急性心肌梗死后心率变异性的特点及其临床意义

目的　探讨急性心肌梗死 ( AMI)早期心率变异性 ( HRV)特点及其临床意义。方法　 AMI病人 5 2例入院 48小时内进行 2 4小时动态心电图检查 ,应用计算机软件进行 HRV的时域分析 ,并观察 HRV与心脏事件的关系。结果　所有 AMI患者的 HRV时域值均较正常对照组 32例明显降低 ( P<0 .0 1) ,发生心脏事件组的 HRV时域值更进一步降低。结论　早期检测 AMI后的 HRV指标可预测心脏事件的发生。     

Prognostic value of heart rate variability after acute myocardial infarction in the era of immediate reperfusion

Introduction  The incidence and significance of impaired heart rate variability (HRV) after acute myocardial infarction (AMI) have not yet been evaluated in cohorts of patients in whom early reperfusion was systematically attempted. Therefore, HRV was evaluated in 412 unselected patients with AMI (311 men, mean age: 60±12 years, anterior AMI in 172 patients) treated with direct coronary angioplasty (PTCA) within 12 hours of symptom onset (mean 3.5±2.0 h). Standard deviation of normal RR intervals (SDNN), square root of the mean of the sum of the squares of differences between adjacent RR intervals (RMSSD) and left ventricular ejection fraction (LVEF, mean: 55±15%) were measured 11±9 days after AMI before discharge. Angiotensin-converting enzyme (ACE) inhibitors and beta-blockers were prescribed at discharge in 81.1% and 70.1% of patients, respectively. Results  Mean SDNN was 94±30 ms (range 14–155). SDNN was <50 ms in 7% of patients. Mean RMSSD was 34±32 ms (range 2–234). RMSSD was <15 ms in 21% of patients. Low SDNN (<50 ms) was unrelated to gender, age, infarct location or extension of CHD but was related to low LVEF (p<0.001, logistic regression analysis). During mean follow-up of 4.3±3 years, there were 31 deaths; 24 were cardiac. SDNN was higher in long-term survivors (102±39 ms) as compared to nonsurvivors (81±33 ms, p=0.02) but RMSSD was unrelated to the long-term vital status. Four-year survival of patients with a SDNN <50 ms vs >50 ms was 80% vs 92%, respectively (p<0.001, Kaplan Meier analysis). Low SDNN (odds ratio OR=2.0, p<0.05) but not RMSSD was an independent denominator for long-term mortality as were low LVEF (OR=1.0 decrease in LVEF, p<0.01, proportional hazards model) and age (OR=1.1, p<0.001). Only 3/31 fatalities and 1/24 cardiac deaths were predicted by a SDNN <50 ms and only 5/31 fatalities by a RMSSD <15 ms. Conclusion  The incidence of severely depressed HRV in patients after AMI is low (<10%) in the era of early reperfusion of the infarct vessel using direct PTCA. Mortality in patients with a very low HRV when assessed by SDNN is substantial but the positive predictive value of this parameter is low.      

Prediction of sudden cardiac death after myocardial infarction in the beta-blocking era

OBJECTIVES: This study assessed the predictive power of arrhythmia risk markers after an acute myocardial infarction (AMI). BACKGROUND: Several risk variables have been suggested to predict the occurrence of sudden cardiac death (SCD), but the utility of these variables has not been well established among patients using medical therapy according to contemporary guidelines. METHODS: A consecutive series of 700 patients with AMI was studied. The end points were total mortality, SCD, and nonsudden cardiac death (non-SCD). Nonsustained ventricular tachycardia (nsVT), ejection fraction (EF), heart rate variability, baroreflex sensitivity, signal-averaged electrocardiogram (SAECG), QT dispersion, and QRS duration were analyzed (n = 675). Beta-blocking therapy was used by 97% of the patients at discharge and by 95% at one and two years after AMI. RESULTS: During a mean (+/-SD) follow-up of 43 +/- 15 months, 37 non-SCDs (5.5%) and 22 SCDs (3.2%) occurred. All arrhythmia risk variables differed between the survivors and those with non-SCD (e.g., the standard deviation of N-N intervals was 98 +/- 32 vs. 74 +/- 21 ms [p < 0.001] and the QRS duration was 103 +/- 22 vs.89 +/- 16 ms [p < 0.001]). Sudden cardiac death was weakly predicted only by reduced EF (<0.40; p < 0.05), nsVT (p < 0.05), and abnormal SAECG (p < 0.05), but not by autonomic markers or standard ECG variables. The positive predictive accuracy of EF, nsVT, and abnormal SAECG as predictors of SCD was relatively low (8%, 12%, and 13%, respectively). CONCLUSIONS: The common arrhythmia risk variables, particularly the autonomic and standard ECG markers, have limited predictive power in identifying patients at risk of SCD after AMI in the beta-blocking era.     

Natriuretic peptides as predictors of non-sudden and sudden cardiac death after acute myocardial infarction in the beta-blocking era

OBJECTIVES: This prospective study tested whether the natriuretic peptides predict cardiac death among patients using beta-blocking therapy after an acute myocardial infarction (AMI). BACKGROUND: Natriuretic peptides have provided prognostic information after AMI, but their predictive value has not been well established in the era of beta-blocker use. METHODS: A series of 521 patients (mean age 61 +/- 10 years) with AMI was included in the study. The end points were total mortality and non-sudden and sudden cardiac death (SCD). Plasma concentrations of atrial natriuretic peptide (ANP), N-terminal atrial natriuretic propeptide (N-ANP), brain natriuretic peptide (BNP), and ejection fraction (EF) were analyzed before hospital discharge. The cardiac medication was optimized (e.g., adherence to beta-blocking therapy was 97% at discharge and 95% at one year after AMI). RESULTS: During a mean follow-up of 43 +/- 13 months, total mortality was 11.5% (60/521), cardiac mortality was 6.3% (33/521), and 3.1% (16/521) experienced SCD. On univariate analysis, high levels of all measured peptides and low EF predicted the occurrence of non-SCD (p < 0.001 for all). Peptides and EF also predicted the occurrence of SCD (p < 0.05), with elevated BNP (>23.0 pmol/l) being the most powerful predictor (hazard ratio [HR] 4.4, 95% confidence interval [CI] 1.4 to 13.8; p = 0.01). After adjusting for clinical variables, only elevated BNP (HR 3.9, 95% CI 1.2 to 12.3, p = 0.02) and low EF (<40%) (p = 0.03) remained as significant predictors of SCD. CONCLUSIONS: Natriuretic peptides retain their prognostic value in the beta-blocking era among survivors of AMI. Elevated BNP provides information on the risk of subsequent SCD, independent of clinical variables and left ventricular EF.     

Circadian rhythm of heart rate variability after acute myocardial infarction and its influence on the prognostic value of heart rate variability

This study examined heart rate (HR) variability in patients surviving acute myocardial infarction (AMI) to find the optimum time and duration of recording of the ambulatory electrocardiogram for the prediction of the risk of sudden cardiac death, or serious arrhythmic events, or both. Twenty patients (group I) who initially survived an AMI but later experienced serious events (death or symptomatic sustained ventricular tachycardia) during a 6-month follow-up were compared with 20 patients (group II) who remained free of complications for greater than 6 months after discharge. Groups I and II were matched with regard to age, gender, infarct site, ejection fraction, and beta-blocker treatment. HR variability was assessed in the 24-hour electrocardiograms recorded during the first 2 weeks after an AMI and in various portions of the complete 24-hour recording, with both the beginning and the length of the analyzed portion varied by 20 minutes (a total of 5,113 possibilities). The maximum reduction of HR variability in group I patients was systematically found when assessing HR variability in recordings starting approximately at 6 A.M. and lasting for approximately 8 hours. In the low-risk patient, the diurnal rhythm of HR variability is more marked than in the high-risk patient and the long-term components of HR variability due to the diurnal variation must be included in the measurement of HR variability when using it as a long-term predictor of risk from arrhythmic events after an AMI.     

Clinical and prognostic significance of silent myocardial ischemia in survivors after acute myocardial infarction

To clarify the clinical and prognostic significance of silent myocardial ischemia (SMI) after acute myocardial infarction (MI), the clinical characteristics and long-term prognosis after discharge in 525 medically treated survivors after acute MI were investigated. According to the presence of post-infarction angina and results of all exercise tests during hospitalization, 309 patients without ischemic episodes were classified into control group, 59 patients with SMI into SMI group and 157 patients with post-infarction angina into AP group. Previous MI (29%, 24%, 11%, respectively), non-Q wave MI (34%, 34%, 15%) and multivessel disease (69%, 61%, 33%) were more frequent in the SMI and AP groups than in the control group. These indicated clinical characteristics in patients with SMI were similar to those in patients with angina pectoris. The incidence of angina prior to MI onset in patients with SMI was lower than in patients with post-infarction angina. This may suggest that there is some common mechanism keeping them silent in the pre- and post-MI period. During the mean follow-up period of 5.5 years, 93 patients died and 78 had a recurrent MI. Cumulative total and cardiac mortality, and incidence of recurrent MI by actuarial method were higher in the SMI as well as AP group than in the control group. There was no statistically significant difference in prognosis between SMI and AP group. We conclude total ischemic burden, not only symptomatic but SMI, should be treated using currently available therapeutic modalities for further improvement of long-term prognosis in survivors after acute MI.     

Influence of heart rate on mortality after acute myocardial infarction

Elevated heart rate (HR) during hospitalization and after discharge has been predictive of death in patients with acute myocardial infarction (AMI), but whether this association is primarily due to associated cardiac failure is unknown. The major purpose of this study was to characterize in 1,807 patients with AMI admitted into a multicenter study the relation of HR to in-hospital, after discharge and total mortality from day 2 to 1 year in patients with and without heart failure. HR was examined on admission at maximum level in the coronary care unit, and at hospital discharge. Both in-hospital and postdischarge mortality increased with increasing admission HR, and total mortality (day 2 to 1 year) was 15% for patients with an admission HR between 50 and 60 beats/min, 41% for HR greater than 90 beats/min and 48% for HR greater than or equal to 110 beats/min. Mortality from hospital discharge to 1 year was similarly related to maximal HR in the coronary care unit and to HR at discharge. In patients with severe heart failure (grade 3 or 4 pulmonary congestion on chest x-ray, or shock), cumulative mortality was high regardless of the level of admission HR (range 61 to 68%). However, in patients with pulmonary venous congestion of grade 2, cumulative mortality for patients with admission HR greater than or equal to 90 beats/min was over twice as high as that in patients with admission HR less than 90 beats/min (39 vs 18%, respectively); the same trend was evident in patients with absent to mild heart failure (mortality 18 vs 10%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Early intervention with a beta-blocking drug after acute myocardial infarction

Several controlled studies with long-term administration of beta blockers in postinfarction patients have demonstrated a reduction in cardiac events and mortality. During acute myocardial infarction (AMI), conventional treatment is directed mainly at such complications as pump failure and arrhythmias. Another approach attempts to influence the natural evolution of impending myocardial necrosis by interrupting the process in its reversible phase. In a double-blind trial with metoprolol in suspected or definite AMI, 1,395 patients were studied, 698 of whom received metoprolol and 697 placebo. The 3-month mortality was 36% lower in the metoprolol group (p = 0.024). A reduction in severe ventricular arrhythmias (ventricular fibrillation and tachycardia) was also seen. Chest pain was reduced and there was less need of analgesic drugs in the metoprolol group. Intervention within 12 hours resulted in a limitation of infarct size, a decreased need for furosemide and a shortened hospital stay. A significant reduction in mortality was maintained after 2 years of follow-up despite the same treatment in both groups between 3 and 24 months. Early institution of metoprolol in AMI has resulted in reduced mortality and morbidity.     

Higher heart rate variability of smokers after acute myocardial infarction

Although cigarette smoking is known to be a strong risk factor for the development of coronary artery disease, several large clinical studies have demonstrated that current smokers had a favorable prognosis compared to nonsmokers after myocardial infarction. This study sought to evaluate the effect of smoking status on heart rate variability after onset of acute myocardial infarction. We studied 52 patients (34 smokers, 18 nonsmokers) with a first myocardial infarction within 24 h of onset. We recorded 24-h ambulatory ECG to calculate very low frequency power (VLF), low frequency power (LF) and high frequency power (HF) 14 days after onset. Although smokers had a tendency to be younger than nonsmokers (mean age 57 versus 62, P = 0.0812), clinical characteristics were not statistically different between smokers and nonsmokers. After adjustment for age, left ventricular ejection fraction, history of diabetes, acute revascularization and use of beta-blockers, VLF (P = 0.0183) of smokers 14 days after onset was significantly higher than for nonsmokers. In conclusion, although smoking reduces heart rate variability in the general population, higher heart rate variability was observed in smokers than nonsmokers after acute myocardial infarction under the condition of smoking cessation.     

心肌梗死前后心率变异性的变化及意义

目的　了解心肌梗死前后心率变异性（ＨＲＶ）的变化及心肌梗死前的ＨＲＶ对心肌梗死后心脏猝死的预测价值。方法　２７ 只兔随机分为对照组和心梗组,术前和术后２ 周分别测量ＨＲＶ一次,并行电刺激诱发室颤。结果　梗死组按电刺激能否诱发心室颤动（ＶＦ） 再分为ＶＦ 组和无ＶＦ组,心肌梗死前三组ＨＲＶ无差异,心肌梗死后ＶＦ组ＨＲＶ较心肌梗死前明显降低,无ＶＦ组和对照组无明显变化。结论　心肌梗死后ＨＲＶ 的降低与心脏猝死的发生有关,心肌梗死前ＨＲＶ对心肌梗死后的心脏猝死可能无预测价值。     

急性心肌梗塞患者应激性血糖变化的临床预后意义

目的　探讨急性心肌梗塞（ＡＭＩ）患者应激性血糖变化特点及其急性期的临床预后意义。方法　回顾性分析住院ＡＭＩ患者２２４ 例,分为单纯ＡＭＩ、合并高血压（ＨＴ）、合并Ⅱ型糖尿病（ＤＭ）以及ＤＭ 合并ＨＴ 组。观察其心功能（Ｋｉｌｌｉｐ）、恶性心律失常及病死率差别。结果　（１）无ＤＭ 的ＡＭＩ患者应激性血糖反应（入院２４ 小时血糖≥７．３ ｍ ｍ ｏｌ／Ｌ）出现率为８３ 例／１７１ 例（４８．５％ ）;（２）ＡＭＩ合并ＤＭ 加ＨＴ 患者的临床预后比单纯ＡＭＩ较差;（３）无ＤＭ 的ＡＭＩ患者中的显著血糖应激反应者的临床预后较轻度或无反应者差,而与ＡＭＩ合并ＤＭ 加ＨＴ 组相近。结论　非ＤＭ 的ＡＭＩ患者中发病后２４ 小时内血糖明显升高,提示急性期预后不良     

The significance of nitroglycerin-induced changes in ventricular function after acute myocardial infarction

The potential of nitroglycerin for improving global and regional ventricular function after acute myocardial infarction and predicting serial change in ventricular function at the time of hospital discharge was investigated. Equilibrium multiple gated blood pool scintigrams were performed at rest before and after sublingual administration of nitroglycerin in 18 patients an average of 36 hours after infarction and again at discharge. Global right and left ventricular function and regional left ventricular function of infarct and noninfarct zones were determined scintigraphically.In the early study nitroglycerin increased both mean (± standard deviation) left ventricular ejection fraction (0.51 ± 0.15 to 0.55 ± 0.15; p < 0.02) and mean right ventricular ejection fraction (0.42 ± 0.14 to 0.47 ± 0.13; p < 0.05). Left ventricular ejection fraction significantly increased in 5 of the 18 patients. It Increased late in five of the six patients who exhibited an increase early after nitroglycerin but in only 2 of the 12 patients who did not exhibit an early increase (p < 0.06). Regional ejection fraction in the infarct zone increased late in 7 of the 12 patients who exhibited an early increase after nitroglycerin and in none of the 6 who did not exhibit an early increase (p < 0.05). Both right and left ventricular global ejection fraction and regional ejection fraction showed little late responsiveness to nitroglycerin.Early after infarction, sublingual nitroglycerin improved left, right and regional ejection fraction at the infarct site in some patients. These nitroglycerin-induced changes predicted those patients whose global ventricular function and regional left ventricular function at the infarct site improved late.     

Risk stratification after acute myocardial infarction in the reperfusion era

Historically, risk stratification for survivors of acute myocardial infarction (AMI) has centered on 3 principles: assessment of left ventricular function, detection of residual myocardial ischemia, and estimation of the risk for sudden cardiac death. Although these factors still have important prognostic implications for these patients, our ability to predict adverse cardiac events has significantly improved over the last several years. Recent studies have identified powerful predictors of adverse cardiac events available from the patient history, physical examination, initial electrocardiogram, and blood testing early in the evaluation of patients with AMI. Numerous studies performed in patients receiving early reperfusion therapy with either thrombolysis or primary angioplasty have emphasized the importance of a patent infarct related artery for long-term survival. The predictive value of a variety of noninvasive and invasive tests to predict myocardial electrical instability have been under active investigation in patients receiving early reperfusion therapy. The current understanding of the clinically important predictors of clinical outcomes in survivors of AMI is reviewed in this article.     

急性心肌梗塞患者同时检测窦性心率震荡与心率变异性的临床意义

目的:探讨急性心肌梗塞(AMI)患者同时检测窦性心率震荡(HRT)和心率变异性(HRV)的临床意义.方法:选择78例AMI患者,根据室性早搏Lown分级AMI患者被分为高危组(41例)和低危组(37例);另选择无心血管疾病者61例为正常对照组.所有入选者均行24h动态心电图检查,测定HRT参数震荡初始(TO)、震荡斜率...