Thermodilution-Derived Coronary Blood Flow Pattern Immediately After Coronary Intervention as a Predictor of Microcirculatory Damage and Midterm Clinical Outcomes in Patients With ST-Segment–Elevation Myocardial Infarction
Selected in Circulation Cardiovascular Interventions by M. Dobric
Masashi Fukunaga, Kenichi Fujii, Daizo Kawasaki, Hisashi Sawada, Koujiro Miki, Hiroto Tamaru, Takahiro Imanaka, Toshihiro Iwasaku, Tsuyoshi Nakata, Masahiko Shibuya, Hirokuni Akahori, Motomaru Masutani, Kaoru Kobayashi, Mitsumasa Ohyanagi, Tohru Masuyama
Circ Cardiovasc Interv. 2014 Apr;7(2):149-55
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What is known
Primary percutaneous coronary intervention (pPCI) is superior in establishing epicardial coronary blood flow in patients with ST-segment-elevation myocardial infarction (STEMI). Despite this, up to one third of patients do not achieve adequate myocardial microvascular reperfusion. Furthermore, differentiation between various mechanisms responsible for impaired microvascular perfusion is currently not possible on clinical grounds.
- This study enrolled 88 STEMI patients.
- Thermodilution curves were obtained by injections of room temperature saline through the guiding catheter, during steady-state hyperemia, using an intracoronary pressure/temperature sensor-tipped wire.
- Coronary blood flow patterns were classified into three groups: (1) a narrow unimodal (a rapid fall and rise of temperature–time curves), (2) a wide unimodal (a gradual fall and rise of temperature–time curves), and (3) a bimodal (2 peak shapes).
- The primary end point of this study (MACE) was a composite of cardiac death, nonfatal myocardial reinfarction, and heart failure rehospitalisation within 6 months.
- MACE-free survival was significantly lower in the bimodal group when compared with that in the narrow and wide unimodal groups (p<0.001).
- Cox proportional hazard regression analysis showed that bimodal shape was an independent predictor of MACE (HR 17.12; P=0.00151).
- Index of microcirculatory resistance (IMR) immediately after pPCI was not independently associated with MACE.
This study demonstrates the potential prognostic relevance of immediate post pPCI assessment of coronary blood flow pattern using thermodilution method. Three patterns of coronary blood flow may be encountered immediately after pPCI, which have been shown to correlate with clinical outcomes. The presence of a bimodal shape on the thermodilution curve was associated with microcirculatory damage and poor midterm clinical outcomes, rather than the IMR. The authors propose that shape of thermodilution curve may reflect important/dominant underlying pathophysiology of microvascular impairment. The natural course after the development of the microvascular obstruction varies based on whether the dominant cause is capillary destruction or microembolisation to small arteries. It is proposed that bimodal flow pattern is caused by predominant capillary destruction, while microembolisation does not cause this reverse flow pattern. Since IMR alone cannot differentiate between these two causes of impaired microcirculatory flow, it appears that blood flow pattern, being able to distinguish these, might be a more important surrogate of microvascular reperfusion immediately after pPCI than IMR alone. Further studies are needed to establish the role of this novel marker of microvascular reperfusion.