The management of pulmonary hypertension secondary to chronic thromboembolic disease

Abstract

I N THE UNITED States it is estimated that 600,000 people experience pulmonary embolus each year. 1-3 Approximately 50,000 of these patients die, but in the vast majority, the pulmonary emboli resolve rapidly and substantially, resulting in no residual symptoms or hemodynamic sequelae. However, in a small minority of patients with extensive embolization, the emboli fail to resolve and undergo fibrovascular organization, causing chronic obstruction to pulmonary arterial blood flow. This can subsequently result in a condition known as chronic pulmonary thromboembolic hypertension (CPTH). The diagnosis, pathophysiology, and treatment of acute pulmonary embolism (PE) are discussed elsewhere in this symposium. The concept of chronic pulmonary thromboembolism (CPT) has been known to exist for many years, having been first suspected by Hart (1916) and Moller (1920). 4 An association of CPT with progressive respiratory insufficiency was made in 1928 by Ljungdahl. 5 However, for many years, the condition was regarded as an autopsy curiosity, and antemortem diagnosis was unusual. The small number of patients who were diagnosed with this condition received only medical management for the secondary pulmonary hypertension, including oxygen, vasodilator, fibrinolytic, and anticoagulant therapy. Long-term prognosis was very poor. This changed as advances in cardiac surgical techniques led to the ability to perform thromboendarterectomy which offered a surgical cure. With a potential cure available, there was an increased impetus toward making an early diagnosis. This was facilitated by advances in diagnostic techniques and an increased awareness of the characteristic clinical presentation. The diagnosis of CPT involving the major pulmonary vessels is now made more often during a patient's lifetime, and it has become apparent that CPTH is more common than was once previously thought. Although the exact incidence of pulmonary hypertension secondary to unresolved emboli is not known, Jamieson et al 6 have estimated that this sequel may develop in 0.1% to 0.2% of survivors of an acute embolic event, or in 540 to 1080 patients per year. The disorder is often amenable to surgical therapy, with successful thromboendarterectomy offering the best chance of long-term survival. 6-8 To date, there have been over 400 cases of pulmonary thromboendarterectomy reported, with the vast majority coming from the University of California at San Diego (UCSD) Medical Center (San Diego, California).