Hiroyuki Atsumi

Prediction of functional recovery in acute myocardial infarction: Comparison between sestamibi reverse redistribution and sestamibi/BMIPP mismatch

BackgroundIt has been known that Tc 99m sestamibi/iodine 123 betamethyliodophenylpentadecanoic (123I-BMIPP) (sestamibi/BMIPP) mismatch is an indicator of viable myocardium in acute myocardial infarction (AMI). We have reported that reverse redistribution of sestamibi in AMI indicates the patency of infarct-related artery and a preserved left ventricular function in the chronic stage. In this study we investigated the relationship between reverse redistribution of sestamibi and sestamibi/BMIPP mismatch in patients with AMI.MethodsTwenty-three patients with AMI who received direct percutaneous transluminal coronary angioplasty underwent both BMIPP and sestamibi SPECT within 2 weeks after onset. Sestamibi images were obtained 1 hour (early) and 3 hours (delayed) after injection of sestamibi. BMIPP imaging was carried out 30 minutes after injection. The left ventricle was divided into 17 segments, and regional myocardial uptakes of the tracers in each segment were scored from 0 (normal) to 3 (no activity). A reverse redistribution pattern was defined as an increase of ≽1 in the regional score at the delayed images. More reduced BMIPP uptake than sestamibi uptake in each segment was determined as sestamibi/BMIPP mismatch. Contrast left ventriculography was performed soon after revascularization and repeated 1 month later.ResultsOf 15 patients with sestamibi reverse redistribution, sestamibi/BMIPP mismatch was observed in 14 patients (93%), whereas mismatch was seen in only one of seven patients (14%) without reverse redistribution (p<0.01). In patients with sestamibi reverse redistribution, regional scores of BMIPP agreed with those of early and delayed images of sestamibi in 51 segments (46%) and in 92 segments (83%), respectively. In the chronic stage, both regional wall motion and left ventricular ejection fraction improved in patients with sestamibi reverse redistribution (wall motion score: 6.7±2.4 vs 2.7±2.1, p<0.01; ejection fraction: 56%±7% vs 64% ±8%, p<0.01), but not in those without reverse redistribution.ConclusionBoth reverse redistribution of sestamibi and sestamibi/BMIPP mismatch reflect the recovery of left ventricular function and thus imply myocardial viability in AMI. Because the presence of reverse redistribution of sestamibi agreed with that of sestamibi/BMIPP mismatch, additional BMIPP images can be replaced by the delayed images after a single injection of sestamibi.

Ca2+ Transients, Contractility, and Inotropic Responses in Rabbit Volume-Overloaded Cardiomyocytes

Left ventricular hypertrophy occurs as an adaptation prior to chronic congestive heart failure caused by pressure or volume overload. We examined the modulation of the effects of Ca2+ sensitizers, namely, Org 30029 [N-hydroxy-5,6-dimethoxy-benzo[b]thiophene-2-carboximidamide hydrochloride] and JTV-704 (EGIS-9377) [2-(l-methylthio)-5-(2-mor-pholinoethylamino)-8,9-dihydro-7H-thiopyrano[3,2-d][l,2,4]triazolo[l,5-a]pyrimidine dihydrochloride], in comparison with those of β-adrenoceptor agonists in cardiomyocytes isolated from volume-overloaded rabbits. We isolated ventricular cardiomyocytes by means of collagenase perfusion 12 weeks after the shunt formation, when ventricular weight, aortic flow, left ventricular pressure, and diastolic pressure had been increased significantly. Cell shortening and Ca2+ transients were measured in cardiomyocytes loaded with indo-1. In cardiomyocytes isolated from the volume-overloaded heart, cell length and width were increased proportionally. The duration of Ca2+ transients and cell shortening was significandy prolonged in volume-overloaded cardiomyocytes compared with that in normal (isolated from sham-operated rabbit) cardiomyocytes. The response of Ca2+ transients and cell shortening to the Ca2+ sensitizers, namely, Org 30029 and JTV-704, was unaltered in volume-overloaded cardiomyocytes. By contrast, the response to dobutamine and isoproterenol was significandy attenuated in volume-overloaded cardiomyocytes compared with the response in normal cardiomyocytes. These results indicate that in volume-overloaded rabbit cardiomyocytes, the response to the Ca2+ sensitizers was maintained when the responsiveness to β-adrenoceptor stimulation had been reduced, an indication that the Ca2+ sensitizer may be beneficial for improvement of contractile dysfunction even when β-agonists lose their effectiveness in volume-overloaded cardiomyocytes with hypertrophy.

Quantitative Assessment of Myocardial 99mTc-sestamibi Uptake During Exercise

An increase of 99mTc-sestamibi uptake in the myocardium during exercise was defined as a response rate, and the feasibility of a response rate for detecting coronary artery disease (CAD) was tested. Eighty-seven patients with suspected CAD had myocardial perfusion imaging with 99mTc-sestamibi during exercise and at rest. A dose of 370 MBq of 99mTc-sestamibi was injected at the maximal level of exercise, and a myocardial image was obtained 90 min later (exercise image). Then, 740 MBq of 99mTc-sestamibi was administered at rest, and myocardial imaging was repeated (rest image). The exercise and rest images were corrected for physical decay and injected doses, and the exercise image was subtracted from the rest image to obtain the corrected rest image. A response rate was calculated as follows: (exercise image-corrected rest image)x100/corrected rest image (%). The global response rates of 20 patients without significant coronary stenosis (< or =50%) were higher than those of 67 patients with significant coronary stenosis (81+/-33% and 50+/-28%, p<0.01). Global response rates were correlated with the maximal rate pressure products during exercise (r=0.56, p<0.01) and delta rate pressure products (r=0.53, p<0.01). Regional response rates in myocardial areas perfused by stenotic coronary arteries of < or =50%, 75%, 90% and 99-100% were 60+/-24%,* 56+/-33%,* 40+/-23%* and 30+/-23%,* respectively, (*p<0.01 vs without significant coronary stenosis). The response rates decreased as the severity of coronary artery stenosis advanced, and distinguished between coronary stenoses of graded severity. Accordingly, the response rate from myocardial perfusion imaging with 99mTc-sestamibi may provide complementary information to the conventional inspection with myocardial tomography regarding the severity of CAD.