Clinical Utility of the Cardiorespiratory Optimal Point in Patients with Heart Failure

Abstract

Introduction We assessed the cardiorespiratory optimal point (COP)—the minimal V̇ E/V̇O2 in a given minute of an incremental cardiopulmonary exercise test—in patients with heart failure (HF) and aimed to determine 1) its association with patient and disease characteristics, 2) changes after an exercise-based cardiac rehabilitation program (CR), and 3) the association with clinical outcomes. Methods We studied 277 HF patients (67 (58–74) yr, 30% female, 72% HF with restricted ejection fraction) between 2009 and 2018. Patients participated in a 12- to 24-wk CR program, and COP was assessed pre- and post-CR. Patient and disease characteristics and clinical outcomes (mortality and cardiovascular-related hospitalization) were extracted from patient files. The incidence of clinical outcomes was compared across COP tertiles (low, <26.0; moderate, 26.0–30.7; high, >30.7). Results Median COP was 28.2 (24.9–32.1) and was reached at 51% ± 15% of V̇O2peak. Lower age, female sex, higher body mass index, the absence of a pacemaker or the absence of chronic obstructive pulmonary disease, and lower N-terminal prohormone brain natriuretic peptide concentrations were associated with a lower COP. Participation in CR reduced COP (−0.8; 95% confidence interval, −1.3 to −0.3). Low COP had a reduced risk (adjusted hazard ratio, 0.53; 95% confidence interval, 0.33–0.84) for adverse clinical outcomes as compared with high COP. Conclusions Classic cardiovascular risk factors are associated with a higher, more unfavorable, COP. CR-based exercise training reduces COP, whereas a lower COP is associated with a better clinical prognosis. As COP can be established during a submaximal exercise test, this may offer novel risk stratification possibilities for HF care programs.

High Cardiorespiratory Optimal Point Values Are Related to Cardiovascular Mortality in Men Aged 46 to 70 Years: a Prospective Cohort Study

“…COP has also been the topic of several editorials [26][27][28] and has been included as a variable to be considered in at least two review papers about CPX. 29,30 The current results corroborate previous research findings obtained in distinct cohorts from different countries, including Brazil, 20 Finland, 17,18 Portugal, 31 the United States, 15 the Netherlands, 14 Belgium, 32 and Germany. 33 All these studies have supported the clinical relevance of COP and its prognostic role for survival in adult men and women, while adding new information regarding mortality caused by cardiovascular disease in men in a specific age range.…”

“…23 Details regarding the identification and definition of COP are available in previously published studies. [12][13][14][15][16][17][18][19][20] In brief, during an individualized ramp-protocol cycling CPX (Cateye EC 1600, Japan, from 1994 to 2006 and Inbramed fitness should be considered as a clinical vital sign. More recently, Laukkanen et al 7 published an updated metaanalysis with data from 37 unique studies comprising over 2 million individuals and found a 50% reduction in risk for all-cause mortality when comparing higher and lower cardiorespiratory fitness tertiles.…”

“…In 2012, 12 the CLINIMEX research group initially termed this minimal VE/VO 2 in a given minute of an incremental CPX as the cardiorespiratory optimal point (COP) and characterized its sex-and age-related reference values for healthy adults. Since this first report, several other studies [13][14][15][16][17][18][19][20][21] have used COP as a CPX variable with additional information on aerobic fitness and of clinical relevance. Notwithstanding, more information is still needed to confirm its role as a valid CPX measure for survival.…”

“…21 In addition, unlike several other commonly used CPX variables such as VO 2 max, VO 2 peak, anaerobic or ventilatory thresholds, oxygen uptake efficiency slope, the VE/VCO 2 slope, and others, the determination of COP by the examiner is extremely easy to accomplish, and it is a practically observer-free error variable. COP has been safely determined in different populations, including patients with heart failure 14,31,37 and also in individuals over 80 years of age, 16 performing submaximal and maximal CPX. Indeed, it is possible for anyone retrieving data from a CPX performed in the past with access to the minute-to-minute listing of VE/VO 2 results to precisely identify the COP.…”

Cardiorespiratory Optimal Point: A New Kid in the Block or an Established Star?

“…In all of these studies, it is clear that COP proved to be useful prognostic assessment in several middleaged populations, mostly male, for example, a mixed population of community-dwelling adults, including mainly people with unspecified chronic disease (n = 3331), 6 healthy adults (n = 2190; n = 2205; n = 3160), 5,7,8 HF (n = 442; n = 277) 9,10 and congenital heart disease (n = 30), 11 in terms of identifying subjects or patients with higher risk of cardiovascular death, 9 all-cause mortality, 5,6,8 sudden cardiac death, 7 or clinical severity. 11 Considering the seven published papers, only Reis 9 compared the relative value of COP regarding the most recognized CPET parameters, for example, pVO 2 , VO 2 max, VE/VCO 2 slope, or OUES, for prognostic assessment of the different populations.…”