ECG criteria
- The T wave shape is bicomponent: two consecutive phases of opposite polarity separated by the isoelectric line crossing; there is no separate independent wave between them
- Type A (Wellens A): initial part positive, terminal part negative (+/−)
- Type B (Wellens B): deep symmetrical negative T wave without an obligatory positive phase; type A can evolve into type B
- Localization: typically V2–V3, may extend to V1, V4–V6
- The ST segment is isoelectric or minimally elevated (< 1 mm) in the same leads
- The R wave is preserved, and R-wave progression in the chest leads is not impaired
- Clinical context for the Wellens pattern: changes are recorded after an episode of chest pain, often during the pain-free period
- Myocardial injury biomarkers are normal or minimally elevated
What it looks like on ECG
Biphasic T — a wave with two oppositely directed segments within a single repolarization cycle. Two main variants are distinguished.
| Type | Morphology | Typical localization |
|---|---|---|
| A (Wellens A) | +/− , starts upward, ends downward | V2–V3 |
| B (Wellens B) | deep symmetrical negative T | V2–V3, may be broader |
Type A is a true biphasic T: the initial positive phase transitions into a negative phase, and the wave crosses the isoelectric line within a single complex. Type B is a distinct morphology: a deep symmetrical negative T, which does not necessarily contain a positive phase. Strictly speaking, the term "biphasic T" refers to type A; type B is classified as deep T-wave inversion, but in the context of the Wellens pattern, they are considered together because type A temporally usually precedes type B. Meanwhile, the ST segment remains flat or slightly elevated, without STEMI criteria. There are generally no pathological Q waves, and R-wave progression is preserved; QRS is often narrow, but its width is not an independent criterion of the pattern — concomitant bundle branch block or another wide QRS primarily complicates the assessment of the ST segment and T wave. It is important to describe the finding by leads: a "biphasic T wave in V2–V3" is not a diagnosis, but a descriptive ECG sign that requires clinical interpretation.
Mechanism
The T wave reflects ventricular repolarization. Normally, the repolarization vector is directed the same way as the QRS depolarization vector, so the T wave in most leads is concordant (co-directed) with QRS. Biphasic morphology occurs when repolarization in different areas of the myocardium (e.g., subendocardium and subepicardium, or an ischemic zone and intact myocardium) occurs asynchronously and in different directions. During an ischemic episode in the basin of the proximal left anterior descending artery (LAD), regional alterations in repolarization timing occur in the anteroseptal and apical zones, creating oppositely directed vectors at the beginning and end of the T wave, which is registered in V2–V3 as a biphasic shape. The pattern can dynamically change from a biphasic T (type A) to deep T-wave inversion (type B) following an episode of ischemia and reperfusion; the exact electrophysiological mechanism of this evolution does not reduce to a mandatory expansion of the ongoing ischemia zone and is not fully understood.
Causes
- The Wellens pattern is an ECG finding classically associated with critical stenosis of the proximal LAD in the appropriate clinical setting (the most clinically significant cause)
- Reperfusion following an ischemic episode (pseudonormalization over time)
- Left ventricular hypertrophy with strain
- Electrolyte disturbances (hypokalemia, calcium alterations)
- A normal variant in some healthy individuals, especially in transition zone leads
- Post-extrasystolic repolarization
- Cardiac memory phenomenon following ventricular pacing or bundle branch block
- Intracranial pathology (subarachnoid hemorrhage) — more commonly as part of deep T-wave inversion, but can pass through a biphasic stage
Differential diagnosis
- Negative T wave (symmetrical, without a positive phase) — the difference lies in the presence of the second, positive component
- Flattened T wave — amplitude is small, phases are not distinctly expressed
- Pseudonormalization of the T wave — a dynamic transition from a negative to a positive T wave during reperfusion, which can also pass through a biphasic form; differentiated by serial ECGs and clinical presentation
- De Winter waves — tall, symmetrical T waves in precordial leads preceded by upsloping ST depression at the J point (approximately 1–3 mm); the shape is fundamentally different and indicates acute occlusion, most commonly of the LAD
- Nonspecific ST-T changes — this term is used only if the morphological changes do not fit a specific pattern (Wellens, de Winter, etc.)
Clinical significance and management
Type A biphasic T and deep negative type B T in V2–V3 in a patient with a recent episode of chest pain are grounds to suspect the Wellens pattern, a high-risk marker classically associated with critical stenosis of the proximal LAD. The T-wave morphology itself is nonspecific: the pattern diagnosis is established only by taking into account the clinical context (recent anginal pain) and a combination of ECG signs — appropriate localization, absence of significant ST elevation, absence of pathological Q waves, and preserved R-wave progression. The ECG pattern is not equivalent to an angiographic diagnosis: comparison with serial ECGs, troponin dynamics, clinical findings, and ultimately coronary angiography is necessary; other causes of a biphasic T wave must also be ruled out. The classic finding is recorded during a pain-free period with minimally altered biomarkers. This is not STEMI, and in the absence of very high-risk criteria, an early invasive strategy (coronary angiography) is indicated without stress testing — provocative testing is not performed when Wellens is suspected, as recurrent ischemia during exertion can trigger an extensive anterior infarction. In ongoing or refractory chest pain, hemodynamic instability, life-threatening arrhythmias, dynamic ST-T changes, or intermittent ST elevation, the tactics change to immediate invasive management regardless of the presence of the Wellens pattern. If a biphasic T wave is discovered without a typical pain history, it does not automatically allow the finding to be considered a normal variant: the absence of symptoms does not rule out an asymptomatic ischemic episode. Repeat ECG, troponin assessment, and clinical risk evaluation are necessary, and if the morphology is suspicious, a cardiology evaluation is required; a normal variant can only be diagnosed after ruling out ischemia and other causes.
Common interpretation errors
- Writing "nonspecific ST-T changes" instead of recognizing the specific Wellens pattern in the presence of the appropriate localization and history
- Referring a patient with suspected Wellens pattern for a stress test
- Confusing type A biphasic T with de Winter waves due to a superficial glance at the shape without assessing the ST segment
- Ignoring dynamics: comparing with previous ECGs is important for assessing the recency and evolution of changes
- Automatically considering the finding a normal variant in the absence of a pain history, without evaluating troponin and clinical risk
1. A type A biphasic T wave (Wellens A) in leads V2–V3 after an episode of chest pain in the appropriate clinical picture indicates:
Given the typical localization, history, and absence of other causes, this is a classic finding for the Wellens pattern, which is considered a high-risk marker for proximal LAD disease.
2. What management strategy is indicated when Wellens syndrome is suspected with a biphasic T wave and no very high-risk features?
A stress test is contraindicated due to the risk of provoking an extensive infarction; an early invasive strategy is indicated within NSTE-ACS management.
3. How does a type A biphasic T wave differ from de Winter waves?
ST-segment shape is a key differentiating feature: de Winter syndrome presents with characteristic upsloping ST-segment depression at the J point, whereas with a biphasic T wave, the ST segment remains flat.
Frequently asked questions
How to distinguish a biphasic T wave in Wellens syndrome from a normal variant?
Clinical context is important but insufficient on its own: the classic pattern is identified after a recent pain episode, often during an asymptomatic period, with a normal or minimally altered ST segment. Changes can be dynamic, which makes serial ECGs and comparison with prior tracings essential. In the absence of symptoms, the finding cannot be automatically considered normal — repeat ECG, troponin assessment, and clinical risk evaluation are required.
Is a biphasic T wave dangerous?
The sign itself is not inherently dangerous; the danger is determined by the underlying cause. As part of the Wellens pattern in the appropriate clinical setting, it indicates potential LAD involvement and the risk of a large anterior myocardial infarction if disease progresses, although the pattern itself is not an angiographic diagnosis.
Is emergency PCI required for a Wellens-type biphasic T wave?
This is not STEMI, so the formal primary PCI window of "less than 120 minutes" does not apply automatically. In the absence of very high-risk criteria, an early invasive strategy is indicated per NSTE-ACS management. However, in the presence of ongoing ischemia, instability, arrhythmias, or intermittent ST elevation, an immediate invasive strategy is required.
In which leads is a biphasic T wave most commonly found in Wellens syndrome?
Typically V2–V3, occasionally extending to V1 and V4.
How does Type A differ from Type B in Wellens syndrome?
Type A is a truly biphasic wave with an initial positive and terminal negative portion. Type B is a deeply symmetrical negative T wave without a mandatory initial positive phase. Type A may transition into Type B over time, but this is not a strict morphological equivalence.
ECG Course
Interpretation from basics to myocardial infarction — learn to read any ECG using a systematic algorithm.
- Video lessons and theory for every topic
- Simulator case studies under every lesson
- Unlimited ECG simulator practice
- Study guide: "All ECGs in 25 minutes"
ECG Strip Simulator
ECG, radiology, histology, pathomorphology, pharmacology — thousands of flashcards with detailed explanations.
- Real ECG strips, not textbook drawings
- Instant answers and explanations
- Streaks and progress tracking in your dashboard
Related terms
More in the section «Basics: waves, intervals, axes»
Sources
- Goldberger's Clinical Electrocardiography, current edition
- Hampton «The ECG in Practice»
- Surawicz, Knilans «Chou's Electrocardiography in Clinical Practice»
- ESC Guidelines for the management of acute coronary syndromes without persistent ST-segment elevation, 2023
Educational material for medical students and physicians. Does not replace clinical guidelines and physical examination; the ECG must always be interpreted in conjunction with the clinical picture.