Cardiology · Arrhythmias
The facts most likely to be tested
Ventricular tachycardia (VT) is defined as a wide-complex tachycardia with a rate typically exceeding 100 beats per minute originating from the ventricles.
Hemodynamically unstable patients with monomorphic VT require immediate synchronized cardioversion to restore sinus rhythm.
Pulseless VT is a shockable rhythm that mandates immediate unsynchronized defibrillation and initiation of Advanced Cardiac Life Support (ACLS) protocols.
Stable monomorphic VT is initially managed with antiarrhythmic medications such as amiodarone, procainamide, or lidocaine.
AV dissociation, fusion beats, and capture beats are the most specific electrocardiogram (ECG) findings that confirm a diagnosis of VT over supraventricular tachycardia with aberrancy.
Brugada criteria are utilized to differentiate VT from supraventricular tachycardia with aberrancy in the setting of a wide-complex tachycardia.
Implantable cardioverter-defibrillator (ICD) placement is the definitive long-term management for patients with sustained VT or those at high risk for sudden cardiac death.
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A 68-year-old male with a history of prior myocardial infarction presents to the emergency department with palpitations and lightheadedness. His blood pressure is 88/50 mmHg and his heart rate is 160 bpm. The ECG reveals a wide-complex tachycardia with AV dissociation and fusion beats. The patient is currently diaphoretic and appears lethargic.
What is the most appropriate next step in management?
Immediate synchronized cardioversion
The patient is hemodynamically unstable (hypotension, altered mental status) with VT, necessitating immediate electrical cardioversion as per ACLS guidelines.
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Etiology / Epidemiology
Most common in patients with structural heart disease or prior MI. Often triggered by reentry circuits.
Clinical Manifestations
Presents as palpitations, syncope, or hemodynamic instability. Look for AV dissociation on ECG.
Diagnosis
Diagnosed via 12-lead ECG showing ≥3 consecutive PVCs at a rate of >100 bpm.
Treatment
Unstable: Synchronized cardioversion. Stable: Amiodarone. Avoid CCBs in wide-complex tachycardia.
Prognosis
High risk of sudden cardiac death. LVEF ≤35% is a primary indication for ICD placement.
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Epidemiology & Etiology
Predominantly affects patients with ischemic cardiomyopathy or prior myocardial infarction. Other causes include electrolyte abnormalities (hypokalemia/hypomagnesemia) and prolonged QT syndrome. It is a major cause of morbidity in patients with heart failure.
Pertinent Anatomy
Originates from the ventricular myocardium below the bundle of His. The focus bypasses the normal conduction system, resulting in wide QRS complexes.
Pathophysiology
Most cases involve reentry circuits around areas of myocardial scarring. The rapid, disorganized ventricular contraction leads to decreased cardiac output and impaired coronary perfusion. If sustained, it frequently degenerates into ventricular fibrillation.
Clinical Manifestations
Patients may present with lightheadedness, chest pain, or dyspnea. Physical exam may reveal cannon a-waves due to AV dissociation. Hemodynamic instability (hypotension, altered mental status) requires immediate intervention.
Diagnosis
The 12-lead ECG is the diagnostic standard, demonstrating wide QRS complexes (>120 ms). AV dissociation or fusion beats are highly specific. Electrophysiologic studies may be used to map the focus in recurrent cases.
Treatment
Unstable patients require synchronized cardioversion. Stable patients are treated with Amiodarone or Procainamide. Do not use Verapamil or Diltiazem in wide-complex tachycardia as they can cause cardiovascular collapse.
Prognosis
Risk of progression to ventricular fibrillation is significant. Patients with LVEF ≤35% or symptomatic VT require an Implantable Cardioverter-Defibrillator (ICD) to prevent sudden cardiac death.
Differential Diagnosis
SVT with aberrancy: usually has a known history of SVT
Pre-excited tachycardia: Wolff-Parkinson-White syndrome
Hyperkalemia: presents with peaked T-waves and sine wave pattern
Torsades de Pointes: associated with prolonged QT interval
Ventricular escape rhythm: rate <40 bpm