Changes In Regional Myocardial Function Research Articles

Regional Left Ventricular Myocardial Dysfunction After Cardiac Surgery Characterized by 3-Dimensional Strain.

Three-dimensional (3D) strain is an echocardiographic modality that can characterize left ventricular (LV) function with greater accuracy than ejection fraction. While decreases in global strain have been used to predict outcomes after cardiac surgery, changes in regional 3D longitudinal, circumferential, radial, and area strain have not been well described. The primary aim of this study was to define differential patterns in regional LV dysfunction after cardiac surgery using 3D speckle tracking strain imaging. Our secondary aim was to investigate whether changes in regional strain can predict postoperative outcomes, including length of intensive care unit stay and 1-year event-free survival. In this prospective clinical study, demographic, operative, echocardiographic, and clinical outcome data were collected on 182 patients undergoing aortic valve replacement, mitral valve repair or replacement, coronary artery bypass graft, and combined cardiac surgery. Three-dimensional transthoracic echocardiograms were performed preoperatively and on the second to fourth postoperative day. Blinded analysis was performed for LV regional longitudinal, circumferential, radial, and area strain in the 17-segment model. Regional 3D longitudinal, circumferential, radial, and area strains were associated with differential patterns of myocardial dysfunction, depending on the surgical procedure performed and strain measure. Patients undergoing mitral valve repair or replacement had reduced function in the majority of myocardial segments, followed by coronary artery bypass graft, while patients undergoing aortic valve replacement had reduced function localized only to apical segments. After all types of cardiac surgery, segmental function in apical segments was reduced to a greater extent as compared to basal segments. Greater decrements in regional function were seen in circumferential and area strain, while smaller decrements were observed in longitudinal strain in all surgical patients. Both preoperative regional strain and change in regional strain preoperatively to postoperatively were correlated with reduced 1-year event-free survival, while postoperative strain was not predictive of outcomes. Only preoperative strain values were predictive of intensive care unit length of stay. Changes in regional myocardial function, measured by 3D strain, varied by surgical procedure and strain type. Differences in regional LV function, from presurgery to postsurgery, were associated with worsened 1-year event-free survival. These findings suggest that postoperative changes in myocardial function are heterogeneous in nature, depending on the surgical procedure, and that these changes may have long-term impacts on outcome. Therefore, 3D regional strain may be used to identify patients at risk for worsened postoperative outcomes, allowing early interventions to mitigate risk.

Time-course Study on Left Ventricular Function in a Rabbit Model of Ischemia-reperfusion Injury With Morphine Preconditioning.

To analyze the left ventricular longitudinal function in a rabbit model of myocardial ischemia reperfusion with morphine preconditioning through strain rate imaging and to evaluate the effect of morphine preconditioning. A myocardial ischemia-reperfusion model was induced by occlusion and recanalization of the coronary artery in 40 male New Zealand white rabbits, which were divided into a sham group, morphine group, and vehicle control group. Routine echocardiography data were recorded 1 day before and within 28 days after the operation. Dynamic images were also collected and analyzed off-line using Doppler tissue imaging software. On the first day after the operation, the global and regional systolic functions of the left ventricle in the morphine and vehicle control groups were lower than those in the sham group. After ischemia reperfusion, some of the values of the above-mentioned parameters decreased over time, which was more obvious in the vehicle control group at each examined time point. The current study revealed that detection of changes in regional myocardial function after myocardial ischemia reperfusion by strain rate imaging is objective and accurate. In addition, our results indicated that morphine preconditioning significantly attenuates myocardial ischemia-reperfusion injury in rabbits.

Occult Cardiotoxicity in Childhood Cancer Survivors Exposed to Anthracycline Therapy

More than 50% of >270 000 childhood cancer survivors in the United States have been treated with anthracyclines and are therefore at risk of developing cardiotoxicity. Cardiac magnetic resonance (CMR) has demonstrated utility to detect diffuse interstitial fibrosis and changes in regional myocardial function. We hypothesized that CMR would identify occult cardiotoxicity characterized by structural and functional myocardial abnormalities in a cohort of asymptomatic pediatric cancer survivors with normal global systolic function. Forty-six long-term childhood cancer survivors with a cumulative anthracycline dose ≥200 mg/m(2) and normal systolic function were studied 2.5 to 26.9 years after anthracycline exposure. Subjects underwent transthoracic echocardiography, CMR with routine cine acquisition, tissue characterization, and left ventricular strain analysis using a modified 16-segment model. Extracellular volume was measured in 27 subjects, all of whom were late gadolinium enhancement negative. End-systolic fiber stress was elevated in 45 of 46 subjects. Low average circumferential strain magnitude (εcc) -14.9±1.4; P<0.001, longitudinal strain magnitude (εll) -13.5±1.9; P<0.001, and regional peak circumferential strain were seen in multiple myocardial segments, despite normal global systolic function by transthoracic echocardiography and CMR. The mean T1 values of the myocardium were significantly lower than that of control subjects at 20 minutes (458±69 versus 487±44 milliseconds; P=0.01). Higher mean extracellular volume was observed in female subjects (0.34 versus 0.22; P=0.01). Asymptomatic postchemotherapy pediatric patients have abnormal myocardial characteristics and strain parameters by CMR despite normal global cardiac function by standard transthoracic echocardiography and CMR measures.

Defining late onset occult asymptomatic cardiotoxicity in childhood cancer survivors exposed to anthracycline therapy: a cardiac magnetic resonance imaging study

Background There are over 270,000 childhood cancer survivors in the US. Of these survivors, more than 50% have been treated with anthracyclines and are at risk of developing progressive cardiotoxicity. Novel cardiac magnetic resonance imaging (CMRI) techniques are now able to reliably detect diffuse myocardial fibrosis and changes in regional myocardial function. We hypothesized that these novel CMRI techniques will identify occult asymptomatic cardiotoxicity in a cohort of childhood cancer survivors with normal global systolic function. Methods Twenty seven long-term childhood cancer survivors between 11.8-28.8 years with a cumulative dose >240mg/ m2 (mean 363±89) and normal systolic function (SF>29%) were studied 2.4-24 years after exposure to anthracycline therapy. Patients underwent CMRI techniques to characterize changes in T1 relaxation time, left ventricular myocardial peak circumferential and longitudinal strain parameters and were analyzed using the 17-segment model. Extracellular volume (ECV) was measured in 13 subjects all of whom were late gadolinium enhancement (LGE) negative. We performed standard CMRI assessment and quantification of myocardial mass, end-systolic and end-diastolic volumes, ejection fraction, and end systolic fiber stress. Results Twenty seven of 60 planned subjects have been imaged. End systolic fiber stress was significantly increased with higher cumulative anthracycline dose (R2=0.18, p<0.03) and younger age at diagnosis (R2=0.20, p<0.02). Lower average circumferential strain magnitude (ecc) and regional changes in peak circumferential strain were seen in multiple segments despite n ormal values of global systolic function by echocardiography and CMRI (Figure1). T1 maps are depicted in Figure 1. The mean T1 values of the myocardium were not significantly different between patients and controls at 4 min (375±67ms vs.389±36, p<0.07) and 10 min (433±52 ms vs.435±36, p<0.39), but were significantly lower at 20 minutes (455±50ms vs. 487 ±44, p<0.003) (Figure 2). Low myocardial T1 at 20 minutes was significantly associated with increases in end systolic fiber stress (R2=0.7, p<0.002). Higher mean ECV was observed in patients with cumulative dose ≥400mg/m2 (0.27 vs. 0.21, p<0.05). Conclusions

Experimental study of the change of early regional myocardial function with diabetic using omni-directional Mmode echocardiography

Objective To evaluate the role of detecting early change of left ventricular regional myocardial function in the rabbit with type Ⅰ diabetes using omni-directional M-mode echocardiography (OME).Methods Eighty New Zealand rabbits were selected in this study..40 health rabbits were included in the control group,the other 40 with type Ⅰ diabetes were included in the experiment group.The OME was used to measure the peak time of myocardial motion during systole (Ts) and diastole (Td),myocardial velocity gradient during systole (MVGs) and diastole (MVGd) on the left ventricular short axis.These parameters were measured during the first,second,fourth,sixth and eighth week.Results OME was able to detect significant changes of Td during the second week,Ts and MVGd during the fourth week,and MVGs during sixth week after modeling ( P ＜0.05 ).Conclusions OME is an important method to detect early changes of regional myocardial function in the patients with diabetes. Key words: Echocardiography; Diabetes mellitus; Ventricular function,left

Distal protection beneficial?

The pathogenesis of acute coronary syndromes (ACS) includes the rupture or erosion of a coronary atherosclerotic plaque with variable degrees of superimposed platelet aggregation inducing a thrombus [1]. ST-elevation myocardial infarction (STEMI) is often caused by a total coronary occlusion of the atherothrombotic plaque, whereas in non-ST-elevation myocardial infarction (NSTEMI) the thrombus is mainly nonocclusive or transient occlusive causing less myocardial damage [2]. Conventional percutaneous coronary intervention (PCI) focuses on compressing the atherothrombotic plaque with the aim to normalize flow in the coronary artery and therefore restore perfusion of the ischemic myocardium [3]. However, embolization of atherothrombotic material may occur spontaneously after plaque rupture or due to mechanical crushing of the culprit lesion during PCI [4]. This results in obstruction of distal vessels or the microcirculation in the down-stream bed of the ischemia-related artery. Although normal epicardial flow may be achieved, this will lead to diminished myocardial perfusion, which is associated with larger infarct size, diminished left ventricular ejection fraction and increased mortality [5]. Microvascular obstruction is frequently implicated as the underlying cause through the mechanism of embolization [6–8]. Distal protection devices (DPDs) can be used for transient distal balloon occlusion during PCI, and allow recovery of any liberated plaque by aspiration before restoration of the antegrade flow [9]. Whether myocardial function can be improved with DPDs compared with conventional PCI in patients with acute myocardial infarction (AMI) has still to be proven. Over the years, echocardiography [10–13] and CMR [14–37] have found a fixed niche in the setting of AMI. In particular CMR allows the visualization of infarct site and size whereby the identification of microvascular obstruction has become unique to CMR [38–40]. For echocardiography, there are limited data describing changes in cardiac function in DPDs studies, and no data describing changes in regional myocardial function. Tissue Doppler imaging (TDI) is a useful echocardiographic tool that permits quantitative and objective assessment of both global and regional function [41–43]. In the current issue of the International Journal of Cardiovascular Imaging, Duan et al. [44] assessed the effects of DPDs on global and regional LV systolic and diastolic function were assessed by TDI in 69 patients with anterior AMI, who were randomly assigned to either PCI with DPDs (DPD group, n = 46) or conventional PCI (control group, n = 50). At 3- and 6-month follow-up, the DPD group showed a higher LV ejection fraction than the control group. Moreover, peak systolic and early diastolic mitral annular velocities obtained by TDI were significantly higher in the DPD group than in the control group. Lastly, the systolic and diastolic regional myocardial velocities were significantly improved in the DPD group compared to the control group. The authors concluded that patients with DPDs showed significant improvement of LV function. Especially patients with anterior AMI may benefit from DPDs during PCI. In recent years various distal protection devices and thrombectomy devices have been developed to protect the microcirculation against embolization of atherothrombotic material and to improve myocardial reperfusion and LV function after PCI [45]. As the use of distal protection devices is still under debate, several trials in patients with STEMI have recently focused on thrombus aspiration [46–49]. These trials have clearly shown that thrombus aspiration improves myocardial reperfusion compared to conventional PCI. The largest study to date, the TAPAS-trial, showed that manual thrombus aspiration using the Export Aspiration Catheter (EAC) in patients with STEMI improves myocardial perfusion and one-year clinical outcome compared to conventional PCI [47]. As a consequence, thrombus aspiration has been included in the new European guidelines for patients with STEMI as a therapy to improve myocardial perfusion [50]. To conclude, the study of Duan et al. [44] lends support to the notion that distal protection may be beneficial in patients with STEMI.

Bone marrow cell therapy after acute myocardial infarction: the HEBE trial in perspective, first results.

During the last decennium, the role of bone marrow mononuclear cells (BMMC) has been underscored in the healing process after acute myocardial infarction (AMI). Although these cells improve left ventricular recovery after AMI in experimental studies, results from large-scale randomised trials investigating BMMC therapy in patients with AMI have shown contradictory results. To address this issue the HEBE study was designed, a multicentre, randomised trial, evaluating the effects of intracoronary infusion of BMMCs and the effects of intracoronary infusion of peripheral blood mononuclear cells after primary percutaneous coronary intervention. The primary endpoint of the HEBE trial is the change in regional myocardial function in dysfunctional segments at four months relative to baseline, based on segmental analysis as measured by magnetic resonance imaging. The results from the HEBE trial will provide detailed information about the effects of intracoronary BMMC therapy on post-infarct left ventricular recovery. In addition, further analysis of the data and material obtained may provide important mechanistic insights into the contribution of BMMCs to natural recovery from AMI as well as the response to cell therapy. This may significantly contribute to the development of improved cell-based therapies, aiming at optimising post-infarct recovery and preventing heart failure. (Neth Heart J 2008;16:436-9.).

Investigating Cardiac Function Using Motion and Deformation Analysis in the Setting of Coronary Artery Disease

In the last decade, noninvasive cardiac imaging has played an increasing role in cardiology. As one of the most widespread clinically used techniques, echocardiography has witnessed several technical developments in imaging modalities and image analysis. One of the most recent has been the introduction of velocity-based strain-rate imaging and speckle tracking to quantify regional deformation.1 Coronary artery disease induces important changes in regional myocardial function. Both acute ischemia and chronic ischemia decrease regional wall motion and thickening. Despite recent technical developments in clinical cardiac imaging, the evaluation of regional radial and longitudinal function is often based on visual interpretation of wall motion. This is both qualitative and subjective. This paper discusses regional myocardial deformation and motion, studied in different (experimental) substrates of coronary artery disease, from acute ischemia to chronic infarction. It will be shown that regional deformation at rest, combined with observations during a dobutamine challenge, can uniquely discriminate the different ischemic substrates. Both radial and longitudinal regional peak systolic velocities show a significant fall after β-blockade2,3 but no added effect of additional pacing. Regional displacement shows a tendency to decrease with β-blockade. With the addition of pacing a further significant reduction in displacement takes place. The transmyocardial velocity gradient (the difference between epicardial and endocardial peak velocity, divided by their distance4–6) is influenced by β-blockade in the same way as peak velocities and is not altered by changes in heart rate during β-blockade. With a dobutamine infusion, myocardial velocities increase.2 With induced changes in contractility, either by dobutamine or β-blockade, peak systolic velocities correlate well with fractional shortening, regional stroke work, end-systolic and maximal elastance, as well as preload recruitable stroke work. On the basis of velocities, regional myocardial deformation properties can be assessed noninvasively both in the radial and longitudinal directions. An excellent …

Susceptibility to systolic dysfunction in the myocardium from chronically infarcted spontaneously hypertensive rats

We explored whether the hypertensive heart is susceptible to myocardial dysfunction in viable noninfarcted tissue post-myocardial infarction (MI), the potential mechanisms thereof, and the impact of these changes on pump function. Six to seven months after the ligation of the left anterior descending coronary artery, left ventricular (LV) myocardial systolic function, as assessed from the percent shortening of the noninfarcted lateral wall segmental length determined over a range of filling pressures (ultrasonic transducers placed in the lateral wall in anaesthetized, open-chest, ventilated rats) and the percent thickening of the posterior wall (echocardiography), was reduced in infarcted spontaneous hypertensive rats (SHR-MI) (P < 0.05) but not in normotensive Wistar-Kyoto (WKY-MI) animals compared with corresponding controls [SHR-sham operations (Sham) and WKY-Sham]. This change in the regional myocardial function in SHR-MI, but not in WKY-MI, occurred despite a similar degree of LV dilatation (increased LV end-diastolic dimensions and volume intercept of the LV end-diastolic pressure-volume relation) in SHR-MI and WKY-MI rats and a lack of difference in LV relative wall thinning, LV wall stress, apoptosis [terminal deoxynucleotidyl transferase biotin-dUTP nick-end labeling (TUNEL)], or necrosis (pathological score) between SHR-MI and WKY-MI rats. Although the change in regional myocardial function in the SHR-MI group was not associated with a greater reduction in baseline global LV chamber systolic function [end-systolic elastance (LV E(es)) and endocardial fractional shortening determined in the absence of an adrenergic stimulus], in the presence of an isoproterenol challenge, noninfarct-zone LV systolic myocardial dysfunction manifested in a significant reduction in LV E(es) in SHR-MI compared with WKY-MI and SHR and WKY-Sham rats (P < 0.04). In conclusion, these data suggest that with chronic MI, the hypertensive heart is susceptible to the development of myocardial dysfunction, a change that cannot be attributed to excessive chamber dilatation, apoptosis, or necrosis, but which in turn contributes toward a reduced cardiac adrenergic inotropic reserve.

976 Changes of regional myocardial function and myocardial hypertrophy in patients with severe aortic stenoses during long term follow-up after aortic valve replacement

976 Changes of regional myocardial function and myocardial hypertrophy in patients with severe aortic stenoses during long term follow-up after aortic valve replacement

Acute Improvement in Myocardial Function Assessed by Myocardial Strain and Strain Rate After Aortic Valve Replacement for Aortic Stenosis

We investigated whether Doppler tissue imaging (tissue velocity, strain, and strain rate) could be useful to detect subtle left ventricular (LV) dysfunction in patients with aortic stenosis and changes in regional myocardial function after aortic valve replacement (AVR). We studied 34 patients (age 69.2 +/- 10.4 years) with severe aortic stenosis, 21 of whom underwent AVR. Tissue velocity, systolic strain, strain rate, time to peak strain, and time to peak systolic and diastolic strain rates of basal and midsegments were measured in the apical 4-, 3-, and 2-chamber views before and 2 weeks after AVR. Strain and systolic strain rate showed the best correlation with LV ejection fraction (r = 0.80 and r = 0.70, respectively, both P < .0001). Early and late diastolic strain rates showed significant correlations with LV mass index (r = 0.45, P < .01; and r = 0.64, P < .0001, respectively) and time to peak strain, to peak systolic strain rate, and to peak early diastolic strain rate with aortic pressure gradient (r = 0.45, P < .01; r = 0.44, P < .01; and r = 0.56, P < .001, respectively) before AVR. Although LV mass index and LV systolic function did not change significantly after 2 weeks (LV mass index, 137 +/- 54 vs 125 +/- 36 g/m2; LV ejection fraction, 60 vs 58%, both P = not significant), peak strain and strain rates increased (P < .001) and time to peak strain and strain rate shortened after AVR (P < .001). Tissue velocities did not change significantly after AVR. Strain and strain rate parameters seemed to relate to LV function and aortic stenosis severity. Further, they seemed to be superior to tissue velocity and conventional echocardiography in detecting subtle changes in myocardial function after AVR before LV mass and LV function showed improvement.

Intracoronary infusion of autologous mononuclear bone marrow cells or peripheral mononuclear blood cells after primary percutaneous coronary intervention: Rationale and design of the HEBE trial—A prospective, multicenter, randomized trial

Recently, several preliminary reports have demonstrated that cell transplantation after acute myocardial infarction in humans is safe and leads to better preserved left ventricular function and improved myocardial perfusion and coronary flow reserve. The HEBE trial is a multicenter, prospective, randomized, 3-arm open trial with blinded evaluation of end points. Patients with acute large myocardial infarction treated with primary percutaneous coronary intervention (PCI) will undergo magnetic resonance imaging (MRI) and echocardiography. A total of 200 patients are randomized to treatment with (1) intracoronary infusion of autologous mononuclear bone marrow cells, (2) intracoronary infusion of peripheral mononuclear blood cells, or (3) standard therapy. Mononuclear cells are isolated from bone marrow aspirate or venous blood by density gradient centrifugation. Within 7 days after PCI and within 24 hours after bone marrow aspiration or blood collection, a catheterization for intracoronary infusion of the mononuclear cells in the infarct-related artery is performed. In all patients, follow-up will be obtained at 1, 4, and 12 months. MRI and catheterization are repeated at 4 months, and all images are analyzed by a core laboratory blinded to randomization. The primary end point of the study is the change in regional myocardial function in dysfunctional segments at 4 months relative to baseline, based on segmental analysis as measured by MRI. If intracoronary infusion of autologous mononuclear bone marrow cells or peripheral mononuclear blood cells is proven to be beneficial after primary PCI; it could be a valuable tool in preventing heart failure-related morbidity and mortality after myocardial infarction.

Changes of regional myocardial function during VAD explantation: Echocardiographic strain study

Changes of regional myocardial function during VAD explantation: Echocardiographic strain study

Alteration of the left ventricular contractile reserve in heart transplant patients: a dobutamine stress strain rate imaging study

Background Strain rate imaging (SRI), a recently developed Doppler-derived process, allows quantification of myocardial systolic function. We investigate whether SRI quantifies the contractile reserve during dobutamine stress tests in heart transplant patients (HT), when compared with normal individuals. Methods An incremental dobutamine test (5 to 40 μg/kg per minute) was performed in 10 HT and 15 control subjects, all of whom displayed normal coronary angiography. Gray-scale and color myocardial Doppler data were acquired in standard B-mode views at baseline, low-dose, peak, and recovery. Longitudinal SR was processed from the myocardial velocities for each segment. The changes in maximal systolic SR were used to quantify myocardial contractile reserve. Results Dobutamine infusion failed to induce clinical symptoms or electrocardiographic (ECG) changes in either group. Visually determined wall motion score was considered normal in all segments for each stage of the dobutamine stress. Heart rate was augmented similarly in both groups during dobutamine infusion. In controls, systolic SR increased gradually with incremental dobutamine dose and returned to baseline values upon recovery. Conversely, in HT patients, the increase in systolic SR was blunted at peak dobutamine, at which point it was significantly different vs controls. Conclusions Quantitative assessment of myocardial function using SRI during dobutamine stress revealed an impaired contractile reserve in HT patients with normal coronary angiography. These subtle changes in regional myocardial function could not be identified using visual wall motion scoring. Additional studies are necessary to evaluate whether SR imaging detection of contractile reserve impairment will improve clinical efficiency or event prediction in this population.

783 Changes in regional myocardial function assessed by ultrasonic strain rate imaging in patients undergoing valve reconstruction for primary severe mitral regurgitation

783 Changes in regional myocardial function assessed by ultrasonic strain rate imaging in patients undergoing valve reconstruction for primary severe mitral regurgitation

Identification of acutely ischemic myocardium using ultrasonic strain measurements: A clinical study in patients undergoing coronary angioplasty

ObjectivesThe goal of this study was to investigate whether the changes in myocardial deformation measured with ultrasonic strain could accurately identify acutely ischemic myocardium during coronary angioplasty. BackgroundEarly identification of acute myocardial ischemia has important clinical implications. The accuracy of ultrasonic strain for the detection of acute myocardial ischemia has been validated in animal experiments but has not been investigated in the clinical setting. MethodsIn 73 patients (64 ± 12 years), either radial or longitudinal strain values were monitored in the “at-risk” segments before, during, and early after right, circumflex, and left anterior descending coronary angioplasty. Based on the visual wall motion assessed before the angioplasty, segments were divided into normokinetic (group I) and hypo/akinetic (group II). Strain data in the “at-risk ” segments were compared with values derived from the adjacent nonischemic segments and normal values in 20 controls. ResultsCoronary occlusion induced a marked reduction in the systolic strain both in the radial (from 49 ± 6.9% to 23 ± 4.6% in group I and from 21.9 ± 11% to 11.3 ± 8.4% in group II, p < 0.001) and longitudinal directions. Concomitantly, postsystolic strain increased (from 3.8 ± 3.1% to 14.6 ± 9.5% in group I, and from 4.4 ± 3.7% to 11.3 ± 7.8% in group II in radial direction, p < 0.001). Upon reperfusion, all deformation parameters returned to near preocclusion values. In comparison with control, baseline, and reperfusion data, the systolic and postsystolic strain parameters measured during total coronary occlusion identified acutely ischemic myocardium with a sensitivity of 86% to 95% and a specificity of 83% to 89%. ConclusionsIn this model of acute ischemia, ultrasonic strain indexes differentiate acutely ischemic segments from both normal and dysfunctional myocardium. This should be a promising new approach to the bedside monitoring of acute ischemic changes in regional myocardial function.

Acute changes in systolic and diastolic events during clinical coronary angioplasty: A comparison of regional velocity, strain rate, and strain measurement

Ultrasound-derived natural strain rate and strain are new Doppler myocardial imaging (DMI) parameters, which can measure local deformation independently of overall heart motion and thus could better characterize local contractility than DMI velocities alone. This study was undertaken to evaluate the relative benefits of regional velocity, strain rate, and strain measurements in detecting the range of acute changes in regional myocardial function in the “at-risk” zone during coronary angioplasty. Sixty-one patients (aged 63 ± 12, 18 women) with stable angina pectoris were studied before, at the end of, and during recovery from a 60-second percutaneous transluminal coronary angioplasty (PTCA) balloon occlusion. High frame rate (147 fps) color DMI regional velocity data were derived from basal posterior (parasternal view) and mid, apical septal (apical view) “at-risk” segments as well as from the corresponding segments in healthy subjects and analyzed offline for velocity (VEL), strain rate (SR), and strain (ϵ) measurements. Coronary occlusion resulted in the reduction in VELSYS, SRSYS, and ϵSYS values for both radial (RCA/CX occlusion) and longitudinal data (LAD occlusion) in all segments analyzed. Velocity parameters alone failed to distinguish between baseline and occlusive measurements in the “at-risk” segments with visually abnormal baseline function. SRSYS and ϵSYS had a higher diagnostic accuracy (sensitivity 75%, 80% and specificity 80%, 82%, respectively) than VELSYS velocity alone (sensitivity 68%, specificity 65%,) for identifying acute ischemia in either baseline normal and abnormal segments. DMI-derived indexes can identify and quantify the spectrum of acute systolic and diastolic ischemic changes induced during clinical PTCA. The quantitation of regional deformation rather than motion would appear to be more appropriate in detecting and quantifying acute ischemic changes in myocardial function, especially in segments with pre-existing abnormal function. (J Am Soc Echocardiogr 2002;15:1-12.)

Quantification of the spectrum of changes in regional myocardial function during acute ischemia in closed chest pigs: An ultrasonic strain rate and strain study

The objectives of this study were to define the spectrum of regional myocardial function changes during acute ischemia in closed chest animals by using newly developed ultrasonic strain rate and strain indexes derived from regional color Doppler myocardial imaging (CDMI) velocity data. Myocardial ischemia was induced in 18 pigs either with acute total 20-second occlusions (group 1, n = 12) or graded hypoperfusion (40 to 0 mL/min, group 2, n = 6) of the circumflex coronary artery. In addition, a dobutamine challenge (5 to 10 μg/kg per minute) was performed during sustained subtotal ischemia (10 mL/min) in group 2. CDMI acquisitions with parasternal views monitored the myocardial posterior wall function. Regional radial strain rate and strain (ϵr) were measured for systole, isovolumic relaxation, early diastole, and atrial filling, respectively. During total and graded ischemia, ϵr profiles were consistently modified, showing a delayed onset and a decrease in regional systolic thickening as well as increased postsystolic thickening. Radial strain rate and ϵr indexes decreased consistently during systole and early diastole and increased during isovolumic relaxation. End-systolic ϵr could differentiate total ischemia from severe hypoperfusion (10 mL/min), decreasing from 32% ± 8% to 16% ± 5% (versus 60% ± 10% at baseline). During dobutamine infusion (10 μg/kg per minute), end-systolic ϵr tended to decrease from 27% ± 5% to 18% ± 11%, whereas postsystolic thickening increased by 2-fold (P <.05). The combined analysis of regional deformation characteristics and global cardiac event timing derived from CDMI data can identify and quantify regional function changes induced by experimental acute ischemia in closed chest pigs. This would appear to be a potentially promising new noninvasive approach to the clinical evaluation of ischemia-induced changes in segmental myocardial function. (J Am Soc Echocardiogr 2001;14:874-84.)

Changes in systolic and postsystolic wall thickening during acute coronary occlusion and reperfusion in closed-chest pigs: Implications for the assessment of regional myocardial function

The aim of the study was to characterize the impact of short-lived total coronary occlusions in closed-chest pigs on radial wall thickening within the “at-risk” myocardial segment by using gray-scale M-mode echocardiography. Twelve pigs underwent a series of 20-second total circumflex coronary artery occlusions with an angioplasty balloon. Myocardial thickening/thinning indexes were continuously monitored before ischemia, during ischemia, and on reperfusion by high-resolution M-mode recordings of the posterior wall obtained from parasternal views. The timing of regional events was compared with global systolic time intervals derived from the color Doppler myocardial imaging velocity data. Each occlusion induced a rapid decrease in end-systolic thickening (ϵ ES), closely paralleled by an increase in postsystolic thickening in the ischemic segment. After 20 seconds of ischemia, ϵ ES decreased by −86% and postsystolic thickening increased by +100%, whereas maximal thickening decreased only by −34% in comparison with preocclusion values. All wall thickening parameters returned to baseline after 15 seconds of reperfusion. During acute total ischemia in a closed-chest animal model, the changes in regional myocardial function were best characterized by the combined analysis of systolic and postsystolic thickening abnormalities and by their respective timings relative to global cardiac events markers. (J Am Soc Echocardiogr 2001;14:691-7.)

Changes in regional myocardial function after coronary artery bypass graft surgery are predicted by intraoperative low-dose dobutamine echocardiography.

Left ventricular dysfunction is often reversed after coronary artery bypass graft (CABG) surgery; however, this change is not easily predicted. The authors hypothesized that functional changes after a low dose of dobutamine (5 microgram. kg-1. min-1) intraoperatively would predict functional changes when complete revascularization was achieved. The authors analyzed 560 segments in 40 patients scheduled for elective CABG surgery for regional wall motion (1-5 scoring system) at four stages: baseline (after induction and intubation), with administration of low-dose dobutamine before cardiopulmonary bypass, after separation from cardiopulmonary bypass (early), and after administration of protamine (late). Two independent observers scored the myocardial regions according to a 16-segment model in multiple imaging planes. For each segment, the response to dobutamine was dichotomized as improved or not improved from baseline and analyzed with logistic regression. The influence of covariates (ejection fraction, myocardial infarction, diabetes mellitus, and beta blockers) was also determined with logistic regression models. P < 0.05 was considered significant. Changes in myocardial function after low-dose dobutamine were highly predictive for early (P < 0.0001) and late (P < 0.0001) changes in myocardial function from baseline regional scores. The overall odds ratio for early and late improvement increased by 20.7 and 34.6, respectively, when improvement was observed after low-dose dobutamine was administered. The overall positive predictive value of improved regional wall motion after CABG did not vary with left ventricular ejection fraction, a history of myocardial infarction, or beta blocker use, and it varied little with diabetic status (range, 0.86-0.96) if regional wall motion improved with low-dose dobutamine before CABG. The overall negative predictive value was 0.70; however, the range varied with diabetic status (i.e., lowest in diabetic patients and highest in nondiabetic patients). Intraoperative low-dose dobutamine is a reliable method to predict myocardial functional reserve and to determine functional recovery expected after coronary revascularization.