Dobutamine echocardiography and thallium-201 imaging predict functional improvement after revascularisation in severe ischaemic left ventricular dysfunction

Persistent ventricular asynchrony after coronary artery bypass surgery predicts cardiac events

AIM

The aim of this study was to identify echocardiographic LV systolic and diastolic measurements that predict clinical events post-coronary artery bypass graft (CABG) surgery.

METHODS

We collected data from 27 patients (age 70 +/- 7 years) who underwent elective CABG, before and within 6 weeks after surgery. LV systolic function was assessed by conventional echocardiographic parameters. A number of LV filling measurements were also made, which included total isovolumic time (t-IVT), Tei index, and restrictive filling pattern. Postoperative cardiac events were death or hospitalization for chest pain, breathlessness, or arrhythmia.

RESULTS

Patient's follow-up period was 17 +/- 10 months. Of the 27 patients (age 70 +/- 7 years, 22 male), 10 had postoperative cardiac events. LV ejection fraction (EF) and fractional shortening (FS) were lower (P = 0.01, and P = 0.007, respectively), t-IVT longer (P < 0.001), and Tei index was higher (P < 0.001) preoperatively in patients with events compared to those without. The same differences between groups remained after surgery; EF (P = 0.002), FS (P = 0.002), t-IVT (P < 0.001), and Tei index (P < 0.001). T-IVT was the only preoperative predictor of events (P = 0.038) but its postoperative value as well as that of FS predicted events (P = 0.034, and P = 0.042, respectively). T-IVT of 12.2 s/min and FS of 26% were 80% sensitive and 88% specific for predicting postoperative events.

CONCLUSION

Despite successful surgical revascularization residual impairment of LV systolic function and persistent asynchrony in the form of prolonged t-IVT are associated with postoperative events. Since these abnormalities remained despite full medical therapy, they may thus suggest a need for electrical resynchronization therapy.

Comparison between myocardial contrast echocardiography and (99m)technetium sestamibi single photon emission computed tomography determined myocardial viability in predicting hard cardiac events following acute myocardial infarction

The extent of residual myocardial viability (MV) after acute myocardial infarction (AMI) is an important determinant of the outcome. Single photon emission computed tomography (SPECT) is widely used to assess MV after an AMI. However, myocardial contrast echocardiography (MCE), a relatively new technique for the assessment of MV, has better spatial and temporal resolution than SPECT. The present study evaluated whether MV determined by MCE is comparable to that determined using SPECT for the prediction of hard cardiac events after an AMI. Accordingly, 99 patients who had undergone simultaneous rest low-power MCE and nitrate-enhanced SPECT 7 days after an AMI were followed up for cardiac death and AMIs. Both MCE perfusion (1 = normal; 2 = reduced; and 3 = absent) and SPECT tracer uptake (0 = normal; 1 = mildly reduced; 2 = moderately reduced; 3 = severely reduced; and 4 = absent) were scored on a 16-segment left ventricular model. The contrast perfusion index and SPECT perfusion index were calculated by adding the respective scores in the 16 segments and dividing by 16. The contrast perfusion index and SPECT perfusion index were used as a measure of the residual MV on MCE and SPECT, respectively. Of the 99 patients recruited, 95 were available for the follow-up examination (follow-up 46 +/- 16 months). A total of 15 events (16%) occurred (8 cardiac deaths and 7 AMIs). Of the clinical, biochemical, echocardiographic, and SPECT markers of prognosis, the only independent predictors of cardiac death and cardiac death or AMI were age and MV as determined by MCE (p = 0.01 and p = 0.002, respectively). In conclusion, MV determined by MCE at rest was superior to nitrate-enhanced SPECT for the prediction of hard cardiac events after AMI.

Prolonged total isovolumic time predicts cardiac events following coronary artery bypass surgery

AIMS

Left ventricular (LV) systolic dysfunction may be associated with compromised stroke volume, which may be caused by asynchrony, reflected on the prolongation of isovolumic time (t-IVT). To assess the prognostic role of Doppler echocardiographic measurements in predicting cardiac events after coronary artery bypass grafting (CABG).

METHODS AND RESULTS

The study included 74 patients undergoing routine CABG. A pre-CABG Doppler echocardiographic assessment of LV dimensions, filling and ejection was performed and t-IVT was determined as [60 - (total ejection time + total filling time)]. Follow-up period was 18 +/- 12 months. Of the 74 patients (age 65 +/- 16 years, 59 males), 29 underwent hospital admission for a cardiac event or died. There were no differences in age, gender, incidence of previous infarct or mitral regurgitation, LV-EDD (left ventricular end-diastolic dimension), left atrial or right ventricular size in patients with cardiac events compared with those without events. Left ventricular end-systolic dimension (LV-ESD) was greater (4.5 +/- 0.9 vs. 3.9 +/- 0.9 cm, P = 0.003), fractional shortening (FS) was lower (21 +/- 4 vs. 32 +/- 8%), E:A ratio and Tei index were higher (2.1 +/- 0.8 vs. 1.0 +/- 0.6 and 0.9 +/- 0.3 vs. 0.6 +/- 0.3, all P < 0.001), and t-IVT was longer (16 +/- 5 vs.10 +/- 4 s/min, P < 0.001) in patients with events. Multivariate predictors of post-CABG events (odds ratio 95% confidence interval) were low FS [0.66 (0.50-0.87), P < 0.001], high E:A ratio [l4.13 (1.17-14.60), P = 0.028], large LV-ESD [0.19 (0.05-0.84), P = 0.029], and long t-IVT [1.37 (1.02-1.84), P = 0.035].

CONCLUSION

Despite satisfactory surgical revascularization, long t-IVT and systolic dysfunction suggest persistent ventricular dyssynchrony that contributes to post-CABG cardiac events. Early assessment of such patients for potential benefit from electrical resynchronization may optimize their cardiac performance and hence clinical outcome.

In vivo R1-enhancement mapping of canine myocardium using ceMRI with Gd(ABE-DTTA) in an acute ischemia-reperfusion model

PURPOSE

To demonstrate the usefulness of normalized DeltaR1 (DeltaR1(n)) mapping in myocardial tissue following the administration of the contrast agent (CA) Gd(ABE-DTTA).

MATERIALS AND METHODS

Ischemia-reperfusion experiments were carried out in 11 dogs. The method exploited the relatively long tissue lifetime of Gd(ABE-DTTA), and thus no fast R1 measurement technique was needed. Myocardial perfusion was determined with colored microspheres (MP).

RESULTS

With varying extent of ischemia, impaired wall motion (WM) and lower DeltaR1(n) values were detected in the ischemic sectors, as opposed to the nonischemic sectors where normal WM and higher DeltaR1(n) were observed. Based on the DeltaR1(n), data from the myocardial perfusion assay and the DeltaR1(n) maps were compared in the ischemic sectors. A correlation analysis of these two parameters demonstrated a significant correlation (R = 0.694, P < 0.005), validating the DeltaR1(n)-mapping method for the quantitation of ischemia. Similarly, pairwise correlations were found for the MP, DeltaR1(n), and wall thickening (WT) values in the same areas. Based on the correlation between DeltaR1(n) and MP, DeltaR1(n) maps calculated with a pixel-by-pixel resolution can be converted to similarly high-resolution myocardial perfusion maps.

CONCLUSION

These results suggest that the extent of the severity of ischemia can be quantitatively represented by DeltaR1(n) maps obtained in the presence of our CA.

Prognostic role of single-photon emission computed tomography (SPECT) imaging in myocardial viability

PURPOSE OF REVIEW

Cardiac imaging is evolving rapidly. Appropriate use of this technology could reduce morbidity and mortality, but inappropriate use could have a significant financial burden. Single-photon emission computed tomography imaging is widely available. This review summarizes the clinical utility and limitations of the prognostic role of single-photon emission computed tomography imaging for myocardial viability in patients with coronary artery disease and left-ventricular dysfunction.

RECENT FINDINGS

201Tl single-photon emission computed tomography, 99mTc single-photon emission computed tomography with sestamibi or tetrofosmin, and 18F-fluorodeoxyglucose single-photon emission computed tomography are validated tools for assessing myocardial viability. These techniques have a very similar predictive value in determining regional and global response to revascularization. 201Tl single-photon emission computed tomography viability studies are predictive of reverse left-ventricular remodeling, symptom improvement, and patient outcome after revascularization. Combination imaging with dual-isotope simultaneous acquisition single-photon emission computed tomography or positron-emission tomography/single-photon emission computed tomography may improve the positive and negative predictive values of single-photon emission computed tomography-based viability studies.

SUMMARY

Single-photon emission computed tomography-based myocardial viability testing is an important diagnostic modality due to widespread availability and reasonably good sensitivity and specificity for detecting viable myocardium and predicting clinical and functional responses to revascularization. In the future single-photon emission computed tomography viability techniques may have a prognostic role in predicting responses to cardiac resynchronization therapy and evaluating myocardial stem-cell transplantation.

Diagnostic and imaging considerations: role of viability

Left ventricular systolic dysfunction is a recognised feature of heart failure. In developed nations, the leading cause of left ventricular systolic dysfunction is coronary artery disease. Revascularisation is a treatment strategy for patients with predominant symptoms of heart failure and significant left ventricular dysfunction. Presence or absence of myocardial viability has been shown to affect outcome after revascularisation. There are various techniques to assess myocardial viability. However, limitations of current literature, lack of completed randomised trials and high peri-procedural trials create significant uncertainty about the optimal strategy. This review focuses on the role of non-invasive testing for myocardial viability in patients with left ventricular systolic dysfunction and heart failure and also outlines the pros and cons of each technique.

Myocardial Viability: Nuclear Assessment

There are an estimated 5 million patients with congestive heart failure (CHF) in the United States. The long-term outcome in these patients is poor with a 5-year mortality of 70%. There is evidence suggesting that revascularization in patients with viable myocardium can result in reduced event rate in these patients. The presence of viable myocardium best identifies patients who will improve with revascularization. Noninvasive imaging with radionuclide tracers has been used extensively to identify the presence and extent of viable myocardium. We have summarized the role of radionuclide myocardial perfusion and function evaluation in assessment of viable myocardium in this review.

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.

Ventricular function after coronary artery bypass grafting: Evaluation by magnetic resonance imaging and myocardial strain analysis

OBJECTIVE

Magnetic resonance imaging with radiofrequency tissue tagging permits quantitative assessment of regional systolic myocardial strain. We sought to investigate the utility of this imaging modality to quantitatively determine preoperative impairment and postoperative improvement in ventricular function in patients with ischemic heart disease.

METHODS

Magnetic resonance imaging with radiofrequency tissue tagging was performed on 6 patients (average age 60.2 +/- 13.7 years) with coronary artery disease and 32 control subjects with no known heart disease. Patients with coronary artery disease underwent imaging before and 3 months after coronary artery bypass grafting. The ventricle was divided into 6 segments within a midventricular plane. Regional 2-dimensional left ventricular circumferential strain was calculated from tagged magnetic resonance images throughout systole. Circumferential strain results were compared in patients before and after and 3 months after coronary artery bypass grafting and also in control subjects.

RESULTS

Before the operation circumferential strain identified 100% (10/10) of all regional wall motion abnormalities seen by preoperative ventriculography. Postoperatively, improvements were demonstrated in 56% (20/36) of the regions, and these improvements agreed with viability testing by single-photon emission computed tomography when available. Additionally, preoperative global circumferential strain for the ischemic group was significantly depressed relative to that in control subjects (0.11 +/- 0.05 vs 0.20 +/- 0.03, P <.001). Global circumferential strain correlated with ejection fraction by ventriculography (r = 0.84, P <.01) and improved after coronary artery bypass grafting (0.14 +/- 0.05 vs 0.11 +/- 0.05, P <.01).

CONCLUSIONS

Magnetic resonance imaging with radiofrequency tissue tagging permitted circumferential strain calculation. This technology quantitatively demonstrated improvements in left ventricular wall motion after coronary artery bypass grafting for both individual regions and the entire ventricle. This noninvasive method may prove useful in preoperative evaluation and postoperative serial assessment of left ventricular wall motion.

Association of myocardial viability on nitrate-augmented technetium-99m hexakis-2-methoxylisobutyl isonitrile myocardial tomography and intermediate-term outcome in patients with prior myocardial infarction and left ventricular dysfunction

Seventy-eight patients with prior myocardial infarction and left ventricular dysfunction who underwent nitrate-augmented myocardial tomography were followed for 23 +/- 14 months. Event-free survival was 100% in 34 patients with myocardial viability who underwent coronary artery bypass grafting (CABG) and 53% in those who received medical therapy (p = 0.0008). Of the 44 patients without myocardial viability, event-free survival was not significantly different between patients who underwent CABG and those who received medical therapy (96% vs 90%, p = NS).

Relationship between dobutamine response of dyssynergic myocardium and angiographically documented blood supply

OBJECTIVE

Because hibernation is considered a down-regulation of contractile function in response to reduced regional myocardial perfusion, hibernating myocardium is expected to be supplied by a critically stenosed or even occluded coronary artery. Thus, high-dose dobutamine has been postulated to cause ischemia and reworsening of myocardial function (biphasic response), whereas myocardium that demonstrates sustained improvement with high-dose dobutamine should not be supplied by a significantly stenosed vessel. This study evaluates the type of dobutamine response-biphasic versus sustained improvement-of dyssynergic myocardium in relation to its angiographically documented blood supply.

METHODS

In 38 patients (5 women; mean age 60 +/- 9 years) with chronic coronary artery disease and impaired left ventricular ejection fraction (</=35%), dobutamine echocardiography and quantitative coronary angiography were performed within 4 weeks. Wall-motion response of dyssynergic myocardium to dobutamine, classified as no improvement, biphasic response, or sustained improvement, was compared with the angiographically documented blood supply (presence of coronary stenosis in the corresponding artery, collaterals, and stenoses of the collateral supplying artery) in a segment-by-segment analysis.

RESULTS

Of the 465 segments with abnormal wall motion at rest, 201 (47%) showed improvement during dobutamine infusion at low dose. Of these, 145 (72%) were supplied by significantly stenosed epicardial vessels. Only 27 (19%) of these 145 segments showed a biphasic response whereas in the remaining 118 segments wall-motion improvement persisted during high-dose dobutamine infusion. Although mean stenosis severity in the supplying vessel was significantly greater for segments presenting with biphasic response as compared with sustained improvement (95 +/- 7% and 86 +/- 12% luminal diameter reduction, respectively; P <.0001), 69% of segments with sustained improvement were supplied by a critically stenosed artery. Only 7 of 27 segments with biphasic response and 22 of 118 segments with sustained improvement had visible collaterals supplied by a vessel without significant stenosis. The percentage of segments viable by thallium-single photon emission computed tomography imaging was similar for those with sustained and biphasic response (96% and 83%, respectively).

CONCLUSIONS

In this group of patients with coronary artery disease and impaired left ventricular function, the great majority of dyssynergic segments that exhibited a sustained, rather than biphasic, dobutamine response were supplied by a critically stenosed artery. Furthermore, the percentage of segments viable by thallium-single photon emission computed tomography did not appear to be different for segments with sustained improvement and those with biphasic response. These findings challenge the hypothesis that biphasic response is the best criterion to identify viable myocardium.

The heart failure revascularisation trial (HEART): rationale, design and methodology

BACKGROUND

Most patients with heart failure due to left ventricular systolic dysfunction (LVSD) secondary to coronary artery disease (CAD) have evidence of myocardium in jeopardy (reversible ischaemia and/or stunning hibernation). It is not known whether revascularisation in such cases is safe or beneficial.

AIMS

To determine whether revascularisation will improve the survival of patients with LVSD and heart failure secondary to CAD and myocardium in jeopardy.

METHODS

This is a randomised controlled trial comparing revascularisation or not, in addition to optimal medical therapy with ACE inhibitors, beta-blockers, aldosterone antagonists and an anti-thrombotic agent. Patients must have heart failure requiring treatment with diuretics, a left ventricular ejection fraction <35% and evidence of coronary disease. Myocardial viability and ischaemia are assessed by a broad range of techniques including stress echocardiography and nuclear imaging. All imaging tests are reviewed in core laboratories to ensure uniform reporting. Any conventional revascularisation technique is permitted. The primary outcome measure is all cause mortality. Symptoms, quality of life and health economic issues will also be explored. Assuming an annual mortality of 10% in the control group and allowing for substantial cross-over rates, a study of 800 patients followed for 5 years has 80% power with an alpha of 0.05 (two-sided) to show a 25% reduction in mortality with revascularisation.

RESULTS

At the time of writing 180 patients have been screened for inclusion, 111 have consented to participate and 70 have been randomised. The results of viability testing are awaited in 22 patients. Twenty-six patients had been investigated for myocardial viability and/or by angiography prior to consent, as part of the routine practice in that cardiology department. Of 68 patients who have completed assessment only after consent, 47 (69%) were included. The principal reason for drop-out between consent and randomisation was lack of evidence of myocardial ischaemia or hibernation.

CONCLUSION

The HEART trial will help to determine whether investigation of myocardial ischaemia and/or viability with a view to revascularisation should become part of the routine care of patients with heart failure due to LVSD and CAD.

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.

Use of pharmaceuticals in noninvasive cardiovascular diagnosis

A number of pharmaceuticals are employed as diagnostic agents for cardiovascular diseases. Four groups of agents are reviewed here: 1) vasoactive substances employed as adjuncts to physical maneuvers in diagnosis of structural heart disease; 2) vasodilators used to produce heterogeneity of coronary flow; 3) sympathomimetic agents simulating the effects of exercise on the heart for the purpose of detection of coronary artery stenosis; and 4) ultrasonic contrast agents used to enhance myocardial imaging for the assessment of segmental wall motion. In the first group are amyl nitrate, a vasodilator, and methoxamine and phenylephrine, both vasopressors. The vasodilators of the second group are dipyridamole and adenosine. When combined with scintigraphic perfusion imaging or with echocardiographic assessment of segmental wall motion, these agents can detect single- or multiple-vessel coronary artery disease with sensitivity and specificity comparable to submaximal exercise. They are especially useful for preoperative risk assessment before noncardiac surgery. The sympathomimetic agents of the third group, dobutamine and arbutamine, increase myocardial contractility and heart rate, and dilate the peripheral vasculature. As with the vasodilators, when combined with nuclear or echocardiographic techniques they are equivalent to exercise in detection of coronary disease. They are especially useful in patients with bronchospastic disease and for assessment of myocardial viability. Agents from groups 2 and 3 have acceptable side-effect and safety profiles. The last group reviewed includes echocardiographic contrast agents that, in this investigative setting, are employed to enhance detection of segmental wall motion when used with agents from groups 2 and 3.

Impact of revascularization and myocardial viability determined by nitrate-enhanced Tc-99m sestamibi and Tl-201 imaging on mortality and functional outcome in ischemic cardiomyopathy

BACKGROUND

Nitrate-enhanced perfusion imaging has been shown to detect viability in dysfunctional myocardium, but nitrate-enhanced technetium 99m sestamibi has not been compared with nitrate-enhanced thallium 201.

METHODS AND RESULTS

Fifty-six patients with ischemic cardiomyopathy and heart failure (New York Heart Association classes II-IV) were scheduled for revascularization. Through use of a matching 12-segment model, nitrate-enhanced Tl-201 and Tc-99m sestamibi uptake at rest was assessed by 2 sets of blinded investigators. All single photon emission computed tomography data sets were read separately. Additional exercise Tc-99m sestamibi single photon emission computed tomography was performed on a separate day. Myocardial viability was thought to be present when the tracer uptake score was less than 3 (normal, 0; absent, 4). Of the 56 patients scheduled to undergo revascularization, only 23 (41%) underwent the procedure and the remainder continued medical therapy. Functional assessment by rest echocardiography was performed at 21 +/- 8 months, and survival was determined at 40 +/- 18 months. The baseline clinical and hemodynamic parameters were similar in the revascularization (n = 23) and medical therapy (n = 33) groups. Perfusion scores with nitrate-enhanced Tl-201 and Tc-99m sestamibi were similar in dysfunctional segments. Stress Tc-99m sestamibi reversible defects predicted significant improvement in left ventricular function compared with those without defects (P <.01) after revascularization. Cox regression model showed that when at least 5 reversible segments were viable, revascularization produced greater improvements in New York Heart Association class, a better trend toward survival (P =.07 for Tl-201 and P =.06 for Tc-99m), and a significantly greater impact on reverse remodeling.

CONCLUSIONS

Myocardial viability determined by nitrate-enhanced Tl-201 and myocardial viability determined by Tc-99m sestamibi are equivalent for predicting functional improvements, remodeling, and survival after revascularization in patients with ischemic cardiomyopathy.

Effect of revascularization on left ventricular remodeling in patients with heart failure from severe chronic ischemic left ventricular dysfunction

Few data exist regarding the effect of revascularization on left ventricular (LV) geometry in patients with severe LV systolic dysfunction and viable myocardium. We hypothesized that patients with chronic ischemic LV dysfunction but viable myocardium will have improved LV geometry after revascularization, which in turn will improve long-term outcome. Accordingly, 70 patients with severe ischemic LV dysfunction (LV ejection fraction <0.35) were studied at rest. They then either underwent revascularization (n = 36) or were treated medically (n = 34). Fifty-four patients had viable myocardium, and 16 did not. They were evaluated for change in LV function and geometry (size and shape) a mean of 21 months later. Further follow-up was performed for a mean of 3.5 years to determine outcome. Patients with viable myocardium had improvement not only in regional and global function, but also in LV geometry (shape and size), which was independent of and incremental to the improvement in function. On long-term follow-up, change in LV end-systolic volume was the only multivariate discriminator between 15 patients who died and 55 who did not, irrespective of whether they had undergone revascularization. Thus, measurement of the effect of revascularization of viable myocardium in chronic ischemic heart disease should not only include improvement in resting regional and global LV function, but also LV geometry. Improvement in LV geometry contributes to better LV systolic function, which in turn is the best predictor of survival after revascularization.

Prediction of functional recovery in patients with myocardial infarction after revascularization--comparison of low-dose dobutamine stress echocardiography with fluorine-18 fluorodeoxyglucose positron emission tomography

The present study investigated the agreement between low-dose dobutamine stress echocardiography (LDDSE) and fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) and compared each technique's ability to detect myocardial viability and predict functional recovery in 30 patients. All patients underwent revascularization, followed by echocardiography 5+/-3 months. Of the 390 segments analyzed by echocardiography before revascularization, 110 (28%) had abnormal wall motion. LDDSE showed viability in 66 sites of the 110 dyssynergic segments and 58 of these viable segments recovered their wall motion. With FDG-PET, 78 of the 110 dyssynergic segments were diagnosed as viable and 62 of these showed improvement of the wall motion. The sensitivities for LDDSE and FDG-PET to assess functional recovery were 84% and 90%, respectively; specificities were 80% and 64%, respectively. Positive predictive values for LDDSE and FDG-PET were 88% and 79%; negative predictive values were 75% and 78%, respectively. Both methods had good sensitivity for detecting improvement in regional function after revascularization, but LDDSE had a higher specificity for detecting viability and a better positive predictive value for left ventricular functional recovery.

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.

What is the optimal medical management of ischemic heart failure?

Ischemic heart disease is an important and common contributor to the development of heart failure. Theoretically, all patients with heart failure may benefit from treatment designed to retard progressive ventricular dysfunction and arrhythmias. Patients with ischemic heart disease may also theoretically benefit from the relief of ischemia, the prevention of coronary occlusion, and revascularization. However, there is little evidence to show that the presence or absence of coronary disease modifies the benefits of effective treatments such as angiotensin-converting enzyme inhibitors and beta-blockers. Moreover, there is no evidence that treatment directed specifically at myocardial ischemia or coronary disease alters outcome in patients with heart failure. Treatments aimed at relieving painless myocardial ischemia have not been shown to alter prognosis. Lipid-lowering therapy is theoretically attractive for patients with heart failure and coronary disease; however, theoretical concerns also exist about the safety of such agents, and patients with heart failure have been excluded from large outcome studies very effectively. Some agents, such as aspirin, designed to reduce the risk of coronary occlusion seem ineffective or harmful in patients with heart failure, although warfarin may be safe and possibly effective. There is no evidence yet that revascularization improves prognosis in patients with heart failure, even in patients who are shown to have extensive myocardial hibernation. On current evidence, revascularization should be reserved for the relief of angina. Large-scale, randomized controlled trials are currently underway that are investigating the role of specific treatments targeted at coronary syndromes. The Carvedilol Hibernation Reversible Ischemia Trial: Marker of Success study is investigating the effects of carvedilol in a large cohort of patients with and without hibernating myocardium. The Warfarin and Antiplatelet Therapy in Chronic Heart Failure study is comparing the efficacy of aspirin, clopidogrel, and warfarin. The Heart Revascularization Trial-United Kingdom study is assessing the effect of revascularization on mortality in patients with heart failure and myocardial hibernation. Smaller scale studies are assessing the safety and efficacy of statin therapy in patients with heart failure. Only once the outcomes to these and other planned trials are known can the medical community know how best to treat their patients.

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.

What is the optimal medical management of ischaemic heart failure?

Ischaemic heart disease is probably the most important cause of heart failure. All patients with heart failure may benefit from treatment designed to retard progressive ventricular dysfunction and arrhythmias. Patients with heart failure due to ischaemic heart disease may also, theoretically, benefit from treatments designed to relieve ischaemia and prevent coronary occlusion and from revascularisation. However, there is little evidence to show that effective treatments, such as angiotensin converting enzyme (ACE) inhibitors and beta-blockers, exert different effects in patients with heart failure with or without coronary disease. Moreover, there is no evidence that treatment directed specifically at myocardial ischaemia, whether or not symptomatic, or coronary disease alters outcome in patients with heart failure. Some agents, such as aspirin, designed to reduce the risk of coronary occlusion appear ineffective or harmful in patients with heart failure. There is no evidence, yet, that revascularisation improves prognosis in patients with heart failure, even in patients who are demonstrated to have extensive myocardial hibernation. On current evidence, revascularisation should be reserved for the relief of angina. Large-scale, randomised controlled trials are currently underway investigating the role of specific treatments targeted at coronary syndromes in patients who have heart failure. The CHRISTMAS study is investigating the effects of carvedilol in a large cohort of patients with and without hibernating myocardium. The WATCH study is comparing the efficacy of aspirin, clopidogrel and warfarin. The HEART-UK study is assessing the effect of revascularisation on mortality in patients with heart failure and myocardial hibernation. Smaller scale studies are currently assessing the safety and efficacy of statin therapy in patients with heart failure. Only when the results of these and other studies are known will it be possible to come to firm conclusions about whether patients with heart failure and coronary disease should be treated differently from other patients with heart failure due to left ventricular systolic dysfunction.

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.

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.

Dobutamine echocardiography predicts functional outcome after revascularisation in patients with dysfunctional myocardium irrespective of the perfusion pattern on resting thallium-201 imaging

OBJECTIVE

To evaluate whether the predictive value of dobutamine echocardiography for assessing contractile reserve was altered by differing patterns of regional myocardial perfusion.

PATIENTS

31 consecutive patients with symptomatic congestive heart failure (left ventricular ejection fraction < 35%) caused by coronary artery disease.

SETTING

A district general hospital.

METHODS

Thallium-201 perfusion imaging and low dose dobutamine (5-15 microg/kg/min) echocardiography were performed and resting echocardiography was repeated three months after revascularisation. Perfusion pattern and systolic wall thickening were compared using a 12 segment left ventricular model.

RESULTS

Of the 273 severely dysfunctional segments, 106 (39%) showed a normal perfusion and 167 (61%) an abnormal pattern. After revascularisation, recovery occurred in 71 of the segments with a normal perfusion pattern, and in these a dobutamine response was observed in 61 (86%); recovery also occurred in 56 segments with a mild to moderate abnormality of perfusion, and in these a dobutamine response was seen in 46 (81%) (NS). After revascularisation, the positive and negative predictive values for recovery of dysfunctional segments, where the majority were abnormally perfused, were 88% and 86%, respectively. Systolic wall thickening score indices improved from (mean (SD)) 3.21 (0.58) to 2. 6 (0.66) (p < 0.001) after revascularisation in dobutamine responsive patients (n = 24) compared with patients who did not show a dobutamine response (2.86 (0.65) and 3.13 (0.56), p = 0.61, respectively).

CONCLUSIONS

Dobutamine echocardiography predicted improvement of dysfunctional myocardium after revascularisation irrespective of the resting perfusion pattern seen.

Improvement of left ventricular ejection fraction, heart failure symptoms and prognosis after revascularization in patients with chronic coronary artery disease and viable myocardium detected by dobutamine stress echocardiography

OBJECTIVES

This study was designed to address, in patients with severe ischemic left ventricular dysfunction, whether dobutamine stress echocardiography (DSE) can predict improvement of left ventricular ejection fraction (LVEF), functional status and long-term prognosis after revascularization.

BACKGROUND

Dobutamine stress echocardiography can predict improvement of wall motion after revascularization. The relation between viability, improvement of function, improvement of heart failure symptoms and long-term prognosis has not been studied.

METHODS

We studied 68 patients with DSE before revascularization; 62 patients underwent resting echocardiography/radionuclide ventriculography before and three months after revascularization. Long-term follow-up data (New York Heart Association [NYHA] functional class, Canadian Cardiovascular Society [CCS] classification and events) were acquired up to two years.

RESULTS

Patients with > or =4 viable segments on DSE (group A, n = 22) improved in LVEF at three months (from 27+/-6% to 33+/-7%, p < 0.01), in NYHA functional class (from 3.2+/-0.7 to 1.6+/-0.5, p < 0.01) and in CCS classification (from 2.9+/-0.3 to 1.2+/-0.4, p < 0.01); in patients with <4 viable segments (group B, n = 40) LVEF and NYHA functional class did not improve, whereas CCS classification improved significantly (from 3.0+/-0.8 to 1.3+/-0.5, p < 0.01). A higher event rate was observed at long-term follow-up in group B versus group A (47% vs. 17%, p < 0.05).

CONCLUSIONS

Patients with substantial viability on DSE demonstrated improvement in LVEF and NYHA functional class after revascularization; viability was also associated with a favorable prognosis after revascularization.

The role of neurohormonal antagonists in hibernating myocardium

Hibernating myocardium is characterized by chronic reduction of myocardial blood flow due to obstructive coronary artery disease, causing reversible left ventricular dysfunction and flow-metabolism mismatch. The condition is unstable and increasing demand may lead to further left ventricular dysfunction or necrosis causing death or worsening heart failure. Recognition of the condition is difficult and requires complex cardiac imaging protocols. Treatment protocols are also poorly defined. This review addresses both the diagnostic and therapeutic aspects of hibernating myocardium.

Myocardial viability on echocardiography predicts long-term survival after revascularization in patients with ischemic congestive heart failure

OBJECTIVES

This study was conducted to evaluate the effect of revascularization on survival in patients with congestive heart failure (CHF) due to ischemic left ventricular (LV) systolic dysfunction based on the presence of myocardial viability (MV).

BACKGROUND

There are insufficient data regarding the survival benefit of revascularization in patients with CHF due to ischemic LV systolic dysfunction.

METHODS

Follow-up was obtained in 87 consecutive patients with CHF due to ischemic LV systolic dysfunction (New York Heart Association [NYHA] class II-IV; LV ejection fraction <0.35) who underwent low-dose dobutamine echocardiography (DE). MV within each of 12 myocardial segments representing the LV was defined as having either: 1) normal function or mild dyssynergy at rest; 2) severe resting dyssynergy that improved on DE, or 3) worsening of function on DE except in the case of akinesia.

RESULTS

At a mean follow-up of 40+/-17 months, 37 patients had received revascularization on the basis of clinical grounds, and there were 22 (25%) cardiac-related deaths. Multivariate Cox regression analysis revealed that when patients with at least five segments showing MV underwent revascularization, mortality was reduced by an average of 93% (confidence interval of 22% to 99%), which was associated with improvement in NYHA class as well as LV ejection fraction. Patients with less than five segments showing MV who underwent revascularization (and thus, showing mostly scar), and those with at least 5 segments demonstrating MV who were treated medically, had a much higher mortality.

CONCLUSIONS

Revascularization produces a clear survival benefit in patients with CHF due to ischemic LV systolic dysfunction who have a significant region of the LV demonstrating MV. These data may have wide-ranging implications in the management of patients with coronary artery disease whose main clinical presentation is CHF.

Heart failure due to ischaemic heart disease: epidemiology, pathophysiology and progression

Ischaemic heart disease is the most common underlying cause of heart failure in industrialised countries. Its manifestations are protean with myocardial infarction being only one important facet. The prognosis of patients with heart failure due to ischaemic heart disease also appears to be worse than that associated with many other aetiologies. The presence of ischaemic heart disease may influence both the efficacy and choice of treatment. Agents such as digoxin and amlodipine appear less effective in patients with ischaemic heart disease while ACE inhibitors and beta-blockers appear as or more effective in patients with ischaemic heart disease. Many have expressed an opinion about how coronary disease should be managed in the patient with heart failure supported by little or no evidence. There are major theoretical and practical concerns about the use of anti-coagulant, anti-platelet and statin therapy in patients with heart failure as well as major theoretical benefits. Only randomised controlled trials will resolve these issues. The same may be said of revascularisation. Fortunately trials addressing all these areas are under way. This should put the management of coronary disease in patients with heart failure on a firm evidence-based footing.

Comparison of combination of dipyridamole and dobutamine during echocardiography with thallium scintigraphy with thallium scintigraphy to improve viability detection

The aim of this study was to investigate the relation between radioisotopic and echocardiographic markers of myocardial viability and their correlation with functional recovery after coronary revascularization. Myocardial viability can be detected by techniques exploring various aspects of cell physiology: thallium-201 scintigraphy and dobutamine and dipyridamole echocardiography focus on cell membrane integrity, beta-1 and adrenoceptor, and A2-adenosine receptor-mediated inotropic response, respectively. Fifty-seven patients (mean age 60+/-8 years) with previous myocardial infarction (>3 months), angiographically assessed coronary artery disease, and resting regional dysfunction underwent rest-redistribution 201-thallium scintigraphy and low-dose pharmacologic stress echo with dobutamine (up to 10 microg/kg/min), very low dose regimen of dipyridamole (0.28 mg/kg over 4 minutes), and combined dipyridamole-dobutamine. Criteria for viability in a 13-segment model for both techniques were percent peak activity in redistribution images >55% for thallium-201 and a decrease in wall motion score >1 grade (1 [normal] to 4 [dyskinetic]) for stress echo. Thirty patients underwent coronary revascularization (bypass surgery in 8, angioplasty in 22) and were followed up at 4 weeks from intervention with a resting echocardiogram. The rate of agreement between thallium-201 and stress echo was 63% for dipyridamole, 66% for dobutamine, and 74% for combined dipyridamole-dobutamine (p <0.05 vs dipyridamole and dobutamine). In the 30 patients who underwent revascularization, a regional resting dyssynergy was observed in 225 segments, assuming that postrevascularization functional recovery (which occurred in 126 segments) was the gold standard; combined dipyridamole-dobutamine showed a higher sensitivity (90% confidence interval [CI] 85% to 95%) than thallium-201, dobutamine, or dipyridamole (87%, CI 81% to 92%; 82%, CI 76% to 89%; and 82%, CI 76% to 89%, respectively). Specificity was lower for viability recognition with thallium-201 (61%, CI 51% to 71%) than with dobutamine (93%, CI 88% to 98%), dipyridamole (95%, CI 91% to 99%), and combined dipyridamole-dobutamine (92%; CI 87% to 97%). Combined adrenergic and adenosinergic stimulation recruits an inotropic reserve in a significant proportion of segments with preserved thallium uptake that were nonresponders after either dipyridamole or dobutamine. When functional recovery after successful revascularization is considered as the postoperative gold standard, thallium has a higher sensitivity than dipyridamole or dobutamine; this sensitivity gap is filled with combined dipyridamole-dobutamine. The specificity of all forms of pharmacologic stress echo is better than thallium-201.

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.

Assessment of myocardial perfusion and contractile function by inotropic stress Tc-99m sestamibi SPECT imaging and echocardiography for optimal detection of multivessel coronary artery disease

OBJECTIVE

To assess whether inotropic stress myocardial perfusion imaging, echocardiography, or a combination of the two could enhance the detection of multivessel disease, over and above clinical and exercise electrocardiographic data.

DESIGN

100 consecutive patients investigated by exercise electrocardiography and diagnostic coronary arteriography underwent simultaneous inotropic stress Tc-99m sestamibi SPECT (MIBI) imaging and echocardiography. MIBI imaging and echocardiographic data were analysed using a 12 segment left ventricular model, and each segment was ascribed to a particular coronary artery territory. The presence of perfusion defects with MIBI imaging or of wall thickening abnormality with echocardiography in at least two coronary artery territories at peak stress was taken as diagnostic of multivessel disease. Arteriographic evidence of > or = 50% stenosis was considered significant.

RESULTS

56 patients had multivessel disease. The sensitivity of the combination of MIBI imaging and echocardiography for detecting this was greater than either MIBI imaging or echocardiography alone (82%, 68%, and 68%, respectively; p = 0.005). Clinical and exercise electrocardiographic variables gave an R2 value of 18.2% for predicting multivessel disease. The addition of either MIBI imaging (R2 = 29.2%; p = 0.002) or echocardiography (R2 = 28.8%; p < 0.001) enhanced the detection of multivessel disease, and the inclusion of both had further incremental value (R2 = 34.8%; p = 0.003). Age (p = 0.03), MIBI imaging (p = 0.007), and echocardiography (p = 0.001) were independent predictors of multivessel disease.

CONCLUSIONS

The assessment of both myocardial perfusion and contractile function by simultaneous inotropic stress MIBI imaging and echocardiography optimises the non-invasive detection of multivessel disease.

Value of dobutamine stress echocardiography for the detection of multivessel coronary artery disease

Dobutamine stress echocardiography has been shown to accurately detect coronary artery disease (CAD), but it is not clear whether it has the ability to detect multivessel CAD relative to clinical and exercise electrocardiography. Therefore, the aim of this study was to evaluate the ability of dobutamine stress echocardiography to identify multivessel CAD and ascertain its incremental value when combined with clinical and exercise test variables. One hundred twenty-one consecutive patients referred for coronary arteriography on the basis of symptoms and exercise electrocardiography underwent dobutamine stress echocardiography. Significant multivessel CAD was defined as the presence of > or =70% diameter stenosis in > or =2 major epicardial arteries. Stepwise logistic regression analysis was performed using the clinical exercise test and echocardiographic variables. The strongest independent variables predicting the presence of multivessel CAD were systolic wall thickening index at peak stress (p < 0.0001), presence of wall thickening abnormalities in multiple vascular territories (p = 0.001), and a history of acute myocardial infarction (p = 0.04). Furthermore, dobutamine echocardiography significantly enhanced the prediction of multivessel disease when combined with clinical and exercise test variables (p = 0.001). Dobutamine stress echocardiography adds independent and incremental information to clinical and exercise test variables for identifying multivessel CAD.

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.

Superiority of nitrate-enhanced 201Tl over conventional redistribution 201Tl imaging for prognostic evaluation after myocardial infarction and thrombolysis

BACKGROUND

201Tl imaging has been widely used for postinfarction risk stratification. However, thrombolytic therapy and aspirin have significantly changed outcome, and there are few nuclear imaging studies that assess prognosis in such patients. Furthermore, newer techniques of 201Tl imaging, such as reinjection and nitrate-enhanced rest 201Tl imaging, have been shown to improve the detection of viable but jeopardized myocardium.

METHODS AND RESULTS

We studied 100 consecutive patients, who remained event free 6 weeks after myocardial infarction and thrombolysis. Patients underwent conventional exercise and 4-hour redistribution imaging, followed on a separate day by nitrate-enhanced rest 201Tl study. Planar images were reported semiquantitatively by two experienced observers blinded to clinical data. Redistribution and rest injection images were classified as demonstrating reversible ischemia if they showed improvement in uptake by at least two grades in at least two segments in comparison with the initial exercise scintigram. Patients were followed up for 8 to 32 months (mean, 21 months); during this period, 37 patients had first cardiac events. Reversible ischemia was present in 29 patients on redistribution, of whom 14 (48%) had events; of 71 without reversible defects, 23 (32%) had events (hazard ratio, 1.5; 95% CI, 0.8 to 3.0; P=NS). Nitrate-enhanced rest 201Tl imaging detected reversible defects in 68 patients, of whom 33 (49%) had events, whereas of 32 without reversible defects, only 4 (13%) had subsequent cardiac events (hazard ratio, 8.1; 95% CI, 2.7 to 23.8; P<.001).

CONCLUSIONS

Thus, after myocardial infarction and thrombolysis, even "stable" patients have a high (68%) incidence of viable but jeopardized myocardium, causing a high event rate. Those identified to be at high risk by perfusion imaging may benefit from early intervention.

Inotropic stress with arbutamine is superior to vasodilator stress with dipyridamole for the detection of reversible ischemia with Tc-99m sestamibi single-photon emission computed tomography

BACKGROUND

There is a paucity of data comparing the relative merits of inotropic and vasodilator stress Tc-99m sestamibi single-photon emission computed tomography (SPECT) for the detection of coronary artery disease and reversible ischemia.

METHODS AND RESULTS

Twenty-seven patients referred for diagnostic coronary arteriography underwent separate day dipyridamole and arbutamine Tc-99m sestamibi SPECT imaging with simultaneous two-dimensional echocardiography. The sensitivity of arbutamine and dipyridamole Tc-99m sestamibi for the detection of coronary artery disease was 100% (21 of 21) and 90% (19 of 21), respectively, with a specificity of 66% (4 of 6) for both. Coronary artery disease was detected in all six patients with single vessel disease by both stress modalities. The sensitivity for prediction of multivessel disease was 66% (10 of 15) for arbutamine and 46% (7 of 15) for dipyridamole stress. Arbutamine stress induced a greater extent and severity of perfusion abnormality at peak stress (peak perfusion score 25 +/- 6.2 and 21 +/- 5.9 for arbutamine and dipyridamole, respectively, p = 0.001) and reversible perfusion defects (difference between peak stress and rest scores 8.8 +/- 5.5 and 5.2 +/- 4.4 for arbutamine and dipyridamole, respectively, p = 0.001). Furthermore a significantly higher percentage of reversible defects induced by arbutamine stress was associated with wall thickening abnormality on simultaneous echocardiography, which is a more specific marker of myocardial ischemia (88% and 24% for arbutamine and dipyridamole, respectively, p = 0.002).

CONCLUSION

Inotropic stress may be superior to vasodilators for the determination of the extent and severity of myocardial involvement and reversible ischemia by Tc-99m sestamibi SPECT.

Stress echocardiography for assessing myocardial ischaemia and viable myocardium

Images

Beneficial effects of intravenous and oral carvedilol treatment in acute myocardial infarction. A placebo-controlled, randomized trial

BACKGROUND

Evidence of efficacy and safety of beta-blockers after thrombolysis for acute myocardial infarction (AMI) is equivocal. Newer beta-blockers such as carvedilol have not been tested in this setting.

METHODS AND RESULTS

This study investigated the effects of acute (intravenous) and long-term (6 months, oral) treatment with carvedilol versus placebo in 151 consecutive patients with AMI. Exercise ECG, ambulatory monitoring, and two-dimensional echocardiography were performed before hospital discharge and at 3 and 6 months. All patients were followed up and cardiovascular events recorded. The Cox proportional hazards model was used to compare time from randomization with the occurrence of a cardiovascular event, and Kaplan-Meier survival curves were calculated. Carvedilol was found to be safe, and it significantly reduced cardiac events compared with placebo (18 on carvedilol and 31 on placebo, P < .02). Fifty-four patients had heart failure at study entry; 34 received carvedilol. There were no adverse effects of carvedilol therapy and no excess events in this subgroup. Carvedilol produced significant reductions in heart rate (P < .0001), blood pressure (P < .005) at rest, and rate-pressure product at peak exercise (P < .003), but exercise capacity was unchanged. Left ventricular ejection fraction was not altered significantly by carvedilol, but stroke volume was higher at pre-hospital discharge examination (63 versus 53 mL; P < .01). Diastolic filling of the left ventricle (E/A ratio) was also improved (1.2 versus 0.9; P < .001). In a subgroup with left ventricular ejection fraction < 45% (n = 49 patients; 24 on carvedilol and 25 on placebo), carvedilol showed attenuation of remodeling.

CONCLUSIONS

Carvedilol was well tolerated and safe to use in patients immediately after AMI, including those with heart failure, and significantly improved outcome.

Prognostic value of dobutamine stress echocardiography in patients undergoing diagnostic coronary arteriography

There are only a few studies addressing the prognostic value of dobutamine stress echocardiography in patients with suspected coronary artery disease and none have assessed its value compared with coronary arteriography. Accordingly, graded dobutamine stress echocardiography was performed in 121 patients who underwent coronary arteriography based on symptoms and the findings of treadmill exercise electrocardiography. During the follow-up period of mean (SD) months (15 +/- 9) there were 41 cardiac events (death [n = 5], acute myocardial infarction [n = 2], unstable angina [n = 29], and congestive heart failure [n = 5]). There were a greater number of patients with inducible wall motion abnormality (88%) on dobutamine stress with cardiac events compared with those without (55%, p <0.001). The wall motion score indexes at rest (1.6 +/- 0.6) and at peak stress (2.1 +/- 0.8) were worse in patients with cardiac events compared with those without (1.2 +/- 0.3, p <0.001 and 1.5 +/- 0.6, p <0.001, respectively). When multivariate analysis was performed using clinical, exercise, echocardiographic, and coronary arteriographic data the independent predictors of cardiac events were exercise duration (p = 0.01), presence of inducible wall motion abnormality (p = 0.03), and wall motion score index at peak stress (p <0.001). Thus, dobutamine stress echocardiography is a powerful predictor of future cardiac events in patients undergoing exercise testing and coronary arteriography for evaluation of chest pain and is superior to both exercise electrocardiography and coronary arteriography for the prediction of subsequent cardiac events.

Comparison of arbutamine stress 99mTc-labeled sestamibi single-photon emission computed tomographic imaging and echocardiography for detection of the extent and severity of coronary artery disease and inducible ischemia

BACKGROUND

Arbutamine is a new synthetic catecholamine developed specifically for pharmacologic stress testing.

METHODS AND RESULTS

We investigated 39 patients undergoing coronary arteriography to compare arbutamine stress (99m)Tc-labeled sestamibi single-photon emission computed tomographic imaging and echocardiography for detection of the extent and severity of coronary artery disease and inducible ischemia. Rest and stress studies were analyzed blindly according to a 12-segment left ventricular model for both techniques. Each segment was graded according to severity of wall thickening abnormality and perfusion defect (1 = normal to 4 = severe). Total perfusion defect and wall thickening scores were calculated at peak stress and the difference in scores between stress and rest (delta perfusion defect; delta wall thickening) were used as indexes of inducible ischemia. Twenty-one patients had multivessel disease, nine had single-vessel disease, and nine had normal coronary arteries. Diagnostic accuracies for the detection of coronary artery disease for single-photon emission computed tomographic imaging and echocardiography were 95% and 92%, respectively. Extent and severity of coronary artery disease indicated by a peak stress perfusion defect score of 26 +/- 6.4 and wall thickening score of 25.1 +/- 8.4 were similar, and there was no significant difference in the delta perfusion defect and delta wall thickening scores of 8.7 +/- 5.5 and 10.4 +/- 7.1, respectively. Segmental concordance rates for the detection of coronary artery disease and inducible ischemia were 74% (K = 0.47; confidence interval 0.39 to 0.55) and 74% (kappa = 0.42; confidence interval 0.34 to 0.51), respectively. Regional concordance for coronary artery disease was 84% (kappa = 0.68; confidence interval 0.51 to 0.84). Where discordance was present, there was a greater prevalence of perfusion abnormality compared with wall thickening abnormality.

CONCLUSION

Arbutamine stress single-photon emission computed tomographic imaging and echocardiography provide largely equivalent and accurate pathophysiologic information for the evaluation of coronary artery disease and inducible ischemia.