Cardiac effects of 6 months' dietary nitrate and spironolactone in patients with hypertension and with/at risk of type 2 diabetes, in the factorial design, double-blind, randomized controlled VaSera trial

Aims: The aims of the present study were to explore whether a long-term intervention with dietary nitrate [(NO ₃ ⁻), a potential tolerance-free source of beneficial vasoactive nitric oxide] and spironolactone (to oppose aldosterone's potential deleterious cardiovascular effects) improve cardiac structure/function, independently of blood pressure (BP), in patients with/at risk of type 2 diabetes (a population at risk of heart failure).

Methods: A subsample of participants in our double-blind, randomized, factorial-design intervention (VaSera) trial of active beetroot juice as a nitrate source (≤11.2 mmol) or placebo (nitrate depleted) beetroot juice, and either ≤50 mg spironolactone or ≤16 mg doxazosin (control), had transthoracic cardiac ultrasounds at baseline (n = 105), and at 3 months and 6 months (n = 87) after the start of the intervention. Analysis was by modified intent-to-treat.

Results: Nitrate-containing juice (n = 40) decreased left ventricular (LV) end-diastolic volume {−6.3 [95% confidence interval (CI) –11.1, –1.6] ml} and end-systolic volume [−3.2 (95% CI −5.9, –0.5) ml], and increased end-diastolic mass/volume ratio [+0.04 (95% CI 0.00, 0.07)], relative to placebo juice (n = 47). Spironolactone (n = 44) reduced relative wall thickness compared with doxazosin (n = 43) [−0.01 (95% CI −0.02, –0.00)]. Although spironolactone reduced LV mass index relative to baseline [−1.48 (95% CI −2.08, –0.88) g m ^–2.7], there was no difference vs. doxazosin [−0.85 (95% CI −1.76, 0.05) g m ^–2.7]. Spironolactone also decreased the E/A ratio [−0.12 (95% CI −0.19, –0.04)] and increased S′ (a tissue-Doppler systolic function index) by 0.52 (95% CI 0.05, 1.0) cm s ^–1. BP did not differ between the juices, or between the drugs.

Conclusions: Six months' dietary nitrate decreased LV volumes ~5%, representing new, sustained, BP-independent benefits on cardiac structure, extending mechanisms characterized in preclinical models of heart failure. Spironolactone's effects on cardiac remodelling and systolic–diastolic function, although confirmatory, were independent of BP.