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Evaluation of Coronary Flow Reserve After Myocardial Ischemia Reperfusion in Rats
Published on: June 28, 2019
Pressure-bounded coronary flow reserve to assess the extent of microvascular dysfunction in patients with
Roberto Scarsini1, Giovanni Luigi De Maria, Mayooran Shanmuganathan
1Oxford Heart Centre, NIHR Biomedical Research Centre, Oxford University Hospitals, Oxford, United Kingdom.
Insights
Pressure-bounded coronary flow reserve (pb-CFR) can identify microvascular dysfunction after ST-elevation myocardial infarction (STEMI). However, the index of microcirculatory resistance (IMR) is superior to pb-CFR for predicting microvascular obstruction and myocardial injury.
Area of Science:
- Cardiology
- Cardiovascular Physiology
- Medical Imaging
Background:
- Microvascular function assessment is crucial for ST-elevation acute myocardial infarction (STEMI) treatment strategies.
- The role of pressure-bounded coronary flow reserve (pb-CFR) in STEMI microvascular assessment requires further elucidation.
Purpose of the Study:
- To compare pb-CFR with thermodilution-derived physiology (IMR, CFRthermo) in STEMI patients.
- To evaluate pb-CFR's ability to predict microvascular obstruction (MVO) and myocardial injury using cardiovascular magnetic resonance (CMR) imaging.
Main Methods:
- 148 STEMI patients underwent thermodilution-pressure-wire assessment before or after primary percutaneous coronary intervention (PPCI).
- CMR imaging assessed MVO and myocardial injury at 48 hours and six months post-STEMI.
- Patients were stratified based on post-PPCI pb-CFR values (<2, >2, or indeterminate).
Main Results:
- Post-PPCI pb-CFR was impaired in 69.9%, normal in 9.0%, and indeterminate in 21.1% of patients.
- pb-CFR showed poor correlation with thermodilution-derived CFR (k=0.03, p=0.39).
- IMR differed significantly across pb-CFR subgroups, and significant differences were observed in MVO, area at risk, and infarct size (IS). pb-CFR was inferior to IMR in predicting MVO and IS.
Conclusions:
- pb-CFR can identify microvascular dysfunction post-STEMI and outperforms thermodilution-derived CFR in predicting MVO.
- The index of microcirculatory resistance (IMR) demonstrated superior accuracy in predicting all CMR-assessed myocardial injury endpoints compared to both pb-CFR and thermodilution-derived CFR.
Aims:
Assessment of microvascular function in patients with ST-elevation acute myocardial infarction (STEMI) may be useful to determine treatment strategy. The possible role of pressure-bounded coronary flow reserve (pb-CFR) in this setting has not been determined. In this study we aimed to compare pb-CFR with thermodilution-derived physiology including the index of microcirculatory resistance (IMR) and CFRthermo in a consecutive series of patients enrolled in the OxAMI study. Moreover, we aimed to assess the presence of microvascular obstruction (MVO) and myocardial injury on cardiovascular magnetic resonance (CMR) imaging performed at 48 hours and six months in STEMI patients stratified according to pb-CFR.
Methods And Results:
Thermodilution-pressure-wire assessment of the infarct-related artery was performed in 148 STEMI patients before stenting and/or at completion of primary percutaneous coronary intervention (PPCI). The extent of the myocardial injury was assessed with CMR imaging at 48 hours and six months after STEMI. Post-PPCI pb-CFR was impaired (<2) and normal (>2) in 69.9% and 9.0% of the cases, respectively. In the remaining 21.1% of the patients, pb-CFR was "indeterminate". In this cohort, pb-CFR correlated poorly with thermodilution-derived coronary flow reserve (k=0.03, p=0.39). The IMR was significantly different across the pb-CFR subgroups. Similarly, significant differences were observed in MVO, myocardium area at risk and 48-hour infarct size (IS). A trend towards lower six-month IS was observed in patients with high (>2) post-PPCI pb-CFR. Nevertheless, pb-CFR was inferior to IMR in predicting MVO and the extent of IS.
Conclusions:
Pb-CFR can identify microvascular dysfunction in patients after STEMI. It provided superior diagnostic performance compared to thermodilution-derived CFR in predicting MVO. However, IMR was superior to both pb-CFR and thermodilution-derived CFR and, consequently, IMR was the most accurate in predicting all of the studied CMR endpoints of myocardial injury after PPCI.
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