Hemodynamic Effects of Long-Term Cardiac Resynchronization Therapy

Background— Acute hemodynamic effects of cardiac resynchronization therapy (CRT) were reported previously, but detailed invasive studies showing hemodynamic consequences of long-term CRT are not available.Methods and Results— We studied 22 patients scheduled for implantation of a CRT device based on conventional criteria (New York Heart Association class III or IV, left ventricular [LV] ejection fraction 120 ms). During diagnostic catheterization before CRT, we acquired pressure-volume loops using conductance catheters during atrial pacing at 80, 100, 120, and 140 bpm. Studies were repeated during biventricular pacing at the same heart rates after 6 months of CRT. Our data show a significant clinical benefit of CRT (New York Heart Association class change from 3.1±0.5 to 2.1±0.8; quality-of-life score change from 44±12 to 31±16; and 6-minute hall-walk distance increased from 260±149 to 396±129 m; allP <0.001), improved LV ejection fraction (from 29±10% to 40±13%,P <0.01), decreased end-diastolic pressure (from 18±8 to 13±6 mm Hg,P <0.05), and reverse remodeling (end-diastolic volume decreased from 257±67 to 205±54 mL,P <0.01). Previously reported acute improvements in LV function remained present at 6 months: dP/dtmax increased 18%, −dP/dtmin increased 13%, and stroke work increased 34% (allP <0.01). Effects of increased heart rate were improved toward more physiological responses for LV ejection fraction, cardiac output, and dP/dtmax . Moreover, our study showed improved ventricular-arterial coupling (69% increase,P <0.01) and improved mechanical efficiency (44% increase,P <0.01).Conclusions— Hemodynamic improvements with CRT, previously shown in acute invasive studies, are maintained chronically. In addition, ventricular-arterial coupling, mechanical efficiency, and chronotropic responses are improved after 6 months of CRT. These findings may help to explain the improved functional status and exercise tolerance in patients treated with CRT.