Identification of transient and persistent segmental wall motion abnormalities in patients with unstable angina by two-dimensional echocardiography

Detection of coronary artery disease using multi-modal feature fusion and hybrid feature selection

Objective: Coronary artery disease (CAD) is a common fatal disease. At present, an accurate method to screen CAD is urgently needed. This study aims to provide optimal detection models for suspected CAD detection according to the differences in medical conditions, so as to assist physicians to make accurate judgments on suspected CAD patients.Approach: Electrocardiogram (ECG) and phonocardiogram (PCG) signals of 32 CAD patients and 30 patients with chest pain and normal coronary angiograms (CPNCA) were simultaneously collected for this paper. For each subject, the ECG and PCG multi-domain features were extracted, and the results of Holter monitoring, echocardiography (ECHO), and biomarker levels (BIO) were obtained to construct a multi-modal feature set. Then, a hybrid feature selection (HFS) method was developed using mutual information, recursive feature elimination, random forest, and weight of support vector machine to obtain the optimal feature subset. A support vector machine with nested cross-validation was used for classification.Main results: Results showed that the Holter model achieved the best performance as a single-modal feature model with an accuracy of 82.67%. In terms of multi-modal feature models, PCG-Holter, PCG-Holter-ECHO, PCG-Holter-ECHO-BIO, and ECG-PCG-Holter-ECHO-BIO were the optimal bimodal, three-modal, four-modal, and five-modal models, with accuracies of 90.38%, 91.92%, 95.25%, and 96.67%, respectively. Among them, the ECG-PCG-Holter-ECHO-BIO model, which was constructed by combining ECG and PCG signals features with Holter, ECHO, and BIO examination results, achieved the best classification results with an average accuracy, sensitivity, specificity, and F1-measure of 96.67%, 96.67%, 96.67%, and 96.64%, respectively.Significance: The study indicated that multi-modal feature fusion and HFS can obtain more effective information for CAD detection and provide a reference for physicians to diagnose CAD patients.

Intraoperative assessment of transient and persistent regional left ventricular wall motion abnormalities in patients undergoing coronary revascularization surgery using real time three-dimensional transesophageal echocardiography: A prospective observational study

OBJECTIVE

To evaluate the feasibility of intraoperative real time three-dimensional echocardiography (RT3DE) for identification and quantification of transient and persistent regional wall motion abnormalities (RWMAs) in patients with ischemic cardiomyopathy undergoing coronary artery bypass grafting (CABG).

DESIGN

A prospective observational study SETTING: Single-center study in an academic tertiary care hospital PARTICIPANTS: A series of 42 patients undergoing elective CABG over a 2-year period were included.

INTERVENTION

After induction of anesthesia, a comprehensive transesophageal echocardiography (TEE) examination was performed to evaluate regional wall motion using two-dimensional wall motion score index (WMSI) and RT3D echocardiographic parameters at three specific time points during the operative phase.

MEASUREMENTS AND MAIN RESULTS

The 3D assessment of LV function was based on the quantification of change in LV chamber volume over time from each segment excursion. Patients were divided into two groups and subgroups based on TEE findings. There was significant mechanical dyssynchrony in patients with RWMAs (WMSI > 1; systolic dyssynchrony index [SDI] = 7.0 ± 3.66) as compared to the patients having normal wall motion (WMSI = 1; SDI = 2.0 ± 0.95; P = .001). Patients with contractile dysfunction were found to have low values of segmental excursion and high values of negative excursion on parametric imaging. Persistent RWMAs due to hibernating myocardium showed significant resolution of mechanical dyssynchrony after revascularization. Parametric imaging could detect transient RWMAs due to stunning and graft dysfunction. Early activating segments (EAS) on "timing bull's-eye" may represent hypercontractile segments and may influence inotrope administration.

CONCLUSION

The RT3DE is a valuable modality for precise quantification of regional wall motion during revascularization procedure.

Postischemic infusion of sivelestat sodium hydrate, a selective neutrophil elastase inhibitor, protects against myocardial stunning in swine

PURPOSE

It seems controversial whether or not neutrophil elastase inhibitors are effective in attenuating myocardial ischemia/reperfusion injury. We thus investigated possible protective effects of sivelestat, a neutrophil elastase inhibitor, against myocardial stunning i.e., prolonged myocardial dysfunction following a brief episode of ischemia.

METHODS

Swine were divided into control group (group C), low-dose sivelestat group (group L), and high-dose sivelestat group (group H) (n = 7 for each group). All the swine were subjected to myocardial ischemia through ligation of the left anterior descending (LAD) coronary artery for 12-min, followed by 90-min reperfusion. Sivelestat was infused intracoronally at concentrations of 6 and 60 mg/ml throughout the reperfusion period in groups L and H, respectively, while saline was infused in the group C. Heart rate (HR), left ventricular developed pressure (LVdP), maximum rate of LVdP (LVdP/dt (max)), LV end-diastolic pressure (LVEDP), percentage of segment shortening (%SS, an index of regional myocardial contractility), and coronary venous interleukin-6 concentration in the LAD perfusion area were measured before ischemic induction and during reperfusion.

RESULTS

The ischemia/reperfusion insult did not cause any significant changes in HR, LVdP, LVdP/dt (max), and LVEDP in all groups. However, it significantly reduced %SS in the LAD perfusion area and increased the interleukin-6 concentration in group C. Those changes in %SS and the interleukin-6 concentration were both greatly attenuated, but not prevented, in groups L and H.

CONCLUSION

Sivelestat presumably attenuates myocardial contractile dysfunction due to myocardial stunning by inhibiting neutrophil-derived elastase, thereby suppressing the production of interleukin-6 in activated neutrophils.

Detecting patients with acute coronary syndrome in the chest pain center of the emergency department with cardiac magnetic resonance imaging

Managing patients with chest pain in the Emergency Department (ED) remains a challenge where advanced imaging technology may play a role. Detecting acute coronary syndrome in the emergency department with cardiac magnetic resonance imaging (MRI) was studied in 161 consecutive chest pain patients in a prospective observational study. Patients with ST elevation myocardial infarction were excluded from study participation. All patients underwent MRI study when hemodynamically stable, free of ongoing chest pain, and within 12 hours of symptoms onset. The MRI study takes an average of 38 +/- 12 minutes and included global and regional left ventricular function, myocardial perfusion, and gadolinium-enhanced myocardial infarction detection. The sensitivity and specificity for detecting acute coronary syndrome was 84% and 85% by MRI. The MRI was more sensitive than strict electrocardiogram (ECG) criteria for ischemia (P < 0.001) and peak troponin-I (P < 0.001). The MRI was more specific than an abnormal ECG (P < 0.001). Multivariate logistic regression analysis showed MRI was the strongest predictor of acute coronary syndrome and added diagnostic value over clinical parameters (P < 0.001). A nonstress cardiac MRI performed in this urgent clinical setting is safe and exhibited diagnostic operating characteristics suitable for triage of patients with chest pain in the emergency department. MRI accurately detected a high fraction of patients with acute coronary syndrome including patients with enzyme negative unstable angina.

Improved risk stratification in unstable angina: identification of patients at low risk for in-hospital cardiac events by admission echocardiography

BACKGROUND

Current protocols for risk stratification of patients with acute chest pain syndromes rely on clinical parameters and are oriented toward identification of patients at high risk for adverse cardiac events; however, this paradigm for risk stratification does not adequately address the observation that adverse cardiac events are relatively uncommon in this population. In an era of cost containment, consideration also should be given to identification of patients at low risk for adverse cardiac events, who may be safely discharged without expensive inpatient hospitalization.

HYPOTHESIS

The purpose of this study was to develop echocardiographic predictors that identify unstable angina patients at low risk for adverse cardiac events and that discriminate between low- and high-risk patients.

METHODS

The predictive accuracy of retrospectively determined echocardiographic predictors were compared in a population-based sample of 66 consecutive unstable angina patients undergoing echocardiography within 24 h of admission.

RESULTS

Echocardiographic predictors of adverse events included wall motion score index > or = 0.2, ejection fraction < or = 40%, and mitral regurgitation severity > 2. One or more echocardiographic predictors of adverse events were present in 32 patients (48%). A composite echocardiographic predictor of adverse events was specific, had a high positive predictive value for the identification of high-risk patients, and discriminated between unstable angina patients at high and low risk for adverse cardiac events.

CONCLUSION

Echocardiographic predictors of adverse events are specific and discriminate between unstable angina patients at high and low risk for adverse cardiac events.

Mechanisms leading to reversible mechanical dysfunction in severe CAD: alternatives to myocardial stunning

Patients with severe chronic coronary artery disease (CAD) exhibit a highly altered myocardial pattern of perfusion, metabolism, and mechanical performance. In this context, the diagnosis of stunning remains elusive not only because of methodological and logistic considerations, but also because of the pathophysiological characteristics of the myocardium of these patients. In addition, a number of alternative pathophysiological mechanisms may act by mimicking the functional manifestations usually attributed to stunning. The present review describes three mechanisms that could theoretically lead to reversible mechanical dysfunction in these patients: myocardial wall stress, the tethering effect, and myocardial expression and release of auto- and paracrine agents. Attention is focused on the role of these mechanisms in scintigraphically “normal” regions (i.e., regions usually showing normal perfusion, glucose metabolism, and cellular integrity as assessed by nuclear imaging techniques), in which stunning is usually considered, but these mechanisms could also operate throughout the viable myocardium. We hypothesize that reversion of these three mechanisms could partially explain the unexpected functional benefit after reperfusion recently highlighted by high-spatial-resolution imaging techniques.

Asynchrony of Left Ventricular Systolic Performance After the First Acute Myocardial Infarction in Patients with Narrow QRS Complexes: Doppler Tissue Imaging Study

BACKGROUND

Left ventricular (LV) electromechanical delay results in asynchronized contraction. However, it is not known if the presence of cardiac diseases without QRS prolongation may result in interventricular or intraventricular asynchrony. Doppler tissue imaging is now established for detecting regional contractile abnormalities and asynchrony in the LV.

OBJECTIVES

The aim of the study was to assess the degree of LV asynchrony after the first acute myocardial infarction (AMI) in patients with a narrow QRS complex using Doppler tissue imaging and correlate this with the site and extent of the infarction.

METHODS

Echocardiography with Doppler tissue imaging was performed within 1 week of AMI in 155 patients and compared with 50 age- and sex-matched healthy volunteers. Regional myocardial velocities were assessed at the 4 mitral annular sites, and the corresponding systolic velocity (Sm), early diastolic velocity (Em), time to peak Sm (Ts), and time to peak Em (Te) were measured. To assess LV synchronicity, SDs of Ts (Ts-SD) and Te (Te-SD) of all the 4 mitral annular sites were computed. Location and size of infarct were confirmed by echocardiographic wall-motion score index.

RESULTS

QRS complex duration was normal in all patients. Wall-motion score index was significantly higher in patients with anterior than inferior AMI (2.02 +/- 0.34 vs 1.24 +/- 0.21, P < .001). Ts-SD was significantly higher in patient than control group, and in patients with anterior than inferior AMI (38.21 +/- 2.59 vs 21.06 +/- 0.52 milliseconds and 43.18 +/- 3.77 vs 33.24 +/- 1.4 milliseconds, respectively, P < .001 for each), whereas Te-SD did not differ significantly among these groups (20.35 +/- 1.77 vs 18.17 +/- 1.14 milliseconds and 21.6 +/- 1.35 vs 19.1 +/- 1.11 milliseconds, respectively, P > .05 for each). A strong positive correlation was detected between LV systolic asynchrony (Ts-SD) and wall-motion score index (r = .77), LV mass (r = .67), LV end-systolic dimension (r = .65), and LV end-diastolic dimension (r = .5). The correlation was negative with LV ejection fraction (r = -.70) and Sm (r = -.6); the correlation was weak with Em (r = -.33) (P < .001 for all). In multivariate logistic regression analysis, infarct size was found to be the most independent predictor for systolic asynchrony (odds ratio 3.59, 95% confidence interval [1.43-9.33], P < .001).

CONCLUSION

AMI has a significant impact on regional myocardial contractility and LV systolic (but not diastolic) synchronicity early in the course even in the absence of QRS widening or bundle branch block. The degree of LV systolic asynchrony is greater with anterior than inferior AMI and mainly determined by infarct size.

Left ventricular systolic asynchrony after acute myocardial infarction in patients with narrow QRS complexes

BACKGROUND

The aim of the study was to assess the degree of left ventricular (LV) asynchrony after myocardial infarction (MI) in patients with a narrow QRS complex using tissue Doppler imaging (TDI) and correlate this with the site and extent of the infarction measured by contrast-enhanced magnetic resonance imaging (Ce-MRI).

METHODS

Echocardiography with TDI and Ce-MRI was performed within 6 days of acute MI in 47 patients and compared with 69 age-matched healthy volunteers. Regional myocardial velocities were assessed in 12 segments, and the corresponding systolic velocity (Sm), early diastolic velocity (Em), as well as the time to peak Sm (Ts) and time to peak Em (Te) were measured. To assess LV synchronicity, SDs of Ts (Ts-SD) and Te (Te-SD) of all 12 segments were computed. Location and size of infarct were confirmed by Ce-MRI with a 16-segment model.

RESULTS

All the patients had a normal QRS complex duration. The Ts-SD was significantly prolonged in the MI group when compared with controls (42.2 +/- 13.7 vs 18.0 +/- 7.0 milliseconds, P < .001). The Ts-SD was longer in patients with anterior than inferior MI (46.8 +/- 13.9 vs 34.6 +/- 8.5 milliseconds, P = .002). Stepwise multiple regression analysis revealed that infarct size was the main independent predictor of systolic asynchrony ( B = 0.79, 95% CI 0.75-1.23, P < .001). Asynchrony was not related to the transmurality of the infarction.

CONCLUSIONS

Myocardial infarction has a significant impact on LV synchronicity even in those with a narrow QRS complex. The degree of LV systolic asynchrony is mainly determined by the infarct size and not transmurality.

Assessment of Myocardial Viability with Dobutamine Stress Echocardiography in Patients with Ischemic Left Ventricular Dysfunction

The noninvasive assessment of myocardial viability has proved clinically useful for distinguishing hibernating and/or stunned myocardium from irreversibly injured myocardium in patients with chronic ischemic heart disease or recent myocardial infarction, with marked regional and/or global left ventricular (LV) dysfunction. Noninvasive techniques utilized for the detection of viability in asynergic myocardial regions include positron emission tomographic imaging of residual metabolic activity, single photon emission tomography (SPECT) of radioisotope uptake with thallium-201, low-dose dobutamine echocardiography assessment of inotropic reserve and myocardial contrast echocardiography for evaluation of microvascular integrity. Of these techniques, dobutamine stress echocardiography is a safe, widely available and relatively inexpensive modality for the identification of myocardial viability for risk stratification and prognosis. Low-dose dobutamine response can accurately predict improvement of dysfunctional yet viable myocardial regions, and thus identify a subset of patients whose LV function will improve following successful coronary revascularization.

Diagnosis of multivessel coronary vasospasm by detecting postischemic regional left ventricular delayed relaxation on echocardiography using color kinesis

BACKGROUND

It is not known whether multivessel coronary spasm occurs spontaneously in patients who have variant angina (VA) with demonstrated multivessel spasm induced by intracoronary injection of acetylcholine (ACh). Regional left ventricular (LV) diastolic dysfunction or wall motion abnormality may persist after an episode of coronary vasospasm. Color kinesis (CK) is a recent development that facilitates the echocardiographic evaluation of regional diastolic wall motion.

METHODS AND RESULTS

Regional diastolic wall motion was evaluated using CK in 26 patients with VA within 1 week of the last episode of angina. The LV segmental filling fraction in the short-axis view during the first 30% of the diastolic filling time, expressed as a percentage, was used to objectively identify postischemic diastolic endocardial motion asynchrony. Diastolic asynchrony or regional LV delayed relaxation was noted in all 26 (100%) patients and in 14 (54%) it was detected in multiple vascular territories, suggesting multivessel spasm. Multivessel spasm was induced by ACh in 11 (79%) of the patients with suspected multivessel spasm by CK. In 11 (92%) of the 12 patients with multivessel spasm induced by ACh multiple regions of delayed relaxation had been noted by CK. The regions of delayed relaxation were largely consistent with the territories perfused by the arteries reacting to ACh (sensitivity: 96%, specificity: 91%).

CONCLUSION

ACh induced spasm in the same coronary arteries as those perfusing the regions with delayed diastolic wall motion detected by CK in most of the patients with VA, suggesting that multivessel spasm does occur spontaneously in patients with susceptible arteries.

Diagnosis of coronary vasospasm by detection of postischemic regional left ventricular delayed relaxation using echocardiographic evaluation with color kinesis

BACKGROUND

Coronary vasospasm has been diagnosed by invasive provocative procedures during coronary arteriography. It would be useful to have a reliable, noninvasive, and safe diagnostic method for coronary vasospasm. Regional left ventricular (LV) diastolic dysfunction may persist without systolic dysfunction after an episode of coronary vasospasm. Color kinesis (CK) has been recently developed to facilitate the echocardiographic evaluation of regional wall motion.

HYPOTHESIS

Color kinesis may be useful for diagnosis of coronary vasospasm by detection of postischemic regional LV diastolic wall motion abnormality.

METHODS

Fifty-one consecutive patients with the last chest symptom within 2 weeks (4 +/- 3 days) were studied echocardiographically. Regional fractional area change during the first 30% of LV filling time in percentage of the segmental end-diastolic area change (CK diastolic index) was used to identify diastolic endocardial motion asynchrony.

RESULTS

After diagnostic coronary arteriography with spasm provocation, 26 patients were diagnosed with coronary spastic angina (CSA) and the other 25 with chest pain syndrome (CPS). Regional delayed relaxation (CK-diastolic index < or = 50%) or diastolic asynchrony had been observed in at least one region in 25 (96%) patients with CSA, whereas it had been noted in 2 (8%) patients with CPS. In 17 (65%) patients with CSA, it had been detected in multiple vascular territories, suggesting multivessel spasm. The diastolic asynchrony disappeared in CSA after a month of angina-free period.

CONCLUSION

Analysis of CK images allows identification of regional LV delayed relaxation or diastolic asynchrony in patients with coronary vasospasm, differentiating them from patients with chest pain syndrome (sensitivity 96%, specificity 92%).

Hibernation, Stunning, and Preconditioning: Historical Perspective, Current Concepts, Clinical Applications, and Future Implications

Despite considerable advances, coronary artery disease is the leading cause of morbidity and mortality in the Western world. The development of effective therapeutic strategies for protecting the myocardium from ischemia would have major impact on patients with coronary artery disease. It is now accepted that patients with coronary artery disease can experience prolonged regional ischemic dysfunction that does not necessarily arise from irreversible tissue damage, and to some extent, can be reversed by restoration of blood flow. The initial stages of dysfunction are probably caused by chronic stunning that can be reversed after revascularization, resulting in rapid and complete functional recovery. On the other hand, the more advanced stages of dysfunction likely correspond to chronic hibernation. After revascularization, functional recovery will probably be quite delayed and mostly incomplete. Over the past decade, the possibility that an innate mechanism of myocardial protection might be inducible in the human heart has generated considerable excitement. In the last two decades, there was phenomenal growth in the understanding of the mechanism known as ischemic preconditioning that is responsible for the innate myocardial protection. Continued research and progress in this area may soon lead to the availability of preconditioning-mimetic treatments. The current concepts, mechanisms, and potential clinical applications of myocardial hibernation, stunning, and ischemic preconditioning are reviewed.

Myocardial stunning in man

Myocardial stunning refers to the contractile dysfunction that occurs following an episode of acute ischaemia, despite the return of normal blood flow. The phenomenon was initially identified in animal models, where it has been very well characterised, and there was initial doubt about whether a similar syndrome occurred in humans, and if it did, whether it was of any clinical relevance. This article outlines the conditions that must be met to diagnose myocardial stunning and why it has been difficult to confirm its presence in humans. The clinical scenarios where it has now been clearly identified and those others where it may also occur and be of clinical importance are also reviewed.

Independent value of tissue harmonic echocardiography for risk stratification in patients with non-ST-segment elevation acute chest pain

BACKGROUND

Clinical factors, electrocardiography, and cardiac troponins provide a satisfactory, although not ideal, means for risk-stratifying patients with non-ST-segment elevation acute chest pain. Tissue harmonic echocardiography enables improved assessment of wall motion abnormalities compared with fundamental echocardiography and may be a useful adjunct for the detection of myocardial ischemia and infarction. We aimed to determine the value of tissue harmonic echocardiography in relation to electrocardiographic and biochemical factors for risk stratification of these patients.

RESULTS

Eighty patients with non-ST-segment elevation chest pain were studied using tissue harmonic echocardiography and troponin-T and -I. Fifty-five (69%) patients had abnormal electrocardiograms and 47 (59%) patients had abnormal echocardiograms. Thirteen patients (17%) had elevated troponin-T levels and 17 (21%) had elevated levels of troponin-I. Twelve patients (15%) had a myocardial infarction as the presenting event and, of the remaining 68 patients, 24 sustained an adverse cardiac event during the follow-up period (3 cardiac deaths, 4 nonfatal myocardial infarctions, 17 revascularization procedures). Troponin-T (98%), troponin-I (97%), and echocardiography (97%) all had similar negative predictive values for myocardial infarction as the presenting event, but troponin-T was the only independent predictor of this endpoint (relative risk 230, 95% CI 22-2427). An abnormal echocardiogram was the only independent predictor of subsequent events. The independent predictors of all events were age, troponin-T, and echocardiography.

CONCLUSION

Tissue harmonic echocardiography provides independent information for risk stratification of patients with non-ST-segment elevation acute chest pain.

Prognostic value of 2D echocardiography in patients presenting with acute chest pain and non-diagnostic ECG for ST-elevation myocardial infarction

The purpose of the present study was to test the hypothesis that early detection of regional wall motion abnormalities (WMA) by 2D echocardiography (ECHO) accurately predicts further cardiac events in patients presenting with acute chest pain. A prospective analysis was performed in subjects admitted with the first presentation of acute chest pain and a non-diagnostic ECG for acute ST-elevation myocardial infarction. Patients with known coronary artery disease were excluded. All subjects were contacted by phone for a 30days follow-up regarding cardiac events defined as PCI/CABG, AMI, and death. In 132 consecutive patients (89 male, 43 female) complete data sets consisting of case history (H; abnormal: typical angina), ECG (abnormal: ST-depression, T-inversion, atypical ST-elevation, LBBB), serum markers (TnI; abnormal: elevation of troponin I=0.5 ng/ml), ECHO (abnormal: WMA) and follow-up were available. In 45 patients, 60 cardiac events occurred (three deaths, 24 AMI, 33 PCI/CABG). Positive (PPV; %) and negative predictive values (NPV; %) of ECHO were superior to all other diagnostic tests (P<0.05 each) for adverse cardiac events, evolving AMI or death, and superior to history and ECG for later need of revascularisation (PCI/ACVB). Multivariate analysis revealed that WMA in ECHO predict cardiac events independently of age, gender, and the common combination of investigations (H/ECG/TnI). A significant independent impact of ECHO was also determined for the prediction of AMI/death or PCI/CABG. The study shows that early 2D echocardiography provides superior prognostic information concerning the risk of subsequent complications in patients with acute chest pain and a non-diagnostic ECG for ST-elevation-AMI.

Evidence for stunned myocardium in humans: a 2001 update

This article describes clinical situations in which stunning occurs and updates previous reviews on the topic. Stunning following angioplasty, angina and exercise-induced ischemia, infarction, and after cardiac surgery are described. In addition, newer concepts regarding stunning, including neurogenic stunned myocardium, are discussed. Left atrial stunning following cardioversion is a recently recognized phenomenon with important clinical implications, but differs from the original concept of post-ischemic stunning.

Ischemically compromised myocardium displays different time-courses of functional recovery: correlation with morphological alterations?

OBJECTIVE

It has been demonstrated that positron emission tomography (PET) predicts the functional recovery of viable but ischemically compromised myocardium. Reversible contractile dysfunction after revascularization has been reported for 'hibernating myocardium' and stunned myocardium, however, there are little data concerning the time-course and the extent of improvement of the two different pathophysiological conditions.

METHODS

Twenty-nine patients with advanced coronary artery disease and severely reduced left ventricular function (EF 18--35%) who were referred for isolated coronary artery bypass grafting underwent preoperative PET viability assessment and were functionally assessed by two-dimensional echocardiography preoperatively at 11 days, 14 weeks, and more than 12 months after surgical revascularization. Intraoperative biopsies were taken from dysfunctional areas defined by PET as segments of normal perfusion and normal metabolism (stunned myocardium) and from areas with a 'mismatch' between perfusion and metabolism (hibernating myocardium). The degree of morphological alterations was evaluated by electron microscopy.

RESULTS

In 70% of the 240 dysfunctional segments, 'stunned myocardium' was present whereas 'hibernating myocardium' could be detected in only 24% (P < 0.01). Hibernating myocardium was associated with more severe preoperative wall motion abnormalities and incomplete postoperative recovery. After 1 year, 31% of 'stunned' segments vs. only 18% of 'hibernating' segments showed complete functional restoration (P < 0.05). This incomplete improvement was associated with more severe morphological alterations including depletion of sarcomeres, accumulation of glycogen, loss of sarcoplasmatic reticulum, and cellular sequestration.

CONCLUSIONS

These data indicate that in patients with severe ischemic left ventricular dysfunction 'stunned myocardium' is more prevalent than 'hibernation'. Functional normalization is more frequent in 'stunned' segments, whereas areas of 'hibernation' showed more severe tissue injury and protracted recovery. Different degrees of myocardial injury coexist in most patients, which determines the time-course and the extent of improvement after revascularization.

Clinical importance of stunned and hibernating myocardium

Myocardial stunning and hibernation are states of potentially reversible myocardial dysfunction, which were first described more than 20 years ago (c.1980). Important advances have now been made in the ability to detect stunned and hibernating myocardium, as well as in the understanding of the impact of these conditions on patient outcomes. We discuss here the clinical importance of stunned and hibernating myocardium for patients with several common cardiac conditions.

Clinical manifestations of myocardial stunning

The phenomenon of myocardial stunning has been observed in all animal species studied. The possible occurrence of myocardial stunning in man has been demonstrated after either regional ischemia (such as exercise-induced angina, vasospastic or unstable angina) or after global ischemia (i.e., after cardioplegic arrest during cardiac surgery, or cardiac arrest, or heart transplantation). Finally, it may also be observed in patients with acute myocardial infarction, subjected to recanalization therapy, because viable myocardium, salvaged by reperfusion, may remain stunned, with delayed contractile recovery. Occurrence of stunning may aggravate hemodynamic conditions in already unstable patients, and it may lead to underestimation of the extent of myocardium salvaged by thrombolysis. Repeated episodes of stunning may lead to a condition of apparently 'chronic' contractile dysfunction that may be difficult to differentiate from hibernation, because of the technical difficulties in accurately measuring myocardial blood flow in patients, and because both phenomena may coexist and overlap in the same patient. In addition, recent evidence suggests that repeated episodes of stunning may lead to a progressive worsening of the residual contractile dysfunction and to longer recovery times, and it has thus been suggested, and it is much debated, that hibernation might at least in part be the consequence of repetitive episodes of stunning.

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

OBJECTIVES

This 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.

BACKGROUND

Previous 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.

METHODS

Twenty-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.

RESULTS

In 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).

CONCLUSIONS

These 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.

Myocardial perfusion and oxygen consumption in reperfused noninfarcted dysfunctional myocardium after unstable angina: direct evidence for myocardial stunning in humans

OBJECTIVES

To positively establish the diagnosis of myocardial stunning in patients with unstable angina and persistent wall motion abnormalities after reperfusion by coronary angioplasty.

BACKGROUND

Although myocardial stunning is thought to occur in several clinical conditions, definite proof of its existence in humans is still lacking, owing to the difficulty of measuring myocardial blood flow (MBF) in absolute terms.

METHODS

We studied 14 patients with unstable angina due to proximal left anterior descending coronary artery disease who presented persistent anterior wall motion abnormalities despite revascularization of the culprit lesion by percutaneous coronary angioplasty (PTCA) and who did not have clinical evidence of necrosis. Dynamic positron emission tomography (PET) with [13N]-ammonia and [11C]-acetate was performed 48 h after PTCA to determine absolute MBF and oxygen consumption (MVO2). Regional wall thickening and regional cardiac work were determined using two-dimensional echocardiography. Improvement of segmental wall motion abnormalities was followed for a median of 4 months (1.5 to 14 months).

RESULTS

As judged from the changes in segmental wall motion score, regional dysfunction was spontaneously reversible in 12/14 patients and improved from 2.2 +/- 0.3 to 1.2 +/- 0.3 at late follow-up (p < 0.001). With PET, [13N]-ammonia MBF was similar among dysfunctional and remote normally contracting segments (85 +/- 29 vs. 99 +/- 20 ml x min (-1) x 100g(-1), p = not significant [n.s.]), thus demonstrating a perfusion-contraction mismatch. Despite the reduced contractile function, dysfunctional myocardium presented near normal levels of MVO2 (6.5 +/- 4.2 vs. 8.0 +/- 1.9 ml x min (-1)x 100g(-1), p = n.s.). Consequently, the regional myocardial efficiency (regional work divided by MVO2) of the dysfunctional myocardium was found to be markedly decreased as compared with normally contracting myocardium (6 +/- 6% vs. 26 +/- 6%, p < 0.001).

CONCLUSIONS

This study demonstrates that human dysfunctional myocardium capable of spontaneously recovering contractile function after unstable angina endures a state of perfusion-contraction mismatch. These data for the first time provide unequivocal direct evidence for the existence of acute myocardial stunning in humans.

Is routine echocardiography useful in patients hospitalized for chest pain? Evidence of areal myocardial dysfunction detected only by echocardiography

To assess the diagnostic value of routine two-dimensional echocardiography in the coronary care unit setting, we studied 81 unselected patients admitted for acute chest pain. Using electrocardiography (ECG), clinical history and serum markers of myocardial injury, the patients were retrospectively diagnosed as having had definite acute myocardial infarction (AMI) with (n=13) or without (n=31) previous infarction, possible AMI with (n=14) or without (n=15) previous infarction, and non-coronary cardiac or other causes of chest pain (n=8). Abnormal wall motion was observed in 75/77 patients with a cardiac origin of symptoms (sensitivity 97%), and there were no false-positive wall motion findings. In the 73 patients who were finally diagnosed with coronary artery disease (CAD), echocardiography showed wall motion abnormality in at least one additional coronary territory area in which there were no diagnostic ECG changes for 56% of patients with CAD (41/73) (P<0. 001). These areas were considered to be indicative of the presence of myocardium at risk for future cardiac events. We conclude that in addition to being a sensitive and accurate tool for detection of ischaemic wall motion abnormalities, two-dimensional echocardiography can give valuable information about the area of myocardium at risk. Therefore, therapeutic decisions can be affected by the findings of the routine echocardiographic examination, which is recommended even in unselected coronary care unit patients.

Reperfusion injury: experimental evidence and clinical implications

Postischemic reperfusion may profoundly alter cardiac function. Principal mediators of this phenomenon are oxygen radicals and neutrophils. Upon reflow, oxygen radicals are generated in large amounts, overwhelming cellular defenses and inducing oxidative tissue damage; biochemical markers of oxygen radical formation and attack can be found in postischemic myocardium. Reintroduction of neutrophils in postischemic tissues is accompanied by their activation, with release of lytic enzymes that directly induce tissue damage and proinflammatory mediators that amplify the local inflammatory reaction. Neutrophils may also plug capillaries, mechanically blocking flow. Oxidants can also modulate various events, ultimately leading to tissue injury, such as nitric oxide formation, platelet-activating factor metabolism, tissue factor synthesis, and exposure of adhesion molecules. In the clinical setting, important consequences of postischemic reperfusion are reversible contractile dysfunction ("stunning"), which is mostly caused by oxygen radical attack, and impairment to flow at the microvascular level ("no-reflow") secondary to neutrophil plugging and vasoconstriction.

Role of Echocardiography in the Emergency Department for Identifying Patients with Myocardial Infarction and Ischemia

Echocardiography is a valuable, noninvasive diagnostic tool that can provide information on systolic function and valvular abnormalities and can provide alternative explanations for causes of chest pain. Experimental as well as clinical studies have shown that wall motion abnormalities have a high sensitivity for predicting myocardial infarction. More recent studies, performed in the emergency department on patients evaluated for myocardial ischemia, have reported similar results. An important aspect is that necrosis is not necessary to cause wall motion abnormalities; therefore, echocardiography can also be used to identify patients with ischemia without infarction. Importantly, sensitivity is significantly higher than that for electrocardiography and is comparable to that for myocardial perfusion imaging. Newer developments, such as digital transmission over telephone lines, may lead to more widespread routine use in the emergency department. Acute emergency department echocardiography appears to be a promising tool when used in the evaluation of patients with chest pain.

Basic and clinical aspects of myocardial stunning

Although the pathogenesis of myocardial stunning has not been definitively established, the two major hypotheses are that it is caused by the generation of oxygen-derived free radicals on reperfusion and by a loss of sensitivity of contractile filaments to calcium. These hypotheses are not mutually exclusive and are likely to represent different facets of the same pathophysiological cascade. For example, a burst of free radical generation after reperfusion could alter contractile filaments in a manner that renders them less responsive to calcium. Increased free radical formation could also cause cellular calcium overload, which would damage the contractile apparatus of the myocytes. There is now considerable evidence that myocardial stunning occurs clinically in various situations in which the heart is exposed to transient ischemia, such as unstable angina, acute myocardial infarction with early reperfusion, exercise-induced ischemia, cardiac surgery, and cardiac transplantation. Recognition of myocardial stunning is clinically important and may impact patient treatment. Although no ideal diagnostic technique for myocardial stunning has yet been developed, thallium-201 scintigraphy or dobutamine echocardiography are available and can be useful to identify viable myocardium with reversible wall motion abnormalities. An intriguing possibility is that so-called chronic hibernation may in fact be the result of repetitive episodes of stunning, which have a cumulative effect and cause protracted postischemic left ventricular dysfunction. A better understanding of myocardial stunning will expand our knowledge of the pathophysiology of myocardial ischemia and provide a rationale for developing new therapeutic strategies designed to prevent postischemic dysfunction.

Postischemic stunning can affect left ventricular ejection fraction and regional wall motion on post-stress gated sestamibi tomograms

OBJECTIVES

This study was designed to investigate whether left ventricular ejection fraction (LVEF) calculated from post-stress single-photon emission computed tomography (SPECT) reflects the basal value for LVEF or whether post-stress LVEF is reduced in some patients with stress-induced ischemia.

BACKGROUND

Automated programs are now commercially available for assessing global left ventricular (LV) function from post-stress technetium-99m sestamibi gated SPECT performed >15 min after completion of exercise.

METHODS

Eighty-one sequential patients who underwent a 2-day stress/rest sestamibi imaging protocol and showed perfusion defects on the post-stress tomogram underwent gated acquisition of the second-day rest tomogram. The post-stress and rest tomographic images were read for presence, location, severity and reversibility of defects by consensus of two to three experienced observers with the aid of circumferential count displays. Defects were scored as mild, moderate or severe and as completely or partially reversible or fixed, and a summed defect severity score was calculated. Of these 81 scans, 20 showed nonreversible perfusion defects (group 3), whereas 61 showed reversible perfusion defects. Post-stress and rest LVEF was calculated from the processed gated SPECT data. From 15 additional patients who underwent rest gated SPECT studies on separate days, serial reproducibility of LVEF values calculated from the gated SPECT data was determined to be +/-5.2%. Coronary angiography was performed within 3 months of the scan without intervening events in 47 of 81 patients, including 39 of 61 with reversible perfusion defects.

RESULTS

In 22 (36%) of 61 patients with reversible perfusion defects, post-stress LVEF was >5% lower than that at rest (group 2), whereas in the remaining 39 patients, post-stress LVEF was either +/-5% or greater than that at rest (group 1). Segmental chordal shortening analysis performed in group 2 studies showed that differences in chordal shortening between rest and post-stress were significantly greater in the reversible perfusion defect territories than in the nonischemic perfusion defect territories ([mean +/- SD] 0.14 +/- 0.14 vs. 0.02 +/- 0.09, respectively, p < 0.0001). There were no significant differences among groups for any of the following variables: age, gender, previous myocardial infarction and type of stress. Time to imaging and stress and scan variables were correlated with the change in LVEF by univariate analysis, and the two variables that correlated significantly were the summed defect reversibility score on the scan and a left anterior descending coronary artery location of the scan defect. Only summed defect reversibility score was significant on multivariate analysis.

CONCLUSIONS

When the only gated sestamibi scan is the post-stress scan, global and regional LV function will not represent basal LV function in all patients with stress-induced ischemia.

Evaluation of chest pain in the emergency department

The evaluation of chest pain in the emergency setting should be systematic, risk based, and goal driven. An effective program must be able to evaluate all patients with equal thoroughness under the assumption that any patient with chest pain could potentially be having an MI. The initial evaluation is based on the history, a focused physical examination, and the ECG. This information is sufficient to categorize patients into groups at high, moderate, and low risk. Table 14 is a template for a comprehensive chest-pain evaluation program. Patients at high risk need rapid initiation of appropriate therapy: thrombolytics or primary angioplasty for the patients with MIs or aspirin/heparin for the patients with unstable angina. Patients at moderate risk need to have an acute coronary syndrome ruled in or out expediently and additional comorbidities addressed before discharge. Patients at low risk also need to be evaluated, and once the likelihood of an unstable acute coronary syndrome is eliminated, they can be discharged with further evaluation performed as outpatients. Subsequent evaluation should attempt to assign a definitive diagnosis while also addressing issues specific to risk reduction, such as cholesterol lowering and smoking cessation. It is well documented that 4% to 5% of patients with MIs are inadvertently missed during the initial evaluation. This number is surprisingly consistent among many studies using various protocols and suggests that an initial evaluation limited to the history, physical examination, and ECG will fail to identify the small number of these patients who otherwise appear at low risk. The solution is to improve the sensitivity of the evaluation process to identify these patients. It appears that more than simple observation is required, and at the present time, no simple laboratory test can meet this need. However, success has been reported with a number of strategies including emergency imaging with either radionuclides such as sestamibi or echocardiography. Early provocative testing, either stress or pharmaceutic, may also be effective. The added value of these tests is only in their use as part of a systematic protocol for the evaluation of all patients with acute chest pain. The initial evaluation of the patient with chest pain should always consider cardiac ischemia as the cause, even in those with more atypical symptoms in whom a cardiac origin is considered less likely. The explicit goals for the evaluation of acute chest pain should be to reduce the time to treat MIs and to reduce the inadvertent discharge of patients with occult acute coronary syndromes. All physicians should become familiar with appropriate risk stratification of patients with acute chest pain. Systematic strategies must be in place to assure rapid and consistent identification of all patients and the expedient initiation of treatment for those patients with acute coronary syndromes. These strategies should include additional methods of identifying acute coronary syndromes in patients initially appearing as at moderate or low risk to assure that no unstable patients are discharged. All patients should be followed up closely until the cardiovascular evaluation is completed and, when possible, a definitive diagnosis is determined. Finally, this must be done efficiently, cost-effectively, and in a manner that will result in an overall improvement in patient care.

Asynchronous left ventricular wall motion in unstable angina

The objective of the study was to assess the nature of left ventricular wall motion disturbances in patients with unstable angina and the relative contributions of the severity of symptoms and the severity of coronary artery disease (CAD) to their genesis. A prospective examination was performed on 30 patients with unstable angina (UA) with triple CAD, 34 matched patients with chronic stable angina (CSA) (20 with triple CAD and 14 with isolated left anterior descending (LAD) artery disease), and compared to 21 normals. LV cavity size was normal in all three groups. Twenty-two of 30 patients with UA had marked (>3 mm) abnormal long axis shortening during isovolumic relaxation time (IVRT), 65% of LV sites being abnormal. In CSA, minor (<3 mm) shortening during IVRT occurred in 7 patients with triple CAD, and in 5 with LAD disease, with 12% of LV sites involved in both groups, P<0.001 vs. UA. The incidence of other long axis abnormalities, including reduced extent and peak rate of shortening and lengthening as well as the delay in the onset of shortening and lengthening was increased between patients with CSA and triple CAD compared with LAD but not between the two groups of patients with triple CAD, CSA and UA. Transmitral E/A ratio was also reduced in the two groups with triple vessel disease, CSA and UA. Thus, the incidence of minor long axis abnormalities is similar in CSA and UA and is related to the severity of CAD. However, abnormal shortening during IVRT is more severe and generalised in UA but not in CSA with triple vessel disease. We suggest that these abnormalities of wall motion bear a close relation to the development of instability within the setting of CAD.

[Role of noninvasive examinations in the management of ischemic heart disease. III. Assessment of myocardial viability]

Assessment of myocardial viability is a field of growing interest. This article summarizes the pathophysiology of myocardial stunning and hibernation; both phenomena are associated with the presence of dysfunctional, viable myocardium. The techniques that are currently available for the assessment of viability, and the clinical situations in which these assessments may be more useful are discussed.

Reperfusion injury: a review of the pathophysiology, clinical manifestations and therapeutic options

Lack of blood supply or ischaemia underlies many of the most important cardiovascular and cerebrovascular diseases faced by clinicians in their daily practice. Many of these ischaemic episodes can be reversed at an early stage by surgical or pharmacological means with the ultimate aim of preventing infarction and cell necrosis in the ischaemic tissues. However, reperfusion of ischaemic areas, in particular the readmission of oxygen, may contribute to further tissue damage (reperfusion injury). For example, the use of thrombolytic therapy in acute myocardial infarction and other revascularisation procedures, such as percutaneous transluminal angioplasty and coronary artery bypass surgery, may be associated with reperfusion of ischaemic myocardium. Such ischaemia and reperfusion may result in injury to one of more of the biochemical, cellular and microvascular components of the heart. Our understanding of the significance of reperfusion injury is however restricted by the profuse literature in animal models and limited literature in the clinical situation. This article reviews the pathophysiology, clinical manifestations of reperfusion injury to the heart and discusses the possible therapeutic approaches to avoiding any adverse effects.

Myocardial stunning, hibernation, and ischemic preconditioning

From the present review, it may be concluded that myocardial ischemia results in far more complicated syndromes than previously realized. Although not all aspects of the issues discussed in this review are currently a clinical reality in the daily practice of cardiovascular anesthesiologists, the understanding and application of these concepts are growing rapidly. Indications for revascularization procedures will be adjusted in patients with evidence of hibernating myocardium. In the future, postoperative myocardial dysfunction may be diminished by the prevention of myocardial stunning, for instance by altering the composition of the cardioplegic solution and other interventions. Finally, additional advances may involve reduction of the extent of perioperative myocardial infarctions by application of ischemic preconditioning.

Effects of nifedipine and nitroglycerin on left ventricular systolic dysfunction and impaired diastolic filling after exercise-induced ischemia in humans

OBJECTIVES

This study sought to determine whether calcium antagonist, compared with nitroglycerin, administration attenuates left ventricular dysfunction after exercise-induced ischemia in humans.

BACKGROUND

Exercise-induced ischemia impairs left ventricular systolic function and diastolic filling after exercise. The mechanism of this phenomenon is unknown but may relate to intracellular calcium overload.

METHODS

Echocardiography was performed in 131 patients before and 30 min, 2 h and 4 h after exercise stress test. Ischemia was defined as a reversible thallium stress defect. No medication, sublingual nitroglycerin or nifedipine was randomly given to each patient at peak exercise.

RESULTS

Isovolumetric relaxation time was significantly prolonged from rest (100 +/- 19 ms [mean +/- SD]) to 30 min (118 +/- 20 ms, p < 0.0005), 2 h (117 +/- 18 ms, p < 0.0005) and 4 h (110 +/- 22 ms, p < 0.05) after exercise in 21 patients with exercise-induced ischemia who received no medication (ischemia-none group). Isovolumetric relaxation time similarly increased after exercise in 23 patients who received nitroglycerin and had exercise-induced ischemia (ischemia-NTG group) but was unchanged in 20 patients with exercise-induced ischemia who received nifedipine (ischemia-nifedipine group). Peak early filling velocity decreased in the ischemia-none and ischemia-NTG groups from rest to 30 min and 2 h after exercise, but peak early filling velocity was unchanged in the ischemia-nifedipine group. Ejection fraction decreased from rest to 30 min after exercise in the ischemia-none group (59 +/- 12% vs. 51 +/- 13%, p < 0.025) and ischemia-NTG group (59 +/- 14% vs. 49 +/- 14%, p < 0.005) but was unchanged in the ischemia-nifedipine group (60 +/- 19% vs. 64 +/- 18%, p = NS). A new regional left ventricular wall motion abnormality occurred more frequently 30 min after exercise in the ischemia-none group (11 [52%] of 21) and ischemia-NTG group (9 [39%] of 23) compared with the ischemia-nifedipine group (2 [10%] of 20, both p < 0.05). No change occurred in left ventricular systolic function and diastolic filling after exercise in the control groups.

CONCLUSIONS

Exercise-induced ischemia impairs systolic function and diastolic filling after exercise. Sublingual nifedipine but not nitroglycerin attenuates this process and suggests that altered calcium homeostasis may play a role in left ventricular dysfunction that occurs after exercise-induced ischemia.

Changes in wall motion in patients treated for unstable angina. A suggestion of the stunned and hibernating myocardium in humans. UNASEM Collaborative Study Group. Unstable Angina Study Using Eminase

BACKGROUND

A double-blind, placebo-controlled study using anistreplase was performed in 159 patients with unstable angina. All patients had a history of unstable angina combined with typical ECG changes and without evidence of a previous, recent, or ongoing myocardial infarction. The purpose of the present study was to analyze the relationship between the patency of the culprit artery and the behavior of the ischemia-related regional left ventricular (LV) wall motion.

METHODS AND RESULTS

On entry to the study, all patients received conventional drug therapy: i.v. nitroglycerin therapy, an oral beta-blocking agent, and a calcium antagonist. Baseline angiography was carried out within 3 h after randomization, a mean of 4.2 +/- 3.0 h (range, 1 to 17 h) after the last attack of chest pain. Treatment with trial medication was withheld in 33 cases. Sixty-five patients with coronary artery disease received anistreplase (30 U/5 min)/heparin and 61 patients heparin-only therapy. Angiography was repeated 20.6 +/- 4.6 h (mean +/- SD; range, 12 to 39 h) after the baseline angiographic study. To assess changes in regional myocardial wall motion, the LV wall was divided into seven segments. The ischemia-related coronary artery stenosis was calculated quantitatively and related to the quantitatively assessed mean regional left ventricular ejection fraction (RLVEF) of the ischemia-related segments. In 118 of 126 patients who received trial medication, we found that anistreplase/heparin therapy leads to a significantly (p < 0.01) greater reduction in coronary artery diameter stenosis than heparin-only therapy (n = 63, mean +/- SD, 11 +/- 22, vs n = 55, mean +/- SD, 3 +/- 11%). Anistreplase/heparin therapy was related to a larger significant improvement of the ischemia-related RLVEF than heparin-only therapy, although the latter association was not statistically significant (n = 63, mean +/- SD, 7 +/- 15, vs n = 55, mean +/- SD, 5 +/- 14%). The effects of change of coronary artery stenosis on regional LV wall motion were also determined. A paradoxical finding was that a persistently occluded vessel or a vessel showing an increase in coronary artery stenosis was associated with a greater improvement of the ischemia-related RLVEF than a reopened vessel or a vessel with a reduction in coronary artery stenosis (n = 15, mean +/- SD, 7 +/- 11, vs n = 41, mean +/- SD, 8 +/- 13, vs n = 15, mean +/- SD, 1 +/- 12, vs n = 47, mean +/- SD, 5 +/- 16%, NS). One day after the last attack of chest pain, the regional LV wall motion was still abnormal in about 20% of patients.

CONCLUSION

In these patients with unstable angina, the LV wall motion improved both in the treated and the control group at follow-up angiography 1 day later. Improved coronary arterial anatomy was associated with a lesser improvement of the LV contractile function than when worsening of the coronary angiographic appearance occurred. There is no rational explanation of these results. This is a beginning of an effort to elucidate the clinical significance of the stunned and hibernating myocardium in humans.

Comparative study of left ventricular function in patients with unstable angina, non-Q wave myocardial infarction and stable angina pectoris: assessment with atrial pacing and digital ventriculography

To compare left ventricular global and segmental function at rest and during right atrial pacing in patients with unstable angina, non-Q wave myocardial infarction, and stable angina (class III angina), low-dose digital subtraction ventriculography was performed at rest and after abrupt cessation of pacing in 42 patients with unstable angina, 8 patients with non-Q wave myocardial infarction and 15 patients with stable angina during selective coronary arteriography. Left ventricular ejection fraction was significantly lower at rest in patients with unstable angina (P < 0.01) and non-Q wave myocardial infarction (P < 0.05) and during pacing (P < 0.01). These two groups of patients had significantly higher values of left ventricular end-diastolic and end-systolic volumes at rest and during pacing as compared with stable angina group. In comparing various clinical patterns of unstable angina, ejection fraction was significantly (P < 0.05) lower during pacing in patients with crescendo angina than in new-onset angina. However, ejection fraction was significantly (P < 0.01) lower in crescendo angina only at rest as compared with rest angina. The length of zone of severe hypokinesia was greater in unstable angina (P < 0.01) as well as in non-Q wave myocardial infarction (P < 0.05) both at rest and during pacing as compared with stable angina. Contractility of region of hypokinesia during pacing was higher (P < 0.01) in stable angina than in unstable angina and non-Q wave myocardial infarction. In analyzing segmental function in various subgroups of unstable angina, the authors found that the length of total hypokinesia was significantly higher (P < 0.05) during pacing in crescendo angina than in new-onset angina. Contractility of region of hypokinesia was lowest at rest and during pacing in patients with crescendo angina. This study demonstrates that patients with unstable angina as well as non-Q wave myocardial infarction were characterized by more pronounced global and segmental left ventricular dysfunction at rest and during pacing as compared with patients with stable angina, which may explain the poorer prognosis in the former two groups. This study also shows that patients with crescendo angina have more profound left ventricular global and regional dysfunction as compared with patients with new-onset as well as rest angina.