis. The first step often involves blood tests to check for markers of heart muscle damage or to assess electrolyte levels.
For a closer look at the heart’s structure and function, an echocardiogram is frequently ordered. This ultrasound test provides moving images of the heart, allowing doctors to visualize the size of the chambers, the strength of the muscle contractions, and the function of the heart valves. If the EKG suggests an intermittent rhythm problem, a Holter monitor may be used, which is a portable EKG device worn for 24 to 48 hours to capture electrical activity during a person’s normal daily routine.
If the abnormality is suspected to be related to reduced blood flow, a cardiac stress test may be performed. This test monitors the EKG while the person exercises, helping to reveal electrical changes that only become apparent when the heart is working harder and requires more oxygen. Ultimately, the interpretation of an abnormal EKG is a process of clinical correlation, combining the electrical data with imaging, blood work, and the patient’s presentation to arrive at an accurate diagnosis.