LV Mechanics in HF Patients at Different Pacing Modalities and Long Term Responsiveness

CRT enables biventricular single or dual site activation as part of resynchronization therapy for HF patients. Our objective was to compare the LV mechanics during RV pacing (R), biventricular single point (S) & MPP – multipoint (M) pacing after implantation or upgrade of a CRTD device with a multipolar pacing ability.

15 HF patients, 67±9 y.o., implanted with a CRTD device echoed within 24 h. The cines were analyzed for LV circumferential & longitudinal strain, rotation & torsion evaluation. The patients were discharged with single point pacing & followed in 6 months.

Results:
LV longitudinal strain measurements showed an average global strain of -6.5±1.9 % (R), -7.6±2.3% (S) & -6.2±2.2% (M), a mild improvement of strain using CRT; (P=NS). No differences were observed in the radial & circumferential strains. The segmental rotation showed an average apical rotation (APR) of 3.2±5.1° (R), 4.7±6° (S) & 5.1±5.1° (M) & mitral valve rotations (MVR) of -1.6±3.5° (R), -2.0±3.8° (S) & -1.7±3.8° (M). Torsion improved from 3.5±4.9° (R), to 5.7±5.1° (S) & 6.6±5.4° (M), (P<0.08, suggestive).

11 patient reached 6 months follow up. 6 patients showed above 17% decrease in LV end systolic volume - responders. The analysis showed there were no indicative changes in the longitudinal or circumferential strains which could predict long term responsiveness. Responding patients had better initial LV synchrony with APR of 4.5±1.5° (R), 4.8±1.5° (S) & 5.6±1.7° (M) & minor torsion changes of 5.7±1.7° (R), 6.6±1.7° (S) & 6.8±2.0° (M) while non-responders had initial dyssynchrony with APR of 2.2±1.9° (R), growing to 5.2±1.9° (S) & 7.0±1.9° (M) and torsion going up from 2±2.1° (R) to 6.5±2.1° (S) & 9.7±2.1° (M) with mild MVR changes.

Discussion:
short term increased longitudinal strain didnot correspond with long term LV responsiveness. LV dyssynchrony improving significantly using CRT pacing, correlated with 6 months non-response.