title: Higher events rate in patients with a normal gated myocardial perfusion imaging with dipyridamole than exercise: "Run for reliability".
abstract: OBJECTIVE
  The aim of this is to evaluate the negative predictive value (NPV) of a normal gated myocardial perfusion imaging (NGMPI) with exercise and dipyridamole in a propensity matched population.
  
  
  METHODS
  This is a prospective study conducted at Nuclear Cardiology Department of Karachi Institute of Heart Diseases, Karachi from December 2008 until June 2010. A total of 809 patients with a NGMPI with adequate exercise (558/809) or dipyridamole (251/809) stress were included and followed-up for 12-30 months (mean 24 ± 3 months) for fatal or non-fatal myocardial infarctions (MI).
  
  
  RESULTS
  Mean ejection fraction (%), end diastolic volume (ml), and end systolic volume (ml) in exercise and dipyridamole cohorts were (72 ± 08, 66 ± 11), (68 ± 13, 81 ± 17), and (19 ± 11, 26 ± 12) respectively. On follow-up, in dipyridamole cohort 2 fatal and 6 non-fatal MIs were reported. While in exercise cohort only 2 non-fatal MIs were reported. The NPV of a NGMPI with exercise was 99.7% (95% confidence interval [CI] 98.93-99.96%) with an event rate of 0.3% (95% CI; 0.03-0.6%) and annualized event rate of 0.15%. The NPV of NGMPI with dipyridamole was 96.80% (95% CI; 2.2-4.3%) with an event rate of 3.2% (95% CI; 1.39-3.83%) and annualized event rate of approximately 1.6%. Event free survival for dipyridamole group was significantly lower than exercise analyzed by Log-rank test (14.509, P < 0.001).
  
  
  CONCLUSIONS
  A NGMPI with dipyridamole stress has higher event rate (low-NPV) as compared with exercise and this raises concern over its credibility to label these patients into low-risk group.
authors.affiliation: Department of Nuclear Cardiology, Karachi Institute of Heart Diseases, Karachi, Pakistan ; Department of Nuclear Medicine, Dr Ziauddin Medical University, Karachi, Pakistan.
authors.forename: Nosheen
authors.initials: N
authors.lastname: Fatima
authors.forename: Maseeh
authors.initials: M
authors.lastname: Uz Zaman
authors.forename: Mohd
authors.initials: M
authors.lastname: Ishaq
authors.forename: S Zahed
authors.initials: SZ
authors.lastname: Rasheed
authors.forename: Dad J
authors.initials: DJ
authors.lastname: Baloch
authors.forename: Asif
authors.initials: A
authors.lastname: Wali
authors.forename: Javeria
authors.initials: J
authors.lastname: Bano
authors.forename: Kawish
authors.initials: K
authors.lastname: Rehman
keywords: Annualized event rate; Tc-99m methoxy isobutyl isonitrile; ejection fraction; negative predictive value; normal gated myocardial perfusion imaging
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