Recovery of regional left ventricular dysfunction after coronary revascularization. Impact of myocardial viability assessed by nuclear imaging and vessel patency at follow-up angiography

Carvedilol Improves Myocardial Contractility Compared With Metoprolol in Patients With Chronic Hibernating Myocardium After Revascularization

Background: We tested the hypothesis of whether carvedilol delays morphologic degeneration and improves functional outcome compared with metoprolol tartrate in patients with hibernating myocardium undergoing surgical revascularization. We have previously shown that patients with chronic hibernating myocardium undergo progressive cellular degeneration and fibrosis.

Methods: Twenty patients with multivessel coronary artery disease revascularization and hibernating myocardium as assessed by technetium-99m perfusion scintigraphy and fluorine-18-fluorodeoxyglucose positron emission tomography were randomized to receive either carvedilol or metoprolol tartrate for at least 2 months before surgery, and this was continued for 7 months postoperatively. Left ventricular ejection fraction and regional wall motion abnormalities were assessed by left ventriculography at baseline and 7 months postoperatively. Intraoperative transmural needle biopsy samples were obtained for microscopic analysis.

Results: Postoperatively, the ejection fraction increased from 31% ± 5% to 44% ± 4% ( P < .005) in the carvedilol group (n = 10), and from 30% ± 6% to 40% ± 6% in the metoprolol tartrate group ( P < .05 vs preoperatively and vs carvedilol). Wall motion abnormalities in the carvedilol group improved from -2.1 ± 0.4 to -0.6 ± 0.5 ( P < .05) and from -2.3 ± 0.5 to -1.6 ± 0.6 in the metoprolol tartrate group ( P < .05 vs preoperatively and vs carvedilol). Microscopic analysis after 72 ± 18 days of either treatment showed mild cardiomyocyte degeneration and moderate-to-severe fibrosis (28% ± 7%) in the carvedilol group compared with moderate cardiomyocyte degeneration and moderate-to-severe fibrosis (33% ± 6%) in the metoprolol tartrate group. Apoptosis, as assessed by the terminal deoxynucleotidyl transferase nick end labeling method, was observed in only 1 patient in each group.

Conclusions: Carvedilol treatment of hibernating myocardium results in improved functional recovery after revascularization compared with metoprolol tartrate, and this might partially be related to reduced cardiomyocyte degeneration.

Low-carbohydrate diet versus euglycemic hyperinsulinemic clamp for the assessment of myocardial viability with 18F-fluorodeoxyglucose-PET: a pilot study

Positron emission tomography with (18)F-fluorodeoxyglucose (FDG-PET) is considered the gold standard for myocardial viability. A pilot study was undertaken to compare FDG-PET using euglycemic hyperinsulinemic clamp before (18)F-fluorodeoxyglucose ((18)F-FDG) administration (PET-CLAMP) with a new proposed technique consisting of a 24-h low-carbohydrate diet before (18)F-FDG injection (PET-DIET), for the assessment of hypoperfused but viable myocardium (hibernating myocardium). Thirty patients with previous myocardial infarction were subjected to rest (99m)Tc-sestamibi-SPECT and two (18)F-FDG studies (PET-CLAMP and PET-DIET). Myocardial tracer uptake was visually scored using a 5-point scale in a 17-segment model. Hibernating myocardium was defined as normal or mildly reduced metabolism ((18)F-FDG uptake) in areas with reduced perfusion ((99m)Tc-sestamibi uptake) since (18)F-FDG uptake was higher than the degree of hypoperfusion-perfusion/metabolism mismatch indicating a larger flow defect. PET-DIET identified 79 segments and PET-CLAMP 71 as hibernating myocardium. Both methods agreed in 61 segments (agreement = 94.5 %, κ = 0.78). PET-DIET identified 230 segments and PET-CLAMP 238 as nonviable. None of the patients had hypoglycemia after DIET, while 20 % had it during CLAMP. PET-DIET compared with PET-CLAMP had a good correlation for the assessment of hibernating myocardium. To our knowledge, these data provide the first evidence of the possibility of myocardial viability assessment with this technique.

Pacing to reduce refractory angina in patients with severe coronary artery disease: a crossover pilot trial

Biventricular pacing (BiV) has been shown to reduce wall stress and workload in regions near the pacing sites. This trial investigated if BiV near the ischemic region would reduce chest pain in patients with refractory angina due to severe coronary artery disease (CAD). Eleven patients were implanted with BiV devices with leads positioned at or adjacent to their ischemic regions as detected by single-photon emission computed tomography (SPECT) and randomized to either pacing turned ON or OFF for 3 months, and then crossed over for 3 months. With pacing turned ON, a Dynamic atrioventricular (AV) delay was set for approximately 90% and 70% of the intrinsic AV delay at the resting heart rate and at the onset of symptoms, respectively. One patient was excluded from the analysis due to a large amount of RV pacing during the OFF periods (24-64%) and due to an inability to properly deliver therapy because of an excessive number of ventricular premature complexes. Overall, with the device ON vs. OFF, the number of angina episodes (0.8 ± 0.4 vs. 1.2 ± 0.7 per week, P = 0.03) and amount of nitroglycerin used (0.2 ± 0.1 vs. 1.0 ± 0.7 per week, P = 0.11) was lower with BiV pacing. Furthermore, the treadmill exercise time to symptoms trended higher (427 ± 65 vs. 408 ± 64 s, P = 0.19), and the sum of fluorodeoxyglucose-positron emission tomography (FDG-PET) scores trended lower (7.9 ± 3.5 vs. 12.0 ± 4.0, P = 0.11) with the device ON vs. OFF. Nevertheless, there were no significant differences in SPECT myocardial perfusion scores, left ventricle ejection fraction, wall motion score index, and quality of life scores with device programmed ON vs. OFF (all P > 0.05). In conclusion, this pilot study demonstrated that BiV-P at or near the ischemic region was feasible and associated with significant reductions in angina in patients with severe CAD. Adequately powered prospective studies are needed to confirm these findings.

Clinical relevance of hibernating myocardium in ischemic left ventricular dysfunction

Patients with chronic ischemic left ventricular dysfunction may have a substantial amount of viable, hibernating myocardium, which is a state of chronic contractile dysfunction with reduced blood flow at rest. Coronary revascularization in these patients may result in improvement of left ventricular function; in the absence of viability, left ventricular function will not improve postrevascularization. Various noninvasive imaging techniques are available for detection of viable myocardium, including magnetic resonance imaging, dobutamine stress echocardiography, and nuclear imaging with single photon emission computed tomography or positron emission tomography. Because these techniques probe different characteristics of viable myocardium, the sensitivities and specificities of the techniques are not precisely identical; in general, dobutamine stress echocardiography has the highest specificity, whereas the nuclear techniques have the highest sensitivity. The presence of myocardial viability also is related to prognosis: patients with viable myocardium who undergo revascularization have a good prognosis, whereas patients with viable myocardium who are treated medically have poor outcome. Accordingly, assessment of viability is important in the therapeutic decision-making process of patients with chronic ischemic left ventricular dysfunction.

Coronary stenting versus balloon angioplasty for acute myocardial infarction: A meta-regression analysis of randomized trials

INTRODUCTION

Although stenting has been shown to reduce the need for target vessel revascularization (TVR) in acute myocardial infarction (AMI), the benefits in terms of mortality and reinfarction are still unclear. Previous meta-analyses have failed to include all currently available randomized trials. The aim of the current study was to perform an updated meta-analysis to evaluate the benefits of coronary stenting for AMI in terms of mortality, reinfarction, and TVR, and whether these benefits correlated with the patient's risk profile.

METHODS

The literature was scanned by formal searches of electronic databases (MEDLINE and CENTRAL) from January 1990 to September 2006. We examined all completed, published, randomized trials of coronary stenting for AMI. The following key words were used for study selection: randomized trial, myocardial infarction, reperfusion, primary angioplasty, rescue angioplasty, stenting, and balloon angioplasty. Information on study design, type of stent, inclusion and exclusion criteria, primary endpoint, number of patients, angiographic and clinical outcome, were extracted by two investigators. Disagreements were resolved by consensus.

RESULTS

A total of 13 randomized trials were identified and analyzed involving 6922 patients (3460 or 50% randomized to stent and 3462 or 50% to balloon). Stenting was not associated with a significant reduction in 30-day (2.9% versus 3.0%, p=0.81) and 1-year mortality (5.1% versus 5.2%, p=0.81), as compared to balloon angioplasty. However, a significant relationship was observed between patient's risk profile and mortality benefits from coronary stenting at 30-day (beta -0.63 [-25.4; -2.45], p=0.022) and 1-year follow-up (beta -0.61 [-15.9; -0.76], p=0.034). Stenting was associated with benefits in terms of TVR at both 30-day (3.1% versus 5.1%, p<0.0001) and 6 to 12 months (11.3% versus 18.4%, p<0.0001) follow-up, without any difference in terms of reinfarction.

CONCLUSIONS

Among AMI patients undergoing primary angioplasty, coronary stent implantation, when anatomically and technically feasible, may be considered, in addition to benefits in terms of TVR, to reduce mortality in high-risk patients, who may be identified by the use of validated risk scores.

Hibernating myocardium: diagnosis and patient outcomes

Approximately 50% of the patients with chronic obstructive coronary artery disease resulting in chronic contractile dysfunction have hibernating myocardium and may benefit from revascularization. This pooled analysis describes the relative merits of dobutamine echocardiography, thallium-201 and technetium-99m scintigraphy, positron emission tomography, and magnetic resonance imaging, for the diagnosis of hibernating myocardium and prediction of patient outcomes.

Attenuation-corrected 99mTc-MIBI SPECT in overweight patients with chronic ischaemic dysfunction: a comparison to NH3 PET and implications for the diagnosis of myocardial viability

OBJECTIVE

We determined the value of attenuation correction (AC) of myocardial perfusion estimation with (99m)Tc-MIBI SPECT in overweight patients by comparison of uncorrected (filtered back-projection (FBP) and corrected (an iterative algorithm with a measured attenuation coefficients map (FL-AC)) (99m)Tc-MIBI relative uptake to perfusion data obtained in the same patients with NH3 PET. In addition, the impact of attenuation correction for the assessment of myocardial viability with (99m)Tc-MIBI SPECT was determined using FDG PET as the reference method.

METHODS

Thirty consecutive overweight patients (BMI=28+/-4) with left ventricular dysfunction underwent a resting (99m)Tc-MIBI SPECT and a PET study (NH3 and FDG). (99m)Tc-MIBI SPECT scans were reconstructed without attenuation correction (FBP) and with attenuation correction (FL-AC). The left ventricle was divided into 16 segments, in which the relative uptake was quantified using circumferential profiles. A relative uptake > or = 60% was considered consistent with viable myocardium for FDG and MIBI.

RESULTS

The absolute difference between (99m)Tc-MIBI SPECT and NH3 PET uptakes was less pronounced in the inferior (12+/-10% vs. 17+/-12%, P<0.001), anteroseptal (12+/-11% vs. 16+/-12%, P=0.009) and septal (15+/-12% vs. 18+/-14%, P=0.003) regions (FL-AC vs. FBP, respectively). The sensitivity of MIBI for diagnosing myocardial viability increased from 83 to 100% (P=0.034), without loss in specificity.

CONCLUSION

Attenuation correction improves myocardial perfusion estimation by (99m)Tc-MIBI SPECT in the inferior, anteroseptal and septal regions and increases its sensitivity for the diagnosis of myocardial viability.

Comparative assessment of18F-fluorodeoxyglucose PET and99mTc-tetrofosmin SPECT for the prediction of functional recovery in patients with reperfused acute myocardial infarction

PURPOSE

Although preserved glucose metabolism is considered to be a marker of myocardial viability in the chronic stage, it has not been fully elucidated whether this is also true with regard to reperfused acute myocardial infarction (AMI). The aim of this study was to compare the diagnostic performance of(99m)Tc-tetrofosmin SPECT and(18)F-fluorodeoxyglucose (FDG) PET for the prediction of functional recovery in reperfused AMI.

METHODS

The study population comprised 28 patients. Both tetrofosmin SPECT and FDG PET were performed in all 28 patients at ca. 2 weeks and in 23 at 6 months. The tetrofosmin and FDG findings in infarct-related segments were compared with the regional wall motion score assessed by left ventriculography over 6 months to determine the predictive value for functional recovery.

RESULTS

Of 120 infarct-related segments, 83 had preserved flow (tetrofosmin uptake >/=50%) and 81 had preserved glucose metabolism (FDG uptake >/=40%). The sensitivity and specificity of tetrofosmin SPECT for the prediction of functional recovery tended to be superior to those of FDG PET (90.0% and 72.5% vs 85.0% and 67.5%, respectively). Thirteen segments with preserved flow and decreased glucose metabolism demonstrated marked recovery of contractile function from 2.5+/-1.0 to 1.4+/-1.4 (p<0.01), with restoration of glucose metabolism at 6 months. In contrast, 11 segments with decreased flow and preserved glucose metabolism demonstrated incomplete functional improvement from 3.0+/-0.8 to 2.2+/-1.2.

CONCLUSION

In the subacute phase, preserved myocardial blood flow is more reliable than glucose metabolism in predicting functional recovery in reperfused myocardium.

Assessment of reversible myocardial dysfunction in chronic ischaemic heart disease: comparison of contrast-enhanced cardiovascular magnetic resonance and a combined positron emission tomography-single photon emission computed tomography imaging protocol

AIMS

The aim of the study was to compare, in patients with chronic ischaemic cardiomyopathy, contrast-enhanced cardiovascular magnetic resonance (ce-CMR) imaging and a combined (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET) and (99m)Tc-sestamibi single-photon emission computed tomography (SPECT) protocols for the prediction of functional recovery after revascularization, as assessed by cine CMR.

METHODS AND RESULTS

Twenty-nine patients with ischaemic cardiomyopathy (ejection fraction 32 +/- 10%) were investigated with ce-CMR and PET/SPECT. For the assessment of global and regional functions, cine CMR was performed at baseline and at 6 months follow-up. For ce-CMR, the segmental extent of hyperenhancement (SEH) was quantitated, and for PET/SPECT, different viability categories were defined according to a validated quantitative protocol. Functional improvement was related to the SEH by ce-CMR, as well as to the viability categories by PET/SPECT. Sensitivity and specificity for the prediction of functional recovery at follow-up was 97 and 68% for ce-CMR and 87 and 76% for PET/SPECT. The positive predictive value was identical for both techniques (73%). However, ce-CMR achieved a higher negative predictive value (93 vs. 77%, respectively), indicating that ce-CMR may be superior to PET/SPECT for the identification of segments unlikely to recover function after revascularization. Both methods had a similar yield in the prediction of global functional improvement.

CONCLUSION

ce-CMR is comparable with a PET/SPECT imaging protocol for the prediction of regional and global functional improvement after revascularization. However, ce-CMR may be superior to nuclear imaging for the identification of segments that are unlikely to recover function at follow-up.

EANM/ESC procedural guidelines for myocardial perfusion imaging in nuclear cardiology

The European procedural guidelines for radionuclide imaging of myocardial perfusion and viability are presented in 13 sections covering patient information, radiopharmaceuticals, injected activities and dosimetry, stress tests, imaging protocols and acquisition, quality control and reconstruction methods, gated studies and attenuation-scatter compensation, data analysis, reports and image display, and positron emission tomography. If the specific recommendations given could not be based on evidence from original, scientific studies, we tried to express this state-of-art. The guidelines are designed to assist in the practice of performing, interpreting and reporting myocardial perfusion SPET. The guidelines do not discuss clinical indications, benefits or drawbacks of radionuclide myocardial imaging compared to non-nuclear techniques, nor do they cover cost benefit or cost effectiveness.

Strain rate analysis allows detection of differences in diastolic function between viable and nonviable myocardial segments

Analysis of diastolic function for assessment of myocardial viability has not been evaluated. Strain rate (SR) analysis allows quantitative segmental analysis of myocardial function and has been used during dobutamine stimulation for assessment of systolic functional reserve. In 37 patients with ischemic left ventricular dysfunction diastolic function was evaluated at rest and during low-dose dobutamine stimulation (10 mug/kg/min) using SR imaging and related to F18-fluorodeoxyglucose positron emission tomography. Analysis of peak early (E waves) and late (A waves) diastolic myocardial SR was performed using apical views. In all, 317 segments had normal function at rest by 2-dimensional echocardiography. A total of 192 segments with dyssynergy at rest were classified by positron emission tomography as viable in 94 cases and nonviable in 98 cases. Dys-synergic segments had lower E and A waves SR compared with normal contracting segments. There were no significant differences in peak E and A waves SR at rest between dys-synergic viable and nonviable segments. With dobutamine stimulation peak E waves SR increased significantly for viable segments (0.89 +/- 0.51-1.06 +/- 0.51 L/s, P < .01) whereas it was unchanged for nonviable segments (0.77 +/- 0.49-0.78 +/- 0.48 L/s, P = .835). Peak A waves SR increased for viable (0.71 +/- 0.55-1.00 +/- 0.56 L/s, P < .01) and nonviable (0.57 +/- 0.47-0.71 +/- 0.58 L/s, P = .023) segments. However, during dobutamine stimulation peak A waves SR was larger ( P < .001) for viable than for nonviable segments. In conclusion, normal contracting segments at rest have higher E and A waves SR compared with dys-synergic segments. Dys-synergic viable myocardial segments demonstrate an increase in E and A waves SR with dobutamine stimulation whereas nonviable segments are less responsive to dobutamine.

Changes in myocardial perfusion due to physical exercise in patients with stable coronary artery disease

PURPOSE

Percutaneous transluminal coronary angioplasty (PTCA) is one of the main therapy options for patients with coronary artery disease (CAD), resulting in an improvement in myocardial perfusion and exercise capacity. Nevertheless, studies have also demonstrated a positive effect of regular exercise training on myocardial perfusion and maximum exercise capacity. The aim of this study was to evaluate changes in myocardial stress perfusion after 1 year of exercise training in comparison with the effects of PTCA in patients with CAD.

METHODS

In 66 male patients with angiographically confirmed significant coronary artery stenosis in one target vessel, myocardial perfusion scintigraphy was performed at baseline and 12 months after randomisation into either a physical exercise group or a PTCA group. Circumferential count rate profiles in 16 wall segments were classified according to their relative count rate and localisation within or outside the area supplied by the stenosed vessel.

RESULTS

Ischaemic segments showed a significant improvement in myocardial count rate within the target area after 12 months in both the PTCA and the training group (PTCA group: from 76.8+/-4.9% to 86.6+/-10.9%, p=0.03; training group: from 74.0+/-7.3% to 83.7+/-10.8%, p<0.01). Outside the target area only the training group showed a significant improvement (from 77.7+/-4.4% to 91.7+/-4.8%, p<0.01).

CONCLUSION

Our data indicate a significant improvement in stress myocardial perfusion in the training group after 12 months. The ischaemia is reduced not only in the target region of the leading stenosis but also in other ischaemic myocardial areas. In contrast, after PTCA stress perfusion improves only in the initially ischaemic parts of the target area.

Clinical usefulness of ECG-gated 18F-FDG PET combined with 99mTC-MIBI gated SPECT for evaluating myocardial viability and function

OBJECTIVES

This study sought to evaluate an imaging approach using gated 99mTc-MIBI (MIBI) SPECT and gated 18F-FDG (FDG) PET for assessment of myocardial viability and cardiac function.

METHODS

Forty-eight patients (38 men, mean age 68.1 +/- 9.6 years) underwent ECG-gated FDG PET and MIBI SPECT within a week. The baseline diagnoses were coronary artery disease (31), mitral regurgitation (1), paroxysmal arrhythmia (10), and dilated cardiomyopathy (6). The gated FDG PET data were analyzed using pFAST software, and the gated MIBI SPECT data were analyzed using QGS software. Fifteen patients were diagnosed with myocardial infarction, and follow-up study was performed to assess the functional outcome four months later. An improvement in LVEF of >5% was defined as significant. The LV myocardium was divided into 17 segments, and regional defect scores were visually assessed using a 4-point scale for each segment (0 = normal, 1 = mildly reduced, 2 = moderately reduced, 3 = absent). A segment with a greater defect score on MIBI SPECT than on FDG PET was defined as a mismatch. The patients were divided into two groups: those with at least two mismatched segments (MM-group), and those with none or one (M-group).

RESULTS

LVEF, EDV and ESV measured by gated FDG PET were highly correlated with those obtained by gated MIBI SPECT (r = 0.848, 0.855 and 0.911, p < 0.0001, respectively). The mean values of LVEF did not differ significantly, but EDV and ESV obtained by gated FDG PET were significantly grater than those obtained by gated MIBI SPECT (p < 0.0001). In 15 patients diagnosed with myocardial infarction, a significant association (p < 0.05) was found between the relative uptake of FDG PET and MIBI SPECT and the functional outcome 4 months later. Global LV function improved in 6 of the 8 patients showing mismatch but in only 1 of the 7 patients with matched defects, resulting in a sensitivity of 86% and specificity of 75%. The overall accuracy to predict global functional outcome was high (80%).

CONCLUSION

This imaging approach allows accurate evaluation of myocardial viability. Furthermore, the high correlations of gated FDG PET and gated MIBI SPECT measurements hold promise for the assessment of left ventricular function using gated FDG PET.

Validation of an evaluation routine for left ventricular volumes, ejection fraction and wall motion from gated cardiac FDG PET: a comparison with cardiac magnetic resonance imaging

The aim of this study was to validate the estimation of left ventricular end-diastolic and end-systolic volumes (EDV, ESV) and ejection fraction (LVEF) as well as wall motion analysis from gated fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) in patients with severe coronary artery disease (CAD) using software originally designed for gated single-photon emission tomography (SPET). Thirty patients with severe CAD referred for myocardial viability diagnostics were investigated using a standard FDG PET protocol enhanced with gated acquisition (8 gates per cardiac cycle). EDV, ESV and LVEF were calculated using standard software designed for gated SPET (QGS). Wall motion was analysed using a visual four-point wall motion score on a 17-segment model. As a reference, all patients were also examined within a median of 3 days with cardiovascular cine magnetic resonance imaging (cMRI) (20 gates per cardiac cycle). Furthermore, all gated FDG PET data sets were reoriented in a second run with deliberately misaligned axes to test the quantification procedure for robustness. Correlation between the results of gated FDG PET and cMRI was very high for EDV and ESV ( R=0.96 and R=0.97) and for LVEF ( R=0.95). With gated FDG PET, there was a non-significant tendency to underestimate EDV (174+/-61 ml vs 179+/-59 ml, P=0.21) and to overestimate ESV (124+/-58 ml vs 122+/-60 ml, P=0.65), resulting in underestimated LVEF values (31.5%+/-9.4% vs 34.2%+/-12.4%, P<0.003). The results of reorientations 1 and 2 showed very high correlations (for all R>/=0.99). Segmental wall motion analysis revealed good agreement between gated FDG PET data and cMRI (kappa =0.62+/-0.03). In conclusion, despite small systematic differences which contributed mainly to the lower temporal resolution of gated FDG PET, agreement between gated FDG PET and cMRI was good across a wide range of volumes and LVEF values as well as for wall motion analysis. Therefore, gated FDG PET provides clinically relevant information on function and volumes, using the commercially available software package QGS.

Strain rate measurement by doppler echocardiography allows improved assessment of myocardial viability inpatients with depressed left ventricular function

OBJECTIVES

This study sought to evaluate whether objective assessment of the myocardial functional reserve, using strain rate imaging (SRI), allows accurate detection of viable myocardium.

BACKGROUND

Strain rate imaging is a new echocardiographic modality that allows quantitative assessment of segmental myocardial contractility.

METHODS

In 37 patients (age 58 +/- 9 years) with ischemic left ventricular dysfunction, myocardial viability was assessed using low-dose (10 microg/kg body weight per min) two-dimensional dobutamine stress echocardiography (DSE), tissue Doppler imaging, SRI and (18)F-fluorodeoxyglucose ((18)FDG) positron emission tomography (PET). The peak systolic tissue Doppler velocity and peak systolic myocardial strain rate were determined at baseline and during low-dose dobutamine stress from the apical views.

RESULTS

A total of 192 segments with dyssynergy at rest were classified by (18)FDG PET as viable in 94 and nonviable in 98. An increase of peak systolic strain rate from rest to dobutamine stimulation by more than -0.23 1/s allowed accurate discrimination of viable from nonviable myocardium, as determined by (18)FDG PET with a sensitivity of 83% and a specificity of 84%. Receiver operating characteristic (ROC) curve analysis showed an area under the curve for prediction of nonviable myocardium, as determined by (18)FDG PET using SRI, of 0.89 (95% confidence interval [CI] 0.88 to 0.90), whereas the area under the ROC curve using tissue Doppler imaging was 0.63 (95% CI 0.61 to 0.65).

CONCLUSIONS

The increase in the peak systolic strain rate during low-dose dobutamine stimulation allows accurate discrimination between different myocardial viability states. Strain rate imaging is superior to two-dimensional DSE and tissue Doppler imaging for the assessment of myocardial viability.

Electromechanical assessment of left ventricular function following successful percutaneous coronary revascularization

Percutaneous electromechanical mapping was applied to evaluate the impact of coronary revascularization on electrical and mechanical parameters in patients with prior myocardial infarction. In 15 patients with prior (> or = 4 weeks) myocardial Q-wave infarction and regional wall motion abnormalities, left ventricular endocardial mapping was performed immediately prior to percutaneous coronary revascularization. Patients underwent repetitive mapping during 6-month follow-up angiography with good revascularization results in all patients. Mean regional unipolar electrogram (UP) amplitude of all regions remained unchanged (10.4 +/- 4.2 mV prerevascularization vs. 10.2 +/- 4.4 mV postrevascularization), whereas mean local shortening (LS) of all regions increased from 6.0% +/- 5.8% to 9.7% +/- 5.3% (P < 0.001). The percentage of electromechanical match regions (LS < 6% and UP < 9 mV) remained unchanged after revascularization (15% vs. 10%; NS), whereas the percentage of mismatch regions (LS < 6% and UP > 9 mV) declined from 38% to 10% (P < 0.0001). We conclude that electromechanical mapping allows the sensitive detection of improved mechanical function after successful revascularization. Electrical activity remains unchanged 6 months after revascularization and the number of regions with an electromechanical mismatch decrease.

Myocardial viability assessment by endocardial electroanatomic mapping: comparison with metabolic imaging and functional recovery after coronary revascularization

OBJECTIVES

The objective of this study was to compare electroanatomic mapping for the assessment of myocardial viability with nuclear metabolic imaging using positron emission computed tomography (PET) and with data on functional recovery after successful myocardial revascularization.

BACKGROUND

Animal experiments and first clinical studies suggested that electroanatomic endocardial mapping identifies the presence and absence of myocardial viability.

METHODS

Forty-six patients with prior (> or =2 weeks) myocardial infarction underwent fluorine-18 fluorodeoxyglucose (FDG) PET and Tc-99m sestamibi single-photon emission computed tomography (SPECT) before mapping and percutaneous coronary revascularization. The left ventricular endocardium was mapped and divided into 12 regions, which were assigned to corresponding nuclear regions. Functional recovery using the centerline method was assessed in 25 patients with a follow-up angiography.

RESULTS

Regional unipolar electrogram amplitude was 11.0 mV +/- 3.6 mV in regions with normal perfusion, 9.0 mV +/- 2.8 mV in regions with reduced perfusion and preserved FDG-uptake and 6.5 mV +/- 2.6 mV in scar regions (p < 0.001 for all comparisons). At a threshold amplitude of 7.5 mV, the sensitivity and specificity for detecting viable (by PET/SPECT) myocardium were 77% and 75%, respectively. In infarct areas with electrogram amplitudes >7.5 mV, improvement of regional wall motion (RWM) from -2.4 SD/chord +/- 1.0 SD/chord to -1.5 SD/chord +/- 1.1 SD/chord (p < 0.01) was observed, whereas, in infarct areas with amplitudes <7.5 mV, RWM remained unchanged at follow-up (-2.3 SD/chord +/- 0.7 SD/chord to -2.4 SD/chord +/- 0.7 SD/chord).

CONCLUSIONS

These data suggest that the regional unipolar electrogram amplitude is a marker for myocardial viability and that electroanatomic mapping can be used for viability assessment in the catheterization laboratory.

18-Fluorodeoxyglucose imaging with positron emission tomography and single photon emission computed tomography: cardiac applications

The assessment of myocardial viability has become an important aspect of the diagnostic and prognostic work-up of patients with ischemic cardiomyopathy. Although revascularization may be considered in patients with extensive viable myocardium, patients with predominantly scar tissue should be treated medically or evaluated for heart transplantation. Among the many viability tests, noninvasive assessment of cardiac glucose use (as a marker of viable tissue) with F18-fluorodeoxyglucose (FDG) is considered the most accurate technique to detect viable myocardium. Cardiac FDG uptake has traditionally been imaged with positron emission tomography (PET). Clinical studies have shown that FDG-PET can accurately identify patients with viable myocardium that are likely to benefit from revascularization procedures, in terms of improvement of left ventricular (LV) function, alleviation of heart failure symptoms, and improvement of long-term prognosis. However, the restricted availability of PET equipment cannot meet the increasing demand for viability studies. As a consequence, much effort has been invested over the past years in the development of 511-keV collimators, enabling FDG imaging with single-photon emission computed tomography (SPECT). Because SPECT cameras are widely available, this approach may allow a more widespread use of FDG for the assessment of myocardial viability. Initial studies have directly compared FDG-SPECT with FDG-PET and consistently reported a good agreement for the assessment of myocardial viability between these 2 techniques. Additional studies have shown that FDG-SPECT can also predict improvement of LV function and heart failure symptoms after revascularization. Finally, recent developments, including coincidence imaging and attenuation correction, may further optimize cardiac FDG imaging (for the assessment of viability) without PET systems.

Evaluation of myocardial viability in asymptomatic patients early after infarction with perfusion/metabolism single-photon-emission computed tomographic imaging and dobutamine echocardiography

OBJECTIVE

To study the impact of detection of viability of myocardium in asymptomatic patients early (3-10 days) after Q-wave myocardial infarction on segmental recovery of left ventricular function after elective revascularization.

METHODS

Patients were studied with low-dose dobutamine echocardiography (LDDE) and single photon-emission computed tomography with 99mTc sestamibi and [18F]-fluorodeoxyglucose (FDG) imaging. Viability of myocardium was defined as detection of improvement in segmental thickening of left ventricle by LDDE (versus baseline echocardiographic data), uptake of 99mTc sestamibi > 50% of maximum counts, uptake of [18F]-FDG > 50% of maximum normal, combined uptake of 99mTc sestamibi or [18F]-FDG > 50% of normal maximum, uptake of [18F]-FDG > 50% or mismatched pattern (uptake of [18F]-FDG greater than that of 99mTc sestamibi). Functional recovery was defined as improvement of segmental thickening of left ventricle detected at follow-up 8 weeks after infarction (versus baseline resting echocardiographic data). Interpretation of the tests was blinded with respect to the angiographic data and the results of the alternative method.

RESULTS

In total 18 patients with 133 left-ventricle segments with abnormal contractile function at baseline were analysed; 29% were hypocontractile and 71% were noncontractile. Examination with LDDE showed that 18% of the segments had normal contractility and 26% were hypocontractile; the respective percentages were 29 and 28% according to follow-up resting echocardiography. Radionuclide tests for viability of myocardium gave positive results in 57% (uptake of [18F]-FDG > 50%) and 62% (uptake of 99mTc sestamibi > 50%) of cases. With respect to segmental analysis, there was a 25-27% positive concordance, a 24-27% negative concordance, and a 48-50% discordance between the LDDE and the radionuclide definitions of viability of myocardium. Additionally, there was no significant difference among sensitivities and specificities for the definitions of viability. The sensitivity was 69% for the uptake of 99mTc sestamibi > 50% criterion, and the highest specificity was 66% for the LDDE. Incorporation of imaging with [18F]-FDG into the analysis yielded a marginally higher sensitivity of 71% for the criterion of uptake of [18F]-FDG or 99mTc sestamibi > 50%, versus imaging with the 99mTc sestamibi alone.

CONCLUSION

LDDE was more specific and radionuclide imaging more sensitive for detection of viability of myocardium in asymptomatic patients early after infarction. Possibly defective myocardial metabolization of glucose in the period early after infarction and the specific LDDE protocol applied account for the limited benefit of these studies in terms of facilitating prediction of segmental functional recovery after revascularization in this clinical setting.

Exercise Radionuclide Cineangiography for Predicting Long Term Prognosis in Elderly Post Coronary Artery Bypass Graft Patients

ISSUE: The immediate benefits of coronary artery bypass grafting may only be transient. Recent studies which showed that exercise radionuclide cineangiography studies may predict cardiac events and survival had evaluated post coronary artery bypass grafting patients of all ages. This prospective study was done on an elderly subgroup. METHODS: The results of exercise radionuclide cineangiography performed early (4-8 months) post coronary artery bypass grafting were correlated over six years of follow up with mortality, major surgical and nonsurgical cardiac events, and cardiac event free survival in 87 consecutive patients at or above 65 years. RESULTS: The rest to peak exercise difference in left ventricular ejection fraction correlated with later cardiac death and the need for surgical interventions, while rest left ventricular ejection fraction correlated only with the latter parameter. CONCLUSIONS: Assessment of left ventricular ejection fraction at rest and at exercise has prognostic values after coronary artery bypass grafting in elderly patients. Exercise radionuclide cineangiography carried out soon after coronary artery bypass grafting might be considered an useful tool to assess patient prognosis. The efficacy of exercise radionuclide cineangiography carried out soon after coronary artery bypass grafting should be confirmed in larger and more varied patient subgroups. (c) 2000 by CVRR, Inc.

Myocardial viability detected by dobutamine echocardiography in patients with chronic coronary artery disease, and long-term outcome after coronary angioplasty

Viable but dysfunctional myocardium detected by dobutamine echocardiography (DE) predicts early improvement in regional left ventricular (LV) function after percutaneous transluminal coronary angioplasty (PTCA). Whether DE can predict the long-term (>2 years) outcome after PTCA is still unclear. Thus, 50 patients (age 60.4+/-9.5 years) with chronic coronary artery disease and regional LV dysfunction who underwent DE 1 week before PTCA to assess myocardial viability were followed for 4.0+/-0.8 years. Regional LV function and LV ejection fraction (LVEF) were evaluated by 2-dimensional echocardiography in patients who remained event-free (cardiac death or myocardial infarction or unstable angina pectoris) after PTCA. At late follow-up (>2 years after PTCA), 29 patients showed regional LV function improvement, 15 showed no improvement, 3 showed worsening and 3 patients had cardiac events (1 nonfatal myocardial infarction and 2 unstable angina pectoris). LVEF improved (0.53+/-0.09 to 0.60+/-0.09, p<0.001) in patients with improved regional LV function, but deteriorated (0.38+/-0.03 to 0.30+/-0.03) in the 3 patients with worsened regional LV function. Of the 29 patients with improvement, 27 (93%) had viable myocardium, whereas only 3 (20%) of the 15 with no improvement had viable myocardium and all 6 of those with poor outcomes (3 with cardiac events and 3 with worsening) had viable myocardium (chi2 = 28.9, p<0.001). Patients with viable myocardium and a poor outcome had a lower mean LVEF before PTCA, and at 1 week and 3 months after PTCA (p = 0.004, <0.001, and =0.001, respectively), and a higher restenosis rate (p = 0.007) than patients with viable myocardium and without a poor outcome. It is concluded that viable myocardium detected by DE may predict long-term improvement in regional and global LV function after PTCA. However, patients with viable myocardium and persistent low LVEF are at risk for cardiac events or worsening of LV function.

Hypoxic Hypoperfusion Fails to Induce Myocardial Hibernation in Anesthetized Swine

BACKGROUND: Congenital origin of the left coronary artery from the pulmonary artery (ALCAPA) results in chronically dysfunctional myocardium with the partial ability to recover after revascularization. We attempted to establish an ALCAPA syndrome in anesthetized pigs for 24 hours and to compare it with stunned and infarcted myocardium. METHODS AND RESULTS: In group 1 (n = 12), a bypass graft was interposed between the pulmonary artery and the left anterior descending coronary artery (LAD). Reduction of flow in the LAD with gradual increases in flow from the pulmonary artery resulted in an incremental reduction of segment shortening (8.9 +/- 5.3% at 24 hours vs 26.6 +/- 10% at baseline, P <.005). In group 3 (n = 5), 2 cycles of 10-minute LAD occlusion resulted in decreased segment shortening with slow recovery (at 24 hours 18.7 +/- 1.3% vs 24.2 +/- 4% at baseline, segment shortening with slow recovery (at 24 hours 18.7 +/- 1.3% vs 24.2 +/- 4% at baseline, P <.05). In group 3 (n = 6), 1-hour LAD occlusion reduced segment shortening at 24 hours to 4.7 +/- 5.2% (P <.005 vs baseline). Histological analysis of the LAD territory revealed severe degeneration, myolysis, and alteration of the chromatin structure in group 1 comparable to ischemic cell death in group 3, whereas control areas and the LAD area in group 2 showed only minor structural alterations. Infarct size/risk area, as measured by tetrazolium staining, was 49.8 +/- 11.2% in group 1, 9.3 +/- 8.1% in group 2 (P <.005), and 60.3 +/- 9% in group 3. CONCLUSION: Hypoxic myocardial hypoperfusion from the pulmonary artery results in myocardial necrosis in anesthetized pigs. These findings are in contrast to the concept of myocardial hibernation in the ALCAPA syndrome because in this model, hypoxic hypoperfusion failed to induce adaptation to preserve myocardial structure.

Functional recovery after coronary artery bypass grafting in patients with severe left ventricular dysfunction and preserved myocardial viability in the left anterior descending arterial territory as assessed by thallium-201 myocardial perfusion imaging

To evaluate the functional recovery after coronary bypass surgery in patients with severe left ventricular (LV) dysfunction (ejection fraction (EF) < or = 35%), 100 consecutive patients with viable myocardium in the territory supplied by the left anterior descending artery (LAD) underwent coronary bypass grafting. In addition, cardiac catheterization and single-photon emission computed tomography (SPECT) perfusion imaging with thallium-201 were repeated 1-year postoperatively. Although 12 patients with severe LV dysfunction were preoperatively in a worse New York Heart Association functional class (3.1+/-0.7 vs 2.4+/-0.8; p<0.01), had a higher incidence of heart failure (10/12 vs 14/88; p<0.001) and had a worse LVEF (29+/-5 vs 61+/-14%; p<0.001) compared with 88 patients without severe LV dysfunction, the operative mortality was similar in the 2 groups (1/12 vs 2/88; p=NS). The postoperative NYHA functional class in the patients with severe LV dysfunction was similar to that in the patients without such dysfunction (1.6+/-0.7 vs 1.3+/-0.6; p=NS). In addition, the 1-year postoperative study revealed a significant improvement in the thallium defect score in both the LAD territory (1.7+/-1.2 to 0.7+/-1.0, p=0.01) and all the territories (5.2+/-2.2 to 3.2+/-1.9, p=0.002) in patients with severe LV dysfunction, whereas no improvement in defect score was found in either of these territories in those without severe LV dysfunction (LAD: 0.6+/-1.4 to 0.4+/-1.2, p=NS; All: 1.9+/-2.2 to 1.8+/-2.0, p=NS). Furthermore, a marked 1-year postoperative improvement (15-24%; 95% confidence interval) in LVEF (29+/-5 to 48+/-10%, p<0.001) was demonstrated in patients with severe LV dysfunction, but not in those without such dysfunction (60+/-13 to 61+/-11%, p=NS). These results indicate that myocardial viability in the LAD territory, as demonstrated by thallium-201 SPECT perfusion imaging, predicts a significant improvement in functional class and LVEF of at least 10% or more after coronary artery bypass grafting in patients with severe LV dysfunction.

Efficacy of coronary angioplasty for the treatment of hibernating myocardium

OBJECTIVES

To determine the efficacy of coronary angioplasty as the sole method of revascularisation in patients with coronary artery disease and chronically dysfunctional but viable myocardium (hibernating myocardium), and to assess the effect of restenosis on functional outcome.

DESIGN AND PATIENTS

24 consecutive patients with hibernating myocardium were studied. Positron emission tomography was used to assess myocardial viability, blood flow, and flow reserve. One patient refused angioplasty, one had bypass surgery, and one died while waiting for an elective procedure. The procedure failed in three patients. The remaining 18 patients had repeat echocardiography, 15 had repeat coronary angiography, and nine had repeat assessments of blood flow and flow reserve at mean (SD) 17 (2) weeks after angioplasty. In three patients restenosis was documented.

RESULTS

The wall motion score index in the revascularised territories improved from 1.71 (0.37) to 1.34 (0.47) (p = 0.008). Thirty of 51 dysfunctional segments improved in territories without restenosis compared with three of 14 in restenosed territories (p = 0.001). Hibernating and normal segments had comparable flows (0.82 (0.26) v 0.89 (0.24) ml/min/g; NS) while flow reserve was lower in hibernating segments (1.55 (0.68) v 2.07 (1.08); p = 0.03). In segments without restenosis flow reserve improved from 2.03 (1.25) to 2.33 (1.4) (p = 0.03). Sensitivity, specificity, and positive and negative predictive accuracy of the viability study were 97%, 77%, 82%, and 96%, respectively. After excluding patients with restenosis, specificity and positive predictive accuracy improved to 90% and 93%.

CONCLUSIONS

Angioplasty improves function in hibernating myocardium, and restenosis prevents recovery; hibernating myocardium is characterised by an impairment of flow reserve; restenosis affects the diagnostic accuracy of viability studies.

Reciprocal ST-segment depression associated with exercise-induced ST-segment elevation indicates residual viability after myocardial infarction

OBJECTIVES

We evaluated the clinical significance of reciprocal ST-segment depression associated with exercise-induced ST-segment elevation for detecting residual viability within the infarcted area.

BACKGROUND

Although the relation between residual viability and exercise-induced ST-segment elevation has been described, there are no reports focusing on the relation between myocardial viability and reciprocal ST-segment depression associated with exercise-induced ST-segment elevation.

METHODS

We evaluated regional blood flow and glucose utilization using N-13 ammonia (NH3) and F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) in 30 patients with a previous Q-wave myocardial infarction (anterior in 15, inferior in 15). All subjects had single-vessel disease and had exercise-induced ST-segment elevations (> or =1 mm) in electrocardiographic leads.

RESULTS

Reciprocal ST-segment depression (> or =1 mm) was present in 16 patients (Group A; anterior in 6, inferior in 10) but not in the remaining 14 patients (Group B). The degree of exercise-induced ST-segment elevation (1.8+/-0.2 vs. 2.0+/-0.2 mm) and the time from the onset of infarction to the study (75+/-49 vs. 74+/-52 days) did not differ between groups. There were no significant differences between groups in the severity of left ventricular dysfunction and the residual luminal narrowing in the infarct-related artery (45+/-21 vs. 48+/-25%). The presence and site of infarction were confirmed by NH3-PET in all patients. FDG-PET demonstrated residual tissue viability within infarct-related area in all patients in Group A and in 3 (21%) of 14 patients in Group B (p < 0.01). The sensitivity, specificity and accuracy of reciprocal ST-segment depression associated with exercise-induced ST-segment elevation for detecting residual viability were 84%, 100% and 90%, respectively.

CONCLUSIONS

The occurrence of reciprocal ST-segment depression associated with exercise-induced ST segment elevation in patients with a previous Q-wave infarction who had single-vessel disease indicates residual tissue viability within the infarct-related area.

Attenuation-corrected 99mTc-tetrofosmin single-photon emission computed tomography in the detection of viable myocardium: comparison with positron emission tomography using 18F-fluorodeoxyglucose

OBJECTIVES

The purpose of this study was to assess the efficacy of attenuation-corrected (AC) technetium-99m (99mTc)-tetrofosmin single-photon emission computed tomography (SPECT) in detecting viable myocardium compared to 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET).

BACKGROUND

The role of 99mTc-labeled perfusion tracers in the assessment of myocardial viability remains controversial. Attenuation artifacts affect the diagnostic accuracy of SPECT images.

METHODS

Twenty-four patients with coronary artery disease (mean left ventricular ejection fraction 30%) underwent resting 99mTc-tetrofosmin SPECT and FDG PET imaging. Both AC and non-attenuation-corrected (NC) SPECT images were generated.

RESULTS

Using a 50% threshold for viability by FDG PET, the percentage of concordant segments of viability between 99mTc-tetrofosmin and FDG on the patient basis increased from 79.8%+/-14.0% (mean+/-SD) on the NC images to 90.8%+/-10.6% on the AC images (p=0.002). The percentage of 99mTc-tetrofosmin defect segments within PET-viable segments, an estimate for the degree of underestimation of viability, decreased from 19.8%+/-15.2% on the NC images to 9.7%+/-12.6% on the AC images (p=0.01). Similar results were obtained when a 60% threshold was used to define viability by FDG PET. When the anterior-lateral and inferior-septal regions were separately analyzed, the effect of attenuation correction was significant only in the inferior-septal region.

CONCLUSIONS

The results indicate that AC 99mTc-tetrofosmin SPECT improves the detection of viable myocardium mainly by decreasing the underestimation of viability particularly in the inferior-septal region, although some underestimation/overestimation of viability may still occur even with attenuation correction.

Measurements of myocardial metabolism in patients with ischemic heart disease

Therapeutic approaches to left ventricular dysfunction in ischemic heart disease are likely to be guided by the answers to 2 major questions: (1) which mechanisms account for the deterioration or loss of contractile function, and (2) can contractile function be improved or restored therapeutically? Both questions can face considerable diagnostic challenges. Two main mechanisms have been implicated in the pathophysiology of reversible dysfunction-myocardial hibernation and myocardial stunning. Both general concepts share a number of clinical features so that standard clinical approaches often fail to discriminate between them. The presence of regionally increased fibrosis in scar tissue formation associated with decreased blood flow further complicates the search for truly reversible dysfunction.

Correlation of SPECT and PET cardiac images by a surface matching registration technique

Complementary information provided by Single Photon and Positron Emission Tomography (SPECT and PET) in nuclear cardiology allows a better comprehension of the physiopathology of the heart. In this work a surface matching registration technique is evaluated in the spatial correlation of SPECT and PET cardiac images. The method is based on matching correspondent anatomical surfaces extracted from transmission (TR) SPECT and PET studies, usually performed for attenuation correction. The accuracy of the technique was evaluated by phantom experiments and on patient data (201Tl SPECT and 13NH3 PET perfusion studies). An application of the method is presented for the correlation of SPECT 201Tl perfusion and PET 18FDG metabolic studies in the evaluation of myocardial viability.

Coronary revascularization in the treatment of moderate and severe postischemic left ventricular dysfunction

Chronic postischemic left ventricular (LV) dysfunction can improve following coronary revascularization (hibernating myocardium). However, it is not clear whether the severity of LV dysfunction determines functional outcome after revascularization and the accuracy of tests to predict myocardial viability. We studied 47 patients with coronary artery disease and chronic LV dysfunction. Before coronary bypass, patients underwent (18F)2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) during euglycemic hyperinsulinemic clamp to assess viability. Global and regional LV function were assessed before and 4 to 6 months after surgery. Patients were arbitrarily divided into 2 groups with moderate and severe LV dysfunction. Group 1 (n = 26) had an ejection fraction (EF) of < or = 30% and group 2 (n = 21) > 30%. After bypass, the EF (22+/-6% vs 31+/-10%; p <0.0001) and global wall motion score (WMS) (2.05+/-0.39 vs 1.56+/-0.34; p <0.001) improved in group 1, whereas the EF (43+/-9% vs 43+/-12%; p = NS) was unchanged in group 2, although WMS tended to improve (1.42+/-0.38 vs 1.32+/-0.39; p = 0.09). The proportion of dysfunctional segments (72% vs 32%; p <0.0001) and FDG uptake in these segments (0.44+/-0.15 vs 0.34+/-0.15 micromol/g/min, p <0.0001) were greater in group 1 than in group 2. The baseline EF influenced the predictive accuracy of PET, with highest positive predictive accuracy in group 2 and highest negative predictive accuracy in group 1. Thus, coronary revascularization has the potential for greatest benefit in patients with the most severe dysfunction, but with evidence of viability, and the entity of LV dysfunction affects the predictive accuracy of viability studies.

Prolonged myocardial hibernation exacerbates cardiomyocyte degeneration and impairs recovery of function after revascularization

OBJECTIVES

We sought to define the effects of time on contractile function, morphology and functional recovery after coronary revascularization in patients with dysfunctional but viable (hibernating) myocardium.

BACKGROUND

Functional recovery after coronary artery bypass graft surgery in patients with chronic myocardial hibernation is incomplete or delayed. The proposed cause is a progressive temporal degeneration of cardiomyocytes.

METHODS

In 32 patients with multivessel coronary disease, regional wall motion analysis was performed in hypoperfused but metabolically active areas before and 6 months after bypass surgery. During bypass surgery, transmural biopsy samples were obtained from the center of the hypokinetic zone for light and electron microscopic analyses. The proposed duration of myocardial hibernation was retrospectively assessed.

RESULTS

Patients with a subacute hibernating condition (<50 days) demonstrated a higher preoperative ejection fraction (EF, 50+/-8%), and a better preserved wall motion (WM) in the supraapical wall (-1.4+/-0.4) than did patients with intermediate-term (>50 days, EF 37+/-9%, p < 0.05; WM -2.4+/-1.5, p = 0.08) or chronic (>6 months, EF 40+/-14%, WM -2.7+/-0.9, p < 0.005) ischemia. Structural degeneration correlated with the duration of ischemia (r = 0.56, p < 0.05). Postoperative recovery of function was enhanced in patients with a short history of hibernation compared with patients with an intermediate-term or chronic condition (EF 60+/-10% vs. 40+/-10%, p < 0.001, and vs. 47+/-14%, p < 0.05).

CONCLUSIONS

Hibernating myocardium exhibits time-dependent deterioration due to progressive structural degeneration with enhanced fibrosis. Early revascularization should be attempted to salvage the jeopardized tissue and improve postoperative outcome.

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.

Effect of left ventricular function on the assessment of myocardial viability by technectium-99m sestamibi and correlation with positron emission tomography in patients with healed myocardial infarcts or stable angina pectoris, or both

The accuracy of technetium-99m (Tc-99m) sestamibi single-photon emission computed tomography (SPECT) for the assessment of myocardial viability in patients with coronary artery disease and left ventricular (LV) dysfunction is not defined completely. This study determines whether the performance of Tc-99m sestamibi SPECT for viability detection differs between patients with mild-to-moderate coronary artery disease. Patients with regional and/or global LV dysfunction were separated into 2 groups on the basis of LV ejection fraction (EF) at rest: group 1 (LVEF > 25%, mean 36 +/- 6%, n = 9), and group 2 (LVEF < or = 25%, mean 17 +/- 5%, n = 11). All patients underwent semiquantitative Tc-99m sestamibi SPECT and positron emission tomography (PET) at rest with N-13 ammonia and F-18 fluorodeoxyglucose. The overall regional concordance of SPECT and PET for viability detection was 89% in group 1 and 78% in group 2 (p = 0.002). Discordance in group 2 was almost exclusively due to PET viable and/or SPECT nonviable regions. In regions with hypoperfusion at rest by PET, concordance was 78% in group 1 and only 64% in group 2 (p = 0.0015). In regions with reduced perfusion and relatively increased metabolic activity ("flow: metabolism mismatch"), Tc-99m sestamibi SPECT identified 88% of regions in group 1 as viable, but only 42% of regions in group 2 (p = 0.002). Thus, while Tc-99m sestamibi semiquantitative SPECT at rest shows a good concordance with PET for the detection of myocardial viability in patients with coronary artery disease with mild-to-moderate LV dysfunction, it may underestimate myocardial viability in patients with severe LV dysfunction, particularly in those patients with hypoperfusion at rest as assessed by PET.

Early changes in left ventricular anterior wall dynamics and coordination after coronary artery surgery

OBJECTIVE

To study how asynchronous left ventricular wall motion changes early after uncomplicated coronary artery surgery.

DESIGN

A prospective study done before, and at 0.5, 1, and 3 hours after coronary artery grafting, with intraoperative transoesophageal cross sectional guided M mode echocardiograms, high fidelity left ventricular pressure, and thermodilution cardiac output measurements. The extent and velocity of left ventricular anterior wall thickening were measured, along with regional work and power production. Abnormal thickness changes during the isovolumic periods were detected, and their effect on energy transfer quantified as cycle efficiency.

SETTING

Tertiary referral cardiac centre.

PATIENTS

25 patients with a history of chronic stable angina, mean (SD) age 60 (9) years with three vessel coronary artery disease, undergoing uncomplicated coronary artery bypass grafting.

RESULTS

4 patients had primary incoordination, as shown by wall thinning during isovolumic contraction and delayed onset of thickening (group A), and nine had premature thickening due to incoordination elsewhere (group B). The extent (thickening fraction 43 (12)% v 73 (19)%) and velocity (1.7 (0.4) v 2.5 (0.6) cm/s) of thickening were reduced in group A v group B (P < 0.001), as were regional stroke work (2.2 (0.8) v 3.3 (0.4) mJ/cm2) and peak power production (19 (5) v 32 (7) mW/cm2), P < 0.05. In group A, these values all increased significantly within 30 minutes of operation. In group B, the extent of wall thickening and peak power production were unaffected by surgery, though cycle efficiency and regional stroke work both improved by 30 minutes v before operation (73 (9)% v 61 (8)%, 4.5 (0.9) v 3.3 (0.4) mJ/cm2, P < 0.01). Surgery had no consistent effect on left ventricular cavity size, shortening fraction, or cardiac output in either group.

CONCLUSIONS

Even in the absence of evidence of overt ischaemia, major disturbances of ventricular synchrony--both regional and generalised--are present in patients with a history of chronic stable angina requiring coronary artery bypass grafting. They regress within 30 minutes of revascularisation, suggesting that they are the direct result of coronary stenosis.