An electrocardiogram (EKG or ECG) is a non-invasive medical test that records the heart’s electrical activity. It helps healthcare providers assess heart function by translating electrical impulses into a visible tracing. The EKG’s primary purpose is to detect various heart conditions, from irregular heartbeats to signs of heart damage.
What a Normal EKG Shows
A typical EKG tracing displays a series of waves corresponding to specific electrical events in the heart. The P wave represents electrical activity in the atria, causing them to contract. The QRS complex signifies the electrical impulse moving through the ventricles, triggering their contraction to pump blood. The T wave indicates the electrical recovery of the ventricles as they prepare for the next beat.
A “normal sinus rhythm” describes a regular and consistent heartbeat originating from the heart’s natural pacemaker, the sinoatrial node. In adults, a healthy resting heart rate typically falls between 60 to 100 beats per minute. A normal EKG shows these waves occurring in a predictable sequence and within specific time intervals, reflecting efficient electrical conduction and coordinated heart muscle activity.
Common Abnormal EKG Findings
An EKG can reveal various deviations from the normal pattern, signaling potential issues with heart function. These abnormalities are often categorized by the type of electrical disturbance they represent.
Rhythm abnormalities, also known as arrhythmias, involve irregular heartbeats. This can include tachycardia (heart beating over 100 beats per minute), bradycardia (heart rate below 60 beats per minute), atrial fibrillation (rapid, irregular atrial beating), and premature beats (extra or early heartbeats).
Conduction abnormalities occur when electrical signals do not travel correctly through the heart’s pathways. Heart blocks describe delays or interruptions in the electrical signal from atria to ventricles. Bundle branch blocks involve delayed or blocked impulses along specialized ventricular pathways, causing them to contract out of sync.
An EKG can also show signs of reduced blood flow to the heart muscle (ischemia) or actual heart muscle damage (infarction or heart attack). Specific EKG changes, such as ST-segment elevation or depression, or T-wave inversions, can indicate heart muscle stress or damage due to lack of oxygen.
Beyond electrical signaling, an EKG may indirectly suggest structural changes within the heart, such as an enlarged heart chamber (hypertrophy). This occurs when the heart muscle works harder than normal, leading to thickening of its walls. Additionally, imbalances in essential minerals like potassium, calcium, or magnesium (electrolytes) can alter the heart’s electrical activity and manifest as abnormal EKG readings.
What Causes EKG Abnormalities
Various underlying factors, both cardiac and non-cardiac, can lead to abnormal EKG readings. Heart-related conditions directly impact the heart’s electrical activity or structure, including:
- Coronary artery disease, where heart arteries become narrowed, causing ischemia and EKG changes.
- Previous heart attacks, leaving lasting electrical scars.
- Heart failure, valvular heart disease, or cardiomyopathy, altering electrical patterns due to changes in pumping efficiency or structure.
- Congenital heart defects, structural problems present from birth.
Factors outside the heart can also influence EKG results:
- Electrolyte imbalances, such as high or low levels of potassium or calcium, significantly disrupting heart rhythm.
- Thyroid disorders (overactive or underactive), affecting heart rate and rhythm.
- Certain medications, including antidepressants, antiarrhythmics, or blood pressure drugs, altering EKG readings as a side effect.
- Uncontrolled high blood pressure, causing heart muscle thickening.
- Lung diseases, indirectly impacting heart function and electrical signals.
Sometimes, an abnormal EKG may be due to temporary factors or not indicate a serious condition. Stress, anxiety, or physical exercise can temporarily increase heart rate and alter EKG patterns. Technical issues during the EKG test, such as improper electrode placement or patient movement, can also create artifacts. In some cases, an abnormal EKG finding might even be a normal variation for an individual.
Interpreting Abnormal EKG Results
Receiving an abnormal EKG result does not automatically mean a severe heart problem is present. The interpretation of these findings requires a comprehensive approach, considering the individual’s full clinical picture. Healthcare providers evaluate EKG results in the context of a patient’s reported symptoms, medical history, a thorough physical examination, and other diagnostic tests. For example, an EKG showing slight variations might be insignificant in a healthy, asymptomatic person but concerning in someone experiencing chest pain or shortness of breath.
When an EKG shows an abnormality, further evaluation is often necessary to determine the cause and severity. This might involve additional diagnostic tests to gather more detailed information about the heart’s function and structure. Common follow-up tests include:
- Repeat EKGs to observe changes over time.
- Holter monitoring for continuous heart rhythm recording.
- Echocardiograms (ultrasound scans of the heart’s chambers and valves).
- Stress tests (monitoring heart activity during exercise).
- Blood tests to check for specific markers or electrolyte levels.
It is important for individuals to discuss any EKG results with their doctor and adhere to medical advice. While some EKG abnormalities are benign and require no treatment, others may indicate conditions that necessitate ongoing monitoring or immediate medical attention. Understanding the implications of an abnormal EKG is the first step toward appropriate management and maintaining heart health.