Effects of postconditioning in ST-elevation myocardial infarction : assessment of myocardium at risk and infarct size

Background: Myocardial infarction remains a major health problem, despite recent improvements in detection and treatment. Infarct size is a major determinant of future mortality and morbidity. Management strategies aimed at limiting infarct size, beyond what is achieved with early revascularization in combination with platelet stabilization, could be of great prognostic importance. Although opening of the infarct-related artery is mostly beneficial, it also initiates harmful processes that contribute to the final infarct size, so called reperfusion injury. When performing studies aiming at myocardial protection, it is important to have methods that accurately quantify ischemic but viable myocardium and the final infarct size. Postconditioning, a method that consists of cycles of brief reperfusion and ischemia during early stages of revascularization, seems to limit reperfusion injury. Further knowledge is important for understanding how efficient this technique is and if the protection leads to long-lasting benefits. Methods and results: Study I investigated if postconditioning in addition to primary percutaneous coronary intervention (PCI) would limit infarct size and improve left ventricular ejection fraction (LVEF), compared with standard PCI. This was determined with cardiovascular magnetic resonance (CMR) after one week in 76 patients with ST-elevation myocardial infarction (STEMI). There was no difference in infarct size and LVEF within the total study population. Postconditioning did, however, have a beneficial effect on final infarct size and LVEF in patients with the largest volumes of myocardium at risk (MaR). Study II investigated if the results from study I were consistent during long-term follow-up in 68 patients. In order to quantify infarct size and LVEF, the patients were re-examined with CMR at three and 12 months. There was no difference between patients who were postconditioned and those who underwent ordinary PCI in the complete study group. Postconditioned patients in the upper quartile of MaR did, however, still have less myocardial damage and improved LVEF after one year. Study III compared MaR estimated with a new modified contrast-enhanced CMR sequence one week after admission with the reference standard method, myocardial perfusion singlephoton emission computed tomography (SPECT), in 16 patients with STEMI. There was a good correlation between the two methods. Study IV investigated 21 patients with STEMI one week after revascularization with CMR. T2-weighted (edema) images were compared with contrast-enhanced CMR sequence for the assessment of MaR. A strong agreement was found between the two methods. Conclusions: Postconditioning did not decrease infarct size or improve LVEF one week or 12 months after the procedure in all patients with first time STEMI subjected to this method. Patients with large MaR seemed, however, to have a consistent benefit over time in the form of smaller infarct sizes and improved LVEF. There is a strong agreement between the newly developed contrast-enhanced CMR sequence compared with both reference standard SPECT and T2-weighted edema images. The implication is that the new technique can be used for quantification of MaR and final infarct size in patients with STEMI, through a single investigation performed several days after the event

Assessment of myocardium at risk with contrast enhanced steady-state free precession cine cardiovascular magnetic resonance compared to single-photon emission computed tomography

<p>Abstract</p> <p>Background</p> <p>Final infarct size following coronary occlusion is determined by the duration of ischemia, the size of myocardium at risk (MaR) and reperfusion injury. The reference method for determining MaR, single-photon emission computed tomography (SPECT) before reperfusion, is impractical in an acute setting. The aim of the present study was to evaluate whether MaR can be determined from the contrast enhanced myocardium using steady-state free precession (SSFP) cine cardiovascular magnetic resonance (CMR) performed one week after the acute event in ST-elevation myocardial infarction (STEMI) patients with total coronary occlusion.</p> <p>Results</p> <p>Sixteen patients with STEMI (age 64 ± 8 years) received intravenous 99 m-Tc immediately before primary percutaneous coronary intervention. SPECT was performed within four hours. MaR was defined as the non-perfused myocardial volume derived with SPECT. CMR was performed 7.8 ± 1.2 days after the myocardial infarction using a protocol in which the contrast agent was administered before acquisition of short-axis SSFP cines. MaR was evaluated as the contrast enhanced myocardial volume in the cines by two blinded observers. MaR determined from the enhanced region on cine CMR correlated significantly with that derived with SPECT (r²= 0.78, p < 0.001). The difference in MaR determined by CMR and SPECT was 0.5 ± 5.1% (mean ± SD). The interobserver variability of contrast enhanced cine SSFP measurements was 1.6 ± 3.7% (mean ± SD) of the left ventricle wall volume.</p> <p>Conclusions</p> <p>Contrast enhanced SSFP cine CMR performed one week after acute infarction accurately depicts MaR prior to reperfusion in STEMI patients with total occlusion undergoing primary PCI. This suggests that a single CMR examination might be performed for determination of MaR and infarct size.</p

Quantification of myocardium at risk in ST- elevation myocardial infarction: a comparison of contrast-enhanced steady-state free precession cine cardiovascular magnetic resonance with coronary angiographic jeopardy scores

Abstract Background Clinical outcome following acute myocardial infarction is predicted by final infarct size evaluated in relation to left ventricular myocardium at risk (MaR). Contrast-enhanced steady-state free precession (CE-SSFP) cardiovascular magnetic resonance imaging (CMR) is not widely used for assessing MaR. Evidence of its utility compared to traditional assessment methods and as a surrogate for clinical outcome is needed. Methods Retrospective analysis within a study evaluating post-conditioning during ST elevation myocardial infarction (STEMI) treated with coronary intervention (n = 78). CE-SSFP post-infarction was compared with angiographic jeopardy methods. Differences and variability between CMR and angiographic methods using Bland-Altman analyses were evaluated. Clinical outcomes were compared to MaR and extent of infarction. Results MaR showed correlation between CE-SSFP, and both BARI and APPROACH scores of 0.83 (p < 0.0001) and 0.84 (p < 0.0001) respectively. Bias between CE-SSFP and BARI was 1.1% (agreement limits -11.4 to +9.1). Bias between CE-SSFP and APPROACH was 1.2% (agreement limits -13 to +10.5). Inter-observer variability for the BARI score was 0.56 ± 2.9; 0.42 ± 2.1 for the APPROACH score; -1.4 ± 3.1% for CE-SSFP. Intra-observer variability was 0.15 ± 1.85 for the BARI score; for the APPROACH score 0.19 ± 1.6; and for CE-SSFP -0.58 ± 2.9%. Conclusion Quantification of MaR with CE-SSFP imaging following STEMI shows high correlation and low bias compared with angiographic scoring and supports its use as a reliable and practical method to determine myocardial salvage in this patient population. Trial registration Clinical trial registration information for the parent clinical trial: Karolinska Clinical Trial Registration (2008) Unique identifier: CT20080014. Registered 04th January 200

Contrast Enhancement and Image Quality Influence Two- and Three-dimensional Echocardiographic Determination of Left Ventricular Volumes: Comparison With Magnetic Resonance Imaging

Purpose: To evaluate the effect of image quality and contrast enhancement (CE) on left ventricular (LV) volume determination by two- (2D) and three-dimensional (3D) echocardiography (2DE/3DE). Methods: We studied 32 post-myocardial infarction (MI) patients without (2DE/3DE) and with CE (CE2DE/CE3DE), in comparison with cardiac magnetic resonance imaging (CMR). Results: Two-dimensional echocardiography showed the largest negative bias versus CMR for diastolic and systolic volumes (−59, −28 mL, respectively) with lower biases for CE2DE (−37, −22 mL), 3DE (−31, −17 mL), and CE3DE (−17, −11 mL). Bias for ejection fraction (EF) ranged from −2.1% for 2DE to +1.4% for CE3DE. Agreement (intraclass correlation coefficient, ICC) for EF between CMR and 3DE (0.86 without and 0.85 with contrast) was better than for 2DE (0.73 without and 0.69 with contrast). The inter-/intra-observer coefficients of variation for EF varied from 16%/10% (2DE) to 6.9%/6.6% (CE2DE), and 8.3%/4.8% (3DE) to 6.7%/6.8% (CE3DE), respectively. The agreement (ICC) with CMR for EF measured by 2DE/3DE changed from 0.64/0.84 with poor image quality to 0.81/0.87 with moderate to good image quality. Conclusions: Three-dimensional echocardiography was more accurate than 2DE for estimating LV volumes, with less inter-/intra-observer variability in EF values. Contrast enhancement improved accuracy for both 2DE and 3DE and improved the inter-observer variability of EF estimates for 2DE and 3DE. Image quality had more impact on the agreement of EF values with CMR for 2DE than for 3DE. Our results emphasize the importance of using the same technique for longitudinal studies of LV EF and specially LV volumes

Effects of Myocardial Postconditioning on the Recruitment of Endothelial Progenitor Cells.

Background: Ischemic postconditioning (PostC), brief repetitive cycles of ischemia and reperfusion during early reperfusion, is suggested to protect the myocardium in patients with stent thrombosis-elevation myocardial infarction (STEMI) by improved endothelial dysfunction and alteration of cytokine release. These mechanisms are also of importance for the recruitment of endothelial progenitor cells (EPC), an endogenous repair mechanism for re-endothelialization and neoangiogenesis. The aim of this study was to investigate the effect of PostC on recruitment of EPC. Methods: EPC were analyzed in 20 patients with STEMI randomized to receive four cycles of PostC following percutaneous coronary intervention (PCI) or conventional PCI. Different subpopulations of EPC were quantified immediately and on day 4 using flow cytometry. Myocardium at risk, and infarct size was determined by cardiovascular magnetic resonance. Results: There was no influence of PostC on the number of different EPC (CD34(+) , CD133(+) , CD34(+) CD133(+) , CD34(+) KDR(+) , CD34(-) CD133(+) KDR(+) , CD34(+) CD133(+) KDR(+) ). Left ventricular ejection fraction, myocardium at risk, and infarct size did not correlate to the mobilization of EPC. There was an inverse correlation between the symptom-to-balloon time and the mobilization of progenitor precursor cells (CD34(+) cells: R =-0.527, P = 0.02; CD133(+) cells: R =-0.624, P = 0.004; CD34(+) CD133(+) cells: R =-0.466, P = 0.04). Discussion: Ischemic PostC did not result in improved mobilization of EPC in STEMI patients. The recruitment of progenitor cells seems to be related to the duration of ischemia rather than the size of the ischemic myocardial area. More effort is needed to understand the changes of endothelial surface markers by PostC and their role in EPC recruitment and homing. (J Interven Cardiol 2012;**1-8)