When Notched T-Waves Appear
Notched T-waves appear in several distinct clinical contexts: most characteristically in long QT syndrome type 2 (LQT2), during hypothermia (Osborn waves), in early repolarization patterns, and as a normal variant in elite endurance athletes.
Primary Clinical Contexts
Long QT Syndrome Type 2 (Most Clinically Significant)
Notched T-waves are a hallmark electrocardiographic feature of LQT2 (HERG mutations), appearing far more frequently than in LQT1 or normal individuals 1. The classification system distinguishes:
- Grade 1 (G1) notches: A bulge at or below the horizontal baseline
- Grade 2 (G2) notches: A distinct protuberance above the horizontal baseline
G2 notches are seen exclusively in LQT2 patients (63% prevalence) and are highly specific for this genotype 1. These abnormalities are:
- More pronounced in symptomatic patients (81% vs 19% in asymptomatic) 2
- Associated with higher risk of syncope or cardiac arrest 2
- Better detected on Holter monitoring than standard 12-lead ECG 1
- More common with missense mutations and core domain HERG mutations 1
Provocation Testing
Low-dose epinephrine infusion (≤0.05 μg/kg/min) can unmask notched T-waves specifically in LQT2 patients, with G2-notched T-waves appearing exclusively in this subtype during provocation 3. This is diagnostically useful for patients with borderline or non-diagnostic baseline QTc intervals.
Early Repolarization and Terminal QRS Patterns
According to AHA guidelines, terminal QRS notches represent low-frequency deflections at the end of the QRS complex, initially described by Osborn as J waves during experimental hypothermia 4. The terminology distinguishes:
- Terminal QRS notch: Part of early repolarization patterns
- Osborn waves: Specifically associated with hypothermia
- Epsilon waves: Terminal QRS notching in arrhythmogenic right ventricular cardiomyopathy (anteroseptal precordial leads)
Athletic Heart
Notched T-waves occur in 19% of elite endurance athletes (professional cyclists), associated with QT prolongation and increased left ventricular volumes 5. In this population, they appear benign without arrhythmic events, though may indicate repolarization inhomogeneity.
Other Conditions
- Duchenne muscular dystrophy: Notched T-waves in 46.7% of patients, associated with increased sympathetic activity rather than cardiac structural disease 6
- Artifact: Bizarre T-wave notching can result from improper electrode placement near pulsatile structures 7
Prognostic Implications
Asymmetric, flattened, and notched T-waves (high morphology combination scores) independently predict mortality with adjusted hazard ratios of 1.75 in women and 1.61 in men, beyond QTc and baseline comorbidities 8.
Clinical Pitfall
The critical distinction is between benign notching in athletes or normal variants versus pathologic notching in LQT2. When encountering notched T-waves, evaluate for:
- Personal or family history of syncope, sudden death
- QTc prolongation (particularly >460 ms)
- Response to low-dose epinephrine if LQT2 suspected
- Proper electrode placement to exclude artifact