ABC | Volume 114, Nº2, February 2020

Short Editorial Cardiopulmonary Exercise Test in the Evaluation of Heart Transplant Candidates with Atrial Fibrillation Miguel Mende s CHLO - Hospital de Santa Cruz, Carnaxide - Portugal Short Editorial related to the article: Prognostic Prediction of Cardiopulmonary Exercise Test Parameters in Heart Failure Patients with Atrial Fibrillation Mailing Address: Miguel Mendes • CHLO - Hospital de Santa Cruz – Cardiologia - Av. Prof. Reynaldo dos Santos, Carnaxide 2790-134 – Portugal E-mail: miguel.mendes.md@gmail.com Keywords Heart Failure; Atrial Fibrillation; Heart Transplantation; Patient Selection; Oxygen Consumption; Exercise Test. DOI: https://doi.org/10.36660/abc.20200051 Antonio Valentim Gonçalves et al., 1 authors of the original article “Prognostic Prediction of the Cardiopulmonary Exercise Test Parameters in Patients with Heart Failure and Atrial Fibrillation”, 1 published in this issue of Arquivos Brasileiros de Cardiologia , intended to evaluate whether the cutoff points of two parameters of the cardiopulmonary exercise test (CPET), routinely used in the selection of patients for heart transplant (HT), would also be efficient in the presence of permanent or persistent atrial fibrillation (AF) in patients with heart failure with reduced ejection fraction (HFREF). In their work, the authors assessed whether the study primary endpoint was reached in the presence of two recommendations of the International Society for Heart and Lung Transplantation (ISHLT) guideline: 2 1) peak oxygen consumption (pVO 2 ) ≤ 12 (under betablocker therapy) - BB) or 14 mL/Kg/min (in the absence of BB) and, 2) slope of ventilation (VE) / carbon dioxide elimination (VCO 2 ) > 35, when the respiratory exchange ratio (RER) during the exercise is < 1.05. This study included 274 consecutive patients with left ventricular ejection fraction (LVEF) < 40%, from a single center, assessed by CPET, of which 51 were in AF and 223 in sinus rhythm (SR). The primary endpoint [HT or cardiac death (CD)] was observed in 17.6% of patients with AF and 8.1% of patients in SR (p < 0.0038). In the context of AF, the VO 2 -related cutoff point (with or without BB) performed very well, with a positive predictive value (PPV) of 100% and a negative predictive value (NPV) of 95.5%. In contrast, the VE/VCO 2 slope cutoff point was found to have a PPV of 33.8% and a NPV of 92.3%. In the group of patients in SR, the results of the cutoff point related to pVO 2 were lower, with a PPV of 38.5% and a NPV of 94.3%, similar to the cutoff point of the VE/VCO 2 slope, with a PPV of 29.8% and a NPV of 98.3%. They concluded that the current cutoff points accurately stratify patients in AF, corroborating the initial hypothesis of their research. To the best of my knowledge, this is the first study that specifically assessed the application of the ISHLT criteria for the selection of patients with AF and HFREF for HT. The study is valuable for having assessed the application of these criteria in this group that has a significant dimension in heart failure (HF) clinics. Clinical application of the study findings The main conclusions of the article are as follows: 1) The two ISHLT criteria were better suited to patients with AF than to those in SR. 2) In the context of AF, the performance of the peak VO 2 criterion ≤ 12 or 14 mL/Kg/min, depending on whether or not the patient was under betablocker medication, has a much higher value than the VE/VCO 2 slope. 3) In patients in SR, either of the two criteria (peak VO 2 and VE/VCO 2 slope > 35) have a low PPV (< 40%) and high NPV (> 90%); thus, they are more suitable to identify patients who do not need HT. It seems logical that patients in AF, with LVEF < 40%, have a lower functional capacity than those in SR, because the AF reduces the maximum cardiac output by a percentage of not less than 25%. On the other hand, many of these patients have advanced HF, 3,4 with less capacity to extract oxygen at the muscle level, as a result of the muscular atrophy caused by inactivity and the myopathy inherent to HF. As pVO 2 is related not only to the cardiac output at the level of maximum effort, but also to the oxygen extraction capacity at the peripheral level, it is easy to understand why they have decreased pVO 2 . It would have been interesting also to evaluate the criterion of pVO 2 < 50% of the predicted maximum, in individuals under the age of 50 years or of the female gender, which was classified as class IIa, [level of evidence (LE) B], higher than the criterion VE/VCO 2 slope, which was rated as class IIb (LE C). The criterion VE/VCO 2 slope is indicated by the ISHLT for alternative use when a respiratory rate > 1.05 is not obtained during the exercise period. The inefficient performance of the criteria used in the SR group, which obtained a PPV < 40%, is surprising. Part of the explanation may be related to the presence of 40% of women in the SR group, compared to 27.5% in the AF group (although with p < 0.087). Indeed, it has been shown that women have a better prognosis, despite having significantly lower pVO 2 values than men. 5 The ISHLT criteria for risk stratification in HFREF The 2016 ISHLT guideline 2 for placing patients on a HT list was conservative and generally maintained the recommendations of 2006. It included once more a recommendation (class I, LE B) confirming the suitability of the pVO 2 generic cutoff for patients with a cardiac 219