Grading of myocardial dysfunction by tissue Doppler echocardiography: a comparison between velocity, displacement, and strain imaging in acute ischemia

Early diastolic strain rate in relation to long term prognosis following isolated coronary artery bypass grafting

BACKGROUND

The ratio of early mitral inflow velocity to early diastolic strain rate (E/e'sr) is a novel echocardiographic measure to estimate early left ventricular (LV) filling pressure. We hypothesize that E/e'sr is a predictor of outcome following coronary artery bypass grafting (CABG) and that it is superior to the conventionally used E/e'.

METHODS & RESULTS

Consecutive patients undergoing isolated CABG at Gentofte Hospital (n = 652) were included. The mean age of the study population was 67 ± 9 years, 84% were male, mean LVEF was 50 ± 11%. Prior to surgery, all patients underwent an extensive echocardiographic examination. The outcome was all-cause mortality. During follow-up (median 3.8 years [IQR: 2.7; 4.9 years]), a total of 73 (11.2%) died. Both E/e' and E/e'sr were significant predictors in univariable models. In a multivariable model, E/e'sr remained an independent predictor of outcome (HR:1.05 [1.01-1.10], p = 0.049, per 10 cm increase) whereas E/e' did not (HR:1.05 [0.99-1.11], p = 0.053, per 1-unit increase). The relationship between E/e'sr, and the outcome was significantly modified by GLS (p for interaction = 0.043). In the multivariable model, E/e'sr was still significantly associated with the outcome in patients with high GLS (≥13.6%) (HR:1.18 [1.02-1.36], p = 0.029) but not in patients with low GLS (HR 1.04 CI95%: [0.99-1.10], p = 0.14). E/e' was not a significant predictor of all-cause mortality after multivariable adjustment in neither of the groups. E/e'sr improved net reclassification with 33% when added to EuroSCOREII.

CONCLUSION

Following CABG, preoperative E/e'sr is an independent predictor of all-cause mortality, especially in patients with preserved systolic function and superior to E/e'.

Myocardial Strain Measured by Epicardial Transducers-Comparison Between Velocity Estimators

This study describes results from an experimental ultrasound system with miniature transducers sutured directly onto the epicardial surface and used to measure heart contractions continuously. This system was used to find velocity distributions through the myocardium. The resulting velocities were used to track the motion of four layers at different depths through the myocardium and to find the regional strain in each of the four layers. Velocities inside the myocardium vary from the epicardial to the endocardial borders. Conventional velocity estimators based on Doppler and on time delay estimation were modified to better handle these variations. Results from four different velocity estimators were tested against a simulation model for ultrasound echoes from moving tissue and on ultrasound recordings from five animals. We observed that the tested velocity estimators were able to reproduce the myocardial velocity distributions, track the myocardial layer motion and estimate strain at different positions inside the myocardium for both simulated and real ultrasound recordings. The most accurate results were obtained when the digitized ultrasound scanlines were upsampled by a factor of 10 before applying cross-correlation to estimate time delays. A modified Doppler algorithm allowing the velocity to vary linearly with time throughout the duration of the pulse packet (constant acceleration Doppler) was found to be better at capturing rapidly changing velocities compared with conventional Doppler processing. The best results were obtained using upsamling and time delay estimation, but the long computation time required by this method may make it best suited in a laboratory setting. In a real-time system, the computationally quicker constant acceleration Doppler may be preferred.

Monitoring cardiac function by accelerometer - detecting start systole from the acceleration signal makes additional ECG recordings for R-peak detection redundant

A miniaturized accelerometer attached to the heart has been used for monitoring functional parameters such as early systolic velocity and displacement. Currently, processing of the accelerometer signal for derival of these functional parameters depends on determining start systole by detecting the ECG R-peaks. This study proposes an alternative method using only the accelerometer signal to detect start systole, making additional ECG recordings for this purpose redundant. A signal processing method for automatic detection of start systole by accelerometer alone was developed and compared with detected R-peaks in 15 pigs during 5 different interventions showing a difference of 30 ± 17 ms. Furthermore, the derived early systolic velocity and displacement using only accelerometer measurements correlated well (r²=0.91 and 0.82, respectively) with minor differences compared to the current method using ECG R-peaks as time reference. The results show that an accelerometer can be used to monitor cardiac function without the need to measure ECG which can simplify the monitoring system.

Estimating Regional Myocardial Contraction Using Miniature Transducers on the Epicardium

This paper describes an ultrasound system to monitor cardiac motion using miniature transducers attached directly to the epicardial surface. Our aim was to develop both a research tool for detailed studies of cardiac mechanics and a continuous, real time system for peri-operative evaluation of heart function. The system was tested on a porcine model. Two 3 mm diameter, 10 MHz ultrasound transducers were sutured to the epicardial surface. As the epicardial surface was the reference for the velocity and strain estimations, this procedure compensated for the motion of the heart. The short distance allowed for the use of high frequencies and pulse repetition rates. The system was driven in pulse-echo mode, using electronics developed for the application, and radio frequency (RF) lines were recorded at a pulse repetition rate of 2500 s^-1. The endocardial border was detected using an algorithm based on fuzzy logic with filtration to reduce noise and remove outliers, and the myocardium was divided into four layers. Inside the myocardium, radial tissue velocity as a function of depth was calculated from the recorded RF signals, and the velocity estimates were used to estimate radial strain rate and strain and to track the motion of the myocardial layers. The scope of this paper is technical, giving a detailed description of system design, hardware electronics and algorithms, with examples of processed velocity patterns and myocardial strain curves. The results from this study on a porcine model demonstrate the system's ability to estimate myocardial velocity and strain patterns and to track the motion of the myocardial layers, thereby obtaining detailed information of the regional function of the myocardium.

Dynamic gravity compensation does not increase detection of myocardial ischemia in combined accelerometer and gyro sensor measurements

Previous studies have shown that miniaturised accelerometers can be used to monitor cardiac function and automatically detect ischemic events. However, accelerometers cannot differentiate between acceleration due to motion and acceleration due to gravity. Gravity filtering is essential for accurate integration of acceleration to yield velocity and displacement. Heart motion is cyclic and mean acceleration over time is zero. Thus, static gravity filtering is performed by subtracting mean acceleration. However, the heart rotates during the cycle, the gravity component is therefore not constant, resulting in overestimation of motion by static filtering. Accurate motion can be calculated using dynamic gravity filtering by a combined gyro and accelerometer. In an animal model, we investigated whether increased accuracy using dynamic filtering, compared to using static filtering, would enhance the ability to detect ischemia. Additionally, we investigated how well the gyro alone could detect ischemia based on the heart’s rotation. Dynamic filtering tended towards lower sensitivity and specificity, using receiver operating characteristics analysis, for ischemia-detection compared to static filtering (area under the curve (AUC): 0.83 vs 0.93, p = 0.125). The time-varying gravity component indirectly reflects the heart’s rotation. Hence, static filtering has the advantage of indirectly including rotation, which alone demonstrated excellent sensitivity to ischemia (AUC = 0.98).

Duration of myocardial early systolic lengthening for diagnosis of coronary artery disease

Objective

Myocardial early systolic lengthening (ESL) duration is prolonged in patients with coronary artery disease (CAD). However, the relationship between the fractional flow reserve (FFR), the current gold standard for evaluating physiological myocardial ischaemia, and ESL has not been studied. The aims of this study were to investigate whether left ventricular (LV) ESL duration could identify patients with CAD, and to examine the relationship between FFR and LV ESL duration.

Methods

In this single-centre, cross-sectional, prospective study of 75 patients with suspected or known CAD, we performed two-dimensional speckle tracking echocardiography at rest on the day before coronary angiography or percutaneous coronary intervention. Apical 3 views were used to examine ESL duration, defined as time from onset of the Q wave to maximum myocardial systolic lengthening.

Results

Thirty-five patients had non-significant stenosis. Forty patients with CAD underwent FFR testing: 17 had an FFR≥0.8 and 23 had an FFR<0.8. Global ESL duration was 20.9±22.2 ms in patients with non-significant stenosis, 36.4±23.2 ms in patients with FFR≥0.8 and 39.6±29.5 ms in patients with FFR<0.8 (p=0.020). However, global and regional ESL durations were not significantly correlated with FFR and demonstrated poor reproducibility.

Conclusion

Although myocardial ESL duration was significantly prolonged in patients with CAD compared with patients without CAD, ESL at rest showed poor reproducibility, and this new parameter did not predict FFR in patients with suspected CAD.

Non-invasive assessment of the haemodynamic significance of coronary stenosis using fusion of cardiac computed tomography and 3D echocardiography

Aims

Abnormal computed tomography coronary angiography (CTCA) often leads to stress testing to determine haemodynamic significance of stenosis. We hypothesized that instead, this could be achieved by fusion imaging of the coronary anatomy with 3D echocardiography (3DE)-derived resting myocardial deformation.

Methods and results

We developed fusion software that creates combined 3D displays of the coronary arteries with colour maps of longitudinal strain and tested it in 28 patients with chest pain, referred for CTCA (256 Philips scanner) who underwent 3DE (Philips iE33) and regadenoson stress CT. To obtain a reference for stenosis significance, coronaries were also fused with colour maps of stress myocardial perfusion. 3D displays were used to detect stress perfusion defect (SPD) and/or resting strain abnormality (RSA) in each territory. CTCA showed 56 normal arteries, stenosis <50% in 17, and >50% in 8 arteries. Of the 81 coronary territories, SPDs were noted in 20 and RSAs in 29. Of the 59 arteries with no stenosis >50% and no SPDs, considered as normal, 12 (20%) had RSAs. Conversely, with stenosis >50% and SPDs (haemodynamically significant), RSAs were considerably more frequent (5/6 = 83%). Overall, resting strain and stress perfusion findings were concordant in 64/81 arteries (79% agreement).

Conclusions

Fusion of CTCA and 3DE-derived data allows direct visualization of each coronary artery and strain in its territory. In this feasibility study, resting strain showed good agreement with stress perfusion, indicating that it may be potentially used to assess haemodynamic impact of coronary stenosis, as an alternative to stress testing that entails additional radiation exposure.

Fusion of Three-Dimensional Echocardiographic Regional Myocardial Strain with Cardiac Computed Tomography for Noninvasive Evaluation of the Hemodynamic Impact of Coronary Stenosis in Patients with Chest Pain

BACKGROUND

Combined evaluation of coronary stenosis and the extent of ischemia is essential in patients with chest pain. Intermediate-grade stenosis on computed tomographic coronary angiography (CTCA) frequently triggers downstream nuclear stress testing. Alternative approaches without stress and/or radiation may have important implications. Myocardial strain measured from echocardiographic images can be used to detect subclinical dysfunction. The authors recently tested the feasibility of fusion of three-dimensional (3D) echocardiography-derived regional resting longitudinal strain with coronary arteries from CTCA to determine the hemodynamic significance of stenosis. The aim of the present study was to validate this approach against accepted reference techniques.

METHODS

Seventy-eight patients with chest pain referred for CTCA who also underwent 3D echocardiography and regadenoson stress computed tomography were prospectively studied. Left ventricular longitudinal strain data (TomTec) were used to generate fused 3D displays and detect resting strain abnormalities (RSAs) in each coronary territory. Computed tomographic coronary angiographic images were interpreted for the presence and severity of stenosis. Fused 3D displays of subendocardial x-ray attenuation were created to detect stress perfusion defects (SPDs). In patients with stenosis >25% in at least one artery, fractional flow reserve was quantified (HeartFlow). RSA as a marker of significant stenosis was validated against two different combined references: stenosis >50% on CTCA and SPDs seen in the same territory (reference standard A) and fractional flow reserve < 0.80 and SPDs in the same territory (reference standard B).

RESULTS

Of the 99 arteries with no stenosis >50% and no SPDs, considered as normal, 19 (19%) had RSAs. Conversely, with stenosis >50% and SPDs, RSAs were considerably more frequent (17 of 24 [71%]). The sensitivity, specificity, and accuracy of RSA were 0.71, 0.81, and 0.79, respectively, against reference standard A and 0.83, 0.81, and 0.82 against reference standard B.

CONCLUSIONS

Fusion of CTCA and 3D echocardiography-derived resting myocardial strain provides combined displays, which may be useful in determination of the hemodynamic or functional impact of coronary abnormalities, without additional ionizing radiation or stress testing.

Detection of intraoperative myocardial dysfunction by accelerometer during aortic valve replacement

OBJECTIVES

Myocardial dysfunction may occur during weaning from cardiopulmonary bypass (CPB). Epicardial accelerometers have been shown to be useful in continuous monitoring of myocardial ischaemia during beating-heart surgery. We aimed to investigate whether an accelerometer can detect myocardial dysfunction during weaning from CPB.

METHODS

In 23 patients undergoing isolated aortic valve replacement (AVR), a three-axis accelerometer was attached to the left ventricle and 3D velocity was calculated from the signals. Peak early systolic velocity (Vsys) and velocity at aortic valve closure (Vavc) were measured. Measurements were undertaken during normothermia with 50% bypass flow and atrial pacing (90 beats/min) before aortic cross-clamping and after cross-clamp removal. Myocardial dysfunction was defined as Vsys < Vavc, and patients were classified as having normal function or dysfunction. Left ventricular (LV) stroke work via pulmonary artery catheter and systolic velocity by echocardiography were compared between groups and used as reference methods.

RESULTS

The accelerometer identified a substantial proportion of patients with myocardial dysfunction during weaning from CPB, 56% of patients compared with 11% before aortic cross-clamping. Patients classified with normal myocardial function during weaning significantly improved their LV stroke work and systolic velocity by echocardiography in response to AVR, whereas those classified with dysfunction did not. Accelerometer classification of normal function predicted an increase in echocardiographic systolic velocity [r = 0.63, regression coefficient 1.98, 95% CI (0.57, 3.40) (P < 0.01)].

CONCLUSIONS

The accelerometer detected myocardial dysfunction during weaning from CPB in accordance with measures obtained by echocardiography and pulmonary artery catheter.

Clinical Trials identifier

NCT01926067. https://clinicaltrials.gov/.

Role of speckle tracking imaging in the assessment of myocardial regional ventricular function in experimental blunt cardiac injury

PURPOSE

To evaluate the usefulness and information collecting ability of speckle tracking imaging techniques in the assessment of myocardial regional ventricular contractility in a rabbit model with blunt cardiac injury.

METHODS

Fifteen healthy New Zealand rabbits weighing (2.70 ±0.28) kg were anesthetized (3% pentobarbital sodium/i.v) and impacted using the BIM-II biological impact machine to induce myocardial contusion (MC). Hemodynamic parameters, such as heart rate, systolic pressure, mean arterial pressure, diastolic pressure and central venous pressure, were determined before and after MC. Further, parameters reflecting left ventricular functions, such as left ventricular end systolic pressure, left ventricular end diastolic pressure, isovolumic pressure (IP) and the maximal increasing/decreasing rate of left intraventricular pressure (±dp/dtmax), were also determined before and after MC. Left ventricular functions were determined either by two dimensional transthoracic echocardiography or by speckle tracking imaging for segmental abnormal ventricular wall motions.

RESULTS

Heart rate, systolic pressure, diastolic pressure and mean arterial pressure decreased significantly but transiently, while central venous pressure markedly increased after MC. In contrast to significant changes in diastolic functions, there was no significant change in cardiac systolic functions after MC. The speckle tracking imaging demonstrated that strain values of different myocardial segment significantly decreased post impact, and that of the ventricular segment decreased from segment to segment.

CONCLUSION

Speckle tracking imaging is useful and informative to assess myocardial regional dysfunctions post MC.

Delivering stem cells to the healthy heart on biological sutures: effects on regional mechanical function

Current cardiac cell therapies cannot effectively target and retain cells in a specific area of the heart. Cell-seeded biological sutures were previously developed to overcome this limitation, demonstrating targeted delivery with > 60% cell retention. In this study, both cell-seeded and non-seeded fibrin-based biological sutures were implanted into normal functioning rat hearts to determine the effects on mechanical function and fibrotic response. Human mesenchymal stem cells (hMSCs) were used based on previous work and established cardioprotective effects. Non-seeded or hMSC-seeded sutures were implanted into healthy athymic rat hearts. Before cell seeding, hMSCs were passively loaded with quantum dot nanoparticles. One week after implantation, regional stroke work index and systolic area of contraction (SAC) were evaluated on the epicardial surface above the suture. Cell delivery and retention were confirmed by quantum dot tracking, and the fibrotic tissue area was evaluated. Non-seeded biological sutures decreased SAC near the suture from 0.20 ± 0.01 measured in sham hearts to 0.08 ± 0.02, whereas hMSC-seeded biological sutures dampened the decrease in SAC (0.15 ± 0.02). Non-seeded sutures also displayed a small amount of fibrosis around the sutures (1.0 ± 0.1 mm2 ). Sutures seeded with hMSCs displayed a significant reduction in fibrosis (0.5 ± 0.1 mm2 , p < 0.001), with quantum dot-labelled hMSCs found along the suture track. These results show that the addition of hMSCs attenuates the fibrotic response observed with non-seeded sutures, leading to improved regional mechanics of the implantation region. Copyright © 2014 John Wiley & Sons, Ltd.

Impact of effect-site concentration of propofol on cardiac systolic function assessed by tissue Doppler imaging

Objective

To evaluate the relationship between effect-site concentration (C_E) of propofol during total intravenous anaesthesia (TIVA) and cardiac systolic function using tissue Doppler imaging (TDI) in patients undergoing cardiovascular procedures.

Methods

Stepwise increments of C_E of propofol of 1.0, 2.0, 3.0 and 4.0 µg/ml (modified Marsh model) were achieved using a target-controlled infusion device. Transthoracic echocardiographic assessments using TDI were performed for each C_E of propofol and corresponding systolic myocardial velocity (s′), mean arterial blood pressure (MAP), heart rate (HR) and bispectral index (BIS) were evaluated.

Results

Data from 31 patients were analysed in this prospective study. The s′ velocity decreased with increasing propofol C_E and values recorded at propofol C_E 3.0 and 4.0 µg/ml were near or below 8 cm/s indicating abnormal cardiac systolic function. MAP, HR and BIS also decreased with each propofol C_E increment.

Conclusion

Although the recommended dosage for propofol is up to 4.0 µg/ml, caution should be taken when using propofol concentrations above 2.0 µg/ml during TIVA in patients with underlying cardiovascular diseases.

Successful ECMO-cardiopulmonary resuscitation with the associated post-arrest cardiac dysfunction as demonstrated by MRI

Background

Veno-arterial extracorporeal membrane oxygenation (ECMO-CPR) is a life-saving rescue for selected patients when standard cardiopulmonary resuscitation fails. The use is increasing although the treatment modality is not fully established. Resuscitated patients typically develop a detrimental early post-arrest cardiac dysfunction that also deserves main emphasis. The present study investigates an ECMO-CPR strategy in pigs and assesses early post-arrest left ventricular function in detail. We hypothesised that a significant dysfunction could be demonstrated with this model using magnetic resonance imaging (MRI), not previously used early post-arrest.

Methods

In eight anaesthetised pigs, a 15-min ventricular fibrillation was resuscitated by an ECMO-CPR strategy of 150-min veno-arterial ECMO aiming at high blood flow rate and pharmacologically sustained aortic blood pressure and pulse pressure of 50 and 15 mmHg, respectively. Pre-arrest cardiac MRI and haemodynamic measurements of left ventricular function were compared to measurements performed 300-min post-arrest.

Results

All animals were successfully resuscitated, weaned from the ECMO circuit, and haemodynamically stabilised post-arrest. Cardiac output was maintained by an increased heart rate post-arrest, but left ventricular ejection fraction and stroke volume were decreased by approximately 50 %. Systolic circumferential strain and mitral annular plane systolic excursion as well as the left ventricular wall thickening were reduced by approximately 50–70 % post-arrest. The diastolic function variables measured were unchanged.

Conclusions

The present animal study demonstrates a successful ECMO-CPR strategy resuscitating long-lasting cardiac arrest with adequate post-arrest haemodynamic stability. The associated severe systolic left ventricular dysfunction could be charted in detail by MRI, a valuable tool for future cardiac outcome assessments in resuscitation research.

Trial registration

Institutional protocol number: FOTS 4611/13.

Electronic supplementary material

The online version of this article (doi:10.1186/s40635-015-0061-2) contains supplementary material, which is available to authorized users.

Principles of transthoracic echocardiographic evaluation

Transthoracic echocardiography is the most widely used imaging test in cardiology. Although completely noninvasive, transthoracic echocardiography has a well-established role in the diagnosis of numerous cardiovascular diseases, and also provides critical qualitative and quantitative information on their prognosis and pathophysiological processes. The aim of this Review is to outline the broad principles of transthoracic echocardiography, including the traditional techniques of two-dimensional, colour, and spectral Doppler echocardiography, and newly developed advances including tissue Doppler, myocardial deformation imaging, torsion, stress echocardiography, contrast and three-dimensional echocardiography. The advantages and disadvantages, clinical application, prognostic value, and salient research findings of each modality are described. Advances in complex imaging techniques are expected to continue unabated, and this Review highlights technical improvements that will influence the diagnosis and improve our understanding of cardiovascular function and disease.

Continuous monitoring of regional function by a miniaturized ultrasound transducer allows early quantification of low-grade myocardial ischemia

BACKGROUND

Sensitive methods for the early detection of myocardial dysfunction are still needed, as ischemia is a leading cause of decreased ventricular function during and after heart surgery. The aim of this study was to test the hypothesis that low-grade ischemia could be detected quantitatively by a miniaturized epicardial ultrasound transducer (Ø = 3 mm), allowing continuous monitoring.

METHODS

In 10 pigs, transducers were positioned in the left anterior descending and circumflex coronary artery areas. Left ventricular pressure was obtained by a micromanometer. The left internal mammary artery was grafted to the left anterior descending coronary artery, which was occluded proximal to the anastomosis. Left internal mammary artery flow was stepwise reduced by 25%, 50%, and 75% for 18 min each. From the transducers, M-mode traces were obtained, allowing continuous tissue velocity traces and displacement measurements. Regional work was assessed as left ventricular pressure-displacement loop area. Tissue lactate measured from intramyocardial microdialysis was used as reference method to detect ischemia.

RESULTS

All steps of coronary flow reduction demonstrated reduced peak systolic velocity (P < .05) and regional work (P < .01).The decreases in peak systolic velocity and regional work were closely related to the degree of ischemia, demonstrated by their correlations with lactate (R = -0.74, P < .01, and R = -0.64, P < .01, respectively). The circumflex coronary artery area was not affected by any of the interventions.

CONCLUSIONS

The epicardially attached miniaturized ultrasound transducer allowed the precise detection of different levels of coronary flow reduction. The results also showed a quantitative and linear relationship among coronary flow, ischemia, and myocardial function. Thus, the ultrasound transducer has the potential to improve the monitoring of myocardial ischemia and to detect graft failure during and after heart surgery.

Assessment of 3D motion increases the applicability of accelerometers for monitoring left ventricular function

OBJECTIVES

Miniaturized accelerometers attached to the epicardium have been shown to provide useful clinical information. However, attachment of such a sensor has been cumbersome due to requirement of aligning the three sensor axes with the cardiac coordinate axes, limiting clinical utility. We propose a new method to process the three-dimensional (3D) accelerometer signal that does not require such alignment.

METHODS

In 20 open-chest pigs, miniaturized 3D accelerometers were fixated on the epicardium in apical and basal regions of left ventricle. Accelerations in circumferential, longitudinal and radial directions were measured and a 3D velocity vector was calculated. Systolic velocity along the 3D vector and velocities in circumferential, longitudinal and radial directions were compared with the positive time derivate of left ventricular pressure during changes in global left ventricular function (epinephrine, esmolol and fluid loading) and to strain echocardiography during left anterior descending artery occlusion.

RESULTS

Distinct changes in all accelerometer velocities were observed during alterations on global and regional left ventricular function. Accelerometer 3D and circumferential systolic velocities in apical region best reflected left ventricular function during interventions on global function by correlating significantly with the positive time derivate of left ventricular pressure, r = 0.83 and r = 0.86, respectively. The accelerometer 3D velocity also demonstrated equally good capacity as circumferential velocity in discriminating coronary occlusion from interventions on global left ventricular function with sensitivity/specificity of 0.90/0.83 and 0.90/0.86, respectively.

CONCLUSIONS

Accelerometer 3D systolic velocity showed very good correspondence to changes in global and regional left ventricular function. Our results demonstrate that by the use of the accelerometer 3D motion vector, no alignment of the sensor with the cardiac coordinate axes was required. This increases potential clinical applicability of the accelerometer in cardiac surgery.

Echocardiographic assessment of anomalous origin of the left coronary artery from the pulmonary artery

Transthoracic echocardiography of a 4-month-old boy with heart failure revealed poor left ventricular contractility with severe mitral regurgitation. Deformation analysis revealed significantly decreased circumferential strain in the anterior and anteroseptal segments. Furthermore, post-systolic shortening was evident in the anterior and lateral segments. The pulmonary arterial short-axis view showed that the left coronary artery originated from the pulmonary artery and color Doppler flow mapping showed retrograde flow in the left coronary artery. These findings were quite helpful for concluding the anomalous origin of the left coronary artery from the pulmonary artery.

Perioperative assessment of myocardial deformation

Evaluation of left ventricular performance improves risk assessment and guides anesthetic decisions. However, the most common echocardiographic measure of myocardial function, the left ventricular ejection fraction (LVEF), has important limitations. LVEF is limited by subjective interpretation that reduces accuracy and reproducibility, and LVEF assesses global function without characterizing regional myocardial abnormalities. An alternative objective echocardiographic measure of myocardial function is thus needed. Myocardial deformation analysis, which performs quantitative assessment of global and regional myocardial function, may be useful for perioperative care of surgical patients. Myocardial deformation analysis evaluates left ventricular mechanics by quantifying strain and strain rate. Strain describes percent change in myocardial length in the longitudinal (from base to apex) and circumferential (encircling the short-axis of the ventricle) direction and change in thickness in the radial direction. Segmental strain describes regional myocardial function. Strain is a negative number when the ventricle shortens longitudinally or circumferentially and is positive with radial thickening. Reference values for normal longitudinal strain from a recent meta-analysis by using transthoracic echocardiography are (mean ± SD) -19.7% ± 0.4%, while radial and circumferential strain are 47.3% ± 1.9% and -23.3% ± 0.7%, respectively. The speed of myocardial deformation is also important and is characterized by strain rate. Longitudinal systolic strain rate in healthy subjects averages -1.10 ± 0.16 s. Assessment of myocardial deformation requires consideration of both strain (change in deformation), which correlates with LVEF, and strain rate (speed of deformation), which correlates with rate of rise of left ventricular pressure (dP/dt). Myocardial deformation analysis also evaluates ventricular relaxation, twist, and untwist, providing new and noninvasive methods to assess components of myocardial systolic and diastolic function. Myocardial deformation analysis is based on either Doppler or a non-Doppler technique, called speckle-tracking echocardiography. Myocardial deformation analysis provides quantitative measures of global and regional myocardial function for use in the perioperative care of the surgical patient. For example, coronary graft occlusion after coronary artery bypass grafting is detected by an acute reduction in strain in the affected coronary artery territory. In addition, assessment of left ventricular mechanics detects underlying myocardial pathology before abnormalities become apparent on conventional echocardiography. Certainly, patients with aortic regurgitation demonstrate reduced longitudinal strain before reduction in LVEF occurs, which allows detection of subclinical left ventricular dysfunction and predicts increased risk for heart failure and impaired myocardial function after surgical repair. In this review, we describe the principles, techniques, and clinical application of myocardial deformation analysis.

Left ventricular function can be continuously monitored with an epicardially attached accelerometer sensor

OBJECTIVES

Preservation of left ventricular (LV) function is crucial for a beneficial outcome in high-risk patients undergoing cardiac surgery. The present study evaluated a motion sensor (accelerometer) for continuous monitoring of LV performance during changes in global and regional LV function.

METHODS

In 11 pigs, an accelerometer was sutured to the epicardium on the anterior apical LV region. Global LV function was modulated by esmolol, epinephrine and fluid loading, whereas regional LV dysfunction was induced by a 3-min occlusion of left anterior descending (LAD) coronary artery. Epicardial acceleration in the circumferential direction was obtained by the accelerometer, and from this signal, epicardial velocity was calculated. Peak systolic velocity was measured and used as an index of LV performance. The accelerometer was compared with left ventricular stroke work (LVSW), ejection fraction and myocardial strain by echocardiography.

RESULTS

Accelerometer peak systolic velocity and LVSW changed significantly during all interventions, affecting global LV function. Systolic velocity by the accelerometer increased during epinephrine and fluid loading from 14.1 [10.2; 17.3] to 25.4 [16.7; 28.5] (P < 0.05) and 14.8 [12.5; 18.5] cm/s (P < 0.05), respectively. Esmolol infusion significantly decreased accelerometer peak systolic velocity to 9.4 [7.3; 10.7] cm/s (P < 0.05). Minor changes were seen in the echocardiographic measurements, with significant changes only observed in myocardial strain during the interventions with esmolol and epinephrine. Regional LV dysfunction was clearly detected by the accelerometer during LAD occlusion, and peak systolic velocity was reduced from 14.1 [10.2; 17.3] to 5.7 [5.0; 6.8] cm/s (P < 0.05). The accelerometer demonstrated higher sensitivity and specificity for the detection of myocardial ischaemia than LVSW and ejection fraction. For all interventions, accelerometer peak systolic velocity correlated strongly with LVSW (r = 0.81, P < 0.01) and myocardial strain (r = 0.80; P < 0.01).

CONCLUSIONS

It was possible to obtain accurate information on LV performance by the use of an epicardially attached accelerometer. The method allows continuous monitoring of LV function and may therefore improve perioperative monitoring of cardiac surgery patients.

Mitral annular displacement by Doppler tissue imaging may identify coronary occlusion and predict mortality in patients with non-ST-elevation myocardial infarction

BACKGROUND

Mitral annular displacement (MAD) is a simple marker of left ventricular (LV) systolic function. The aim of this study was to test the hypothesis that MAD can distinguish patients with non-ST-segment elevation myocardial infarctions (NSTEMIs) from those with significant coronary artery disease without infarctions, identify coronary occlusion, and predict mortality in patients with NSTEMIs. MAD was compared with established indices of LV function.

METHODS

In this retrospective study, 167 patients with confirmed NSTEMIs were included at two Scandinavian centers. Forty patients with significant coronary artery disease but without myocardial infarctions were included as controls. Doppler tissue imaging was performed at the mitral level of the left ventricle in the three apical planes, and velocities were integrated over time to acquire MAD. LV ejection fraction, global longitudinal strain (GLS), and wall motion score index were assessed according to guidelines.

RESULTS

MAD and GLS could accurately distinguish patients with NSTEMIs from controls. During 48.6 ± 12.1 months of follow-up, 22 of 167 died (13%). MAD, LV ejection fraction, and GLS were reduced and wall motion score index was increased among those who died compared with those who survived (P < .001, P < .001, P < .001, and P = .02, respectively). Multivariate Cox proportional-hazards analyses revealed that MAD was an independent predictor of death (hazard ratio, 1.36; 95% confidence interval, 1.07-1.73; P = .01). MAD and GLS were reduced and wall motion score index was increased in patients with coronary artery occlusion compared with those without occlusion (P = .006, P = .001, and P = .02), while LV ejection fraction did not differ (P = .20).

CONCLUSIONS

MAD accurately identified patients with NSTEMIs, predicted mortality, and identified coronary occlusion in patients with NSTEMIs.

Risk stratification of patients with non-ST-elevation acute coronary syndromes by assessing global longitudinal strain

Noninvasive detection of left main/three-vessel diseases (LM/3VD) among patients with non-ST-elevation acute coronary syndromes (NSTEACS) has been difficult using echocardiography. However, two-dimensional (2D) strain/strain-rate analysis is more sensitive in quantitatively assessing contractile abnormality. Accordingly, we aimed to clarify the usefulness of 2D strain/strain-rate analysis for risk stratification of NSTEACS. A total of 50 patients with NSTEACS underwent echocardiography and coronary angiography. We evaluated global longitudinal peak strain (global PS), peak systolic strain rate (global SSR), early diastolic global peak strain rate (global ESR), time from aortic valve closure to peak strain (TAVC-global PS), and global ESR (TAVC-global ESR) in apical four-, two-, and three-chamber views. Patients were divided into two groups according to coronary angiographic findings, the high-risk group (n = 15) with either of left main or three-vessel disease, and the low-risk group (n = 35). There were no significant differences in global SSR and global ESR between the two groups. The amplitude of global PS was significantly reduced in high-risk patients with LM/3VD in comparison with low-risk patients (-17.5 ± 2.4% vs -19.8 ± 2.7%, P = 0.007, respectively). TAVC-global PS and TAVC-global ESR were significantly prolonged in high-risk patients with LM/3VD in comparison with low-risk patients (15.3 ± 25.7 ms vs -36.8 ± 32.7 ms, P < 0.0001 and 162.8 ± 32.7 ms vs 135.7 ± 41.5 ms, P < 0.03, respectively). Receiver-operating characteristic analysis demonstrated that TAVC-global PS most strongly detected high-risk patients with sensitivity of 100% and specificity of 74.3% (area under the curve = 0.938, 95 % confidence interval 0.832-0.986, P = 0.0001). Temporal analysis of 2D strain appeared to be useful in detecting high-risk patients with LM/3VD among patients with NSTEACS.

Value of segmental myocardial strain by 2-dimensional strain echocardiography for assessment of scar area induced in a rat model of myocardial infarction

OBJECTIVES

Two-dimensional strain echocardiography (2DSE) technique has enabled accurate quantification of regional myocardial function. This experimental study was aimed to investigate the value of 2DSE in detection of segmental regional myocardial dysfunction induced by fibrosis following myocardial infarction in a small animal (rat) model.

METHODS

A rat model of myocardial infarction was established by ligation of the proximal left anterior descending coronary artery in 17 SD rats. Regional myocardial function was detected by 2DSE at baseline and 4-weeks post-infarction, including end-systolic radial strain and strain rate (SR and SrR) and end-systolic circumferential strain and strain rate (SC and SrC) of each of six segments at papillary level. According to the size of scar found by histologic Masson staining, the optimal cutoff points of parameters for detecting scar area were analyzed and the sensitivity and specificity of every parameter to detect myocardial scar were obtained using ROC.

RESULTS

(1) Comparing with parameters measured at baseline, there were significant decreases in SR, SrR, SC and SrC of each segment at 4 weeks post-infarction, with the worst in the infarct area (32.90 ± 8.79 vs 11.18 ± 3.89, 6.28 ± 1.35 vs 3.18 ± 0.47, -14.46 ± 2.21 vs -6.30 ± 2.17 and 4.93 ± 0.95 vs 2.59 ± 1.16, respectively) (all P < 0.05). (2)By 4 weeks, the myocardium of infarct area (anteroseptum, anterior and anterolateral) had fibrosis (31.33 ± 9.89, 73.42 ± 13.21 and 13.99 ± 3.24%, respectively) with minimal fibrosis in inferoseptal segment (0.32 ± 0.19%), no fibrosis was found in the inferior and inferolateral segments. (3)Significant negative correlations were found between the size of segmental scar and 2DSE parameters (r-value -0.61 ~ -0.80, all P < 0.01) with the strongest correlation in SR. SR less than 10% has 84% sensitivity and 98% specificity for detecting segments of scar area greater than 30% with AUC = 0.97.

CONCLUSIONS

2DSE is able to assess regional myocardial dysfunction in a rat model of myocardial infarction and has high accuracy in detecting infarct segments with scar area greater than 30%.

Septal Deformation Patterns Delineate Mechanical Dyssynchrony and Regional Differences in Contractility

Background—

Response to cardiac resynchronization therapy depends both on dyssynchrony and (regional) contractility. We hypothesized that septal deformation can be used to infer integrated information on dyssynchrony and regional contractility, and thereby predict cardiac resynchronization therapy response.

Methods and Results—

In 132 cardiac resynchronization therapy candidates with left bundle branch block (LBBB)-like electrocardiogram morphology (left ventricular ejection fraction 19±6%; QRS width 170±23 ms), longitudinal septal strain was assessed by speckle tracking echocardiography. To investigate the effects of dyssynchronous activation and differences in septal and left ventricular free wall contractility on septal deformation pattern, we used the CircAdapt computer model of the human heart and circulation. In the patients, 3 characteristic septal deformation patterns were identified: LBBB-1=double-peaked systolic shortening (n=28); LBBB-2=early systolic shortening followed by prominent systolic stretching (n=34); and LBBB-3=pseudonormal shortening with less pronounced late systolic stretch (n=70). LBBB-3 revealed more scar (2 [2–5] segments) compared with LBBB-1 and LBBB-2 (both 0 [0–1], P <0.05). In the model, imposing a time difference of activation between septum and left ventricular free wall resulted in pattern LBBB-1. This transformed into pattern LBBB-2 by additionally simulating septal hypocontractility, and into pattern LBBB-3 by imposing additional left ventricular free wall or global left ventricular hypocontractility. Improvement of left ventricular ejection fraction and reduction of left ventricular volumes after cardiac resynchronization therapy were most pronounced in LBBB-1 and worst in LBBB-3 patients.

Conclusions—

A double-peaked systolic septal deformation pattern is characteristic for LBBB and results from intraventricular dyssynchrony. Abnormal contractility modifies this pattern. A computer model can be helpful in understanding septal deformation and predicting cardiac resynchronization therapy response.

Impaired subendocardial wall thickening and post-systolic shortening are signs of critical myocardial ischemia in patients with flow-limiting coronary stenosis

BACKGROUND

The early diagnosis of myocardial ischemia is still challenging. The aim of the present study was to determine whether subendocardial hypokinesis and post-systolic contraction could be early markers of myocardial ischemia.

METHODS AND RESULTS

Thirty-one consecutive patients with flow-limiting severe coronary stenosis but without visually abnormal left ventricular wall motion underwent quantitative echocardiography. Myocardial strain was measured using layer-by-layer analysis in severely hypoperfused segments. Radial strain (RS) was measured in the subendocardial, subepicardial, and total wall (innerRS, outerRS, and totalRS, respectively). Circumferential strain (CS) was also measured as 3 separate layers: subendocardial, mid-layer, and subepicardial layers (innerCS, midCS, and outerCS, respectively). Post-systolic shortening (PSS) was defined as the peak strain after end systole, and post-systolic strain index (PSI) was calculated as PSS divided by end-systolic strain. TotalRS was similar between ischemic and normally perfused segments, but innerRS and inner/outer RS ratio were significantly smaller in the ischemic segments than in corresponding segments in healthy subjects. Receiver operating characteristic analysis identified an optimum cut-off for PSI of 0.6. The combined criteria of inner/outer RS ratio <1.0 and PSI >0.6 achieved 95% specificity for the presence of flow-limiting stenosis.

CONCLUSIONS

Combined assessment of both subendocardial contractile impairment and PSS is very useful in identifying a severely hypoperfused left ventricular wall even without visual wall motion abnormality.

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.

Longitudinal peak strain detects a smaller risk area than visual assessment of wall motion in acute myocardial infarction

BACKGROUND

Opening of an occluded infarct related artery reduces infarct size and improves survival in acute ST-elevation myocardial infarction (STEMI). In this study we performed tissue Doppler analysis (peak strain, displacement, mitral annular movement (MAM)) and compared with visual assessment for the study of the correlation of measurements of global, regional and segmental function with final infarct size and transmurality. In addition, myocardial risk area was determined and a prediction sought for the development of infarct transmurality >or=50%.

METHODS

Twenty six patients with STEMI submitted for primary percutaneous coronary intervention (PCI) were examined with echocardiography on the catheterization table. Four to eight weeks later repeat echocardiography was performed for reassessment of function and magnetic resonance imaging for the determination of final infarct size and transmurality.

RESULTS

On a global level, wall motion score index (WMSI), ejection fraction (EF), strain, and displacement all showed significant differences (p <or= 0.001, p <or= 0.001, p <or= 0.001 and p = 0.03) between the two study visits, but MAM did not (p = 0.17). On all levels (global, regional and segmental) and both pre- and post PCI, WMSI showed a higher correlation with scar transmurality compared to strain. We found that both strain and WMSI predicted the development of scar transmurality >or=50%, but strain added no significant information to that obtained with WMSI in a logistic regression analysis.

CONCLUSIONS

In patients with acute STEMI, WMSI, EF, strain, and displacement showed significant changes between the pre- and post PCI exam. In a ROC-analysis, strain had 64% sensitivity at 80% specificity and WMSI around 90% sensitivity at 80% specificity for the detection of scar with transmurality >or=50% at follow-up.

Cardiac assessment in chronic kidney disease

Patients with chronic kidney disease are well recognized to develop a wide range of cardiac structural and functional abnormalities. These changes may be progressive and relate directly to a grossly aggravated risk of cardiovascular events and reduced survival. Although conventional methods of cardiac assessment have been shown to be useful, they are limited by insufficient sensitivity and specificity, to fully appreciate the overall degree of myocardial distress that is common in these patients. This article aims to review the use of established and emerging cardiac imaging tools and, in particular, their application in patients with chronic kidney disease.

Left ventricular longitudinal strain for perioperative cardiac monitoring in aortic aneurysm surgery using transthoracic 2-dimensional echocardiography: a feasibility and repeatability study

OBJECTIVE

This study investigated perioperative echocardiographic image quality, the feasibility, and intra- and interobserver repeatability of left ventricular longitudinal two-dimensional strain echocardiography (2DSE) in aortic aneurysm surgery.

DESIGN

A prospective, descriptive method evaluation.

SETTING

A single-center study.

PARTICIPANTS

Eighteen patients undergoing elective open infrarenal aortic aneurysm repair.

INTERVENTION

No intervention was made.

MEASUREMENTS AND MAIN RESULTS

Four echocardiographic examinations were made: E1, preoperatively; E2, within 4 hours after surgery; E3, the first postoperative day; and E4, the second postoperative day. Four-chamber, 2-chamber, and longitudinal axis apical views were achieved. Image quality was scored visually on a scale from 1 to 5 with 5 as the best, and the 2-dimensional strain echocardiography (2DSE) software was applied to measure peak systolic strain. Blinded analyses were performed twice by 1 observer and once by a second observer. Image quality decreased significantly after surgery as compared with the preoperative examination, but 72% of patients had at least 1 image scoring >/=3 through all examinations. The software was able to measure the segmental and global left ventricular peak systolic strain in 80% and 61%, respectively, for the first observer and 71% and 26%, respectively, for the second observer. The coefficients of repeatability for intra- and interobserver measurements were 5.5% and 7.3% for segmental strain and 1.6% and 3.5% for global strain. 2DSE was more feasible and repeatable when echocardiographic images were good.

CONCLUSION

Feasibility and repeatability of 2DSE is good but affected by image quality. This study shows that 2DSE can be used in a clinical setting.

Diagnostic approaches for diabetic cardiomyopathy and myocardial fibrosis

In diabetes mellitus, alterations in cardiac structure/function in the absence of ischemic heart disease, hypertension or other cardiac pathologies are termed diabetic cardiomyopathy. In the United States, the prevalence of diabetes mellitus continues to rise and the disease currently affects about 8% of the general population. Hence, the use of appropriate diagnostic strategies for diabetic cardiomyopathy, which may help correctly identify the disease at early stages and implement suitable corrective therapies is imperative. Currently, there is no single diagnostic method for the identification of diabetic cardiomyopathy. Diabetic cardiomyopathy is known to induce changes in cardiac structure such as, myocardial hypertrophy, fibrosis and fat droplet deposition. Early changes in cardiac function are typically manifested as abnormal diastolic function that with time leads to loss of contractile function. Echocardiography based methods currently stand as the preferred diagnostic approach for diabetic cardiomyopathy, due to its wide availability and economical use. In addition to conventional techniques, magnetic resonance imaging and spectroscopy along with contrast agents are now leading new approaches in the diagnosis of myocardial fibrosis, and cardiac and hepatic metabolic changes. These strategies can be complemented with serum biomarkers so they can offer a clear picture as to diabetes-induced changes in cardiac structure/function even at very early stages of the disease. This review article intends to provide a summary of experimental and routine tools currently available to diagnose diabetic cardiomyopathy induced changes in cardiac structure/function. These tools can be reliably used in either experimental models of diabetes or for clinical applications.

Left ventricle longitudinal deformation assessment by mitral annulus displacement or global longitudinal strain in chronic ischemic heart disease: are they interchangeable?

BACKGROUND

Increasing infarct mass is associated with impaired prognosis in chronic ischemic heart disease. Global strain by echocardiographic assessment relates closely to infarct mass assessed by delayed enhancement magnetic resonance imaging but requires deformation analysis in a 16-segment model of the left ventricular. Mitral annular (MA) displacement reflects longitudinal left ventricular deformation and could provide similar information.

METHODS

Global longitudinal strain and MA displacement by Doppler tissue imaging were assessed in 61 patients 9 months after first myocardial infarctions and compared with global myocardial infarct mass assessed using contrast-enhanced magnetic resonance imaging.

RESULTS

Both indices significantly separated medium-sized infarcts from small or large infarcts (P < .05) and correlated significantly with global infarct mass (P < .01 for both). There was a good correlation between global strain and MA displacement (r = 0.65, P < .01). The sensitivities and specificities to identify myocardial infarcts differed only slightly among the indices, but global longitudinal strain tended to be the best.

CONCLUSIONS

Longitudinal deformation by global strain or MA displacement correlated well with myocardial infarct mass and could discriminate between different extents of myocardial infarctions. Global longitudinal strain tended to be better, especially for the identification of the smallest infarcts.

In vivo detection of myocardial ischemia in pigs using visible light spectroscopy

BACKGROUND

Monitoring tissue oxygenation (StO(2)) by visible light spectroscopy (VLS) can identify tissue ischemia, but its feasibility for detecting myocardial ischemia is not known. We hypothesized that VLS can reliably detect changes in myocardial StO(2) in pigs subjected to acute regional or global myocardial ischemia.

METHODS

In 11 pigs, regional myocardial ischemia was created by ligation of left anterior descending artery (LAD). Myocardial StO(2) was determined from the ischemic and nonischemic left ventricular (LV) regions and compared to coronary venous saturations. Myocardial function was assessed by echocardiography. In six pigs, LV-StO(2) was measured during cardiopulmonary bypass (CPB), after cardioplegic cardiac arrest, and during CPB with inadequate myocardial protection. Additionally, right ventricular (RV)- and LV-StO(2) were assessed during acute RV pressure overload from pulmonary artery (PA) banding.

RESULTS

StO(2) baselines in pigs undergoing LAD occlusion were similar in the ischemic and nonischemic myocardium (70% +/- 8% vs 74% +/- 5%). After LAD ligation, StO(2) rapidly declined (30 s: 59% +/- 8%; 1 min:50 +/- 9; 5 min:42% +/- 4%; P < 0.05) in the ischemic myocardium. Decreases in StO(2) correlated with coronary venous saturations (r = 0.88) and were associated with myocardial dysfunction. In pigs undergoing CPB, LV-StO(2) remained unchanged with initiation of CPB or after cardioplegic cardiac arrest, but LV ischemia was detected by StO(2) after aortic cross-clamp without adequate myocardial protection. Similarly, PA banding resulted in a profound decrease of RV-StO(2) from 69% +/- 6% to 52% +/- 7% (P < 0.05) with recovery after PA release.

CONCLUSIONS

VLS is a reliable method of detecting alterations in myocardial StO(2) and can be a useful monitor for rapid identification of myocardial ischemia.

Axial black blood turbo spin echo imaging of the right ventricle

Black blood turbo spin echo (TSE) imaging of the right ventricle (RV) free wall is highly sensitive to cardiac motion, frequently resulting in nondiagnostic images. Temporal and spatial parameters of a black blood TSE pulse sequence were evaluated for visualization of the RV free wall. Seventy-four patient studies were retrospectively evaluated for the effects of acquisition timing on image quality. Axial black blood TSE images were acquired on 10 healthy volunteers to assess the role of spatial misregistration on right ventricle visualization; increasing the double inversion recovery (DIR) slice thickness beyond 300% had no effect on image quality (P = 0.2). Thirty-five patient studies were prospectively evaluated with inversion times (TIs) corresponding to the mid-diastolic rest period and end-systole based on visual analysis of a four chamber cine. When TIs were chosen to be within the patients' RV rest period, mean image quality score was significantly improved (2.3 vs 1.86; P < 0.001) and the number of clinically diagnostic images increased from 32% to 46%. Black blood TSE imaging of the RV free wall is highly sensitive to cardiac motion. Image quality can be improved by choosing TIs concordant with the rest period of the patient's RV that may occur at mid-diastole or end-systole.

Feasibility of a three-axis epicardial accelerometer in detecting myocardial ischemia in cardiac surgical patients

OBJECTIVE

We investigated the feasibility of continuous detection of myocardial ischemia during cardiac surgery with a 3-axis accelerometer.

METHODS

Ten patients with significant left anterior descending coronary artery stenosis underwent off-pump coronary artery bypass grafting. A 3-axis accelerometer (11 x 14 x 5 mm) was sutured onto the left anterior descending coronary artery-perfused region of left ventricle. Twenty episodes of ischemia were studied, with 3-minute occlusion of left anterior descending coronary artery at start of surgery and 3-minute occlusion of left internal thoracic artery at end of surgery. Longitudinal, circumferential, and radial accelerations were continuously measured, with epicardial velocities calculated from the signals. During occlusion, accelerometer velocities were compared with anterior left ventricular longitudinal, circumferential, and radial strains obtained by echocardiography. Ischemia was defined by change in strain greater than 30%.

RESULTS

Ischemia was observed echocardiographically during 7 of 10 left anterior descending coronary artery occlusions but not during left internal thoracic artery occlusion. During ischemia, there were no significant electrocardiographic or hemodynamic changes, whereas large and significant changes in accelerometer circumferential peak systolic (P < .01) and isovolumic (P < .01) velocities were observed. During 13 occlusions, no ischemia was demonstrated by strain, nor was any change demonstrated by the accelerometer. A strong correlation was found between circumferential strain and accelerometer circumferential peak systolic velocity during occlusion (r = -0.76, P < .001).

CONCLUSIONS

The epicardial accelerometer detects myocardial ischemia with great accuracy. This novel technique has potential to improve monitoring of myocardial ischemia during cardiac surgery.

Determinants of enhanced left atrial active emptying with aging: left atrial preload, contractility or both?

OBJECTIVE

Senile persons have reduced left ventricular (LV) relaxation and increased late diastolic filling. However, the determinant factor of the enhanced active emptying of the left atrium has not been well established.

METHODS

Subjects were 62 healthy individuals with a mean age of 58+/-19 (21-85) years. The biplane modified Simpson's rule was applied to measure left atrial (LA) volume at pre-atrial contraction (LAVpre) as an index of LA preload and LA volume change during atrial contraction (LASV) as an index of active LA emptying. These values were divided by the body surface area and represented as LAVpreI and LASVI, respectively. Postero-basal (dorsal cranial) left atrial wall velocity (LAWV) during atrial contraction as an index of LA contractility was measured in the apical three-chamber view by two-dimensional tissue Doppler echocardiography.

RESULTS

Age significantly correlated with mitral flow velocity (TMA), velocity-time integral during atrial contraction (TMAVTI) and LASVI (r= 0.63, p<0.001 and r=0.71, p<0.001, r=0.21, p=0.049, respectively). LAVpreI was significantly correlated with age (r=0.44, p<0.001), LASVI (r=0.71, p<0.001), TMA (r=0.31, p=0.008) and TMAVTI (r=0.40, p<0.001). LAWV remained unchanged with aging and had no correlation with TMA, TMAVTI or LASVI.

CONCLUSION

The enlargement of the LA in senile persons may be a major determinant of enhanced active LA emptying and the increased LA contractility may be less contributory.