Reversible segmental left ventricular dysfunction after coronary angioplasty

Assessment of myocardial ischemia with cardiovascular magnetic resonance

Assessment of myocardial ischemia in symptomatic patients remains a common and challenging clinical situation faced by physicians. Risk stratification by presence of ischemia provides important utility for both prognostic assessment and management. Unfortunately, current noninvasive modalities possess numerous limitations and have limited prognostic capacity. More recently, ischemia assessment by cardiovascular magnetic resonance (CMR) has been shown to be a safe, available, and potentially cost-effective alternative with both high diagnostic and prognostic accuracy. Cardiovascular magnetic resonance has numerous advantages over other noninvasive methods, including high temporal and spatial resolution, relatively few contraindications, and absence of ionizing radiation. Furthermore, studies assessing the clinical utility and cost effectiveness of CMR in the short-term setting for patients without evidence of an acute myocardial infarction have also demonstrated favorable results. This review will cover techniques of ischemia assessment with CMR by both stress-induced wall motion abnormalities as well as myocardial perfusion imaging. The diagnostic and prognostic performance studies will also be reviewed, and the use of CMR for ischemia assessment will be compared with other commonly used noninvasive modalities.

Is detection of hibernating myocardium necessary in deciding revascularization in systolic heart failure?

Although the prognosis of systolic heart failure, also called heart failure with reduced ejection fraction, has improved with advances in therapy, the prognosis remains poor in patients who become refractory to such therapies. That cardiac transplantation improves the quality of life and survival of such patients has been established, but it is available to a very small number of patients. Thus, newer pharmacologic and nonpharmacologic therapies for patients with refractory systolic heart failure are being explored. Because chronic ischemic heart disease is the most common cause of systolic heart failure, potential exists for revascularization therapy. Although revascularization can be performed with low procedural mortality, improvement in left ventricular function, relief of symptoms, and long-term prognosis appear to be related to the presence and extent of viable ischemic hibernating myocardium. In conclusion, the detection of hibernating myocardium is highly desirable before revascularization treatment is undertaken.

Relationship between post-systolic motion during dobutamine stress echocardiography and functional recovery of myocardium after successful percutaneous coronary intervention

BACKGROUND AND OBJECTIVES

Doppler myocardial imaging (DMI) has been suggested as a method of quantifying inducible ischemia during dobutamine stress echocardiography (DSE). Post-systolic motion (PSM) detected by DMI is related to peri-infarct ischemia during DSE. We hypothesized that PSM during DSE would predict recovery of dysfunctional myocardium after successful percutaneous coronary intervention (PCI).

SUBJECTS AND METHODS

Thirty patients with dysfunctional myocardium in the left anterior descending coronary artery (LAD) territory were divided into two groups according to improvement of wall motion score index (WMSI) in the LAD territory at 6 months after successful PCI of the LAD. DMI was evaluated in the LAD territory during DSE. Fifteen patients showed improved WMSI (1.42+/-0.39) while the other 15 had unchanged WMSI (1.75+/-0.46) 1 month after PCI. Myocardial velocity was measured in the mid-septal, apico-septal, and basal anterior segments of the LAD artery territory. PSM was defined as a positive wave appearing after the curve of systolic ejection had reached the zero line.

RESULTS

Although there was no difference between resting PSMs in both groups, PSM during DSE was significantly higher in the improved WMSI group than in the WMSI group where it was unchanged.

CONCLUSION

PSM during DSE predicts recovery of dysfunctional myocardium after successful PCI.

Relationship between myocardial viability and coronary run-off in jeopardized myocardium

OBJECTIVE

The aim of this study was to evaluate the relationship between coronary run-off and myocardial viability in jeopardized regions.

METHOD

We studied 50 patients (40 male, mean age: 55.63 +/- 10.54 years) with coronary artery stenosis >70% and ejection fraction <40% referred for viability study via dobutamine stress echocardiography. The relationship between coronary run-off and viability was evaluated. Good run-off demonstrates good or moderate and no run-off means poor or no run-off.

RESULTS

In the apical region, 33% of the segments with good antegrade run-off were viable and 67% nonviable. Also, 72% of the segments with no run-off were nonviable and 28% viable. In the midportion region, 70% of the segments with good antegrade run-off were viable and 30% nonviable; 50% of the segments with no run-off were nonviable and 50% viable. In the basal region, 85% of the segments with good antegrade run-off were viable and 15% nonviable; 19% of the segments with no run-off were nonviable and 81% viable. The proportion of the nonviable segments increased significantly from the basal to apical regions either with good (p < 0.001) or no run-off (p = 0.004). From 239 viable segments, 58.6% had antegrade, 15.4% retrograde, and 25.5% no run-off. Of 181 nonviable segments, 44% had antegrade, 34% retrograde, and 34.8% no run-off.

CONCLUSION

There was more susceptibility to nonviability in the apical regions despite good run-off, while the basal segments showed more viability in spite of having no run-off. The findings may be helpful for selecting patients with coronary artery disease and left ventricular systolic dysfunction that benefit from revascularization.

Medical treatment of patients with heart failure or left ventricular dysfunction undergoing percutaneous coronary intervention

Management of ischemic patients with pre-existing or new-onset left ventricular (LV) dysfunction poses a special challenge in terms of the timing of percutaneous coronary intervention (PCI) and appropriate adjunctive medications to optimize outcome while minimizing risk. In a systematic fashion, this review attempts to provide a management scheme for patients with heart failure or LV dysfunction that present with stable angina, ST-segment elevation myocardial infarction, or unstable angina/non-ST-segment elevation myocardial infarction. By addressing therapeutic approaches to acute or decompensated heart failure and timing of coronary angiography based on severity of ischemia, we provide evidence-based recommendations for medications to initiate before, during, and following PCI.

99mTc-HL91 is inferior to 201Tl in scintigraphic detection of chronic myocardial ischaemia

AIM

99mTc-HL91 is a new hypoxia agent and can identify acutely ischaemic viable myocardium in a canine model using a standard gamma camera. The purpose of the study was to determine whether this tracer could be used to detect regional ischaemia in chronic ischaemic myocardium in a swine model.

METHOD

Using a porcine model of chronic myocardial ischaemia, five mini-pigs with proximal left anterior descending artery (LAD) stenoses were studied. Injection of 462.5 MBq (12.5 mCi) 99mTc-HL91 was followed by imaging over 2 h. Coronary angiography and dipyridamole stress-re-injection 201Tl single photon emission computed tomography (SPECT) were performed within 1 day of each other.

RESULTS

None of the five pigs demonstrated positive hot 99mTc-HL91 uptake throughout the 2 h imaging, whereas four of the five animals showed significant myocardial ischaemia on 201Tl SPECT. The region of interest analysis of LAD/left circumflex artery count ratios at 1 and 2 h demonstrated similar 99mTc-HL91 uptake and retention in chronic ischaemic as well as non-ischaemic myocardium.

CONCLUSION

99mTc-HL91 is inferior to 201Tl in scintigraphic detection of chronic myocardial ischaemia.

[Comparison of dobutamine echocardiography and rest-redistribution 201-thallium SPECT in the assessment of myocardial viability taking PET as gold standard]

BACKGROUND AND AIM

To compare Tl-201 SPECT and dobutamine stress echocardiography for the detection of myocardial viability in patients with severe left ventricular dysfunction using metabolic imaging by positron emission tomography as the standard reference.

MATERIAL AND METHODS

We studied 25 consecutive patients with severe coronary artery disease and left ventricular dysfunction that underwent two different diagnostic modalities for evaluating myocardial viability: stress echocardiography with incremental doses of dobutamine from 5 up to 40 g/kg/min in 3 min stages, and 201 Tl SPECT using a rest-redistribution protocol with delayed images obtained at 4 hours. Fluorodeoxyglucose uptake by PET was used as the gold standard. Viability criteria were as follows, for 201Tl SPECT imaging: normal uptake at rest and presence of redistribution in the delayed images, for dobutamine stress echocardiography: sustained improvement and biphasic response.

RESULTS

Sensitivity of thallium redistribution was 46%, for normal uptake, plus redistribution 82%, 34% for dobutamine biphasic response and 58% for sustained improvement plus biphasic response. Specificity of biphasic response was 82% and that of redistribution 67%. Stepwise logistic regression indicated that biphasic wall motion response during dobutamine stress echocardiography (2.01 CI 95%; 1.10 to 3.99) and the presence of redistribution plus normal uptake at rest with thallium imaging (2.68 CI 95%; 1.42 to 5.13) were the best predictors of viability. These results were the same when both techniques were analyzed together.

CONCLUSIONS

Biphasic wall motion response during dobutamine stress echocardiography and the normal uptake plus presence of redistribution with thallium imaging were the best pre

Beneficial effects of ramipril on left ventricular end-diastolic and end-systolic volume indexes after uncomplicated invasive revascularization are associated with a reduction in cardiac events in patients with moderately impaired left ventricular function and no clinical heart failure

OBJECTIVES We sought to assess the effect of ramipril on left ventricular (LV) volumes, and the clinical significance thereof, in patients with moderate LV dysfunction and no clinical heart failure undergoing invasive revascularization for chronic stable angina.

BACKGROUND

It is unsettled whether treatment with an angiotensin-converting enzyme inhibitor has an impact on LV volumes in this patient group, and, if so, whether this is associated with the clinical outcome.

METHODS

A total of 133 patients with a left ventricular ejection fraction (LVEF) between 0.30 and 0.50 and no clinical heart failure undergoing invasive revascularization for chronic stable angina were randomized to receive ramipril 10 mg once daily or placebo and were followed for a median of 33 months with echocardiography at baseline and 3, 12 and 24 months postoperatively.

RESULTS

Repeated measures analysis of all time points showed that ramipril significantly reduced the end-diastolic volume index (EDVI) (p = 0.032) and end-systolic volume index (ESVI) (p = 0.006) as compared with placebo. Ramipril also reduced the incidence of the triple composite end point of cardiac death, acute myocardial infarction or development of heart failure (p = 0.046). Cox regression analysis, controlling for baseline LVEF and assignment to ramipril, revealed: 1) that increases in EDVI and ESVI up to three months predicted an increasing risk of a future adverse clinical outcome; and 2) that the benefit with ramipril on clinical outcome was partly dependent on a reduction in LV volumes.

CONCLUSIONS

Even in this patient group, LV dilation may supervene and lead to an adverse clinical outcome. Ramipril reduces the postoperative increase in LV volumes and may thereby improve clinical outcome.

[Thallium-201 scintigraphy and dobutamine echocardiography in the assessment of myocardial viability]

BACKGROUND

The possibility of differentiating viable from non-viable tissue among patients with severe coronary artery disease and severe left ventricular impairment entails relevant clinical and therapeutic implications since it may influence the indication of patient revascularization. To evaluate the presence of myocardial viability two techniques are available in the clinical setting: echocardiography with intravenous infusion of dobutamine and scintigraphy with myocardial perfusion with thalliem-201 by means of single-photon emission tomography.

OBJECTIVE

To compare prospectively the value of these techniques for detecting viable myocardium.

MATERIAL AND METHODS

Thirty-five patients with severe coronary disease and severe left ventricular dysfunction were included in the study. All patients underwent an echocardiogram using incremental doses of dobutamine, from 5 up to 40 micrograms/kg/min in three-minute periods. For thallium-201 scintigraphy the rest redistribution protocol with delayed images at 4 hours was used. The criteria for detecting viability were: a) for thallium-201, the presence of redistribution in delayed images and normal uptake at rest, and b) for dobutamine echocardiography, a sustained improvement in regional motion, biphasic response, and worsening.

RESULTS

By considering the segmental improvement post-revascularization as "gold standard" of viability, the statistically significant variables in a logistic regression model and, therefore, predictors of segmental functional recovery were the biphasic response and the sustained response for dobutamine echocardiography and normal uptake at rest and redistribution in the delayed images for thallium-201. Taken together, the result was significant for the biphasic response of dobutamine echocardiography.

CONCLUSIONS

The biphasic response with dobutamine echocardiography is the echocardiographic pattern that best predicts the functional recovery of the ischemic myocardium. A normal uptake and redistribution at four hours is the only scintigraphic pattern that can predict functional improvement. Of both patterns, the biphasic response is the best predictor of the functional recovery of the dysfunctional myocardium.

Prediction of viability by pulsed-wave Doppler tissue sampling of asynergic myocardium during low-dose dobutamine challenge

Dobutamine stress echocardiography is widely used to predict reversible left ventricular dysfunction, but evaluation with this method is subjective. Pulsed-wave tissue Doppler imaging is a new technique that allows to obtain quantitative data on wall motion velocities of different myocardial segments through sample-volume placement. Therefore, this tool in combination with DSE may be suitable for identifying viability in asynergic myocardium. To evaluate this, in 40 patients (mean age 57+/-9) with resting dyssynergy (akinesis in 52, hypokinesis in 30) baseline wall motion scores and tissue Doppler variables were collected before and after 5 min infusion of 10 microg/kg per min dobutamine. Forty-six of 82 segments were classified as viable (a reduction in segmental score of at least one grade) according to follow-up echocardiography that was performed 4 weeks after revascularization. While myocardial S velocity percent increase in viable segments was 45+/-10, the increase was 25+/-12 in necrotic segments (n=36) during 10 microg dobutamine infusion (P=0.0001). Assuming 35% as a cut-off for viability the increase in S velocities by DSE yielded an 89% sensitivity and 86% specificity for predicting post-revascularization functional recovery. In conclusion, pulsed-wave tissue Doppler imaging of asynergic myocardium during dobutamine stress echocardiography can identify the viability quantitatively.

Percutaneous transluminal coronary angioplasty performed 24-48 hours after the onset of acute myocardial infarction improves chronic-phase left ventricular regional wall motion

The authors investigated the capacity of percutaneous transluminal coronary angioplasty (PTCA) performed 24-48 hours after the onset of acute myocardial infarction (AMI) to improve regional left ventricular wall motion. Twenty-four patients were divided into two groups: a PTCA group who received successful PTCA (14 cases) and a non-PTCA group (10 cases) who did not receive PTCA. Left ventricular end-diastolic volume (LVEDV) increased significantly (p<0.01) from 57+/-14 mL/m2 during the acute phase to 83+/-16 mL/m2 during the chronic phase in the non-PTCA group, whereas no significant change in LVEDV was seen in the PTCA group (69+/-26 vs. 76+/-16 mL/m2). In addition, in patients with 99% stenosis/thrombolysis in myocardial infarction (TIMI) grade 3 flow, increases in regional left ventricular wall motion (delta(sd)/chord) at the infarcted site between the acute and chronic phases were significantly greater in the PTCA group than in the non-PTCA group (2.49+/-1.05 vs. 0.67+/-0.65, p<0.01). PTCA performed 24-48 hours after the onset of AMI improved wall motion at the infarcted site.

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.

Metabolic changes in hibernating myocardium after percutaneous transluminal coronary angioplasty and the relation between recovery in left ventricular function and free fatty acid metabolism

To elucidate the changes in oxidative metabolism in hibernating myocardium after coronary revascularization, we performed myocardial single-photon emission computed tomography with a free fatty acid analog, I-123 beta-methyliodophenylpentadecanoic acid (BMIPP), and thallium-201 before and 1 month after percutaneous transluminal coronary angioplasty (PTCA) in 11 patients with angina pectoris caused by single artery stenosis. All patients had improvement in wall motion after PTCA at the region with coronary stenosis; the wall motion abnormality score evaluated by left ventriculography decreased from 5.5+/-0.8 (mean +/- SE) to 2.1+/-0.9, p <0.01) after PTCA. The defect score of I-123 BMIPP images was significantly larger than that of thallium-201 images either before (14+/-1.3 vs 8.9+/-1.1, p <0.01) or 1 month after (7.4+/-1.5 vs 3.7+/-0.8, p <0.01) PTCA. The decrease in the defect score of both images was significant (p <0.01). Changes in the wall motion abnormality score showed a significant correlation with both the change in the defect score of thallium-201 images (r = 0.58, p < 0.01) and that of I-123 BMIPP images (r = 0.75, p <0.01). These results indicate that the metabolism of free fatty acid is impaired in hibernating myocardium, and that improvement in left ventricular function after successful PTCA is strongly associated with the recovery of oxidative metabolism.

Prognostic value of detection of myocardial viability using low-dose dobutamine echocardiography in infarcted patients

Revascularization can improve ventricular function in patients with viable myocardium, but whether and how the presence of viable myocardium affects prognosis of infarcted patients is still far from clear. Thus, 202 patients (173 men, 59 +/- 9 years old) with a previous or recent myocardial infarction (MI) and regional asynergies underwent low-dose dobutamine echocardiography (5-15 microg/kg per min) to assess myocardial viability and were followed for a period of 16 +/- 11 months after revascularization (89 patients) or medical therapy (113 patients). Four groups of patients were defined: (1) patients with viability, revascularized (n = 64); (2) patients with viability, treated medically (n = 52); (3) patients without viability, revascularized (n = 25); and (4) patients without viability, treated medically (n = 61). Of these patients, 45 (23%) patients suffered 57 cardiac events: 18 cardiac deaths (9%), 7 MIs, 12 unstable angina, 9 heart failures, and 11 new revascularization procedures. Patients with viability, revascularized, experienced a slightly lower event rate (22%) compared with patients with viability, treated medically, patients without viability, treated medically and patients without viability, revascularized (29%, 31%, and 36%, respectively; p = not significant [NS]). The frequency of events was then evaluated in those 108 patients with an ejection fraction < or =33%, in whom 14 cardiac deaths occurred: the incidence of cardiac death was slightly lower in patients with viability, revascularized (3/37, 8%) than in the patients with viability, treated medically (4/26, 15%), patients without viability, revascularized (2/11, 18%), or patients without viability, treated medically (5/34, 15%) (p = NS). Nonfatal cardiac events were significantly fewer (p <0.05) in patients with viability, revascularized (8%) and in patients without viability, treated medically (6%) than in patients with viability, treated medically and patients without viability, revascularized (27%). In infarcted patients with severe left ventricular dysfunction, the presence of viable myocardium, if left unrevascularized, leads to further events. On the contrary, in the absence of myocardial viability, revascularization could lead to a worse prognosis than medical therapy.

Echocardiography for the assessment of myocardial viability

The identification of viable myocardium in the setting of acute myocardial infarction or chronic coronary artery disease with reduced left ventricular function has important prognostic and therapeutic implications. Many noninvasive methods have been used to assess viability, and recently, dobutamine stress echocardiography has been studied for this purpose. Dobutamine stress echocardiography is a safe, accessible, and relatively inexpensive technique. Moreover, its accuracy for detecting viability approaches that of positron emission tomography and thallium scintigraphy. In addition to dobutamine stress echocardiography, other echocardiographic techniques, such as myocardial contrast echocardiography and dipyridamole stress echocardiography, are being developed to delineate viability. In the future, echocardiographic methods may identify viability with enough accuracy to allow us to better select patients for revascularization procedures when the indications are otherwise unclear.

Impact of restenosis after optimal directional coronary atherectomy on regional left ventricular function

To assess the effect of optimal directional coronary atherectomy (DCA) on restenosis and left ventricular (LV) function, 95 patients who underwent DCA and adjunctive balloon angioplasty for de novo lesions were prospectively followed for 6 months. Absolute and relative coronary lumen measurements were analyzed with online quantitative coronary angiography. LV volumes, ejection fraction, and segmental wall motion were measured off-line according to the radial method for LV cineangiograms acquired in a right anterior oblique projection. Target vessels were the left anterior descending artery in 63 patients and right coronary artery in 32. Mean (+/- SD) reference diameter was 3.58 +/- 0.65 mm. Mean lumen diameter improved significantly after DCA from 1.19 +/- 0.44 to 3.03 +/- 0.45 mm, yielding a 14 +/- 10% residual stenosis. Overall angiographic restenosis rate (> 50% stenosis in diameter) at control was 23%. In patients without restenosis, there were no significant changes in LV volumes or in LV pressures. In this subgroup, ejection fraction improved significantly in the left anterior descending group (mean difference 3 +/- 10%, p < 0.04). Moreover, there was an increase in fractional shortening of all anterior segments (mean difference 11 +/- 16%, p < 0.005). Improvement in fractional shortening was less marked in the right coronary artery group even without restenosis. We conclude that: (1) optimal DCA can achieve a low restenosis rate in selected large vessels, (2) long-term beneficial effects on regional LV function are possible, particularly in patients with left anterior descending disease and in the absence of coronary restenosis.

Detection of myocardial viability in the prediction of improvement in left ventricular function after successful coronary revascularization by using the dobutamine stress echocardiography and quantitative SPECT rest-redistribution-reinjection 201TI imaging after dipyridamole infusion

The aim of this study was to assess the feasibility, safety, and respective diagnostic accuracy of low-dose dobutamine infusion and rest-redistribution-reinjection thallium 201 single photon emission computed tomography (SPECT) after dipyridamole infusion (Th-DIP), in the prediction of functional improvement of asynergic infarcted zones, after successful revascularization in patients with chronic ischemic heart disease. Thirty-one patients with a previous myocardial infarction and left ventricular dysfunction (mean ejection fraction: 41 +/- 5.8%) were studied. The regional wall motion of the left ventricle was evaluated by basic echocardiography before and 14 +/- 1.7 weeks after successful revascularization (19 by percutaneous transluminal coronary angioplasty and 12 by coronary artery bypass grafting). Dobutamine stress echocardiography (DSE) was performed in all patients with dobutamine infusion of 5 and 10 micrograms/kg/minute over five minutes. Within three days after DSE and prior to revascularization, all patients underwent Th-DIP for myocardial viability assessment. A 16-ventricular-segment model was used for basic, DSE, and Th-DIP images. Viability was assessed by applying the standard criteria for each technique. In the 31 patients, 496 segments were analyzed. By basic echocardiography, 164 (33%) of them were classified as asynergic. The DSE detected viable tissue in 69/496 (14%) segments, whereas Th-DIP identified viability in 95/496 (19%) segments. When the postrevascularization basic echocardiographic study was used as the gold standard in identifying myocardial viability, the sensitivity and specificity for the DSE and Th-DIP were 86.5%, 94.4% and 90.5%, 69%, respectively. No major side effects were observed with both techniques. In conclusion, DSE seems to be an accurate method for identifying viable but asynergic myocardium in patients with chronic ischemic heart disease, whereas Th-DIP overestimates the postrevascularization recovery. Detection of hibernating myocardium can be obtained by these two noninvasive methods. However, DSE seems to be more useful in determining the prospective selection of patients who are going to benefit from revascularization.

Effect of late percutaneous angioplastic recanalization of total coronary artery occlusion on left ventricular remodeling, ejection fraction, and regional wall motion

The clinical benefit of late recanalization of complete coronary occlusion is debated. Left ventricular (LV) function and volumes are major prognostic determinants in patients with coronary artery disease. We sought to assess comprehensively the evolution of global and regional LV function and LV volumes after percutaneous recanalization of chronic complete coronary artery occlusions. A consecutive series of 55 patients who underwent successful percutaneous recanalization of a chronic (> or = 10 days), total (Thrombolysis in Myocardial Infarction trial flow grade 0) occlusion of the left anterior descending or dominant right coronary arteries, and in whom a complete angiographic evaluation was available before angioplasty and at follow-up was studied. At follow-up, 38 patients had a patent artery (group 1) and 17 had a reocclusion (group 2). Baseline parameters were similar in the 2 groups. In group 1, LV ejection fraction increased from 55 +/- 14% to 62 +/- 13% (p <0.001), with an increase in fractional shortening in the occluded artery territory (0.43 +/- 0.30 to 0.71 +/- 0.34, p <0.001), while LV end-diastolic volume remained unchanged. In group 2, ejection fraction and regional wall motion were unchanged, while LV end-diastolic volume index increased (86 +/- 22 ml/m2 to 99 +/- 34 ml/m2, p <0.02). The evolution in LV global and regional function was similar in patients with or without previous myocardial infarction; however, prevention of LV remodeling was observed only in patients with previous infarction. Maintained potency after successful recanalization of totally occluded coronary arteries improves global and regional LV function and, in patients with previous myocardial infarction, avoids LV remodeling.

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

OBJECTIVES

This study sought to evaluate an imaging approach using technetium-99m sestamibi scintigraphy and positron emission tomography with fluorine-18 fluorodeoxyglucose for assessment of myocardial viability proved by serial quantitative left ventricular angiography. Furthermore, the influence of successful long-term revascularization on functional recovery was studied.

BACKGROUND

Previous studies using positron emission tomography of myocardial perfusion and metabolism have demonstrated accurate identification of myocardial viability. However, most of these studies used a qualitative or semiquantitative wall motion analysis approach.

METHODS

Nuclear imaging with semiquantitative analysis of tracer uptake was performed in 193 patients with regional wall motion abnormalities. Regions were categorized as normal, viable with perfusion/metabolism mismatch, viable without mismatch (intermediate) and scar. Seventy-two of 103 patients with subsequent revascularization underwent follow-up angiography. In 52 of 72 patients, changes in regional wall motion were measured by the centerline method from serial angiography.

RESULTS

Wall motion improved in mismatch regions from -2.2 +/- 1.0 to -1.1 +/- 1.4 SD (p < 0.001). In contrast, regions with an intermediate pattern and those with scar did not improve. Restenosis or graft occlusion influenced functional outcome because regions with preoperative mismatch and successful long-term revascularization improved at follow-up (from -2.3 +/- 1.0 to -0.8 +/- 1.4 SD, p < 0.001), whereas wall motion did not change with recurrent hypoperfusion. Metabolic imaging added diagnostic information, particularly in regions with mild and moderate perfusion defects.

CONCLUSIONS

This imaging approach allows detection of viability in regions with myocardial dysfunction. Wall motion benefits most in myocardium with perfusion/metabolism mismatch and successful long-term revascularization.

Myocyte degeneration and cell death in hibernating human myocardium

OBJECTIVES

The aim of this study was to analyze the morphologic characteristics of myocyte degeneration leading to replacement fibrosis in hibernating myocardium by use of electron microscopy and immunohistochemical techniques.

BACKGROUND

Data on the ultrastructure and the cytoskeleton of cardiomyocytes in myocardial hibernation are scarce. Incomplete or delayed functional recovery might be due to variable degree of cardiomyocyte degeneration in hibernating myocardium.

METHODS

In 24 patients, regional wall motion abnormalities were analyzed by use of the centerline method before and 6 +/- 1 months after coronary artery bypass surgery. Preoperative technetium-99m sestamibi uptake was measured by single-photon emission computed tomography for assessing regional perfusion. Fluorine-18 fluorodeoxyglucose uptake was measured by positron emission tomography to assess glucose metabolism. Transmural biopsy specimens were taken during coronary artery bypass surgery from the center of the hypocontractile area of the anterior wall.

RESULTS

The myocytes showed varying signs of mild-to-severe degenerative changes and an increased degree of fibrosis. Immunohistochemical analysis demonstrated disruption of the cytoskeletal proteins titin and alpha-actinin. Electron microscopy of the cell organelles and immunohistochemical analysis of the cytoskeleton showed a similarity in the degree of degenerative alterations. Group 1 (n = 11) represented patients with only minor structural alterations, whereas group 2 (n = 13) showed severe morphologic degenerative changes. Wall motion abnormalities showed postoperative improvements, and nuclear imaging revealed a perfusion-metabolism mismatch without significant differences between the groups.

CONCLUSIONS

Long-term hypoperfusion causes different degrees of morphologic alterations leading to degeneration. Preoperative analysis of regional contractility and perfusion-metabolism imaging does not distinguish the severity of morphologic alterations nor the functional outcome after revascularization. The insufficient act of self-preservation in hibernating myocardium may lead to a progressive structural degeneration with an incomplete and delayed recovery of function after restoration of blood flow.

Clinical importance of viability assessment in chronic ischemic heart failure

BACKGROUND AND HYPOTHESIS

Revascularization has provided an effective treatment of depressed left ventricular function in patients with chronically ischemic or "viable" myocardium. Assessment of viable myocardium can be achieved by several noninvasive techniques including dobutamine stress echo or radionuclides such as flurodeoxyglucose (F18DG). F18DG uptake studies are based on the assumption that enhanced glucose uptake in areas of diminished blood flow provides evidence of viable myocardium. To determine the clinical utility of viability assessment in the management of chronic ischemic left ventricular dysfunction, we reviewed the findings and short-term treatment of a series of patients referred for heart failure evaluation who had subsequent F18DG uptake scans.

METHODS

We retrospectively reviewed 59 consecutive F18DG viability studies in a series of patients who had documented coronary artery disease and depressed left ventricular function. Single photon emission computerized tomography (SPECT) with F18DG was performed in the patients and these images were compared to SPECT images of resting myocardial perfusion using thallium, sestamibi, or teboroxime. Clinical decisions based on the results of these scans were obtained from chart review. Thirty-day mortality was determined from chart review or contact with the patient's physician. The patients were divided into those without and with F18DG uptake consistent with viable ischemic myocardium. Further analysis included subgroups of patients who were advised to undergo transplantation, revascularization, or to continue medical therapy.

RESULTS

Of 34 patients referred for cardiac transplantation, 18 had viable myocardium and 13 underwent revascularization. In the entire study group, 34 of 59 (58%) had evidence of viable myocardium and 29 had subsequent revascularization procedures. Thirty-day survival for all revascularization patients was 86%.

CONCLUSION

Assessment of myocardial viability with F18DG SPECT imaging in patients with ischemic left ventricular dysfunction led to a clinical decision for revascularization in approximately half the patients with severe coronary disease and left ventricular dysfunction who were evaluated for myocardial viability in our institution.

The clinical impact of thallium-201 reinjection for the detection of myocardial hibernation

Thallium-201 reinjection improves detection of hibernating myocardium in about 30%-50% of persisting defects. The main goal of cardiac revascularization techniques is amelioration of clinical symptoms such as angina and dyspnoea; however, improvement in regional and global pump function is an additional and important target. The aim of this study was to investigate whether fill-in in the reinjection study is correlated with improved contractile function after treatment (percutaneous transluminal coronary angioplasty/aortocoronary bypass surgery). We studied 32 patients with coronary heart disease and impaired regional wall motion (RWM). RWM and ejection fraction (EF) were assessed by analysing ventriculographic images using the centreline method (values in standard deviations from mean values found in a healthy control group). Three 201Tl single-photon emission tomographic studies (stress, redistribution and reinjection) were performed prior to revascularization and analysed using a bull s-eye scheme. Patients were divided into two groups (group FI-=no fill-in, n=16; group FI+=fill-in, n=16). Fifty-six percent of all patients showed persisting defects, and 56% of these defects showed fill-in after reinjection. Fill-in in our patient group was independent of the size of the persisting defects. After revascularization RWM increased significantly in group FI+ (from -1.9 to 0.0 SD, P<0.001) whereas group FI- showed no significant change (from -1.6 to -1.8 SD). EF increased from -4.3 preoperatively to -2.1 SD postoperatively in group FI+ and did not change significantly in group FI- (-2.5 to -3.2 SD). The predictive value of reinjection for improvement of RWM was 88%. It is concluded that fill-in in the 201Tl reinjection image can predict recovery of RWM and EF after revascularization and should be used in all patients with impaired RWM and persisting defects independent of their extent.

Assessing myocardial viability: correlation of myocardial wall motion abnormalities and pathologic Q waves with technetium 99m sestamibi single photon emission computed tomography

The clinical benefit of coronary revascularization depends largely on the viability of the myocardium that is perfused. To determine if the combination of electrocardiogram and left ventriculography findings could be used to predict viability, the presence of pathologic Q waves and wall motion abnormalities on contrast left ventriculography were correlated with findings on stress sestamibi scanning in 201 patients. Wall motion was abnormal in 51.5% of 103 Q regions; 30 (56.6%) of these had fixed sestamibi defects, and 22.6% had fully or partially reversible sestamibi defects. Q waves were associated with 43.4% of 122 regions with wall motion abnormality; 67.9% of these areas had fixed or partially fixed sestamibi defects. Wall motion abnormalities were present in 46.1% of 104 areas with fixed sestamibi defects. Although there was a statistically significant correlation among Q waves, left ventricular wall motion abnormalities, and stress sestamibi uptake (and various combinations of these data), the relatively large number (53.8%) of discordant findings (e.g., normal ventricular wall motion in the presence of fixed sestamibi defects) suggests that nonviability cannot be assumed without at least assessing both contractile left ventricular motion and metabolic (e.g., sestamibi scanning) function.

Dobutamine stress echocardiography predicts early wall motion improvement after elective percutaneous transluminal coronary angioplasty

In 24 patients with chronic coronary artery disease, dobutamine stress echocardiography (DSE) was performed within 2 days before and after successful elective percutaneous transluminal coronary angioplasty (PTCA) in a blinded fashion. Patients with ischemic response on DSE before PTCA had significant improvement in the global peak-dose DSE score index after PTCA (1.62 +/- 0.35 to 1.40 +/- 0.29, p < 0.001), whereas patients without ischemic response had no improvement. The positive and negative predictive values of pre-PTCA DSE on early myocardial ischemia relief after angioplasty were 93% and 80%, respectively. In patients showing contractility recruitment during low-dose dobutamine infusion in the DSE before PTCA, there was significant improvement in the global resting wall motion score index in the DSE after PTCA (1.48 +/- 0.43 to 1.34 +/- 0.33, p = 0.004), while patients without contractility recruitment showed no improvement. Again, the positive and negative predictive values of pre-PTCA DSE on early hibernation recovery following angioplasty were 80% and 89%, respectively. In conclusion, DSE in patients with chronic, stable coronary artery disease accurately predicts wall motion improvement after successful angioplasty, and the expected improvement is safely demonstrated early after the procedure.

Identification of hibernating myocardium by dobutamine stress echocardiography: comparison with thallium-201 reinjection imaging

The aim of this study was to determine the diagnostic value of dobutamine stress echocardiography (DSE) in the identification of hibernating myocardium and to compare its predictive accuracy with that of thallium-201 reinjection (RI) imaging. The subjects were 26 patients with wall motion abnormalities related to stenosed coronary arteries. DSE predicted postrevascularization improvement in 31 of 33 segments that were considered to be hibernating and identified 8 of 10 nonhibernating segments. In contrast, thallium-201 scintigraphy predicted all 33 hibernating segments when a post-RI myocardial thallium uptake in ischemic areas of > or = 50% of the maximum count in normal segments was used as a positive marker of myocardial viability. However, thallium studies predicted only 30 of 33 hibernating segments when thallium redistribution (RD) was used as a marker of viability in delayed or RI images. Among the 10 nonhibernating segments, an uptake of < 50% was observed in 4 segments and negative thallium-201 RD was observed in 5 segments. The sensitivity, specificity, and predictive values (PV) of DSE were 94%, 80%, positive PV 94%, and negative PV 80%, respectively. In contrast, the sensitivity, specificity, and PV of thallium-201 RI imaging were 100%, 40%, 85%, and 100% with uptake > or = 50% and 91%, 50% 86%, and 63% with RD, respectively. These results suggest that DSE may be useful for identifying hibernating myocardium and could therefore be helpful in selecting candidates for coronary revascularization.

From coronary artery disease to heart failure: role of the hibernating myocardium

Hibernating myocardium is defined as persistently impaired myocardial and left ventricular (LV) function at rest resulting from reduced myocardial blood flow. It may occur in unstable angina and chronic stable angina, acute myocardial infarction, and LV dysfunction and congestive heart failure. Recovery of the hibernating myocardium has clearly been shown to occur with the establishment of successful revascularization either by coronary bypass surgery or by percutaneous transluminal coronary angioplasty. It may be possible to show recovery of the viable myocardium by reducing myocardial oxygen demand and/or by increasing coronary blood flow with pharmaceutical agents.

Influence of reversible segmental left ventricular dysfunction on heart period variability in patients with one-vessel coronary artery disease

OBJECTIVES

This study evaluated the relation between reversible segmental left ventricular dysfunction and frequency domain measures of heart period variability in patients with coronary artery disease.

BACKGROUND

Heart period variability is frequently reduced in patients with coronary artery disease. However, the mechanisms of this reduction are still unclear.

METHODS

Echocardiographic left ventricular wall motion and frequency domain measures of heart period variability were evaluated in 32 patients with one-vessel coronary artery disease before and 16 to 24 days after successful percutaneous transluminal coronary angioplasty. Of these, 12 patients (Group A) had normal and 20 patients (Group B) had abnormal regional wall motion. A control group of 15 healthy subjects (Group C) underwent 24-h Holter recording twice at 2-week intervals to check for spontaneous variations.

RESULTS

At baseline, low and high frequency power were lower in Group B than in Groups A and C, whereas no difference was detectable in ultra low and very low frequency and total power. After coronary angioplasty, regional wall motion and frequency domain measures of heart period variability were unchanged in Group A. In Group B the mean (+/- SD) summed segment score improved from 17.1 +/- 3.6 to 12.8 +/- 2.0 (p < 0.01), and mean low and high frequency power (logarithmic units) increased from 6.14 +/- 0.23 to 6.35 +/- 0.34 (p < 0.01) and from 5.43 +/- 0.32 to 5.68 +/- 0.52 (p < 0.01), respectively. Furthermore, low and high frequency power, lower at baseline in Group B than in the other two groups, were comparable in the three groups after coronary angioplasty.

CONCLUSIONS

This study demonstrates that segmental left ventricular dysfunction is involved in determining sympathovagal imbalance in patients with one-vessel coronary artery disease; the reversal of left ventricular dysfunction by successful coronary angioplasty improves the heart period power spectrum. Thus, alterations in cardiac geometry influence the discharge of afferent sympathetic mechanoreceptors, contributing to the derangement in autonomic control of heart rate.

The detection of residual ischemia and stenosis in patients with acute myocardial infarction with dobutamine stress echocardiography

The aim of this study was to validate the usefulness of dobutamine stress echocardiography to detect residual ischemia and significant stenosis at the infarct zone in patients with acute myocardial infarction. Dobutamine stress echocardiography and stress thallium-201 single-photon emission computed tomography were performed on 40 consecutive patients 1 month after the onset of acute myocardial infarction. Dobutamine was infused incrementally, and wall motion score index at the infarct zone was calculated before and at peak dobutamine infusion. The patients were divided into three groups according to the change in wall motion at the infarct zone (improved, unchanged, or worsened wall motion, respectively). Tomographic thallium images of the infarct zone were assessed visually. All patients underwent quantitative coronary angiography, and significant stenosis was defined as 50% or greater stenosis. In patients who showed a persistent defect and significant stenosis of the infarct-related artery, resting thallium-201 single-photon emission computed tomography was performed when possible. There was a significantly higher incidence of residual ischemia at the infarct zone in patients with worsened wall motion (85%) and unchanged wall motion (63%) than in those with improved wall motion (8%). The residual stenosis of the infarct-related artery was more severe in patients with worsened or unchanged wall motion than in those with improved wall motion (worsened 82.6% +/- 17.7%, unchanged 93.7% +/- 12.6%, and improved 37.1% +/- 24.4%). The use of worsened or unchanged wall motion at the infarct zone for detecting significant residual stenosis of the infarct-related artery resulted in a sensitivity of 93% and a specificity of 91%, respectively. Worsened wall motion at the infarct zone by dobutamine stress echocardiography strongly suggests residual ischemia. Conversely, less ischemia and less significant stenosis are associated with improved wall motion. Unchanged wall motion suggests severe residual stenosis and sometimes indicates ischemia. It may reflect a hibernating myocardium, but the prognostic significance of this finding should be determined by revascularization.

Left ventricular dysfunction due to stunning and hibernation in patients

Left ventricular dysfunction is in most cases the consequence of myocardial ischemia. It may occur transiently during an attack of angina and usually it is reversible. It may persist over hours or even days in patients after an episode of ischemia followed by reperfusion, leading to the so-called condition of stunning. In patients with persistent limitation of coronary flow, left ventricular dysfunction may be present over months and years, or indefinitely in subjects with fibrosis, scar formation, and remodeling after myocardial infarction. However, chronic left ventricular dysfunction does not mean permanent or irreversible cell damage. Hypoperfused myocytes can remain viable but akinetic. This type of dysfunction has been called hibernating myocardium. The dysfunction due to hibernation can be partially or completely restored to normal by reperfusion. It is, therefore, important to clinically recognize a hibernating myocardium. In the present article we evaluate stunning and hibernation with respect to clinical decision making and, when possible, we refer to our ongoing clinical experience.

Beneficial effects of metoprolol in heart failure associated with coronary artery disease: a randomized trial

OBJECTIVES

This clinical trial was performed to determine the safety and clinical impact of titrated metoprolol therapy in patients with heart failure, documented coronary artery disease and a low ejection fraction.

BACKGROUND

Despite known cardiodepressant effects, long-term use of beta-adrenergic antagonists appears to be beneficial in patients with idiopathic dilated cardiomyopathy. However, this therapy has not been critically evaluated in patients with heart failure and coronary artery disease.

METHODS

In 50 patients with heart failure, known coronary artery disease and an ejection fraction < or = 0.40, we examined the impact of metoprolol therapy in a 6-month double-blind, placebo-controlled randomized trial, assessing the frequency of heart failure exacerbations and changes in symptoms (New York Heart Association functional class), ejection fraction and exercise duration. Placebo-treated patients who completed 6-month follow-up studies then underwent a trial with metoprolol therapy (crossover group).

RESULTS

Metoprolol was titrated to a mean maximal dose of 87 mg/day (range 25 to 100) without serious adverse reactions. During double-blind therapy, use of a beta-blocker was associated with a significant reduction in the number of hospital admissions (4% vs. 32%, p < 0.05), overall improved functional class (p = 0.02), increased ejection fraction (4 +/- 7% [mean +/- SD] compared with 0 +/- 6%, p < 0.05) and a greater increase in exercise duration (193 +/- 276 vs. 38 +/- 213 s with placebo, p < 0.01). Crossover outcome paralleled the favorable impact seen during randomized metoprolol therapy.

CONCLUSIONS

Cautious use of titrated metoprolol appears to be safe and beneficial when added to standard heart failure therapy in patients with dilated cardiomyopathy associated with coronary artery disease.

Echocardiography during infusion of dobutamine for identification of reversibly dysfunction in patients with chronic coronary artery disease

OBJECTIVES

The aim of this study was to test whether the contractile response of akinetic myocardium to low dose dobutamine is useful for detecting myocardial viability in patients with coronary artery disease and persistent left ventricular dysfunction.

BACKGROUND

In some patients with chronic coronary artery disease, persistent abnormalities of left ventricular wall motion can be reversed by successful coronary artery bypass surgery. Thus, identification of potentially reversible dysfunction has important therapeutic and prognostic implications. Echocardiography during infusion of low dose dobutamine can detect viable myocardium in patients after thrombolytic therapy. However, there is no detailed information on the use of this method in patients with chronic left ventricular dysfunction without reperfusion.

METHODS

We studied 33 selected patients with angiographically proved coronary artery disease and persistent left ventricular dysfunction. The effect of dobutamine infusion (5 micrograms/kg body weight per min, followed by 10 micrograms/kg per min) on left ventricular wall motion was evaluated by transthoracic echocardiography before coronary artery bypass grafting and compared with that obtained immediately after the operation (evaluated by intraoperative epicardial echocardiography) and both 2 weeks and 3 months later. Left ventricular wall motion was analyzed qualitatively by dividing the left ventricle into 16 segments, and a score was assigned to each region.

RESULTS

Before coronary artery bypass surgery, 314 segments were akinetic. Of these, 183 became normokinetic immediately after revascularization, and 15 became hypokinetic. Dobutamine infusion was able to predict improvement in 178 of the 205 segments that recovered function after revascularization (sensitivity 86.8%) and to identify 89 of the 109 segments that did not recover postoperatively (specificity 81.6%). Mean (+/- SD) segment scores were 2.24 +/- 0.35 at baseline, 1.49 +/- 0.34 (p < 0.001) after dobutamine infusion, 1.51 +/- 0.38 (p < 0.001) immediately after and 1.51 +/- 0.38 (p < 0.001) 2 weeks after coronary artery bypass and 1.55 +/- 0.37 (p < 0.001) at 3-month follow-up.

CONCLUSIONS

Echocardiography during infusion of low dose dobutamine is a safe and accurate method for identifying reversible dysfunctioning myocardium and predicts early reversibility of wall motion after surgical revascularization in selected patients with coronary artery disease with chronic left ventricular dysfunction.

Effects of coronary angioplasty on left ventricular function

It is well known that myocardial revascularization after successful coronary bypass surgery results in improved left ventricular function. Coronary angioplasty also results in successful revascularization, favorably affecting both stunned and hibernating myocardium. We studied 22 patients with chronic stable angina who underwent successful angioplasty for an isolated narrowing of the proximal or midportion of the left anterior descending artery. These patients also performed isometric exercises before and after angioplasty, which can be used to characterize left ventricular function. Revascularization after angioplasty induced an immediate improvement in left ventricular function in those patients with dysfunction secondary to hibernating myocardium. Further studies are needed to assess the possibility of the myocardial stunning phenomenon occurring after angioplasty in those patients without left ventricular improvement.

Silent ischemia and loss of reversible myocardial dysfunction following myocardial infarction

Sixty-seven asymptomatic patients were enrolled after a first uncomplicated myocardial infarction (MI) so as to study the relevance of reversible myocardial dysfunction in determining left ventricular function soon after the acute episodes and 12 months later. Moreover, the potential role of silent ischemia in conditioning the evolutive aspects of contractile dysfunction has been investigated. Postextrasystolic potentiation during two-dimensional echocardiographic (2-D echo) monitoring has been used to detect the presence of viable myocardium in asynergic myocardial segments. Results of electrocardiographic (ECG) ambulatory monitoring at predischarge determined patient groups: Group A included 49 patients without ST changes during monitoring, while Group B included 18 patients with silent ischemia. Incidence of reversible myocardial dysfunction was similar in the two study groups (82 vs. 86%, p = NS). Group B patients were older (59.6 +/- 6.7 vs. 50.6 +/- 10.6 years, p < 0.015) and had lower ejection fractions (EFs, 43.4 +/- 6.4% vs. 51.2 +/- 8.3%, p = 0.026) and higher at-rest wall-motion scores (WMSs, 11.4 +/- 5.9 vs. 7.2 +/- 3.8, p = 0.019). Left ventricular end-diastolic volume (LVEDV) and potentiated WMS did not differ. At 1-year examination, Group B patients exhibited a greater LVEDV index (96 +/- 6.5 vs. 70.7 +/- 14 ml/m2, p < 0.002) with a worsening both in rest and in potentiated wall-motion score index (12.8 +/- 4.6 vs. 5.3 +/- 1.8, p < 0.001; 9.2 +/- 3.6 vs. 4.8 +/- 2.2, p < 0.001, respectively). Left ventricular EF remained significantly depressed in Group B patients (42 +/- 8.7% vs. 55.5 +/- 8.1%, p < 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Dobutamine stress echocardiography identifies hibernating myocardium and predicts recovery of left ventricular function after coronary revascularization

BACKGROUND

The identification of hibernating myocardium is important in selecting patients who will benefit from coronary revascularization. This study was performed to determine whether dobutamine stress echocardiography (DSE) could identify hibernating myocardium and predict improvement in regional systolic wall thickening after revascularization.

METHODS AND RESULTS

DSE was performed in 49 consecutive patients with multivessel coronary disease and depressed left ventricular function. Contractile reverse during DSE was defined by the presence of two criteria: (1) improved systolic wall thickening in at least two adjacent abnormal segments and (2) > or = 20% improvement in regional wall thickening score. Postoperative echocardiograms were evaluated for improved regional wall thickening in 25 patients at least 4 weeks after successful coronary revascularization. All studies were read in blinded fashion. Contractile reserve during DSE was present in 24 (49%) of 49 patients. The presence or absence of contractile reserve on preoperative DSE predicted recovery of ventricular function in the 25 patients who underwent successful revascularization. Thus, 9 of 11 patients with contractile reserve had improved systolic wall thickening after revascularization (hibernating myocardium), whereas 12 of 14 patients without contractile reserve did not improve (P = .003).

CONCLUSIONS

Dobutamine stress echocardiography provides a simple, cost-effective, and widely available method of identifying hibernating myocardium and predicting improvement in regional left ventricular wall thickening after coronary revascularization. This technique may be clinically valuable in the selection of patients for coronary revascularization.

The noninvasive assessment of myocardial viability

The major objective of noninvasive imaging for detection of myocardial viability is to assist in the improved selection of patients with coronary artery disease and severe left ventricular dysfunction who would benefit most from revascularization. The techniques most commonly used to identify viable myocardium are thallium-201 (201Tl) scintigraphy, positron emission tomography (PET) using a flow tracer in combination with a metabolic tracer, technetium-99m (99mTc) sestamibi imaging, and dobutamine echocardiography. On stress 201Tl scintigraphy, asynergic regions showing normal thallium uptake, an initial defect with delayed redistribution at 3-4 h, late redistribution at 24 h, or defect reversibility after reinjection of a second dose of 201Tl at rest all suggest preserved viability. The greater the final uptake of 201Tl in areas of regional myocardial dysfunction preoperatively, the greater the improvement in ejection fraction after coronary revascularization. Demonstration of uptake of fluoro-18 deoxyglucose (FDG) in regions of diminished blood flow on PET imaging also correlates well with improved systolic function after revascularization. 99mTc sestamibi may also be useful for assessment of myocardial viability, particularly after thrombolytic therapy for acute myocardial infarction. Dobutamine echocardiography has good positive predictive value for viability determination, but absence of systolic thickening in an akinetic zone in response to intravenous infusion of the drug may still be associated with viable myocardium in 25-50% of segments. Of all the techniques cited above, quantitative resting 201Tl scintigraphy may be the best approach for distinguishing between viable and irreversibly injured myocardium.

Myocardial viability in patients with Q wave myocardial infarction and no residual ischemia

BACKGROUND

Coronary revascularization in patients with persistent angina after myocardial infarction reduces the incidence of recurrent angina pectoris and myocardial infarction and improves left ventricular function. The results of revascularization after a Q wave myocardial infarction when there is no residual ischemia may depend on myocardial viability.

METHODS AND RESULTS

To determine whether there was viable myocardium in the infarct area in the absence of clinical and scintigraphic evidence of myocardial ischemia, 15 asymptomatic patients with a Q wave myocardial infarction, no redistribution on stress 201Tl test, and single-vessel disease (greater than 70% stenosis) with persistent anterograde blood flow were randomized to percutaneous transluminal coronary artery angioplasty (PTCA) or conservative medical treatment. After 2 months of follow-up, mean coronary blood flow measured by Doppler catheter in the infarct-related artery was higher in the PTCA treatment group (33 +/- 6 ml/min, n = 8) than in the conservative treatment group (16 +/- 4 ml/min, n = 7; p less than 0.05 between groups). The 201Tl pathological-to-normal ratios measured on postexercise images did not change in patients treated conservatively during the follow-up period (delta = +1.1 +/- 2.2%; NS from baseline) but increased significantly in patients treated by PTCA (delta = +8.5 +/- 2.3%; p less than 0.01 from baseline; p less than 0.05 between groups). Segmental wall motion improved on left ventricular angiography 2 months after PTCA (delta = +11.5 +/- 2.2%; p less than 0.001 from baseline) significantly more than in the conservative treatment group (delta = +4.1 +/- 1.4%; p less than 0.05 between both groups). Improvements of 201Tl ratios and segmental wall motion indexes correlated significantly (r = 0.73, p = 0.002). The mild improvement of global left ventricular ejection fraction measured in the PTCA treatment group did not differ significantly from changes in the conservative treatment group.

CONCLUSIONS

Successful angioplasty of the stenotic infarct artery in patients with a Q wave myocardial infarction and no residual ischemia improved coronary flow, 201Tl uptake in the infarct area, and regional wall motion. Therefore, myocardial viability may last several weeks, as long as residual blood flow persists in the infarct-related artery. Optimal assessment of viability by imaging techniques should identify patients who are most likely to benefit from revascularization.

Frequency and predictors of left ventricular segmental dysfunction in patients with recent rest angina

The relation between coronary artery lesion morphology and associated segmental left ventricular (LV) dysfunction in patients with unstable angina is unclear. Fifty-two patients with angina occurring at rest who underwent cardiac catheterization within 3 days of the last episode of pain and had no enzymatic evidence for myocardial necrosis were evaluated. Coronary artery narrowings deemed responsible for the ischemic episodes were analyzed with regard to the artery involved, maximal diameter of the narrowing, presence of thrombus, and complex appearance. Time to catheterization, age, sex and electrocardiographic evidence of ischemia were also noted. Segmental LV dysfunction in the territory supplied by the "culprit lesion" was present in 58% of patients. It occurred significantly more often with lesion location in the left anterior descending coronary artery, and was less frequent with lesions in the left circumflex and ramus coronary arteries. Ischemic electrocardiographic changes were more sensitive in predicting LV dysfunction with culprit lesion location in the left anterior descending or right coronary artery. LV dysfunction could not be predicted by any other parameter analyzed. It is concluded that postischemic LV dysfunction occurs frequently in rest angina, especially when the severest narrowing is in the left anterior descending coronary artery.

Recovery of myocardial function in the hibernating heart

Impaired contractile performance at rest is not necessarily due to irreversible tissue damage but may relate to the "hibernating" myocardium. Hibernating myocardium has been defined as potentially reversible, chronic contractile dysfunction during prolonged, painless ischemia. The extent and time course of functional recovery after restoration of flow is of major importance for clinical decision making. The existence of hibernating myocardium was first documented in patients following bypass surgery. Angiographic studies in patients undergoing coronary angioplasty revealed immediate recovery of global and regional systolic, as well as diastolic, function after revascularization. Subgroup analysis showed an improvement in patients without previous myocardial infarctions and in those with non-Q-wave infarctions, but a benefit was not consistently seen in patients with transmural infarctions. A further improvement of systolic function after 15 weeks suggests a biphasic course of recovery. Prospective studies must clarify whether the potential for improvement in function constitutes an indication for revascularization independent of clinical symptoms.

Effect on global and regional left ventricular functions by percutaneous transluminal coronary angioplasty in the chronic stage after myocardial infarction

Data are reported on 145 consecutive patients with prior myocardial infarction who had successful percutaneous transluminal coronary angioplasty (PTCA) of the infarct-related artery (5 +/- 6 months after infarction), and left ventricular (LV) angiograms before PTCA and during follow-up (7 +/- 4 months). There was a significant long-term improvement in LV function, ejection fraction increased from 60 +/- 13% to 64 +/- 13% (p less than 0.001), and regional wall motion abnormalities decreased by 40%. Multivariate discriminant analysis identified reduced LV function and a high degree of stenosis before PTCA as predictors for improvement in LV function (ejection fraction less than 60%: ejection fraction from 48 +/- 9% to 57 +/- 14%, p less than 0.001; and stenosis greater than or equal to 90%: ejection fraction from 59 +/- 15% to 66 +/- 14%, p = 0.003). Restenosis greater than or equal to 90% in patients with initial stenosis less than 90% decreased ejection fraction from 59 +/- 16% to 51 +/- 14% (p less than 0.05). Other factors tested (treatment of infarction by thrombolysis, time between infarction and PTCA, and severity of angina pectoris) had no effect on long-term changes in LV function. It is concluded that successful elective PTCA of a high-grade stenosis in an infarct-related artery may improve LV ejection fraction and regional wall motion abnormalities, especially in patients with impaired LV function.

Continuous on-line monitoring of left ventricular function with a new nonimaging detector:validation and clinical use in the evaluation of patients post angioplasty

A new miniaturized nonimaging radionuclide detector (Cardioscint, Oxford, England) was evaluated for the continuous on-line assessment of left ventricular function. This cesium iodide probe can be placed on the patient's chest and can be interfaced to an IBM compatible personal computer conveniently placed at the patient's bedside. This system can provide a beat-to-beat or gated determination of left ventricular ejection fraction and ST segment analysis. In 28 patients this miniaturized probe was correlated against a high resolution gamma camera study. Over a wide range of ejection fraction (31% to 76%) in patients with and without regional wall motion abnormalities, the correlation between the Cardioscint detector and the gamma camera was excellent (r = 0.94, SEE +/- 2.1). This detector system has high temporal (10 msec) resolution, and comparison of peak filling rate (PFR) and time to peak filling (TPFR) also showed close agreement with the gamma camera (PFR, r = 0.94, SEE +/- 0.17; TPFR, r = 0.92, SEE +/- 6.8). In 18 patients on bed rest the long-term stability of this system for measuring ejection fraction and ST segments was verified. During the monitoring period (108 +/- 28 minutes) only minor changes in ejection fraction occurred (coefficient of variation 0.035 +/- 0.016) and ST segment analysis showed no significant change from baseline. To determine whether continuous on-line measurement of ejection fraction would be useful after coronary angioplasty, 12 patients who had undergone a successful procedure were evaluated for 280 +/- 35 minutes with the Cardioscint system.(ABSTRACT TRUNCATED AT 250 WORDS)

Myocardial perfusion-contraction matching. Implications for coronary heart disease and hibernation

Experimental studies demonstrate that short-term regional perfusion-contraction matching, in which the energy demands of regional myocardial contraction are reduced to match the diminished myocardial substrate supply, occurs during states of low coronary blood flow under resting conditions and during exercise-induced ischemia. This phenomenon is rapidly reversible and appears to occur in several clinical settings. Sustained perfusion-contraction matching is observed in states of partial experimental ischemia of intermediate duration lasting several hours. This condition might be called short-term hibernation and resembles clinical conditions such as unstable angina pectoris or myocardial infarction with some residual perfusion in which the contractile defect can be improved by reperfusion provided the ischemia is not severe enough to cause transmural necrosis. Such experimental and clinical observations may or may not relate to the setting of regional dysfunction at rest in patients with chronic coronary heart disease, in whom manifestations of acute ischemia may be absent but improvement of wall motion abnormalities occurs after CABG or balloon angioplasty. This condition may constitute the hypothetical state of chronic myocardial hibernation, for which tentative evidence exists from metabolic and perfusion studies using PET. Whether such a condition of prolonged perfusion-contraction matching might be associated with adaptive processes that could allow its persistence for long periods without manifest ischemia remains to be investigated.

Evidence of hibernating myocardium by a new transesophageal echocardiographic technique

Reversal of resting wall motion abnormalities after successful coronary angioplasty were documented in a patient with the use of a novel approach to stress testing. Transesophageal stress echocardiography utilizes transesophageal atrial pacing to provoke myocardial ischemia while the left ventricular contractility is being monitored by means of transesophageal echocardiography. The potential use of this technique is illustrated in this report.