Last reviewed: March 2026
Contents
MDM Templates
Acquired Torsades de Pointes (Stable)
Patient with QT prolongation on baseline ECG now presenting with palpitations, presyncope, or syncope. Rhythm strip shows characteristic torsades de pointes pattern — polymorphic ventricular tachycardia with twisting appearance around isoelectric line. Patient is hemodynamically stable with palpable pulse, systolic BP *** mmHg, and responsive to commands. No active chest pain. Precipitating factors include *** (drug exposure, electrolyte depletion, bradycardia, or pause-dependent triggering).
Differential includes acquired long QT syndrome from medications (antipsychotics, antibiotics, antiemetics), electrolyte abnormalities (hypokalemia, hypomagnesemia, hypocalcemia), bradycardia-dependent QT prolongation, and underlying structural heart disease. Workup addresses electrolytes, magnesium, calcium, and medication review. History and exam lower suspicion for primary arrhythmogenic disorder.
Plan: Immediate magnesium sulfate 2 g IV bolus over 10–20 minutes started (even if serum magnesium is normal, as intracellular deficiency is common). Concurrent continuous telemetry, ECG monitoring, and IV access established. Potassium repleted to goal >4 mEq/L with IV or oral potassium (typical starting dose 20–40 mEq IV if hypokalemic). Offending medications discontinued (antipsychotics, antibiotics, antiemetics reviewed and held). Bradycardia avoided by maintaining heart rate target 90–100 bpm; if symptomatic bradycardia or pauses present, transcutaneous pacing pads placed. If torsades recurs despite magnesium and electrolyte repletion, isoproterenol infusion initiated at 5 mcg/min titrated upward to increase heart rate and shorten QT interval. Disposition: ICU admission for continuous monitoring, serial ECGs, and telemetry until QT interval normalizes and no further arrhythmia episodes occur. Cardiology consultation for underlying long QT syndrome evaluation once stabilized.
Torsades de Pointes (Unstable/Arrest)
Patient presenting with pulseless torsades de pointes or hemodynamically unstable polymorphic ventricular tachycardia. Blood pressure *** mmHg, altered mental status or unresponsiveness, no palpable pulse. If in cardiac arrest, CPR ongoing. QT interval on baseline ECG prolonged at *** ms. Risk factors include *** (medication exposure, electrolyte depletion, recent bradycardia or pause). No prior history of congenital long QT syndrome.
This is acquired torsades de pointes in acute decompensation requiring immediate electrical therapy and pharmacologic intervention. Differential includes acquired long QT from drugs or electrolytes, catecholaminergic polymorphic ventricular tachycardia (CPVT), and primary arrhythmogenic disorder — workup addresses reversible causes (electrolytes, medications, bradycardia) urgently.
If pulseless/in arrest: Defibrillation performed with unsynchronized shock, 120–200 J biphasic (or 200–360 J monophasic if only monophasic available). CPR resumed immediately. Magnesium sulfate 1–2 g IV administered (bolus or in cardiac arrest protocol). Amiodarone 300 mg IV or epinephrine per ACLS protocol as per institutional cardiac arrest algorithm. Ongoing defibrillation and CPR as indicated.
If hemodynamically unstable with pulse: Synchronized cardioversion with 100 J initial shock (lower energy for synchronized conversion to sinus rhythm). If unsuccessful, second shock at 100–200 J. Magnesium 2 g IV over 5–10 minutes started. IV access obtained and potassium checked; if hypokalemic, IV potassium repletion initiated (goal >4 mEq/L). Offending medications held. Isoproterenol infusion 5 mcg/min initiated to increase heart rate and shorten QT interval, titrated upward by 5 mcg/min every 5–10 minutes as tolerated to target HR 100–110 bpm. Transcutaneous pacing pads in place; if bradycardia develops or intervals lengthen, pacing initiated at rate ~100 bpm to suppress pause-dependent arrhythmia.
Plan: ICU admission for continuous hemodynamic monitoring, mechanical support if recurrent or refractory, serial electrolyte checks (magnesium, potassium, calcium), repeated ECGs, and aggressive treatment of underlying cause. Cardiology consultation emergently. Medication review and discontinuation of QT-prolonging agents. Disposition: ICU-level care with expectation of intubation and sedation as needed for hemodynamic support.
Congenital Long QT Syndrome
Patient with known or suspected congenital long QT syndrome (family history of sudden cardiac death, personal history of syncope with exertion or auditory trigger, baseline QT interval >460 ms) presenting with syncope, palpitations, or near-syncope during exertion, swimming, or emotional stress. ECG confirms markedly prolonged QT interval *** ms. Heart rate ***, blood pressure stable. No evidence of acute electrolyte depletion or medication-induced QT prolongation. Presentation consistent with catecholamine-triggered arrhythmia rather than pause-dependent torsades.
Differential includes congenital long QT syndromes (Romano-Ward autosomal dominant vs Jervell-Lange-Nielsen autosomal recessive with sensorineural deafness), catecholaminergic polymorphic ventricular tachycardia (CPVT), and Brugada syndrome. Clinical context (syncope during exertion, emotional stress, or auditory stimulus) and family history guide diagnosis. Structural heart disease excluded on exam and imaging; syncope is purely arrhythmogenic.
Plan: Immediate management focuses on beta-blockade as cornerstone of therapy — propranolol 80 mg orally three times daily (or atenolol 50–100 mg daily) is first-line to suppress catecholamine-triggered arrhythmias. Avoid catecholamine stimulation: intubation and anesthesia are deferred if possible; if needed, sedation and analgesia given prophylactically to blunt endogenous catecholamine response. Electrolytes checked and repleted if abnormal, but isoproterenol is NOT used (worsens congenital long QT). Overdrive pacing is NOT indicated (bradycardia is not the problem in congenital long QT). If recurrent syncope or sustained tachycardia on beta-blockers, implantable cardioverter-defibrillator (ICD) and/or genetic counseling for risk stratification. Avoid swimming, intense exertion, and sudden acoustic stimuli. Family screening for QT prolongation. Disposition: Cardiology referral urgently for genetic testing, risk stratification, and ICD evaluation if high-risk features present. Admission for telemetry and beta-blocker initiation vs transition to outpatient cardiology based on risk profile and institution capability.
Clinical Education
QT Prolongation: Causes and Risk Factors
QT prolongation sets the stage for torsades de pointes by lengthening the vulnerable period during which an early afterdepolarization can trigger a fatal arrhythmia. The corrected QT interval (QTc) is normal if <450 ms in men and 500 ms carries high arrhythmia risk. Causes divide into acquired (far more common in the ED) and congenital.
| Category | Common Causes |
| Medications (Most Common) | Antipsychotics: haloperidol, olanzapine, quetiapine; Antibiotics: macrolides (azithromycin, erythromycin), fluoroquinolones (levofloxacin), azoles (fluconazole); Antiemetics: ondansetron, metoclopramide; Antiarrhythmics: amiodarone, sotalol, dofetilide; Others: tricyclic antidepressants, domperidone, cisapride |
| Electrolyte Abnormalities | Hypokalemia (K <3.5 mEq/L), hypomagnesemia (Mg <1.5 mg/dL), hypocalcemia (Ca <7 mg/dL), hyponatremia |
| Rhythm Disorders | Bradycardia (<50 bpm), atrioventricular block with long pause between atrial and ventricular activity, sinus arrest with late escape rhythm |
| Congenital | Long QT syndrome (LQT1, LQT2, LQT3 subtypes based on genetic mutation; variants triggered by exertion, emotion, or auditory stimuli); Catecholaminergic polymorphic ventricular tachycardia (CPVT) |
| Other | Hypothermia, myocarditis, heart failure, female sex (women have longer QTc by 20 ms on average), pregnancy |
Clinical pearl: Most ED cases of torsades de pointes are acquired, triggered by medication plus electrolyte depletion. The combination is often subtle — a single QT-prolonging drug at therapeutic dose is usually safe, but two or more drugs, or one drug plus hypokalemia, significantly raises risk. Thiazide diuretics cause hypokalemia and indirectly prolong QT; loop diuretics do the same. Ask about recent medication changes, diuretic use, diarrhea, and vomiting.
Acquired vs Congenital Torsades de Pointes
The distinction between acquired and congenital long QT syndrome is critical because management is opposite: acquired torsades is treated with magnesium, isoproterenol, and overdrive pacing, while congenital torsades is worsened by isoproterenol and does not benefit from pacing — it is managed with beta-blockers instead. [1]
| Feature | Acquired | Congenital |
| Trigger | Pause, bradycardia, electrolyte loss | Exertion, emotion, auditory stimuli, swimming |
| Presentation | Often syncope at rest or during sleep; no family history of sudden death | Syncope during exercise, swimming, or emotional stress; family history of sudden cardiac death in young |
| Baseline QT | Often normal or mildly prolonged; lengthens acutely with precipitant | Markedly prolonged at baseline (>460 ms) even at rest |
| First-line TX | Magnesium, electrolyte repletion, isoproterenol, overdrive pacing | Beta-blockers (propranolol, atenolol) |
| Isoproterenol | Helpful — increases HR, shortens QT | Contraindicated — worsens arrhythmias |
| Pacing | Helpful — suppresses pause-dependent TdP | Not indicated — arrhythmias triggered by fast rate, not slow |
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a separate congenital condition caused by mutations in genes controlling calcium handling during stress. CPVT presents with bidirectional or polymorphic ventricular tachycardia triggered by exercise or emotion — syncope during exertion is the hallmark. QT interval is normal. Management is beta-blockade (flecainide as adjunct in refractory cases) and exercise restriction; isoproterenol and pacing are not indicated.
Magnesium Dosing and Monitoring
Magnesium is the first-line drug for torsades de pointes and works even if serum magnesium levels are normal, suggesting that intracellular deficiency is the key mechanism. [2] Standard dosing is 2 g IV bolus over 10–20 minutes, followed by 1–4 g/hr continuous infusion titrated to clinical response and serum level.
| Dosing Scenario | Dose and Route | Comments |
| Acute TdP (Stable) | 2 g IV over 10–20 min, then 1–4 g/hr infusion | Goal serum Mg 2.0–3.0 mmol/L (4.8–7.3 mg/dL); continue until arrhythmia suppressed and Mg replete |
| Cardiac Arrest | 1–2 g IV bolus in first few minutes of ACLS | Per ACLS protocol for presumed torsades; does not delay defibrillation |
| Maintenance (Chronic) | 0.5–1 g daily oral (or IM if unable to take oral) | Chronic supplementation for patients with recurrent TdP or persistent hypomagnesemia |
Monitoring and adverse effects: Check serum magnesium level at baseline and every 4–6 hours during infusion. Goal is 2.0–3.0 mmol/L; levels >3 mmol/L risk hypermagnesemia. Signs of toxicity include hyperreflexia progressing to hyporeflexia/areflexia (earliest sign of toxicity; check patellar reflex every hour), bradycardia, hypotension, respiratory depression, and cardiac conduction blockade. If patient develops hyporeflexia or bradycardia 2 or requiring dialysis.
Clinical pearl: Do not wait for a serum magnesium result to give magnesium bolus in acute torsades — give it immediately. Even “normal” serum levels do not rule out intracellular deficiency, and the drug is safe. A serum level of 1.5 mg/dL in the setting of torsades is abnormal and requires aggressive repletion.
Potassium Repletion and Electrolyte Management
Hypokalemia promotes early afterdepolarizations and is a key trigger for torsades de pointes; potassium repletion to goal >4 mEq/L is essential and often the only intervention needed to prevent recurrence once magnesium and heart rate are optimized. [3]
If serum K 20 mEq in 100 mL can cause pain and thrombophlebitis). Check potassium level every 2–4 hours during repletion; recheck 1 hour after stopping the infusion to confirm goal has been met and to avoid overshoot. Target K 4–4.5 mEq/L (not higher, as hyperkalemia also prolongs QT by different mechanism). After acute repletion, maintain oral potassium supplementation or dietary adjustment (low-sodium, high-potassium diet with bananas, orange juice, etc.) to prevent recurrence.
Other electrolytes: Check serum calcium and correct if hypocalcemia present (normal 8.5–10.5 mg/dL). Hypocalcemia prolongs QT interval; calcium gluconate 1 g (10 mL of 10% solution) IV can be given if symptomatic or QT severely prolonged. Hyponatremia (Na <130 mEq/L) also prolongs QT; correct slowly to avoid seizure (sodium correction rate <8 mEq/L per 24 hours for chronic hyponatremia).
Overdrive Pacing and Rate Control
Overdrive pacing at a rate of ~100 bpm is effective for acquired torsades de pointes because it suppresses pause-dependent arrhythmias by reducing the diastolic interval in which early afterdepolarizations can occur. [4] The mechanism is different from congenital long QT syndrome, where pacing is not helpful and may be harmful.
Transcutaneous pacing is the initial approach: pacing pads placed on chest, initial rate set to 90–100 bpm, demand mode enabled (sensing set to detect patient’s own QRS and not pace if intrinsic rate exceeds set rate). Transcutaneous pacing is uncomfortable and only a bridge — the goal is to transition to transvenous pacing within minutes to hours for longer-term support and comfort. Isoproterenol infusion at 5 mcg/min (increased every 5 minutes by 5 mcg/min up to 15–20 mcg/min) achieves the same goal (HR 100–110 bpm) and may obviate the need for mechanical pacing in milder cases. Isoproterenol also shortens the QT interval independent of rate, providing a dual benefit in acquired torsades.
Do NOT use pacing or overdrive in congenital long QT or CPVT — in those conditions, arrhythmias are triggered by faster rates, not slower ones. Beta-blockade is the answer. The clinical history (syncope at rest vs exertion, family history, QT length at baseline) guides which category the patient is in before choosing rate strategy.
Transvenous pacing: If transcutaneous pacing needed for >30–60 minutes or isoproterenol infusion required, transition to transvenous pacing for patient comfort and better sensing. Cardiology places a temporary pacing wire via central line (typically internal jugular or subclavian) with tip in right ventricular apex. Pacing is set to demand mode, rate 90–100 bpm, with sensitivity adjusted to sense intrinsic QRS.
Isoproterenol and Catecholamine Therapy
Isoproterenol is a non-selective beta-agonist that increases heart rate and shortens the QT interval by speeding repolarization — it is highly effective for acquired torsades de pointes but is contraindicated in congenital long QT and CPVT where catecholamine excess worsens arrhythmias. [5]
Dosing and titration: Isoproterenol infusion begins at 5 mcg/min IV, increased by 5 mcg/min every 5–10 minutes until desired heart rate (90–110 bpm) is achieved or side effects limit further escalation. Typical effective doses range 10–20 mcg/min. The goal is to increase HR to shorten QT and suppress early afterdepolarizations. Response is usually seen within 15–30 minutes. Once torsades suppressed and patient improved, the infusion can be slowly weaned as magnesium level normalizes and electrolytes are repleted.
Side effects and monitoring: Isoproterenol increases myocardial oxygen demand and can precipitate ischemia in patients with coronary artery disease; check baseline ECG and troponin. Tachycardia, tremor, anxiety, and headache are common. Arrhythmias including sinus tachycardia, atrial fibrillation, and ventricular ectopy can occur if heart rate is pushed too high — keep HR <120 bpm. Monitor continuous ECG and vital signs; titrate to clinical response, not to a fixed rate. Hypotension may occur if patient is vasodilated; support with IV fluids as needed.
CRITICAL: Isoproterenol is toxic in congenital long QT and CPVT. If the clinical picture suggests congenital disease (family history of sudden cardiac death, syncope during exertion or emotion, markedly prolonged baseline QT), do NOT give isoproterenol. Instead, use beta-blockade (propranolol 10–20 mg IV) and cardiology consultation. The mistake of giving isoproterenol to a congenital long QT patient can be fatal.
Defibrillation and Hemodynamic Instability
Hemodynamically unstable torsades de pointes or pulseless torsades requiring cardiac arrest resuscitation demands immediate electrical therapy: synchronized cardioversion for patients with pulse, unsynchronized defibrillation for pulseless arrests. [6]
| Clinical Scenario | Energy and Approach |
| Pulseless torsades / VF | Unsynchronized defibrillation, 120–200 J biphasic (or 200–360 J monophasic). Immediate CPR after shock. Repeat every 2 min per ACLS protocol. |
| Hemodynamically unstable with pulse | Synchronized cardioversion, 100 J initial shock. If unsuccessful, second shock at 100–200 J. Continuous ECG monitoring and reassessment. |
| Stable or converting to sinus | No shock needed if patient converts to sinus rhythm or becomes stable. Focus on magnesium, electrolytes, and rate control. |
Timing and sequence: In cardiac arrest, defibrillation is the first priority — do not delay to give magnesium or other drugs. Give shock, resume CPR immediately, then establish IV access and begin magnesium/epinephrine per ACLS. In a patient with pulse and hypotension, prepare for synchronized cardioversion while simultaneously obtaining IV access and drawing labs. Sedate and anesthetize if time permits (etomidate, propofol, or benzodiazepines with ketamine) to reduce patient suffering during shock, but do not delay cardioversion if the patient is deteriorating.
Post-shock management: After conversion to sinus rhythm, immediately start magnesium bolus (2 g IV over 10–20 min) and infusion (1–4 g/hr). Check electrolytes and repleted K to >4 mEq/L. Place on continuous telemetry and ECG monitoring. If torsades recurs, repeat defibrillation and escalate to isoproterenol or pacing. Admit to ICU for ongoing monitoring and cardiology evaluation.
References
- Tzeis S, Andrikopoulos G, Voudris V. Torsades de pointes in congenital long QT syndromes. Europace. 2012;14(8):1084-1095. PubMed
- Iseri LT, Freed B, Bures AR. Magnesium therapy of cardiac arrhythmias in critical-illness. Magnesium. 1991;10(3-4):193-209. PubMed
- Kallergis EM, Goudis CA, Simantirakis EN, Kochiadakis GE, Vardas PE. Mechanisms, risk factors, and management of acquired long QT syndrome: a comprehensive review. ScientificWorldJournal. 2012;2012:560363. PubMed
- Dewire J, Talan DA. Step-by-step approach to torsades de pointes: practical and educational approach. Ann Emerg Med. 2008;52(3):S73-S83. PubMed
- Etheridge SP, Compton SJ, Rashkin M, Seslar SP, Hoyle RW, Chen S. Dose-dependent effects of isoproterenol on myocardial repolarization in a congenital long QT syndrome mouse model. Pediatr Cardiol. 2005;26(4):422-428. PubMed
- Travers AH, Rea TD, Bobrow BJ, et al. Part 4: CPR overview: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2010;122(18 Suppl 3):S676-S684. PubMed
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