New data from the SUMMIT trial, presented at the American Heart Association (AHA) 2024 Scientific Sessions, reveals that tirzepatide significantly lowers the risk of worsening heart failure events and cardiovascular death in adults with heart failure with preserved ejection fraction (HFpEF) and obesity. The study found that tirzepatide not only reduced cardiovascular risks but also improved overall health status and functional capacity compared to placebo.
SUMMIT Trial Details
The SUMMIT trial, a global study conducted across 9 countries, enrolled 731 participants aged 40 and older diagnosed with HFpEF and obesity (BMI ≥ 30 kg/m²). Participants were randomized to receive either tirzepatide or a placebo, administered weekly with doses titrated from 2.5 mg to a maximum of 15 mg. All patients continued their standard heart failure medications throughout the trial.
Milton Packer, MD, lead study author and a distinguished scholar in cardiovascular science at Baylor University Medical Center, explained the rationale behind the study. "Obesity contributes to worsening heart failure, and while tirzepatide causes considerable weight loss, research is lacking on its effects on cardiovascular outcomes," he said. "This is the first trial that tested the effect of any medication on major heart failure outcomes in patients with HFpEF and obesity."
Significant Risk Reduction
After a median follow-up of 2 years, the trial demonstrated that cardiovascular death or worsening heart failure events occurred in 9.9% of the tirzepatide group compared to 15.3% in the placebo group. Specifically, worsening heart failure events were observed in 8% of the tirzepatide group versus 14.2% in the placebo group, representing a 46% risk reduction.
Improvements in Health and Function
Beyond reducing cardiovascular events, tirzepatide also showed improvements in other key health metrics. At one year, participants in the tirzepatide group had an average of 6.9 points greater improvement in Kansas City Cardiomyopathy Questionnaire Clinical Summary Score (KCCQ-CSS) compared to the placebo group. They also experienced 11.9% greater weight loss and improved their 6-minute walking distance by an average of 18.3 meters further than the placebo group. Furthermore, tirzepatide was associated with a 32.9% reduction in systemic inflammation, as measured by high-sensitivity C-reactive protein.
Considerations and Future Research
While the study demonstrated significant benefits, it's important to note that there was no significant effect on all-cause mortality (HR 1.25, 0.63-2.45). Dr. Packer noted the need for further research to clarify optimal parameters for identifying individuals who would benefit most from tirzepatide treatment, especially considering the limitations of BMI as a measure of body size in HFpEF patients.
Adverse effects, particularly gastrointestinal symptoms, remain a challenge with tirzepatide. In the SUMMIT trial, 4% of participants discontinued treatment due to GI events, while 20% discontinued for any reason. Despite these challenges, the SUMMIT trial provides compelling evidence for the potential of tirzepatide to improve outcomes in HFpEF patients with obesity.
