Bjørnar Grenne

Diagnostic Capability and Reproducibility of Strain by Doppler and by Speckle Tracking in Patients With Acute Myocardial Infarction

OBJECTIVES The objective of the present study was to investigate the ability of strain by Doppler and by speckle tracking echocardiography in the acute phase in patients with ST-segment elevation myocardial infarction (STEMI) to diagnose left ventricular (LV) infarct size. Furthermore, we wanted to study at which time during the cardiac cycle strain should be measured. BACKGROUND The assessment of regional myocardial dysfunction may be an important diagnostic tool in the evaluation of acute myocardial injury. METHODS Strain by Doppler and speckle tracking were assessed in the acute phase and after 10 days in 36 patients (61 +/- 11 years) with STEMI treated with thrombolysis. In a 16-segment model of the LV, peak systolic, end systolic, and peak negative strain were validated against the corresponding myocardial segments measured by contrast-enhanced cardiac magnetic resonance. The 16 segments were averaged to assess LV global longitudinal strain. In addition, 6 segments were analyzed from parasternal short-axis recordings at the papillary muscle level to assess circumferential strain. Reproducibility was tested in 20 patients. RESULTS The different segmental strain assessments separated significantly (p < 0.0001) between the different levels of infarct transmurality regardless of method, with better reproducibility for speckle strain. Circumferential strain separated better than longitudinal strain. With a cutoff value of -13.3% for segmental circumferential strain, sensitivity was 80% and specificity was 74% for prediction of transmural infarction. The LV global strain showed a good correlation with LV infarct size, with the best correlation for LV global peak systolic speckle strain (beta = 0.76, p < 0.0001). CONCLUSIONS On a segmental level, circumferential strain separated transmural from subendocardial necrosis better than longitudinal strain in the acute phase in patients with STEMI. Our findings suggest that in the acute phase in patients treated with thrombolysis, LV global peak systolic speckle strain should be the preferred method for predicting final LV infarct size.

Strain Echocardiography Improves Risk Prediction of Ventricular Arrhythmias After Myocardial Infarction

OBJECTIVES The aim of this study was to test the hypothesis that strain echocardiography might improve arrhythmic risk stratification in patients after myocardial infarction (MI). BACKGROUND Prediction of ventricular arrhythmias after MI is challenging. Left ventricular ejection fraction (LVEF) <35% is the main parameter for selecting patients for implantable cardioverter-defibrillator therapy. METHODS In this prospective, multicenter study, 569 patients >40 days after acute MI were included, 268 of whom had ST-segment elevation MIs and 301 non-ST-segment elevation MIs. By echocardiography, global strain was assessed as average peak longitudinal systolic strain from 16 left ventricular segments. Time from the electrocardiographic R-wave to peak negative strain was assessed in each segment. Mechanical dispersion was defined as the standard deviation from these 16 time intervals, reflecting contraction heterogeneity. RESULTS Ventricular arrhythmias, defined as sustained ventricular tachycardia or sudden death during a median 30 months (interquartile range: 18 months) of follow-up, occurred in 15 patients (3%). LVEFs were reduced (48 ± 17% vs. 55 ± 11%, p < 0.01), global strain was markedly reduced (-14.8 ± 4.7% vs. -18.2 ± 3.7%, p = 0.001), and mechanical dispersion was increased (63 ± 25 ms vs. 42 ± 17 ms, p < 0.001) in patients with arrhythmias compared with those without. Mechanical dispersion was an independent predictor of arrhythmic events (per 10-ms increase, hazard ratio: 1.7; 95% confidence interval: 1.2 to 2.5; p < 0.01). Mechanical dispersion and global strain were markers of arrhythmias in patients with non-ST-segment elevation MIs (p < 0.05 for both) and in those with LVEFs >35% (p < 0.05 for both), whereas LVEF was not (p = 0.33). A combination of mechanical dispersion and global strain showed the best positive predictive value for arrhythmic events (21%; 95% confidence interval: 6% to 46%). CONCLUSIONS Mechanical dispersion by strain echocardiography predicted arrhythmic events independently of LVEF in this prospective, multicenter study of patients after MI. A combination of mechanical dispersion and global strain may improve the selection of patients after MI for implantable cardioverter-defibrillator therapy, particularly in patients with LVEFs >35% who did not fulfill current implantable cardioverter-defibrillator indications.

Acute coronary occlusion in non-ST-elevation acute coronary syndrome: outcome and early identification by strain echocardiography

Objectives To compare infarct size and left ventricular ejection fraction in patients with non-ST-elevation myocardial infarction (NSTEMI) with and without acute coronary occlusions, and determine if myocardial strain by speckle-tracking echocardiography can identify acute occlusions in patients presenting with non-ST-elevation acute coronary syndrome (NSTE-ACS). Methods 111 patients with suspected NSTE-ACS were enrolled shortly after admittance. Echocardiographic measurements were performed a median of 1 h (interquartile range 0.5–4) after admittance, and coronary angiography 36±21 h after onset of symptoms. Territorial longitudinal and circumferential strain was calculated based on the perfusion territories of the three major coronary arteries in a 16-segment model of the left ventricle, and compared with traditional echocardiographic parameters. Long-term follow-up was by echocardiography and contrast-enhanced magnetic resonance imaging (ceMRI). Results Patients with NSTEMI due to acute coronary occlusion had higher peak troponin T than patients with NSTEMI without acute occlusions (4.9±4.7 vs 0.9±1.1 μg/l, p<0.001), larger infarct size by ceMRI (13±8% vs 3±3%, p<0.001) and poorer left ventricular ejection fraction (48±6% vs 57±6%, p<0.001) at follow-up. Territorial circumferential strain was the best parameter for predicting acute coronary occlusion. A territorial circumferential strain value >−10.0% had 90% sensitivity, 88% specificity and area under the curve=0.93 for identification of acute occlusions. Conclusions Patients with NSTEMI due to acute coronary occlusions develop larger infarcts and more impaired left ventricular function than patients with NSTEMI without occlusions, regardless of infarct-related territory. Territorial circumferential strain by echocardiography enables very early identification of acute coronary occlusions in patients with NSTE-ACS and may be used for detection of patients requiring urgent revascularisation.

Comparison of left ventricular ejection fraction and left ventricular global strain as determinants of infarct size in patients with acute myocardial infarction.

BACKGROUND The aim was to compare left ventricular ejection fraction (LVEF) and left ventricular (LV) global strain by speckle tracking as predictors of final infarct size. METHODS LV global strain and LVEF by echocardiography were assessed in the acute phase and after revascularization in 39 patients with ST-elevation myocardial infarction treated with thrombolysis. RESULTS After revascularization, global strain and LVEF correlated well with infarct size measured by contrast-enhanced cardiac magnetic resonance. A cutoff value of -15.0% for global strain had a sensitivity of 90% and a specificity of 86% to identify myocardial infarcts larger than 20%. Interobserver variability, expressed by intraclass correlation coefficients, for global strain and LVEF was 0.91 and 0.72, respectively. CONCLUSIONS LV global strain is a more precise diagnostic predictor of large infarcts compared with LVEF and is more reproducible. Global strain measured after revascularization demonstrates advantages over LVEF in the evaluation of LV injury in patients with ST-elevation myocardial infarction.

Strain Echocardiography and Wall Motion Score Index Predicts Final Infarct Size in Patients With Non–ST-Segment–Elevation Myocardial Infarction

Background—Infarct size is a strong predictor of mortality and major adverse cardiovascular events after myocardial infarction. Acute reperfusion therapy limits infarct size and improves survival, but its use has been confined to patients with ST-segment–elevation myocardial infarction. The purpose of this study was to assess the relationship between echocardiographic parameters of left ventricular (LV) systolic function obtained before revascularization and final infarct size in patients with non–ST-segment–elevation myocardial infarction, as well as the ability of these parameters to identify patients with substantial infarction. Methods and Results—Sixty-one patients with non–ST-segment–elevation myocardial infarction were examined by echocardiography immediately before revascularization, 2.1±0.6 days after hospitalization. LV systolic function was assessed by ejection fraction, wall motion score index, and circumferential, longitudinal, and radial strain in a 16-segment LV model. Global strain represents average segmental strain values. Infarct size was assessed after 9±3 months by late-enhancement MRI, as a percentage of total LV myocardial volume. A good correlation was found between infarct size and wall motion score index (r=0.74, P<0.001) and global longitudinal strain (r=0.68, P<0.001). Global longitudinal strain >−13.8% and wall motion score index >1.30 accurately identified patients with substantial infarction (≥12% of myocardium, n=13; area under the receiver operator curve, 0.95 and 0.92, respectively). Conclusions—Echocardiographic parameters of LV systolic function correlate to infarct size in patients with non–ST-segment–elevation myocardial infarction. Global longitudinal strain and wall motion score index are both excellent parameters to identify patients with substantial myocardial infarction, who may benefit from urgent reperfusion therapy.

Strain echocardiography predicts acute coronary occlusion in patients with non-ST-segment elevation acute coronary syndrome.

AIMS Patients with acute coronary occlusion may lack typical signs of myocardial infarction in the electrocardiogram. We tested the ability of different echocardiographic modalities to identify coronary occlusion by quantifying myocardial dysfunction in patients with non-ST-elevation acute coronary syndrome (NSTE-ACS). METHODS AND RESULTS One hundred and fifty patients were examined by echocardiography immediately prior to coronary angiography, 2.2 +/- 0.7 days (mean +/- SD) after hospitalization for a first NSTE-ACS. Thirty-three patients (22%) had acute coronary occlusion. These patients had impaired left ventricular function as ejection fraction was reduced (54.9 +/- 9.6 vs. 59.1 +/- 7.6%, P = 0.02). Regional myocardial function was assessed in a 16-segment model by two methods: longitudinal strain by speckle tracking echocardiography and wall motion score (WMS) by visual assessment. Patients with acute coronary occlusion had an increased number of adjacent dysfunctional segments. The median size of the dysfunctional area by strain was 7 [inter-quartile range (IQR) 4.5-9] vs. 2 (IQR 0-5) segments (P < 0.001). An area of >or=4 adjacent dysfunctional segments (strain greater than or equal to -14%) had the best ability to identify patients with acute coronary occlusion, with sensitivity 85% and specificity 70%. WMS demonstrated slightly less accuracy than strain. CONCLUSION Strain echocardiography identifies NSTE-ACS patients with acute coronary occlusion, who may benefit from urgent reperfusion therapy.

Postsystolic shortening is a strong predictor of recovery of systolic function in patients with non-ST-elevation myocardial infarction.

AIMS Differentiation between necrotic and viable myocardium is difficult in the setting of acute myocardial infarction (MI). Post-systolic shortening (PSS) has been proposed as a marker of recovery after revascularization, but has not previously been assessed in patients with NSTEMI prior to revascularization. In this study, we aimed to examine the relation between PSS and improvement of contractile function after successful revascularization. METHODS AND RESULTS Thirty-five patients with non-segment elevation MI and regional systolic dysfunction were examined immediately prior to revascularization, and at follow-up 9 ± 3 months after successful revascularization. Regional systolic function was assessed by speckle tracking echocardiography as regional strain, expressed as mean peak negative longitudinal strain in segments supplied by the culprit artery. Recovery of systolic function was assessed as the difference between regional strain at follow-up and baseline (ΔStrain). Post-systolic shortening was defined as shortening in diastole beyond minimum systolic length. By multivariate regression analysis, several other variables that may affect viability were also assessed. Post-systolic shortening was observed in 32 patients (91%), mean -1.9 ± 1.4%. Mean ΔStrain was -3.3 ± 2.9%. After adjustment for baseline systolic function, PSS (β = 0.77, P= 0.022), and angiographic severity were independent predictors of viability by multiple regression analysis. Interestingly, troponin T was not a significant predictor. CONCLUSIONS Post-systolic shortening is associated with improved myocardial function after revascularization in patients with acute MI. It predicts long-term systolic function, and provides information on the potential benefit of the procedure.

Early Assessment of Strain Echocardiography Can Accurately Exclude Significant Coronary Artery Stenosis in Suspected Non–ST-Segment Elevation Acute Coronary Syndrome

BACKGROUND Many patients with suspected non-ST-segment elevation acute coronary syndrome (NSTE-ACS) do not have significant coronary artery disease. The current diagnostic approach of repeated electrocardiography and cardiac biomarker assessment requires observation for >6 to 12 hours. This strategy places a heavy burden on hospital facilities. The objective of this study was to investigate whether myocardial strain assessment by echocardiography could exclude significant coronary artery stenosis in patients presenting with suspected NSTE-ACS. METHODS Sixty-four patients presenting to the emergency department with suspected NSTE-ACS without known coronary artery disease, inconclusive electrocardiographic findings, and normal cardiac biomarkers at arrival were enrolled. Twelve-lead electrocardiography, troponin T assay, and echocardiography were performed at arrival, and all patients underwent coronary angiography. Significant coronary stenosis was defined as >50% luminal narrowing. Global myocardial peak systolic longitudinal strain was measured using speckle-tracking echocardiography. Left ventricular ejection fraction and wall motion score index were calculated. RESULTS No significant stenosis in any coronary artery was found in 35 patients (55%). Global peak systolic longitudinal strain was superior to conventional echocardiographic parameters in distinguishing patients with and without significant coronary artery stenosis (area under the curve, 0.87). Sensitivity and specificity were calculated as 0.93 and 0.78, respectively, and positive predictive value and negative predictive value as 0.74 and 0.92, respectively. Feasibility of the strain measurements was excellent, with 97% of segments analyzed. CONCLUSIONS Myocardial strain by echocardiography may facilitate the exclusion of significant coronary artery stenosis among patients presenting with suspected NSTE-ACS with inconclusive electrocardiographic findings and normal cardiac biomarkers.

Mean strain throughout the heart cycle by longitudinal two-dimensional speckle-tracking echocardiography enables early prediction of infarct size.

BACKGROUND Early prediction of infarct size directs therapy in patients with acute myocardial infarction (AMI). Global strain by echocardiography describes myocardial deformation and correlates with infarct size. However, peak strain measures deformation at a single time point, whereas ischemia and necrosis influence deformation throughout the heart cycle. It was hypothesized that the measurement of myocardial deformation throughout the heart cycle by mean strain is a more comprehensive expression of myocardial deformation. The aim of this study was to assess the ability of mean strain to predict infarct size and to identify large infarctions at admission and after revascularization in patients with AMI. METHODS Seventy-six patients with AMI were included. Echocardiographic measurements were performed at admission and after revascularization. Myocardial strain was calculated using speckle-tracking echocardiography. Infarct size was measured using contrast-enhanced magnetic resonance imaging ≥3 months after revascularization. RESULTS There were significant correlations between infarct size and longitudinal global mean strain, longitudinal global strain, and left ventricular ejection fraction (P < .0001), both at admission and after revascularization. The correlations improved after revascularization. Longitudinal global mean strain had the best correlation with infarct size and the best ability to discriminate between different infarct size categories. At admission, a cutoff value of -7.6 had 89% sensitivity, 88% specificity, and an area under the receiver operating characteristic curve of 0.92 for the identification of large infarctions. Prediction of infarct size improved for all parameters after revascularization. CONCLUSIONS Longitudinal global mean strain provides improved early prediction of infarct size in patients with AMI compared with longitudinal global strain and left ventricular ejection fraction.

Are the guidelines for treatment of myocardial infarction complied with

BACKGROUND New guidelines recommend early invasive evaluation and treatment for most patients with acute myocardial infarction--including patients with myocardial infarction without ST elevation in the ECG. This study examines compliance with the new guidelines at Sørlandet Hospital Arendal. MATERIAL AND METHOD All patients admitted to Sørlandet Hospital Arendal with acute myocardial infarction in 2012 were registered in the Norwegian Myocardial Infarction Register. Data from the register were used to analyse the time that passed from symptom onset to coronary angiography and revascularisation. RESULTS In 2012, 788 patients were admitted to Sørlandet Hospital Arendal with acute myocardial infarction. Of these, 269 (34.1%) had ST elevation mycardial infarction (STEMI) and 519 (65.9%) had non-ST elevation myocardial infarction (NSTEMI). Most patients with ST elevation infarction (220 (81.8%)) were admitted directly to Sørlandet Hospital Arendal, and the median time from admission to revascularisation was 31 minutes. 347 (66.9%) of the patients with non-ST elevation infarction were first admitted to a local hospital before being transferred to Sørlandet Hospital Arendal. Only four (1.2%) of them underwent angiography within two hours of admission to the first hospital. 13 (9.0%) of the patients with non-ST elevation infarction who were admitted directly and underwent angiography (n = 144) had an angiogram within two hours of admission. Angiography was performed within 24 hours in 119 (34.3%) of those transferred (n = 347) and in 82 (56.9%) of the directly admitted patients who underwent angiography (n = 144). INTERPRETATION Many patients with non-ST elevation infarction did not receive revascularisation with percutaneous coronary intervention (PCI) within the recommended time frame. Where there is a strong clinical suspicion of acute myocardial infarction, more patients should be admitted directly to hospitals with PCI preparedness.