CAD: Acute Coronary Syndromes
Keyur Vora, MD, MSc, FACC
Assistant Professor of Medicine, Division of Cardiology
Krannert Cardiovascular Research Center, Indiana University School of Medicine
Carmel, Indiana, United States
Keyur Vora, MD, MSc, FACC
Assistant Professor of Medicine, Division of Cardiology
Krannert Cardiovascular Research Center, Indiana University School of Medicine
Carmel, Indiana, United States
Daoyuan Ren, MD
Cardiologist
Zhongshan Hospital, Fudan University and Shanghai Institute of Medical Imaging, China (People's Republic)
Yinyin Chen, MD
Attending Radiologist
Zhongshan Hospital, Fudan University and Shanghai Institute of Medical Imaging, Shanghai, China
LOS ANGELES, California, China (People's Republic)
Kinjal Bhatt, MD
Cardiologist
Synergy Multispecialty Hospital, India
Khalid Youssef, PhD
Senior Scientist
Indiana University School of Medicine
Plainfield, Indiana, United States
Gabriel Gruionu, PhD
Assistant Research Professor of Medicine
Krannert Cardiovascular Research Center, Indiana University School of Medicine, United States
Balaji Tamarappoo, MD, PhD
Medical Director, Cardiovascular Imaging Program
Indiana University Health, United States
Kyle Frick, MD
Assistant Professor of Clinical Medicine
Krannert Cardiovascular Research Center, Indiana University School of Medicine, United States
Rolf Kreutz, MD
Associate Professor of Clinical Medicine
Krannert Cardiovascular Research Center, Indiana University School of Medicine, United States
Rohan Dharmakumar, PhD
Professor of Medicine, Radiology & Imaging Sciences, Anatomy, Cell Biology & Physiology
Krannert Cardiovascular Research Center, Indiana University School of Medicine
Indianapolis, Indiana, United States
Annual incidence of acute myocardial infarction is approximately 1 million in the United States alone. 'Time is Muscle' is the principle that drives emergency coronary angiography (CAG) and percutaneous coronary intervention (PCI) to limit infarct size in ST-elevation myocardial infarction (STEMI). Recent studies have shown that intramyocardial hemorrhage (IMH), a consequence of reperfusion injury, is a second factor contributing to final infarct size. The ischemic burden is a well-known contributor to the development of IMH and it has been evidenced through studies that show longer ischemic time is instrumental in the development of IMH. Another factor that modulates ischemic burden is coronary collaterals, which can blunt ischemia. However, whether coronary collaterals play a role in the development of IMH has not been investigated. We tested the hypothesis that coronary collaterals can alter the incidence and extent of IMH in mechanically revascularized STEMI patients.
Methods:
STEMI patients (n=80) who underwent emergency CAG and PCI were identified for collaterals based on Rentop Classification. T2* mapping and LGE CMR were performed 3 days post PCI to determine the presence and extent of IMH volume (based on T2* CMR), and MI size respectively. Imaging parameters included contiguous, slice-and-resolution matched, short-axis, cine (repetition time (TR) = 3.1 ms; echo time (TE) = 1.6 ms; flip angle = 40o; 25- 30 cardiac phases), multiple gradient-recalled echo (mGRE, 8 echoes with TE = 2.0 – 20.0 ms; ΔTE = 2 ms, TR = 20 ms; and flip angle = 12o).
Results:
Representative cases of collaterals based on Rentop classification are shown in Fig. 1. IMH was observed in 58 (73%) patients. Collaterals were absent (Gr. 0) in 35 patients; of these, 32 (91%) had IMH. Collaterals were present (Gr. I/II/III) in 45 patients; of these, 26 (58%) had IMH. Representative cases are shown in Fig. 2. Patients with IMH had 43% larger MI than those with IMH (M 45.43 ± SD 12.94 %LV vs 19.73 ± 10.91 %LV, p< 0.05). Among patients with IMH, those without collaterals had a 10% larger MI size (41.23 ± 9.1 %LV vs 31.84 ± 12.77 %LV, p< 0.05). Hemorrhage volume in patients with IMH was 6.88 ± 5.7 %LV. Among these patients, those without collaterals had a larger hemorrhage volume than those with collaterals (9.10 ± 6.5 %LV vs. 4.05 ± 2.95 %LV, p< 0.05). These details are captured in Figure 3.
Conclusion:
In STEMI patients, coronary collaterals reduced IMH incidence by more than 40% and IMH volume by 50%. This data lends support to our hypothesis that coronary collaterals reduce the incidence and extent of IMH in revascularized STEMI patients. Accordingly, the absence of collaterals during CAG can provide early guidance on which patients may be at a greater risk of developing hemorrhage and thus stand to experience the greatest loss of salvageable myocardium following reperfusion.