Importance of myocardial infarct artery patency on the prevalence of ventricular arrhythmia and late potentials after thrombolysis in acute myocardial infarction

Predictors of ventricular tachyarrhythmia in high-risk myocardial infarction patients treated with primary coronary intervention

Background. We investigated the association between clinical characteristics, angiographic data and ventricular arrhythmia in patients with ST-elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI)Methods. In patients with STEMI (n=225), a Holter analysis was performed the first 12 hours after primary PCI.Results. A total of 151 (66%) patients had >/=1 episode of ventricular tachycardia (VT). Age <70 years (RR 4.9, 95% CI 1.8 to 12.7), TIMI 0-1 pre-PCI (RR 2.6, 95% CI 1.1 to 6.1) and peak CK (RR 3.5, 95% CI 1.9 to 5.8) were independent predictors of VT. One-year mortality was 7%, no association between mortality and presence of early VT was found.Conclusion. Ventricular tachycardia is common in the first 12 hours after primary PCI for STEMI. Independent predictors of VT are younger age, TIMI 0-1 flow prior to PCI and larger infarct size. The presence of early VT was not significantly associated with one-year mortality. (Neth Heart J 2010;18:122-8.).

The antiarrhythmic effect and clinical consequences of ischemic preconditioning

Potentially hazardous short ischemic episodes increase the tolerance of myocardium to ischemia paradoxically. This condition decreases the infarct area markedly caused by a longer duration of coronary occlusion. This phenomenon is known as 'ischemic preconditioning' and its powerful cardioprotective effect has been shown in experimental and clinical studies. Ischemic preconditioning decreases cardiac mortality markedly by preventing the development of left ventricular dysfunction and ventricular and supraventricular arrhythmias after acute myocardial infarction. Ischemia-induced opening of ATP-sensitive potassium channels and synthesis of stress proteins via activation of adenosine, bradykinin and prostaglandin receptors seem to be the possible mechanisms. By understanding the underlying mechanisms of ischemic preconditioning, it may be possible to develop new pharmacologic agents that cause ischemic preconditioning with antiischemic and antiarrhythmic properties without causing myocardial ischemia.

[Effects of reperfusion on late potentials of the QRS complex in acute myocardial infarction]

INTRODUCTION

Cardiac rhythm disorders are common in patients after myocardial infarction. They play an important role in the course and in prognosis of this illness. Signal-averaged electrocardiogram (SAECG) is a non-invasive diagnostic method for the induction of sustained monomorphic ventricular tachycardia. Early opening of the infarct-related artery decreases occurrence of ventricular disorders in these patients. The aim of this study was to establish the connection between the late potentials of the QRS complex (SAECG) and unsuccessful reperfusion in patients with acute myocardial infarction (AMI).

MATERIAL AND METHODS

After myocardial infarction, presence of SAECG was examined in patients receiving reperfusion therapy in order to establish the treatment outcome. Late potentials in SAECG were determined by computer measurements in regard to criteria for its positivity.

RESULTS

The study group consisted of 33 patients. Out of 23 patients with successful reperfusion, only 6 (26.1%) had late potentials, in contrast to the group without reperfusion, 8 (80%) out of 10 patients had late potentials.

CONCLUSION

Based on our results, we can conclude that there is a significant association between the presence of late ORS-complex potentials (SAECG) and unsuccessful reperfusion. Also, we can conclude that presence of late potentials is an independent predictor of infarct-related artery patency in patients with AMI treated with thrombolytic therapy.

Impacto de la angioplastia primaria en la indicación de desfibrilador implantable en pacientes con infarto de miocardio

INTRODUCTION AND OBJECTIVES

Implantable cardiac defibrillators (ICD) have been shown to improve survival in patients with myocardial infarctionand LVEF < 0.30 or LVEF < 0.40 + nonsustained ventricular tachycardia + inducible sustained arrhythmias. However, these risk stratification criteria have not been evaluated in patients who are candidates for primary percutaneous transluminal coronary angioplasty (PTCA). The objective of this study was to assess the impact of both strategies on the indication for ICD in a consecutive series of post-infarction patients treated with primary PTCA.

PATIENTS AND METHOD

One hundred and two consecutive patients with myocardial infarction (80 men, mean age 63.6 11.5 years) included in a single-center-based regional program of primary PTCA were included in the study. A 24-h continuous ECG recording was obtained 2 to 6 weeks after the acute event, and LVEF was determined by 2D-echocardiography one month after the infarct. Patients with nonsustained ventricular tachycardia and LVEF < 0.40 underwent programmed ventricular stimulation using a standard protocol.

RESULTS

Twenty-two patients (21.6%; 95% CI, 13.6-29.6) showed at least one episode of nonsustained ventricular tachycardia in the 24 h recording. Six of them had LVEF < or = 0.40, and sustained ventricular arrhythmia was induced in 2 out of 5. LVEF < or = 0.30 was found in 3 patients, none of whom had nonsustained ventricular tachycardia. Thus, 5 patients had an indication for ICD according to either of the two risk stratification criteria.

CONCLUSIONS

The prevalence of nonsustained ventricular tachycardia in post-infarction patients treated with primary PTCA is high. However, because most of them have preserved ventricular function, primary prevention with an ICD is indicated in approximately 5% of the population.

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.

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).

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.

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.

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.

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.

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.

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.

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.

Open infarct artery, late potentials, and other prognostic factors in patients after acute myocardial infarction in the thrombolytic era. A prospective trial

BACKGROUND

Successful reperfusion of the infarct-related artery in patients with acute myocardial infarction has been shown to reduce in-hospital as well as 1-year mortality. Besides the thrombolysis-induced myocardial salvage, there is increasing evidence that an open infarct-related artery results in increased electrical stability of the heart and that this effect is at least in part responsible for the favorable long-term outcome of these patients. The exact incidence of arrhythmic events during the first year after myocardial infarction and the predictive value of different risk factors for these complications, however, have not been determined in patients in the thrombolytic era.

METHODS AND RESULTS

A total of 173 patients with acute myocardial infarction, 51% treated with thrombolysis, were prospectively entered into the study. At the time of hospital discharge, signal-averaged ECG, Holter monitoring, radionuclide angiography, coronary angiography, and levocardiography were performed in all patients. An open infarct-related artery was documented in 136 patients. The overall incidence of late potentials was 24% (41 patients). By multivariate analysis, an occluded infarct-related artery (P = .04) and the presence of regional wall motion abnormalities (P = .02) were the strongest independent predictors for the development of a late potential. Residual ischemia was treated by either percutaneous transluminal coronary angioplasty or surgery in 86 of 173 patients (50%). Seventy percent of the patients received beta-blocker therapy. During a mean follow-up of 12 +/- 5 months, 7 patients died suddenly or had ventricular fibrillation documented, while only 2 developed sustained monomorphic ventricular tachycardia. Overall 1-year mortality was 4.1%. Multivariate analysis revealed only an occluded infarct-related artery as an independent predictor of arrhythmic complications (P = .017).

CONCLUSIONS

In patients with acute myocardial infarction treated according to contemporary therapeutic guidelines, with a large proportion of individuals undergoing coronary artery revascularization, a low incidence of arrhythmic events, particularly of ventricular tachycardia, was observed in the first year after the index infarction. The presence or absence of an open infarct-related artery was the strongest independent predictor of these events, whereas other traditional risk factors, such as late potentials, were less helpful in identifying patients prone to sudden death. These findings emphasize the importance of the open artery hypothesis in patients recovering from acute myocardial infarction.

Should every patient undergo cardiac catheterization after myocardial infarction?

During the past few decades, management of patients with myocardial infarction has dramatically evolved. High-risk patients are now identified by a variety of noninvasive tests, and aggressive use of reperfusion strategies has improved clinical outcomes. Despite the benefits of reperfusion, only a few patients are eligible to receive thrombolytic therapy. Mortality rates among patients excluded from thrombolytic trials (15% to 20%) have been far greater than those eligible for treatment (3% to 10%). Because most deaths occur within the first few days of infarction, interventions designed to reduce mortality should be performed acutely. Immediate catheterization allows identification of high-risk anatomy that may benefit from surgery and allows coronary angioplasty to be performed as a reperfusion strategy (when appropriate). Furthermore, catheterization allows documentation of ejection fraction, vessel patency, number of diseased vessels, and residual stenosis, all of which have been predictive of prognosis. Conversely, frequently repeated noninvasive diagnostic tests are associated with increased cost, are generally performed in low-risk patients, and 60% to 80% of patients with myocardial infarction ultimately require catheterization anyway. It is possible that early catheterization and percutaneous transluminal coronary angioplasty when indicated may effectively risk stratify patients (eliminating the need for noninvasive testing), may reduce morbidity and mortality, and shorten the length of hospital stay.

Effects of thrombolytic therapy administered 6 to 24 hours after myocardial infarction on the signal-averaged ECG. Results of a multicenter randomized trial. LATE Ancillary Study Investigators. Late Assessment of Thrombolytic Efficacy

BACKGROUND

Thrombolytic therapy reduces mortality after acute myocardial infarction, even when treatment is initiated relatively late after onset of symptoms. The mechanism underlying this survival benefit is incompletely understood.

METHODS AND RESULTS

In a prospectively designed ancillary study of a randomized, placebo-controlled trial of late thrombolytic therapy (LATE), the signal-averaged (SA) ECG was recorded before hospital discharge in an effort to assess the effect of thrombolytic therapy on arrhythmia substrate. Three hundred ten patients were enrolled at 23 participating sites; 160 patients received placebo, and 150 patients received recombinant tissue-type plasminogen activator (rTPA) therapy 6 to 24 hours after onset of symptoms. Compared with placebo, rTPA tended to reduce the frequency of SAECG abnormality (filtered QRS duration > 120 milliseconds) by 37% (95% CI, -64%, +6%; P = .087) and the filtered QRS duration (105.7 +/- 13.8 versus 108.8 +/- 14.6 milliseconds, P = .05). In the prespecified subgroup of 185 patients with ST elevation on the qualifying ECG, rTPA resulted in a 52% reduction (95% CI, 4% to 77%, P = .011) of SAECG abnormality and a shorter filtered QRS duration (105.7 +/- 10.9 versus 110.7 +/- 15.9 milliseconds, P = .01). No benefit was seen in patients without ST elevation on ECG.

CONCLUSIONS

Late thrombolytic therapy produced a more stable electrical substrate, which probably represents an important mechanism of mortality benefit.

Effects of thrombolysis and atenolol or metoprolol on the signal-averaged electrocardiogram after acute myocardial infarction. Late Potentials Italian Study (LAPIS)

Late potentials (LPs) detected on the signal-averaged (SA) electrocardiogram (ECG) predict arrhythmic events after acute myocardial infarction (AMI). The effect of thrombolysis on the incidence of LPs after AMI is controversial and its impact on subsequent arrhythmic events is not known. Moreover, the effects of beta blockers on the SAECG have not been studied. Six hundred eighteen patients with AMI were studied; thrombolysis was given to 228 (37%). In comparison with patients treated conventionally, those receiving thrombolysis were significantly younger and more frequently male, had higher peak values of creatine kinase, a lower prevalence of non-Q-wave AMI, and a higher incidence of ventricular fibrillation in the acute phase, and more frequently received beta blockers. An SAECG obtained 6 to 8 days after AMI showed LPs in 24% of patients receiving and in 25% not receiving thrombolysis (p = NS). On admission, intravenous beta blockers were administered to 110 patients (18%); those receiving beta blockers were younger, had lower peak values of creatine kinase and more frequently received thrombolysis. LPs were less frequently found in patients treated than in those not treated with beta blockers (15 vs 27%; p = 0.007); however, this effect was found only in those with an ejection fraction > or = 40%. Independent predictors of LPs by multivariate analysis were an ejection fraction < 40% (p = 0.007), ventricular fibrillation in the acute phase (p = 0.02), and absence of beta-blocking therapy (p = 0.03). During a mean follow-up of 12 +/- 7 months, there were 39 cardiac deaths (6%), 13 of which were sudden (2%), and 9 sustained ventricular tachycardias.(ABSTRACT TRUNCATED AT 250 WORDS)

Continuous 12-lead ST-segment recovery analysis in the TAMI 7 study. Performance of a noninvasive method for real-time detection of failed myocardial reperfusion

BACKGROUND

If a practical, reliable, noninvasive marker of failed reperfusion was available in real time, the benefits of further therapy in this patient subgroup could be tested. We developed a method of 12-lead ST-segment recovery analysis using continuously updated reference points to provide such a marker.

METHODS AND RESULTS

In this study, our method was prospectively tested in 144 patients given thrombolytic therapy early in myocardial infarction. All patients had 12-lead continuous ST-segment monitoring and acute angiography, each analyzed in an independent, blinded core laboratory. ST-segment recovery and re-elevation were analyzed up to the moment of angiography, at which time patency was predicted. Predictions were correlated to angiographic infarct artery flow, with TIMI flow 0 to 1 as occluded and TIMI flow 2 to 3 as patent. Infarct artery occlusion was seen on first injection in 27% of patients. The positive predictive value of incomplete ST recovery or ST re-elevation by our method was 71%, negative predictive value 87%, with 90% specificity and 64% sensitivity for coronary occlusion. ST recovery analysis predicted patency in 94% of patients with TIMI 3 flow versus 81% of patients with TIMI 2 flow and predicted occlusion in 57% of patients with collateralized occlusion versus 72% of patients with non-collateralized occlusion. In a regression model including other noninvasive clinical descriptors, ST recovery alone contained the vast majority of predictive information about patency.

CONCLUSIONS

In a blinded, prospective, angiographically correlated study design, 12-lead continuous ST-segment recovery analysis shows promise as a practical noninvasive marker of failed reperfusion that may contribute substantially to currently available bedside assessment. Our data also suggest that patients with TIMI 2 flow or with collateralized occlusions may represent a physiological spectrum definable with ST-segment recovery analysis.

Effects on the signal-averaged electrocardiogram of opening the coronary artery by thrombolytic therapy or percutaneous transluminal coronary angioplasty during acute myocardial infarction

One hundred twenty-nine patients were retrospectively analyzed and divided into 3 groups according to (1) the presence of a patent artery obtained either spontaneously or after thrombolytic therapy but without percutaneous transluminal coronary angioplasty (PTCA) (group I, n = 83), (2) the presence of a patent artery after opening by PTCA (group II, n = 29), or (3) absence of reperfusion despite thrombolytic therapy or PTCA (group III, n = 17). Thrombolytic therapy was given within 4 hours after onset of symptoms (mean 2.5 +/- 1.0 hours) and PTCA was performed within 24 hours after the onset of symptoms (mean 6 +/- 6 hours). Signal averaging was performed within 24 hours after cardiac catheterization. An abnormal signal-averaged electrocardiogram was present in 10 of 83 (12%) group I, 9 of 29 (31%) group II and 7 of 17 (41%) group III patients (p < 0.05 group I vs II, p < 0.01 group I vs III, no statistical difference group II vs III). Therefore, in contrast to reperfusion by thrombolytic therapy the incidence of abnormalities on the signal-averaged electrocardiogram early after myocardial infarction is not reduced by an early opening of the culprit vessel by PTCA.

Infarct artery patency predicts outcome of serial electropharmacological studies in patients with malignant ventricular tachyarrhythmias

BACKGROUND

Surviving myocardial cells near the infarct border zone form the arrhythmogenic substrate for sustained ventricular tachycardia (VT) in humans. Infarct-related artery (IRA) patency may modulate the electrophysiological function of this arrhythmogenic substrate and its response to antiarrhythmic drug therapy. We postulated that effective antiarrhythmic drug therapy selected during serial electrophysiological studies in patients with VT after a myocardial infarction would be identified more frequently when the IRA is patent than when chronically occluded.

METHODS AND RESULTS

Consecutive patients (n = 64) with documented coronary artery disease and remote myocardial infarction presenting with spontaneous sustained VT or ventricular fibrillation (VF) were studied. These patients underwent 4 +/- 2 electropharmacological studies identifying effective antiarrhythmic drug therapy in 16 (25%) patients. Drug responders did not differ significantly from nonresponders in demographic, electrocardiographic, angiographic, or hemodynamic measurements. A patent IRA was associated with antiarrhythmic drug response significantly more frequently than was an occluded IRA (45% versus 9%, p = 0.001). Patency of the IRA was the only independent predictor of response to antiarrhythmic drug therapy in this study population. The sensitivity and specificity of using a patent IRA to predict successful drug testing were 81% and 67%, respectively.

CONCLUSIONS

The outcome of electropharmacological studies was predicted by the patency of the IRA. A patent IRA was associated with a greater probability of finding effective drug therapy.