Thirty-year trends (1975-2005) in the magnitude, patient characteristics, and hospital outcomes of patients with acute myocardial infarction complicated by ventricular fibrillation

Association between new-onset right bundle branch block and primary or secondary ventricular fibrillation in ST-segment elevation myocardial infarction

AIMS

New-onset right bundle branch block (RBBB) in myocardial infarction (MI) is often associated with ventricular fibrillation (VF) but the nature of this relationship has not been determined.

METHODS AND RESULTS

Between 1998 and 2014, among other data, incidence and duration of RBBB and VF occurrence were prospectively collected in 5301 patients with ST-segment elevation MI (STEMI) admitted to two University Hospitals in Murcia (Spain). Multinomial adjusted logistic regression analyses were used to examine the association between RBBB, attending to its duration, and VF according to its primary VF (PVF) or secondary VF (SVF) character. Among 284 (5.4%) patients with new-onset RBBB, 158 were transient and 126 permanent. VF occurred in 339 (6.4%) patients, 201 PVF and 138 SVF, documented within the first 2 h of symptoms-onset in 78% and 60%, respectively. New-onset RBBB was more frequent in PVF (11.4%) and SVF (20.3%), than in non-VF (4.7%). Transient RBBB incidence was higher in PVF (9.0%) and SVF (9.4) than in non-VF (2.6%), whereas permanent RBBB was higher in SVF (10.9%) than PVF (2.5%) and non-VF (2.1%). New-onset RBBB 1.83 [95% confidence interval (CI): 1.07-3.11] and new-onset transient RBBB 2.39 (95% CI: 1.32-4.32) were independently associated with PVF. New-onset 3.03 (95% CI: 1.83-5.02), transient 2.40 (95% CI: 1.27-4.55), and permanent 2.99 (95% CI: 1.52-5.86) RBBB were independently associated with SVF.

CONCLUSION

New-onset RBBB and VF in STEMI are independently associated and show particularities based on the duration of the conduction disturbance and/or the primary or secondary character of the arrhythmia.

MD1 Depletion Predisposes to Ventricular Arrhythmias in the Setting of Myocardial Infarction

BACKGROUND

Myeloid differentiation protein 1 (MD1) is expressed in the human heart and is a negative regulator of Toll-like receptor 4 (TLR4) signalling. MD1 exerts anti-arrhythmic effects.

AIM

The aim of this study was to determine the role of MD1 in myocardial infarction (MI)-related ventricular arrhythmias (VAs).

METHOD

Myocardial infarction was induced by surgical ligation of the left anterior coronary artery in MD1 knockout (KO) mice and their wild-type littermates. Myocardial infarction-induced vulnerability to VAs and its underlying mechanisms were evaluated.

RESULTS

Myeloid differentiation protein 1 was downregulated in the MI mice. Myeloid differentiation protein 1 deficiency decreased post-MI left ventricular (LV) function and increased the infarct size. The MI mice exhibited prolonged action potential duration (APD), enhanced APD alternans thresholds, and a higher incidence of VAs. Myocardial infarction-induced LV fibrosis and inflammation decreased the expression levels of Kv4.2, Kv4.3, Kv1.5, and Kv2.1, increased Cav1.2 expression, and disturbed Ca²⁺ handling protein expression. These MI-induced adverse effects were further exacerbated in KO mice. Mechanistically, MD1 deletion markedly enhanced the activation of the TLR4/calmodulin-dependent protein kinase II (CaMKII) signalling pathway in post-MI mice.

CONCLUSIONS

Myeloid differentiation protein 1 deletion increases the vulnerability to VAs in post-MI mice. This is mainly caused by the aggravated maladaptive LV fibrosis and inflammation and interference with the expressions of ion channels and Ca²⁺ handling proteins, which is related to enhanced activation of the TLR4/CaMKII signalling pathway.

Feasibility of management of hemodynamically stable patients with acute myocardial infarction following primary percutaneous coronary intervention in the general ward settings

BACKGROUND

Although current guidelines recommend admission to the intensive/coronary care unit (ICU/CCU) for patients with ST-segment elevation myocardial infarction (MI), routine use of the CCU in uncomplicated patients with acute MI remains controversial. We aimed to evaluate the safety of management in the general ward (GW) of hemodynamically stable patients with acute MI after primary percutaneous coronary intervention (PCI).

METHODS

Using a large nationwide administrative database, a cohort of 19426 patients diagnosed with acute MI in 52 hospitals where a CCU was available were retrospectively analyzed. Patients with mechanical cardiac support and Killip classification 4, and those without primary PCI on admission were excluded. A total of 5736 patients were included and divided into the CCU (n = 3488) and GW (n = 2248) groups according to the type of hospitalization room after primary PCI. Propensity score matching was performed, and 1644 pairs were matched. The primary endpoint was in-hospital mortality at 30 days.

RESULTS

The CCU group had a higher rate of Killip classification 3 and ambulance use than the GW group. There was no significant difference in the incidence of in-hospital mortality within 30 days among the matched subjects. Multivariable Cox proportional hazard model analysis among unmatched patients supported the findings (hazard ratio 1.12, 95% confidence interval 0.66-1.91, p = 0.67).

CONCLUSIONS

The use of the GW was not associated with higher in-hospital mortality in hemodynamically stable patients with acute MI after primary PCI. It may be feasible for the selected patients to be directly admitted to the GW after primary PCI.

Twenty-five year trends (1986-2011) in hospital incidence and case-fatality rates of ventricular tachycardia and ventricular fibrillation complicating acute myocardial infarction

BACKGROUND

Long-term trends in the incidence rates (IRs) and hospital case-fatality rates (CFRs) of ventricular tachycardia (VT) and ventricular fibrillation (VF) among patients hospitalized with acute myocardial infarction (AMI) have not been recently examined.

METHODS

We used data from 11,825 patients hospitalized with AMI at all 11 medical centers in central Massachusetts on a biennial basis between 1986 and 2011. Multivariable adjusted logistic regression modeling was used to examine trends in hospital IRs and CFRs of VT and VF complicating AMI.

RESULTS

The median age of the study population was 71 years, 57.9% were men, and 94.7% were white. The hospital IRs declined from 14.3% in 1986/1988 to 10.5% in 2009/2011 for VT and from 8.2% to 1.7% for VF. The in-hospital CFRs declined from 27.7% to 6.9% for VT and from 49.6% to 36.0% for VF between 1986/1988 and 2009/2011, respectively. The IRs of both early (<48 hours) and late VT and VF declined over time, with greater declines in those of late VT and VF. The incidence rates of VT declined similarly for patients with either an ST-segment elevation myocardial infarction (STEMI) or non-STEMI, whereas they only declined in those with VF and a STEMI.

CONCLUSIONS

The hospital IRs and CHRs of VT and VF complicating AMI have declined over time, likely because of changes in acute monitoring and treatment practices. Despite these encouraging trends, efforts remain needed to identify patients at risk for these serious ventricular arrhythmias so that preventive and treatment strategies might be implemented as necessary.

Association of serum potassium concentration with mortality and ventricular arrhythmias in patients with acute myocardial infarction: A systematic review and meta-analysis

Background

Challenging clinical practice guidelines that recommend serum potassium concentration between 4.0–5.0 mEq/L or ≥4.5 mEq/L in patients with acute myocardial infarction, recent studies found increased mortality risks in patients with a serum potassium concentration of ≥4.5 mEq/L. Studies investigating consequences of hypokalemia after acute myocardial infarction revealed conflicting results. Therefore, the aim of this systematic review and meta-analysis was to combine evidence from previous studies on the association of serum potassium concentration with both short and long-term mortality as well as the occurrence of ventricular arrhythmias.

Design

Systematic review and meta-analysis.

Methods

A structured search of MEDLINE and EMBASE databases yielded 23 articles published between 1990 and January 2017 that met the inclusion criteria. Study selection, data extraction and quality assessment were carried out by three reviewers. Random effects models were used to pool estimates across the included studies and sensitivity analyses were performed when possible.

Results

Twelve studies were included in the meta-analysis. Both pooled results from six studies investigating short-term mortality and from five studies examining long-term mortality revealed significantly increased risks in patients with serum potassium concentrations of <3.5 mEq/L, 4.5–<5.0 mEq/L and ≥5.0 mEq/L after acute myocardial infarction. In addition, a serum potassium concentration of <3.5 mEq/L was significantly associated with the occurrence of ventricular arrhythmias.

Conclusions

Mortality, both short and long term, and the occurrence of ventricular arrhythmias in patients with acute myocardial infarction seem to be negatively associated with hypokalemic serum potassium concentration. There is evidence for adverse consequences of serum potassium concentrations of ≥4.5 mEq/L. Due to the heterogeneity among existing studies, further research is necessary to confirm the need to change clinical practice guidelines.

Potassium Fluctuations Are Associated With Inhospital Mortality From Acute Myocardial Infarction. Soroka Acute Myocardial Infarction II (SAMI-II) Project

Potassium levels (K, mEq/L) fluctuate in patients with acute myocardial infarction (AMI). Potassium was reported to be associated with prognosis in patients with AMI; however, studies evaluating the prognostic value of K fluctuations in this setting are scarce. We retrospectively analyzed patients with AMI hospitalized in a tertiary medical center, through 2002 to 2012. Patients on chronic dialysis or mechanical ventilation were excluded. Based on all K values during hospitalization, minimal, maximal, and fluctuation (gap between 2 consecutive K) were recorded. Primary outcome was inhospital all-cause mortality. Overall, 10 032 patients were studied (age 68.1 ± 14.3 years, 65.4% males, 44.2% ST-segment elevation MI), of which 507 (3.7%) died in hospital. Potassium decreased during the first 2 to 3 days ( P for trend <.001), followed by stabilization ( P for trend = .807). Potassium in the extreme categories (<3.8 and ≥4.7) and absolute fluctuations >0.1 mEq/L were more common among nonsurvivors than survivors ( P < .001 each). In a multivariate analysis, combinations of minimal K <3.8 with maximal K ≥4.7 (odds ratio [OR] = 18.1), K ≥4.4 with fluctuation ≥0.1 (OR = 1.74), or <−0.1 (OR = 2.6) and minimal K after the first 2 admission days (OR = 2.07) were associated with increased risk of mortality ( P < .001 each). Potassium fluctuations, peak and nadir K, and its timing independently predict inhospital mortality in patients with AMI.

Oxygen therapy for acute myocardial infarction

BACKGROUND

Oxygen (O₂) is widely used in people with acute myocardial infarction (AMI). Previous systematic reviews concluded that there was insufficient evidence to know whether oxygen reduced, increased or had no effect on heart ischaemia or infarct size. Our first Cochrane review in 2010 also concluded there was insufficient evidence to know whether oxygen should be used. Since 2010, the lack of evidence to support this widely used intervention has attracted considerable attention, prompting further trials of oxygen therapy in myocardial infarction patients. It is thus important to update this Cochrane review.

OBJECTIVES

To assess the effects of routine use of inhaled oxygen for acute myocardial infarction (AMI).

SEARCH METHODS

We searched the following bibliographic databases on 6 June 2015: the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, MEDLINE (OVID), Embase (OVID), CINAHL (EBSCO) and Web of Science (Thomson Reuters). LILACS (Latin American and Caribbean Health Sciences Literature) was last searched in September 2016. We also contacted experts to identify eligible studies. We applied no language restrictions.

SELECTION CRITERIA

Randomised controlled trials in people with suspected or proven AMI (ST-segment elevation myocardial infarction (STEMI) or non-STEMI) within 24 hours after onset, in which the intervention was inhaled oxygen (at normal pressure) compared to air, regardless of co-therapies provided to participants in both arms of the trial.

DATA COLLECTION AND ANALYSIS

Two authors independently reviewed the titles and abstracts of identified studies to see if they met the inclusion criteria and independently undertook the data extraction. We assessed the quality of studies and the risk of bias according to guidance in the Cochrane Handbook for Systematic Reviews of Interventions. The primary outcome was death. The measure of effect used was the risk ratio (RR) with a 95% confidence interval (CI). We used the GRADE approach to evaluate the quality of the evidence and the GRADE profiler (GRADEpro) to import data from Review Manager 5 and create 'Summary of findings' tables.

MAIN RESULTS

The updated search yielded one new trial, for a total of five included studies involving 1173 participants, 32 of whom died. The pooled risk ratio (RR) of all-cause mortality in the intention-to-treat analysis was 0.99 (95% CI 0.50 to 1.95; 4 studies, N = 1123; I² = 46%; quality of evidence: very low) and 1.02 (95% CI 0.52 to 1.98; 4 studies, N = 871; I² = 49%; quality of evidence: very low) when only analysing participants with confirmed AMI. One trial measured pain directly, and two others measured it by opiate usage. The trial showed no effect, with a pooled RR of 0.97 for the use of opiates (95% CI 0.78 to 1.20; 2 studies, N = 250). The result on mortality and pain are inconclusive. There is no clear effect for oxygen on infarct size (the evidence is inconsistent and low quality).

AUTHORS' CONCLUSIONS

There is no evidence from randomised controlled trials to support the routine use of inhaled oxygen in people with AMI, and we cannot rule out a harmful effect. Given the uncertainty surrounding the effect of oxygen therapy on all-cause mortality and on other outcomes critical for clinical decision, well-conducted, high quality randomised controlled trials are urgently required to inform guidelines in order to give definitive recommendations about the routine use of oxygen in AMI.

Serum potassium levels, cardiac arrhythmias, and mortality following non-ST-elevation myocardial infarction or unstable angina: insights from MERLIN-TIMI 36

BACKGROUND

In acute coronary syndrome (ACS), potassium levels <3.5 mEq/L are associated with ventricular arrhythmias. Current guidelines therefore recommend a potassium target >4.0 mEq/L in ACS. Our study evaluated the association between potassium levels, cardiac arrhythmias, and cardiovascular death in patients with non-ST-segment elevation myocardial infarction or unstable angina.

METHODS

Potassium levels were measured in 6515 patients prior to randomization to receive either ranolazine or a placebo in the MERLIN-TIMI 36 trial. A seven-day continuous electrocardiographic assessment was obtained to determine the incidence of non-sustained ventricular tachycardia (NSVT) and ventricular pauses. The association between potassium levels and cardiovascular death was evaluated using a Cox proportional hazards regression model with multivariable adjustment.

RESULTS

NSVT lasting for at least eight consecutive beats occurred more frequently at potassium levels <3.5 mEq/L than at potassium levels ⩾5 mEq/L (10.1 vs. 4.5%, p=0.03 for trend), whereas the inverse pattern was observed for ventricular pauses >3 s, which occurred more frequently at potassium levels ⩾5 mEq/L than at potassium levels <3.5 mEq/L (5.9 vs. 2.0%, p=0.03 for trend). There was a U-shaped relationship between the potassium level at admission and both early and late risk of cardiovascular death. Compared with patients with potassium levels of 3.5 to <4 mEq/L, a potassium level <3.5 mEq/L was associated with an increased risk of cardiovascular death at day 14 (2.4 vs. 0.8%, HR_adj 3.1, p=0.02) and at one year (6.4 vs. 3.0%, HR_adj 2.2, p=0.01). The risk of cardiovascular death at one year was also significantly increased at potassium levels ⩾4.5 mEq/L and a similar trend was noted at potassium levels ⩾5 mEq/L.

CONCLUSIONS

The lowest risk of cardiovascular death was observed in patients with admission potassium levels between 3.5 and 4.5 mEq/L. Both lower and higher levels of potassium were associated with tachyarrhythmias and bradyarrhythmias, suggesting a potential mechanistic explanation for the increased risk of cardiovascular death at the extremes of potassium homeostasis.

Hospital variation in admission to intensive care units for patients with acute myocardial infarction

BACKGROUND

The treatment for patients with acute myocardial infarction (AMI) was transformed by the introduction of intensive care units (ICUs), yet we know little about how contemporary hospitals use this resource-intensive setting and whether higher use is associated with better outcomes.

METHODS

We identified 114,136 adult hospitalizations for AMI from 307 hospitals in the 2009 to 2010 Premier database using codes from the International Classification of Diseases, Ninth Revision, Clinical Modification. Hospitals were stratified into quartiles by rates of ICU admission for AMI patients. Across quartiles, we examined in-hospital risk-standardized mortality rates and usage rates of critical care therapies for these patients.

RESULTS

Rates of ICU admission for AMI patients varied markedly among hospitals (median 48%, Q1-Q4 20%-71%, range 0%-98%), and there was no association with in-hospital risk-standardized mortality rates (6% all quartiles, P = .7). However, hospitals admitting more AMI patients to the ICU were more likely to use critical care therapies overall (mechanical ventilation [from Q1 with lowest rate of ICU use to Q4 with highest rate 13%-16%], vasopressors/inotropes [17%-21%], intra-aortic balloon pumps [4%-7%], and pulmonary artery catheters [4%-5%]; P for trend < .05 in all comparisons).

CONCLUSIONS

Rates of ICU admission for patients with AMI vary substantially across hospitals and were not associated with differences in mortality, but were associated with greater use of critical care therapies. These findings suggest uncertainty about the appropriate use of this resource-intensive setting and a need to optimize ICU triage for patients who will truly benefit.

Impact of early interventions by a cardiac rehabilitation team on the social rehabilitation of patients resuscitated from cardiogenic out-of-hospital cardiopulmonary arrest

OBJECTIVE

We examined the effects of intervention performed by a multidisciplinary cardiac rehabilitation (CR) team on the social rehabilitation of patients with cardiogenic out-of-hospital cardiopulmonary arrest (OHCA) in the acute phase.

METHODS

This study included 122 patients who were resuscitated after cardiogenic OHCA during a 10-year period. They were divided into two groups: including a non-CR group of patients (n=58) who were admitted before the CR team started performing systematic intervention and a CR group (n=64) who were admitted after the intervention was initiated. The following items were examined for each group: treatment condition at onset, contents of treatment, primary disease, presence or absence of underlying disease, presence or absence of complications, general physical and neurological outcome, duration of hospital stay, and status of social rehabilitation.

RESULTS

Although the number of patients with cardiogenic OHCA did not markedly change, the number of bystanders participating in cardiopulmonary resuscitation (CPR) was significantly higher in the CR group versus the non-CR group (p<0.01). The effect of bystanders participating in CPR also significantly reduced the mortality outcome (p<0.05 versus the group without CPR), and patients in the CR group were more likely to achieve social rehabilitation (p<0.05 versus the group without CPR). Moreover, the number of patients who returned to society one year later was increased in the CR group versus the non-CR group (p<0.05). The incidence of respiratory complications was also significantly lower in the CR group versus the non-CR group (p<0.05).

CONCLUSION

Along with the usefulness of rapid pre-hospital aid, our results suggest that systemic intervention performed by the CR team administered while the patient was in the acute phase may have promoted social rehabilitation of patients resuscitated after cardiogenic OHCA.

Relation of serum potassium level to long-term outcomes in patients with acute myocardial infarction

Potassium plays a key role in normal myocardial function, and current guidelines recommend that serum potassium levels be maintained from 4.0 to 5.0 mEq/L in patients with acute myocardial infarction (AMI). However, the impact of serum potassium levels on long-term mortality has not been evaluated. We retrospectively studied 1,924 patients diagnosed with AMI. The average serum potassium levels measured throughout the hospitalization were obtained and statistically analyzed. Patients were categorized into 5 groups to determine the relation between mean serum potassium and long-term mortality: <3.5, 3.5 to <4.0, 4.0 to <4.5, 4.5 to <5.0, and ≥5 mEq/L. The long-term mortality was lowest in the group of patients with potassium levels of 3.5 to <4.0 mEq/L, whereas mortality was higher in the patients with potassium levels≥4.5 or <3.5 mEq/L. In a multivariate Cox-proportional regression analysis, the mortality risk was greater for serum potassium levels of >4.5 mEq/L (hazard ratio [HR] 1.71, 95% confidence interval [CI] 1.04 to 2.81 and HR 4.78, 95% CI 2.14 to 10.69, for patients with potassium levels of 4.5 to <5.0 mEq/L and ≥5.0, respectively) compared with patients with potassium levels of 3.5 to <4.0 mEq/L. The mortality risk was also higher for patients with potassium levels<3.5 mEq/L (HR 1.55, 95% CI 0.94 to 2.56). In contrast to the association with long-term mortality, there was no relation between serum potassium levels and the occurrence of ventricular arrhythmias. The results of the current analysis suggest that there is a need for change in our current concepts of the ideal serum potassium levels in patients with AMI.

Oxygen therapy for acute myocardial infarction

BACKGROUND

Oxygen (O₂) is widely used in people with acute myocardial infarction (AMI) although it has been suggested it may do more harm than good. Previous systematic reviews have concluded that there was insufficient evidence to know whether oxygen reduced, increased or had no effect on heart ischaemia or infarct size, as did our original Cochrane review on this topic in 2010. The wide dissemination of the lack of evidence to support this widely-used intervention since 2010 may stimulate the needed trials of oxygen therapy, and it is therefore important that this review is updated regularly.

OBJECTIVES

To review the evidence from randomised controlled trials to establish whether routine use of inhaled oxygen in acute myocardial infarction (AMI) improves patient-centred outcomes, in particular pain and death.

SEARCH METHODS

The following bibliographic databases were searched last in July 2012: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library), MEDLINE (OVID), EMBASE (OVID), CINAHL (EBSCO) and Web of Science (ISI). LILACS (Latin American and Caribbean Health Sciences Literature) and PASCAL were last searched in May 2013. We also contacted experts to identify any studies. We applied no language restrictions.

SELECTION CRITERIA

Randomised controlled trials of people with suspected or proven AMI (ST-segment elevation myocardial infarction (STEMI) or non-STEMI), less than 24 hours after onset, in which the intervention was inhaled oxygen (at normal pressure) compared to air and regardless of cotherapies provided these were the same in both arms of the trial.

DATA COLLECTION AND ANALYSIS

Two authors independently reviewed the titles and abstracts of identified studies to see if they met the inclusion criteria, and independently undertook the data extraction. The quality of studies and the risk of bias were assessed according to guidance in the Cochrane Handbook. The primary outcomes were death, pain and complications. The measure of effect used was the risk ratio (RR) with a 95% confidence interval (CI).

MAIN RESULTS

The updated search identified one new trial. In total, four trials involving 430 participants were included and 17 deaths occurred. The pooled RR of death was 2.05 (95% CI 0.75 to 5.58) in an intention-to-treat analysis and 2.11 (95% CI 0.78 to 5.68) in participants with confirmed AMI. While suggestive of harm, the small number of deaths recorded means that this could be a chance occurrence. Pain was measured by analgesic use. The pooled RR for the use of analgesics was 0.97 (95% CI 0.78 to 1.20).

AUTHORS' CONCLUSIONS

There is no conclusive evidence from randomised controlled trials to support the routine use of inhaled oxygen in people with AMI. A definitive randomised controlled trial is urgently required, given the mismatch between trial evidence suggestive of possible harm from routine oxygen use and recommendations for its use in clinical practice guidelines.

Incidence, prognosis, and factors associated with cardiac arrest in patients hospitalized with acute coronary syndromes (the Global Registry of Acute Coronary Events Registry)

OBJECTIVES

Contemporary data are lacking with respect to the incidence rates of, factors associated with, and impact of cardiac arrest from ventricular fibrillation or tachycardia (VF-CA) on hospital survival in patients admitted with an acute coronary syndrome (ACS). The objectives of this multinational study were to characterize trends in the magnitude of in-hospital VF-CA complicating an ACS and to describe its impact over time on hospital prognosis.

METHODS

In 59 161 patients enrolled in the Global Registry of Acute Coronary Events Study between 2000 and 2007, we determined the incidence, prognosis, and factors associated with VF-CA.

RESULTS

Overall, 3618 patients (6.2%) developed VF-CA during their hospitalization for an ACS. Incidence rates of VF-CA declined over time. Patients who experienced VF-CA were on average older and had a greater burden of cardiovascular disease, yet were less likely to receive evidence-based cardiac therapies than patients in whom VF-CA did not occur. Hospital death rates were 55.3% and 1.5% in patients with and without VF-CA, respectively. There was a greater than 50% decline in the hospital death rates associated with VF-CA during the years under study. Patients with a VF-CA occurring after 48 h were at especially high risk for dying during hospitalization (82.8%).

CONCLUSION

Despite reductions in the magnitude of, and short-term mortality from, VF-CA, VF-CA continues to exert an adverse effect on survival among patients hospitalized with an ACS. Opportunities exist to improve the identification and treatment of ACS patients at risk for VF-CA to reduce the incidence of, and mortality from, this serious arrhythmic disturbance.

Nifekalant in the treatment of life-threatening ventricular tachyarrhythmias

The aim of the present study is to review the literature and discuss nifekalant's potential use as a first aid drug in an emergency care setting. The PubMed database was used to identify papers, using keywords nifekalant, MS-551, amiodarone and lidocaine. Nifekalant hydrochloride, formally known as MS-551, is a class III antiarrhythmic agent which acts only by increasing the time course of myocardial repolarization. It was developed and is currently being used only in Japan for the treatment of ventricular tachyarrhythmias. It is a non-selective K(+) channel blocker without any β-blocking actions. Administration of nifekalant suppressed sustained ventricular tachyarrhythmias in acute coronary syndrome patients, and in cardiac arrest victims as well as during or after cardiac surgery. The major adverse effect of nifekalant is QT interval prolongation and occurrence of torsades de pointes which requires frequent monitoring of the QT interval during nifekalant infusion with adequate dose adjustment. Nifekalant is a possible effective antiarrhythmic agent for refractory ventricular tachyarrhythmias. Further clinical studies are required before nifekalant is routinely used in the emergency care setting.

Oxygen therapy for acute myocardial infarction

BACKGROUND

Oxygen (O(2)) is widely recommended for patients with myocardial infarction yet a narrative review has suggested it may do more harm than good. Systematic reviews have concluded that there was insufficient evidence to know whether oxygen reduced, increased or had no effect on the heart ischaemia or infarct size.

OBJECTIVES

To review the evidence from randomised controlled trials to establish whether routine use of inhaled oxygen in acute myocardial infarction (AMI) improves patient-centred outcomes, in particular pain and death.

SEARCH STRATEGY

The following bibliographic databases were searched (to the end of February 2010): Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library), MEDLINE, MEDLINE In-Process, EMBASE, CINAHL, LILACS and PASCAL, British Library ZETOC, Web of Science ISI Proceedings. Experts were also contacted to identify any studies. No language restrictions were applied.

SELECTION CRITERIA

Randomised controlled trials of people with suspected or proven AMI, less than 24 hours after onset, in which the intervention was inhaled oxygen (at normal pressure) compared to air and regardless of co-therapies provided these were the same in both arms of the trial.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed the titles and abstracts of identified studies to see if they met the inclusion criteria and independently undertook the data extraction. The quality of studies and the risk of bias were assessed according to guidance in the Cochrane Handbook. The primary outcomes were death, pain and complications. The measure of effect used was the relative risk (RR).

MAIN RESULTS

Three trials involving 387 patients were included and 14 deaths occurred. The pooled RR of death was 2.88 (95% CI 0.88 to 9.39) in an intention-to-treat analysis and 3.03 (95% CI 0.93 to 9.83) in patients with confirmed AMI. While suggestive of harm, the small number of deaths recorded meant that this could be a chance occurrence. Pain was measured by analgesic use. The pooled RR for the use of analgesics was 0.97 (95% CI 0.78 to 1.20).

AUTHORS' CONCLUSIONS

There is no conclusive evidence from randomised controlled trials to support the routine use of inhaled oxygen in patients with acute AMI. A definitive randomised controlled trial is urgently required given the mismatch between trial evidence suggestive of possible harm from routine oxygen use and recommendations for its use in clinical practice guidelines.

Acute myocardial infarction hospitalization in the United States, 1979 to 2005

BACKGROUND

We reported earlier that there was no decline of acute myocardial infarction hospitalization from 1988 to 1997. We now extend these observations to document trends in acute myocardial infarction hospitalization rates and in-hospital case-fatality rates for 27 years from 1979 to 2005.

METHODS

We determined hospitalization rates for acute myocardial infarction by age and gender using data from the National Hospital Discharge Survey and US civilian population from 1979 to 2005, aggregated by 3-year groupings. We also assessed comorbid, complications, cardiac procedure use, and in-hospital case-fatality rates.

RESULTS

Age-adjusted hospitalization rate for acute myocardial infarction identified by primary International Classification of Diseases code was 215 per 100,000 people in 1979-1981 and increased to 342 in 1985-1987. Thereafter, the rate stabilized for the next decade and then declined slowly after 1996 to 242 in 2003-2005. Trends were similar for men and women, although rates for men were almost twice that of women. Hospitalization rates increased substantially with age and were the highest among those aged 85 years or more. Although median hospital stay decreased from 12 to 4 days, intensity of hospital care increased, including use of coronary angioplasty, coronary bypass, and thrombolytics therapy. During the period, reported comorbidity from diabetes and hypertension increased. Acute myocardial infarction complicated by heart failure increased, and cardiogenic shock decreased. Altogether, the in-hospital case-fatality rate declined.

CONCLUSION

During the past quarter century, hospitalization for acute myocardial infarction increased until the mid-1990s, but has declined since then. At the same time, in-hospital case-fatality rates declined steadily. This decline has been associated with more aggressive therapeutic intervention.

Effects of intravenous nifekalant as a lifesaving drug for severe ventricular tachyarrhythmias complicating acute coronary syndrome

BACKGROUND

Intravenous amiodarone (AMD) has been used for the treatment of ventricular tachycardia/fibrillation (VT/VF) in emergency care medicine. However, AMD acts slowly and is occasionally accompanied by hypotension and bradycardia. The antiarrhythmic effect of intravenous nifekalant (NIF) was assessed in patients with VT/VF complicating acute coronary syndrome (ACS) according to our study protocol.

METHODS AND RESULTS

Among a series of 1,143 ACS patients, 41 patients who suffered sustained VT/VF were enrolled; 19 failed to respond to a preceding lidocaine (LID) injection. NIF was given first as an intravenous bolus injection (0.2 mg/kg) and then as a continuous intravenous infusion at a relatively low dose level (0.2 mg x kg(-1) x h(-1)). Sustained VT/VF was successfully inhibited by NIF in 34 patients (83%). In subgroup analysis, NIF achieved VT/VF inhibition in 79% of patients who received preceding LID and in 86% of patients who received direct NIF. There were no significant changes in systolic blood pressure or heart rate following NIF therapy. A corrected QT interval was significantly prolonged (P<0.01), whereas torsade de pointes developed in only 1 patient (2%).

CONCLUSIONS

An intravenous bolus injection and subsequent continuous infusion of NIF at a relatively low dosage were effective in treating severe ventricular tachyarrhythmias complicating ACS, reducing the potential risk of proarrhythmia.