An electrocardiogram, commonly known as an EKG or ECG, is a non-invasive medical test that records the electrical activity of the heart. This procedure involves placing small electrodes on the skin of the chest, arms, and legs to detect the tiny electrical signals generated by the heart with each beat. The EKG machine then translates these signals into a waveform tracing on paper or a screen, providing a visual representation of the heart’s rhythm and electrical conduction. This diagnostic tool helps healthcare professionals assess the overall health of the heart by identifying various patterns that can indicate underlying issues.
Heart-Related Conditions
Abnormal EKG readings frequently stem from conditions directly affecting the heart’s structure or its primary electrical system. Irregular heartbeats, known as arrhythmias, are a common cause, manifesting as the heart beating too quickly, too slowly, or with an erratic rhythm. Conditions such as atrial fibrillation, where the upper chambers quiver instead of contracting effectively, or ventricular tachycardia, a rapid rhythm originating in the lower chambers, directly alter the normal electrical pathways. Bradycardia, a slower-than-normal heart rate, also presents specific patterns reflecting reduced electrical impulses.
Reduced blood flow to the heart muscle, termed myocardial ischemia, or actual heart muscle damage, known as myocardial infarction (a heart attack), profoundly impacts the heart’s electrical activity. Ischemia often shows up as changes in the ST segment on the EKG, indicating that heart cells are not receiving enough oxygen. A full infarction, where heart tissue dies, can lead to more permanent EKG changes, such as the appearance of pathological Q waves, which signify areas of electrical silence from damaged muscle.
Structural heart diseases also contribute to abnormal EKG readings by altering the heart’s physical characteristics. Cardiomyopathies, which are diseases of the heart muscle like dilated cardiomyopathy (enlarged, weakened heart chambers) or hypertrophic cardiomyopathy (thickened heart muscle), can strain the heart and disrupt its electrical conduction. Significant valvular heart disease, where heart valves do not open or close properly, can lead to chamber enlargement as the heart works harder to pump blood. This increased strain and chamber size can result in specific EKG patterns, such as indications of ventricular hypertrophy or atrial enlargement, reflecting the altered electrical pathways within the remodeled heart.
Systemic Health Issues
Conditions originating outside the heart can also indirectly influence its electrical activity, leading to abnormal EKG readings. Thyroid disorders significantly impact heart rhythm and function due to the thyroid hormones’ direct influence on cardiac cells. Hyperthyroidism, characterized by an overactive thyroid, can accelerate heart rate and increase the force of contractions, potentially causing fast heart rhythms like sinus tachycardia or atrial fibrillation, which are visible on an EKG. Conversely, hypothyroidism, an underactive thyroid, can slow the heart rate, leading to bradycardia and other conduction abnormalities.
Severe anemia, a condition where the blood lacks enough healthy red blood cells to carry adequate oxygen, can force the heart to work harder to meet the body’s oxygen demands. This increased workload and strain on the heart muscle can manifest as EKG changes, such as ST-T wave abnormalities, indicating that the heart is under stress.
Chronic lung diseases, particularly severe conditions like Chronic Obstructive Pulmonary Disease (COPD), can place considerable strain on the right side of the heart. The reduced oxygen levels and increased pressure in the lung arteries associated with COPD can lead to pulmonary hypertension, causing the right ventricle to enlarge and thicken. This right ventricular strain and hypertrophy can produce characteristic EKG patterns, including right axis deviation or prominent P waves (P pulmonale), reflecting the altered electrical forces within the strained right heart chambers.
Long-standing and uncontrolled high blood pressure, or hypertension, can also lead to changes detectable on an EKG. Persistent elevated pressure in the arteries forces the left ventricle, the heart’s main pumping chamber, to work harder to eject blood. Over time, this sustained workload can cause the left ventricular muscle to thicken and enlarge, a condition known as left ventricular hypertrophy. This thickening alters the electrical signals traveling through the heart, resulting in specific EKG patterns such as increased QRS voltage or ST-T wave changes, reflecting the enlarged muscle mass.
Medications and Chemical Imbalances
Various medications can interfere with the heart’s electrical signals, leading to abnormal EKG readings. Certain anti-arrhythmic drugs, while used to treat irregular heartbeats, can paradoxically cause new arrhythmias or conduction blocks by altering ion channel function within heart cells. Other medications, including some tricyclic antidepressants, antipsychotics, and specific antibiotics like macrolides (e.g., azithromycin), can prolong the QT interval on an EKG. A prolonged QT interval indicates a delay in the heart’s repolarization phase, increasing the risk of dangerous ventricular arrhythmias.
Imbalances in the body’s electrolytes, which are minerals carrying an electrical charge, profoundly affect heart function and can cause significant EKG abnormalities. Potassium, sodium, calcium, and magnesium play a direct role in the electrical excitability and conduction within heart muscle cells. For instance, high potassium levels (hyperkalemia) can lead to peaked T waves and widening of the QRS complex, while low potassium (hypokalemia) can cause flattened T waves and prominent U waves. Abnormal calcium levels can affect the QT interval (hypocalcemia prolongs it, hypercalcemia shortens it), and magnesium imbalances also influence heart’s electrical stability. These electrolyte disturbances directly alter the flow of ions across heart cell membranes, disrupting the precise electrical sequence required for normal heartbeats.