True or False

A 68-year-old man with a previous myocardial infarction (1 year ago) is performing a cardiac stress test. He is on a treadmill and reaches his target heart rate without chest pain or claudication. You are watching the cardiac monitor and his sinus tachycardia turns into ventricular tachycardia. Nevertheless, the man is still walking.

True or False?

You should provide an unsynchronized cardioversion (“shock”) to treat this man’s ventricular tachycardia?

Answer

FALSE! There are two shockable rhythms in advanced cardiovascular life support: ventricular fibrillation and pulseless ventricular tachycardia. Ventricular tachycardia can occur without lowering blood pressure and without causing symptoms. In fact, non-sustained ventricular tachycardia is a relatively common occurrence in people with coronary artery disease and often causes no symptoms whatsoever.

Non-sustained ventricular tachycardia is generally defined as three or more consecutive ventricular beats at a rate of greater than 120 bpm over a duration of less than 30 seconds. It is commonly noted in people having a routine electrocardiogram or performing exercise while attached to a cardiac monitor. Initial reports were that non-sustained ventricular tachycardia is associated with lower life expectancy, but newer work has shown that when one controls for other variables, this arrhythmia does not affect long-term cardiac health or life expectancy.

Consequently, non-sustained ventricular tachycardia should not be “shocked” nor should the Observer be shocked if they see this rhythm. If the man were to lose consciousness, ventricular tachycardia with sustained and the man has no palpable pulse then this would be a shockable rhythm and ACLS algorithms should be followed. In this clinical case, however, non-sustained ventricular tachycardia is an incidental finding that should be noted, but not treated with unsynchronized cardioversion.

References

Echt DS, Liebson PR, Mitchell LB, et al. Mortality and morbidity in patients receiving encainide, flecainide, or placebo. The Cardiac Arrhythmia Suppression Trial. N Engl J Med. Mar 21 1991;324(12):781-788. doi:10.1056/nejm199103213241201

Marine JE, Shetty V, Chow GV, et al. Prevalence and prognostic significance of exercise-induced nonsustained ventricular tachycardia in asymptomatic volunteers: BLSA (Baltimore Longitudinal Study of Aging). J Am Coll Cardiol. Aug 13 2013;62(7):595-600. doi:10.1016/j.jacc.2013.05.026

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