Prognostic and pathophysiological marker for patients with chronic thromboembolic pulmonary hypertension: Usefulness...

Chronic thromboembolic pulmonary hypertension (CTEPH) is a progressive disease in some patients, despite improved treatments. Microvasculopathy has been implicated in the poor outcomes of patients with CTEPH. A reduction in the diffusing capacity for carbon monoxide (DL_CO ) was previously suggested to indicate microvasculopathy in CTEPH patients; therefore, we assessed DL_CO /alveolar ventilation (DL_CO /V_A ) as a prognostic and pathophysiological marker in CTEPH.

We performed a retrospective cohort study of 214 CTEPH patients consecutively diagnosed between 1986 and 2011. After exclusion of 24 patients because of missing DL_CO data or severe obstructive impairment, the mortality rates of medically treated patients classified with normal or decreased DL_CO values were compared, and prognostic factors were determined. The relationship between long-term surgical outcomes and DL_CO /V_A was also investigated.

Ninety-one inoperable patients were treated medically, two of whom underwent balloon pulmonary angioplasty. Ninety-nine underwent pulmonary endarterectomy. The 5-year survival rate of medically treated patients was significantly lower in patients with decreased DL_CO /V_A than in those with normal values (61.4% vs 90.4%, P = 0.017). Decreased preoperative DL_CO /V_A was associated with a smaller percent decrease in post-operative pulmonary vascular resistance, but not with the extent of proximal thrombi; these results may support our hypothesis that DL_CO reflects microvascular involvement.

Decreased DL_CO /V_A was associated with poor outcomes of medically treated CTEPH patients; and may be useful for identifying high-risk patients, potentially leading to earlier and more appropriate interventions.