How do you differentiate supraventricular tachycardia (SVT) chest pain from acute coronary syndrome (ACS)?

Differentiating SVT Chest Pain from Acute Coronary Syndrome

The key to differentiating SVT from ACS lies in obtaining a 12-lead ECG within 10 minutes of presentation, measuring serial cardiac troponins, and recognizing that SVT typically presents with a regular, narrow-complex tachycardia (heart rate >150-220 bpm) that terminates abruptly with vagal maneuvers or adenosine, whereas ACS shows ischemic ECG changes and elevated biomarkers. 1, 2

Initial ECG Assessment

Obtain a 12-lead ECG immediately (within 10 minutes) for any patient presenting with chest pain. 1, 2

SVT Characteristics on ECG:

• Regular, narrow-complex tachycardia (QRS <0.09 seconds) with heart rate typically >150 bpm in adults, >180 bpm in children, >220 bpm in infants 1, 3
• P waves may be absent, buried in QRS, or seen at the end of QRS complex (appearing as pseudo R' in V1) 1
• No ST-segment elevation or depression indicative of ischemia 1
• Rhythm is perfectly regular without beat-to-beat variation 1

ACS Characteristics on ECG:

• ST-segment elevation (STEMI) or ST-segment depression/T-wave inversions (NSTE-ACS) 1, 2
• May have normal or nondiagnostic ECG initially - this does NOT rule out ACS 1, 2
• Heart rate variable, often with sinus tachycardia as a secondary response to ischemia 1

Diagnostic Maneuver: Response to Vagal Stimulation

A critical distinguishing feature is the response to vagal maneuvers or adenosine. 1

SVT Response:

• Abrupt termination of tachycardia with vagal maneuvers (Valsalva, carotid massage, ice to face) or adenosine 1, 4
• Immediate return to normal sinus rhythm when successful 1
• This response is diagnostic for AV node-dependent SVT 1

ACS Response:

• No termination of rhythm - may see slight slowing of sinus tachycardia but no abrupt conversion 1
• Chest pain persists despite rate control 1

Cardiac Biomarker Assessment

Measure cardiac troponin (preferably high-sensitivity) as soon as possible after ED presentation. 1, 2

SVT Pattern:

• Troponins typically normal unless SVT has been prolonged enough to cause demand ischemia 2
• If elevated, levels are usually modest and related to rate-related demand rather than plaque rupture 2

ACS Pattern:

• Elevated troponins with rising or falling pattern over serial measurements (at 0 and 6-12 hours) 1, 2
• The dynamic change (rise/fall) is key to diagnosing acute myocardial injury 1, 2

Clinical Presentation Patterns

SVT Presentation:

• Sudden onset of palpitations with chest discomfort 4, 3
• Dizziness or lightheadedness more prominent than chest pain 4
• Chest discomfort described as pressure or tightness related to rapid heart rate 4, 3
• Symptoms terminate abruptly when rhythm converts 4, 3
• Patient may report previous similar episodes that resolved spontaneously 3

ACS Presentation:

• Chest pain is primary symptom - pressure, squeezing, or heaviness 1
• Diaphoresis, dyspnea, nausea commonly associated 1
• Pain may radiate to arm, jaw, or back 1
• Symptoms persist despite position changes or rest 1
• May have hemodynamic instability (hypotension, pulmonary edema) 1

High-Risk Features Requiring ACS Workup

Even if SVT is diagnosed, pursue ACS evaluation if any of these features are present: 1, 2

• Elevated troponin levels 1, 2
• Persistent chest pain after rhythm conversion 1, 2
• Hemodynamic instability (hypotension, pulmonary edema) 1
• Diabetes mellitus 1
• Known coronary artery disease 1
• ECG changes suggesting ischemia (ST depression, T-wave inversions) 1

Critical Pitfalls to Avoid

Do not rely on a single normal or nondiagnostic ECG to exclude ACS - serial ECGs are essential when clinical suspicion remains high, especially if symptoms persist or change. 1, 2

Do not assume chest pain during tachycardia is purely rate-related - SVT can unmask underlying coronary disease or cause demand ischemia in patients with coronary stenosis. 1

Do not delay troponin measurement - it should be obtained immediately upon ED arrival, not after rhythm conversion. 1, 2

Avoid administering verapamil or diltiazem if QRS >120 ms until ventricular tachycardia is excluded, as this can cause hemodynamic collapse. 1

Algorithmic Approach

1. Obtain 12-lead ECG within 10 minutes 1, 2
2. If regular narrow-complex tachycardia (HR >150 bpm): Attempt vagal maneuvers 1
3. If rhythm terminates abruptly: Likely SVT - but still measure troponin 1, 2
4. If ST-segment changes present or troponin elevated: Manage as ACS regardless of rhythm 1, 2
5. If chest pain persists after rhythm conversion: Pursue full ACS evaluation with serial troponins and repeat ECGs 1, 2
6. If initial ECG nondiagnostic but suspicion high: Obtain serial ECGs and consider supplemental leads V7-V9 for posterior MI 1