Orthodromic accessory pathway manifests on an ECG as a delta wave.

Orthodromic accessory pathway manifests on an ECG as a delta wave.

• A. True
• B. False
• C. Only during tachycardia
• D. It depends on conduction velocity

Answer: (B)

Delta waves appear when an accessory pathway conducts antegradely from atria to ventricles, causing preexcitation and a shortened PR interval with a slurred initial QRS. In orthodromic AVRT, the ventricles are activated through the normal AV node antegradely, and the accessory pathway is used only retrogradely during tachycardia. So during normal rhythm there is no preexcitation via the pathway, and no delta wave is seen. Delta waves would be present only if the pathway conducted antegradely (preexcitation), as in WPW pattern or antidromic AVRT. Hence the statement is false.

Delta waves appear when an accessory pathway conducts antegradely from atria to ventricles, causing preexcitation and a shortened PR interval with a slurred initial QRS. In orthodromic AVRT, the ventricles are activated through the normal AV node antegradely, and the accessory pathway is used only retrogradely during tachycardia. So during normal rhythm there is no preexcitation via the pathway, and no delta wave is seen. Delta waves would be present only if the pathway conducted antegradely (preexcitation), as in WPW pattern or antidromic AVRT. Hence the statement is false.