Biventricular pacing: impact on exercise-induced increases in mitral insufficiency in patients with chronic heart failure.

INTRODUCTION: Mitral regurgitation (MR) in chronic heart failure (CHF) patients frequently worsens with exercise. Cardiac resynchronization therapy (CRT) reduces MR at rest, but its effects on exercise-induced worsening of MR are incompletely explored. The present study examined the influence of CRT on MR during submaximal exercise in CHF patients. METHODS: Eleven patients with CHF who were treated with CRT underwent echocardiography while performing steady-state exercise during four conduction modes (intrinsic rhythm, right ventricular [RV], biventricular [BiV] and left ventricular [LV] pacing). Measurements of MR were jet area planimetry, effective regurgitant orifice area, peak MR flow rate and regurgitant volume. RESULTS: At rest and during exercise, there were no differences in dyssynchrony between intrinsic rhythm and RV pacing. BiV and LV pacing reduced dyssynchrony at rest and during exercise compared with intrinsic conduction and RV pacing, and there were no differences in the magnitude of these effects between these two pacing modes. At rest, RV pacing increased MR compared with intrinsic conduction (MR regurgitant volume; P<0.05), whereas BiV and LV pacing reduced MR (reductions in effective regurgitant orifice area and jet area; P<0.02, and MR flow rate; P<0.05 with BiV pacing from intrinsic conduction). MR significantly increased on exercise with intrinsic rhythm and RV pacing, whereas with LV and BiV pacing, there were no significant exercise-induced increases in any MR variable. There were relationships between changes in measures of dyssynchrony and reductions in MR at rest and during exercise. CONCLUSIONS: CRT reduces MR at rest and during exercise, and prevents exercise-induced MR. Reductions in MR during exercise correlate with improvements in dyssynchrony.

Cardiac resynchronization therapy: an option for inotrope-supported patients with end-stage heart failure?

BACKGROUND: Patients with refractory heart failure requiring inotropic support have a very poor prognosis. Cardiac resynchronization therapy (CRT) offers symptomatic and possibly a survival benefit for patients with stable chronic heart failure (CHF) and a prolonged QRS, but its role in the management of end-stage heart failure requiring inotropic support has not been evaluated. METHODS: We performed a retrospective observational study of patients undergoing CRT at our institution. RESULTS: We identified 10 patients who required inotropic support for refractory CHF and who underwent CRT while on intravenous inotropic agents. Patients had been in hospital for 30+/-29 days and had received inotropic support for 11+/-6 days prior to CRT. All patients were weaned from inotropic support (2+/-2 days post-CRT) and all patients survived to hospital discharge (12+/-13 days post-CRT). Furosemide dose fell from 160+/-38 mg on admission to 108+/-53 mg on discharge (p<0.01). Serum creatinine fell from 192+/-34 micromol/l prior to CRT to 160+/-37 micromol/l on discharge (p<0.05). Serum sodium was 131+/-4 mmol/l prior to CRT and remained low at 132+/-5 mmol/l on discharge. At short-term follow up (mean 47 days), all patients were alive; mean furosemide dose was 130+/-53 mg (p=0.056 versus pre-CRT). Serum creatinine was 157+/-36 micromol/l and serum sodium had increased to 138+/-6 mmol/l (p<0.05 and p<0.01, respectively, versus pre-CRT). CONCLUSION: CRT may offer a new therapeutic option for inotrope-supported CHF patients with a prolonged QRS.