ABSTRACT
BACKGROUND: The time course of infarct evolution, i.e. how fast myocardial infarction (MI) develops during coronary artery occlusion, is well known for several species, whereas no direct evidence exists on the evolution of MI size normalized to myocardium at risk (MaR) in man. Despite the lack of direct evidence, current literature often refers to the "golden hour" as the time during which myocardial salvage can be accomplished by reperfusion therapy. Therefore, the aim of the present study was to investigate how duration of myocardial ischemia affects infarct evolution in man in relation to previous animal data. Consecutive patients with clinical signs of acute myocardial ischemia were screened and considered for enrollment. Particular care was taken to assure uniformity of the patients enrolled with regard to old MI, success of revascularization, collateral flow, release of biochemical markers prior to intervention etc. Sixteen patients were ultimately included in the study. Myocardium at risk was assessed acutely by acute myocardial perfusion single photon emission computed tomography (MPS) and by T2 imaging (T2-STIR) cardiovascular magnetic resonance (CMR) after one week in 10 of the 16 patients. Infarct size was measured by late gadolinium enhancement (LGE) at one week. RESULTS: The time to reach 50% MI of the MaR (T50) was significantly shorter in pigs (37 min), rats (41 min) and dogs (181 min) compared to humans (288 min). There was no significant difference in T50 when using MPS compared to T2-STIR (p = 0.53) for assessment of MaR (288 +/- 23 min vs 310 +/- 22 min, T50 +/- standard error). The transmural extent of MI increased progressively as the duration of ischemia increased (R2 = 0.56, p < 0.001). CONCLUSION: This is the first study to provide direct evidence of the time course of acute myocardial infarct evolution in relation to MaR in man with first-time MI. Infarct evolution in man is significantly slower than in pigs, rats and dogs. Furthermore, infarct evolution assessments in man are similar when using MPS acutely and T2-STIR one week later for determination of MaR, which significantly facilitates future clinical trials of cardioprotective therapies in acute coronary syndrome by the use of CMR.
Subject(s)
Coronary Occlusion/complications , Myocardial Infarction/etiology , Myocardium/pathology , Adult , Aged , Aged, 80 and over , Animals , Coronary Occlusion/diagnosis , Coronary Occlusion/therapy , Disease Models, Animal , Disease Progression , Dogs , Female , Humans , Magnetic Resonance Imaging , Male , Middle Aged , Myocardial Infarction/diagnosis , Myocardial Infarction/therapy , Myocardial Perfusion Imaging/methods , Myocardial Reperfusion , Myocardial Revascularization , Rats , Species Specificity , Swine , Time Factors , Tomography, Emission-Computed, Single-PhotonABSTRACT
OBJECTIVES: To find the time-to-peak for creatine kinase MB(mass) (CKMB) and cardiac troponin T (cTnT) after acute reperfusion, to compare peak and cumulative values to estimate infarct size (IS), and to evaluate clinical routine sampling for assessment of IS. DESIGN: Acute primary percutaneous coronary intervention (PCI) was performed in 38 patients with first-time myocardial infarction. In 21 patients, CKMB and cTnT were acquired before PCI and at 1.5, 3, 6, 12, 18, 24, and 48 hours thereafter. In 17 patients, clinical routine samples were acquired at arrival, and at 10 and 20 h. IS was assessed by delayed contrast-enhanced MRI (DE-MRI). RESULTS: Time-to-peak was 7.6+/-3.6 h for CKMB and 8.1+/-3.4 h for cTnT. Peak values correlated strongly to cumulative values (r(s)=0.97-0.98) as well as to DE-MRI (r(s)=0.8-0.82). Clinical routine sampling showed lower rs values (0.47-0.60). CONCLUSIONS: Peak values are likely captured if CKMB and cTnT are acquired at 3, 6, and 12 h after acute PCI. These peak values can be used to estimate myocardial infarct size after acute PCI.
