The main finding
In one sentence: Among the 4,286 SELECT participants who already had heart failure, weekly semaglutide 2.4 mg lowered the rate of major cardiovascular events compared with placebo, with a hazard ratio of 0.72.
Group averages, not an individual prediction. A trial result describes what happened to a defined group over a defined time.
On this page
Why this study matters
Heart failure means the heart cannot pump as well as it should. It is common in people living with obesity and heart disease, and it comes in different types depending on how much blood the heart pushes out with each beat (the ejection fraction). Before this analysis, it was not known whether semaglutide (Wegovy, Ozempic) helped people who had both heart disease and heart failure, or whether the type of heart failure mattered. Canadian readers with heart failure may hear this analysis quoted, so it helps to know exactly what it is.
Who was in the study
SELECT enrolled 17,604 adults between 31 October 2018 and 31 March 2021 in 41 countries. Everyone was aged 45 or older, had a BMI of 27 or higher, and had established cardiovascular disease. BMI (body mass index) compares weight with height. The mean age was 61.6 years and the mean BMI was 33.4. In total, 8,803 people were assigned to semaglutide and 8,801 to placebo.
At enrolment, 4,286 people (24.3%) had heart failure as defined by the study investigators. Of these, 2,273 (53.0%) had heart failure with preserved ejection fraction, 1,347 (31.4%) had heart failure with reduced ejection fraction, and 666 (15.5%) were unclassified. Other characteristics were similar between people with and without heart failure. The number of weeks of follow-up was not extracted.
What the researchers did
SELECT was a randomized, double-blind, placebo-controlled, event-driven phase 3 trial. Randomized means chance decided the treatment. Double-blind means neither participants nor staff knew who was on the medicine. Event-driven means it ran until enough heart events had occurred. People were assigned 1:1 to semaglutide, built up over 16 weeks to 2.4 mg injected once a week, or placebo.
This paper is a prespecified subgroup analysis, meaning the researchers planned before the trial to compare results in people with and without heart failure, and by heart failure type. The outcomes were MACE (a composite of non-fatal heart attack, non-fatal stroke and cardiovascular death), a heart failure composite (cardiovascular death, or hospital admission or urgent visit for heart failure), cardiovascular death, and death from any cause.
What they found
People with heart failure had more clinical events overall than those without. Within the heart failure group, semaglutide lowered the rate of every outcome compared with placebo (R32-C41).
| Outcome in people with heart failure at the start | Hazard ratio (95% CI), semaglutide versus placebo |
|---|---|
| MACE | 0.72 (0.60 to 0.87) |
| Heart failure composite | 0.79 (0.64 to 0.98) |
| Cardiovascular death | 0.76 (0.59 to 0.97) |
| Death from any cause | 0.81 (0.66 to 1.00) |
A hazard ratio compares event rates over time; below 1.0 means fewer events with semaglutide. The 95% confidence interval is the range where the true value most likely sits. The authors reported that the benefit did not differ meaningfully between people with and without heart failure (all interaction P values above 0.19).
By heart failure type, the MACE hazard ratio was 0.65 (95% CI 0.49 to 0.87) in reduced ejection fraction and 0.69 (0.51 to 0.91) in preserved ejection fraction. For the heart failure composite, it was 0.79 (0.58 to 1.08) in reduced ejection fraction and 0.75 (0.52 to 1.07) in preserved ejection fraction. These last two confidence intervals cross 1.0, so on their own they do not rule out no difference. People with reduced ejection fraction had higher absolute event rates. Benefits did not differ significantly by age, sex, BMI, symptom class or diuretic use. The summary we reviewed does not report the percentage of people with events in each group.
Side effects and people who stopped
Serious adverse events were less frequent with semaglutide than placebo, regardless of heart failure type. The summary we reviewed does not report the percentages or how many people stopped treatment. See the SELECT safety analysis page for detail.
What this study does not tell you
- It is a subgroup analysis of one trial, not an independent heart failure trial, so it should not be counted as a second piece of evidence (R32-C42).
- Heart failure was defined by the investigators at enrolment, not by a standard test protocol.
- For the heart failure composite within each heart failure type, the confidence intervals included no difference.
- Everyone had established cardiovascular disease and no diabetes.
- Event percentages and follow-up in weeks were not extracted.
- The trial was funded by the maker of semaglutide, and our data extraction relied on the abstract only.
What it means in Canada
This analysis supports the idea that the heart benefit seen in SELECT also applied to participants who had heart failure. It does not make semaglutide a heart failure treatment on its own, and it does not cover people with heart failure but no other cardiovascular disease. For how the medicine is used and covered here, see semaglutide in Canada and public drug coverage by province.
Common questions
Did semaglutide reduce heart events in SELECT participants with heart failure?
Yes. In people with heart failure at the start, the hazard ratio for major cardiovascular events was 0.72 (95% CI 0.60 to 0.87) and for the heart failure composite 0.79 (0.64 to 0.98).
How many people in SELECT had heart failure?
4,286 of 17,604 participants (24.3%) had investigator-defined heart failure at enrolment: 2,273 with preserved ejection fraction, 1,347 with reduced ejection fraction and 666 unclassified.
Is this a separate heart failure trial?
No. It is a subgroup analysis within the SELECT cardiovascular trial, planned in advance but not an independent trial.
Related reading
Other studies in this library that bear on the same question.
SELECT: semaglutide and heart attack or stroke risk without diabetes
SUMMIT: tirzepatide in heart failure with preserved ejection fraction
SELECT safety analysis: semaglutide side effects in heart disease
SELECT: semaglutide and kidney outcomes in adults without diabetes
Source
Original paper: John Deanfield, SELECT heart-failure subgroup, Lancet (London, England), 2024. PubMed: https://pubmed.ncbi.nlm.nih.gov/39181597/. DOI: https://doi.org/10.1016/S0140-6736(24)01498-3. Funding: The analysis was funded by Novo Nordisk, the company that makes semaglutide. How we summarized it: abstract and extracted data.
This page explains a published study. It is not medical advice and does not describe whether a medicine is right for you. Talk to your doctor, nurse practitioner or pharmacist about your own situation. Reviewed and signed by two pharmacists registered in British Columbia, 2026-09-18.
Evidence records behind this page
Each record is a row in the clinical evidence file, taken from the published paper named above. The caution column is the limit the researcher recorded for that number.
This table scrolls sideways.
| Record | What the paper reports | Type | Population | Caution | Source |
|---|---|---|---|---|---|
| R32-C41 | In SELECT participants with heart failure at baseline, semaglutide reduced major cardiovascular events compared with placebo, with a hazard ratio of 0.72 (95% CI 0.60 to 0.87). | direct evidence | SELECT adults ≥45 with cardiovascular disease and BMI ≥27; subgroup with investigator-defined heart failure | Subgroup analysis of SELECT, not an independent trial; HF investigator-defined; confidence intervals for individual HF-type HF-composite effects included no difference. | PubMed 39181597 |
| R32-C42 | The SELECT heart-failure analysis was a subgroup of the same cardiovascular trial, so it should not be counted as an independent trial when summarizing the evidence. | direct evidence | SELECT adults ≥45 with cardiovascular disease and BMI ≥27; subgroup with investigator-defined heart failure | Subgroup analysis of SELECT, not an independent trial; HF investigator-defined; confidence intervals for individual HF-type HF-composite effects included no difference. | PubMed 39181597 |