A simple MR algorithm for estimation of myocardial salvage following acute ST segment elevation myocardial infarction

Reduction of QTD--A Novel Marker of Successful Reperfusion in NSTEMI. Pathophysiologic Insights by CMR

BACKGROUND/OBJECTIVES

Non-ST segment elevation myocardial infarction (MI) poses similar detrimental long-term prognosis as ST-segment elevation MI. No marker on ECG is established to predict successful reperfusion in NSTEMI. QT dispersion is increased by myocardial ischemia and reduced by successful restoration of epicardial blood flow by PCI. Whether QT dispersion reduction translates to smaller infarcts and thus indicates successful reperfusion is unknown. We hypothesized that the relative reduction of QT dispersion (QTD-Rrel ) on a standard ECG in acutely reperfused NSTEMI is related to infarct size and infarct transmurality as assessed by delayed enhancement CMR (DE-CMR).

METHODS AND RESULTS

69 patients with a first acute NSTEMI were included. QTD-Rrel was stratified according to LV function and volumes, infarct transmurality and size as assessed by DE-CMR. Extensive myocardial infarction was defined as above median infarct size. LV function and end-systolic volume were only mildly related to QTD-Rrel . QTD-Rrel was inversely related to infarct size (r=-0.506,p=0.001) and infarct transmurality (r=-0.415, p=0.001). QTD-Rrel was associated with extensive myocardial infarction in univariate analysis (odds ratio (OR) 0.958, CI 0.935-0.982; p=0.001). Compared to clinical and angiographic data QTD-Rrel remained the only independent predictor of non-transmural infarcts (OR 1.110, CI 1.055-1.167; p=0.049).

CONCLUSION

In patients with acute Non-ST-Segment Myocardial infarction QTd-Rrel calculated on a surface ECG prior and post PCI for restoration of epicardial blood flow detects small, non-transmural infarcts as assessed by delayed enhancement CMR. Thus, QTd-Rrel can indicate successful reperfusion therapy.

Sham surgery and inter-individual heterogeneity are major determinants of monocyte subset kinetics in a mouse model of myocardial infarction

Aims

Mouse models of myocardial infarction (MI) are commonly used to explore the pathophysiological role of the monocytic response in myocardial injury and to develop translational strategies. However, no study thus far has examined the potential impact of inter-individual variability and sham surgical procedures on monocyte subset kinetics after experimental MI in mice. Our goal was to investigate determinants of systemic myeloid cell subset shifts in C57BL/6 mice following MI by developing a protocol for sequential extensive flow cytometry (FCM).

Methods and Results

Following cross-sectional multiplex FCM analysis we provide for the first time a detailed description of absolute quantities, relative subset composition, and biological variability of circulating classical, intermediate, and non-classical monocyte subsets in C57BL/6 mice. By using intra-individual longitudinal measurements after MI induction, a time course of classical and non-classical monocytosis was recorded. This approach disclosed a significant reduction of monocyte subset dispersion across all investigated time points following MI. We found that in the current invasive model of chronic MI the global pattern of systemic monocyte kinetics is mainly determined by a nonspecific inflammatory response to sham surgery and not by the extent of myocardial injury.

Conclusions

Application of sequential multiplexed FCM may help to reduce the impact of biological variability in C57BL/6 mice. Furthermore, the confounding influence of sham surgical procedures should always be considered when measuring monocyte subset kinetics in a murine model of MI.

T2-weighted cardiac MR assessment of the myocardial area-at-risk and salvage area in acute reperfused myocardial infarction: comparison of state-of-the-art dark blood and bright blood T2-weighted sequences

PURPOSE

To compare different state-of-the-art T2-weighted (T2w) imaging sequences combined with late gadolinium enhancement (LGE) for myocardial salvage area (MSA) assessment by cardiac magnetic resonance (CMR). T2w imaging has been used to assess the myocardial area at risk (AAR) in acute myocardial infarction (AMI) patients, but its clinical application is challenging due to technical and physical limitations.

MATERIALS AND METHODS

Thirty patients with reperfused AMI underwent complete CMR imaging 2-5 days after hospital admission. Myocardial AAR and MSA were quantified on four different T2w sequences: (a) free-breathing T2-prepared single-shot balanced steady-state free precession (T2p_ssbSSFP); (b) breathhold T2-weighted acquisition for cardiac unified T2 edema (ACUTE); (c) breathhold T2w dark-blood inversion recovery turbo-spin echo (IR-TSE) (short-term inversion recovery: STIR); and (d) free-breathing high-resolution T2 dark-blood navigated BLADE. The diagnostic performance of each technique was also assessed.

RESULTS

Quantitative analysis showed significant differences in myocardial AAR extent as quantified by the four T2w sequences (P < 0.05). There were also significant differences in sensitivity, specificity and overall diagnostic performance.

CONCLUSION

Detection and quantification of AAR, and thus of MSA, by T2wCMR in reperfused AMI patients varied significantly between different T2w sequences in the same clinical setting.

Impact of hyperglycemia at admission in patients with acute ST-segment elevation myocardial infarction as assessed by contrast-enhanced MRI

BACKGROUND

Blood glucose level at admission in ST-segment elevation myocardial infarction (STEMI) is a predictor of heart failure and mortality. This study was performed to investigate the impact of hyperglycemia at admission in non-diabetic patients on infarct size, microvascular obstruction, and long-term outcome using contrast-enhanced magnetic resonance imaging (CMR) in patients with acute STEMI.

METHODS

One hundred and seven consecutive patients (84 males; mean age 59.4 years ± 11.3 years) with a first acute STEMI successfully treated by primary PCI were included. Admission hyperglycemia was defined as blood glucose above 7.8 mmol/l. CMR was performed 3.6 days ± 1.9 days after admission on a 1.5-tesla MR system. The imaging protocol included single-shot steady-state free precession (SSFP) cine sequences for assessing segmental and global left ventricular (LV) function and microvascular obstruction (MVO)/late gadolinium enhancement (LGE) imaging immediately and 10 min after the administration of 0.2 mmol gadodiamide/kg of body weight using an inversion-recovery SSFP (IR-SSFP) sequence. A receiver operating characteristics analysis was used to detect the best cut-off point of microvascular obstruction that predicted myocardial infarction and death during follow-up.

RESULTS

Of 107 patients, 37 (35%) had hyperglycemia on admission. Compared to normoglycemic patients, patients with admission hyperglycemia had a lower LV ejection fraction (38.6 ± 13.7% vs. 47.5 ± 12.2%, p < 0.001), greater ESV (88.8 ± 41.8 ml vs. 72.3 ml ± 35.1 ml, p = 0.01), greater infarct size (LGE% 21.1 ± 14.9% vs. 9.8 ± 8.7%, p < 0.001), and greater MVO (MVO% 9.6 ± 9.9% vs. 2.5 ± 4.3%, p < 0.001). Admission hyperglycemia was an independent predictor of the presence and extent of microvascular obstruction. Microvascular obstruction as a percentage of left ventricular mass was the only variable independently related to clinical outcome in a Cox proportional hazard model (Wald 18.78, HR 1.155, p < 0.001).

CONCLUSION

Hyperglycemia at admission in STEMI patients who are successfully treated by PCI is independently associated with the presence and extent of microvascular obstruction on contrast-enhanced CMR. Thus, microvascular obstruction as assessed by CMR may be a mechanism that relates admission hyperglycemia in acute STEMI to worse outcome.

T2-weighted cardiovascular magnetic resonance in acute cardiac disease

Cardiovascular magnetic resonance (CMR) using T2-weighted sequences can visualize myocardial edema. When compared to previous protocols, newer pulse sequences with substantially improved image quality have increased its clinical utility. The assessment of myocardial edema provides useful incremental diagnostic and prognostic information in a variety of clinical settings associated with acute myocardial injury. In patients with acute chest pain, T2-weighted CMR is able to identify acute or recent myocardial ischemic injury and has been employed to distinguish acute coronary syndrome (ACS) from non-ACS as well as acute from chronic myocardial infarction.T2-weighted CMR can also be used to determine the area at risk in reperfused and non-reperfused infarction. When combined with contrast-enhanced imaging, the salvaged area and thus the success of early coronary revascularization can be quantified. Strong evidence for the prognostic value of myocardial salvage has enabled its use as a primary endpoint in clinical trials. The present article reviews the current evidence and clinical applications for T2-weighted CMR in acute cardiac disease and gives an outlook on future developments."The principle of all things is water"Thales of Miletus (624 BC - 546 BC).

Diagnosis of early myocarditis after respiratory or gastrointestinal tract viral infection: insights from cardiovascular magnetic resonance

Background

The diagnosis of myocarditis continues to be a challenging task in clinical practice. The purpose of our study was to investigate cardiovascular magnetic resonance imaging in the diagnostic workup of ambulatory patients with the suspicion of early myocarditis after respiratory or gastrointestinal tract viral infection. The need for accurate diagnosis of early myocarditis arises from the low diagnostic accuracy of routine clinical tests.

Methods

We examined 67 consecutive patients with symptoms of weakness, palpitations, and fatigue after respiratory or gastrointestinal tract infection. We compared these patients to 31 controls. ECG-triggered, T2-weighted, fast-spin-echo triple inversion recovery sequences and delayed enhancement imaging were obtained in all patients, as well as functional parameters of left ventricular function and dimensions. In addition, in 25 patients and 10 controls, ECG-triggered, T1-weighted, multi-slice spin-echo images were obtained in axial orientation.

Results

We found a significant difference between patients with suspected myocarditis and controls in T2-global myocardial signal intensity. In addition, the ratio of global myocardial signal intensity/muscle signal intensity was 2.3 ± 0.4 in patients and 1.8 ± 0.3 in controls, which was highly significant (p < 0.001). In 23 patients, a pathological late enhancement pattern was seen, but only in one of the controls. There was no significant difference in T1-signal parameters.

Conclusion

Cardiovascular magnetic resonance technique is able to detect early myocardial involvement after respiratory or gastrointestinal tract infection.

Visualization of transcoronary ablation of septal hypertrophy in patients with hypertrophic obstructive cardiomyopathy: a comparison between cardiac MRI, invasive measurements and echocardiography

Objective

Hypertrophic obstructive cardiomyopathy (HOCM) is treated by surgical myectomy or transcoronary ablation of septal hypertrophy (TASH). The aim of this study was to visualize the feasibility, success and short-term results of TASH on the basis of cardiac MRI (CMR) in comparison with cardiac catheterization and echocardiography.

Methods

In this in vivo study, nine patients with HOCM were treated with TASH. Patients were evaluated by transthoracic echocardiography, invasive cardiac angiography and CMR. Follow-up examinations were carried out after 1, 3 and 12 months. MR imaging was performed on a 1.5-T scanner. All images were processed using the semiautomatic Argus software and were evaluated by an attending thoracic radiologist and cardiologist.

Results

The echocardiographic pressure gradient (at rest) was 69.3 ± 15.3 mmHg before and 22.1 ± 5.7 mmHg after TASH (P < 0.01, n = 9). The flux acceleration over the aortic valve examined (V_max) was 5.1 ± 0.6 m/s before and 3.4 ± 0.3 m/s after the TASH procedure (P < 0.05). Also, there was a decrease of septum thickness from 22.0 ± 1.2 to 20.2 ± 1.0 mm (P < 0.05) after 6 ± 3 weeks. The invasively assessed pressure gradient at rest was reduced from 63.7 ± 15.2 to 21.2 ± 11.1 mmHg (P < 0.01) and the post-extrasystolic gradient was reduced from 138.9 ± 12.7 to 45.6 ± 16.5 mmHg (P < 0.01). All differences as well as the quantity of injected ethanol were plotted against the size or amount of scar tissue as assessed in the MRI. There was a statistically significant correlation between the post-extrasystolic gradient decrease and the amount of scar tissue (P = 0.03, r² = 0.5). In addition, the correlation between the quantity of ethanol and scar tissue area was highly significant (P < 0.01, r² = 0.6), whereas the values for the gradient deviation (P = 0.10, r² = 0.34), ΔV_max (P = 0.12, r² = 0.31), as well as the gradient at rest (P = 0.27, r² = 0.17) were not significant.

Conclusion

TASH was consistently effective in reducing the gradient in all patients with HOCM. In contrast to the variables investigated by echocardiography, the invasively measured post-extrasystolic gradient correlated much better with the amount of scar tissue as assessed by CMR. We conclude that the optimal modality to visualize the TASH effect seems to be a combination of CMR and the invasive identification of the post-extrasystolic gradient.