Ventilatory power: a novel index that enhances prognostic assessment of patients with heart failure.
BACKGROUND
Minute ventilation/CO(2) production (VE/Vco(2)) slope is an index determined by cardiopulmonary exercise testing, which incorporates pertinent cardiac, pulmonary, and skeletal muscle physiology into a substantive composite assessment. The VE/Vco(2) slope has many applications, including utility as a well-validated prognostic gauge for patients with heart failure (HF). In this study, we combine VE/Vco(2) slope with systolic blood pressure, creating a novel index that we labeled ventilatory power. Ventilatory power links the combined physiology inherent in the VE/Vco(2) slope to peripheral pressure, adding an additional dimension pertinent to HF assessment. Whereas the related concept of circulatory power links peak oxygen consumption with peak systolic blood pressure as a prognostic index, we hypothesized that ventilatory power would provide greater prognostic discrimination than VE/Vco2 slope, peak oxygen consumption, and circulatory power for patients with systolic HF.


RESULTS
Patients with systolic HF (left ventricular ejection fraction ≤35%) underwent symptom-limited cardiopulmonary exercise testing as part of routine management and were followed for up to 4 years for major cardiac events (mortality, left ventricular assist device implantation, and heart transplantation). Eight hundred seventy-five patients with HF (left ventricular ejection fraction, 26±9%; mean age, 55±14) were studied. Cardiopulmonary exercise testing indices peak oxygen consumption, VE/Vco(2) slope, circulatory power, and ventilatory power were all predictive of cardiac events (P<0.001). Multivariate analysis demonstrated that ventilatory power was the strongest indicator of prognosis.


CONCLUSIONS
Although circulatory power and traditional cardiopulmonary exercise testing parameters can be used to predict prognosis among patients with HF, ventilatory power provides relatively greater prognostic discrimination and may constitute a relatively more useful composite tool.
Division of Cardiovascular Medicine, Brigham and Women's Hospital, 75 Francis St., Boston, MA 02115, USA. deforman@partners.org
Daniel E
DE
Forman
Marco
M
Guazzi
Jonathan
J
Myers
Paul
P
Chase
Daniel
D
Bensimhon
Lawrence P
LP
Cahalin
Mary Ann
MA
Peberdy
Euan
E
Ashley
Erin
E
West
Karla M
KM
Daniels
Ross
R
Arena
D000328:Adult; D000368:Aged; D001794:Blood Pressure; D016009:Chi-Square Distribution; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology / Q000628:therapy; D016027:Heart Transplantation; D006353:Heart-Assist Devices; D006801:Humans; D007558:Italy; D053208:Kaplan-Meier Estimate; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010101:Oxygen Consumption; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D012123:Pulmonary Ventilation; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013318:Stroke Volume; D013599:Systole; D013997:Time Factors; D014481:United States; D016277:Ventricular Function, Left