The implantation of an interatrial shunt device (IASD) may improve pulmonary vascular function at rest and during exercise in patients with heart failure (HF) and ejection fraction ≥40%, according to study results published in the Journal of the American College of Cardiology.

Left atrial hypertension tends to develop during exercise in patients with HF with preserved ejection fraction to increase the risk for complications including lung congestion and mortality. In this study, researchers performed a pooled analysis to evaluate the effects of an IASD on pulmonary vascular function at rest and during exercise in patients with HF and ejection fraction ≥40%. The analysis used data from the REDUCE LAP-HF and REDUCE LAP-HF I trials — both of which were designed to assess the performance and safety of a transcatheter IASD in patients with HF and ejection fraction ≥40%.

The REDUCE LAP-HF trial was a multicenter, nonrandomized, open-label, single-arm, phase 1 trial (ClinicalTrials.gov Identifier: NCT01913613), in which implantation of the IASD was successful in all 64 participants. The REDUCE LAP-HF I (ClinicalTrials.gov Identifier: NCT02600234) trial was a multicenter, prospective, phase 2, randomized, blinded controlled trial in which none of the 21 participants who received an IASD experienced device-related adverse events between 1 and 12 months of follow-up (although there was 1 major adverse cardiac event at 12 months in the IASD group).

The current study included 79 patients who had successfully received IASD treatment and completed repeated right heart catheterization. All patients underwent regular hemodynamic evaluation between 1 and 6 months to determine how the IASD affected blood flow during rest and exercise. At baseline, patients were elderly, obese, highly symptomatic, and had comorbidities including diabetes, hypertension, and history of atrial fibrillation.

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Results revealed that during rest after IASD implantation, pulmonary blood flow increased by 27%, pulmonary vascular resistance decreased by 17%, pulmonary elastance decreased by 12%, and pulmonary artery compliance increased by 24%. During supine exercise after IASD implantation, exercise duration increased by 14% (7.4±3 min to 8.4±3.8 min; P =.006), and peak workload achieved increased by 12% (43±18 W to 48±20 W; P =.003). After the IASD implantation, researchers observed a greater increase in resting pulmonary blood flow in patients with atrial fibrillation than in patients without (37% vs 20%; P =.001), which was associated with greater reductions in pulmonary vascular resistance and pulmonary elastance (-30% vs -2%; P =.003 and -23% vs -5%; P =.01, respectively).

This study had several limitations. First, there was selection bias because the study only included patients who successfully underwent IASD implantation and subsequent repeat right heart catheterization. Second, results may not apply to patients with more significant pulmonary vascular disease or right ventricular dysfunction, as patients with these characteristics were excluded from the study. Third, results may not apply to upright exercise, as hemodynamics were assessed only during supine exercise. Fourth, the results may have been influenced by the 1- and 6-month difference in follow-up between the 2 trials for right heart catheterization. Fifth, systemic blood flow during exercise was estimated after IASD and caval blood samples were not obtained, which may have led to some variability. Lastly, researchers did not perform correction for multiple hypothesis testing.

The study researchers concluded that implantation of an IASD may improve pulmonary vascular function at rest and during exercise in patients with HF and ejection fraction ≥40% without causing significant pulmonary vascular disease or right ventricular dysfunction. 

“Further study is required to identify the mechanisms by which increased pulmonary blood flow improves pulmonary vascular function and to assess the long-term pulmonary vascular effects of this therapy,” the investigators advised.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Obokata M, Reddy YNV, Shah SJ, et al. Effects of interatrial shunt on pulmonary vascular function in heart failure with preserved ejection fraction. J Am Coll Cardiol. 2019;74(21):2539-2550.