Analysis of abnormal intra-QRS potentials. Improved predictive value for arrhythmic events with the signal-averaged electrocardiogram

BACKGROUND: Using the signal-averaged ECG (SAECG), this study developed a new electrical index for predicting arrhythmic events: abnormal intra-QRS potentials (AIQP). METHODS AND RESULTS: We studied 173 patients followed after myocardial infarction for a mean duration of 14 +/- 7 months. Sixteen arrhythmic events occurred, defined as sudden cardiac death, documented sustained ventricular tachycardia, or non-fatal cardiac arrest. Noninvasive indices of arrhythmia risk were measured, including AIQP, conventional SAECG, Holter, and left ventricular ejection fraction (LVEF). Abnormal intra-QRS potentials were defined as abnormal signals occurring anywhere within the QRS period. They were estimated with a lead-specific, parametric modeling method that removed the smooth, predictable part of the QRS. AIQPs are characterized by the remaining transient, unpredictable component of the QRS and manifest as low-amplitude notches and slurs. A combined XYZ-lead AIQP index exhibited higher specificity (95%) and predictive value (PV) (+PV, 47%; -PV, 94%) than the conventional SAECG in combination with Holter and LVEF (specificity, 89%; +PV, 25%; -PV, 93%). CONCLUSIONS: AIQP improved specificity and predictive value, compared with conventional tests, for prediction of arrhythmic events. AIQP emerged as the best noninvasive univariate predictor of arrhythmic events after myocardial infarction in this study. A review of several other reports shows that AIQP in the present study outperformed the conventional predictive indices reported in those other data sets.     

Distinction between arrhythmic and nonarrhythmic death after acute myocardial infarction based on heart rate variability, signal-averaged electrocardiogram, ventricular arrhythmias and left ventricular ejection fraction

OBJECTIVES: We investigated whether heart rate variability, the signal-averaged electrocardiogram (ECG), ventricular arrhythmias and left ventricular ejection fraction predict the mechanism of cardiac death after myocardial infarction. BACKGROUND: Postinfarction risk stratification studies have almost exclusively focused on predicting the risk of arrhythmic death. The factors that identify and distinguish persons at risk for arrhythmic and nonarrhythmic death are poorly known. METHODS: Heart rate variability, the signal-averaged ECG, ventricular arrhythmias and left ventricular ejection fraction were assessed in 575 survivors of acute myocardial infarction. The patients were followed up for 2 years; arrhythmic and nonarrhythmic cardiac deaths were used as clinical end points. During the follow-up period, 47 cardiac deaths occurred, 29 (62%) arrhythmic and 18 (38%) nonarrhythmic. RESULTS: All risk factors were associated with cardiac mortality in univariate analysis. With the exception of left ventricular ejection fraction, they were also predictors of arrhythmic death. Depressed heart rate variability (p < 0.001), ventricular ectopic beats (p < 0.001) and low ejection fraction (p < 0.001) were related to nonarrhythmic death. In multivariate analysis, depressed heart rate variability (p < 0.001) and runs of ventricular tachycardia (p < 0.05) predicted arrhythmic death. Nonarrhythmic death was associated with depressed heart rate variability (p < 0.001), ventricular ectopic beats (p < 0.001) and low ejection fraction (p < 0.01). By selecting patients with depressed heart rate variability, long filtered QRS duration or ventricular arrhythmias and excluding patients with the lowest ejection fraction, we identified a group in which 75% of deaths were arrhythmic. Similarly, by selecting patients with a low ejection fraction and excluding patients with the lowest heart rate variability, we identified a group in which 75% of deaths were nonarrhythmic. CONCLUSIONS: Arrhythmic death was associated predominantly with depressed heart rate variability and ventricular tachycardia runs, and nonarrhythmic death with low ejection fraction, ventricular ectopic beats and depressed heart rate variability. A combination of risk factors identified patient groups in which a majority of deaths were either arrhythmic or nonarrhythmic.     

The differing prognostic utility of exercise radionuclide ventriculography in coronary artery disease patients with and without prior myocardial infarction

Previous studies have documented the prognostic utility of left ventricular ejection fraction response to exercise primarily in populations without prior myocardial infarction. We undertook a study to assess the prognostic utility of exercise left ventricular ejection fraction and segmental wall motion response during exercise radionuclide ventriculography in coronary artery disease patients with and without prior myocardial infarction. METHODS: We examined the comparative prognostic utility of left ventricular ejection fraction and segmental wall motion response during upright bicycle exercise radionuclide ventriculography in 419 coronary artery disease patients with (n = 217) and without (n = 202) prior myocardial infarction using univariate and multivariate hierarchical regression analyses. RESULTS: During an average followup period of 61 months, 96 patients (23%) suffered cardiac events, including 55/217 (25%) of the patients with prior myocardial infarction and 41/200 (21%) of the patients without prior myocardial infarction (p = ns). Both cumulative Kaplan-Meier survival analyses and stepwise hierarchical Cox survival analyses demonstrated that peak left ventricular ejection fraction < 55% was a significant predictor of cardiac events in patients without prior myocardial infarction (p = 0.04), whereas an exercise wall motion worsening score > or = 2 was a significant predictor in patients with a prior myocardial infarction (p = 0.0001). CONCLUSIONS: The prognostic utility of exercise radionuclide ventriculography variables differ according to the presence or absence of prior myocardial infarction. Global function, assessed by peak left ventricular ejection fraction, adds the greatest prognostic information in patients without prior myocardial infarction, whereas regional function, assessed by exercise wall motion worsening, is the best predictor among patients with prior myocardial infarction.     

Influence of infarct-related artery patency on the indexes of parasympathetic activity and prevalence of late potentials in survivors of acute myocardial infarction

OBJECTIVES: The purpose of this study was to determine whether infarct-related coronary artery patency influences myocardial electrical stability as measured by the prevalence of late potentials or heart rate variability. BACKGROUND: Several studies have suggested that loss of vagal activity is associated with an increased incidence of arrhythmic death after myocardial infarction. METHODS: A short-duration, high resolution electrocardiogram (ECG) was performed before hospital discharge in 175 patients with a first myocardial infarction. Seventy-three patients received thrombolytic therapy. All patients underwent coronary angiography. Coronary occlusion was defined as minimal or no anterograde flow. Eighty-eight patients (50.3%) had an occluded infarct-related artery. Sixty-two healthy subjects served as control subjects to determine the normal range of heart rate variability. RESULTS: Comparison between the control group and patients without patency of the infarct-related artery in the time domain and spectral analyses revealed in the latter patients a reduced heart rate variability (p < 0.0001) and a lower power spectrum density in both the 0.05- to 0.15-Hz band (p < 0.0001) and the 0.15- to 0.35-Hz band (p < 0.0001). The heart rate variability in patients with late potentials was lower than in those with a normal signal-averaged ECG. Those patients with spontaneous or thrombolysis-induced reperfusion have less occurrence of late potentials and higher parasympathetic activity than do patients with a closed artery. CONCLUSIONS: This study suggests that the patency of the infarct-related artery determines both the absence of late potentials and the preservation of vagal tone and may explain the reduction in mortality induced by thrombolytic therapy in myocardial infarction.     

Clinical applications of signal-averaged electrocardiography in patients after myocardial infarction

In conclusion, signal-averaged electrocardiography is a useful, noninvasive technique to identify patients after myocardial infarction at risk for future arrhythmic events, especially in conjunction to existing tools, such as 24 hour ambulatory monitoring, echocardiography, nucleotide angiography and coronary angiography. It has a limited positive predictive value, but has an excellent negative predictive value. The optimum time to do signal-averaged electrocardiograms after myocardial infarction is unclear, 6 to 14 days after myocardial infarction has the highest sensitivity. Time domain analysis remains the most common method used to record late potentials. The definition of late potential and the scoring of a high resolution electrocardiogram as normal and abnormal have not yet been resolved. The criteria proposed by the Task Force Committee of the European Society of Cardiology, the American Heart Association and the American College of Cardiology (see introduction) should be observed at present. Many studies on signal-averaging were done in the prethrombolytic era. In patients who have received thrombolytic therapy, the positive predictive value of signal-averaged electrocardiograms has decreased. There are other limitations in applying signal averaging technique. The faster the ventricular tachycardia is induced in electrophysiological studies, the shorter is the late potential. Thus, a faster tachycardia which causes sudden cardiac death may not be detected by late potentials. The management strategies for patients who have abnormal signal-averaged electrocardiograms after myocardial infarction have not be defined. One should note that any management strategy has to prove that it improves prognosis. More prospective, randomized clinical trials are required to address these issues.     

Erwin Payr, Hans von Haberer, Ernst Jeger--a set of 3 stars in the universe of vascular surgery]

BACKGROUND: Previous studies have demonstrated the prognostic value of radionuclide ventriculography at rest and exercise in patients post myocardial infarction (MI). The number of studies in patients treated with modern reperfusion techniques, including thrombolysis or primary angioplasty, however, is limited. HYPOTHESIS: The aim of this study was to evaluate the prognostic significance of predischarge radionuclide ventriculography at rest and exercise in patients with acute MI treated with thrombolysis or primary angioplasty. METHODS: A total of 272 consecutive patients with acute MI who were randomized to thrombolysis or primary coronary angioplasty underwent predischarge resting and exercise radionuclide ventriculography. Left ventricular ejection fraction at rest, decrease in ejection fraction during exercise > 5 units below the resting value, angina pectoris, ST-segment depression, and exercise test ineligibility were related to subsequent cardiac events (cardiac death, nonfatal reinfarction) during follow-up. RESULTS: During a mean follow-up of 30 +/- 10 months, cardiac death occurred in 11 (4%) patients and nonfatal reinfarction in 14 (5%) patients. Resting left ventricular ejection fraction was the major risk factor for cardiac death. In patients with an ejection fraction < 40%, cardiac death occurred in 16% compared with 2% in those with an ejection fraction > or = 40% (p = 0.0004). In addition, cardiac death tended to be higher in patients ineligible than in those eligible for exercise testing (11 vs. 3%, p = 0.08). None of the other exercise variables (decrease in ejection fraction during exercise > 5 units below the resting value, angina pectoris or ST-segment depression) were predictive for cardiac death. When all exercise test variables in each patient were combined and expressed as a risk score, a low risk (n = 185) and a higher risk (n = 87) group of patients could be identified, with cardiac death occurring in 1 and 10%, respectively. As the predictive accuracy of a negative test was high, radionuclide ventriculography was of particular value in identifying patients at low risk for cardiac death. Radionuclide ventriculography was not able to predict recurrent nonfatal MI. CONCLUSION: In patients with MI treated with thrombolysis or primary angioplasty, radionuclide ventriculography may be helpful in identifying patients at low risk for subsequent cardiac death. In this respect, left ventricular ejection fraction at rest was the major determinant. Variables reflecting residual myocardial ischemia were of limited prognostic value. Identification of a large number of patients at low risk allows selective use of medical resources during follow-up in this subgroup and has significant implications for the cost effectiveness of reperfusion therapies.     

Spectral turbulence versus time-domain analysis of signal-averaged ECG used for the prediction of different arrhythmic events in survivors of acute myocardial infarction

INTRODUCTION: Spectral turbulence analysis of the signal-averaged ECG (SAECG) combines spectral analysis with statistical evaluation of spectrograms of individual parts of the QRS complex. It has been suggested that it may be superior to conventional time-domain analysis of the SAECG. METHODS AND RESULTS: This study compared the power of conventional time-domain (40 to 250 Hz) and spectral turbulence analyses of SAECG for the prediction of cardiac death, ventricular tachycardia, sudden arrhythmic death, and arrhythmic events (ventricular tachycardia or fibrillation, and/or sudden arrhythmic death) after acute myocardial infarction in 603 patients. The population excluded patients with bundle branch block and other conduction abnormalities. During the first 2 years of follow-up, there were 40 cardiac deaths, 21 cases of ventricular tachycardia, 1 sudden arrhythmic deaths, and 29 arrhythmic events. The positive predictive accuracy of spectral turbulence analysis was significantly higher than time-domain analysis for cardiac death at most levels of sensitivity (e.g., 26% vs 20% at 40% sensitivity, P < 0.05). The positive predictive accuracies of the two techniques were not statistically different for the prediction of ventricular tachycardia. For the prediction of sudden arrhythmic death and arrhythmic events, the positive predictive accuracy of spectral turbulence was better than that of time-domain analysis only at the higher levels of sensitivity (9% vs 2%, P < 0.001 for sudden arrhythmic death at 60% sensitivity, and 14% vs 11%, P < 0.05 for arrhythmic events at 60% sensitivity). CONCLUSIONS: Spectral turbulence analysis is essentially equivalent to time-domain analysis for the prediction of arrhythmic events after myocardial infarction. However, it performed significantly better than time-domain analysis for the prediction of cardiac death.     

Prognostic value of ventricular arrhythmia in hypertensive patients

OBJECTIVE: Hypertensive left ventricular hypertrophy (LVH) is associated with increased risk of arrhythmias and mortality. However, no clinical study demonstrated a significant relation between ventricular arrhythmias and mortality in systemic hypertension. DESIGN AND METHODS: To evaluate the prognostic value of arrhythmogenic markers in systemic hypertension, we included between 1987 and 1993. 214 hypertensive patients, 59.1 +/- 12.8 years old, without symptomatic coronary disease, myocardial infarction, systolic dysfunction, electrolyte disturbances or antiarrhythmic therapy. At inclusion, an ECG, a 24 h Holter ECG (204 patients) with Lown classification of ventricular arrhythmias, an echocardiography (reliable in 187 patients) with left ventricular mass index and ejection fraction calculation, a SAECG (125 patients, enrolled after 1988) with ventricular late potentials (LP) were recorded. QT interval dispersion (QTd) was calculated on 12 leads standard ECG and LVH was appreciated. RESULTS: At baseline echocardiographic LVH was recorded in 63 patients (33.7%) with normal ejection fraction (75 +/- 7.4%). Non-sustained ventricular tachycardia (Lown IVb) was found in 33 pts (16.2%) and LP in 27 patients (21.6%). After a mean follow up of 42.4 +/- 26.8 months, all-cause mortality was 11.2% (24 patients); 17 patients died of cardiac causes (7.9%); of these 9 patients (4.2%) died suddenly. In univariate analysis, age, strain pattern of LVH, advanced Lown classes and abnormal QT dispersion (> 80 ms) were significantly related to global, cardiac and sudden death (p < or = 0.01). Left ventricular mass index was closely related to cardiac mortality (p = 0.002). LP failed to predict mortality. In multivariate analysis, only Lown class IVb was an independent predictor of global and cardiac mortality, increasing the risk of global death 2.6 fold [1.2-6.0] (CI 95%) and the risk of cardiac death 3.5 fold [1.2-9.7] (CI 95%). CONCLUSIONS: In hypertensive patients the presence of non-sustained ventricular tachycardia on 24 h Holter has a prognostic value.     

Should survivors of myocardial infarction with low ejection fraction be routinely referred to arrhythmia specialists?

Because survivors of myocardial infarction are at risk for ventricular arrhythmias and sudden death, physicians must decide whether to refer these patients to specialists for arrhythmia assessment and therapy. However, this decision is complex as few randomized data are available concerning either diagnostic or therapeutic options. Therefore, we modeled the potential impact of current arrhythmia detection and management strategies on mortality in survivors of myocardial infarction with reduced left ventricular function who are managed in a contemporary manner. Based on recent data we estimated that the mortality for myocardial infarction survivors with left ventricular ejection fraction less than 0.40 is 20 percent over 3.5 years and that half of the deaths are sudden. The sensitivity and specificity of a Holter electrocardiogram (ECG), a signal-averaged ECG, and an invasive electrophysiology study for predicting sudden death were obtained from a literature review of trials published after 1990 that included more than 300 patients. A series of models were constructed to predict mortality achieved by different arrhythmia management strategies that reduced sudden death by 50 percent and 75 percent--reductions estimated to be within the range for amiodarone and implantable defibrillators. We found that, when routinely applied to all infarct survivors with depressed ventricular function, a therapy that reduces sudden death by 50 percent with 1 percent fatal adverse effects (potentially amiodarone) saves approximately 1 life for every 25 patients treated. Therapy that reduces sudden death by 75 percent with 2 percent fatal adverse effects (potentially implantable defibrillators) saves 1 life for every 14 patients treated. Using Holter ECG recordings, a signal-averaged ECG, or an invasive electrophysiology study to select higher-risk groups, 1 life can be saved for every 4 to 11 patients treated, and the negative impact of adverse effects can be reduced. However, to achieve this benefit, additional and potentially invasive arrhythmia testing must be applied to 28 to 47 patients for each life saved. Thus, with contemporary management of acute myocardial infarction, the risk of sudden death for survivors is sufficiently low that broad application of available antiarrhythmic therapies has limited potential for further improving survival, particularly if therapy also has significant adverse effects. Thus, routine referral to arrhythmia specialists is not warranted for the majority of infarct survivors and should be largely reserved for patients with serious, symptomatic arrhythmias.     

Influence of bypass grafting to the infarct artery on late potentials in coronary operations

BACKGROUND: Late potentials (LPs) after myocardial infarction identify the risk of arrhythmic events and sudden death, and the absence of anterograde flow in the infarct-causing occluded coronary artery frequently is associated with LPs on signal-averaged electrocardiography. The present study was designed to clarify the influence of revascularization of the infarct artery on the LPs in the late course after myocardial infarction. METHODS: We studied 21 patients after myocardial infarction with positive LPs who had at least one occluded infarct coronary artery. We investigated the LPs on signal-averaged electrocardiograms on the day of elective coronary artery bypass grafting (CABG) and 1 week after CABG. RESULTS: There were 25 infarct arteries in the study patients, 13 of which were grafted. The positive LPs disappeared soon after CABG in 13 patients, 10 of whom had grafts to all of the infarct arteries. The LPs persisted in 8, who received no graft to the infarct artery. One week after CABG, the LPs were still present in 4, all of whom had no graft to the infarct right coronary artery. CONCLUSIONS: In patients with positive LPs late after myocardial infarction, grafting to the infarct artery eliminated the LPs soon after CABG.     

High-resolution electrocardiography in acute myocardial infarct

The author starts by highlighting the importance of risk stratification in patients who have survived a myocardial infarction. High resolution electrocardiography, also called signal-averaged electrocardiography (SAECG), appears in this setting as a diagnostic tool that, by providing important information about the way the intraventricular conduction of the electrical impulse is made, contributes to the characterization of the arrhythmogenic substrate, which is the basis of ventricular tachycardia and fibrillation. By resorting to the averaging of the electrocardiographic signal, SAECG enables us to detect ventricular late potentials whenever the analysis of that signal is made in time-domain. Further details, which will enrich the information on ventricular activation, can be obtained if the analysis is made in the frequency-domain (spectral analysis). The importance of detecting abnormalities in the SAECG recordings lies in the fact that those abnormalities are related to the occurrence of ventricular tachycardia and fibrillation, which are responsible for arrhythmic death. After referring to the criteria of positivity of SAECG and its reproducibility, the author approaches the most important part of the paper: the clinical applications of SAECG. After focusing on the interest of the method in noncoronary conditions, its usefulness in patients with acute myocardial infarction is pointed out. The author then mentions the prevalence of abnormalities in SAECG in patients with acute myocardial infarction and emphasizes the interest of the method in risk stratification. The author then presents the results of his Group in what concerns prevalence and prognosis. Finally, the author refers to the application of SAECG in other forms of coronary artery disease besides myocardial infarction.     

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CONTEXT: Early risk stratification of patients with myocardial infarction is critical to determine optimum treatment strategies and enhance outcomes, but knowledge of the prognostic importance of the initial electrocardiogram (ECG) is limited. OBJECTIVE: To assess the independent value of the initial ECG for short-term risk stratification after acute myocardial infarction. DESIGN: Retrospective analysis of the Global Utilization of Streptokinase and t-PA (alteplase) for Occluded Coronary Arteries (GUSTO-I) clinical trial database. SETTING: A total of 1081 hospitals in 15 countries. PATIENTS: From the 41 021 patients enrolled in the overall study, we selected those who presented within 6 hours of chest pain onset with ST-segment elevation and no confounding factors (paced rhythms, ventricular rhythms, or left bundle-branch block) on the ECG performed before thrombolysis was administered (n=34 166). MAIN OUTCOME MEASURE: Ability of initial ECG to predict all-cause mortality at 30 days. RESULTS: Most ECG variables were associated with 30-day mortality in a univariable analysis. In a multivariable analysis combining the initial ECG variables and clinical predictors of mortality, the sum of the absolute ST-segment deviation (both ST elevation and ST depression: odds ratio [OR], 1.53; 95% confidence interval [CI], 1.38-1.69), ECG, heart rate (OR, 1.49; 95% CI, 1.41-1.59), QRS duration (for anterior infarct: OR, 1.55; 95% CI, 1.43-1.68), and ECG evidence of prior infarction (for new inferior infarct: OR, 2.47; 95% CI, 2.02-3.00) were the strongest ECG predictors of mortality. A nomogram based on the multivariable model produced excellent discrimination of 30-day mortality (C-index, 0.830). CONCLUSIONS: In patients presenting with myocardial infarction accompanied by ST-segment elevation, components of the initial ECG help predict 30-day mortality. This information should be valuable in early risk stratification, when the opportunity to reduce mortality is greatest, and may help in assessing outcomes adjusted for patient risk.     

Silent myocardial ischemia in patients with different clinical forms of IHD

70 IHD patients underwent ambulatory Holter ECG monitoring two times. Out of 357 episodes of transitory ischemia registered in the course of exercise and presenting primarily as ST depression the proportion of silent episodes reached 75.6%. The number of episodes, their duration and mean value of ST depression were significantly greater in subjects 1 year after myocardial infarction. These patients more frequently developed ventricular arrhythmia and had ejection fraction below 50%. The findings evidence a significant clinical value of silent myocardial ischemia. It may serve a predictor of repeated acute coronary accidents in postmyocardial infarction patients.     

Survival and incidence of myocardial infarction in men with ambulatory ECG-detected frequent and complex ventricular arrhythmias. 10 year follow-up of the 'Men born 1914' study in Malm?, Sweden

AIM: To assess to what extent do frequent or complex ventricular arrhythmias, detected during 24 h ambulatory electrocardiographic recording (ECG), influence prognosis with regard to survival and incidence of ischaemic heart disease. METHODS AND RESULTS: The study subjects were the 456 randomly selected men born in 1914, the population-based cohort study of 1982-83, in Malm?, Sweden. The main outcome measures were total mortality and incidence of cardiac event (myocardial infarction and death from ischaemic heart disease). Frequent or complex ventricular arrhythmias (Lown classes 2-5) were detected in 49% of the men with (n = 77), and in 35% of those without, a history of myocardial infarction or angina pectoris at baseline, P = 0.019. Independent of clinically evident coronary artery disease at baseline, and after adjustment for traditional atherosclerotic risk factors and use of digitalis or beta-blocker therapy, frequent or complex ventricular arrhythmias were associated with an increased mortality from ischaemic heart disease (relative risk (RR), 2.1; 95% confidence interval (CI), 1.2-3.9) and an increased cardiac event rate (RR, 1.6; 95% CI, 1.0-2.5)). Men free from both ischaemic-type ST depression and frequent or complex ventricular arrhythmias (used as the control group) had the lowest ischaemic heart disease death rate, 5.9 per 1000 person-years. The combination of ST depression and frequent or complex ventricular arrhythmias was associated with an ischaemic heart disease death rate of 20.9 per 1000 person-years. The cardiac event rate in these two groups was 15.6 and 76.1 per 1000 person-years, respectively (adjusted RR, 2.3; CI, 1.1-4.6). CONCLUSIONS: In elderly men without a history of myocardial infarction and angina pectoris, frequent or complex ventricular arrhythmias during ambulatory ECG recording is associated with an increased incidence of myocardial infarction and mortality. Men who, during ambulatory ECG recording, also demonstrate ST-segment depression have an even less favourable prognosis.     

Long-term (5 year) effects of transient (silent) ischaemia on left ventricular systolic function in stable angina. Clinical and radionuclide study

AIMS: (a) to assess short (1 year) and long-term (5 year) changes in left ventricular ejection fraction in patients with stable coronary disease with or without ECG evidence of transient ischaemia during daily life on routine therapy, and (b) to assess whether patients with recurrent transient ischaemic episodes have a particular propensity to gradual deterioration in left ventricular ejection fraction in the absence of infarction. METHODS AND RESULTS: One hundred and forty eight patients (127 males; mean age 59 years), part of a natural history cohort of 172 patients who had undergone exercise testing, 48 h ambulatory ST monitoring, and resting radionuclide ventriculography at baseline, and who had not suffered any intervening cardiac event, underwent repeat radionuclide ventriculography at 1 year follow-up on identical or very similar medications. Furthermore, 56 patients (50 males; mean age 65 years) of this cohort, who had ischaemia both on exercise testing and ambulatory monitoring at baseline (n=33), or no ischaemia on either test at baseline (n=23), and who had suffered no intervening event, underwent repeat exercise testing, ambulatory monitoring and radionuclide ventriculography at a mean of 61.8 months follow-up. In 38 of these 56 cases, long-term testing mirrored baseline testing in terms of presence or absence of ischaemia (both tests +, n=25; both tests -, n=13). At one year there was no change in left ventricular ejection fraction, either for the whole group (n=148; left ventricular ejection fraction 47=11.6% - 47.13+11.07%, P=ns) or for subgroups with (n=62; left ventricular ejection fraction 48+12.1%-48.5+10.5%, P=ns) and without (n=86; left ventricular ejection fraction 46.2+10.4%-46.2+11.3%, P=ns) evidence of transient ischaemia at baseline. At 61 months, there was a small fall in mean left ventricular ejection fraction for the total study group (n=56; left ventricular ejection fraction 45.8+9.3%-42.1+8.8%, P<0.05); however, this fall was not significant for those patients with both baseline and 5 year evidence of transient ischaemia (n=25; left ventricular ejection fraction 44.9+8.7%-41.3+7.5%, P=0.056). CONCLUSION: In medically treated stable coronary patients who do not suffer any intervening cardiac event, recurrent transient (silent) ischaemic episodes do not, in themselves, lead to gradual deterioration in left ventricular systolic function over a 1-5 year period.     

Long-term beneficial effect of late reperfusion for acute anterior myocardial infarction with percutaneous transluminal coronary angioplasty

BACKGROUND: Although the short-term and long-term beneficial effects of early coronary revascularization by primary PTCA or thrombolytic therapy have been established for acute myocardial infarction, thrombolytic therapy >24 hours after the onset of acute myocardial infarction has not been shown to improve clinical outcome. The purpose of this study was to assess the effect of late revascularization by primary PTCA over a 5-year period. METHODS AND RESULTS: Eighty-three patients with initial Q-wave anterior myocardial infarction >24 hours after onset were randomized into a PTCA group (n=44) and a no-PTCA group (n=39). Long-term follow-up was conducted with regard to end points, which included cardiac death, nonfatal recurrence of myocardial infarction, and development of congestive heart failure. Left ventricular ejection fraction and regional wall motion at 6 months after myocardial infarction were similar in the 2 groups. Left ventricular end-diastolic and end-systolic volume indexes were significantly smaller in the PTCA group than in the no-PTCA group (P<0.0001). With cardiac events as end points, a 5-year Kaplan-Meier event-free survival analysis revealed that the no-PTCA group had a worse prognosis than the PTCA group (P<0.0001). Patency of the infarct-related artery, left ventricular ejection fraction, end-diastolic volume index, and end-systolic volume index were significantly associated with cardiac events by a Cox proportional hazards analysis (hazard ratios 0.120, 0.845, 1.065, and 1.164, respectively). CONCLUSIONS: In initial Q-wave anterior myocardial infarction, we conclude that even with late reperfusion, PTCA had beneficial effects on cardiac events over the 5-year period after myocardial infarction, with the prevention of left ventricular dilation after myocardial infarction being a possible mechanism.     

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STUDY OBJECTIVE: Accurate diagnosis in emergency department patients with possible myocardial ischemia is problematic. Two-dimensional echocardiography has a high sensitivity for identifying patients with myocardial infarction (MI); however, few studies have investigated its diagnostic ability when used acutely in ED patients with possible myocardial ischemia. Therefore we investigated the ability of ED echocardiography for predicting cardiac events in patients with possible myocardial ischemia. METHODS: Echocardiography was performed within 4 hours of ED presentation in 260 patients with possible myocardial ischemia, and was considered positive if there were segmental wall motion abnormalities or the ejection fraction was less than 40%. ECGs were considered abnormal if there was an ST-segment elevation or depression of greater than or equal to 1 mm, or ischemic T-wave inversion. Cardiac events included MI and revascularization. RESULTS: Of the 260 patients studied, 45 had cardiac events (23 MI, 19 percutaneous transluminal angioplasty, 3 coronary bypass surgery). The sensitivity of echocardiography for predicting cardiac events was 91% (95% confidence interval 79% to 97%]), which was significantly higher than the ECG (40% [95% CI 27% to 55%]: P < .0001), although specificity was lower (75% [95% CI 69% to 81%] versus 94% [95% CI 90% to 97%]; P < .001). Addition of the echocardiography results to baseline clinical variables and the ECG added significant incremental diagnostic value (P < .001). With use of multivariate analysis, only male gender (P < .03, odds ratio [OR] 2.4 [1.1 to 5.3]), and a positive echocardiographic finding (P < .0001, OR 24 [9 to 65]) predicted cardiac events. Excluding patients with abnormal ECGs (N = 30) did not affect sensitivity (85%) or specificity (74%) of echocardiography. CONCLUSION: Echocardiography performed in ED patients with possible myocardial ischemia identifies those who will have cardiac events, is more sensitive than the ECG, and has significant incremental value when added to baseline clinical variables and the ECG.     

Dispersion of the Q-T interval after myocardial infarct

Non-homogenity of ventricular myocardial repolarization is a substrate for the reentry mechanism of ventricular arrhythmias. It is manifestant by dispersion of Q-T and Q-Tc intervals on the standard ECG curve. The authors studied the possibility of using the dispersity of Q-T and Q-Tc intervals in clinical practice. They evaluated the dispersion of these intervals within the set of 21 patients after myocardial infarction with sustained ventricular tachycardia, and compared it with the dispersion within the control set of 17 patients after myocardial infarction without an arrhythmic episode. By means of comparison, they have discovered that: 1) the dispersion of Q-T and Q-Tc intervals is significantly higher in patients with ventricular tachycardia: Q-T (mean +/- SE) 82.8 +/- 7.8 msec vs 42.2 +/- 4.8 msec, Q-Tc 93.0 +/- 10.2 msec vs 47.1 +/- 4.8 msec, p > 0.001, 2) the dispersion of Q-Tc when higher than 60 msec is an optimum discrimination value for the prognosis of sudden arrhythmic death after myocardial infarction (sensitivity 81%, specificity 76%) and 3) the dispersion of Q-T and Q-Tc intervals has no relation to the function of the left ventricle. Therefore the authors consider the dispersion of Q-T and Q-Tc intervals as being a useful marker of malignant ventricular arrhythmia which could be included into the algorithm of assessment of the risk of sudden arrhythmic death after myocardial infarction.     

A simple electrocardiographic predictor of the outcome of patients with acute myocardial infarction treated with a thrombolytic agent. A Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico (GISSI-2)-Derived Analysis

OBJECTIVES: This analysis aimed to evaluate in a large patient cohort the relation between ST segment alterations after fibrinolytic therapy for acute myocardial infarction and 1) the combined end point of in-hospital mortality plus clinical congestive heart failure or extensive left ventricular damage, and 2) mortality 30 and 180 days after randomization. BACKGROUND: Angina relief, enzyme release acceleration and ST segment normalization are related to coronary artery reperfusion and prognosis. Electrocardiographic (ECG) evaluation before and after fibrinolytic drug administration has been used to predict short- and long-term clinical outcome in acute myocardial infarction. METHODS: Patients enrolled in the Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico (GISSI-2) trial underwent a standard ECG on admission and after 4 h of alteplase or streptokinase therapy; 7,426 recordings were suitable for ST segment analysis. A decrease > or = 50% in the sum of ST segment elevation in all ECG leads was adopted as the cutoff for predicting coronary artery patency. Recanalization was deemed to have occurred in 4,951 patients (group A) versus 2,475 patients without reperfusion (group B). RESULTS: Group A patients experienced a lower incidence of the combined end point than did group B patients (16.2% vs. 22.9%, respectively), as well as of all its components (death, clinical heart failure, ejection fraction < 35%, injured myocardial segment > 45%, QRS score > 10). Thirty- and 180-day mortality rates were lower in group A than group B (3.5% and 5.7% vs. 7.4% and 9.9%, respectively); relative risk (Cox) was 0.46 (95% confidence interval [CI] 0.37 to 0.57) for 30-day and 0.58 (95% CI 0.48 to 0.70) for 180-day mortality. Patients in group A had significantly less ventricular fibrillation and sustained ventricular tachycardia but more ischemic episodes (early recurrent angina plus myocardial infarction recurrence). CONCLUSIONS: A simple, inexpensive instrumental evaluation, unaffected by different epidemiologic and clinical characteristics of the population analyzed, can allow early assessment of the effectiveness of fibrinolytic treatment with respect to the main clinical outcomes.     

T wave alternans as a predictor of recurrent ventricular tachyarrhythmias in ICD recipients: prospective comparison with conventional risk markers

INTRODUCTION: The current standard for arrhythmic risk stratification is electrophysiologic (EP) testing, which, due to its invasive nature, is limited to patients already known to be at high risk. A number of noninvasive tests, such as determination of left ventricular ejection fraction (LVEF) or heart rate variability, have been evaluated as additional risk stratifiers. Microvolt T wave alternans (TWA) is a promising new risk marker. Prospective evaluation of noninvasive risk markers in low- or moderate-risk populations requires studies involving very large numbers of patients, and in such studies, documentation of the occurrence of ventricular tachyarrhythmias is difficult. In the present study, we identified a high-risk population, recipients of an implantable cardioverter defibrillator (ICD), and prospectively compared microvolt TWA with invasive EP testing and other risk markers with respect to their ability to predict recurrence of ventricular tachyarrhythmias as documented by ICD electrograms. METHODS AND RESULTS: Ninety-five patients with a history of ventricular tachyarrhythmias undergoing implantation of an ICD underwent EP testing, assessment of TWA, as well as determination of LVEF, baroreflex sensitivity, signal-averaged ECG, analysis of 24-hour Holter monitoring, and QT dispersion from the 12-lead surface ECG. The endpoint of the study was first appropriate ICD therapy for electrogram-documented ventricular fibrillation or tachycardia during follow-up. Kaplan-Meier survival analysis revealed that TWA (P < 0.006) and LVEF (P < 0.04) were the only significant univariate risk stratifiers. EP testing was not statistically significant (P < 0.2). Multivariate Cox regression analysis revealed that TWA was the only statistically significant independent risk factor. CONCLUSIONS: Measurement of microvolt TWA compared favorably with both invasive EP testing and other currently used noninvasive risk assessment methods in predicting recurrence of ventricular tachyarrhythmias in ICD recipients. This study suggests that TWA might also be a powerful tool for risk stratification in low- or moderate-risk patients, and needs to be prospectively evaluated in such populations.