Prevention of sudden death in patients with coronary artery disease: the Multicenter Unsustained Tachycardia Trial (MUSTT)

Programmed Ventricular Stimulation: Risk Stratification and Guiding Antiarrhythmic Therapies

Electrophysiologic testing with programmed ventricular stimulation (PVS) has been utilized to induce ventricular tachycardia (VT), thereby improving risk stratification for patients with ischemic and nonischemic cardiomyopathies and determining the effectiveness of antiarrhythmic therapies, especially catheter ablation. A variety of procedural aspects can be modified during PVS in order to alter the sensitivity and specificity of the test including the addition of multiple baseline pacing cycle lengths, extrastimuli, and pacing locations. The definition of a positive result is also critically important, which has varied from exclusively sustained monomorphic VT (>30 seconds) to any ventricular arrhythmia regardless of morphology. In this review, we discuss the history of PVS and evaluate its role in sudden cardiac death risk stratification in a variety of patient populations. We propose an approach to future investigations that will capitalize on the unique ability to vary the sensitivity and specificity of this test. We then discuss the application of PVS during and following catheter ablation. The strategies that have been utilized to improve the efficacy of intraprocedural PVS are highlighted during a discussion of the limitations of this probabilistic strategy. The role of noninvasive programmed stimulation is also reviewed in predicting recurrent VT and informing management decisions including repeat ablations, modifications in antiarrhythmic drugs, and implantable cardioverter-defibrillator programming. Based on the available evidence and guidelines, we propose an approach to future investigations that will allow clinicians to optimize the use of PVS for risk stratification and assessment of therapeutic efficacy.

2022 HRS expert consensus statement on evaluation and management of arrhythmic risk in neuromuscular disorders

This international multidisciplinary document is intended to guide electrophysiologists, cardiologists, other clinicians, and health care professionals in caring for patients with arrhythmic complications of neuromuscular disorders (NMDs). The document presents an overview of arrhythmias in NMDs followed by detailed sections on specific disorders: Duchenne muscular dystrophy, Becker muscular dystrophy, and limb-girdle muscular dystrophy type 2; myotonic dystrophy type 1 and type 2; Emery-Dreifuss muscular dystrophy and limb-girdle muscular dystrophy type 1B; facioscapulohumeral muscular dystrophy; and mitochondrial myopathies, including Friedreich ataxia and Kearns-Sayre syndrome, with an emphasis on managing arrhythmic cardiac manifestations. End-of-life management of arrhythmias in patients with NMDs is also covered. The document sections were drafted by the writing committee members according to their area of expertise. The recommendations represent the consensus opinion of the expert writing group, graded by class of recommendation and level of evidence utilizing defined criteria. The recommendations were made available for public comment; the document underwent review by the Heart Rhythm Society Scientific and Clinical Documents Committee and external review and endorsement by the partner and collaborating societies. Changes were incorporated based on these reviews. By using a breadth of accumulated available evidence, the document is designed to provide practical and actionable clinical information and recommendations for the diagnosis and management of arrhythmias and thus improve the care of patients with NMDs.

The Canadian Women's Heart Health Alliance Atlas on the Epidemiology, Diagnosis, and Management of Cardiovascular Disease in Women - Chapter 6: Sex- and Gender-Specific Diagnosis and Treatment

This chapter summarizes the sex- and gender-specific diagnosis and treatment of acute/unstable presentations and nacute/stable presentations of cardiovascular disease in women. Guidelines, scientific statements, systematic reviews/meta-analyses, and primary research studies related to diagnosis and treatment of coronary artery disease, cerebrovascular disease (stroke), valvular heart disease, and heart failure in women were reviewed. The evidence is summarized as a narrative, and when available, sex- and gender-specific practice and research recommendations are provided. Acute coronary syndrome presentations and emergency department delays are different in women than they are in men. Coronary angiography remains the gold-standard test for diagnosis of obstructive coronary artery disease. Other diagnostic imaging modalities for ischemic heart disease detection (eg, positron emission tomography, echocardiography, single-photon emission computed tomography, cardiovascular magnetic resonance, coronary computed tomography angiography) have been shown to be useful in women, with their selection dependent upon both the goal of the individualized assessment and the testing resources available. Noncontrast computed tomography and computed tomography angiography are used to diagnose stroke in women. Although sex-specific differences appear to exist in the efficacy of standard treatments for diverse presentations of acute coronary syndrome, many cardiovascular drugs and interventions tested in clinical trials were not powered to detect sex-specific differences, and knowledge gaps remain. Similarly, although knowledge is evolving about sex-specific difference in the management of valvular heart disease, and heart failure with both reduced and preserved ejection fraction, current guidelines are lacking in sex-specific recommendations, and more research is needed.

Significance of Ventricular Arrhythmia Based on Stored Electrogram Analysis in a Pacemaker Population

The incidence of ventricular arrhythmia in patients with an implanted pacemaker is not yet known. The aim of this study was to analyze non-sustained ventricular tachycardia (NSVT) episodes based on stored electrograms (EGM) and determine the occurrence rate and risk factors for NSVT in a pacemaker population.This study included 302 consecutive patients with a dual-chamber pacemaker. A total of 1024 EGMs stored in pacemakers as ventricular high-rate episodes were analyzed. The definition of NSVT was ≥ 5 consecutive ventricular beats at ≥ 150 bpm lasting < 30 seconds.In baseline, most patients (94.8%) had ≥ 60% left ventricular ejection fraction. Of 1024 EGMs, 420 (41.0%) showed appropriate NSVT episodes, as well as premature atrial contractions, atrial tachyarrhythmia, or atrial fibrillation with a rapid ventricular response, whereas other EGMs did not show an actual ventricular arrhythmia. On EGM analysis, during a mean follow-up period of 46.1 months, NSVT occurred one or more times in 82 patients (33.1%). On multivariate analysis, ≥ 50% right ventricular pacing was an independent risk factor for NSVT (odds ratios, 4.519; P < 0.001), but NSVT was not associated with increased all-cause mortality.Moreover, in the pacemaker population, ≥ 50% right ventricular pacing is an independent risk factor for NSVT; however, NSVT was not associated with increased all-cause mortality because of the preserved left ventricular function.

Prognostic significance of non-sustained ventricular tachycardia on stored electrograms in pacemaker recipients

Background

Little is known about the prognostic significance of non-sustained ventricular tachycardia (NS-VT) in outpatients scheduled for routine pacemaker controls. We therefore sought to investigate the prognostic significance of non-sustained ventricular tachycardia on stored electrograms in pacemaker recipients.

Methods

We enrolled patients implanted with dual chamber pacemaker for atrioventricular block or sinus node dysfunction from 2010 to 2016, with LVEF> 45%, older than 18 years, with at least 3 device interrogations at follow-up. Data were collected about medical history, pharmacological therapy at implantation, pacemaker programming, NS-VT occurrence, long-term survival.

Results

A total of 308 patients were included in the final analysis, with median follow-up time of 56 months. No ventricular arrhythmic episodes were documented in 221 patients (Group 1), whereas 87 had at least 1 episode of NS-VT during follow-up (Group 2). As a whole, 282 episodes of NS-VT were documented. There was a higher prevalence of previous myocardial infarction and slightly lower left ventricular ejection fraction (LVEF) in Group 2. The primary endpoint (all-cause mortality) occurred in 50 patients (22%) of Group 1 and 12 (14%) patients of Group 2 (p = 0.07). Clinical predictors of all-cause mortality at univariate analysis included age, LVEF and coronary artery disease (CAD). Only age and CAD, however, remained as predictors of mortality at multivariable analysis. A sizeable, but not statistically significant, portion of patients who died had a de novo occurrence of NS-VT at the last pacemaker check.

Conclusion

Our data do not support a prognostic role for the detection of NS-VT during pacemaker controls.

Relation of multicenter automatic defibrillator implantation trial implantable cardioverter-defibrillator score with long-term cardiovascular events in patients with implantable cardioverter-defibrillator

OBJECTIVE

To test the hypothesis that multicenter automatic defibrillator implantation trial (MADIT) - implantable cardioverter-defibrillator (ICD) scores predict replacement requirement and appropriate shock in a mixed population including both primary and secondary prevention and long-term adverse cardiovascular events.

METHODS

The study has a retrospective design. Patients who were implanted with ICD in the cardiology clinic of Atatürk University Faculty of Medicine between 2000 and 2013 were included in the study. For this purpose, 1394 patients who were implanted with a device in our clinic were reviewed. Then, those who were implanted with permanent pacemaker (n=1005), cardiac resynchronization treatment (CRT) (n=45) and CRT-ICD (n=198) were excluded.

RESULTS

A total of 146 patients (98 males, 67.1%) with a mean age of 61.1 (±14.8) years were recruited. The median follow-up time was 21.5 months (mean 30.6±25.9 months; minimum 4 months, and maximum 120 months). The median MADIT-ICD scores in the patients were 2. MADIT-ICD scores were categorized as low in 15.1%, intermediate in 57.5%, and high score in 27.4% of patients. Accordingly, MADIT-ICD scores (1.29 [1.00-1.68], p=0.050), hemoglobin (0.86 [0.75-0.99], p=0.047), and left ventricular ejection fraction (EF) (0.97 [0.94-0.99], p=0.023) were determined as independent predictors of major adverse cardiovascular events in the long-term follow-up of ICD-implanted population.

CONCLUSION

In this study, we showed that there was an independent association of long-term adverse cardiovascular events with MADIT-ICD score, hemoglobin, and EF in patients implanted with ICD.

Notas sobre <em>Tanacetum corymbosum s. l.</em> (Asteraceae)

Se presenta un estudio nomenclatural y taxonómico sobre Chrysanthemum italicum L., C. achilleae L., C. tanacetifolium Pourr., Pyrethrum cinereum Griseb., P. clusii Fisch. ex Rchb., P. clusii Tausch, P. daucifolium Pers. y P. tenuifolium Ten., táxones que pertenecen al grupo crítico de Tanacetum corymbosum. Se propone una nueva clasificación infraespecífica de Tanacetum corymbosum (L.) Sch. Bip. s. l. y se reconocen cinco subespecies sobre la base de un estudio morfológico del material tipo y otros especímenes. Se proporciona una clave de diagnóstico de los táxones estudiados. Se propone también un cambio nomenclatural, i.e. Tanacetum corymbosum subsp. daucifolium (Pers.) Iamonico comb. nov. Se designan lectotipos para los nombres Chrysanthemum cinereum (espécimen conservado en GOET), Chrysanthemum achilleae (imagen de Micheli), Chrysanthemum italicum (en LINN), Pyrethrum clusii de Rechenbach (ilustración de Clusius), Pyrethrum tenuifolium (en G) y Pyrethrum clusii de Tausch (imagen de Clusius). Se designa un neotipo para Chrysanthemum tanacetifolium (en P).

Impact of a hybrid decision support system to improve the adherence to implantable cardioverter defibrillator therapy guidelines for primary prevention of sudden cardiac death

OBJECTIVES

Despite the well-documented benefit of implantable cardioverter defibrillator (ICD) in patients with severe left ventricular dysfunction, there is a large number of patients who had not been offered this therapy. The aim of this study is to evaluate the utility of a hybrid decision support system (hCDSS) to improve the adherence to indicate ICD therapy in our institution.

METHODS

We conducted a retrospective, observational and single-center study. An hCDSS focused on patients with severe deterioration of the left ventricular function was implemented, creating a mandatory field containing the value of left ejection fraction and three options to choose: >35%, ≤ 35% or unknown. When the option ≤ 35% is checked, an email is automatically sent to the electrophysiology section where the staff can contact the treating physician to discuss the indication of ICD therapy. We measured the number of ICDs implanted before the alert (month 1-21), immediate post and late post alert (month 22-27 and 28-48 months respectively) RESULTS: The rate of ICD implantation increased from 1.76% per month in the pre-intervention period to 4.48% after the intervention (p < 0.001). This increase in the rate of ICD implantation remained stable between the immediate and late post-intervention period (4.6 vs. 4.4; p = .8) CONCLUSION: The implementation of a hybrid decision support system was associated with improved adherence to clinical guidelines for prevention of sudden cardiac death, as evidenced by a rapid and sustained increase in the number of ICD implants in patients with severe left ventricular dysfunction.

Clinical Significance of Nonsustained Ventricular Tachycardia on Stored Electrograms in Permanent Pacemaker Patients

BACKGROUND

Permanent pacemaker electrograms record a variety of arrhythmias, including nonsustained ventricular tachycardia (NSVT). Little has been reported regarding incidence and clinical significance of NSVT in pacemaker patients after long-term monitoring.

METHODS

Records from all patients implanted with Medtronic pacemakers (Medtronic, Minneapolis, MN, USA) at a single institution from January 1, 2009 to February 27, 2012 were reviewed. Demographic characteristics, imaging studies, pacemaker interrogations, and the Social Security Death Index were examined in patients older than 18 years of age who had ≥ 2 follow-up device interrogations.

RESULTS

A total of 262 patients with an ejection fraction (EF) >40% were included in the final analysis with a mean follow-up of 29.2 months. Of these patients, 83.2% (n = 218) had hypertension (HTN) and 45.4% (n = 119) had NSVT. Among patients with an EF ≥ 55%, hypertensive patients had a NSVT burden 2.46 times greater than normotensive patients (incidence rate ratio: 2.46, 95% confidence interval: 1.10-5.50; P < 0.028). NSVT was not associated with increased mortality (P < 0.1229).

CONCLUSION

In this cohort of patients, there was a high prevalence of HTN and while hypertensive subjects had a significantly higher NSVT burden, NSVT was not associated with an increased mortality.

In vivo Electrophysiological Study of Induced Ventricular Tachycardia in Intact Rat Model of Chronic Ischemic Heart Failure

OBJECTIVE

The objective of this study was to define the clinical relevance of in vivo electrophysiologic (EP) studies in a rat model of chronic ischemic heart failure (CHF).

METHODS

Electrical activation sequences, voltage amplitudes, and monophasic action potentials (MAPs) were recorded from adult male Sprague-Dawley rats six weeks after left coronary artery ligation. Programmed electrical stimulation (PES) sequences were developed to induce sustained ventricular tachycardia (VT). The inducibility of sustained VT was defined by PES and the recorded tissue MAPs.

RESULTS

Rats in CHF were defined ( 0.05) by elevated left ventricular (LV) end-diastolic pressure (5 ± 1 versus 18 ± 2 mmHg), decreased LV + d P/dt (7496 ± 225 versus 5502 [Formula: see text] s), LV - dP/dt (7723 ± 208 versus 3819 [Formula: see text]), LV ejection fraction (79 ± 3 versus [Formula: see text]), peak developed pressure (176 ± 4 versus 145 ± 9 mmHg), and prolonged time constant of LV relaxation Tau (18 ± 1 versus 29 ± 2 ms). The EP data showed decreased ( 0.05) electrogram amplitude in border and infarct zones (Healthy zone (H): 8.7 ± 2.1 mV, Border zone (B): 5.3 ± 1.6 mV, and Infarct zone (I): 2.3 ± 1.2 mV), decreased MAP amplitude in the border zone (H: [Formula: see text] 1.0 mV, B: 9.7 ± 0.5 mV), and increased repolarization heterogeneity in the border zone (H: 8.1 ± 1.5 ms, B: 20.2 ± 3.1 ms). With PES we induced sustained VT (>15 consecutive PVCs) in rats with CHF (10/14) versus Sham (0/8).

CONCLUSIONS

These EP studies establish a clinically relevant protocol for studying genesis of VT in CHF.

SIGNIFICANCE

The in vivo rat model of CHF combined with EP analysis could be used to determine the arrhythmogenic potential of new treatments for CHF.

Clinical Presentation and Outcomes by Sex in Arrhythmogenic Right Ventricular Cardiomyopathy: Findings from the North American ARVC Registry

BACKGROUND

Sex differences in clinical presentation and outcomes of hereditary arrhythmias are commonly reported. We aimed to compare clinical presentation and outcomes in men and women with arrhythmogenic right ventricular cardiomyopathy (ARVC) enrolled in the North American ARVC Registry.

METHODS

A total of 125 ARVC probands (55 females, mean age 38 ± 12; 70 males, mean age 41 ± 15) diagnosed, as either "affected" or "borderline" were included. Baseline clinical characteristics and time-dependent outcomes including syncope, ventricular tachycardia (VT), fast VT (>240 bpm), ventricular fibrillation (VF), and death were compared between males and females.

RESULTS

The percentage of ARVC subjects diagnosed as "affected" (84% vs. 89%; P = 0.424) or "borderline" (16% vs. 11%; P = 0.424) was similar between females and males. Among the baseline characteristics, inverted T-waves in V2 trended to be more common in women (P = 0.09), whereas abnormal signal-averaged ECGs (SAECGs; P < 0.001) and inducible VT/VF (P = 0.026) were more frequent in men. During a mean follow-up of 37 ± 20 months, the probability of ICD-recorded VT/VF or death was not significantly different between men and women (P = 0.456). However, there was a trend toward lower risk of fast VT/VF or death in women compared to men (hazard ratio 0.41, 95% CI 0.151-1.113, P = 0.066). Abnormal SAECG and evidence of intramyocardial fat by cardiac MRI was associated with adverse outcomes in men (P = 0.006 and 0.02 respectively).

CONCLUSION

In the North American ARVC Registry, we found similar frequency of "affected" and "borderline" subjects between men and women. Sex-related differences were observed in baseline ECG, SAECG, Holter-recorded ventricular arrhythmias, and VT inducibility. Men showed a trend toward greater risk of fast VT than women.

A Challenging Case Of Ventricular Arrhythmia In A Patient With Myocarditis: ICD Yes/No After Ablation

In patients with myocarditis, early diagnosis and appropriate therapy are mandatory, as well as close clinical follow-up with particular regard to progression of disease and ventricular arrhythmia recurrences. The management of ventricular arrhythmias should follow current guidelines for ICD implantation, but new therapeutic options could be evaluated in these patients, such as combined epicardial/endocardial ablation and external wearable defibrillator. Particularly, depressed left ventricular ejection fraction (LVEF) represents the only risk marker for sudden cardiac death currently used in myocarditis, although the use of a single risk factor has limited utility. On this regard, combined analysis of myocardial tissue structure by cardiac magnetic resonance (CMR) and endomyocardial biopsy, in association with resting cardiac systolic function, could improve predictive accuracy for SCD in patients with myocarditis.

Catheter ablation for ventricular tachycardia: indications and techniques

Ventricular tachycardia (VT) may be secondary to many different underlying pathophysiologies. The nature of the underlying disorder determines amenability to catheter ablation, thus, dictating the circumstances under which it should be undertaken. The differing substrates also influence the choice of techniques that are used. The most intensively studied clinical subgroup of VT is re-entrant VT in the setting of ischemic heart disease. The approach to ablation in such patients is discussed in detail. Subsequent discussion focuses on other clinically encountered varieties of VT and the ablation methods used in each individual disease state.

Microvolt T-wave alternans and electrophysiologic testing predict distinct arrhythmia substrates: implications for identifying patients at risk for sudden cardiac death

BACKGROUND

Better risk stratification of patients receiving an implantable cardioverter-defibrillator (ICD) for primary prevention of sudden cardiac death (SCD) is needed. Although microvolt T-wave alternans (MTWA) and electrophysiologic study (EPS) are independent markers for SCD, the Alternans Before Cardioverter Defibrillator (ABCD) trial found the combination to be more predictive than either test alone.

OBJECTIVE

The purpose of this study was to test the hypothesis that EPS and MTWA measure different elements of the arrhythmogenic substrate and, therefore, predict distinct arrhythmia outcomes.

METHODS

The ABCD trial enrolled 566 patients with ischemic cardiomyopathy, left ventricular ejection fraction (LVEF) <or=0.40, and nonsustained ventricular tachycardia. All patients underwent both MTWA test and EPS. The performance of MTWA and EPS in predicting stable ventricular tachyarrhythmic events (S-VTEs) versus unstable ventricular tachyarrhythmic events (U-VTEs), defined as either polymorphic ventricular tachycardia or ventricular fibrillation, was analyzed using Kaplan-Meier event rates and the log rank test.

RESULTS

MTWA and EPS were abnormal in 71% and 39% of patients, respectively. There were 28 S-VTEs and 10 U-VTEs. MTWA was predictive of U-VTEs (event rate 2.7% in abnormals vs 0% in normals, P = .04), whereas EPS was not (1.5% vs 3.2%, P = .55). In contrast, EPS predicted S-VTEs (9.7% vs 2.2%, P <.01), but MTWA did not (5.5% vs 4.4%, P = .57). Whereas the extent of left ventricular contractile dysfunction alone (LVEF <or=0.30 vs LVEF 0.31-0.40) did not predict events, MTWA predicted events better than did EPS in subjects with LVEF <or=0.30. In contrast, EPS predicted events better than did MTWA test in subjects with LVEF >0.30.

CONCLUSION

The study data suggest that EPS and MTWA identify distinct arrhythmogenic substrates and, when used in combination, may better predict the complex electroanatomic substrates that underlie the risk for SCD.

Different substrates of non-sustained ventricular tachycardia in post-infarction patients with and without left ventricular dilatation

BACKGROUND

We investigated the relationship between nonsustained ventricular tachycardia (NSVT) and left ventricular (LV) dilatation, function, remodeling, and scar tissue extent in patients with previous myocardial infarction (MI).

METHODS AND RESULTS

Eighty-two patients (ages 64+/-10 years) with first previous MI were referred for 24-hour electrocardiogram recording and cine and delayed enhancement (DE) cardiac magnetic resonance (CMR). LV volumes, ejection fraction, systolic wall thickening, sphericity index, and core and peri-infarctual areas of scar tissue by CMR were evaluated. LV dilatation was observed in 39 patients. Episodes of NSVT were recorded in 32 patients: 23 with LV dilatation and 9 without. In the entire population, NSVT was related to ejection fraction, LV volumes, LV mass, and sphericity index; end-systolic volume (P=.001) resulted in the only independent predictor at multivariate analysis. In patients without LV dilatation, the occurrence of NSVT was only positively related with percentage of contracting segments with DE (P=.008). Conversely, in patients with LV dilatation, increase in LV mass (P=.020) and end-systolic volume (P=.038) were independent predictors of NSVT.

CONCLUSIONS

Necrotic and viable myocardium coexistence within the same wall segments predicted occurrence of NSVT in patients without LV dilatation, whereas LV mass and end-systolic volume were predictors of NSVT in those with LV dilatation.

Arrhythmogenic right ventricular cardiomyopathy/dysplasia clinical presentation and diagnostic evaluation: results from the North American Multidisciplinary Study

BACKGROUND

Prior reports on patients with arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) focused on individuals with advanced forms of the disease. Data on the diagnostic performance of various testing modalities in newly identified individuals suspected of having ARVC/D are limited.

OBJECTIVE

The purpose of the Multidisciplinary Study of Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia was to study the clinical characteristics and diagnostic evaluation of a large group of patients newly identified with ARVC/D.

METHODS

A total of 108 newly diagnosed patients with suspected ARVC/D were prospectively enrolled in the United States and Canada. The patients underwent noninvasive and invasive tests using standardized protocols that initially were interpreted by the enrolling center and adjudicated by blind analysis in six core laboratories. Patients were followed for a mean of 27 +/- 16 months (range 0.2-63 months).

RESULTS

The clinical profile of these newly diagnosed patients differs from the profile of reported patients with more advanced disease. There was considerable difference in the initial and final classification of the presence of ARVC/D after the diagnostic tests were evaluated by the core laboratories. Final clinical diagnosis was 73 affected, 28 borderline, and 7 unaffected. Individual tests agreed with the final diagnosis in 50% to 70% of the 73 patients with a final classification of affected.

CONCLUSION

The clinical profile of 108 newly diagnosed probands with suspected ARVC/D indicates that a combination of diagnostic tests is needed to evaluate the presence of right ventricular structural, functional, and electrical abnormalities. Echocardiography, right ventricular angiography, signal-averaged ECG, and Holter monitoring provide optimal clinical evaluation of patients suspected of ARVC/D.

The ABCD (Alternans Before Cardioverter Defibrillator) Trial: strategies using T-wave alternans to improve efficiency of sudden cardiac death prevention

OBJECTIVES

Because risk stratification with electrophysiological study (EPS) improves efficiency but is invasive, we sought to determine whether noninvasive microvolt T-wave alternans (MTWA) testing could identify patients who benefit from implantable cardioverter-defibrillators (ICDs) as well as EPS.

BACKGROUND

Prevention of sudden cardiac death on the basis of left ventricular ejection fraction (LVEF) alone is inefficient, because most ICDs never deliver therapy.

METHODS

The ABCD (Alternans Before Cardioverter Defibrillator) trial is a multicenter prospective study that enrolled patients with ischemic cardiomyopathy (LVEF < or =0.40) and nonsustained ventricular tachycardia. All patients underwent MTWA and EPS. ICDs were mandated if either test was positive.

RESULTS

Of 566 patients followed for a median of 1.9 years, 39 (7.5%) met the primary end point of appropriate ICD discharge or sudden death at 1 year. As hypothesized, primary analysis showed that MTWA achieved 1-year positive (9%) and negative (95%) predictive values that were comparable to EPS (11% and 95%, respectively). In addition, secondary analysis showed that at the pre-specified 1-year end point, event rates were significantly higher in patients with both a positive MTWA-directed strategy (hazard ratio: 2.1, p = 0.03) and a positive EPS-directed strategy (hazard ratio: 2.4, p = 0.007). Moreover, the event rate in patients with both negative MTWA test and EPS was lower than in those with 2 positive tests (2% vs. 12%; p = 0.017).

CONCLUSIONS

The ABCD study is the first trial to use MTWA to guide prophylactic ICD insertion. Risk stratification strategies using noninvasive MTWA versus invasive EPS are comparable at 1 year and complementary when applied in combination. Strategies employing MTWA, EPS, or both might identify subsets of patients least likely to benefit from ICD insertion. (Study to Compare TWA Test and EPS Test for Predicting Patients at Risk for Life-Threatening Heart Rhythms [ABCD Study]; NCT00187291).

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.

Innovation focus: the patient with arrhythmia

Great strides have been made over the last two decades in the management of patients with rhythm disorders. Despite this, however, the remaining critical problems of stroke related to atrial fibrillation or as a result of radiofrequency ablation require innovative solutions to fully realize the potential of these recent advances. Similarly, implanted cardiac devices have revolutionized the care of patients with bradyrhythmias and tachyarrhythmias. Dyssynchronus ventricular pacing associated with present devices; however, results in heart failure, tricuspid regurgitation, and inappropriate device therapy once again create a demand for creative solutions. While not technically an arrhythmia, epilepsy management today is riddled with many of the problems that plagued cardiac arrhythmia management previously, and thus an appreciation of the similarities in requirement for investigative solutions may yield groundbreaking solutions. In this paper, we describe some novel methods to reduce complications associated with rhythm disorders and their treatment and apply the lessons learned from cardiovascular arrhythmia management to the brain. These include: a method to reduce coagulum formation and thus subsequent thromboembolism with indwelling catheters specifically during radiofrequency ablation procedures; a technique to ligate the left atrial appendage through percutaneous subxiphoid pericardial access; development and testing of a novel intramyocardial pace-sense lead, particularly used in a unique anatomic location (the atrioventricular septum) to allow pacing the ventricles in a relatively synchronous manner without crossing the tricuspid valve or entering the coronary sinus; finally, novel modifications of the cardiovascular mapping and ablation techniques used for the management of the central nervous system disorders primarily via the venous drainage of the brain. Innovative and potential solutions to treat the patient with arrhythmia are presented.

Mortality rates and clinical predictors of reduced survival after cardioverter defibrillator implantation

We aimed to identify mortality rates and clinical predictors of reduced survival in a large cohort of patients after implantation of an implantable cardioverter-defibrillator (ICD). Although existing data from clinical trials report annual mortality after ICD implantation from 2% to 9%, there are few data available on mortality rates or predictors of reduced survival in this patient population in clinical practice. In this single-center, retrospective analysis of 286 patients who underwent ICD implantation between June 1, 2000 and December 30, 2003, candidate predictors of mortality were assessed and subjected to multivariable analysis. Outcomes were documented using the Social Security Death Master File and hospital medical records. Overall annualized mortality was 11.3% after ICD implantation. Mortality rates in patients with left ventricular ejection fraction (LVEF) <25% were 27.2% at 1 year and 50.5% at 3 years. Digoxin (hazard ratio 1.86, 95% confidence interval [CI] 1.21 to 2.86, p = 0.0046) and loop diuretics (hazard ratio 1.59, 95% CI 1.06 to 2.38, p = 0.024) were associated with reduced survival. Angiotensin-converting enzyme inhibitor or aldosterone receptor blocker use was associated with reduced mortality (hazard ratio 0.50, 95% CI 0.31 to 0.80, p = 0.0038). In conclusion, mortality after ICD implantation is higher than demonstrated in primary or secondary prevention ICD trials; LVEF remains a potent predictor of mortality after ICD implantation, particularly in patients with an LVEF <25%; loop diuretic and digoxin use is associated with an approximate twofold increase in mortality in this population; and angiotensin-converting enzyme inhibitor or aldosterone receptor blocker use is associated with improved survival after ICD implantation.

Limitations of ejection fraction for prediction of sudden death risk in patients with coronary artery disease: lessons from the MUSTT study

OBJECTIVES

We determined the contribution of multiple variables to predict arrhythmic death and total mortality risk in patients with coronary disease and left ventricular dysfunction. We then constructed an algorithm to predict risk of mortality and sudden death.

BACKGROUND

Many factors in addition to ejection fraction (EF) influence the prognosis of patients with coronary disease. However, there are few tools to use this information to guide clinical decisions.

METHODS

We evaluated the relationship between 25 variables and total mortality and arrhythmic death in 674 patients enrolled in the MUSTT (Multicenter Unsustained Tachycardia Trial) study that did not receive antiarrhythmic therapy. We then constructed risk-stratification algorithms to weight the prognostic impact of each variable on arrhythmic death and total mortality risk.

RESULTS

The variables having the greatest prognostic impact in multivariable analysis were functional class, history of heart failure, nonsustained ventricular tachycardia not related to bypass surgery, EF, age, left ventricular conduction abnormalities, inducible sustained ventricular tachycardia, enrollment as an inpatient, and atrial fibrillation. The model demonstrates that patients whose only risk factor is EF < or =30% have a predicted 2-year arrhythmic death risk <5%.

CONCLUSIONS

Multiple variables influence arrhythmic death and total mortality risk. Patients with EF < or =30% but no other risk factor have low predicted mortality risk. Patients with EF >30% and other risk factors may have higher mortality and a higher risk of sudden death than some patients with EF < or =30%. Thus, risk of sudden death in patients with coronary disease depends on multiple variables in addition to EF.

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.

Designation and distribution of events in the Multicenter UnSustained Tachycardia Trial (MUSTT)

Patients with coronary artery disease, depressed left ventricular ejection fraction, and nonsustained ventricular tachycardia (VT) have a high mortality rate due to arrhythmic (arrhythmic death/cardiac arrest) and other cardiac causes. The Multicenter UnSustained Tachycardia Trial (MUSTT) investigated whether electrophysiologic study (EPS) was helpful in choosing drug or defibrillator therapy in patients induced into sustained VT. The events committee attempted to categorize follow-up events in patients in MUSTT and to present a detailed breakdown of events. A derivative of the Hinkle-Thaler classification was used, incorporating lessons from other multicenter studies. The committee was blinded to results of EPS and implantable cardioverter-defibrillator (ICD) or other antiarrhythmic therapy status of patients. The primary end point was cardiac arrest or death from arrhythmia. Secondary end points were death from all causes, cardiac causes, and spontaneous sustained VT. Classifications were death and cardiac arrest. Each was similarly divided as arrhythmic with 14 subcategories, e.g., unwitnessed or related to EPS and nonarrhythmic with 10 subcategories, e.g., ischemia. Terminal VF in progressive heart failure was considered nonarrhythmic. Events were reviewed by 2 members. Disagreements were resolved by the 2 members or, if needed, by the full committee. Of the 2,202 patients in MUSTT, there were 902 deaths. Sustained VT requiring cardioversion occurred in 182 patients. An additional 94 patients had resuscitated cardiac arrests. Events occurred in 1,027 patients, and all were reviewed. The 3 leading events were deaths that were classed as sudden/unwitnessed (23% of 902), due to progressive heart failure (22%), or due to noncardiovascular causes (18%). Arrhythmic deaths or cardiac arrests were highest in inducible patients randomized to no antiarrhythmic therapy; next were inducible patients receiving an ICD; and lowest were in patients who were noninducible. In conclusion, the classification system provided a detailed breakdown of events in consistent categories, showing utility for event analysis and interpretation and development of therapeutic strategies. The classifications assigned by the committee were used in all MUSTT outcomes reports, thus affecting all reported outcomes and overall interpretations of the MUSTT.

Sudden cardiac death: epidemiologic and financial worldwide perspective

The term sudden cardiac death (SCD) implies the sudden and unexpected loss of an active, productive member of the community. SCD is typically attributed to lethal ventricular arrhythmias; however, these arrhythmias are impossible to diagnose after the fact. Epidemiologic analyses, therefore, rely on inference of the cause of death. Estimates of the incidence of are SCD variable but it may be as high as 1 per 1,000 per year. The cost of SCD to society is incalculable. Current strategies for preventing SCD rely on risk assessment for cardiology patients and implantation of defibrillators (ICD) in high risk patients. Unfortunately, the absolute number of SCDs that occur in the general (relatively low-risk) population is large compared to the number of SCDs in the high risk population. Therefore, prevention of SCD in high risk populations is unlikely to prevent the majority of SCDs. Cost-effectiveness of ICD implantation for prevention of SCD has been studied; ICDs appear to meet U.S. and European criteria for cost-effectiveness if their benefit extends to at least 7-8 years. However, therapies considered cost-effective may nonetheless be too costly for most worldwide societies. Currently, investigators are focusing on refining risk stratification, partly in hopes of identifying patients for whom ICD implantation will not be useful.

Renal insufficiency predicts the time to first appropriate defibrillator shock

BACKGROUND

Indications for implantable cardioverter defibrillator (ICD) implantation are expanding, but many primary and secondary ICD trials have excluded patients with advanced renal insufficiency. We investigated the effect of renal function on the incidence and time to first appropriate ICD shock.

METHOD

We analyzed data from all new ICD implantations at a tertiary care center from July 2001 to December 2002.

RESULTS

During a mean follow-up time of 445 +/- 285 days, 29 (13%) of 230 patients (age 63 +/- 14 years, 79% men, 77% white, 75% coronary artery disease, left ventricular ejection fraction 0.28 +/- 0.14) received 41 appropriate shocks. Patients were divided into tertiles according to their serum creatinine level. The 1-year incidence of appropriate ICD shock was 3.8%, 10.8%, and 22.7% in the first, second, and third tertiles, respectively (P = .003). Using the same cut off values of serum creatinine, the 1-year incidence of appropriate ICD therapy (shock and antitachycardia pacing) was 8.8%, 20.8%, and 26.3% (P = .02). After correcting for age, sex, race, left ventricular ejection fraction, indication for ICD implantation, and use of beta-blockers in a Cox regression model, serum creatinine was still an independent predictor of the time to first appropriate ICD shock (hazard ratio 6.0 for the third compared with the first tertile, P = .001).

CONCLUSION

Renal insufficiency is a strong predictor of appropriate ICD shocks. Defibrillator therapy should therefore not be withheld based on the presence of this comorbidity. The mechanisms underlying the relationship between renal function and ventricular arrhythmias deserve further investigation.

Usefulness of programmed ventricular stimulation in predicting future arrhythmic events in patients with cardiac sarcoidosis

The utility of programmed ventricular stimulation to predict future arrhythmic events in patients with cardiac sarcoidosis is unknown. Similarly, the long-term benefit of implantable cardioverter-defibrillators (ICDs) in cardiac sarcoidosis has not been established. Thirty-two consecutive patients with cardiac sarcoidosis underwent programmed ventricular stimulation. Patients with spontaneous or inducible sustained ventricular arrhythmias (n = 12) underwent ICD insertion. All study patients were followed for the combined arrhythmic event end point of appropriate ICD therapies or sudden death. Mean length of follow-up to sustained ventricular arrhythmia or sudden death was 32 +/- 30 months. Five of 6 patients (83%) with spontaneous sustained ventricular arrhythmias and 4 of 6 patients (67%) without spontaneous but with inducible sustained ventricular arrhythmias received appropriate ICD therapy. Two of 20 patients (10%) with neither spontaneous nor inducible sustained ventricular arrhythmias experienced sustained ventricular arrhythmias or sudden death. Programmed ventricular stimulation predicted subsequent arrhythmic events in the entire population (relative hazard 4.47, 95% confidence interval [CI] 1.30 to 15.39) and in patients who presented without spontaneous sustained ventricular arrhythmias (relative hazard 6.97, 95% CI 1.27 to 38.27). No patient with an ICD died of a primary arrhythmic event. In patients with spontaneous or inducible sustained ventricular arrhythmias, mean survival from first appropriate ICD therapy to death or cardiac transplant was 60 +/- 46 months, with only 2 patients dying or reaching transplant at study end. In conclusion, programmed ventricular stimulation identifies patients with cardiac sarcoidosis at high risk for future arrhythmic events. ICDs effectively terminate life-threatening arrhythmias in high-risk patients, with significant survival after first appropriate therapy.

Ongoing and planned clinical trials of anti-arrhythmic drugs: an update

Anti-arrhythmic drug therapy is frequently used for the control of ventricular arrhythmias in the setting of heart disease. These agents have been used in many randomised clinical trials in an attempt to demonstrate improved survival. However, most studies have been disappointing, showing little or no improvement in survival, and, in some cases, deterioration. This report reviews ongoing clinical trials designed to evaluate survival in specific patient populations.

Detection of Repolarization Alternans With an Implantable Cardioverter Defibrillator Lead in a Porcine Model

Mechanistic links have been suggested between repolarization alternans (RPA) and the onset of ventricular tachycardia (VT) and/or fibrillation. Endocardial detection of RPA may, therefore, be an important step in future device-based treatments of arrhythmias. Here, we investigate if RPA could be detected during acute ischemia using an implantable cardioverter defibrillator (ICD) lead (tip to distal coil) located in the right ventricular apex. In 18 pigs, the right coronary (n = 10) or left anterior descending coronary (n = 8) artery was occluded for 10 min using a balloon catheter, followed by reperfusion for 30 min, and re-occlusion for 30 min. RPA magnitude, computed using the modified moving average (MMA) method, showed a sharp increase in all 18 animals, from a mean baseline level of 1.9 +/- 1.3 mV to 3.0 +/- 1.3 mV during first occlusion (p < 0.001). RPA magnitude showed a prominent increase in 10 animals during re-occlusion, from a mean baseline level of 1.7 +/- 1.0 mV to 3.3 +/- 1.5 mV (p < 0.001). The protocol was terminated during the first two stages of occlusion and reperfusion for the remaining 8 animals due to the occurrence of ventricular fibrillation (VF). These results confirm that RPA increases under ischemic conditions and that it is possible to detect and track RPA dynamics with an ICD lead that is positioned in a clinically realistic location. Such an approach may be useful in formulating improved arrhythmia detection and control algorithms.

Late ventricular potentials in risk assessment of the occurrence of complex ventricular arrhythmia in patients with myocardial infarction and heart failure

AIM

To determine the prognostic significance of late ventricular potentials on signal-averaged electrocardiogram and left ventricular ejection fraction for the occurrence of complex ventricular arrhythmia in patients treated with accelerated tissue-type plasminogen activator, using the rapid protocol, within six months of acute myocardial infarction.

METHODS

In this analytic observational prospective study patients were divided into four groups: patients with left ventricular ejection fraction bellow 40% and late ventricular potentials, patients with left ventricular ejection fraction bellow 40% and without late ventricular potentials, patients with left ventricular ejection fraction over 40% and late ventricular potentials, and patients with left ventricular ejection fraction over 40% and without late ventricular potentials. Complex ventricular arrhythmias (Lown grade IVa, IVb, and V) were recorded using standard electrocardiography and 24-hour Holter monitoring 21, 60, and 90 days after acute myocardial infarction, respectively. Serial recordings of signal-averaged electrocardiogram were obtained 30, 90, and 180 days after acute myocardial infarction. Left ventricular ejection fraction was determined by echocardiography between 15 and 21 days after acute myocardial infarction. Multivariant logistic regression analysis was used to evaluate the relation between late ventricular potentials and left ventricular ejection fraction with the occurrence of complex ventricular arrhythmias. Sensitivity, specificity, positive and negative predictive values of late ventricular potentials and left ventricular ejection fraction for the occurrence of complex ventricular arrhythmias were determined.

RESULTS

The prospective study included 80 patients (73% men), mean age 64 +/- 3.5 years. Complex ventricular arrhythmias were recorded in 34 (42.5%) of patients, all 17 (50%) of which were from the first group (p < 0.01). Complex ventricular arrhythmias were recorded in 25 (73.5%) patients with late ventricular potentials, and in 23 (67.6%) patients with left ventricular ejection fraction bellow 40%. Left ventricular ejection fraction bellow 40% and late ventricular potentials represented independent predictors for the occurrence of complex ventricular arrhythmias (RR = 14.33, p < 0.01). When combined with left ventricular ejection fraction bellow 40%, late ventricular potentials had sensitivity (0.50), specificity (0.93), and positive predictive accuracy (0.85) higher than late ventricular potentials alone (0.44, 0.67, and 0.37, respectively) for the occurrence of complex ventricular arrhythmias following acute myocardial infarction.

CONCLUSION

In this study, late ventricular potentials in patients with left ventricular ejection fraction bellow 40% represented the independent predictor for the occurrence of complex ventricular arrhythmias in the first six months after the first myocardial infarction treated with accelerated tissue-type plasminogen activator, using the rapid protocol.

Ventricular Dysrhythmias in Heart Failure

Left-ventricular systolic dysfunction, or heart failure (HF), is a chronic, progressive condition with a poor prognosis. Approximately 50% of deaths, especially in mild to moderate cases, are sudden. Most sudden deaths are thought to be due to ventricular tachycardia; however, premature ventricular contractions and couplets parallel severity of HF and have been associated with increased mortality risk as opposed to dysrhythmic death. Ventricular arrhythmogenesis results from many mechanisms (afterdepolarizations, reentry, and enhanced automaticity) and preconditions (electrophysiologic abnormalities, neuroendocrine activation, electrolyte imbalances, scar from an ischemic event in ischemic cardiomyopathy, fibrosis in dilated cardiomyopathy, hemodynamic abnormalities, and HF medical management). Nurses are key caregivers in optimally managing HF, either by direct actions or by using advocacy, communication, and collaboration skills to promote positive outcomes. Ventricular dysrhythmia management consists of facilitating core HF pharmacologic and nonpharmacologic medical therapies, using amiodarone to improve symptoms, as needed, and utilizing implantable cardioverter-defibrillator therapy to reduce the risk of sudden cardiac death.

Influence of Gender on Arrhythmia Characteristics and Outcome in the Multicenter UnSustained Tachycardia Trial

INTRODUCTION

Previous studies have demonstrated gender differences in risk of sudden death in patients with ischemic heart disease. The Multicenter UnSustained Tachycardia Trial (MUSTT) evaluated the ability of therapy guided by electrophysiologic (EP) testing to reduce mortality in patients with coronary disease, ejection fraction < or =40%, and spontaneous nonsustained ventricular tachycardia.

METHODS AND RESULTS

We analyzed the influence of gender on results of EP testing and outcome of patients enrolled in MUSTT. Women made up 14% of the overall MUSTT population and were less likely than men to have inducible sustained randomizable ventricular arrhythmias (24% vs 36%, P < 0.001). Baseline characteristics differed between men and women. In randomized patients, women were older, more likely to have had an infarction within 6 months, more likely to have a history of heart failure, and more likely to have recent angina prior to enrollment than men (P < 0.05). In the EP-guided therapy group, there was no difference in implantable cardioverter defibrillator implantation rate in men and women (45% vs 53%, P = 0.38). There also were no significant gender influences on risk of arrhythmic death or cardiac arrest (2-year event rate 9% in women and 12% in men, adjusted hazard ratio 0.88) or overall mortality (2-year event rate 32% in women vs 21% in men, adjusted hazard ratio 1.51).

CONCLUSION

The outcome and benefit of EP-guided therapy in this trial did not appear to be influenced by gender. However, due to the small numbers of women in the trial, small differences in outcome may not be apparent. Plans for future primary prevention trials should include careful risk stratification of women who less often have inducible sustained ventricular arrhythmias and better left ventricular function despite more frequent heart failure.

Effectiveness of early implantation of cardioverter defibrillator for postoperative ventricular tachyarrhythmia

The effectiveness of implantable cardioverter defibrillators (ICDs) implanted in the early postoperative period after cardiac surgery for ventricular tachyarrhythmias is unknown, because all of the major trials excluded this patient population. Thus, a 10-year retrospective study was conducted of patients who had ICDs implanted for de novo postoperative ventricular tachyarrhythmias during the index admission for cardiac surgery. There was a high rate of early recurrence of ventricular tachyarrhythmia treated by defibrillators, and this finding questions the exclusion of this important patient population from large trials.