Common ECG Findings in Congestive Heart Failure
ECG abnormalities are common in heart failure patients, with specific findings varying based on etiology, but a completely normal ECG makes heart failure diagnosis unlikely (less than 10%) 1.
Key ECG Findings in Heart Failure
Rhythm Abnormalities
- Atrial fibrillation (most common arrhythmia in HF)
- Sinus tachycardia (particularly in decompensated HF)
- Ventricular arrhythmias
Conduction Abnormalities
- Left bundle branch block (LBBB)
- More common than right bundle branch block
- QRS duration ≥120 ms
- Associated with worse LV function and poorer prognosis 2
- Prolonged PR interval (first-degree AV block)
- Intraventricular conduction delays
Structural Indicators
- Left ventricular hypertrophy (LVH)
- Pathological Q waves (suggesting prior myocardial infarction)
- Low QRS voltage (can indicate obesity, emphysema, pericardial effusion, or amyloidosis)
Repolarization Abnormalities
- ST-segment depression
- T-wave abnormalities
- QT interval prolongation
Clinical Significance of ECG Findings
Prognostic Value
- QRS duration ≥120 ms is associated with:
- More advanced myocardial disease
- Worse left ventricular function
- Higher all-cause mortality 2
- Progressive increase in QRS duration worsens prognosis
- Presence of LBBB may indicate cardiac dyssynchrony (potential target for cardiac resynchronization therapy)
Diagnostic Value
- A completely normal ECG makes heart failure unlikely (negative predictive value >90% in non-acute presentations) 1
- The European Society of Cardiology notes that if the ECG is completely normal, heart failure, especially due to LV systolic dysfunction, is unlikely 1
ECG Findings by Heart Failure Type
Heart Failure with Reduced Ejection Fraction (HFrEF)
- More likely to show:
- Q waves from prior infarction
- LBBB
- LVH with strain pattern
Heart Failure with Preserved Ejection Fraction (HFpEF)
- May show:
- Left atrial enlargement
- LVH (especially with hypertensive etiology)
- Atrial fibrillation
Monitoring Heart Failure with ECG
- Serial ECGs can track disease progression
- Changes in QRS amplitude may reflect changes in volume status 3
- QRS widening over time may indicate worsening ventricular function
Important Caveats
- While ECG abnormalities are common in heart failure, they have low specificity
- An abnormal ECG alone has limited predictive value for confirming heart failure 1
- ECG should be interpreted in conjunction with clinical findings, natriuretic peptide levels, and echocardiography
- Some patients with HFpEF may have relatively normal ECGs compared to those with HFrEF
Remember that while ECG is an essential diagnostic tool in heart failure evaluation, echocardiography remains the gold standard for confirming cardiac dysfunction and determining ejection fraction, which guides treatment decisions.