C-11 | Correlation Between Thermodilution-Derived Coronary Flow Reserve and Rubidium-82 PET Myocardial Flow Reserve in Patients Undergoing Invasive Coronary Function Testing

Coronary microvascular dysfunction (CMD) can be diagnosed with non-invasive positron emission tomography (PET) stress perfusion imaging, or invasively with coronary thermodilution or Doppler. The correlation between 82-Rubidium (Rb82) PET myocardial flow reserve (MFR) and thermodilution coronary flow reserve (CFR), and agreement for the diagnosis of CMD, is unknown. Methods: This was a retrospective analysis of patients undergoing Rb82 PET stress followed by invasive coronary function testing between 04/2018 and 04/2023. We obtained baseline demographics, global PET myocardial blood flow (MBF) at stress and rest, global MFR, thermodilution CFR, index of microcirculatory resistance (IMR), and post procedure diagnosis of CMD (MFR < 2; CFR ≤ 2.5, or IMR ≥ 25). We performed a descriptive analysis of the patient population, assessed correlation, and determined diagnostic agreement. Results: We included 22 patients with an average age of 57 ± 6.4 years, 73% female, and 86% with chest pain on presentation. Baseline comorbidities included hypertension 81%, hyperlipidemia 82%, diabetes 27%, pulmonary disease 41%, and obstructive sleep apnea 41%. Median time between Rb82 PET stress and invasive physiology testing was 232 days. There was a significant correlation between Rb82 PET MFR and CFR (0.62, p<0.01). Using an IMR-based diagnosis of CMD, there was 59% agreement with a Rb82 PET MFR-determined CMD diagnosis. Using IMR and CFR for the diagnosis of CMD, there was 91% agreement with the Rb82 PET MFR diagnosis. Conclusions: We found excellent agreement (91%) between a diagnosis of CMD by Rb82 PET and invasive coronary thermodilution (using both CFR and IMR) with correlation between the numerical PET MFR and thermodilution CFR after ruling out obstructive coronary artery disease. The agreement for the diagnosis of CMD between Rb82 PET and thermodilution IMR (without CFR) was modest, suggesting that an invasive diagnostic approach using both CFR and IMR may be more concordant with non-invasive imaging than relying on IMR alone. Large-scale studies in diverse populations are needed to further understand the correlation between Rb82 PET and thermodilution- derived coronary physiology. S. M. Shah: Abbott: Research support; US Food and Drug Administration: Research support; N. Cigarroa, A. Abushouk, N. Latif, C. Gallegos, M. Maayah, S. J. Kunnirickal, N. Odanovic, S. Pfau, Nothing to disclose.