What is the significance and management of a notched QRS (electrocardiogram) complex on an ECG (electrocardiogram)?

Significance and Management of Notched QRS on ECG

A notched QRS complex on an ECG can represent either a benign early repolarization pattern or a marker of underlying cardiac pathology, requiring clinical correlation and potentially further cardiac evaluation when found in multiple leads or specific locations. 1

Definition and Classification

• A terminal QRS notch is defined as a low-frequency deflection at the end of the QRS complex, initially described by Osborn as J waves (referring to injury) 1
• QRS notching is part of the early repolarization pattern (ERP), which is an umbrella term that can refer to ST-segment elevation in the absence of chest pain, terminal QRS slur, or terminal QRS notch 1
• The J point should be measured with the peak representing the peak of the notch or onset of a slur when present 1

Clinical Significance

Benign vs. Pathological Findings

• Early repolarization pattern with QRS notching was originally considered a normal variant with a benign outcome, with prevalence as high as 10% in the general population 1
• More recent studies have demonstrated associations between certain patterns of QRS notching and adverse outcomes, including idiopathic ventricular fibrillation and sudden cardiac death 1
• Left precordial terminal QRS notching (especially in leads V4, V5, and V6) is more prevalent in malignant variants of early repolarization than in benign cases 2

Diagnostic Value

• QRS notching has a sensitivity of 62.2% and a specificity of 93.8% for the detection of ischemic heart disease in selected patients 3
• The presence of QRS notching in multiple leads increases the likelihood of underlying cardiac disease, with an odds ratio of 3.97 when more than one lead shows notching 4
• QRS notching may reflect heterogeneity of ventricular myocardial depolarization and electrical activity 5

Evaluation Algorithm

Initial Assessment

• Determine the number and location of leads showing QRS notching 2, 4
• Assess for other ECG abnormalities that may indicate specific cardiac pathologies 1
• Distinguish between terminal QRS notching and other similar patterns:
  • Epsilon waves (seen in arrhythmogenic right ventricular cardiomyopathy) 1
  • Brugada pattern (characterized by downward coved and saddleback ST-segment elevations) 1

Risk Stratification

• Higher risk features include:
  • QRS notching in left precordial leads (V4-V6) 2
  • Presence of notching in multiple leads (≥2 myocardial segments) 5, 4
  • Association with symptoms such as syncope, palpitations, or family history of sudden cardiac death 1
• Lower risk features include:
  • Isolated QRS notching in a single lead 4
  • QRS notching in the context of a normal cardiac evaluation 4

Management Recommendations

• For isolated QRS notching in a single lead without other concerning features, routine cardiac follow-up may be sufficient 4
• For QRS notching in multiple leads (≥2), particularly in left precordial leads, further cardiac evaluation is warranted 2, 4
• Cardiac evaluation may include:
  • Echocardiography to assess for structural heart disease 6
  • Cardiac MRI to evaluate for myocardial scarring or fibrosis 6
  • Exercise stress testing to evaluate for ischemic heart disease 3
  • Ambulatory ECG monitoring if arrhythmias are suspected 1

Special Considerations

• In patients with bundle branch blocks or ventricular pacing, QRS notching has different implications and should be interpreted with caution 5
• QRS fragmentation (multiple notches) may be a marker of myocardial scar and fibrosis and has been associated with increased risk of cardiac events 6
• The presence of QRS notching on paced ECGs after cardiac resynchronization therapy may predict a poor response to therapy 5

Common Pitfalls

• Misinterpreting technical artifacts as QRS notching 1
• Failing to distinguish between benign early repolarization and potentially pathological QRS notching patterns 1
• Not recognizing the increased significance of QRS notching when present in specific locations (left precordial leads) or in multiple leads 2, 4