© 2005 European Society of Cardiology
CRT improves the exercise capacity and functional reserve of the failing heart through enhancing the cardiac flow- and pressure-generating capacity
a Molecular Cardiovascular Medicine, University of Leeds, Leeds General Infirmary Great George Street, Leeds LS1 3EX, UK
b Cardiology Department, Leeds General Infirmary Leeds, LS1 3EX, UK
c Cardiology Department, Bradford Royal Infirmary Bradford, UK
* Corresponding author. Molecular Vascular Medicine, Leeds General Infirmary, Great George Street, Leeds LS1 3EX, UK. Tel.: +44 113 392 5401; fax: +44 113 392 5395.
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Abstract |
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Background: While information on how cardiac resynchronisation therapy (CRT) affects cardiac performance at rest is readily available, the mechanisms whereby CRT alters cardiac function during maximal exercise are unclear.
Aims: We examined the medium-term effects of CRT on cardiac and physical functional reserve of patients with severe heart failure (CHF) and prolonged QRS duration.
Methods: Seventeen consecutive patients with severe CHF (NYHA III–IV) and widened QRS underwent maximal cardiopulmonary exercise testing with non-invasive central haemodynamic measurements before and 6–8 weeks after CRT pacemaker implantation.
Results: After CRT there were significant increases in exercise cardiac output by 19.3% (P=0.0048) from 9.5±3.4 l min–1, peak mean arterial blood pressure by 14.1% (P=0.0001) from 91.3±13.6 mm Hg, and peak cardiac power output by 37.2% (P=0.0008) from 1.92±0.74 W. There were no significant changes in these variables at rest. Exercise duration (+42.3%, P=0.0002), NYHA functional class (P=0.0001) and SF-36 symptom score (P=0.0006) were also significantly improved. Powerful surrogate indicators of prognosis were also significantly improved with CRT: peak O2 consumption (+20.9%, P=0.0007), VE/VCO2 slope (–20.0%, P=0.005) and circulatory power (+42.0%, P=0.0012).
Conclusion: In this cohort of patients, post-implant CRT significantly improved the flow-, pressure- and power-generating capacity of the failing hearts. This may be causally related to the improvements observed in exercise capacity, functional class and symptom scores.
Key Words: Heart failure • Cardiac resynchronisation therapy • Cardiac function • Cardiac power output • Exercise capacity
Received May 7, 2005; Revised September 28, 2005; Accepted November 3, 2005
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