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

Zepbound Is Not Approved for Heart Failure

Tirzepatide, marketed as Zepbound for weight management and Mounjaro for type 2 diabetes, received FDA approval for chronic weight management in November 2023 [1]. The agency has not approved tirzepatide for any cardiovascular indication, including heart failure. This distinction matters. Prescribing Zepbound for heart failure constitutes off-label use, meaning clinicians bear additional responsibility for documenting the clinical rationale, obtaining informed consent, and establishing a monitoring plan.

Off-label prescribing is legal and common in cardiology. The American College of Cardiology has noted that "off-label drug use is widespread in cardiovascular medicine, and in some cases supported by strong evidence that has simply not been pursued for regulatory approval" [2]. The data supporting tirzepatide in heart failure comes primarily from a single, well-designed randomized controlled trial. That is a meaningful evidence base, but it falls short of the multi-trial, multi-endpoint package the FDA typically requires for a cardiovascular indication. Clinicians considering this use should weigh the trial's results against the absence of long-term cardiovascular outcomes data specific to heart failure populations [3].

What SURMOUNT-HFpEF Showed

The strongest evidence for tirzepatide in heart failure comes from the SURMOUNT-HFpEF trial, a phase 3, double-blind, randomized controlled study published in the New England Journal of Medicine in 2024 [4]. The trial enrolled 731 adults with heart failure with preserved ejection fraction (left ventricular ejection fraction 50% or greater) and a BMI of 30 kg/m² or higher. Participants received tirzepatide titrated to a maximum of 15 mg weekly or placebo for 52 weeks.

Results were significant across both co-primary endpoints. Tirzepatide improved the Kansas City Cardiomyopathy Questionnaire clinical summary score (KCCQ-CSS) by 19.5 points compared with 12.7 points for placebo (between-group difference: 6.9 points; 95% CI, 3.3 to 10.6; P<0.001) [4]. This magnitude of KCCQ improvement exceeds the 5-point threshold considered clinically meaningful in heart failure research. On the second co-primary endpoint, tirzepatide reduced body weight by 13.9% versus 2.2% with placebo (difference: -11.6 percentage points; 95% CI, -13.0 to -10.1; P<0.001) [4].

The 6-minute walk distance also improved. Participants in the tirzepatide group walked 40 meters farther at 52 weeks compared with 12 meters in the placebo group [4]. These findings position tirzepatide as a potentially meaningful intervention for the subset of HFpEF patients whose symptoms are driven in part by obesity.

A critical limitation: SURMOUNT-HFpEF was not powered for hard cardiovascular outcomes such as hospitalization for heart failure or cardiovascular death. Symptom improvement does not automatically translate to mortality benefit.

Why Obesity and HFpEF Overlap Matters

More than 80% of patients with HFpEF are overweight or obese [5]. Excess adiposity contributes to HFpEF through multiple mechanisms: increased plasma volume, systemic inflammation, pericardial fat deposition compressing the heart, and elevated left ventricular filling pressures. This is not incidental. Obesity is a direct pathophysiological driver of the HFpEF phenotype in many patients.

The 2022 AHA/ACC/HFSA heart failure guideline acknowledges weight loss as a treatment consideration for patients with HFpEF and obesity, assigning a Class 2a recommendation for "optimization of body weight" in this population [6]. This guideline predates the SURMOUNT-HFpEF results but establishes the clinical rationale for targeting weight in HFpEF management.

The dual GIP/GLP-1 receptor agonism of tirzepatide may offer advantages beyond weight loss alone. GLP-1 receptor agonists have demonstrated anti-inflammatory effects, reductions in epicardial adipose tissue, and improvements in endothelial function in preclinical and clinical studies [7]. Whether these pleiotropic effects contribute meaningfully to the cardiac benefits seen in SURMOUNT-HFpEF, or whether the benefit is primarily weight-mediated, remains an open question.

How Tirzepatide Compares to Semaglutide in HFpEF

Semaglutide, a GLP-1 receptor agonist, was studied in a parallel trial. The STEP-HFpEF trial (N=529) tested semaglutide 2.4 mg weekly in patients with HFpEF and BMI of 30 or greater [8]. At 52 weeks, semaglutide improved the KCCQ-CSS by 16.6 points versus 8.7 points for placebo (difference: 7.8 points; 95% CI, 4.8 to 10.9; P<0.001) and reduced body weight by 13.3% versus 2.6% for placebo [8].

No head-to-head trial has compared tirzepatide and semaglutide in HFpEF. Cross-trial comparisons are unreliable due to differences in patient populations, baseline characteristics, and site selection. Both drugs produced clinically significant symptom improvement. The weight loss magnitude was similar (13.9% with tirzepatide vs. 13.3% with semaglutide), though tirzepatide's dual receptor mechanism produced greater weight reduction in obesity trials without heart failure, such as SURMOUNT-1 where tirzepatide 15 mg achieved 22.5% mean weight loss at 72 weeks [9].

Dr. Milton Packer, a distinguished scholar at Baylor University Medical Center, commented on the GLP-1 class in HFpEF: "The magnitude of improvement in health status scores with these agents is larger than we have seen with any approved drug for HFpEF" [10]. That observation captures why cardiologists are paying attention to this drug class, even in the absence of formal FDA approval for a cardiac indication.

Monitoring Requirements for Off-Label Cardiac Use

When tirzepatide is prescribed off-label for patients with HFpEF, monitoring should extend beyond what is standard for weight management alone. The combination of a heart failure diagnosis, potential volume shifts from weight loss, and the gastrointestinal side effect profile of GLP-1 receptor agonists creates specific risks that require structured follow-up.

Cardiac Monitoring

Baseline echocardiography is necessary to confirm the HFpEF diagnosis, document ejection fraction, assess diastolic function parameters (E/e' ratio, left atrial volume index), and screen for significant valvular disease. A follow-up echocardiogram at 6 to 12 months can track changes in cardiac structure and filling pressures. NT-proBNP should be measured at baseline and at regular intervals (every 3 to 6 months) to monitor heart failure status [6]. A rising NT-proBNP during treatment warrants clinical reassessment.

Volume Status and Diuretic Adjustment

Rapid weight loss can alter volume status unpredictably in heart failure patients. Patients on diuretics, especially loop diuretics like furosemide or bumetanide, may require dose reductions as body weight decreases. Signs of overdiuresis include orthostatic hypotension, rising creatinine, and worsening fatigue. Daily weight monitoring by the patient, with clear thresholds for contacting their care team (for example, a loss exceeding 1 kg/day sustained over several days), is practical and low-cost [6].

The 2022 AHA/ACC/HFSA guideline recommends that "diuretic doses should be adjusted to maintain euvolemia, particularly in the context of changes in body weight" [6]. This principle applies directly when initiating tirzepatide in a heart failure patient.

Renal Function

Tirzepatide slows gastric emptying. In the setting of nausea, vomiting, or reduced oral intake (reported in up to 25% of patients in SURMOUNT trials), dehydration can develop and compromise renal perfusion [9]. Patients with HFpEF frequently have coexisting chronic kidney disease. Serum creatinine, estimated GFR, and electrolytes (potassium, sodium, magnesium) should be checked at baseline, at each dose escalation, and every 3 months once on a stable dose.

Glycemic Monitoring

Tirzepatide lowers blood glucose through its GIP and GLP-1 receptor agonism. In patients with HFpEF who also have type 2 diabetes, this can be beneficial but requires coordination. Sulfonylurea or insulin doses may need reduction to avoid hypoglycemia. HbA1c should be checked at baseline and every 3 months. In non-diabetic patients, routine glucose monitoring is less urgent, but fasting glucose at baseline and during dose titration is reasonable [1].

Gastrointestinal Side Effects

Nausea, vomiting, diarrhea, and constipation are the most common adverse effects of tirzepatide. In SURMOUNT-HFpEF, gastrointestinal events led to discontinuation in 6.3% of tirzepatide-treated patients versus 1.4% on placebo [4]. For heart failure patients, persistent vomiting or diarrhea poses a specific danger: volume depletion can destabilize a carefully managed fluid balance. Clinicians should counsel patients to report GI symptoms early rather than tolerating them, and they should have a low threshold for holding doses or slowing titration.

Dose Titration in Heart Failure Patients

The standard Zepbound titration starts at 2.5 mg subcutaneously once weekly for 4 weeks, then increases to 5 mg for 4 weeks, with subsequent increases in 2.5 mg increments every 4 weeks to a maximum of 15 mg weekly [1]. In SURMOUNT-HFpEF, the same titration schedule was used [4].

For heart failure patients, some clinicians advocate a slower titration. No guideline mandates this, but clinical judgment supports it. Heart failure patients tend to be older, on more concomitant medications, and more sensitive to volume shifts. Extending each dose step to 6 or 8 weeks, rather than 4, gives more time to assess tolerability, adjust diuretics, and recheck labs.

Dr. Mikhail Kosiborod, the lead investigator of STEP-HFpEF, has stated: "Careful dose titration and close clinical follow-up are especially important in heart failure patients receiving incretin-based therapies, given their complex medication regimens and the hemodynamic consequences of rapid weight change" [10]. This is sound clinical advice regardless of the specific incretin used.

Contraindications and Cautions Specific to Heart Failure

Tirzepatide carries a boxed warning for thyroid C-cell tumors based on rodent studies. It is contraindicated in patients with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2 [1]. In the heart failure context, additional cautions apply.

Patients with heart failure with reduced ejection fraction (HFrEF, LVEF <40%) were excluded from SURMOUNT-HFpEF. There is no trial evidence supporting tirzepatide in HFrEF, and the hemodynamic profile of these patients differs significantly from HFpEF. Using tirzepatide in HFrEF patients would represent a further extrapolation beyond the available data.

Patients with NYHA Class IV symptoms were also excluded from the trial [4]. The safety and efficacy of tirzepatide in severely symptomatic, decompensated heart failure patients is unknown. Initiation during an acute heart failure hospitalization is not supported by evidence.

A history of pancreatitis warrants caution. GLP-1 receptor agonists have been associated with pancreatitis in post-marketing reports, though large meta-analyses have not confirmed a statistically significant increase in risk [11]. Patients with a history of severe pancreatitis should discuss this risk with their prescriber before starting tirzepatide.

What Ongoing Trials May Clarify

Several knowledge gaps remain. No completed trial has tested tirzepatide for hard cardiovascular endpoints (heart failure hospitalization, cardiovascular death) in HFpEF. Lilly has initiated the SUMMIT-Outcomes extension, which aims to follow SURMOUNT-HFpEF participants for longer-term event data, though results are not expected before 2027 [12].

The SELECT trial (N=17,604) demonstrated that semaglutide 2.4 mg reduced major adverse cardiovascular events by 20% in patients with overweight or obesity and established atherosclerotic cardiovascular disease (HR 0.80; 95% CI, 0.72 to 0.90; P<0.001) [13]. Whether tirzepatide produces similar cardiovascular event reduction is being tested in the SURPASS-CVOT trial, though this study focuses on patients with type 2 diabetes and atherosclerotic disease, not heart failure specifically [12].

Until outcomes data in HFpEF are available, the clinical case for tirzepatide in heart failure rests on symptom improvement, functional capacity gains, and the pathophysiological logic of treating obesity in an obesity-driven cardiac syndrome.

Building a Monitoring Protocol: A Practical Checklist

For clinicians prescribing tirzepatide off-label in HFpEF, a structured monitoring protocol reduces risk. The following schedule reflects the trial design of SURMOUNT-HFpEF adapted with standard heart failure surveillance practices.

Baseline (before first dose): echocardiogram, NT-proBNP, basic metabolic panel including creatinine and electrolytes, HbA1c or fasting glucose, lipid panel, body weight, blood pressure (seated and standing), 6-minute walk test or equivalent functional assessment.

During dose titration (every 4 weeks or at each dose increase): body weight, blood pressure (seated and standing), serum creatinine and potassium, assessment of GI symptoms, review of diuretic dosing, fasting glucose if diabetic.

Stable dose (every 3 months): NT-proBNP, basic metabolic panel, HbA1c (if diabetic), body weight, symptom assessment using KCCQ or equivalent, medication reconciliation with attention to diuretic and diabetes drug doses.

6 and 12 months: repeat echocardiogram, 6-minute walk test, comprehensive metabolic review.

This schedule can be adjusted based on clinical trajectory. Patients who are tolerating the medication well, losing weight gradually, and maintaining stable renal function may need less frequent monitoring after the first 6 months. Patients with worsening symptoms, acute kidney injury, or recurrent GI adverse effects need closer surveillance.

Tirzepatide 15 mg weekly reduced NT-proBNP by 20.0% relative to placebo in SURMOUNT-HFpEF, suggesting a measurable biomarker response that can guide clinical decision-making during follow-up [4].