As part of procedures to audit referrals for stress myocardial perfusion scans we routinely carried out a simple risk assessment using a standard software tool [1]. This calculates the probability of suffering a cardiac event or stroke over the next 10 years. The calculation is based on gender, age, cholesterol levels, blood pressure, smoking, diabetes and left ventricular hypertrophy. The model does not apply to patients with known atherosclerotic disease. The calculated risk of coronary events in 200 sequential patients was compared with the presence of perfusion defects reported on stress myocardial perfusion scans. Sixty-six patients had a 10 year risk of coronary events of 515%. Of these, 22 (33%) had perfusion defects reported on the scan. In 63 patients with risks of 15-30%, 21 (33%) had positive scans. In 16 patients with risks of >30%, 11 (69%) had positive scans. The remaining 54 patients had known atherosclerotic disease. Of these, 39 (72%) had positive scans. These results suggest that the frequency of positive scans is not related to calculated risk of coronary events using this model for patients with risks of <15% compared with risks of 15-30%. This may be due to the presence of other risk factors (e.g., family history, premature menopause) which are not included in the model but which may increase clinical suspicion. The model is therefore unlikely to be helpful in selecting or prioritizing the majority of patients who are referred for myocardial perfusion scans. Patients with either a risk of >30% or pre-existing atherosclerotic disease were found to have a markedly increased likelihood of a positive scan.
1 Anderson et al. Am Heart J 1990; 121: 293-298.
Chandler ST, Carr S, Watson J. Clinical risk of coronary heart disease: does it relate to perfusion defects on myocardial perfusion scans? Nuclear Medicine Communications: Volume 24(3) March 2003 p 339.
Mr. Steve Chandler, Darlington Unit, Darlington. Tel: +44 (0)1325-743-347.
Regional Medical Physics Department, Newcastle General Hospital, Newcastle upon Tyne, NE4 6BE, UK.
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