During a sinus node pause, which event occurs?

During a sinus node pause, which event occurs?

• A. The SA node fails to generate a signal
• B. The SA node generates a signal but exits normally
• C. The AV node blocks conduction
• D. The ventricles fail to depolarize

Answer: (A)

A sinus node pause is defined by a temporary failure of the SA node to generate an electrical impulse. Because the SA node is the heart’s natural pacemaker, its pause creates a gap in atrial activity, so there’s no P wave and no subsequent QRS complex for that brief interval. After the pause, the SA node usually resumes firing, or, if the pause is long, an escape rhythm from the AV node (or below) may take over to maintain a heartbeat. This differs from AV block, where conduction from atria to ventricles is impaired, or from ventricular arrest, where the ventricles fail to depolarize. It also wouldn’t produce a pause if the SA node were generating impulses that exit normally without a stoppage.

A sinus node pause is defined by a temporary failure of the SA node to generate an electrical impulse. Because the SA node is the heart’s natural pacemaker, its pause creates a gap in atrial activity, so there’s no P wave and no subsequent QRS complex for that brief interval. After the pause, the SA node usually resumes firing, or, if the pause is long, an escape rhythm from the AV node (or below) may take over to maintain a heartbeat. This differs from AV block, where conduction from atria to ventricles is impaired, or from ventricular arrest, where the ventricles fail to depolarize. It also wouldn’t produce a pause if the SA node were generating impulses that exit normally without a stoppage.