IJCS | Volume 32, Nº1, January/ February 2019

45 Nascimento et al. Exercise in adults with congenital heart disease Int J Cardiovasc Sci. 2019;32(1)41-47 Original Article patients in our sample (87.1%) allow us to infer that the decreased O 2 P was probably a consequence of a limited increase in systolic volume during exercise. We corroborate this hypothesis, as we found lowO 2 P values evenwhen cyanotic patients (9.1mL/beat) were excluded from analysis. As previously mentioned, the decreased response of SAP reinforces the hypothesis of a modest inotropic response during exercise. VO 2 max has been recognized as the most important marker of morbidity and mortality in HF. Recent evidences, however, have suggested other parameters related to ventilatory efficiency, notably VE/VCO 2 slope and OUES, as better prognostic predictors in HF. 32 Similar phenomenon was seen in congenial heart disease in adults. Dimopoulos et al., 13 reported that adults with congenial heart disease had higher VE/VCO 2 slope than healthy individuals, and such difference was observed in all types of congenital heart diseases and was directly proportional to the functional class. According to the authors, cyanosis was the main predictor of an increased VE/VCO 2 slope. This parameter was the most important marker of mortality in adults with congenial heart disease in acyanotic patients (cut-off point of 38). 13 Similarly, Inuzuka et al., 8 reported that a VE/VCO 2 slope > 39 was a predictor of mortality only in acyanotic congenital heart disease patients. In our study, mean VE/VCO 2 slope was 27, which is considered normal. This may be explained, at least in part, by the small frequency of cyanotic patients in our sample. In addition to ventilatory inefficiency for carbon dioxide, adults with congenital heart disease commonly have a ventilatory inefficiency for oxygen consumption also, represented by lowOUES values. 18 We found amean OUES of 1.49, corresponding to only 61.4% of predicted. It is worth pointing out, for sake of comparison, that an OUES lower than 1.47 is associatedwith a poor prognosis of HF, 33 which indicates that our study population had a ventilatory efficiency for oxygen similar to that in patients with more severe HF. HR responses during incremental exercise, particularly in the presence of chronotropic incompetence, were equally important for risk stratification of adults with congenital heart disease. Diller et al., 14 reported that aHRR lower than 51 bpm was a predictor of lower survival in this population, especially when associated with a VO 2 max lower than 16.7 mL.kg -1 .min -1 , which increased the mortality risk by 3.8 times. 14 The authors also identified the chronotropic index and reduction inHRrec as parameters associatedwith unfavorable prognosis. Similarly, Inuzuka et al., 8 identified the VO 2 max combined with HRR as the main marker of mortality in cyanotic and acyanotic congenital heart disease. However, the cut-off point was 71 bpm. 8 Since we found a mean HRR of 69 bpm, our patients would be at increased risk according to these results reported by Inuzuka et al., 8 but not according to those reported by Diller et al. 14 The prevalence of chronotropic incompetence in our study was 44.4%, lower than that reported by Diller et al., 14 (62%); chronotropic index, however, were similar in both studies (0.64 and 0.70, respectively). We found a mean HRrec of 23.5 bpm, which was considered normal and suggestive of adequate parasympathetic autonomous modulation. Only 22.2% of our population met criteria for parasympathetric dysautonomia. Recently, CP and VP have emerged as important markers of adverse events in HF, 34 by using the product of SAP with VO 2 max, and the quotient of PAS by VE/ VCO 2 slope, respectively. The cut-off points for CP and VP in HF were 1,750 mmHg.mLO 2 .kg -1 .min -1 and 3.5 mmHg, respectively. 34 In adults with congenital heart disease, Giardini et al., 12 found that lowCP values (lower than 1,476mmHg.mLO 2 . kg -1 .min -1 ) were associatedwith a 15.4-fold increase in the 4-year risk of death. The authors described that despite an inverse relationship between CP and functional class, even asymptomatic patients had a lower CP than healthy individuals. We found an adequate CP (2,890.4 mmHg. mLO 2 .kg -1 .min -1 ), as compared with that in HF patients and also with the findings by Giardini et al., 12 In addition, we found adequate VP values taking into account HF patients, although we did not find other studies evaluating this parameter in adults with congenital heart disease in the literature. Limitations Limitations of this study included the relatively small sample size, which is common in studies involving low- prevalence conditions. The lack of a control group could also be considered a limitation of our study. However, our results were compared with those obtained from well-established prediction equations basedon age, sex and anthropometric indexes. Comparisons of our resultswith predicted values, previous studies onadultswithcongenital heart disease and especially on patients with HF, a recognized high severity condition, allowus tomake important inferences about the cardiovascular conditions of the study population.