Zepbound for Heart Failure: Off-Label Evidence, Risks, and Clinical Tradeoffs

What Zepbound Is Actually Approved For

Zepbound (tirzepatide) received FDA approval in November 2023 specifically for chronic weight management. The drug is a dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist administered as a once-weekly subcutaneous injection. It is not approved for heart failure, type 2 diabetes (that indication belongs to Mounjaro, the same molecule under a different brand), or any cardiovascular condition.

The distinction matters. Off-label prescribing is legal and common in medicine, with estimates suggesting roughly 20% of all prescriptions in the United States are written off-label. But off-label use shifts the burden of clinical justification onto the prescribing physician, who must document why the expected benefit outweighs known risks for that specific patient. For a drug class this new, that calculus depends heavily on the quality of available trial data.

Tirzepatide's mechanism of action provides biological plausibility for cardiac benefit. GLP-1 receptor agonists reduce systemic inflammation, improve endothelial function, and decrease epicardial adipose tissue. The addition of GIP receptor agonism may amplify these effects. But plausibility alone does not equal proof of safety or efficacy in heart failure populations.

The SURMOUNT-HFpEF Trial: What the Data Actually Show

The strongest evidence for tirzepatide in heart failure comes from the SURMOUNT-HFpEF program, a pair of randomized, double-blind, placebo-controlled trials published in the New England Journal of Medicine in 2024. These trials enrolled 731 patients with HFpEF (ejection fraction ≥50%) and a BMI of 30 or higher, randomizing them to tirzepatide (up to 15 mg weekly) or placebo for 52 weeks.

The results were notable. Patients receiving tirzepatide experienced a 19.5-point improvement in the Kansas City Cardiomyopathy Questionnaire Clinical Summary Score (KCCQ-CSS) compared to 12.7 points with placebo. That 6.9-point difference exceeds the 5-point threshold considered clinically meaningful for this instrument [1]. The 6-minute walk distance improved by 40.0 meters with tirzepatide versus 11.2 meters with placebo [2]. Patients also achieved a mean body weight reduction of 13.9% versus 1.6% in the placebo group.

These are symptom-oriented outcomes. They tell us patients felt better, walked farther, and lost weight. What the trials did not measure, and this is the critical gap, are hard cardiovascular endpoints: hospitalization for heart failure, cardiovascular death, or all-cause mortality. No trial to date has demonstrated that tirzepatide reduces these events in heart failure patients.

Dr. Milton Packer, a cardiologist at Baylor University Medical Center, noted in an accompanying NEJM editorial that "the improvement in symptoms and functional capacity is real and meaningful, but we cannot yet conclude that tirzepatide changes the natural history of heart failure." This distinction between symptomatic benefit and disease modification is one every clinician weighing off-label use must confront.

HFpEF vs. HFrEF: Why the Type of Heart Failure Matters

Heart failure is not a single disease. The distinction between heart failure with preserved ejection fraction (HFpEF, where the heart squeezes normally but fills poorly) and heart failure with reduced ejection fraction (HFrEF, where pumping strength is diminished) is clinically fundamental. Current tirzepatide data apply exclusively to HFpEF in patients with obesity.

This matters because HFpEF accounts for roughly half of all heart failure cases and has historically been far more difficult to treat. Until the EMPEROR-Preserved and DELIVER trials established SGLT2 inhibitors as effective, the American College of Cardiology and American Heart Association guidelines had almost no pharmacologic therapies with strong evidence for HFpEF [3]. Obesity worsens HFpEF through multiple pathways: increased blood volume, higher filling pressures, greater systemic inflammation, and excessive epicardial fat deposition.

There is no published evidence supporting tirzepatide use in HFrEF. The hemodynamic profile is different. The treatment targets are different. Extrapolating SURMOUNT-HFpEF results to patients with reduced ejection fractions would be clinically inappropriate. Clinicians considering off-label tirzepatide should confirm that the patient has documented HFpEF, not HFrEF, before proceeding.

How Tirzepatide Compares to Semaglutide in Heart Failure

Semaglutide (Wegovy/Ozempic), a pure GLP-1 receptor agonist, has its own heart failure data. The STEP-HFpEF trial (N=529) showed semaglutide 2.4 mg weekly improved KCCQ-CSS by 16.6 points versus 8.7 points with placebo at 52 weeks, a treatment difference of 7.8 points [4]. The SELECT trial (N=17,604) demonstrated that semaglutide reduced major adverse cardiovascular events by 20% in patients with established cardiovascular disease and obesity, though this was not a heart failure-specific population [5].

Tirzepatide's dual GIP/GLP-1 mechanism produces greater weight loss than semaglutide (the SURMOUNT trials demonstrated roughly 20-22% weight loss versus 15-17% with semaglutide in obesity populations), which might translate to greater hemodynamic unloading in HFpEF. The KCCQ improvements in SURMOUNT-HFpEF and STEP-HFpEF are broadly comparable, though cross-trial comparisons are inherently limited.

One difference: semaglutide has the SELECT cardiovascular outcomes trial behind it, providing hard endpoint data that tirzepatide currently lacks. The SURPASS-CVOT trial evaluating tirzepatide's cardiovascular outcomes is ongoing, with results expected around 2027 [6]. Until those data arrive, semaglutide has a more complete cardiovascular evidence base, even if tirzepatide may offer greater weight reduction.

Risks and Side Effects Specific to Heart Failure Patients

The gastrointestinal side effect profile of tirzepatide deserves particular attention in heart failure patients. Nausea affected 24% of participants in SURMOUNT-HFpEF, diarrhea 18%, and vomiting 10%, consistent with rates seen in the broader SURMOUNT obesity program [7]. For a heart failure patient on diuretics, persistent vomiting or diarrhea introduces real risk.

Volume depletion compounds the effect of loop diuretics and can precipitate hypotension, prerenal kidney injury, and electrolyte disturbances (particularly hypokalemia and hypomagnesemia). Heart failure patients are already prone to these complications. Adding a medication that causes fluid losses through GI side effects requires careful monitoring of renal function, serum electrolytes, and volume status, especially during the dose-escalation phase.

Lean mass loss is another concern. Weight loss from GLP-1 receptor agonists is not purely fat mass. Data from body composition analyses of tirzepatide trials suggest approximately 25-40% of weight lost is lean mass [8]. In older heart failure patients, loss of skeletal muscle can worsen sarcopenia, reduce functional capacity, and increase fall risk. This partially counteracts the benefit of reduced cardiac loading from fat mass loss. The American Heart Association's 2024 scientific statement on obesity and heart failure recommends combining pharmacologic weight loss with resistance exercise to preserve lean tissue [9].

Pancreatitis risk, while low (incidence <0.5% in clinical trials), remains a black box warning consideration. Reports of gallbladder-related events, including cholelithiasis and cholecystitis, were also more common with tirzepatide than placebo across the SURMOUNT program. Rapid weight loss itself increases gallstone formation through changes in bile composition and gallbladder motility.

The Insurance and Access Problem

Prescribing tirzepatide off-label for heart failure faces a practical barrier that is as significant as any clinical one: insurance coverage. Most commercial payers and Medicare Part D plans authorize Zepbound only for its FDA-approved weight management indication, and many impose strict criteria even then (BMI thresholds, documentation of failed lifestyle intervention, sometimes exclusion of patients with certain comorbidities).

Off-label coverage requires the prescriber to submit prior authorization with clinical justification, often including peer-reviewed literature supporting the off-label use. Approval rates for off-label GLP-1 receptor agonist prescriptions remain low. At list price, Zepbound costs approximately $1,060 per month, making out-of-pocket payment prohibitive for most patients.

Some clinicians work around this by prescribing Zepbound for the weight management indication in patients who independently also have HFpEF, since many of these patients do meet the BMI criteria for the on-label use. This is technically appropriate, if the patient genuinely qualifies for weight management therapy, but requires transparent documentation.

Who Might Be a Reasonable Candidate

Not every heart failure patient should receive tirzepatide. Based on the available evidence and current ACC/AHA heart failure guidelines, a clinically reasonable candidate for off-label consideration would meet several criteria simultaneously [10].

The patient should have confirmed HFpEF (ejection fraction ≥50%) with a BMI ≥30. They should have persistent symptoms (NYHA Class II-III) despite guideline-directed medical therapy, including an SGLT2 inhibitor if tolerated. Stable renal function (eGFR >30 mL/min/1.73m²) is important given the GI side effect risk. No history of pancreatitis, medullary thyroid carcinoma, or MEN2 syndrome. The patient should be able to tolerate potential GI side effects without dangerous volume depletion, meaning their diuretic regimen is stable and they are not already volume-depleted.

Patients with HFrEF, acute decompensated heart failure, or cachexia (BMI <20) should not receive tirzepatide for this purpose. The evidence does not support it, and the risk-benefit calculus shifts heavily toward harm.

What the Guidelines Say Right Now

The 2022 AHA/ACC/HFSA guideline for management of heart failure does not mention tirzepatide by name, as the SURMOUNT-HFpEF data postdate its publication [10]. The guideline does recommend weight loss in obese patients with HFpEF (Class IIa, Level of Evidence B), but this recommendation references caloric restriction and bariatric surgery, not GLP-1-based pharmacotherapy.

The 2023 ACC Expert Consensus Decision Pathway on the role of GLP-1 receptor agonists acknowledges the emerging heart failure signal but stops short of recommending routine use in HFpEF [11]. Updated guideline statements incorporating the SURMOUNT-HFpEF data are anticipated in 2026. The European Society of Cardiology's 2023 focused update on heart failure similarly predates the tirzepatide HFpEF trial results and does not include specific GLP-1 receptor agonist recommendations for HFpEF [12].

Until formal guideline endorsement arrives, off-label tirzepatide for HFpEF sits in the space between promising trial data and validated clinical practice. Clinicians should document their rationale, discuss the off-label nature with patients, and monitor closely.

Ongoing Trials That Will Shape the Future

Several trials will determine whether tirzepatide earns a formal role in heart failure treatment. The SURPASS-CVOT trial (NCT04255433) is the largest cardiovascular outcomes study of tirzepatide, enrolling approximately 13,500 patients with type 2 diabetes and established atherosclerotic cardiovascular disease. While not a heart failure-specific trial, its results will establish whether tirzepatide reduces major adverse cardiovascular events, including heart failure hospitalization [6].

Lilly has also initiated a dedicated study examining tirzepatide in heart failure patients with mildly reduced ejection fraction (HFmrEF, ejection fraction 41-49%), a population where no GLP-1 receptor agonist has been tested in a randomized trial. If positive, this would extend the potential patient population beyond HFpEF.

The combination of SURPASS-CVOT results (expected 2027) and potential FDA supplemental approval submissions could fundamentally change how tirzepatide is positioned. For now, any use in heart failure remains off-label, supported by GRADE B evidence from a single trial program showing symptom improvement without hard outcome data. Clinicians prescribing tirzepatide for HFpEF should start at 2.5 mg weekly, titrate no faster than every four weeks, monitor serum creatinine and potassium at each dose increase, and reassess the KCCQ or 6-minute walk test at 12 and 24 weeks to confirm clinical response.