Electrophysiological testing and nonsustained ventricular tachycardia. Use and limitations in patients with coronary artery disease and impaired ventricular function

Programmed ventricular stimulation in structural heart disease: Implications of patterns of ventricular arrhythmias induced to long-term outcomes

INTRODUCTION

Currently available data gives some credence to utility of VT induction studies in patients with stable ischemic cardiomyopathy, there are some unresolved questions as to define sensitive threshold for low-risk and the prognostic relevance of ill sustained or non-specific tachycardia on induction study. We evaluated potential ability of VT inducibility to predict likelihood of SHD (Structural heart disease) patients for subsequent arrhythmic or adverse cardiac events.

MATERIAL AND METHODS

All consecutive patients with syncope/documented arrhythmia who had VT induction done were included and patients with VT storm, ACS,uncontrolled HF were excluded. We studied in 4 groups-monomorphic VT, sustained polymorphicVT, ill sustainedVT/VF and no VT/VF induced. The primary-endpoints were - Sudden death, all-cause mortality and secondary-endpoints were - MACE (AICD shock, death,HF, recurrence of VT). We screened 411 patients and included 169 within inducible (n = 79) and non-inducible group (n = 90).

RESULTS

There were a higher number of patients with coronary artery disease, LV dysfunction, patients on amiodarone in inducible group and no difference in usage of beta-blockers. Recurrence of VT, composite of MACE was significantly higher in inducible group (p < 0.05). Mortality was not different in 3 groups compared with no VT/VF group. We found that monomorphic VT group had significantly higher MACE as compared to others and also predicted recurrence of VT and AICD shock and showed a trend towards significance for prediction of mortality. Inducible patients on AICD had mortality similar to non-inducible group.

CONCLUSION

Induction of monomorphicVT/polymorphicVT with ≤3extrastimuli is associated with a higher number of MACE events on follow up. Induction of monomorphicVT predicts recurrence of VT/ICD shock.

Electrophysiology testing for risk stratification of patients with ischaemic cardiomyopathy: a call for action

Current guidelines recommendations, based on the results of primary sudden cardiac death prevention trials, use the left ventricular ejection fraction (LVEF) as a sole criterion for the indication of implantable cardioverter defibrillator therapy for primary prevention purposes. In this article, we review the sensitivity and specificity of LVEF for predicting arrhythmic vs. non-arrhythmic cardiac death and examine existing evidence on the use of electrophysiology testing for risk stratification of ischaemic patients with reduced left ventricular function.

Visualizing Nerve Injury in a Neuropathic Pain Model with [18F]FTC-146 PET/MRI

The ability to locate nerve injury and ensuing neuroinflammation would have tremendous clinical value for improving both the diagnosis and subsequent management of patients suffering from pain, weakness, and other neurologic phenomena associated with peripheral nerve injury. Although several non-invasive techniques exist for assessing the clinical manifestations and morphological aspects of nerve injury, they often fail to provide accurate diagnoses due to limited specificity and/or sensitivity. Herein, we describe a new imaging strategy for visualizing a molecular biomarker of nerve injury/neuroinflammation, i.e., the sigma-1 receptor (S1R), in a rat model of nerve injury and neuropathic pain. The two-fold higher increase of S1Rs was shown in the injured compared to the uninjured nerve by Western blotting analyses. With our novel S1R-selective radioligand, [18F]FTC-146 (6-(3-[18F]fluoropropyl)-3-(2-(azepan-1-yl)ethyl)benzo[d]thiazol-2(3H)-one), and positron emission tomography-magnetic resonance imaging (PET/MRI), we could accurately locate the site of nerve injury created in the rat model. We verified the accuracy of this technique by ex vivo autoradiography and immunostaining, which demonstrated a strong correlation between accumulation of [18F]FTC-146 and S1R staining. Finally, pain relief could also be achieved by blocking S1Rs in the neuroma with local administration of non-radioactive [19F]FTC-146. In summary, [18F]FTC-146 S1R PET/MR imaging has the potential to impact how we diagnose, manage and treat patients with nerve injury, and thus warrants further investigation.

Amiodarone versus other pharmacological interventions for prevention of sudden cardiac death

BACKGROUND

Sudden cardiac death (SCD) is one of the main causes of cardiac death. There are two main strategies to prevent it: managing cardiovascular risk factors and reducing the risk of ventricular arrhythmias. Implantable cardiac defibrillators (ICDs) constitute the standard therapy for both primary and secondary prevention; however, they are not widely available in settings with limited resources. The antiarrhythmic amiodarone has been proposed as an alternative to ICD.

OBJECTIVES

To evaluate the effectiveness of amiodarone for primary or secondary prevention in SCD compared with placebo or no intervention or any other antiarrhythmic drugs in participants at high risk (primary prevention) or who have recovered from a cardiac arrest or a syncope due to Ventricular Tachycardia/Ventricular Fibrillation, or VT/VF (secondary prevention).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OVID), EMBASE (OVID), CINAHL (EBSCO) and LILACS on 26 March 2015. We reviewed reference lists of included studies and selected reviews on the topic, contacted authors of included studies, screened relevant meetings and searched in registers for ongoing trials. We applied no language restrictions.

SELECTION CRITERIA

Randomised and quasi-randomised trials assessing the efficacy of amiodarone versus placebo, no intervention, or other antiarrhythmics in adults. For primary prevention we considered participants at high risk for SCD. For secondary prevention we considered participants recovered from cardiac arrest or syncope due to ventricular arrhythmias.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trials for inclusion and extracted relevant data. We contacted trial authors for missing data. We performed meta-analyses using a random-effects model. We calculated risk ratios (RR) for dichotomous outcomes with 95% confidence intervals (CIs). Three studies included more than one comparison.

MAIN RESULTS

We included 24 studies (9,997 participants). Seventeen studies evaluated amiodarone for primary prevention and six for secondary prevention. Only three studies used an ICD concomitantly with amiodarone for the comparison (all of them for secondary prevention).For primary prevention, amiodarone compared to placebo or no intervention (17 studies, 8383 participants) reduced SCD (RR 0.76; 95% CI 0.66 to 0.88), cardiac mortality (RR 0.86; 95% CI 0.77 to 0.96) and all-cause mortality (RR 0.88; 95% CI 0.78 to 1.00). The quality of the evidence was low.Compared to other antiarrhythmics (three studies, 540 participants), amiodarone reduced SCD (RR 0.44; 95% CI 0.19 to 1.00), cardiac mortality (RR 0.41; 95% CI 0.20 to 0.86) and all-cause mortality (RR 0.37; 95% CI 0.18 to 0.76). The quality of the evidence was moderate.For secondary prevention, amiodarone compared to placebo or no intervention (two studies, 440 participants) appeared to increase the risk of SCD (RR 4.32; 95% CI 0.87 to 21.49) and all-cause mortality (RR 3.05; 1.33 to 7.01). However, the quality of the evidence was very low. Compared to other antiarrhythmics (four studies, 839 participants) amiodarone appeared to increase the risk of SCD (RR 1.40; 95% CI 0.56 to 3.52; very low quality of evidence), but there was no effect in all-cause mortality (RR 1.03; 95% CI 0.75 to 1.42; low quality evidence).Amiodarone was associated with an increase in pulmonary and thyroid adverse events.

AUTHORS' CONCLUSIONS

There is low to moderate quality evidence that amiodarone reduces SCD, cardiac and all-cause mortality when compared to placebo or no intervention for primary prevention, and its effects are superior to other antiarrhythmics.It is uncertain if amiodarone reduces or increases SCD and mortality for secondary prevention because the quality of the evidence was very low.

[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.

Nonsustained ventricular tachycardia

Nonsustained ventricular tachycardia (NSVT) has been recorded in a wide range of conditions, from apparently healthy individuals to patients with significant heart disease. In the absence of heart disease, the prognostic significance of NSVT is debatable. When detected during exercise, and especially at recovery, NSVT indicates increased cardiovascular mortality within the next decades. In trained athletes, NSVT is considered benign when suppressed by exercise. In patients with non-ST-segment elevation acute coronary syndrome, NSVT occurring beyond 48 h after admission indicates an increased risk of cardiac and sudden death, especially when associated with myocardial ischemia. In acute myocardial infarction, in-hospital NSVT has an adverse prognostic significance when detected beyond the first 13 to 24 h. In patients with prior myocardial infarction treated with reperfusion and beta-blockers, NSVT is not an independent predictor of long-term mortality when other covariates such as left ventricular ejection fraction are taken into account. In patients with hypertrophic cardiomyopathy, and most probably genetic channelopathies, NSVT carries prognostic significance, whereas its independent prognostic ability in ischemic heart failure and dilated cardiomyopathy has not been established. The management of patients with NSVT is aimed at treating the underlying heart disease.

[Limits and scopes of invasive risk stratification. Do we still need programmed ventricular stimulation?]

Patients with ischemic heart disease and left ventricular systolic dysfunction (ICM), dilated (DCM), hypertrophic (HCM), or arrhythmogenic right ventricular cardiomyopathy (ARVCM) carry a high risk of sudden cardiac death (SCD). Ventricular tachyarrhythmias are most often the cause of SCD, which can be treated with internal cardioverter defibrillators (ICDs). However, a great proportion of these high-risk patients will never experience potentially lethal ventricular arrhythmias, and as such will never be in need of these devices. Given the risks, inconvenience, and costs of ICDs, markers that adequately stratify patients according to their risk of SCD are needed. Programmed ventricular stimulation (PVS) has long been used to identify the patients' risk of SCD. However, the prognostic ability of PVS is only modest and the negative predictive value is poor. As far as patients with ICM are concerned, recent data from the MUSTT and MADIT II trials demonstrate that in patients with a left ventricular ejection fraction between 30% and 40%, inducibility by PVS can help to identify patients who are at particularly increased risk of SCD. The value of PVS in patients with DCM, HCM, and ARVCM for risk stratification of SCD is less clear and the available data even more limited. In these patients, the inducibility of ventricular tachyarrhythmias does not clearly correlate with VT/VF (ventricular tachycardia/ventricular fibrillation) risk, and more importantly, noninducibility does not portend good prognosis. The current German guidelines appreciate these uncertainties of PVS for risk stratification with class IIb recommendations in certain patients with ICM, HCM or ARVCM. In the future, combining the results of invasive PVS with other noninvasive parameters may improve its prognostic value. Furthermore, expanding the role of PVS to guiding therapeutic ablation of ventricular arrhythmias may influence patient's future risk of SCD.

Implantable Cardioverter Defibrillator in Patients with Coronary Artery Disease

Patients with ischemic left ventricular dysfunction are at a high risk for ventricular tachyarrhythmias and sudden cardiac death. Randomized clinical trials have demonstrated that pharmacologic management with antiarrhythmic drugs has limited efficacy for the prevention of arrhythmic mortality in this high-risk population, whereas the implantable cardioverter defibrillator (ICD) has significant life-saving benefit in primary and secondary prevention trials. However, secondary analyses of these studies have identified some limitations of the ICD in subsets of patients with coronary artery disease, including limited defibrillator efficacy early after coronary revascularization and acute myocardial infarction. We review current knowledge from primary and secondary prevention clinical trials regarding the benefit and limitations of the ICD in high-risk patients with coronary artery disease.

Sudden death in dilated cardiomyopathy

The purpose of this review is to examine the potential contribution of arrhythmia to the occurrence of sudden death in dilated cardiomyopathy (DCM) and to discuss current treatment options. We performed a search of the MEDLINE database from 1985 to the present and the reference citations of selected articles pertaining to the prognostic significance, management, and pathophysiology of arrhythmias in DCM. A large proportion of patients with DCM die suddenly, most secondary to ventricular arrhythmia and a smaller proportion due to bradyarrhythmia. The presence and severity of ventricular ectopy may predict risk for sudden death, but the role of electrophysiologic study and signal-averaged electrocardiography in further risk stratifying patients remains uncertain. Abnormalities of the autonomic nervous system and renin-angiotensin-aldosterone axis appear to promote the occurrence of ventricular arrhythmias. Angiotensin-converting enzyme inhibitors improve overall mortality in congestive heart failure, and the use of direct angiotensin-receptor antagonists is currently being studied. In addition, beta-receptor antagonists appear to improve morbidity and may prove to improve mortality in heart failure as well. Other interventions still under investigation include amiodarone and the implantable cardioverter-defibrillator. The underlying pathophysiology of sudden death in DCM involves primarily ventricular tachyarrhythmia. Angiotensin-converting enzyme inhibitors remain a mainstay of improving overall mortality, while further study on the roles for newer drugs and devices is ongoing.

Inducible ventricular arrhythmias and patency of infarct-related artery in survivors of acute myocardial infarction

BACKGROUND

Patency of infarct-related artery in patients who suffered an acute myocardial infarction (AMI) has been shown to be associated with improved survival. Ventricular tachyarrhythmias induced by programmed electrical stimulation may be predictive of arrhythmic events and sudden death.

HYPOTHESIS

The study was undertaken to assess the possible effect of a patent infarct-related coronary artery on induced ventricular tachyarrhythmias during programmed ventricular stimulation in survivors of AMI.

METHODS

In this prospective study, programmed electrical stimulation was performed before hospital discharge (14 +/- 2 days) in 79 patients who survived an AMI. Patients were subdivided into two groups: Group I with patent infarct-related coronary artery (n = 64) and Group 2 with occluded infarct-related artery (n = 15) at coronary angiography performed at 14 +/- 2 days. These two groups were comparable in terms of mean left ventricular ejection fraction, location of infarct-related artery, number of diseased vessels, peak creatine kinase value, and infarct location.

RESULTS

Ventricular arrhythmias were induced in 21 patients ( 32.6%) of Group I and 4 patients (26.6%) of Group 2. This difference was not statistically significant.

CONCLUSION

This study suggests that ventricular arrhythmias induced by programmed ventricular stimulation in survivors of AMI did not differ whether the infarct-related artery was patent or occluded. Other factors may play a role in electrical instability as assessed by programmed ventricular stimulation.

Amiodarone: what have we learned from clinical trials?

Amiodarone is an antiarrhythmic agent commonly used in the treatment of supraventricular and ventricular tachyarrhythmias. This paper reviews clinical trials in which amiodarone was used in one of the treatment arms. Key post-myocardial infarction trials include EMIAT and CAMIAT, both of which demonstrated that amiodarone reduced arrhythmic but not overall mortality. In patients with congestive heart failure (CHF), amiodarone was associated with a neutral survival in CHF/STAT and improvement in survival in GESICA. In patients with nonsustained ventricular tachycardia, the MADIT trial demonstrated that therapy with an implantable cardioverter-defibrillator (ICD) improved survival compared with the antiarrhythmic drug arm in such patients, most of whom were taking amiodarone. In sustained VT/VF patients, the CASCADE trial demonstrated that empiric amiodarone lowered arrhythmic recurrence rates compared with other drugs guided by serial Holter or electrophysiologic studies. Several trials including AVID, CIDS, and CASH have demonstrated the superiority of ICD therapy compared with empiric amiodarone in improving overall survival. Clinical implications of these trials are discussed.

The role of electrophysiology study in risk stratification of sudden cardiac death

Patients with ischemic heart disease and left ventricular systolic dysfunction are at high risk of sudden cardiac death. However, most of these high-risk patients will never develop potential fatal ventricular arrhythmias. Thus, modalities that stratify patients according to their risk of sudden cardiac death are needed. The electrophysiology study has, for decades, been used to prognosticate on patients' risk of sudden cardiac death. Recent data from the Multicenter Unsustained Tachycardia Trial (MUSTT) and Multicenter Automatic Defibrillator Implantation Trial II (MADIT II) demonstrate that in patients with ischemic heart disease and left ventricular systolic dysfunction, an electrophysiology study can help identify patients who are at high risk of sudden cardiac death. However, in these patient populations, the prognostic ability of an electrophysiology study is only modest and the negative predictive value is poor. In the future, combining the results of noninvasive modalities with invasive electrophysiology testing may improve our prognostic ability. Furthermore, expanding the role of the electrophysiology study to include therapeutic ablations may alter a patient's future risk of sudden cardiac death.

Surgery for ventricular tachycardia and left ventricular aneurysm provides arrhythmia control

OBJECTIVES

Report long-term freedom from ventricular tachycardia (VT), survival, and causes of death in patients with left ventricular aneurysm and VT, who underwent a combined procedure for VT and surgical ventricular restoration (SVR).

DESIGN

The primary outcome measures VT, survival, and cause of death, were ascertained by review of patients' records, interrogation of implanted cardioverter-defibrillators and use of national registers.

RESULTS

Mean follow-up was 5.2 years. Overall survival was 62% at 5 years and 51% at 9 years. Freedom from spontaneous VT was 89%. In 32 patients who were non-inducible at postoperative testing, there was no occurrence of VT during a mean follow-up of 6.0 years. Causes of death were cardiac in 17 patients, and non-cardiac in 6 patients. No patient died from ventricular arrhythmia.

CONCLUSIONS

Direct surgery for VT combined with SVR resulted in a very low risk of late recurrence of VT and good long-term survival. Implantation of a cardioverter-defibrillator can safely be withheld in patients who are non-inducible on postoperative programmed electrical stimulation.

Implantable device therapy

Sudden cardiac death (SCD) accounts for two-thirds of fatal events related to heart disease. Coronary heart disease and non-ischemic cardiomyopathy are the most common causes of SCD. Data from major randomized trials have consistently shown that therapy with an implantable cardioverter defibrillator (ICD) results in a significant and meaningful effect on survival through a reduction in the risk of SCD in these population. These data have resulted in a marked increase in the application of implantable device therapy in the past 2 decades from secondary prevention with an implantable cardioverter/defibrillator (ICD) in survivors of a cardiac arrest to primary prevention of SCD in asymptomatic patients with ischemic and non-ischemic left ventricular dysfunction, and prevention of symptomatic heart failure progression and death with cardiac resynchronization therapy (CRT), and devices that combine CRT and ICD therapies (CRT-D). However, there are still areas of uncertainty regarding device therapy that include inconsistent benefit in risk-subgroups of patients with low ejection fraction; increased risk of heart failure after life-prolonging ICD therapy, and a considerable rate of device malfunction despite increasing sophistication. In the present review we focus on current data regarding the clinical indications as well as the safety and efficacy of implantable device therapy, including ICD, CRT, and CRT-D.

Surgery for ventricular tachycardia in patients undergoing surgical ventricular restoration: The Karolinska approach

This article presents a review on the efficacy of surgical ventricular restoration and direct surgery for ventricular tachycardia in patients with left ventricular aneurysm or dilated ischemic cardiomyopathy. The procedure includes a non-electrophysiologically guided subtotal endocardiectomy and cryoablation in addition to endoventricular patch plasty of the left ventricle. Coronary artery bypass surgery and mitral valve repair are performed concomitantly as needed. In our experience, this procedure yielded a 90% success rate in terms of freedom from spontaneous ventricular tachycardia, with an early mortality rate of 3.8%. A practical guide to the pre- and postoperative management of these patients is provided.

Sustained Polymorphic Arrhythmias Induced by Programmed Ventricular Stimulation have Prognostic Value in Patients Receiving Defibrillators

BACKGROUND

Patients with ischemic cardiomyopathy (ICM) who have monomorphic ventricular tachycardia (VT) induced by programmed ventricular stimulation (PVS) are at increased risk of sudden cardiac death (SCD). Among a primary prevention population, the prognostic significance of induced polymorphic ventricular arrhythmias is unknown.

METHODS

A total of 105 consecutive patients who received an implantable cardioverter-defibrillator (ICD) for primary prevention of SCD in the setting of ICM and non-sustained VT were retrospectively evaluated. Seventy-five patients (group I) had induction of monomorphic VT and 30 patients (group II) had a sustained ventricular arrhythmia other than monomorphic VT (ventricular flutter, ventricular fibrillation, and polymorphic VT) induced during PVS.

RESULTS

Baseline characteristics were similar between group I and group II except for ejection fraction (25% vs. 31%, P = 0.0001) and QRS duration (123 milliseconds vs. 109 milliseconds, P = 0.04). Sixteen of 75 (21.3%) patients in group I and 6 of 30 (20%) patients in group II received appropriate ICD therapy (P = 0.88). Survival free from ICD therapy was similar between groups (P = 0.54). There was a trend toward increased all-cause mortality among patients in group I by Kaplan-Meier analysis (P = 0.08). However, when adjusted for age, EF, and QRS duration mortality was similar (P = 0.45).

CONCLUSIONS

There is no difference in rates of appropriate ICD discharge or mortality between patients dichotomized by type of rhythm induced during PVS. These results suggest that patients in this population who have inducible VF or sustained polymorphic VT have similar rates of subsequent clinical ventricular tachyarrhythmias as those with inducible monomorphic VT.

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.

Predictive Value of Ventricular Arrhythmia Inducibility for Subsequent Ventricular Tachycardia or Ventricular Fibrillation in Multicenter Automatic Defibrillator Implantation Trial (MADIT) II Patients

In the Multicenter Automatic Defibrillator Implantation Trial (MADIT) II, implantable cardioverter-defibrillator (ICD)-randomized patients underwent electrophysiologic testing. Both inducible and noninducible patients received an ICD. We correlated inducibility with the occurrence of subsequent ventricular tachycardia (VT) or ventricular fibrillation (VF). Intracardiac ICD electrograms for subsequent events were analyzed to categorize the spontaneous arrhythmia as VT or VF. The two-year Kaplan-Meier event rate for VT in inducible patients was 29.0% versus 19.3% in noninducible patients. However, ICD therapy for spontaneous VF was less common at two years in inducible patients (3.2%) than in noninducible patients (8.6%). In the MADIT II study, inducibility predicted an increased likelihood of VT but decreased VF.

OBJECTIVES

We correlated electrophysiologic inducibility with spontaneous ventricular tachycardia (VT) or ventricular fibrillation (VF) in the Multicenter Automatic Defibrillator Implantation Trial (MADIT) II.

BACKGROUND

In the MADIT II study, 593 (82%) of 720 implantable cardioverter-defibrillator (ICD) randomized patients underwent electrophysiologic testing. Patients received an ICD whether they were inducible or not.

METHODS

A "standard" inducibility definition included sustained monomorphic or polymorphic VT induced with three or fewer extrastimuli or VF induced with two or fewer extrastimuli. We compared a narrow inducibility definition (only monomorphic VT) and a broad definition (standard definition plus VF with three extrastimuli). We used ICD-stored electrograms to categorize spontaneous VT or VF.

RESULTS

Inducible patients (standard definition) had a greater likelihood of experiencing ICD therapy for VT than noninducible patients (p = 0.023). Unexpectedly, ICD therapy for spontaneous VF was less common (p = 0.021) in inducible patients than in noninducible patients. The two-year Kaplan-Meier event rate for VT or VF was 29.4% for inducible patients and 25.5% for noninducible patients. Standard inducibility did not predict the combined end point of VT or VF (p = 0.280, by log-rank analysis). The narrow inducibility definition outperformed the standard definition, whereas the broad definition appeared inferior to the standard definition.

CONCLUSIONS

In the MADIT II study patients, inducibility was associated with an increased likelihood of VT. Noninducible MADIT II study subjects using this electrophysiologic protocol had a considerable VT event rate and a higher VF event rate than inducible patients. Induction of polymorphic VT or VF, even with double extrastimuli, appears less relevant than induction of monomorphic VT.

Surgery for Ventricular Tachycardia in Patients Undergoing Left Ventricular Reconstruction by the Dor Procedure

BACKGROUND

Surgical ventricular restoration (the Dor procedure) is an option in patients with coronary artery disease and postinfarction left ventricular aneurysm. The procedure can be extended to treat ventricular tachycardia (VT). The aim of this study was to evaluate the Dor procedure including VT surgery in our institution.

METHODS

From July 1997 to December 2003, 53 consecutive patients with left ventricular aneurysm and VT underwent surgical ventricular restoration including nonguided endocardiectomy and cryoablation. Twenty-four patients had at least one preoperative episode of spontaneous VT, of which 8 were survivors of sudden cardiac death. Twenty-nine patients had inducible-only VT. In 45 patients, who underwent preoperative programmed stimulation, sustained uniform VT could be initiated. Arrhythmia control was evaluated by programmed stimulation or analysis of events registered by implanted defibrillators and by review of patient's records.

RESULTS

Early mortality was 2 of 53 (3.8%). Mean follow-up was 3.7 years. At 1, 3, and 5 years overall actuarial survival was 94%, 80%, and 59%, respectively. Surgical success rate in patients with preoperative spontaneous VT was 91%. Inducible VT was found in 5 of 35 patients who underwent postoperative programmed stimulation. There was no arrhythmia-related late death and there was no loss to follow-up.

CONCLUSIONS

The Dor procedure including VT surgery is an effective treatment for postinfarction left ventricular aneurysm and VT and eliminates the need for an implantable defibrillator in most patients. Early and long-term results are good in terms of survival and arrhythmia control.

Sudden cardiac death: mechanisms, therapies and challenges

Sudden cardiac death (SCD) is the leading cause of cardiac death in the US. In the past few years, intensive efforts have been made to expand public awareness of SCD and to increase our understanding of its pathophysiology, medical treatment options and device therapy. Significant advances have been made in our ability to prevent SCD in both primary and secondary health care. Two critical issues remain, however: the identification of patients who would benefit from such therapies, and how to achieve even greater prevention, especially primary prevention. The goal of this article is to provide a review of the topic of SCD in the setting of abnormal myocardial substrate, to outline the techniques that are useful in identifying patients at risk, and available treatment options.

Indications for implantable cardiac defibrillators in patients with congestive heart failure: implications of the sudden cardiac death in heart failure trial

Sudden cardiac death (SCD) is a significant cause of mortality in patients suffering from heart failure and left ventricular dysfunction. Implantable cardioverter defibrillators have been shown to effectively reduce the incidence of SCD in this population. Recent clinical trials have redefined the indications and patient profiles for their use: from secondary prevention to primary prevention of SCD. In this article, we review the clinical trials contributing to the current practice guidelines, which include device therapy.

Long-Term Incidence of Malignant Ventricular Arrhythmia and Shock Therapy in Patients with Primary Defibrillator Implantation Does Not Differ from Event Rates in Patients Treated for Survived Cardiac Arrest

INTRODUCTION

Recent trials have demonstrated benefit of prophylactic defibrillator (ICD) implantation compared to conventional treatment in high-risk patients. However, many patients have rare or no sustained arrhythmias following implantation. Our study addresses the question, whether patients with prophylactic defibrillator implantation have a lower risk for life-threatening ventricular tachycardia (VT) or ventricular fibrillation (VF) compared to sudden cardiac death (SCD) survivors.

METHODS AND RESULTS

Over 7 years we enrolled 245 patients. Occurrence of spontaneous sustained VT/VF resulting in adequate ICD treatment was the endpoint. Incidence, type, and treatment of sustained arrhythmia in 43 previously asymptomatic ICD recipients (group B) were compared to data of 202 survivors of imminent SCD (group A). All patients had severely impaired left ventricular ejection fraction (<45%). Group B patients had long runs (>6 cycles, <30 s) of VT during Holter monitoring and inducible sustained arrhythmia. Incidence of rapid VT and VF (cycle length <240 ms/heart rate >250 bpm) after 4 years (35% in both groups, P = ns) and adequate defibrillator therapies (57% vs 55%, P = ns) were similar in both groups after univariate and multivariate analysis. Cumulative mortality tended to be lower in group B compared to group A, but the difference was not statistically significant.

CONCLUSION

During long-term follow-up, incidence of sustained rapid ventricular arrhythmia in prophylactically treated patients is as high as that of SCD survivors. Benefit from defibrillator implantation for primary prevention (group B) appears to be comparable to that for survived cardiac arrest (group A).

Implantable cardioverter defibrillator therapy in postinfarction patients

PURPOSE OF REVIEW

In the past few years, new clinical trials were conducted to determine the effectiveness of implantable cardioverter defibrillators (ICDs) for prevention of mortality in patients with ischemic and nonischemic cardiomyopathies. This paper aims to provide an overview of the current state of knowledge regarding ICD therapy in postinfarction patients.

RECENT FINDINGS

Postinfarction patients with severe left ventricular dysfunction are at high risk of sudden cardiac death. Antiarrhythmic therapy does not improve survival in such patients and, therefore, ICDs emerged as treatment of choice for both primary and secondary prevention of mortality after MI. The MADIT (Multicenter Automatic Defibrillator Implantation Trial) and MUSTT (Multicenter Unsustained Tachycardia Trial) trials were the first primary prevention ICD trials documenting a substantial reduction in mortality with an ICD in postinfarction patients with depressed ejection fraction, nonsustained ventricular tachycardia, and inducible sustained ventricular tachycardia. The recently completed MADIT II trial broadened indications for prophylactic use of ICD in postinfarction patients with ejection fraction of 30% or less without a requirement for additional risk stratifiers. The benefit from ICD therapy in patients with low ejection fraction was recently confirmed by results from the SCD-HeFT (Sudden Cardiac Death in Heart Failure) and COMPANION (Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure) trials.

SUMMARY

Recent clinical trials established ICD as an important therapeutic modality for primary and secondary prevention of mortality in postinfarction patients.

Incidence and electrophysiological characteristics of spontaneous ventricular tachyarrhythmias in high risk coronary patients and prophylactic implantation of a defibrillator

OBJECTIVES

To assess the incidence and electrophysiological characteristics of spontaneous ventricular tachyarrhythmias after implantable cardioverter-defibrillator (ICD) implantation for primary prevention.

DESIGN

Prospective observational study.

PATIENTS

41 consecutive patients, who fulfilled MADIT (multicenter automatic defibrillator implantation trial) I criteria, except for suppressibility by procainamide, and who received a prophylactic ICD.

INTERVENTIONS

Subpectoral implantation of an ICD.

MAIN OUTCOME MEASURES

Incidence of ventricular tachyarrhythmias and their electrophysiological characteristics with respect to timing of the arrhythmia, tachyarrhythmia cycle length, mode of termination, and clinical relevance.

RESULTS

During a mean (SD) follow up of 30 (21) months 18 of 41 (43.9%) patients experienced 142 appropriate ICD treatments. The mean (SD) time to first event was 9.6 (15.1) months. One patient had ventricular fibrillation (VF), 12 patients ventricular tachycardia (VT), and five both VT and VF. The mean (SD) cycle length of monomorphic VT was 306 (42) ms. Of 142 episodes, 117 (82.3%) were terminated by antitachycardia pacing and another 25 (17.6%) by ICD discharges. Cumulative survival of hypothetical death, defined as treated VT with a cycle length < 260 ms or VF, was 83.2% after one year and 78.4% after two years.

CONCLUSIONS

Patients with a left ventricular ejection fraction < 35%, a history of myocardial infarction, non-sustained VT, and inducible VT/VF are at high risk of VT/VF early after implantation. Therefore, implantation of a tiered treatment defibrillator seems to be justified.

Long-term prognosis of inducible ventricular flutter: not an innocent finding

BACKGROUND

The prognostic significance of ventricular flutter (VFL) induced during programmed electrical stimulation (PES) is currently unknown.

METHODS

This study examined patients who had PES-induced VFL and assessed their long-term prognosis compared with patients who had inducible sustained monomorphic ventricular tachycardia (SMVT).

RESULTS

Of 3414 patients undergoing PES, 74 (2%) had sustained VFL. They were compared with a group of 71 patients undergoing PES in the same time frame who had inducible SMVT. Patients with inducible VFL had a higher ejection fraction than patients with SMVT (0.39 vs 0.33; P =.05). More aggressive pacing was required for arrhythmia induction in patients with VFL, with more stimuli (2.7 +/- 0.5 vs 2.2 +/- 0.6; P <.01) and tighter S(2), S(3), and S(4) intervals. After a mean follow-up of 30 +/- 31 months, the mortality rate was 34% in patients with VFL and 30% in patients with SMVT (P =.41). No difference in the 2 groups in overall survival or a combined end point of sudden death or appropriate implantable cardioverter defibrillator shock was revealed with Kaplan-Meier analysis.

CONCLUSION

The long-term prognosis of patients with inducible VFL is similar to that of patients with inducible SMVT, even when VFL is induced with a relatively aggressive protocol.

Usefulness of QRS prolongation in predicting risk of inducible monomorphic ventricular tachycardiain patients referred forelectrophysiologic studies

QRS prolongation on surface electrocardiography has been identified as a marker for increased cardiac mortality. A potential mechanism for increased mortality is ventricular tachycardia (VT). This study aimed to evaluate the relation between bundle branch block and sustained monomorphic VT inducibility in patients referred for electrophysiologic studies. We analyzed a cohort of 777 patients (age 63 +/- 18 years, 67% men, left ventricular [LV] ejection fraction [EF] 45% +/- 16, prior myocardial infarction 41%) referred for electrophysiologic studies between 1994 and 2001 who underwent programmed stimulation for VT. Forty-five percent of patients were referred for syncope or a history of VT and/or ventricular fibrillation. Thirty-one percent of patients had prolonged QRS duration (> or =120 ms). Patients with prolonged QRS duration were older, had lower LVEFs, and were more likely to have a history of myocardial infarction. Prolonged QRS was a significant predictor of sustained monomorphic VT inducibility (p <0.0001). On multivariate analysis correcting for age, sex, LVEF, history of myocardial infarction, medications, and QRS conduction delay proved to be independently associated with sustained monomorphic VT inducibility (relative risk 3.290, 95% confidence interval 2.185 to 4.953 for prolonged vs normal QRS duration). Thus, a prolonged QRS duration on surface electrocardiography is a strong, independent predictor of inducible sustained monomorphic VT. Conduction delay may be an important risk factor, providing a substrate for the development of reentrant monomorphic VT, and furthermore suggests a potential mechanism for the increased mortality observed in patients with prolonged QRS.

Comparative follow up of patients with implanted cardioverter-defibrillators after induction of sustained monomorphic ventricular tachycardias or ventricular fibrillation by programmed stimulation

OBJECTIVE

To investigate the prognostic value of induced monomorphic ventricular tachycardia (VT) and ventricular flutter or fibrillation (VF) during programmed electrical stimulation in patients with a high risk for sudden arrhythmogenic cardiac death.

DESIGN

Prospective cohort study.

PATIENTS

102 patients at high risk for arrhythmogenic sudden cardiac death who received an automated implantable cardioverter-defibrillator (AICD) were evaluated. 56 patients received the AICD for primary prevention and 46 for secondary prevention. 58 patients had induction of a monomorphic VT (VT group) and 44 had induction of a polymorphic VT, ventricular flutter, or ventricular fibrillation (VF group) during programmed electrical stimulation. Average follow up was 20 months in both groups.

MAIN OUTCOME MEASURES

Appropriate AICD protocol.

RESULTS

In patients who received the AICD for primary prevention, 16 of 32 patients in the VT group, compared with only four of 24 patients in the VF group, received an appropriate AICD protocol (p = 0.02). In the entire study population, 479 appropriate AICD protocols were recorded in 28 (48%) patients in the VT group and 28 appropriate protocols in 11 (25%) patients in the VF group. Cumulative Kaplan-Meier event-free survival curves were significantly different (p = 0.02).

CONCLUSION

Induction of VF during programmed electrical stimulation is of no prognostic value even in high risk patients without previously documented ventricular fibrillation.

Effectiveness of implantable defibrillators for preventing arrhythmic events and death: a meta-analysis

OBJECTIVES

The aim of this study was to compare the effectiveness of the implantable cardioverter defibrillator (ICD) and medical strategies for prevention of arrhythmic events and death.

BACKGROUND

The ICD is a potential strategy to reduce mortality in patients at risk of sudden death.

METHODS

The MEDLINE, EMBASE, and Cochrane Library electronic databases were searched from January 1966 to April 2002. All published randomized controlled trials comparing ICD implantation with medical therapy were reviewed. Four independent reviewers extracted data on all-cause mortality, nonarrhythmic death, and arrhythmic death using a standardized protocol.

RESULTS

Nine studies including over 5,000 patients were synthesized using both fixed-effects and random-effects models. The primary and secondary prevention trials showed a significant benefit of the ICD with respect to arrhythmic death, with relative risks (RR) of 0.34 and 0.50, respectively (both p < 0.001). The mortality benefit of the ICD was entirely attributable to a reduction in arrhythmic death (all trials: p < 0.00001). Whereas the secondary prevention trials exhibited a robust decrease in all-cause ICD mortality (RR 0.75; p < 0.001), the pooled primary prevention trials demonstrated decreased all-cause ICD mortality (RR 0.66; p < 0.05) which was dependent on selected individual trials. The disparity in ICD-related mortality reductions in the primary prevention trials was related to variability in the incidence of arrhythmic death between individual studies.

CONCLUSIONS

Although the ICD decreases the risk of arrhythmic death, its impact on all-cause mortality is related to the underlying risk of arrhythmia-related death relative to competing causes. Given the cost of the device strategy, policies of targeted intervention based on the future risk of arrhythmia are warranted.

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

INTRODUCTION AND OBJECTIVES

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

PATIENTS AND METHOD

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

RESULTS

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

CONCLUSIONS

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

Significance and control of cardiac arrhythmias in patients with congestive cardiac failure

A wide spectrum of ventricular and supraventricular tachyarrhythmias occurs in the setting of congestive cardiac failure. However, the two most clinically significant are atrial fibrillation and ventricular tachycardia and fibrillation. In the past there has been much emphasis on premature ventricular contractions and more recently, on nonsustained ventricular tachycardia. For the most part, these arrhythmias are asymptomatic in heart failure. They are markers of sudden arrhythmic death but their suppression by antiarrhythmic drugs have not resulted in a reduction of total mortality. Two approaches have been used to this end. The first is the use of beta-adrenergic blocking drugs and antiarrhythmic agents such as amiodarone. Beta-blockers have been shown to significantly reduce sudden death as well as total mortality, while the effects of amiodarone have been less decisive. The prospective role of the implantable cardioverter defibrillator (ICD) is undergoing critical evaluation in patients with cardiac failure at high risk for sudden death. The elective role of the ICD is well established as first-line therapy in patients with heart failure resuscitated from sudden death and in those with sustained ventricular tachycardia in conjunction with conventional therapies for cardiac decompensation. The prevalence of atrial fibrillation rises as a function of severity of cardiac failure, but it is also in known that persistent atrial fibrillation with an uncontrolled ventricular response may induce heart failure. Controlled ventricular response may prevent congestive heart failure and improve left ventricular function. The two most common causes of atrial fibrillation in cardiac failure in Europe and America are ischemic heart disease and hypertension, while mitral valve disease remains the prevalent cause elsewhere. The choice of antiarrhythmic drugs for maintaining sinus rhythm is critical in the prevention of heart failure aggravation and proarrhythmic reactions of antiarrhythmic drugs. Amiodarone and dofetilide are most widely used in this context.

Differences in inducibility and prognosis of in-hospital versus out-of-hospital identified nonsustained ventricular tachycardia in patients with coronary artery disease: clinical and trial design implications

OBJECTIVES

The goal of this study was to describe the influence of the clinical setting (in-hospital vs. out-of-hospital) in which nonsustained ventricular tachycardia (NSVT) is discovered on the rate of inducibility of sustained ventricular tachycardia (VT), arrhythmic events and survival in patients with coronary artery disease (CAD) and left ventricular (LV) dysfunction.

BACKGROUND

In-hospital presentation of sustained VT is independently associated with lower long-term overall survival. The impact of the clinical setting in which NSVT is documented is unknown.

METHODS

In the Multicenter Unsustained Tachycardia Trial (MUSTT), designed to assess the benefit of randomized antiarrhythmic therapy guided by electrophysiologic testing in patients with asymptomatic NSVT, CAD and LV dysfunction, eligible patients were enrolled irrespective of the setting in which the index arrhythmia was discovered. In this retrospective analysis, we compared the rate of VT inducibility and outcome of MUSTT-enrolled patients with in-hospital versus out-of-hospital presentation of NSVT.

RESULTS

Monomorphic sustained VT was induced in 35% and 28% of the patients whose index NSVT occurred in-hospital and out-of-hospital, respectively (adjusted p = 0.006). Cardiac arrest or death due to arrhythmia at two- and five-year follow-ups were 14% and 28% for untreated patients with in-hospital-identified NSVT and 11% and 21% for the out-of-hospital group (adjusted p = 0.10). Overall mortality rates at two- and five-year follow-ups were 24% and 48% for inpatients and 18% and 38% for outpatients (adjusted p = 0.018). In patients randomized to antiarrhythmic therapy, there was no significant interaction between patient status (in-hospital vs. out-of-hospital) and treatment impact on the rates of total mortality (p = 0.98) and arrhythmic events (p = 0.08).

CONCLUSIONS

In patients with CAD and impaired LV function, asymptomatic NSVT identified in-hospital, compared with that identified out-of-hospital, is associated with a higher rate of induction of sustained VT and overall mortality. Therefore, in similar patients, the clinical setting in which NSVT is discovered should be taken into account when formulating patient risk, treatment and clinical trial design.

Current status of the implantable cardioverter-defibrillator

Clinical trials have established the superiority of the implantable cardioverter-defibrillator (ICD) over antiarrhythmic drug therapy in survivors of sudden cardiac death and in high-risk patients with coronary artery disease. The ICD has evolved to overcome the limitation of earlier devices that required thoracotomy for implantation and were fraught with inappropriate shock delivery. Current ICDs are implanted in a similar manner to cardiac pacemakers and incorporate sophisticated rhythm-discrimination algorithms to prevent inappropriate therapy. Managing the patient with an ICD requires an understanding of the multiprogrammable features of modern devices. Drug interactions and potential sources of electromagnetic interference may adversely affect ICD function. Driving restrictions may be necessary under certain conditions. The cost-effectiveness of ICD therapy appears favorable, given the marked survival benefit seen in randomized trials relative to antiarrhythmic drug treatment. The growing number of ICD recipients necessitates an understanding of the specialized features of the modern ICD and the role of device therapy in clinical practice.