Smaller right heart size and better right ventricular function have been observed in individuals with pulmonary arterial hypertension (PAH) or chronic thromboembolic pulmonary hypertension (CTEPH) undergoing long-term riociguat treatment, according to a study recently published in Respiratory Research.

This retrospective study included 71 participants, 45% of whom had PAH and 55% of whom had CTEPH. A little more than 50% of the participants were women, the average age was 60, and had taken 1.0 to 2.5 mg of riociguat 3 times daily for 3 to 12 months within the CHEST, Early Access Study, PATENTplus, or PATENT trials. Blinded, offline analysis of echocardiography by investigators took place at baseline, 3, 6, and 12 months. The change in right atrial area at 1 year constituted the study’s primary end point. The t-test and Wilcoxon signed rank test were used to compare values at baseline and follow-up.

Participants’ mean baseline pulmonary arterial pressure was 46±10 mm Hg and mean pulmonary vascular resistance was 700±282 dynes·sec·cm-5. At the 6-month mark, there were significant decreases in right ventricular thickness tricuspid regurgitation velocity (–0.48±0.63 cm/sec; 95% CI, –0.71 to –0.25; P <.001), right atrial area (–2.4±3.7 cm2; 95% CI, –3.73 to –1.13; P <.001), and right ventricular area (–3.01±3.15 cm2; 95% CI, –4.23 to –1.96; P <.001). At 12 months, decreases from baseline were observed in right ventricular area (–3.5±5.2 cm2; 95% CI, –5.1 to –1.9; P <.001), right ventricular thickness (–0.76±2.2 mm; 95% CI, –1.55 to 0.03), and right atrial area (–2.58±4.37 cm2; 95% CI, –3.84 to –1.33; P <.001). Increases at 12 months included right ventricular fractional area change (8.12±8.87 mm; 95% CI, 4.61-11.62) and tricuspid annular plane systolic excursion (2.95±4.78 mm; 95% CI, 1.52-4.39).

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Study limitations included potential bias from participants who did not receive results from echocardiography, a retrospective study design, a small number of study centers, and small sample size.

The researchers concluded that “treatment with riociguat may improve right heart function in patients with PAH and CTEPH within 12 months of treatment. Prospective, controlled studies are needed to confirm the effects of riociguat on right heart size and function in these patients.”

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Disclosures: This study received funding from Bayer AG and Merck Sharp & Dohme Corp. Several authors report financial associations with pharmaceutical companies. For a full list of author disclosures, please visit the reference link.


Marra AM, Halank M, Benjamin N, et al. Right ventricular size and function under riociguat in pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension (the RIVER study). Respir Res. 2018;19(1):258.