Out-of-hospital cardiac arrest. Use of electrophysiologic testing in the prediction of long-term outcome

Dissolution of spiral wave's core using cardiac optogenetics

Rotating spiral waves in the heart are associated with life-threatening cardiac arrhythmias such as ventricular tachycardia and fibrillation. These arrhythmias are treated by a process called defibrillation, which forces electrical resynchronization of the heart tissue by delivering a single global high-voltage shock directly to the heart. This method leads to immediate termination of spiral waves. However, this may not be the only mechanism underlying successful defibrillation, as certain scenarios have also been reported, where the arrhythmia terminated slowly, over a finite period of time. Here, we investigate the slow termination dynamics of an arrhythmia in optogenetically modified murine cardiac tissue both in silico and ex vivo during global illumination at low light intensities. Optical imaging of an intact mouse heart during a ventricular arrhythmia shows slow termination of the arrhythmia, which is due to action potential prolongation observed during the last rotation of the wave. Our numerical studies show that when the core of a spiral is illuminated, it begins to expand, pushing the spiral arm towards the inexcitable boundary of the domain, leading to termination of the spiral wave. We believe that these fundamental findings lead to a better understanding of arrhythmia dynamics during slow termination, which in turn has implications for the improvement and development of new cardiac defibrillation techniques.

Long term risk of recurrence among survivors of sudden cardiac arrest: A systematic review and meta-analysis

AIMS

With a growing number of survivors of sudden cardiac arrest globally, their natural disease progression is of interest. This systematic review and meta-analysis aimed to determine the risk of recurrence after sudden cardiac arrest and its associated risk factors.

METHODS

Medline, Embase, Cochrane Library and Scopus were searched from inception to October 2021. Studies involving survivors of an out-of-hospital sudden cardiac arrest event of any non-traumatic aetiology were included. Meta-analyses of proportions using the random-effects model estimated the primary outcome of first recurrent sudden cardiac arrest incidence as well as secondary outcomes including cumulative incidence of recurrence at 1-year and incidence of second recurrence among survivors of first recurrence. A recurrent episode was defined as a sudden cardiac arrest that occurs 28 or more days after the index event. Subgroup and meta-regression analyses were conducted for predetermined variables. The Newcastle-Ottawa Scale was used to assess risk of bias for most studies.

RESULTS

35 studies of moderate to high quality comprising a total of 7186 survivors were analysed. The pooled incidence of first recurrence was 15.24% (32 studies; 95%CI, 11.01-19.95; mean follow-up time, 41.3 ± 29.3 months) and second recurrence was 35.03% (3 studies; 95%CI, 19.65-51.93; mean follow-up time, 161.1 ± 54.3 months). At 1-year, incidence of recurrence was 10.62% (3 studies; 95%CI, 0.25-30.42). Subgroup analyses found no significant difference (p = 0.204) between incidence of first recurrence published from 1975-1992 and 1993-2021, and between studies with mean follow-up time of <24 months, 24-48 months, and >48 months. On meta-regression, initial shockable rhythm increased incidence of first recurrence (p = 0.01).

CONCLUSION

15.24% of sudden cardiac arrest survivors experienced a recurrence, and of these, 35.03% experienced a second recurrence. Most recurrences occurred in the first year. Initial shockable rhythm increased this risk. Despite the limitations of inter-study heterogeneity, these findings can still guide intervention and follow-up of sudden cardiac arrest survivors.

Timing of coronary angiography in patients following out-of-hospital cardiac arrest without ST-segment elevation: A systematic review and Meta-analysis of randomized trials

INTRODUCTION

Out-of-hospital cardiac arrest (OHCA) has a poor prognosis. The timing and role of early coronary angiography (CAG) in OHCA patients without ST elevation remains unclear.

OBJECTIVE

We performed a meta-analysis of randomized controlled trials (RCTs) that compared early CAG to delayed CAG in OHCA patients without ST elevation.

METHODS

We searched PubMed, Cochrane, and ClinicalTrials.gov databases (from inception to September 2021) for studies comparing early CAG to delayed CAG in OHCA patients without ST elevation. We used a random-effect model to calculate relative ratio (RR) with 95% confidence interval (CI). The primary outcome was all-cause mortality at 30 days. Secondary outcomes included neurological status with cerebral performance category ≤2 (CPC) and the rate of percutaneous coronary intervention (PCI) following CAG.

RESULTS

A total of 6 RCTs including 1822 patients, of whom 895 underwent early CAG, and 927 underwent delayed CAG, were included in this meta-analysis. There was no statistically significant difference between the 2 groups in terms of 30-day all-cause mortality (Relative risk [RR] 1.06; 95%CI 0.94-1.20; P = 0.32; I² = 13%), neurological status (CPC ≤2) (RR 1.01; 95%CI 0.90-1.13; P = 0.85, I² = 37%), and rates of PCI following CAG (RR 1.08; 95%CI 0.84-1.39; P = 0.56; I² = 49%).

CONCLUSION

In patients suffering OHCA without ST-elevation, early CAG is not associated with reduced 30-day mortality when compared to patients who underwent delayed CAG. Given our meta-analysis results including multiple trials that have not shown a benefit, it is likely that updated guidelines will not support early angiography in patients suffering OHCA without ST-elevation.

Incidence and predictors of early and late sudden cardiac death in hospitalized Japanese patients with new-onset systolic heart failure

BACKGROUND

Patients with heart failure (HF) and low left ventricular ejection fraction (LVEF) are at high risk of sudden cardiac death (SCD). Optimal HF treatment can improve LVEF and reduce the risk of SCD. The aim of this study was to evaluate the incidence and predictors of SCD in Japanese patients with new-onset systolic HF and to investigate factors that affect LVEF improvement.

METHODS

We retrospectively studied 174 consecutive hospitalized patients with new-onset HF and LVEF ≤35% (median age, 66 years; men, 71%). The primary outcome was a composite of SCD, sustained ventricular arrhythmias, and appropriate implantable cardioverter-defibrillator therapy.

RESULTS

The cumulative rates of meeting of the primary outcome at 3, 12, and 36 months after discharge were 3.9%, 8.1%, and 10.5%, respectively. Atrial fibrillation was a significant predictor of the primary outcome within 12 months after discharge (odds ratio, 5.87; 95% confidence interval [CI], 1.60-21.57). Among 104 patients who completed follow-up echocardiography within 12 months after discharge, changes in LVEF were inversely associated with SCD (odds ratio/1% increase, 0.78; 95% CI, 0.65-0.93). A QRS duration <130 ms and a B-type natriuretic peptide level <170 pg/mL were predictors of LVEF improvement to >35% (odds ratio, 3.69; 95% CI, 1.15-11.77; odds ratio, 3.19; 95% CI, 1.33-7.69, respectively).

CONCLUSIONS

Our results showed a high incidence of meeting of the primary outcome within 12 months after discharge in hospitalized patients with new-onset systolic HF. An improved LVEF may reduce the risk of late SCD.

Secondary prevention of sudden cardiac death

The prevention and treatment of sudden cardiac death (SCD) remains a significant public health challenge. For patients with a history of sudden death attributable to ventricular arrhythmia, implantable cardioverter-defibrillator (ICD) therapy is a mainstay of treatment, although these patients remain at high risk for recurrent ventricular arrhythmia and defibrillator therapies. In this review, we summarize landmark clinical trials evaluating the efficacy of ICD therapy in secondary prevention patients, review clinical outcomes including mode of death in survivors of SCD, and highlight the role for systematic diagnostic evaluation. We additionally discuss the invasive electrophysiological management of these patients, including ICD selection and programming as well as the role and timing of antiarrhythmic drug therapy and catheter ablation. Finally, we frame future challenges and needs to advance the care for secondary prevention patients.

Recommendations for the use of electrophysiological study: Update 2018

The field of cardiac electrophysiology has greatly developed during the past decades. Consequently, the use of electrophysiological studies (EPSs) in clinical practice has also significantly augmented, with a progressively increasing number of certified electrophysiology centers and specialists. Since Zipes et al published the Guidelines for Clinical Intracardiac Electrophysiology and Catheter Ablation Procedures in 1995, no official document summarizing current EPS indications has been published. The current paper focuses on summarizing all relevant data of the role of EPS in patients with different types of cardiac pathologies and provides up-to-date recommendations on this topic. For this purpose, the PubMed database was screened for relevant articles in English up to December 2018 and ESC and ACC/AHA Clinical Practice Guidelines, and EHRA/HRS/APHRS position statements related to the current topic were analyzed. Current recommendations for the use of EPS in clinical practice are discussed and presented in 17 distinct cardiac pathologies. A short rationale, evidence, and indications are provided for each cardiac disease/group of diseases. In conclusion, because of its capability to establish a diagnosis in patients with a variety of cardiac pathologies, the EPS remains a useful tool in the evaluation of patients with cardiac arrhythmias and conduction disorders and is capable of establishing indications for cardiac device implantation and guide catheter ablation procedures.

Electrophysiologic Considerations After Sudden Cardiac Arrest

Background:

Sudden Cardiac Death (SCD) remains a major public health concern, accounting for more than 50% of cardiac deaths. The majority of these deaths are related to ischemic heart disease, however increasingly recognized are non-ischemic causes such as cardiac channelopathies. Bradyarrhythmias and pulseless electrical activity comprise a larger proportion of out-of-hospital arrests than previously realized, particularly in patients with more advanced heart failure or noncardiac triggers such as pulmonary embolism. Patients surviving Sudden Cardiac Arrest (SCA) have a substantial risk of recurrence, particularly within 18 months post event. The timing of tachyarrhythmias complicating acute infarction has important implications regarding the likelihood of recurrence, with those occurring within 48 hours having a more favorable long-term outcome. In the absence of a clear reversible cause, implantable cardioverter defibrillators remain the mainstay in the secondary prevention of SCD. Post defibrillation electromechanical dissociation is common in patients with cardiomyopathy and can lead to SCD despite successful defibrillation of the primary tachyarrhythmia. Antiarrhythmic agents are highly effective in preventing recurrent arrhythmias in specific diseases such as the congenital long QT syndrome.

Conclusion:

Catheter ablation is used most commonly to prevent recurrent ICD therapies in patients with structural heart disease-related ventricular arrhythmias, however recent publications have shown substantial benefit in other entities such as idiopathic ventricular fibrillation.

Genetics of inherited primary arrhythmia disorders

A sudden unexplained death is felt to be due to a primary arrhythmic disorder when no structural heart disease is found on autopsy, and there is no preceding documentation of heart disease. In these cases, death is presumed to be secondary to a lethal and potentially heritable abnormality of cardiac ion channel function. These channelopathies include congenital long QT syndrome, catecholaminergic polymorphic ventricular tachycardia, Brugada syndrome, and short QT syndrome. In certain cases, genetic testing may have an important role in supporting a diagnosis of a primary arrhythmia disorder, and can also provide prognostic information, but by far the greatest strength of genetic testing lies in the screening of family members, who may be at risk. The purpose of this review is to describe the basic genetic and molecular pathophysiology of the primary inherited arrhythmia disorders, and to outline a rational approach to genetic testing, management, and family screening.

[Risk stratification for sudden cardiac death in ischemic heart disease. Programmed ventricular stimulation]

Programmed ventricular stimulation was used extensively in the 1970s and has markedly improved our knowledge about the electrophysiological mechanisms of reentrant ventricular arrhythmias. In numerous observational but also randomized studies, it was shown that the induction of a monomorphic ventricular tachycardia by programmed ventricular stimulation was associated with an increased risk of spontaneous ventricular tachycardia or even sudden cardiac death in the future. Despite these results and the guidelines of ACC and ESC recommending the use of programmed ventricular stimulation in patients with recent and remote myocardial infarction, reduced ejection fraction, and complex ventricular arrhythmias or syncope, programmed ventricular stimulation is only seldom used and does not play a relevant role in clinical practice today. The purpose of this overview is to reevaluate the importance of programmed ventricular stimulation for the risk evaluation of patients with ischemic heart disease in consideration of the current literature.

Mechanisms of arrhythmias and conduction disorders in older adults

Aging is associated with an increased prevalence of cardiac arrhythmias, which contribute to higher morbidity and mortality in the elderly. The frequency of cardiac arrhythmias, particularly atrial fibrillation and ventricular tachyarrhythmia, is projected to increase as the population ages, greatly impacting health care resource utilization. Several clinical factors associated with the risk of arrhythmias have been identified in the population, yet the molecular bases for the increased predisposition to arrhythmogenesis in the elderly are not fully understood. This review highlights the epidemiology of cardiac dysrhythmias, changes in cardiac structure and function associated with aging, and the basis for arrhythmogenesis in the elderly.

Risk stratification for sudden cardiac death

Sudden cardiac death (SCD) is a leading cause of mortality in industrialized countries, and ventricular fibrillation and sustained ventricular tachycardia are the major causes of SCD. Although there are now effective devices and medications that can prevent such serious arrhythmias, it is crucial to have methods of identifying patients at risk. Numerous studies suggest that most patients dying of SCD have coronary artery disease or cardiomyopathy. Functional or electrophysiological measurements are effective in risk stratification. Left ventricular ejection fraction measured by echocardiography or cardiac imaging techniques is the gold standard to detect high-risk patients. Electrophysiological studies have also been used for risk stratification. Noninvasive techniques and measurements, such as T-wave alternans, signal-averaged electrocardiography, nonsustained ventricular tachycardia, heart rate variability, and heart rate turbulence, have been proposed as useful tools in identifying patients at risk for SCD. This article reviews the epidemiology, mechanisms, substrates, and current status of risk stratification of SCD.

Prediction of fatal or near-fatal cardiac arrhythmia events in patients with depressed left ventricular function after an acute myocardial infarction

Aims

To determine whether risk stratification tests can predict serious arrhythmic events after acute myocardial infarction (AMI) in patients with reduced left ventricular ejection fraction (LVEF ≤ 0.40).

Methods and results

A total of 5869 consecutive patients were screened in 10 European centres, and 312 patients (age 65 ± 11 years) with a mean LVEF of 31 ± 6% were included in the study. Heart rate variability/turbulence, ambient arrhythmias, signal-averaged electrocardiogram (SAECG), T-wave alternans, and programmed electrical stimulation (PES) were performed 6 weeks after AMI. The primary endpoint was ECG-documented ventricular fibrillation or symptomatic sustained ventricular tachycardia (VT). To document these arrhythmic events, the patients received an implantable ECG loop-recorder. There were 25 primary endpoints (8.0%) during the follow-up of 2 years. The strongest predictors of primary endpoint were measures of heart rate variability, e.g. hazard ratio (HR) for reduced very-low frequency component (<5.7 ln ms²) adjusted for clinical variables was 7.0 (95% CI: 2.4–20.3, P < 0.001). Induction of sustained monomorphic VT during PES (adjusted HR = 4.8, 95% CI, 1.7–13.4, P = 0.003) also predicted the primary endpoint.

Conclusion

Fatal or near-fatal arrhythmias can be predicted by many risk stratification methods, especially by heart rate variability, in patients with reduced LVEF after AMI.

Risk factor assessment: defining populations and individuals at risk

This article summarizes the current knowledge on risk stratification in patients who have structural heart disease, notably coronary artery disease and nonischemic cardiomyopathy. Although other types of structural heart disease and inherited ion channel abnormalities are also associated with a risk of SCD, the risk stratification strategies and data in these entities are diverse and beyond the scope of this article.

Role of electrophysiologic study (EPS)-guided preventive therapy for the management of ventricular tachyarrhythmias in patients with heart failure

BACKGROUND

Ventricular tachyarrhythmias (VT/VF) are 1 of the most important factors determining the prognosis of patients with heart failure (HF). Although priority is given to implantable cardioverter defibrillator (ICD) therapy for the prevention of sudden cardiac death, electrophysiologic-study (EPS)-guided preventive therapy could be important for reducing the number of cardiac events.

METHODS AND RESULTS

Of 864 patients with a history of HF, an EPS was performed in 168 and 121 had inducible VT/VF. Under the basic therapy of an ICD, additional catheter ablation was attempted for 95 of 124 monomorphic VT foci in 74 patients, and 78 of the VT were successfully ablated. The prognoses were compared among 5 patient groups with different results for the EPS and catheter ablation: (1) success group (n=43), (2) failure group (n=15), (3) not attempted group (n=16), (4) VF group (n=47), and (5) no inducible VT/VF group. During a follow-up period of 31+/-22 months, the incidence of VT/VF was lower in the success and no inducible VT/VF groups than in the other groups (p=0.0018), although a significant difference was not observed for the total deaths.

CONCLUSION

EPS-guided preventive therapy using an ICD and catheter ablation can be useful, at least for the reduction of arrhythmic events in patients with HF.

Bisoprolol inhibits sodium current in ventricular myocytes of rats with diastolic heart failure

1. Changes in sodium currents (I(Na)) in heart failure contribute to cardiac electrophysiological alterations and, thereby, to ventricular arrhythmias. Bisoprolol has anti-arrhythmic effects, but its direct effect on I(Na) in cardiac cells remains unclear. Accordingly, in the present study we investigated the effects of bisoprolol on ventricular I(Na) in diastolic heart failure (DHF) and normal rats. 2. The DHF model was produced by abdominal aortic coarctation for 4 weeks and single ventricular myocytes were isolated by enzymatic dissociation. The electrophysiological actions of bisoprolol on I(Na) currents were investigated using a whole-cell patch-clamp technique. 3. The membrane capacitance of rats in the DHF group was significantly greater than that of the control group and the current-voltage curve was simultaneously shifted downward. Bisoprolol concentration-dependently decreased I(Na) in ventricular myocytes of both groups (at -45 mV), with IC(50) values of 19.53 +/- 0.06 and 40.78 +/- 0.03 micromol/L in the control and DHF groups, respectively. 4. In both groups, the current-voltage curves were shifted upwards, whereas activation potentials, peak currents and reversal potentials showed no significant changes. At -45 mV, the descent ratio of current densities in the DHF group was lower than that of the control group. In both groups, inactivation curves were shifted to more negative potentials, but activation curves and recovery curves were not altered. Changes in the half-inactivation voltage, V(0.5), and the slope of the inactivation curve, S, were similar for both groups. 5. In conclusion, bisoprolol concentration-dependently decreases I(Na) in ventricular myocytes of DHF and normal rats, which could be responsible, at least in part, for its anti-arrhythmic effects.

[Coronary artery disease--relevance of total coronary revascularization on the incidence of malignant arrhythmias]

Myocardial ischemia induces redistribution of different ions (H(+), K(+), Na(+), Ca(++)) across the cardiomyocyte membrane, as well as the loss of intracellular ATP content. This results in changes in the electrical properties including shortening of the action potential, appearance of delayed afterpotentials, and a modified refractoriness of the cardiomyocyte. These changes may induce or support malignant cardiac arrhythmias. Supersensitivity of sympathetic denervated myocardium may further support the electrical instability of ischemic myocardium.Virtues of studies indicate that patients with coronary artery disease who develop complex arrhythmias during or after exercise bear a substantially increased risk for sudden cardiac death. Other studies report about arrhythmic stabilization and reduced mortality if patients with reversible myocardial ischemia receive complete revascularization. However, none of these studies is without methodological flaws. Due to the lack of methodologically sound studies in sufficiently large patient cohorts, the question whether complete coronary revascularisation improves the prognosis of patients with coronary artery disease and which strategy (medical, interventional, or surgical) warrants the best outcomes remains open.

Clinical usefulness of electrophysiologic study (EPS)-guided risk stratification for life-threatening arrhythmia in patients with heart failure

BACKGROUND

Ventricular tachyarrhythmia is one of the most important factors determining the prognosis of patients with heart failure and sudden death can be observed even during stable therapy controlling clinical heart failure. In this study, the usefulness of electrophysiologic study (EPS) for the prediction of a future arrhythmic event was evaluated in patients with heart failure.

METHODS AND RESULTS

The patient population consisted of 474 patients with a history of clinical heart failure but without an episode of spontaneous sustained ventricular tachycardia or fibrillation (VT/VF). A Holter ECG was performed in all patients, and 177 of the 474 patients underwent EPS because of a recording of nonsustained VT (NSVT, > 5 beats). When sustained VT/VF was inducible in EPS, the patient was assigned to implantation of a defibrillation device. The patients were divided into 3 groups, ie, 1) no NSVT (n = 297), 2) NSVT + no inducible VT/VF (n = 134), and 3) NSVT + inducible VT/VF (n = 43), and were followed-up for > 12 months. All patients were followed-up under standard therapy for heart failure. There were no significant differences in basic clinical characteristics and therapies among the 3 groups. During the follow-up period of 32 +/- 18 months, 56/474 patients suffered a VT/VF episode, ie, 21/297 in no NSVT, 14/134 in NSVT + no inducible VT/VF, and 21/43 in NSVT + inducible VT/VF patients (P = 0.032). All patients were rescued from sudden death among patients with an implanted defibrillator, but 11 patients without a defibrillator died.

CONCLUSION

In patients with heart failure, future arrhythmic events could be predicted by EPS and Holter ECG. EPS-guided risk stratification seems to be useful in managing patients with heart failure.

Sudden cardiac death: the role of risk stratification

Sudden cardiac death syndrome remains a major health problem responsible for approximately 400,000 deaths annually in the US. Effective therapies exist but are costly and are associated with potential complications. Currently used strategies for selection of the best candidates for implantable cardioverter defibrillator (ICD) therapy are imperfect and leave a large number of high-risk patients unprotected. At the same time, many patients who received ICDs will never develop tachyarrhythmia and require ICD intervention. The article summarizes the current status and applicability of the noninvasive and invasive tests used for sudden cardiac death risk assessment with the emphasis on the increasingly recognized value of microvolt T wave alternans.

Bepridil for drug-refractory ventricular tachyarrhythmias

AIMS

To avoid frequent discharges of implantable cardioverter defibrillators, antiarrhythmic drugs may be needed in some patients with ventricular tachyarrhythmias. For ventricular tachyarrhythmias refractory to conventional antiarrhythmic drugs, we evaluated the efficacy of bepridil, a multiple ion-channel blocker.

METHODS AND RESULTS

Sixteen patients with structural heart disease and ventricular tachyarrhythmias refractory to multiple antiarrhythmic drugs (4.1+/-1.6 drugs including class III drugs) were enrolled. Bepridil was prescribed at a mean dose of 156+/-40 mg/day. Bepridil prolonged the QT/QTc interval without affecting heart rate or the QRS duration. During a mean follow-up of 52+/-44 months, bepridil completely suppressed ventricular tachyarrhythmias in 6 of the 16 patients (38%) and the drug decreased the frequency of ventricular tachyarrhythmia recurrences by >75% in 3 of the other 10 patients. The markers of complete suppression of ventricular tachyarrhythmias during bepridil treatment included a smaller number of VT morphologies, a better NYHA functional class, and a greater drug-induced prolongation of the QT/QTc interval. The result of electrophysiologic study-guided evaluation of bepridil was closely associated with the clinical efficacy of bepridil in 7 of 8 patients.

CONCLUSION

Bepridil appears to be useful to suppress drug-refractory ventricular tachyarrhythmia recurrence.

Clinical review: beyond immediate survival from resuscitation-long-term outcome considerations after cardiac arrest

A substantial body of literature concerning resuscitation from cardiac arrest now exists. However, not surprisingly, the greater part concerns the cardiac arrest event itself and optimising survival and outcome at relatively proximal time points. The aim of this review is to present the evidence base for interventions and therapeutic strategies that might be offered to patients surviving the immediate aftermath of a cardiac arrest, excluding components of resuscitation itself that may lead to benefits in long-term survival. In addition, this paper reviews the data on long-term impact, physical and neuropsychological, on patients and their families, revealing a burden that is often underestimated and underappreciated. As greater numbers of patients survive cardiac arrest, outcome measures more sophisticated than simple survival are required.

Clinical significance of the electrophysiologic study (EPS)-guided therapy for the secondary prevention of ventricular tachycardia

BACKGROUND

Although electrophysiologic study (EPS) is one of the most reliable methods for selecting preventive therapy for patients with sustained ventricular tachycardia (VT), VT may recur during EPS-guided effective therapy; therefore, the importance of implantable cardioverter-defibrillator (ICD) has been emphasized. In this study, the prognoses of VT patients were evaluated to clarify the importance of EPS-guided therapy for the secondary prevention of VT.

METHODS AND RESULTS

The study population consisted of 99 consecutive patients with a history of sustained VT, which was inducible in EPS. The VT induction protocol used 1-3 extrastimuli and rapid ventricular pacing at 2 right ventricular sites and included additional isoproterenol infusion. ICD implantation was applied to all patients with an episode of hemodynamically unstable VT, regardless of the result of preventive therapy. For preventive therapy, an antiarrhythmic drug and/or catheter ablation were selected, and they were defined as being effective in the EPS-guided therapy when the induction of VT was completely prevented. When no therapy was effective for prevention, an antiarrhythmic drug was prescribed under ICD implantation. During the follow-up period of 19+/-20 months, VT recurred in 17 of 32 patients (53%) in the ineffective group and in 10 of 67 patients (15%) in the effective group (p=0.0001). The therapies used in the effective group were class I antiarrhythmic drug in 9, class III in 15, and catheter ablation in 35 patients. Between the patients with and without VT recurrence, there were no significant differences in the left ventricular ejection fraction and the maximum number of repetitive ventricular responses that remained in VT induction in EPS.

CONCLUSIONS

Although VT may recur in up to 15% of patients with EPS-guided effective therapy, the recurrence rate was significantly reduced in comparison to that in the ineffective group. EPS-guided therapy may be useful to reduce the clinical recurrence of VT, as well as the action of ICD.

Determinants of Recurrent Ventricular Arrhythmia or Death in 300 Consecutive Patients with Ischemic Heart Disease Who Experienced Aborted Sudden Death: Data from the Leiden Out-of-Hospital Cardiac Arrest Study

OBJECTIVE

Evaluation of the relation between clinical characteristics and incidence of recurrent ventricular arrhythmias (VAs) or death during long-term follow-up in a cohort of 300 consecutive ischemic heart disease (IHD) patients who had survived an episode of sudden cardiac arrest (SCA).

BACKGROUND

Survivors of life-threatening VA are at high risk for recurrent events.

METHODS

A total of 300 consecutive survivors of SCA with IHD were included in a standardized screening and evaluation protocol. Multivariable Cox regression analysis was performed to determine the relation between clinical variables at baseline and the incidence of recurrent VA, all-cause mortality and the composite of both (composite endpoint).

RESULTS

The presenting arrhythmia was VT in 156 (52%) patients and VF in 144 (48%) patients. Revascularization was performed in 78 (26%) patients and an ICD was implanted in 216 (72%) patients. During follow-up (mean 30 +/- 21 months) 37 (12%) patients died and 88 (29%) patients experienced a recurrence. Advanced age (adjusted hazard ratio (HR) 2.0; 1.2-3.3), history of heart failure (HR 1.8; 1.2-2.6), and amiodarone use (HR 3.1; 2.1-4.6) were independent predictors for the composite endpoint. VT as presenting arrhythmia was an independent predictor for all-cause mortality only (HR 2.4; 1.2-4.8). A decreased risk of recurrences was determined by beta-blocker use (HR 0.5; 0.4-0.8) and coronary revascularization (HR 0.3; 0.2-0.6).

CONCLUSION

In a cohort of 300 consecutive survivors of SCA the incidence of recurrent VA and death is dependent on patient age, history of heart failure, and use of amiodarone. In contrast, use of beta-blockers and aggressive coronary revascularization improve the outcome.

Clinical Assessment of Antiarrhythmic Agents for Paroxysmal Atrial Fibrillation Guided by Modification of Electrophysiologic Arrhythmogenicity

INTRODUCTION

Rapid atrial pacing alters atrial electrophysiology, promoting initiation and maintenance of atrial fibrillation (AF). The aim of this study was to assess differences in the electrophysiologic properties of atrial tissue between patients with and without AF episodes and to determine whether electrophysiologic properties can predict the clinical efficacy of antiarrhythmic agents.

METHODS AND RESULTS

Sixty patients were studied, 33 with documented episodes of paroxysmal atrial fibrillation (PAF) and 27 control patients. Atrial effective refractory period (AERP), atrial vulnerability, and intra-atrial conduction time were measured at baseline and after rapid constant atrial pacing for 5 minutes at rates of 130, 150, 170, and 190 beats/min. The clinical efficacy of antiarrhythmic agents for PAF prophylaxis was assessed over 14 months with an antiarrhythmic agent identical to that administered intravenously, and the antiarrhythmic agent effects on AERP, atrial vulnerability, and intra-atrial conduction time were assessed. AERP shortening and atrial vulnerability increase were significantly larger in the PAF group. Antiarrhythmic agents that were clinically effective in suppressing PAF significantly attenuated AERP shortening, but antiarrhythmic agents that were clinically ineffective did not.

CONCLUSION

Changes in AERP and atrial vulnerability observed after rapid atrial pacing are considered indicative of the electrophysiologic substrate of PAF. Attenuation of AERP and atrial vulnerability by antiarrhythmic agents might be useful in predicting their clinical efficacy.

Standardized screening and treatment of patients with life-threatening arrhythmias: The leiden out-of-hospital cardiac arrest evaluation study

OBJECTIVES

The aim of this study was to evaluate the effect of a systematic screening/treatment protocol on outcome in patients after aborted sudden death.

BACKGROUND

Patients after aborted sudden death are at high risk for recurrent events. In this regard, systematic screening is mandatory to reveal the underlying etiology, to detect and subsequently treat reversible causes, and to establish patient-tailored antiarrhythmic treatment.

METHODS

A total of 417 consecutive patients after aborted sudden death due to ventricular arrhythmias underwent echocardiography and coronary angiography. In the presence of coronary artery disease and myocardial ischemia, using stress-rest myocardial perfusion imaging/exercise testing, subsequent revascularization was performed. Patients without ischemic heart disease were further evaluated with magnetic resonance imaging, contrast echocardiography, right ventricular angiography and/or flecainide/ergonovine testing. After these diagnostic steps, final antiarrhythmic therapy was based on the outcome of electrophysiologic testing.

RESULTS

The majority of patients had ischemic heart disease (n = 300, 72%). After screening, 78 (78 of 300, 26%) patients underwent revascularization. In 69% of patients, ventricular arrhythmias were inducible during electrophysiologic testing. Therapy consisted of implantable defibrillators in 301 (72%) patients, antiarrhythmic drugs in 239 (57%) patients, and catheter ablation in 58 (14%) patients. During 5-year follow-up, only 3 (<1%) patients died suddenly. The 5-year survival rate was 82%; of 39 deaths, 10 (26%) patients died due to non-cardiac disease and 26 (67%) due to heart failure.

CONCLUSIONS

Screening and treatment of patients after aborted sudden death according to a standardized protocol resulted in <1% arrhythmic deaths during 5-year follow-up. The majority of patients died of heart failure, stressing the importance of optimizing medical and surgical therapy and screening.

Clinical significance and contributing factors of long-term variability in induced ventricular tachyarrhythmias

Long-Term Variability in Induced Tachyarrhythmias.

INTRODUCTION

Ventricular arrhythmias induced during electrophysiologic study (EPS) may vary over time, making arrhythmia induction studies unreliable. The aim of this prospective study was to clarify the clinical significance of long-term variability in induced arrhythmias and to elucidate factors determining this variability.

METHODS AND RESULTS

Three noninvasive EPSs were performed 1, 13, and 25 months after implantation of a cardioverter defibrillator in 40 patients with ventricular tachyarrhythmias, without a change in their antiarrhythmic drug regimens. The induced ventricular arrhythmias were categorized into five grades. Long-term variability, which was defined as a variation in the grades during the three EPSs, was observed in 23 patients (group A) and not in the remaining 17 patients (group B). During the 2-year period, spontaneous sustained ventricular arrhythmias developed in 15 patients (65%) in group A but in only 4 patients (24%) in group B (P = 0.01). Inducibility of sustained tachyarrhythmias was not associated with emergence of spontaneous arrhythmias. All patients also underwent thallium-201 and iodine-123-metaiodobenzylguanidine (MIBG) scans to evaluate the extent of the regions showing normal thallium uptake with reduced MIBG uptake. Group A patients showed greater thallium/MIBG mismatched regions than did group B patients (P = 0.01). Logistic regression analysis revealed that long-term variability (relative risk [RR] 7.55, P = 0.03), amiodarone therapy (RR 0.14, P = 0.04), and left ventricular ejection fraction <35% (RR 6.26, P = 0.04) were independent predictors of spontaneous arrhythmia occurrence.

CONCLUSION

In patients with ventricular tachyarrhythmias, long-term variability in induced arrhythmias, but not the inducibility of arrhythmias, is associated with a higher incidence of spontaneous arrhythmias. Regional cardiac sympathetic denervation may be an important mechanism of this variability. These results also may explain why inducibility-based antiarrhythmic drug testing does not predict patient prognosis.

Sudden death in patients without structural heart disease

Sudden unexpected cardiac death generally occurs in persons with known or previously unrecognized heart disease. However, it has become evident that it occurs often enough in patients without any identifiable structural abnormality to warrant the cardiologist's attention. Mostly, it concerns young, active, and otherwise healthy individuals. This paper focuses on various categories of patients with life-threatening events considered to have occurred on a solely "electrical" basis. Currently, several entities are recognized with distinct electrophysiological abnormalities, including Wolff-Parkinson-White syndrome, long QT syndrome, the Brugada syndrome, short-coupled torsade de pointes, and catecholamine-induced polymorphic ventricular tachyarrhythmia. The remaining patients without such distinct abnormalities are categorized as having idiopathic ventricular fibrillation. Although mechanical cardiac function may seem normal, such patients might have certain discrete anatomic abnormalities, unidentifiable with current investigational tools. Possibly in the future, with development of newer and more sophisticated tools (magnetic resonance imaging, positron emission tomography, genetic testing), some or all cases of idiopathic ventricular fibrillation must be redefined as having specific genetic and/or anatomic bases. All patients successfully resuscitated from cardiac arrest due to ventricular tachyarrhythmia without clear precipitating factors (acute myocardial infarction, severe electrolyte or metabolic disturbances) are at high risk of recurrences. Long-term prophylactic therapy is indicated. Contrasting with older belief, survivors of idiopathic ventricular fibrillation are now also considered high-risk patients. The implantable cardioverter-defibrillator appears to be the safest and most effective therapy.

Comparison of arrhythmia recurrence in patients presenting with ventricular fibrillation versus ventricular tachycardia in the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial

Because many episodes of ventricular fibrillation (VF) are believed to be triggered by ventricular tachycardia (VT), patients who present with VT or VF are usually grouped together in discussions of natural history and treatment. However, there are significant differences in the clinical profiles of these 2 patient groups, and some studies have suggested differences in their response to therapy. We examined arrhythmias occurring spontaneously in 449 patients assigned to implantable cardioverter-defibrillator (ICD) therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial to determine whether patients who receive an ICD after VT have arrhythmias during follow-up that are different from patients who present with VF. ICD printouts were analyzed both by a committee blinded to the patients' original presenting arrhythmia and by the local investigator. During 31 +/- 14 months of follow-up, 2,673 therapies were reported. Patients who were enrolled in the AVID trial after an episode of VT were more likely to have an episode of VT (73.5% vs 30.1%, p <0.001), and were less likely to have an episode of VF (18.3% vs 28.0%, p = 0.013) than patients enrolled after an episode of VF. Adjustment for differences in ejection fraction, previous infarction, and beta-blocker and antiarrhythmic therapy did not appreciably change the results. Ventricular arrhythmia recurrence during follow-up is different in patients who originally present with VT than in those who originally present with VF. These findings suggest there are important differences in the electrophysiologic characteristics of these 2 patient populations.

Impact of percutaneous coronary intervention or coronary artery bypass grafting on outcome after nonfatal cardiac arrest outside the hospital

Survivors of cardiac arrest due to ventricular arrhythmias are at risk for recurrent events. The role of revascularization in secondary prevention for survivors of cardiac arrest has been addressed in various studies with conflicting results. A total of 142 survivors of cardiac arrest with coronary artery disease were evaluated according to a standardized protocol, including 2-dimensional echocardiography, myocardial perfusion scintigraphy, coronary angiography, and electrophysiologic testing. Revascularization of scintigraphically documented ischemic myocardial regions was performed in 44 patients (31%). Final therapy was based on the results of electrophysiologic testing. Four-year survival rates were 100% for revascularized noninducible patients, 84% for revascularized inducible patients, 91% for nonrevascularized noninducible patients, and 72% for nonrevascularized inducible patients. Only 1 patient (<1% of study population) died suddenly. Recurrences were much more frequent in patients without revascularization (38% vs 7%, p <0.001) and the recurrence rate was 0% in the revascularized noninducible patients. Thus, revascularization of ischemically jeopardized myocardium in survivors of cardiac arrest resulted in excellent survival; moreover, in absence of inducible ventricular arrhythmias, the recurrence rate was 0%. Systematic evaluation of survivors of cardiac arrest due to ventricular arrhythmias allows risk stratification and guidance of subsequent antiarrhythmic therapy.

Surgical coronary revascularization and antiarrhythmic therapy in survivors of out-of-hospital cardiac arrest

BACKGROUND

Patients who survive out-of-hospital cardiac arrest are at high risk for recurrent arrest. Coronary artery bypass grafting (CABG) confers a survival advantage, but it is unclear whether antiarrhythmic drugs or an implanted defibrillator confer added benefit. This study was designed to determine predictors for further treatment, survival, and therapeutic internal cardiac defibrillator (ICD) discharge in this patient population.

METHODS

One hundred and eight patients undergoing CABG after out-of-hospital cardiac arrest were identified over a 12-year period. Case records were retrospectively reviewed. Follow-up was obtained and predictors of outcome events were analyzed.

RESULTS

Fifty-four (50%) patients underwent CABG only. Fifty-four received additional treatment that included ICD placement in 23 (21%), antiarrhythmic medications in 19 (18%), or both in 12 (11%). Predictors of ICD placement included left ventricular ejection fraction (LVEF) less than 40% and perioperative intraaortic balloon counterpulsation. ICD or medical management increased survival in patients with LVEF <40%. Predictors of increased mortality included age >65 years, Cleveland Severity Score >8, and female gender. Predictors of therapeutic ICD discharge included age >65 years, reoperative CABG, LVEF <40%, and positive postoperative electrophysiological (EP) study. No patient with a negative postoperative EP study received an ICD, and none suffered sudden cardiac death during follow-up.

CONCLUSIONS

Patients with coronary artery disease anatomically suitable for CABG who survive an acute out-of-hospital cardiac arrest should undergo EP testing after CABG. Approximately half of these patients are adequately treated by CABG alone. The remainder may benefit from ICD placement or medical antiarrhythmic management.

Prognostic value of baseline electrophysiology studies in patients with sustained ventricular tachyarrhythmia: the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial

OBJECTIVES

We sought to determine the value of electrophysiology (EP) testing in patients with ventricular fibrillation (VF), ventricular tachycardia (VT) with syncope, or sustained VT in the setting of left ventricular dysfunction.

BACKGROUND

Traditionally, EP testing is part of the workup of patients with sustained VT or VF. Recently, some have suggested that EP testing is unnecessary in these patients, many of whom are likely to receive an implantable cardioverter-defibrillator (ICD).

METHODS

Within a multicenter trial (Antiarrhythmics Versus Implantable Defibrillators) designed to evaluate whether drugs or ICD resulted in a better outcome, data were analyzed regarding EP testing. Although this testing was not required, it was performed in >50% of patients. Information regarding the results of EP testing was correlated to baseline clinical characteristics and outcome.

RESULTS

Of 572 patients subjected to an EP test, 384 (67%) had inducible sustained VT or VF. Inducible patients were more likely to have coronary artery disease, previous infarction, and VT as their index arrhythmic event. Inducibility of VT or VF did not predict death or recurrent VT or VF.

CONCLUSIONS

Information derived from EP testing in this patient population, particularly those with VF, is of limited value and may not be worth the risks and costs of the procedure, particularly in those patients likely to receive an ICD.

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.

Role of Antiarrhythmic Therapy in Patients at Risk for Sudden Cardiac Death: An Evidence-Based Review

Sudden cardiac death (SCD) accounts for more than half of all cardiac deaths occurring each year in the United States. Although it has several causes, patients at greatest risk are those with coronary artery disease and impaired left ventricular function, heart failure secondary to ischemia or idiopathic dilated cardiomyopathy, hypertrophic cardiomyopathy, documented sustained ventricular tachycardia or ventricular fibrillation, and survivors of cardiac arrest. The presence of asymptomatic ventricular arrhythmias, positive signal-averaged electrocardiogram (ECG), low heart rate variability index, or inducible ventricular tachycardia or ventricular fibrillation increases the risk. In primary prevention trials in patients with ischemic heart disease, beta-blockers reduced both total mortality and SCD, whereas class I antiarrhythmic drugs, especially class IC, increased mortality. Among class III agents, d,l-sotalol and dofetilide have a neutral effect on mortality, whereas d-sotalol increases mortality. Amiodarone has a neutral effect on total and cardiac mortality but does reduce the risk of arrhythmic death and cardiac arrest. Three primary prevention trials in patients with ischemic heart disease were conducted with implantable cardioverter-defibrillators (ICDs). Patients with low ejection fractions (EFs), asymptomatic ventricular arrhythmias, and inducible ventricular tachycardia or ventricular fibrillation had significant reductions in total, cardiac, and arrhythmic death with ICDs compared with either no drug therapy or conventional antiarrhythmic agents. The ICDs did not reduce mortality in patients with low EFs and a positive signal-averaged ECG undergoing coronary bypass graft. In those with heart failure, beta-blockers reduced total and SCD mortality, but dofetilide and amiodarone had a neutral effect on mortality. In the secondary prevention of SCD, antiarrhythmic drugs alone generally are not thought to improve survival. In three trials in patients with documented sustained ventricular tachycardia or ventricular fibrillation, or survivors of SCD, ICDs reduced cardiac and arrhythmic mortality. Total mortality, however, was significantly reduced in only one of these trials. The role of antiarrhythmic drugs in secondary prevention of SCD is limited to patients in whom ICD is inappropriate or in combination with ICD. Antiarrhythmics can be given selectively with ICDs to decrease episodes of ventricular tachycardia or fibrillation to reduce ICD discharges, to suppress episodes of nonsustained ventricular tachycardia that trigger ICD discharges, to slow the rate of ventricular tachycardia to increase hemodynamic stability, to allow effective antitachycardia pacing, or to suppress supraventricular arrhythmias.

Clinical characteristics of unexplained sudden cardiac death in Korea

In Western countries, sudden cardiac death (SCD) is closely related to coronary artery disease, but in Korea the clinical characteristics of SCD are not well determined. Over a 4-year period (June 1995 to May 1999), 186 cases of SCD, ranging in age from 16 to 75 years, were admitted to the Chonnam National University Hospital. In 82 (44.1%) of these, neither symptoms nor evidence of structural heart disease was found and so their clinical characteristics were investigated. There were 66 (80.5%) men and 16 (19.5%) women (male/female ratio = 4.1:1). The mean age was 50 +/- 14 years: 19 (23.2%) were in their 40s, 21 (25.6%) in their 50s, and 17 (20.7%) in their 60s. The time of circulatory collapse witnessed in 68 cases of SCD showed 2 peaks: between midnight and 03.00h (n=16, 23.5%) and between 09.00h and midday (n=15, 22.1%). Unexplained SCD occurred at home in 48 (64.9%) cases and on the street in 12 (16.2%); it occurred during normal daily routine activity in 23 (39.6%) and during sleep in 15 (25.9%). Thirty-three patients (40.2%) experienced various prodromal symptoms, including chest discomfort (n=13, 15.9%) and dyspnea (n=8, 9.8%). The electrocardiogram taken on arrival recorded asystole in 65 (79.3%) and ventricular fibrillation in 17 (20.7%). Idiopathic ventricular fibrillation was diagnosed in 14 (10 men, 4 women; 45 +/- 11 years) of 21 patients who recovered spontaneous circulation. Five (6.1%) patients were discharged alive, and an implantable cardioverter-defibrillator was implanted in 2. Unexplained SCD is common in Korea and develops predominantly in middle-aged males around midnight or in the late morning usually with no prodromal symptoms (59.8%). Idiopathic ventricular fibrillation is thought to be one of the important causes.