title: Higher event rate in patients with known CAD despite a normal myocardial perfusion scan.
abstract: OBJECTIVE
  The negative predictive value of a normal single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is very high. However, prognostic implication of a normal SPECT MPI in patients with known coronary artery disease (CAD) is not clear. Objective of this study was to evaluate the cardiac event rate in patients with known CAD who had a normal stress SPECT MPI.
  
  
  METHODS
  This prospective study accrued 428 consecutive patients with a history of CAD [revascularization or previous myocardial infarction (MI)] who had a normal stress (dynamic exercise or dipyridamole intervention) and rest Tc-99m-MIBI SPECT MPI. These patients were followed for 2-5 years (median: 3.1 years) for all-cause and cardiac mortality and non-fatal MI. Univariate and multivariate analyses were performed to identify predictors of outcome.
  
  
  RESULTS
  During a follow-up period, all-cause mortality was found in 60 patients (14%) and 41 (10%) died of cardiac reasons. Non-fatal MI was found in 77 (18%) patients. Annualized cardiac mortality and non-fatal MI rates were 2% and 3.6% respectively. Smoking, congestive heart failure (CHF) and failure to achieve 85% age predicted heart rate were found to be predictors for all-cause and cardiac mortality. Diabetes, dyslipidemia, smoking and limited functional capacity (<7 METS) were found to be predictors for non-fatal MI.
  
  
  CONCLUSIONS
  Patients with known CAD had higher cardiac event rates despite a normal stress SPECT MPI. Diabetes, dyslipidemia, smoking and limited functional capacity were the predictors for fatal and non-fatal cardiac events. A cost effective but comprehensive surveillance strategy is warranted.
authors.affiliation: 1 Department of Radiology, The Aga Khan University Hospital (AKUH), Karachi, Pakistan ; 2 Department of Nuclear Cardiology, Karachi Institute of Heart Diseases (KIHD), Karachi, Pakistan ; 3 Department of Nuclear Medicine, Dr Ziauddin Medical University, Karachi, Pakistan ; 4 MBBS Students, Dow University of Health Sciences (DUHS), Karachi, Pakistan.
authors.forename: Maseeh Uz
authors.initials: MU
authors.lastname: Zaman
authors.affiliation: 1 Department of Radiology, The Aga Khan University Hospital (AKUH), Karachi, Pakistan ; 2 Department of Nuclear Cardiology, Karachi Institute of Heart Diseases (KIHD), Karachi, Pakistan ; 3 Department of Nuclear Medicine, Dr Ziauddin Medical University, Karachi, Pakistan ; 4 MBBS Students, Dow University of Health Sciences (DUHS), Karachi, Pakistan.
authors.forename: Nosheen
authors.initials: N
authors.lastname: Fatima
authors.affiliation: 1 Department of Radiology, The Aga Khan University Hospital (AKUH), Karachi, Pakistan ; 2 Department of Nuclear Cardiology, Karachi Institute of Heart Diseases (KIHD), Karachi, Pakistan ; 3 Department of Nuclear Medicine, Dr Ziauddin Medical University, Karachi, Pakistan ; 4 MBBS Students, Dow University of Health Sciences (DUHS), Karachi, Pakistan.
authors.forename: Unaiza
authors.initials: U
authors.lastname: Zaman
authors.affiliation: 1 Department of Radiology, The Aga Khan University Hospital (AKUH), Karachi, Pakistan ; 2 Department of Nuclear Cardiology, Karachi Institute of Heart Diseases (KIHD), Karachi, Pakistan ; 3 Department of Nuclear Medicine, Dr Ziauddin Medical University, Karachi, Pakistan ; 4 MBBS Students, Dow University of Health Sciences (DUHS), Karachi, Pakistan.
authors.forename: Areeba
authors.initials: A
authors.lastname: Zaman
authors.affiliation: 1 Department of Radiology, The Aga Khan University Hospital (AKUH), Karachi, Pakistan ; 2 Department of Nuclear Cardiology, Karachi Institute of Heart Diseases (KIHD), Karachi, Pakistan ; 3 Department of Nuclear Medicine, Dr Ziauddin Medical University, Karachi, Pakistan ; 4 MBBS Students, Dow University of Health Sciences (DUHS), Karachi, Pakistan.
authors.forename: Dad J
authors.initials: DJ
authors.lastname: Balcoh
authors.affiliation: 1 Department of Radiology, The Aga Khan University Hospital (AKUH), Karachi, Pakistan ; 2 Department of Nuclear Cardiology, Karachi Institute of Heart Diseases (KIHD), Karachi, Pakistan ; 3 Department of Nuclear Medicine, Dr Ziauddin Medical University, Karachi, Pakistan ; 4 MBBS Students, Dow University of Health Sciences (DUHS), Karachi, Pakistan.
authors.forename: S Zahed
authors.initials: SZ
authors.lastname: Rasheed
keywords: Myocardial perfusion imaging (MPI); coronary artery disease (CAD); event rate; prognosis