Development of a ventilatory classification system in patients with heart failure.
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.


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: < or = 29; (2) VC II: 30.0 to 35.9; (3) VC III: 36.0 to 44.9; and (4) VC IV: > or = 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.
Arena
Ross
R
Department of Physical Therapy, Box 980224, Virginia Commonwealth University, Health Sciences Campus, Richmond, VA 23298-0224, USA. raarena@vcu.edu
Myers
Jonathan
J
Abella
Joshua
J
Peberdy
Mary Ann
MA
Bensimhon
Daniel
D
Chase
Paul
P
Guazzi
Marco
M
D000328:Adult; D000368:Aged; D002245:Carbon Dioxide / Q000032:analysis; D015331:Cohort Studies; D018572:Disease-Free Survival; D005080:Exercise Test; D005260:Female; D005500:Follow-Up Studies; D006331:Heart Diseases / Q000401:mortality; D006333:Heart Failure / Q000503:physiopathology*; D016027:Heart Transplantation / Q000706:statistics & numerical data; D006353:Heart-Assist Devices / Q000706:statistics & numerical data; D006801:Humans; D007558:Italy / Q000453:epidemiology; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D012123:Pulmonary Ventilation; D012372:ROC Curve; D018570:Risk Assessment; D012720:Severity of Illness Index; D013318:Stroke Volume; D014481:United States / Q000453:epidemiology
D002245:Carbon Dioxide