Assessment of ischemic myocardium by strain-rate imaging during adenosine stress echocardiography

The Systolic and Diastolic Cardiac Function of Patients With Type 2 Diabetes Mellitus: An Evaluation of Left Ventricular Strain and Torsion Using Conventional and Speckle Tracking Echocardiography

Objectives: This study aimed to quantify left ventricular (LV) myocardial strain and torsion in patients with type 2 diabetes mellitus (T2DM) and evaluate their systolic and diastolic function using conventional and speckle tracking echocardiography.

Methods: Forty-seven patients with T2DM were divided into a group without microvascular complications (the DM A group) and a group with microvascular complications (the DM B group), while another 27 healthy participants acted as the control group. All the participants had had an echocardiography examination. All the original data were imported into EchoPAC workstation for the analysis and quantification of LV strain and torsion.

Results: Compared with the control group, the LV end-diastolic volume, end-systolic volume, and ejection fraction of the DM A and DM B groups showed no significant differences, but the global longitudinal strain and the global circular strain were reduced in the DM B group. There were significant differences in the left ventricular relative wall thickness (RWT), left ventricular mass index (LVMI), the early mitral valvular blood flow velocity peak/left ventricular sidewall mitral annulus late peak velocity, left ventricular sidewall mitral annulus early peak velocity/left ventricular sidewall mitral annulus late peak velocity, isovolumic relaxation time, peak twisting, peak untwisting velocity (PUV), untwisting rate (UntwR), time peak twisting velocity (TPTV), and time peak untwisting velocity (TPUV) between the DM A, DM B, and control groups. While the peak twisting velocity (PTV) was slower in the DM B group compared with the control group, the RWT, PTV, PUV, UntwR, TPTV, and TPUV in the DM B group were significantly different from the DM A group.

Conclusion: The cardiac function of patients with T2DM in its early stages, when there are no microvascular complications, could be monitored with the analysis of two-dimensional strain and torsion.

13 N-ammonia PET-derived right ventricular longitudinal strain and myocardial flow reserve in right coronary artery disease

PURPOSE

We developed a feature-tracking algorithm for use with electrocardiography-gated high-resolution ¹³ N-ammonia positron emission tomography (PET) imaging, and we hypothesized it could be used to clarify the association between right ventricular (RV) longitudinal strain (LS) and right coronary artery (RCA) ischemia. The aim of this study was to investigate the association between the reduction of regional myocardial flow reserve (MFR) in RCA territories and PET-derived LS of the RV free wall.

METHODS

Ninety-three patients with coronary artery stenosis > 50%, diagnosed by coronary computed tomography angiography, and 10 controls were retrospectively analyzed. RV-LS in the free wall was measured by a feature-tracking technique on the resting and stressed ¹³ N-ammonia PET images of horizontal long axis slices. The patients were sub-grouped according to regional MFR values at the territories of RCA, left anterior descending artery (LAD), and left circumflex coronary artery (LCx): RCA-MFR < 2.0 [n = 34], RCA-MFR ≥ 2.0 but MFR < 2.0 at LAD or LCx territories [n = 11], and MFR ≥ 2.0 for all territories [n = 48]. Stress and resting RV-LS were compared in each of the four groups. Multiple comparisons of RV-LS among the four groups were performed in the stress and resting state.

RESULTS

Decreased stress RV-LS in patients with an RCA-MFR < 2.0 was observed. In the patients with MFR ≥ 2.0 for all territories, the stressed RV-LS was significantly increased compared to that in the resting state. Significantly decreased RV free wall LS during adenosine stress in patients with RCA-MFR < 2.0 was observed in the other three groups.

CONCLUSIONS

We measured RV myocardial LS using feature tracking in cine imaging of ¹³ N-ammonia PET. The results of this study suggest that PET-derived stressed RV-LS is useful for detecting reduced RV myocardial motion due to ischemia in the RCA territory.

Strain and strain rate: An emerging technology in the perioperative period

Newer noninvasive parameters are being used for perioperative detection of myocardial ischaemia. TDI and global strain rate are some of these parameters. TDI signal is a modification of the routine Doppler flow signal. It is obtained by using thresholding and filtering algorithms that reject echoes originating from the blood pool (by-passing the high pass filter). Set-Up of the machine by activating the TDI function allows decreasing the system gain using a low pass filter and eliminates the signal produced by blood flow. Doppler shift obtained from myocardial tissue motion are of higher amplitudes (reflectivity 40 dB higher) and move about 10 times slower than blood (velocity range: 0.06 to 0.24 m/s). Speckle tracking echocardiography (tissue tracking, 2D strain) utilizes routine gray-scale 2D echo images to calculate myocardial strain. Interactions of ultrasound with myocardium result in reflection and scattering. These interactions generate a finely gray-shaded, speckled pattern (acoustic marker). This speckled pattern is unique for each myocardial region and relatively stable throughout the cardiac cycle. Spatial and temporal image processing of acoustic speckles in both 2D and 3D allows for the calculation of myocardial velocity, strain, and Strain rate.

Temporal analysis of regional strain rate during adenosine triphosphate stress before and after percutaneous coronary interventions

Regional myocardial ischemia is thought to be characterized by diastolic dysfunction. We aimed to clarify whether temporal analysis of strain rate (SR) index derived from two-dimensional speckle-tracking echocardiography (2DTE) can assess the regional myocardial ischemia or not. Forty-two patients with significant coronary stenoses were referred for percutaneous coronary intervention (PCI). 2DTE was performed before and a day after PCI. Time from aortic valve closure to peak early diastolic longitudinal SR ∆(TAVC-E SR) was measured both at baseline and during adenosine triphosphate (ATP) infusion. TAVC-E SR was calculated as TAVC-E SR during ATP infusion subtracted by TAVC-E SR at baseline. In forty-five target ischemic regions, TAVC-E SR at baseline was significantly longer than that of control regions (166 ± 28 vs. 136 ± 32 ms, P < 0.0001). TAVC-E SR in target ischemic regions significantly prolonged during ATP stress to 221 ± 37 ms (P < 0.0001), while it did not change in control regions. Immediately after PCI, TAVC-E SR in target regions significantly decreased to 135 ± 27 ms, P < 0.0001 without prolongation during ATP stress. Receiver operating characteristic curves demonstrated that ∆TAVC-E SR could assess regional myocardial ischemia by a cutoff criterion of 14 ms with sensitivity of 93% and specificity of 95%. 2DTE-derived TAVC-E SR significantly increased during ATP stress only in ischemic myocardium. This phenomenon disappeared immediately after PCI. Temporal analysis of TAVC-E SR appeared to be useful to assess the regional myocardial ischemia.

Strain measurements during adenosine triphosphate infusion before and after percutaneous coronary intervention

BACKGROUND

In regional myocardial ischemia, contractile delay develops, which can be assessed by measuring time to peak strain (TPS) on tissue Doppler imaging. The aims of the present study were to clarify the usefulness of TPS measurements during adenosine triphosphate (ATP) stress in assessing myocardial ischemia and to evaluate whether prolongation of TPS disappears immediately after percutaneous coronary intervention (PCI) or not.

METHODS AND RESULTS

A total of 26 patients underwent strain measurements before and after PCI. Corrected TPS for heart rate (TPSc) in target regions and in control regions were measured both at baseline and during ATP infusion. TPSc ratio was calculated as a ratio of TPSc during ATP stress to TPSc at baseline. TPSc in the target region significantly increased during ATP infusion before PCI, which was significantly longer than hyperemic TPSc in control regions. Accordingly, TPSc ratio in the target regions before PCI was significantly greater than that in control regions (1.22+/-0.17 vs 0.96+/-0.09, respectively, P<0.0001). Following PCI, the TPSc ratio in the target regions significantly decreased to 0.98+/-0.05 (P<0.0001). Receiver operating characteristic curve analysis provided a cut-off of 1.04 in TPSc ratio for detecting myocardial ischemia with a sensitivity of 93% and specificity of 93%.

CONCLUSIONS

TPS measurements during ATP stress differentiated target from control myocardium before PCI. The prolongation of TPSc disappeared immediately after PCI.

Strain and strain rate imaging by echocardiography - basic concepts and clinical applicability

Echocardiographic strain and strain-rate imaging (deformation imaging) is a new non-invasive method for assessment of myocardial function. Due to its ability to differentiate between active and passive movement of myocardial segments, to quantify intraventricular dyssynchrony and to evaluate components of myocardial function, such as longitudinal myocardial shortening, that are not visually assessable, it allows comprehensive assessment of myocardial function and the spectrum of potential clinical applications is very wide. The high sensitivity of both tissue Doppler imaging (TDI) derived and two dimensional (2D) speckle tracking derived myocardial deformation (strain and strain rate) data for the early detection of myocardial dysfunction recommend these new non-invasive diagnostic methods for extensive clinical use. In addition to early detection and quantification of myocardial dysfunction of different etiologies, assessment of myocardial viability, detection of acute allograft rejection and early detection of allograft vasculopathy after heart transplantation, strain and strain rate data are helpful for therapeutic decisions and also useful for follow-up evaluations of therapeutic results in cardiology and cardiac surgery. Strain and strain rate data also provide valuable prognostic information, especially prediction of future reverse remodelling after left ventricular restoration surgery or after cardiac resynchronization therapy and prediction of short and median-term outcome without transplantation or ventricular assist device implantation of patients referred for heart transplantation.The Review explains the fundamental concepts of deformation imaging, describes in a comparative manner the two major deformation imaging methods (TDI-derived and speckle tracking 2D-strain derived) and discusses the clinical applicability of these new echocardiographic tools, which recently have become a subject of great interest for clinicians.

The quantification of dipyridamole induced changes in regional deformation in normal, stunned or infarcted myocardium as measured by strain and strain rate: an experimental study

Strain rate imaging (SRI) during dobutamine stress-echocardiography (DSE) has been shown to differentiate between ischemic substrates based on the segmental response. Dipyridamole stress echo (DIPSE) is currently used as an alternative to DSE in detecting coronary artery disease. The aim of this study was: (a) to determine the normal response in peak-systolic myocardial strain (S) and strain-rate (SR) during DIPSE and (b) to compare the S and SR responses of DSE and DIPSE in the same chronically ischemic/infarcted segments in the setting of single vessel disease.

METHODS

The deformation response to DIPSE was studied in 7 normal pigs and in an additional 18 pigs, with a spectrum of ischemic substrates. S and SR data were extracted from a posterior wall "at risk" segment at baseline and during both DSE and DIPSE. The animals were divided into different ischemic substrate (stunning, non-transmural and transmural infarction), based on the DSE response as previously suggested.

RESULTS

In normal myocardium, dipyridamole induced no changes in regional systolic deformation neither during nor after the infusion. Furthermore there was no detectable response in S and SR in segments with either a non-transmural or a transmural infarction. However, in myocardial segments with a DSE "stunning response", both end systolic S and peak-systolic SR tended to "normalize" at peak dipyridamole dose.

CONCLUSIONS

These results suggest that dipyridamole does not induce changes in regional deformation in normal or (partially) infarcted myocardium. Only in stunned myocardium (in the setting of single-vessel disease), dipyridamole tends to normalize deformation.