Comment
Valuable advances have been made in understanding the risk factors and mechanisms responsible for the development of PAH in thalassemic patients. It is now known that chronic hemolysis with the resulting nitric oxide depletion can lead to endothelial dysfunction and vascular remodeling and, in due course, to PAH [1]. Additionally, vascular thromboembolic occlusions can also develop due to in situthrombosis as well as to pulmonary thromboembolism attributable to the well-recognized hypercoagulable state [2]. The relative contribution of hemolysis-related vasculopathy versus pulmonary thromboembolism in the development of PAH in a specific patient depends on the severity of the genetic defect and the provided treatment methods (such as transfusion rates, chelation therapy and splenectomy) [1]. This needs to be evaluated in every case individually employing a detailed and systematic analysis of lung perfusion [6].
Conventional management approaches to PAH in thalassemic patients include hemoglobinopathy-targeted therapy, PAH-specific medications as well as general supportive treatment. Existing evidence indicates that currently available drug therapies only temporarily and sporadically improve symptoms in CTEPH, and remain ineffective in ameliorating the mechanical obstructions of the pulmonary arteries or in improving patients’ survival [7]. In this context, given that PTE has been established as the gold-standard therapy for CTEPH, it is conceivable that PTE may comprise the only potentially curative therapy for CTEPH in thalassemic patients.
Experience to date with PTE in thalassemic patients with CTEPH is limited to small series or isolated case reports, nevertheless these reports favor PTE as an effective treatment of surgically accessible CTEPH [3, 4]. We reported here the successful performance of PTE surgery in a thalassemic patient with CTEPH irresponsive medical treatment. Pre-operative assessment indicated that this patient was an appropriate candidate for PTE despite a slightly increased potential surgical risk owing to the underlying thalassemia. The post-operative course was relatively uneventful, and was coupled with an early substantial improvement in hemodynamics and functional status.
It is notable that the post-operative reduction in PAP in our patient was less than that commonly expected following PTE [3] which is likely to be due to the multifactorial nature of PAH in thalassemia. In fact, concern remains that the chronic hemolysis-related vasculopathy in the distal vessels may place thalassemic patients at increased risk of residual or recurrent PAH after PTE [4]. Therefore, long-term results of PTE in thalassemic patients remains to be elucidated through long-term follow-up. It is noteworthy here that balloon pulmonary angioplasty has recently been proposed as a potential new therapeutic option for this process [8].
In conclusion, this case report supports the feasibility of PTE in thalassemic patients with surgically accessible CTEPH. Given the complexity of the pathophysiology of PAH in thalassemia, a comprehensive evaluation for both the presence and cause of PAH is imperative prior to determining the likelihood of surgical cure in each individual patient.