The evolution and the current state of the art of pulmonary thromboendarterectomy

Surgical Management of Chronic Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension is a progressive disease, which may lead to severe right ventricular dysfunction and debilitating symptoms. Pulmonary thromboendarterectomy (PTE) provides the best opportunity for complete resolution of obstructing thromboembolic disease and functional improvement in appropriately selected patients. In this article, the authors review preoperative workup, patient selection, operative technique, postoperative care, and outcomes after PTE.

Cardiopulmonary bypass does not induce lung dysfunction after pulmonary thrombarterectomy: role of pulmonary compliance

OBJECTIVES

Pulmonary endarterectomy is a heavy surgical procedure that is performed under cardiopulmonary bypass (CPB) and aimed to cure postembolic pulmonary hypertension. Reperfusion oedema is both the hallmark of successful surgical procedure and the most frequent postoperative complication. Post-CPB lung dysfunction was not mentioned in any report. We undertook a study to determine whether post-CPB lung dysfunction was present in these patients.

METHODS

In a retrospective cohort study with matching on some baseline covariates, we selected 41 patients who had undergone pulmonary endarterectomy and in whom pre-, intra- and postoperative records were complete. The control group was composed of 39 patients operated on from elective cardiac surgery during the same period and matched with a study group for age, gender, body mass index, blood creatinine, diabetes and baseline partial pressure of oxygen/fraction of inspired oxygen ratio. Criteria for post-CPB lung dysfunction were partial pressure of oxygen/fraction of inspired oxygen ratio decrease and bilateral basal oedema. Explanatory variables for post-CPB lung dysfunction were coronary arterial bypass, pleura opening, static pulmonary compliance measured at the time of thorax closed then retracted, fluid infusion, transfusion and vasopressors.

RESULTS

All patients operated on from pulmonary endarterectomy presented radiological oedema reperfusion in surgical unblocking areas. Among them, only 2 had bilateral basal oedema when compared to the 24 patients from the control group (P < 0.001). Partial pressure of oxygen/fraction of inspired oxygen ratio increased in the study group and decreased in the control group (30 ± 109 vs -67 ± 134 mmHg, P < 0.001). Control group patients with high-baseline pulmonary compliance were at risk for post-CPB lung dysfunction.

CONCLUSIONS

Patients operated on from pulmonary endarterectomy were saved from post-CPB lung dysfunction. The latter could be induced by a mechanical phenomenon.

Chronic thromboembolic pulmonary hypertension

The description of organized thrombus in major pulmonary arteries can be found in autopsy reports dating back to the late nineteenth and early twentieth centuries. Not until the 1950s was the antemortem diagnosis and clinical syndrome of chronic thrombotic obstruction of the major pulmonary arteries better characterized. The first surgical attempt to remove the adherent thrombus from the vessel wall occurred in 1958. This operation provided the conceptual foundation for the distinction between acute and chronic thromboembolic disease of the pulmonary vascular bed, and established that an endarterectomy, and not an embolectomy, would be necessary if a surgical remedy for this disease was to be successful.

Surgery for chronic thromboembolic pulmonary hypertension--inclusive experience from a national referral center

BACKGROUND

Chronic thromboembolic pulmonary hypertension represents a unique form of pulmonary hypertension amenable to curative intervention with a pulmonary thromboendarterectomy (PTE). Canada's first successful and sustainable program for PTE surgery was established at the University of Ottawa Heart Institute in 1995. Inclusive results from similarly sized programs are not readily available owing to selective reporting, therefore making it difficult to benchmark outcomes. The purpose of this report is to provide a review of the inclusive results from our moderately sized national program for all PTE, with a particular emphasize on the aspects of the learning curve in terms of patient management.

METHODS

Since 1995, 180 patients have been referred for consideration of PTE, and 106 patients have undergone surgery with a perioperative 30-day mortality rate of 9.4%.

RESULTS

There was a significant improvement in all hemodynamic parameters except right ventricular ejection fraction in nonsurvivors (mean pulmonary artery pressure pre 47 +/- 12 mm Hg versus post 28 +/- 9 mm Hg, p < 0.0001; pulmonary vascular resistance pre 814 +/- 429 dynes x sec(-1) x cm(-5), post 224 +/- 145 dynes x sec(-1) x cm(-5), p < 0.0001; cardiac index pre 2.0 +/- 0.7 L x min(-1) x m(-2), post 3.2 +/- 0.7 L x min(-1) x m(-2), p < 0.0001). A postoperative pulmonary vascular resistance of 500 dynes x sec(-1) x cm(-5) or more was associated with increased perioperative mortality (odds ratio, 12 +/- 8.7; p = 0.001). On average, these procedures were associated with significant resource use involving operating room time (610 +/- 243 minutes), intensive care unit and hospital days (11.2 +/- 13.7 and 19.5 +/- 15.6 days), and ventilation time (7.8 +/- 10.0 days). There was no significant change in hospital or intensive care unit length of stay, or the mortality rate during this first decade.

CONCLUSIONS

PTE programs are resource-intensive surgical specialty services that demand excellence in cardiothoracic expertise. The initial decade reflected an expanding referral basis and likely parallel increases in patient complexity and expertise. The current results at a national referral center have emphasized the importance of centralization of resources to optimize patient outcome.

Anaesthesia management for pulmonary endarterectomy

PURPOSE OF REVIEW

Options for the surgical treatment of chronic thromboembolic pulmonary hypertension are either lung transplantation or pulmonary endarterectomy. Pulmonary endarterectomy is considered permanently curative and the treatment of choice. The procedure dramatically improves functional status and provides an excellent immediate and long-term survival, much better than transplantation. Pulmonary endarterectomy, until recently performed in only a few highly specialized centres, is now spreading worldwide with good results. This review will focus on the understanding of the pathophysiology of the disease and on recent advances in assessment and treatment strategies.

RECENT FINDINGS

Recent data reinforce the thromboembolic nature of chronic thromboembolic pulmonary hypertension, and have shown that the disorder is more common than was thought and remains underdiagnosed. There has recently been a remarkable surge in the understanding of the mechanisms involved in the pathogenesis of pulmonary hypertension. Advances in diagnosis, surgical techniques, preoperative treatment, and perioperative management have improved the prognosis of this debilitating disease. New information about pretreatment and medical treatment with prostanoids and endothelin receptor antagonists is now available.

SUMMARY

Pulmonary endarterectomy can be successfully performed in selected centres using a multidisciplinary approach involving the specialities of surgery, pulmonary medicine, cardiology, radiology, anaesthesiology and critical care medicine. The largest risk factor remains the degree of operability related to a high pulmonary vascular resistance caused by permanent changes in the pulmonary vascular bed. Early operation is now recommended to prevent these irreversible changes. Further investigations are warranted to establish the role of new drugs in surgical patients with chronic thromboembolic pulmonary hypertension.

Circulating big endothelin-1: An active role in pulmonary thromboendarterectomy?

BACKGROUND

Pulmonary thromboendarterectomy is an effective treatment for patients with chronic thromboembolic pulmonary hypertension. The early postoperative course may be associated with pulmonary vasoconstriction and profound systemic vasodilation. We investigated the potential involvement of endothelins in these hemodynamic alterations.

METHODS

Seventeen patients with chronic thromboembolic pulmonary hypertension (pulmonary vascular resistance, 1015 +/- 402 dyne x s x cm(-5) [mean +/- SD]) underwent pulmonary thromboendarterectomy with cardiopulmonary bypass and deep hypothermic circulatory arrest. Peripheral arterial blood samples were drawn before sternotomy, during cardiopulmonary bypass before and after deep hypothermic circulatory arrest, and 0, 8, 16, and 24 hours after surgery and were analyzed for big endothelin-1. The patients were divided into 2 groups according to whether their preoperative big endothelin-1 plasma level was above or below the cutoff point of 2.1 pg/mL, as determined by receiver operating characteristic curve analysis (group A, big endothelin-1 <2.1 pg/mL, n = 8; group B, big endothelin-1 > or =2.1 pg/mL, n = 9).

RESULTS

Patients in group B, with higher preoperative big endothelin-1 levels (3.2 +/- 1.0 pg/mL vs 1.5 +/- 0.4 pg/mL; P < .001), were poorer operative candidates (preoperative mean pulmonary artery pressure, 51.3 +/- 7.1 mm Hg vs 43.6 +/- 6.2 mm Hg; P = .006) and had a poorer outcome (mean pulmonary artery pressure 24 hours after surgery, 32.6 +/- 9.5 mm Hg vs 21.8 +/- 6.2 mm Hg; P < .001). Positive correlations were found between preoperative big endothelin-1 levels and preoperative mean pulmonary artery pressure (r = 0.56; P = .02) as well as postoperative mean pulmonary artery pressure at 0 hours (r = 0.70; P = .002) and 24 hours (r = 0.63; P = .006) after surgery. Preoperative big endothelin-1 levels predicted outcome (postoperative mean pulmonary artery pressure at 24 hours after surgery) after pulmonary thromboendarterectomy (area under the receiver operating characteristic curve, 0.85). Peak big endothelin-1 levels also correlated with maximal vasopressor dosage (r = 0.65; P = .004).

CONCLUSIONS

Preoperative big endothelin-1 levels seem to correlate with the hemodynamic alterations observed in pulmonary thromboendarterectomy and may be used to predict hemodynamic outcome after pulmonary thromboendarterectomy.

Cytokine response to pulmonary thromboendarterectomy

BACKGROUND

Pulmonary thromboendarterectomy (PTE) is an effective but challenging treatment for chronic thromboembolic pulmonary hypertension (CTEPH). PTE is associated with marked hemodynamic instability in the perioperative course, suggesting the involvement of circulating mediators. The aim of this study was to characterize the expression of proinflammatory and anti-inflammatory cytokines in patients undergoing PTE.

METHODS

Fourteen patients with CTEPH (mean [+/- SD] pulmonary vascular resistance, 1,056 +/- 399 dyne.s.cm(-5)) underwent PTE using cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest (DHCA). Peripheral arterial blood samples were drawn prior to patients undergoing sternotomy, during CPB, before and after DHCA, and 0, 8, 16, 24, and 48 h after surgery. An enzyme-linked-immunosorbent assay was used to analyze the plasma levels of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-10. Seven patients undergoing aortic arch replacement (ARCH) in DHCA served as a control group.

RESULTS

Prior to and during PTE, the CTEPH patients exhibited elevated TNF-alpha levels, which decreased within the first 24 postoperative hours (p = 0.02). There was no TNF-alpha release among patients in the ARCH group. IL-6 levels were similar in both groups throughout the perioperative course. A profound anti-inflammatory response was observed in the PTE group, which was reflected by elevated IL-10 levels prior to surgery and a marked peak level immediately after surgery. A positive correlation was found between maximum vasopressor support and peak levels of IL-6 (r = 0.82) in the PTE patients.

CONCLUSION

Heart failure due to CTEPH appears to generate a pronounced inflammatory response with the release of proinflammatory and anti-inflammatory cytokines. PTE results in the rapid normalization of preoperatively elevated TNF-alpha levels. IL-6-mediated systemic inflammatory cascades may be involved in the regulation of peripheral vascular tone after PTE.

Pulmonary thromboendarterectomy surgery

Considerable progress has been made over the past decade in understanding the etiology, prevalence, natural history, and therapeutic approach to chronic thromboembolic pulmonary hypertension. Pulmonary endarterectomy is now widely recognized as the definitive treatment for chronic pulmonary hypertension resulting from thromboembolic disease. This article focuses on the surgical treatment of chronic thromboembolic pulmonary hypertension.

Chronic thromboembolic pulmonary hypertension

During the past 2 decades, there has been a steady rise in the number of patients with chronic thromboembolic pulmonary hypertension (CTEPH) undergoing surgery and in the number of programs worldwide dedicated to the diagnosis and management of this patient population. This article discusses the natural history and clinical presentation of CTEPH, the evaluation of patients for pulmonary thromboendarterectomy, and the outcomes following surgery, along with a brief review of the procedure as performed at the University of California, San Diego.

Pulmonary thromboendarterectomy almost 50 years after the first surgical attempts

With increased experience in preoperative evaluation, surgical approach and postoperative care of chronic thromboembolic pulmonary hypertension, pulmonary thromboendarterectomy can be performed with an acceptably low risk of death. Most patients, even those in a very compromised state, have excellent, long lasting results.

Tricuspid valvular disease in the patient with chronic pulmonary thromboembolic disease

Chronic thromboembolic pulmonary hypertension is associated with right ventricular dilatation, high right-sided filling pressures, and functional tricuspid regurgitation. The tricuspid regurgitation resulting from this disease has been postulated to be caused by tricuspid annular dilatation with displacement of the papillary muscles. Pulmonary endarterectomy is an operation that corrects the pulmonary hypertension resulting from chronic thromboemboli. As a result of this operation, most patients show significant improvement in tricuspid valve function. Thus, pulmonary endarterectomy is one of the few cardiac operations in which surgery remote to a valve restores valve function. This review analyzes the factors responsible for changes in tricuspid valve regurgitation after pulmonary endarterectomy and provides a strategy to predict the small subset of patients who will not show improvement in tricuspid valve function after this operation.

Prostacyclin therapy before pulmonary thromboendarterectomy in patients with chronic thromboembolic pulmonary hypertension

OBJECTIVES

The continuous IV administration of prostacyclin improves pulmonary hemodynamics and prognosis in patients with primary pulmonary hypertension. We investigated whether the administration of prostacyclin therapy to patients before they undergo pulmonary thromboendarterectomy ameliorates pulmonary hypertension in patients with the most severe form of chronic thromboembolic pulmonary hypertension (CTEPH).

METHODS

Of the 33 patients with CTEPH who were candidates for pulmonary thromboendarterectomy, 12 patients with severe pulmonary hypertension (pulmonary vascular resistance, > 1,200 dyne. s. cm(-5)) received IV prostacyclin prior to undergoing pulmonary thromboendarterectomy. Right heart catheterization and plasma brain natriuretic peptide (BNP) measurements were repeated at baseline, immediately before surgery, and 1 month after surgery.

RESULTS

During a mean (+/- SEM) follow-up period of 46 +/- 12 days, the IV administration of prostacyclin resulted in a 28% decrease in pulmonary vascular resistance (1,510 +/- 53 to 1,088 +/- 58 dyne. s. cm(-5); p < 0.001) before surgery. Prostacyclin therapy markedly decreased plasma BNP level (547 +/- 112 to 188 +/- 30 pg/mL; p < 0.01), suggesting improvement in right heart failure. Pulmonary thromboendarterectomy caused a further reduction of pulmonary vascular resistance (302 +/- 47 dyne. s. cm(-5)) and plasma BNP levels (60 +/- 11 pg/mL) compared to each preoperative value (p < 0.05). Operative mortality rates were relatively low (8.3%) in patients with the most severe form of CTEPH.

CONCLUSION

The IV administration of prostacyclin caused beneficial hemodynamic effects in patients with severe CTEPH and may serve as pretreatment for patients undergoing pulmonary thromboendarterectomy.

Operative classification of thromboembolic disease determines outcome after pulmonary endarterectomy

OBJECTIVE

We sought to determine whether type and location of thromboembolic disease in the pulmonary vascular tree predicts the hemodynamic result and clinical outcome in patients undergoing pulmonary endarterectomy.

METHODS

From 1998 to 2000, 202 patients with pulmonary hypertension and pulmonary vascular resistance ranging from 194 to 2950 dynes-s-cm(-5) underwent pulmonary endarterectomy. Preoperative and postoperative tricuspid valve function, pulmonary artery pressure, and pulmonary vascular resistance were determined by means of transthoracic echocardiography and measurements with a Swan-Ganz catheter (Edwards Lifesciences, Irvine, Calif), respectively. Patients underwent intraoperative classification of thromboembolism as follows: type 1 (76 patients), fresh thrombus in the main-lobar pulmonary arteries; type 2 (81 patients), intimal thickening and fibrosis proximal to the segmental arteries; type 3 (38 patients), disease within distal segmental arteries only; and type 4 (7 patients), distal arteriolar vasculopathy without visible thromboembolic disease.

RESULTS

Overall perioperative mortality was 4.5% (9/202 patients). By means of univariate analysis, patients with type 3 or 4 disease (distal pulmonary vasculopathy) had more residual postoperative tricuspid regurgitation (P <.0001), higher postoperative pulmonary artery systolic pressure (P <.0001), and greater postoperative pulmonary vascular resistance (P <.0001) compared with that seen in patients with type 1 or 2 disease, in whom thromboembolic disease was more surgically accessible. Factors such as severity of preoperative tricuspid regurgitation, patient age, and circulatory arrest time had no correlation with postoperative hemodynamic improvement. Patients with distal thromboembolic disease (type 3-4) had higher perioperative mortality, required longer inotropic support, and had longer hospital stays compared with patients with type 1 or 2 thromboembolic disease.

CONCLUSION

The degree of improvement in pulmonary hypertension and tricuspid regurgitation after pulmonary endarterectomy is determined by the type and location of pulmonary thromboembolic disease. Classification of thromboembolism is useful for predicting patient outcome after pulmonary endarterectomy.

Chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) should be differentiated from other etiologies of pulmonary hypertension since surgical intervention may be potentially curative. The presentation of this illness is nonspecific and may mimic other cardiopulmonary disease states. Without treatment, progressive pulmonary hypertension, right heart failure, and death will ensue. Echocardiography, lung ventilation-perfusion scan, right heart catheterization, and angiography are required for proper diagnosis and preoperative assessment. Definitive treatment requires surgical resection of thromboembolic material. The role of medical therapy remains to be defined.

Chronic thromboembolic pulmonary hypertension

Remarkable advances have occurred over the past 2 decades in the diagnostic approach, surgical management, and postoperative care of patients afflicted with chronic thromboembolic pulmonary hypertension. Despite these advances, a great deal needs to be achieved if the morbidity and mortality of the disease process are to be reduced further. First, the preliminary insights that have been achieved into the natural history of the disease must be defined further. The level of pulmonary hypertension encountered in most patients with chronic thromboembolic pulmonary hypertension at the time of initial clinical recognition cannot be reached on an acute basis. Gradual hemodynamic progression, therefore, must occur over time. The basis for this progression, why it occurs in certain patients and not others, following an acute thromboembolic event and why it seems to occur over months in certain patients and over decades in others, remain entirely speculative. It is possible that the overall extent of central pulmonary vascular obstruction represents the primary pathophysiologic determinant of disease progression. Given the lack of correlation between the degree of central thromboembolic obstruction and hemodynamic impairment in certain patients, however, it is also possible that other factors, such as the circulating vasoconstrictors, the development of a hypertensive pulmonary arteriopathy, an individual genetic predisposition to pulmonary hypertension, or the compensatory adaptations of the right ventricle, contribute to the extent and rate of disease progression. By identifying and sequentially evaluating patients with persistent pulmonary vascular obstruction or pulmonary hypertension following an acute thromboembolic event, valuable insights into the natural history of thromboembolic pulmonary hypertension and other variants of pulmonary hypertension might be achieved. It is also important to recognize that the development of chronic thromboembolic pulmonary hypertension represents a failure in the long-term management or follow-up surveillance of those with documented acute thromboembolic disease. Recent insights into the recurrent nature of acute thromboembolic disease and its potential for only partial resolution in a number of afflicted individuals suggest that a repeat perfusion scan and, if abnormal, an echocardiogram be performed at the time of anticipated discontinuation of anticoagulation in patients with documented pulmonary embolic disease. Although the cost-effectiveness of this approach has been questioned in the past, recent data suggest that doing so would help identify that subset of patients with unresolved embolism, provide additional information regarding the optimal duration of anticoagulation, and provide a new baseline study for patients in whom anticoagulation is discontinued and who subsequently present with suspected embolic recurrence. Improved diagnostic techniques are also necessary if the mortal risk of thromboendarterectomy is to be reduced. Even in the setting of a broad experiential base, prognostic uncertainty exists in approximately 10% of patients before operative intervention. Because many of these patients will benefit from the procedure, and because many are ineligible for transplantation for reason of age or other restriction, it has been the authors' practice to offer surgery to these patients, although at an assumed higher risk. To not do so would be to deny a potentially lifesaving procedure to many who would benefit and who might be left without an effective therapeutic alternative. The ability to better define the group of patients who will not benefit from surgery, however, would spare those patients the morbid and mortal risks of the procedure and provide a basis for the investigation of other therapeutic alternatives such as pulmonary vasodilating agents. Finally, this patient population offers a unique opportunity to enhance understanding of the pathophysiologic mechanisms involved in acute lung injury. The population involved is uniform, the predisposing event is consistent, the time of onset is predictable, and, compared with other populations at risk for acute lung injury, the presence of confounding variables is negligible. It also provides a unique opportunity to evaluate pharmacologic interventions designed to prevent or diminish the occurrence of acute lung injury and postoperative management strategies designed to minimize its impact.