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J Thorac Cardiovasc Surg 2007;134:269-270
© 2007 The American Association for Thoracic Surgery
Letter to the Editor |
Department of Thoracic and Cardiovascular Surgery, Loyola University Medical Center, Chicago, Ill
To the Editor:
We read with interest the article by Oto and associates1
in the December 2006 issue of the Journal. The authors underestimate the importance of unilateral infiltrates. We disagree with the statement, "only bilateral infiltrates should be used as part of the definition of primary graft dysfunction" despite their convincing statistical methods. We explain why.
The guidelines of pulmonary graft dysfunction (PGD)2 and validation3 thereof is for the clinician to make sense of the data and standardize reporting. The emphasis by the consensus committee on PGD was on providing a definition that could also help in management and prognosis.2 PGD is a biological process of reperfusion–ischemic injury redefined with respect to alveolar–capillary injury. This process is biological, with reversible and irreversible pathways4,5 and along a spectrum that cannot be dichotomous, hence the association of time, arterial oxygen tension/inspired oxygen fraction (PaO
2/FIO
2) ratios and radiographic findings that are in the context of the International Society of Heart and Lung Transplantation definition. The authors do not reveal their perioperative bronchoscopy protocol, which itself can influence radiographic findings with respect to presence or absence of infiltrates. It is not uncommon that infiltrates could be due to segmental and/or subsegmental mucus plugging, which when it extends to main bronchi can cause significant ventilation–perfusion mismatch and reduction of PaO
2/FIO
2 ratios. The population sample, as quite correctly stated by the authors, remains small and heterogeneous; primary pulmonary hypertension is a bilateral problem and requires bilateral lung transplantation. The authors should analyze their findings with respect to a clean cohort of infectious lung disease, for example, to avoid the confounding effect of pulmonary hypertension. The reader will soon realize that the majority of patients with pulmonary hypertension were among the cohort with bilateral infiltrates.
Moreover, patients with fixed pulmonary hypertension are more likely to experience reperfusion–ischemic injury with higher PGD grades.5 Recently, aprotinin has been shown to reduce reperfusion injury and allograft dysfunction. It is unclear from the manuscript which antifibrinolytic was administered during transplantation—the type of antifibrinolytic being a potential confounder. The authors state that unilateral infiltrates were associated with PGD grade 3, but that diminished at T48 hours. However, when compared with the absence of infiltrates at T0, it had decreased. It may be more appropriate to look at the absolute difference from T0 to T48 rather than the relative difference, which in a larger homogeneous population sample would minimize confounding. Short of radiographic findings, a clinician can be at loss if PaO
2/FIO
2 ratios are the only information provided to make a diagnosis of PGD and/or to intervene with medical therapy or bronchoscopy. Given the therapeutic and diagnostic power of bronchoscopy, any infiltrate on the chest radiograph is of paramount importance in decision making and detection of this biological PGD process. Furthermore, despite the inherently subjective interpretation of a chest radiograph, a transplant physician can recognize patterns of unilateral infiltrates that are typical of the most severe and rapidly progressing to grade 3 PGD, which could go unnoticed if only bilateral infiltrates are considered.
References
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