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New protocol limits use of SPECT MPI

A new stress test protocol that investigates reducing the use of perfusion imaging in low risk patients undergoing single-photon emission computed tomography (SPECT) myocardial perfusion imaging for possible angina symptoms was found to be diagnostically safe in a study1 reported at the International Conference on Nuclear Cardiology and Cardiac CT (ICNC11), held in Berlin, Germany, May 5–May 8.

Researchers from the Mount Sinai School of Medicine (New York, USA) set out to investigate retrospectively if a provisional injection protocol, in which patients meeting certain criteria were converted to exercise treadmill tests without imaging, maintained diagnostic accuracy and prognostic ability. For the retrospective study, data was reviewed from a total of 24,689 patients who had undergone SPECT MPI between February 2004 and June 2010. After exclusion of patients older than 65 years of age, who had known coronary artery disease (CAD) and uninterruptable resting electrocardiograms (ECGs), 5,352 subjects were identified for analysis.

Subjects were divided into those who would have met all the criteria for not undergoing SPECT MPI (the No injection group n= 1,561 [29.2%]) and those who met the criteria for undergoing SPECT MPI (the Yes injection group, n=3,791, [70.8%]). For the study the criteria laid down for patients considered eligible for not undergoing SPECT MPI included achieving a maximal predicted heart rate >85%, > 10 METs of exercise, no symptoms of chest pain or significant shortness of breath during stress, and no ECG changes (ST depression or arrhythmia). Outcomes for the two groups at five years were then compared based on their actual myocardial perfusion imaging results and all-cause mortality that had been retrospectively identified from the National Death Index.

At a mean follow-up of 60.6 months, 1.1% of patients had died in the No-injection cohort compared to 2.2% Yes injection cohort (P=.01). Furthermore perfusion results were abnormal in 5.9% of the No injection group compared to 14.4% in the Yes injection group.

“Our results are reassuring in that there are few patients whose diagnosis of CAD would be missed,” said Professor Milena Henzlova, the first author of the study. “Not only would widespread adoption of this approach reduce radiation exposure, it would also save considerable amounts of time and money.”

Eliminating the need for imaging in 6% of the 9 million SPECT MPI studies performed annually in the USA, the authors added, would result in significant cost savings and the total test time would be halved from three hours to roughly one hour. “There’s a need to accept that less can be more. By individualizing therapy we can reduce radiation exposure and costs without jeopardizing the quality, the diagnostic utility or missing something important,” said Professor Henzlova.

References

1.  M Henzlova, EJ Levine, S Moonthungal, et al. A protocol for the provisional use of perfusion imaging with exercise stress testing. Final Programme number 58. ICNC11 2013

Published on: May 22, 2013

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  • ArrhythmiaAlliance
  • Stars
  • Anticoagulation Europe
  • Atrial Fibrillation Association
 

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