The effect of ventricular sequential contraction on helical heart during pacing: high septal pacing versus biventricular pacing

Objective: To investigate the effect of biventricular and high septal pacing on the normal contraction sequence of the helical ventricular myocardial band, and its impact on left ventricular function. Methods: Ten pigs (25—68 kg) underwent analysis of percent segmental shortening (SS%) by sonomicrometry, with crystals placed along the fiber orientation of the ascending, descending segments, and posterior LV wall within the spatial geometry of the helical heart. Unipolar pacing electrodes stimulated the right atrium (RA) and either the right ventricular apex and left ventricular posterior wall (atrio-biventricular), or the proximal high septum (atrio-high septal). Systemic hemodynamics, QRS-interval, cardiac index (CI), systolic and diastolic LV functions and pressure—dimension loops (P—D) were analyzed and cardiac motion was monitored by video analysis