Effects of intravenous magnesium in suspected acute myocardial infarction: overview of randomised trials.

OBJECTIVE--To investigate the effect of intravenous magnesium on mortality in suspected acute myocardial infarction. DESIGN--Systematic overview of all available randomised trials in which patients were allocated to receive either intravenous magnesium or otherwise similar treatment without magnesium. SETTING--Coronary care units of several hospitals. PATIENTS--1301 patients in seven randomised trials. MAIN OUTCOME MEASURE--Short term mortality. RESULTS--Considering the seven trials collectively there were 25 (3.8%) deaths among 657 patients allocated to receive magnesium and 53 (8.2%) deaths among 644 patients allocated control, generally during hospital follow up. This represents a 55% reduction in the odds of death (p less than 0.001) with 95% confidence intervals ranging from about one third to about two thirds. 70 of 648 patients allocated magnesium compared with 109 of 641 controls had serious ventricular arrhythmias, suggesting that magnesium reduces the incidence, though the definition varied among trials. Other adverse effects were rare in the limited number of patients for whom this data were available. CONCLUSION--Despite the limited number of patients randomised this overview suggests that intravenous magnesium therapy may reduce mortality in patients with acute myocardial infarction. Further large scale trials to confirm (or refute) these findings are desirable.     

Anaesthetic-related occurrence of early ventricular arrhythmias during acute myocardial ischaemia in rats

The cardiovascular responses of rats anaesthetised with different anaesthetic agents to acute coronary artery ligation were studied. Before thoracotomy, urethane-anaesthetised animals exhibited significantly lower blood pressures. Ligation of the left coronary artery induced a high incidence of ventricular tachycardia or fibrillation in rats anaesthetised with pentobarbitone, urethane, or ether inhalation followed by chloralose. Ketamine-anaesthetised animals had a significantly lower incidence of ventricular arrhythmias. The mortality rate was also lower, though not statistically significant. However, all groups of rats showed essentially similar blood pressure and heart rate changes following coronary artery ligation as well as the time of onset of ventricular tachycardia or fibrillation. The findings demonstrate the influence of anaesthetics on the occurrence of early ventricular arrhythmias following acute coronary artery ligation in rats.     

Randomised trial comparing propranolol with atenolol in immediate treatment of suspected myocardial infarction.

The value of beta-blockade for suspected acute myocardial infarction was assessed by determining the six-week and one-year mortality rates in patients started on propranolol, atenolol, or placebo immediately on entry to a coronary care unit. A total of 388 patients entered this double-blind, randomised study, and when analysed on the basis of the initial, intention-to-treat categories there was no significant difference between the three groups in respect of the mortality rate at one year. There was, however, a high withdrawal rate from the trial; the reasons for this illustrate problems of physician compliance and interpretation of data, which are common to all early-entry trials of haemodynamically active agents in acute myocardial infarction.     

Haemodynamic effects of intravenous morphine in patients with acute myocardial infarction complicated by severe left ventricular failure.

The haemodynamic effects of intravenous morphine sulphate (0.2 mg/kg body weight) were measured in 10 patients with acute myocardial infarction complicated by severe left ventricular failure. Fifteen minutes after morphine injection there was a significant fall in mean heart rate (from 109 to 101 beats/min) and mean systemic arterial pressure (from 80 to 65 mm HG), and a small fall in mean cardiac index (from 2.4 to 2.21/min/m2). Haemodynamic changes at 45 minutes were similar. Neither stroke index nor indirect left ventricular filling pressure (measured as pulmonary artery end-diastolic pressure) were consistently improved 15 or 45 minutes after injection. The useful action of morphine in relieving distressing cardiac dyspnoea is not adequately explained by systemic venous blood pooling. These results suggest that the effects of morphine on the central nervous system are more important.     

The effect of bretylium tosylate on ventricular arrhythmias in patients with acute myocardial infarction]

Sixty three patients with the acute myocardial infarction, aged between 34 and 85 years, admitted to the Intensive Cardiological Care Unit during the first 12 hours following the infarction were randomly divided into two groups. Patients of group I (20 subjects) were treated with nitroglycerin and additional intravenous infusions of bretylium tosylate in the dose of 5 mg/kg administered every 6 hours for 48-72 hours. Patients of group II (33 subjects) were mainly treated with intravenous nitroglycerin. A type and incidence of the ventricular arrhythmias, conduction disorders in AV node, and hemodynamic complications were analysed during the first 72 hours. It was found that bretylium tosylate reduces the incidence of ventricular arrhythmias accompanying myocardial infarction but after 2-3 hours following its administration (p < 0.05). Therefore, bretylium tosylate should be administrated to patients with the acute myocardial infarction in combination with other rapidly acting anti-arrhythmic drug. Bretylium tosylate increases also the effectiveness of electric defibrillation in patients with ventricular fibrillation or ventricular tachyarrhythmia. No evidence of the effectiveness of bretylium tosylate on atrio-ventricular conduction and hemodynamic complications of myocardial infarction was found.     

Ten year mortality in patients with suspected acute myocardial infarction.

OBJECTIVE--To describe the 10 year mortality in patients with suspected acute myocardial infarction. DESIGN--Follow up of all patients below 76 years of age admitted with acute chest pain to 16 coronary care units participating in the Danish verapamil infarction trial in 1979-81. SUBJECTS--Of the 5993 patients included, 2586 had definite infarction, 402 had probable infarction, and 3005 did not have infarction. MAIN OUTCOME MEASURES--Death and cause of death. Standardised mortality ratio (observed mortality/expected mortality in background population). RESULTS--The estimated 10 year mortalities were 58.8%, 55.5%, and 42.8% in patients with definite, probable, and no infarction, respectively (P < 0.0001). Stratified Cox''s analysis identified a hazard ratio for mortality of 1.25 (95% confidence interval 1.08 to 1.44) for probable infarction compared with no infarction and of 1.15 (1.00 to 1.32) for definite compared with probable infarction. The standardised mortality ratio in the first year was 7.1 (6.5 to 7.8) for definite infarction, 5.0 (3.6 to 6.3) for probable infarction, and 4.7 (4.2 to 5.2) for no infarction. From the second year and onwards the annual standardised mortality ratio in the three groups did not differ significantly. Cardiac causes of deaths were recorded in 89%, 84%, and 71% of the deaths in patients with definite, probable, and no infarction, respectively. CONCLUSIONS--The 10 year mortality of patients with and without infarction is significantly higher than in the background population. Most deaths are caused by coronary heart disease, and these patients should consequently be further evaluated at the time of discharge and followed up closely.     

Lack of relation between venous plasma total catecholamine concentrations and ventricular arrhythmias after acute myocardial infarction.

Electrocardiographic tracings were recorded continuously to monitor ventricular tachycardia and R-on-T and R-on-apex-T ventricular premature beats, and repeated estimations of venous plasma total catecholamine concentrations were carried out in 26 patients admitted to a coronary care unit with acute myocardial infarction. No relation existed between the increased catecholamine concentrations found in these patients and the incidence of ventricular arrhythmias occurring six to 48 hours after the onset of symptoms.     

急性心肌梗塞静脉溶栓后冠脉再通对左心室功能的影响

为进一步探讨静脉溶栓后冠脉再通对左室功能的有益影响,回顾性分析了88例静脉溶栓急性心肌梗塞(AMI)病人的二维超声心动图和部分病人的冠脉造影资料。根据溶栓再通标准分为再通组和未通组。在AMI发病后平均24.8±11.6天和22.9±24.4天分别进行了心超和冠造检查,观察室壁运动情况并测量左室射血分数(LVEF)。结果显示:未通组LVEF明显低于再通组,而室壁运动异常积分却显著高于再通组。左室扩大和室壁瘤的发生上,两组未发现有统计学差异。以上结果提示:AMI静脉溶栓使冠脉再通对左室功能和室壁运动障碍的改善起到有益的作用。     

Risk of death and recurrent ventricular arrhythmias in survivors of cardiac arrest concurrent with acute myocardial infarction

Aims

Cardiac arrest (CA) is an indication for defibrillator (ICD) implantation unless it occurs in the context of an acute myocardial infarction (AMI). We investigated the ventricular arrhythmia (VA)-free survival of patients resuscitated from CA in the setting of AMI.

Methods

We reviewed a database of 1600 AMI and CA survivors from which 48 patients were identified as having concurrent CA and AMI (CA+AMI group). Those patients were matched by age, gender, race, and left ventricular ejection fraction (LVEF) to 96 patients with AMI but no CA (AMI group) and 48 patients with CA but no AMI (CA group).

Results

Patients and controls were followed for 3.9±3.2 years. Patients in the 3 groups had similar baseline characteristics (age 63±14 yrs, 78% men, 98% white, 53% with CAD, LVEF 33±14%). The 5-year VA-free survival was 67%, 92%, and 80% for the CA+AMI, AMI, and CA groups, respectively, p<0.001.

Conclusion

Patients with concurrent CA and AMI are at high risk of recurrent VA, with VA-free survival rates significantly worse than those of patients with AMI but no CA, and comparable to those of patients with CA outside the context of an AMI. Accordingly, these patients should be considered for ICD implantation.     

Losartan and acute myocardial infarction in insulin-resistant Zucker fatty rats: reduced ventricular arrhythmias and improved survival

Insulin resistance (IR) and diabetes increase the risk of acute myocardial infarction (MI). Angiotensin receptor blockers (ARBs) have been shown to reduce the risk of cardiovascular events in patients with hypertension and diabetes, and to be beneficial after a large MI. Whether pretreatment with ARBs is beneficial in acute MI is unknown. We evaluated whether pre-, peri-, and post-MI treatment with the ARB losartan improved the outcome in the IR Zucker fatty rat (ZFR). ZFR (n=264) received either losartan (3 mg/kg daily) or vehicle for 7 d prior to MI. Early (24 h) protocol (n=31): ventricular arrhythmias were evaluated post-MI using continuous ambulatory ECG monitoring. Late (38 d) protocol (n=233): losartan was increased to 10 mg/kg daily 10 d post-MI and to 30 mg/kg daily 20 d post-MI. Blood glucose, cardiac hemodynamics and remodeling, GLUT-4, fetal gene expression, and survival were evaluated. In large-MI rats, losartan improved early survival (43% vs. 27% in controls, p=0.01) and late survival (23% vs.15% in controls, p=0.02). Improved early survival was associated with a reduction in ventricular arrhythmias. Losartan reduced pulmonary congestion, cardiac hypertrophy, and fetal gene expression in the absence of statistically significant changes in ventricular dilatation and hemodynamics. Blood glucose and cardiac GLUT-4 expression did not change with losartan. In IR ZFR, losartan improves post-MI survival, likely as a result of an early reduction in ventricular arrhythmias. There was also an associated reduction in pulmonary congestion, hypertrophy, and fetal gene expression.     

Policy for early discharge after acute myocardial infarction.

Simple criteria were used to select a low-risk group of patients after acute myocardial infarction. The criteria depended on the presence or absence of diabetes, pulmonary oedema, serious rhythm disorders, and recurrent cardiac pain. Patients in the low-risk category with a suitable home environment were discharged from hospital after five to seven days (mean 6.2 days); they constituted 47% of the 267 hospital survivors over 18 months. Mortality in the selected patients was 2.4% at six weeks and 7% at one year. Most complications preventing early discharge were identified on the first day. Provisional selection for a short hospital stay was made after two days, and 76% of those judged suitable at 48 hours remained free of complications. Early selection of a low-risk category is justifiable and of practical value, though subsequent events will delay discharge for some patients. All patients who died in hospital or within two weeks after infarction had developed overt complications by the end of the fourth day. The results suggest that a policy of hospital discharge after four days would be justifiable for a low-risk group selected by the present criteria.     

Effect of intravenous infusion of insulin in diabetics with acute myocardial infarction.

Diabetes mellitus is associated with a high mortality after myocardial infarction. To see whether this may be decreased by improved diabetic control the effect of an insulin infusion regimen was studied in patients with acute myocardial infarction. From April 1982 to April 1983, 33 diabetics were admitted with acute myocardial infarction. Those being treated with diet alone or oral hypoglycaemic drugs continued with this unless control was poor, when they were changed to a "sliding scale" regimen of subcutaneous insulin injections thrice daily. Those already receiving insulin were maintained on thrice daily subcutaneous injections. From April 1983 to April 1984, 29 diabetics had acute myocardial infarction. Those receiving treatment with oral hypoglycaemic drugs or insulin were changed to continuous intravenous infusion of insulin, the aim being to maintain the blood glucose concentration at 4-7 mmol/I (72-126 mg/100 ml). Those being treated with diet alone continued with this if blood glucose concentrations were acceptable. Total mortality fell from 42% in the first year to 17% in the second (p less than 0.05). Over the same period mortality among non-diabetic patients with myocardial infarction did not change significantly. There was a significant fall in cardiac arrhythmias (expressed as the percentage of patients in whom arrhythmias were recorded) from 42% to 17% (p less than 0.05). The most significant fall in the incidence of complications occurred in those who had been receiving oral hypoglycaemic drugs on entry to the study (87% to 50%, p less than 0.05).     

Late ventricular potentials--a new risk factor for cardiac arrhythmias in recent myocardial infarction

The study involved 150 patients with recent myocardial infarction. Ventricular lat potentials were registered in these patients during the first 48 hours and repeated in the third week. Ventricular late potentials were found in 31 patients (21%) in the first 48 hours, and in 27 out of 134 patients (20%) before the release from the hospital. Comparing potentials registration in the acute and late phase of the myocardial infarction it was found that ventricular late potentials occurred in 6 and disappeared in 4 patients. Stable ventricular tachycardia was significantly more frequent (p less than 0.001) within the first 48 hours in patients with ventricular late potentials than those without them (19% vs 3%). Ventricular late tachycardia (over 48 hours) was more frequent (p less than less than 0.001) in patients with ventricular late potentials (21% vs 1%). Premature ventricular excitations of Lown class 2-5 were also more frequent (p less than 0.001) in the group of patients with ventricular late potentials than those without these potential (81% vs 24%) when registered with a 24-hour Holter ECG in the third week following myocardial infarction. Antiarrhythmic drugs did not produce the regression of ventricular late potentials. Non-invasive registration of ventricular late potentials helps to select patients with life-threatening ventricular arrhythmias following the acute myocardial infarction.