Transmural, haemorrhagic myocardial infarction after intracoronary streptokinase. Clinical, angiographic, and necropsy findings

Hypothermia for Cardioprotection in Acute Coronary Syndrome Patients: From Bench to Bedside

Early revascularization for patients with acute myocardial infarction (AMI) is of outmost importance in limiting infarct size and associated complications, as well as for improving long-term survival and outcomes. However, reperfusion itself may further damage the myocardium and increase the infarct size, a condition commonly recognized as myocardial reperfusion injury. Several strategies have been developed for limiting the associated with reperfusion myocardial damage, including hypothermia. Hypothermia has been shown to limit the degree of infarct size increase, when started before reperfusion, in several animal models. Systemic hypothermia, however, failed to show any benefit, due to adverse events and potentially insufficient myocardial cooling. Recently, the novel technique of intracoronary selective hypothermia is being tested, with preclinical and clinical results being of particular interest. Therefore, in this review, we will describe the pathophysiology of myocardial reperfusion injury and the cardioprotective mechanics of hypothermia, report the animal and clinical evidence in both systemic and selective hypothermia and discuss the potential future directions and clinical perspectives in the context of cardioprotection for myocardial reperfusion injury.

Coronary No-Reflow after Primary Percutaneous Coronary Intervention-Current Knowledge on Pathophysiology, Diagnosis, Clinical Impact and Therapy

Coronary no-reflow (CNR) is a frequent phenomenon that develops in patients with ST-segment elevation myocardial infarction (STEMI) following reperfusion therapy. CNR is highly dynamic, develops gradually (over hours) and persists for days to weeks after reperfusion. Microvascular obstruction (MVO) developing as a consequence of myocardial ischemia, distal embolization and reperfusion-related injury is the main pathophysiological mechanism of CNR. The frequency of CNR or MVO after primary PCI differs widely depending on the sensitivity of the tools used for diagnosis and timing of examination. Coronary angiography is readily available and most convenient to diagnose CNR but it is highly conservative and underestimates the true frequency of CNR. Cardiac magnetic resonance (CMR) imaging is the most sensitive method to diagnose MVO and CNR that provides information on the presence, localization and extent of MVO. CMR imaging detects intramyocardial hemorrhage and accurately estimates the infarct size. MVO and CNR markedly negate the benefits of reperfusion therapy and contribute to poor clinical outcomes including adverse remodeling of left ventricle, worsening or new congestive heart failure and reduced survival. Despite extensive research and the use of therapies that target almost all known pathophysiological mechanisms of CNR, no therapy has been found that prevents or reverses CNR and provides consistent clinical benefit in patients with STEMI undergoing reperfusion. Currently, the prevention or alleviation of MVO and CNR remain unmet goals in the therapy of STEMI that continue to be under intense research.

The coronary circulation in acute myocardial ischaemia/reperfusion injury: a target for cardioprotection

The coronary circulation is both culprit and victim of acute myocardial infarction. The rupture of an epicardial atherosclerotic plaque with superimposed thrombosis causes coronary occlusion, and this occlusion must be removed to induce reperfusion. However, ischaemia and reperfusion cause damage not only in cardiomyocytes but also in the coronary circulation, including microembolization of debris and release of soluble factors from the culprit lesion, impairment of endothelial integrity with subsequently increased permeability and oedema formation, platelet activation and leucocyte adherence, erythrocyte stasis, a shift from vasodilation to vasoconstriction, and ultimately structural damage to the capillaries with eventual no-reflow, microvascular obstruction (MVO), and intramyocardial haemorrhage (IMH). Therefore, the coronary circulation is a valid target for cardioprotection, beyond protection of the cardiomyocyte. Virtually all of the above deleterious endpoints have been demonstrated to be favourably influenced by one or the other mechanical or pharmacological cardioprotective intervention. However, no-reflow is still a serious complication of reperfused myocardial infarction and carries, independently from infarct size, an unfavourable prognosis. MVO and IMH can be diagnosed by modern imaging technologies, but still await an effective therapy. The current review provides an overview of strategies to protect the coronary circulation from acute myocardial ischaemia/reperfusion injury. This article is part of a Cardiovascular Research Spotlight Issue entitled 'Cardioprotection Beyond the Cardiomyocyte', and emerged as part of the discussions of the European Union (EU)-CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

Reperfusion therapy-What's with the obstructed, leaky and broken capillaries?

Microvascular dysfunction is well established as an early and rate-determining factor in the injury response of tissues to ischemia and reperfusion (I/R). Severe endothelial cell dysfunction, which can develop without obvious morphological cell injury, is a major underlying cause of the microvascular abnormalities that accompany I/R. While I/R-induced microvascular dysfunction is manifested in different ways, two responses that have received much attention in both the experimental and clinical setting are impaired capillary perfusion (no-reflow) and endothelial barrier failure with a transition to hemorrhage. These responses are emerging as potentially important determinants of the severity of the tissue injury response, and there is growing clinical evidence that they are predictive of clinical outcome following reperfusion therapy. This review provides a summary of animal studies that have focused on the mechanisms that may underlie the genesis of no-reflow and hemorrhage following reperfusion of ischemic tissues, and addresses the clinical evidence that implicates these vascular events in the responses of the ischemic brain (stroke) and heart (myocardial infarction) to reperfusion therapy. Inasmuch as reactive oxygen species (ROS) and matrix metalloproteinases (MMP) are frequently invoked as triggers of the microvascular dysfunction elicited by I/R, the potential roles and sources of these mediators are also discussed. The available evidence in the literature justifies the increased interest in the development of no-reflow and hemorrhage in heart and brain following reperfusion therapy, and suggests that these vascular events may be predictive of poor clinical outcome and warrant the development of targeted treatment strategies.

Effect of thrombolytic therapy on the patterns of post myocardial infarction ventricular septal rupture

OBJECTIVES

Ventricular septal rupture (VSR) is a rare but feared complication after myocardial infarction (MI). The objective of this study was to investigate the effects of thrombolytic therapy on the patterns of VSR following MI.

METHODS

30 consecutive patients admitted to a single tertiary level cardiac hospital with a diagnosis of acute MI and developed VSR in the hospital were included. The effect on thrombolytic therapy on the formation of VSR and its clinical outcome was studied.

RESULTS

Out of 30 patients, 15 patients received thrombolytic therapy.10 received early (<12h) and 5 received late (>12h). The median time to post MI VSR formation was significantly shorter in thrombolysis group compared to non thrombolysis group at 1 vs 3 days(p=0.026). The median time for VSR formation was shorter in early thrombolysis group compared to late thrombolysis group at 1 vs 3 days (p=0.022). There was no difference between late and no thrombolytic therapy (3 vs 3 days, p=0.672). There was no significant difference in the mortality between thrombolytic and no thrombolytic therapy (p=0.690). Patients treated medically had a significant higher mortality compared to patients treated surgically (p=0.005).

CONCLUSION

Thrombolytic therapy results in an earlier presentation of VSR after MI. This earlier presentation may be due to reduction in the number of patients developing late VSR after thrombolytic therapy, while the number of patients developing an early VSR remaining unaffected. Despite improvements in medical therapy and percutaneous and surgical techniques, mortality with this complication remains extremely high.

Analytic Review: Thrombolytic Therapy in Acute Myocardial Infarction

The salvage of myocardium in the setting of acute myocardial infarction has long been a goal of physicians involved in the care of patients with coronary artery disease. Understanding the role of thrombosis in the pathogenesis of acute myocardial infarction has led the way to an entirely new approach to the treatment of this entity. Thrombolytic therapy has now become a widely used form of treatment with encouraging results. Both intravenous and intracoronary administration of thrombolytic agents have been shown to promote recanalization of acutely occluded coronary arteries. Results of studies using the clot-specific agent, tissue plasminogen activator, intravenously have been most encouraging; successful reperfusion has been obtained in approximately 70% of patients treated. In addition, a recent large-scale trial has shown a reduction in morbidity and mortality with the early use of thrombolytic agents.

Ongoing trials should help delineate the precise role and timing of these agents as the initial form of therapy for acute myocardial infarction. Other issues that remain unresolved are the frequency of restenosis and the role of percutaneous transluminal coronary angioplasty in addition to thrombolytic therapy in the treatment of acute myocardial infarction.

Trends in the clinical and pathological characteristics of cardiac rupture in patients with acute myocardial infarction over 35 years

Background

There is little known about whether the clinical and pathological characteristics and incidence of cardiac rupture (CR) in patients with acute myocardial infarction (AMI) have changed over the years.

Methods and Results

The incidence and clinical characteristics of CR were investigated in patients with AMI, who were divided into 3 cohorts: 1977–1989, 1990–2000, and 2001–2011. Of a total of 5699 patients, 144 were diagnosed with CR and 45 survived. Over the years, the incidence of CR decreased (1977–1989, 3.3%; 1990–2000, 2.8%; 2001–2011, 1.7%; P=0.002) in association with the widespread adoption of reperfusion therapy. The mortality rate of CR decreased (1977–1989, 90%; 1990–2000, 56%; 2001–2011, 50%; P=0.002) in association with an increase in the rate of emergent surgery. In multivariable analysis, first myocardial infarction, anterior infarct, female sex, hypertension, and age >70 years were significant risk factors for CR, whereas impact of hypertension on CR was weaker from 2001 to 2011. Primary percutaneous coronary intervention (PPCI) was a significant protective factor against CR. In 64 autopsy cases with CR, myocardial hemorrhage occurred more frequently in those who underwent PPCI or fibrinolysis than those who did not receive reperfusion therapy (no reperfusion therapy, 18.0%; fibrinolysis, 71.4%; PPCI, 83.3%; P=0.001).

Conclusions

With the development of medical treatment, the incidence and mortality rate of CR have decreased. However, first myocardial infarction, anterior infarct, female sex, and old age remain important risk factors for CR. Adjunctive cardioprotection against reperfusion‐induced myocardial hemorrhage is emerging in the current PPCI era.

Intramyocardial hemorrhage and microvascular obstruction after primary percutaneous coronary intervention

Reperfusion may cause intramyocardial hemorrhage (IMH) by extravasation of erythrocytes through severely damaged endothelial walls. The purpose of the study was to evaluate the clinical significance of IMH in relation to infarct size, microvascular obstruction (MVO) and function in patients after primary percutaneous intervention. Forty-five patients underwent cardiovascular MR imaging (CMR) 1 week and 4 months after primary stenting for a first acute myocardial infarction. T2-weighted spin-echo imaging (T2W) was used to assess infarct related edema and IMH, and delayed enhancement (DE) was used to assess infarct size and MVO. Cine CMR was used to assess left ventricular volumes and function at baseline and at 4 months follow-up. In 22 (49%) patients, IMH was detected as areas of attenuated signal in the core of the high signal intensity region on T2W images. Patients with IMH had larger infarcts, higher left ventricular volumes and lower ejection fraction. Contrast-to-noise ratio (CNR) between hyperintense periphery and the hypo-intense core of the T2W ischemic area correlated to peak CKMB, total infarct size and MVO size. Using univariable analysis, CNR predicted ejection fraction at baseline (β = −0.62, P = 0.003) and follow-up (β = −0.84, P < 0.001). However, after multivariable analysis, baseline ejection fraction and presence of MVO were the only parameters that predicted functional changes at follow-up. IMH was found in the majority of patients with MVO after reperfused myocardial infarction. It was closely related to markers of infarct size, MVO and function, but did not have prognostic significance beyond MVO.

Influence of thrombolytic therapy on the patterns of ventricular septal rupture after acute myocardial infarction

BACKGROUND

Post-myocardial infarction ventricular septal defect (VSD) complicates approximately 2% of myocardial infarctions. Thrombolytic therapy may accelerate the time from myocardial infarction to VSD formation. The effects of thrombolytic therapy in patients with a post-myocardial infarction VSD were investigated.

METHOD

Demographic, procedural, and event data were retrospectively analysed in patients transferred to a regional cardiothoracic centre with the diagnosis of post-myocardial infarction VSD over five years.

RESULTS

Twenty nine patients were analysed; 15 received thrombolytic therapy: 10 (<12 hours) early and five (> or =12 hours) late. The median time to post-myocardial infarction VSD was shorter with thrombolytic therapy at 1 v 5.5 days (p=0.01). The median time to post-myocardial infarction VSD was shorter with early compared with late thrombolytic therapy at 1 v 6 days (p<0.01). There was no difference between late and no thrombolytic therapy, 5.5 v 6 days. Patients treated with thrombolytic therapy had a trend towards higher mortality at 11/15 (73%) compared with 5/14 (36%) (p=0.066). Twenty five (86%) patients had surgery. All four not having surgery died. Surgical survival was 13/25 (52%) at discharge and six months of follow up. Within the surgical group survival with prior thrombolytic therapy was 4/25 (25%) and 9/13 (69%) without (p=0.07).

CONCLUSION

There appears to be an earlier presentation of post-myocardial infarction VSD when thrombolytic therapy has been used. An early presentation can carry a worse prognosis and may have implications for the identification and treatment of this life threatening complication.

A subacute left ventricular free wall rupture after thrombolytic and glycoprotein IIb/IIIa inhibitor treatment: an overlooked finding of left ventriculography

Subacute left ventricular free wall rupture is a rare complication in acute myocardial infarction. With the increasing use of thrombolytic agents and glycoprotein IIb/IIIa inhibitors, this complication has been increasing recently. We report a case of subacute cardiac rupture with frank pericardial effusion receiving thrombolytic and glycoprotein IIb/IIIa inhibitor therapies.

[A clinicopathologic study of autopsy cases with myocardial infarction treated with coronary intervention (PTCA/Stenting)]

A clinicopathologic study was made in 28 patients who died after acute myocardial infarction (AMI) treated with coronary intervention (CI: Percutaneous transluminal coronary angioplasty (PTCA) or Stenting). Nineteen patients received PTCA (12 men and 7 women, 42 to 85 years of age, mean 71.4 years), and 9 patients received stenting after PTCA (8 men and 1 woman, 49 to 86 years of age, mean 67.7 years). Hemorrhagic infarction was found in 23 cases. Compared to direct PTCA, more severe hemorrhage was found in cases treated with PTCA after intracoronary thrombolytic therapy (rescue PTCA: r-PTCA). Also, severe hemorrhage in the infarct area was found in cases treated with percutaneous cardiopulmonary support (PCPS) after AMI. Hemorrhagic infarction was found even in patients treated with CI in the early phase after AMI, and also in some patients who recovered from initial heart failure after AMI. Compared to usual ischemic infarct, healing was greatly delayed in the hemorrhagic infarct area. We conclude that special care is required in the treatment of patients who received CI, because of a high possibility of hemorrhage in the infarct area after CI and the delay in healing in the hemorrhagic infarction area.

Thrombolytic therapy can reduce the arrhythmogenic substrate after acute myocardial infarction: a study using the signal-averaged electrocardiogram, endocardial catheter mapping and programmed ventricular stimulation

Thrombolytic therapy improves survival after acute myocardial infarction (AMI) primarily by preserving left ventricular function. Its influence on the arrhythmogenic substrate remains uncertain. To investigate the electrophysiologic effects of thrombolytic therapy, signal-averaged electrocardiography, endocardial catheter mapping and programmed stimulation were performed in 93 consecutive patients with their first AMI who underwent thrombolytic therapy. Early reperfusion was achieved in 75 patients (group 1), but not in 18 patients (group 2). The incidence of the signal-averaged electrocardiogram abnormality was 11% in group 1 (8 of 75 patients) and 33% in group 2 (6 of 18 patients) (p<0.02). Catheter mapping detected delayed endocardial electrograms in 30 group 1 patients and 10 group 2 patients (p=NS). The spatial distribution of these electrograms was smaller, and the longest duration of endocardial electrograms was shorter in group 1 than in group 2 (p<0.01). Sustained monomorphic ventricular tachycardia was induced less commonly in group 1 (20%) than in group 2 (44%) (p<0.05). In conclusion, thrombolytic therapy can reduce the arrhythmogenic substrate and improve electrical stability after AMI. This antiarrhythmic effect may contribute, in part, to the improved survival of patients treated with thrombolytic drugs.

Limitation of myocardial infarct size after primary angioplasty: is a higher patency the only mechanism?

BACKGROUND

Several studies demonstrate a better outcome after primary angioplasty compared with thrombolysis. The mechanism is assumed to be a higher rate of open infarct-related vessels.

METHODS AND RESULTS

We conducted a randomized trial of primary coronary angioplasty compared with thrombolysis. A total of 401 patients with acute myocardial infarction were randomly assigned to either primary angioplasty or thrombolytic therapy. Radionuclide left ventricular ejection fraction was performed before hospital discharge. Infarct size was estimated by measurement of serial lactate dehydrogenase activity (LDH Q72). Separate analyses were performed in patients with an open infarct-related vessel, either after thrombolysis or angioplasty. Baseline characteristics were comparable between the 2 treatment groups. Of the 197 patients treated with angioplasty, 176 (89%) had an open infarct-related vessel compared with 126 (62%) of the 204 patients treated with thrombolysis (P <.001). In patients with an open infarct-related vessel, those treated with primary angioplasty had a lower enzyme release compared with those treated with thrombolysis: LDH Q72 949 (748) and 1200 (1117), respectively (P <.05). Compared with angioplasty, patients treated with thrombolysis had a lower left ventricular ejection fraction. In the subgroup of patients with an open infarct-related vessel, after thrombolysis or angioplasty, patients treated with thrombolysis still had a lower ejection fraction (47% vs 50%, P <.05). Multivariate analysis, adjusting for differences in several clinical variables, did not change these results. Patients with an open infarct-related vessel and thrombolysis had a higher risk of an ejection fraction <40% compared with patients treated with primary angioplasty (relative risk 1.9, 95% confidence interval 1.0 to 2.7).

CONCLUSIONS

Despite successful thrombolysis, with sustained patency of the infarct-related vessel, primary angioplasty remains superior to thrombolytic therapy with regard to left ventricular function and enzymatic infarct size. This may be caused by adverse effects of fibrinolytics on infarcted myocardium.

Fatal cardiac rupture among patients treated with thrombolytic agents and adjunctive thrombin antagonists: observations from the Thrombolysis and Thrombin Inhibition in Myocardial Infarction 9 Study

OBJECTIVES

The purpose of this study was to determine the incidence and demographic characteristics of patients experiencing cardiac rupture after thrombolytic and adjunctive anticoagulant therapy and to identify possible associations between the mechanism of thrombin inhibition (indirect, direct) and the intensity of systemic anticoagulation with its occurrence. BACKGROUND Cardiac rupture is responsible for nearly 15% of all in-hospital deaths among patients with myocardial infarction (MI) given thrombolytic agents. Little is known about specific patient- and treatment-related risk factors. METHODS Patients (n = 3,759) with MI participating in the Thrombolysis and Thrombin Inhibition in Myocardial Infarction 9A and B trials received intravenous thrombolytic therapy, aspirin and either heparin (5,000 U bolus, 1,000 to 1,300 U/h infusion) or hirudin (0.1 to 0.6 mg/kg bolus, 0.1 to 0.2 mg/kg/h infusion) for at least 96 h. A diagnosis of cardiac rupture was made clinically in patients with sudden electromechanical dissociation in the absence of preceding congestive heart failure, slowly progressive hemodynamic compromise or malignant ventricular arrhythmias. RESULTS A total of 65 rupture events (1.7%) were reported-all were fatal, and a majority occurred within 48 h of treatment Patients with cardiac rupture were older, of lower body weight and stature and more likely to be female than those without rupture (all p < 0.001). By multivariable analysis, age >70 years (odds ratio [OR] 3.77; 95% confidence interval [CI] 2.06, 6.91), female gender (OR 2.87; 95% CI 1.44, 5.73) and prior angina (OR 1.82; 95% CI 1.05, 3.16) were independently associated with cardiac rupture. Independent predictors of nonrupture death included age >70 years (OR 3.68; 95% CI 2.53, 5.35) and prior MI (OR 2.14; 95%, CI 1.45, 3.17). There was no association between the type of thrombin inhibition, the intensity of anticoagulation and cardiac rapture. CONCLUSIONS Cardiac rupture following thrombolytic therapy tends to occur in older patients and may explain the disproportionately high mortality rate among women in prior dinical trials. Unlike major hemorrhagic complications, there is no evidence that the intensity of anticoagulation associated with heparin or hirudin administration influences the occurrence of rupture.

Primary angioplasty reduces risk of myocardial rupture compared to thrombolysis for acute myocardial infarction

Although the mechanical complications of acute ventricular septal defect and acute mitral regurgitation are uncommon after acute myocardial infarction, these complications are associated with an extremely high morbidity and mortality. We hypothesized that the administration of thrombolytic drugs may result in hemorrhagic infarction as well as the potential for incomplete revascularization and thus may lead to an increased incidence of mechanical complications compared to primary angioplasty. Accordingly, we reviewed the data of the most contemporary thrombolytic and primary angioplasty trials and compared the incidence of mechanical complications among 36,303 patients treated with thrombolytics reported in the GUSTO trial to the incidence of mechanical complications among 1,295 patients treated with primary angioplasty obtained from the PAMI-1 and PAMI-2 trials. We found that angioplasty resulted in an overall 86% relative risk reduction in mechanical complications (2.20% vs. 0.31%, P < 0.001). In comparison to thrombolytic therapy, angioplasty resulted in an 82% decrease in acute mitral regurgitation (1.73% vs. 0.31%, P < 0.001) and a 100% decrease in acute ventricular septal defect (0.47% vs. 0.00%, P < 0.03). In conclusion, in patients with acute myocardial infarction, reperfusion with primary angioplasty is associated with less myocardial rupture and mechanical complications than thrombolytics. This finding may, in part, explain the improved prognosis observed in myocardial infarction patients treated with primary angioplasty.

Primary coronary angioplasty in acute myocardial infarction

It is well established that recanalisation of the infarct-related artery is of great benefit in the early hours after acute myocardial infarction. This can be achieved by the use of thrombolytic agents and/or by percutaneous transluminal coronary angioplasty (PTCA). This article reviews data on the role of primary PTCA and summarises current opinion on its use.

Healing of myocardial infarcts in dogs. Effects of late reperfusion

BACKGROUND

Early reperfusion salvages ischemic myocardium and limits myocardial infarct size. However, the effects of late reperfusion, after the possibility for limitation of infarct size has passed, have not been completely elucidated. The purpose of this study was to ascertain the effect of reperfusion after 6 hours of ischemia on the rate of infarct healing and on the size and geometry of the resulting scars, as determined by gross and microscopic quantification.

METHODS AND RESULTS

Myocardial infarcts were produced in anesthetized, open-chest dogs by occlusion of the circumflex coronary artery. They either were reperfused by removal of the occluding snare or were nonreperfused. The animals were allowed to recover for either 4 days, 2 weeks, or 6 weeks. At these times, infarct size, infarct dimensions (wall thickness and circumferential extent), and the proportion of infarct occupied by necrotic myocardium versus granulation tissue (evolving scar) were measured. At 4 days, infarcts were swollen in both nonreperfused and reperfused groups (increased thickness and circumferential extent of the area at risk). Conversely, at 6 weeks, the size, thickness, and circumferential extent of the scar all were decreased. Two common anatomic complications of human infarction, cardiac rupture and chronic infarct expansion (aneurysm), did not occur in this experimental model. Reperfusion at 6 hours did not affect initial infarct size (4 days) or scar size (6 weeks). At 2 weeks, reperfused infarcts were smaller and were composed of proportionately more granulation tissue and less nonresorbed necrosis than nonreperfused infarcts.

CONCLUSIONS

Thus, reperfusion accelerated the rate of infarct repair, ie, the replacement of necrotic myocardium by scar. Acceleration of infarct repair may be a beneficial effect of late reperfusion even after the opportunity for limitation of infarct size has passed.

Deleterious effects of a systemic lytic state on reperfused myocardium. Minimization of reperfusion injury and enhanced recovery of myocardial function by direct angioplasty

BACKGROUND

The beneficial effects of flow restoration and the deleterious impact of reperfusion injury on ischemic myocardium are well known. However, most experimental studies have induced reperfusion by mechanical release of nonthrombotic occlusions, only occasionally in the presence of a systemic lytic state. Conditions differ markedly in patients undergoing pharmacological or mechanical recanalization of thrombotically occluded coronary arteries. Accordingly, this study was designed to determine whether the method of coronary occlusion and mode of recanalization influence the response of the heart to reperfusion.

METHODS AND RESULTS

The acute effects of reperfusion on right ventricular (RV) function and histology were studied in open-chest dogs subjected to right coronary artery (RCA) balloon occlusion and deflation alone (group 1), pharmacological lysis of thrombotic occlusions (group 2), balloon occlusion with reperfusion induced by balloon deflation in the presence of a systemic lytic state (group 3), and recanalization of thrombotically occluded vessels by direct angioplasty (group 4). In all groups, 1 hour of RCA occlusion led to RV free wall (FW) dyskinesis. In group 1, reperfusion promptly improved RVFW function, with normal RVFW thickness and only minimal edema by microscopy. In contrast, in group 2, clot lysis led to acute RVFW swelling and impaired recovery of RVFW contraction associated with striking interstitial edema, contraction band necrosis, and hemorrhage by microscopy. In group 3, balloon deflation in the presence of a lytic state led to a similar but less severe pattern of abrupt RVFW swelling and impaired recovery of RVFW function but lesser histological alterations than in group 2. However, mechanical recanalization of thrombotically occluded vessels (group 4) led to prompt recovery of RVFW function without significant RVFW swelling or histological abnormalities.

CONCLUSIONS

Our observations indicate that the responses of ischemic myocardium to reperfusion are influenced by factors beyond those effects attributable to ischemia and reperfusion per se. Pharmacological lysis of coronary thrombi results in alterations characteristic of reperfusion injury and associated with impaired functional recovery. Such changes are also evident, although to a lesser extent, when reperfusion of northrombotic occlusions is induced by mechanical recanalization in the presence of a systemic lytic state but not in its absence. However, such effects were not seen with direct mechanical recanalization of thrombotically occluded vessels. In aggregate, these findings indicate that induction of a systemic lytic state, together with products released by lysis of intracoronary thrombi, generates an inurious milieu that exerts adverse effects on reperfused myocardium.

Timing, mode, and predictors of death after direct angioplasty for acute myocardial infarction

The timing and mechanisms of early (30 day) mortality in 330 consecutive patients treated with direct angioplasty less than 12 hr after onset of myocardial infarction without antecedent thrombolysis were studied. There were 38 deaths (11.5% of pts), with a majority being due to cardiogenic shock (76%). Other causes included acute closure (11%), death after emergency bypass surgery (5%), ventricular arrhythmias (5%), and respiratory failure (3%). No deaths from stroke or cardiac rupture were seen, in contrast to trials of thrombolytic agents. Most deaths were seen early, with 47% occurring within 1 day, 35% from days 2-7, and 18% from days 8-30. Death from cardiogenic shock was the most common cause of death throughout this period: 83% of deaths in days 0-3, 88% of deaths in days 4-6, and 43% of deaths in days 8-30. Significant predictors of early death included older age (P < .0001), multi-vessel disease (P < .05), direct angioplasty failure (P < .05), reduced ejection fraction (P < .0001), and anterior myocardial infarction (P < .0005). Gender, prior myocardial infarction, and prior bypass surgery did not affect mortality. Cardiogenic shock is the most common cause of early death after direct angioplasty for myocardial infarction. Patients with one or more risk factors for early death may benefit from additional myocardial salvage or revascularization efforts in the early post-infarct period. Certain causes of death after direct angioplasty (cardiac, rupture, stroke) appear to be less common than data reported for lytic therapy for myocardial infarction.

Cardiac rupture associated with thrombolytic therapy: impact of time to treatment in the Late Assessment of Thrombolytic Efficacy (LATE) study

OBJECTIVES

This prospective ancillary study was conducted to determine the association between the time from symptom onset to treatment and cardiac rupture in patients with acute myocardial infarction.

BACKGROUND

There is strong evidence that the time window for thrombolytic therapy should be extended to at least 12 h; however, many clinicians are concerned that late treatment may cause an excessive occurrence of death from cardiac rupture. Because up to 30% of patients with acute myocardial infarction arrive in the hospital > 6 h from symptom onset, resolving this issue is of paramount clinical importance.

METHODS

A total of 5,711 patients with acute myocardial infarction were randomized to receive intravenous recombinant tissue-type plasminogen activator (rt-PA) (100 mg over 3 h) or matching placebo, within 6 and 24 h from symptom onset. Both groups received immediate oral aspirin, and a majority of patients received intravenous heparin during the initial 48 h.

RESULTS

By 35 days, 177 patients had died, with the cause of death specified as cardiac rupture (53 patients), electromechanical dissociation (42 patients) or asystole (82 patients). An additional 370 patients had died of other causes. In patients treated within 12 h, the proportion of rupture deaths in the group given rt-PA was higher than that observed in those who received placebo, but the difference was not statistically significant. In patients treated after 12 h, there was no evidence of an increased incidence of rupture with rt-PA, and the proportion of deaths due to rupture in this group was lower than that in patients given placebo. However, there was evidence of a difference between rt-PA and placebo with respect to the time that rupture became clinically manifest (treatment by time to death interaction, p = 0.03).

CONCLUSIONS

This study provides unequivocal evidence that late treatment (6 to 24 h after symptom onset) with rt-PA is not associated with an increased risk of cardiac rupture. However, for reasons that are unclear, coronary thrombolysis appears to accelerate rupture events, typically to within 24 h of treatment.

Assessment of postreperfusion myocardial hemorrhage using proton NMR imaging at 1.5 T

BACKGROUND

Intramyocardial hemorrhage occurs frequently after reperfusion of acute myocardial infarction. However, its significance has not yet been established, mainly because of the lack of methods for detecting such hemorrhage. The following ex vivo study was carried out to assess the potential of nuclear magnetic resonance (NMR) imaging to detect and quantitate postreperfusion intramyocardial hemorrhage.

METHODS AND RESULTS

Sixteen adult mongrel dogs underwent 3 hours of coronary occlusion followed by 1 hour of reperfusion, and three dogs underwent 4 hours of occlusion without reperfusion. Radiolabeled microspheres and 51Cr-labeled red blood cells were used to assess flow and evaluate the extent of hemorrhage. These results were later compared with both NMR and histology. Spin-echo NMR imaging was performed on the excised hearts using a 1.5-T system. Macroscopic assessment of the sliced myocardium revealed the existence of hemorrhage in 14 of the 16 dogs that underwent reperfusion but in none of those with occlusion only. In all 16 dogs with reperfusion, zones of increased signal intensity (SI) ratio (1.68 +/- 0.41 compared with control, p less than 0.05) were seen in regions relating to the distribution of the occluded coronary artery, whereas in 13 of the 16 dogs, areas of decreased SI within the zone of increased SI ratio (0.81 +/- 0.16 compared with control, p less than 0.05) were also seen, corresponding to regions with macroscopic hemorrhage. In contrast, in the three dogs without reperfusion, no macroscopic hemorrhage was observed, and likewise, no NMR zones of reduced SI were detected. Hemorrhage size by NMR (decreased SI zones), correlated well with hemorrhage size calculated from tissue slices (r = 0.96, SEE = 0.92%, p less than 0.01), or by 51Cr labeling (r = 0.78, SEE = 1.5, p = 0.1). In the reperfusion group, T2 relaxation times in the infarcted hemorrhagic zone (58 +/- 9 msec) were significantly lower than the infarcted zones without hemorrhage (98 +/- 13 msec, p less than 0.001). In contrast, when compared with control (964 +/- 72 msec), T1 relaxation times were significantly increased in both infarct zones, either with (1,284 +/- 176 msec) or without (1,266 +/- 103 msec) hemorrhage. The selective shortening of T2 relaxation times in the hemorrhagic regions is consistent with the paramagnetic effects of deoxyhemoglobin.

CONCLUSIONS

NMR imaging may provide a noninvasive approach for the detection and quantitation of intramyocardial hemorrhage. This observation may provide a means to further characterize pathological processes associated with acute myocardial infarction and assess the role of myocardial hemorrhage after reperfusion therapy.

Cardiac rupture complicating hemorrhagic infarction after intracoronary thrombolysis

An 80-year-old woman with acute myocardial infarct received intracoronary thrombolysis by a large dose of urokinase four hours after the onset of chest pain. Despite the patient having no chest pain after intracoronary thrombolysis and her general condition being stable, she died suddenly on the 4th hospital day. Autopsy revealed hemopericardium due to cardiac rupture, which occurred at the center of the transmural hemorrhagic infarction of the anteroseptal wall. The massive hemorrhagic infarction was promoted by reperfusion from thrombolytic therapy. She had also classic risk factors for cardiac rupture, such as hypertension, senility, female gender, and first acute myocardial infarct. Therefore, the present case demonstrated that hemorrhagic infarction increased the incidence of cardiac rupture.

Cardiac free wall rupture in acute myocardial infarction: ameliorative effect of coronary reperfusion

To investigate the pathophysiology of cardiac free wall rupture (cardiac rupture) following acute myocardial infarction (AMI), and to clarify whether reperfusion therapy prevents cardiac rupture, 1,329 cases of AMI (conventional therapy group: 807 cases and reperfusion therapy group: 533 cases) were studied retrospectively. The overall incidence of cardiac rupture was 2.3% (2.7% in the conventional therapy group vs. 1.7% in the reperfusion therapy group). Patients with cardiac rupture were divided into two subgroups according to the time interval from the onset of AMI to cardiac rupture (early rupture less than or equal to 72 h and late rupture greater than or equal to 4 days). The indices of initial evolution of AMI was a significant risk of early cardiac rupture. The reperfusion therapy group showed significantly lower incidence of late rupture (0.4 vs. 1.5% in conventional therapy group; p less than 0.05). The incidence of cardiac rupture in the unsuccessful reperfusion therapy group was higher than that of the successful group (5.9% of 118 cases vs. 0.5% of 404 cases; p less than 0.05). It is concluded that the etiology of cardiac rupture following AMI cannot be explained by any single factor. Early rupture depends on the initial evolution of AMI, and early reperfusion and collateral flow prevent the late onset cardiac rupture.

Intramyocardial hemorrhage due to prolonged intracoronary infusion of urokinase into a totally occluded saphenous vein bypass graft

A 0.038 inch perfusion wire was used to selectively administer a 24-hr infusion of urokinase into the occluded saphenous vein bypass graft of a 69-yr-old woman. Immediately following subsequent reperfusion by balloon angioplasty, she developed a hemorrhagic myocardial infarction.

Cardiac tamponade early after thrombolysis for acute myocardial infarction: a rare but not reported hemorrhagic complication

Among 392 consecutive patients admitted for acute myocardial infarction and treated with thrombolytic drugs, 4 patients (1%) developed an early hemorrhagic pericardial effusion (without ventricular wall rupture) evolving within 24 h to cardiogenic shock consequent to cardiac tamponade. They all suffered from a large anterior myocardial infarction treated within 4 h after onset of symptoms with intravenous anisoylated plasminogen streptokinase activator complex (one case), recombinant tissue-type plasminogen activator (rt-PA) (two cases) or streptokinase (one case), anticoagulation with heparin (all cases) and aspirin (three cases). As soon as pericardial effusion was established by echocardiography, emergency percutaneous pericardiocentesis was performed at the bedside 20 +/- 6 h after thrombolytic therapy was started. This corrected immediately the clinical and hemodynamic status of each patient and a catheter was left in the pericardial space for 34 +/- 18 h. Thus, in the presence of unexplained clinical and hemodynamic deterioration occurring during the first 24 h after thrombolytic treatment of a large myocardial infarction, cardiac tamponade should be suspected. Immediate percutaneous pericardiocentesis followed by continuous drainage is a simple and definitive treatment for this complication.

Timing and mechanism of in-hospital and late death after primary coronary angioplasty during acute myocardial infarction

The effect of early myocardial reperfusion on patterns of death after acute myocardial infarction (AMI) is unknown. Thus, the mechanism and timing of in-hospital and late deaths among a group of 614 patients treated with coronary angioplasty without antecedent thrombolytic therapy for AMI were determined. Death occurred in 49 patients (8%) before hospital discharge. Four patients died in the catheterization laboratory. Death was due to cardiogenic shock in 22 patients, acute vessel reclosure in 5 patients, was sudden in 8 patients and followed elective coronary artery bypass surgery in 8 patients. Cardiac rupture was observed in only 2 patients after failed infarct angioplasty, and did not occur among the 574 patients with successful infarct reperfusion. Intracranial hemorrhage did not occur. Multivariate predictors of in-hospital death included failed infarct angioplasty, cardiogenic shock, 3-vessel coronary artery disease and age greater than or equal to 70 years. During a follow-up period of 32 +/- 21 months (range 1 to 87), 55 patients died. The cause of death was cardiac in 36 patients, including an arrhythmic death in 23 patients and was due to circulatory failure in 13 others. One patient died of reinfarction due to late reclosure of the infarct artery. Actuarial survival curves demonstrated overall survival after hospital discharge of 95 and 87% at 1 and 4 years, respectively. Freedom from cardiac death at 1 and 4 years was 96 and 92%. Multivariate predictors of late death included 3-vessel disease, a baseline ejection fraction of less than or equal to 40%, age greater than 70 years and female gender.(ABSTRACT TRUNCATED AT 250 WORDS)

Emergency percutaneous transluminal coronary angioplasty for acute myocardial infarction in patients 70 years of age and older

Direct percutaneous transluminal coronary angioplasty (PTCA) was performed as the primary means of establishing reperfusion during acute myocardial infarction in 105 elderly patients (mean age +/- standard deviation 75 +/- 4 years) at a mean of 5.5 +/- 4.0 hours from symptom onset. Fifty-two patients (50%) had anterior infarctions, 70 (67%) had significant narrowing in greater than 1 vessel, and 12 (11%) were in cardiogenic shock. Primary success was achieved in 91% of the infarct-related arteries. Four patients with failed PTCA underwent emergency bypass surgery; 10 had early symptomatic reocclusion of the dilated vessel. There was 1 death acutely in the catheterization laboratory. The overall in-hospital mortality was 18%. Three-vessel coronary artery disease and cardiogenic shock on presentation were the strongest predictors of in-hospital death. Global ejection fraction improved from 54 +/- 13 to 61 +/- 15% (p less than 0.001). The 1- and 5-year survival rates, including in-hospital deaths, were 73 and 67%, respectively. It is concluded that direct PTCA is an effective means of salvaging ischemic myocardium during acute myocardial infarction in the elderly patient. It is associated with a high success rate and low complication rate. The short- and long-term survival in this high-risk group of patients are improved compared with survival rates in historical controls.

Cardiac rupture, mortality and the timing of thrombolytic therapy: a meta-analysis

This study examined the relation between the risk of cardiac rupture and the timing of thrombolytic therapy for acute myocardial infarction. To test the hypothesis that cardiac rupture is prevented by early thrombolytic therapy but is promoted by late treatment, randomized controlled trials of thrombolytic agents for myocardial infarction were pooled. A logistic regression model including 58 cases of cardiac rupture among 1,638 patients from four trials showed that the odds ratio (treated/control) of cardiac rupture was directly correlated with time to treatment (p = 0.01); at 7 h, the odds ratio was 0.4 (95% confidence limits 0.17 to 0.93); at 11 h, it was 0.93 (0.53 to 1.60) and at 17 h, it was 3.21 (1.10 to 10.1). Analysis of data from the Gruppo Italiano per lo Studio della Streptochinasi nell'Infarto Miocardico (GISSI) trial independently confirmed the relation between time to thrombolytic therapy and risk of cardiac rupture (p = 0.03). Analysis of 4,692 deaths in 44,346 patients demonstrated that the odds ratio of death was also directly correlated with time to treatment (p = 0.006); at 3 h, the odds ratio for death was 0.72 (0.67 to 0.77); at 14 h, it was 0.88 (0.77 to 1.00) and at 21 h, it was 1 (0.82 to 1.37). Thrombolytic therapy early after acute myocardial infarction improves survival and decreases the risk of cardiac rupture. Late administration of thrombolytic therapy also appears to improve survival but may increase the risk of cardiac rupture.

Detection, characterization and functional assessment of reperfused Q-wave acute myocardial infarction by cine magnetic resonance imaging

The capability of dynamic gradient-refocused magnetic resonance imaging (cine MRI) to detect, localize and functionally assess acute myocardial infarction (AMI) in 25 patients at a mean time interval of 7 days after AMI was evaluated. Fifteen asymptomatic volunteers were also examined to determine the specificity of the observations. Upon presentation, each patient received intravenous thrombolytic therapy, underwent immediate cardiac catheterization and had percutaneous transluminal coronary angioplasty performed when coronary reperfusion was absent. Twenty-four of the patients had documented coronary reperfusion at a mean interval of 259 +/- 129 minutes. Global ejection fraction and regional wall motion abnormalities were evaluated at 7 days by cine MRI, left ventriculography and radionuclide angiography. Twenty patients with both an absolute decrease in myocardial signal and a matched regional wall motion abnormality had AMI properly identified by cine MRI. In contrast, the finding of both decreased signal intensity and a matched regional wall motion abnormality was absent in the group of asymptomatic volunteers. The ejection fraction by cine MRI correlated better with the ejection fraction by left ventriculography (r = 0.94, standard error of the estimate = 3.6) than did the ejection fraction by radionuclide angiography (r = 0.82, standard error of the estimate = 5.8). The regional wall motion concordance rate in comparison to left ventriculography was similar for both cine MRI (69%) and radionuclide angiography (65%). These findings suggest that cine MRI may play an important role in the future detection and functional characterization of AMI.

Detection of intramyocardial hemorrhage using high-field proton (1H) nuclear magnetic resonance imaging

Proton (1H) nuclear magnetic resonance (NMR) imaging has been used to define zones of myocardial infarction (MI), which appear as areas of relatively increased signal intensity (SI). However, zones of decreased SI have been observed within the areas of infarction and have been postulated to result from intramyocardial hemorrhage. To explore this phenomenon further, ex vivo spin-echo 1H NMR imaging at 1.5 Tesla was performed in 17 dogs after 24 hr (n = 9) and after 72 hr (n = 8) of coronary artery occlusion. In all dogs, a zone of increased SI (118 +/- 9% compared with normal myocardium) was observed in the distribution of the occluded coronary artery. In 12 of the 17 dogs, zones of decreased SI (92 +/- 8% compared with normal) were seen within or around the central zone of increased SI. Gross inspection and histological assessment of sliced myocardium usually disclosed hemorrhage in the regions of decreased SI. In three of the five dogs with no apparent zones of decreased SI on NMR, the infarct was small, and only minor hemorrhage was observed by gross inspection, whereas in the remaining two dogs no hemorrhage was seen. Myocardial flow in the hemorrhagic regions was significantly higher than in the necrotic core (59 +/- 29% vs. 31 +/- 24% compared with control, P less than 0.05). Image-derived calculation of T2 relaxation times in the different infarcted regions revealed a significant shortening of T2 in the infarcted hemorrhagic zones with decreased SI compared with the infarct zones with increased SI (49 +/- 8 msec vs. 66 +/- 8 msec, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac morphologic findings in patients with acute myocardial infarction treated with recombinant tissue plasminogen activator

The hearts of 52 patients (aged 61 +/- 11 years, 34 men) who participated in the Thrombolysis in Myocardial Infarction (TIMI) Study and died from 5 hours to 260 days (median 2.7 days) after onset of chest pain were studied. One heart became available at cardiac transplantation. Of the 52 patients, 38 received recombinant tissue plasminogen activator (rt-PA) not followed by percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass grafting (CABG). Eight had PTCA, and 6 had CABG. The infarcts were hemorrhagic by gross inspection (with histologic confirmation) in 23 patients, nonhemorrhagic in 20, not visible grossly in 2 and, in 7, there was no myocardial necrosis by either gross or histologic examination.(ABSTRACT TRUNCATED AT 250 WORDS)

Multiple microemboli after disintegration of clot during thrombolysis for acute myocardial infarction

Seven of 475 consecutive patients treated with thrombolysis for acute myocardial infarction had severe embolic complications that were believed to be caused by disintegration of pre-existing clot. Three patients had symptoms that persisted for many weeks, and five died. Any potential site of pre-existing blood clot within the vascular system, notably an enlarged left atrium, ventricular aneurysm, or aortic aneurysms, should be regarded as a contraindication to treatment with thrombolytic agents.

Successful and unsuccessful coronary thrombolysis

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Pathological changes after intravenous streptokinase treatment in eight patients with acute myocardial infarction

At necropsy five of eight patients (mean age 57 years) who died after intravenous streptokinase treatment for severe acute myocardial infarction (mean Peel index = 18) were found to have a patent infarct related coronary artery. Coronary artery stenoses were caused by fibrofatty atheromatous plaques; there were no residual thrombi in the lumen or acute intimal lesions. Three of these infarcts were of partial thickness (less than two thirds wall width) with sparing of the outer third of the myocardium and subendocardial zones. In the other three patients the infarct related coronary arteries remained histologically closed with residual lumen thrombi and underlying intimal lesions. Two infarcts were transmural. Six of the eight infarcts were noticeably haemorrhagic. Myocardial haemorrhage was confined to areas of necrotic myocardium and did not affect viable regions. These findings suggest that thrombus overlying a complex lesion may be more difficult to lyse than thrombus overlying a simple fibrofatty plaque. They also suggest that myocardial haemorrhage outside the infarct area, which might lead to cardiac rupture or delayed healing, does not usually occur.

Cineangiographic and pathological features of the infarct related vessel in successful and unsuccessful thrombolysis

The postmortem histology and the results of cineangiography after selective intracoronary thrombolysis in vessels that were recanalized and in those that were not were compared in 21 patients who died within seven days (mean 2 days) of selective intracoronary thrombolysis. There was a persistent intraluminal thrombus in the infarct related coronary artery in five of six segments in which recanalisation was unsuccessful and in one of 15 segments in which recanalisation was successful. Rupture and haemorrhage of the atheromatous plaque were seen in most of the infarct related segments, both in those in which recanalisation was achieved and in those in which it was not. Irregular narrowing and filling defects on the coronary cineangiograms were associated with rupture and haemorrhage of the atheromatous plaque. These results suggest that failure of coronary thrombolysis to recanalize the infarct related artery does not indicate that the occlusion was not caused by thrombus.

Hemorrhagic myocardial infarction complicated by free wall-rupture: a case associated with unusual clinical features following intravenous thrombolytic therapy

A patient is described who developed a systolic murmur soon after she was administered intravenous thrombolytic therapy for acute myocardial infarction. She died and autopsy revealed extensive hemorrhagic myocardial infarction and a free-wall rupture. A review of the literature suggests that this may be an unusual complication of thrombolytic therapy.

Electrically induced ventricular arrhythmias in acute myocardial infarction treated with thrombolytic agents

Ninety-two patients underwent programmed ventricular stimulation 12 +/- 3 days after acute myocardial infarction (AMI) treated with thrombolytic agents (streptokinase, recombinant tissue plasminogen activator, or both). Cardiac catheterization was performed in all patients on admission to hospital and was repeated in 97% of them 13 +/- 5 days later. Sustained ventricular arrhythmias--either tachycardia (VT) or fibrillation--were induced in 20 (22%) patients, with nonsustained VT induced in another 12 (13%). Multivariate analysis was used to identify predictors of induction of sustained VT, with short right ventricular effective refractory period (p = 0.0061), site of AMI (inferior or posterior, p = 0.008), infarct-related artery (right or circumflex coronary artery, p = 0.018), multivessel coronary artery disease (p = 0.043) and male sex (p = 0.028) being significant predictors of sustained VT. Neither successful reperfusion, time to reperfusion, nor residual stenosis in the infarct-related artery was significant. All patients in whom VT was induced were treated with electrophysiologically guided antiarrhythmic therapy. Cardiac mortality after hospital discharge was 1% over 30 +/- 16 months.

Topographic correspondence of contrast echocardiographic perfusion mapping and myocardial infarct extent after varying durations of coronary occlusion

After acute coronary occlusion, the extent of dysfunction exceeds the extent of infarction by a variable amount. Contrast echocardiography has been shown to be a good predictor of the extent of acute infarction after permanent occlusion. We used hydrogen peroxide contrast echocardiography to study the temporal and topographic relationship between contrast enhancement and tissue viability during acute myocardial infarction in 32 dogs undergoing 1, 2, 3, or 4 hours of circumflex occlusion before reperfusion. To account for changes in collateral blood flow, contrast studies were performed by aortic root injection immediately before reperfusion. The area, circumference, and transmural extent of the region at risk in vivo by contrast echocardiography were statistically unchanged regardless of the duration of occlusion before reperfusion. Echo contrast defect analysis of the risk region predicted the area, circumference, and transmural extent of infarcts reperfused at 2 or more hours (r = 0.81, 0.84, 0.71, respectively). For the 1-hour occlusion group, contrast defect analysis predicted the circumference at risk but markedly overestimated the area and transmural extent of infarction. These data indicate that the circumferential extent of infarction can be identified by contrast echo and is fixed by 1 hour of occlusion. Infarction progression transmurally within the circumferential boundaries had nearly reached the transmural contrast extent by 2 hours of occlusion in this model. Assuming the development of a similar high contrast agent safe for human injection, aortic root contrast echocardiography could be useful to predict myocardium at risk of infarction early after occlusion. Late after occlusion it could be of value to predict the presence of still viable myocardial layers within the dysfunctional infarct region.

Pathomorphological changes in experimentally induced canine myocardial infarction

We performed a pathological study of experimental canine myocardial infarction (MI) induced by coronary thrombosis which was made by endothelial denudation and induction of luminal stenosis in 20 dogs (Group I). Another model of experimental MI by coronary ligation was also evaluated in Groups II and III. Thirteen dogs of Group I and 7 of Group II underwent persistent coronary occlusion for 6-8 h (Group IA and Group IIA), and 7 of Group I and 7 of Group II underwent coronary reperfusion with intravenous urokinase (UK) (20,000 IU/kg) in Group IB for 5 h following temporary coronary occlusion for 3 h (Groups IB and IIB). The remaining 5 dogs underwent coronary reperfusion for 5 h following intravenous 20,000 IU/kg UK after 3 h ligation. Microscopically, myocardial hemorrhage was present in 6 (86%) Group IB, 4 (31%) Group IA and in no Group IIA dogs (p less than .025 and p less than .005 vs. IB). Four Group IIB and 3 Group III dogs also showed myocardial hemorrhage. Moderate hemorrhage was present only in Group I and slight hemorrhage was frequently observed in reperfused hearts. Contraction band necrosis (CBN) was present in 8 (62%) Group IA, all Group IB, all Group IIB, and 4 (80%) Group III dogs. However, there was no hemorrhage with CBN in Group IIA (p less than .005 vs. IIB). Marked CBN was present only in Group I.(ABSTRACT TRUNCATED AT 250 WORDS)