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Clinical Medicine

Test yourself: Ventricular tachycardia

From the April ACP Hospitalist, copyright © 2009 by the American College of Physicians

The following cases and commentary, which address ventricular tachycardia, are excerpted from ACP’s Medical Knowledge Self- Assessment Program (MKSAP14).

Case 1: Ongoing ventricular fibrillation

A 73-year-old woman who has been hospitalized for chest pain and placed on a cardiac monitor develops ventricular fibrillation. She is evaluated immediately and found to be cyanotic, pulseless, and not breathing. Within seconds, a defibrillator is brought to the room, and advanced cardiac life support is begun, including three shocks, intubation, and ventilation; intravenous access is established. She remains in ventricular fibrillation.

Which of the following would be appropriate immediate therapy in this patient?

A. Amiodarone
B. Lidocaine
C. Magnesium sulfate
D. Procainamide
E. Vasopressin

View correct answer.

Case 2: Cardiac arrest in a young woman

A 26-year-old woman is admitted to the hospital for evaluation after having survived a cardiac arrest. She had been resuscitated promptly using an automated external defibrillator. The initial rhythm was ventricular fibrillation. She does not smoke or use illicit drugs, and was feeling well before the event. Her medical history is unremarkable, and there is no family history of cardiovascular disease.

The cardiac examination is pertinent for a grade 2/4 early systolic murmur along the left sternal border. The echocardiogram demonstrates a septal wall thickness of 3.2 cm (normal <1.1 cm).

What therapeutic intervention would improve her survival?

A. Septal myomectomy
B. Beta-blocker therapy
C. Placement of an implantable cardioverter defibrillator
D. Avoidance of strenuous exercise

View correct answer.

Case 3: Palpitations during exercise

A 23-year-old man is evaluated for palpitations that occur during exercise. He is otherwise healthy and takes no medications. Both the physical examination and the resting electrocardiogram are normal. A stress test demonstrates sustained monomorphic ventricular tachycardia at 201/min at peak exercise. There were no ischemic changes until the arrhythmia developed. The ventricular tachycardia had a left bundle and inferior axis morphology and terminated spontaneously after seven minutes of rest. An echocardiogram is normal, and an MRI shows no abnormalities in the right or left ventricles.

What is the most likely etiology of ventricular tachycardia in this patient?

A. Coronary spasm
B. Idiopathic
C. Arrhythmogenic right ventricular cardiomyopathy
D. Infiltrative heart disease
E. Anomalous origin of the coronary arteries

View correct answer.

Answers and commentary

.

Case 1

Correct answer: E. Vasopressin.

Vasopressin therapy would be an acceptable alternative to epinephrine in this patient with ventricular fibrillation. Historically, the treatment has been epinephrine, but now vasopressin is an alternative to epinephrine as a single 40-U intravenous bolus for asystole, ventricular fibrillation or pulseless ventricular tachycardia. It is not indicated for the treatment of pulseless electrical activity. Randomized studies and meta-analysis have failed to demonstrate superior outcome associated with vasopressin therapy compared to epinephrine.

As a result of studies showing a favorable response to vasopressin, the current American Heart Association guidelines for advanced cardiac life support state that a single dose of vasopressin can be administered as a one-time alternative to epinephrine in patients with ventricular fibrillation or pulseless ventricular tachycardia. The sequence of events to be followed includes defibrillation, COTE (cardiopulmonary resuscitation, oxygen, tubes [endotracheal and intravenous], epinephrine [or vasopressin]), and more defibrillation. Amiodarone, lidocaine, magnesium sulfate, and procainamide are not included in the guidelines as immediate management options for ventricular fibrillation.

Key points The advanced cardiac life support guidelines state that a single dose of vasopressin can be administered as a one-time alternative to epinephrine in patients with ventricular fibrillation or pulseless ventricular tachycardia. In patients with ventricular fibrillation or pulseless ventricular tachycardia, the guidelines for advanced cardiac life support recommend the following sequence of interventions: defibrillation, COTE (cardiopulmonary resuscitation, oxygen, tubes [endotracheal and intravenous], epinephrine [or vasopressin]), and more defibrillation.

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Case 2

Correct answer: C. Placement of an implantable cardioverter defibrillator.

This patient’s echocardiographic findings indicate that she has hypertrophic cardiomyopathy. Survivors of cardiac arrest due to ventricular tachycardia or ventricular fibrillation without a reversible cause remain at risk for recurrent arrhythmia with a high mortality rate. Implantable cardioverter defibrillator therapy is the treatment of choice in this population, and has been shown to be superior to antiarrhythmic drug therapy. In addition, nonrandomized studies have shown that patients with hypertrophic cardiomyopathy at high risk of sudden death benefit from an implantable cardioverter defibrillator, even those patients who are already on beta-blocker therapy.

Myomectomy is mainly reserved for patients who are symptomatic from outflow obstruction (the case patient was feeling well prior to her arrest), but it is unclear whether relief of outflow obstruction affects survival. Beta-blockers have not been shown to improve survival in patients with hypertrophic cardiomyopathy. Avoidance of strenuous exercise is recommended to patients with hypertrophic cardiomyopathy, but it is not known whether this helps survival.

Key point Implantable cardioverter defibrillator therapy reduces risk of sudden death in survivors of cardiac arrest due to ventricular tachycardia or ventricular fibrillation without a reversible cause.

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Case 3

Correct answer: B. Idiopathic.

Unlike other types of ventricular tachycardia, idiopathic ventricular tachycardia (ventricular tachycardia without structural heart disease) carries a good prognosis. Idiopathic ventricular tachycardia is diagnosed based on the electrocardiogram characteristics of ventricular tachycardia after excluding the presence of structural heart disease. Fewer than 5% of patients presenting with ventricular tachycardia have the idiopathic type.

Because the prognosis is good in these patients, therapy is aimed at controlling symptoms. Medical therapy can be tried initially with beta-blockers for those with right ventricular outflow tract tachycardia, and with verapamil for those with idiopathic left ventricular tachycardia. For refractory symptoms, the cure rate with radiofrequency catheter ablation is excellent.

Coronary spasm can result in ventricular arrhythmia, but patients usually present with chest pain and ST-segment elevation, which this patient did not report. The normal resting electrocardiogram, MRI, and echocardiogram rule out infiltrative diseases or arrhythmogenic right ventricular cardiomyopathy (fatty infiltration of the right ventricle). Anomalous origin of the coronary arteries can result in ventricular tachycardia or ventricular fibrillation in young people, but an MRI would detect this defect.

Key points Ventricular tachycardia without structural heart disease carries a good prognosis. For idiopathic ventricular tachycardia with refractory symptoms, radiofrequency catheter ablation has an excellent cure rate.

The information included herein should never be used as a substitute for clinical judgment and does not represent an official position of ACP. For more information on MKSAP, go to mksap.acponline.org.

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