Systematic review of trials using vasodilators in pulmonary arterial hypertension: why a new approach is needed

BACKGROUND

In a previous meta-analysis on the approved treatments for pulmonary hypertension, we reported that all therapies caused small changes in 6-minute walk distance over a short period, with minimal effects on hemodynamics and no effect on survival. Since that last review, 10 new clinical trials with about 1,500 patients have been published, which has increased the statistical power of our observations.

METHODS

A systematic review of all clinical trials in pulmonary arterial hypertension was done.

RESULTS

The pooled effect of all treatments strategies (relative risk [95% CI], P) now shows a significant reduction of 39% (2%-62%, P = .041) in all-cause mortality. The benefits were confined only to patients with advanced disease for 16 weeks, regardless of which class of drug is used. When considering the effects within each drug family, no class of drug produced a statistically significant reduction in all-cause mortality. The improved survival bore no relationship with the change in 6-minute walk, the primary end point in most of the trials.

CONCLUSIONS

The impact of vasodilators on long-term survival in pulmonary arterial hypertension remains uncertain. Future trials need to (a) adopt new trial designs that can better address clinical benefits, (b) use new end points that incorporate our best understanding of the disease rather than the ones that are easy to administer, and (c) include longer durations of study and other strategies to clarify if survival is affected.

The haematocrit and platelet target in polycythemia vera

Polycythemia vera (PV) is a chronic myeloproliferative disorder whose major morbidity and mortality are thrombohaemorragic events and progression to acute leukaemia or myelofibrosis. Whether the haematocrit and platelet count predict such complications remains unclear. The European Collaboration on Low-dose Aspirin in Polycythemia Vera prospective study included 1638 PV patients. A total of 164 deaths (10%), 145 (8.85%) major thrombosis and 226 (13.8%) total thrombosis were encountered during 4393 person-years follow-up (median 2.8 years). In time-dependent multivariable analysis, a haematocrit in the evaluable range of 40-55% was neither associated with the occurrence of thrombotic events, mortality nor with haematological progression in the studied population. The haematocrit of patients in the highest and lowest deciles at baseline was maintained within a narrow interval of haematocrit values ranging from 40% to 47% throughout follow-up. High platelet count was associated with a lower progression rate to acute leukaemia/myelofibrosis, whereas it had no significant relationship with thrombotic events or mortality. Our findings do not suggest that the range of haematocrit (<55%) and platelet counts (<600 x 10(9)/l) we encountered in our population had an impact on the outcome of PV patients treated by current therapeutic strategies.

Leukocytosis as a major thrombotic risk factor in patients with polycythemia vera

In polycythemia vera, vascular risk assessment is based on age and thrombotic history, while the role of other potential predictors of this risk is still uncertain. Thus, we exploited the large database collected by the observational study of the European Collaboration on Low-Dose Aspirin in Polycythemia Vera (ECLAP) to investigate the association of hematologic variables and cardiovascular risk factors with the thrombotic risk. Among 1638 polycythemic patients followed for 2.7 +/- 1.3 years, there were 205 thromboses. Subjects with hypertension had a mild nonsignificant increase in the risk of arterial thrombosis, while this risk was significantly increased by smoking (hazard ratio [HR], 1.90; 95% confidence interval [CI], 1.15-3.14; P = .012). The time-dependent analysis adjusted for potential confounders showed that patients with a white blood cell count above 15 x 10(9)/L, compared with those with a white blood cell count below 10 x 10(9)/L, had a significant increase in the risk of thrombosis (HR, 1.71; 95% CI, 1.10-2.65; P = .017), mainly deriving from an increased risk of myocardial infarction (HR, 2.84; 95% CI, 1.25-6.46; P = .013). Thus, leukocyte count may help in defining the vascular risk of polycythemic subjects.