A 64-year-old man presents to the emergency department because of sudden-onset palpitations and lightheadedness that began 30 minutes ago. He denies chest pain, syncope, or shortness of breath. His medical history includes an anterior myocardial infarction 3 years ago, ischemic cardiomyopathy with a left ventricular ejection fraction of 32%, hypertension, and type 2 diabetes mellitus. Medications include aspirin, atorvastatin, sacubitril-valsartan, metoprolol succinate, spironolactone, and empagliflozin. Temperature is 36.8°C (98.2°F), blood pressure is 108/68 mm Hg, pulse is 168/min and regular, respiratory rate is 18/min, and oxygen saturation is 97% on room air. He is alert and answers questions appropriately. On physical examination, the jugular venous pressure is normal, the lungs are clear, and the extremities are warm. Cardiac examination reveals a rapid regular rhythm without a new murmur. ECG demonstrates a regular wide-complex tachycardia with a QRS duration of 180 milliseconds. The QRS complexes have a uniform morphology. Occasional P waves are visible without a consistent relationship to the QRS complexes, and intermittent fusion beats are present. Serum potassium and magnesium concentrations are normal.
Which of the following is the most appropriate initial treatment?
The correct answer is:
B) Intravenous amiodarone
This patient has sustained monomorphic ventricular tachycardia and is currently hemodynamically stable. The regular wide-complex rhythm, marked QRS prolongation, atrioventricular dissociation, and fusion beats strongly support a ventricular origin. His prior myocardial infarction and reduced ejection fraction provide the underlying substrate: reentry around an area of ventricular scar.
Management of ventricular tachycardia depends primarily on whether the patient has a pulse and whether the rhythm is causing hemodynamic instability. This patient remains alert, has preserved blood pressure, and has no ischemic chest pain, pulmonary edema, or signs of shock. Stable monomorphic ventricular tachycardia can therefore be treated initially with an intravenous antiarrhythmic medication such as amiodarone, procainamide, or sotalol, with continuous monitoring and immediate access to cardioversion if deterioration occurs.
The rhythm should be presumed to be ventricular tachycardia in an older patient with structural heart disease and a regular wide-complex tachycardia. Treating presumed ventricular tachycardia as a supraventricular rhythm can be dangerous, particularly if AV nodal–blocking drugs are administered.
Even if the acute episode terminates, this patient will require evaluation for secondary prevention of sudden cardiac death. Sustained ventricular tachycardia in the setting of ischemic cardiomyopathy is generally an indication for an implantable cardioverter-defibrillator after reversible causes have been excluded.
Answer choice A: Intravenous adenosine, is incorrect.
Adenosine transiently blocks AV nodal conduction and is most effective for AV node–dependent supraventricular tachycardias. It may occasionally be used diagnostically in a stable, regular monomorphic wide-complex tachycardia when supraventricular tachycardia with aberrancy remains possible. However, this patient has structural heart disease, AV dissociation, and fusion beats, all of which strongly indicate ventricular tachycardia. A ventricular antiarrhythmic is more appropriate.
Answer choice C: Intravenous diltiazem, is incorrect.
Diltiazem is useful for ventricular rate control in selected supraventricular tachyarrhythmias. It should not be administered for an undifferentiated wide-complex tachycardia because it can worsen hypotension and may precipitate cardiovascular collapse in ventricular tachycardia. The patient’s reduced ejection fraction provides an additional reason to avoid its negative inotropic effects.
Answer choice D: Immediate unsynchronized defibrillation, is incorrect.
Unsynchronized defibrillation is indicated for ventricular fibrillation or pulseless ventricular tachycardia. This patient has a pulse and remains hemodynamically stable. Delivering an unsynchronized shock in a perfusing rhythm could induce ventricular fibrillation if the shock occurs during ventricular repolarization.
Answer choice E: Synchronized electrical cardioversion, is incorrect.
Synchronized cardioversion is the preferred immediate treatment when ventricular tachycardia causes hypotension, altered mental status, ischemic chest discomfort, acute heart failure, or other evidence of instability. Although cardioversion would be appropriate if this patient deteriorates or fails pharmacologic therapy, his current stability permits initial treatment with an intravenous antiarrhythmic.
Key Learning Point
A regular wide-complex tachycardia in a patient with prior myocardial infarction or structural heart disease should be presumed to be ventricular tachycardia. Stable monomorphic ventricular tachycardia can be treated with an intravenous antiarrhythmic, whereas unstable ventricular tachycardia requires synchronized cardioversion.
