High negative predictive value of workload ≥7 METS on exercise testing in patients with normal gated myocardial perfusion imaging: Was imaging really required?

Introduction: Good functional capacity has a high negative predictive value (NPV) in patients with known or suspected coronary artery disease (CAD) similar to a normal gated myocardial perfusion imaging (GMPI). Aim of this study was to evaluate NPV of functional capacity during treadmill exercise in patients with normal GMPI in Pakistani population. Methods: This was a prospective study which included 1318 individuals with normal exercise GMPI. On the basis of maximal age predicted heart rate (MAPHR) and metabolic equivalents (METS) achieved, these patient were divided into Group A: ≥ 85% MAPHR and ≥7 METS (714 patients), Group B: ≥85% MAPHR and <7METS (145 patients), Group C: <85% MAPHR and ≥7 METS (289 patients) and Group D: <85% MAPHR and <7 METS (170 patients). Patients were followed up on telephone (15 ±3 months) for fatal or non-fatal myocardial infarction (FMI and NFMI). Results: There was no MI in any group but NFMIs was reported in 2.07% in Group B and 2.35% in Group D. NPV of a normal GMPI in relation with functional capacity was found to be 100% for Group A and C (≥7METS), 97.9% and 97.6% for Group B and D (<7METS) respectively. Conclusion: We conclude that patients with ≥7 METS with normal GMPI had 100% NPV for FMI or NFMIs and omitting GMPI in these patients would save cost and avoid radiation exposure.