ECG Findings in Patent Ductus Arteriosus
The ECG in PDA may be completely normal if the ductus is small, but will show left atrial enlargement and left ventricular hypertrophy when there is a moderate left-to-right shunt, or right ventricular hypertrophy if pulmonary arterial hypertension has developed. 1
ECG Findings Based on PDA Severity
Small PDA
- Normal ECG is the expected finding when the ductus is hemodynamically insignificant 1, 2
- No chamber enlargement patterns present 1
- Normal axis and voltages 1
Moderate PDA with Left-to-Right Shunt
- Left atrial enlargement (LAE) manifests as the primary finding, reflecting chronic volume overload 1, 2
- Left ventricular hypertrophy (LVH) develops from sustained LV volume overload due to the shunt 1, 2
- These findings correlate with echocardiographic evidence of dilated left atrium and left ventricle 2
Large PDA with Pulmonary Arterial Hypertension
- Right ventricular hypertrophy (RVH) becomes the dominant pattern when PAH develops 1, 2
- RVH indicates elevated pulmonary vascular resistance and pressure overload on the right ventricle 1
- This finding suggests potential progression toward Eisenmenger physiology 3, 2
Clinical Context for ECG Interpretation
The ECG findings must be interpreted alongside the clinical presentation:
- Continuous machinery murmur at the left infraclavicular area suggests moderate-to-large PDA with preserved pulmonary vascular resistance 1, 2
- Systolic murmur only indicates that PAH has developed, which correlates with RVH on ECG 2
- Bounding pulses and wide pulse pressure accompany the LVH pattern in moderate PDA 2
Critical Diagnostic Pitfall
Do not rely on ECG alone for PDA diagnosis or hemodynamic assessment. 1 The ECG provides supportive information about chamber consequences but cannot:
- Confirm the presence of PDA (requires echocardiography with color Doppler) 1
- Quantify shunt magnitude 1
- Distinguish between different causes of LVH or RVH 1
Integration with Other Diagnostic Modalities
- Echocardiography is the definitive diagnostic test, providing direct visualization of the PDA and assessment of chamber sizes and pulmonary pressures 1, 2
- Chest radiograph complements ECG findings by showing cardiomegaly, increased pulmonary vascular markings, and chamber enlargement 1
- Cardiac catheterization is reserved for cases with suspected severe PAH to measure pulmonary vascular resistance 1, 2
Baseline ECG Recommendations
Obtain a baseline ECG for rhythm assessment in all patients with diagnosed PDA, particularly those with Eisenmenger physiology, as atrial arrhythmias are common with chronic volume/pressure overload and carry risk of sudden death 3