Efficacy of iodine-123-15-(p-iodophenyl)-3-R, S-methylpentadecanoic acid single photon emission computed tomography imaging in detecting myocardial ischemia in children with Kawasaki disease

Exercise myocardial perfusion stress testing in children with Kawasaki disease

AIM

Kawasaki disease is the commonest cause of acquired coronary artery disease in children. Although echocardiography and treadmill stress testing have been the traditional methods of assessing coronary artery abnormalities and detecting myocardial ischaemia, respectively, these are inadequate for assessing perfusion and performance. We studied the safety and utility of exercise myocardial perfusion stress testing in children with previous Kawasaki disease.

METHODS

Eleven subjects (median age 12 years; seven male and four female adolescents) with a history of childhood Kawasaki disease underwent 99mTechnetium-Tetrofosmin myocardial perfusion scan using a modified protocol. All had New York Heart Association effort tolerance class 1 and were asymptomatic at time of testing. Eight of 11 subjects had been treated with intravenous immunoglobulin during the acute phase. Six of 11 subjects had transient coronary artery dilatation. One subject with persistently dilated coronary arteries suffered an acute myocardial infarction 6 months after onset of Kawasaki disease but recovered well. Results were compared with clinical and echocardiographic findings.

RESULTS

All subjects were able to complete the exercise test. There were no side effects associated with radioisotope injection. Ten of 11 patients, including the one who suffered a myocardial infarction had normal tests. The single subject with an abnormal scan showed a minimal (2%) fixed defect in the left ventricular wall.

CONCLUSION

Exercise myocardial perfusion stress is a safe and useful method for the assessment of myocardial perfusion in co-operative children with a history of Kawasaki disease and is a useful addition to conventional methods for coronary risk stratification in such patients.

A Tc-99m-labeled long chain fatty acid derivative for myocardial imaging

C-11- and I-123-labeled long chain fatty acid derivatives have been reported as useful radiopharmaceuticals for the estimation of myocardial fatty acid metabolism. We have reported that Tc-99m-labeled N-[[[(2-mercaptoethyl)amino]carbonyl]methyl]-N-(2-mercaptoethyl)-6-aminohexanoic acid ([(99m)Tc]MAMA-HA), a medium chain fatty acid derivative, is metabolized by beta-oxidation in the liver and that the MAMA ligand is useful for attaching to the omega-position of fatty acid derivatives as a chelating group for Tc-99m. On the basis of these findings, we focused on developing a Tc-99m-labeled long chain fatty acid derivative that reflected fatty acid metabolism in the myocardium. In this study, we synthesized a dodecanoic acid derivative, MAMA-DA, and a hexadecanoic acid derivative, MAMA-HDA, and performed radiolabeling and biodistribution studies. [(99m)Tc]MAMA-DA and [(99m)Tc]MAMA-HDA were prepared using a ligand-exchange reaction. Biodistribution studies were carried out in normal mice and rats. Then, a high initial uptake of Tc-99m was observed, followed by a rapid clearance from the heart. The maximum heart/blood ratio was 3.6 at 2 min postinjection of [(99m)Tc]MAMA-HDA. These kinetics were similar to those with postinjection of p-[(125)I]iodophenylpentadecanoic acid. Metabolite analysis showed [(99m)Tc]MAMA-HDA was metabolized by beta-oxidation in the body. In conclusion, [(99m)Tc]MAMA-HDA is a promising compound as a long chain fatty acid analogue for estimating beta-oxidation of fatty acid in the heart.

Diagnostic Use of T2-Weighted Inversion-Recovery Magnetic Resonance Imaging in Acute Coronary Syndromes Compared With 99mTc-Pyrophosphate, 123I-BMIPP and 201TlCl Single Photon Emission Computed Tomography

BACKGROUND

The incidence of missed diagnoses of acute cardiac ischemia in the emergency department could be reduced by a new imaging modality. In the present study, the clinical significance of (99m)Tc-pyrophosphate (PYP), (123)I-beta-methyl-p-iodephenyl-pentadecanoic acid (BMIPP), (201)TlCl scintigraphy (imaging) and T2-weighted inversion-recovery magnetic resonance imaging (MRI) for the detection of culprit lesion in patients with acute coronary syndromes (ACS) was compared.

METHODS AND RESULTS

The study group comprised 18 patients with ACS: 12 patients with acute myocardial infarction (AMI) (11 males; mean age, 63+/-11 years) and 6 patients with unstable angina (UA) (3 males, mean age, 67+/-5 years). Of the 12 patients with AMI, 10 underwent (201)TlCl and PYP single photon emission computed tomography (SPECT) studies as a dual-energy acquisition ((201)TlCl/PYP) and 8 underwent (201)TlCl SPECT within 1 week of the BMIPP study. All 18 patients underwent BMIPP SPECT and MRI. The MRI pulse sequence was black blood turbo short-inversion-time inversion recovery (STIR) (breath-hold T2-weighted studies). The T2-weighted inversion-recovery MRI showed higher sensitivity and negative predictive value than PYP and (201)TlCl, and higher specificity and positive predictive value than BMIPP and (201)TlCl. The area under the receiver-operating characteristic curve for PYP, BMIPP, (201)TlCl and MRI was 0.787, 0.725, 0.731 and 0.878, respectively. The difference between the areas of MRI and BMIPP was significant (p<0.05).

CONCLUSION

Accurate detection of culprit lesion is improved by using MRI rather than BMIPP, particularly for patients with ACS.