Published Online
on April 23, 2007

A more recent version of this article appeared on May 8, 2007

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Submitted on February 7, 2007
Accepted on February 16, 2007

Development of a Ventilatory Classification System in Patients With Heart Failure

Ross Arena PhD, PT^*, Jonathan Myers PhD, Joshua Abella MD, Mary Ann Peberdy MD, Daniel Bensimhon MD, Paul Chase MEd, and Marco Guazzi MD, PhD

From the Department of Physical Therapy (R.A.) and Department of Internal Medicine (M.A.P.), Virginia Commonwealth University, Health Sciences Campus, Richmond, Va; VA Palo Alto Health Care System (J.M., J.A.), Cardiology Division, Stanford University, Palo Alto, Calif; LeBauer Cardiovascular Research Foundation (D.B., P.C.), Greensboro, NC; and University of Milano (M.G.), San Paolo Hospital, Cardiopulmonary Laboratory, Cardiology Division, University of Milano, San Paolo Hospital, Milano, Italy.

^* To whom correspondence should be addressed. E-mail: raarena{at}.vcu.edu.

Background--Ventilatory efficiency, commonly assessed by the minute ventilation (VE)-carbon dioxide production (VCO₂) slope, is a powerful prognostic marker in the heart failure population. The purpose of the present study is to refine the prognostic power of the VE/VCO₂ slope by developing a ventilatory class system that correlates VE/VCO₂ cut points to cardiac-related events.

Methods and Results--Four hundred forty-eight subjects diagnosed with heart failure were included in this analysis. The VE/VCO₂ slope was determined via cardiopulmonary exercise testing. Subjects were tracked for major cardiac events (mortality, transplantation, or left ventricular assist device implantation) for 2 years after cardiopulmonary exercise testing. There were 81 cardiac-related events (64 deaths, 10 heart transplants, and 7 left ventricular assist device implantations) during the 2-year tracking period. Receiver operating characteristic curve analysis revealed the overall VE/VCO₂ slope classification scheme was significant (area under the curve: 0.78 [95% CI, 0.73 to 0.83], P<0.001). On the basis of test sensitivity and specificity, the following ventilatory class system was developed: (1) ventilatory class (VC) I: 29; (2) VC II: 30.0 to 35.9; (3) VC III: 36.0 to 44.9; and (4) VC IV: 45.0. The numbers of subjects in VCs I through IV were 144, 149, 112, and 43, respectively. Kaplan-Meier analysis revealed event-free survival for subjects in VC I, II, III, and IV was 97.2%, 85.2%, 72.3%, and 44.2%, respectively (log-rank 86.8; P<0.001).

Conclusions--A multiple-level classificatory system based on exercise VE/VCO₂ slope stratifies the burden of risk for the entire spectrum of heart failure severity. Application of this classification is therefore proposed to improve clinical decision making in heart failure.

Key words: prognosis • ventilation • heart failure • exercise

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