Junya Chiba

Heterogeneous myocardial distribution of iodine-123 15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid (BMIPP) in patients with hypertrophic cardiomyopathy.

It has been proposed that iodine-123 15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid (123I-BMIPP) is an agent for myocardial fatty acid metabolism in animal models. The aim of the present study was to determine whether alterations in fatty acid uptake and/or utilization in patients with hypertrophic cardiomyopathy (HCM) could be detected by 123I-BMIPP. Myocardial imaging with 123I-BMIPP and thallium-201 (201Tl) was performed in 14 fasted patients. A dose of 111 MBq of 123I-BMIPP was administered intravenously at rest, and myocardial emission computed tomography was obtained 20 min and 3 h after injection. The 201Tl imaging was also performed within 1 week after the 123I-BMIPP study. The regional myocardial uptake and clearance of 123I-BMIPP and 201Tl were assessed quantitatively. The myocardial distribution of 123I-BMIPP was more heterogeneous than that of 201Tl in patients with HCM. The myocardial uptake of 123I-BMIPP was lower in the anteroseptal region of the left ventricle than in the posterolateral region (74% vs. 85%, P < 0.001). The anteroseptal wall showed a faster clearance of 123I-BMIPP than the posterolateral wall (33% vs. 27%, P < 0.01). Both a decreased uptake and rapid clearance of 123I-BMIPP were observed in the hypertrophied myocardium of the anteroseptal wall, where 201Tl uptake was normal or even increased. Myocardial segments with a markedly increased thickness showed a lower uptake and faster clearance of 123I-BMIPP than those with mild hypertrophy (uptake 73% vs. 82%, P < 0.05; clearance 30% vs. 25%, P < 0.05). Myocardial imaging with 123I-BMIPP was thus applicable to patients with HCM for detecting myocardial regions with altered fatty acid metabolism.

Functional recovery of hibernating myocardium after coronary bypass surgery: does it coincide with improvement in perfusion?

To determine the relationship between functional recovery and improvement in perfusion after coronary artery bypass graft surgery (CABG), 49 patients were studied. Radionuclide angiography was performed before, 1 month after, and 6 to 12 months after CABG to evaluate regional wall motion. Exercise thallium-201 myocardial perfusion imaging was done before and 1 month after CABG to assess regional perfusion. Preoperative asynergy was observed in 108 segments, and 74 of them showed an improvement in wall motion 1 month after CABG (segment A). Sixty-six of these segments (89%) were associated with an improvement in perfusion. Eight segments that had not improved 1 month after CABG demonstrated a delayed recovery of wall motion 6 to 12 months after CABG (segment B). However, seven of eight segments (88%) already showed an improvement in perfusion 1 month after CABG. A total of 82 segments exhibited functional recovery after CABG and were considered hibernating segments. In the preoperative study segment B more frequently had areas of akinesis or dyskinesis than segment A (75% vs 34%, p less than 0.05). The mean percent thallium-201 uptake in segment B was lower than that in segment A (74% +/- 9% vs 83% +/- 8%, p less than 0.05). Functional recovery of hibernating myocardium usually coincided with an improvement in perfusion. However, delayed functional recovery after reperfusion was observed in some instances. Severe asynergy and severe thallium-201 defects were more frequently observed in these segments with delayed recovery. Hibernating myocardium might remain stunned during those recovery periods.

Noninvasive identification of left main and three-vessel coronary artery disease by thallium-201 single photon emission computed tomography during adenosine infusion.

Advanced coronary artery disease, defined as left main or three-vessel coronary disease, was identifiable noninvasively by means of adenosine Tl-201 single photon emission tomography. Among 75 consecutive patients with angiographically documented coronary artery disease, there were 11 patients with the presence (group 1) and 64 patients with the absence (group 2) of advanced coronary artery disease. The lung-to-heart ratio (L/H ratio) of Tl-201 uptake was calculated as the fraction of average Tl-201 counts per pixel in the lung divided by those in the myocardium. The left ventricular dilation ratio (LVDR) was determined as a ratio of left ventricular cavity size in the early image to that in the delayed image. The patients in group 1 had more defects (2.3 ± 0.6 seg. vs. 0.9 ± 0.7 seg., p < 0.001), ahigher L/H ratio (35 ± 4% vs. 28 ± 5%, p < 0.001) and a higher LVDR (1.13 ± 0.04 vs. 1.06 ± 0.04, p < 0.001) than those in group 2. The diagnostic accuracy of the identification of advanced coronary artery disease was 89% by perfusion defects, 68% by L/H ratio and 81% by LVDR. Stepwise discriminant analysis revealed that LVDR (F = 36.2, p < 0.0001) and perfusion defects (F = 8.9, p < 0.004) were the significant and independent discriminators of advanced coronary disease.Identification of patients with left main or three-vessel coronary disease was enhanced by additional analysis of cavity dilation of the left ventricle and increased Tl-201 activity in the lung.

Adenosine-induced heterogeneous perfusion accompanies myocardial ischemia in the presence of advanced coronary artery disease

The aim of the present study was to elucidate the characteristics of patients in whom transient myocardial ischemia was evoked during adenosine infusion. Thallium-201 (Tl-201) myocardial imaging and two-dimensional echocardiography during adenosine infusion were performed simultaneously in 61 consecutive patients enrolled for the diagnosis of coronary artery disease. Transient reduction of systolic wall motion after adenosine infusion was considered evidence of myocardial ischemia. Tl-201 redistribution was noted in 38 patients, and 23 of them showed a wall motion abnormality during adenosine infusion. Stepwise discriminant analysis was applied to eight variables that showed significant differences by the univariate analysis between patients with the presence and the absence of adenosine-induced wall motion abnormality: myocardial infarction, anginal pain, ST depression, collateral vessels, Tl-201 redistribution, number of diseased vessels of > or = 75% or 90% stenosis and number of segments with Tl-201 redistribution. The number of diseased vessels with > or = 75% stenosis (F = 43.5, p < 0.0001), ST depression (F = 16.0, p < 0.0002), collateral vessels (F = 11.7, p < 0.001) and Tl-201 redistribution (F = 5.6, p < 0.02) were the statistically significant discriminators relating to adenosine-induced wall motion abnormality. Adenosine-induced myocardial ischemia was related to the number of coronary stenoses, reflecting the presence of severe coronary artery disease, and well-developed collaterals that might be integral factors in a coronary steal phenomenon.

Organ distribution of thallium-201 during intravenous adenosine infusion: Comparison with exercise☆

Thallium-201 (Tl-201) distribution during adenosine infusion was assessed quantitatively and compared with that of exercise imaging. Adenosine and exercise Tl-201 single-photon emission computed tomography (SPECT) were performed in 40 patients with suspected coronary artery disease. In the whole-body images (n = 5) and the unprocessed anterior projection images acquired as part of the initial imaging (n = 35), Tl-201 counts in the myocardium were normalized for the injected dose. Total heart counts were higher during adenosine infusion than during exercise (190 +/- 43 counts/MBq vs 145 +/- 31 counts/MBq, p < 0.01). A heart-to-lung count ratio between adenosine infusion and exercise was not different. A heart-to-liver count ratio was lower during adenosine infusion than during exercise (1.3 +/- 0.3 vs 2.3 +/- 0.5, p < 0.01). Regional Tl-201 uptakes at the inferior wall of the left ventricle during adenosine infusion were closely correlated with those uptakes during exercise (r = 0.94, p < 0.01, slope = 0.96). The sensitivity, specificity, and accuracy of adenosine Tl-201 SPECT for the detection of right coronary artery stenosis were comparable with those of exercise imaging. These results indicated that higher Tl-201 uptake in the liver during adenosine than during exercise did not interfere with the interpretation of myocardial images. Tl-201 counts in the myocardium that were larger during adenosine infusion than during exercise reflected a larger increase in coronary blood flow and thus resulted in better image quality.

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.