Cardiopulmonary Exercise Testing and Outcomes in Women With Heart Failure-Examining the "Female Advantage".

Cardiopulmonary exercise testing (CPET) has long been shown to provide important prognostic information in patients with heart failure. Since the 1991 publication by Mancini et al, CPET, and specifically peak oxygen consumption (pVO2), has been used in prognostication for patients with heart failure being assessed for cardiac transplantation. pVO2 is essentially an assessment of cardiac reserve (the ability of the heart to increase cardiac output), and patients unable to achieve a pVO2 of 14 mL/kg/min were shown to have improved survival with transplantation as opposed to without transplantation. However, multiple subsequent studies have shown that women with heart failure have better overall survival than do their male counterparts, despite women having a comparatively low pVO2, 2-5 placing into question the role of CPET in prognostication for women with heart failure. pVO2 is, of course, far from the only parameter assessed with CPET, despite being arguably the most used by heart failure clinicians. Also commonly used is ventilatory response; the response of minute ventilation to CO2 production (VE/VCO2 slope), which is an indicator of the presence of heart failureerelated physiological consequences such as V:Q mismatch and aberrancies of autonomic function. VE/VCO2 has been shown to be of prognostic value in heart failure, with higher values corresponding to worse prognosis, and specifically may be more predictive of adverse heart failure outcomes in women. There are many potential reasons for the sex-related discrepancy in the predictive value of CPET parameters. Women were not well represented in the initial studies done to derive the equations for prediction of maximum VO2, resulting in a sex bias on this basis alone. There is also a significant male predominance in studies assessing CPET for prognosis. The reasons for this are likely related to the demographics of women