Detection of left ventricular dysfunction by global longitudinal systolic strain in patients with chronic aortic regurgitation.

BACKGROUND: The purpose of this study was to investigate whether global longitudinal strain measured by two-dimensional speckle tracking echocardiography could detect incipient myocardial dysfunction in patients with chronic aortic regurgitation (AR). Disclosing left ventricular (LV) dysfunction is of decisive importance for optimal timing of surgery but challenging because of the altered loading conditions. METHODS: Forty-seven patients referred for aortic valve replacement because of chronic AR were studied, along with 31 healthy controls. Myocardial deformation as determined by longitudinal, circumferential, and radial strain was calculated using two-dimensional speckle-tracking echocardiography technique, in addition to LV volumes, dimensions, and ejection fraction. Strain values were normalized to end-diastolic volume to correct for the volume dependency of deformation. RESULTS: Global systolic longitudinal strain was significantly lower in patients with AR before surgery compared with the healthy controls (-17.5 ± 3.1% vs -22.1 ± 1.8%, P < .01), while global circumferential strain and LV ejection fraction did not differ (-21.7 ± 3.4% vs -22.6 ± 2.5%, P = .22 and 59 ± 5% vs 59 ± 6%, P = .59, respectively). However, differences between patients and controls were evident for both longitudinal and circumferential strain when normalized to end-diastolic volume (-0.09 ± 0.04 vs -0.23 ± 0.08, P < .01, and -0.11 ± 0.05 vs -0.24 ± 0.08, P < .01, respectively). In contrast to their absolute values, both normalized variables demonstrated improvement in myocardial shortening after valve replacement (P < .01). CONCLUSIONS: The study demonstrated reduced global longitudinal strain in patients with chronic AR with preserved LV ejection fractions. Global longitudinal strain might therefore disclose incipient myocardial dysfunction with a consequent potential for improved timing of aortic valve surgery.

Detecting myocardial ischaemia using miniature ultrasonic transducers--a feasibility study in a porcine model.

BACKGROUND: Detection of myocardial ischaemia during and after cardiac surgery remains a challenge. Echocardiography is more sensitive in ischaemia detection than echocardiography (ECG) and haemodynamic monitoring, but demands repeated examinations for monitoring over time. We have developed and validated an ultrasonic system that permits continuous real-time assessment of myocardial ischaemia using miniature epicardial ultrasound transducers. METHODS: In an open-chest porcine model (n=8), prototype ultrasound transducers were fixed on the epicardium in the left anterior descending and circumflex coronary artery supply regions, providing continuous measurement of transmural myocardial velocities. Peak systolic velocity and post-systolic velocity were recorded simultaneously with ECG, left ventricular pressure and arterial pressure. Two-dimensional (2D) echocardiographic strain was used as a reference. Global changes were induced by infusing fluid, epinephrine, nitroprusside and esmolol. Regional changes were induced by occluding the left anterior descending coronary artery (LAD). Subsequent LAD stenosis was performed in a subgroup, with flow reduction to 50% of baseline level and further to occlusion. RESULTS: Systolic velocity in the LAD region decreased during LAD occlusion (0.9+/-0.1 to 0.1+/-0.1 cm s(-1), P<0.01), whereas post-systolic velocity increased (0.3+/-0.1 to 2.3+/-0.1 cm s(-1), P<0.01). No changes occurred in the circumflex coronary artery (CX) region. Severe ischaemia was confirmed by reduction in 2D echocardiography strain calculations. Changes in myocardial velocities assessed by miniature transducer during ischaemia differed from changes during all global interventions. Significant reduction in systolic velocity occurred at 50% LAD flow (0.9+/-0.1 to 0.5+/-0.1 cm s(-1), P=0.02) with further decrease on following occlusion (0.0+/-0.0 cm s(-1), P<0.01). Post-systolic velocity increased both from baseline to 50% LAD flow, and further to occlusion. CONCLUSION: The epicardial transducers provided continuous assessment of regional myocardial function and detected ischaemia with high sensitivity and specificity. Further development of this system may provide a useful tool for myocardial monitoring during and after cardiac surgery.

Diagnostic capability and reproducibility of strain by Doppler and by speckle tracking in patients with acute myocardial infarction.

OBJECTIVES: The objective of the present study was to investigate the ability of strain by Doppler and by speckle tracking echocardiography in the acute phase in patients with ST-segment elevation myocardial infarction (STEMI) to diagnose left ventricular (LV) infarct size. Furthermore, we wanted to study at which time during the cardiac cycle strain should be measured. BACKGROUND: The assessment of regional myocardial dysfunction may be an important diagnostic tool in the evaluation of acute myocardial injury. METHODS: Strain by Doppler and speckle tracking were assessed in the acute phase and after 10 days in 36 patients (61 +/- 11 years) with STEMI treated with thrombolysis. In a 16-segment model of the LV, peak systolic, end systolic, and peak negative strain were validated against the corresponding myocardial segments measured by contrast-enhanced cardiac magnetic resonance. The 16 segments were averaged to assess LV global longitudinal strain. In addition, 6 segments were analyzed from parasternal short-axis recordings at the papillary muscle level to assess circumferential strain. Reproducibility was tested in 20 patients. RESULTS: The different segmental strain assessments separated significantly (p < 0.0001) between the different levels of infarct transmurality regardless of method, with better reproducibility for speckle strain. Circumferential strain separated better than longitudinal strain. With a cutoff value of -13.3% for segmental circumferential strain, sensitivity was 80% and specificity was 74% for prediction of transmural infarction. The LV global strain showed a good correlation with LV infarct size, with the best correlation for LV global peak systolic speckle strain (beta = 0.76, p < 0.0001). CONCLUSIONS: On a segmental level, circumferential strain separated transmural from subendocardial necrosis better than longitudinal strain in the acute phase in patients with STEMI. Our findings suggest that in the acute phase in patients treated with thrombolysis, LV global peak systolic speckle strain should be the preferred method for predicting final LV infarct size.

Clinical assessment of left ventricular rotation and strain: a novel approach for quantification of function in infarcted myocardium and its border zones.

Left ventricular (LV) circumferential strain and rotation have been introduced as clinical markers of myocardial function. This study investigates how regional LV apical rotation and strain can be used in combination to assess function in the infarcted ventricle. In healthy subjects (n = 15) and patients with myocardial infarction (n = 23), LV apical segmental rotation and strain were measured from apical short-axis recordings by speckle tracking echocardiography (STE) and MRI tagging. Infarct extent was determined by late gadolinium enhancement MRI. To investigate mechanisms of changes in strain and rotation, we used a mathematical finite element simulation model of the LV. Mean apical rotation and strain by STE were lower in patients than in healthy subjects (9.0 +/- 4.9 vs. 12.9 +/- 3.5 degrees and -13.9 +/- 10.7 vs. -23.8 +/- 2.3%, respectively, P < 0.05). In patients, regional strain was reduced in proportion to segmental infarct extent (r = 0.80, P < 0.0001). Regional rotation, however, was similar in the center of the infarct and in remote viable myocardium. Minimum and maximum rotations were found at the infarct borders: minimum rotation at the border zone opposite to the direction of apical rotation, and maximum rotation at the border zone in the direction of rotation. The simulation model reproduced the clinical findings and indicated that the dissociation between rotation and strain was caused by mechanical interactions between infarcted and viable myocardium. Systolic strain reflects regional myocardial function and infarct extent, whereas systolic rotation defines infarct borders in the LV apical region. Regional rotation, however, has limited ability to quantify regional myocardial dysfunction.

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.

Mechanisms of preejection and postejection velocity spikes in left ventricular myocardium: interaction between wall deformation and valve events.

BACKGROUND: Normal left ventricular myocardium demonstrates distinct spikes in the velocity trace before and after left ventricular ejection. We tested the hypothesis that the preejection and postejection velocity spikes reflect early systolic shortening and late systolic lengthening that are interrupted by mitral and aortic valve closure, respectively. METHODS AND RESULTS: In 11 anesthetized dogs, timing of valve closure was determined by pressure variables; left ventricular dimensions were determined by sonomicrometry. Myocardial shortening started 20+/-10 ms (mean+/-SD; P<0.001) before mitral valve closure and was interrupted at the time of mitral valve closure (time difference, 4+/-7 ms). Similarly, myocardial lengthening started 31+/-15 ms (P<0.001) before aortic valve closure and was interrupted at the time of aortic valve closure (time difference, 0+/-3 ms). Prevention of mitral (n=4) and aortic (n=4) valve closure by stenting the valves abolished the preejection and postejection velocity spikes, respectively. Echocardiographic measurements of patients (n=15) with severe mitral regurgitation showed that the preejection velocity spike was reduced after prosthetic valve replacement (43+/-25 versus 32+/-15 mm/s; P=0.036), indicating that preejection shortening was larger with a leaking valve. Similarly, late systolic lengthening was reduced in patients (n=15) with severe aortic regurgitation after prosthetic valve replacement; minimum postejection velocity spike was increased from -32+/-11 to -17+/-11 mm/s; P=0.0003). Asynchronous onset of contraction/relaxation and atrioventricular interaction were investigated as alternative mechanisms of the velocity spikes in dogs and patient groups but were found implausible. CONCLUSIONS: This study supports the hypothesis that normal left ventricular preejection and postejection velocity spikes are attributed to valve closures that interrupt early systolic shortening and late systolic lengthening, respectively.

Noninvasive separation of large, medium, and small myocardial infarcts in survivors of reperfused ST-elevation myocardial infarction: a comprehensive tissue Doppler and speckle-tracking echocardiography study.

BACKGROUND: The objective of the study was to evaluate the ability of established and new parameters of global systolic left ventricle function to estimate myocardial infarct size. Increasing infarct extent is associated with impaired prognosis in chronic ischemic heart disease. Systolic myocardial deformation is a complex 3D process that is mainly influenced by the amount and transmural distribution of viable myocardium. Speckle-tracking echocardiography (2D-STE) enables deformation assessment along the 3 main cardiac axes independent of insonation angle. METHODS AND RESULTS: Global longitudinal, circumferential, and radial strain and left ventricle twist by 2D-STE, global longitudinal strain rate and strain by tissue Doppler imaging, and left ventricle ejection fraction and wall motion score index were assessed in 40 patients 8.5+/-5.4 months after a first myocardial infarct and compared with global myocardial infarct mass assessed by contrast-enhanced MRI. Longitudinal and circumferential strain by 2D-STE and longitudinal strain and strain rate by tissue Doppler imaging significantly separated medium-sized infarcts from small or large infarcts at the global level (P<0.05). All deformation indices correlated significantly with global infarct mass (P<0.01). Circumferential and longitudinal strains by 2D-STE demonstrated the best ability to identify medium-sized global myocardial infarcts. CONCLUSIONS: Circumferential and longitudinal strains by 2D-STE correlate with myocardial infarct mass and significantly differentiate among large, medium, and small myocardial infarcts.

Global longitudinal strain measured by two-dimensional speckle tracking echocardiography is closely related to myocardial infarct size in chronic ischaemic heart disease.

2D-STE (two-dimensional speckle tracking echocardiography) is a novel echocardiographic modality that enables angle-independent assessment of myocardial deformation indices. In the present study, we tested whether peak systolic epsilon(parallel) (longitudinal strain) values measured by 2D-STE could identify areas of MI (myocardial infarction) as determined by CE MRI (contrast-enhanced magnetic resonance imaging). Conventional echocardiographic apical long-axis recordings were performed in 38 patients, 9 months after a first MI. Peak systolic epsilon(parallel) measured by 2D-STE in 16 left ventricle segments was compared with segmental infarct mass and transmurality assessed by CE MRI. Segmental values were averaged to global and territorial values for assessment of global function and myocardial function in the coronary distribution areas. CE MRI identified transmural infarction in 27 patients, and a mean infarct size of 36+/-25 g. Peak systolic epsilon( parallel) correlated with the infarct mass at the global level (r=0.84, P<0.001). A strain value of -15% identified infarction with 83% sensitivity and 93% specificity at the global level and 76% and 95% at the territorial level, and a strain value of -13% identified transmural infarction with 80% sensitivity and 83% specificity at the segmental level. Global infarct mass correlates with the wall motion score index (r=0.70, P<0.001), and left ventricular ejection fraction measured by MRI or echocardiography (r=-0.71 and -0.58, both P<0.001). In chronic infarction, peak systolic epsilon(parallel) measured by 2D-STE correlates with the infarct mass assessed by CE MRI at a global level, and separates infarcted from non-infarcted tissue. Global strain is an excellent predictor of myocardial infarct size in chronic ischaemic heart disease.

Early prediction of infarct size by strain Doppler echocardiography after coronary reperfusion.

OBJECTIVES: The objective of this study was to investigate whether strain Doppler echocardiography performed immediately after revascularization by percutaneous coronary intervention could predict the extent of myocardial scar, determined by contrast-enhanced magnetic resonance imaging (MRI). BACKGROUND: There is considerable variability in survival rate after percutaneous coronary intervention, and accurate early risk stratification is therefore of major clinical importance. METHODS: Thirty individuals with acute anterior myocardial infarction were examined with longitudinal strain by Doppler 1.5 h after revascularization. The extent of scarring 9 months later was analyzed by MRI in 16 corresponding myocardial segments. Strain in all left ventricular segments was averaged to obtain a global value. Infarct size was estimated by clinical parameters and cardiac markers. RESULTS: A good correlation was found between the global strain and total infarct size (R = 0.77, p < 0.00001). A multivariate regression analysis showed that global peak strain and serum glutamic oxaloacetic transaminase correlated with the infarct size measured by MRI (p = 0.0001 and p = 0.001, respectively). Furthermore, a clear inverse relationship was found between the segmental strain and the transmural extent of infarction in each segment (R = 0.67, p < 0.0001). CONCLUSIONS: This study demonstrates that assessment of regional and global strain at 1.5 h after reperfusion therapy correlates with size and transmural extent of myocardial infarction as determined by contrast-enhanced MRI. The novel global strain parameter is a valuable predictor of the total extent of myocardial infarction and may therefore be an important clinical tool for risk stratification in the acute phase of myocardial infarction.

Communication of medical images, text, and messages in inter-enterprise systems: a case study in Norway.

There is an increasing demand to discuss diagnostic images and reports of difficult cases with experienced staff. A possible solution besides physically transporting patients and material is to use high-speed communication networks to transfer images and reports electronically. With the web application PACSflow we have developed a solution to transfer images, reports, and messages as a single package in a one-step procedure. The PACSflow is an interoperable and standard compliant web-based application, which gives clinicians a user-friendly interface for their work on a daily basis. The solution assumes that the diagnostic images are compatible with the digital imaging and communications in medicine (DICOM) format. The Department of Cardiology at the Rikshospitalet University Hospital in Oslo, Norway, and the Department of Internal Medicine at the Sørlandet Sykehus in Arendal, Norway, are making clinical use of the system. Initial tests indicate that use of PACSflow has reduced the time required to prepare and transfer data by a factor of 3.

Clinical and echocardiographic assessment of the Medtronic Advantage aortic valve prosthesis: the Scandinavian multicentre, prospective study.

OBJECTIVE: The aim of this report is the prospective, multicentre evaluation of clinical results and haemodynamic performance of the Medtronic Advantage aortic valve prosthesis. METHODS: From April 2001 to June 2003, 166 patients (male:female 125:41; mean (SD) age 61.8 (11.8) years) received an aortic advantage valve prosthesis. Complete cumulative follow-up was 242.7 patient-years (maximum 3.2; mean 1.6 years). Postoperatively, patients underwent early (within 30 days) and 1 year transthoracic echocardiography. RESULTS: 30 day mortality was 2.4% (n = 4). Kaplan-Meier estimates of freedom from complications and linearised rates were as follows: 96.9 (1.6)% survival; 94.7 (1.3)% (2.06 patients/year) thrombo-embolism; 99.4 (0.6)% (0.4 patients/year) bleeding; 98.8 (0.9)% (0.8 patients/year) non-structural valve dysfunction; 98.8 (0.9)% (0.8 patients/year) reoperation. Valvular mean pressure gradients ranged from 16 (3) mm Hg for size 19 to 7 (2) mm Hg for size 27 and the corresponding effective orifice areas ranged from 1.2 (0.25) to 3.2 (0.66) cm(2). In all, left ventricular mass significantly decreased (p<0.001) and fractional shortening increased (p<0.001) from postoperative to 1 year echocardiography. CONCLUSIONS: Haemodynamic performance and early clinical results of Medtronic advantage in the aortic position were satisfactory and comparable with those of other bileaflet valves in current clinical use.

Mechanisms behind the postprandial increase in cardiac output: a clue obtained from transplanted hearts.

Consumption of a meal is followed by an increase in cardiac output (CO) which appears to be closely related to the concomitant increase in blood flow to the gastrointestinal organs. To gain information on the mechanism behind this increase in CO we have previously used Doppler ultrasound technique to record circulatory responses to a standardized meal in five patients with recently transplanted and thus denervated hearts. We obtained the surprising result that they reacted to the consumption of a meal with a greater increase in CO than did five matched normal controls. The patients also presented above-normal levels of heart rate (HR) and CO at rest. The same five patients have now been tested 18 months later to re-examine their remarkable cardiac response to ingestion of a meal. The hearts of two patients showed some signs of reinnervation, whereas the hearts of the other three were apparently still fully denervated. However, all five patients once again evolved a marked cardiac response to ingestion of a meal. Postprandial CO reached significantly higher levels in the patients than in the controls. The persistence of such a pronounced postprandial augmentation of CO in transplanted and largely denervated hearts strengthens the assumption that the heart is induced to increase its postprandial performance through the action of a humoral agent of some sort, possibly one of the hormones from the duodenal-pancreatic region.

Reduced left ventricular function in hypoxemic newborn pigs: a strain Doppler echocardiographic study.

Myocardial dysfunction, hypotension, and increased pulmonary artery pressure are induced by asphyxia in neonates. We sought to define left ventricular (LV) systolic function by measuring longitudinal and radial contraction by strain Doppler echocardiography (SDE) in hypoxemic newborn pigs. Hypoxemia was induced in 11 anesthetized and instrumented newborn pigs by ventilation with 8% O2 in nitrogen. When mean arterial blood pressure (BP) decreased to 15 mm Hg or arterial base excess reached -20 mmol/L or less, the pigs were reoxygenated and ventilated for 150 min. Echocardiography was performed at baseline and during hypoxemia and reoxygenation. Baseline measurements of myocardial peak systolic strain demonstrated normal longitudinal shortening and radial thickening. During hypoxemia, systolic longitudinal shortening in the mid-posterior and septal segments changed to systolic stretching. Peak strain in the mid-lateral and anterior segments decreased but without signs of paradox wall motion. Short-axis peak strain remained positive during hypoxemia, although the amplitude was reduced and delayed with respect to timing. In the newborn pig heart, we found a complex and heterogeneous systolic pattern with distinct regional differences during global hypoxemia. Rapid changes in LV function during hypoxemia and reoxygenation are assessable by SDE, and the results indicate that longitudinal systolic contraction is more vulnerable to hypoxemic changes than radial contraction. To explore the full picture of a global hypoxemic injury, both long- and short-axis functions have to be considered.

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

OBJECTIVES: The aim of the study was to compare the ability of the tissue Doppler echocardiographic imaging (TDI) modalities velocity, strain, and displacement to quantify systolic myocardial function. BACKGROUND: Several TDI modalities may be used to quantify regional myocardial function, but it is not clear how the different modalities should be applied. METHODS: In 10 anesthetized dogs we measured left ventricular pressure, longitudinal myocardial velocity, strain, and displacement by TDI at baseline and during left anterior descending coronary artery (LAD) stenosis and occlusion. Reference methods were segmental shortening by sonomicrometry and segmental work. In 10 patients with acute anterior wall infarction (LAD occlusion) and 15 control subjects, velocity, strain, and displacement measurements were performed. RESULTS: In the animal study, systolic strain correlated well with segmental shortening (r = 0.96, p < 0.01) and work (r = 0.90, p < 0.01), and differentiated well between non-ischemic (-13.5 +/- 3.2% [mean +/- SD]), moderately ischemic (-6.5 +/- 2.8%), and severely ischemic myocardium (7.1 +/- 13.2%). The ratio post-systolic strain/total strain also differentiated well between levels of ischemia. Displacement and ejection velocity had weaker correlations with segmental shortening (r = 0.92 and r = 0.74, respectively) and regional work (r = 0.85 and r = 0.69), and there was marked overlap between values at baseline and at different levels of ischemia. In the human study, systolic strain differentiated well between infarcted and normal myocardium (1.0 +/- 5.0% vs. -17.8 +/- 3.8%), whereas systolic displacement (-0.3 +/- 1.3 mm vs. -2.3 +/- 0.6 mm) and ejection velocity (0.9 +/- 0.6 cm/s vs. 2.2 +/- 0.6 cm/s) showed overlap. In the infarction group, strain was reduced in segments with infarcted tissue, while systolic velocity and displacement were reduced in all segments and did not reflect the extension of the infarct. CONCLUSIONS: Strain was superior to velocity and displacement for quantification of regional myocardial function. Provided technical limitations can be solved, strain Doppler is the preferred TDI modality for assessing function in ischemic myocardium.

Noninvasive myocardial strain measurement by speckle tracking echocardiography: validation against sonomicrometry and tagged magnetic resonance imaging.

OBJECTIVES: The aim of this study was to validate speckle tracking echocardiography (STE) as a method for angle-independent measurement of regional myocardial strain, using sonomicrometry and magnetic resonance imaging (MRI) tagging as reference methods. BACKGROUND: Tissue Doppler imaging allows non-invasive measurement of myocardial strain in the left ventricle (LV), but is limited by angle dependency. METHODS: Strain measurements with STE were obtained by a custom-made program that allowed tracking of two-dimensional motion of speckle patterns in a B-mode image. In anesthetized dogs, we compared LV long- and short-axis measurements by STE to sonomicrometry during preload changes and regional myocardial ischemia. Measurements in the two orthogonal axes were obtained simultaneously in a single imaging plane. In human subjects, long-axis strain by STE and MRI tagging were compared in multiple segments of the LV. RESULTS: In the experimental study there was good correlation and agreement between STE and sonomicrometry for systolic strain in the long axis (r = 0.90, p < 0.001; 95% limits of agreement -4.4% to 5.0%) and systolic shortening in the short axis (r = 0.79, p < 0.001; -5.6% to 5.1%). In the clinical study, 80% of the segments could be analyzed, and correlation and agreement between STE and MRI tagging were good (r = 0.87, p < 0.001; -9.1% to 8.0%). CONCLUSIONS: Speckle tracking echocardiography provides accurate and angle-independent measurements of LV dimensions and strains and has potential to become a clinical bedside tool for quantifying myocardial strain.

Myocardial strain analysis in acute coronary occlusion: a tool to assess myocardial viability and reperfusion.

BACKGROUND: This study proposes 2 new echocardiographic indices with potential application in acute coronary artery occlusion to differentiate between viable and necrotic myocardium and to identify reperfusion. We investigated whether the ratio between systolic lengthening and combined late and postsystolic shortening (L-S ratio) could identify viable myocardium and whether systolic myocardial compliance, calculated as systolic lengthening divided by systolic pressure rise, could identify necrotic myocardium. METHODS AND RESULTS: In anesthetized dogs, we measured left ventricular (LV) pressure and long-axis strain by Doppler echocardiography (SDE) and sonomicrometry. The left anterior descending coronary artery was occluded for 15 minutes with 3-hour reperfusion (n=6), for 4 hours with 3-hour reperfusion (n=6), or for 4 hours with no reperfusion (n=6). Myocardial work was quantified by pressure-segment length analysis, necrosis by triphenyltetrazolium chloride staining, and edema by water content. L-S ratio and systolic compliance were calculated by SDE. The L-S ratio ranged between 0.00 and 1.00 and was well correlated with regional myocardial work (r=0.77, P<0.0001). In entirely passive myocardium, the L-S ratio approached 1 and was similar in viable (0.88+/-0.02) and necrotic (0.81+/-0.03) myocardium. Compliance, however, was reduced in necrotic myocardium owing to edema (0.07+/-0.01%/mm Hg) but was preserved in viable myocardium (0.15+/-0.01%/mm Hg, P<0.05). Reperfusion of viable myocardium caused a reduction of the L-S ratio after 15 minutes (0.57+/-0.06, P<0.05), reflecting recovery of function. Reperfusion of necrotic myocardium caused no change in the L-S ratio, but compliance was further reduced within 15 minutes (0.03+/-0.01%/mm Hg, P<0.05). CONCLUSIONS: Myocardial L-S ratio and compliance by SDE identified active contraction and necrosis, respectively. These indices should be tested clinically for assessment of myocardial viability and reperfusion.

New noninvasive method for assessment of left ventricular rotation: speckle tracking echocardiography.

BACKGROUND: Left ventricular (LV) torsion is due to oppositely directed apical and basal rotation and has been proposed as a sensitive marker of LV function. In the present study, we introduce and validate speckle tracking echocardiography (STE) as a method for assessment of LV rotation and torsion. METHODS AND RESULTS: Apical and basal rotation by STE was measured from short-axis images by automatic frame-to-frame tracking of gray-scale speckle patterns. Rotation was calculated as the average angular displacement of 9 regions relative to the center of a best-fit circle through the same regions. As reference methods we used sonomicrometry in anesthetized dogs during baseline, dobutamine infusion, and apical ischemia, and magnetic resonance imaging (MRI) tagging in healthy humans. In dogs, the mean peak apical rotation was -3.7+/-1.2 degrees (+/-SD) and -4.1+/-1.2 degrees, and basal rotation was 1.9+/-1.5 degrees and 2.0+/-1.2 degrees by sonomicrometry and STE, respectively. Rotations by both methods increased (P<0.001) during dobutamine infusion. Apical rotation by both methods decreased during left anterior descending coronary artery occlusion (P<0.007), whereas basal rotation was unchanged. In healthy humans, apical rotation was -11.6+/-3.8 degrees and -10.9+/-3.3 degrees, and basal rotation was 4.8+/-1.7 degrees and 4.6+/-1.3 degrees by MRI tagging and STE, respectively. Torsion measurement by STE showed good correlation and agreement with sonomicrometry (r=0.94, P<0.001) and MRI (r=0.85, P<0.001). CONCLUSIONS: The present study demonstrates that regional LV rotation and torsion can be measured accurately by STE, suggesting a new echocardiographic approach for quantification of LV systolic function.

Interaction between left ventricular wall motion and intraventricular flow propagation in acute and chronic ischemia.

Myocardial ischemia has been associated with left ventricular (LV) postsystolic shortening. The combination of tissue Doppler imaging and high frame-rate acquisition of two-dimensional color flow makes it possible to study the interaction between LV wall motion and intraventricular flow propagation. The aim of this study was to examine in a clinical model the impact that acute myocardial ischemia and prior myocardial infarct might have on LV flow patterns and to explain the underlying mechanisms from the tissue Doppler data. LV flow propagation and tissue velocities during early diastole were studied in 18 healthy individuals, 17 patients with prior anterior myocardial infarct, and 16 patients before and during percutaneous coronary intervention (PCI) of the left anterior descending artery. Normal individuals had intraventricular flow propagation toward the apex during isovolumic relaxation. During this early diastolic time phase, myocardial velocities measured at mid- and apical septal segment were directed away from the apex. Before PCI, patients without myocardial infarction had similar findings as in normal individuals. In contrast, each patient with either prior myocardial infarction or PCI-induced acute ischemia had flow propagation opposite to normal individuals, and tissue velocities reversed toward the apex during early diastole. Reversal of early diastolic LV flow propagation in acute and chronic anterior myocardial ischemia reflects postsystolic shortening in the dyskinetic apical and septal myocardial segments.

Regional myocardial work by strain Doppler echocardiography and LV pressure: a new method for quantifying myocardial function.

There is a need for better methods to quantify regional myocardial function. In the present study, we investigated the feasibility of quantifying regional function in terms of a segmental myocardial work index as derived from strain Doppler echocardiography (SDE) and invasive pressure. In 10 anesthetized dogs, we measured left ventricular (LV) pressure by micromanometer and myocardial longitudinal strains by SDE and sonomicrometry. The regional myocardial work index (RMWI) was calculated as the area of the pressure-strain loop. As a reference method for strain, we used sonomicrometry. By convention, the loop area was assigned a positive sign when the pressure-strain coordinates rotated counterclockwise. Measurements were done at baseline and during volume loading and left anterior descending coronary artery (LAD) occlusion, respectively. There was a good correlation between RMWI calculated from strain by SDE and strain by sonomicrometry (y = 0.73x + 0.21, r = 0.82, P < 0.01). Volume loading caused an increase in RMWI from 1.3 +/- 0.2 to 2.2 +/- 0.1 kJ/m3 (P < 0.05) by SDE and from 1.5 +/- 0.3 to 2.7 +/- 0.3 kJ/m3 (P = 0.066) by sonomicrometry. Short-term ischemia (1 min) caused a decrease in RMWI from 1.3 +/- 0.2 to 0.3 +/- 0.04 kJ/m3 (P < 0.05) and from 1.3 +/- 0.3 to 0.5 +/- 0.2 kJ/m3 (P < 0.05) by SDE and sonomicrometry, respectively. In the nonischemic ventricle and during short-term ischemia, the pressure-strain loops rotated counterclockwise, consistent with actively contracting segments. Long-term ischemia (3 h), however, caused the pressure-strain loop to rotate clockwise, consistent with entirely passive segments, and the loop areas became negative, -0.2 +/- 0.1 and -0.1 +/- 0.03 kJ/m3 (P < 0.05) by SDE and sonomicrometry, respectively. A RMWI can be estimated by SDE in combination with LV pressure. Furthermore, the orientation of the loop can be used to assess whether the segment is active or passive.

Detection of ischemia and new insight into left ventricular physiology by strain Doppler and tissue velocity imaging: assessment during coronary bypass operation of the beating heart.

BACKGROUND AND OBJECTIVES: Detection of myocardial ischemia in humans by strain Doppler and tissue velocity imaging was validated in a novel, experimentally designed study model during coronary bypass operation of the beating heart. METHODS: Assessment of ischemia was made with an opened chest and pericardium inherent in the operative procedure. Longitudinal strain and tissue velocity of interventricular septal regions were measured by transesophageal echocardiography during occlusion of the left anterior descending coronary artery (LAD). RESULTS: Unexpectedly, baseline velocities demonstrated that the apical and basal septum moved toward each other during systole. This occurred when the apex was dislodged from the pericardial sac to obtain access to the LAD, without any change in strain. The preceding motion of all septal regions toward the apex was reestablished after the heart was repositioned within the pericardium. In 16 patients with antegrade LAD flow, strain Doppler detected ischemia during LAD occlusion by disclosing systolic lengthening of the apical septum ( P <.01) and reduced shortening of the mid septum ( P <.05). The location and degree of ischemic changes coincided with the concomitant deterioration of wall motion. Tissue velocity changed in the basal and mid septum ( P <.05) but not in the apical region, explained by tethering effects and the distinctive motion pattern at baseline. There was no evidence of ischemia by invasive hemodynamic measures. In 7 patients with retrograde LAD flow, there were no significant changes in strain or tissue velocity measurements during LAD occlusion. CONCLUSIONS: Strain by Doppler is a sensitive means for detecting myocardial ischemia, also capable of correctly localizing the ischemia, as opposed to tissue velocity assessment. However, velocity measurements provided new physiological information by disclosing the normal longitudinal motion of the heart to be dependent on the pericardial sac enveloping the apex, irrespective of the structural integrity of the pericardium.