Identification Of Viable Myocardium Research Articles

Complementary Value of Tissue Doppler Imaging in Dobutamine Stress Echocardiography: A Prospective Cohort Study

Introduction: In patients with Coronary Artery Diseases (CAD), the presence of viable myocardium predicts the recovery of Left Ventricular (LV) systolic function after revascularisation. The identification of myocardial viability during dobutamine stress echocardiography is subjective and with observer bias. Tissue Doppler Imaging (TDI) echocardiography has opened new possibilities for non-invasive quantification of myocardial function by directly interrogating myocardial velocity with high temporal and spatial resolution. Aim: To determine the baseline regional myocardial and mitral annular Maximum Systolic Velocities (MSV) in patients with LV dysfunction and to compare the MSV values in viable and nonviable myocardium. Materials and Methods: In this prospective Cohort study, TDI of regional and annular LV myocardial velocities was performed at the baseline (at rest) in 352 patients with CAD and LV dysfunction who were referred for Dobutamine stress Echocardiography. Viability assessment by 2 Dimensional (2D) methods was done simultaneously using routine Dobutamine stress protocol. Patients were grouped in two groups based on the presence or absence of viability with 2D stress echocardiography. TDI velocities were compared in the two groups of patients with and without myocardial viability. Measurements of regional wall thickness, Ejection Fraction(EF) and Wall Motion Score Index (WMSI) were done to assess the regional and global LV function in these patients. Those patients who underwent revascularisation were subsequently assessed for functional recovery by 2D and TDI echocardiography before discharge from the hospital. Analyses were conducted using Statistical Package for Social Sciences(SPSS) version 16.0. Results: Among 352 patients studied (124 females and 228 males), mean age 58 years (range 36 to 75 years). A total of 243 patients (69%) with viable myocardium as per 2D echocardiography had higher cut-off Baseline Regional Maximum Systolic Velocity (BRMSV) >0.03 m/s and baseline mitral annular systolic velocity >0.06 m/s with high sensitivity and specificity compared to patients with severe contractile dysfunction and non-viable myocardium. Conclusion: Tissue doppler parameters like regional myocardial systolic and mitral annular velocities have shown significantly higher cut-off values in those patients with ischaemic and viable myocardium compared to non-viable myocardium.

Multimodality imaging of myocardial viability: an expert consensus document from the European Association of Cardiovascular Imaging (EACVI).

In clinical decision making, myocardial viability is defined as myocardium in acute or chronic coronary artery disease and other conditions with contractile dysfunction but maintained metabolic and electrical function, having the potential to improve dysfunction upon revascularization or other therapy. Several pathophysiological conditions may coexist to explain this phenomenon. Cardiac imaging may allow identification of myocardial viability through different principles, with the purpose of prediction of therapeutic response and selection for treatment. This expert consensus document reviews current insight into the underlying pathophysiology and available methods for assessing viability. In particular the document reviews contemporary viability imaging techniques, including stress echocardiography, single photon emission computed tomography, positron emission tomography, cardiovascular magnetic resonance, and computed tomography and provides clinical recommendations for how to standardize these methods in terms of acquisition and interpretation. Finally, it presents clinical scenarios where viability assessment is clinically useful.

Delayed Hyper-Enhancement in Cardiac MRI Compared to Nuclear Perfusion Scintigraphy in Identification of Viable Myocardium in Patients of Myocardial Infarction – A Study

Delayed Hyper-Enhancement in Cardiac MRI Compared to Nuclear Perfusion Scintigraphy in Identification of Viable Myocardium in Patients of Myocardial Infarction – A Study

Prediction of Post-revascularization Ejection Fraction in Patients with Coronory Artery Disease Using Cavity-to-Myocardial Ratio of Thallium Reinjection Image (Multicenter Trial)

Background: We reported the high correlation between cavity-to-myocardial (C/M) count ratio at stress and rest thallium SPECT, and stress-rest EF calculated by MUGA test, this was confirmed by others. This correlation was explained partially by the functional mass. On the other hand, two important prognostic parameters should be considered before any revascularization technique: (1) Identification of viable myocardium and its amount, (2) Prediction of EF improvement post revascularization. Aim of the study: Correlating EF (C/M) on RD and RI image (EFRD & EFRI) image to actual EF (prevascularization EF1) and 1 year post revascularization EF2. Patients and methods: 78 patients with CAD (68 males and 10 females with mean age of 54.2+9 years) had been subjected to: (1) St-RD-RI thallium SPECT with assessment of reversible or fixed perfusion defects and calculation of C/M and consequently the EFC/M at the three settings. (2) Assessment of EF by MUGA at rest pre and 1 year post revascularization EF1 & EF2 respectively. These patients had been subjected to revascularization either by PTCA and stent (23/78 i.e., 29.5%) or by CABG (55/78, i.e., 70.5%). Results: Out of the 1560 myocardial segments (20 segments × 78 patients), 780 (50%) segments had abnormal resting wall motion. 441/780 (56.5%) of these segments were either of normal thallium uptake or with reversible perfusion defects while the rest (43.5%) showed fixed defects. 233/441 (52.8%) of those normal uptake or reversible segments showed recovery of wall motion post revascularization (PRV) while only 29/339 (15.1%) showed similar improvements. EFRI was found higher than EFRD in 44/78 of patients, no change in 23/78 patients and worsened in 11/78 patients with total agreements of 63/78 (80.8%) with EF2. On the other hand, EFRD was matched with EF1 in 64/78 of patients. 30/64 (46.9%) showed higher EF2, 23/64 (35.9%) showed similar EF2 while 11/64 (17.2%) showed lower EF2. The rest of cases 14/78 showed mismatch between EFRD and EF1 with higher values of EFRD. These patients still had higher values of EFRI and EF2 than EFRD. Conclusion: (1) Mismatch between EFRD and EF1 is an indication of presence of stunning myocardium and of good prognosis. (2) EFRI can be used to predict EF2 and so helps on selecting patients who can benefit from revascularization.

A Post-marketing Clinical Study to Confirm the Efficacy of <sup>18</sup>F-fluorodeoxyglucose for the Diagnosis of Myocardial Viability

Background: A number of previous studies have shown that myocardial viability can be assessed by positron emission tomography (PET) using 18 F-fluorodeoxyglucose ( 18 F-FDG). However, there has been no multicenter study that verified the ability of this modality for diagnosing myocardial viability in Japan. We therefore conducted a prospective one arm's unrandomized multicenter clinical trial in order to confirm the diagnostic ability of 18 F-FDG (95% two-sided confidence interval) in the 30 patients of the efficacy-analysis set was 63.9 %( 54.6-72.5%). Moreover, the proportion of patients with improved wall motion, on a per-patient basis, was 86.7 %( 26 of 30 cases). As for the safety, no serious adverse events occurred and the agent was well-tolerated. Conclusions: The identification of myocardial viability by 18 F-FDG will be widely beneficial in predicting improvement in myocardial wall motion after coronary revascularization. No serious safety concerns associated with the use of 18 F-FDG were observed.

PET imaging with FDG to guide revascularization in patients with systolic heart failure

Abstract The assessment of myocardial viability is important in the management of patients with coronary artery disease and left ventricular systolic dysfunction. There are several different imaging modalities currently available for the identification of viable myocardium: dobutamine stress echocardiography, single photon emission computed tomography, delayed-enhancement cardiac magnetic resonance imaging, and F-18 fluorodeoxyglucose positron emission tomography. The goal of viability imaging is to determine the likelihood of recovery of systolic function after revascularization. Positron emission tomography with F-18 fluorodeoxyglucose (FDG-PET) provides information about perfusion as well as myocardial metabolism, requires meticulous patient preparation, and is currently the gold standard imaging modality for the assessment of myocardial viability. Viability imaging for the purposes of predicting which patients will have improvement in left ventricular systolic function is supported under current guidelines, but the results of the recent STICH-viability substudy have created uncertainty about the incremental benefit. This review article will provide a summary of the currently available imaging modalities with an emphasis on FDG-PET and discuss the clinical relevance of viability imaging in light of the STICH-viability substudy.

Identification of Viable Myocardium in Acute Anterior Infarction Using Duration of Systolic Lengthening by Tissue Doppler Strain: A Preliminary Study

The aim of this study was to investigate whether strain Doppler echocardiography before reperfusion therapy could quantify ischemic dysfunction and predict viable myocardium in acute myocardial infarction as determined by magnetic resonance imaging. Twenty-six patients (mean age, 60 ± 12 years; seven women) with acute myocardial infarctions who underwent acute percutaneous coronary intervention were examined using strain Doppler echocardiography immediately before the procedure. Percutaneous coronary intervention was performed 296 ± 122 min after the onset of pain. Peak left ventricular systolic longitudinal strain and the duration of systolic lengthening were analyzed. Magnetic resonance imaging was performed 11 ± 5 months after therapy. Scarring exceeding 50% of the segment area was considered nonviable. Peak systolic strain fell gradually (becoming less negative) from normal segments to segments with transmural infarction (P < .0001), and the duration of systolic lengthening increased (P < .0001). Myocardial scarring was closely correlated with peak systolic strain (R = 0.76, P < .00001) and the duration of systolic lengthening (R = 0.88, P < .00001). There was a significant correlation between the degree of scarring and time to percutaneous coronary intervention (R = 0.40, P = .045). In segments with systolic lengthening, the improvement in strain after remodeling was significantly higher (5.5 ± 5.1%) than in segments with duration of systolic lengthening > 67% of systole (2.2 ± 3.7%) (P < .001). Receiver operating characteristic curve analyses showed that duration of systolic lengthening > 67.3% could identify nonviable myocardium (sensitivity, 90%; specificity, 94%). In patients with acute myocardial infarctions in the anterior wall, strain measurements can identify myocardium with nontransmural scarring. The duration of systolic lengthening is a novel, easily implemented variable that may identify ischemic but viable myocardium. Myocardial infarctions in other left ventricular regions should be investigated in future studies.

Two-dimensional strain combined with adenosine stress echocardiography assessment of viable myocardium

The objective of this study was to explore a new method for the identification of viable myocardium by means of two-dimensional (2D) strain imaging combined with adenosine stress echocardiography. A total of 15 anesthetized open-chest healthy mongrel dogs underwent left anterior descending coronary artery occlusion for 90 min followed by 120-min reperfusion. Adenosine was infused at 140 μg kg(-1) min(-1) over a period of 6 min. Images were acquired at baseline (when pericardial cradle was made), after reperfusion (when reperfusion finished) and after adenosine administration (while administration stopped). Measurements of the regional peak-systolic strain in radial, circumferential, and longitudinal motion on anterior wall and anterior septum were, respectively, performed under different conditions. The dogs were killed after the echocardiographic studies finished and then the area of infracted myocardium was defined by triphenyltetrazolium chloride histology. A segment with equal or less than 50% area of infracted myocardium was considered to be viable. As a result, 37 regions were viable whereas 53 were non-viable among 90 regions in 15 dogs. At baseline, there was no significant difference in peak-systolic radial strain (Rs), circumferential strain (Cs), and longitudinal strain (Ls) between the viable and non-viable groups. After reperfusion, Rs, Cs, and Ls in absolute value decreased compared to those at baseline in both groups, although there was no significant difference between these groups. Rs and Ls increased after adenosine administration compared to reperfusion (p < 0.01; p < 0.05) in viable group while there were no changes in non-viable group. Compared with non-viable group Rs, Cs and Ls in viable group increased significantly (p < 0.01; 0.05) after adenosine administration. There was a negative correlation between Rs and infarct size (r = -0.72). Cs and Ls correlated well with infarct size, respectively (r = 0.40; 0.67). A change of Rs more than 13.5% has a sensitivity of 83.8% and a specificity of 83.0% for viable whereas a change of Ls more than 11% allowed a sensitivity of 78.4% and a specificity of 88.7%. Combined with these two variables, the sensitivity and specificity could reach 91.9 and 79.2%. Two-dimensional strain imaging combined with adenosine stress echocardiography can provide a new way to distinguish viable myocardium from the non-viable.

Evaluation of Myocardial Viability – Contrast and Stress Echocardiography

Viable myocardium are myocardial segments with reduced function that often appear dyssynergic. These dyssynergic myocardial segments are capable of functional recovery, either spontaneously or after the offending insult, usually ischaemia, is removed by revascularisation. Patients with impaired left ventricular function but with viable myocardium are at increased risk of death and adverse cardiovascular outcome. The detection and recognition of viable myocardium is critical for risk stratification, guiding the selection of patients likely to benefit from revascularisation and predicting left ventricular remodelling. Contrast and stress echocardiography are important clinical tools for the assessment of myocardial viability. An end diastolic wall thickness of &lt;0.6cm at the dyssynergic segments generally indicates scarring. The presence of post-systolic thickening at these segments suggests either myocardial viability or ischaemia. Useful in assessing contractile reserve in dyssynergic segments, dobutamine echocardiography is an established tool for detecting myocardial viability with accuracies comparable to other techniques. A biphasic response is diagnostic and specific for hibernating myocardium. The newer techniques of strain and strain rate imaging are the focus of research activities and have been used in conjunction with dobutamine stress to improve overall accuracy. Myocardial contrast echocardiography (MCE) is useful in assessing coronary microvascular integrity, a pre-requisite for myocardial viability. The presence of an intact coronary microvasculature alone is insufficient for myocardial viability, however, explaining the high sensitivity but low specificity of MCE for such purposes. MCE, therefore, with its high negative predictive value, should be used in conjunction with dobutamine stress for the identification of viable myocardium. Due to its availability, safety, relatively low costs and high accuracy, rest and stress echocardiography are indispensable tools in the assessment of myocardial viability.

Predictors of contractile recovery after revascularization in patients with anterior myocardial infarction who received thrombolysis

Identification of viable myocardium after myocardial infarction has gained paramount importance with the current progress in coronary revascularization. To explore the prognostic power of certain patient characteristics to predict myocardial contractile recovery after revascularization in patients presenting with acute anterior ST elevation myocardial infarction (STEMI) who received thrombolytic therapy. Seventy-three consecutive patients presenting with first acute anterior STEMI who had received thrombolytic therapy and had significant coronary stenosis or occlusion of the infarct-related artery amenable for revascularization were enrolled. All patients underwent echocardiographic assessment of regional wall motion and left ventricular ejection fraction. Patients underwent coronary revascularization by either percutaneous angioplasty or surgical bypass. Echocardiography was repeated two to three months following revascularization. Patients were classified into two groups: group 1 had evidence of contractile recovery after revascularization at follow-up echocardiography and group 2 had no such evidence of recovery. Predictors of contractile recovery after revascularization included a shorter time from symptom onset to the institution of thrombolytic therapy, a lower baseline wall motion score index, the presence of grade 3 collaterals to the infarct-related artery and the use of beta-blockers. Instead, the presence of diabetes mellitus and a totally occluded infarct-related artery predicted poor contractile recovery. Myocardial contractile recovery after revascularization in patients presenting with first acute anterior STEMI may be predicted by the absence of diabetes, a shorter time from symptom onset to thrombolytic therapy, the use of beta-blockers, a lower initial wall motion index score and the presence of collaterals to the infarct-related artery.

Regional Diastolic and Systolic Function by Strain Rate Imaging for the Detection of Intramural Viability during Dobutamine Stress Echocardiography in a Porcine Model of Myocardial Infarction

The aim of this study was to evaluate diastolic and systolic strain rate measurements for differentiation of transmural/nontransmural infarction during dobutamine stress echocardiography (DSE). An ameroid constrictor was placed around the circumflex artery in 23 pigs inducing chronic vessel occlusion. Five pigs without constrictor served as controls. During high-dose DSE systolic strain rates (SR(sys)), systolic and postsystolic strain values (epsilon(sys), epsilon(ps)) and early and late diastolic strain rates (SR(E) and SR(A)) were determined. At week 6, animals were evaluated regarding myocardial fibrosis. Histology revealed nontransmural in 14 and transmural infarction in 9 animals. In controls, dobutamine induced a linear increase of SR(sys) to 12.3 + or - 0.4 s(-1) at 40 microg/kg per minute (P = 0.001) and a linear decrease of SR(E) to -6.6 + or - 0.3 s(-1) (P = 0.001). In the nontransmural group, SR(sys), epsilon(sys), epsilon(ps) at rest, and during DSE were higher and SR(E) was lower than in the transmural infarction group (P = 0.01). Best predictors for viability were SR(sys) (ROC 0.96, P = 0.0003), SR(E) at 10 microg/kg per minute dobutamine stimulation (ROC 0.94, P = 0.001) and positive SR values during isovolumetric relaxation at 40 microg/kg per minute dobutamine (ROC 0.86, P = 0.004). The extension of fibrosis correlated with SR(sys) at rest, epsilon(sys) at rest, and SR(E) at rest (P < 0.001). For the detection of viability similar diagnostic accuracies of SR(E) and SRsys were seen (sensitivity 93%/93%, specificity 96%/94%, respectively). Diastolic SR analysis seems to be equipotent for the identification of viable myocardium in comparison to systolic SR parameters and allows the differentiation of nontransmural from transmural myocardial infarction with high diagnostic accuracy. (Echocardiography 2010;27:552-562).

Comparison of low-dose dobutamine stress echocardiography and single photon emission computed tomography and delayed contrast MRI in the diagnosis of myocardial viability: Meta-analysis

Objective To assess the diagnostic value of different imaging methods including low-dose dobutamine stress echocardiography, SPECT and contrast enhancement MRI with Meta-analysis in the diagnosis of myocardial viability. Methods Articles published from 1998 to 2008 were searched in Cochrane library, Medline, Embase database, OVID database and CNKI for relevant English and Chinese articles. According to the criteria for diagnostic research published by Cochrane Method Group on screening and diagnostic tests, each article was critically screened and appraised, including the absolute numbers of true-positive, false-negative, true-negative, and false-positive. Statistical analysis was performed employing Meta-test Heterogeneity was tested, pooled weighted sensitivity and specificity and the corresponding 95% CI were calculated. Characteristic (SROC) curve was performed and the area under the curve was calculated. Finally, sensitivity analysis was performed. Results Twenty-one of 438 retrieved articles were included, in which there were ten articles about Low-dose dubutamine stress echocardiography, and six articles about 99Tcm-MIBI/99Tcm-Tetrofosmin SPECT, and six articles about contrast enhancement MRI, and one of both 99Tcm-MIBI/99Tcm-tetrofosmin SPECT and contrast enhancement MRI. All groups had heterogeneity, and a random effects regression was developed. The pooled weighted sensitivity and specificity and area under SROC curve for low-dose dobutamine stress echocardiography to diagnose myocardial viability was 0.73(0.62-0. 82)/0. 82 (0.77-0. 86) and 87.07% respectively. They were 0. 82 (0. 59-0. 94)/ 0. 77(0. 64-0. 86) and 86. 97% for 99Tcm-MIBI/99Tcm-Tetrofosmin SPECT respectively, while they were 0. 94 (0. 86-0. 97)/0. 75 (0. 66-0. 83) and 91.41% for contrast enhancement MRI respectively. Conclusion As noninvasive testing technologies, low-dose dobutamine stress echocardiography and 99Tcm-MIBI/99Tcm-tetrofosmin SPECT and delayed contrast enhanced MRI allow the identification of viable myocardium, but delayed contrast enhanced MRI showed significant different pooled sensitivity in comparison to low-dese dobutamine stress echocardiography. Key words: Myocardium; Echocardiography; Tomography; emission-computed; single-photon; Magnetic resonance imaging; Meta-analysis

Interactive 3D Hybrid PET/CT Imaging in the Identification of Myocardial Viability in Patients After Myocardial Infarction: Feasibility Study and Clinical Implications

Clinical decision-making in coronary artery disease requires integrated information on myocardial viability and coronary arteries, and cross-modality registration could facilitate this process. The recent emergence of hybrid positron emission tomography (PET)/computed tomography (CT) allows acquisition of this information in one study session; however, clinically useful software capable of presenting three-dimensional (3D) fused images to assess the relationship between myocardium and coronary arteries is limited. Patients with prior myocardial infarction were examined using electrocardiographically gated 18F-fluorodeoxyglucose PET and 16-slice CT. There were seven patients; mean age was 59 +/- 15 years and six were male. Using 3D reconstruction, coregistration and interactive display, the topographical relationship between myocardial viability and coronary arteries was clearly identified. We present a protocol to acquire CT coronary angiography and PET data and to visualize 3D fused images with an interactive visualization interface. This image coregistration is potentially useful to facilitate the process of image interpretation and decision-making.

186 Comparison of low-dose dipyridamole radionuclide ventriculography and low-dose dipyridamole stress echocardiography for identification of myocardial viability

186 Comparison of low-dose dipyridamole radionuclide ventriculography and low-dose dipyridamole stress echocardiography for identification of myocardial viability

Tissue velocity imaging during dobutamine stimulation for assessment of myocardial viability: Segmental analysis in patients after myocardial infarction

Background Dobutamine stress echocardiography (DSE) is an established method for the detection of viable myocardium, but evaluation of this method is subjective. Tissue velocity Imaging (TVI) allows quantitative analysis of regional myocardial wall motion by assessment of systolic myocardial velocities. The aim of this study was to evaluate the diagnostic value of DSE and TVI for detection of viable myocardium. Methods In 56 patients (58 ± 12 years) with previous myocardial infarction (130 ± 42 days, mean ejection fraction 42 ± 15%) low-dose DSE was combined with analysis of peak systolic myocardial velocities ( V peak) by TVI for assessment of myocardial viability. As reference served a follow-up echocardiography after successful revascularization (mean 91 ± 3 days). Results Of a total of 896 segments 200 showed abnormal wall motion (31 mildly hypokinetic, 50 severely hypokinetic, 115 akinetic, 4 dyskinetic). In 125 of these 200 segments regional improvement of regional wall motion was observed (62.5% viable). An increase of V peak > 1 cm/s during dobutamine stimulation allowed the identification of viable myocardium with a sensitivity of 82% and a specificity 82% (DSE: 77% and 80%). By receiver operating characteristic (ROC) curve analysis, a cut-off value of 1.0 cm/s was the best parameter to differ viable from nonviable myocardium (area under the curve 0.85; p < 0.01; 95% CI 0.79 to 0.90). Improvement of global ejection fraction after revascularization (47 ± 13%, p = 0.11) corresponded with three TVI viable segments with a sensitivity of 92% and a specificity of 89% ( p = 0.012). Conclusions TVI allows the identification of viable myocardium during dobutamine stimulation and enables a quantitative interpretation of DSE.

Correlation between ECG and myocardial perfusion after mechanical reperfusion of acute myocardial infarction

The identification of viable myocardium after myocardial infarction (MI) carries major prognostic impact. Due to myocardial stunning early after successful mechanical reperfusion of acute myocardial infarction, analysis of myocardial perfusion but not of contractile function can be used to differentiate between necrotic and viable myocardium. Although being widely regarded as an indicator of infarct transmurality, the relation between post-infarct Q-wave formation and the amount of viable myocardium has not been studied. We hypothesized that there was a correlation between the extent of Q-wave formation and the extent of perfusion abnormalities on myocardial contrast echocardiography early after successful mechanical reperfusion of first acute myocardial infarction and that the extent of post-infarct Q-wave formation might therefore be used as a simple estimate of the amount of viable myocardium. Methods and results 47 patients with first MI and treated by direct PCI were enrolled. Patients were divided into 3 groups according the presence and number of abnormal Q waves (group A—no abnormal Q wave; group B—≤2 abnormal Q waves, group C—≥3 abnormal Q waves). Left ventricular pumpfunction was defined by ejection fraction (EF) on ventriculography and wall motion score index (WMSI) on echocardiography. Myocardial perfusion was defined by perfusion score index (PSI) on myocardial contrast echocardiography. Patients in group A had significantly better LV function than patients in other groups [EF 57 ± 5 vs. 48 ± 11% (group B) and 47 ± 10% (group C); p < 0.05], also WMSI was the best in this group [1.34 ± 0.22 vs. 1.67 ± 0.39 (group B) and 1.68 ± 0.31 (group C); p < 0.01]. Myocardial perfusion assessed by PSI was best in group A (1.2 ± 0.3, p < 0.05). With respect to PSI, there was a significant difference between group B and C (1.41 ± 0.21 vs. 1.56 ± 0.29; p < 0.05), even though EF and WMSI did not differ in these groups. The amount of perfused segments with severe wall motion abnormality was higher in group B compared to group C (47% vs. 25%; p < 0.05). Conclusion In patients after successful mechanical reperfusion of first MI, the extent of Q-wave formation on ECG may be regarded as a corollary of the amount of myocardial microvascular damage and may, therefore, be used to estimate the amount of viable myocardium post-infarct.

The identification of reversible dysfunctional myocardium is influenced by the severity of contractile dysfunction and by the length of follow-up

To evaluate the influence of the severity of regional myocardial dysfunction and of the length of follow-up on the identification of myocardial viability with rest-redistribution Tl single photon emission computed tomography (SPECT) and low-dose dobutamine echocardiography (LDDE). Twenty-six patients with chronic coronary artery disease and wall motion abnormalities, candidates for revascularization, were included in this study. All patients underwent, in the same week, Tl SPECT and LDDE for pre-revascularization evaluation of myocardial viability. Reversibility of regional dysfunction was assessed by two-dimensional echocardiography, 40+/-20 days (early follow-up) and 12+/-5 months (late follow-up) after revascularization. In a/dyskinetic segments, Tl SPECT showed similar values of sensitivity (78% vs. 71%, P=NS) and slightly higher values of specificity (43% vs. 18%, P<0.01) compared to hypokinetic segments, in predicting functional recovery at early follow-up. No significant changes were observed in the diagnostic accuracy of Tl SPECT at late follow-up. On the contrary, LDDE provided significantly lower values of sensitivity (56% vs. 94%, P<0.05) and higher values of specificity (73% vs. 9%, P<0.01) in a/dyskinetic compared to hypokinetic segments. Specificity of LDDE in a/dyskinetic segments significantly increased from early (73%) to late follow-up (95%; P<0.05). Similarly, positive predictive value in a/dyskinetic segments significantly increased from early (69%) to late follow-up (96%; P<0.05). The severity of regional dysfunction and the length of follow-up significantly influence the diagnostic accuracy of LDDE but not of rest-redistribution Tl SPECT in the identification of myocardial viability.

Assessment of Myocardial Viability with Dobutamine Stress Echocardiography in Patients with Ischemic Left Ventricular Dysfunction

The noninvasive assessment of myocardial viability has proved clinically useful for distinguishing hibernating and/or stunned myocardium from irreversibly injured myocardium in patients with chronic ischemic heart disease or recent myocardial infarction, with marked regional and/or global left ventricular (LV) dysfunction. Noninvasive techniques utilized for the detection of viability in asynergic myocardial regions include positron emission tomographic imaging of residual metabolic activity, single photon emission tomography (SPECT) of radioisotope uptake with thallium-201, low-dose dobutamine echocardiography assessment of inotropic reserve and myocardial contrast echocardiography for evaluation of microvascular integrity. Of these techniques, dobutamine stress echocardiography is a safe, widely available and relatively inexpensive modality for the identification of myocardial viability for risk stratification and prognosis. Low-dose dobutamine response can accurately predict improvement of dysfunctional yet viable myocardial regions, and thus identify a subset of patients whose LV function will improve following successful coronary revascularization.

Evaluation of myocardial viability with contrast echocardiography

Identification of viable myocardium after acute myocardial infarction (MI) or in the setting of severe chronic ischemic heart disease has important clinical implications. Myocardial contrast echocardiography (MCE) has been used for the evaluation of myocardial viability by assessing myocardial perfusion and microvascular integrity. In acute MI, MCE can identify the no-reflow phenomenon after revascularization, which has significant implications regarding recovery of function and clinical outcomes. Serial changes in myocardial perfusion can also be evaluated for the prediction of ultimate recovery of function. In the setting of chronic ischemic left ventricular dysfunction, early studies have shown that MCE is helpful in the identification of myocardial hibernation and in the prediction of recovery of function after revascularization, with accuracy similar to radionuclide techniques. Preliminary studies using the new quantitative MCE parameters of myocardial blood flow and velocity derived from intravenous contrast administration appear to enhance the diagnostic accuracy of MCE in the evaluation of myocardial viability.

Identification of viable myocardium early after acute myocardial infarction using closed-loop arbutamine echocardiography: comparison with positron emission tomography

Objective —This study sought to evaluate the safety and efficacy of arbutamine echocardiography in identifying contractile reserve and predicting functional improvement early after acute myocardial infarction (AMI).Methods and results — Seventeen patients with first AMI underwent arbutamine echocardiography 48 to 96 hours after AMI. Arbutamine was infused by a closed-loop delivery device. The heart rate slope was 4 beats/min and the heart rate target was 20 beats/min above baseline heart rate. A follow-up echocardiogram was obtained one month later. N-13 ammonia and F-18 FDG positron emission tomographic (PET) imaging were performed 6 ± 2 days after AMI, before coronary angiography. Mean duration of arbutamine infusion was 6 ± 2 min. There was no complication and there were no major side effects. Myocardial viability was identified with PET in 15 of the 17 patients. Contractile reserve was observed in 10 patients during arbutamine infusion. Functional recovery was identified in 12 patients. Sensitivity, specificity and accuracy of PET and arbutamine echocardiography for predicting functional recovery were 100%, 40%, 76% and 67%, 80%, 84%, respectively.Conclusions — Low-dose arbutamine stress testing is safe early after AMI. Contractile reserve can be rapidly identified by echocardiography and is specific, but moderately sensitive for predicting reversible dysfunction.