[Pulmonary hypertension and lung transplantation]

Abstract

Background: With the development of effective drug treatment in the last 2 decades, lung transplantation has become the final option in the management of pulmonary arterial hypertension (PAH). Its main advantage is the curative aspect with recovery of cardiopulmonary capacity. Scarcity of donor organs and chronic graft rejection, however, remain serious limitations to short- and long-term success, and emphasize the need for judicial patient selection. Timely presentation of the patient to the transplant center is of critical importance.

Indication: Guidelines have been presented by the International Society for Heart and Lung Transplantation (ISHLT), the American Thoracic Society (ATS) and the American Society of Transplant Physicians (ASTP) in the year 1998. Selection criteria are clinical status (NYHA [New York Heart Association] > or = III and progressing, right heart insufficiency symptoms), hemodynamic data (mean pulmonary arterial pressure > 55 mmHg, systolic arterial pressure < 120 mmHg, cardiac index < 2 l/min/m2, central venous pressure > 15 mmHg, right heart function on echocardiography), and functional parameters (peak oxygen uptake < 10-12 ml/kg/min, 6-min walk test [MWT] < 332 m). Functional parameters have been shown to correlate with a 1-year mortality of 40% with a 6-MWT < 332 m, of 50% with a peak oxygen uptake < 10.4 ml/kg/min, and of 70% with a systolic arterial pressure < 120 mmHg. Combinations of the above lead to a 1-year survival of 23%. Mean survival of patients with primary pulmonary hypertension (PPH) is 2.8 years and is reduced to 6 months, when NYHA IV is reached (National Institutes of Health-PPH Registry 2002). These data underline the potential survival benefit from transplantation for patients with advanced lung failure due to PAH.

Transplantation: Single lung, bilateral lung and heart-lung transplantation are the transplantation procedures available. Even though heart-lung transplantation was the first procedure to be performed in 1981, bilateral lung transplantation is the procedure most commonly performed at present. Choice of transplantation procedure should be made after thorough evaluation, taking the potential reversibility of right ventricular dysfunction after the operation into account (Figure 1). Hemodynamic instability from right and/or left ventricular failure, however, may complicate early postoperative management. Heart and lung transplantation should only be considered, if structural heart damage is present. Lung function improves immediately postoperatively and increases in the following 6 months. Most patients have normal function studies 1 year after transplantation.

Statistics: The Registry of the ISHLT (01/1982-06/2003) reports PAH as primary diagnosis in 4.2% of all lung transplantations (457/10,959) and 24.3% (550/2,263) of all heart-lung transplantations. This corresponds to 1.1% of all single (66/5,793) and 7.6% of all bilateral lung transplantations (391/5,166). Single lung transplantation is associated with shorter ischemia, cardiopulmonary bypass and operation time. The procedure, however, is accompanied by ventilation/perfusion mismatch, a higher likelihood of reperfusion injury and less functional reserve in case of progressive chronic rejection. The advantages of bilateral lung transplantation are under discussion, particularly as 5-year survival seems to be higher in some centers. Heart and lung transplantation is reported to have similar results as bilateral lung transplantation (Table 1), showing survival advantages only in patients with Eisenmenger's syndrome or ventricular septal defect. Bilateral lung transplantation, therefore, is the procedure of choice at the Essen Transplant Center, provided donor organs are available.

Conclusion: Thoracic transplantation has become a feasible therapeutic option in terminal PAH patients. Judicious patient selection, choice and timing of procedure are critical to a successful outcome.