Can Pectus Excavatum Cause Low Voltage on ECG?
Pectus excavatum does not typically cause low voltage on ECG; instead, it causes a distinct pattern of ECG abnormalities including right axis deviation, RBBB patterns, anterior T wave inversions, and abnormal P wave morphology—but not the generalized low voltage seen in conditions like pericardial effusion or obesity.
Understanding the ECG Manifestations of Pectus Excavatum
The provided evidence does not support low voltage as a characteristic finding in pectus excavatum. The most comprehensive recent study examining ECG changes in pectus excavatum 1 evaluated 310 patients and documented specific abnormalities, but low voltage was not among them.
Actual ECG Abnormalities in Pectus Excavatum
The predominant ECG findings in pectus excavatum include:
P wave abnormalities: Predominantly negative P wave morphology in V1 (86.9% preoperatively) and abnormal P wave amplitude in lead II >2.5 mm (7.1% of cases) 1
Right-sided conduction patterns:
Repolarization abnormalities: T wave inversion in leads V1-V3 occurs in 62.3% of patients 1, which is clinically significant as it correlates with reduced exercise capacity (OR = 2.3; 95% CI 1.3-4.2) 1
Axis deviations: Cardiac axis deviation is common 2, though the specific direction varies based on the degree of cardiac displacement
Why Not Low Voltage?
Low voltage on ECG (defined as QRS amplitude <5 mm in limb leads or <10 mm in precordial leads) typically results from:
- Increased distance between heart and recording electrodes (obesity, emphysema, pericardial effusion)
- Reduced myocardial mass (infiltrative diseases, myocarditis)
- Diffuse myocardial injury
Pectus excavatum causes mechanical cardiac compression and displacement, not increased electrode distance or myocardial pathology, which explains why the ECG shows specific morphologic changes rather than generalized low voltage.
Clinical Implications
When to Suspect Cardiac Compression
The presence of RBBB (OR = 4.8; 95% CI 1.1-21.6) or anterior T wave inversions strongly suggests hemodynamically significant cardiac compression requiring cardiopulmonary exercise testing 1. These findings indicate the need for surgical evaluation rather than being dismissed as benign variants.
Reversibility After Surgical Correction
The ECG abnormalities in pectus excavatum are largely reversible 1:
- Negative P waves in V1: decreased from 86.9% to 57.4% postoperatively (p < 0.001)
- RBBB: decreased from 9.4% to 3.9% (p < 0.001)
- rsr' patterns: decreased from 40.6% to 12.9% (p < 0.001)
- Anterior T wave inversions: decreased from 62.3% to 37.7% (p < 0.001)
This reversibility confirms these findings are mechanical rather than representing intrinsic conduction system disease.
Critical Pitfall to Avoid
Do not misattribute a Brugada-type ECG pattern in pectus excavatum patients as true Brugada syndrome 3. The combination of RBBB and ST elevation in right precordial leads can occur in pectus excavatum due to mechanical factors and may be clinically benign, though this requires careful evaluation to exclude true channelopathy.
If you encounter an ECG showing low voltage in a patient with pectus excavatum, search for alternative explanations (pericardial effusion, obesity, COPD, hypothyroidism, amyloidosis) rather than attributing it to the chest wall deformity itself.