Improvement In Regional Wall Motion Research Articles

Time Course and Extent of Improvement of Dysfunctioning Myocardium in Patients with Coronary Artery Disease and Severely Depressed Left Ventricular Function after Revascularization: Correlation with Positron Emission Tomographic Findings

Time Course and Extent of Improvement of Dysfunctioning Myocardium in Patients with Coronary Artery Disease and Severely Depressed Left Ventricular Function after Revascularization: Correlation with Positron Emission Tomographic Findings

Time course and extent of improvement of dysfunctioning myocardium in patients with coronary artery disease and severely depressed left ventricular function after revascularization: correlation with positron emission tomographic findings

OBJECTIVESThis study was performed to evaluate the prevalence, time course of recovery and extent of improvement of segments with a positron emission tomographic (PET) flow–metabolism mismatch and match pattern, as well as of PET segments with normal perfusion but with impaired myocardial function.BACKGROUNDPrevious studies have shown that scintigraphic techniques evaluating myocardial viability provide predictive information about the improvement of regional wall motion. However, there are little data concerning the time course and extent of improvement of segments according to preoperative scintigraphic patterns.METHODSTwenty-nine patients with ischemic cardiomyopathy (ejection fraction 18% to 35%) underwent preoperative PET viability assessment and were functionally assessed by two-dimensional echocardiography preoperatively and at 11 days, 14 weeks and >12 months after coronary artery bypass graft surgery.RESULTSIn 168 (70%) of 240 dysfunctional segments, a “normal” scintigraphic pattern was present, whereas a “mismatch” pattern was observed in 24% (p < 0.01). Mismatch areas were associated with more severe preoperative wall motion abnormalities and incomplete postoperative recovery. After one year, 31% of normal scintigraphic segments, compared with only 18% of mismatch segments, showed complete functional restoration (p < 0.05).CONCLUSIONSThese data suggest that in patients with severe left ventricular dysfunction, a scintigraphic pattern of normal perfusion and normal metabolism is more prevalent than a flow–metabolism mismatch pattern. Functional recovery is more frequent in normal scintigraphic segments, whereas in mismatch segments, postoperative recovery remains incomplete even after one year.

Evaluating signal intensity of movement-impaired myocardial segments in MR delayed images after administration of Gd-DTPA. Correlation of regional increase in contraction after revascularization

The aim of the study was to correlate delayed contrast enhancement of dysfunctional regions of the myocardium after injection of Gd-DTPA with the improvement of regional contractility 3 months after revascularization. Eleven patients with coronary artery disease and wall motion abnormalities underwent MR imaging before and 3 months after revascularization therapy (PTCA or CABG). Short-axis images were acquired using a cine gradient echo sequence. After revascularization, a representative slice was analyzed 14 +/- 1 min after injection of 0.1 mmol/kg Gd-DTPA using a T1-weighted turbo fast low-angle shot sequence. Improved systolic wall thickening 3 months after revascularization served as criterion of viability and was correlated with delayed contrast enhancement patterns. After revascularization, 6 patients showed complete recovery of the dysfunctional area, 1 patient partial recovery, and 4 patients remained unchanged. All 4 patients with persisting wall motion abnormalities, 1/6 patients with recovery and the patient with partial recovery revealed a delayed enhancement. Three months after revascularization, delayed enhancement of dysfunctional myocardium is evident in patients without regional wall motion improvement, while the lack of delayed enhancement correlates with improvement of regional contractility.

Viability of Q-wave infarcted myocardium with restored positive and persistent negative T waves after optimal revascularization compared with dobutamine stress echocardiography

To clarify the clinical difference in viability of myocardium with negative and positive T waves in Q-wave anterior or anteroseptal myocardial infarction, we performed low-dose dobutamine stress echocardiography in 17 patients with negative T waves and in 13 patients with positive T waves with optimal revascularization of infarct-related arteries in the chronic phase of infarction. At baseline the wall motion score (WMS) of the negative and positive T groups was 25.8 ± 3.0 and 22.3 ± 2.2 points (p <0.05), respectively. At peak stress WMS in each group was 27.2 ± 4.2 and 19.8 ± 2.4 points (p <0.0001), respectively. With dobutamine stress WMS in the positive T group was more decreased than that of the negative T group (p <0.0001). We conclude that the restored positive T waves in Q-wave myocardial infarction indicate a significantly greater amount of viable myocardium than the negative T waves, showing better regional wall motion improvement with low-dose dobutamine stress.

Myocardial tissue characterization after acute myocardial infarction with wavelet image decomposition: a novel approach for the detection of myocardial viability in the early postinfarction period.

Only a few texture measures can be used for texture characterization of infarcted myocardium and detection of reperfused myocardium early after infarction. This study was conducted to establish the relationship between texture properties of infarcted myocardium and infarct-related artery patency by quantitative computer analysis of 2-dimensional echocardiographic images with the wavelet-based method for texture characterization, evaluate the relationship between texture properties and myocardial viability, and correlate histopathologic changes after experimental infarction with the texture measures. We analyzed 2-dimensional transthoracic echocardiographic images in 18 patients at different time points after infarction using the wavelet transform method. Regional wall motion of infarcted segments was analyzed on a follow-up echocardiographic study obtained 6 months after infarction. To verify the accuracy of the proposed texture measure and energy difference cutoff value, we prospectively evaluated another group of 19 patients. In addition, histopathologic changes in 9 dogs with experimental infarction were correlated with the texture measures. Sensitivity, specificity, and accuracy of the wavelet method for detection of reperfusion in the study group were 73%, 86%, and 78%, respectively, on day 2; 91%, 86%, and 89%, at 1 week; and 100%, 100%, and 100% at 3 weeks. Among 9 patients with improvement in regional wall motion on a follow-up study, 7 on day 2, 8 at 1 week, and 9 at 3 weeks were classified into the reperfused group by the wavelet method. Histopathologic features associated with the classification of reperfusion by the wavelet method were infarct transmurality (P=0.024) and degree of necrosis (P=0.028). Our clinical and experimental data suggest that the wavelet method can be used to differentiate between viable myocardium with recovery potential and definite myocardial necrosis in the early postinfarction period.

Exercise-induced T-wave normalization predicts recovery of regional contractile function after anterior myocardial infarction.

We investigated the ability of T-wave pseudonormalization and ST-segment elevation, which are demonstrated in infarct-related leads during submaximal exercise testing, to predict late recovery of contractile function. We studied 88 consecutive patients (73 males, mean age 59 +/- 8 years) with anterior infarction, persistent T-wave inversion and a documented lesion of the proximal segment of the left anterior descending coronary artery. They all underwent 2D-echocardiography on admission, 4 weeks as well as 6 months after myocardial infarction to evaluate the dysfunction score and the ejection fraction. Submaximal (75% of maximal predicted heart rate) exercise testing was performed in 80 patients 2 weeks after myocardial infarction following discontinuation of treatment. During exercise testing, 59 of the 88 patients showing negative T-waves on the resting electrocardiogram exhibited pseudonormalization (group A) in at least three adjacent precordial leads, whilst 29 (group B) did not. Patients of group A more frequently exhibited an early creatine kinase peak (41% vs 24%, P < 0.05) and residual angiographic perfusion (97% vs 69%, P < 0.05). The dysfunction score did not change in group B (from 19 +/- 7 to 22 +/- 4), but decreased in group A (from 18 +/- 4 to 11 +/- 6 P < 0.05). The ejection fraction was similar in the two groups on admission (group A: 48 +/- 7%, group B: 45 +/- 10%), but was significantly different at 4-week (52 +/- 99 vs 42 +/- 11%, P < 0.05) and 6-month follow-up (58 +/- 9 vs 44 +/- 10%, P < 0.01). The concomitant presence of ST-segment elevation and T-wave normalization showed the highest positive predictive value for left ventricular function recovery (100%). T-wave normalization induced by submaximal exercise test is frequently associated with residual perfusion to the infarct area and predicts progressive improvement in regional wall motion, especially if associated with ST-segment elevation. Therefore, these electrocardiographic findings may be used as easily obtainable markers of residual viability that predict late recovery in contractile function.

The impact of subendocardial scarring on prediction of improvement of regional wall motion after revascularization by dobutamine echocardiography

The impact of subendocardial scarring on prediction of improvement of regional wall motion after revascularization by dobutamine echocardiography

F18-fluorodeoxyglucose single-photon emission computed tomography predicts functional outcome of dyssynergic myocardium after surgical revascularization

Background. Prediction of functional recovery after revascularization is possible with positron emission tomography and F18-fluorodeoxyglucose (FDG). Recently, the use of FDG in combination with single-photon emission computed tomography (SPECT), with 511 keV collimators, has been proposed to allow more widespread use of FDG. In the current study we aimed to predict improvement of regional left ventricular function after surgical revascularization with FDG and SPECT. Methods and Results. Twenty-seven patients with regional wall motion abnormalities (on echocardiography) underwent early thallium-201 (T1-201) SPECT to assess perfusion and FDG SPECT to assess regional glucose uptake. The left ventricular myocardium was divided into 13 segments. For each segment, tracer uptake was evaluated visually (with the use of a 4-point scoring system) by consensus of two observers. Myocardial viability was determined in dyssynergic segments on echocardiography and defined as normal perfusion or increased FDG uptake in a perfusion defect (mismatch). Absence of viability was defined as a perfusion defect without increased FDG uptake (match). Improvement of regional wall motion was assessed 3 months after revascularization. In the group of segments that were viable on FDG/T1-201 SPECT ( n = 64), the segmental wall motion score decreased from 1.4 ± 0.5 to 0.6 ± 0.7 ( p < 0.01), whereas the segmental wall motion score remained unchanged in nonviable segments ( n = 72): 1.6 ± 0.5 versus 1.5 ± 0.6 (not significant). Forty-six (72%) of the 64 segments that were viable on FDG/T1-201 SPECT demonstrated improved contractile function after coronary revascularization. In contrast, only 7 (10%) of 72 nonviable segments on FDG/T1-201 SPECT showed improvement in function after revascularization ( p < 0.01 versus viable segments). The sensitivity, specificity, and positive and negative predictive values were 87%, 78%, 72%, and 90%, respectively. Conclusion. This study shows that FDG/T1-201 SPECT can identify patients who improve in regional ventricular function after revascularization.

Combined use of dobutamine echocardiography and myocardial contrast echocardiography in predicting regional dysfunction recovery after coronary revascularization in patients with recent myocardial infarction

Myocardial contrast echocardiography and dobutamine echocardiography have recently emerged as potentially useful clinical tools to detect reversible myocardial dysfunction. However, the relative accuracy of these two techniques in predicting regional wall motion improvement after coronary interventions is still unclear. The aim of the present study was to compare their diagnostic value in predicting functional recovery after coronary revascularization in patients with recent acute myocardial infarction. Twenty-four patients with acute myocardial infarction underwent myocardial contrast echocardiography and dobutamine echocardiography within 2 weeks of hospital admission. Infarct zone contrast score and wall motion score indexes were derived in each patient. Infarct-related artery revascularization was performed before hospital discharge in all selected patients. Resting echocardiography was repeated 3 months after revascularization, and regional function recovery was analysed. The degree of wall motion score improvement at 3-month follow-up and the percentage of positive responses to dobutamine echo were greater (P < 0.001 and P < 0.002, respectively) in patients with a higher baseline contrast score (> or = 0.50). Conversely, no significant changes were observed either during dobutamine echo or after revascularization in the group of patients without residual perfusion within the infarct area. Diagnostic agreement between both techniques in predicting reversible dysfunction was high (81% of segments). The sensitivity and negative predictive value in predicting functional outcome were 100% (95% confidence interval [CI], 87% to 100%) and 100% (95% CI, 93% to 100%) by contrast echo, and 85% (95% CI, 66% to 96%) and 93% (95% CI, 84% to 98%) by dobutamine echo. The specificity and positive predictive value were 90% (95% CI, 80% to 96%) and 81% (95% CI, 64% to 93%) by contrast echo, and 88% (95% CI, 78% to 95%) and 76% (95% CI, 58% to 90%) by dobutamine echo. The combination of myocardial contrast and dobutamine echocardiography positive responses improved specificity and positive predictive value in detecting functional recovery after revascularization to 100% (95% CI, 94% to 100%) and 100% (95% CI, 85% to 100%), respectively. However, the sensitivity and negative predictive value slightly decreased with the use of both methods (85% [95% CI, 66% to 96%)] and (93%[95% CI, 85% to 98%)], respectively. In patients with recent myocardial infarction, reversible dysfunction after coronary revascularization and the response to dobutamine infusion are strictly dependent on microvascular integrity. However, microvascular perfusion does not always imply functional recovery after coronary revascularization. The integration with dobutamine echo results seems particularly helpful to further improve myocardial contrast echo specificity and positive predictive values.

Diagnostic performance of myocardial contrast echocardiography for detection of stunned myocardium

Improvement in regional wall motion after acute myocardial infarction has been described up to 2 to 3 weeks after the acute event despite restoration of blood flow by early successful reperfusion therapy. The prospective identification of potentially reversible ventricular dysfunction caused by stunned myocardium has significant clinical implications. Twenty-seven patients with acute myocardial infarction underwent myocardial contrast echocardiography (MCE) before, immediately after, and 4 weeks after successful reperfusion therapy. MCE was performed by imaging a parasternal short-axis view during intracoronary arterial injection of 2 ml sonicated ioxaglate (Hexabrix-320). The contrast defect area and contrast-filled area before reperfusion were defined as the risk area and noninfarct area, respectively. The normalized gray level was defined as the ratio of the gray level in the risk area/gray level in the noninfarct area. In 21 patients, wall motion was akinectic or dyskinetic immediately after reperfusion, and 10 of 21 patients in whom wall motion recovered during the chronic stage were defined as patients with stunned myocardium. In patients who showed asynergic wall motion immediately after reperfusion, MCE predicted the recovery of left ventricular wall motion (stunned myocardium) during the chronic stage with a sensitivity of 77%, specificity of 100%, and predictive accuracy of 86%, when a normalized gray level of more than 0.4 was presumed to predict stunned myocardium. We conclude that MCE provided the prospective identification of potentially reversible ventricular dysfunction caused by stunned myocardium, and wall motion in the area of nonenhanced myocardium on MCE immediately after reperfusion is not expected to show reversible dysfunction.

Correlation between post-ejection shortening and improvement in regional wall motion after revascularization in patients with coronary artery disease

This study investigates the relationship between regional post-ejection shortening and improvement in wall motion after revascularization in patients with severe regional left ventricular contractile dysfunction. Canine studies have documented the phenomenon of post-systolic shortening during acute ischemia, and this predicted recovery of contractile function when ischemia was relieved. This delayed shortening from the ischemic segment would cause regional emptying while the other normal portion of the left ventricle starts to have diastolic relaxation. This was detectable by standard phase analysis of the radionuclide ventriculogram, the abnormal region with delayed emptying being distinguished from the normal portion of left ventricle as an area with a homogeneous phase delay. Twelve patients with successful revascularization and a pre-operative study demonstrating a single homogeneous area of phase delay were identified. The area was demarcated and the regional volume-time curve constructed. The volume-time curve of the abnormal region is analogous to the myocardial segment length versus time relationship in the canine model. We quantitated the amount of delayed (post-systolic) emptying in the demarcated region as the difference between end-systole counts and post-systolic nadir counts, and this was normalised to left ventricular stroke count. After revascularization, regional ejection fraction improved from 44 ± 10% to 62 ± 14% ( P < 0.001), representing a 47 ± 50% improvement over baseline. The percentage improvement in regional ejection fraction correlated with post-systolic emptying ( r = 0.74, P < 0.05) but not with initial regional ejection fraction. In conclusion, post-ejection shortening causes regional post-systolic emptying and this correlates with post-revascularization improvement in regional wall motion.

986-76 β·Blockade Alters the Biphasic Response of Hibernating Myocardium to Incremental Doses of Dobutamine: Implications for Dobutamine Stress Echocardiography

We have previously shown that an incremental dobutamine infusion induces a biphasic pattern of regional LV wall thickening in hibernating myocardium, with initial improvement and subsequent deterioration. This study was designed to evaluate whether and how a, β -blocker alters this pattern. A model of myocardial hibernation was created in 6 pigs (35–45 kg). A LAD stenosis was produced to decrease LAD flow to 40–70% of baseline. This decreased regional LV wall thickening by 45 to 100% and caused transient regional lactate production. This condition was maintained for 6–8 days, at which time dobutamine echocardiography with incremental doses from 2.5–30 μ g/kg/min was performed, both with and without an esmolol infusion of 50 μ g/kg/min. The stenosis was released after dobutamine echocardiography and the animals recovered for 7 days to evaluate the reversibility of the regional wall motion abnormalities. In all 6 pigs regional wall thickening initially improved but subsequently deteriorated during the dobutamine infusion. The maximal improvement was 10 ± 5% at a dose of 4.2 ± 3.5 μ g/kg/min. Esmolol infusion during dobutamine echocardiography did not alter the magnitude of the initial improvement, 12 ± 4% (p = NS); however, the time to peak improvement was delayed, so that it occurred at a higher dose of dobutamine, 17 ± 5 μ g/kg/min (p &lt; 0.01). Esmolol prevented the late deterioration of wall thickening to below baseline in 3 of the 6 animals. By 1 week after restoration of LAD flow, one pig had died from a non-cardiac cause and regional wall motion recovered in the 5 others. The response pattern of chronic hibernating myocardium to dobutamine stress echocardiography is modified by a β -blocker: the initial improvement, though of similar magnitude, is delayed and late deterioration of regional wall thickening is attenuated. However, if initial improvement in regional wall motion is the criterion for viability, premedication with a β -blocker will not affect sensitivity.

Evaluation of regional myocardial perfusion in areas of old myocardial infarction after revascularization by means of intraoperative myocardial contrast echocardiography

Because myocardial revascularization to areas of old myocardial infarction brings about functional recovery to some extent to myocytes in those areas, the assessment of regional myocardial perfusion on those areas after myocardial revascularization may allow myocardial viability to be estimated. Using intraoperative myocardial contrast echocardiography by direct injection of 2 ml sonicated 5% human albumin into saphenous vein grafts, we assessed regional myocardial perfusion in 16 revascularized areas of old myocardial infarction. We estimated the myocardial viability of areas with respect to myocardial perfusion, and we compared these results to both the improvement of regional wall motion after myocardial revascularization (increase in segmental wall thickening during systole) and relative thallium 201 activity obtained by quantitative analysis of preoperative exercise myocardial thallium 201 distribution on delayed images. The background-subtracted peak peak intensity of myocardial enhancement and the ratio of endocardial to epicardial intensity were determined in each revascularized area. An inverse correlation existed between peak intensity (18 +/- 7) and the endocardial/epicardial ratio (0.88 +/- 0.17) (r = -0.63, p < 0.01). A good correlation was found between peak intensity and both the percent increase in segmental wall thickening (r = 0.73, p < 0.005) and the relative thallium 201 activity (r = 0.81, p < 0.005). These results suggested that regional myocardial perfusion after myocardial revascularization in areas of old myocardial infarction distributed better to the epicardial halves than to the endocardial halves, and that the peak intensity could be related to myocardial viability.

Paradoxic Improvement in Regional Wall Motion During High-Dose Dobutamine Stress Echocardiography: A Marker for Hibernating Myocardium?

Dobutamine stress echocardiography detects myocardial ischemia by inducing regional left ventricular systolic dysfunction. Augmentation of wall motion in hypokinetic segments has also been noted with low-dose dobutamine, suggesting myocardial viability. We report a case of regional ventricular improvement during high-dose dobutamine therapy, which may represent relief from myocardial hibernation or changes in regional loading conditions.

Improvement of regional wall motion in medically treated myocardial infarction with single-vessel coronary artery disease.

Long-term changes in regional wall motion (RWM) following acute myocardial infarction (AMI) in 42 patients with uncomplicated single-vessel disease were examined retrospectively by repeat cardiac catheterizations. The first and second cardiac catheterizations were performed at an average of 28 days and 6.6 years after the onset of AMI, respectively. All 42 patients underwent first and second cardiac catheterizations without undergoing coronary artery bypass surgery or coronary angioplasty. Regional left ventricular functions were analyzed by the centerline method using a right anterior oblique left ventriculogram. The wall motion abnormality score (WMAS) was defined as [# chord below -2SD] x [mean SD chord below -2SD]. The improvement in the WMAS was more prominent in cases with an occluded infarct-related artery. Thus, we concluded that 1) RWM improves significantly with medical treatment in long-term follow-up in cases of uncomplicated AMI with single-vessel disease, and 2) the improvement of RWM is completed within the first few weeks after AMI in cases with a patent infarct-related artery.

Importance of ischemic preconditioning and collateral circulation for left ventricular functional recovery in patients with successful intracoronary thrombolysis for acute myocardial infarction

We studied the effects of myocardial ischemic preconditioning and preexistent collateral circulation on the preservation of left ventricular function in 30 patients who had successful intracoronary thrombolysis within 6 hours after the onset of a first acute anterior myocardial infarction. The existence of ischemic preconditioning was defined as the episode of recurrent ischemic chest pain within 4 hours before the onset of acute myocardial infarction. In 16 patients with ischemic preconditioning (group A), the left ventricular ejection fraction during the convalescence of myocardial infarction was 57% ± 11% (mean ± SD); regional wall motion in the infarct area was 13% ± 9%. In 14 patients without ischemic preconditioning (group B), the left ventricular ejection fraction and regional wall motion in the infarct area were 46% ± 9% and 5% ± 9% (both p < 0.05 vs group A). Moreover, among group A patients, seven patients having a well-developed collateral circulation during the acute stage of myocardial infarction showed a more prominent improvement in regional wall motion in the infarct area compared with nine patients having poor or no collateral circulation (18% ± 8% vs 9% ± 7%, p < 0.05). These data indicate that ischemic preconditioning is effective for the preservation of left ventricular function in patients with successful intracoronary thrombolysis and that preexistent coronary collateral circulation potentiates this favorable effect of ischemic preconditioning.

Non-invasive assessment of residual viability in post-myocardial infarction patients. Role of nuclear techniques.

The failure of non-imaging techniques in identifying viable segments has favoured the clinical application of nuclear imaging. The main pathways that support radionuclide imaging are cell membrane integrity, persistence of intermediary metabolism and demonstration of a residual coronary reserve. Thallium-201 reinjection or rest protocols allow the identification of viable myocardium in most of patients with wall motion abnormalities and appear to be the most diffuse, low-cost and available method to detect viable myocardium. More complex approaches use positron emission tomography and matched flow/metabolic information. Flow/metabolic 'mismatch' usually identifies most of hypoperfused regions that show post-operative improvement of regional wall motion. The last promising approach is represented by the demonstration of a maintained regional coronary reserve in dyssynergic areas. Technetium-99m-microspheres (or Teboroxime in the future) can be successfully used for this purpose. The clinical application of radionuclides appears to be one of the principal imaging tools able to identify residual viability.

Current expectations in dynamic cardiomyoplasty

Dynamic cardiomyoplasty has been evaluated in the treatment of severe cardiomyopathies. This report outlines the results of this procedure in 21 patients with dilated or ischemic cardiomyopathy who were in New York Heart Association class III or IV before operation. There were no operative deaths. Patients were followed up for a mean of 17.6 months. Eight patients died during late follow-up, and actuarial survival rates were 73.2% at 1 year and 65.9% at 2 years of follow-up. Functional class improvement was documented in the surviving patients. Furthermore, significant improvement in left ventricular function was demonstrated by radioisotopic angiography and by heart catheterization for more than 2 years after the operation. These studies documented that left ventricular ejection fraction increased as a result of global improvement in regional wall motion. Absence of clinical and hemodynamic improvement after cardiomyoplasty seems to be related to muscle flap ischemic compromise, whereas the patient's condition before operation seems to influence the long-term outcome of cardiomyoplasty.

Effect of buckberg cardioplegia and peripheral cardiopulmonary bypass on infarct size in the closed chest dog

Objectives. To simulate a human catheterization laboratory setting of controlled reperfusion during myocardial infarction, regional infusion of commercially available Buckberg cardioplegic solution and peripheral vented bypass were administered in the closed chest dog.Background. Studies in open-chest dogs have demonstrated a significant reduction in infarct size and improvement in regional wall motion with a similar controlled reperfusion method using infusion of substrate-enriched (Buckberg) cardioplegic solution during cardiopulmonary bypass coupled with left ventricular venting.Methods. After 100 or 180 min of balloon occlusion of the proximal left anterior descending artery, controlled reperfusion was performed with cardioplegic infusion and vented bypass. Dogs matched for occlusion time underwent balloon deflation without bypass or cardioplegia (uncontrolled reperfusion groups). Microspheres were used to quantify coronary ischemia during balloon inflation. All four groups (n = 8 to 9 per group) were followed up at 1 week to determine regional wall motion and infarct size.Results. Qualitative echocardiographic analysis demonstrated no significant difference among groups in recovery of regional wall motion at 1 week; however, wall motion improved significantly in all groups between the ischemia and 1-week recovery periods. The histologic infarct size compared with the area at risk for dogs with uncontrolled versus controlled reperfusion, respectively, was 17.9 ± 10.5% versus 31.9 ± 8.3% (p < 0.05) for dogs with 100 min of occlusion and 40.1 ± 11.7% versus 46.2 ± 8.4% (p = NS) for dogs with 180 min of occlusion. A greater rate-pressure product in the dogs with controlled reperfusion after 100 min of occlusion (p < 0.05) may explain the larger infarct size observed for that group.Conclusions. These results demonstrate that regional infusion of substrate-enriched cardioplegic solution in combination with peripheral vented bypass does not further reduce infarct size after prolonged ischemia in the closed chest dog (compared with uncontrolled reperfusion).

A new strategy for the assessment of viable myocardium and regional myocardial blood flow using 15O-water and dynamic positron emission tomography.

We have developed a new measure of myocardial viability, the water-perfusable tissue index (PTI), which is calculated from transmission, C15O, and H2(15)O positron emission tomography (PET) data sets. It is defined as the proportion of the total anatomical tissue within a given region of interest (ROI) that is capable of rapidly exchanging water and has units g (perfusable tissue)/g (total anatomical tissue). The aim of this study was to assess the prognostic value of PTI in predicting improvement in regional wall motion after successful thrombolysis for acute myocardial infarction (AMI) and to measure the myocardial blood flow to the perfusable tissue (MBFp, ml/min/g [perfusable tissue]). Furthermore, PTI was compared with 18FDG metabolic imaging in patients with old myocardial infarction (OMI). PET scans were performed in healthy volunteers (group 1, n = 8), patients with OMI (group 2, n = 15), and in patients who were successfully thrombolysed after an AMI (group 3, n = 11). Systolic wall thickening was measured by two-dimensional echocardiography within 2-4 days of AMI and after 4 months to assess contractile recovery. In the healthy volunteers, MBFp was 0.95 +/- 0.13 ml/min/g (perfusable tissue). PTI in these regions was 1.08 +/- 0.07 g (perfusable tissue)/g (total anatomical tissue), which was consistent with all normal myocardium being perfusable by water. In the OMI group, the ratio of the relative 18FDG activity to the relative MBFp defect (metabolism-flow ratio) was calculated for each asynergic segment. Regions in which the metabolism-flow ratio was greater than or equal to 1.20 were considered reversibly injured, whereas those in which the ratio was less than 1.20 were deemed irreversibly injured. PTI in the former group of regions (n = 9) was 0.75 +/- 0.14 g (perfusable tissue)/g (total anatomical tissue) and was significantly higher than in irreversibly injured regions (n = 6) (0.53 +/- 0.12 g [perfusable tissue]/g [total anatomical tissue], p less than 0.01). Values of MBFp were similar in these segments. Seven of 12 segments in the AMI patients showed improved systolic wall thickening on follow-up. PTI in these recovery segments was 0.88 +/- 0.10 g (perfusable tissue)/g (total anatomical tissue) (p = NS versus control). PTI in the nonrecovery regions was 0.53 +/- 0.11 g (perfusable tissue)/g (total anatomical tissue), which was similar to the segments in group 2 in which 18FDG uptake was absent. MBFp was similar in both the recovery and nonrecovery segments in the subacute phase. These data indicate that PTI may be a good prognostic indicator for the recovery of contractile function after successful thrombolysis and show that myocardial viability may be assessed by PET without metabolic imaging.