Changes in Non-invasive Myocardial Stroke Work Related to Variation in Pacing Sites and Heart Rates in Adolescents.

Non-invasive assessment of myocardial work is a newly described technique to assess myocardial energetics. This has not been previously studied to assess the effects of right ventricular pacing at different sites or at different heart rates in children. We aimed to study the effects of right ventricular apical, septal, and His bundle pacing on myocardial work along with the effects of increasing heart rate. This was a prospective pilot study performed on six patients with structurally normal hearts and function following an electrophysiology study. Global work index and global work efficiency was highest during His pacing and lowest during right ventricular apical pacing. The global constructive work, index, and efficiency were progressively worse with increasing heart rates. In this prospective pilot study, we demonstrated that myocardial work indices differ depending on myocardial activation pattern and at different heart rates in pediatric patients. Myocardial performance as assessed by myocardial work efficiency is worse when pacing is performed at the right ventricular apex when compared to His and right ventricular septal pacing. Myocardial performance can be affected by higher heart rates, following a work-frequency relationship.