[Thromboembolic pulmonary arterial hypertension]

Thromboembolic pulmonary hypertension can occur in two different settings: either acute pulmonary embolism or chronic pulmonary thromboembolism. During acute pulmonary embolism, when the heart and lungs are normal, the mean pulmonary artery pressure never excesses 40 mmHg, this is the maximum pressure the right ventricle can stand. During chronic thromboembolism, the right ventricle can adapt to slowly increasing pulmonary artery pressure. The mean pulmonary artery pressure is usually very elevated and right heart failure is delayed. Diagnosis is difficult when an history of acute pulmonary embolism or phlebitis is lacking. At the beginning, the main differential is psychogenic dyspnea. A clue to the diagnosis is given by the pulmonary function test mainly arterial blood gases at rest and exercise and radionuclide perfusion scan. When the pulmonary hypertension is patent the main differential is primary pulmonary hypertension. No definitive clear cut can be made between multiple distal chronic thromboembolism and primary pulmonary hypertension.