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The SUMMIT trial showed that the long-acting glucose-dependent insulinotropic polypeptide receptor and glucagon-like peptide 1 receptor agonist tirzepatide decreased the risk of cardiovascular death or worsening heart failure (HF) in patients with obesity-related heart failure with preserved ejection fraction (HFpEF). Effects may differ by baseline obesity severity, distribution, or magnitude of weight loss.

In this analysis, the authors compared baseline characteristics and effects of tirzepatide on primary and other endpoints according to baseline obesity severity and distribution, and we explored relationships between degree of weight loss achieved and outcomes.

In the SUMMIT trial, 731 patients with NYHA functional class II-IV HFpEF and body mass index (BMI) ≥30 kg/m² were randomly assigned to tirzepatide (n = 364) or placebo (n = 367). The primary outcomes were time to cardiovascular death or worsening HF and change in Kansas City Cardiomyopathy Questionnaire Clinical Summary Score (KCCQ-CSS) at 52 weeks. Key secondary outcomes included changes in 6-minute walk distance (6MWD), C-reactive protein (CRP), and body weight (BW) at 52 weeks. In this secondary analysis, primary and secondary endpoints were analyzed based on obesity severity (BMI) and distribution (waist-height ratio [WHR]). Time-to-event endpoints were analyzed with the use of a Cox regression model, and continuous endpoints were assessed with the use of a mixed-effects model for repeated measures. Relationships between changes in BW and waist circumference (WC) on treatment with tirzepatide and changes in key endpoints also were evaluated.

Patients with obesity-related HFpEF and higher BMI were younger and more likely to be female, with more severe HF symptoms and physical limitations, greater volume expansion despite higher diuretic use and lower natriuretic peptide levels, and more severe systemic inflammation compared with patients with lower BMI. These findings were largely similar when contrasting patients by baseline WHR, but those with higher WHR also had poorer exercise capacity and more severe kidney disease. There was no evidence of heterogeneity in the effect of tirzepatide on the risk of worsening HF or cardiovascular death by BMI or WHR tertile. However, with increasing tertiles of baseline BMI, there were greater improvements in 6MWD (estimated treatment difference [ETD]: 9.9 vs 26.3 vs 37.5 m; P = 0.025), and greater decreases in BW (ETD: -10.7% vs -11.8% vs -14.4%; P = 0.006) and systolic blood pressure (ETD: -1.00 vs -6.65 vs -6.62 mm Hg; P = 0.035) with tirzepatide compared with placebo, with a trend for greater improvement in KCCQ-CSS (P = 0.097). Among those randomized to tirzepatide, greater weight loss at 52 weeks was associated with larger improvements in 6MWD, KCCQ-CSS, CRP, and blood pressure, and a greater decrease in WC was associated with larger increases in 6MWD and KCCQ-CSS. Patients with elevated WHR but lower BMI had higher NYHA functional class and N-terminal pro-B-type natriuretic peptide, poorer kidney function, and lower 6MWD compared with those with lower WHR but higher BMI.

Among patients with obesity-related HFpEF, greater BMI is associated with younger age, female sex, more volume overload and inflammation, and more severe HF, and those with greater WHR also showed greater impairment in kidney function and exercise capacity. Tirzepatide consistently reduced the risk of HF or cardiovascular death regardless of baseline BMI, but there was evidence suggesting greater improvement in 6MWD in those with higher BMI at baseline. Greater weight loss on treatment with tirzepatide was associated with greater improvements in 6MWD and KCCQ. (A Study of Tirzepatide [LY3298176] in Participants With Heart Failure With Preserved Ejection Fraction [HfpEF] and Obesity [SUMMIT]; NCT04847557).