Original contributionPulmonary thromboendarterectomy: a clinicopathologic study of 200 consecutive pulmonary thromboendarterectomy cases in one institution
Introduction
Pulmonary thromboendarterectomy (PTE) is recognized as an effective treatment for pulmonary hypertension caused by chronic thromboembolic disease (CTED) in patients with surgically accessible thromboemboli [1]. CTED of sufficient severity requiring surgical intervention occurs in approximately 0.1% to 0.3% of patients who have survived an acute embolic event [2]. Recent data, however, suggest that incomplete anatomic and hemodynamic recovery may occur more frequently than previously realized in patients who have been diagnosed with acute thromboembolic disease despite an appropriate therapy [2]. The pathophysiologic events leading to CTED are not entirely understood; CTED is usually progressive and often fatal without treatment.
PTE is a true endarterectomy excising the fibrotic organized thromboembolic material that adheres to the vessel wall [3]. An endarterectomy plane is established between the intima and the fibrotic thromboembolic material [3]. Considerable experience is required to identify and establish the correct plane [3]. During PTE procedure, any loose thrombus, if present, is removed. Then, a microtome knife is used to develop the endarterectomy plane under clear visualization in a completely bloodless field provided by circulatory arrest [3]. Dissection in the correct plane is critical because if the plane is too deep, the pulmonary artery may perforate with fatal results, and if the dissection plane is not deep enough, inadequate amounts of the partially reabsorbed thromboembolic material will be removed. Typically, the PTE specimens contain little or no media. An absolute criterion for surgery is the presence of accessible chronic thrombi, and the experience of the surgical team dictates what can be considered accessible [4]. Current surgical techniques allow removal of organized thrombi in the main and lobar levels, extending to the proximal segmental vessels.
The outcome of PTE is largely dependent on patient suitability. The decision to undertake PTE must be tailored to an individual patient based on CTED type. A crucial element in the preoperative assessment of CTED is the evaluation of microvascular disease as well as proximal disease. Preoperative classification of CTED has not been established to date but is under investigation for the selection of patients for PTE and for the planning of a long-term clinical management. An intraoperative classification of CTED introduced by Thistlethwaite et al [5] has been useful in providing information to guide patient management [5]: type I—fresh thrombus in the main or lobar pulmonary arteries; type II—intimal thickening and fibrosis proximal to segmental arteries; type III—fibrosis, intimal webbing, and thickening within distal segmental and subsegmental arteries only; and type IV—microscopic distal arteriolar vasculopathy without visible thromboembolic disease. Type IV disease does not represent classic CTED and is deemed inoperable. It has been shown that patients with type III and type IV diseases have more residual postoperative tricuspid regurgitation, a higher postoperative pulmonary artery systolic pressures, and a higher postoperative pulmonary vascular resistance than those with type I or type II disease [5].
Probably fewer than 3000 cases of PTE have been performed worldwide. Approximately 2000 patients referred from national and international referral sources have undergone PTE at the University of California, San Diego (UCSD), by May of 2006, which accounts for the highest number of PTE procedures performed at a single institution. The number of referrals has been increasing steadily at UCSD with low perioperative mortality rates and marked improvement of pulmonary hemodynamic status, functional outcome, and long-term survival in many of these patients.
Clinicopathologic study on PTE has been scarce because of the relative rarity of this procedure in any given institution, and the largest series in the literature was based on 54 cases from 1990 to 2001 at Mayo Clinic [6]. In the present study, we documented histopathologic and clinical findings from 200 consecutive PTE cases at UCSD over a recent 20-month period.
Section snippets
Case selection
Consecutive 200 PTE cases were identified in the period from June 2004 to February 2006 via computer searches of the archives of the surgical pathology file at UCSD. This study was approved by the institutional review board at UCSD (IRB# 060430X).
Clinical and operative data
Pertinent clinical information and intraoperative findings were obtained from the medical record and operative report. For each patient, age at the time of surgery, sex, and past medical history with a particular note of a documented deep vein
Clinical groups of patients
Among the 200 PTE cases, 2 cases were diagnosed as pulmonary artery sarcoma (PAS), and one case as metastatic tumor emboli from a testicular germ cell tumor. Two cases were diagnosed as isolated pulmonary arteritis with full-thickness pulmonary artery biopsy at the time of PTE. The remaining 195 PTE cases having thromboembolic disease were used in the histopathologic analysis.
Clinicopathologic summary of malignancy
In the study group, there were 2 cases of PAS and 1 case of metastatic tumor emboli. One patient with PAS was a
Discussion
Demographics, history of DVT, and presence of hypercoagulable conditions in our 195 patients with CTED were comparable to the published data in previous studies [6], [7]. It occurred almost equally in men and women commonly in their sixth decade of life. The vast majority of CTED had a bilateral involvement with a documented history of DVT in 38.5% and procoagulation abnormalities in 16.4% of 195 cases. As in previous reports, the gross volume of PTE specimen was significantly greater in the
Acknowledgment
The authors thank Lynn Sandweiss, MPH, for her contribution to statistical analysis for the study.
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