Exercise assessment of sinoatrial node function following the Mustard operation

Area of Science:

• Pediatric Cardiology
• Electrophysiology
• Congenital Heart Disease

Background:

• The Mustard procedure is a palliative surgery for transposition of the great arteries.
• Sinoatrial node dysfunction can be a long-term complication following this procedure.
• Assessing chronotropic response is crucial for identifying cardiac issues in pediatric patients.

Purpose of the Study:

• To evaluate maximal exercise testing as a noninvasive method for screening sinoatrial node dysfunction.
• To determine the prevalence of chronotropic incompetence in patients post-Mustard procedure.
• To correlate exercise-induced heart rate abnormalities with clinical outcomes.

Main Methods:

• Studied 29 patients at a mean of 6.7 years post-Mustard procedure.
• Assessed chronotropic response to graded maximal treadmill exercise.
• Performed intracardiac electrophysiologic evaluation in a subset of patients with abnormal responses.

Main Results:

• 93% had normal resting heart rate (HR), but 83% showed depressed maximum or recovery HR during/after exercise.
• Abnormal HR responses were observed even in patients with normal exercise tolerance.
• Electrophysiologic studies confirmed sinoatrial node dysfunction in 9 out of 16 patients with abnormal exercise responses.

Conclusions:

• Maximal exercise testing is a sensitive, noninvasive tool for detecting sinoatrial node dysfunction in children after the Mustard procedure.
• Abnormal heart rate responses to exercise are common, even without overt symptoms or arrhythmias.
• Early identification of sinoatrial node dysfunction can guide management in postoperative patients.