-Original-

Evaluation of No-Reflow Phenomenon Using ²⁰¹TlCl/¹²³I-BMIPP Dual-isotope Myocardial SPECT

Yasuhiro Shimizu¹, Shin-ichiro Kumita¹, Keiichi Cho¹, Masahiro Toba¹, Sunao Mizumura¹, Keiji Tanaka², Teruo Takano² and Tatsuo Kumazaki¹

¹Department of Clinical Radiology, Nippon Medical School Graduate School of Medicine
²Department of Functional Pathophysiology for Human Organs, Nippon Medical School Graduate School of Medicine

Objectives: We assessed the usefulness of ²⁰¹thallous chloride (TlCl)/¹²³I-beta-methyl iodophenyl pentadecanoic acid (BMIPP) dual-isotope single-photon emission computed tomography (SPECT) to identify the "no-reflow phenomenon," defined as inadequate myocardial perfusion through a given segment of the coronary circulation without angiographic evidence of mechanical vessel obstruction.
Methods: ²⁰¹TlCl/¹²³I-BMIPP SPECT was performed in 73 patients within approximately 1 week of initial acute myocardial infarction (AMI) after percutaneous coronary intervention (PCI). We divided the left ventricular myocardium into 17 segments on each SPECT image and scored tracer accumulation in each segment with a five-point scoring system according to the American Heart Association criteria. Total severity scores were calculated by summing the scores for all 17 segments. The mismatch ratio between myocardial perfusion and metabolism was derived from the ²⁰¹TlCl and ¹²³I-BMIPP total severity scores: mismatch ratio=(¹²³I-BMIPP total severity score -²⁰¹TlCl total severity score)/¹²³I-BMIPP total severity score. Patients were classified according to Thrombolysis in Myocardial Infarction (TIMI) flow grade as having TIMI reflow grade 0-I (TIMI 0-I reflow group; n=11), II (TIMI II reflow group; n=17) and III (TIMI III reflow group; n=45). The TIMI III reflow group was subdivided into two groups with ²⁰¹TlCl total severity scores of ≤13 (TIMI III (A) reflow group; n=36) and ≥14 (TIMI III (B) reflow group; n=9), respectively.
Results: The mismatch ratios in the TIMI II (0.4 ± 0.3) and TIMI III (0.4 ± 0.2) reflow groups were significantly higher than that in the TIMI 0-1 reflow group (0.1 ± 0.1, p<0.05). Although coronary angiography revealed TIMI III flow after reperfusion, the mismatch ratios in the TIMI III (B) reflow group (0.2 ± 0.1) and in the TIMI 0-I reflow group (0.1 ± 0.1) were significantly lower than that in the TIMI III (A) reflow group (0.4 ± 0.2, p<0.01), reflecting noneffective recanalization (so called no-reflow phenomenon).
Conclusion: ²⁰¹TlCl/¹²³I-BMIPP dual-isotope myocardial SPECT reveals the biochemical degree of the no-reflow phenomenon, whereas coronary angiography shows recanalized vascular flow only. Dual-isotope myocardial SPECT might be useful for evaluating reperfusion therapy.

J Nippon Med Sch 2006; 73: 258-264

Keywords
no-reflow phenomenon, reperfusion therapy, dual-isotope SPECT, ²⁰¹TlCl, ¹²³I-BMIPP

Correspondence to
Yasuhiro Shimizu, MD, Department of Radiology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan
yasu-s@nms.ac.jp

Received, June 7, 2006
Accepted, July 27, 2006