What Does Sinus Rhythm with Possible Left Atrial Enlargement Mean?
Your EKG shows a normal heart rhythm (sinus rhythm) but suggests your left atrium may be enlarged, which requires further evaluation with an echocardiogram to confirm the finding and identify any underlying cardiac condition that needs treatment. 1, 2
Understanding the EKG Finding
What "Possible Left Atrial Enlargement" Means
The term "left atrial abnormality" is the preferred modern terminology rather than "enlargement," because EKG changes reflect a combination of factors including actual chamber enlargement, increased pressure, muscular thickening, and electrical conduction delays. 1, 2
Your EKG likely shows one or more of these specific patterns: 1, 2
- P wave duration ≥120 milliseconds (prolonged atrial activation time)
- A notched or "M-shaped" P wave with ≥40 ms separation between peaks
- Increased P terminal force in lead V1 (a deep negative deflection at the end of the P wave)
The EKG has moderate accuracy for detecting left atrial enlargement: approximately 63-80% predictive value when present, and 78% predictive value when absent. 3, 4 This is why confirmation with imaging is essential.
What You Should Do Next
Immediate Action Required
Obtain a transthoracic echocardiogram to confirm left atrial size and identify the underlying cause. 2 This is the gold standard for measuring left atrial dimensions and evaluating cardiac structure. 2
What the Echocardiogram Will Assess
The echocardiogram will measure: 3
- Left atrial transverse dimension (normal is <4.0 cm)
- Left atrial area (enlargement defined as >28 cm²)
- Ratio of left atrial to aortic root dimension (abnormal if >1.17)
- Left ventricular function and any valve abnormalities
Evaluation for Underlying Causes
Your physician should specifically evaluate for these common conditions that cause left atrial abnormality: 2
- Mitral valve disease (stenosis or regurgitation) - the most common structural cause 1
- Hypertension - a leading cause of left atrial pressure elevation 2
- Heart failure with impaired ventricular filling 2
- Cardiomyopathy (particularly hypertrophic cardiomyopathy) 1
Clinical Significance and Risks
Stroke Risk Consideration
Left atrial enlargement in patients with sinus rhythm (normal rhythm like yours) is associated with increased stroke risk, even without atrial fibrillation. 5
Stroke rates range from 0.59 to 2.06 per 100 person-years depending on the patient population, which is significantly elevated compared to those with normal left atrial size. 5
If echocardiography confirms significant left atrial enlargement (diameter >50 mm), discuss with your physician whether anticoagulation therapy is appropriate, particularly if you have other risk factors. 1 The target INR range would be 2.5-3.5 if anticoagulation is initiated. 1
Atrial Fibrillation Risk
Left atrial enlargement substantially increases your risk of developing atrial fibrillation in the future. 2, 5
Monitor for symptoms of atrial fibrillation including palpitations, shortness of breath, fatigue, or lightheadedness. 1
Management Based on Findings
If Underlying Condition Is Identified
Treatment should target the underlying cause: 2
- For hypertension: Aggressive blood pressure control to reduce left atrial pressure
- For mitral valve disease: Consider valve repair or replacement if severe and symptomatic 1
- For heart failure: Optimize heart failure medications including diuretics, ACE inhibitors, or beta-blockers
Ongoing Monitoring
Regular follow-up with repeat echocardiography at intervals determined by the severity of left atrial enlargement and underlying condition. 1
Serial EKGs to monitor for development of atrial fibrillation or other arrhythmias. 2
Important Caveats
Do not assume the EKG finding is definitive - approximately 20-37% of patients with EKG criteria for left atrial abnormality have normal left atrial size on echocardiography. 3, 4
Normal variants and technical factors can create false-positive findings on EKG. 2
The finding may represent intraatrial conduction delay (particularly in Bachmann's bundle) rather than true chamber enlargement. 1, 2
If you are an athlete, be aware that some EKG changes can be physiologic adaptations to training, though left atrial enlargement is considered a "borderline" finding requiring further evaluation even in athletes. 1