Woods, Paul R.

Background Patients with heart failure (HF) often develop pulmonary system abnormalities. Specifically, an abnormal ventilation relative to metabolic demand (V E /VCO 2 , ventilatory efficiency) during exercise has been shown to be an important marker of disease severity and prognosis. The purpose of this investigation was to focus on the factors that underlie the abnormal breathing efficiency in this population. Methods 14 controls (10 male) and 40 (36 male) mod‐severe HF patients, age 52±12 and 56±8 yrs, respectively, performed graded exercise on a cycle ergometer. Gas exchange and blood gas measurements were made during submaximal exercise (~65% peak VO 2 ) and used to quantify the influence of hyperventilation (PaCO 2 ) and dead space ventilation (V D ) on V E /VCO 2 . Results The V E /VCO 2 ratio was lower in controls (30±4) than in HF (45±9, p<0.001) due to a lower PaCO 2 and higher V D /V T that contributed an estimated 29% and 71%, respectively, to the increased V E /VCO 2 (p<0.05). The elevated V D /V T in HF was in turn the result of a tachypneic breathing pattern (lower V T , 877±306 vs 2003±504ml, p<0.01) in the presence of a relatively normal V D (9.6±3.8 vs 11.9±5.7 L/min, p=0.094). Conclusion The abnormal ventilation in relation to metabolic demand in HF during exercise is predominantly due to alterations in breathing pattern, rather than hyperventilation or changes in ventilation/perfusion relationships. HL71478

Introduction Submaximal exercise gas exchange may be a useful tool to track responses to therapy in pulmonary arterial hypertension (PAH) patients. Methods Three patients diagnosed with idiopathic PAH, on differing therapies, were included. Standard clinical tests (echocardiography; 6 minute walk) were performed pre and 3-5 months after treatment. Gas exchange was measured during 3 minutes of step exercise at both time points. Results Gas exchange variables, end tidal CO 2 (P ET CO 2 ) and the ratio of ventilation to CO 2 production (V E /VCO 2 ), during submaximal exercise were able to track patient responses to therapy over a 3-5 month period. Two patients demonstrated positive improvements, with an increased P ET CO 2 and decreased V E /VCO 2 during light exercise, in response to an altered therapeutic regime. The third patient had a worsening of gas exchange (decreased P ET CO 2 and increased V E /VCO 2 ) following no changes in the medical regime from the baseline visit. Conclusion Gas exchange variables measured during light submaximal exercise, such as P ET CO 2 and V E /VCO 2 , may be able to better detect small changes in functional status following treatment and could, therefore, be a useful tool to track disease severity in PAH patients. Further study is required to determine the clinical usefulness of these gas exchange variables.

Abstract Aims Traditionally, VO2peak has been used to determine prognosis in heart failure; however, this measure has limitations. Hence, other exercise and gas exchange parameters measured submaximally, e.g. breathing efficiency (VE/VCO2), end-tidal CO2 (PETCO2), oxygen uptake efficiency slope (OUES), and circulatory power [ systolic blood pressure (SBP)], have been investigated. The aim of this study was to investigate the prognostic relevance of submaximal exercise gas exchange in heart failure patients. Method and results One hundred and thirty-two consecutive heart failure patients (mean age 56 ± 12 years, ejection fraction 29 ± 11%) performed peak treadmill testing. Gas exchange and haemodynamic variables were measured continuously. Gas exchange data obtained from the first 2 min of exercise and at a respiratory exchange ratio (RER) of 0.9 were the measurements of interest. Over a median follow-up period of 62.4 (range 0–114) months, there were 44 endpoints (death or transplant). Univariate analysis demonstrated submaximal predictors of survival, which included VE/VCO2 slope and ratio, PETCO2, OUES, and circulatory power (P≤ 0.01). When these and additional submaximal variables were included together in the multivariable analysis, the strongest submaximal exercise predictive model (C-statistic 0.75) comprised data from the first stage of exercise (VE and circulatory power) and at an RER of 0.9 (VE/VCO2 ratio). The inclusion of VO2peak and demographic data, with submaximal data (VE/VCO2 ratio at an RER = 0.9), increased the predictiveness of the model (C-statistic 0.78). Conclusion Submaximal exercise measures provide useful prognostic information for predicting survival in heart failure. This form of testing is logistically easier, cheaper, and safer for patients compared with maximal exercise.