Abnormal elevation of myocardial necrosis biomarkers after coronary artery bypass grafting without established myocardial infarction assessed by cardiac magnetic resonance

BACKGROUND

The diagnosis of peri-procedural myocardial infarction is complex, especially after the emergence of high-sensitivity markers of myocardial necrosis.

METHODS

In this study, patients with normal baseline cardiac biomarkers and formal indication for elective on-pump coronary bypass surgery were evaluated. Electrocardiograms, cardiac biomarkers, and cardiac magnetic resonance imaging with late gadolinium enhancement were performed before and after procedures. Myocardial infarction was defined as more than ten times the upper reference limit of the 99th percentile for troponin I and for creatine kinase isoform (CK-MB) and by the findings of new late gadolinium enhancement on cardiac magnetic resonance. We assessed the release of cardiac biomarkers in patients with no evidence of myocardial infarction on cardiac magnetic resonance.

RESULTS

Of 75 patients referred for on-pump coronary bypass surgery, 54 (100%) did not have evidence of myocardial infarction on cardiac magnetic resonance. However, all had a peak troponin I above the 99th percentile; 52 (96%) had an elevation 10 times higher than the 99th percentile. Regarding CK-MB, 54 (100%) patients had a peak CK-MB above the 99th percentile limit, and only 13 (24%) had an elevation greater than 10 times the 99th percentile. The median value of troponin I peak was 3.15 (1.2 to 3.9) ng/mL, which represented 78.7 times the 99th percentile.

CONCLUSION

In this study, different from CK-MB findings, troponin was significantly increased in the absence of myocardial infarction on cardiac magnetic resonance. Thus, CK-MB was more accurate than troponin I for excluding procedure-related myocardial infarction. These data suggest a higher troponin cutoff for the diagnosis of coronary bypass surgery related myocardial infarction.

CLINICAL TRIAL REGISTRATION

http://www.isrctn.com/ISRCTN09454308 . Registered 08 May 2012.

Significant elevation of biomarkers of myocardial necrosis after coronary artery bypass grafting without myocardial infarction established assessed by cardiac magnetic resonance

The release of myocardial necrosis biomarkers after off-pump coronary artery bypass grafting (OPCAB) frequently occurs. However, the correlation between biomarker release and the diagnosis of procedure-related myocardial infarction (MI) (type 5) has been controversial. This study aimed to evaluate the amount and pattern of cardiac biomarker release after elective OPCAB in patients without evidence of a new MI on cardiac magnetic resonance (CMR) imaging with late gadolinium enhancement (LGE).Patients with normal baseline cardiac biomarkers referred for elective OPCAB were prospectively included. CMR with LGE was performed in all patients before and after interventions. Measurements of troponin I (cTnI) and creatine kinase MB fraction (CK-MB) were systematically performed before and after the procedure. Patients with new LGE on the postprocedure CMR were excluded.All of the 53 patients without CMR evidence of a procedure-related MI after OPCAB exhibited a cTnI elevation peak above the 99th percentile. In 48 (91%), the peak value was >10 times this threshold. However, 41 (77%) had a CK-MB peak above the limit of the 99th percentile, and this peak was >10 times the 99th percentile in only 7 patients (13%). The median peak release of cTnI was 0.290 (0.8-3.7) ng/mL, which is 50-fold higher than the 99th percentile.In contrast with CK-MB, considerable cTnI release often occurs after an elective OPCAB procedure, despite the absence of new LGE on CMR.

Accuracy of Myocardial Biomarkers in the Diagnosis of Myocardial Infarction After Revascularization as Assessed by Cardiac Resonance: The Medicine, Angioplasty, Surgery Study V (MASS-V) Trial

BACKGROUND

The lack of a correlation between myocardial necrosis biomarkers and electrocardiographic abnormalities after revascularization procedures has resulted in a change in the myocardial infarction (MI) definition.

METHODS

Patients with stable multivessel disease who underwent percutaneous or surgical revascularization were included. Electrocardiograms and concentrations of high-sensitive cardiac troponin I (cTnI) and creatine kinase (CK)-MB were assessed before and after procedures. Cardiac magnetic resonance and late gadolinium enhancement were performed before and after procedures. MI was defined as more than five times the 99th percentile upper reference limit for cTnI and 10 times for CK-MB in percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG), respectively, and new late gadolinium enhancement for cardiac magnetic resonance.

RESULTS

Of the 202 patients studied, 69 (34.1%) underwent on-pump CABG, 67 (33.2%) off-pump CABG, and 66 (32.7%) PCI. The receiver operating characteristic curve showed the accuracy of cTnI for on-pump CABG, off-pump CABG, and PCI patients was 21.7%, 28.3%, and 52.4% and for CK-MB was 72.5%, 81.2%, and 90.5%, respectively. The specificity of cTnI was 3.6%, 9.4%, and 42.1% and of CK-MB was 73.2%, 86.8%, and 96.4%, respectively. Sensitivity of cTnI was 100%, 100%, and 100% and of CK-MB was 69.2%, 64.3%, and 44.4%, respectively. The best cutoff of cTnI for on-pump CABG, off-pump CABG, and PCI was 6.5 ng/mL, 4.5 ng/mL, and 4.5 ng/mL (162.5, 112.5, and 112.5 times the 99th percentile upper reference limit) and of CK-MB was 37.5 ng/mL, 22.5 ng/mL, and 11.5 ng/mL (8.5, 5.1, and 2.6 times the 99th percentile upper reference limit), respectively.

CONCLUSIONS

Compared with cardiac magnetic resonance, CK-MB was more accurate than cTnI for diagnosing MI. These data suggest a higher troponin cutoff for the diagnosis of procedure-related MI.

A case of mid-apical obstructive hypertrophic cardiomyopathy treated with a transapical myectomy approach: a case report

INTRODUCTION

Hypertrophic cardiomyopathy is a genetic cardiac disease characterized by marked variability in morphological expression and natural history. The hypertrophic myocardium is often confined to the septum or lateral wall of the left ventricle, but it can also be encountered in the middle or apical segments of the myocardium. Treatment is based on medical therapy. Others therapies, such as embolization of the septal artery or ventriculomyectomy, are indicated in special situations. Surgery is the standard treatment, and it is classically done via a transaortic approach; however, in cases in which the hypertrophic myocardium is confined to mid-apical segments, a transapical approach is an option. Only a few cases of mid-apical obstructive hypertrophic cardiomyopathy treated with a myectomy using a transapical approach have been reported in the English-language literature. In this report, we present a case of a patient with mid-apical obstructive hypertrophic cardiomyopathy treated using this new approach.

CASE PRESENTATION

A 63-year-old Caucasian woman presented with a history of chest pain and shortness of breath causing significant limitations on her daily life activities. She had a history of coronary artery disease. Her physical examination was unremarkable. Transthoracic echocardiography revealed normal systolic function and significant concentric left ventricular hypertrophy that was greater in the mid-apical region. Nuclear magnetic resonance imaging confirmed significant hypertrophy of the median segments of the left ventricle. The patient had persistent symptoms despite receiving optimized medical treatment, and a surgical approach was indicated. As a myectomy using transaortic technique was thought to be difficult to perform in her case, a transapical approach was used. No complications occurred, and her symptoms resolved.

CONCLUSION

A transapical myectomy should be taken into consideration for patients with mid-apical obstructive hypertrophic cardiomyopathy that is refractory to medical treatment.

Hypotheses, rationale, design, and methods for evaluation of ischemic preconditioning assessed by sequential exercise tests in diabetic and non-diabetic patients with stable coronary artery disease--a prospective study

BACKGROUND

Ischemic preconditioning is a powerful mechanism of myocardial protection and in humans it can be evaluated by sequential exercise tests. Coronary Artery Disease in the presence of diabetes mellitus may be associated with worse outcomes. In addition, some studies have shown that diabetes interferes negatively with the development of ischemic preconditioning. However, it is still unknown whether diabetes may influence the expression of ischemic preconditioning in patients with stable multivessel coronary artery disease.

METHODS/DESIGN

This study will include 140 diabetic and non-diabetic patients with chronic, stable coronary artery disease and preserved left ventricular systolic function. The patients will be submitted to two sequential exercise tests with 30-minutes interval between them. Ischemic parameters will be compared between diabetic and non-diabetic patients. Ischemic preconditioning will be considered present when time to 1.0 mm ST-segment deviation is greater in the second of two sequential exercise tests. Exercise tests will be analyzed by two independent cardiologists.

DISCUSSION

Ischemic preconditioning was first demonstrated by Murry et al. in dog's hearts. Its work was reproduced by other authors, clearly demonstrating that brief periods of myocardial ischemia followed by reperfusion triggers cardioprotective mechanisms against subsequent and severe ischemia. On the other hand, the demonstration of ischemic preconditioning in humans requires the presence of clinical symptoms or physiological changes difficult to be measured. One methodology largely accepted are the sequential exercise tests, in which, the improvement in the time to 1.0 mm ST depression in the second of two sequential tests is considered manifestation of ischemic preconditioning.Diabetes is an important and independent determinant of clinical prognosis. It's a major risk factor for coronary artery disease. Furthermore, the association of diabetes with stable coronary artery disease imposes worse prognosis, irrespective of treatment strategy. It's still not clearly known the mechanisms responsible by these worse outcomes. Impairment in the mechanisms of ischemic preconditioning may be one major cause of this worse prognosis, but, in the clinical setting, this is not known. The present study aims to evaluate how diabetes mellitus interferes with ischemic preconditioning in patients with stable, multivessel coronary artery disease and preserved systolic ventricular function.

Hypotheses, rationale, design, and methods for prognostic evaluation of cardiac biomarker elevation after percutaneous and surgical revascularization in the absence of manifest myocardial infarction. A comparative analysis of biomarkers and cardiac magnetic resonance. The MASS-V Trial

BACKGROUND

Although the release of cardiac biomarkers after percutaneous (PCI) or surgical revascularization (CABG) is common, its prognostic significance is not known. Questions remain about the mechanisms and degree of correlation between the release, the volume of myocardial tissue loss, and the long-term significance. Delayed-enhancement of cardiac magnetic resonance (CMR) consistently quantifies areas of irreversible myocardial injury. To investigate the quantitative relationship between irreversible injury and cardiac biomarkers, we will evaluate the extent of irreversible injury in patients undergoing PCI and CABG and relate it to postprocedural modifications in cardiac biomarkers and long-term prognosis.

METHODS/DESIGN

The study will include 150 patients with multivessel coronary artery disease (CAD) with left ventricle ejection fraction (LVEF) and a formal indication for CABG; 50 patients will undergo CABG with cardiopulmonary bypass (CPB); 50 patients with the same arterial and ventricular condition indicated for myocardial revascularization will undergo CABG without CPB; and another 50 patients with CAD and preserved ventricular function will undergo PCI using stents. All patients will undergo CMR before and after surgery or PCI. We will also evaluate the release of cardiac markers of necrosis immediately before and after each procedure. Primary outcome considered is overall death in a 5-year follow-up. Secondary outcomes are levels of CK-MB isoenzyme and I-Troponin in association with presence of myocardial fibrosis and systolic left ventricle dysfunction assessed by CMR.

DISCUSSION

The MASS-V Trial aims to establish reliable values for parameters of enzyme markers of myocardial necrosis in the absence of manifest myocardial infarction after mechanical interventions. The establishments of these indices have diagnostic value and clinical prognosis and therefore require relevant and different therapeutic measures. In daily practice, the inappropriate use of these necrosis markers has led to misdiagnosis and therefore wrong treatment. The appearance of a more sensitive tool such as CMR provides an unprecedented diagnostic accuracy of myocardial damage when correlated with necrosis enzyme markers. We aim to correlate laboratory data with imaging, thereby establishing more refined data on the presence or absence of irreversible myocardial injury after the procedure, either percutaneous or surgical, and this, with or without the use of cardiopulmonary bypass.