Heart failure is a chronic medical condition where the heart muscle struggles to pump enough blood to meet the body’s demands for oxygen and nutrients. This occurs because the heart has become too weak or stiff to function effectively. An electrocardiogram (ECG or EKG) is a non-invasive test that measures the heart’s electrical activity. It serves as a common initial screening tool in cardiology to gather information about heart function.
How an ECG Works and Its Purpose in Heart Failure
An ECG machine operates by detecting and recording the tiny electrical signals generated by the heart, which control its contractions. Electrodes are placed on the chest, arms, and legs to pick up these impulses. These electrical signals are then translated into a waveform displayed on paper or a screen, visualizing heart activity.
The heart’s internal pacemaker, the sinoatrial node, initiates each heartbeat with an electrical signal that spreads throughout the heart muscle. The ECG records this signal and tracks heart chamber contraction and relaxation. For heart failure, an ECG identifies electrical abnormalities, such as irregular rhythms, or signs of structural changes that may indicate the condition.
Key ECG Indicators of Heart Failure
ECG findings indicate heart failure. Left ventricular hypertrophy (LVH) suggests a thickened heart muscle, often due to the heart working harder to pump blood. On an ECG, LVH can appear as increased voltage or duration of the QRS complexes, reflecting the larger muscle mass of the left ventricle.
Arrhythmias, or irregular heart rhythms, are common in heart failure. Conditions like atrial fibrillation or ventricular tachycardia can be both a cause and a consequence of heart failure. The ECG detects these rhythm disturbances.
Conduction abnormalities, such as bundle branch blocks, are common in heart failure. A left bundle branch block (LBBB), for instance, appears on an ECG as a widened QRS complex, indicating a delay in electrical conduction to the left ventricle. The presence of LBBB, especially with a reduced ejection fraction, may indicate a need for specialized therapies.
An ECG can also reveal past or ongoing heart attacks (myocardial infarction) or ischemia, reduced blood flow to the heart. These conditions are common causes of heart failure, and their presence on an ECG provides insights into cardiac damage. Findings related to the right side of the heart, such as right ventricular hypertrophy or strain, are also detectable.
Limitations and Complementary Diagnostic Tools
While an ECG provides information, it is not a standalone diagnostic tool for heart failure. It cannot directly measure pumping function or fluid retention. A normal ECG does not rule out heart failure, and an abnormal ECG does not automatically confirm the diagnosis.
Other diagnostic tests are used with an ECG to confirm a heart failure diagnosis and assess its severity. An echocardiogram (echo) directly visualizes the heart’s structure and function, including its pumping ability (ejection fraction). Blood tests, like B-type natriuretic peptide (BNP) or N-terminal pro-B-type natriuretic peptide (NT-proBNP), indicate heart strain and fluid overload. A chest X-ray checks for an enlarged heart or fluid accumulation in the lungs, common heart failure signs.