Cardiac phase variability in pulmonary root geometry: implications for electrophysiological mapping and ablation.

Background: The pulmonary root has emerged as a critical target for catheter ablation of ventricular arrhythmias, accounting for approximately 11% of idiopathic outflow tract arrhythmias. Current electroanatomical mapping systems assume stable cardiac geometry throughout the cardiac cycle, yet the dynamic behavior of the pulmonary root during interventional procedures remains poorly characterized. The aim of this study was to quantify geometric, morphometric, and positional variability of the pulmonary root between systole and diastole using ECG-gated computed tomography angiography, establishing clinically relevant reference values for electrophysiological interventions.

Methods: We analyzed ECG-gated contrast-enhanced CTA scans from 100 adult patients (51% female; mean age 59.5 ± 12.1 years) with normal cardiac function. Three-dimensional reconstructions were generated for both systolic and diastolic phases. Morphometric parameters were measured at four anatomical levels: basal ring, coaptation center plane, commissural plane, and tubular plane. Pulmonary root displacement and angulation changes were quantified.

Results: The basal ring demonstrated remarkable dimensional variability with 32.3 ± 30.7% reduction in cross-sectional area during systole, while the coaptation center plane remained relatively stable (6.0% variation). The entire pulmonary root underwent significant three-dimensional displacement (median 8.0 mm) with predominant caudal, ventral, and leftward movement during systole, accompanied by 5.6° increase in sagittal angulation. Pulmonary root volume increased significantly during systole (4.1% median increase, p = 0.001).

Conclusions: The pulmonary root undergoes substantial cardiac cycle-dependent anatomical changes that challenge current mapping system assumptions. These findings have immediate implications for catheter stability, procedural planning, and the development of motion-compensated electrophysiological technologies.