Background: Noninvasive assessment of coronary artery disease (CAD) in obese patients is challenging due to suboptimal image quality. We performed a prespecified secondary analysis of obese patients from the second Phase III trial of flurpiridaz-¹⁸F positron emission tomography (PET).

Methods: In total, 604 patients with suspected CAD underwent flurpiridaz-¹⁸F PET and ^99mTc-single-photon emission computerized tomography (SPECT) myocardial perfusion imaging (MPI) before invasive coronary angiography (ICA) across 48 sites. MPI images were interpreted by three blinded experts. The primary endpoint was sensitivity and specificity for diagnosing CAD (≥50% stenosis on quantitative coronary angiography), requiring the lower 95% confidence interval to exceed 60% by 2 same blinded expert core lab readers, assessed using one-sided z-test (α = 0.025). Sensitivity and specificity were compared between PET and SPECT and between obese (body mass index [BMI] ≥30 kg/m²) and nonobese patients.

Results: Of 578 evaluable patients, 298 (51.6%) were obese (mean age: 62.0 years, 64.4% male, mean BMI: 35.6 kg/m²) and 117 (39.3%) had CAD by ICA. In obese patients, flurpiridaz-¹⁸F PET MPI met the primary endpoint, with lower 95% confidence limits greater than 60% and one-sided P < 0.025 by the same 2 readers (Readers 1 and 2). Sensitivity across 3 readers ranged from 70.1% to 88.0% and specificity ranged from 53.6% to 74.0%. In obese patients, flurpiridaz-¹⁸F PET MPI showed significantly higher sensitivity compared to ⁹⁹ᵐTc-SPECT MPI by Readers 1 and 3 (Reader 1: 72.6% vs 60.7%, P = 0.01; Reader 3: 88.0% vs 74.4%, P = 0.002), with non-inferior specificity by the same two readers (Reader 1: 68.0% vs 61.3%; Reader 3: 53.6% vs 50.8%; P < 0.01 for noninferiority, for both), noting that the primary endpoint was met by a partially overlapping reader pair (Readers 1 and 2). Diagnostic performance of flurpiridaz-¹⁸F PET was higher than SPECT across BMI categories. No statistically significant difference in diagnostic performance was observed between obese and nonobese patients (Sensitivity P = 0.26, specificity P = 0.25 and accuracy P = 1.0).

Conclusion: Flurpiridaz-¹⁸F PET MPI demonstrates high diagnostic efficacy for detecting CAD across BMI categories in obese patients compared to ICA and ^99mTc-SPECT, with no loss of diagnostic performance in obese relative to nonobese patients.

Clinical trial registration: NCT03354273.

Keywords: Cardiac PET; Coronary artery disease; F-18 flurpiridaz; Myocardial perfusion imaging; Obesity; Radiotracers.