Nigel J. Artis

Left ventricular wall segment motion after ultra-endurance exercise in humans assessed by myocardial speckle tracking

AIMS Assessment of the left ventricular responses to prolonged exercise has been limited by technology available to assess cardiac tissue movement. Recently developed strain and strain rate imaging provide the unique opportunity to assess tissue deformation in all planes of motion. METHODS AND RESULTS Nineteen runners (mean+/-SD age; 41+/-9 years) were assessed prior to and within 60 min (34+/-10 min) of race finish (Comrades Marathon, 89 km). Standard echocardiography assessed ejection fraction and the ratio of early to atrial (E/A) peak transmitral blood flow velocities. Myocardial speckle tracking determined segmental strain as well as systolic and diastolic strain rates in radial, circumferential, and longitudinal planes. Cardiac troponin T (cTnT) assessed cardiomyocyte insult. Ejection fraction (71+/-5 to 64+/-6%) and E/A (1.47+/-0.35 to 1.25+/-0.30) were reduced (P<0.05). Peak strain and peak systolic and diastolic strain rates were altered post-race in circumferential (e.g. peak strain reduced from 21.3+/-2.4 to 17.3+/-3.2%, P<0.05) and radial planes. Some individual heterogeneity was observed between segments and planes of motion. A post-race elevation in cTnT (range 0.013-0.272 microg/L) in 5/12 runners did not differentiate changes in LV function. CONCLUSION Completion of the Comrades Marathon resulted in a depression in ejection fraction, E/A, as well as radial and circumferential strain and strain rates. Group data, however, masked some heterogeneity in cardiac function.

Timing of Cardiovascular MR Imaging after Acute Myocardial Infarction: Effect on Estimates of Infarct Characteristics and Prediction of Late Ventricular Remodeling

PURPOSE To define the evolution of infarct characteristics with cardiovascular magnetic resonance (MR) imaging and to assess which of the cardiovascular MR data acquired at day 2 or at 1 week after acute myocardial infarction (AMI), is the stronger predictor of infarct size and left ventricular (LV) function measured at 3 months. MATERIALS AND METHODS The study protocol was reviewed and approved by the local research ethics committee, and written informed consent was obtained. Forty-eight patients with reperfused AMI underwent cine, T2-weighted, and late gadolinium enhancement cardiovascular MR imaging at days 2, 7, 30, and 90 after index presentation. Continuous data between times were compared by using paired t tests or one-way analysis of variance. Multiple linear regression analyses were used to predict linear end points. RESULTS Infarct size and extent of myocardial edema decreased significantly between day 2 and 1 week: Mean scar as a percentage of LV mass and standard deviation (SD), respectively, were 27.2 and 13.9 versus 21.6 and 14.1 (P < .001), and myocardial edema as a percentage of LV mass and SD, respectively, were 37.9 and 15.2 versus 32.3 and 14.3 (P = .003). These changes were accompanied by a significant improvement in LV ejection fraction (LVEF): Mean percentage of LVEF and SD, respectively, were 41.7 and 9.6 versus 44.6 and 10.1 (P < .001). When comparing data acquired at day 2 and 1 week, only cardiovascular MR data acquired at 1 week were independent predictors of LVEF and infarct size at 3 months. CONCLUSION LVEF, infarct size, and extent of myocardial edema changed significantly during the 1st week after AMI. Overall, cardiovascular MR measurements acquired after 1 week have greater predictive value for infarct size and LV function at 3 months than data acquired at day 2.

Interpretation of two-dimensional and tissue Doppler-derived strain ( ε ) and strain rate data: is there a need to normalize for individual variability in left ventricular morphology?

AIMS This study examined the relationships between myocardial strain (epsilon) and strain rate (SR) data, derived from both two-dimensional (2D) speckle tracking and tissue Doppler imaging (TDI), and indices of left ventricular (LV) morphology to assess size-(in)dependence of these functional parameters. METHODS AND RESULTS 2D speckle tracking and TDI echocardiograms were performed in 79 healthy adult male volunteers (age range: 22-76 years). 2D speckle tracking allowed the determination of myocardial epsilon and peak systolic and early diastolic SR in radial, circumferential, and longitudinal planes, whereas TDI provided longitudinal epsilon only. Mean circumferential and radial epsilon and SR were calculated from data collected at six basal myocardial regions, whereas mean longitudinal epsilon and SR derived from both 2D speckle tracking and TDI were calculated from the basal septum and basal lateral walls. Standard 2D echocardiography allowed the assessment of LV morphology including LV length, LV end-diastolic volume, LV end-diastolic diameter, mean wall thickness, and LV mass. The association of myocardial epsilon and SR data with relevant LV morphology indices was determined by adoption of the general, non-linear allometric model (y= ax(b)). The b exponent +/- 95% confidence intervals were reported. The relationships between the measures of LV morphology and myocardial epsilon and SR were highly variable and generally weak. Only two relationships displayed at least a moderate effect size (r > or = 0.30): (i) 2D circumferential peak systolic SR and LV end-diastolic dimension (b = -0.92; -1.35 to 0.5, r = 0.44) and (ii) TDI longitudinal peak systolic SR and LV length (b = -1.39; -2.11 to -0.66, r = 0.41). CONCLUSION The empirical relationships derived in this cohort do not support the need to scale myocardial epsilon and SR derived from 2D speckle or TDI for any index of LV morphology.

Diagnostic Value of CMR in Patients With Biomarker-Positive Acute Chest Pain and Unobstructed Coronary Arteries

the universal definition of myocardial infarction requires an elevated troponin value exceeding the 99th percentile of the upper reference limit (URL) together with at least 1 of the following: symptoms of ischemia; electrocardiogram (ECG) changes of new ischemia; development of pathological Q-waves

Short-Axis 2D Strain from Speckle Tracking Predicts Echocardiographic Response to Cardiac Resynchronization Therapy

Aims: Two‐dimensional (2D) strain imaging from speckle tracking is a Doppler independent technique allowing assessment of left ventricular (LV) strain (ɛ); systolic strain rate (SRs’) and early diastolic strain rate (SRe’) in the radial and circumferential planes. We set out to investigate whether (i) these parameters facilitated assessment of dyssynchronous contraction and (ii) these measures could predict response to cardiac resynchronization therapy (CRT). Methods and Results: Forty‐one patients with severe, symptomatic heart failure on optimal medical therapy were recruited. Thirty‐two healthy subjects were used as controls. Time to peak ɛ, SRs’, and SRe’ of 6 LV segments were measured in the parasternal short axis prior to and 6 weeks post CRT implantation. Time delays between segments were then calculated and ANOVA assessed for prediction of response, classified as reduction in LV end systolic volume of >15%. 2D strain demonstrated significantly more dyssynchronous contraction in the heart failure population at baseline compared to healthy controls. Significant reduction in dyssynchrony was seen in ɛ and SRs’ following CRT, largely confined to those with evidence of remodeling. The time delay between peak circumferential SRs’ of opposing walls was the best predictor of reverse remodeling. Conclusion: 2D strain imaging appears to be a useful measure to predict response to CRT. The time to peak circumferential SR is a new predictor of response. (Echocardiography 2011;28:76‐84)

Percutaneous Closure of Postinfarction Ventricular Septal Defect: Cardiac Magnetic Resonance-Guided Case Selection and Postprocedure Evaluation

Despite modern surgical techniques, complications and early mortality remain high following postinfarction ventricular septal defect (VSD) repair. It is now possible to close these acquired defects percutaneously using, for example, the Amplatzer postinfarct muscular VSD device. Cardiovascular magnetic resonance is an important tool in determining appropriate case selection and device sizing as it can provide a multicomponent assessment of the VSD anatomy, ventricular volumes and function, infarct extent, and left-to-right shunt calculations.

Timing of cardiovascular magnetic resonance imaging after acute myocardial infarction: effect on estimates of infarct characteristics and prediction of late ventricular remodelling

Cardiovascular Magnetic Resonance (CMR) permits a comprehensive assessment of infarct characteristics following acute myocardial infarction (AMI). The pathophysiological remodelling processes associated with AMI evolve over time and as such, the optimal acute imaging time point to predict medium-term surrogates for outcome has not been established.

Cardiac magnetic resonance imaging of a patient with an magnetic resonance imaging conditional permanent pacemaker

Cardiac magnetic resonance imaging (MRI) is increasingly used as the optimum modality for cardiac imaging. An aging population and rising numbers of patients with permanent pacemakers means many such individuals may require cardiac MRI scanning in the future. Whilst the presence of a permanent pacemaker is historically regarded as a contra-indication to MRI scanning, pacemaker systems have been developed to limit any associated risks. No reports have been published regarding the use of such devices with cardiac MRI in a clinical setting. We present the safe, successful cardiac MRI scan of a patient with an MRI-conditional permanent pacing system.

Investigation of the change in myocardial blood flow by perfusion CMR after revascularisation of chronically occluded coronary arteries.

The perceived clinical benefits of undertaking revascularisation to coronary artery chronic total occlusions (CTO) relate to improvements in angina symptoms and prognosis1,2. Long term survival benefits from CTO revascularisation has been suggested in several large observational studies despite a significant failure rate1,3. Data about the physiological consequences of successful opening of a CTO are limited and heterogeneous4. CMR imaging can provide quantitative information on MBF (myocardial blood flow) in this context.

127 Timing of cardiovascular MRI after acute myocardial infarction: effect on estimates of infarct characteristics and prediction of late ventricular remodelling

Background The pathophysiological remodelling processes associated with acute myocardial infarction (AMI) evolve over time and the optimal acute imaging time point to predict medium-term surrogates for outcome has not been established. This study aimed to define the evolution of infarct characteristics by cardiovascular magnetic resonance (CMR), and to assess whether CMR data acquired at “day 2” or at “1 week” post-AMI are stronger predictors of infarct size and left ventricular (LV) function measured at 3 months. Methods Fifty-seven patients were recruited with first presentation ST elevation AMI treated successfully with primary percutaneous coronary intervention. Cine, T2- weighted and late gadolinium enhancement CMR imaging were performed at days 2, 7, 30 and 90 after index presentation. Results Infarct size and extent of myocardial oedema decreased significantly between “day 2” and “1 week” (mean %LV-scar (SD) 27.2 (13.9) vs 21.6 (14.1), p<0.001 and %LV-AAR (Area At Risk) (SD), 37.9 (15.2) vs 32.3 (14.3), p=0.003). These changes were accompanied by a significant improvement in LV ejection fraction (%LVEF (SD), 41.7 (9.6) vs 44.6 (10.1), p<0.001). CMR data acquired at “1 week” were better predictors of LVEF and infarct size at “3 months” than data collected at “day 2”. Conclusions The extent of myocardial oedema and infarct size decrease significantly during the first week after reperfusion for AMI and these changes are associated with a significant improvement in LVEF over the same interval. These findings have implications for the timing of CMR studies in the early post-infarct period. We found that the percentage myocardial salvage index did not change significantly between “day 2” and “1 week”. Therefore, accurate assessment of the efficacy of reperfusion therapy can be made up to one week after revascularization. In addition, CMR data acquired at “1 week” were better predictors of CMR endpoints measured at “3 months”. Thus, we conclude that the optimal time point to image patients post-reperfusion therapy for AMI is at 1 week.