Decreased incidence of ventricular late potentials after successful thrombolytic therapy for acute myocardial infarction

The presence of late potentials after percutaneous coronary intervention for the treatment of acute coronary syndrome as a predictor for future significant cardiac events resulting in re-hospitalization

INTRODUCTION

We previously reported that LP positive patients after percutaneous coronary intervention (PCI) had higher rate of re-hospitalization in the small-scale study (135 patients). In this study, we evaluated correlation between LP and later cardiac events leading to re-hospitalization more extensively in greater population.

METHODS AND RESULTS

A 24-h high-resolution (HR) ambulatory electrocardiogram (ECG) was performed in 421 patients that received PCI for the treatment of acute coronary syndrome (ACS) within 30 days. Various baseline characteristics and post-PCI ECG parameters including LP were examined for correlation with later re-hospitalization. LP was evaluated based on 3 different conditions, i.e., the worst, mean and best values, from 24-h signal-averaged QRS wave data. During the post-PCI follow-up period (611 ± 489.0 days), 90 patients were re-hospitalized due to cardiac events. Multivariate analysis identified only positive LP based on the worst value as an independent predictor for re-hospitalization with OR 2.26. Most of re-hospitalization cases (>75%) were predominantly attributed to ischemic events. LP positive population had significantly higher incidences of ischemic events as well as overall re-hospitalization compared to LP negative population. The predictive power of LP was decreased when it was combined with other variables. The receiver operating characteristic analysis determined the LP cut-off values consistent with the LP positive criteria previously reported and standardized.

CONCLUSION

The presence of LP in the 24-h HR ambulatory ECG post-PCI was an independent predictor for a risk of re-hospitalization due to ischemic cardiac events in ACS patients.

Effects of early captopril therapy after myocardial infarction on the incidence of late potentials

BACKGROUND

Late potentials (LP) on signal-averaged electrocardiography (SAECG), recorded 6 to 30 days after an acute myocardial infarction (AMI), identify patients at risk for late arrhythmic events. Angiotensin-converting enzyme (ACE) inhibitors have been shown to reduce ventricular remodeling and cardiovascular mortality after AMI.

HYPOTHESIS

The aim of this study was to investigate the effect of early (< 24 h) administration of captopril on the presence of LP on Days 6-30 after AMI.

METHODS

The study included 117 patients with a first AMI; 63 patients (53 men and 10 women, aged 59 +/- 12 years), 35 with an anterior and 28 with an inferior AMI (44 thrombolyzed), received early captopril therapy. The control group consisted of 54 age-matched patients (39 men and 15 women, aged 60 +/- 12 years), 19 with an anterior and 35 with an inferior AMI (31 thrombolyzed, p = NS), who did not receive early therapy with an ACE inhibitor. The mean left ventricular ejection fraction was similar in both groups (48 vs. 46%). Time domain analysis of SAECG was performed using a band-pass filter of 40-250 Hz. Late potentials were considered present if any two of three criteria were met: (1) Filtered QRS duration (QRSD) > 114 ms, (2) root-mean-square voltage of the last 40 ms of the QRS complex (RMS) < 20 microV, and (3) duration of low amplitude (< 40 microV) signal of the terminal portion of the QRS (LAS) > 38 ms.

RESULTS

In the two groups of patients there were no differences in mean values of SAECG parameters. No patient was receiving any antiarrhythmic drugs. In the captopril group LPs were present in 9 of 63 patients (14%) and in the control group in 17 of 54 patients (31%) (p = 0.046). There was no difference in the number of patients with a patent infarct-related artery in the two groups (76 vs. 59%).

CONCLUSION

Captopril treatment early after an AMI reduces the incidence of LPs recorded on Days 6-30 and may thus favorably affect the arrhythmogenic substrate.

Surgery for myocardial salvage in acute myocardial infarction and acute coronary syndromes

This article addresses the pathophysiology, the treatment options, and their rationale in the setting of life-threatening acute myocardial infarction and acute on chronic ischemia. Although biases may exist between cardiologists and surgeons, with this review, we hope to provide the reader with information that will shed light on the options that best suit the individual patient in a given set of circumstances.

The electrocardiogram as a prognostic tool for predicting major cardiac events

Among patients with cardiac disease, the identification of those who are at low risk and those who are at high risk for major cardiac events is crucial for a rational clinical management of individual patients. A correct noninvasive risk stratification of cardiac patients, in particular, has relevant clinical implications because it would avoid unnecessary exposure to potentially risky invasive diagnostic or interventional procedures in low-risk patients, whereas it would allow an appropriate aggressive diagnostic and therapeutic approach in high-risk patients. Furthermore, the appropriate identification of low- and high-risk patients would also have social and economic implications by favoring optimization of resource distribution and costs. A large number of studies in previous decades provided evidence that several methods and variables derived from the analysis of the electrocardiogram (ECG) are powerful predictors of major cardiac events in several clinical conditions. Despite that, there has been limited attention about how several of these findings can be used in clinical practice. Furthermore, in recent years, most studies about risk stratification of cardiac patients have mainly been focused on the use of a number of serum/plasma biomarkers with reduced attention to ECG variables. Surprisingly, however, there have been few attempts to establish whether the various proposed risk markers add any significant information to that obtainable from ECG methods. In this article, the evidence for the prognostic value of variables derived from the assessment of the ECG signal by several methods and techniques will be briefly reviewed. Because of the largeness of the topic, this review will be necessarily incomplete. Because most of the clinical research in this field concerned risk stratification of patients with coronary artery disease, the article will be largely focused on this population of patients. The role of ECG methods in specific cardiac diseases and, in particular, in the general population of asymptomatic subjects will be briefly discussed when believed appropriate and helpful. Furthermore, only major clinical events (ie, cardiac death, arrhythmic events, acute myocardial infarction) will be taken into account as end points in this article. Minor clinical events (eg, coronary revascularization procedures, coronary artery restenosis, recurrences of symptoms) are indeed less robust as end points because they are widely biased by subjective judgments.

Is the change of late potential over time related to enzyme levels? Ischemic burden in acute myocardial infarction

BACKGROUND

The ventricular late potential (VLP) detected using the technique of signal average electrocardiography (SAECG) interacts with several factors, primarily time.

METHOD

In this study, we examined the interaction, over time, of VLP with the initial ischemic burden and enzyme levels in acute myocardial infarction. Patients diagnosed as having acute myocardial infarction were included in the study. On the first day, the patients underwent enzyme analysis and electrocardiography (ECG) follow-up every 6 hours. A 24-hour ambulatory ECG was performed on the seventh day in order to determine the ischemic burden. SAECG findings (TQRS, RMS, LAS) were obtained on the seventh day, in the first and third months. The study was continued with the patients who did not require angioplasty as decided with angiographic evaluation in the first month.

RESULTS

The study included 30 patients with acute myocardial infarction (mean age 51 +/- 12, 28 males and 2 females). The initial mean CK-MB levels and the mean ischemic burden were 98 +/- 31 U/L and 44 +/- 96 minutes. The TQRS (ms), LAS (ms), and RMS (microV) values (mean +/- SD ) obtained at day 7, month 1, and month 3 are 97 +/- 12, 96 +/- 9, 103 +/- 11, P = 0.01; 31 +/- 10, 31 +/- 11, 32 +/- 10, P = 0.46; 43 +/- 28, 41 +/- 26, 33 +/- 25, P = 0.01, respectively. We observed that the TQRS and RMS values changed significantly with time, but these levels of significance disappeared when adjusted for the initial ischemic burden and CK-MB levels (P = 0.06; P = 0.53). The VLP frequency was 33% at day 7 and 23% at month 3. Unlike the CK-MB level, the initial ischemic burden was significantly different between the patients with and without VLP at month 3 (150.85 +/- 149.28, 12.34 +/- 26.48, P = 0.001 ). When tested together with age and gender, it was found that the high initial ischemic burden increased the possibility of VLP (OR: 24, CI: 2.09-279.52, P = 0.01 ) at month 3.

CONCLUSION

SAECG findings in patients with myocardial infarction changed with time; however, this change occurred depending on the initial ischemic burden and CK-MB levels. Of these, only the initial ischemic burden, especially in high levels, was a determinant for the presence of VLP in the late period of myocardial infarction.

The effect of myocardial surgical revascularization on left ventricular late potentials

BACKGROUND

The presence of ventricular late potentials (LP) is an important indicator for the development of ventricular tachyarrhythmias due to ischemic heart disease. The effect of myocardial revascularization on LP has remained controversial. The purpose of this study was to determine whether complete myocardial surgical revascularization (CABG) documented by myocardial perfusion scintigraphy might alter the substrate responsible for LP.

METHODS

Prospectively, enrolled patients undergoing elective CABG were evaluated with thallium-201 myocardial perfusion scintigraphy and signal- averaged ECG pre- and postoperatively. SAECG recordings were obtained serially: before, 48-72 hours and 3 months after CABG. LPS were defined as positive if SAECG met at least two of Gomes criteria. Scintigraphies were performed pre- and 3 months postoperatively for determination of the success of revascularization. Changes observed in SAECG recordings after CABG were compared between those with and without successful revascularization.

RESULTS

CABG resulted in successful revascularization in 23 patients and was unsuccessful in 17 (no change or deterioration of the perfusion defects). Preoperative SAECG values were not different between groups except for RMS values. The incidence of LP decreased significantly postoperatively in patients with improved myocardial perfusion, whereas there were no changes in patients who did not have postoperative perfusion improvement (McNemar test, P < 0.05).

CONCLUSIONS

LPs disappear following the elimination of myocardial ischemia by complete surgical revascularization. Persistence of ischemia following CABG usually results in the persistence of late potentials. The incidence of ventricular arrhythmias is expected to be unchanged in these patients and they should be reevaluated for reinterventions.

Reduced ejection fraction after myocardial infarction: is it sufficient to justify implantation of a defibrillator?

BACKGROUND

Improved survival after prophylactic implantation of a defibrillator in patients with reduced left ventricular ejection fraction (EF) after myocardial infarction (MI) has been demonstrated in patients who experienced remote MIs in the 1990s. The absolute survival benefit conferred by this recommended strategy must be related to the current risk of arrhythmic death, which is evolving. This study evaluates the mortality rate in survivors of MI with impaired left ventricular function and its relation to pre-hospital discharge baseline characteristics.

METHODS

The clinical records of patients who had sustained an acute MI between 1999 and 2000 and had been discharged from the hospital with an EF of < or = 40% were included. Baseline characteristics, drug prescriptions, and invasive procedures were recorded. Bivariate and multivariate analyses were performed using a primary end point of total mortality.

RESULTS

One hundred sixty-five patients were included. During a median follow-up period of 30 months (interquartile range, 22 to 36 months) 18 patients died. The 1-year and 2-year mortality rates were 6.7% and 8.6%, respectively. Variables reflecting coronary artery disease and its management (ie, prior MI, acute reperfusion, and complete revascularization) had a greater impact on mortality than variables reflecting mechanical dysfunction (ie, EF and Killip class).

CONCLUSIONS

The mortality rate among survivors of MIs with reduced EF was substantially lower than that reported in the 1990s. The strong decrease in the arrhythmic risk implies a proportional increase in the number of patients needed to treat with a prophylactic defibrillator to prevent one adverse event. The risk of an event may even be sufficiently low to limit the detectable benefit of defibrillators in patients with the prognostic features identified in our study. This argues for additional risk stratification prior to the prophylactic implantation of a defibrillator.

Effects of reperfusion obtained two to six months after acute myocardial infarction on myocardial electrical stabilization in patients with an occluded infarct-related coronary artery

To assess the changes in electrical stability markers in patients with previous myocardial infarction after very late reopening of the infarct-related artery, we studied QT dispersion, corrected-QT dispersion, and late potentials before and 1, 3, and 6 months after an attempt at late percutaneous coronary intervention (PCI) in 31 consecutive patients with single-vessel disease (infarct-related artery occlusion or subocclusion) diagnosed > or = 4 weeks after the ST-elevation myocardial infarction. Patients underwent PCI 3.9 +/- 2 months after ST-elevation myocardial infarction. PCI was successful in 24 patients (group A) and unsuccessful in 7 (group B). The 2 groups were similar in clinical and angiographic characteristics, as well as the prevalence of basal late potentials, average QT dispersion, and corrected-QT dispersion. One month after PCI, the successful reperfusion group had a significant 67% decrease in the prevalence of late potentials and average QT dispersion and corrected QT dispersion (51 +/- 9 vs 72 +/- 11 ms, p <0.00001, and 51 +/- 10 vs 76 +/- 15 ms, p <0.00001, respectively). These benefits remained stable at 3 and 6 months after PCI. Conversely, the unsuccessful group did not show any improvement in electrical stability markers after PCI failed. Thus, reperfusion obtained very late after ST-elevation myocardial infarction confers significant electrical stabilization that may contribute to a better outcome in patients with patent infarct-related arteries.

Reduced prognostic power of ventricular late potentials in post-infarction patients of the reperfusion era

AIMS

To test the prognostic value of ventricular late potentials (LPs) in a large cohort of post-infarction patients in the modern reperfusion era.

METHODS AND RESULTS

1800 consecutive survivors of acute myocardial infarction in sinus rhythm and under 76 years of age were enrolled. Many (99%) of the patients received reperfusion/revascularization therapy (91% percutaneous coronary intervention) and up-to-date pharmacological treatment (99% aspirin, 93% beta-blockers, 90% ACE-inhibitors, and 85% statins). LPs were calculated in 968 patients and found to be present in 90 (9.3%). The primary endpoint was the composite of cardiac death and serious arrhythmic events. The secondary endpoint was the composite of sudden cardiac death and serious arrhythmic events. During follow-up (median 34 months), 26 patients reached the primary endpoint. The presence of LPs was not significantly associated with the primary endpoint in univariable or multivariable analysis. In contrast, low (< or = 30%) left ventricular ejection fraction (hazard ratio 9.6, 95% confidence interval 4.1-22.4), heart rate turbulence category 2 (7.5, 2.4-23.9) and category 1 (5.3, 1.9-14.9) were significant predictors in both univariable and multivariable analysis.

CONCLUSION

Ventricular LPs are of limited use for risk stratification in unselected post-infarction patients in the modern reperfusion era.

The effects of right ventricular involvement on heart rate variability and ventricular late potentials in acute inferior myocardial infarction

Depressed heart rate variability and presence of ventricular late potentials in acute myocardial infarction are associated with a poor prognosis. Although it is known that the abnormalities vary according to anterior or inferior location of acute myocardial infarction, the relationship with right ventricular acute myocardial infarction is not clear. The effects of right ventricular myocardial infarction on heart rate variability and ventricular late potentials are studied. The study was performed with a total of 46 patients (38 males; aged 56 +/-13 yr, range, 33 to 70 yr). Twenty-six patients had isolated inferior myocardial infarction while 20 patients had accompanying right ventricular involvement. For all patients, ambulatory Holter recordings between 24 and 48 hours following myocardial infarction, echocardiography in first 48 hours, and signal-averaged electrocardiography with submaximal exercise at average day 6 (range, 5 to 8 days) were performed. Heart rate variability and signal-averaged electrocardiography recordings were repeated after discharge (average, 39 days). During the first 24 to 48 hr, time domain parameters (SDNN1 and SD1) were significantly lower (SDNN1: 62 +/- 17 vs 100 +/- 20 ms, p = 0.001; SD: 37 +/- 10 vs 50 +/- 16 ms, p = 0.03) in patients with isolated inferior MI than in those with right ventricular involvement, whereas root-mean-square voltage (RMS-SD1) showed no significant difference in both groups (28 +/- 7 vs 35 +/- 8 ms). In post-discharge heart rate variability recordings, there were no significant differences (SDNN2: 86 +/- 13 vs 95 +/- 15 ms; SD2: 48 +/- 11 vs 57 +/- 13 ms; RMS-SD2: 32 +/- 14 vs 35 +/- 9 ms). In pre-discharge tests, the mean value of low-amplitude signals (LAS1) was higher (26 +/- 9 vs 33 +/- 11 ms, p = 0.03) in patients with isolated inferior myocardial infarction than in those with right ventricular involvement, while other signal-averaged electrocardiography parameters were not significantly different (filtered QRS: 102 +/- 5 vs 105 +/- 10 ms, RMS-40(1): 44 +/- 13 vs 26 +/- 10 microV; incidence of ventricular late potentials: 23% vs 30%, p = NS, respectively). In post-discharge tests, all of signal-averaged electrocardiography parameters were similar in both groups (filtered QRS2: 112 +/- 12 vs 114 +/- 8 ms, LAS2: 28 +/- 9 vs 32 +/- 13 ms, RMS-40(2): 36 +/- 10 vs 34 +/- 11 microV, and frequency of ventricular late potentials2: 23% vs 30%, p = NS). These data suggest that right ventricular involvement in an acute inferior myocardial infarction is associated with improved heart rate variability parameters but not ventricular late potentials in pre-discharge period. However, the influence of right ventricular involvement on heart rate variability parameters fades away in the post-discharge period.

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.

Thrombolytic therapy can reduce the arrhythmogenic substrate after acute myocardial infarction: a study using the signal-averaged electrocardiogram, endocardial catheter mapping and programmed ventricular stimulation

Thrombolytic therapy improves survival after acute myocardial infarction (AMI) primarily by preserving left ventricular function. Its influence on the arrhythmogenic substrate remains uncertain. To investigate the electrophysiologic effects of thrombolytic therapy, signal-averaged electrocardiography, endocardial catheter mapping and programmed stimulation were performed in 93 consecutive patients with their first AMI who underwent thrombolytic therapy. Early reperfusion was achieved in 75 patients (group 1), but not in 18 patients (group 2). The incidence of the signal-averaged electrocardiogram abnormality was 11% in group 1 (8 of 75 patients) and 33% in group 2 (6 of 18 patients) (p<0.02). Catheter mapping detected delayed endocardial electrograms in 30 group 1 patients and 10 group 2 patients (p=NS). The spatial distribution of these electrograms was smaller, and the longest duration of endocardial electrograms was shorter in group 1 than in group 2 (p<0.01). Sustained monomorphic ventricular tachycardia was induced less commonly in group 1 (20%) than in group 2 (44%) (p<0.05). In conclusion, thrombolytic therapy can reduce the arrhythmogenic substrate and improve electrical stability after AMI. This antiarrhythmic effect may contribute, in part, to the improved survival of patients treated with thrombolytic drugs.

Circadian variability of late potential analysis in Holter electrocardiograms

Appearance of ventricular tachycardia, ventricular fibrillation, and sudden cardiac death has diurnal variations. We retrospectively studied, using digital Holter electrocardiogram, whether a time course in the appearance of late potentials may be associated with malignant ventricular arrhythmias. The 24-hour recordings in 200 patients after myocardial infarction (50 patients with documented, sustained, monomorphic and reproducibly inducible ventricular tachycardia (< 270/min) (group I), 50 patients resuscitated from ventricular fibrillation (group II), and 100 patients without ventricular arrhythmias (group III) were divided into 24 segments, 60 minutes each. Late potential analysis was performed using the Simson method in the time domain in each segment and compared to a conventional short-term registration. Late potential analysis in conventional short-term recordings during arbitrarily chosen daytimes revealed late potentials in 80% of patients in group I, 38% of patients in group II, and in 16% of patients without ventricular arrhythmias. In at least one 60-minute segment late potentials were found in group I in 92%, in group II in 88% (P < 0.05 vs conventional analysis), and in group III in 19%. Interestingly, in patients with a history of ventricular fibrillation late potentials appeared significantly more often during morning hours (6-12 AM: 82% vs 26% at 12 AM-6 PM, 30% at 6 PM-12 PM, and 42% at 12 PM-6 AM, P < 0.05), especially during phases with heart rate accelerations. Late potential analysis for risk stratification in conventional short-term recordings is feasible for patients prone to ventricular tachycardia, but patients prone to ventricular fibrillation would be more effectively stratified using 24-hour registrations with detection of circadian variations of late potential appearance.

Ischemia-induced changes of the signal-averaged electrocardiogram: experimental investigation during percutaneous transluminal coronary angioplasty balloon-occluded coronary artery

INTRODUCTION

The influence of myocardial ischemia on the detection of an arrhythmogenic substrate with the signal-averaged ECG is unclear.

METHODS AND RESULTS

In 80 patients with single vessel coronary artery disease and a critical stenosis of the left anterior descending vessel selected after coronary angiography in whom percutaneous transluminal coronary angioplasty (PTCA) was planned, we retrospectively investigated the signal-averaged ECGs in the time domain before, during, and after occlusion of the coronary artery by the PTCA balloon. Forty patients were resuscitated from ventricular fibrillation (VF group), and 40 patients had no ventricular arrhythmia (non-VF group). Late potentials were seen at rest in 26 of 40 patients in the VF group. During ischemia, the duration of the filtered QRS complex and the duration of low-amplitude signals < 40 microV increased significantly. In another 14 patients in the VF group, late potentials were observed only during ischemia. In 4 of 26 patients in the VF group without prior infarction but with severe ischemia present at rest, successful PTCA eliminated preexistent late potentials. In the non-VF group, one patient had late potentials present at rest. In two patients with prior infarction, late potentials were provokable only during transmural ischemia.

CONCLUSION

Myocardial ischemia is able to modify detection of an arrhythmogenic substrate with the signal-averaged ECG.

Relation between infarct artery patency at late angiography after acute myocardial infarction and signal-averaged electrocardiography

The angiograms of 89 patients were reviewed from the LATE Ancillary Study (randomized trial of recombinant tissue plasminogen activator vs placebo in patients with symptom onset after 6 hours of myocardial infarction) to determine patency of the infarct-related artery (IRA). In the occluded IRA group (n = 35), the incidence of signal-averaged electrocardiographic abnormality (fQRS > 120 ms) was significantly higher (p = 0.04), the filtered QRS duration was significantly longer (p = 0.007), and the V40 was significantly shorter (p = 0.02), compared with the patent IRA group (n = 54).

Angiographically documented late reocclusion after successful coronary angioplasty of an infarct-related lesion is a powerful predictor of long-term mortality

BACKGROUND

Late reocclusion of an infarct-related artery (IRA) that was patent in the early days after acute myocardial infarction (MI) is a frequent event; the reocclusion rate may be as high as 30%. Few studies have been designed to analyze the impact of late reocclusion of the IRA on late survival.

METHODS AND RESULTS

We studied 528 patients who all had a patent IRA after a successful PTCA procedure 10+/-6 days after MI and who underwent systematic 6-month angiographic follow-up to assess late patency of the IRA. We compared long-term survival of patients with and without late reocclusion. Based on the results of 6-month follow-up angiography, 2 groups of patients were defined: (1) 90 patients (17%) with reocclusion (Thrombolysis In Myocardial Infarction [TIMI] flow 0 or 1) and (2) 438 patients (83%) without reocclusion. Long-term clinical follow-up was obtained for all 528 patients at a median of 5.7 years after follow-up angiography (6.4 years after PTCA). The overall actuarial 8-year total mortality rate was 13%. At the end of follow-up, there were 35 deaths (8%) among the 438 patients without reocclusion and 18 deaths (20%) among the 90 patients with reocclusion (P=0.002). The actuarial 8-year total mortality rate was 10% in patients without reocclusion and 28% in patients with reocclusion (P=0.0003). The actuarial cardiovascular mortality rate was 7% in patients without reocclusion and 25% in patients with reocclusion (P<0.0001). The impact of reocclusion on long-term mortality was greater in patients with anterior MI.

CONCLUSIONS

Late IRA patency is strongly associated with long-term survival after MI. These observations should encourage prospective studies to evaluate the impact of strategies designed to prevent late reocclusion in postinfarction patients.

Support for the open-artery hypothesis in survivors of acute myocardial infarction: analysis of 11,228 patients treated with thrombolytic therapy

We examined the possible benefits of achieving and maintaining infarct-related artery potency beyond the time when preservation of left ventricular function would be expected. The open-artery hypothesis suggests that a patent infarct-related artery confers a survival benefit greater than that expected from myocardial salvage alone, which extends beyond the time when preservation of left ventricular function is expected. We examined the survival experience of patients undergoing thrombolysis in the Global Utilization of Streptokinase and TPA for Occluded Arteries (GUSTO-I) trial for whom data on the potency of the infarct artery were available. Univariable analysis was used to determine the unadjusted relations of angiographic variables and revascularization procedures to both 30-day and 1-year mortality in 30-day survivors. Multivariable analysis was used to test for interactions between patency and each characteristic and to adjust both for all other variables and for baseline characteristics known to predict mortality. In both univariable and multivariable analysis, patients with an open rather than a closed infarct-related artery had significantly lower 30-day mortality (p <0.001). This benefit cannot be accounted for by myocardial salvage alone, because it remained after adjustment for left ventricular ejection fraction. Patency was also associated with lower 1-year mortality in 30-day survivors, but not after adjustment for other variables affecting late mortality. Having an open infarct-related artery at the time of first catheterization confers a survival advantage that extends beyond the benefit of myocardial salvage from thrombolytic therapy, and is independent of ejection fraction.

Risk stratification following myocardial infarction in the thrombolytic era: a two-step strategy using noninvasive and invasive methods

OBJECTIVES

We prospectively performed a two-step risk assessment in patients in the early phase after acute myocardial infarction (MI).

BACKGROUND

Noninvasive methods like Holter electrocardiographic monitoring (HM) and determination of the left ventricular ejection fraction (EF) as well as the invasive technique of programmed ventricular stimulation (PVS) have been used to identify patients in the late phase after MI as candidates for prophylactic implantation of a cardioverter/defibrillator. However, it is unclear whether these results can be transferred to patients following acute MI.

METHODS

A series of 657 patients with acute MI (< or = 75 years) underwent HM and EF. If one of the two methods yielded abnormal findings (HM > or = 20 ventricular ectopic beats/h/> or =10 ventricular pairs/day/ventricular tachycardia; EF < or = 40%), PVS was done (abnormal PVS: induction of monomorphic ventricular tachycardia, duration >10 s, cycle length > or = 230 ms).

RESULTS

Of 657 patients, 304 (46%) had either an abnormal HM or EF. The PVS performed in 146 of 304 patients was abnormal in 22. During a mean follow-up of 37 months, there were 106 (16%) deaths, being sudden in 24 (3.6%), nonsudden cardiac in 45 (6.8%). The incidence of arrhythmic events (sudden cardiac death, symptomatic ventricular tachycardia, cardiac arrest) was 18% (4/22) with an abnormal PVS and only 4% (5/124) with a normal PVS (odds ratio 4.0, p=0.032).

CONCLUSIONS

The rate of arrhythmic events is low in post-MI patients in the 1990s. Nevertheless, a two-step risk stratification is helpful in selecting candidates for a defibrillator trial aiming at primary prevention of sudden cardiac death after MI.

Late coronary angioplasty and ventricular late potentials

To assess the effect of successful late coronary angioplasty of an occluded infarct-related artery on the prevalence of ventricular late potentials, signal-averaged electrocardiograms were recorded in 123 consecutive patients surviving a first acute myocardial infarction (58 with and 65 without mechanical reperfusion of the occluded coronary artery). Multivariate analysis showed that successful reperfusion by late angioplasty of the infarct artery contributes to a decrease in the prevalence of late potentials.

Multivariate associates of QT dispersion in patients with acute myocardial infarction: primacy of patency status of the infarct-related artery. TEAM-3 Investigators. Third trial of Thrombolysis with Eminase in Acute Myocardial Infarction

BACKGROUND

QT dispersion (QTd; QT interval maximum minus minimum) has been shown to reflect regional variations in ventricular repolarization and is increased in patients with life-threatening ventricular arrhythmias.

METHODS

To determine correlates of QTd in patients who had had myocardial infarction (MI), 207 patients (158 men, aged 57 +/- 11 years) with acute MI who were treated with alteplase or anistreplase within 2.7 +/- 0.9 hours of symptom onset were studied. Angiograms at a median of 27 hours after thrombolysis showed reperfusion (Thrombolysis in Myocardial Infarction grade > or =2) in 184 (88%) patients. QT was measured in 10 +/- 2 leads on discharge electrocardiograms with a computerized analysis program interfaced with a digitizer. Associations of QTd with 24 variables related to patient characteristics, acute MI, angiography, interventions, and radionuclide ventriculography were evaluated by univariate and multivariate regression.

RESULTS

Univariate associations with QTd (p < or = 0.10) were Thrombolysis in Myocardial Infarction flow grade 0/1 versus 2/3 (QTd = 75 +/- 33 msec vs 53 +/- 22 msec, p < 0.0001), minimal luminal diameter (p = 0.007), left ventricular ejection fraction at discharge (p = 0.007), reinfarction (p = 0.01), number of leads with ST elevation (p = 0.05), end-systolic volume at discharge (p = 0.04), time to peak creatine kinase (p = 0.06), and YST elevation (p = 0.10). Independent associates of QTd were Thrombolysis in Myocardial Infarction grade 0/1 versus 2/3 (p < 0.0001), reinfarction (p = 0.005), and ejection fraction (p = 0.02).

CONCLUSIONS

Successful thrombolysis is associated with less QTd in patients after acute MI. Our results support the hypothesis that QTd after MI depends on reperfusion status, reinfarction, and left ventricular function. Reduction in QTd may be an additional mechanism by which the benefit of thrombolytic therapy is realized.

Significance of development of late potentials after anterior wall acute myocardial infarction despite successful primary angioplasty of the left anterior descending coronary artery

We classified 33 patients with a first anterior infarction and single-vessel disease who had undergone successful primary angioplasty and had a patent infarct-related artery into groups based on the development of late potentials. Left ventricular function improved between 1 and 3 months after angioplasty only in patients without late potentials; the development of late potentials after acute anterior infarction was associated with prolonged left ventricular dysfunction despite successful revascularization with primary angioplasty.

The open-artery hypothesis

Early reperfusion of an infarct-related coronary artery results in myocardial salvage, with subsequent improvement in left ventricular function and survival. However, late reperfusion, which occurs at a time when myocardial salvage is no longer possible, still exerts a favorable impact on left ventricular function and survival. This concept is known as the open-artery hypothesis. Possible mechanisms for this benefit include improved infarct healing, limitation of ventricular remodeling, decreased ventricular arrhythmias, and reperfusion of hibernating myocardium. Although an open infarct-related coronary artery is crucial, it has not been proven that opening an occluded coronary artery using angioplasty is beneficial. A large randomized clinical trial is clearly needed.

Antiarrhythmic drug effects on QT interval dispersion in patients undergoing electropharmacologic testing for ventricular tachycardia and fibrillation

The effects of antiarrhythmic drugs on QT interval dispersion as a predictor of antiarrhythmic drug therapy has not been rigorously assessed. This study was performed to determine whether the effects of antiarrhythmic drugs on QT interval dispersion predict antiarrhythmic drug response in patients undergoing electropharmacologic testing for ventricular tachycardiarrythmias. Precordial QT intervals and QT interval dispersions were measured at baseline and during steady-state antiarrhythmic drug therapy in 72 consecutive patients with documented coronary artery disease and remote myocardial infarction presenting with spontaneous sustained ventricular tachyarrhythmias who underwent electropharmacologic studies to assess arrhythmia suppression. QT interval dispersion was similar at baseline in drug responders (42 +/- 21 ms) and drug nonresponders (46 +/- 21 ms), whereas during antiarrhythmic therapy QT interval dispersion was shorter in drug responders (33 +/- 15 ms) than in drug nonresponders (55 +/- 29 ms, p <0.001). QT interval dispersion was shorter in 7 drug responders during their effective drug trials (27 +/- 14 ms) than during their ineffective drug trials (47 +/- 24 ms, n = 9, p <0.05). QT dispersion < or = 50 ms (p <0.002) and a patent infarct-related artery (p <0.003) were independent predictors of antiarrhythmic therapy. The positive and negative predictive value of QT interval dispersion during drug therapy to predict a successful drug response was 32% and 96%, respectively. QT interval dispersion predicted the outcome of electropharmacologic studies independent of infarct-related artery patency. QT interval dispersion >50 ms during drug therapy was associated with ineffective drug therapy.

Relationship between the site of a myocardial infarction and signal-averaged electrocardiogram indices

We evaluated the relationship between the site of a myocardial infarction (MI) and signal-averaged electrocardiogram (SAECG) indices in both time-domain (TDA) and spectral turbulence (STA) analyses, and their implications in the prediction of infarct-related artery (IRA) patency, in 114 survivors of a first MI. They were divided into two groups based on MI location (57 anterior and 57 inferior). Patients with bundle branch block were not included. Fifty patients had been treated with thrombolytic therapy (TT). The STA was done in both XYZ-leads and in vector magnitude. Forty patients had an abnormal SAECG in TDA and 37 in STA, but only 22 (19%) in both (71% of agreement, kappa=0.35). Fifty-four patients (47%) had an occluded IRA. The best predictors from multivariate analysis of having an occluded IRA in the inferior MI group were: an abnormal Y-lead in STA (odds ratio 4.9; P=0.005); an abnormal RMS40 in TDA (odds ratio, 4.8; P=0.02); absence of TT (odds ratio, 9.15; P=0.001). Conversely, in the anterior MI group they were: an abnormal SAECG in TDA (odds ratio 6.83; P=0.005); absence of TT (odds ratio, 4.3; P=0.02). The multivariate receiver operator characteristic curves clearly showed the effect of MI location on the SAECG indices. This study suggests that the myocardial infarction site is an important factor for the variability and poor concordance between TDA and STA. Such differences may alter the predictive accuracy of SAECG. TDA and STA should be complementary methods, and the exploration in each orthogonal lead appears to be better than in vector magnitude.

Long-term prognostic significance of ventricular late potentials after a first acute myocardial infarction

Ventricular late potentials (VLP) have been shown to be independent predictors of arrhythmic events after myocardial infarction. However, many studies have had one or more limitations: limited follow-up period, small study group, possible selection bias, inadequate statistical analysis, or inclusion of patients with previous infarction. The purpose of this study was to assess the long-term prognostic value of VLP in a large group of unselected patients after a first acute myocardial infarction. Time-domain signal averaging was performed in 458 patients (380 male, 78 female, mean age 59 +/- 11 years) a mean of 10 days (range 7 to 13 days) after a first acute myocardial infarction. The overall prevalence of VLP was 20% (90 of 458 patients). By univariate analysis a left ventricular ejection fraction <40% (p = 0.002) and the presence of an occluded infarct-related artery (p = 0.006) were the only statistically significant predictors for the development of VLP. During a median follow-up of 70 months, 21 (5%) patients died suddenly, and 11 (2%) patients had documented sustained ventricular tachycardia. The presence of VLP (p < 0.0001), older age (p = 0.02), and an occluded infarct-related artery (p = 0.045) were the only variables significantly associated with the occurrence of serious arrhythmic events during follow-up. The probability of having no arrhythmic events was 99% at 1 year and 96% at 5 years in the absence of VLP and 87% at 1 year and 80% at 5 years in the presence of VLP (4.6-fold increase in arrhythmic risk; 95% confidence interval: 2.3 to 9.1). VLPs are powerful predictors of serious arrhythmic events in patients after a first acute myocardial infarction, and their prognostic value, although waning with time, persists for at least 7 years. This study also provides further evidence that an open infarct-related artery may reduce the arrhythmic risk after myocardial infarction.

Effects of coronary stenting on restenosis and occlusion after angioplasty of the culprit vessel in patients with recent myocardial infarction

BACKGROUND

PTCA of an infarct-related lesion is associated with a high rate of restenosis and/or vessel occlusion. Recent studies have shown that coronary stenting in patients with stable or unstable angina is associated with a significant reduction in the restenosis rate compared with conventional balloon angioplasty. However, no information is available concerning the long-term effect of coronary stenting at infarct-related lesions compared with balloon angioplasty alone.

METHODS AND RESULTS

One hundred consecutive patients undergoing stent implantation at an infarct-related lesion and systematic 6-month angiographic follow-up were matched for major pre-PTCA clinical and angiographic variables with a group of patients undergoing conventional angioplasty. Preprocedural, postprocedural, and 6-month follow-up angiograms were analyzed with quantitative angiography. Coronary stenting was performed as a bailout procedure after failed balloon angioplasty in 20%, for a suboptimal result after balloon angioplasty in 71%, and electively in 9%. Stent implantation was associated with a higher acute gain than balloon angioplasty. At follow-up, the minimal lumen diameter was significantly (P<.0001) larger in the stent group (1.72+/-0.69 versus 1.23+/-0.72 mm). Restenosis (>50% DS at follow-up) occurred in 27% of the stent group versus 52% of the balloon group (P<.005). At follow-up, total occlusion at the dilated site occurred in 1% of the stent group versus 14% of the balloon group (P<.005).

CONCLUSIONS

Coronary stenting of infarct-related lesions is associated with a highly beneficial effect on 6-month angiographic outcome compared with balloon angioplasty alone. Further studies are needed to establish whether the beneficial effect of coronary stenting on long-term vessel patency is associated with an improvement in left ventricular function or in clinical outcome.

Quantification of the benefit of earlier thrombolytic therapy: five-year results of the Grampian Region Early Anistreplase Trial (GREAT)

OBJECTIVES

This report presents the 5-year results of the Grampian Region Early Anistreplase Trial (GREAT) and quantifies the benefit of earlier thrombolysis in terms that are generally applicable.

BACKGROUND

Although it is accepted that the earlier thrombolytic therapy is given for acute myocardial infarction the greater the benefit, there are widely differing estimates of the magnitude of the time-related benefit of thrombolysis because of inappropriate trial design and analysis.

METHODS

In a previously reported randomized trial, anistreplase (30 U) was given intravenously either before hospital admission or in the hospital, at a median time of 105 and 240 min, respectively, after onset of symptoms. Intention to treat and multivariate analyses of the 5-year results were performed.

RESULTS

By 5 years, 41 (25%) of 163 patients had died in the prehospital treatment group compared with 53 (36%) of 148 in the hospital treatment group (log-rank test, p < 0.025). Delaying thrombolytic treatment by 1 h increases the hazard ratio of death by 20%, equivalent to the loss of 43/1,000 lives within the next 5 years (95% confidence interval 7 to 88, p = 0.012). Delaying thrombolytic treatment by 30 min reduces the average expectation of life by approximately 1 year.

CONCLUSIONS

The magnitude of the benefit from earlier thrombolysis is such that giving thrombolytic therapy to patients with acute myocardial infarction should be accorded the same degree of urgency as treatment of cardiac arrest. Policies should be developed for giving thrombolytic therapy on-site if practicable and by the first qualified person to see the patient.

Prognostic value of thrombolysis, coronary artery patency, signal-averaged electrocardiography, left ventricular ejection fraction, and Holter electrocardiographic monitoring for life-threatening ventricular arrhythmias after a first acute myocardial infarction

Prognostic studies after acute myocardial infarction (AMI) have mainly been performed in the prethrombolytic era. Despite the fact that modern management of AMI has reduced mortality rates, the occurrence of malignant ventricular arrhythmias in the late phase of AMI remains an important issue. We prospectively studied 244 consecutive patients (97 treated with thrombolytics) who survived a first AMI. All patients underwent time domain signal-averaged electrocardiography (vector magnitude: measurements of total QRS duration, terminal low [<40 microV] amplitude signal duration, and root-mean-square voltage of the last 40 ms of the QRS complex), Holter electrocardiographic monitoring, and cardiac catheterization. Late life-threatening ventricular arrhythmias were recorded. Eighteen arrhythmic events occurred during a mean follow-up period of 57 +/- 18 months. Three independent factors were associated with a higher risk of arrhythmic events: (1) left ventricular ejection fraction (odds ratio 1.9/0.10 decrease), (2) terminal low-amplitude signal duration (odds ratio 1.5/5 ms increase), and (3) absence of thrombolytic therapy (odds ratio 3.9). Low-amplitude signal duration sensitivity for sudden cardiac death was low (30%). Left ventricular ejection fraction had the highest positive predictive value for sudden cardiac death (10%). Thus, thrombolysis decreases both the incidence of ventricular tachycardia and sudden cardiac death with a higher reopening rate of the infarct-related vessel. Signal averaging predicts the occurrence of ventricular tachycardia and an impaired left ventricular ejection fraction predicts the occurrence of sudden cardiac death.

Risk of ventricular arrhythmias in survivors of myocardial infarction

The most recent studies have made it clear that the prognosis of asymptomatic post-MI patients has significantly improved in the last two decades. Holter monitoring as well as a low LVEF still is an important method for the risk stratification in the thrombolytic era of patients with post-MI. Patients with normal noninvasive tests do have a good prognosis. The electrophysiological stimulation seems to be the clinically most valuable single method to predict arrhythmic events. However, as an invasive procedure it is not suitable as a screening test for a large cohort. The stepwise risk stratification technique using first noninvasive followed by invasive procedures seem to be most suitable and effective for identifying asymptomatic infarct survivors which incidence of arrhythmic events is as high as the recurrence rate of patients who had been resuscitated from ventricular fibrillation. Consequently, prophylactic implantation of a defibrillator in asymptomatic MI patients, whose positive predictive value is around 30% becomes more and more interesting.

Prediction of arrhythmia risk based on signal-averaged ECG in postinfarction patients

In patients surviving acute MI, identification of those at high risk for life-threatening ventricular tachyarrhythmias and/or sudden death is of great importance. Numerous strategies based on indices such as the degree of left ventricular dysfunction, complex ventricular arrhythmias, or parameters of autonomic dysfunction have not yet led to an effective identification of the individual patient at risk. During the past decade, many investigators have recorded low amplitude, high frequency components in the terminal QRS complex (so-called late potentials) from patients prone to sustained ventricular tachycardia. The SAECG has been used to predict life-threatening tachyarrhythmias in patients after acute MI and to screen for inducible ventricular tachycardia in patients with unexplained syncope or sustained ventricular tachycardia. This review article describes the most frequently applied methodology and clinical applications of the SAECG in post-MI patients and discusses the usefulness of noninvasive recordings in various other clinical settings.

Prognostic value of clinical markers of reperfusion in patients with acute myocardial infarction treated by thrombolytic therapy

Patients who cannot be reperfused after thrombolytic therapy have a high mortality rate. Noninvasive clinical markers of reperfusion have been widely studied, yet their prognostic significance remains unclear. To assess the prognostic value of commonly used noninvasive clinical markers of early reperfusion we studied 327 patients who received intravenous thrombolytic treatment (1.5 MU streptokinase in 1 hour or 100 mg alteplase in 3 hours) within 6 hours of acute infarction. Successful clinical reperfusion (SCR) was defined as the presence of at least two of the following criteria at 2 hours after thrombolytic treatment: (1) significant relief of pain (a 5-point reduction on a 1 to 10 subjective scale), (2) > or =50% reduction of sum of ST segment elevation, and (3) abrupt initial increase of creatine kinase levels (more than twofold over the upper-normal or baseline elevated values). Clinical variables that were significantly associated by univariate analysis were tested by multivariate analysis to obtain independent predictors of 30-day mortality rate. SCR was present in 210 (64%) patients (group 1), and absent in 117 (36%) patients (group 2). The groups were similar for most baseline characteristics, although group 2 patients were slightly older (mean 60 vs 57 years, p < 0.02). Thirty-day outcomes for group 2 patients compared with group 1 patients were heart failure in 23.1% and 10.5% (p < 0.005), progression to cardiogenic shock in 12.8% and 0.5%, (p < 0.00001), and death in 16.2% and 3.8% (p < 0.0001), respectively. By multivariate analysis the Killip class at admission (p < 0.00001), the absence of SCR (p = 0.017), anterior infarct location (p = 0.021), and age (p = 0.03) were independent predictors of mortality rate, and sex (p = 0.051) had borderline significance. The absence of SCR defined a group of patients with significantly higher mortality rate (odds ratio 4.89, 95% confidence interval 2.07 to 11.57). Three simple noninvasive clinical criteria of successful reperfusion may be used to identify a group of patients with poor prognosis after thrombolytic therapy in whom alternative strategies could be applied.

Evolution of late potential parameters in thrombolyzed acute myocardial infarction might predict patency of the infarct-related artery

The objective was to predict the patency grade of an infarct-related artery by identifying the time course of the changes of the late potential parameters before, during, and shortly after thrombolysis. The study population consisted of 51 patients with acute myocardial infarction (AMI) who received thrombolytic therapy within 3.2 +/- 1.3 hours from the onset of symptoms. Multiple signal-averaged electrocardiograms (SAECGs) were recorded before, during, and shortly after thrombolysis. A total of 489 single-averaged electrocardiographic tracings were evaluated. Late potentials were defined as: QRS duration > 114 ms, low amplitude signals (LASs) > 38 ms, and root mean square (RMS) < 20 microV. Late potentials were found in 37% of patients (21 before and 16 during the first 2 hours of thrombolysis), disappeared in all of patients within 89 +/- 75 minutes (range 25 to 350) but reappeared and persisted in 12% of patients, all with an occluded artery (grade 0). The late potential parameters (QRS, LAS, RMS) showed a gradual improvement which occurred earlier (2 vs 4 hours) and was more marked (0.01 vs 0.05) in cases with a patent artery. This improvement expressed by the late potential parameter index (LnQRS + LnLAS - LnRMS) predicts the patent artery with a sensitivity of 0.94 and specificity of 0.79. The improvement of late potential parameters jointly with close to normal initial values or the late potential parameter index and its changes constituted a satisfactory prediction of the patency grade. Thus, the signal-averaged electrocardiographic technique is capable of predicting the early success or failure of thrombolytic therapy.

Determinants of the natural course of ventricular late potentials after thrombolytic therapy for acute myocardial infarction

The intraindividual changes of ventricular late potentials and their possible determinants were examined prospectively in 88 consecutive patients (male: 75; mean age: 58 +/- 9 years) after thrombolytic therapy for acute myocardial infarction. Late potential analysis was performed 4 weeks and 12 months after acute myocardial infarction. At the same time, a left heart catheterization was performed to assess the extent of coronary heart disease and left ventricular ejection fraction. The incidence of late potential 4 weeks after acute myocardial infarction was 15% (13/88 patients). Eighteen percent (16/88) of the patients revealed changing results of late potential analysis: 9 patients lost late potential (late potential pos./neg.) 1 year after acute myocardial infarction and 7 patients presented new formation of late potential (late potential neg./pos.). Preserved late potentials were found in four patients (late potential pos./pos.). Late potential analysis remained negative in 68 patients (late potential neg./neg.). There was no influence of age, gender, site of infarction, clinical course, and medical treatment on the natural course of late potential. Changing results of late potential analysis seemed to be correlated with the evolution of left ventricular ejection fraction and the dynamics of coronary heart disease. In the group late potential pos./pos., comparable values for left ventricular ejection fraction were measured at both examinations, whereas late potential neg./neg. had a significant increase in ejection fraction. In the group late potential pos./neg., a significant improvement in left ventricular function was also measured. In contrast, the late potential neg./pos. group tended to have lower left ventricular ejection fractions 1 year after infarction. In the late potential neg./pos. and late potential pos./pos. groups, the extent of coronary artery disease returned to conditions comparable to baseline despite an initial reduction after coronary revascularization performed 4 weeks after infarction. Late potential neg./neg. and late potential pos./neg. revealed a stable benefit gained from coronary revascularization with a persistent reduction in the number of diseased vessels. Dynamic changes in the results of the signal-averaged ECG 1 year after thrombolytic therapy for acute myocardial infarction were observed in 18% of the patients. These changes seem to be correlated with the evolution of left ventricular function and the dynamics of coronary artery disease.

Evolution of late potentials during the first 8 hours of myocardial infarction treated with thrombolysis

It has been demonstrated that successful thrombolytic therapy is associated with a reduction of late potentials in the signal-averaged electrocardiogram (SAECG) recorded within 48 hours after hospital admission. This study extends these observations, using for the first time a longitudinal design investigating whether ischemia and its potential reversal by thrombolytic therapy are associated with dynamic changes in SAECG recordings obtained continuously for 8 hours after the start of therapy in patients with acute myocardial infarction (MI). SAECGs were obtained from 12 patients (2 women and 10 men; ages 63 +/- 13 years) with acute MI. The SAECG (X2 + Y2 + Z2)1/2 was generated with a high pass filter of 40 Hz, noise < or = 0.3 microV. Comparing the SAECG recordings during the first and eighth hours, there was a significant decrease in filtered QRS duration (fQRS; 119.5 +/- 17.1 vs 106.3 +/- 15.3 ms) and duration of the low amplitude signals < or = 40 microV of the terminal QRS (LAS40; 48.8 +/- 18 vs 34.2 +/- 14.2 ms), and increase of root mean square voltage of the last 40 ms of the QRS (t-RMS; 14.8 +/- 9.3 vs 37.8 +/- 34.4 microV) (rank test, P < or = 0.05). In this patient series, there was a significant improvement of fQRS, t-RMS, and LAS40 during the first 8 hours of acute MI, perhaps indicating reversal of ischemia with thrombolysis. Even during acute MI, these markers of delayed conduction allow investigation of intervention induced changes in myocardial conduction and possibly prediction of the patency of the infarct related artery using signal-averaging techniques.

Aortic counterpulsation may improve late patency of the occluded coronary artery in patients with early failure of thrombolytic therapy

OBJECTIVES

Using a prospective, randomized design, we tested our hypothesis that the augmentation of diastolic pressure by intraaortic balloon counterpulsation (IABP) would improve the late patency of the occluded coronary artery in patients with early failure of thrombolytic therapy.

BACKGROUND

Rescue angioplasty is often performed in patients in whom thrombolysis has failed, although 30% to 60% of the infarct-related arteries that are closed early after thrombolytic therapy will open later with conservative therapy.

METHODS

The study included 45 patients in whom thrombolysis had failed, despite treatment with intravenous tissue-type plasminogen activator (alteplase 0.75 mg/kg body weight) delivered over 60 min within 12 h of the onset of symptoms. All patients underwent coronary angiography 60 min after initiation of thrombolytic therapy (baseline), and Thrombolysis in Myocardial Infarction (TIMI) grade 0, 1 or 2 flow was defined as failed thrombolysis. The patients were randomized to groups receiving IABP for 48 h (n = 23) or conservative therapy (n = 22, control subjects) at the end of cardiac catheterization. The late patency of the infarct-related artery, the primary end point of the study, was evaluated 3 weeks after myocardial infarction. Stenosis of the infarct-related artery was measured using a computer-assisted quantitative angiographic system in blinded manner. Data are expressed as mean value +/- SEM.

RESULTS

There was no difference with regard to the baseline value for TIMI flow grade between the groups. However, 3 weeks after myocardial infarction, the patients treated with IABP had a significantly higher frequency of TIMI flow grade 3, lower residual percent stenosis and larger minimal lumen diameter of the infarct-related artery than did the control subjects (74% vs. 32%, p < 0.05; 42 +/- 5% vs. 68 +/- 6%, p < 0.01; and 1.6 +/- 0.1 vs. 0.9 +/- 0.2 mm, p < 0.01, respectively).

CONCLUSIONS

These findings suggest that in patients with early failure of thrombolytic therapy, IABP may improve late patency of the occluded coronary artery, probably due to augmented perfusion pressure.

The signal-averaged electrocardiogram: update on clinical applications

The signal-averaged electrocardiogram (SAECG) facilitates noninvasive recording of low-amplitude cardiac signals such as ventricular late potentials. The SAECG has been used to accurately predict life-threatening ventricular tachyarrhythmias in patients after acute myocardial infarction and with nonischemic dilated cardiomyopathy, and to screen for inducible ventricular tachycardia in patients with unexplained syncope and with nonsustained ventricular tachycardia. This review focuses on currently accepted methodology and clinical and research applications of the SAECG.

Relationship between late potentials and the predischarge electrocardiographic pattern in patients with acute anterior wall myocardial infarction

HYPOTHESIS

The presence of late potentials on the signal-averaged electrocardiogram (SAECG) identifies patients at high risk for development of ventricular tachyarrhythmias after myocardial infarction (MI).

METHODS

The electrocardiogram and left ventricular function in 65 patients recovering from a first acute anterior wall MI were analyzed. We compared the pattern of the ST segment (isoelectric or elevated) and of the T wave (positive or negative) with the SAECG using an orthogonal bipolar lead configuration (X, Y, Z) with bidirectional Butterworth filtering (Simson's method).

RESULTS

Abnormal SAECG was found in 17 (26%) patients; 11 of 18 patients with ST elevation had abnormal SAECG, and only 6 of 47 patients with isoelectric ST segment developed abnormal SAECG (p < 0.0001, odds ratio = 10.74). Of 19 patients with positive T waves, 10 had abnormal SAECG, and abnormal SAECG was found in 7 of 46 patients with negative T waves (p < 0.003, odds ratio = 5.27). When both parameters were considered together, 9 of 12 patients with ST elevation and positive T wave developed abnormal SAECG, and 35 of 40 patients with isoelectric ST and negative T wave had normal SAECG (p < 0.0002). Left ventricular ejection fraction was similar in patients with abnormal SAECG (43 +/- 14%) and normal SAECG (46 +/- 11%).

CONCLUSION

These findings suggest that patients with anterior wall MI and a predischarge pattern of ST elevation and positive T wave have a higher incidence of abnormal SAECG and therefore may have a worse prognosis, especially related to the subsequent development of ventricular arrhythmias.

Importance of infarct-related artery patency for recovery of left ventricular function and late survival after primary angioplasty for acute myocardial infarction

OBJECTIVES

The purpose of this study was to evaluate the importance of late infarct-related artery patency for recovery of left ventricular function and late survival after primary angio-plasty for acute myocardial infarction.

BACKGROUND

Infarct-related artery patency is thought to improve late survival by its effect on preservation of left ventricular function. Patency may also enhance late survival by preventing left ventricular dilation and reducing arrhythmias, independent of myocardial salvage. However, most studies have not shown patency to be an independent predictor of survival when late left ventricular function is taken into account.

METHODS

We followed up 576 hospital survivors of acute myocardial infarction treated with primary angioplasty for 5.3 years. Ejection fraction and infarct-related artery patency were determined at follow-up catheterization at 6 months. Predictors of late cardiac survival were determined using Cox regression models.

RESULTS

Patients with patent arteries had more improvement and a better late ejection fraction than patients with occluded arteries (56.3% vs. 47.9%, p = 0.001). In patients with acute ejection fraction < 45%, late survival was better in those with patent versus occluded arteries (89% vs. 44%, p = 0.003), but patency was not a significant predictor after improvement in ejection fraction was taken into account. In patients with a large anterior infarction, patency was a significant independent predictor of late survival.

CONCLUSIONS

Infarct-related artery patency is important for recovery of left ventricular function, and in patients with acute ejection fraction < 45%, patency is important for late survival. Our data are consistent with the hypothesis that the survival benefit is due primarily to the effect of patency on recovery of left ventricular function. In patients with a large anterior infarction, patency appears to provide an additional late survival benefit independent of myocardial salvage. These observations support the need for additional clinical trials of late reperfusion in patients with a large anterior infarction.

Effects of reperfusion after thrombolysis for myocardial infarction on the signal-averaged electrocardiogram

Patients with early reperfusion after thrombolysis for acute myocardial infarction revealed a significantly reduced incidence of ventricular late potentials in the signal-averaged electrocardiogram obtained in the chronic post-infarction period in comparison to patients who did not meet the criteria for early successful thrombolysis (14 vs. 39%; P < 0.05). This data demonstrates that early reperfusion might prevent the development of an abnormal electrophysiological milieu after myocardial infarction.

Signal-averaged ECG prior to and serially after thrombolytic therapy for acute myocardial infarction

Signal averaging has been performed to evaluate late potentials following infarction and the administration of thrombolytic therapy. Most studies have recorded signal-averaged electrocardiograms (SAECGs) at least 12 hours after the onset of the infarction. In this study, SAECGs were recorded before thrombolytic therapy and serially over 7-10 days following infarction in 21 patients. The high frequency QRS duration was significantly shortened at 1 and 24 hours compared to presentation (96.8 +/- 11.3 ms and 93.4 +/- 8.0 ms vs 103.3 +/- 14.3 ms, respectively, P < 0.05) and there was an increase in the terminal voltage over time, significant at 1 hour and 3 days (57.3 +/- 29.1 microV and 58.6 +/- 44.7 microV vs 44.4 +/- 35.5 microV, respectively, P < 0.01). Five patients met criteria for ventricular late potentials on at least one SAECG. The prevalence of late potentials was higher in patients with Q wave infarctions, or with occluded infarct related arteries. These changes in myocardial activation may be related to ischemia and reperfusion, and may not correlate with the development of a fixed substrate for reentry.

Post-myocardial infarction trials: beta blockers, antiarrhythmics, thrombolytics

This paper reviews trials of postmyocardial infarction therapies including beta adrenergic blockers, antiarrhythmic agents other than amiodarone, and thrombolytic drugs. The results of certain beta blockers on overall cardiovascular mortality and sudden death mortality after myocardial infarction are discussed, along with the results of CAST and subgroup analyses on patients at high risk for death. The effects of thrombolysis during acute myocardial infarction on subsequent arrhythmic mortality are also reviewed.

Decreased prevalence of late potentials with mechanical versus thrombolysis-induced reperfusion in acute myocardial infarction

OBJECTIVES

We sought to evaluate the influence of the method used to achieve early coronary reperfusion (i.e., intravenous thrombolysis or percutaneous transluminal coronary angioplasty) on the prevalence of late potentials after acute myocardial infarction.

BACKGROUND

After myocardial infarction, late potentials are associated with an increased risk of ventricular tachyarrhythmia and sudden death. Although their prevalence is lower in patients with coronary reperfusion, the influence of the method used to achieve reperfusion remains debated.

METHODS

We retrospectively analyzed 109 patients with acute myocardial infarction who were treated within 6 h of symptom onset and had angiographically proved early reperfusion. A signal-averaged electrocardiogram was recorded > or = 5 days after infarction.

RESULTS

Reperfusion was successfully achieved by intravenous thrombolysis alone in 37 patients (34%), by "rescue" coronary angioplasty in 26 (24%) and by primary angioplasty in 46 (42%). There was no significant difference between groups in terms of gender ratio, infarct location, time to admission or to reperfusion, peak creatine kinase value or left ventricular ejection fraction. The prevalence of late potentials was similar in the two groups in which patency was achieved by primary and rescue coronary angioplasty (17.4% and 7.7%, respectively [p=NS]) but higher in patients who had successful thrombolysis (35.1%, p < 0.05). Multivariate analysis showed that the use of thrombolysis instead of angioplasty as the reperfusion method was the only variable significantly associated with the presence of late potentials.

CONCLUSION

This study suggests that after acute myocardial infarction the prevalence of late potentials is lower when reperfusion is achieved by angioplasty (either primary or as a rescue procedure after failed thrombolysis) than by thrombolysis.