A thought-provoking paper was published recently in JACC.
Over 1100 largely asymptomatic intermediate Framingham risk patients underwent calcium scoring and perfusion imaging by SPECT. The commonest indication for testing was atypical chest pain. Follow-up was for almost a decade and there were a large number of CV events. The investigators, from Houston, Texas, concluded that calcium scoring was a good predictor of long-term cardiovascular events, with SPECT imaging a better predictor of near-term events.
It's already known that a normal SPECT study confers an annual CV event rate <1%. This finding was confirmed here. But the fascinating part for me was data showing that the 'warranty period' for the reassurance of a normal SPECT study expires after about 3 years if the calcium score is greater than 400. Presumably this is because calcium scoring is a surrogate marker for both 'high risk' non-calcified plaques (at risk of rupture) as well as calcified plaque. SPECT will only be sensitive to coronary plaques once they have become flow-limiting. The authors suggest obtaining a calcium score in subjects with a normal SPECT study, if patients are perceived to be at high risk of future events.
This advice is the opposite of that currently endorsed by the ACCF/ASNC guidelines, which suggest SPECT imaging is useful in patients who have calcium scores>400.
Do you think this is a useful way forward for patients falling into the intermediate and high risk Framingham categories with a normal SPECT study? Are you worried about the radiation burden of SPECT plus CT? Should we just prescribe lifestyle/lipid management rather than further imaging?