Prolonged wall motion abnormalities after chest pain at rest in patients with unstable angina: a possible manifestation of myocardial stunning

Myocardial stunning and hibernation revisited

Unlike acute myocardial infarction with reperfusion, in which infarct size is the end point reflecting irreversible injury, myocardial stunning and hibernation result from reversible myocardial ischaemia-reperfusion injury, and contractile dysfunction is the obvious end point. Stunned myocardium is characterized by a disproportionately long-lasting, yet fully reversible, contractile dysfunction that follows brief bouts of myocardial ischaemia. Reperfusion precipitates a burst of reactive oxygen species formation and alterations in excitation-contraction coupling, which interact and cause the contractile dysfunction. Hibernating myocardium is characterized by reduced regional contractile function and blood flow, which both recover after reperfusion or revascularization. Short-term myocardial hibernation is an adaptation of contractile function to the reduced blood flow such that energy and substrate metabolism recover during the ongoing ischaemia. Chronic myocardial hibernation is characterized by severe morphological alterations and altered expression of metabolic and pro-survival proteins. Myocardial stunning is observed clinically and must be recognized but is rarely haemodynamically compromising and does not require treatment. Myocardial hibernation is clinically identified with the use of imaging techniques, and the myocardium recovers after revascularization. Several trials in the past two decades have challenged the superiority of revascularization over medical therapy for symptomatic relief and prognosis in patients with chronic coronary syndromes. A better understanding of the pathophysiology of myocardial stunning and hibernation is important for a more precise indication of revascularization and its consequences. Therefore, this Review summarizes the current knowledge of the pathophysiology of these characteristic reperfusion phenomena and highlights their clinical implications.

Prevalence of troponin elevations in patients with cardiac arrest and implications for assessing quality of care in hypothermia centers

The prevalence of troponin elevations in patients with cardiac arrest (CA) using newer generation troponin assays when the ninety-ninth percentile is used has not been well described. We studied patients admitted with CA without ST elevation myocardial infarction (MI). Treatment included a multidisciplinary protocol that included routine use of hypothermia for appropriate patients. Serial assessment of cardiac biomarkers, including troponin I was obtained over the initial 24 to 36 hours. Patients were classified into 1 of 5 groups on the basis of multiples of the ninety-ninth percentile (upper reference limit [URL]), using the peak troponin I value: <1×, 1 to 3×, 3 to 5×, 5 to 10×, and >10×. Serial changes between the initial and second troponin I values were also assessed. A total of 165 patients with CA (mean age 58 ± 16, 67% men) were included. Troponin I was detectable in all but 2 patients (99%); all others had peak troponin I values that were greater than or equal to the URL. Most patients had peak troponin I values >10× URL, including patients with ventricular fibrillation or ventricular tachycardia (85%), asystole (50%), and pulseless electrical activity (59%). Serial changes in troponin I were present in almost all patients: ≥20% change in 162 (98%), ≥30% change in 159 (96%), and an absolute increase of ≥0.02 ng/ml in 85% of patients. In conclusion, almost all patients with CA who survived to admission had detectable troponin I, most of whom met biomarker guideline criteria for MI. Given the high mortality of these patients, these data have important implications for MI mortality reporting at CA treatment centers.

Role of imaging for acute chest pain syndromes

Acute chest pain suggestive of ischemic cardiac origin, with a normal or nondiagnostic electrocardiogram and negative initial cardiac markers for myocardial necrosis represent a significant diagnostic dilemma for clinicians. Multiple imaging modalities play a pivotal role in early diagnosis and safe discharge of these patients. In this review, we compare the current imaging modalities available for these patients including their diagnostic accuracy, feasibility, and cost effectiveness. Acute rest myocardial perfusion imaging significantly improves the clinical outcome in these patients and reduces the overall cost when incorporated into the decision making pathway. The choice of imaging modality recommended should be based on local institutional expertise and the overall clinical presentation. The imaging modality with high diagnostic accuracy and negative predictive value will provide for precise risk stratification which is important to clinical decision making, including patients who require admission to the hospital and those who can be safely discharged.

Decreased incidence of low output syndrome with a switch from tepid to cold continuous minimally diluted blood cardioplegia in isolated coronary artery bypass grafting

OBJECTIVES

The optimal temperature for blood cardioplegia remains unclear.

METHODS

A retrospective analysis was performed on 138 patients undergoing isolated myocardial revascularization by a single surgeon in our institution over a period of 2 years. Patients operated on early in the study period received tepid (29°C) continuous minimally diluted blood cardioplegia (minicardioplegia), delivered in an antegrade continuous fashion. Later, our surgeon began using cold (7°C) blood minicardioplegia in all patients. Data pertaining to clinical outcomes and postoperative biochemical data were obtained, and the two groups were compared.

RESULTS

Low cardiac output syndrome, defined as the need for intra-aortic balloon pump counter pulsation or inotropic medication for haemodynamic instability, was more frequent in the tepid cardioplegia group than in the cold cardioplegia group (16.0 vs 2.4%, P = 0.006). There was no difference in the maximal serum creatine kinase MB between the two groups (cold 25.4 ± 3.21 μg/ml vs tepid 36.5 ± 7.10 μg/ml, P = 0.62), in the rates of perioperative myocardial infarction (cold 1.2% vs tepid 6.0%, P = 0.15) and the need for postoperative insertion of an intra-aortic balloon pump (cold 4.8% vs tepid 0.0%, P = 0.3). There was no other statistically significant difference between the two groups in the measured parameters.

CONCLUSIONS

A higher rate of low cardiac output syndrome in the tepid cardioplegia group suggests inferior myocardial protection with the tepid cardioplegia. Cold cardioplegia may provide better protection than tepid cardioplegia when minicardioplegia is used.

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.

Value of simultaneous functional assessment in association with acute rest perfusion imaging for predicting short- and long-term outcomes in emergency department patients with chest pain

BACKGROUND

Rest tomographic myocardial perfusion imaging (MPI) has significant utility for clinical decision making in emergency department chest pain patients. The role of functional data, commonly acquired with perfusion, has not been systematically evaluated.

METHODS AND RESULTS

Low- to moderate-risk patients undergoing rest MPI for risk stratification were included. The patients' MPI findings were classified as normal (normal perfusion or function), abnormal (perfusion defect with abnormal regional function), or discordant (perfusion defect with normal regional function). Ejection fraction was determined from the gated MPI studies. Events based on perfusion classifications and ejection fraction were evaluated. A total of 2,826 consecutive patients (abnormal MPI results in 40%, normal in 32%, and discordant in 27%) were studied. Outcomes were similar for those with normal MPI results versus those with discordant MPI results (myocardial infarction [MI] based on troponin I [TnI], 3.5% vs 4.0%; MI based on creatine kinase-MB, 1.5% vs 1.7%; revascularization, 5.2% vs 5.5%; and MI/revascularization based on TnI, 7.9% vs 8.1%) (P = not significant for all). Both groups had significantly fewer events (P < .001 for all) when compared with patients with abnormal MPI studies (MI based on TnI, 15%; MI based on creatine kinase-MB, 10%; revascularization, 17%; MI based on TnI or revascularization, 24%). The mortality rate was not different among the 3 groups. Multivariate analysis showed that mild/moderate and severe systolic dysfunction were independent predictors of 30-day and 1-year mortality rates (P = .001).

CONCLUSIONS

The concurrent evaluation of perfusion and function (regional and global) with MPI provides significant risk/outcome predictive power.

The Acute Cardiac Effects of Dialysis

It is well recognized that the procedure of hemodialysis is associated with significant changes in blood pressure and systemic hemodynamics; 20-30% of treatments are complicated by intradialytic hypotension (IDH). There are now an increasing number of studies using electrocardiographic, isotopic and echocardiographic techniques that show that subclinical myocardial ischemia occurs during dialysis. This concept is supported by some studies showing that dialysis can induce acute rises in troponins and creatinine kinase MB, although this has not been found by all authors. Some of this controversy may at least in part be due to the collection of blood samples immediately postdialysis, which is likely to be too early to reliably detect dialysis-induced elevations of cardiac enzymes. Cardiovascular death is the biggest single cause of mortality in dialysis patients and of this sudden death comprises the largest proportion. As such, there is a large body of evidence examining whether dialysis is pro-arrhythmogenic. It is clear that dialysis can increase QTc interval and QT dispersion and is capable of inducing arrhythmias on Holter monitoring, likely due to the interaction of multiple factors, some of which prime for the development of arrhythmias (particularly the presence of preexisting cardiac disease), and some of which act as triggers. However, the link between these electrocardiographic alterations and sudden death is relatively poorly studied. This review summarizes the available literature regarding the acute cardiac effects of dialysis in relation to the above, and discusses how these acute changes may contribute to the genesis of uremic cardiomyopathy and longer term cardiac outcomes.

Occurrence of Regional Left Ventricular Dysfunction in Patients Undergoing Standard and Biofeedback Dialysis

BACKGROUND

Cardiac failure and cardiovascular death are extremely prevalent in dialysis patients. Recurrent subclinical myocardial ischemia is important in the genesis of heart failure in nondialysis patients. We examined whether this phenomenon occurs in response to the stress of hemodialysis (HD).

METHODS

Eight patients prone to intradialytic hypotension were recruited for a randomized crossover study to compare the development of left ventricular regional wall motion abnormalities during standard (HD) and biofeedback dialysis. Patients underwent serial echocardiography with quantitative analysis to assess ejection fraction and regional left ventricular systolic function during both types of dialysis. Blood pressure and hemodynamic variables also were measured by using continuous pulse wave analysis.

RESULTS

Forty-two new regional wall motion abnormalities developed in all 8 patients during HD compared with 23 regional wall motion abnormalities that developed in 7 patients during biofeedback dialysis (odds ratio, 1.8; 95% confidence interval, 1.1 to 3.0). The majority of regional wall motion abnormalities showed improvement in function by 30 minutes postdialysis. Overall mean regional function was significantly more impaired during HD (P = 0.022). At peak stress, ejection fraction (measured by percentage of change from baseline) was significantly lower during HD (P = 0.043). Blood pressure was higher during biofeedback dialysis, with significantly fewer episodes of hypotension (odds ratio, 2.0; 95% confidence interval, 1.01 to 4.4). Significantly smaller decreases in stroke volume and cardiac output and a greater increment in pulse rate were observed during biofeedback dialysis.

CONCLUSION

This study shows that reversible left ventricular wall motion abnormalities develop during dialysis with ultrafiltration. We also show that this phenomenon can be ameliorated by the improved hemodynamic stability of biofeedback dialysis and therefore is a potential target for intervention.

Echocardiography in the evaluation of patients in chest pain units

Using percutaneous angioplasty to induce the ischemic cascade in the cardiac catheterization laboratory, echocardiographic wall motion abnormalities have been documented to precede electrocardiographic abnormalities and angina. Therefore, detection of cardiac wall motion abnormalities is potentially more sensitive than the history, physical examination, and ECG for identification of myocardial ischemia. Echocardiography is highly reliable for assessing cardiac wall motion and, thus, it has been used for diagnosis and risk assessment in patients presenting to the emergency department (ED) with symptoms suggestive of myocardial ischemia. In patients who have acute ST-elevation myocardial infarction (MI), echocardiography is comparable to invasive left ventriculography for detecting wall motion abnormalities. However, the usefulness of echocardiography in the low-risk population that has chest pain of uncertain origin and a nondiagnostic initial presentation is less well established.

Congestive heart failure complicating non-ST segment elevation acute coronary syndrome: incidence, predictors, and clinical outcomes

There are limited data regarding the incidence and clinical significance of congestive heart failure (CHF) in patients with non-ST segment elevation acute coronary syndromes (ACS). The objectives of this study were to examine the incidence, predictors, and clinical outcomes in patients with ACS without ST elevation who develop CHF. We studied patients with unstable angina or non-ST segment elevation myocardial infarction (NSTEMI) randomized to hirudin or unfractionated heparin in the Organisation to Assess Strategies for Ischemic Syndromes (OASIS-2) trial. The diagnosis of CHF was based on a combination of clinical and radiographic features. Patients were followed for 6 months. Of 10 141 randomized patients, 501 (4.9%) developed CHF within the first week and 643 (6.3%) during 6 months of followup. Independent predictors for the development of CHF were older age, female sex, diabetes, prior MI, prior CHF, and NSTEMI at presentation. Compared with patients who did not develop CHF, patients who developed CHF were at increased risk of death (odds ratio (OR) 3.4, 95% CI 2.7-4.3), new MI (OR 2.8, 95% CI 2.2-3.6), and the need for intra-aortic balloon pump insertion (OR 5.4, 95% CI 3.5-8.4) at 7 days and 6 months. There was no increase in use of cardiac catheterization (OR 0.8, 95% CI 0.7-1.0) or revascularization (OR 0.9, 95% CI 0.7-1.1) in patients who developed CHF. CHF is a common complication in patients presenting with non-ST segment elevation ACS and is strongly associated with adverse clinical outcomes including new MI and death. Despite this worse prognosis, patients with ACS developing CHF are less likely to be referred for invasive management.

Segmental myocardial wall motion during minimally invasive coronary artery bypass grafting using open and endoscopic surgical techniques

Current options for minimally invasive surgical treatment of single-vessel coronary artery disease include beating heart procedures without cardiopulmonary bypass (CPB) via mini-thoracotomy (MIDCAB) and totally endoscopic robot-assisted techniques (TECAB) with CPB. Both procedures are associated with potential myocardial stress before revascularization, such as single-lung ventilation (SLV), temporary coronary artery occlusion, cardiac luxation, intrathoracic carbon dioxide insufflation, and extended CPB and operating time. In this echocardiographic study we sought to evaluate the extent of intraoperative segmental wall motion abnormalities (SWMA) during MIDCAB and TECAB surgery and to identify factors affecting SWMA. Forty-six patients with single-vessel coronary artery disease were studied. Sixteen patients were operated using the MIDCAB technique and 30 patients with TECAB. In both groups sequential transesophageal echocardiograms were recorded during the entire procedure. Hemodynamic data and oxygenation variables were acquired simultaneously. In both groups, mild but obvious perioperative SWMA were identified and noted to increase during the course of the operation. These SWMA were more pronounced in the TECAB group. Independent of operating time, these changes disappeared completely after revascularization. No significant hemodynamic compromise was observed. We conclude that MIDCAB and TECAB techniques are associated with significant perioperative SWMA. The appearance of more profound SWMA in the TECAB group compared with the MIDCAB patients might have been the result of intrathoracic CO(2) insufflation, as SLV was used in both groups. No persistent SWMA or post-CPB SWMA were apparent in either group. More extensive intraoperative ventricular SWMA was detected in the TECAB group, suggesting that a more frequent risk for right ventricular dysfunction may exist during TECAB procedures.

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.

Evidence that stunning can be cumulative in man

Myocardial stunning and hibernation are two entities that have become increasingly recognised as clinically important causes of reversible left ventricular (LV) dysfunction. Their occurrence is important as resting myocardial dysfunction, which was once thought to be irreversible, may recover if ischaemia is lessened or abolished. Recent evidence has suggested that cumulative stunning can occur in man and may in fact be responsible for the phenomenon of hibernation. In this chapter we will review the evidence supporting the occurrence of cumulative stunning in man.

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.

Segmental wall motion abnormalities during telerobotic totally endoscopic coronary artery bypass grafting

In addition to single-lung ventilation (SLV), intrathoracic CO2 insufflation is mandatory for adequate exposure during totally endoscopic coronary artery bypass grafting. With transesophageal echocardiography, we investigated biventricular myocardial wall motion in 25 patients with isolated disease of the left anterior descending coronary artery who underwent totally endoscopic coronary artery bypass grafting with the "Da Vinci" robotic surgical system. At distinct time points during the operation, a cine loop of both ventricles was registered from a transgastric mid-short-axis view. Myocardial wall motion analysis was performed according to an established segmentation model of the left ventricle and to an established five-point scale for wall motion (1, normal; 5, dyskinesia). Significant alterations from preoperative baseline wall motion were visible in the septal, inferior, and anterior segments of the left ventricle at some time during the prebypass period, combined with a markedly decreased PaO2 under SLV and increased intrathoracic pressure. The same findings applied to the right ventricle; however, wall motion abnormalities were more pronounced here. After myocardial revascularization, weaning from cardiopulmonary bypass, CO2 deflation, and return to double-lung ventilation, myocardial wall motion recovered to baseline values. Clinically significant hemodynamic instability did not occur. The data suggest that robot-assisted coronary artery bypass grafting leads to significant prebypass alterations of biventricular segmental wall motion. On the basis of our data, it cannot be definitively stated whether the observed results were due to reduced oxygenation during SLV and thus "real" myocardial ischemia, intrathoracic CO2 insufflation with positive pressure leading to mechanical compromise of the heart, absolute or relative hypovolemia, or a combination of these factors. However, in this cohort, which consisted of patients with single-vessel disease and good ventricular function, these changes were of limited clinical relevance.

IMPLICATIONS

Segmental myocardial wall motion was evaluated with transesophageal echocardiography during robot-assisted totally endoscopic coronary artery bypass grafting. Significant biventricular segmental wall motion abnormalities occurred before cardiopulmonary bypass under single-lung ventilation and carbon dioxide insufflation. The changes in myocardial wall motion were of limited clinical relevance.

Acute ischemic syndromes. Chest pain center concept

CPCs have been developed to meet the clinical challenge posed by the diverse group of patients presenting to the ED with findings suggestive of a coronary event. Using a protocol-driven approach, high- and low-risk patients can be identified on presentation, facilitating urgent therapy in the former and triage of the latter to more deliberate management. Most CPCs focus on low-risk patients who are being increasingly managed by accelerated diagnostic protocols. These methods comprise systematic strategies that include innovative diagnostic approaches during a 6 to 12 hour period of observation with serial ECGs, continuous monitoring and cardiac biomarker measurements. A negative evaluation is usually followed by predischarge stress testing, and positive findings mandate admission. An essential aspect of the CPC strategy is continuity of care for patients with negative cardiac evaluations. Current data indicate that management of low-risk patients with chest pain in a CPC is safe accurate, and appears to be cost-effective.

Consequences of brief ischemia: stunning, preconditioning, and their clinical implications: part 1

In experimental studies in the dog, total proximal coronary artery occlusions of up to 15 minutes result in reversible injury, meaning that the myocytes survive this insult. The 15 minutes of ischemia, however, induce numerous changes in the myocardium, including certain monuments to the brief episode of ischemia that may persist for days. One of these monuments is stunned myocardium, which represents "prolonged postischemic contractile dysfunction of myocardium salvaged by reperfusion." The mechanism of stunning involves generation of oxygen radicals as well as alteration in calcium homeostasis and possibly alteration in contractile protein structure. Stunning has been observed in several clinical scenarios, including after percutaneous transluminal coronary angioplasty, unstable angina, stress-induced ischemia, after thrombolysis, and after cardiopulmonary bypass. Oxygen radical scavengers and calcium channel blockers have been shown to enhance function of stunned myocardium in experimental studies, and in a few clinical studies, calcium channel blockers have been shown to ameliorate stunning. Although brief periods of ischemia can contribute to prolonged left ventricular dysfunction and even heart failure, they paradoxically play a cardioprotective role. Episodes of ischemia as short as 5 minutes, followed by reperfusion, protect the heart from a subsequent longer coronary artery occlusion by markedly reducing the amount of necrosis that results from the test episode of ischemia. This phenomenon, called ischemic preconditioning, has been observed in virtually every species in which it has been studied and is a powerful cardioprotective effect. The mechanism of ischemic preconditioning involves both triggers and mediators and involves complex second messenger pathways that appear to involve such components as adenosine, adenosine receptors, the epsilon isoform of protein kinase C, the ATP-dependent potassium channels, as well as others, including a paradoxical protective role of oxygen radicals. Both an early and a late phase of preconditioning have been described, and the mechanisms underlying their induction are under investigation. That preconditioning may occur in humans is suggested by the observations that repetitive balloon inflations in the coronary artery are associated with progressively less chest pain, ST-segment elevation, lactate production, the protective effects of preinfarction angina, the anginal "warm-up phenomenon," and studies performed on human cardiac biopsies that show metabolic properties suggesting preconditioning. Development of pharmacological agents that stimulate second messenger pathways thought to be involved in preconditioning, but without causing ischemia, could result in novel approaches to treating ischemia. Hence, on one hand, brief episodes of ischemia can have a negative effect on the heart: stunning; and on the other hand, they have a protective effect: preconditioning. The future challenge is how to minimize the stunning phenomenon and maximize the preconditioning phenomenon in clinical practice.

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.

Pathobiology and Clinical Impact of Reperfusion Injury

Reperfusion injury refers to cellular death or dysfunction caused by restoration of blood flow to previously alchemic tissue. This should be differentiated from the normal reparative processes that follow an ischemic insult. Four types of reperfusion injury have been described in the literature: (1) lethal reperfusion injury, (2) nonlethal reperfusion injury, (myocardial stunning), (3) reperfusion arrhythmias, and (4) vascular injury (including the "no-reflow" phenomenon). There is continued debate whether reperfusion itself is capable of killing viable myocytes, which otherwise would have survived the ischemic insult. However, there is firm evidence for the existence of myocardial stunning following various ischemic syndromes, including reperfusion therapy for acute myocardial infarction, unstable angina pectoris, vasospastic angina, effort-induced ischemia, coronary artery bypass surgery, and cardiac transplantation. Reperfusion arrhythmia is more common after short ischemic episodes than after long ischemic periods. Thus, while reperfusion arrhythmias in the setting of acute myocardial infarction are relatively rare, reperfusion arrhythmias may be an important cause of sudden death. The "no-reflow" phenomenon has been described following reperfusion in patients with acute myocardial infarction. Three major components have been proposed as mediators of reperfusion injury: (1) oxygen free radicals, (2) the complement system, and (3) neutrophils. Numerous experimental studies have shown short-term benefit by blocking various stages of the postischemic inflammatory response. Oxygen free radicals scavengers, complement inhibition, leukocyte depletion, and the use of antibodies against various adhesion molecules have shown a reduction of infarct size in many ischemic/reperfusion experimental models. However, many of these agents failed to show a benefit in the clinical setting. Moreover, the long-term benefit of such intervention is still unknown.

Pathobiology and Clinical Impact of Reperfusion Injury

Reperfusion injury refers to cellular death or dysfunction caused by restoration of blood flow to previously ischemic tissue. This should be differentiated from the normal reparative processes that follow an ischemic insult. Four types of reperfusion injury have been described in the literature: (1) lethal reperfusion injury, (2) nonlethal reperfusion injury (myocardial stunning), (3) reperfusion arrhythmias, and (4) vascular injury (including the "no-reflow" phenomenon). There is continued debate whether reperfusion itself is capable of killing viable myocytes, which otherwise would have survived the ischemic insult. However, there is firm evidence for the existence of myocardial stunning following various ischemic syndromes, including reperfusion therapy for acute myocardial infarction, unstable angina pectoris, vasospastic angina, effort-induced ischemia, coronary artery bypass surgery, and cardiac transplantation. Reperfusion arrhythmia is more common after short ischemic episodes than after long ischemic periods. Thus, while reperfusion arrhythmias in the setting of acute myocardial infarction are relatively rare, reperfusion arrhythmias may be an important cause of sudden death. The "no-reflow" phenomenon has been described following reperfusion in patients with acute myocardial infarction. Three major components have been proposed as mediators of reperfusion injury: (1) oxygen free radicals, (2) the complement system, and (3) neutrophils. Numerous experimental studies have shown short-term benefit by blocking various stages of the postischemic inflammatory response. Oxygen free radicals scavangers, complement inhibition, leukocyte depletion, and the use of antibodies against various adhesion molecules have shown a reduction of infarct size in many ischemic/reperfusion experimental models. However, many of these agents failed to show a benefit in the clinical setting. Moreover, the long-term benefit of such intervention is still unknown.

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.

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.

Early echocardiography can predict cardiac events in emergency department patients with chest pain

STUDY OBJECTIVE

Accurate diagnosis in emergency department patients with possible myocardial ischemia is problematic. Two-dimensional echocardiography has a high sensitivity for identifying patients with myocardial infarction (MI); however, few studies have investigated its diagnostic ability when used acutely in ED patients with possible myocardial ischemia. Therefore we investigated the ability of ED echocardiography for predicting cardiac events in patients with possible myocardial ischemia.

METHODS

Echocardiography was performed within 4 hours of ED presentation in 260 patients with possible myocardial ischemia, and was considered positive if there were segmental wall motion abnormalities or the ejection fraction was less than 40%. ECGs were considered abnormal if there was an ST-segment elevation or depression of greater than or equal to 1 mm, or ischemic T-wave inversion. Cardiac events included MI and revascularization.

RESULTS

Of the 260 patients studied, 45 had cardiac events (23 MI, 19 percutaneous transluminal angioplasty, 3 coronary bypass surgery). The sensitivity of echocardiography for predicting cardiac events was 91% (95% confidence interval 79% to 97%]), which was significantly higher than the ECG (40% [95% CI 27% to 55%]: P < .0001), although specificity was lower (75% [95% CI 69% to 81%] versus 94% [95% CI 90% to 97%]; P < .001). Addition of the echocardiography results to baseline clinical variables and the ECG added significant incremental diagnostic value (P < .001). With use of multivariate analysis, only male gender (P < .03, odds ratio [OR] 2.4 [1.1 to 5.3]), and a positive echocardiographic finding (P < .0001, OR 24 [9 to 65]) predicted cardiac events. Excluding patients with abnormal ECGs (N = 30) did not affect sensitivity (85%) or specificity (74%) of echocardiography.

CONCLUSION

Echocardiography performed in ED patients with possible myocardial ischemia identifies those who will have cardiac events, is more sensitive than the ECG, and has significant incremental value when added to baseline clinical variables and the ECG.

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.

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.

Attenuation of myocardial stunning in isolated rat hearts by a 21-aminosteroid lazaroid (U74389G)

The purpose of this study was to evaluate the effects of reperfusion or in vivo pretreatment with a lipid peroxidation inhibitor, lazaroid (U74389G), on attenuating systolic and diastolic alterations occurring during myocardial stunning in isolated rat hearts. Male Sprague-Dawley rats (350-400 g) were randomized into three groups: control animals (n = 13) received no drugs; hearts from reperfused animals (n = 11) received 5 microM U74389G in the reperfusion solution; pretreated animals (n = 11) received 6 mg/kg U74389G by i.v. infusion 30 min before killing. Isolated, isovolumic rat hearts were subjected to 20 min of ischemia at 37 degrees C and subsequent reperfusion for 30 min. Left ventricular isovolumic developed pressure (LVDP), its first derivative (LVDPdP/dt), end-diastolic pressure (LVEDP), and the time constant of diastolic relaxation (tau) were measured. At baseline, no statistically significant differences were detected in systolic or diastolic function in hearts of rats with or without U74389G treatment. After reperfusion, LVDP stabilized at 87 and 92% in both drug-treated groups compared with 52% in the control group (p < 0.01) and dP/dtmax recovered to 101 and 110% of baseline compared with 58% in the control group (p < 0.01). Diastolic dysfunction showed significant improvement in both U74389G pretreatment groups. The increases in LVEDP and tau were 2.0- and 1.2-fold in pretreated hearts and 2,8-fold and 1.5-fold in drug-reperfused hearts, respectively (compared with 6-fold increases in LVEDP and a 2.5-fold increase in tau in controls; p < 0.05). In conclusion, whether administered before ischemia or during reperfusion, U74389G effectively attenuated the systolic and diastolic dysfunction in this model of myocardial stunning, probably protecting cell membranes from peroxidation by oxygen-derived metabolites.

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.

Absence of Q waves after thrombolysis predicts more rapid improvement of regional left ventricular dysfunction

Although the natural history of regional left ventricular (LV) dysfunction after Q-wave and non-Q-wave myocardial infarction (MI) was well defined in the prethrombolytic era, the functional and structural implications of the absence of Q waves after thrombolysis are less clear. Echocardiography was performed within 48 hours of admission (entry) in 86 patients treated with thrombolysis for their first MI. The extent of abnormal wall motion (AWM; square centimeters) and LV endocardial surface area index (ESA; square centimeters per square meters) were quantified by using a previously validated echocardiographic endocardial surface-mapping technique. Electrocardiography (ECG) performed at 48 hours after thrombolysis was used to classify patients into groups with (Q; n=70) and without (non-Q; n=16) Q waves. All patients in the Q group had regional LV dysfunction on initial echocardiogram compared with 69 percent of those in the non-Q group (p<0.001). When the patients in the non-Q group without AWM were excluded from analysis, there was no significant difference in the extent of AWM between the Q and non-Q groups. Among those patients with AWM on entry, follow-up echocardiography at 6 to 12 weeks demonstrated a significant reduction in extent of AWM for both the Q and non-Q groups. However, the fractional change in AWM was significantly greater in the non-Q than in the Q group (-0.74 +/- 0.28 vs -0.29 +/- 0.44; p<0.02), with a trend toward less AWM at follow-up in the non-Q than in the Q group. The mean ESAi was not significantly different between the two groups at entry or at follow-up. In conclusion, failure to develop Q waves after thrombolysis predicts a lower likelihood of developing regional LV dysfunction and, when such dysfunction is present, predicts a greater degree of recovery.

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.