Dobutamine echocardiography in predicting improvement in global left ventricular systolic function after coronary bypass or angioplasty in patients with healed myocardial infarcts

Dobutamine echocardiography for assessment of viability in the current era

PURPOSE OF REVIEW

Studies from the 1990s and early 2000s documented the utility of dobutamine echocardiography for the prediction of functional recovery and prognosis with revascularization. The results of The Surgical Treatment of Ischemic Heart Failure (STICH) trial called into question the value of viability assessment using dobutamine echocardiography. The purpose of this review is to re-examine the literature on dobutamine echocardiography, put into context the STICH results, and provide insight into the current role of dobutamine echocardiography viability testing.

RECENT FINDINGS

In contrast to the results of previous nonrandomized trials, the STICH trial showed that patients with viability defined by nuclear perfusion imaging or dobutamine echocardiography did not have improved survival with CABG compared with optimal medical therapy. Viability by dobutamine echocardiography was defined as the presence of contractile reserve in at least five segments with baseline dysfunction. The results of dobutamine echocardiography studies published before and after initiation of the STICH trial suggest that the definition of viability utilized in that trial may be suboptimal for assessment of improvement in global function and prognosis in patients undergoing revascularization. Assessment of global contractile reserve using wall motion score (WMS) or ejection fraction may be superior to utilization of a binary definition of viability confined to assessment of contractile reserve in a fixed number of segments because these indices provide information on both the magnitude and extent of contractile reserve of the entire left ventricle (LV).

SUMMARY

Assessment of WMS or ejection fraction with dobutamine echocardiography may be the optimal means of evaluating the impact of viability on prognosis.Video abstract http://links.lww.com/HCO/A56.

Low dose wall motion score predicts the short and long-term benefit of surgical revascularization in patients with ischemic left ventricular dysfunction

We investigated the influence of the extent of viability using low dose dobutamine wall motion score index (WMS) on the survival benefit of surgical revascularization (CABG) versus medical therapy. In the STICH trial, viability assessment was not helpful in determining the benefit of CABG. However, the extent of viable myocardium with contractile function was not assessed in the trial. Dobutamine echocardiography was performed in 250 patients with ischemic left ventricular dysfunction (125-medically treated, 125-CABG). The mean ejection fraction (EF) was 32% in both groups. WMS during low dose dobutamine infusion was used to classify patients into groups with extensive (WMS < 2.00), intermediate (WMS 2.00-2.49), and limited (WMS ≥ 2.50) viability. Survival free of cardiac death was assessed at 2 years and for the complete duration of follow-up. There were 44 (35.2%) and 67 (53.6%) cardiac deaths in the revascularized and medically treated patients respectively (follow-up of 5.7 ± 5.8 years). Revascularized and medically treated patients with extensive viability had similar 2-year survival (p = 0.567) but revascularized patients had improved long-term survival (p = 0.0001). In those with intermediate viability, revascularization improved both 2 year (p = 0.014) and long-term survival (p = 0.0001). In patients with limited viability, 2-year survival was worse in revascularized patients (p = 0.04) and long-term survival was similar (p = 0 .25) in revascularized and medically treated groups. Patients with extensive and intermediate amounts of viability have improved survival with CABG but those with limited viability have poorer short-term outcome and no long-term benefit.

Radionuclide imaging in stage B heart failure

This article discusses currently available radionuclide techniques in the diagnostic and prognostic evaluation of patients with chronic heart failure, with a focus on stage B/asymptomatic left ventricular dysfunction. Radionuclide imaging is promising for such patients because it can simultaneously determine left ventricular function, evaluate for the presence of obstructive coronary disease, determine the extent of viable myocardium, and evaluate dyssynchronous left ventricular contraction. Radionuclide imaging can thus provide important noninvasive insights into the pathophysiology, prognosis, and management of patients with asymptomatic left ventricular dysfunction as well as more advanced heat failure.

Role of echocardiography in the assessment of myocardial viability

In the assessment of chronic myocardial infarction, echocardiography plays a vital role through the recognition of hibernating yet potentially viable myocardium that could benefit from revascularization. Echocardiography provides information through basic evaluation of cardiac structure and through evaluation of the functional response to dobutamine stress. In addition, a number of newer modalities such as myocardial contrast echocardiography, tissue Doppler imaging, and strain imaging provide further diagnostic capability. This review assesses the role of echocardiography in the identification of patients with chronic myocardial infarction who could benefit from revascularization.

Cell therapy in patients with left ventricular dysfunction due to myocardial infarction

OBJECTIVES

The purpose of this study was to determine the impact of autologous transplantation of mononuclear bone marrow cells on myocardial function in patients with left ventricular (LV) dysfunction due to an acute myocardial infarction.

METHODS

The randomized study included 82 patients with a first acute myocardial infarction treated with a stent implantation. This presentation is a subanalysis of 47 patients with left ventricular dysfunction-EF (ejection fraction) <or= 40%. Group H patients (n = 17) received higher number (100,000,000) of cells; Group L patients (n = 13) received lower number (10,000,000) of cells. The patients of control Group C (n = 17) were not treated with cells. The Doppler tissue imaging and single photon emission computed tomography were performed before cell transplantation and 3 months later.

RESULTS

At 3 months of follow-up, the baseline EF of 35%, 36%, 35% in Groups H, L, and C increased by 6% (P < 0.01 vs. baseline), 5% (P < 0.01 vs. baseline), and 4% (P = NS vs. baseline), respectively, as assessed by single photon emission computed tomography (P = NS between groups). The baseline number of akinetic segments of 6.9, 7.0, and 6.2 in H, L, and C groups decreased by 1.7 (P < 0.01 vs. baseline), 1.5 (P < 0.01 vs. baseline), and 0.7 (P = NS vs. baseline, P = NS between groups), respectively, as demonstrated by echocardiography.

CONCLUSION

In our study, the statistically important effect of transplantation of mononuclear bone marrow cells on myocardial function was not found. Only an insignificant trend toward the improvement of global LV EF fraction was found at 3-month follow-up.

Early predictors of left ventricular function improvement late after myocardial infarction

BACKGROUND/AIM

Prognosis after acute myocardial infarction (AIM) depends on the extent of irreversibly damaged myocardium and viable tissue due to stunning or hibernation. The aim of the study was to assess the prognostic significance of early echocardiographic parameters of myocardial viability in prediction of late recovery of regional and global ventricular function.

METHODS

The study prospectively included 40 patients after the first, uncomplicated univessel AIM treated with percutaneous coronary intervention (PCI). Low dose dobutamine echocardiography (LDDE) was preformed 7-10 days after AIM and follow-up resting echocardiography from 7 to 12 months later.

RESULTS

The sensitivity and specificity for the prediction of post revascularisation regional, dys synergy improvement were 61.29% and 94.59% respectively. The positive and negative predicative values were 90.48% and 74.47% re spectively. The number of viable segments (p = 0.01) and extent of contractile reserve (p = 0.01) were univariate, independent predictors of improvement in ejection fraction (EF). From the multivariate stepwise regression analysis contractile reserve was selected as most powerful predictor of late recovery of left ventricular contractile function (p = 0.007). Receiving-operator characteristic curve (ROC) analysis demonstrated that three or more recovered segments were necessary for an improvement of left ventricular ejection fraction (LVEF) > or = 5% after the revascularisation, with the highest sensitivity, 100% and specificity 56% (p = 0.01).

CONCLUSION

Low-dose dobutamine echocardiography is a powerful predictor of the regional dys synergy recovery late after AIM treated with PTCA with implantation stent. Late full functional improvement of the left ventricle is related to the extent of contractile reserve and amount of viable tissue. At least three recovered segments are necessary for a significant recovery of the global left ventricular contractility.

Contrast-enhanced magnetic resonance and thallium scintigraphy in the detection of myocardial viability: a prospective comparative study

The aim of the present study was to prospectively compare contrast-enhanced magnetic resonance imaging (CE-MRI) with single-photon emission tomography using (201)Thallium chloride (SPECT Tl) in the detection of myocardial viability. Patients with chronic coronary artery disease and systolic dysfunction defined by an ejection fraction (EF) <or= 45% were included. CE-MRI was performed 10-15 minutes after the administration of a gadolinium-based contrast agent using an Inversion Recovery Turbo FLASH (fast low-angle shot) sequence. A 4-hour rest redistribution protocol was used for SPECT Tl. Radionuclide ventriculography was used for the assessment of EF. Forty patients with an EF of 33.1 +/- 7.7% were included. Thirty-two underwent a follow-up examination after revascularization. Comparison of viability assessment was performed in 1360 segments. Agreement was noted in 1065 (78.3%) segments, resulting in a kappa value of 0.336. Discrepancies were observed in 96 SPECT Tl viable segments that were described as nonviable according to CE-MRI and in 199 SPECT Tl nonviable segments that were viable in the CE-MRI study. In patients undergoing the follow-up examination, EF increased by 5.5 +/- 7.3% (33.6 +/- 8.6% to 39.2 +/- 9.7%), but the relation between the amount of dysfunctional viable myocardium defined by both methods studied and the change in EF after revascularization was very weak and not statistically significant. Moderate agreement in the myocardial viability assessment between CE-MRI and SPECT Tl was observed. CE-MRI seems to be more accurate in identifying myocardial viability in inferior and inferolateral segments. We were unable to verify if either of the methods studied is useful for the prediction of EF improvement after revascularization.

Incremental Value of Strain Rate Analysis as an Adjunct to Wall-Motion Scoring for Assessment of Myocardial Viability by Dobutamine Echocardiography

Background— Assessment of myocardial viability based on wall-motion scoring (WMS) during dobutamine echocardiography (DbE) is difficult and subjective. Strain-rate imaging (SRI) is quantitative, but its incremental value over WMS for prediction of functional recovery after revascularization is unclear.

Methods and Results— DbE and SRI were performed in 55 stable patients (mean age, 64±10 years; mean ejection fraction, 36±8%) with previous myocardial infarction. Viability was predicted by WMS if function augmented during low-dose DbE. SR, end-systolic strain (ESS), postsystolic strain (PSS), and timing parameters were analyzed at rest and with low-dose DbE in abnormal segments. Regional and global functional recovery was defined by side-by-side comparison of echocardiographic images before and 9 months after revascularization. Of 369 segments with abnormal resting function, 146 showed regional recovery. Compared with segments showing functional recovery, those that failed to recover had lower low-dose DbE SR, SR increment (ΔSR), ESS, and ESS increment (ΔESS) (each P <0.005). After optimal cutoffs for the strain parameters were defined, the sensitivity of low-dose DbE SR (78%, P =0.3), ΔSR (80%, P =0.1), ESS (75%, P =0.6), and ΔESS (74%, P =0.8) was better though not significantly different from WMS (73%). The specificity of WMS (77%) was similar to the SRI parameters. Combination of WMS and SRI parameters augmented the sensitivity for prediction of functional recovery above WMS alone (82% versus 73%, P =0.015; area under the curve=0.88 versus 0.73, P <0.001), although specificities were comparable (80% versus 77%, P =0.2).

Conclusions— The measurement of low-dose DbE SR and ΔSR is feasible, and their combination with WMS assessment improves the sensitivity of viability assessment with DbE.

The relation between viable segments and left ventricular ejection fraction improvement

For patients with coronary artery disease and left ventricular dysfunction who undergo revascularization, it is important to estimate the left ventricular ejection fraction (LVEF) improvement after revascularization, as this is a strong indicator of the long-term outcome. Identification of viable segments from echocardiography has been considered a predictive sign of LVEF improvement. However, a quantitative relation between segmental function recovery and global ejection fraction improvement has not been established. There is a clinical need to determine parameters that are predictive to LVEF improvement. A cylindrical left ventricular model is proposed to establish the relation between segmental myocardial function and LVEF based on a 12-segment echocardiograph model. Model results show that LVEF improvement is directly related to the contraction ratio in normal segments and a weighted sum of the number of viable segments that recover to normal or hypokinetic, which is equal to a weighted sum of the change in wall motion scores. This new combined parameter is a better predictor of the amount of LVEF improvement than the total number of viable segments or preoperative ejection fraction. The predictive value of the model was illustrated in a group of four patients with coronary artery disease who underwent revascularization.

Revascularization and ventricular restoration in patients with ischemic heart failure: the STICH trial

PURPOSE OF REVIEW

As techniques for the management of patients with ischemic heart failure have evolved, controversy has arisen with respect to the roles of revascularization and ventricular restoration procedures. This review addresses current thinking on the management of these patients and describes a prospective randomized trial that will have an impact on future treatment selection.

RECENT FINDINGS

Although the basis for improved survival with coronary artery bypass grafting lies in the viability of ischemic myocardium, nuclear medicine studies and stress echocardiography have failed to adequately select for tissues that are capable of recovery. Recent studies have suggested an additional benefit to combining ventricular restoration with bypass surgery. However, the role for these techniques has not been definitively established.

SUMMARY

The currently enrolling Surgical Treatment for Ischemic Heart Failure (STICH) trial promises to address these issues and thereby improve the management of patients with this disease.

Prognostic and therapeutic implications of myocardial viability in patients with heart failure

Substantial progress has been made in understanding the pathophysiology of regional and global left ventricular (LV) dysfunction and the states of hibernation and stunning in patients with heart failure. The clinical literature on the use of noninvasive imaging to assess myocardial viability has evolved from predicting improvement in regional LV function to predicting patient-related outcomes, including heart failure symptom improvement and survival after revascularization. A substantial body of observational cohort data demonstrates that mortality risk is high in patients with coronary artery disease and LV dysfunction who have substantial viable myocardium, and that risk is reduced by revascularization. Thus, noninvasive imaging of myocardial ischemia and viability can provide important prognostic information in patients with heart failure and LV dysfunction, and provide a signal of the potential benefit of revascularization.

Comparison of functional recovery of mildly hypokinetic versus severely dysfunctional left ventricular segments after revascularization in patients with ischemic cardiomyopathy

Dysfunctional left ventricular (LV) segments showing contractile reserve during dobutamine stress echocardiography (DSE) are considered viable myocardium; functional recovery is expected after revascularization. Many segments, however, particularly mildly hypokinetic segments, do not recover. The reason for this failure is unknown. Two-dimensional echocardiography at rest and low-high-dose DSE were performed before revascularization in 114 consecutive patients with ischemic cardiomyopathy. Two-dimensional echocardiography at rest was repeated after 9 to 12 months. Segmental function was scored by a 5-point grading score. Functional recovery after revascularization was assessed in mildly hypokinetic (score 2, group I) and severely dysfunctional segments (score 3 to 5, group II). For each segment, functional recovery was defined as an improvement in functional score of > or =1 grade compared with the baseline score at rest. During low-dose DSE (up to 10 microg/kg/min), 183 group I segments (68%) and 438 group II (39%) segments had contractile reserve (p <0.0001). However, functional recovery was observed less frequently in group I segments (41%) than in group II segments (55%) with contractile reserve (p <0.005). During high-dose DSE (up to 40 microg/kg/min), in the group I segments with contractile reserve at the low dose, the sustained improvement pattern (indicating subendocardial scar) was prevalent (73%). After revascularization, 73% of segments with sustained improvement did not recover. Conversely, the biphasic response (indicating ischemically jeopardized myocardium) was observed only in 27% of group I segments. Functional recovery occurred in 39 of these segments (78%) (p <0.001 vs sustained improvement). Hence, mildly hypokinetic segments probably indicate the presence of subendocardial scars, and may explain the failure in functional recovery after revascularization.

Prognostic importance of the quantification of myocardial viability in revascularized patients with coronary artery disease and moderate-to-severe left ventricular dysfunction

The aim of this study was to assess the prognostic value of the amount of dysfunctional but viable myocardium in revascularized patients with coronary artery disease and left ventricular dysfunction. To quantify the amount of dysfunctional but viable myocardium, low-dose dobutamine echocardiography was performed. The wall motion was scored using a 16-segment model. The dysfunctional segments were defined as viable if they exhibited functional improvement of at least 1 grade with any dose of dobutamine, or only worsening with dobutamine infusion. Two hundred and twenty patients were revascularized and followed-up for a mean period of 33+/-23 months (range, 0-86) for cardiac-related death and hospitalization for heart failure. Standard follow-up echocardiography was performed 3-6 months after revascularization. Receiver operating characteristic curve analysis identified six dysfunctional but viable segments as the optimal cutoff value for discriminating patients with and without risk of cardiac events. Thirty-eight patients exhibited a large amount of dysfunctional but viable myocardium (>or=6 segments, group A), 103 patients had a small amount of dysfunctional but viable myocardium (2-5 segments, group B), and 79 patients were found to have dysfunctional myocardium irreversibly damaged (group C). Similar baseline left ventricular ejection fractions of 36+/-4, 34+/-5, 35+/-5% in groups A, B, and C increased to 46+/-6% (P<0.01 versus baseline and versus groups B and C), to 39+/-5% (P<0.01 versus baseline and group C), and to 36+/-7% (P<0.01 versus baseline), respectively, after revascularization. The greatest functional improvement after revascularization in group A patients was accompanied by a lower frequency of cardiac events during follow-up (1 vs. 27 in group B, P<0.01, and versus 18 in group C, P<0.01) and by a better cardiac event-free survival according to Kaplan-Meier survival analysis (P<0.01 versus groups B and C, respectively). In conclusion, in revascularized patients with coronary artery disease and moderate-to-severe left ventricular dysfunction, the presence of >or=6 dysfunctional but viable segments identifies patients with the best prognosis.

The non-invasive assessment of hibernating myocardium in ischaemic cardiomyopathy--a myriad of techniques

Heart failure is placing an ever-increasing burden on society. Many subjects with heart failure and underlying coronary artery disease have a significant amount of akinetic but viable myocardium that is able to contract should myocardial perfusion improve (hibernating myocardium). Non-randomised studies have shown prognostic benefit in subjects with hibernating myocardium undergoing revascularisation. Several non-invasive techniques have been developed to assess the presence or absence of hibernating myocardium. This review will examine the epidemiology and underlying pathogenesis of hibernating myocardium; evaluate the non-invasive techniques for diagnosing hibernating myocardium, and look at therapeutic intervention in subjects with hibernating myocardium.

Gated fluorine 18 fluorodeoxyglucose positron emission tomography: determination of global and regional left ventricular function and myocardial tissue characterization

BACKGROUND

Our objectives were to investigate the accuracy of global and regional left ventricular (LV) function parameters determined from gated fluorine 18 deoxyglucose (FDG) positron emission tomography (PET) and to determine whether this approach complements viability imaging data for tissue characterization. Nongated FDG-PET is a clinical standard for viability imaging, but LV function is often determined with other techniques, which increases patient burden, expenditure, and co-registration errors. Better tissue characterization may be achieved if data were acquired with one test. Methods and results Forty-eight patients with LV dysfunction (including 35 with ejection fraction [EF] </=35%) underwent perfusion/FDG imaging with gating of the FDG images and radionuclide angiography (RNA) 6 +/- 6 days apart. Regional function (wall motion/thickening) and viability pattern (normal, mismatch, nontransmural scar, and transmural scar) were determined for 301 segments. Global EFs from FDG-PET (29.3% +/- 11.5%) and RNA (31.1% +/- 10.4%) were well correlated: EF(FDG-PET) = 0.91 x EF(RNA) + 0.91 (r = 0.83, P <.00001). Regional wall motion concordance between PET and RNA with three wall motion scores was 67% with moderate agreement (kappa = 0.50, P <.001). PET viability was also determined for each segment. The relative frequency of normal motion compared with abnormal motion decreased with worsening viability classification. Of the normal segments, 96 of 139 (69%) had reduced wall motion, suggesting repetitively stunned myocardium. Segments classified as normal or mismatch had a higher frequency of normal wall thickening (65% and 52%) than wall motion (31% and 17%). No segments classified as transmural scar exhibited normal wall thickening.

CONCLUSION

Gated FDG-PET accurately measures global LV function. Regional function can also be determined with reasonable accuracy. This approach also provides precise co-registration of function with metabolic information and thus improved tissue characterization of the myocardium. Gated FDG-PET has the potential to assist in optimizing management of this patient population.

Prognosis of patients with chronic coronary artery disease and severe left ventricular dysfunction. The importance of myocardial viability

BACKGROUND AND AIM

The choice of optimal treatment strategy in patients with coronary artery disease (CAD) and severe left ventricular (LV) dysfunction is often difficult. The aim of this study was to compare long-term results of patients with chronic CAD, severe heart failure and a defined scope of myocardial viability treated with coronary revascularization, heart transplantation, or kept on medical therapy.

METHODS

From 1993 to 2000, viability evaluation using low-dose dobutamine echocardiography was performed in 124 patients with CAD and LV ejection fraction <or=30%. The dysfunctional myocardial segments were defined as viable if they exhibited improvement in their thickening at any dose of dobutamine or worsening without initial improvement. The patients were divided into five groups and followed up for a mean period of 27+/-23 months. Group A consisted of 39 patients with viability (at least two dysfunctional but viable segments) who were revascularized. Group B consisted of 29 patients with viability treated medically. Groups C (n=23) and D (n=22) comprised patients with non-viable dysfunctional myocardial segments who were revascularized or kept on medical therapy, respectively. Eleven patients referred for heart transplantation after dobutamine echocardiography and 62 patients with ischemic cardiomyopathy transplanted in the same time interval were included in the group of transplanted patients (Group E).

RESULTS

The Kaplan-Meier survival analysis demonstrated a significantly better survival of group A patients as compared with group B patients (P<0.05). The prognostic benefit of revascularization in patients with viability was not manifested until 3 years after the procedure. At 5 years, survival in groups A, B, C, D and E was 89, 60, 67, 50 and 78%, respectively.

CONCLUSION

In patients with CAD, severe LV dysfunction, and the evidence of viability in dysfunctional myocardium, coronary revascularization improves survival. At least 3-years follow-up is necessary to objectively assess the prognostic effect of coronary revascularization.

Early prediction of improvement in ejection fraction after acute myocardial infarction using low dose dobutamine echocardiography

OBJECTIVE

To evaluate the relation between changes in ejection fraction during the first three months after acute myocardial infarction and myocardial viability.

PATIENTS

Myocardial viability was assessed using low dose dobutamine echocardiography in 107 patients at mean (SD) 3 (1) days after acute myocardial infarction. Cross sectional echocardiography was repeated three months later. Left ventricular volumes and ejection fraction were determined from apical views using the Simpson biplane formula.

RESULTS

In patients with viability, ejection fraction increased by 4.4 (4.3)%; in patients without viability it remained unchanged (0.04 (3.6)%; p < 0.001). A > or = 5% increase in ejection fraction was present in 21 of 107 patients (20%). Receiver operating characteristic analysis showed that myocardial viability in > or = 2 segments predicted this increase in ejection fraction with a sensitivity of 81% and a specificity of 65%. Multivariate logistic regression analysis was used to define which clinical and echocardiographic variables were related to > or = 5% improvement in ejection fraction. Myocardial viability, non-Q wave infarction, and anterior infarction all emerged as independent predictors, myocardial viability being the best (chi(2) = 14.5; p = 0.0001). Using the regression equation, the probability of > or = 5% improvement in ejection fraction for patients with a non-Q wave anterior infarct with viability was 73%, and for patients with a Q wave inferior infarct without viability, only 2%.

CONCLUSIONS

Myocardial viability after acute myocardial infarction is the single best predictor of improvement in ejection fraction. In combination with infarct location and Q wave presence, the probability of > or = 5% improvement can be estimated in individual patients at the bedside.

Predicting revascularization outcome in patients with coronary artery disease and left ventricular dysfunction (data from the SEMINATOR study)

A main goal of revascularization in patients with chronic ischemic cardiomyopathy is to improve global left ventricular (LV) function. This study aimed to verify whether it is possible to predict an increase in LV ejection fraction (EF) after revascularization on the basis of the extent of LV asynergy, myocardial viability, and revascularization completeness. We studied 77 patients with chronic LV ischemic dysfunction using baseline resting and nitrate-enhanced technetium-99m sestamibi single-photon emission computed tomography. Regional wall motion and global LVEF were assessed with echocardiography before and after revascularization, which was complete in 51 patients and incomplete in 26. The number of viable asynergic segments included in revascularized coronary artery territories was the strongest predictor of significant (> or = 5 EF U) functional improvement in univariate discriminant analysis. According to multivariate stepwise discriminant analysis, this parameter, together with the number of baseline asynergic segments, allowed the detection of patients with significant LVEF improvement with 75% accuracy. With use of a multivariate regression model, including the 2 mentioned variables, the measure of postrevascularization LVEF increase could be accurately quantified (R(2) 0.43, p <0.000001). In conclusion, this study suggests that the severity of baseline asynergy, the extent of myocardial viability, and the completeness of revascularization are the main determinants of postrevascularization functional recovery in patients with LV ischemic dysfunction, and that on the basis of these variables it is possible to predict the measure of LVEF increase.

Role of dobutamine echocardiography in detection of myocardial viability for predicting outcome after revascularization in ischemic cardiomyopathy

Coronary artery disease is the most common cause of heart failure in the Western world. Compared with medical therapy, surgical revascularization has been shown to improve survival rates in nonrandomized trials in patients with ischemic cardiomyopathy. However, perioperative mortality is high in this group of patients who do not demonstrate significant viable myocardium. Echocardiography during dobutamine infusion has been shown to reliably detect viable myocardium. Several studies have demonstrated its ability to provide high predictive value for recovery of both regional and global left ventricular function after revascularization. Indeed, nonrandomized studies also have indicated its value in predicting which patients with severe ischemic cardiomyopathy are likely to survive after revascularization. Dobutamine stress echocardiography has emerged as a safe and valuable technique for the assessment of myocardial viability and for the selection of patients for revascularization.

The identification of myocardial hibernation in patients with ischemic heart failure by echocardiography and radionuclide studies

Dobutamine echocardiography and myocardial radionuclide tomography are widely used to assess viability in patients with ischemic cardiomyopathy and left ventricular dysfunction. The main goal of viability evaluation has been the identification of reversible regional dysfunction in the attempt to identify patients in whom revascularization may determine an improvement of global left ventricular ejection fraction. In this application, echocardiographic and radionuclide techniques are used to characterize different pathophysiologic aspects of viable myocardium, ie, integrity of cell membrane and contractile reserve. This explains why the information of the 2 techniques are often divergent and why radionuclide techniques have the highest sensitivity but reduced specificity compared with echocardiography for predicting recovery of regional dysfunction. The identification of residual viable myocardium by either technique is strongly associated with adverse prognosis if the patients are not revascularized, and this substantially contributes to the decision-making process in individual patients. Although it has been assumed that prognostic advantages of revascularization are linked to an increase of ejection fraction, pathophysiologic and clinical observations challenge us with the possibility that benefits of revascularization may also ensue independently on the recovery of ejection fraction through alternative pathophysiologic mechanisms. Therefore, clinical application of viability tests should be evaluated against relevant endpoints, mainly represented by prolongation of life and improvement of life quality, and not by surrogate endpoints as represented by recovery of global ejection fraction. Future studies are needed to assess whether a more clinically oriented approach will provide a better selection of patient candidates for revascularization.

Non-invasive investigations

The most commonly used techniques for imaging the effects of coronary artery disease (CAD) on the heart are myocardial perfusion scintigraphy (MPS) and echocardiography. Both tests have been validated during exercise and pharmacological stress and they are valuable for the diagnosis and aiding management decisions in patients with suspected or known CAD. In a proportion of these patients, repetitive episodes of myocardial ischaemia can lead to intracellular and extracellular changes so that myocytes, although viable, have insufficient energy to sustain contraction. This phenomenon is known as myocardial hibernation and it can be detected accurately by both MPS and stress echocardiography. The review that follows highlights the role of these techniques as powerful diagnostic and prognostic tools in clinical cardiology. In order to make the best use of them, attention to detail and planning are required to design the test to suit the clinical problem and to obtain the most accurate data possible.

Value of dobutamine echocardiography for the assessment of myocardial viability for revascularization

Coronary artery disease accounts for a majority of heart failure cases in the western world. Many cardiologists believe that abnormal regional contractions in patients with coronary artery disease is equivalent to irreversibly damaged myocardium. Studies now challenge this long-held assumption. Data exist regarding the value of assessing myocardial viability in those patients with severe left ventricular dysfunction and coronary artery disease. This report discusses dobutamine echocardiography as a technique for assessing myocardial viability and for selecting patients for revascularization. (c)2001 by CHF, Inc.

Echocardiographic assessment of viable myocardium

Left ventricular function is one of the most important determinates of long-term prognosis in patients with coronary artery disease. In recent years, it has become apparent that left ventricular dysfunction in patients with coronary artery disease is not always an irreversible process stemming from myocardial necrosis and fibrosis. Myocardial tissue can undergo both a state of potential reversible dysfunction because of prolonged sustained ischemia (hibernating myocardium) or episodes of acute ischemia (stunned myocardium). Revascularization of this tissue may improve regional and global left ventricular function and therefore prognosis. Numerous studies have now firmly established dobutamine echocardiography as a safe, reliable, and accurate imaging modality in the assessment of reversible left ventricular dysfunction. Furthermore, dobutamine echocardiography has been shown to have good sensitivity, specificity, and, more importantly, positive predictive accuracy in identifying both acute and chronic reversible left ventricular dysfunction for risk satisfaction and prognosis.

Decreased left ventricular contractility reserve in patients with never-treated essential hypertension

1. Left ventricular diastolic dysfunction is often present in patients with essential hypertension. To determine whether left ventricular systolic function is normal or subnormal, we evaluated the global left ventricular contractile reserve in patients with untreated essential hypertension. 2. Thirty-one untreated men with essential hypertension and 12 normotensive healthy men were evaluated. Hypertensives were divided into two groups based on the presence (group Hc; n = 21) or absence (group Hn; n = 10) of concentric left ventricular geometric remodelling, which was defined as a relative wall thickness > or = 0.45 on M-mode echocardiography. We compared echocardiographic data of left ventricular function in hypertensive men with those in healthy men under beta-adrenoreceptor activation by up to 10 microg/kg per min dobutamine infusion. 3. At baseline, endocardial (eFS) and midwall fractional shortening of the left ventricle, the early peak filling velocity (E), the peak late filling velocity (A) and the ratio E/A were similar in the three groups. During dobutamine infusion, eFS was significantly lower in groups Hc and Hn (54.1+/-9.2 and 54.1+/-7.9%, respectively) than that observed in group N (61.7+/-7.4%). In addition, eFS was highly correlated with circumferential end-systolic wall stress (ESS) during dobutamine infusion in the three groups. In 11 subjects in group Hc (52%), the eFS-ESS relationship was lower than the 95% confidence limit of the normal regression. Comparing group Hc with groups N and Hn, it was found that E (0.52+/-0.12, 0.71+/-0.16 and 0.63+/-0.15 m/s, respectively) and E/A (0.74+/-0.23, 1.24+/-0.53 and 0.98+/-0.37, respectively) were significantly lower. 4. Our results suggest that, in addition to diastolic dysfunction, the reserve of systolic function decreased under beta-adrenoceptor activation in patients with essential hypertension.

Reversible left ventricular dysfunction

The extent and degree of myocardial viability are important parameters in the risk stratification of patients with significant left ventricular dysfunction secondary to coronary artery disease. Although several imaging modalities can identify viable myocardium, dobutamine stress echocardiography has gained considerable importance as an accurate, safe, and reliable method. In patients with significant left ventricular dysfunction secondary to coronary artery disease, identification of the presence and extent of contractile reserve and, therefore, viable myocardium during low-dose dobutamine infusion can predict the recovery of left ventricular function after revascularization, survival rate, and future cardiac events.

Do the presence and amount of dysfunctional but viable myocardium affect the perioperative outcome of coronary artery bypass graft surgery?

The aim of our study was to assess the influence of the presence and amount of dysfunctional but viable myocardium on the perioperative outcomes in patients with coronary artery disease and moderate-to-severe left ventricular systolic dysfunction, who underwent coronary artery bypass graft surgery. Viability evaluation with low-dose dobutamine echocardiography was performed in 302 consecutive patients with coronary artery disease and left ventricular ejection fraction < or =40%, who were referred for coronary angiography and potential coronary revascularization. To quantify the amount of dysfunctional but viable myocardium, wall motion was scored using a 16-segment model. The dysfunctional segments were defined as viable if they exhibited improvement in their thickening by at least one grade. One hundred and twenty-seven patients underwent coronary artery bypass graft surgery. The perioperative outcomes were evaluated in 122 of them. Five patients were excluded because of inability to revascularize all vessels supplying dysfunctional but viable myocardial segments. Twenty-five patients exhibited a large amount of dysfunctional but viable myocardium (> or =6 segments, group A), 59 patients had a small amount of such myocardium (2-5 segments, group B), and 38 patients were found to have their dysfunctional myocardium irreversibly damaged (group C). The perioperative mortality in groups A, B, and C was 4, 10, and 11% (all P = NS), respectively. The rate of perioperative Q-wave myocardial infarction was 8, 10, and 3% (all P = NS), respectively. Similarly, there were no significant differences among the groups with respect to perioperative outcome variables including ventricular arrhythmias, duration and magnitude of catecholamine support, renal failure, pulmonary edema, and need for mechanical ventricular support or artificial ventilation. In patients with coronary artery disease and moderate-to-severe left ventricular dysfunction who underwent coronary artery bypass graft surgery, the presence and amount of dysfunctional but viable myocardium did not influence the perioperative outcome.

Incremental prognostic value of rest-redistribution (201)Tl single-photon emission computed tomography

BACKGROUND

The incremental prognostic value of rest-redistribution (201)Tl compared with stress and rest perfusion abnormalities has not been defined.

METHODS AND RESULTS

We identified 458 patients who underwent rest (201)Tl /stress (exercise or adenosine) (99m)Tc sestamibi single-photon emission computed tomography (SPECT) and had late (18 to 24 hours) (201)Tl imaging, were not revascularized within 60 days of SPECT, and were followed up at >1 year. SPECT images were visually analyzed with the use of a 20-segment model on a scale of 0 to 4. Thirty-seven cardiac deaths (CDs) and 17 nonfatal myocardial infarctions occurred. Univariate Cox proportional hazards analysis showed that the presence of a large amount of rest (201)Tl reversibility (rest-late summed difference score [SDS] of >8) was a significant predictor of CD (chi(2) = 5.77, P = 0.02) and CD or myocardial infarction (chi(2) = 5.3, P = 0.02). The CD rate was 9.3% y(-1) in patients with rest-late SDS of >8 compared with 3.6% y(-1) in patients with a mild/moderate amount of rest reversibility (rest-late SDS 3 to 8) and 3.4% y(-1) in patients with no rest reversibility (rest-late SDS <3) (P = 0.029). Kaplan-Meier survival analysis demonstrated significantly lower cumulative survival rates in patients with rest-late SDS of >8 (P = 0.01). Multivariate Cox proportional hazards analysis demonstrated that the presence of a large amount of resting reversibility was an independent and incremental predictor of CD after adjustment for stress and rest perfusion information. Multivariate logistic regression analysis demonstrated that resting reversibility was not an independent predictor of referral to coronary angiography and revascularization.

CONCLUSIONS

The identification of a large amount of resting (201)Tl reversibility is an independent predictor of CD over stress and rest perfusion abnormalities.

Objective evaluation of regional left ventricular wall motion during dobutamine stress echocardiographic studies using segmental analysis of color kinesis images

OBJECTIVES

To test the feasibility of objective and automated evaluation of echocardiographic stress tests, we studied the ability of segmental analysis of color kinesis (CK) images to detect dobutamine-induced wall motion abnormalities and compared this technique with inexperienced reviewers of conventional gray-scale images.

BACKGROUND

Conventional interpretation of stress echocardiographic studies is subjective and experience dependent.

METHODS

CK images were obtained in 89 of 104 consecutive patients undergoing clinical dobutamine stress studies and were analyzed using custom software to calculate regional fractional area change in 22 segments in four standard views. Each patient's data obtained at rest was used as a control for automated detection of dobutamine-induced wall motion abnormalities. Independently, studies were reviewed without CK overlays by two inexperienced readers who classified each segment's response to dobutamine. A consensus reading of two experienced reviewers was used as the gold standard for comparisons. In a subgroup of 16 patients, these consensus readings and CK detection of wall motion abnormalities were compared with coronary angiography.

RESULTS

The consensus reading detected ischemic response to dobutamine in 43 of 1958 segments in 23 of 89 patients. Automated detection of stress-induced wall motion abnormalities correlated more closely with the standard technique than the inexperienced reviewers (sensitivity 0.76 vs. 0.55, specificity 0.98 vs. 0.94 and accuracy 0.97 vs. 0.92). When compared with coronary angiography in a subgroup of patients, analysis of CK images differentiated between normal and abnormal wall motion more accurately than expert readers of gray-scale images (accuracy of 0.93 vs. 0.82).

CONCLUSIONS

Analysis of CK images allows fast, objective and automated evaluation of regional wall motion, sensitive enough for clinical dobutamine stress data and more accurate than inexperienced readers. This method may result in a valuable adjunct to conventional visual interpretation of dobutamine stress echocardiography.

Dobutamine-induced hypotension is an independent predictor for mortality in patients with left ventricular dysfunction following myocardial infarction

Dobutamine echocardiography was performed on 297 patients after acute myocardial infarction to assess the prognostic value of dobutamine-induced hypotension in patients with left ventricular dysfunction. Patients were divided into two groups according to ejection fraction (group I, ejection fraction <0.45, n = 123; group II, ejection fraction > or =0.45, n = 174) and were followed for 20+/-8 months. Hypotension was defined as a decrease in systolic blood pressure > or =20 mm Hg, compared with baseline values. The incidence of hypotension was similar in groups I and II (23.6% vs. 18.4%, P = 0.28), and the hypotension was not related to positive dobutamine echocardiography. Univariate analysis showed that the development of hypotension was associated with a higher incidence of cardiac death in group I but not in group II. Multivariate analysis showed that dobutamine-induced hypotension was an independent predictor only for cardiac death in group I and was not related to any other cardiac events in either group. In conclusion, the development of hypotension during dobutamine stress can identify a subgroup with poor ventricular functional reserve and at high risk for cardiac death among patients complicated with left ventricular dysfunction.

Myocardial viability

This article reviews various means to assess myocardial viability by imaging, and provides recommendations for current clinical practice. This article also discusses future directions in assessing myocardial viability.

Low-dose dobutamine testing using contrast left ventriculography in the same session as coronary angiography predicts the improvement of left ventricular function after coronary angioplasty in postinfarction patients

The role of percutaneous transluminal coronary angioplasty (PTCA) in the subacute or chronic phases of myocardial infarction remains controversial. This study investigates the usefulness of dobutamine contrast left ventriculography in a single session with coronary angiography for predicting the improvement of ventricular function after PTCA. The study group consisted of 30 patients in whom a contrast left ventricular angiogram and PTCA were performed after a first myocardial infarction. The centerline method was used to calculate dysfunction extent at baseline and its variation during dobutamine infusion at 7.5 microg/kg/min; contractile reserve was defined as a significant (> or = 15%) reduction of dysfunction extent. A second ventricular angiogram was performed 6 months later in all patients. Abnormal wall motion extent decreased at 6 months after PTCA (84+/-21% vs 70+/-29%, p = 0.0001). Wall motion improvement after PTCA correlated with the response to dobutamine (r = 0.54, p = 0.002). Ten patients showed a significant reduction (> or = 15%) of dysfunction extent at 6 months; dobutamine testing had a 80% sensitivity, 84% specificity, 67% positive predictive value, and 89% negative predictive value in detecting regional function improvement. In the subgroup of 21 patients without restenosis, both the correlation between dysfunction improvement after PTCA and response to dobutamine (r = 0.72, p = 0.0001) and the accuracy of dobutamine testing (sensitivity 88%, specificity 92%, positive predictive value 88%, and negative predictive value 92%) increased. The ejection fraction significantly increased (>5%) after PTCA in 6 patients; dobutamine testing had a 67% sensitivity, 74% specificity, 44% positive predictive value, and 88% negative predictive value in predicting the increase in the ejection fraction. In the subgroup without restenosis the improvement of the ejection fraction correlated with the response to dobutamine (r = 0.63, p = 0.007), and the sensitivity of dobutamine testing was 80%, specificity 83%, positive predictive value 67%, and negative predictive value 91%. In conclusion, dobutamine contrast left ventriculography testing in the same session as coronary angiography predicts regional function and ejection fraction improvement after PTCA in postinfarction patients, particularly when restenosis does not develop.

Prognostic value of the amount of dysfunctional but viable myocardium in revascularized patients with coronary artery disease and left ventricular dysfunction. Investigators of this Multicenter Study

OBJECTIVES

The purpose of our study was to assess the prognostic importance of the amount of dysfunctional but viable myocardium in revascularized patients with coronary artery disease (CAD) and left ventricular (LV) dysfunction.

BACKGROUND

The amount of dysfunctional but viable myocardium predicts the functional improvement after revascularization and may offer more precise risk stratification of patients referred for bypass surgery or coronary angioplasty.

METHODS

Two hundred and seventy-four consecutive patients with CAD and LV ejection fraction < or =40% underwent low-dose dobutamine echocardiography for viability assessment. One hundred and thirty-three of them were revascularized using either coronary artery bypass surgery (118 patients) or coronary angioplasty (15 patients) and entered this study. To quantify the amount of dysfunctional but viable myocardium, wall motion was scored using 16-segment model. The dysfunctional segments were defined as viable if they exhibited improvement in their thickening by at least 1 grade with dobutamine infusion. The patients were followed up for a mean period of 20+/-12 months (range, 2 to 48) for cardiac mortality and nonfatal cardiac events including myocardial infarction, unstable angina pectoris requiring hospitalization and hospitalization for heart failure. Standard follow-up echocardiography was performed 3 to 6 months after revascularization.

RESULTS

Twenty-nine patients exhibited a large amount of dysfunctional but viable myocardium (> or =6 segments, group A), 60 patients had a small amount of dysfunctional but viable myocardium (2 to 5 segments, group B) and 44 patients were found to have dysfunctional myocardium irreversibly damaged (group C). Similar prerevascularization LV ejection fractions of 35%+/-5%, 34%+/-4%, 36%+/-4% in groups A, B and C increased to 47%+/-6% (p < 0.01 vs. baseline, p < 0.01 vs. groups B and C), to 40%+/-5% (p < 0.01 vs. baseline) and to 37%+/-6% (p = NS vs baseline), respectively, after revascularization. The greatest functional improvement after revascularization in group A patients was accompanied by a lower rate of cardiac events during follow-up (2 vs. 18 in group B, p < 0.05, and vs. 17 in group C, p < 0.01) and better cardiac event-free survival according to Kaplan-Meier survival analysis (p < 0.05 vs. groups B and C, respectively).

CONCLUSION

In revascularized patients with CAD and moderate or severe LV dysfunction, the presence of a large amount of dysfunctional but viable myocardium identifies patients with the best prognosis.

Ultrasonic tissue characterization in predicting residual ischemia and myocardial viability for patients with acute myocardial infarction

The identification of viable myocardium and residual ischemia in patients with acute myocardial infarction has important prognostic implications. The ultrasonic tissue characterization with integrated backscatter and dobutamine-atropine stress echocardiography were performed 8.3+/-3 days after AMI in 30 patients. After coronary angioplasty for the residual stenosis of infarct-related artery, both modalities were repeated. The parameter obtained from ultrasonic tissue characterization, phase-weighted variation, could differentiate the myocardium with residual coronary stenosis or nonviable myocardium from the viable myocardium without residual coronary stenosis (p < 0.001). Using the cutoff value of 5.8 dB, the sensitivity, specificity and accuracy for detecting viable myocardium without residual coronary stenosis were 75%, 100% and 90.2%, respectively. The phase-weighted variation of the viable infarction zone restored after the coronary stenosis was relieved. In contrast, the nonviable myocardium had a small phase-weighted variation that was irrelevant to the patency of the infarct-related artery. The ultrasonic tissue characterization may be used in identifying patients with acute myocardial infarction whose infarction zones are viable without residual ischemia.

Myocardial viability during dobutamine echocardiography predicts survival in patients with coronary artery disease and severe left ventricular systolic dysfunction

OBJECTIVES

The purpose of this study was to assess whether the presence or absence of myocardial viability during dobutamine echocardiography (DE) predicts survival in patients with coronary artery disease (CAD) and severe left ventricular (LV) dysfunction.

BACKGROUND

In patients with CAD, the presence of myocardial viability during DE identifies viable myocardium and predicts recovery of LV systolic function after revascularization. However, there is little data on the relation between myocardial viability and clinical outcome in patients with CAD and severe LV dysfunction.

METHODS

We studied 318 patients with CAD and a LV ejection fraction (EF) < or =35% who underwent DE and were followed for 18+/-10 months. Patients were classified into four groups. Group I (n=85) consisted of patients who had evidence of myocardial viability and subsequently underwent revascularization. Group II (n=119) consisted of patients with myocardial viability who did not undergo revascularization. Group III (n=30) consisted of patients who did not have myocardial viability and underwent revascularization. Finally, group IV (n=84) patients lacked myocardial viability and did not undergo revascularization.

RESULTS

The four groups had similar baseline characteristics and rest LVEF. During follow-up there were 51 deaths (16%). The mortality rate was 6% in group I, 20% in group II, 17% in group III and 20% in group TV (p=0.01, group I vs. other groups).

CONCLUSIONS

In patients with CAD and severe LV dysfunction who demonstrated myocardial viability during DE, revascularization improved survival compared with medical therapy.

Role of stress echocardiography in heart failure

Most patients presenting with heart failure have severe coronary artery disease. The identification of viable hibernating myocardium is of paramount clinical importance for a correct indication of revascularization. Contractile reserve may be identified when regional asynergy improves during low or moderate doses of dobutamine. Dipyridamole, given at infra-low dose, alone or preferably in association with a low dose of dobutamine, is another possible pharmacologic stress protocol. Dobutamine echocardiography has been found to be more specific than thallium scintigraphy for predicting functional recovery after revascularization. However, the absence of contractile reserve does not exclude the presence of myocardial viability: perfusion reserve may be too low because of a critical coronary artery stenosis, or profound ultrastructural changes of myocardial cells may be present, including significant loss of contractile material. Inotropic reserve can also be assessed by dobutamine stress echocardiography in patients with idiopathic cardiomyopathy. The evolution of hemodynamic variables can be measured during the stress test. Stress echocardiography, especially during exercise, could probably provide important information about heart failure associated with valvular heart disease.

Biphasic response to dobutamine predicts improvement of global left ventricular function after surgical revascularization in patients with stable coronary artery disease: implications of time course of recovery on diagnostic accuracy

OBJECTIVES

This study sought to evaluate the time course of improvement of left ventricular (LV) dysfunction in stable patients and its implications on the accuracy of dobutamine echocardiography for predicting improvement after surgical revascularization.

BACKGROUND

Little is known about the optimal timing for evaluation of postrevascularization recovery of the contractile function of viable myocardium.

METHODS

Sixty-one patients with chronic ischemic LV dysfunction scheduled for elective surgical revascularization were prospectively selected. They underwent dobutamine echocardiography (5 to 40 microg/kg body weight per min) and radionuclide ventriculography both preoperatively and at 3-month follow-up. At 14 months, another evaluation of LV function was obtained. To analyze echocardiograms, a 16-segment model and a five-point scoring system were used. Dyssynergic segments were considered likely to recover in the presence of a biphasic contractile response to dobutamine. Improvement of global function was defined as a > or =5% increase in LV ejection fraction (LVEF).

RESULTS

Of the 61 patients, LVEF improved in 12 at 3 months and in 19 at late follow-up (from 32+/-8% to 42+/-9%, p < 0.0001). The frequency and time course of improvement of LVEF were similar in patients with mild and severe LV dysfunction. A biphasic response, identified in 186 of the 537 dyssynergic segments, was predictive of recovery in 63% at 3 months and in 75% at late follow-up. The positive predictive value was best in the most severe dyssynergic segments (90% vs. 67%). Other responses were highly predictive for nonrecovery (92%). The sensitivity and specificity for improvement of global function on a patient basis (> or =4 biphasic segments) were 89% and 81%, respectively, at late follow-up.

CONCLUSIONS

Serial postoperative follow-up studies demonstrate incomplete recovery of contractile function at 3 months. The diagnostic accuracy of dobutamine echocardiography for predicting recovery is dependent on three factors: the combining of low and high dobutamine dosages, the severity of regional dyssynergy and the timing of evaluation.

Does dobutamine stress echocardiography induce damage during viability diagnosis of patients with chronic regional dysfunction after myocardial infarction?

Experimental hibernating-model investigations of animals have shown that myocardial necrosis can be induced by longer-term intracoronary dobutamine infusion. This study was designed to determine whether myocardial infarction could be ascertained in patients with chronic regional wall motion abnormalities and greater than 75% stenosis in the supplying coronary artery through dobutamine stress echocardiography. Twenty patients with coronary artery disease and regional resting wall motion abnormalities were examined with a standard dobutamine protocol (5 to 50 microg/kg/min). Exclusion criteria were an acute coronary syndrome, severe heart failure, and severe hypertension. Creatine kinase (CK, CKMB), myoglobin, and troponine-I were measured before and at each of the first 7 hours after beginning of infusion. Fourteen of these 20 patients exhibited viable myocardium. The serum markers CK, CKMB, myoglobin, and troponin-I demonstrated no increase beyond the reference range, suggesting that with this protocol, no myocardial necrosis was induced.

Accuracy of currently available techniques for prediction of functional recovery after revascularization in patients with left ventricular dysfunction due to chronic coronary artery disease: comparison of pooled data

OBJECTIVES

This study evaluated the relative merits of the most frequently used techniques for predicting improvement in regional contractile function after coronary revascularization in patients with left ventricular dysfunction due to chronic coronary artery disease.

BACKGROUND

Several techniques have been proposed for predicting improvement in regional contractile function after revascularization, including thallium-201 (Tl-201) stress-redistribution-reinjection, Tl-201 rest-redistribution, fluorine-18 fluorodeoxyglucose with positron emission tomography, technetium-99m sestamibi imaging and low dose dobutamine echocardiography (LDDE).

METHODS

A systematic review of all reports on prediction of functional recovery after revascularization in patients with chronic coronary artery disease (published between 1980 and March 1997) revealed 37 with sufficient details for calculating the sensitivity and specificity of each imaging modality. From the pooled data, 95% and 99% confidence intervals were also calculated.

RESULTS

Sensitivity for predicting regional functional recovery after revascularization was high for all techniques. The specificity of both Tl-201 protocols was significantly lower (p < 0.05) and LDDE significantly higher (p < 0.01) than that of the other techniques.

CONCLUSIONS

Pooled analysis of 37 studies showed that although all techniques accurately identify segments with improved contractile function after revascularization, the Tl-201 protocols may overestimate functional recovery. The evidence available thus far indicates that LDDE appears to have the highest predictive accuracy.

Hibernating myocardium: clinical and functional response to revascularisation

OBJECTIVE

We assessed the effects of coronary bypass grafting on left ventricular (LV) function, exercise capacity and symptom profile in patients with LV impairment and evaluated the role of identifying myocardial hibernation in a prospective non-randomised study.

METHODS

Of 120 patients screened, 47 patients with LV ejection fraction < 35% and three vessel coronary artery disease were studied. All underwent stress/redistribution and separate day rest/redistribution T1-201 imaging together with cine MRI at enrolment, and cine MRI at follow-up. Group 1, 30 patients undergoing bypass surgery, underwent symptom limited treadmill exercise testing with peak VO2 measurement, and symptom profile evaluation less than 3 months before, and 3-6 months after operation. Revascularisation was assessed by post-operative T1-201 imaging and repeat coronary angiography. Group 2, 17 patients treated on medical therapy alone underwent symptom profile assessment at enrolment and follow-up for those who survived. Segmental hibernation was defined as the equivalent of greater than 50% of maximal T1-201 uptake where wall motion was severely impaired on resting imaging. Patients were considered to be hibernating where two of nine LV segments fulfilled these criteria.

RESULTS

In group 1, five patients died (17%), peri-or post-operatively, two defaulted and 23 attended follow-up studies. In group 2, three patients died prior to follow-up (18%). In the surgical group there was an increase in mean LVEF from 24.0 +/- 8% to 29.7 +/- 11% (P < 0.05) while in the medical group there was a fall from 25.7 +/- 10% to 20.6 +/- 8% (P < 0.05). In group 1, the mean NYHA dyspnoea grade improved from 2.7 to 1.4 while in the medical group it was unchanged, 2.6 to 2.5. In patients with myocardial hibernation identified pre-operatively, 18/19 (95%) improved LVEF after CABG compared with 2/4 (50%) of patients without hibernation. 17/19 (86%) patients with hibernation improved NYHA dyspnoea class compared with 2/4 (50%) of patients without. 60/93 (65%) of hibernating segments improved function after revascularisation while 47/53 (89%) hibernating segments showed no improvement on medical therapy alone.

CONCLUSION

In patients with severe LV impairment with myocardial hibernation, coronary artery bypass grafting improves both global and regional systolic LV function, and symptom profile. Medical treatment of patients with LV impairment and myocardial hibernation does not improve LV contractile function or symptoms. Both surgical and medical therapy carry a high mortality rate.

[II. Role of Doppler echocardiography in the management of chronic ischemic cardiopathy]

Doppler echocardiography is a simple, fast and non-invasive method to identify abnormal regional and global left ventricular function. One could consider this method the best application for this end within the techniques of imaging. This chapter reviews the role of Doppler echocardiography in the management of chronic coronary artery disease, as well as for studying the global and regional function at rest, as in the applications derived from their use during stress testing. Frequent techniques of stress echocardiography for the diagnosis of ischemic heart disease, their utility in the study of myocardial viability, and the establishment of recommendations for their use in clinical practice are analyzed.