Sudden cardiac death following acute myocardial infarction

Myocardial Viability on Cardiac Magnetic Resonance

The study of myocardial viability is of great importance in the orientation and management of patients requiring myocardial revascularization or angioplasty. The technique of delayed enhancement (DE) is accurate and has transformed the study of viability into an easy test, not only for the detection of fibrosis but also as a binary test detecting what is viable or not. On DE, fibrosis equal to or greater than 50% of the segmental area is considered as non-viable, whereas that below 50% is considered viable. During the same evaluation, cardiac magnetic resonance (CMR) may also use other techniques for functional and perfusion studies to obtain a global evaluation of ischemic heart disease. This study aims to highlight the current concepts and broadly emphasize the use of CMR as a method that over the last 20 years has become a reference in the detection of infarction and assessment of myocardial viability. Resumo O estudo de viabilidade miocárdica é de grande importância para a orientação e manejo de pacientes que necessitam de cirurgia de revascularização miocárdica ou angioplastia. A técnica de realce tardio (RT) é precisa e transformou o estudo de viabilidade em um teste fácil, não só para a detecção de fibrose, mas também como um modelo binário para a detecção do que é ou não é viável. Uma fibrose identificada pelo RT é considerada como não viável quando igual ou maior do que 50% da área segmentar e como viável quando menor que 50%. A ressonância magnética cardíaca (RMC) também pode lançar mão de outras técnicas para estudo funcional e de perfusão para uma avaliação global da doença isquêmica do coração no mesmo exame. Este estudo tem como objetivo destacar os conceitos atuais e enfatizar amplamente o uso da RMC como um método que nos últimos 20 anos se tornou referência na detecção de infarto e avaliação de viabilidade miocárdica.

Sudden cardiac death with left main coronary artery occlusion in a patient whose presenting ECG suggested Brugada syndrome

This article describes a patient who died suddenly during Holter ECG monitoring. A ventricular premature systole with an extremely short coupling interval of 240 ms was immediately followed by torsades de pointes, soon degenerating into ventricular fibrillation. Retrospective survey of the patient's medical records revealed an incomplete right bundle branch block (iRBBB) configuration with fluctuating saddle back-type ST elevation in leads V1 and V2, these suggesting Brugada syndrome. Autopsy showed complete thrombotic occlusion of the left main coronary artery.

Acute coronary syndrome as a cause of sudden death in patients with old myocardial infarction: a pathological analysis

Old myocardial infarction (OMI) is one of the most important pathological manifestations in sudden cardiac death. Fatal arrhythmia arising from a fibrotic scar has been determined as the cause of death in most cases with old myocardial infarction. However, the significance of acute plaque disruption/thrombosis of the coronary arteries in those patients has not been investigated. We examined a series of 33 hearts from individuals with OMI who died suddenly during the period from 1998 to 2001. Detailed coronary pathological findings on these hearts indicated fresh or recent rupture of the coronary plaque with thrombosis in 18 cases (55%). As a result of comprehensive analysis, the sudden deaths were explained by acute coronary syndrome in 18 cases (55%), fatal arrhythmia in eight (24%), cardiac pump failure in five (14%), and other causes in two (6%) cases. Our findings revealed that a new coronary plaque rupture independent of the old infarct was a major cause of sudden cardiac death with OMI.

Effects of metabolically ischemic, but viable, myocardium on QT dispersion in patients with acute myocardial infarction: a study with resting I-123-BMIPP/thallium-201 myocardial single-photon emission computed tomography

In chronic Q-wave myocardial infarction, QT dispersion is closely correlated with infarct size, but this correlation has not been evaluated for acute myocardial infarction (AMI). The effects of abnormal fatty acid metabolism on QT dispersion were examined in 123 patients with AMI who underwent resting iodine-123-15-iodophenyl 3-methyl pentadecanoic acid (BMIPP)/thallium-201(201Tl) myocardial single photon emission computed tomography (SPECT) and electrocardiographic analysis in the subacute phase. The relationship between BMIPP and 201Tl was defined as match when the total defect score for BMIPP was equal to or smaller than that for 201Tl, and as mismatch when the total defect score for BMIPP was larger than that for 201Tl. Twenty-six patients (21%) demonstrated BMIPP-201Tl match and 97 (79%) demonstrated mismatch. Infarct size was closely correlated with QT dispersion (r=0.67, p<0.001) in patients with BMIPP-201Tl match, but weakly correlated (r=0.30, p<0.005) in patients with BMIPP-201Tl mismatch. For small infarctions, QT dispersion was significantly larger in patients with BMIPP-201Tl mismatch than in those with BMIPP-201Tl match (62+/-24 ms vs 41+/-18 ms, p=0.03), but did not differ between the 2 groups for large infarctions. This study shows that QT dispersion is influenced by infarct size and by the presence of metabolically ischemic but viable myocardium in patients with AMI.

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.

Can antiarrhythmic drugs survive survival trials?

Sudden cardiac death due to arrhythmic events is the major cause of mortality among early post-myocardial infarction (MI) patients, accounting for > 250,000 deaths annually in the United States alone. Antiarrhythmic drugs can be used in such patients as well as in those who have not had a recent MI but are at high risk for sudden cardiac death (e.g., those with ventricular tachycardia/fibrillation, or who have survived cardiac arrest). Most antiarrhythmic drugs available, however, have limitations arising from their toxic and proarrhythmic potential. Thus, research and development of new agents and treatment modalities are desirable. This article seeks to enumerate the lessons of past clinical trials with these agents and to provide guidelines for future trials. That a variety of antiarrhythmic drugs have been associated with an increased mortality has been a disturbing observation. It is therefore imperative that candidates for antiarrhythmic therapy be selected appropriately. We recommend that future clinical trials use stringent criteria for the identification of patients at "high risk" for arrhythmia or sudden cardiac death, and limit recruitment to such patients. Traditional markers, such as the increased frequency and complexity of ventricular premature beats, and low left ventricular ejection fraction, have not been successful in identifying these high-risk patients. However, decreased heart rate variability and cardiac late potentials recorded on a signal-over-aged electrocardiogram appear to be more specific markers of post-MI arrhythmia or sudden cardiac death and may, in conjunction with the traditional markers, be used to improve selection of trial populations. Since the risk of sudden cardiac death diminishes with time after MI, it is also recommended that the temporal window of treatment with antiarrhythmic agents be limited to 1 year post-MI. It is also important to define clearly the endpoints of efficacy evaluations. A short-term reduction on markers like ventricular ectopic beats, for example, does not translate into a long-term decrease in arrhythmia-related mortality. Therefore, a reduction in overall mortality is the only meaningful endpoint to define the true risk-benefit ratio. To limit exposure to the potentially adverse effects of these agents, target populations for prophylactic antiarrhythmic drugs should be limited to recent post-MI patients at high risk for sudden cardiac death due to arrhythmia. Avoiding exposure of low-risk patients to antiarrhythmic drugs is equally imperative. "Low risk" of all-cause mortality includes the group of post-MI patients with a left ventricular ejection fraction >36%. Risk must be continuously evaluated in the setting of other pharmacologic (angiotensin-converting enzyme [ACE] inhibitors, aspirin, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors ["statins"], and others) and/or nonpharmacologic interventions (coronary artery bypass graft, angioplasty, implantable cardioverter/defibrillator). There is also a need to improve noninvasive techniques for identifying patients in the high-risk category-at present, the presence of ventricular premature beats and a left ventricular ejection fraction <36% is considered somewhat predictive of sudden cardiac death. Thus, patients with a recent MI and moderately low left ventricular ejection fraction (< or = 36% but not <20%) may be considered for antiarrhythmic therapy. A subset analysis of patients with low heart rate variability can provide valuable additional information. It is important to note that although all-cause mortality is a valid endpoint for such trials, stratification by specific cause of mortality is desirable.

Stepwise strategy on the cost of risk stratification after acute myocardial infarction: a retrospective simulation study

Stratification of postinfarction patients at high risk of mortality and/or other adverse events can be improved by combining several prognostic markers. As the clinical impact of risk stratification has only recently emerged in prospective trials, there are a lack of data regarding the cost-effectiveness of multimarker strategies. This study performed a comprehensive search of a postinfarction database and simulated different risk stratification strategies involving left ventricular ejection fraction, signal-averaged electrocardiography, Holter monitoring, and heart rate variability, The parameters were assessed before discharge in 417 survivors of acute myocardial infarction followed-up for 1 year. Cardiac mortality was used as the clinical endpoint. A statistical computer model of a stepwise strategy using every feasible sequence of the four tests was used and, based on prices derived from European and American centers, the cost estimates of all possible combinations were compared. During the 1 year after myocardial infarction there were 24 cardiac deaths (5.8%). In all the population, 6% had all four tests positive (cardiac mortality 20%); 25% had at least three tests positive (cardiac mortality 12.5%); 58% had at least two tests positive (cardiac mortality 8.3%); and 92% presented with at least one test positive (cardiac mortality 6.3%). The cost of performing all the tests ranged between $398 and $1,887 for each patient. However, by selecting patients according to a step wise strategy, the costs ranged from $96 (> or = 1 test positive) to $510 (for the least expensive sequences of four tests positive). For each of the centers considered, the costs resulting from the risk stratification protocol were determined by the number of variables combined and sequences of tests adopted. Thus, a step wise strategy using the combination of all four parameters, starting with analysis of Holter variables and finishing with signal-averaged electrocardiography, appears to be the most appropriate and the least expensive approach for selecting patients at high risk of cardiac death.

Unexpected cardiac arrest after cardiac surgery: incidence, predisposing causes, and outcome of open chest cardiopulmonary resuscitation

STUDY OBJECTIVES

To assess the incidence of acute mechanical causes precipitating sudden cardiac arrest in cardiac surgery patients during the immediate postoperative period. In addition, we report the success rate of cardiopulmonary resuscitation (CPR) in which open-chest CPR was employed at an early stage of the resuscitation effort.

METHODS

Data on all cardiac surgical patients who suffered a sudden cardiac arrest during the first 24 h after surgery were collected prospectively. CPR consisted of conventional closed-chest CPR initially and was followed within 3 to 5 min, if needed, by open-chest CPR.

RESULTS

Of 3,982 patients undergoing cardiac surgery over a 30-month period, 29 patients (0.7%) had a sudden cardiac arrest. Of these, 13 patients (45%) were successfully resuscitated with closed-chest CPR, 14 (48%) with open-chest CPR, and 2 (7%) died despite closed- and open-chest CPR. Four CPR survivors died subsequently in the ICU, yielding an overall hospital discharge rate of 79%. Perioperative myocardial infarction was the underlying cause of sudden cardiac arrest in 14 patients (48%), and mechanical impediments to cardiac function (tamponade or graft malfunction) in another 8 (28%) patients; in the remaining 7 patients (24%), no underlying cause was found. The length of ICU stay was 6+/-1 (mean+/-SE) days. None of the patients developed wound infection and all were neurologically intact at hospital discharge.

CONCLUSION

Mechanical factors account for a substantial portion (28%) of causes of sudden cardiac arrest occurring in hemodynamically stable patients during the immediate postoperative period. This high incidence, in conjunction with the high survival rate achieved by open CPR, supports an early approach to open-chest CPR in this group of patients.

Sudden cardiac death in Japanese people aged 20-60 years--an autopsy study of 133 cases

In order to elucidate the principal cause and actual circumstances of sudden cardiac death in Japan, especially among people in the prime of life, we investigated 133 out of 161 autopsied patients (82.6%) (106 men and 27 women, mean age 47.5 years). Coronary artery disease (CAD) was the most frequently detected disorder (50 cases, 37.6%), and included 15 cases of acute myocardial infarction (AMI) (11.3%). We found that CAD was less frequent among younger patients than in Western countries: 10.0% in subjects in their twenties and 22.2% among subjects in their thirties. The left anterior descending artery (LAD) was the vessel most often affected by infarction (47.0%), but the proportion of LAD lesions was not different from that in AMI patients who were survived for least 1 day after the attack. In conclusion, CAD was infrequent among patients aged 20-39 years in comparison with Western countries and LAD was the most commonly affected vessel, but the proportion was not different from that found among AMI patients who survived for at least 1 day after the attack.

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.

Value of programmed ventricular stimulation in predicting sudden death and sustained ventricular tachycardia in survivors of acute myocardial infarction

To assess the prognostic value of the response to programmed ventricular stimulation in selected post-acute myocardial infarction (AMI) patients identified at risk of sudden death and spontaneous sustained ventricular tachycardia (VT) (arrhythmic events) by noninvasive, highly sensitive testing, 286 consecutive patients were evaluated prospectively and followed for 12 months. One hundred three patients (group 1) with either left ventricular ejection fraction < or = 40% or ventricular late potentials or spontaneous complex ventricular arrhythmias were considered at risk of late arrhythmic events and eligible for programmed ventricular stimulation; the remaining 183 patients (group 2) were discharged without any further evaluation. Electrophysiologic study was performed 11 to 20 days after AMI utilizing up to 2 extrastimuli and rapid ventricular burst pacing. At the end of the follow-up period, 10 patients in group 1 and 2 in group 2 died of cardiac causes; in addition, 10 patients in group 1 and 1 in group 2 had arrhythmic events. Sustained monomorphic VT was the only inducible arrhythmia related either to cardiac death (p <0.0005) or to arrhythmic events (p <0.0001). It was induced in 11 patients (3 died suddenly, and 3 had spontaneous VT). Multivariate analysis showed that such arrhythmia was the strongest independent predictor of arrhythmic events (F = 9.76; p <0.0001). In the entire study population, it allowed identification of patients at risk, with a sensitivity, specificity, and positive predictive value of 55%, 99%, and 67%, respectively. We conclude that programmed ventricular stimulation performed in selected post-AMI patients, utilizing a moderately aggressive stimulation protocol, is a specific but less sensitive procedure for predicting arrhythmic events; the induction of sustained monomorphic VT allows the accurate identification of patients who may profit by prophylactic antiarrhythmic therapy.

Does the induction of ventricular flutter or fibrillation at electrophysiologic testing after myocardial infarction have any prognostic significance?

This study examines the significance of inducing sustained ventricular fibrillation (VF) or ventricular flutter by programmed stimulation after infarction. Programmed ventricular stimulation was performed for prognostic reasons from the right ventricular apex at twice diastolic threshold using a protocol containing 4 extrastimuli. Of 502 patients tested 11 +/- 4 days after acute infarction, VF was induced in 164 (33%), ventricular flutter in 134 (27%), ventricular tachycardia (VT) in 44 (9%), and no arrhythmia in 160 (32%). All groups were similar in age, sex distribution, and sites of index infarction. Those with inducible VT had a higher incidence of multiple infarctions and a lower mean left ventricular ejection fraction at the time of testing. Without antiarrhythmic drug therapy, 8 patients (18%) with inducible VT experienced spontaneous VT or died instantaneously during the first year of follow-up. By contrast, only 1 (0.6%) patient with inducible VF, 1 (0.7%) with ventricular flutter, and 1 (0.6%) without any inducible arrhythmias experienced similar events in the same period (p < 0.001). By relating the cycle length of the induced monomorphic arrhythmia to later spontaneous electrical events, induced arrhythmias with cycle length as low as 230 ms still identified patients at high risk for spontaneous arrhythmias. Only the induction of sustained monomorphic VT with a cycle length > 230 ms indicates patients with ventricular electrical instability after infarction. The induction of VF or ventricular flutter is a negative test result with no adverse long-term prognostic significance.

Prediction of late arrhythmic events after acute myocardial infarction from combined use of noninvasive prognostic variables and inducibility of sustained monomorphic ventricular tachycardia

A combined use of noninvasive techniques and electrophysiologic study in the prediction of arrhythmic events was prospectively evaluated in 303 surviving patients of acute myocardial infarction (AMI). The most powerful combination of noninvasive prognostic variables in identifying patients suitable for invasive strategies was also assessed. Patients who had > or = 2 variables among left ventricular ejection fraction < 0.4, ventricular late potentials and repetitive ventricular premature complexes (VPCs) were considered eligible for programmed ventricular stimulation. After 15 +/- 7 months of follow-up, 19 patients (6%) had an arrhythmic event. Left ventricular dyskinesia (p < 0.00001) and ejection fraction < 0.4 (p < 0.000001), late potentials (p < 0.001), filtered QRS duration > or = 106 ms (p < 0.00001), VPCs/hour > 6 (p < 0.05), paired VPCs (p < 0.01), > or = 2 runs of unsustained ventricular tachycardia (VT) per monitoring (p < 0.001), heart rate variability index < or = 29 (p < 0.00001) and mean RR interval < or = 750 ms (p < 0.01) were found to be significant univariate predictors of events. At multivariate analysis, only low left ventricular ejection fraction, prolonged filtered QRS duration, reduced heart rate variability index and detection of > or = 2 runs of unsustained VT per monitoring had an independent relation to late arrhythmic events. Of 67 eligible patients, 47 (70%) consented to undergo programmed stimulation. A positive electrophysiologic study was found to be the strongest independent predictor of events among patients preselected by noninvasive techniques. With a good sensitivity (81%), a combined use of noninvasive tests and electrophysiologic study selected a group of post-AMI patients at sufficiently high risk (event rate 65%) to be considered candidates for interventional therapy. The combination of > or = 2 variables among left ventricular ejection fraction < 0.4, filtered QRS duration > or = 106 ms and > or = 2 runs of unsustained VT was superior to the other ones in identifying high-risk subjects (positive and negative predictive values for arrhythmic events of 44 and 99%, respectively). On the basis of the data, this scheme appears to be the most appropriate for selecting patients suitable for electrophysiologic testing and invasive strategies after AMI.

A pathological study of sudden coronary death in China: report of 89 autopsy cases

This paper reports the results of a forensic pathological study of 89 autopsy cases of Sudden Coronary Death (SCD). Of 89 cases, 63 (52 male, 11 female) were narrowed by 76-100% in cross-sectional area (XSA) of the coronary artery (CA) and 26 (22 male, 4 female), by 51-75%. Atherosclerotic plaques in the CA were serious and extensive, especially in the left anterior descending and often involved several branches of CA at the same time. Recent thrombosis was found in 18 cases, haemorrhage in plaques in 17 cases. Only 2 cases had visible acute myocardial infarction. Inflammatory cell infiltration was found in coronary plaques in 36 cases. Myocardial fibrosis or small scar formation was detected in 51 cases. It is suggested that although the incidence of coronary heart disease (CHD) is low in China, SCD is the commonest mode of Sudden Unexpected Death. The majority of SCD (52%) were middle aged males (30-49 years old). Most of the cases died suddenly during sleep without any clear precipitating factors. The characteristics of occurrence and pathological changes in the CA and myocardium and the pathological diagnosis of SCD are also analysed and discussed.

How long should high-risk patients with acute anterior wall myocardial infarction be monitored?

In 143 patients with an acute anterior wall myocardial infarction, left ventricular ejection fraction was determined within 72 h of admission. Left ventricular ejection fraction was below 40% in 114 patients. In this group late ventricular tachycardia or ventricular fibrillation occurred in 30 patients (26%). A left ventricular ejection fraction below 40% identified all patients who developed any late ventricular tachycardia and a left ventricular ejection fraction below 30% identified all who developed late ventricular fibrillation. After discharge another 2 patients with late ventricular tachycardia were detected. Death between 48 h and 3 weeks only occurred in patients with a left ventricular ejection fraction below 30%. Thus in patients with an acute anterior wall myocardial infarction a left ventricular ejection fraction below 30% within the first 72 h after the acute event identifies a high risk for late ventricular tachycardia or ventricular fibrillation. The occurrence of late ventricular tachycardia showed a gradual increase during 3 weeks of monitoring and no cut-off point could be detected within this time-window.

The management and outcome of late post-infarct ventricular tachycardia presenting to a district general hospital

A review was undertaken of late post-infarct ventricular tachycardia in a district hospital cardiac care unit in order to study the clinical course of a total population of such patients from initial presentation to ultimate outcome. Thirty-six patients with this diagnosis were identified over a 3 1/2-yr period. Twelve were treated by empirically chosen antiarrhythmic drugs. Twenty-four were referred for electrophysiologically guided treatment, of whom 16 were treated by antiarrhythmic drugs, 3 by anti-ischaemic measures alone, and 5 by non-pharmacological antiarrhythmic treatments (antiarrhythmic surgery, percutaneous ablation, defibrillator implantation, cardiac transplantation). Of those treated empirically, 4 died in hospital of their arrhythmia, 1 died suddenly at home, and 2 suffered non-fatal arrhythmia recurrences during mean follow-up of 20 months. There were no arrhythmic deaths in those whose treatment was guided by serial electrophysiology studies, although 4 patients died of cardiac failure or reinfarction, and 3 were hospitalised with a recurrence of ventricular tachycardia during mean follow-up of 16 months. Age, concomitant medical problems and the apparent response to initial antiarrhythmic therapy were the main factors influencing management decisions. The apparent superiority of more intensive management strategies based on electrophysiology studies must be interpreted in the context of the selection processes applied to the total population initially presenting.

Ventricular arrhythmias in perspective: a current view

While clinical management of patients with ventricular arrhythmias continues to evolve, some basic principles are generally accepted. First, patients with sustained ventricular tachyarrhythmias (ventricular tachycardia or ventricular fibrillation) require treatment. Second, patients with frequent ventricular ectopy or nonsustained ventricular tachycardia in the absence of underlying structural heart disease do not require treatment except when relief of symptoms is warranted. However, the indication for treatment of patients with frequent ventricular ectopy or nonsustained ventricular tachycardia in the presence of underlying structural heart disease remains uncertain. The concern is that these ventricular arrhythmias may be a precursor for sustained, potentially life-threatening ventricular tachyarrhythmias. Available data suggest that patients with underlying structural heart disease, particularly coronary artery disease and a previous myocardial infarction, who manifest frequent ventricular ectopy or more particularly nonsustained ventricular tachycardia, are at increased risk for sudden cardiac death. However, no studies have demonstrated to date that treatment of these arrhythmias will favorably affect outcome. Data are accumulating to suggest that use of the principles of risk stratification permits identification of patients at very high risk for developing sustained ventricular tachyarrhythmias. Carefully designed clinical trials are required before firm guidelines for the management of these patients can be defined.(ABSTRACT TRUNCATED AT 250 WORDS)

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

Sustained infarct artery patency is an important determinant of survival in patients with acute myocardial infarction. We studied 61 patients with acute myocardial infarction who received intravenous recombinant tissue-type plasminogen activator, aspirin or heparin within 6 hours of symptom onset, to determine if infarct artery patency after intravenous thrombolytic therapy influences myocardial electrical stability as measured by the prevalence of spontaneous ventricular ectopy or late potential activity. Infarct artery patency was determined by angiographic evaluation 2.5 +/- 3 days after infarction. Forty-eight patients (79%) had a patent infarct-related artery and 13 (21%) patients had an occluded vessel. The mean number of ventricular premature complexes (VPCs)/hour (p less than 0.01) and the prevalence of late potentials (54 vs 19%; p less than 0.03) were significantly higher in patients with an occluded versus patent-infarct related vessel. Although VPC frequency and late potentials were not influenced by the time to thrombolytic treatment, patients with a patent infarct-related artery had a lower prevalence of late potentials regardless of whether treatment was initiated less than or equal to 2 hours (25% patent vs 50% occluded; p = not significant) or 2 to 6 hours (16% patent vs 55% occluded; p greater than 0.03) after symptom onset. Thus, successful thrombolysis decreases the frequency of ventricular ectopic activity and late potentials in the early postinfarction phase. The reduction in both markers of electrical instability may help explain why the prognosis after successful thrombolysis is improved after acute myocardial infarction.

Routine programmed electrical stimulation in survivors of acute myocardial infarction for prediction of spontaneous ventricular tachyarrhythmias during follow-up: results, optimal stimulation protocol and cost-effective screening

Of 3,286 consecutive patients treated for acute myocardial infarction, electrophysiologic testing was performed in 1,209 survivors (37%) free of significant complications at the time of hospital discharge to determine their risk of spontaneous ventricular tachyarrhythmias during follow-up. Sustained monomorphic ventricular tachycardia was inducible by programmed electrical stimulation in 75 (6.2%). Antiarrhythmic therapy was not routinely prescribed regardless of the test results. During the 1st year of follow-up, 14 infarct survivors (19%) with inducible ventricular tachycardia experienced spontaneous ventricular tachycardia or fibrillation in the absence of new ischemia compared with 34 (2.9%) of those without inducible ventricular tachycardia (p less than 0.0005). During the extended follow-up period (median 28 months) of those with inducible ventricular tachycardia, 19 (25%) had a spontaneous electrical event; 37% of these first events were fatal. These results suggest that the most cost-effective strategy for predicting arrhythmia will be obtained by restricting electrophysiologic testing to infarct survivors whose left ventricular ejection fraction is less than 40% and using a stimulation protocol containing four extrastimuli. Electrophysiologic testing is the single best predictor of spontaneous ventricular tachyarrhythmias during follow-up in infarct survivors. The majority (94%) with a negative test benefit from the more reliable reassurance that all is well, whereas the 25% risk of electrical events in those with inducible ventricular tachycardia justifies a prospective trial of effective prophylactic antiarrhythmic interventions.

Usefulness of right ventricular pulse pressure as a potential sensor for hemodynamically unstable ventricular tachycardia

The automatic implantable cardioverter defibrillator has had a major impact on the management of patients with ventricular tachyarrhythmias. Future devices will offer tiered therapy for ventricular arrhythmias, based on a sensor capable of discriminating hemodynamically stable from unstable ventricular tachycardia (VT). We studied 27 patients with sustained VT/ventricular fibrillation during 70 episodes of sustained ventricular arrhythmias (greater than 30 seconds or requiring cardioversion). In this study, phasic arterial pressure (mm Hg), VT cycle length (ms) and right ventricular (RV) pulse pressure (mm Hg) were measured before, during the first 30 beats and after each episode of VT. During the first 10 beats of 23 episodes of unstable VT, the mean (+/- standard error of the mean) decrease in RV pulse pressure from baseline was 22 +/- 1.8 mm Hg; it was 13.8 +/- 2.4 mm Hg during the first 10 beats of 47 episodes of stable VT, (p = 0.01, stable vs unstable). For the next 20 beats of VT, RV pulse pressure decreased from baseline by 22 +/- 2.5 mm Hg during unstable and by 12.0 +/- 2.5 mm Hg during stable VT (p = 0.0001, stable vs unstable). The percent decrease of RV pulse pressure correlated well with the percent decrease in mean arterial pressure and percent decrease in systolic arterial pressure (r = 0.70; r = 0.69, respectively; p less than 0.001) during VT, but poorly with the VT cycle length (r = 0.27, p less than 0.05). The percent decrease in RV pulse pressure is a useful hemodynamic sensor for discriminating between stable and unstable VT.

Clinical implications of new studies in the treatment of benign, potentially malignant and malignant ventricular arrhythmias

For purposes of clinical management, ventricular arrhythmias have been divided into risk categories of benign, prognostically important (potentially malignant) and malignant. Benign arrhythmias occur in the setting of structurally normal hearts and do not require therapy unless associated with debilitating symptoms. Malignant arrhythmias such as sustained ventricular tachycardia or fibrillation deserve aggressive therapy to prevent recurrence. Arrhythmias occurring in the presence of organic heart disease (often ischemic disease) are frequently asymptomatic but prognostically important as a risk factor for sudden death or cardiac arrest. The common empiric practice to treat such arrhythmias (by about 40 to 50% of cardiologists in the United States) needs to be reassessed in the face of the Cardiac Arrhythmia Suppression Trial. For malignant arrhythmias, class IA agents (procainamide and quinidine) continue to be the standard of treatment, and class IB agents (e.g., mexiletine) may be used as alternative or additive therapy. Class IC agents are used as second-line therapy, especially in the setting of ischemic heart disease. Class III therapy with amiodarone is reserved for refractory patients because of potential toxicity. Sotalol, a new class II-III agent, may become a first-line drug. For prognostically important arrhythmias, beta blockers remain the agents of choice, class IC agents are contraindicated, and class IA or IB drugs, or both, should be used conservatively (i.e., only for symptomatic arrhythmias). For symptomatic but benign arrhythmias requiring treatment, beta blockers are safe although not always effective. Class IA, IB and IC agents may then be considered. In these patients, the proarrhythmic potential of quinidine and class IC agents remains a concern.(ABSTRACT TRUNCATED AT 250 WORDS)

A perspective on ventricular arrhythmias: patient assessment for therapy and outcome

Clinical management of patients with ventricular arrhythmias continues to evolve. It is generally accepted that patients with sustained ventricular tachyarrhythmias (ventricular tachycardia [VT] or fibrillation) require treatment. It is also generally accepted that patients with frequent or complex ventricular ectopy or nonsustained VT, in the absence of underlying heart disease, do not require treatment unless relief of symptoms is warranted. Whether patients with frequent or complex ventricular ectopy or nonsustained VT require treatment in the presence of underlying organic heart disease remains uncertain. The concern is that these ventricular arrhythmias may be a precursor for sustained, potentially life-threatening ventricular tachyarrhythmias. Available data suggest that patients with underlying heart disease, particularly coronary artery disease and a previous myocardial infarction, who manifest frequent or complex ventricular ectopy or nonsustained VT are at increased risk for sudden cardiac death. However, no studies have shown that treatment of these arrhythmias will affect outcome. Data are accumulating to suggest that use of the principles of risk stratification permits identification of patients at very high risk for developing sustained ventricular tachyarrhythmias. Carefully designed clinical trials are required before one can provide firm guidelines for the management of these patients. Nevertheless, when several risk factors for sudden cardiac death (e.g., abnormal ejection fraction, a late potential on a signal-averaged electrocardiogram, and frequent or complex ventricular ectopy or nonsustained VT) are present in a patient, especially after a recent myocardial infarction, invasive electrophysiologic testing may help identify those who need treatment (sustained VT is inducible) and those who do not (no sustained VT is inducible).

Depression increases mortality and morbidity in acute life-threatening medical illness

The presence of depression in consecutive admissions with life-threatening illness was assessed using the Montgomery-Asberg Depression Rating Scale (MADRS). The 211 patients had one of four conditions, myocardial infarction (N = 100), subarachnoid haemorrhage (N = 41), pulmonary embolism (N = 40), and acute upper gastrointestinal haemorrhage (N = 30). Depression was measured using both the standard MADRS, and a modified version excluding somatic items which might be influenced by the underlying illness. The patients were also assessed for severity of illness and cognitive dysfunction. The results showed that immediately following a life-threatening illness approximately 34% of the patients were depressed, using the modified scale, but that the depressed group did not have a more severe physical illness. However, the depressed patients had a significantly poorer outcome over the 28 days following admission, with 47% of the depressed patients dying or having life-threatening complications, as opposed to 10% of the non-depressed group. This study demonstrates that the psychological state of an individual can affect their individual risk of mortality following physical illness.

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

In some patients with acute myocardial infarction, low-amplitude potentials that prolong the QRS complex, termed "late potentials," can be recorded on a signal-averaged electrocardiogram. The presence of these late potentials is known to be associated with an increase in the risk of ventricular tachycardia and sudden death. Because patients with acute myocardial infarction who receive thrombolytic therapy have a reduced incidence of ventricular tachyarrhythmia and sudden death, we sought to determine whether such patients also have a decreased incidence of late potentials. We studied 106 patients less than 75 years of age who were admitted with a first myocardial infarction and in whom a signal-averaged electrocardiogram was recorded within 48 hours of admission. Within four hours of the onset of chest pain, tissue plasminogen activator (t-PA) was given to 44 patients, and 62 were treated conventionally. In the t-PA group, late potentials were recorded in 2 of 44 patients (5 percent), as compared with 14 of 62 (23 percent) in the conventionally treated group (P = 0.01). Furthermore, among the patients treated with t-PA, continued occlusion of the infarct-related artery was related to the presence of late potentials. In the t-PA group, late potentials were recorded within 24 hours of angiography in 2 of the 6 patients with an occluded infarct-related artery, as compared with none of the 38 patients with a patient infarct-related artery. Our data suggest that successful thrombolytic therapy is associated with a marked reduction in the incidence of late potentials on the signal-averaged electrocardiogram. Long-term follow-up will be required to determine whether this finding predicts a reduced incidence of subsequent ventricular tachyarrhythmia and sudden death.

Automatic external defibrillation of patients after myocardial infarction by family members: practical aspects and psychological impact of training

Automatic external defibrillation (AED) offers the potential for minimally trained individuals to convert life-threatening ventricular arrhythmias prior to arrival of emergency rescue personnel but optimum usage of AED remains undefined. To test the practical aspects of home AED in high risk patients after myocardial infarction, we identified 40 consecutive high risk post-MI patients, who satisfied inclusion and exclusion criteria. Fifteen (38%) patients were eliminated at their physician's request and nine others refused to participate. Twenty-six family members of the remaining 16 patients were trained in AED with follow-up testing at 3 months. Level of skill, especially in CPR performance, decline to unsatisfactory levels in 35% of trainees, including all over age 55. Trainees felt more confident due to availability of AED and 90% felt no strain in intrapersonal relationships. Psychological testing revealed a decrease in patient and trainee depression scores and no change in anxiety or obsessiveness during the study. These observations suggest the following: (1) better awareness of benefits of AED by physicians and lay persons is necessary, (2) retraining at less than 3 month intervals will be required for many spouse trainees and (3) there are no common adverse psychologic sequelae to training in AED.

Programmed stimulation after anterior myocardial infarction complicated by bundle branch block--late ventricular tachyarrhythmias and outcome

One hundred and thirty consecutive patients with anterior myocardial infarction complicated by bundle branch block were retrospectively analyzed. Sixty died within 1 week of infarction. Of the remaining 70 patients, 36 had electrophysiology study with programmed stimulation 8-90 (mean 20) days after infarction. Of these, nine patients (35%) who clinically had not manifested either ventricular tachycardia or ventricular fibrillation more than 72 hours after infarction, had inducible ventricular tachycardia which was sustained more than 30 seconds in eight patients. By contrast, assessment of atrioventricular conduction added little to clinical management, long-term follow-up, extending up to 127 months, was available both in those patients whose therapy was directed by electrophysiology study, and was assessed among the other 34 patients who survived at least 7 days after myocardial infarction, but who did not undergo electrophysiology study. While the overall mortality was 55%, the majority of deaths (22/35) occurred within 4 months of infarction and many long-term survivors enjoy a gratifying quality of life. Although programmed stimulation in survivors of anterior myocardial infarction complicated by bundle branch block may identify a high risk subgroup, a prospective randomized trial is required to define the utility of more aggressive stimulation protocols following NASPE recommendations, to identify subgroups of patients in whom newer therapeutic interventions, including antiarrhythmic agents, electrical devices and surgery may be indicated.

Predictors of sudden death up to 18 years after a first attack of unstable angina or myocardial infarction

Factors related to the occurrence of sudden death were examined in 551 men aged less than 60 years who survived a first attack of unstable angina or myocardial infarction by at least 28 days. There were 301 deaths over an average follow up period of 9.4 years and 138 (46%) of these were sudden. Life table techniques permitted the estimation of mortality up to 18 years after the index event. The proportion of sudden deaths showed a decrease with length of follow up. In those who were non-smokers and in those aged less than 45 years on admission sudden deaths in the first two years were very common (80% (95% confidence interval: 69%-91%) and 79% (95% confidence interval: 68%-90%) respectively). The proportion of sudden deaths in the remaining 16 years of follow up was related inversely to age at initial attack. After the first two years of follow up sudden death rates were similar in those who continued to smoke and those who stopped smoking, although those who continued to smoke had a significantly higher overall mortality. The risk of sudden death should be borne in mind when planning the investigation and rehabilitation of young and non-smoking subjects presenting with a first coronary event.

Ventricular arrhythmias in elderly patients. Evaluation and management

In evaluating and managing ventricular arrhythmias in elderly patients, the clinician must first decide which patients are appropriate candidates for therapy. Arrhythmias can be categorized as to their potential for causing sudden cardiac death as benign, potentially malignant, or malignant by considering their type and the underlying structural cardiac disease present. Factors that may aggravate the arrhythmias should be identified and corrected. The ventricular arrhythmias should be well characterized using ambulatory monitoring or electrophysiologic studies to gauge the efficacy of subsequent therapy. If pharmacologic therapy is to be initiated, the most appropriate antiarrhythmic drug should be chosen with consideration of potential efficacy, potential adverse cardiovascular and systemic side effects, pharmacokinetics, and drug interactions. In selected patients with malignant ventricular arrhythmias, the failure of antiarrhythmic medication may lead the clinician to consider nonpharmacologic therapy such as surgical endocardial resection or the automatic implantable cardioverter-defibrillator.

Outcome after cardiac arrest during acute myocardial infarction

A community-wide study of acute myocardial infarction (AMI) was conducted in all 16 acute-care general hospitals in the Worcester, Massachusetts, metropolitan area during the years 1975, 1978, 1981 and 1984. The in-hospital and long-term prognoses of 667 patients with AMI complicated by cardiac arrest (CA) was compared with that of 2,596 AMI patients without CA. The incidence of CA complicating AMI was similar (21%) during each of the 4 study years. Among patients with AMI who had CA, 36% had CA within the first day of hospitalization and 48% within the first 2 days. The in-hospital case-fatality rate was much higher for AMI patients with CA (78%) than for those without CA (4%) (p less than 0.001). For patients discharged alive from the hospital, a trend toward a higher mortality rate was seen at 1 and 2 years after hospital discharge for patients with CA; however, long-term survival rates were not significantly different between AMI patients with and without CA. When time of occurrence of CA relative to in-hospital survival was examined, patients with early CA (within 1 day or within 2 days of hospital admission) had a significantly greater in-hospital survival (39% and 34%) than did those with late CA (after 1 day or after 2 days) (13% and 12%). Similarly, patients discharged from the hospital after early CA had a significantly better chance of long-term survival than patients discharged after late CA.

Recainam, a potent new antiarrhythmic agent: effects on complex ventricular arrhythmias

The antiarrhythmic efficacy and safety of intravenous recainam, a newly synthesized compound displaying potent class I antiarrhythmic activity, were tested in 10 hospitalized patients with frequent (greater than 30/h) complex ventricular ectopic beats. There were seven men and three women of average age 57 years (range 21 to 74); five had ischemic heart disease, three had cardiomyopathy and two had valvular heart disease. Recainam was given as a 3.0 mg/kg per 40 min loading infusion followed by a 0.9 mg/kg per h maintenance infusion over a 24 hour observation period. Arrhythmia response was assessed both in the short term (comparing 2 hours before and 1 hour after drug loading) and in the long term (comparing 48 hours before drug loading and 23 hours of maintenance infusion). The median frequency of total premature ventricular complexes decreased in the short term by 99.6% (from 392.5 to 1.5/h, p less than 0.005) and in the long term by 99.7% (from 435 to 1.3/h, p less than 0.01). Repetitive beats were suppressed by a median of 100% both in the short term (p less than 0.006) and during 24 hour infusion (from 80.9 to 0/h, p less than 0.003). More than 90% suppression of repetitive beats occurred in all 10 patients (100%) and more than 90% suppression of total arrhythmias occurred in 9 patients (90%) during the maintenance period. Electrocardiographic PR and QRS intervals increased by 19% (p less than 0.001) and 24% (p less than 0.003), respectively, during therapy, but the JTc interval decreased (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Contraction-band necrosis: patterns of distribution in the myocardium and their diagnostic usefulness in sudden cardiac death

Experimentally-produced acute regional myocardial infarcts of 2 or more hours duration show a characteristic pattern of myocardial cell alteration known as "contraction-band necrosis". To investigate the potential usefulness of this feature in assessing the myocardial status in sudden cardiac death, detailed histological examinations of the coronary arteries and midventricular myocardium were carried out on hearts from 70 unselected cases of sudden cardiac death. Contraction-band necrosis was frequently encountered and occurred in 3 main patterns which could be correlated with the coronary artery pathology and the case history: a regional distribution consistent with early subendocardial or transmural infarction, not yet characterized by coagulative necrosis, associated in most cases with a recent thrombotic event in the relevant supply artery (27.1%); adjacent to pre-existing infarction (recent or healed) or to subendocardial fibrosis resulting from severe coronary artery disease, consistent with recent extension of ischemic injury (18.6%); a global, full-transmural distribution, consistent with reperfusion injury from delayed resuscitation in the absence of significant coronary artery pathology (8.6%). Thus, examination of the myocardium for a specific pattern of contraction-band necrosis may frequently facilitate the definitive diagnosis of sudden cardiac death.