High rate right ventricular pacing causes global impairment of myocardial blood flow in an experimental model of heart failure

Abstract

Purpose: Prolonged right ventricular (RV) pacing at high heart rate (HR) induces progressive left ventricle (LV) dysfunction in the experimental animal. It is unclear whether RV stimulation, either acute or prolonged, may also alter regional and global myocardial blood flow (MBF). The aim of this study is to assess regional and global MBF at spontaneous sinus rhythm and during RV apical pacing at baseline and after 4 weeks of prolonged high rate RV stimulation in a group of minipigs. Methods: Six adult minipigs underwent RV pacing (220 beats/min) for 4 weeks. Positron emission tomography (ECAT HR Plus, Siemens, CTI Inc.) and 2D-echocardiography (ECHO) were performed at baseline (PRE) and soon after interruption of 4 weeks high rate pacing (POST). Global and regional myocardial blood flow (MBF) ([13N]ammonia as a flow tracer) were quantified from PET data at spontaneous HR (PM-off) and during pacing at 20 beats over spontaneous HR (PM-on). LV fractional shortening (FS) was measured from ECHO. Results: From PRE to POST, FS significantly decreased from 37±0.8% to 20±0.5% (p<0.01). Prolonged high rate pacing caused also a significant decrease of global MBF from 1.09±0.24 ml/min/g (mean HR 71 bpm) to 0.78±0.26 ml/min/g (mean HR 83 bpm) (P<0.001) at PM-off and from 1.33±0.40 ml/min/g (mean HR 94 bpm) to 1.12±0.39 ml/min/g (mean HR 103 bpm) (p<0.001) at PM-on. Acute RV pacing induced LV dyssynchrony at ECHO and inhomogeneity of regional MBF distribution (higher flow in the septum than in the lateral wall) at baseline. After 4 weeks pacing acute RV stimulation still caused LV dyssynchrony which was no more able to induce regional MBF inhomogeneity (Table I). Table I MBF values are in ml/min/g. *p<0.001 vs PRE. Conclusions: Prolonged high rate RV pacing in minipigs causes global reduction in LV function and a global decrease of MBF as observed in clinical dilated cardiomyopathy. LV dyssynchrony, caused by acute RV stimulation, is associated with regional differences in MBF only at baseline. These results suggest that prolonged tachycardia more than dyssynchrony causes MBF impairment in RV pacing induced heart failure.