Tomoko Machino

Validation of 3-Dimensional Speckle Tracking Imaging to Quantify Regional Myocardial Deformation

Background—Three-dimensional speckle tracking imaging (3D-STI) has been introduced to assess regional left ventricular (LV) myocardial function. This study was designed to validate LV strain measurements by 3D-STI against data obtained by sonomicrometry. Methods and Results—In each of 10 anesthetized sheep, sonomicrometry crystals were implanted on the endocardium and epicardium at the LV basal, mid, and apical anterior and lateral walls. LV 3D-STI data sets were obtained from the apical approach at a frame rate of approximately 30 frames/s. Segmental longitudinal (LS), radial (RS), and circumferential strain (CS) measurements by 3D-STI were compared with those by sonomicrometry at baseline and during pharmacological stress tests (dobutamine and propranolol infusion) and acute myocardial ischemia induced by coronary artery occlusion. Data were available from 136 LS, 108 CS, and 175 RS measurements. Good correlations were observed between strain measurements by 3D-STI and those by sonomicrometry (LS: r=0.89, P<0.001; RS: r=0.84, P<0.001; CS: r=0.90, P<0.001). In each segmental study, significant correlations of the 3 strain components were observed (LS: r=0.65 to 0.68, P<0.001; RS: r=0.59 to 0.70, P<0.001; CS: r=0.71 to 0.78, P<0.001). Conclusions—The newly developed 3D-STI technique can estimate LV regional circumferential, longitudinal, and radial strain components with reasonable correlation to sonomicrometry data. This methodology could be applied clinically to assess alteration of myocardial function by accurately measuring strain in basal, mid, and apical LV segments, even during pharmacological and ischemic interventions. Therefore, 3D-STI appears to be a reliable tool to assess LV regional wall function.

Experimental validation of left ventricular transmural strain gradient with echocardiographic two-dimensional speckle tracking imaging

AIMS To validate intramural strain measured by a speckle tracking imaging (STI) system against that measured by sonomicrometry crystals. METHODS AND RESULTS In 11 anaesthetized sheep, six sets of three sonomicrometry crystals were implanted in endo-, mid-wall, and epimyocardium on the anterior and lateral walls. Circumferential strain (CS) was calculated at three layers from endo-, mid-wall, and epicardial speckle. Radial strain (RS) was assessed for inner and outer halves of the myocardium. We compared ultrasound-derived strain measurements against those by sonomicrometry at baseline and during pharmacological stress and coronary occlusion. Intraclass correlation coefficients at baseline and during coronary occlusion were as follows: endocardial CS 0.80, 0.97; mid-wall CS 0.58, 0.89; epicardial CS 0.71, 0.81; endocardial RS 0.50, 0.78; epicardial RS 0.35, 0.83; and total RS 0.33, 0.71; respectively. At baseline, endocardial strains were higher than mid-wall and epicardial strains, resulting in an inner/outer wall RS gradient and inner/mid/outer wall CS gradients. Ischaemia caused significant reduction in all strains and disappearance of the strain gradient. CONCLUSION A newly developed STI system can accurately assess the intramural heterogeneity of CS distribution in normal and ischaemic myocardial segments and has the potential to become a non-invasive bedside tool for characterizing myocardial strain gradient.

Analysis of the Left Atrial Appendage by Three-Dimensional Transesophageal Echocardiography

This study was designed to determine the ability and reliability of 3-dimensional (3D) transesophageal echocardiography (TEE) to assess the geometry and size of the left atrial appendage (LAA). Three-dimensional TEE may allow more accurate assessment of, and provide additional information on, LAA morphology compared to 2-dimensional TEE. Validation studies for LAA morphology data derived from 3D TEE were performed using 10 isolated porcine LAA specimens. Of 107 enrolled patients, 55 patients were in sinus rhythm (normal sinus rhythm), in whom 3D transesophageal echocardiographic images were obtained from full-volume mode imaging, and in 52 patients with atrial fibrillation, zoom-mode imaging was used. LAA orifice area, depth, and volume and the number of LAA lobes were assessed on reconstructed 3D imaging. Left atrial volume was calculated using 2-dimensional echocardiographic imaging. In experimental studies, excellent correlations (r >0.90, p <0.001) between the measurements by full-volume or zoom-mode imaging and reference data were observed in all parameters. The mean LAA orifice long diameter was 29.7 +/- 7.4 mm, the mean short diameter was 20.6 +/- 5.9 mm, the mean orifice area was 5.1 +/- 2.5 cm(2), the mean LAA depth was 38.5 +/- 8.2 mm, and the mean volume was 9.2 +/- 5.6 ml. The most frequent number of LAA lobes was 2 (n = 52), followed by 3 (n = 28), 1 (n = 18), and 4 (n = 3). Left atrial volume was weakly correlated with LAA orifice long diameter (r = 0.33, p = 0.001), short diameter (r = 0.40, p <0.001), area (r = 0.39, p <0.001), LAA depth (r = 0.21, p = 0.03), and volume (r = 0.36, p = 0.001). In conclusion, 3D TEE is a reliable modality to evaluate LAA geometry and provides detailed information to quantify varied LAA characteristics.

Mechanical Dyssynchrony Assessed by Speckle Tracking Imaging as a Reliable Predictor of Acute and Chronic Response to Cardiac Resynchronization Therapy

Speckle tracking echocardiography (STE) has the potential to detect the heterogeneous initiation of active myocardial contraction, which is the primary cause of left ventricular (LV) systolic dysfunction in patients with mechanical dyssynchrony. This study was designed to assess the ability to predict response to cardiac resynchronization therapy (CRT) of STE-derived dyssynchrony parameters in comparison with invasive hemodynamic assessments. Thirty patients referred for CRT were studied. The time difference of first peak (Td-(first peak)) and the maximum peak (Td-(max peak)) on the radial strain-time curves of the earliest and the latest segments were measured as the dyssynchrony parameter. Peak positive dP/dt (dP/dt(max)) was measured as the indicator of global LV systolic performance. CRT responders were defined as patients with LV end-systolic volume reduction greater than 15% at 3 months after CRT. CRT increased the dP/dt(max) compared with the baseline study (P < .001). Percent changes in the dP/dt(max) (dP/dt(max)) were significantly correlated with Td-(first peak) (R = 0.743, P < .001), but weakly correlated with Td-(max peak) (R = 0.390, P = .03). Twenty patients (66%) were identified as chronic CRT responders. Receiver operating characteristics analysis revealed that Td-(first peak) shared a similar ability with dP/dt(max) to detect chronic responders (Td-(first peak) >167.0 ms, area under the curve [AUC] 0.945; dP/dt(max) >16.2%, AUC 0.934) compared with Td-(max peak) (>194.5 ms, AUC 0.820). STE-derived Td-(first peak) showed a reliable ability to predict the acute and chronic response to CRT as well as dP/dt(max).

Analysis of the Origin of Cardiac Wall Motion that Constitutes Myocardial Velocity-Time Curves in Patients with Left Bundle Branch Block

Septal and lateral wall myocardial velocity-time curves from tissue Doppler imaging were analyzed to determine wall motion from which the velocity originated in 34 patients with left bundle branch and systolic dysfunction (ejection fraction < 45%). Longitudinal strain rate by speckle tracking imaging was assessed to identify whether corresponding wall motion was active or passive. All lateral peak velocities during the ejection period were derived from delayed active movement. However, septal peak velocities were more numerous and complex. Septal peak velocities during pre-ejection were derived from the first active movement in 29 patients (85.2%). Septal peak velocities during the ejection period were derived from the second active movement in 20 patients, passive movement in 9 patients, and first active movement in 5 patients. Because septal peak velocities were consistent with various wall motion types, identification of the origin of septal peak velocities, including during pre-ejection, may be important in identifying LV dyssynchrony based on the propagation of first active myocardial movements.

Prognostic impact of plaque echolucency in combination with inflammatory biomarkers on cardiovascular outcomes of coronary artery disease patients receiving optimal medical therapy

OBJECTIVE The incremental prognostic impact on cardiovascular outcomes of assessment of carotid plaque ultrasound characteristics in addition to inflammatory biomarkers remains controversial in coronary artery disease (CAD) patients receiving optimal medical treatment. The present study prospectively compared carotid ultrasonic imaging with several biomarkers to stratify cardiovascular risk. METHODS One hundred and sixty patients with angiographically confirmed stable CAD underwent carotid ultrasonography and were prospectively followed with optimal medical therapy including statins. Carotid atherosclerotic burden was assessed by mean intima-media thickness (IMT) at the far-wall from the common carotid to proximal internal carotid artery. Carotid plaque echolucency was quantified by measuring gray-scale median value (GSM). Major cardiovascular event was defined as cardiovascular death, newly developed myocardial ischemia, or cerebrovascular infarction. RESULTS Of 154 subjects completing follow-up, 27 experienced a major cardiovascular event during a median 41-month follow-up period. Events comprised cardiovascular death (n = 6), newly developed myocardial ischemia (n = 16), and ischemic stroke (n = 5). Univariate Cox regression analysis showed C-reactive protein (CRP) and several ultrasonic parameters to be significant determinants for cardiovascular events. Multivariate Cox analysis determined CRP and plaque echolucency to be independent variables predicting cardiovascular events after adjustment for classic CAD risk factors. In Kaplan-Meier plots, patients with both high CRP (≥ 1.0mg/L) and echolucent plaque (GSM ≤ 65) showed higher event rates than did patients with high CRP but without echolucent plaque. CONCLUSION Ultrasonic findings of echolucent carotid plaque may have incremental prognostic impact on risk assessment by CRP in CAD patients receiving contemporary optimal medical therapy.