Relationship between rest myocardial perfusion imaging and biochemical markers of myocardial injury in patients with chest pain

Abstract Background: In patients (pts) with chest pain and acute coronary syndromes, troponins provide diagnostic sensitivity and prognostic information, but there is a 6 hour lag between symptoms and elevation. An earlier marker of necrosis is myoglobin, but it has a brief duration of elevation and a low specificity. Rest myocardial perfusion imaging (RMPI) may offer further information over both of these markers. The purpose of this study was to compare the relationship between the extent of perfusion defects with the measurements of myoglobin and troponin I (TnI). Methods: We enrolled hemodynamically stable pts, without prior infarction, presenting with ongoing chest pain or an episode within the last six hours. Following clinical evaluation, a blood sample was drawn for assessment of serum TnI and myoglobin levels. Perfusion images were acquired after an injection of 15 mCi of 99m Tc-tetrofosmin and visual scoring was performed using a 17 segment system. The summed rest score was expressed as a percentage of the maximal possible score (% summed rest perfusion score SRPS). Regarding the result of the exam, 3 groups were established: I - %SRPS ≤ 15%; II 15% 30%. Continuous variables were expressed as mean ± SD. Statistical analysis was performed using ANOVA. Results: Ninety-two patients were enrolled, 52 in group I (56.6%), 28 in group II (30.4%) and 12 in group III (13.0%). Twenty-nine patients were found to have a myocardial infarction (31.5%). The relationship between myoglobin and troponin levels in the 3 groups is shown in table 1. Table 1 . I (52) II (28) III (12) p Tnl 0.2 ± 0.6;*> 2.1 ± 7.2;*> 0.7 ± 1.3 ns myoglobin 64.4 ± 50.3 127.2 ± 153.6 308.1 ± 489.9 0.0009 p = 0.05. Conclusion: In this study, myoglobin, but not TnI, levels were significantly related to the extent of perfusion defects on RMPI. The delayed rise in TnI limit it as a marker for initial diagnosis of acute coronary syndromes. Myoglobin levels were related to the extent of rest perfus ion defects and this finding maybe supported by the earlier rise of this marker.