Angiographic findigs and prognostic indicators in patients resuscitated from sudden cardiac death

Comparison of role of early (less than six hours) to later (more than six hours) or no cardiac catheterization after resuscitation from out-of-hospital cardiac arrest

Despite reports of patients with resuscitated sudden cardiac arrest (rSCA) receiving acute cardiac catheterization, the efficacy of this strategy is largely unknown. We hypothesized that acute cardiac catheterization of patients with rSCA would improve survival to hospital discharge. A retrospective cohort of 240 patients with out-of-hospital rSCA caused by ventricular tachycardia or fibrillation was identified from 11 institutions in Seattle, Washington from 1999 through 2002. Patients were grouped into those receiving acute catheterization within 6 hours (≤6-hour group, n = 61) and those with deferred catheterization at >6 hours or no catheterization during the index hospitalization (>6-hour group, n = 179). Attention was directed to survival to hospital discharge, neurologic status, extent of coronary artery disease, presenting electrocardiographic findings, and symptoms before arrest. Propensity-score methods were used to adjust for the likelihood of receiving acute catheterization. Survival was greater in patients who underwent acute catheterization (72% in the ≤6-hour group vs 49% in the >6-hour group, p = 0.001). Percutaneous coronary intervention was performed in 38 of 61 patients (62%) in the ≤6-hour group and 13 of 170 patients (7%) in the >6-hour group (p <0.0001). Neurologic status was similar in the 2 groups. A significantly larger percentage of patients in the acute catheterization group had symptoms before cardiac arrest and had ST-segment elevation on electrocardiogram after resuscitation. Age, bystander cardiopulmonary resuscitation, daytime presentation, history of percutaneous coronary intervention or stroke, and acute ST-segment elevation were positively associated with receiving cardiac catheterization. In conclusion, in this series of patients who sustained out-of-hospital cardiac arrest, acute catheterization (<6 hours of presentation) was associated with improved survival.

State of the art in forensic investigation of sudden cardiac death

The sudden death of a young person is a devastating event for both the family and community. Over the last decade, significant advances have been made in understanding both the clinical and genetic basis of sudden cardiac death. Many of the causes of sudden death are due to genetic heart disorders, which can lead to both structural (eg, hypertrophic cardiomyopathy) and arrhythmogenic abnormalities (eg, familial long QT syndrome, Brugada syndrome). Most commonly, sudden cardiac death can be the first presentation of an underlying heart problem, leaving the family at a loss as to why an otherwise healthy young person has died. Not only is this a tragic event for those involved, but it also presents a great challenge to the forensic pathologist involved in the management of the surviving family members. Evaluation of families requires a multidisciplinary approach, which should include cardiologists, a clinical geneticist, a genetic counselor, and the forensic pathologist directly involved in the sudden death case. This multifaceted cardiac genetic service is crucial in the evaluation and management of the clinical, genetic, psychological, and social complexities observed in families in which there has been a young sudden cardiac death. The present study will address the spectrum of structural substrates of cardiac sudden death with particular emphasis given to the possible role of forensic molecular biology techniques in identifying subtle or even merely functional disorders accounting for electrical instability.

Ablation of ventricular fibrillation in an orthotopic heart lung transplant

Arrhythmia is well described following cardiac transplantation. We report a case of recurrent ventricular fibrillation (VF) originating from an orthotopic cardiac allograft. VF was consistently initiated on each occasion by a relatively early-coupled monomorphic ventricular ectopic. Antiarrhythmic agents failed to suppress the arrhythmia. Electrophysiological testing with noncontact mapping showed a high-frequency potential at the earliest activation site. Radiofrequency ablation resulted in abolition of ventricular ectopy with no further VF recurrence. Although there is substantial experience with ablation of atrial tachycardias in this setting, experience with ablation for ventricular arrhythmias is limited and ablation of VF not described.

A comprehensive review and analysis of 25 years of data from an in vivo canine model of sudden cardiac death: implications for future anti-arrhythmic drug development

Sudden cardiac death resulting from ventricular tachyarrhythmias remains the leading cause of death in industrially developed countries, accounting for between 300,000 and 500,000 deaths each year in the United States. Yet, despite the enormity of this problem, the development of safe and effective anti-arrhythmic agents remains elusive. The identification of effective anti-arrhythmic agents is critically dependent upon the use of appropriate animal models of human disease. During the last 25 years, a canine model of sudden cardiac death has proven to be useful in both the identification of factors contributing to ventricular fibrillation (VF) and the evaluation of potential anti-arrhythmic therapies. The present review provides a detailed retrospective analysis of the data obtained with this model. Briefly, VF was reliably and reproducibly induced by the combination of acute myocardial ischemia at site distant from a previous myocardial infarction during submaximal exercise (to activate the autonomic nervous system). This exercise plus ischemia test identified 2 stable populations of dogs: those that development malignant arrhythmias (susceptible, n=303) and those that rarely developed even single premature ventricular activation (resistant, n=209). The susceptible animals exhibited an elevated sympathetic activation (due to an enhanced beta2-adrenoceptor responsiveness) and a subnormal parasympathetic regulation. Several interventions have proven to be particularly effective in preventing VF in the susceptible dogs; including calcium channel antagonists, left stellate ganglion disruption, ATP-sensitive potassium channel antagonists, beta-adrenoceptor antagonists, and non-pharmacological interventions (endurance exercise training and dietary omega-3 fatty acids).

Stretch-induced ventricular arrhythmias during acute ischemia and reperfusion

Mechanical stretch has been demonstrated to have electrophysiological effects on cardiac muscle, including alteration of the probability of excitation, alteration of the action potential waveform, and stretch-induced arrhythmia (SIA). We demonstrate that regional ventricular ischemia due to coronary artery occlusion increases arrhythmogenic effects of transient diastolic stretch, whereas globally ischemic hearts showed no such increase. We tested our hypothesis that, during phase Ia ischemia, regionally ischemic hearts may be more susceptible to triggered arrhythmogenesis due to transient diastolic stretch. During the first 20 min of regional ischemia, the probability of eliciting a ventricular SIA ( PSIA) by transient diastolic stretch increased significantly. However, after 30 min, PSIA decreased to a value comparable with baseline measurements, as expected during phase Ib, where most ventricular arrhythmias are of reentrant mechanisms. We also suggest that mechanoelectrical coupling may contribute to the nonreentrant mechanisms underlying reperfusion-induced arrhythmia. When coronary artery occlusion was relieved after 30 min of ischemia, we observed an increase in PSIA and the maintenance of this elevated level throughout 20 min of reperfusion. We conclude that mechanoelectrical coupling may underlie triggered arrhythmogenesis during phase 1a ischemia and reperfusion.

Sudden cardiac death

Sudden cardiac death (SCD) due to ventricular tachyarrhythmias is a leading cause of death in the United States. This phenomenon is associated with coronary artery disease, valvular heart disease, nonischemic cardiomyopathies, congenital heart disease, primary electrical abnormalities, autonomic nervous system abnormalities, and other less common disorders. Evaluation and management of patients at risk for SCD (primary prevention) and of patients who have survived at least 1 episode of SCD (secondary prevention) have evolved in recent years because clinical trials have shown consistent benefit from implantation of cardioverter-defibrillators in appropriately selected patients. An evidence-based approach to primary and secondary prevention of SCD is presented.

Update on cardiac resuscitation for sudden death: International Guidelines 2000 on Resuscitation and Emergency Cardiac Care

Cardiopulmonary resuscitation developed over the past one half century largely from empiric science and consensus opinions and recommendations. Treatment algorithms and protocols were originally developed to summarize existing recommendations for systematic and regimented use by a heterogenous group of health care providers. Now, resuscitation science and health care teams are focusing on major issues and continuing questions as sudden death rates remain undaunted and the population at risk is rapidly increasing. For the first time, the international resuscitation community has developed an international consensus on Guidelines for Resuscitation and Emergency Cardiac Care. More than 400 basic scientists, clinical trial investigators, and educators defined common priority and scientific areas during the Evidence Evaluation International Meeting in 1999. The science of resuscitation and emergency cardiac care was reviewed for evidence-based support in randomized clinical trials. In 2000, this review was used as a foundation to structure international guidelines. The participants from seven resuscitation councils and foundations realized that regional differences in systems may exist, but the underlying science should be the same. Presented in this article are some of the major issues and controversies discussed in adult advanced cardiac life support, primarily focusing on the major problem of prehospital adult cardiac arrest.

Risk of sudden versus nonsudden cardiac death in patients with coronary artery disease

BACKGROUND

Patients at high risk of sudden cardiac death, yet at low risk of nonsudden death, might be ideal candidates for antiarrhythmic drugs or devices. Most previous studies of prognostic markers for sudden cardiac death have ignored the competitive risk of nonsudden cardiac death. The goal of the present study was to evaluate the ability of clinical factors to distinguish the risks of sudden and nonsudden cardiac death.

METHODS

We identified all deaths during a 3.3-year follow-up of 30,680 patients discharged alive after admission to the cardiac care unit of a Seattle hospital. Detailed chart reviews were conducted on 1093 subsequent out-of-hospital sudden deaths, 973 nonsudden cardiac deaths, and 442 randomly selected control patients.

RESULTS

Patients who died in follow-up (suddenly or nonsuddenly) were significantly different for many clinical factors from control patients. In contrast, patients with sudden cardiac death were insignificantly different for most clinical characteristics from patients with nonsudden cardiac death. The mode of death was 20% to 30% less likely to be sudden in women, patients who had angioplasty or bypass surgery, and patients prescribed beta-blockers. The mode of death was 20% to 30% more likely to be sudden in patients with heart failure, frequent ventricular ectopy, or a discharge diagnosis of acute myocardial infarction. A multivariable model had only modest predictive capacity for mode of death (c-index of 0.62).

CONCLUSION

Standard clinical evaluation is much better at predicting overall risk of death than at predicting the mode of death as sudden or nonsudden.

Effect of surgical revascularization in patients with coronary artery disease and ventricular tachycardia or fibrillation in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Registry

BACKGROUND

Patients who undergo resuscitation from near-fatal ventricular arrhythmias often have significant coronary artery disease, and revascularization has been shown to reduce myocardial ischemia and cardiac arrest episodes in this patient population. The magnitude of benefit attributed to revascularization has varied by study, and the use of adjunct implantable cardioverter defibrillator (ICD) therapy has not been well-characterized.

METHODS AND RESULTS

The Antiarrhythmics Versus Implantable Defibrillators (AVID) registry included 3117 patients with life-threatening ventricular arrhythmias, of whom 2321 (77%) had documented coronary artery disease and 281 (17%) underwent a coronary artery bypass grafting revascularization procedure after the index event. Patients who underwent a revascularization procedure were younger, had a lower incidence rate of prior myocardial infarction and ventricular arrhythmia, had a higher left ventricular ejection fraction, had less congestive heart failure, and were more likely to have had ventricular fibrillation as the presenting arrhythmia. Patients who underwent revascularization had a better survival rate than did those who did not undergo such a procedure after the index event, and adjustment for differing baseline patient covariates did not alter the relative survival rate benefit. Further, ICD implantation offered a similar survival rate advantage to those patients in the AVID registry with coronary artery disease independent of revascularization.

CONCLUSION

Coronary revascularization in the AVID registry patients with coronary artery disease effected a survival rate benefit that was not attributable to differences in baseline patient characteristics. The benefit of ICD on patient survival rate was not attenuated by a revascularization procedure.

Life-threatening ventricular arrhythmias due to transient or correctable causes: high risk for death in follow-up

OBJECTIVES

This study evaluated the prognosis of patients resuscitated from ventricular tachycardia (VT) or ventricular fibrillation (VF) with a transient or correctable cause suspected as the cause of the VT/VF.

BACKGROUND

Patients resuscitated from VT/VF in whom a transient or correctable cause has been identified are thought to be at low risk for recurrence and often receive no primary treatment for their arrhythmias.

METHODS

In the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial, patients with a potentially transient or correctable cause of VT/VF were not eligible for randomization. The mortality of these patients was compared with the mortality of patients with a known high risk of recurrence of VT/VF in the AVID registry.

RESULTS

Compared with patients having high risk VT/VF, those with a transient or correctable cause for their presenting VT/VF were younger and had a higher left ventricular ejection fraction. These patients were more often treated with revascularization as the primary therapy, more commonly received a beta-blocker, less often required therapy for congestive heart failure and less commonly received either an antiarrhythmic drug or an implantable cardioverter defibrillator. Nevertheless, subsequent mortality of patients with a transient or correctable cause of VT/VF was no different or perhaps even worse than that of the primary VT/VF population.

CONCLUSIONS

Patients identified with a transient or correctable cause for their VT/VF remain at high risk for death. Further research is needed to define truly reversible causes of VT/VF. Meanwhile, these patients may require more aggressive evaluation, treatment and follow-up than is currently practiced.

TACHYARRHYTHMIAS ASSOCIATED WITH ACUTE MYOCARDIAL INFARCTION

The occurrence of tachyarrhythmias in the setting of an MI is quite common. As appropriate therapy for the MI is underway, any tachyarrhythmia should be quickly recognized, the cause determined, and appropriate therapy initiated because of instability or before the onset of a cycle of ischemia, begetting tachycardia, begetting more ischemia.

Sudden cardiac death

SCD continues to be an important cause of death and morbidity. Despite expanding insight into the mechanisms causing SCD, the population at high risk is not being effectively identified. Although there is still much to do in the management phase of SCD (predicting the efficacy of various therapies), recent clinical trials have helped define the relative risks and benefits of therapies in preventing SCD. Trials are underway to determine whether treating other patient populations, including asymptomatic patients after MI, will improve survival rate. The approach to reducing mortality rate will always be multifaceted; primary prevention of coronary artery disease and prompt salvage of jeopardized myocardium are 2 important aspects of this approach. In addition to interventions for MI, such as myocardial revascularization when indicated, simple and easily administered therapies that are likely to remain the most effective prophylactic interventions are aspirin, ACE inhibitors, beta-blockers, and cholesterol-lowering agents. However, the MADIT and AVID data clearly demonstrate a role for ICD therapy in a subgroup of patients who have VT/VF and are at risk of cardiac arrest. Even though the absolute magnitude of benefit associated with ICDs is still to be determined, the AVID study and other recent reports provide convincing evidence that patients who have VT/VF fare better with ICDs than with antiarrhythmic drug therapy. For the high-risk population described in this article, in addition to aggressive anti-ischemic and heart failure therapy, ICDs are now a mainstay of life-saving treatment. Still to be surmounted is the challenge of identifying patients who have nonischemic substrates and of providing them with the appropriate therapy. Guided by genetic studies and new insight into the mechanisms of such problems as congenital long QT syndrome, life-saving and life-enhancing therapies may soon be available for the management of SCD.

Secondary prevention of sudden death: the Dutch Study, the Antiarrhythmics Versus Implantable Defibrillator Trial, the Cardiac Arrest Study Hamburg, and the Canadian Implantable Defibrillator Study

Although indisputably effective in the prevention of sudden death, use of implantable cardioverter defibrillator (ICD) therapy may not necessarily affect all-cause mortality, as most patients at risk also present with severely depressed left ventricular dysfunction. Correction of the sudden death risk in these patients creates a new clinical condition in need of a careful assessment. Should all-cause mortality be affected by the expected reduction in sudden death rate associated with ICD therapy, issues of critical importance, such as the time extent of life prolongation and the associated quality of life, still remain to established. To investigate the potential benefit of ICD therapy compared with antiarrhythmic drug treatment, 4 prospective studies--the Dutch trial, the Antiarrhythmics Versus Implantable Defibrillators (AVID) study, the Cardiac Arrest Study Hamburg (CASH), and the Canadian Implantable Defibrillator Study (CIDS)--have been conducted in which patients with documented sustained ventricular arrhythmia were randomized to 1 of these 2 treatment strategies. The enrollment criteria differed in these 4 studies: (1) in the Dutch trial, they included cardiac arrest secondary to a ventricular arrhythmia, old (> 4 weeks) myocardial infarction, and inducible ventricular arrhythmia; (2) in AVID and CIDS, ventricular fibrillation or poorly tolerated ventricular tachycardia; and (3) in CASH, cardiac arrest secondary to a ventricular arrhythmia regardless of the underlying disease. With regard to the antiarrhythmic drugs, the Dutch trial tested class I and III agents, whereas AVID and CIDS compared ICD therapy with class III agents (mostly amiodarone). In CASH, 3 drug subgroups were investigated: propafenone, amiodarone, and metoprolol. All trials used all-cause mortality as the primary endpoint. Data from these trials provide support for ICD as a therapy superior to antiarrhythmic drugs in prolonging survival in patients meeting the entry criteria. This review briefly summarizes the methods, results, limitations, and clinical implications of these 4 studies.

Cardiac mechano-electric feedback in man: clinical relevance

Clinical conditions associated with sudden cardiac death due to arrhythmia are frequently accompanied by abnormalities of mechanical loading and wall stretch. These arrhythmias may result from several mechanisms including secondary depolarisations during or following the action potential or from a combination of conduction slowing and action potential shortening. Mechanical perturbations have been shown to reproduce these electrophysiological effects experimentally. However the effect of mechanical intervention is complex depending on the timing and intensity of the stimulus and the interplay between effects mediated via stretch activated channels and calcium cycling. Studies in patients during cardiac catheterisation or cardiac surgery using monophasic action potentials have shown alteration in the time course and shape of action potential repolarisation in response to changes in ventricular loading. Although stretch in experimental preparations has been shown to be arrhythmogenic, particularly in pathological conditions, the role of mechanically induced electrophysiological changes in important clinical ventricular arrhythmias remains to be established.

Stretch-induced changes in heart rate and rhythm: clinical observations, experiments and mathematical models

Clinical and research data indicate that active and passive changes in the mechanical environment of the heart are capable of influencing both the initiation and the spread of cardiac excitation via pathways that are intrinsic to the heart. This direction of the cross-talk between cardiac electrical and mechanical activity is referred to as mechano-electric feedback (MEF). MEF is thought to be involved in the adjustment of heart rate to changes in mechanical load and would help to explain the precise beat-to-beat regulation of cardiac performance as it occurs even in the recently transplanted (and, thus, denervated) heart. Furthermore, there is clinical evidence that MEF may be involved in mechanical initiation of arrhythmias and fibrillation, as well as in the re-setting of disturbed heart rhythm by 'mechanical' first aid procedures. This review will outline the clinical relevance of cardiac MEF, describe cellular correlates to the responses observed in situ, and discuss the role that quantitative mathematical models may play in identifying the involvement of cardiac MEF in the regulation of heart rate and rhythm.

Myocardial perfusion during cardiopulmonary resuscitation (CPR): effects of 10, 25 and 50% coronary stenoses

Myocardial blood flow under normal physiologic conditions remains relatively unaltered by coronary lesions with diameter stenosis of less than 70%. However, during cardiac arrest and cardiopulmonary resuscitation (CPR), autoregulation of coronary blood flow is compromised. We studied the effect of previously considered 'trivial' coronary stenoses of 10, 25 and 50% on distal myocardial perfusion in 39 swine undergoing CPR for cardiac arrest. Endocardial blood flow distal to the stenosis was significantly less than that proximal in all the different stenoses groups (P < 0.05). A 50% diameter stenosis also compromised epicardial blood flow distal to the stenosis (P < 0.05). This study suggests that any coronary lesion may compromise myocardial perfusion during CPR. Since the vast majority of cardiac arrest victims have coronary artery disease, careful attention to maximizing myocardial blood flow during CPR is needed.

Segmental wall motion abnormalities alter vulnerability to ventricular ectopic beats associated with acute increases in aortic pressure in patients with underlying coronary artery disease

OBJECTIVE

To evaluate whether patients with coronary artery disease are susceptible to pressure related ventricular arrhythmias, and if so to identify possible risk factors.

DESIGN

Interventional study.

METHODS

Metaraminol was given to 43 patients undergoing coronary arteriography for ischaemic heart disease to increase their aortic pressure, provided their systolic blood pressure was < 160 mm Hg and they were in sinus rhythm, without any ventricular ectopic activity (or with fewer than six ventricular ectopic beats a minute) during a five minute control period.

RESULTS

During the metaraminol infusion, systolic aortic pressure rose from 131 (15) to 199 (12) mm Hg (mean (SD)). Ventricular ectopy appeared (or ventricular ectopic beats increased by > 100%) in 13/43 patients. Ventricular ectopy was not related to age, sex, presence of hypertension, history of myocardial infarction, use of beta blockers, positive exercise test, number of vessels diseased, or heart rate change during metaraminol infusion. There was a strong relation between the appearance of ventricular arrhythmia and segmental wall motion abnormalities: 1/19 (5.3%, 95% confidence interval 0.1% to 26.0%) without abnormality; 2/12 (16.7%, 2.1% to 48.4%) with hypokinesia; and 10/12 (83.3%, 51.6% to 97.1%) with akinesia or dyskinesia, chi 2 = 22.7, p < 0.001). Ejection fraction was also a significant but not independent risk factor.

CONCLUSIONS

Patients with segmental wall motion abnormalities are predisposed to ventricular ectopic beats during an increase in systolic aortic pressure. This could be explained by associated electrophysiological inhomogeneity. The presence of mechanical inhomogeneity, as may occur in postinfarction akinesia or dyskinesia, may affect the aortic pressure above which ventricular arrhythmias appear.

Adverse effects of interrupting precordial compression during cardiopulmonary resuscitation

OBJECTIVES

In the current operation of automated external defibrillators, substantial time may be consumed for a "hands off" interval during which precordial compression is discontinued to allow for automated rhythm analyses before delivery of the electric countershock. The effects of such a pause on the outcomes of cardiopulmonary resuscitation were investigated.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

Research laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Ventricular fibrillation was electrically induced in 25 Sprague-Dawley rats. After 4 mins of untreated ventricular fibrillation, precordial compression was begun and continued for 6 mins. Animals were then randomized to receive an immediate defibrillation shock or the defibrillation attempt was delayed for intervals of 10, 20, 30, or 40 secs.

MEASUREMENTS AND MAIN RESULTS

Immediate defibrillation restored spontaneous circulation in each instance. When defibrillation was delayed for 10 or 20 secs, spontaneous circulation was restored in three of five animals in each group. After a 30-sec delay, spontaneous circulation was restored in only one of five animals (p < .05). No animal was successfully resuscitated after a 40-sec delay (p < .01). With increasing delays, 24- and 48-hr survival rates were correspondingly reduced.

CONCLUSIONS

During resuscitation from ventricular fibrillation, prolongation of the interval between discontinuation of precordial compression and delivery of the first electric countershock substantially compromises the success of cardiac resuscitation. Accordingly, automated defibrillators are likely to be maximally effective if they are programmed to secure minimal "hands off" delay before delivery of the electric countershock.

Pattern of coronary artery disease in patients with ventricular tachycardia and fibrillation exposed by exercise-induced ischemia

The majority of patients with serious exercise-induced ventricular arrhythmias have extensive coronary artery disease. These arrhythmias develop, however, only in a minority of patients with angina pectoris. The purpose of the present study was therefore to investigate whether these arrhythmia patients are characterized by any specific "arrhythmogenic" pattern of coronary artery disease. Among 1100 consecutive patients undergoing coronary artery bypass grafting, 30 (2.7%) patients had ventricular tachycardia or fibrillation during preoperative exercise testing. For each of these patients, two matched controls with angina pectoris but no ventricular arrhythmia were selected. All patients underwent angiocardiography by standard techniques. The recordings were blinded and interpreted in random order by an experienced invasive cardiologist. Significant stenosis (> or = 50%) of the main left coronary artery was found in 27% of the case patients compared to 12% of the matched controls (p = 0.069, two-tailed t test); proximal left anterior descending artery stenoses were more frequent in the arrhythmia patients. Although stenosis > or = 75% was only moderately more frequent in the case patients, the difference was highly significant for stenosis > or = 95%, which was seen in 47% of the case patients compared to 22% of the controls (p = 0.015). The difference was even more pronounced for the combination of main left coronary artery stenosis and/or high-grade stenosis (> or = 95%) of the left anterior descending artery. This pattern was seen in 60% of the case patients compared to 28% of the matched controls (p = 0.004).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of coronary bypass graft surgery for the prevention of sudden cardiac death: recurrent episodes after ICD implantation and review of literature

Sudden cardiac death (SCD) accounts for at least 50% of the mortality of patients with ischemic heart failure. Ventricular arrhythmias are responsible for most cases of sudden cardiac death. There is some evidence that coronary artery bypass graft (CABG) surgery may reduce the incidence of recurrent episodes of SCD by prevention of myocardial ischemia. To test the hypothesis that CABG surgery is effective in the prevention of SCD, we compared the recordings of implantable cardioverter defibrillators (ICD) in patients who underwent ICD implantation alone (n = 64) or ICD implantation and concomitant CABG surgery respectively (n = 11). All patients had experienced out of hospital cardiac arrest. ICD recordings were obtained every 3 months and the number of recurrent episodes of ventricular tachycardia (VT) for each time period was noted. Three months following ICD implantation patients in the surgically treated group had an average of one episode of VT per patient as compared to 2.7 episodes in the nonsurgical group. This difference was observed during the following months as well. However, at no time (up to 18 months of follow-up) this difference reached statistical significance. There were no deaths in the surgically treated group. Although we could not demonstrate a statistical significant difference between the two groups, there was a tendency in the surgically treated group to have less episodes of recurrent VT than in the medically treated group. We, therefore, conclude that survivors of SCD presenting with multivessel coronary artery disease (CAD) should undergo coronary artery bypass grafting to prevent myocardial ischemia as the triggering event for lethal ventricular arrhythmias.

Antiarrhythmic versus antifibrillatory actions: inference from experimental studies

Pathophysiology of the coronary circulation is a major contributor to altering the myocardial substrate, rendering the heart susceptible to the onset of arrhythmias associated with sudden cardiac death. Antiarrhythmic drug therapy for the prevention of sudden cardiac death has been provided primarily on the basis of trial and error and in some instances based on ill-suited preclinical evaluations. The findings of the Cardiac Arrhythmia Suppression Trial (CAST) requires a reexamination of the manner in which antiarrhythmic drugs are developed before entering into clinical testing. The major deficiency in this area of experimental investigation has been the lack of animal models that would permit preclinical studies to identify potentially useful or deleterious therapeutic agents. Further, CAST has emphasized the need to distinguish between pharmacologic interventions that suppresses nonlethal disturbances of cardiac rhythm as opposed to those agents capable of preventing lethal ventricular tachycardia or ventricular fibrillation. Preclinical models for the testing of antifibrillatory agents must consider the fact that the superimposition of transient ischemic events on an underlying pathophysiologic substrate makes the heart susceptible to lethal arrhythmias. Proarrhythmic events, not observed in the normal heart, may become manifest only when the myocardial substrate has been altered. We describe a model of sudden cardiac death that may more closely simulate the clinical state in humans who are at risk. The experimental results show a good correlation with clinical data regarding agents known to reduce the incidence of lethal arrhythmias as well as those showing proarrhythmic actions.

Cardiac arrest and sudden unexpected death in variant angina: complications of coronary spasm that can occur in the absence of severe organic coronary stenosis

Experiences in 81 patients with variant angina were reviewed with the goal of determining which clinical features were associated with the greatest risk of angina-linked cardiac arrest (13 patients) or sudden unexpected death (9 patients). The risk of occurrence of one of these actually or potentially fatal events was approximately tripled by the presence of either a history of angina-linked syncope or documentation of serious arrhythmia complicating attacks. An unexpected finding was that the risk was increased 1.5-fold by the absence of high-grade organic coronary stenosis. Cardiac arrest and sudden death are important risks of variant angina, which can occur without the presence of severe organic coronary stenosis. These risks can be reduced by adequate vasodilator therapy that includes a calcium channel blocker.

Minimal coronary stenoses and left ventricular blood flow during CPR

STUDY OBJECTIVE

To assess the effect of a 33% coronary stenosis on myocardial blood flow during normal sinus rhythm and CPR.

DESIGN

Prospective, before and after cardiac arrest and CPR; before and after creation of a 33% stenosis.

SETTING

The University of Arizona Resuscitation Research Laboratory.

SUBJECTS

Ten domestic closed-chest swine with patent coronary stenoses.

INTERVENTIONS

A Teflon cylinder was placed in the mid-left anterior descending coronary artery to create a 33% stenosis. Myocardial blood flow was measured with colored microspheres both proximal and distal to the stenosis during normal sinus rhythm and during CPR.

MEASUREMENTS AND MAIN RESULTS

During normal sinus rhythm, the stenosis did not alter the amount of myocardial blood flow distribution or quantity. Proximal to the stenosis the endocardial/epicardial flow ratio was 1.49 +/- 0.33, and distal to the stenosis it was 1.50 +/- 0.50. Likewise, during normal sinus rhythm, blood flow proximal and distal to the stenosis did not differ for either the epicardium (79 +/- 9 versus 66 +/- 13 mL/min/100 g) or the endocardium (111 +/- 27 versus 83 +/- 19 mL/min/100 g). However, the distribution of myocardial blood flow was markedly altered during CPR. The resultant endocardial/epicardial flow ratios were significantly less than during normal sinus rhythm, 0.49 +/- 0.11 (three minutes of CPR) and 0.74 +/- 0.07 (eight minutes of CPR) proximal to the stenosis and 0.39 +/- 0.15 (three minutes of CPR) and 0.49 +/- 0.14 (eight minutes of CPR) distal to the stenosis (P less than .05 versus normal sinus rhythm). In the presence of a 33% mid-left anterior descending coronary artery stenosis, endocardial blood flow at eight minutes of CPR was significantly lower distal to the stenosis compared with proximal to the stenosis (23 +/- 7 mL/min/100 g versus 74 +/- 18 mL/min/100 g; P less than .02).

CONCLUSION

Minimal coronary lesions that do not diminish myocardial perfusion during normal physiologic conditions appear to significantly decrease subendocardial blood flow during cardiac arrest and CPR.

Influence of coronary bypass surgery on subsequent outcome of patients resuscitated from out of hospital cardiac arrest

The effect of coronary bypass surgery on recurrent cardiac arrest was estimated in 265 patients resuscitated from out of hospital cardiac arrest between 1970 and 1988. From this cohort, 85 patients (32%) underwent coronary bypass surgery after recovery from cardiac arrest and 180 patients (68%) were treated medically. A multivariate Cox analysis was used to estimate the effect of coronary bypass surgery on subsequent survival after adjusting for effects of age, prior cardiac history, ejection fraction, year of the event, history of angina, antiarrhythmic drug use and whether the arrest was related to acute myocardial infarction. The use of coronary bypass surgery had a significant effect in reducing the incidence of subsequent cardiac arrest during follow-up study (risk ratio [RR] 0.48, 95% confidence interval [CI] 0.24 to 0.97, p less than 0.04). There was also a trend consistent with a reduction in total cardiac mortality (RR 0.65, 95% CI 0.39 to 1.10, p = 0.10). These findings suggest that coronary bypass surgery may reduce the incidence of sudden death in suitable patients resuscitated from an episode of ventricular fibrillation.

Monophasic action potential recordings during acute changes in ventricular loading induced by the Valsalva manoeuvre

OBJECTIVE

The strong association between ventricular arrhythmia and ventricular dysfunction is unexplained. This study was designed to investigate a mechanism by which a change in ventricular loading could alter the time course of repolarisation and hence refractoriness. A possible mechanism may be a direct effect of an altered pattern of contraction on ventricular repolarisation and hence refractoriness. This relation has been termed contraction-excitation feedback or mechano-electric feedback.

METHODS

Monophasic action potentials were recorded from the left ventricular endocardium as a measure of the time course of local repolarisation. The Valsalva manoeuvre was used to change ventricular loading by increasing the intrathoracic pressure and impeding venous return, and hence reducing ventricular pressure and volume (ventricular unloading).

PATIENTS

23 patients undergoing routine cardiac catheterisation procedures: seven with no angiographic evidence of abnormal wall motion or history of myocardial infarction (normal), five with a history of myocardial infarction but with normal wall motion, and 10 with angiographic evidence of abnormal wall motion--with or without previous infarction. One patient was a transplant recipient and was analysed separately.

SETTING

Tertiary referral centre for cardiology.

RESULTS

In patients with normal ventricles during the unloading phase of the Valsalva manoeuvre (mean (SD)) monophasic action potential duration shortened from 311 (47) ms to 295 (47) ms (p less than 0.001). After release of the forced expiration as venous return was restored the monophasic action potential duration lengthened from 285 (44) ms to 304 (44) ms (p less than 0.0001). In the group with evidence of abnormal wall motion the direction of change of action potential duration during the strain phase was normal in 7/21 observations, abnormal in 6/21, and showed no clear change in 8/21. During the release phase 11/20 observations were normal, five abnormal, and four showed no clear change. In those with myocardial infarction four out of five patients had changes that resembled those with normal ventricles but the changes were less pronounced. There were no differences in any of the three groups between the changes in monophasic action potential duration in patients taking beta blockers and those who were not. The changes in monophasic action potential duration in the transplanted heart resembled those in the group with normal ventricles. Inflections on the repolarisation phase of the monophasic action potential consistent with early afterdepolarisations were seen in three of the patients with abnormal wall motion and in none of those with normal wall motion.

CONCLUSIONS

These results are further evidence that changes in ventricular loading influence repolarisation. When wall motion was abnormal the effects on regional endocardial repolarisation were often opposite in direction to those when it was normal. Thus regional differences in wall motion could generate local electrophysiological inhomogeneity which may be relevant to the association of arrhythmia with impaired left ventricular function.

Unsuccessful emergency medical resuscitation--are continued efforts in the emergency department justified?

BACKGROUND

The majority of attempts to resuscitate victims of prehospital cardiopulmonary arrest are unsuccessful, and patients are frequently transported to the emergency department for further resuscitation efforts. We evaluated the efficacy and costs of continued hospital resuscitation for patients in whom resuscitation efforts outside the hospital have failed.

METHODS

We reviewed the records of 185 patients presenting to our emergency department after an initially unsuccessful, but ongoing, resuscitation for a prehospital arrest (cardiac, respiratory, or both) by an emergency medical team. Prehospital and hospital characteristics of treatment for the arrest were identified, and the patients' outcomes in the emergency room were ascertained. The hospital course and the hospital costs for the patients who were revived were determined.

RESULTS

Over a 19-month period, only 16 of the 185 patients (9 percent) were successfully resuscitated in the emergency department and admitted to the hospital. A shorter duration of prehospital resuscitation was the only characteristic of the resuscitation associated with an improved outcome in the emergency department. No patient survived until hospital discharge, and all but one were comatose throughout hospitalization. The mean stay in the hospital was 12.6 days (range, 1 to 132), with an average of 2.3 days (range, 1 to 11) in an intensive care unit. The total hospital cost for the 16 patients admitted was $180,908 (range per patient, $1,984 to $95,144).

CONCLUSIONS

In general, continued resuscitation efforts in the emergency department for victims of cardiopulmonary arrest in whom prehospital resuscitation has failed are not worthwhile, and they consume precious institutional and economic resources without gain.

Late outcome of survivors of out-of-hospital cardiac arrest with left ventricular ejection fractions greater than or equal to 50% and without significant coronary arterial narrowing

In a retrospective survey of 1,195 survivors of out-of-hospital ventricular fibrillation, 43 patients were identified in whom left ventricular ejection fraction was greater than or equal to 0.50 and in whom no coronary artery stenosis of greater than or equal to 50% luminal diameter were present. Thirteen (30%) of these patients had hypokinesia on left ventriculography, and 20 patients (47%) had a persistently abnormal electrocardiogram. Seven patients (16%) had recurrent out-of-hospital cardiac arrest during an average follow-up of 86 +/- 54 months. The presence of either wall motion or electrocardiographic abnormalities defined patients with a several-fold higher risk of recurrent cardiac arrest than those without such abnormalities. The risk for recurrent cardiac arrest within 5 years was 30% in those with abnormal electrocardiograms versus 5% in the others (p less than 0.03). Age was an independent predictor of recurrent cardiac arrest in this group (p less than 0.01); surprisingly, recurrent cardiac arrest was occurring more often among younger patients. Although cardiac arrest is unusual in patients without major structural heart disease, its recurrence in such survivors is common. Patients at relatively high risk for recurrent ventricular fibrillation can be identified by their youth and by abnormalities detected on the surface 12-lead electrocardiogram or by contrast left ventriculography.

The effect of coronary artery lesions on the relationship between coronary perfusion pressure and myocardial blood flow during cardiopulmonary resuscitation in pigs

In subjects without coronary disease, coronary perfusion pressure generated with closed-chest cardiopulmonary resuscitation (CPR) bears a direct relationship to myocardial blood flow. The effect of coronary lesions on this relationship was studied in an experimental porcine model not requiring thoracotomy. Coronary stenoses (a 50% reduction in coronary cross-sectional area) or total coronary occlusions were created by percutaneous, transarterial catheter placement of a Teflon cylinder in the left anterior descending artery of 21 swine (30 to 60 kg). Coronary perfusion pressure, defined as the aortic diastolic pressure minus right atrial diastolic pressure, was correlated with myocardial blood flow measured with nonradioactive, colored microspheres during external chest compression CPR. Complete occlusion of the left anterior coronary artery resulted in essentially no CPR-generated blood flow to the anterior myocardium distal to the site of occlusion. Coronary perfusion pressure showed a positive correlation with myocardial blood flow above the area of occlusion (r = 0.783; p less than 0.01) but did not correlate with myocardial blood flow below the occlusion site (r = 0.239). In the presence of a patent coronary artery stenosis, coronary perfusion pressure correlated with myocardial blood flow both above (r = 0.841; p less than 0.001) and below (r = 0.508; p less than 0.05) the stenosis. During closed-chest CPR producing coronary perfusion pressures between 30 and 60 mm Hg, anterior myocardial blood flow was 109 +/- 16 ml/min/100 gm above a patent stenosis and 66 +/- 13 ml/min/100 gm below the stenosis (p less than 0.005). Over a wide range of coronary perfusion pressures, myocardial blood flow below a coronary lesion was significantly less than that above the lesion. Coronary occlusions and stenoses can substantially affect the amount of CPR-generated coronary perfusion pressure needed to produce distal myocardial blood flow.

Significance of ventricular tachyarrhythmias complicating cardiac catheterization: a CASS Registry Study

Ventricular tachycardia and ventricular fibrillation are recognized complications of cardiac catheterization. Despite numerous reports documenting the frequency of these occurrences, their significance has not been systematically examined. Accordingly, the outcome of 108 patients who experienced either ventricular tachycardia or ventricular fibrillation during coronary angiography between 1975 and 1979 in the Coronary Artery Surgery Study (CASS) Registry were examined. There were 20,142 patients analyzed. Patients with ventricular tachyarrhythmias had more objective evidence of left ventricular impairment, clinical heart failure, and ventricular arrhythmia recorded as a clinical symptom. The overall 5-year survival rates were 83% and 88% for patients with and without ventricular tachyarrhythmias, respectively (p = 0.07). When ventricular function, age, gender, angina, and previous myocardial infarction were added in a stepwise Cox survival analysis, the presence of arrhythmias was not significant (p = 0.66). At 5 years, 80% of the medically treated patients and 82% of the surgically treated patients remained alive (p = 0.95). The only statistically significant differences in the patients with ventricular arrhythmias who were treated medically or surgically were age (medically treated patients 52 +/- 10 years, surgical patients 57 +/- 9 years, p = 0.01) and number of diseased vessels (p less than 0.001). In a stepwise Cox survival analysis, functional impairment secondary to congestive heart failure was the only significant covariate to affect survival in the medical and surgical groups (p = 0.0001). Surgical therapy itself was not significant (p = 1.00). The incidence of sudden death during 5 years for patients with and without ventricular tachyarrhythmias during catheterization was 5% and 4%, respectively (p = 0.28).(ABSTRACT TRUNCATED AT 250 WORDS)

Surgical coronary revascularization in survivors of prehospital cardiac arrest: its effect on inducible ventricular arrhythmias and long-term survival

In a selected subgroup of 50 survivors of cardiac arrest, the impact of surgical myocardial revascularization on inducible arrhythmias, arrhythmia recurrence and long-term survival was examined. The effects of several clinical, angiographic and electrophysiologic variables on arrhythmia recurrence and survival were also analyzed. All patients had a prehospital cardiac arrest and severe operable coronary artery disease and underwent myocardial revascularization. Preoperative electrophysiologic study was performed in 41 patients; 33 (80%) had inducible ventricular arrhythmias. Of 42 patients studied off antiarrhythmic drugs postoperatively, 19 (45%) had inducible ventricular arrhythmias. Thirty patients with inducible arrhythmias preoperatively underwent postoperative testing off antiarrhythmic drugs; arrhythmia induction was suppressed in 14 (47%). By multivariate analysis, the induction of ventricular fibrillation at the preoperative electrophysiologic study was the only significant predictor of induced ventricular arrhythmia suppression by coronary surgery (p less than 0.001). Inducible ventricular fibrillation was not present postoperatively in any of the 11 patients who manifested this arrhythmia preoperatively. In contrast, inducible ventricular tachycardia persisted in 80% of patients in whom preoperative testing induced this arrhythmia. Patients were followed up for 39 +/- 29 months. There were four arrhythmia recurrences; one was fatal. There were three nonsudden cardiac deaths and three noncardiac deaths. By life-table analysis, 5 year survival, cardiac survival and arrhythmia-free survival rates were 88%, 98%, and 88%, respectively. Depressed left ventricular ejection fraction and advanced age were predictive of death (p = 0.015 and 0.026, respectively) and cardiac death (p = 0.037 and 0.05, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Sudden arrhythmic cardiac death--mechanisms, resuscitation and classification: the Seattle perspective

Ventricular fibrillation (VF) is the first recorded arrhythmia in 75% of patients who have a sudden cardiovascular collapse. Rarely (1%) does sustained ventricular tachycardia (VT) alone cause collapse and unconsciousness. Whether all VF begins as VT is unknown. Early application of cardiopulmonary resuscitation and rapid defibrillation are essential to ensure survival and satisfactory neurologic recovery. During the last 2 years in Seattle, the initial resuscitation rate for VF was 269 of 447 patients (60%), with 114 of 447 patients (26%) surviving long-term. Survivors of VF have a high overall risk of recurrent VF, with many univariate risk factors identified: evidence of poor left ventricular function (history of congestive heart failure, prior myocardial infarction [MI] or low ejection fraction), extensive coronary artery disease, absence of a new MI (either Q wave or non-Q wave) with VF, male gender, advanced age, complex or high-frequency ventricular ectopy on Holter recording, inducibility at electrophysiologic study, exercise-induced angina or hypotension, and smoking. Classification of cardiac deaths as arrhythmic or nonarrhythmic is important in interpreting the therapeutic response. However, because many patients have chronic symptoms, timing of the onset of a new event is difficult. Furthermore, accurate timing of an event does not guarantee correct classification. Sudden death is not necessarily arrhythmic, nor is all arrhythmic death sudden. Total cardiac mortality may be a simpler and more relevant end point to measure the overall effect of antiarrhythmic therapy.

Exercise electrophysiology testing: the effect of exercise on the induction of ventricular arrhythmias by programmed ventricular stimulation

In order to assess the effect of acute, reversible myocardial ischemia on the outcome of programmed ventricular stimulation (PVS), ventricular stimulation was performed at rest, during exercise, and during recovery in 10 patients with coronary artery disease. Of these ten patients, four were tested while off antiarrhythmic drugs and six were tested on antiarrhythmic drug therapy. Nine of the ten patients developed acute myocardial ischemia during exercise PVS. However, in only two of these ten patients ventricular arrhythmia could be induced by PVS, one during exercise and one during recovery.

Prevalence of silent myocardial ischemia in survivors of cardiac arrest

The prevalence and type of ischemia (silent vs painful) in survivors of cardiac arrest not associated with acute myocardial infarction were studied to test the hypothesis that survivors may have an increased prevalence of silent ischemia. Of 48 survivors of cardiac arrest over a 4-year period who had undergone exercise testing, 24 met inclusion criteria. These 24 subjects had documented ventricular fibrillation and coronary artery disease proven by cardiac catheterization or a previous electrocardiographic pattern of myocardial infarction. Thirteen of 24 (54%) had a positive treadmill stress test (greater than or equal to 1.0 mm flat or downsloping ST depression). The mean resting left ventricular ejection fraction was 43%. Nine of 11 patients (82%) who had exercise radionuclide studies performed had ischemic abnormalities (less than 5% increase in left ventricular ejection fraction with new or worsened wall motion abnormalities). Thus, 16 of 24 (67%) had a positive treadmill stress test or radionuclide ventriculogram. Only 1 of 16 (6%) had painful ischemia (p less than 0.001 relative to an even distribution of painful vs painless ischemia). Thus, survivors of cardiac arrest have a high prevalence of exercise-induced ischemia, and in most the ischemia is silent.

Sudden cardiac death: etiologies, pathogenesis, and management

Sudden death claims an estimated 350,000 lives per year in the United States. When death occurs within 1 hour of the onset of symptoms, 90% are the result of ventricular tachyarrhythmias. The majority of victims are middle-aged men with coronary artery disease, but in approximately 25%, sudden death is the presenting manifestation of their problem. In some populations, the detection of premature ventricular complexes (PVCs) by ambulatory monitoring is predictive of an increased risk of sudden death. However, the arrhythmia that best predicts this risk is unclear, and ambient arrhythmias are only a modest marker of this risk. Therapy to suppress asymptomatic PVCs has not been shown to be effective in preventing sudden death, and in some cases, lethal arrhythmias can be prevented without significant effects on ambient arrhythmias. Other risk markers such as depressed left ventricular function and the presence of low-amplitude, long-duration, late potentials recorded on a signal averaged electrocardiogram are more powerful predictors of risk than are PVCs. These latter findings in particular support the presence of areas of slow electrical conduction (a requirement for reentrant mechanism arrhythmias) and suggest that an abnormal electrical environment or "substrate" is the most important factor in this problem. The management of patients at risk for sudden death is controversial. While postinfarct survivors with arrhythmias constitute a population at increased risk, the absolute risk is only about 5% in the first year and has not been shown to be improved by conventional antiarrhythmic drugs. Small study size, arrhythmia variability, ill-defined end points, and proarrhythmia may partially explain this apparent lack of efficacy. The prophylactic use of antiarrhythmic drugs other than beta-blockers to prevent sudden death in asymptomatic populations at risk is therefore of unproven benefit. By contrast, patients who have survived a life-threatening arrhythmia unrelated to an acute myocardial infarction have an approximately 30% risk of recurrence in the following year. In these patients, the use of ambulatory monitoring to guide therapy is limited by the high incidence of false-negative responses (lethal arrhythmia recurrence despite ambient arrhythmia suppression) and the lack of frequent spontaneous arrhythmias in many patients. In this patient population, electrophysiological testing can be used to prognosticate recurrence and gain insight into arrhythmia mechanism, stability, and hemodynamic tolerance. The technique is also useful in guiding both pharmacological and nonpharmacological therapy.(ABSTRACT TRUNCATED AT 400 WORDS)