IJCS | Volume 32, Nº1, January/ February 2019

44 Table 3 - Results of the cardiopulmonary exercise test Parameter n Mean ± SD VO 2 max, mL.kg -1 .min -1 31 19.1 ± 10.3 V’O 2 max, % of predicted 31 44.9 ± 18.0 AT, mL.kg -1 .min -1 23 15.2 ± 6.8 AT, % do V’O 2 max predicted 23 36.9 ± 12.9 VE/VCO 2 slope 31 27.0 ± 9.8 OUES 30 1.49 ± 0.89 OUES, % of predicted 30 61.4 ± 26.6 O 2 P, mL/beat 27 8.7 ± 3.8 O 2 P, % of predicted 27 58.9 ± 22.2 O 2 P in acyanotics, mL/beat 23 9.1 ± 3.8 O 2 P in acyanotics, % of predicted 23 60.9 ± 23.3 ∆SAP, mmHg 31 31.4 ± 21.6 HRR, bpm 27 69.1 ± 33.5 Chronotropic index 27 0.64 ± 0.3 HRrec, bpm 27 23.5 ± 15.6 CP, mmHg.mLO 2 .kg -1 .min -1 31 2,890.4 ± 1,919.3 VP, mmHg 31 5.9 ± 2.0 VO 2 max: peak exercise oxygen consumption; AT: anaerobic threshold; VE/VCO 2 slope: ventilatory equivalent for carbon dioxide; OUES: oxygen uptake efficiency plateau; O 2 P: peak exercise oxygen pulse; ∆ SAP: changes in systolic arterial pressure, from resting to peak exercise; HRR: heart rate reserve; HRrec: heart rate recovery, from peak exercise to the first minute of recovery phase; CP: circulatory power; VP: ventilatory power. Nascimento et al. Exercise in adults with congenital heart disease Int J Cardiovasc Sci. 2019;32(1)41-47 Original Article capacity, with a decrease not only in maximum aerobic power (indicated by VO 2 max), but also in aerobic capacity for submaximal activities (indicated by the AT). In addition, results of the CPET revealed ventilatory inefficiency for oxygen consumption and limited inotropic response to exercise. Previous studies have reported lower values of VO 2 max 4-6,9,27 and AT 5 in adults with congenital heart disease as compared with healthy adults. 5 Reduced aerobic capacity is a common condition in this population, and 80% of these patients have a VO 2 max lower than predicted for age and sex. 4 It is worth mentioning that many adults with congenital heart disease overestimate their own clinical conditions in light of the long period of exercise restriction. The level of exercise intolerance is more accurately assessed by measurement of the VO 2 max, and even asymptomatic patients considered as New York Heart Association class 1 have lower VO 2 max when comparedwith healthy individuals of the same age, 9 suggesting a discrepancy between a subjective and an objective approach of exercise capacity in this population. The decrease inmaximal aerobic capacity in congenital heart disease adults is so important that VO 2 max in these patients is comparable to that in patients with HF caused by other conditions. 9 VO 2 max is a traditional marker of an unfavorable prognosis of HF and has a central role in the evaluation of eligibility for heart transplantation in this group. 28 Similarly, a reduced VO 2 max is associated with higher morbidity and mortality in adults with congenital heart disease. 8,9 We found a mean VO 2 max of 19.1 mL.kg -1 .min -1 . Diller et al., 9 evaluating a large group of patients with congenital heart disease, suggested a VO 2 max of 15.5 mL.kg -1 .min -1 as a cut-off for predicting cardiac events. Patients with a VO 2 max lower than this had a three- time higher risk of death and hospitalization. Based on the studies by Diller et al., 9,10 our patients had a good prognosis. However, this was a young population (< 35.7 years of age) and, in fact, VO 2 max found in these patients was only 44.9% of predicted, i.e., considerably lower than that expected for healthy individuals of the same sex and age. Inuzuka et al., 8 also evaluated adults with congenital heart disease and suggested a cut-off value of 64% of predicted VO 2 max to identify patients with a low or high 5-year survival mortality risk. 8 Therefore, according to these authors, our study group could be, in fact, at risk of a poor prognosis. Modern concepts of HF classify this syndrome in progressive stages. Patients with cardiac structural abnormalities but no signs of HF would be designated as stage B. 29,30 Although this classification did not include congenital heart disease, in a scientific statement published in 2016, the American Heart Association recommended that patients with congenital structural heart disease should be classified as being at least stage B of HF. 31 In agreement with this position, our results demonstrated a depressed response of SAP (∆SAP: 31.4 mmHg) concomitantly with reduced O 2 P in absolute (8.7 mL/beats) and relative (58.9% of predicted) values, suggesting a limited inotropism during exercise. Although O 2 P response cannot be attributed only to the systolic volume behavior during incremental exercise (since it also depends on the arteriovenous oxygen difference, which in turn is altered in cyanotic and hypoxemic patients), the higher frequency of acyanotic