Implantable Cardioverter Defibrillator Discharges Research Articles

Myocardial Injury Secondary to ICD Shocks: Insights from Patients with Lead Fracture

Patients who receive appropriate implantable cardioverter defibrillator (ICD) shocks have a subsequent adverse prognosis. Most data suggest that patients with inappropriate ICD shocks also have a subsequent adverse prognosis, although this is more controversial. The shocks may be an epiphenomenon, that is, a marker of underlying disease progression; however, it cannot be excluded that shocks cause direct myocardial damage. This latter question is difficult to clarify as the arrhythmia provoking the shock can also cause troponin release. Inappropriate shocks secondary to lead fracture are an ideal situation to examine this question; any troponin release in an otherwise well and hemodynamically stable patient, is likely due directly to the shocks. All patients with Fidelis lead fracture admitted to our institution with inappropriate shocks were included in this study. Troponin (I or T) was considered positive if the level was above the 99th percentile reference cutoff. Elevated troponin levels were recorded in 16 of 22 patients (73%). Patients with elevated troponin received a higher number of shocks (20.3 ± 30.1 vs 5.3 ± 4.8, P = 0.07) compared with patients with normal troponin. Very elevated troponin levels (>0.8 mcg/L) were seen in five of 22 (22%) patients. The mean peak troponin level for these five patients was 7.06 ± 8.56 mcg/L; two patients had troponin levels that would be expected from a medium-sized myocardial infarction or severe myocarditis. Troponin elevation occurred in the majority of our patients after inappropriate ICD discharges secondary to lead fracture. This indicates that ICD shocks can cause myocardial injury.

Impact of atrial fibrillation in an implantable cardioverter defibrillator cohort

Purpose: Atrial fibrillation (AF) is the most common supraventricular arrhythmia in patients with an implantable cardioverter defibrillator (ICD). We evaluated the prognostic significance of AF in ICD patients with ischemic or dilated heart disease. Methods: 647 consecutive patients with ischemic or dilated heart disease (81% male, mean age 64±10 years, 70% primary prevention) receiving an ICD in the Thoraxcenter Twente were included. Demographic data, including existence and type of AF (permanent or non-permanent) was collected. Primary endpoints were all cause mortality and ICD discharge (appropriate or inappropriate). Results: At implantation, 183 (28%) had a history of AF (13% non-permanent and 15% permanent. During 41±15 months follow up, 135 (21%) patient died, 142 (22%) patients experienced an ICD shock, of which 104 (16%) appropriate and 58 (9%) inappropriate. After multivariate analysis permanent AF was significantly related to mortality (HR 1.63 (95% CI: 1.08-2.47)) and shock therapy (HR 2.10 (95% CI 1.39-3.15), both appropriate (HR 1.67 (95% CI 1.03-2.71) and inappropriate (HR 3.62 (95% CI 1.92-6.84)). Non-permanent AF was only related to inappropriate shock therapy (HR 2.43 (95% CI 1.21-4.87)). During follow up, 29 patients (6.3%) with sinusrhythm developed AF, this was related to inappropriate shock therapy (HR 2.83 (95% CI 1.08-7.41). Conclusion: In real-world ICD recipients, almost a third have a history of permanent or non-permanent AF, which leads to higher rates of mortality and ICD discharge. Especially permanent AF is associated with higher rates of mortality and ICD discharge (both appropriate and inappropriate). Non-permanent AF and new onset AF are associated with inappropriate ICD discharge.

Assessment of sports activity in patients diagnosed with familial cardiopathies

Background: Sports activity was associated with an increased risk of sudden cardiac death (SCD) in adolescents and young adults with undiagnosed cardiomyopathies or channelopathies. It is estimated that one in 1000 athletes may be affected. The present study sought to determine the percentage of patients diagnosed with familial cardiopathies that do physical exercise regularly, their clinical characteristics, and follow-up through a specialized consultation. Methods: A prospective observational study was designed. 1128 consecutive patients (age 49±19, 418 (37%) women) from 765 families that satisfied diagnostic criteria for cardiomyopathy or channelopathy were included. Age of diagnosis, clinical characteristics, and electrocardiographic and echocardiographic parameters were collected. Rate of events was determined in both groups: SCD; resuscitated sudden cardiac death (RSCD); and implantable cardioverter defibrillator (ICD) discharge. Results: 85 athletes (7,5%) were identified. The mean age at diagnosis was significantly lower in the group of patients that practiced sports (31,5±15 years vs 45,6±20 years; p<0,001). Among patients diagnosed with hypertrophic cardiomyopathy, athletes group presented a lower thickness of ventricular septum (median 15mm, range 14 to 20mm vs 19mm, range 16 to 22mm; p=0,001). Left ventricular ejection fraction (LVEF) in patients diagnosed with idiopathic dilated cardiomyopathy was higher in the group of athletes (mean 51,1±5,6% vs 35,4±13,6%; p<0,001). Four patients that practiced sports routinely had events: 3 SCD and one RSCD; while in the group of non-athlete patients, 64 of them presented events: 23 SCD, 26 RSCD, and 15 ICD discharges. There were no significant differences in the development of events between the two groups. Conclusions: A significant proportion of patients with familial cardiopathies practice sport regularly. Diagnosis of heart disease was earlier in the group of athletes. In this group, the thickness of ventricular septum among patients with hypertrophic cardiomyopathy was lower and patients with idiopathic dilated cardiomyopathy had higher LVEF than in the group of non-athletes. There were no differences between both groups in the development of events. Further studies are required to understand the relationship between sport and the development of adverse events in patients diagnosed with familial cardiopathies.

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Efficacy of Implantable Cardioverter Defibrillators in Young Patients With Catecholaminergic Polymorphic Ventricular Tachycardia

Background— The effectiveness of implantable cardioverter-defibrillator (ICD) therapy for the management of catecholaminergic polymorphic ventricular tachycardia (VT) in young patients is not known. ICD discharges are not always effective and inappropriate discharges are common, both resulting in morbidity and mortality. Methods and Results— This is a multicenter, retrospective review of young patients with catecholaminergic polymorphic VT and ICDs from 5 centers. ICD discharges were evaluated to determine arrhythmia mechanism, appropriateness, efficacy of therapy, and complications. A total of 24 patients were included. Median (interquartile range) ages at onset of catecholaminergic polymorphic VT symptoms and ICD implant were 10.6 (5.0–13.8) years and 13.7 (10.7–16.3) years, respectively. Fourteen patients received 140 shocks. Ten patients (42%) experienced 75 appropriate shocks and 11 patients (46%) received 65 inappropriate shocks. On actuarial analysis, freedom from appropriate shock at 1 year after ICD implant was 75%. Of appropriate shocks, only 43 (57%) demonstrated successful primary termination. All successful appropriate ICD discharges were for ventricular fibrillation. No episodes of polymorphic VT or bidirectional VT demonstrated successful primary termination. The adjusted mean (95% confidence interval) cycle length of successful discharges was significantly shorter than unsuccessful discharges (168 [152–184] ms versus 245 [229–262] ms; adjusted P =0.002). Electrical storm occurred in 29% (4/14) and induction of more malignant ventricular arrhythmias in 36% (5/14). There were no deaths. Conclusions— ICD efficacy in catecholaminergic polymorphic VT depends on arrhythmia mechanism. Episodes of ventricular fibrillation were uniformly successfully treated, whereas polymorphic and bidirectional VT did not demonstrate successful primary termination. Inappropriate shocks, electrical storm, and ICD complications were common.

Baseline ECG and VT ablation: Is there more to it than just skimming the surface?

A growing body of literature supports left ventricular scar as an outcome predictor in patients with ischemic cardiomyopathy. While ejection fraction has been traditionally recognized as a “risk stratifier” in patients with coronary artery disease, limitations clearly exist as evidenced by relatively low rates of appropriate implantable cardioverterdefibrillator (ICD) discharges in devices placed for primary prophylaxis. Scar burden is emerging as a new marker to predict outcomes. Cardiac magnetic resonance imaging (MRI) is the gold standard for determining location and burden of myocardial scar in patients with ischemic cardiomyopathy, and emerging data from several studies have shown a relation not only to mortality 1,2 but also to arrhythmia burden. 3,4 Late gadolinium enhancement is used to delineate scar, but several factors can affect this determination, including methods to quantify scar (which in some cases may be semiautomated) and impact of the infarct border zone is still unclear. Cardiac MRI is not readily available at all centers and not readily feasible in patients with ICDs at least in their current iteration. Therefore, electrocardiogram (ECG) quantification of scar is a useful proposition as a simple, noninvasive analysis and the Selvester score has been used as a surrogate. This score has been shown to correlate with MRI scar and to predict inducible monomorphic ventricular tachycardia (VT)

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CMR Imaging Predicts Death and Other Adverse Events in Suspected Cardiac Sarcoidosis

This study aimed to demonstrate that the presence of late gadolinium enhancement (LGE) is a predictor of death and other adverse events in patients with suspected cardiac sarcoidosis. Cardiac sarcoidosis is the most important cause of patient mortality in systemic sarcoidosis, yielding a 5-year mortality rate between 25% and 66% despite immunosuppressive treatment. Other groups have shown that LGE may hold promise in predicting future adverse events in this patient group. We included 155 consecutive patients with systemic sarcoidosis who underwent cardiac magnetic resonance (CMR) for workup of suspected cardiac sarcoid involvement. The median follow-up time was 2.6 years. Primary endpoints were death, aborted sudden cardiac death, and appropriate implantable cardioverter-defibrillator (ICD) discharge. Secondary endpoints were ventricular tachycardia (VT) and nonsustained VT. LGE was present in 39 patients (25.5%). The presence of LGE yields a Cox hazard ratio (HR) of 31.6 for death, aborted sudden cardiac death, or appropriate ICD discharge, and of 33.9 for any event. This is superior to functional or clinical parameters such as left ventricular (LV) ejection fraction (EF), LV end-diastolic volume, or presentation as heart failure, yielding HRs between 0.99 (per % increase LVEF) and 1.004 (presentation as heart failure), and between 0.94 and 1.2 for potentially lethal or other adverse events, respectively. Except for 1 patient dying from pulmonary infection, no patient without LGE died or experienced any event during follow-up, even if the LV was enlarged and the LVEF severely impaired. Among our population of sarcoid patients with nonspecific symptoms, the presence of myocardial scar indicated by LGE was the best independent predictor of potentially lethal events, as well as other adverse events, yielding a Cox HR of 31.6 and of 33.9, respectively. These data support the necessity for future large, longitudinal follow-up studies to definitely establish LGE as an independent predictor of cardiac death in sarcoidosis, as well as to evaluate the incremental prognostic value of additional parameters.

Sinus node disease in subjects with type 1 ECG pattern of Brugada syndrome

BackgroundThe spectrum of phenotypes related to mutations of the SCN5A gene include Brugada syndrome (BS), long QT syndrome, progressive cardiac conduction defect, and sinus node disease (SND). The present study investigated the incidence of SND in subjects with type 1 electrocardiogram (ECG) pattern of BS. Methods and resultsThe study population consisted of 68 individuals (55 males, mean age 44.8±12.8 years) with spontaneous (n=27) or drug-induced (n=41) type 1 ECG pattern of BS. Twenty-eight subjects were symptomatic with a history of syncope (41.2%). SND was observed in 6 symptomatic subjects (8.8%), and was mainly attributed to sino-atrial block with sinus pauses. Two patients were initially diagnosed with SND, and received a pacemaker. Patients with SND displayed an increased P-wave duration in leads II and V2, PR interval in leads II and V2, QRS duration in leads II and V2, and increased QTc interval in lead V2 (p<0.05). AH and HV intervals as well as corrected sinus node recovery time (cSNRT) were significantly prolonged in subjects with SND (p<0.05). During a mean follow-up period of 5.0±3.6 years, five subjects with a history of syncope suffered appropriate implantable cardioverter defibrillator (ICD) discharges due to ventricular arrhythmias (7.4%). None of those diagnosed with SND suffered syncope or ICD therapies. ConclusionSND is not an uncommon finding in subjects with type 1 ECG pattern of BS. The occurrence of SND in relatively young patients may deserve meticulous investigation including sodium channel blocking test.

Volumetric Left Ventricular Ejection Fraction is Superior to 2-Dimensional Echocardiography for Risk Stratification of Patients for Primary Prevention Implantable Cardioverter-Defibrillator Implantation

Current guidelines recommend an implantable cardioverter-defibrillator (ICD) according to the left ventricular ejection fraction (LVEF). However, they do not mandate volumetric LVEF assessment. We sought to determine whether volumetric LVEF measurement using cardiovascular magnetic resonance imaging (CMR-LVEF) is superior to conventional LVEF measurement using 2-dimensional transthoracic echocardiography (Echo-LVEF) for risk stratifying patients referred for primary prevention ICD. Patients who underwent primary prevention ICD implantation at our institution and had undergone preimplantation CMR-LVEF from November 2001 to February 2011 were identified. Volumetric CMR-LVEF was determined from cine short-axis data sets. CMR-LVEF and Echo-LVEF were extracted from the clinical reports. The end point was appropriate ICD discharge (shock and/or antitachycardia pacing). Of 48 patients, appropriate ICD discharge occurred in 9 (19%) within 29 ± 25 months (range 1 to 99, median 20). All patients met the Echo-LVEF criteria for ICD implantation; however 25% (95% confidence interval 13% to 37%) did not meet the CMR-LVEF criteria. None (0%) of these latter patients had received an appropriate ICD discharge. Using CMR-LVEF ≤30% as a threshold for ICD eligibility, 19 patients (40%) with a qualifying Echo-LVEF would not have been referred for ICD, and none (0%) received an ICD discharge.For primary prevention ICD implantation, volumetric CMR-LVEF might be superior to clinical Echo-LVEF for risk stratification and can identify a large minority of subjects in whom ICD implantation can be safely avoided. In conclusion, if confirmed by larger prospective series, volumetric methods such as CMR should be considered a superior "gatekeeper" for the identification of patients likely to benefit from primary prevention ICD implantation.

Autonomic markers and cardiovascular and arrhythmic events in heart failure patients: still a place in prognostication? Data from the GISSI‐HF trial

To investigate the prognostic value of autonomic variables in patients with symptomatic chronic heart failure (HF) treated according to current recommendations. We analysed 24 h time-domain [standard deviation of all normal-to-normal RR intervals (SDNN)], frequency-domain [very low frequency and low frequency power (VFLP and LFP)], and non-linear [detrended fluctuation analysis (DFA)] heart rate variability, deceleration capacity (DC), and heart rate turbulence (HRT) in 388 sinus rhythm HF patients enrolled in the GISSI-HF Holter substudy [82% males, age 65 ±10 years, New York Heart Association (NYHA) functional class III-IV 20%, left ventricular ejection fraction (LVEF) 33 ±8%]. Cardiovascular (CV) mortality and combined sudden death + implantable cardioverter defibrillator (ICD) discharge were assessed as a function of continuous variables in the entire population and in patients with LVEF >30% in univariate and multivariable Cox proportional hazards models. After a median of 47 months, 57 patients died of CV causes and 47 experienced the arrhythmic endpoint. For CV mortality, VLFP, LFP, and turbulence slope (TS) improved predictive discrimination (c-index) and risk classification [integrated discrimination improvement (IDI)] when added to clinical variables [age ≥70 years, LVEF, non-sustained ventricular tachycardia (NSVT), serum creatinine], while for arrhythmic mortality although the c-index increased in all three autonomic markers, the results of the IDI were statistically significant only for TS when added to NSVT, serum creatinine, and ischaemic aetiology. In 194 patients with LVEF >30% (20 arrhythmic events), the hazard ratio of an impaired TS (<2.5 msper RR interval) was 3.81 (95% confidence interval 1.35-10.7,P = 0.012) after adjustment for serum creatinine. Autonomic indexes still have independent predictive value on long-term outcome in HF patients. HRT may help in identifying patients with LVEF >30% at increased arrhythmic risk. Trial registration NCT00336336.

Implantable Cardioverter Defibrillators in Patients with Valvular Cardiomyopathy

Implantable cardioverter-defibrillators (ICDs) are beneficial for preventing sudden cardiac death (SCD) in patients with previous SCD or left ventricular dysfunction. The objective was to investigate the outcomes of ICD implantation in patients who have surgery for valvular cardiomyopathy (VCM). We identified patients with VCM who had ICD implantation after valve surgery. Age- and sex-matched patients who received an ICD for ischemic cardiomyopathy (ICM) and dilated cardiomyopathy (DCM) served as controls. Patients with VCM who had valve surgery but did not receive an ICD served as an additional control group. We compared mortality and appropriate ICD discharges between the study group and control groups. Mean (SD) age (31 patients with VCM with ICD, 30 with ICM, 26 with DCM, and 62 patients with VCM without ICD) was 60 (15) years, 73% were men. Ejection fraction at ICD implantation was 34%, 26%, and 23% for the VCM with ICD, ICM, and DCM groups, respectively (P = 0.03). After a median follow-up of 4.1 years, survival was not significantly different among ICD groups (P = 0.06). The annual appropriate shock rate was 5%, 10%, and 4% for the VCM with ICD, ICM, and DCM groups, respectively (P = 0.71). Compared to VCM without ICD, patients with VCM and ICD had comparable survival (P = 0.82) despite a reduced LVEF following valve surgery. Patients with VCM who undergo ICD implantation for SCD prevention have similar appropriate ICD discharge rates and mortality as do those with ICM and DCM. These data are hypothesis generating and deserve confirmation with large-scale prospective studies.

Phospholamban R14del mutation in patients diagnosed with dilated cardiomyopathy or arrhythmogenic right ventricular cardiomyopathy: evidence supporting the concept of arrhythmogenic cardiomyopathy

To investigate whether phospholamban gene (PLN) mutations underlie patients diagnosed with either arrhythmogenic right ventricular cardiomyopathy (ARVC) or idiopathic dilated cardiomyopathy (DCM). We screened a cohort of 97 ARVC and 257 DCM unrelated index patients for PLN mutations and evaluated their clinical characteristics. PLN mutation R14del was identified in 12 (12 %) ARVC patients and in 39 (15 %) DCM patients. Haplotype analysis revealed a common founder, estimated to be between 575 and 825 years old. A low voltage electrocardiogram was present in 46 % of R14del carriers. Compared with R14del- DCM patients, R14del+ DCM patients more often demonstrated appropriate implantable cardioverter defibrillator discharge (47 % vs. 10 % , P < 0.001), cardiac transplantation (18 % vs. 2 % , P < 0.001), and a family history for sudden cardiac death (SCD) at < 50 years (36 % vs. 16 % , P = 0.007). We observed a similar pattern in the ARVC patients although this was not statistically significant. The average age of 26 family members who died of SCD was 37.7 years. Immunohistochemistry in available myocardial samples revealed absent/depressed plakoglobin levels at intercalated disks in five of seven (71 %) R14del+ ARVC samples, but in only one of nine (11 %) R14del+ DCM samples (P = 0.03). The PLN R14del founder mutation is present in a substantial number of patients clinically diagnosed with DCM or ARVC. R14del+ patients diagnosed with DCM showed an arrhythmogenic phenotype, and SCD at young age can be the presenting symptom. These findings support the concept of 'arrhythmogenic cardiomyopathy'.

Ventricular tachycardia/fibrillation early after defibrillator implantation in patients with hypertrophic cardiomyopathy is explained by a high-risk subgroup of patients

Implantable cardioverter-defibrillator (ICD) studies in patients with coronary artery disease report higher risk of ventricular tachycardia/fibrillation (VT/VF) early post-implant, potentially related to local proarrhythmic effects of ICD leads. To characterize early and long-term risk of ICD discharge for VT/VF in a large hypertrophic cardiomyopathy (HCM) cohort. By using HCM multicenter registry data, we compared long-term risk of VT/VF subsequent to an early post-implant period (a priori defined as within 3 months of implant) between patients with or without VT/VF within 3 months after ICD implantation. Over a median follow-up of 4.3 years, 109 of 506 (22%) patients with HCM who received ICDs received at least 1 ICD discharge for VT/VF. Risk of first ICD discharge for VT/VF was highest in the first year post-implant (10.8% per person-year; 95% confidence interval 7.9-13.8) and particularly in the first 3 months (17.0% per person-year; 95% confidence interval 9.8-24.3). Patients with early VT/VF (≤3 months post-implant) were older, and more commonly had secondary prevention ICDs following cardiac arrest or systolic dysfunction (end-stage HCM with ejection fraction<50%). Only 2 of 247 (0.7%) patients with primary prevention ICDs and preserved systolic function had early VT/VF. Patients with VT/VF early post-implant (≤3 months) had more than 5-fold higher risk for future VT/VF during long-term follow-up compared with patients without early VT/VF (adjusted hazard ratio 5.4; 95% confidence interval 2.3-12.6). High-risk patients with HCM and VT/VF early after ICD implantation are particularly prone to subsequent VT/VF throughout follow-up. Early ICD interventions for VT/VF are largely confined to patients with prior cardiac arrest or systolic dysfunction and therefore more likely driven by higher arrhythmic risk rather than lead-related proarrhythmia.

Epidemiology, management, and outcomes of sustained ventricular arrhythmias after continuous-flow left ventricular assist device implantation

Left ventricular assist devices (LVADs) are pivotal treatment options for patients with end-stage heart failure. Despite robust left ventricular unloading, the right ventricle remains unsupported and susceptible to hemodynamic perturbations from ventricular arrhythmias (VAs). Little is known about the epidemiology, management, resource use, and outcomes of sustained VAs in continuous-flow LVAD patients. We reviewed data from all consecutive patients receiving a continuous-flow LVAD at the University of North Carolina from January 2006 to February 2011. Patient demographics, pharmacotherapies, resource use, and outcomes were recorded. Descriptive statistics were generated, and multivariable logistic regression was used to assess the independent association of clinical variables on the development of postimplantation VAs. Of 61 patients, 26 (43%) had sustained VAs after LVAD. Most were male (65%), had history of hypertension (65%), and had nonischemic cardiomyopathy (62%). Patients with VAs after LVAD more often had preimplant VAs (62% vs 14%, P < .01), prior implantable cardioverter-defibrillator (92% vs 71%, P = .04), and history of implantable cardioverter-defibrillator discharge (38% vs 11%, P < .01). Although length of stay was similar, those with postimplant VAs had greater rehospitalization rates, greater antiarrhythmic drug use, and frequently required external defibrillation. Using multivariable logistic regression, only history of prior VA was associated with postimplant arrhythmias (odds ratio 13.7, P < .001). Ventricular arrhythmias in LVAD patients are common, often refractory to conservative therapy, and associated with frequent rehospitalization. Post-LVAD VAs, however, did not significantly impact survival or transplantation rates. Arrhythmia burden should be considered before LVAD placement, and future study should focus on the impact of VAs on quality of life.

Is Quinidine the Ideal Drug for Brugada Syndrome?

Brugada syndrome (BrS) is a cardiac disease caused by an inherited ion channelopathy that is associated with a propensity to develop ventricular fibrillation (VF). Patients with BrS and a history of cardiac arrest are considered to be at the highest risk for recurrent arrhythmic events and should be treated with an implantable cardioverter-defibrillator (ICD). However, the beneficial effects of an ICD are solely the result of VF termination by the device, whereas the device does not affect VF occurrence. For the past 3 decades, our group at the Tel-Aviv Medical Center has developed an alternative therapeutic approach to ICD use in BrS patients based on the high efficacy (90%) of quinidine bisulfate at a mean dose of 1.5 g daily to prevent inducibility of VF. This approach has been associated with both excellent reproducibility of electrophysiologic (EP) results and clinical efficacy during the long term as attested by the fact that none of our drug-responder and drug-tolerant patients has yet exhibited a recurrent arrhythmic event. Hermida et al obtained similar results using another slowrelease quinidine preparation (quinidine hydrochloride 600– 900 mg daily). We have been using the latter medication for the past 5 years because of AstraZeneca’s decision to stop production of quinidine bisulfate. Electric storms of VF represent the more malignant form of ventricular arrhythmias in patients with BrS, accounting for up to 10% of the untreated patient population and up to 38% of arrhythmic events in ICD patients. The arrhythmic storms may reveal the disease or occur after ICD implantation, and they are frequently, but not always, triggered by fever. They may lead to multiple DC shocks or ICD discharges with multiple consequences, such as psychologic disorders, proarrhythmia, deleterious effect on cardiac function, electromechanical dissociation, and death. Heart transplantation has even been used as the last resort in a patient with intractable VF (see references in Belhassen et al). Isoproterenol infusion has been shown to be very effective for the acute management of arrhythmic storms in the setting of BrS. However, it can be administered only during a short period of time, and the arrhythmia frequently recurs

QRS fragmentation in patients with arrhythmogenic right ventricular cardiomyopathy and complete right bundle branch block: a risk stratification

Patients with arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) and complete right bundle branch block (RBBB) very often have recurrent ventricular tachycardia and develop biventricular heart failure in the follow up, requiring heart transplantation and/or diuretics. In other patients with ARVC/D excluding RBBB, QRS fragmentation in the S wave of right precordial leads identifies patients with recurrent ventricular tachycardia, primary ventricular fibrillation, and recurrent implantable cardioverter defibrillator discharges; QRS fragmentation ≥3 leads characterized patients who died from sudden cardiac death. In a cohort of 374 patients with ARVC/D (208 males; mean±SD age 46.5±14.8 years), there were 22 patients with complete RBBB: 17 patients with ARVD/C developed complete RBBB and had biventricular heart failure in a follow up of 4-6 years. In five patients with ARVC/D, complete RBBB was initially evident. In all patients with ARVC/D and RBBB, QRS fragmentation ≥3 of all 12 ECG leads and QRS fragmentation in the S wave of right precordial leads were analysed. QRS fragmentation ≥3 of all 12 ECG leads and in the S wave of right precordial leads were present in 16/17 patients who developed RBBB and none of the five patients with initial RBBB. In one patient with initial RBBB, QRS fragmentation ≥3 leads was present (r=17.45; p<0.0001). Patients with recurrent ventricular tachycardia who develop biventricular heart failure requiring heart transplantation and/or diuretics are characterized by QRS fragmentation in the S wave of right precordial leads and ≥3 of all 12 ECG leads. These results are statistically significant. Patients with initial RBBB have an overall benign prognosis.

Assessment of Myocardial Scarring Improves Risk Stratification in Patients Evaluated for Cardiac Defibrillator Implantation

We tested whether an assessment of myocardial scarring by cardiac magnetic resonance imaging (MRI) would improve risk stratification in patients evaluated for implantable cardioverter-defibrillator (ICD) implantation. Current sudden cardiac death risk stratification emphasizes left ventricular ejection fraction (LVEF); however, most patients suffering sudden cardiac death have a preserved LVEF, and many with poor LVEF do not benefit from ICD prophylaxis. One hundred thirty-seven patients undergoing evaluation for possible ICD placement were prospectively enrolled and underwent cardiac MRI assessment of LVEF and scar. The pre-specified primary endpoint was death or appropriate ICD discharge for sustained ventricular tachyarrhythmia. During a median follow-up of 24 months the primary endpoint occurred in 39 patients. Whereas the rate of adverse events steadily increased with decreasing LVEF, a sharp step-up was observed for scar size >5% of left ventricular mass (hazard ratio [HR]: 5.2; 95% confidence interval [CI]: 2.0 to 13.3). On multivariable Cox proportional hazards analysis, including LVEF and electrophysiological-study results, scar size (as a continuous variable or dichotomized at 5%) was an independent predictor of adverse outcome. Among patients with LVEF >30%, those with significant scarring (>5%) had higher risk than those with minimal or no (≤5%) scarring (HR: 6.3; 95% CI: 1.4 to 28.0). Those with LVEF >30% and significant scarring had risk similar to patients with LVEF ≤30% (p = 0.56). Among patients with LVEF ≤30%, those with significant scarring again had higher risk than those with minimal or no scarring (HR: 3.9; 95% CI: 1.2 to 13.1). Those with LVEF ≤30% and minimal scarring had risk similar to patients with LVEF >30% (p = 0.71). Myocardial scarring detected by cardiac MRI is an independent predictor of adverse outcome in patients being considered for ICD placement. In patients with LVEF >30%, significant scarring (>5% LV) identifies a high-risk cohort similar in risk to those with LVEF ≤30%. Conversely, in patients with LVEF ≤30%, minimal or no scarring identifies a low-risk cohort similar to those with LVEF >30%.

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Flecainide Suppresses Defibrillator‐Induced Storming in Catecholaminergic Polymorphic Ventricular Tachycardia

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited condition associated with ventricular tachycardia (VT) triggered by exercise or sympathetic stress. Incessant VT may develop due to defibrillator-induced storming-a condition where implantable cardioverter-defibrillator discharges result in a hyperadrenergic state, provoking further VT and defibrillator discharge. We describe the case of a 14-year-old boy with CPVT caused by a calsequestrin-2 mutation, who presented with defibrillator-induced storming refractory to β-blockers, calcium-channel blockers, amiodarone, and dronedarone. Flecainide and β-blocker use suppressed incessant VT and defibrillator-induced storming.