Which rhythm is common initial rhythm in out-of-hospital witnessed sudden cardiac arrest?

Which rhythm is common initial rhythm in out-of-hospital witnessed sudden cardiac arrest?

• A. Pulseless ventricular tachycardia
• B. Ventricular Fibrillation (VF)
• C. Asystole
• D. Normal sinus rhythm

Answer: (B)

Ventricular fibrillation is a chaotic, unsynchronized electrical activity of the ventricles that produces no effective heartbeat. In out-of-hospital sudden cardiac arrest that is witnessed, collapse is often followed by this disorganized rhythm, so there is no pulse and little or no blood flow. Because there is no coordinated contraction, defibrillation is needed to reset the electrical activity and allow the heart to regain a usable rhythm, ideally very soon after collapse. That makes it the most common initial rhythm in witnessed OHCA and the rhythm you treat first with a shock to maximize chances of survival. Asystole represents no electrical activity at all and is not shockable, and a normal sinus rhythm would indicate the heart is beating normally rather than in arrest, so those are not the typical initial rhythms in this scenario.

Ventricular fibrillation is a chaotic, unsynchronized electrical activity of the ventricles that produces no effective heartbeat. In out-of-hospital sudden cardiac arrest that is witnessed, collapse is often followed by this disorganized rhythm, so there is no pulse and little or no blood flow. Because there is no coordinated contraction, defibrillation is needed to reset the electrical activity and allow the heart to regain a usable rhythm, ideally very soon after collapse. That makes it the most common initial rhythm in witnessed OHCA and the rhythm you treat first with a shock to maximize chances of survival.

Asystole represents no electrical activity at all and is not shockable, and a normal sinus rhythm would indicate the heart is beating normally rather than in arrest, so those are not the typical initial rhythms in this scenario.