Value of myocardial SPECT in early detection of ischaemia in children with sickle cell anaemia

Background: Cardiovascular complications of sickle cell anaemia (SCA) are relatively infrequent compared with other cerebral and skeletal insults. However, myocardial infarction and cardiac dysfunction have been reported in autopsied patients with SCA. When left ventricular functional parameters of gated SPECT and echocardiography were compared incidentally in children with SCA, some 26% of patients were found to have evident myocardial ischaemia. This stimulated the current work with the aim to further analyse these incidental findings and evaluate the possible role of SPECT in early detection of coronary insufficiency in children with SCA.

Patients and methods: Twenty-seven patients (19 girls, 8 boys), mean age 9.2±4.2 years, with SCA were examined by baseline ECG, echocardiography and gated SPECT. They were all free from any cardiac symptoms. Intravenous injection of 5 to 10 mCi ^99MTc-MIBI or ^99MTc-Myoview was administered, according to the predetermined weight-dependent paediatric dose. Stress SPECT was obtained 45 to 60 minutes after tracer injection, which took place at peak physical exercise (6 patients) or 3 to 4 minutes after IV infusion of dipyridamole pharmacological stress (21 patients). Rest SPECT study was acquired 4 to 5 hours later after a second injection of ^99MTc-MIBI/Myoview. A semiquantitative nine-segment stress/rest bull's eye model was used to assess to the presence/extent of myocardial ischaemia.

Results: Myocardial perfusion was normal in 20 patients (74%). Seven patients (26%) had significant perfusion defects in the stress images. Four of them showed perfusion defect in one or two segments. Complete reversibility in the rest study was seen in all patients. Two patients showed a mixture of reversible and fixed perfusion defects in four segments. One patient had evident left ventricular dilatation with multiple fixed and reversible defects (cardiomyopathy). In this case, a diffusely reduced myocardial wall contractility was seen and a low LVEF of 42% as assessed by echocardiography. This was the only case showing agreement between the echo and SPECT findings. In the whole cohort the EF% and FS% by echocardiography were 61.7±5.9% and 33.2±3.4% respectively (mean±SD). There were no significant relations between myocardial perfusion abnormalities when compared with EF% and FS%; (p>0.05).

Conclusion: Cardiac involvement in the form of myocardial ischaemia should be regarded as a high-risk complication in patients with SCA. Myocardial perfusion scintigraphy succeeded in the early detection of myocardial perfusion abnormalities in patients with SCA.