Long-term prognostic importance of patency of the infarct-related coronary artery after thrombolytic therapy for acute myocardial infarction

Prevalence and prognostic implications of reduced left ventricular ejection fraction among patients with STEMI in India

AIMS

To describe clinical characteristics and outcomes for those with STEMI and reduced left ventricular ejection fraction (LVEF) in low-income and middle-income countries (LMICs).

METHODS AND RESULTS

Adults presenting with STEMI to two government-owned tertiary care centres in Delhi, India were prospectively enrolled in the North India ST-elevation myocardial infarction (NORIN-STEMI) registry. LVEF was evaluated at presentation and clinical characteristics were compared across LVEF categories. Overall, 3597 patients were included, of whom 468 (13%) had LVEF >50%, 1482 (41%) had mildly reduced LVEF (40-49%), 1357 (38%) had moderately reduced LVEF (30-39%), and 290 (8%) had severely reduced LVEF (<30%). Presentation delay >24 h, prior MI, and hyperlipidaemia were associated with decreasing LVEF category. Although most patients with reduced LVEF were discharged on appropriate guideline-directed therapies, adherence at 1 year was low (ACE inhibitor/ARB 91% to 41%, beta blocker 98% to 78%, aldosterone receptor antagonist 69% to 6%). After multivariable adjustment, a Cox regression model showed moderately reduced LVEF (HR 1.77, 95% CI 1.20, 2.60) and severely reduced LVEF (HR 3.63, 95% CI 2.41, 5.48) were associated with increased risk of all-cause mortality compared with LVEF ≥50%.

CONCLUSIONS

On presentation for STEMI, almost 90% of NORIN-STEMI participants had at least mildly reduced LVEF and almost half had LVEF <40%. Patients with LVEF <40% had significantly higher risk of mortality at 1 year, and adherence to guideline-directed therapies at 1 year was poor. Systematic initiatives to improve access to timely revascularization and guideline-directed therapies are essential in advancing STEMI care in LMICs.

Comparison of totally automated and manual processing for calculation of left ventricular volumes and ejection fraction using gated myocardial perfusion SPECT

ated single-photon emission computed tomography (SPECT) allows for the assessment of myocardial left ventricular ejection fraction and left ventricular volumes. There is conflicting data regarding the difference between automated and manual processing of gated myocardial SPECT images. The purpose of this retrospective “cross-sectional study is to compare the degree of variability between automated and manual processing of Quantitative Gated SPECT algorithms for assessing left ventricular volumes and ejection percent”. Study was carried out in the Nuclear Medicine department “at the Security Forces Hospital, Riyadh, Saudi Arabia, and comprised of 96 participants who “underwent” both stress and “rest gated” myocardial perfusion “imaging” (MPI) from February to May 2021. Data were analyzed “using SPSS for Windows (version 22; IBM Corp., Armonk, NY, USA). The mean of EF, ESV, and EDV on stress test using the automatic technique were 62.46 ± 14.62%, 45.00 ± 37.10 ml, and 107.01 ± 43.70 ml, respectively while using the manual technique were 57.21±14.80%, 44.35±35.93 ml, and 93.26±39.14 ml, respectively. The mean of EF, ESV, and EDV on rest test using the automatic technique were 62.85± 15.47%, 43.44± 36.35 ml, and 104.27±42.51 ml, respectively while using the manual technique were 57.74±15.33%, 43.30±36.42 ml, and 91.72±41.50 ml, respectively. For LVEF and EDV, the difference between automated and manual techniques is statistically significant (p<0.05). However, no “statistically significant difference” exists between automated and manual ESV techniques (p>0.05). Discrepancies were observed that exist by using the fully automated and manual technique for determining LVEF and Left ventricular volumes by gated MPI.

The recanalization after thrombolysis as surrogate for clinical outcomes in patients with ST-segment elevation acute myocardial infarction: A systematic review and meta-regression analysis of data from randomized controlled trials

AIMS

Thrombolytic therapy has been known to be effective in reducing clinical outcomes and increasing recanalization rate among patients with ST-segment elevation acute myocardial infarction (STEMI). However, whether post-thrombolysis recanalization could be used as a surrogate for clinical outcomes is unknown.

METHODS

We systematically searched PubMed, EMBASE and the Cochrane Library database to identify randomized controlled trials (RCT) that examined effects of thrombolytic agents in STEMI. Recanalization was defined as TIMI grade 2 or 3 flow. The primary outcome was in-hospital all-cause mortality. Secondary outcomes included in-hospital and 30-day recurrent myocardial infarction (re-MI), composite of death and re-MI, major bleeding and all bleeding. Random-effects meta-regression was used for analysis.

RESULTS

We identified 111 eligible study arms and 52 eligible comparisons from 58 RCTs involving 16 536 patients. Our analyses showed that among study arms recanalization rate was significantly inversely associated with the incidence of in-hospital all-cause mortality (β: -0.07, 95% confidence interval [CI]: -0.13 to -0.02), re-MI (β: -0.09, 95%CI: -0.18 to -0.01) and the composite of death and re-MI (β: -0.17, 95%CI: -0.28 to -0.05), and positively associated with in-hospital all bleeding but not with major bleeding. Among paired comparisons, the difference in recanalization rate was associated with the corresponding difference in incidence of in-hospital all-cause mortality (β: -0.15, 95%CI: -0.28 to -0.01) but the relationship was not significant for any other outcome.

CONCLUSION

Pooled evidence from RCTs suggest the potential use of recanalization as a surrogate for clinical outcomes in evaluating the efficacy of thrombolysis among patients with STEMI.

Myocardial Neovascularization by Adult Bone Marrow-Derived Angioblasts: Strategies for Improvement of Cardiomyocyte Function

In the pre-natal period hemangioblasts, derived from the human ventral aorta give rise to cellular elements involved in both hematopoiesis and vasculogenesis, resulting in formation of the primitive capillary network. Endothelial precursors with phenotypic and functional characteristics of embryonic hemangioblasts are also present in human adult bone marrow, and can be used to induce infarct bed vasculogenesis and angiogenesis after experimental myocardial infarction. The neovascularization results in decreased apoptosis of hypertrophied myocytes in the peri-infarct region, long-term salvage and survival of viable myocardium, reduction in collagen deposition, and sustained improvement in cardiac function. Autologous angioblasts may also be useful in cellular therapy strategies aiming to regenerate myocardial tissue after established heart failure. It is likely that protocols using cardiomyocyte/mesenchymal stem cells will require balanced co-administration of angioblasts to provide vascular structures for supply of oxygen and nutrients to both the chronically ischemic, endogenous myocardium and to the newly-implanted cardiomyocytes. Future studies will need to address the timing, relative concentrations, source and route of delivery of each of these cellular populations in animal models of acute and chronic myocardial ischemia.

The Open Artery Hypothesis: Beneficial Effects and Long-term Prognostic Importance of Patency of the Infarct-Related Coronary Artery

There seem to be additional mechanisms of benefit in patients receiving late reperfusion therapy in a time when the opportunity for myocardial salvage has been missed. Previous studies have demonstrated that the restoration of blood flow in the infarct-related coronary artery in patients with acute myocardial infarction improves left ventricular function and reduces mortality. Initially, it was thought that survival was improved because viable myocardium was salvaged. However, data obtained over the past several years have suggested that the restoration of antegrade flow in the infarct-related artery may improve survival via a mechanism independent of the influence on left ventricular function. Clinical interest in the open artery hypothesis has recently resurfaced owing to a substantial improvement in technical aspects of percutaneous coronary interventions (PCI). Observational data suggest a role for late intervention as safer and more effective mechanical reperfusion practices have emerged. Long-term clinical benefits have been shown from balloon angioplasty late after myocardial infarction (MI). Therefore, patients with failed thrombolysis or those with late-presenting MI may still benefit from PCI by mechanisms independent of myocardial salvage. There is accumulative evidence on this matter. Possible mechanisms include reduction of ventricular remodeling, diminished ventricular instability reducing the incidence of arrhythmias, and provision of collaterals to other territories in the event of further coronary artery occlusion. However, caution must be exercised in interpreting the results of studies examining the open artery hypothesis. This hypothesis can be tested in its purest sense in animal experiments; however, the clinical situation is much more complex. Patients may have acute-on-chronic coronary artery occlusion in the presence of multivessel disease and well-developed collateral channels. The pattern of necrosis may also be different with areas of necrosis separated by islands of ischemic, stunned, hibernating, or normal cells. Therefore, the patency of the infarct-related coronary artery in single or multivessel disease days to weeks after infarction markedly influences long-term prognosis unrelated to improvement of left ventricular function. Current technology has made it feasible to open and maintain patency of most occluded infarct-related arteries. However, the hypothesis that late mechanical reperfusion in patients with asymptomatic occluded infarct-related artery will improve long-term clinical outcomes remains to be proved and is currently being tested in a large randomized trial.

OPC-28326, a selective peripheral vasodilator with angiogenic activity, mitigates postinfarction cardiac remodeling

Although OPC-28326, 4-(N-methyl-2-phenylethylamino)-1-(3,5-dimethyl-4-propionyl-aminobenzoyl) piperidine hydrochloride monohydrate, was developed as a selective peripheral vasodilator with α2-adrenergic antagonist properties, it also reportedly exhibits angiogenic activity in an ischemic leg model. The purpose of this study was to examine the effect of OPC-28326 on the architectural dynamics and function of the infarcted left ventricle during the chronic stage of myocardial infarction. Myocardial infarction was induced in male C3H/He mice, after which the mice were randomly assigned into two groups: a control group receiving a normal diet and an OPC group whose diet contained 0.05% OPC-28326. The survival rate among the mice (n = 18 in each group) 4 wk postinfarction was significantly greater in the OPC than control group (83 vs. 44%; P < 0.05), and left ventricular remodeling and dysfunction were significantly mitigated. Histologically, infarct wall thickness was significantly greater in the OPC group, due in part to an abundance of nonmyocyte components, including blood vessels and myofibroblasts. Five days postinfarction, Ki-67-positive proliferating cells were more abundant in the granulation tissue in the OPC group, and there were fewer apoptotic cells. These effects were accompanied by activation of myocardial Akt and endothelial nitric oxide synthase. Hypoxia within the infarct issue, assessed using pimonidazole staining, was markedly attenuated in the OPC group. In summary, OPC-28326 increased the nonmyocyte population in infarct tissue by increasing proliferation and reducing apoptosis, thereby altering the tissue dynamics such that wall stress was reduced, which might have contributed to a mitigation of postinfarction cardiac remodeling and dysfunction.

The influence of obesity on progression of coronary arteriosclerosis and clinical course after ST elevation acute myocardial infarction treated with primary coronary interventions

PURPOSE

Evaluation of influence of obesity on the coronary atherosclerosis development and clinical outcome in patients with STEMI treated by PCI with BMS implantation.

MATERIAL AND METHOD

82 patients (64 men) treated with PCI within 6 hours from 1st STEMI. Three groups of pts were formed according to BMI. Based on coronary angiography number of significant stenoses (NSS), number of stenosed coronary arteries (NSA), and sum of significant stenoses (SSS) were calculated. Echocardiography examination was performed 3 days and 6 months after STEMI. Serial evaluation of TnI, CK, CKMB was performed after admission, and serum BNP was assessed after 2 days, 1 and 6 months after STEMI.

RESULTS

Obese patients revealed higher values of NSA, NSS and SSS than patients with normal BMI and overweight. There were no differences of BNP, maximal values and AUC of CK, CKMB, TnI and echocardiographic parameters between all groups whereas decrease of BNP during follow-up correlated with BMI.

CONCLUSIONS

Results of our prospective study indicate that in obese patients, there is a significantly greater number of atherosclerotic lesions in coronary arteries found during PCI, as compared to those with normal body weight or overweight. We proved that overweight and obesity did not result in significantly greater damage to the myocardium and left ventricular dysfunction, both in the acute phase and 6 months after myocardial infarction treated with primary coronary intervention, as compared to those with normal body weight. In addition correlation was found between BNP concentration profile and body mass index in the 6-month follow-up after STEMI treated with PCI and bare metal stent implantation.

Myocardial ischemia, reperfusion, and infarction in chronically instrumented, intact, conscious, and unrestrained mice

In the United States alone, the National Heart, Lung, and Blood Institute (NHLBI) has invested several hundred million dollars in pursuit of myocardial infarct-sparing therapies. However, due largely to methodological limitations, this investment has not produced any notable clinical application or cardioprotective therapy. Among the major methodological limitations is the reliance on animal models that do not mimic the clinical situation. In this context, the limited use of conscious animal models is of major concern. In fact, whenever possible, studies of cardiovascular physiology and pathophysiology should be conducted in conscious, complex models to avoid the complications associated with the use of anesthesia and surgical trauma. The mouse has significant advantages over other experimental models for the investigation of infarct-sparing therapies. The mouse is inexpensive, has a high throughput, and presents the ability of one to create genetically modified models. However, successful infarct-sparing therapies in anesthetized mice or isolated mouse hearts may not be successful in more complex models, including conscious mice. Accordingly, a conscious mouse model of myocardial ischemia and reperfusion has the potential to be of major importance for advancing the concepts and methods that drive the development of infarct-sparing therapies. Therefore, we describe, for the first time, the use of an intact, conscious, and unrestrained mouse model of myocardial ischemia-reperfusion and infarction. The conscious mouse model permits occlusion and reperfusion of the left anterior descending coronary artery in an intact, complex model free of the confounding influences of anesthetics and surgical trauma. This methodology may be adopted for advancing the concepts and ideas that drive cardiovascular research.

Heart failure after myocardial infarction: clinical implications and treatment

Heart failure is a frequent complication of myocardial infarction. Several factors, such as recurrent myocardial ischemia, infarct size, ventricular remodeling, stunned myocardium, mechanical complications, and hibernating myocardium influence the appearance of left ventricular systolic dysfunction after myocardial infarction. Importantly, its presence increases the risk of death by at least 3- to 4-fold. The knowledge of the mechanisms and clinical features are essential for the diagnosis and treatment of left ventricular dysfunction and heart failure after myocardial infarction. Therefore, this review will focus on the clinical implications and treatment of heart failure after myocardial infarction. © 2011 Wiley Periodicals, Inc. The authors have no funding, financial relationships, or conflicts of interest to disclose.

[III Catalan registry of ST elevation acute myocardial infarction. Comparison with former Catalan registries I and II from Catalonia, Spain]

BACKGROUND AND OBJECTIVE

To analyze the use of reperfusion therapy in patients with ST elevation myocardial infarction (STEMI) in Catalonia in a registry performed in 2006 (IAM CAT III) and its comparison with 2 previous registries

PATIENTS AND METHODS

Frequency of reperfusion therapy and time intervals between symptom onset - reperfusion therapy were the principal variables investigated. The IAM CAT I (June-December 2000) included 1,450 patients, the IAM CAT II (October 2002-April 2003) 1,386, and the IAM CAT III (October-December 2006) 367.

RESULTS

The proportion of patients treated with reperfusion increased progressively (72%, 79% and 81%) as the use of primary angioplasty (5%, 10% and 33%). In the III registry the transfer system most frequently used was the SEM/061 (17%, 32% and 47%, respectively) but the time interval symptom onset-first contact with the medical system did not improve (II, 90 vs III, 105 min), the interval symptom onset-thrombolytic therapy did hardly change (178, 165 and 177 min) and the interval hospital arrival-trombolysis (needle-door) tended to improve (59, 42 and 42 min). Thirty day mortality in STEMI patients declined progressively through the 3 registries (12.1, 10.6 and 7.4%, p=0.012).

CONCLUSIONS

The proportion of STEMI patients treated with reperfusion has improved but the interval to its application has not been shortened. To improve the latter it is mandatory an earlier contact with the medical system, a shortening of the intervals door-needle and door-balloon through better coordination between the 061, the sanitary personnel and the hospital administration, and to consider the subject as a real sanitary priority.

Stem cell therapy with overexpressed VEGF and PDGF genes improves cardiac function in a rat infarct model

Background

Therapeutic potential was evaluated in a rat model of myocardial infarction using nanofiber-expanded human cord blood derived hematopoietic stem cells (CD133+/CD34+) genetically modified with VEGF plus PDGF genes (VIP).

Methods and Findings

Myocardial function was monitored every two weeks up to six weeks after therapy. Echocardiography revealed time dependent improvement of left ventricular function evaluated by M-mode, fractional shortening, anterior wall tissue velocity, wall motion score index, strain and strain rate in animals treated with VEGF plus PDGF overexpressed stem cells (VIP) compared to nanofiber expanded cells (Exp), freshly isolated cells (FCB) or media control (Media). Improvement observed was as follows: VIP>Exp> FCB>media. Similar trend was noticed in the exercise capacity of rats on a treadmill. These findings correlated with significantly increased neovascularization in ischemic tissue and markedly reduced infarct area in animals in the VIP group. Stem cells in addition to their usual homing sites such as lung, spleen, bone marrow and liver, also migrated to sites of myocardial ischemia. The improvement of cardiac function correlated with expression of heart tissue connexin 43, a gap junctional protein, and heart tissue angiogenesis related protein molecules like VEGF, pNOS3, NOS2 and GSK3. There was no evidence of upregulation in the molecules of oncogenic potential in genetically modified or other stem cell therapy groups.

Conclusion

Regenerative therapy using nanofiber-expanded hematopoietic stem cells with overexpression of VEGF and PDGF has a favorable impact on the improvement of rat myocardial function accompanied by upregulation of tissue connexin 43 and pro-angiogenic molecules after infarction.

Impact of chronic patency of infarct-related coronary artery on prevalence of myocardial ischemia during the pharmacologic and exercise stress test

BACKGROUND

Even late restoration of anterograde coronary flow may have beneficial effects on left ventricular function, electrophysiology, and survival in postinfarction patients.

HYPOTHESIS

The patency or occlusion of an infarct-related coronary artery in the chronic phase may also be associated with myocardial ischemia provoked by pharmacologic and physiologic stress tests.

METHODS

High-dose dipyridamole echocardiography test (DET) (up to 0.84 mg/kg over 10 min), exercise electrocardiography (EET), and coronary angiographic data in a group of 127 in-hospital patients who had survived an acute myocardial infarction were analyzed. Patients who had only angiographic evidence of infarct-related single artery disease (> or = 50% luminal diameter reduction) and no previous revascularization were enrolled in the study. DET and EET were performed (DET in all, EET in 118 patients) within 5 days before coronary angiography. Fifty-seven patients had total occluded infarct arteries (Group 1) with various degrees of collateral circulation (2.6 +/- 1.1 collateral score, by a 3 grading system), whereas the other 70 patients had patent infarct arteries (Group 2) with significant residual stenoses (82 +/- 13% diameter reduction).

RESULTS

The prevalence of rest angina or effort angina and topography of the infarct-related coronary artery did not differ between the two groups (all p = NS). There were more patients with Q wave in Group 1 than in Group 2 (72 vs. 57%, p = 0.08) compared with non-Q wave infarction (Group 1 = 28 vs. Group 2 = 43%, p = 0.08). Ischemia in the infarct-related artery territory detected by DET (defined as new wall motion dyssynergy or marked worsening of resting hypokinesia) was 61% in Group 1 and 41% in Group 2 (p = 0.025). EET was positive in 26 of 54 (48%) Group 1 and in 21 of 64 (33%) Group 2 patients (p = 0.09).

CONCLUSIONS

Patients with occluded infarct-related arteries have a higher prevalence of ischemia during DET and EET regardless of the presence of collateral flow. These results suggest that the presence of partial anterograde flow in the prolonged period could have a favorable influence on prevalence of residual ischemia in these patients.

Strategies to attenuate pathological remodeling in heart failure

PURPOSE OF REVIEW

The incidence of heart failure is increasing due to an aging population and improved management of diseases that are precursors to ventricular dysfunction. The success of therapeutic advances has created a challenge for the next generation of investigational heart failure treatments because the mortality rate has decreased to such a degree that larger trials will be needed to demonstrate mortality advantage. Prior work has linked favorable changes in ventricular geometry to improved survival, suggesting that remodeling may be a suitable surrogate endpoint.

RECENT FINDINGS

In addition to the established benefits of neurohormonal blockade, new mechanical and electrical therapies are proving beneficial in heart failure. Passive cardiac support devices and cardiac resynchronization therapy have been recently demonstrated to induce reverse remodeling of the left ventricle and may improve outcomes, including quality of life, functional status, and mortality.

SUMMARY

Ventricular remodeling is strongly correlated with improvement in other heart failure outcomes. Early phase trials of novel therapeutics should carefully examine remodeling to obtain an efficacy signal. Larger clinical investigations should include remodeling metrics as endpoints and consider their use in a composite primary endpoint to reduce trial size.

Beneficial effect of reperfusion therapy beyond the preservation of left ventricular function in patients with acute ST-segment elevation myocardial infarction

BACKGROUND

Reperfusion therapy has been shown to improve mortality in patients with acute ST-segment elevation myocardial infarction. However, in randomized clinical trials there was only a modest improvement in left ventricular ejection fraction with reperfusion therapy, despite a larger improvement in mortality.

METHODS

In the prospective MITRA-Plus registry we compared 1-year mortality of inhospital survivors of ST-segment elevation myocardial infarction (STEMI) divided into nine groups with preserved (>55%), moderately reduced (41-55%) and severely reduced (≤40%) left ventricular ejection fraction (LVEF) and treated with no early reperfusion therapy, fibrinolysis or primary percutaneous coronary intervention (PCI) within 24 h after admission.

RESULTS

A total of 5867 patients were included in this analysis, 1026 (18%) without early reperfusion, 2462 (42%) with fibrinolysis and 2379 (40%) with primary PCI. After adjustment for confounding variables in a propensity score analysis, reperfusion therapy (Odds ratio and 95% CI: 0.27, 0.15-0.48; 0.50, 0.32-0.79; 0.64, 0.44-0.93), fibrinolysis (Odds ratio and 95% CI: 0.27, 0.14-0.52; 0.58, 0.35-0.95; 0.60, 0.39-0.93) and primary PCI (Odds ratio and 95% CI: 0.22, 0.11-0.44; 0.34, 0.19-0.59; 0.56, 0.36-0.88) remained independent predictors of survival in comparison to no reperfusion therapy in the patients with preserved, moderately reduced and severely reduced LVEF, respectively.

CONCLUSIONS

These results suggest a beneficial effect of early reperfusion therapy beyond the preservation of left ventricular function, however the mechanisms need further study.

Inducible ventricular arrhythmias and patency of infarct-related artery in survivors of acute myocardial infarction

BACKGROUND

Patency of infarct-related artery in patients who suffered an acute myocardial infarction (AMI) has been shown to be associated with improved survival. Ventricular tachyarrhythmias induced by programmed electrical stimulation may be predictive of arrhythmic events and sudden death.

HYPOTHESIS

The study was undertaken to assess the possible effect of a patent infarct-related coronary artery on induced ventricular tachyarrhythmias during programmed ventricular stimulation in survivors of AMI.

METHODS

In this prospective study, programmed electrical stimulation was performed before hospital discharge (14 +/- 2 days) in 79 patients who survived an AMI. Patients were subdivided into two groups: Group I with patent infarct-related coronary artery (n = 64) and Group 2 with occluded infarct-related artery (n = 15) at coronary angiography performed at 14 +/- 2 days. These two groups were comparable in terms of mean left ventricular ejection fraction, location of infarct-related artery, number of diseased vessels, peak creatine kinase value, and infarct location.

RESULTS

Ventricular arrhythmias were induced in 21 patients ( 32.6%) of Group I and 4 patients (26.6%) of Group 2. This difference was not statistically significant.

CONCLUSION

This study suggests that ventricular arrhythmias induced by programmed ventricular stimulation in survivors of AMI did not differ whether the infarct-related artery was patent or occluded. Other factors may play a role in electrical instability as assessed by programmed ventricular stimulation.

Benefits of reperfusion beyond infarct size limitation

The most critical determinant of prognosis in patients with acute myocardial infarction (MI) is infarct magnitude, which can be established within several hours of an attack. The importance of the subsequent healing process is not negligible, however. In fact, much experimental and clinical evidence suggests that late reperfusion of the infarct-related coronary artery--i.e. at times too late to salvage the myocardium within the area at risk-is beneficial for reducing left ventricular remodelling and decreasing mortality ('open artery hypothesis'). For instance, one recent study highlighted the beneficial effects of late reperfusion therapy on the infarct tissue cell dynamics following acute MI. Nonetheless, several recent large, randomized clinical trials have failed to provide evidence of such benefits, refuting the clinical efficacy of late reperfusion. In addition, they also underscore the need for revised clinical studies in which there is less heterogeneity in the timing of reperfusion and in the initial infarct size, as well as the need for sustained patency of the recanalized artery. This review focuses on the effects of late reperfusion on the pathophysiology of MI in the context of the infarct tissue dynamics and clinical outcomes. We also discuss the issues that need to be resolved to improve clinical application.

Lack of benefit from percutaneous intervention of persistently occluded infarct arteries after the acute phase of myocardial infarction is time independent: insights from Occluded Artery Trial

AIMS

The Occluded Artery Trial (OAT) (n = 2201) showed no benefit for routine percutaneous intervention (PCI) (n = 1101) over medical therapy (MED) (n = 1100) on the combined endpoint of death, myocardial infarction (MI), and class IV heart failure (congestive heart failure) in stable post-MI patients with late occluded infarct-related arteries (IRAs). We evaluated the potential for selective benefit with PCI over MED for patients enrolled early in OAT.

METHODS AND RESULTS

We explored outcomes with PCI over MED in patients randomized to the </=3 calendar days and </=7 calendar days post-MI time windows. Earlier, times to randomization in OAT were associated with higher rates of the combined endpoint (adjusted HR 1.04/day: 99% CI 1.01-1.06; P < 0.001). The 48-month event rates for </=3 days, </=7 days post-MI enrolled patients were similar for PCI vs. MED for the combined and individual endpoints. There was no interaction between time to randomization defined as a continuous (P = 0.55) or categorical variable with a cut-point of 3 days (P = 0.98) or 7 days (P = 0.64) post-MI and treatment effect.

CONCLUSION

Consistent with overall OAT findings, patients enrolled in the </=3 day and </=7 day post-MI time windows derived no benefit with PCI over MED with no interaction between time to randomization and treatment effect. Our findings do not support routine PCI of the occluded IRA in trial-eligible patients even in the earliest 24-72 h time window.

Sustained coronary patency after fibrinolytic therapy as independent predictor of 10-year cardiac survival Observations from the Antithrombotics in the Prevention of Reocclusion in COronary Thrombolysis (APRICOT) trial

BACKGROUND

Whether late coronary patency after myocardial infarction has prognostic impact independent of left ventricular function remains a matter of debate. Reocclusion rates in the first year after fibrinolysis vary between 20% and 30%. Of all reocclusions, about 30% present as clinical reinfarction, associated with a 2-fold-increased risk of mortality. The clinical impact of reocclusion that presents without reinfarction has not been studied; but an association has been demonstrated with impaired contractile recovery of left ventricular function, the strongest prognosticator of long-term outcome. We therefore studied the impact of 3-month coronary patency after successful fibrinolysis on 10-year cardiac survival.

METHODS

In the APRICOT-1 trial, 248 ST-elevation myocardial infarction patients with an open infarct artery 24 hours after fibrinolysis had 3-month repeated angiography. Ten-year clinical follow-up was complete in 99.6%.

RESULTS

The reocclusion rate was 29% (71/248). Of these reocclusions, 24% presented as clinical reinfarction (17/71). Cardiac survival at 10 years was 73% in patients with a reoccluded infarct artery and 88% in patients with sustained patency (P < .01). This difference was also present in patients in whom reocclusion was only detected as a result of systematic repeated angiography, that is, in the absence of reinfarction or ischemic symptoms between angiograms (70% vs 86%, P < .03). Multivariable analysis identified sustained patency at 3-month angiography as independent predictor of 10-year cardiac survival (hazard ratio 2.10, 95% CI 1.10-4.02) together with left ventricular ejection fraction.

CONCLUSIONS

Sustained infarct artery patency in the first 3 months after successful fibrinolysis is a strong predictor of 10-year cardiac survival, independent of left ventricular function. Notably, this also holds true when reocclusion occurs without signs of clinical reinfarction or recurrent ischemia. Therefore, future preventive strategies should also focus on "clinically silent" reocclusions. Additional studies on better antithrombotic regimens and the combination with a routine invasive strategy early after successful fibrinolysis are warranted.

Lack of benefit with percutaneous intervention for late persistent occlusion after myocardial infarction: summary of the occluded artery trial

The clinical utility of establishing late patency of the persistently occluded infarct-related artery with percutaneous coronary intervention (PCI) was uncertain. The Occluded Artery Trial was a National Heart, Lung, and Blood Institute-supported, international, multicenter, randomized controlled trial comparing a test strategy of late PCI (3-28 days) of the occluded infarct-related artery and optimal medical therapy to optimal medical therapy alone. The primary end point of the trial was a centrally adjudicated composite of death, reinfarction, and New York Heart Association class IV heart failure over 4 years (mean follow-up, 1,059 +/- 11 days). The final study population of 2,166 patients gave the trial 94% power to detect the anticipated 25% reduction in event rate with PCI. The combined primary outcome occurred in 161 patients in the PCI group and in 140 subjects receiving medical therapy alone. The 4-year cumulative primary event rate was 17.2% in the PCI group and 15.6% in the medical therapy group (hazard ratio, 1.16; 95% confidence interval, 0.92-1.45; P = .20; covariate-adjusted hazard ratio, 1.17; 95% confidence interval, 0.93 to 1.47; P = .18). Rates of New York Heart Association class IV heart failure and death were similar in both groups. A trend toward increased nonfatal myocardial infarction in the PCI group (hazard ratio, 1.44; 95% confidence interval, 0.96-2.16; P = .08) unrelated to periprocedural events was apparent. No significant interaction between treatment effect and prespecified subgroups was observed. This lack of clinical benefit supports optimal medical therapy alone for Occluded Artery Trial-eligible patients in current clinical practice.

Late Intervention on an Occluded Infarct-Related Artery: A Meta-analysis of the Randomized Controlled Trials

Context

Late intervention to open an occluded infarct-related artery (IRA) after initial acute myocardial infarction was postulated to lead to clinical benefit.

Objective

To conduct a meta-analysis of the randomized trials.

Study Selection

Eligibility criteria were: 1) randomized trials comparing percutaneous coronary intervention (PCI) in a totally occluded artery (TIMI flow 0-1) versus medical therapy, 2) in stable post myocardial infarction (MI) patients without spontaneous or low level exercise induced ischemia, 3) trials with a time from the onset of symptoms to randomization >24 hours, but <6 weeks, and 4) trials reporting mortality and recurrent MI as an endpoint. Of 961 citations reviewed, 3 disagreements were easily resolved by discussion and 6 trials were selected for inclusion.

Data Synthesis

The primary endpoint was the composite of recurrent MI or death. The secondary endpoints were the development of heart failure or recurrent myocardial infarction. In a meta-analysis of the 6 trials, which included 2642 patients, late intervention of an IRA had a RR of death or recurrent MI of 1.12 (95% CI 0.91-1.38). Data regarding the development of heart failure was available for 4 trials. In a meta-analysis of these 4 trials, which included 2527 patients, late intervention of an IRA had a RR of 0.79 (95% CI 0.58-1.08). Data regarding the occurrence of recurrent MI was available for 5 trials. In a meta-analysis of these 5 trials, which included 2598 patients, late intervention of an IRA had a RR of 1.28 (95% CI 0.91-1.79).

Conclusions

Our meta-analysis of the currently available randomized data addressing late intervention of an occluded IRA failed to reveal clinical benefit with regard to the clinical endpoints of death, heart failure or reinfarction. The trend towards an increase in reinfarction among the PCI treated patients suggested by the Open Artery Trial (OAT) investigators persisted, but did not achieve statistical significance.

Surgery for myocardial salvage in acute myocardial infarction and acute coronary syndromes

This article addresses the pathophysiology, the treatment options, and their rationale in the setting of life-threatening acute myocardial infarction and acute on chronic ischemia. Although biases may exist between cardiologists and surgeons, with this review, we hope to provide the reader with information that will shed light on the options that best suit the individual patient in a given set of circumstances.

Effect of serum creatine kinase-MBmass on the early and hierarchical diagnosis of related artery reperfusion in acute myocardial infarction

AIM

To evaluate creatine kinase-MBmass (CK-MBmass) for the early diagnosis of infarct-related artery (IRA) patency after thrombolysis and the hierarchical diagnosis of related artery reperfusion (RAR).

PATIENTS AND METHODS

CK-MBmass and creatine kinase-MBactivity (CK-MBactivity) were measured kinetically in 48 patients treated with thrombolysis and 96 patients treated with routine drugs.

RESULTS

In the continuous-RAR (CRAR) group, the peak values of CK-MBmass and CK-MBactivity appeared at < or =12 h, the peak durations were maintained for < or =8 h before decreasing to normal at < or =42 h, which occurred more quickly than those values in the non-RAR (NRAR) group. In the temporary-RAR (TRAR) group, the peak values appeared at < or =12 h, but no significant differences were found between the TRAR and NRAR groups in the time that the peak durations lasted before decreasing to normal values. In the reobliteration group after RAR, the peak values appeared at < or =12 h, and the peak durations were maintained for < or =8 h. After returning to the normal, a second peak appeared, and the time required for the values to return to normal was prolonged significantly.

CONCLUSIONS

CK-MBmass could be used as an indicator of RAR after thrombolysis; and the kinetic changes of serum CK-MBmass could be used for the hierarchical diagnosis of RAR in acute myocardial infarction.

Improvement in left ventricular function following coronary stenting in patients with acute myocardial infarction: 6-month and 3-year follow-up

BACKGROUND

This study assesses hemodynamic and angiographic changes in patients with a patent infarct-related artery (IRA) after acute myocardial infarction (AMI).

METHODS

One hundred and seventy-seven patients with first AMI, who received a predischarge stenting to the IRA and sustained a patent IRA over 3 years, were stratified into 3 groups according to the baseline left ventricular ejection fraction (LVEF): group A included 63 patients with a LVEF of >49%, group B 73 patients with a LVEF of 40%-49%, and group C 41 patients with a LVEF of <40%. The hemodynamic and angiographic parameters were compared at baseline, 6-month and 3-year follow-up.

RESULTS

The LV end-diastolic volume index increased 1, 4 and 4 ml/m(2) at 6 months and 4, 5 and 10 ml/m(2) at 3 years, respectively in group A, B and C. The LVEF increased 4%, 7% and 12% at 6 months and 6%, 8% and 14% at 3 years, respectively in group A, B and C. The stroke volume index increased 3, 7 and 12 ml/m(2) at 6 months and 6, 8 and 15 ml/m(2) at 3 years, respectively in group A, B and C. The LV wall motion score decreased 2, 3 and 3 at 6 months and was unchanged at 3 years, respectively in group A, B and C. The LV end-diastolic pressure decreased 2, 3 and 4 mm Hg, respectively in group A, B and C, at 6-month follow-up and remained stable at 3 years.

CONCLUSIONS

Long-term beneficial effects in patients receiving a late predischarge intracoronary stenting following first AMI were seen and these may be related to patent IRA. A progressive improvement in left ventricular remodeling occurs in all patients regardless of their initial left ventricular function and the improvement continues for at least 3 years.

Comparing cardiac ejection fraction estimation algorithms without a gold standard

RATIONALE AND OBJECTIVES

Imaging and estimation of left ventricular function have major diagnostic and prognostic importance in patients with coronary artery disease. It is vital that the method used to estimate cardiac ejection fraction (EF) allows the observer to best perform this task. To measure task-based performance, one must clearly define the task in question, the observer performing the task, and the patient population being imaged. In this report, the task is to accurately and precisely measure cardiac EF, and the observers are human-assisted computer algorithms that analyze the images and estimate cardiac EF. It is very difficult to measure the performance of an observer by using clinical data because estimation tasks typically lack a gold standard. A solution to this "no-gold-standard" problem recently was proposed, called regression without truth (RWT).

MATERIALS AND METHODS

Results of three different software packages used to analyze gated, cardiac, and nuclear medicine images, each of which uses a different algorithm to estimate a patient's cardiac EF, are compared. The three methods are the Emory method, Quantitative Gated Single-Photon Emission Computed Tomographic method, and the Wackers-Liu Circumferential Quantification method. The same set of images is used as input to each of the three algorithms. Data were analyzed from the three different algorithms by using RWT to determine which produces the best estimates of cardiac EF in terms of accuracy and precision.

RESULTS AND DISCUSSION

In performing this study, three different consistency checks were developed to ensure that the RWT method is working properly. The Emory method of estimating EF slightly outperformed the other two methods. In addition, the RWT method passed all three consistency checks, garnering confidence in the method and its application to clinical data.

Heart Failure Following Anterior Myocardial Infarction: An Indication for Ventricular Restoration, a Surgical Method to Reverse Post-Infarction Remodeling

Anterior myocardial infarction produces abrupt left ventricular (LV) dysynergy and global systolic dysfunction. Rapid intense neurohumoral activation, infarct expansion, and early ventricular chamber dilatation all contribute to restoring a normal stroke volume despite a persistently depressed ejection fraction. Continued neurohumoral activation provokes late remodeling of the remote non-infarcted myocardium, characterized by an abnormal progressively increasing LV volume/mass ratio that leads to further LV remodeling. Heart failure is a progressive disorder of LV remodeling. Heart failure from post-infarction remodeling is unique because of the persistent non-functioning scar that self- perpetuates abnormal loading conditions and neurohumoral activation. Medical therapy attenuates remodeling and improves survival but does not change the size of the scar. Surgical ventricular restoration to exclude the non-functioning infarct from the ventricular cavity decreases ventricular volumes, increases global ejection fraction, attenuates neurohumoral activation and yields an excellent 5-year survival. Combined medical and surgical therapy is recommended in this patient population.

Design and methodology of the Occluded Artery Trial (OAT)

Experimental and clinical studies have suggested that late opening of an infarct-related artery (IRA) after myocardial infarction (MI) could improve clinical outcome. However, the suggestive observational data are limited by selection biases. Indeed, most small randomized studies have not demonstrated benefit. Thus, there is no recommendation for routine late opening of the IRA in current national guidelines for management of stable post-MI patients. The OAT is designed to test the hypothesis that opening a totally occluded IRA 3 to 28 days after MI in high-risk asymptomatic patients will improve clinical outcome and be cost-effective. The primary end point is the first occurrence of recurrent MI, hospitalization/treatment of New York Heart Association class IV congestive heart failure, or death. Trial background, design, and preliminary baseline characteristics of 2027 randomized patients are presented. Eligible patients are randomly assigned in equal proportions to optimal evidence-based medical care or optimal care plus late opening of the IRA using percutaneous coronary intervention of the occluded IRA. Treatment groups will be compared using intent-to-treat analysis. The results of OAT should have broad clinical impact by defining an evidence-based approach to the asymptomatic, high-risk, post-MI patient with an occluded IRA. If the efficacy and cost-effectiveness of percutaneous coronary intervention are established, then a policy of routinely seeking and opening persistently occluded IRAs could be advocated. If not, this strategy should be avoided in this large subgroup of post-MI patients.

Pharmacologic effects on cardiac remodeling

Clinical research during the past several decades has shown the importance of cardiac remodeling as a basic mechanism in the progression of heart failure. Changes in cardiac remodeling have high concordance with long-term clinical outcomes. Cardiac remodeling should be regarded as a primary target for treatment and also can serve as a reliable surrogate for clinical outcomes. Neurohormonal blockade with combination treatments that inhibit the renin-angiotensin-aldosterone and sympathetic systems has proven effective in improving cardiac remodeling and clinical outcomes. Such treatment should be standard therapy for patients with left ventricular dysfunction after myocardial infarction and patients with chronic heart failure.

Usefulness of real-time intravenous myocardial contrast echocardiography in predicting left ventricular dilation after successfully reperfused acute myocardial infarction

The ability of real-time intravenous myocardial contrast echocardiography to predict left ventricular remodeling after reperfused acute myocardial infarction was assessed in 47 patients. Intravenous myocardial contrast echocardiography was an independent predictor of left ventricular dilation after acute myocardial infarction. In particular, normal contrast opacification within dyssynergic segments indicated a very low risk of remodeling.

Clinical contribution of the collateral circulation to myocardial protection

This section describes the clinical evidence for benefit from coronary collateral channels. There is data to suggest the presence of a protective effect in patients sustaining myocardial infarction regardless of whether they receive reperfusion therapy, and whether the collaterals were preformed. The role of pre-infarction angina in stimulating collateral development remains a contentious issue.

Infarct zone viability influences ventricular remodelling after late recanalisation of an occluded infarct related artery

OBJECTIVE

To investigate the influence of infarct zone viability on remodelling after late recanalisation of an occluded infarct related artery.

METHODS

A subgroup of 26 volunteers from TOAT (the open artery trial) underwent dobutamine stress cardiovascular magnetic resonance at baseline to assess the amount of viable myocardium present with follow up to assess remodelling at one year. TOAT studied patients with left ventricular dysfunction after anterior myocardial infarction (MI) associated with isolated proximal occlusion of the left anterior descending coronary artery with randomisation to percutaneous coronary intervention (PCI) with stent at 3.6 weeks after MI (PCI group) or to medical treatment alone (medical group).

RESULTS

In the PCI group there was a significant relation between the number of viable segments within the infarct zone and improvement in end systolic volume index (-7.7 ml/m2, p = 0.02) and increased ejection fraction (4.1%, p = 0.03). The relation between viability and improvements in end diastolic volume index (-8.8 ml/m2, p = 0.08) and mass index (-6.3 g/m2, p = 0.01) did not reach significance (p = 0.27 and p = 0.8, respectively). In the medical group, there was no significant relation between the number of viable segments in the infarct zone and the subsequent changes in end diastolic (p = 0.84) and end systolic volume indices (p = 0.34), ejection fraction (p = 0.1), and mass index (p = 0.24).

CONCLUSION

The extent of viable myocardium in the infarct zone is related to improvements in left ventricular remodelling in patients who undergo late recanalisation of an occluded infarct related artery.

Serial changes in plasma brain natriuretic peptide concentration at the infarct and non-infarct sites in patients with left ventricular remodelling after myocardial infarction

OBJECTIVES

To clarify the role of infarct and non-infarct sites on left ventricular (LV) remodelling after myocardial infarction by measuring brain natriuretic peptide (BNP) from each site.

METHODS AND RESULTS

BNP from the aorta and the anterior interventricular vein (AIV) was measured in 45 patients with first anterior myocardial infarction at one, six, and 18 months. The LV was significantly dilated (> 10 ml/m(2) of end diastolic volume from one to 18 months) in 20 patients (remodelling (R) group) but not in 25 others (non-remodelling (NR) group). Patient characteristics and LV functions did not differ significantly at one month but plasma BNP concentration was higher in group R than in group NR (336 (288) v 116 (106) pg/ml, p < 0.01), predicting the degree of LV dilatation. The difference in BNP concentration between the aortic root and AIV (DeltaBNP), reflecting BNP secreted from the infarct site, did not differ at one month. In both groups BNP and DeltaBNP significantly decreased from one to six months (p < 0.05) and decreased from six months to 18 months, but the change was not significant. BNP and DeltaBNP were significantly higher in group R than in group NR after six months, when LV dilatation was not evident in both groups.

CONCLUSION

Enhanced BNP secretion at one month in the non-infarct and infarct ventricular sites predicts subsequent LV dilatation (that is, remodelling). The slower process of LV remodelling decreased BNP secretion at both sites. Thus, BNP concentration should be useful for monitoring ventricular remodelling after infarction.

Dilated versus nondilated cardiomyopathy in the elderly population treated with guideline-based medical therapy for systolic chronic heart failure

BACKGROUND

Although the process by which the left ventricular (LV) remodels in response to an injury generally leads to dilatation, in patients with heart failure (HF) the recognition of a small or mildly dilated left ventricle is not uncommon. We investigated the prevalence and the characteristics of elderly patients with traditional dilated and nondilated cardiomyopathy (CMP). We also assessed the response to the guideline-based medical therapy and the prognosis based on LV dilatation in this population.

METHODS AND RESULTS

We selected 243 patients >70 years of age with HF and LV ejection fraction <40% who underwent clinical and echocardiographic evaluations at baseline and after 12 months. They were subdivided into 2 groups according to baseline LV end-diastolic volume (LVEDV) (values < or =78 mL/m(2) identified nondilated CMP). Nondilated CMP was recognized in 64 patients (26%) who showed at baseline better clinical status, less severe mitral regurgitation, and higher LV ejection fraction than those with dilated CMP. At the final evaluation, favorable changes in clinical and echocardiographic parameters could be detected in both groups. The magnitude of these variations did not differ between the groups. The risk of hospitalization for worsening HF was 2.4-fold higher in patients with nondilated than dilated CMP. Mortality was 11% and 20%, respectively (P = .06). Statistical analysis revealed a direct, approximately linear relationship between LVEDV and outcomes in this population.

CONCLUSIONS

A total of 1 of 4 elderly patients with systolic HF had a nondilated left ventricle. These patients had a better clinical presentation than did counterparts with dilated left ventricles. After HF therapy is optimized, the likelihood of improvement is independent of LV size in this population, whereas the risk of death or worsening HF linearly increases with LV dilatation.

Late coronary artery recanalization effects on left ventricular remodelling and contractility by magnetic resonance imaging

AIMS

To assess the recanalization effects of post-myocardial infarction (MI) on left ventricular (LV) remodelling and contractility in relation to conservative therapy.

METHODS AND RESULTS

Thirty-six patients with occluded infarct-related artery between 12 h and 14 days post-anterior MI were randomized to percutaneous coronary intervention (PCI group) or conservative therapy (no-PCI group). Magnetic resonance imaging was performed at enrollment and after 6 months. The left ventricle was divided into infarct, adjacent, and remote segments. There was no difference in relation to LV volume between groups at the 6 month follow-up. Change in LV ejection fraction was favourable to the PCI group: 5.00% vs. -0.76%, P=0.012. Change in circumferential shortening (Ecc) of the remote segments in the PCI group was significantly better than in the no-PCI group: -1.67+/-6.30% vs. 0.29+/-6.02%, P<0.001. Infarct size and LV mass were similar between groups.

CONCLUSIONS

Late recanalization improved LV ejection fraction and myocardial contractility in late follow-up, but did not change the ventricular volumes. Improvement in the left ventricle global and regional contractility may benefit the long-term outcome in post-MI patients with sustained patency of the infarct-related artery.

Relation of left ventricular sphericity to 10-year survival after acute myocardial infarction

After ST-elevation myocardial infarction, the association between left ventricular sphericity (measured by biplane ventriculography) and survival rate at a median of 6.5 years was determined in 825 patients. The highest tertile of sphericity (vs the lowest and middle tertiles) was associated with a decreased 10-year survival rate in patients who had anterior myocardial infarction (p = 0.002), inferior myocardial infarction (p = 0.011), Thrombolysis In Myocardial Infarction (TIMI) grade 3 flow (p = 0.005), or TIMI grade 0 to 2 flow (p = 0.001) in the infarct artery. The independent multivariate predictors of a 10-year survival rate were ejection fraction (p = 0.002), treadmill exercise duration (p = 0.004), biplane left ventricular sphericity index (p = 0.032), age (p = 0.043), and end-systolic volume index (p = 0.047), but not TIMI flow grade.

Procedural success versus clinical risk status in determining discharge of patients after primary angioplasty for acute myocardial infarction

OBJECTIVES

We evaluated whether patients' clinical status, angioplasty success, or both, should guide discharge after primary angioplasty (i.e., percutaneous coronary intervention [PCI]) for acute myocardial infarction (AMI).

BACKGROUND

Current guidelines do not address a discharge strategy for AMI patients undergoing successful PCI.

METHODS

Patients who underwent PCI in Primary Angioplasty in Myocardial Infarction (PAMI) studies (N = 3,188) were classified as "high clinical risk" if they had either age >70 years, Killip class >1, heart rate >100 beats/min, systolic blood pressure <100 mm Hg, anterior MI, or left bundle branch block, and as "low clinical risk" if none was present. Successful PCI patients were compared with those with unsuccessful PCI in both groups for 30-day major adverse cardiac events (MACE).

RESULTS

Percutaneous coronary intervention was successful in 668 (90%) of 745 low-risk clinical and 2,104 (86%) of 2,443 high-risk clinical patients. Regardless of clinical risk status, patients with successful PCI had lower 30-day MACE than those with unsuccessful PCI (low-risk group: 4.6% vs. 22%, p < 0.0001; high-risk group: 7% vs. 21%; p < 0.0001). Moreover, successful PCI patients with either risk status had few MACE after day 4, whereas unsuccessful PCI patients had more MACE. The success of PCI was the strongest independent predictor of 30-day MACE (odds ratio [OR] 3.7, 95% confidence interval [CI] 2.8 to 5.0). A constellation of three or more high-risk clinical features also predicted higher 30-day MACE (OR 2.25, 95% CI 1.62 to 3.12).

CONCLUSIONS

The success of PCI is the prime determinant of clinical outcome after PCI for AMI. The majority of AMI patients with less than three high-risk clinical features who undergo successful PCI may be discharged from the hospital by day 4. In contrast, patients with more than two high-risk clinical features or unsuccessful PCI may need longer observation.

Feasibility of arresting the process of remodeling

Heart failure (HF) is a massive public health issue. Ventricular remodeling is pivotal to the pathophysiology/progression of HF and an attractive target for intervention. It currently is believed that interdicting the natural history of ventricular remodeling will be crucial to controlling the HF epidemic. This article reviews the current data on the feasibility of arresting this process. This review is not meant to be exhaustive but provides a brief overview of the approaches being contemplated in this field.

Clinical perspectives and therapeutics of thrombolysis

Reperfusion therapy with thrombolytic agents has been a significant advancement in the management of patients with acute ST elevation myocardial infarction. The outcome of acute myocardial infarction has significantly improved by early application of thrombolytic therapy. Intracoronary streptokinase has been used for >30 years, but reawakening interest occurred in the early 1980s in the use of thrombolytic therapy to establish rapid reperfusion during an acute myocardial infarction. Initial studies aimed at direct intracoronary thrombolysis, but owing to its cumbersome process and requirement of an active round the clock cardiac catheterization laboratory, it has been replaced by regimens of intravenous thrombolytic therapy which is as efficacious as intracoronary administration. Consideration of thrombolytic therapy has become a standard treatment for patients presenting with acute ST elevation myocardial infarction and various well-controlled trials have demonstrated the importance of both early and full reperfusion in improving clinical outcome in the setting of acute myocardial infarction. The subject of intravenous thrombolysis is perhaps the most rapidly evolving area in the management of acute myocardial infarction patients in the past decade. The current review focuses on the thrombolysis in the treatment of myocardial infarction and other conditions.

Adjunctive use of direct thrombin inhibitors in patients receiving fibrinolytic therapy for acute myocardial infarction

The direct thrombin inhibitors hirudin and bivalirudin inhibit both fluid-phase and clot-bound thrombin. These agents have been extensively studied in clinical trials in comparison with intravenous unfractionated heparin (UFH), as adjuncts to fibrinolytic therapy for ST-elevation myocardial infarction (STEMI) and in percutaneous coronary intervention (PCI), and they are currently undergoing further evaluation in patients with non-ST elevation acute coronary syndromes (NSTEACS). In angiographic trials there were trends for patients treated with hirudin to be more likely to achieve Thrombolysis In Myocardial Infarction (TIMI) grade 3 flow at 90 minutes than patients treated with UFH (65% versus 57% in TIMI-5; 41% versus 33% in Hirudin for the Improvement of Thrombolysis [HIT]-4; statistically nonsignificant differences in both trials). In Montréal Heart Institute trials and the multicenter Hirulog and Early Reperfusion or Occlusion (HERO)-1 trial the use of bivalirudin was associated with an increased incidence of TIMI grade 3 flow (85% versus 31%, p = 0.006; and 48% versus 35%, p = 0.02, respectively). These studies used streptokinase as the fibrinolytic agent except in TIMI-5 where alteplase was used. The initial clinical outcomes studies (Global Use of Strategies to Open Occluded Coronary Arteries in Acute Coronary Syndromes [GUSTO]-IIA and TIMI-9A) were discontinued early because of a high incidence of intracerebral bleeding (approximately 1.8%). Patients in these studies had either STEMI or NSTEACS, and thus not all were treated with fibrinolytic therapy. These studies were recommenced as GUSTO-IIB and TIMI-9B, using lower dosages of hirudin (0.1 mg/kg bolus + 0.1 mg/kg infusion for 96 hours). Neither TIMI-9B nor GUSTO-IIB showed an improvement in efficacy (death or reinfarction) or an increase in bleeding with hirudin. However, in the 1015 patients with STEMI treated with streptokinase in GUSTO-IIB, there was a 40% reduction in the combined incidence of death or myocardial infarction at 30 days (8.6% versus 14.4%, odds ratio [OR] 0.57, 95% confidence interval [CI] 0.38-0.87, p = 0.004). In the HERO-2 trial, 17073 patients receiving streptokinase for STEMI were randomized to receive either bivalirudin (0.25 mg/kg bolus and 0.5 mg/kg infusion for 12 hours followed by 0.25 mg/kg) or UFH (5000 IU bolus and 800-1000 IU/h infusion titrated to an activated partial thromboplastin time [APTT] of 50-75 seconds) for a total of 48 hours. Thirty-day mortality was similar in both groups (10.8% with bivalirudin versus 10.9% with UFH, OR 0.99, 95% CI 0.90-1.09, p = 0.85). There was a 30% reduction in the incidence of reinfarction before 96 hours (1.6% with bivalirudin versus 2.3% with UFH, OR 0.70, 95% CI 0.56-0.87, p = 0.001). Patients treated with bivalirudin had significantly more moderate bleeding (1.4% versus 1.1% with UFH, OR 1.32, 95% CI 1.0-1.74, p = 0.05). In a meta-analysis of patients with STEMI in the Direct Thrombin Inhibitor Trialists' collaboration, direct thrombin inhibitors were found to reduce the rate of reinfarction at 30 days (3.9% versus 4.8% with UFH, OR 0.80, 95% CI 0.71-0.90, p < 0.001), but did not reduce mortality (9.1% versus 9.0%, OR 1.02, 95% CI 0.94-1.11, p = 0.68) or the combined incidence of death/reinfarction at 30 days (11.8% versus 12.4%, OR 0.95, 95% CI 0.88-1.02, p = 0.18). There was no increase in major bleeding or intracerebral bleeding with direct thrombin inhibitor therapy. In conclusion, direct thrombin inhibitors reduce reinfarction, but not mortality, in patients with STEMI treated with fibrinolytic therapy. The major benefit of direct thrombin inhibitors appears to be in patients undergoing PCI, particularly after STEMI.

Correlates of one-year survival inpatients with cardiogenic shock complicating acute myocardial infarction

OBJECTIVES

The goal of this study was to describe the core laboratory angiographic findings of "SHould we emergently revascularize Occluded Coronaries for cardiogenic shocK" (SHOCK) trial participants and to determine the relationship of angiographic parameters to one-year survival.

BACKGROUND

In the SHOCK trial, emergency revascularization improved one-year survival of patients with cardiogenic shock compared with initial medical stabilization including thrombolysis and intraaortic balloon counterpulsation.

METHODS

Coronary angiography was performed by protocol in 147 of 152 (97%) patients in the emergency revascularization (ERV) group and by clinical selection in 100 of 150 (67%) patients in the initial medical stabilization (IMS) group. Of the other 50 IMS patients, 45 of 50 (90%) died rapidly and did not undergo angiography.

RESULTS

Left ventricular ejection fraction was correlated with one-year survival in both treatment groups (p < 0.001). In the IMS group, the hazard ratio for death was 2.59 (95% confidence interval 1.47 to 4.58, p = 0.001) per diseased vessel (0/1 vs. 2 vs. 3). In the ERV group, the hazard ratio for death per diseased vessel was 1.11 (95% confidence interval 0.79 to 1.56, p = 0.559). Multivariate analysis of the angiography cohort (without regard for left ventriculogram measurements) identified initial Thrombolysis in Myocardial Infarction flow grade (p = 0.032), number of diseased vessels (for IMS patients only, p = 0.024), and culprit vessel (p = 0.004) as independent correlates of one-year survival, even after adjustment for key clinical factors. In the smaller cohort with left ventricular ejection fraction measured (n = 97), ejection fraction and culprit vessel remained independently correlated with survival.

CONCLUSIONS

For patients in cardiogenic shock, left ventricular function and culprit vessel were independent correlates of one-year survival.

High-risk clinical features predict increased post-infarction myocardial apoptosis and the benefits as a result of an open infarct-related artery

BACKGROUND

Infarct-related artery (IRA) patency after acute myocardial infarction (AMI) is associated with a more favourable clinical course, in particular in patients with high-risk features. As it has been recently reported that IRA patency is associated with a reduced postinfarction apoptotic rate (AR), the aim of our study was to assess whether IRA status late after AMI had a different impact on AR in high- vs. low-risk patients.

METHODS AND RESULTS

Co-localization of TUNEL and caspase-3 was used to calculate the AR at the site of infarction at the time of death in 30 subjects. The Norris coronary prognostic index (NI) was calculated (computing age, presence of pulmonary congestion, heart size and history of previous additional AMI) in order to define the patients' individual risk at the time of hospitalization. According to the NI (< or =7 vs. >7), subjects were divided into low and high risk, as NI >7 carries an approximate threefold higher risk of death. The NI was significantly correlated with the AR at the time of death both in infarct and remote areas. Twenty subjects had IRA occlusion at the time of death, and in these patients AR was significantly higher both in infarct and remote areas (P<0.001 and P=0.009 vs. the others, respectively). However the impact of IRA occlusion on AR was significantly different comparing high- vs. low-risk subjects. In particular, AR at the infarct site was 10-fold higher in the high-risk subjects with IRA occlusion (26.1%[20.4-28.7%]) vs. those with open IRA (2.3%[0.6-3.5%]; P=0.002) and was nonsignificantly different in the low-risk subjects vs. those without IRA occlusion (8.2%[2.5-17.5%] vs. 5.4%[1.5-7.9%]; P=0.48). Similarly, in the high-risk subjects, AR in remote areas was significantly greater in cases with occluded vs. open IRA (0.7%[0.4-0.9%] vs. 0.3%[0.3-0.32%]; P=0.009).

CONCLUSION

A significantly higher AR is associated with IRA occlusion late post AMI in subjects with high-risk clinical features, and not in low-risk patients. The diverse impact of IRA occlusion on AR in subjects with different risk profiles may explain the greater benefit associated with coronary reperfusion in high-risk subjects. The overall lower AR in low-risk subjects, independently from the IRA status, may be correlated with the better long-term prognosis after AMI in this case.

Myocardial neovascularization by adult bone marrow-derived angioblasts: strategies for improvement of cardiomyocyte function

In the pre-natal period, hemangioblasts derived from the human ventral aorta give rise to cellular elements involved in both hematopoiesis and vasculogenesis, resulting in formation of the primitive capillary network. Endothelial precursors with phenotypic and functional characteristics of embryonic hemangioblasts are also present in human adult bone marrow, and can be used to induce infarct bed vasculogenesis and angiogenesis after experimental myocardial infarction. The neovascularization results in decreased apoptosis of hypertrophied myocytes in the peri-infarct region, long-term salvage and survival of viable myocardium, reduction in collagen deposition, and sustained improvement in cardiac function. Autologous angioblasts may also be useful in cellular therapy strategies aiming to regenerate myocardial tissue after established heart failure. It is likely that protocols using cardiomyocyte/mesenchymal stem cells will require balanced co-administration of angioblasts to provide vascular structures for supply of oxygen and nutrients to both the chronically ischemic, endogenous myocardium and to the newly-implanted cardiomyocytes. Future studies will need to address the timing, relative concentrations, source and route of delivery of each of these cellular populations in animal models of acute and chronic myocardial ischemia.

New directions in strategies using cell therapy for heart disease

Congestive heart failure remains a major public health problem and is frequently the end result of cardiomyocyte apoptosis and fibrous replacement after myocardial infarction, a process referred to as left ventricular remodeling. Cardiomyocytes undergo terminal differentiation soon after birth and are generally considered to irreversibly withdraw from the cell cycle. In response to ischemic insult adult cardiomyocytes undergo cellular hypertrophy, nuclear ploidy, and a high degree of apoptosis. A small number of human cardiomyocytes retain the capacity to proliferate and regenerate in response to ischemic injury. However, whether these cells are derived from a resident pool of cardiomyocyte stem cells or from a renewable source of circulating bone marrow-derived stem cells that home to the damaged myocardium is at present not known. Replacement and regeneration of functional cardiac muscle after an ischemic insult to the heart could be achieved by either stimulating proliferation of endogenous mature cardiomyocytes or resident cardiac stem cells or by implanting exogenous donor-derived or allogeneic cells such as fetal or embryonic cardiomyocyte precursors, bone marrow derived mesenchymal stem cells, or skeletal myoblasts. The newly formed cardiomyocytes must integrate precisely into the existing myocardial wall in order to augment synchronized contractility and avoid potentially life-threatening alterations in the electrical conduction of the heart. A major impediment to survival of the implanted cells is altered immunogenicity by prolonged ex vivo culture conditions. In addition, concurrent myocardial revascularization is required to ensure viability of the repaired region and prevent further scar tissue formation. Human adult bone marrow contains endothelial precursors which resemble embryonic angioblasts and can be used to induce infarct bed neovascularization after experimental myocardial infarction. This results in protection of cardiomyocytes against apoptosis, induction of cardiomyocyte proliferation and regeneration, long-term salvage and survival of viable myocardium, prevention of left ventricular remodeling, and sustained improvement in cardiac function. It is reasonable to anticipate that cell therapy strategies for ischemic heart disease will need to incorporate (a) a renewable source of proliferating, functional cardiomyocytes, and (b) angioblasts to generate a network of capillaries and larger size blood vessels for supply of oxygen and nutrients to both the chronically ischemic endogenous myocardium and to the newly implanted cardiomyocytes

Benefits of late reperfusion in the treatment of acute myocardial infarction

Early reperfusion of the infarct-related coronary artery is very much effective to treat the patients with acute myocardial infraction. However, there are many clinical as well as experimental evidences supporting the efficacy of late reperfusion therapy. In this article, effects of late reperfusion on mortality, left ventricular function, left ventricular dilatation and remodeling, or electrical stability were summarized. Also, the possible mechanisms for benefits of late reperfusion were discussed and the special role of epicardial rim bring about those benefits was emphasized.

Interventional therapy of the acute coronary syndromes

The acute coronary syndromes (ACS) have in common rupture of a vulnerable plaque, leading to exposure of the subendothelial surface and plaque core. The resultant thrombosis leads to a variable degree of flow occlusion, the extent of which differentiates the three syndromes and their treatment by percutaneous coronary intervention (PCI). The guiding principle in the decision when to use PCI in the ACS is that the more time critical and high risk the clinical situation, the more likely it is that PCI will improve ultimate outcome. The use of risk stratification by clinical variables can lead to better triage of patients with non-ST-elevation myocardial infarction (MI) and unstable angina between PCI and medical management. Patients presenting with symptoms suggestive of prolonged ischemia should have an electrocardiogram searching for ST changes, a targeted physical, and blood drawn for rapid assay of cardiac enzymes. In the event that ST elevations suggest infarction, while medical therapy is initiated, emergency cardiac catheterization can be organized. PCI in ACS requires adjunctive antiplatelet and antithrombin therapy, and, in general, coronary stenting is advisable. Among patients with non-ST-elevation MI or unstable angina who can be medically stabilized, the presence of high clinical risk scores would favor early coronary angiography. In their absence, medical therapy can be pursued, unless recurrent ischemia occurs. When the patient's condition is stable, evaluation by stress testing can be used to guide further decisions.