Which ECG finding is typically associated with SVT?

• A. Narrow QRS complexes with regular rapid rhythm
• B. Wide QRS complexes with irregular rhythm
• C. Prolonged QT interval with slow rhythm
• D. Absent P waves with variable rhythm

Answer: (A)

SVT on ECG is defined by a rapid, regular rhythm with narrow QRS complexes. This happens because the electrical impulse originates above the ventricles and travels through the normal His-Purkinje system, so ventricular depolarization is brief and narrow. The rate is typically around 150–250 beats per minute, and P waves may be hidden in or just after the QRS complex, making them hard to see. This combination—fast, regular rhythm with narrow QRS—is the hallmark of SVT.

Wide QRS with irregular rhythm would point toward something like atrial fibrillation with rapid conduction or a ventricular origin, not SVT. Slow, prolonged QT with rhythm change isn’t characteristic of SVT. Absent P waves with a variable rhythm suggests atrial fibrillation or another atrial tachyarrhythmia, not typical SVT.