13N-ammonia PET/CT stress myocardial blood flow compared to fractional flow reserve in coronary artery disease.

AIM: In this retrospective study, fractional flow reserve was compared to stress myocardial blood flow derived by -ammonia (-NH3) myocardial perfusion PET/CT. METHODS: From a large cohort of patients referred for -NH3 PET/CT, patients who also had fractional flow reserve-measurements within 6 months of the PET study were selected. These fractional flow reserve measurements were compared to PET/CT derived stress myocardial blood flow of the corresponding coronary territory. Results were categorized as concordant or discordant. Patients with discordant results were subdivided into a group with reduced fractional flow reserve but normal stress myocardial blood flow (group A) or into a group with normal fractional flow reserve but reduced stress myocardial blood flow (group B). RESULTS: From September 2013 through July 2016, 46 patients examined with -NH3 PET/CT also had fractional flow reserve-measurements within 6 months. A total of 66 measurements were used for comparison. Discordance was found in 32% of the measurements. Group B showed a significant reduction in stress myocardial blood flow of all coronary territories compared to group A (P = 0.000). During follow-up (median 3.96 years), group B showed more visits to the emergency department and newly developed heart failure. CONCLUSION: Discordance with stress myocardial blood flow in the corresponding flow territory was found in 32% of the fractional flow reserve-measurements. Patients with reduced stress myocardial blood flow but normal fractional flow reserve showed significantly reduced stress myocardial blood flow in all coronaries and a trend towards more cardiac adverse events.

Single Coronary Artery Demonstrating Slightly Decreased 13NH3 Stress Flows in its Distal Flow Territories.

A 54-year-old male patient was referred for computed tomography angiography to rule out cardiovascular disease. The examination revealed a single coronary artery originating from the right sinus of Valsalva, extending to the normal left circumflex artery and left anterior descending artery domains. The computed tomography showed only mild coronary sclerosis. The myocardial stress flow on the subsequently performed 13NH3 myocardial perfusion positron emission tomography demonstrated a relative stress flow reduction in the distal segments along the monocoronary. In the presented patient without significant coronary disease and a benign course of the monocoronary, the relative inability to increase blood flow during stress in the distal segments of the artery is a remarkable finding.