Operability Guidelines for PVRI 4-6 WU.M2: Missing the Target?

Saurabh Kumar Gupta, Shyam S. Kothari

https://doi.org/10.1002/pul2.70183
 

Abstract

Access to infant cardiac surgery is inadequate in large parts of the globe. Consequently, there remains a persistent need for decision-making in children and adults with unoperated shunt lesions and varying pulmonary vascular resistance. Early surgery is the best safeguard against the persistence or progression of changes in the pulmonary vascular bed [1]. If operated within the first 3 months of age, an infant with even a PVRI of 12 wu.m2 may be free from pulmonary vascular disease later in life [2]. Conscientious and elaborate works in the earlier era of open heart surgery by many investigators had highlighted the importance of age, pulmonary vascular resistance index (PVRI), ratio of pulmonary and systemic vascular resistance (Rp/Rs), and quantum of shunt (Qp/Qs) in deciding about the operability [1-4]. Almost all the publications related to this issue highlight that a holistic decision is required, and no single parameter is reliable in guiding the decision of operability. Nevertheless, for over 4 decades or more, PVRI of 4-6 WU.m2 was never considered borderline, and textbooks of cardiology generally taught a PVRI beyond 8 or 10 WU.m2 as a threshold for operation.

More recently, since the 5th World Symposium on pulmonary hypertension held in NICE, France in 2013, the guidelines lowered the operability threshold to 4 WU.m2 and, though not denying surgery for patients with PVRI of 4–6 WU.m2, sounded caution on the decision in the range of PVRI 4–8 WU.m2 [5]. The reason for this change (as referred to in the document) is related to 2 studies that showed the long-term follow-up of operated patients with shunt lesions [6, 7]. A critical review of both the studies and other studies around this question does not support the conclusion that PVRI of 4–6 WU.m2 should be considered indicative of borderline operability in children and young patients with persistent shunt.

In a remarkable study of 30–35 years of follow-up of the earliest cohort of children operated for a ventricular septal defect, Moller et al reported the status of 296 children who survived the surgery [6]. One-fifth (59 of 296) of patients died after the operation due to different causes during the 1-month to 33-year follow-up period. They reported higher risks of death in children operated beyond 5 years of age, and also in those with PVRI > 7 WU.m2. In 16 of 59 deaths, pulmonary vascular disease was considered the cause of death, with most of these patients having been operated beyond 5 years of age with PVRI > 7 WU.m2. This study also highlighted that the long-term survival probabilities decline as the preoperative PVRI is elevated, especially if it is > 7 WU.m2. Amongst the 16 deaths due to pulmonary vascular disease, possibly 3 had PVRI of less than 6 WU.m2. The other hemodynamic parameters in these patients, like the quantum of shunt, ratio of pulmonary to systemic vascular resistance (Rp/Rs), or genetic abnormality, etc, are not known, nor is the denominator of the number of patients with PVRI of 4–6 WU.m2 who benefited from VSD closure known. Thus, it is improper to extrapolate that PVRI 4–6 WU.m2 should be viewed with caution from the information obtained in this study.

The other oft-quoted study for the late rise of PVRI in operated shunt patients by Alto et al [7] is even less persuasive for the need for a change in the guidelines. Of the 22 patients reported in the study, 19 (86%) had a PVRI of > 8 WU.m2. Thirteen of 22 (59%) had an atrial septal defect, and the mean age of operation was 25 years. It is not altogether surprising that a late rise of PVRI was seen in such patients. However, why this data should be construed as suggesting caution for operation in patients with PVRI 4–6 WU.m2 is not clear.

There are other surveys and population-based studies affirming the fact that PAH is more frequently seen in patients with operated shunt lesions as compared to the general population [8, 9]. The PAH in these patients is mostly mild and might result from many causes on follow-up into their 50 s and 60 years of age. These data, by themselves, also do not suggest that the threshold of PVRI for operability should be lowered to 4 WU.m2 instead of the conventional 6 WU.m2.

On the contrary, several publications of salutary effects of shunt closure in patients with raised PVRI have been published [10, 11]. Clearly, late age at operation and raised PVRI are not desirable for patients with shunt lesions. We, like others [12, 13], would suggest a thoughtful, holistic appraisal of the complete clinical and hemodynamic data in patients with PVRI > 6 WU.m2. However, a too conservative threshold for operation in patients with shunt lesions, as is currently being proposed, is not evidence-based. Steady improvements in cardiac surgical techniques and the wide adoption of infant cardiac surgery in the Western world have significantly reduced the urgency and impact of this question of operability and PVRI thresholds. The number of patients with shunt and PVRI in the zone of 4–6 WU.m2 in the rest of the world is unknown, but may not be trivial. The younger generation of cardiologists who have not had enough experience in deciding individual patients’ operability are prone to decline operation at PVRI > 4 WU.m2 based on the current opinion generated by the change in the guidelines. Indeed, such a notion has gathered momentum is apparent to us from a survey conducted among Indian cardiologists, and a similar situation might exist in other parts of the globe. Such a shift towards declining a needed surgery to children and young adults with a PVRI in the range of 4–6 WU.m2 with a persistent shunt is counterproductive. Although the guidelines do not suggest declining surgery at 4–6 WU.m2, and encourage individual patient decision, younger patients with PVRI in the range of 4–6 WU.m2 and significant shunt should be clearly considered operable, in the absence of legitimate reasons to the contrary.

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