Inorganic Nitrite to Amplify the Benefits and Tolerability of Exercise Training in Heart Failure With Preserved Ejection Fraction: The INABLE-Training Trial

Objective To determine whether nitrite can enhance exercise training (ET) effects in heart failure with preserved ejection fraction (HFpEF). Methods In this multicenter, double-blind, placebo-controlled, randomized trial conducted at 1 urban and 9 rural outreach centers between November 22, 2016, and December 9, 2021, patients with HFpEF underwent ET along with inorganic nitrite 40 mg or placebo 3 times daily. The primary end point was peak oxygen consumption (VO2). Secondary end points included Kansas City Cardiomyopathy Questionnaire overall summary score (KCCQ-OSS, range 0 to 100; higher scores reflect better health status), 6-minute walk distance, and actigraphy. Results Of 92 patients randomized, 73 completed the trial because of protocol modifications necessitated by loss of drug availability. Most patients were older than 65 years (80%), were obese (75%), and lived in rural settings (63%). At baseline, median peak VO2 (14.1 mL·kg−1·min−1) and KCCQ-OSS (63.7) were severely reduced. Exercise training improved peak VO2 (+0.8 mL·kg−1·min−1; 95% CI, 0.3 to 1.2; P<.001) and KCCQ-OSS (+5.5; 95% CI, 2.5 to 8.6; P<.001). Nitrite was well tolerated, but treatment with nitrite did not affect the change in peak VO2 with ET (nitrite effect, −0.13; 95% CI, −1.03 to 0.76; P=.77) or KCCQ-OSS (−1.2; 95% CI, −7.2 to 4.9; P=.71). This pattern was consistent across other secondary outcomes. Conclusion For patients with HFpEF, ET administered for 12 weeks in a predominantly rural setting improved exercise capacity and health status, but compared with placebo, treatment with inorganic nitrite did not enhance the benefit from ET. Trial Registration ClinicalTrials.gov identifier: NCT02713126.