Intraoperative assessment of myocardial perfusion using contrast echocardiography

Myocardial contrast echocardiography is a new technique capable of assessing regional myocardial perfusion in vivo in real time. This article reviews the background, principles, experimental validation, and clinical uses of intraoperative myocardial contrast echocardiography. Data can be derived both for online visual and computer analyses. The technique can be useful in determining the sequence of bypass graft placement and the success of graft anastamoses. Anastamoses can be revised immediately if needed. It is hoped that this technique will improve intraoperative myocardial preservation and will diminish the rate of perioperative myocardial infarction.     

Intraoperative echocardiographic assessment of global and regional myocardial function

Intraoperative echocardiography is gaining increasing importance to the anesthesiologist and the surgeon in the management of high-risk patients undergoing cardiac and major noncardiac surgery. It can provide for the noninvasive, immediate assessment of global left ventricular function, and its determinants; preload, afterload, and myocardial contractility. In addition, abnormalities of regional myocardial function, as a marker of myocardial ischemia, can be easily identified. With the advent of transesophageal echocardiography, this imaging technique can be more widely applied without interfering with the surgical procedure, not only increasing our ability to adequately monitor the patient, but also guiding our therapy and providing additional insights into the physiological and pathophysiological processes affecting the heart during surgery.     

Echocardiographic assessment in patients with chronic kidney disease: Current update

Patients with chronic kidney disease (CKD) carry a high cardiovascular risk. An abundance of evidence has emerged in recent years establishing minor reductions in estimated glomerular filtration rate as an independent risk factor for cardiovascular mortality. Additionally, cardiac changes, such as left ventricular hypertrophy and impaired left ventricular systolic function, have been associated with an unfavorable prognosis. Despite the significant prevalence of underlying cardiac abnormalities, symptoms may not manifest in many patients with CKD. A range of available and emerging echocardiographic modalities may assist with diagnosing heart disease in CKD. Furthermore, some of these emerging techniques can give an important insight into the pathophysiology of subclinical dysfunction in CKD. This review discusses how current and emerging echocardiographic modalities such as speckle tracking echocardiography and 3D echocardiography might help cardiologists in providing important information to help with diagnosis and risk stratification of cardiac‐related morbidity and mortality in patients with renal disease, as well applicability of these tools to current clinical practice.     

Echocardiographic advances in hypertrophic cardiomyopathy: Three‐dimensional and strain imaging echocardiography

In the recent past, new ultrasound technologies, such as three‐dimensional echocardiography and strain imaging echocardiography, raised up in clinical practice leading to a better assessment of cardiac morphology and performance. These tools may assess regional cardiac mechanics, detecting clinical and subclinical myocardial dysfunction in different settings such as ischemic heart disease, cardiomyopathies, and heart valve diseases. Interesting results derive from patients affected from hypertrophic cardiomyopathy (HCM). Particularly, the mentioned techniques are progressively redefining the role of echocardiography in diagnostic evaluation of HCM variants such as apical HCM, detection of the underlying conditions of increased wall thickness, assessment of subclinical myocardial impairment, and potentially refine risk stratification and prognosis. In this review, we describe the clinical uses of these methodologies and the perspective application in HCM patients.     

Echocardiographic findings in cardiogenic shock due to right ventricular myocardial infarction

The echocardiographic findings in a patient with cardiogenic shock secondary to acute right ventricular myocardial infarction based on typical clinical, electrocardiographic, and hemodynamic features are described. The echocardiogram demonstrated a large RV/LV minor axis ratio caused by a volume overload of the right ventricle and an underfilled left ventricle. The interventricular septum showed abnormal movement, presumably due to right ventricular overload or severe disease of the left anterior descending coronary artery. Diminished septal systolic thickening, as seen in our patient, may be explained by extension of the infarct from the right ventricle to the adjacent part of the septum. Predominant right ventricular involvement can be a cause for a correctable hypotension in patients with acute myocardial infarction and should therefore be recognized early. The echocardiographic picture demonstrated in our patient, when considered in conjunction with the clinical status, can be useful for early diagnosis.     

Echocardiographic prediction of the site of coronary artery obstruction in acute myocardial infarction

In 49 patients with acute myocardial infarction (AMI), the infarctiontopography was assessed by cross-sectional echocardiographyand the location of coronary artery obstruction were correlated.A ventricular segmentation of 5 right and 16 left ventricularsegments was used. The site of coronary obstruction was determinedin 45 patients by coronary angiography and by necropsy in 4patients. The exact location of the obstruction could not befound in 4 patients. The infarct related vessel was the leftmain artery in 1 patient, the left anterior descending artery(LAD) in 19, the left circumflex in 6 and the right coronaryartery in 24.Specific segments were identified for each of the3 coronary arteries: anteroseptal and anterior segments forLAD, right ventricular segments for the right coronary arteryand basal anterolateral segment for the left circumflex. Specificsegments (specificity 100%) were also identified for the principalcoronary branches: basal anterior for the first anterior descendingdiagonal (sensitivity 71%), basal anteroseptal for the firstseptal perforator (83%), middle anterior for the second diagonal(100%), middle anteroseptal for the second septal (89%), basalposteroseptal for a dominant right coronary artery (89%), rightventricular anterolateral segment for the right ventriclar marginalbranch (83%) Echocardiographic identification of the topography of AMI canbe useful in recognizing the infarct-related vessel and identifyingthe site of coronary artery obstruction.     

Differentiation of pseudodyskinesis of inferior left ventricular wall from inferior myocardial infarction by assessment of regional myocardial strain using two-dimensional speckle tracking echocardiography

Purpose

To differentiate pseudodyskinesis (PD) of the inferior left ventricular (LV) wall from inferior myocardial infarction (IMI) noninvasively, we performed focal site evaluation using two-dimensional speckle tracking transthoracic echocardiography (TTE).

Materials and methods

Speckle tracking TTE was carried out in 57 patients, with 19 subjects in each of three groups (Group A, suspected PD; Group B, LV IMI; and Group C, controls). Inferior wall PD was defined as follows: compression of the inferior LV wall by the diaphragm in the LV short axis view with a normal electrocardiogram and no evidence of previous ischemic events.

Results

Respective values in Groups A-C for LV ejection fraction (EF) were 63.6 ± 4.2%, 52.3 ± 7.6%, and 61.5 ± 3.8%, for inferior wall speckle tracking focal site evaluation peak radial strain of 30.0 ± 14.3%, 7.5 ± 7.1%, and 42.1 ± 22.9%, for peak circumferential strain of 23.1 ± 6.0%, 16.8 ± 8.4%, and 22.7 ± 7.1%, and for longitudinal strain in the mid-inferior wall of 18.4 ± 3.4%, 11.4 ± 4.0% and 15.8 ± 5.9%. LVEF values were significantly lower in Group B than Groups A and C (P < 0.001), as were those of radial, circumferential, and longitudinal strains (P < 0.05). In receiver-operating characteristic analysis the optimal cut-off values with corresponding sensitivities and specificities for differentiation of PD from IMI were > 19% with 84.2% and 94.7% for radial, > 15% with 89.4% and 52.6% for circumferential, and > 15% with 73.6% and 100% for longitudinal strain, respectively.

Conclusions

Determination of regional strain from speckle tracking TTE, especially radial and longitudinal strains, can provide focal and quantitative noninvasive evaluation for distinguishing PD of the inferior wall from IMI.     

Transmural myocardial strain gradient: a new and robust quantitative index of left ventricular wall motion based on myocardial strain imaging

Background: Peak strain has been promising as an index of wall motion but it is sometimes susceptible to the image quality. Objective: We investigated the feasibility of a novel index, transmural myocardial strain gradient (TMSG), derived from myocardial strain M‐mode imaging (TDI‐Q, Toshiba) for quantifying regional systolic wall motion. Method: We measured transmural myocardial strain distribution at the left ventricular lateral, posterior, inferior, septal, anteroseptal and anterior walls in the basal and midventricular short‐axis images using TDI‐Q. Twenty normals (35 ± 3 years) and 35 consecutive patients (63 ± 9 years) with coronary artery disease (CAD, 19 patients with old myocardial infarction, 4 patients with acute myocardial infarction, 12 patients with angina pectoris) were studied. Peak strain, endocardial‐ and epicardial‐half strain and TMSG ((peak strain, ? epicardial strain)/distance between peak and epicardial points) were obtained. Coefficient of variation (CV) of each index was calculated. Results: In control subjects, the best reproducibility of the variables was obtained for TMSG with the smallest CV (11.6%) (27.8%, 28.1%, and 35.5%, respectively for CV of peak strain, endocardial‐ and epicardial‐half strain). All segments in control subjects and normal segments in CAD patients showed no significant difference in TMSG (15.1 ± 1.8 vs. 15.1 ± 1.6%/mm, P = ns). TMSG was the lowest for akinetic segments and highest for the normal segments (P < 0.001). Conclusion: TMSG was more robust than simple strain values to quantitatively assess wall motion. This could successfully identify subtle regional differences in wall function. (Echocardiography 2011;28:181‐187)     

Echocardiographic wall motion abnormalities and the signal averaged electrocardiogram in the acute phase of a first myocardial infarction

We studied the relationship between wall motion abnormalitiesdetermined by echocardiography and the signal-averaged electrocardiogramin 82 consecutive patients during the acute phase of a firstmyocardial infarction. An abnormal signal-averaged electrocardiogramwas defined as the presence of two of the following criteria:a QRS duration 114 ms, a root mean square voltage (RMS) ofthe last 40 ms 25 µV and an amplitude signal lower than40µV lasting 39 ms. The left ventricle was divided into13 segments and the contraction pattern divided into akinesiaalone (including dyskinesia) (group A), hypokinesia alone (groupB) and both hypokinesia and akinesia (group C). An abnormal signal-averaged electrocardiogram was found in 14/82patients (17%) and was correlated with the persistence of occlusionof the infarct-related vessel (32% vs 9%. P < 0.02). In patientswith a patent vessel, the incidence of an abnormal signal-averagedelectrocardiogram was 14% in group A, 9% in group B and 0% ingroup C (NS). In patients with an occluded vessel an abnormalsignal-averaged electrocardiogram was found in 10% of groupA patients, in 36% in group B patients and in 75% of group Cpatients (P = 0.05). Our study suggests that the presence of hypokinetic areas duringthe acute phase of a first myocardial infarction and an abnormalsignal-averaged electrocardiogram indicate an occluded infarct-relatedvessel.     

The feasibility of ultrasonic regional strain and strain rate imaging in quantifying dobutamine stress echocardiography.

BACKGROUND: Ultrasonic strain rate and strain can characterize regional one-dimensional myocardial deformation at rest. In theory, these deformation indices could be used to quantify normal or abnormal regional function during a dobutamine stress echo test. AIMS: The aims of our pilot study were threefold: (1) to determine the percentage of segments in which interpretable strain rate/strain data could be obtained during routine dobutamine stress echo, (2) to establish whether either the increase in heart rate or artefacts induced by respiration during dobutamine stress echo would influence analysis by degrading the data and (3) to determine the optimal frame rate vs image sector angle settings for data acquisition. Furthermore, although the detection of ischaemia was not to be addressed specifically in this study, we would describe the findings on the potential clinical role of regional deformation vs velocity imaging in detecting ischaemia-induced changes. METHODS: A standard dobutamine stress echo protocol was performed in 20 consecutive patients with a history of chest pain (16 with angiographic coronary artery disease and four with normal coronary angiograms). DMI velocities were acquired at baseline, low dose, peak dose, and recovery. To evaluate radial function (basal segment of the left ventricle posterior wall segment), parasternal LAX, SAX views were used. For long axis function data were acquired (4-CH, 2-CH views) from the septum; lateral, inferior and anterior left ventricle walls. Data was acquired using both 15 degrees (>150 frames per second (fps) and 45 degrees (115fps) sector angles. During post-processing each wall was divided into three segments: basal, mid and apical. Strain rate/strain values were averaged over three consecutive heart cycles. RESULTS: Data was obtained from 1936 segments, of which only 54 had to be excluded from subsequent analysis (2.8%) because of suboptimal quality. An increase in heart rates (up to 150/min) was not associated with a significant reduction in the number of interpretable segments. There was a significant correlation between maximal systolic strain rate/strain values obtained at narrow and at wide sector angles (e.g. a correlation for the septal segments: r=0.73,P <0.001 for strain rate, and r=0.71; P<0.001 for strain). The correlation for the timing of events obtained from narrow and wide sector angles was weaker. This would indicate that there was the insufficient temporal resolution for the latter acquisition method. Normal and abnormal regional strain rate/strain responses to an incremental dobutamine infusion were defined. In normal segments, maximal systolic strain rate values increased continuously from baseline, reaching the highest values at the peak dose of dobutamine. The segmental strain response was different. For strain, there was an initial slight increase at low dose of dobutamine (5, 10 microg/kg/min), but no further increase with increasing dose. A pattern representing an ischaemic response was identified and described. CONCLUSIONS: The feasibility study would suggest that with appropriate data collection and post-processing methodologies, strain rate/strain imaging can be applied to the quantification of dobutamine stress echo. However, appropriate post-processing algorithms must be introduced to reduce data analysis time in order to make this a practical clinical technique.     

Myocardial Deformation in Patients with Beta‐Thalassemia Major: A Speckle Tracking Echocardiographic Study

Background: Increasing data suggest that parameters of myocardial deformation are strong indices of ventricular systolic and diastolic function. We sought to determine myocardial deformation of the left ventricle and assess relationship of deformation rates with myocardial iron load in patients with beta‐thalassemia major. Methods: The left ventricular longitudinal, circumferential, and radial myocardial deformation was determined using speckle tracking echocardiography in 42 thalassemia patients aged 24.4 ± 6.4 years. The results were compared with those of 38 age‐matched controls. The rates of longitudinal and circumferential deformation were correlated with cardiac T2* magnetic resonance findings. Results: Compared with controls, patients had significantly greater global systolic radial strain (P = 0.001), but similar global systolic longitudinal (P = 0.12) and circumferential strain (P = 0.84). On the other hand, patients had significantly lower longitudinal systolic strain rate (SR) (P = 0.019), longitudinal early diastolic SR (P = 0.036), and circumferential early diastolic SR (P = 0.04) than controls. The cardiac T2* findings correlated positively with longitudinal (r = 0.44, P = 0.004) and circumferential early diastolic SR (r = 0.37, P = 0.019), but not with the respective systolic SRs and left ventricular ejection fraction (all P > 0.05). Patients with iron overload (T2*< 20 msec), compared to those without, had significantly lower longitudinal (1.45 ± 0.33/sec vs. 1.76 ± 0.27/sec, P = 0.002) and circumferential (1.01 ± 0.31/sec vs. 1.22 ± 0.31/sec, P = 0.03) early diastolic SR. Conclusions: Patients with beta‐thalassemia major have reduced longitudinal systolic SR, longitudinal early diastolic SR, and circumferential early diastolic SR. The rates of diastolic deformation in the longitudinal and circumferential dimensions are inversely related to myocardial iron overload. (Echocardiography 2010;27:253‐259)     

Echocardiographic assessment of atrial septal defects

Echocardiography has become the method of choice for the assessment of patients with a known or suspected atrial septal defect. The majority of patients with defects can be identified by this method. In patients with inconclusive transthoracic studies, transesophageal echocardiography is useful for identification or exclusion of a defect. Echocardiography is useful for quantification of left-to-right shunting, identification of associated anomalies, and estimation of pulmonary pressure. Cardiac catheterization can be reserved for patients who require measurement of pulmonary vascular resistance, those who have a significant risk of coronary artery disease, and those with complex congenital heart disease.     

Quantitative contrast echocardiographic assessment of collateral derived myocardial perfusion during elective coronary angioplasty

OBJECTIVE—To determine whether myocardial contrast echocardiography can be used to quantify collateral derived myocardial flow in humans.
METHODS—In 25 patients undergoing coronary angioplasty, a collateral flow index (CFI) was determined using intracoronary wedge pressure distal to the stenosis to be dilated, with simultaneous mean aortic pressure measurements. During balloon occlusion, echo contrast was injected into both main coronary arteries simultaneously. Echocardiography of the collateral receiving myocardial area was performed. The time course of myocardial contrast enhancement in images acquired at end diastole was quantified by measuring pixel intensities (256 grey units) within a region of interest. Perfusion variables, such as background subtracted peak pixel intensity and contrast transit rate, were obtained from a fitted γ variate curve.
RESULTS—16 patients had a left anterior descending coronary artery stenosis, four had a left circumflex coronary artery stenosis, and five had a right coronary artery stenosis. The mean (SD) CFI was 19 (12)% (range 0-47%). Mean contrast transit rate was 11 (8) seconds. In 17 patients, a significant collateral contrast effect was observed (defined as peak pixel intensity more than the mean + 2 SD of background). Peak pixel intensity was linearly related to CFI in patients with a significant contrast effect (p = 0.002, r = 0.69) as well as in all patients (p = 0.0003, r = 0.66).
CONCLUSIONS—Collateral derived perfusion of myocardial areas at risk can be demonstrated using intracoronary echo contrast injections. The peak echo contrast effect is directly related to the magnitude of collateral flow.


Keywords: collateral circulation; quantitative myocardial contrast echocardiography; intracoronary pressure; myocardial perfusion     

Detection of functional recovery using low-dose dobutamine and myocardial contrast echocardiography after acute myocardial infarction treated with successful thrombolytic therapy

OBJECTIVE: We studied the value of low-dose dobutamine stress echocardiography (LDDE) and myocardial contrast echocardiography (MCE) in early prediction of left ventricular functional recovery (LVFR) after acute myocardial infarction (AMI) treated with successful thrombolysis. DESIGN: LDDE and MCE using second-harmonic intermittent imaging were performed in first week after AMI. LVFR was defined as an absolute > or =5% increase in ejection fraction, from early to 6 months of follow-up by Technetium-99m-Sestamibi single-photon emission computed tomography. PATIENTS: Out of 50 patients studied, 19 evolved with LVFR (group 1) and 31 without LVFR (group 2). Regional dysfunction was detected in 103 (37%) infarcted-related segments in group 1 and in 173 (63%) segments in group 2. RESULTS: Sensitivity, specificity, positive, and negative predictive values and accuracy for detecting LVFR by LDDE were 94.7% (18/19), 87.1% (27/31), 81.8% (18/22), 96.4% (27/28), and 90% (45/50), respectively, and by MCE were 94.7% (18/19), 51.6% (16/31), 54.5% (18/33), 94.1% (16/17), and 68% (34/50). In group 1, functional improvement was observed in 86.9% (53/61) of segments with contractile reserve by LDDE and in 65.8% (52/79) of segments with microvascular perfusion by MCE. In group 2, functional improvement was observed in 78.3% (18/23) of segments with contractile reserve by LDDE and in 25.5% (25/98) of segments with microvascular perfusion by MCE. All segments without perfusion by MCE evolved without functional recovery. CONCLUSION: LDDE was an accurate predictor of late left ventricular function recovery after AMI, while MCE was sensitive and has a high negative predictive value demonstrating that microvascular perfusion is essential for LVFR.     

Echocardiographic assessment of fetal arrhythmias

See article on page 1448     

Myocardial contrast echocardiography: relation between on-line and off-line assessment of myocardial perfusion

Background: Quantitative assessment of myocardial perfusion by myocardial contrast echocardiography has been made possible by the use of custom-made off-line video-intensity programs. A standardized program that could be used by all investigators would improve the reproducibility of results and enhance its clinical utility. Methods and Results: The purpose of this study was to determine if the assessment of myocardial perfusion by contrast echocardiography using a new commercially available, quantitative on-line software program correlates with an off-line custom-made video-intensity program previously validated by our laboratory and with radiolabeled microspheres, under various experimental myocardial perfusion conditions. Two of the measured myocardial contrast echocardiographic parameters (peak intensity, area under the time-intensity curve {area}) correlated well among on-line and off-line methods and radiolabeled microspheres, especially when the data were "normalized" by comparing percent change from baseline or a ratio of ischemic to nonischemic myocardium. The third myocardial contrast echocardiographic parameter examined, half-time of the peak intensity on the washout limb of the curve (t 1/2), correlated only when the percent change from baseline was compared between the two methods or when the off-line method was compared with radiolabeled microspheres. Conclusion: The results of this investigation add further support to the potential use of myocardial contrast echocardiography to evaluate serial changes in myocardial perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)