What does left atrial enlargement on an electrocardiogram (EKG) indicate?

Left Atrial Enlargement on EKG: Meaning and Clinical Significance

Left atrial enlargement (LAE) on an electrocardiogram (EKG) indicates an abnormality in the left atrium that may be due to dilatation, hypertrophy, elevated pressure, impaired ventricular distensibility, or delayed intraatrial conduction. 1

EKG Characteristics of Left Atrial Abnormality

• Left atrial abnormality typically involves prolongation of total atrial activation time, as left atrial activation begins and ends later than right atrial activation 1
• The most common EKG findings include:
  • P-wave duration ≥120 ms 1
  • Notched P wave with a peak-to-peak interval ≥40 ms (widely notched P wave) 1
  • Increased P terminal force in lead V1 (product of amplitude and duration of the terminal negative component) 1
  • Left axis of the terminal P wave (30° to 90°) 1
  • Double-peaked or notched P wave due to separation of right and left atrial peaks 1

Clinical Significance

• Left atrial abnormality on EKG may be an early sign of hypertensive heart disease, even before the development of left ventricular hypertrophy 2
• LAE is associated with significant cardiovascular morbidity and mortality, including:
  • Heart failure
  • Stroke
  • Atrial fibrillation
  • Diastolic dysfunction 3
• In patients with left ventricular hypertrophy, P-wave abnormalities provide major support to the diagnosis and may be the earliest electrocardiographic sign of hypertensive heart disease 1

Diagnostic Accuracy of EKG for LAE

• EKG has limited sensitivity but high specificity for detecting anatomical left atrial enlargement 3, 4
• Individual EKG criteria for LAE have sensitivities ranging from 9.7% to 49.6%, with P-wave duration >120 ms having the highest sensitivity 3
• When multiple criteria are combined, sensitivity increases to approximately 58.1% 3
• Specificity of individual EKG criteria for LAE approaches 100% in some studies 3
• Echocardiography remains the gold standard for accurate measurement of left atrial size 4

Clinical Conditions Associated with LAE

• Hypertension (a common cause of LAE) 2, 3
• Valvular heart disease, particularly mitral valve disease 1
• Left ventricular dysfunction 1
• Congenital heart disease 1
• Atrial fibrillation 5

Recommendations for Clinical Practice

• The term "left atrial abnormality" is preferred over "left atrial enlargement," "atrial hypertrophy," "atrial overload," or "atrial strain" since multiple factors may contribute to the EKG findings 1
• Multiple EKG criteria should be used rather than relying on a single criterion for improved diagnostic accuracy 1
• When LAE is detected on EKG, further evaluation with echocardiography is warranted to confirm anatomical enlargement and determine its severity 1
• In patients with suspected heart disease, an EKG showing LAE should prompt evaluation for underlying conditions such as hypertension, valvular disease, or heart failure 1

Pitfalls and Caveats

• EKG criteria for LAE have low sensitivity (26-66%) but high specificity (>97%) when compared to echocardiography 5, 6
• False positive diagnoses of LAE by EKG criteria are relatively uncommon (approximately 6%) 5
• The presence of atrial fibrillation may affect the ability to detect LAE on EKG 5
• EKG findings should always be correlated with clinical information and, when possible, confirmed with imaging studies 1