Impact of Time to Treatment on Mortality After Prehospital Fibrinolysis or Primary Angioplasty

Automated discrimination of proximal right coronary artery occlusion from middle-to-distal right coronary artery occlusion and left circumflex occlusion in ST-elevation myocardial infarction

BACKGROUND

Classifying the location of an occlusion in the culprit artery during ST-elevation myocardial infarction (STEMI) is important for risk stratification to optimize treatment. We developed a new logistic regression (LR) algorithm for 3-group classification of occlusion location as proximal right coronary artery (RCA), middle-to-distal RCA or left circumflex (LCx) coronary artery with inferior myocardial infarction. We compared the performance of the new LR algorithm with the recently introduced decision tree classifier of Fiol et al (Ann Noninvasive Electrocardiol. 2004;4:383-388) in the classification of the same 3 categories.

METHODS

The new algorithm was developed on a set of electrocardiograms from an emergency department setting (n = 64) and tested on a different set from a prehospital setting (n = 68). All patients met the current STEMI criteria with angiographic confirmation of culprit artery and occlusion location. Using LR, 4 ST-segment deviation features were chosen by forward stepwise selection. Final LR coefficients were obtained by averaging more than 200 bootstrap iterations on the training set. In addition, a separate 4-feature classifier was designed adding ST features of V4R and V8, only available in the training set.

RESULTS

The LR algorithm classified proximal RCA occlusion vs combined LCx occlusion and middle-to-distal RCA occlusion, with a sensitivity of 76% and specificity of 81% as compared with 71% and 62% for the Fiol classifier. The difference in specificity was statistically significant. The LR classifier trained with additional ST features of V4R and V8, but still limited to 4, improved the overall agreement in the training set from 65% to 70%.

CONCLUSION

Discrimination of proximal RCA lesion location from LCx or middle-to-distal RCA using the new LR classifier shows improvement over decision tree–type classification criteria. Automated identification of proximal RCA occlusion could speed up the risk stratification of patients with STEMI. The addition of leads V4R and V8 should further improve the automated classification of the occlusion site in RCA and LCx.

The Critical Imperative: Prehospital Management of the Patient with ST-Elevation Myocardial Infarction

Prehospital care is critical to achieve the goal of timely reperfusion in patients with ST-elevation myocardial infarction. Prehospital care is delivered by emergency medical services (EMS) personnel, which include emergency medical dispatchers, first responders, and ambulance response. There is considerable variation in the training and capabilities of the EMS providers in the United States depending on the location (ie, rural vs urban) and local jurisdictions. In this article, the key components of prehospital care of the patient with ST-elevation myocardial infarction and the various levels of training and capabilities of EMS providers are discussed.

[Myocardial revascularization]

Coronary artery disease (CAD) is a leading cause of morbidity and mortality in western countries and is of significant socio-economic importance due to its increasing prevalence. Until percutaneous coronary interventions (PCI) were established, CAD could only be treated by surgical revascularization or pharmacological therapy. In-stent restenosis remains a major problem after stent implantation. However, the use of new materials and stent coatings have led to a significant reduction in in-stent restenosis. Thus, surgical revascularization and PCI are currently of equal value for the treatment of CAD. The decision-making for PCI or surgical revascularization depends on various factors such as number of diseased vessels, complexity of the coronary stenoses, concomitant diseases, and the patient's general condition. The therapeutic regime of every patient should be adjusted to the recommendations of the European and German Society for Cardiology, while controversial and complex cases should be discussed in an interdisciplinary case conference ("heart team").

The mouse dorsal skinfold chamber as a model for the study of thrombolysis by intravital microscopy

Although intravital microscopy models of thrombosis in mice have contributed to dissect the mechanisms of thrombus formation and stability, they have not been well adapted to study long-term evolution of occlusive thrombi. Here, we assessed the suitability of the dorsal skinfold chamber (DSC) for the study of thrombolysis and testing of thrombolytic agents by intravital microscopy. We show that induction of FeCl3-induced occlusive thrombosis is achievable in microvessels of DSCs, and that thrombi formed in DSCs can be visualised by intravital microscopy using brightfield transmitted light, or fluorescent staining of thrombus components such as fibrinogen, platelets, leukocytes, and von Willebrand factor. Direct application of control saline or recombinant tissue-plasminogen activator (rtPA) to FeCl3-produced thrombi in DSCs did not affect thrombus size or induce recanalisation. However, in the presence of hirudin, rtPA treatment caused a rapid dose-dependent lysis of occlusive thrombi, resulting in recanalisation within 1 hour after treatment. Skin haemorrhage originating from vessels located inside and outside the FeCl3-injured area was also observed in DSCs of rtPA-treated mice. We further show that rtPA-induced thrombolysis was enhanced in plasminogen activator inhibitor-1-deficient (PAI-1-/-) mice, and dropped considerably as the time between occlusion and treatment application increased. Together, our results show that by allowing visualization and measurement of thrombus lysis and potential bleeding complications of thrombolytic treatments, the DSC provides a model for studying endogenous fibrinolysis and for first-line screening of thrombolytic agents. Furthermore, using this system, we found that thrombin and clot aging impair the thrombolytic action of rtPA towards FeCl3-produced thrombi.

Randomized comparison of pre-hospital-initiated facilitated percutaneous coronary intervention versus primary percutaneous coronary intervention in acute myocardial infarction very early after symptom onset: the LIPSIA-STEMI trial (Leipzig immediate prehospital facilitated angioplasty in ST-segment myocardial infarction)

OBJECTIVES

This multicenter trial sought to assess the merits of facilitated percutaneous coronary intervention (PCI) versus primary PCI in an ST-segment elevation myocardial infarction (STEMI) network with long transfer distances in patients presenting early after symptom onset.

BACKGROUND

Facilitated PCI with fibrinolysis might be beneficial in specific high-risk STEMI situations to prevent myocardial necrosis expansion.

METHODS

Patients with STEMI (<3 h after symptom onset) were randomized to either pre-hospital-initiated facilitated PCI using tenecteplase (Group A; n = 81) or primary PCI (Group B; n = 81) plus optimal antithrombotic comedication. The primary endpoint was infarct size assessed by delayed-enhancement magnetic resonance imaging. Secondary endpoints were microvascular obstruction and myocardial salvage, early ST-segment resolution, and a composite of death, repeated myocardial infarctions, and congestive heart failure within 30 days.

RESULTS

The median time from symptom onset to randomization was 64 min (interquartile range [IQR]: 42 to 103 min) in Group A versus 55 min in Group B (IQR: 27 to 91 min; p = 0.26). Despite better pre-interventional TIMI (Thrombolysis In Myocardial Infarction) flow in Group A (71% vs. 35% TIMI flow grade 2 or 3; p < 0.001), the infarct size tended to be worse in Group A versus Group B (17.9% of left ventricle [IQR: 8.4% to 35.0%] vs. 13.7% [IQR: 7.5% to 24.0%]; p = 0.10). There was also a strong trend toward more early and late microvascular obstruction, (p = 0.06 and 0.09) and no difference in ST-segment resolution (p = 0.26). The combined clinical endpoint showed a trend toward higher event rates in Group A (19.8% vs. 13.6%; p = 0.13, relative risk: 0.52, 95% confidence interval: 0.23 to 1.18).

CONCLUSIONS

In STEMI patients presenting early after symptom onset with relatively long transfer times, a fibrinolytic-based facilitated PCI approach with optimal antiplatelet comedication does not offer a benefit over primary PCI with respect to infarct size and tissue perfusion. ([LIPSIA-STEMI] The Leipzig Immediate Prehospital Facilitated Angioplasty in ST-Segment Myocardial Infarction; NCT00359918).

The appropriateness of single page of activation of the cardiac catheterization laboratory by emergency physician for patients with suspected ST-segment elevation myocardial infarction: a cohort study

Background

The early use of reperfusion therapy has a significant effect on the prognosis of patients with ST-segment elevation myocardial infarction (STEMI), and it is recommended that emergency department (ED) physicians activate the cardiac catheterization laboratory (CCL) as soon as possible to treat these patients. The aim of this study was to examine the appropriateness of emergency physician activation of the CCL for patients with suspected STEMI. Inappropriate activations (i.e., false positive activations) were identified according to a variety of criteria.

Methods

All patients with emergency physician CCL activations between August 2009 and April 2011 were included in the study. False positive cases were defined according to ECG criteria and cardiologists' reviews of patients' initial clinical information.

Results

ED physicians used a STEMI page to activate the CCL 117 times. According to reviews by cardiologists, this activation was appropriate 89.8% of the time (in 105/117 cases). Truly unnecessary activation (i.e., cases in which STEMI was not identified by the cardiologists, no clear culprit coronary artery was present, no significant coronary artery disease and cardiac biomarkers were negative) occurred 5.1% of the time (in 6/117 cases).

Conclusions

CCL activation was appropriate for most patients and was unnecessary in a relatively small percentage of cases. This result supports the current recommendation for CCL activation by emergency physicians. Such early activation is a key strategy in the reduction of door-to-balloon time.

Trends in the Use of Evidence-based Therapies Early in the Course of Acute Myocardial Infarction and its Influence on Short Term Patient Outcomes

AIM

To evaluate changes in management practices and its influence on short term hospital outcomes in patients with acute myocardial infarction (AMI) admitted during two different time periods, 2007 and 2004.

METHODS AND RESULTS

We studied AMI patients from two acute coronary syndrome registries carried out in Kuwait in 2007 and 2004. We included 1872 and 1197 patients from the 2007 and 2004 registries, respectively. When compared with 2004, patients from the 2007 registry had similar baseline clinical characteristics. In 2007 compared to 2004, during the in-hospital period, patients with AMI received significantly more statins (94% vs. 73%%, p<0.0001), Angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARB) (70% vs. 47%, p<0.001), and Clopidogrel (38% vs. 4%, p<0.001), while beta-blockers use dropped in 2007 compared to 2004 (63% vs. 68%, p=0.0066). The rates of in-hospital mortality and recurrent ischemia were significantly lower in the 2007 cohort compared with the 2004 cohort (for mortality 2.2% vs. 3.9%, P=0.0008, for recurrent ischemia 13.7% vs. 20.4%, P=0<0.0001).Higher utilization of angiotensin converting enzyme inhibitors, angiotensin receptor blockers and statins were the main contributors to the improved in-hospital mortality and morbidity.

IN CONCLUSION

In the acute management of AMI, there was a significant increase in the use of statins, ACE inhibitors and Clopidogrel in 2007 compared to 2004. This was associated with a significant decrease in the in-hospital mortality and recurrent ischemia. Adherence to guidelines recommended therapies improved in-hospital outcomes.

Letter to the editors: the potential role for prehospital thrombolysis and time-critical stroke transfers in the northern Norway aeromedical retrieval system; In response to: Norum J, Elsbak TM: Air ambulance services in the Arctic: a Norwegian study. Int J Emerg Med 2011, 4:1

The role for prehospital thrombolysis for ST-elevation acute myocardial infarction and time-critical stroke transfers in the northern Norway aeromedical retrieval system as well as the aero-evacuation impact of increased Arctic expedition tourism could benefit from further discussion by Norum and Elsbak. Close ECG surveillance for ST elevation and retrieval thrombolysis en route to the accepting hospital could be of benefit for acute coronary syndrome patients in northern Norway who require prolonged aeromedical transfer. For patients who remain within a reasonable time frame for stroke thrombolysis (up to 4.5 h after symptom onset), expedited transfer for neuroimaging to determine eligibility is recommended.

Cardiogenic shock and heart failure post-percutaneous coronary intervention in ST-elevation myocardial infarction: observations from "Assessment of Pexelizumab in Acute Myocardial Infarction"

BACKGROUND

Mortality after ST-elevation myocardial infarction (STEMI) has reduced with reperfusion by primary percutaneous coronary intervention (PCI), which may have impacted on the adverse outcomes of cardiogenic shock (CS) and congestive heart failure (CHF).

METHODS AND RESULTS

In the APEX-AMI trial, 5,745 patients with STEMI and planned primary PCI were randomly assigned pexelizumab or matching placebo. Post-randomization CS or CHF was adjudicated by a clinical endpoints committee. Treatment assignment to pexelizumab did not influence either endpoint or mortality rates. Cardiogenic shock developed in 196 patients (3.4%) at a median of 6.0 hours (interquartile range 3.9-28.3) post-randomization, and mortality at 90 days was 54.6%. Congestive heart failure occurred in 254 of patients (4.4%) at a median of 2.6 days (IQR 1.0-16.6), and mortality through 90 days was 10.2%; mortality among those with neither endpoint was 2.1%. Patients with CS or CHF were older, were more often female, and had more hypertension and diabetes, but smoked less compared with non-CS/CHF patients (all P < .05). Independent mortality predictors among those with CS or CHF were hyperlipidemia and a history of angina (interaction P = .011 and .008, respectively); procedural predictors among survivors to PCI were pre-PCI Thrombolysis In Myocardial Infarction (TIMI) flow 0-1 and post-PCI TIMI flow <3 (P = .013 and <.0001, respectively).

CONCLUSIONS

Survival after CS remains poor despite aggressive reperfusion. Both CS and CHF remain the major causes of death among STEMI patients undergoing primary PCI. Future studies should examine treatments that aim to reduce mortality in these highest risk patients.

As time goes by?: the fallacy of thrombolysis in STEMI networks

Primary percutaneous coronary intervention (PPCI) is superior to thrombolysis (TL) as reperfusion therapy in ST-elevation myocardial infarction (STEMI). TL is a rapidly available, but semi-effective therapy (effective reperfusion in 50% of patients only), whereas PPCI is a potentially delayed, but highly effective therapy (effective reperfusion in >90%). Since TL loses its efficacy beyond 2-3 h after symptom onset, it is a significant reperfusion alternative to PPCI in early presenters only. The individual decision to treat an early presenter with PPCI or TL requires the evaluation of the time delay between potential start of TL or PPCI, the PCI-related delay (PRD). PRD is greatest, if TL is given in the prehospital setting. Until now, prehospital TL as the most rapidly available reperfusion strategy has failed to demonstrate any prognostic or even any other relevant benefit compared to PPCI in any subgroup of patients, even with time delays for PPCI of up to several hours. On average, a median PRD of at least 90-120 min can be considered a time corridor of prognostic superiority of PPCI over TL. This is already achieved in contemporary registries and myocardial infarction networks.Therefore, the efforts should not focus on the implementation of a dual reperfusion strategy (PPCI, and prehospital TL in selected cases) in established or upcoming myocardial infarction networks, but concentrate on the availability of PPCI in less than 2 h. TL, as rapid as possible, i.e. prehospital, is a vital treatment option in case of non-existing PPCI facilities within a median time limit of 2 h or even more, a scenario not existing or easily to eliminate in European countries by implementing well organized myocardial infarction networks. This is the mission to be accomplished.

Right ventricular function suffers from reperfusion delay: tissue Doppler study

In this study, impact of reperfusion delay on adverse cardiac events and right ventricular (RV) function in patients with acute right ventricular myocardial infarction (RVMI) was assessed. In 70 patients with RVMI, RV function was assessed by M-mode tricuspid annular plane systolic excursion (TAPSE) and by pulsed wave tissue Doppler echocardiography (TDE). Right ventricular early (E'(T)) and late diastolic (A'(T)), peak systolic tricuspid annular velocity, (S'(T)) and right ventricular myocardial performance index (RVMPI) were measured. Patients were divided into 2 groups according to the time between the onset of symptoms and percutaneous transluminal coronary angioplasty (PTCA)-group 1 (n = 25), < or =3 hours and group 2 (n = 45), > 3 hours. During 30-day follow-up, we assessed adverse cardiac events like the following: death, cardiogenic shock, need for intra-aortic counterpulsation, temporary transvenous pacing support (PCM), presence of ventricular septal defect (VSD), cardiac tamponade, or free wall rupture.

RESULTS

Group 1 had significantly higher values of E'(T), S'(T), and TAPSE than group 2. RVMPI was significantly elevated in group 2. A total of 13 (18.2%) patients had a cardiac event, 5 patients (7.1%) died. We observed an increase of cardiac events in patients with reperfusion delayed more than 3 hours (P = .056).

CONCLUSION

TAPSE-derived and TDE-derived right ventricular systolic and early diastolic velocities were less affected in patients with shorter time from pain onset to opening of the occluded right coronary artery (RCA). Presented initial data show that the tissue Doppler technique may be useful for identification of patients with RV infarction with higher rate of adverse cardiac events including death.

Composition of coronary thrombus in acute myocardial infarction

OBJECTIVES

We sought to analyze the composition of coronary thrombus in vivo in ST-segment elevation myocardial infarction (STEMI) patients.

BACKGROUND

The dynamic process of intracoronary thrombus formation in STEMI patients is poorly understood.

METHODS

Intracoronary thrombi (n = 45) were obtained by thromboaspiration in 288 consecutive STEMI patients presenting for primary percutaneous intervention, and analyzed using high-definition pictures taken with a scanning electron microscope. Plasma biomarkers (TnI, CRPus, IL-6, PAI-1, sCD40 ligand, and TNF-α) and plasma fibrin clot viscoelastic properties were measured simultaneously on peripheral blood.

RESULTS

Thrombi were mainly composed of fibrin (55.9 ± 18%) with platelets (16.8 ± 18%), erythrocytes (11.5 ± 9%), cholesterol crystals (5.2 ± 8.4%), and leukocytes (1.3 ± 2.0%). The median ischemic time was 175 min (interquartile range: 140 to 297). Ischemic time impacted thrombi composition, resulting in a positive correlation with intracoronary thrombus fibrin content, r = 0.38, p = 0.01, and a negative correlation with platelet content, r = -0.34, p = 0.02. Thus, fibrin content increased with ischemic time, ranging from 48.4 ± 21% (<3 h) up to 66.9 ± 9% (>6 h) (p = 0.02), whereas platelet content decreased from 24.9 ± 23% (<3 h) to 9.1 ± 6% (>6 h) (p = 0.07). Soluble CD40 ligand was positively correlated to platelet content in the thrombus (r = 0.40, p = 0.02) and negatively correlated with fibrin content (r = -0.36; p = 0.04). Multivariate analysis indicated that ischemic time was the only predictor of thrombus composition, with a 2-fold increase of fibrin content per ischemic hour (adjusted odds ratio: 2.00 [95% confidence interval: 1.03 to 3.7]; p = 0.01).

CONCLUSIONS

In acute STEMI, platelet and fibrin contents of the occlusive thrombus are highly dependent on ischemia time, which may have a direct impact on the efficacy of drugs or devices used for coronary reperfusion.

[Management of acute myocardial infarction: What remains of intravenous thrombolysis?]

ST elevation myocardial infarction (STEMI) is related to acute occlusion of a coronary artery by a fibrin reach thrombus. Early reperfusion may reduce infarct size and improve prognosis. Percutaneous coronary intervention (PCI) is more effective than intravenous fibrinolysis (IVF). Fibrinolysis remains useful in patients when PCI is not feasible. IVF has largely contributed to the knowledge of the physiopathology of STEMI and its management.

[Myocardial infarction: Role of new antiplatelet agents]

Thienopyridines have become the cornerstone of treatment of percutaneous coronary intervention although no survival benefit has ever been shown with clopidogrel despite increasing loading doses. Newly developed P2Y(12) inhibitors are more potent, more predictable and have a faster onset of action than clopidogrel, characteristics that make them particularly attractive for high-risk PCI. Four new P2Y(12) inhibitors have been tested each of them having particular individual properties. Prasugrel is an oral prodrug leading to irreversible blockade of the P2Y(12) receptor and is approved worldwide for ACS PCI. Ticagrelor is a direct-acting and reversible inhibitor of the P2Y(12) receptor with potentially more pleiotropic effects. Cangrelor is an intravenous direct and reversible inhibitor of the P2Y(12) receptor providing the highest level of inhibition and elinogrel is an intravenous and oral P2Y(12) antagonist with a direct and reversible action. Both prasugrel and ticagrelor, opposed to clopidogrel, have shown that stronger P2Y(12) inhibition led respectively to significant 19 % and 16 % relative risk reduction of a similar primary endpoint combining cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke. Both drugs showed a significant 0.6 % absolute excess of TIMI major bleeding not related to CABG surgery. The effect of these new compounds is prompt, predictable and powerful as compared to clopidogrel. Their net benefit is particularly marked in PCI for STEMI patients, in which there is no significant increase in major bleeding when compared with clopidogrel. However, because in clinical trials patients perceived to be at higher risk for bleeding usually are excluded, the risk of major and even fatal bleeding might even be higher in a "real-world" setting i.e. in the elderly patient with comorbidities.

The influence of time from symptom onset and reperfusion strategy on 1-year survival in ST-elevation myocardial infarction: a pooled analysis of an early fibrinolytic strategy versus primary percutaneous coronary intervention from CAPTIM and WEST

BACKGROUND

The CAPTIM trial suggested a survival benefit of prehospital fibrinolysis (FL) compared to primary percutaneous coronary intervention (PCI) in patients with ST-elevation myocardial infarction (STEMI) with a presentation delay of <2 hours. We examined the relationship between reperfusion strategy and time from symptom onset on 1-year mortality in a combined analysis of 1,168 patients with STEMI.

METHODS

Individual patient data from CAPTIM (n = 840, 1997-2000) and the more recent WEST trial (n = 328, 2003-2005) were pooled.

RESULTS

Median age was 58 years, 81% were men, and 41% had anterior myocardial infarction; 640 patients were randomized to FL versus 528 patients to PCI. Both arms received contemporary adjunctive medical therapy. Presentation delay (ie, symptom onset to randomization) was similar in FL and PCI patients (median 105 [72-158] vs 106 [74-162] minutes, P = .712). Rescue PCI after FL occurred in 26% and 27%, and 30-day PCI, in 70% and 71% in CAPTIM and WEST, respectively. Mortality was not different between FL and PCI (4.6% vs 6.5%, P = .263); however, the interaction between presentation delay and treatment was significant (P = .043). Benefit with FL was observed with time <2 hours (2.8% [FL] vs 6.9% [PCI], P = .021, hazard ratio [HR] 0.43, 95% CI 0.20-0.91), whereas beyond 2 hours, no treatment difference was observed (6.9% [FL] vs 6.0% [PCI], P = .529, HR 1.23, 95% CI 0.61-2.46).

CONCLUSIONS

A strategy of early FL demonstrated a reduction in 1-year mortality compared to primary PCI in early presenters. Time from symptom onset should be a key consideration when selecting reperfusion therapy for STEMI.

Temporal trends in patient and treatment delay among men and women presenting with ST-elevation myocardial infarction

BACKGROUND

over the last decade, there have been major changes in the treatment of ST-elevation myocardial infarction (STEMI). Whether these have resulted in changes in sex differences in time to treatment is unknown. We examined temporal trends in time to reperfusion therapy among men and women with STEMI.

METHODS

the study includes 2 cohorts of STEMI patients presenting to a large metropolitan region during the periods August 24, 2000, to August 20, 2002 (Cohort1, n = 753), and August 25, 2006, to December 31, 2008 (Cohort2, n = 885).

RESULTS

in both cohorts, compared with men, women were significantly older and had more comorbidities. Rate of emergency medical services use among women increased from 55% in Cohort1 to 66% in Cohort2 (P = .02). Median time from symptom onset to first medical contact was 84 minutes among men and 121 minutes among women (P < .01) in Cohort1 and 59 minutes among men and 81 minutes among women (P < .01) in Cohort2. Median door-to-balloon time was significantly longer among women compared with men in Cohort2. After multivariable adjustment, female sex was associated with a 34% (or 27-minute) increase in time from symptom onset to first medical contact and with a 23% (or 13-minute) increase in time from hospital arrival to reperfusion therapy.

CONCLUSIONS

in the last decade, there have been significant reductions in patient and system delay, especially among women. However, women continue to have longer presentation and treatment times, suggesting that there continue to be opportunities for improvement.

Management of Acute ST-Elevation Myocardial Infarction: Reperfusion Options

Primary percutaneous coronary intervention and thrombolysis remain therapies of choice for patients presenting with ST-segment elevation myocardial infarction (STEMI). Clinical outcome in the management of acute STEMI is dependent on myocardial reperfusion time and reperfusion strategies. Optimisation of these strategies should take into consideration logistical limitations of the local medical systems and the various patient profiles. We review the reperfusion strategies and its history in Singapore, comparing its clinical application with that in some developed Western countries. Key words: Acute Myocardial Infarction, Primary Percutaneous Coronary Intervention, ST segment Elevation Myocardial Infarction, Thrombolysis

Meta-analysis of studies of patients in the United Arab Emirates with ST-elevation myocardial infarction treated with thrombolytic agents

We performed a meta-analysis of 6 studies we conducted in the United Arab Emirates from 1995 to 2009. These included 1,262 patients with ST-elevation myocardial infarction treated with thrombolytic drugs <6 hours after onset of symptoms and signs of myocardial infarction. All patients were treated with tenecteplase or alteplase to induce coronary thrombolysis. Characteristics of patients in all studies were quite similar. Overall mean age was 47 years, 98% were men, 28% had diabetes, 25% were hypertensive, 20% were hyperlipidemic, 56% were smokers, and 9% had sustained previous myocardial infarction. Incidence of adverse outcomes of 30-day mortality (3%), reinfarction (2.5%), stroke (0.4%), or major bleeding (0%) was low compared to global experience with recanalization regardless of how it was induced. There was no incidence of major bleeding requiring transfusion or laparotomy. In conclusion, in predominantly young men in the United Arab Emirates who were admitted and treated early after onset of an acute ST elevation myocardial infarction, recanalization induced by thrombolysis was an attractive therapeutic approach.

[ST-segment elevation acute coronary syndromes: Prehospital management strategies]

Prehospital management of ST-segment elevation myocardial infarction is a complex issue. Many components are involved, beginning with information of the public on the symptoms of heart attack, up to the choice of the final pathway and destination of the patients, with many intermediate steps including the regulation of emergency calls, the implementation of optimal diagnostic strategies, the choice of reperfusion therapy and of adjuvant medications. In recent years, optimization of these different components has led to improved patients' outcomes in this still life-threatening condition.

Underuse of prehospital strategies to reduce time to reperfusion for ST-elevation myocardial infarction patients in 5 Canadian provinces

OBJECTIVE

Timely reperfusion therapy for ST-elevation myocardial infarction (STEMI) is an important determinant of outcome, yet targets for time to treatment are frequently unmet in North America. Prehospital strategies can reduce time to reperfusion. We sought to determine the extent to which emergency medical services (EMS) use these strategies in Canada.

METHODS

We carried out a cross-sectional survey in 2007 of ground EMS operators in British Columbia, Alberta, Ontario, Quebec and Nova Scotia. We focused on the use of 4 prehospital strategies: 1) 12-lead electrocardiogram (ECG), 2) routine expedited emergency department (ED) transfer of STEMI patients (from a referring ED to a percutaneous coronary intervention [PCI] centre), 3) prehospital bypass (ambulance bypass of local EDs to transport patients directly to PCI centres) and 4) prehospital fibrinolysis.

RESULTS

Ninety-seven ambulance operators were surveyed, representing 15 681 paramedics serving 97% of the combined provincial populations. Of the operators surveyed, 68% (95% confidence interval [CI] 59%-77%) had ambulances equipped with 12-lead ECGs, ranging from 40% in Quebec to 100% in Alberta and Nova Scotia. Overall, 47% (95% CI 46%-48%) of paramedics were trained in ECG acquisition and 40% (95% CI 39%-41%) were trained in ECG interpretation. Only 18% (95% CI 10%-25%) of operators had prehospital bypass protocols; 45% (95% CI 35%-55%) had protocols for expedited ED transfer. Prehospital fibrinolysis was available only in Alberta. All EMS operators in British Columbia, Alberta and Nova Scotia used at least 1 of the 4 prehospital strategies, and one-third of operators in Ontario and Quebec used 0 of 4. In major urban centres, at least 1 of the 3 prehospital strategies 12-lead ECG acquisition, bypass or expedited transfer was used, but there was considerable variation within and across provinces.

CONCLUSION

The implementation of widely recommended prehospital STEMI strategies varies substantially across the 5 provinces studied, and relatively simple existing technologies, such as prehospital ECGs, are underused in many regions. Substantial improvements in prehospital services and better integration with hospital-based care will be necessary in many regions of Canada if optimal times to reperfusion, and associated outcomes, are to be achieved.

Fibrinolysis versus primary percutaneous intervention in ST-elevation myocardial infarction with long interhospital transfer distances

BACKGROUND

Current guidelines recommend rapid initiation of reperfusion therapy for ST-elevation myocardial infarction (STEMI), with short-distance transfer for primary percutaneous coronary intervention (pPCI) preferred over fibrinolysis in non-pPCI-capable hospitals. Comparative outcomes in patients with longer transfer times are unclear.

HYPOTHESIS

We designed this study to assess whether administering fibrinolytics prior to initiating longer-distance interhospital transfer in patients with STEMI leads to a delay in transfer or worse outcomes compared with transfer for pPCI.

METHODS

We analyzed 259 STEMI patients transferred to a receiving pPCI-capable center in eastern North Carolina. The patients were divided into 2 groups, with 43 (16.6%) transferred for pPCI and the remaining 216 (83.4%) transferred following fibrinolysis. The primary endpoint was door-to-door time. We also compared stroke, death, significant bleeding, and combined outcomes between the 2 groups.

RESULTS

The median door-to-door time was similar for pPCI and fibrinolysis patients (135 vs 128 minutes; P = 0.71). Median door-to-balloon time among pPCI patients was 182 minutes from the point of arrival at the referral hospital and 49 minutes from arrival at the receiving pPCI center. Median door-to-needle time in the fibrinolysis patients was 30 minutes, with rescue PCI eventually performed in 81 (37.5%) patients. In-hospital mortality was higher in patients with pPCI (9.3%) compared with fibrinolysis patients (1.9%; P = 0.03). Combined incidence of stroke, significant bleeding, and death was 14% in pPCI patients compared with 7% in fibrinolysis patients (P = 0.13).

CONCLUSIONS

In settings with longer transfer distances, administering fibrinolytics prior to transfer to a pPCI-capable center did not cause any significant delay in transfer or worse outcomes.

Comparative analysis of cardiac magnetic resonance viability indexes to predict functional recovery after successful percutaneous coronary intervention in acute myocardial infarction

The aim of this study was to examine the relative value and the influence of the association of 4 cardiac magnetic resonance (CMR) viability indexes for predicting segmental functional recovery after optimal pharmacologic therapies and early percutaneous coronary intervention in acute myocardial infarction (AMI). CMR has been shown to predict functional recovery after AMI. The relative predictive value of CMR viability indexes remains disputed and has not been described in AMI reperfused within the first 12 hours. Sixty-nine patients with a first reperfused (<12 hours) Thrombolysis In Myocardial Infarction grade 3 AMI (61 men, 57.6 +/- 12.6 years) were studied on day 5 +/- 2. Low-dose (10 microg/kg/min) dobutamine response (DOB), microvascular obstruction (MVO), relative delayed enhancement extent (DE), and transmural DE pattern (TMDE) were assessed in each of the 17 left ventricular segments. Segmental functional outcome was assessed by CMR at 3 months. Logistic regression and Bayesian probabilities evaluated the association between viability indexes and functional segmental outcome. At rest, 27% of segments (314 of 1,173) were dysfunctional of which 53% (165 of 314) recovered at follow-up. Odd ratios for dobutamine response, MVO, DE, and TMDE were 15.8, 5.9, 2.6, and 2.5 respectively. The probability of segmental recovery was 0.84 when dobutamine response was positive and increased successively to 0.91 when adding MVO absence, 0.94 when adding TMDE absence, and 0.97 when adding DE absence. In conclusion, contractile response to low-dose dobutamine is the best predictive factor of segmental recovery after Thrombolysis In Myocardial Infarction grade 3 early reperfused AMI. Its value is further increased by other CMR viability indexes.

Optimizing the use of thrombolytics in ST-segment elevation myocardial infarction

The advent of thrombolytic therapy was a major advance in the treatment of ST-segment elevation myocardial infarction (STEMI). The administration of fibrinolytic reperfusion therapy can reduce mortality rates by as much as 30%, with the greatest benefit observed if therapy is administered soon after symptom onset. Outcomes with thrombolytic therapy are improved if there is adjunctive treatment with aspirin, clopidogrel and an anti-thrombin agent. Although there is evidence that primary percutaneous coronary intervention (PCI) is the most effective reperfusion strategy, the majority of hospitals still do not have PCI capabilities and, thus, thrombolytic therapy remains a cornerstone of treatment for STEMI. Trials of thrombolytic therapy have demonstrated that initial patency rates can approach 85%, but there is still a need for improvement of non-invasive markers that predict failure or re-occlusion of the infarct-related artery. Because of the overwhelming data demonstrating the importance of rapid reperfusion, current studies are examining the role of earlier treatment of patients with STEMI via pre-hospital administration and/or coordinated systems for rapid diagnosis, transfer and delivery of definitive care. Facilitated PCI, a strategy of thrombolytic therapy followed by immediate PCI, has not been shown to be beneficial and current studies are examining the optimal timing of coronary angiography after thrombolytic therapy.

Acute coronary syndromes: Diagnosis and management, part II

At the most severe end of the spectrum of acute coronary syndromes is ST-segment elevation myocardial infarction (STEMI), which usually occurs when a fibrin-rich thrombus completely occludes an epicardial coronary artery. The diagnosis of STEMI is based on clinical characteristics and persistent ST-segment elevation as demonstrated by 12-lead electrocardiography. Patients with STEMI should undergo rapid assessment for reperfusion therapy, and a reperfusion strategy should be implemented promptly after the patient's contact with the health care system. Two methods are currently available for establishing timely coronary reperfusion: primary percutaneous coronary intervention and fibrinolytic therapy. Percutaneous coronary intervention is the preferred method but is not always available. Antiplatelet agents and anticoagulants are critical adjuncts to reperfusion. This article summarizes the current evidence-based guidelines for the diagnosis and management of STEMI. This summary is followed by a brief discussion of the role of noninvasive stress testing in the assessment of patients with acute coronary syndrome and their selection for coronary revascularization.