An International, Multicentered, Evidence-Based Reappraisal of Genes Reported to Cause Congenital Long QT Syndrome

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Background:

Long QT syndrome (LQTS) is the first described and most common inherited arrhythmia. Over the last 25 years, multiple genes have been reported to cause this condition and are routinely tested in patients. Because of dramatic changes in our understanding of human genetic variation, reappraisal of reported genetic causes for LQTS is required.

Methods:

Utilizing an evidence-based framework, 3 gene curation teams blinded to each other’s work scored the level of evidence for 17 genes reported to cause LQTS. A Clinical Domain Channelopathy Working Group provided a final classification of these genes for causation of LQTS after assessment of the evidence scored by the independent curation teams.

Results:

Of 17 genes reported as being causative for LQTS, 9 (AKAP9, ANK2, CAV3, KCNE1, KCNE2, KCNJ2, KCNJ5, SCN4B, SNTA1) were classified as having limited or disputed evidence as LQTS-causative genes. Only 3 genes (KCNQ1, KCNH2, SCN5A) were curated as definitive genes for typical LQTS. Another 4 genes (CALM1, CALM2, CALM3, TRDN) were found to have strong or definitive evidence for causality in LQTS with atypical features, including neonatal atrioventricular block. The remaining gene (CACNA1C) had moderate level evidence for causing LQTS.

Conclusions:

More than half of the genes reported as causing LQTS have limited or disputed evidence to support their disease causation. Genetic variants in these genes should not be used for clinical decision-making, unless accompanied by new and sufficient genetic evidence. The findings of insufficient evidence to support gene-disease associations may extend to other disciplines of medicine and warrants a contemporary evidence-based evaluation for previously reported disease-causing genes to ensure their appropriate use in precision medicine.

An International Multicenter Evaluation of Type 5 Long QT Syndrome: A Low Penetrant Primary Arrhythmic Condition

BACKGROUND

Insight into type 5 long QT syndrome (LQT5) has been limited to case reports and small family series. Improved understanding of the clinical phenotype and genetic features associated with rare KCNE1 variants implicated in LQT5 was sought through an international multicenter collaboration.

METHODS

Patients with either presumed autosomal dominant LQT5 (N = 229) or the recessive Type 2 Jervell and Lange-Nielsen syndrome (N = 19) were enrolled from 22 genetic arrhythmia clinics and 4 registries from 9 countries. KCNE1 variants were evaluated for ECG penetrance (defined as QTc >460 ms on presenting ECG) and genotype-phenotype segregation. Multivariable Cox regression was used to compare the associations between clinical and genetic variables with a composite primary outcome of definite arrhythmic events, including appropriate implantable cardioverter-defibrillator shocks, aborted cardiac arrest, and sudden cardiac death.

RESULTS

A total of 32 distinct KCNE1 rare variants were identified in 89 probands and 140 genotype positive family members with presumed LQT5 and an additional 19 Type 2 Jervell and Lange-Nielsen syndrome patients. Among presumed LQT5 patients, the mean QTc on presenting ECG was significantly longer in probands (476.9±38.6 ms) compared with genotype positive family members (441.8±30.9 ms, P<0.001). ECG penetrance for heterozygous genotype positive family members was 20.7% (29/140). A definite arrhythmic event was experienced in 16.9% (15/89) of heterozygous probands in comparison with 1.4% (2/140) of family members (adjusted hazard ratio [HR] 11.6 [95% CI, 2.6-52.2]; P=0.001). Event incidence did not differ significantly for Type 2 Jervell and Lange-Nielsen syndrome patients relative to the overall heterozygous cohort (10.5% [2/19]; HR 1.7 [95% CI, 0.3-10.8], P=0.590). The cumulative prevalence of the 32 KCNE1 variants in the Genome Aggregation Database, which is a human database of exome and genome sequencing data from now over 140 000 individuals, was 238-fold greater than the anticipated prevalence of all LQT5 combined (0.238% vs 0.001%).

CONCLUSIONS

The present study suggests that putative/confirmed loss-of-function KCNE1 variants predispose to QT prolongation, however, the low ECG penetrance observed suggests they do not manifest clinically in the majority of individuals, aligning with the mild phenotype observed for Type 2 Jervell and Lange-Nielsen syndrome patients.

Quality of life predicting long-term outcomes in cardiac resynchronization therapy patients

AIMS

While improvement in quality of life (QoL) has been widely reported in cardiac resynchronization therapy (CRT) patients, its predictive value is not well-understood. We aimed to assess the predictive role of baseline QoL on long-term heart failure (HF) or death events in mild HF patients enrolled in Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy (MADIT-CRT).

METHODS AND RESULTS

A total of 1791 of 1820 patients had their QoL evaluated at baseline, using the EuroQol-5 dimensions (EQ-5D) and the Kansas City Cardiomyopathy Questionnaires (KCCQ). Kaplan-Meier survival analyses and multivariate Cox models were utilized. Issues within any of the domains of the baseline EQ-5D questionnaire (mobility, self-care, usual activities, pain/discomfort, and anxiety/depression) were associated with long-term mortality (median follow-up 5.6 years) (all P < 0.05). Heart failure or death events were predicted by issues in baseline mobility [hazard ratio (HR) = 1.41, P < 0.001], usual activities (HR = 1.41, P < 0.001), and anxiety/depression (HR = 1.21, P = 0.035). The risk of HF events alone was significantly higher in patients with baseline mobility issues (HR = 1.42, P < 0.001) or usual activity (HR = 1.35, P = 0.003). Every 10% increase in the visual analogue scale (0-100) was associated with an 8% lower risk of all-cause mortality (P = 0.006), and a 6% lower risk of HF/death (P = 0.002). Mobility issues also predicted echocardiographic reverse remodelling (-33.08 mL vs. -31.17 mL, P = 0.043). Using the KCCQ, patients in the lower tertile of the clinical summary or physical limitations score had a significantly higher risk of long-term HF or death (P < 0.05).

CONCLUSION

In mild HF patients enrolled in MADIT-CRT, multiple baseline QoL questionnaire domains were predictors of echocardiographic remodelling, long-term all-cause mortality, and HF events.

Association of Cardiac Resynchronization Therapy With Change in Left Ventricular Ejection Fraction in Patients With Chemotherapy-Induced Cardiomyopathy

IMPORTANCE

The incidence of chemotherapy-induced cardiomyopathy is increasing and is associated with poor clinical outcomes.

OBJECTIVE

To assess the association of cardiac resynchronization therapy (CRT) with improvement in cardiac function, as well as clinical improvement in patients with chemotherapy-induced cardiomyopathy.

DESIGN, SETTING, AND PARTICIPANTS

The Multicenter Automatic Defibrillator Implantation Trial-Chemotherapy-Induced Cardiomyopathy was an uncontrolled, prospective, cohort study conducted between November 21, 2014, and June 21, 2018, at 12 tertiary centers with cardio-oncology programs in the United States. Thirty patients were implanted with CRT owing to reduced left ventricular ejection fraction (LVEF≤35%), New York Heart Association class II-IV heart failure symptoms, and wide QRS complex, with established chemotherapy-induced cardiomyopathy and were followed up for 6 months after CRT implantation. The date of final follow-up was February 6, 2019.

EXPOSURES

CRT implantation according to standard of care.

MAIN OUTCOMES AND MEASURES

The primary end point was change in LVEF from baseline to 6 months after initiating CRT. Secondary outcomes included all-cause mortality and change in left ventricular end-systolic volume and end-diastolic volume.

RESULTS

Among 30 patients who were enrolled (mean [SD] age, 64 [11] years; 26 women [87%]; 73% had a history of breast cancer; 20% had a history of lymphoma or leukemia), primary end point data were available for 26 patients and secondary end point data were available for 23 patients. Patients had nonischemic cardiomyopathy with left bundle branch block, median LVEF of 29%, and a mean QRS duration of 152 ms. Patients with CRT experienced a statistically significant improvement in mean LVEF at 6 months from 28% to 39% (difference, 10.6% [95% CI, 8.0%-13.3%]; P < .001). This was accompanied by a reduction in LV end-systolic volume from 122.7 to 89.0 mL (difference, 37.0 mL [95% CI, 28.2-45.8]) and reduction in LV end-diastolic volume from 171.0 to 143.2 mL (difference, 31.9 mL [95% CI, 22.1-41.6]) (both P < .001). Adverse events included a procedure-related pneumothorax (1 patient), a device pocket infection (1 patient), and heart failure requiring hospitalization during follow-up (1 patient).

CONCLUSIONS AND RELEVANCE

In this preliminary study of patients with chemotherapy-induced cardiomyopathy, CRT was associated with improvement in LVEF after 6 months. The findings are limited by the small sample size, short follow-up, and absence of a control group.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02164721.

Atrial Fibrillation in Long QT Syndrome by Genotype

BACKGROUND

Long QT syndrome (LQTS) is caused by the abnormal function of ion channels, which may also affect atrial electrophysiology and be associated with the risk of atrial fibrillation (AF). However, large-scale studies of AF risk among patients with LQTS and its relation to LQTS manifestations are lacking. We aimed to assess the risk of AF and its relationship to the LQTS genotype and the long-term prognosis in patients with LQTS.

METHODS

Genotype-positive patients with LQTS (784 LQT1, 746 LQT2, and 233 LQT3) were compared with 2043 genotype-negative family members. Information on the occurrence of AF was based on physician-reported ECG-verified events. Multivariate Cox proportional hazards regression analyses were performed for ages 0 to 60 and after 60 years (reflecting an early and late-onset of AF) to assess the risk of incident AF by genotype and the relationship of AF to the risk of cardiac events defined as syncope, documented torsades de pointes, and aborted cardiac arrest or sudden cardiac death.

RESULTS

In patients followed from birth to 60 years of age, patients with LQT3 had an increased risk of AF compared with genotype-negative family members (hazard ratio=6.62; 95% CI, 2.04-21.49; P<0.001), while neither LQT1 nor LQT2 demonstrated increased AF risk. After the age of 60 years, patients with LQT2 had significantly lower risk of AF compared with genotype-negative controls (hazard ratio=0.07; 95% CI, 0.01-0.53, P=0.011). AF was a significant predictor of cardiac events in patients with LQT3 through the age of 60 (hazard ratio=5.38; 95% CI, 1.17-24.82; P=0.031).

CONCLUSIONS

Our data demonstrate an increased risk of early age AF in patients with LQT3 and also indicate a protective effect of the LQT2 genotype in it's association with a decreased risk of AF after the age of 60.

Quantitative T-wave morphology assessment from surface ECG is linked with cardiac events risk in genotype-positive KCNH2 mutation carriers with normal QTc values

INTRODUCTION

Long QT syndrome (LQTS) mutation carriers have elevated the risk of cardiac events even in the absence of QTc prolongation; however, mutation penetrance in patients with normal QTc may be reflected in abnormal T-wave shape, particularly in KCNH2 mutation carriers. We aimed to assess whether the magnitude of a three-dimensional T-wave vector (TwVM) will identify KCNH2-mutation carriers with normal QTc at risk for cardiac events.

METHODS

Adult LQT2 patients with QTc < 460 ms in men and <470 ms in women (n = 113, age 42 ± 16 years, 43% male) were compared with genotype-negative family members (n = 1007). The TwVM was calculated using T-wave amplitudes in leads V6, II, and V2 as the square root of (TV6²  + TII²  + (0.5*TV2)² ). Cox regression analysis adjusted for gender and time-dependent beta-blocker use was performed to assess cardiac event (CE) risk, defined as syncope, aborted cardiac arrest, implantable cardioverter-defibrillator therapy, or sudden death.

RESULTS

Dichotomized by median of 0.30 mV, lower TwVM was associated with elevated CE risk compared to those with high TwVM (HR = 2.95, 95% CI, 1.25-6.98, P = .014) and also remained significant after including sex and time-dependent beta-blocker usage in the Cox regression analysis (HR = 2.64, 95% CI, 1.64-4.24, P < .001). However, these associations were found only in women but not in men who had low event rates.

CONCLUSION

T-wave morphology quantified as repolarization vector magnitude using T-wave amplitudes retrieved from standard 12-lead electrocardiogram predicts cardiac events risk in LQT2 women and appears useful for risk stratification of KCNH2-mutation carriers without QTc prolongation.

P2277Utility of cardiovascular implantable electronic device (CIED)-derived patient activity, a novel digital biomarker, to predict inappropriate therapy

Background

The role of cardiovascular implantable electronic device (CIED)-derived activity to predict inappropriate implantable cardioverter-defibrillator (ICD) therapy is not known. The Multicenter Automatic Defibrillator Implantation Trial – Reduce Inappropriate Therapy (MADIT-RIT) enrolled 1500 patients with contemporary indication for an ICD or a CRT-D. We aimed to identify whether activity, as a digital biomarker, predicted inappropriate therapy.

Methods

In 1500 patients enrolled in MADIT-RIT, CIED-derived patient activity was acquired daily. CIED-derived activity was averaged for the first 30 days following randomization and utilized in this study to predict inappropriate therapy post- 30-day. Kaplan-Meier survival analysis and multivariate Cox proportional hazards regression models were used to evaluate first inappropriate therapy by 30-day CIED-derived patient activity quintiles, and by 30-day device derived patient activity as a continuous measurement.

Results

There were a total of 1463 patients with activity data available (90%), 135 patients received at least one inappropriate therapy during the post-30 day follow-up period. Patients in the highest quintile (Q5) of CIED-derived activity (more active) were younger, more often males and more likely to have had a prior ablation of an atrial arrhythmia. Patients in the highest quintile of 30-day CIED-derived median activity had the highest risk of receiving inappropriate therapy, 21% at 2 years as compared 7–11% in the other four quintiles (Figure, p<0.001 for the overall duration). Patients with the highest level of 30-day median patient activity (Q5) had 1.75 times higher risk of any inappropriate therapy as compared with lower levels of activity, Q1-Q4 (HR=1.75, 95% CI: 1.23–2.50, p<0.002). Each 10% increase in CIED-derived 30-day median patient activity was associated with a significant, 73% increase in risk of receiving inappropriate therapy (HR=1.73, 95% CI: 1.17–2.54, p=0.005). Patients in the highest quintile for activity had a 68% increase in the risk of SVT excluding atrial fibrillation, atrial flutter or atrial tachycardia (HR=1.69, 95% CI: 1.26–2.25, p=0.004), despite 96% receiving beta-blocker medications.

Inappropriate ICD Therapies by Activity

Conclusions

CIED-derived 30-day median patient activity predicted subsequent inappropriate therapy in ICD and CRT-D patients enrolled in MADIT-RIT. Patients with high levels of 30-day CIED-derived median patient activity were at a significantly higher risk of receiving inappropriate therapy. Activity, as a digital biomarker, may have utility in predicting and managing the risk of inappropriate therapy in this population.

Acknowledgement/Funding

Boston Scientific

P2278Risk of life-threatening ventricular tachyarrhythmia events in diabetes patients with higher ejection fraction in MADIT-CRT

Background

Data on the risk of life-threatening ventricular tachyarrhythmia events in diabetes patients with mild heart failure (HF) and higher ejection fraction (LVEF) are not currently known.

Objective

We aimed to assess the risk of life-threatening ventricular tachyarrhythmia events in mild HF patients with diabetes in patients with baseline LVEF ≤30% or >30%.

Methods

We evaluated the risk of life-threatening VT/VF treated with shock in mild HF patients with diabetes, by those with LVEF ≤30% or >30%, enrolled in MADIT-CRT. Kaplan-Meier analysis and multivariate adjusted Cox regression models were utilized.

Results

Out of 542 mild HF patients with diabetes and VT/VF data, 206 (38%) had LVEF >30% and 336 (62%) had LVEF ≤30%. The 5-year cumulative probability of VT/VF treated with shock was 15% in patients with diabetes LVEF >30% as compared to the 15% probability in patients with diabetes and LVEF ≤30% (p=0.342 for the overall difference in event rates during follow-up) (Figure). In Cox models, the risk of VT/VF treated with shock was similar in diabetes patients with LVEF>30% and LVEF ≤30% (HR=0.88, 95% CI= 0.51–1.53, p=0.647) after adjustment for age, ischemic etiology, prior ventricular or atrial arrhythmia, and CRT-D-LBBB interaction. The risk of VT/VF treated with shock was similar regardless of LVEF in both CRT-D patients (HR=1.09, p=0.830) and ICD only patients (HR=0.67, p=0.345).

Conclusion

Diabetes patients with an LVEF >30% are at similarly high risk of life-threatening ventricular tachyarrhythmias to patients with LVEF≤30%. Our findings highlight the need for further investigation and treatment of this uniquely high-risk patient cohort with a higher ejection fraction.

Acknowledgement/Funding

MADIT-CRT was funded by an unrestricted research grant from Boston Scientific to the University of Rochester.

2179Clinical significance of device-derived activity in ICD and CRT-D patients - Data from MADIT-RIT

Background

The Multicenter Automatic Defibrillator Implantation Trial – Reduce Inappropriate Therapy (MADIT-RIT) enrolled 1500 patients and showed that novel ICD programming reduced inappropriate therapy and improved survival. However, the role of device-derived patient activity to predict mortality is not known.

Methods

In 1500 patients enrolled in MADIT-RIT, device-derived patient activity was captured daily. Device-derived activity was averaged for the first 30 days following randomization, and utilized in this study to predict mortality post-30 days. Kaplan-Meier survival analysis and multivariate Cox proportional hazards regression models were used to evaluate all-cause mortality by 30-day device derived patient activity quintiles, and as a 3-level function of 30-day device derived patient activity (Q1, Q2–3, Q4–5).

Results

There were a total of 1463 patients with data available (98%), 66 of them died during the follow-up post-30 days. Patients in the lowest quintile (Q1: 4%∼1 hour daily activity) of device-derived activity were older, they were more often female, and they more often had diabetes and NYHA class III HF symptoms. Patients in the lowest quintile of 30-day device derived median activity (1 hour daily activity) had the highest risk of mortality, 15% in 2 years as compared to Q2–3 (1–2 hours daily activity, 8–7% 2-year mortality), and Q4–5 (>2 hours daily activity, 2–3% 2-year mortality) (Figure, p<0.001 for the overall duration). Each quintile decrease in device-derived 30-day median patient activity was associated with a significant, 41% increase in mortality (HR=1.41, 95% CI: 1.15–1.71, p=0.001). Patients with the lowest level of 30-day median patient activity (Q1) had 4.13-times higher risk of mortality as compared to the highest level of activity patients, Q4–5 (HR=4.13, 95% CI: 1.89–9.03, p<0.001). Patients with intermediate levels of activity (Q2–3) still had a 2.8-fold increase in death as compared to the highest activity level cohort of patients (HR=2.79, 95% CI: 1.31–5.91, p=0.008).

Figure 1

Conclusions

Device-derived 30-day median patient activity predicted subsequent all-cause mortality in ICD and CRT-D patients enrolled in MADIT-RIT. Patients with low and moderate levels of 30-day device-derived median patient activity (less than 2 hours daily activity) were at a significantly higher risk of death, and these cohorts warrant further investigation and management to improve outcomes.

Acknowledgement/Funding

MADIT-RIT was funded by an unrestricted research grant from Boston Scientific to the University of Rochester.

2403Experience with the wearable cardioverter-defibrillator by disease etiology: results from the wearit-II registry

Background

The use of the wearable cardioverter-defibrillator (WCD) in patients with non-ischemic cardiomyopathy has been less characterized.

Objective

We aimed to characterize WCD use and outcomes for patients with ischemic or non-ischemic cardiomyopathy, enrolled in the WEARIT-II Registry.

Methods

In WEARIT-II, we stratified 1,732 patients into ischemic (n=805) and non-ischemic etiology (n=927). WCD wear time, arrhythmia events during WCD use, and implantable cardioverter-defibrillator (ICD) implantation rates, or ejection fraction (EF) improvement at the end of WCD were evaluated for etiology subgroups.

Results

The WCD median wear time was higher in patients with non-ischemic cardiomyopathy (93 vs. 87 days, p=0.003), however daily use was similar (22.4 vs. 22.6 hours, p=0.07). There were 24 ischemic patients (3%) with sustained VT/VF events compared to 10 patients (1%) with non-ischemic cardiomyopathy (p=0.013). About 2/3 of these events were treated with WCD shock in ischemic patients, half of them in the non-ischemic group (1.9% vs. 0.4%). Atrial arrhythmias were frequent in both groups (3.1% vs. 3.1%, p=0.06). At the end of WCD use, 36% of the non-ischemic patients were implanted with an ICD compared to 42% in ischemic (p=0.01), likely due to the lower rate of sustained ventricular arrhythmias (Figure).

Figure 1

Conclusions

In WEARIT-II, patients with non-ischemic cardiomyopathy had longer WCD use than ischemic patients with good compliance. The rate of sustained ventricular arrhythmia events was lower in non-ischemic patients avoiding the need for an ICD implantation in more patients compared to ischemic, following a time period of risk stratification.

Acknowledgement/Funding

WEARIT-II was funded by an unrestricted research grant from ZOLL Inc.

Risk Stratification of Type 2 Long-QT Syndrome Mutation Carriers With Normal QTc Interval: The Value of Sex, T-Wave Morphology, and Mutation Type

BACKGROUND

Long-QT (LQT) syndrome mutation carriers have higher risk of cardiac events than unaffected family members even in the absence of QTc prolongation. Changes in T-wave morphology may reflect penetrance of LQT syndrome mutations. We aimed to assess whether T-wave morphology may improve risk stratification of LQT2 mutation carriers with normal QTc interval.

METHODS

LQT2 mutation carriers with QTc <460 ms in men and <470 ms in women (n=154) were compared with unaffected family members (n=1007). Baseline ECGs recorded at age ≥18 years underwent blinded assessment. Flat, notched, or negative T waves in leads II or V₅ were considered abnormal. Cox regression analysis was performed to assess the association between T-wave morphology, the presence of mutations in the pore region of KCNH2, and the risk of cardiac events defined as syncope, aborted cardiac arrest, defibrillator therapy, or sudden cardiac death. Sex-specific associations were estimated using interactions terms.

RESULTS

LQT2 female carriers with abnormal T-wave morphology had significantly higher risk of cardiac events compared with LQT2 female carriers with normal T waves (hazard ratio, 3.31; 95% confidence interval, 1.68-6.52; P=0.001), whereas this association was not significant in men. LQT2 men with pore location of mutations have significantly higher risk of cardiac events than those with nonpore mutations (hazard ratio, 6.01; 95% confidence interval, 1.50-24.08; P=0.011), whereas no such association was found in women.

CONCLUSIONS

The risk of cardiac events in LQT2 carriers with normal QTc is associated with abnormal T-wave morphology in women and pore location of mutation in men. The findings further indicate sex-specific differences in phenotype and genotype relationship in LQT2 patients.

Prenatal and recent methylmercury exposure and heart rate variability in young adults: the Seychelles Child Development Study

Epidemiologic evidence of an adverse association between exposure to methylmercury (MeHg) from consuming fish and heart rate variability (HRV) is inconclusive. We aimed to evaluate MeHg exposure in relation to HRV parameters in a large cohort of young adults from a high fish consuming population in the Republic of Seychelles. Main Cohort participants in the Seychelles Child Development Study were evaluated at a mean age of 19 years. Prenatal MeHg exposure was determined in maternal hair growing during pregnancy and recent exposure in participant's hair taken at the evaluation. The evaluation consisted of short (~2 h) and long (overnight) Holter recordings obtained in 514 and 203 participants, respectively. Multivariable analyses examined the association of prenatal and recent MeHg exposure (in separate models) with time-domain and frequency-domain HRV parameters in different physiologic circumstances: supine position, standing position, mental stress when undergoing a mathematics test, sleep, and long recording. Prenatal MeHg exposure was not associated with any of the 23 HRV parameters studied after adjustment for multiplicity. The recent MeHg showed a trend toward significance only for few variables in the primary model. However, after additional adjustment for activity levels, polyunsaturated fatty acids, and multiplicity none were significant after a Bonferroni adjustment. In conclusion, prenatal and recent MeHg exposure had no consistent pattern of associations to support the hypothesis that they are adversely associated with heart rate variability in this study population that consumes large amounts of fish.

2019 HRS expert consensus statement on evaluation, risk stratification, and management of arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM) is an arrhythmogenic disorder of the myocardium not secondary to ischemic, hypertensive, or valvular heart disease. ACM incorporates a broad spectrum of genetic, systemic, infectious, and inflammatory disorders. This designation includes, but is not limited to, arrhythmogenic right/left ventricular cardiomyopathy, cardiac amyloidosis, sarcoidosis, Chagas disease, and left ventricular noncompaction. The ACM phenotype overlaps with other cardiomyopathies, particularly dilated cardiomyopathy with arrhythmia presentation that may be associated with ventricular dilatation and/or impaired systolic function. This expert consensus statement provides the clinician with guidance on evaluation and management of ACM and includes clinically relevant information on genetics and disease mechanisms. PICO questions were utilized to evaluate contemporary evidence and provide clinical guidance related to exercise in arrhythmogenic right ventricular cardiomyopathy. Recommendations were developed and approved by an expert writing group, after a systematic literature search with evidence tables, and discussion of their own clinical experience, to present the current knowledge in the field. Each recommendation is presented using the Class of Recommendation and Level of Evidence system formulated by the American College of Cardiology and the American Heart Association and is accompanied by references and explanatory text to provide essential context. The ongoing recognition of the genetic basis of ACM provides the opportunity to examine the diverse triggers and potential common pathway for the development of disease and arrhythmia.

Prognostic Importance of Defibrillator-Appropriate Shocks and Antitachycardia Pacing in Patients With Mild Heart Failure

Background Patients with heart failure and an implantable cardioverter-defibrillator ( ICD ) for primary prevention are at increased mortality risk after receiving shock therapy. We sought to determine the prognostic significance of ICD therapies, both shock and antitachycardia pacing, delivered for different ventricular arrhythmia ( VA ) rates. Methods and Results We evaluated mortality risk among 1790 ICD -implanted patients from MADIT -CRT (Multicenter Automatic Defibrillator Implantation Trial With Cardiac Resynchronization Therapy). For the first analysis, patients were divided into mutually exclusive groups by the rate of treated VA only: slow VA (<200 beats per minute) and fast VA (≥200 beats per minute or ventricular fibrillation). In a secondary analysis, both the type of ICD therapy and VA rate were used. The reference group was always patients who had no ICD therapy. ICD therapy for fast VA was associated with increased mortality risk (hazard ratio [ HR] , 2.27; 95% CI , 1.48-3.48; P<0.001). However, mortality risk after ICD therapy for slow VA was similar to the risk related to no ICD therapy ( HR , 1.45; 95% CI , 0.86-2.44; P=0.162). Consistently, shocks ( HR , 2.96; 95% CI , 1.91-4.60; P<0.001) and antitachycardia pacing ( HR , 2.22; 95% CI , 0.96-5.14; P=0.063) for fast VA were both associated with increased mortality risk. Shocks and antitachycardia pacing for slow VA were not significantly associated with increased mortality risk ( HR , 1.43 [95% CI , 0.52-3.92; P=0.489]; and HR , 1.43 [95% CI, 0.80-2.56; P=0.232], respectively). Conclusions In patients with mild heart failure receiving ICD for primary prevention, mortality is associated with the rate of underlying VA rather than the type of therapy. These findings suggest that fast VA is a marker for increased mortality rather than shock therapy directly contributing to increased risk. Clinical Trial Registration URL : http://www.clinicaltrials.gov . Unique identifier: NCT 00180271.

Predictors of long-term mortality with cardiac resynchronization therapy in mild heart failure patients with left bundle branch block

BACKGROUND

Cardiac resynchronization therapy (CRT) is highly beneficial in patients with heart failure (HF) and left bundle branch block (LBBB); however, up to 30% of patients in this selected group are nonresponders.

HYPOTHESIS

We hypothesized that clinical and echocardiographic variables can be used to develop a simple mortality risk stratification score in CRT.

METHODS

Best-subsets proportional-hazards regression analysis was used to develop a simple clinical risk score for all-cause mortality in 756 patients with LBBB allocated to the CRT with defibrillator (CRT-D) group enrolled in the multicenter automatic defibrillator implantation trial with cardiac resynchronization therapy. The score was used to assess the mortality risk within the CRT-D group and the associations with mortality reduction with CRT-D vs implantable cardioverter defibrillator (ICD) in each risk category.

RESULTS

Four clinical variables comprised the risk score: age ≥ 65, creatinine ≥ 1.4 mg/dL, history of coronary artery bypass graft, and left ventricular ejection fraction (LVEF) < 26%. Every 1 point increase in the score was associated with 2-fold increased mortality within the CRT-D arm (P < 0.001). CRT-D was associated with mortality reduction as compared with ICD only in patients with moderate risk: score 0 (HR = 0.80, P = 0.615), score 1 (HR = 0.54, P = 0.019), score 2 (HR = 0.54, P = 0.016), score 3-4 risk factors (HR = 1.08, P = 0.811); however, the device by score interaction was not significant (P = 0.306). The score was also significantly predictive of left ventricular reverse remodeling (P < 0.001).

CONCLUSIONS

Four clinical variables can be used for improved mortality risk stratification in mild HF patients with LBBB implanted with CRT-D.

Left Ventricular Lead Location and Long-Term Outcomes in Cardiac Resynchronization Therapy Patients

OBJECTIVES

The authors aimed to evaluate the association of left ventricular (LV) lead location and long-term outcomes in MADIT-CRT (Multicenter Automatic Defibrillator Implantation With Cardiac Resynchronization Therapy).

BACKGROUND

There is limited data on the association of lead location with long-term clinical outcomes in patients with cardiac resynchronization therapy with defibrillator (CRT-D).

METHODS

The LV lead location was classified in 797 patients with CRT-D, in 569 patients with left bundle branch block (LBBB), in 228 patients with non-LBBB, and in 505 patients with an implantable cardioverter-defibrillator (ICD) only. Leads were classified into apical (n = 83) and non-apical (n = 486); with the non-apical LV leads further categorized into anterior (n = 99) and posterior/lateral (n = 387) within LBBB. All-cause mortality and heart failure (HF) events were assessed using Kaplan-Meier and Cox analyses.

RESULTS

In CRT-D patients with LBBB and posterior/lateral LV lead location, there was an association with a significant reduction in long-term all-cause mortality (hazard ratio [HR]: 0.54, 95% confidence interval [CI]: 0.37 to 0.79; p = 0.001), and HF events (HR: 0.44, 95% CI: 0.33 to 0.60; p < 0.001) compared to an ICD only, accompanied with better LV reverse remodeling. CRT-D patients with LBBB and an anterior LV lead location were shown to be associated with a significant reduction in HF events compared to an ICD only (anterior HR: 0.50, 95% CI: 0.30 to 0.82; p = 0.006); however, no association with mortality reduction was observed from CRT-D versus an ICD only. CRT-D was not associated with improved outcomes in non-LBBB patients, regardless of LV lead location.

CONCLUSIONS

In mild HF patients with LBBB and an implanted CRT-D, lateral/posterior, and anterior LV lead locations are similarly associated with reduction in the risk of HF or death events compared to ICD alone. Mortality benefit derived from CRT-D is associated only with patients with lateral/posterior LV lead location. An apical LV lead location should be avoided due to the early risk of death whenever possible. (Multicenter Automatic Defibrillator Implantation With Cardiac Resynchronization Therapy [MADIT-CRT], NCT00180271; Multicenter Automatic Defibrillator Implantation Trial With Cardiac Resynchronization Therapy Post Approval Registry [MADIT-CRT-PAR], NCT01294449; and MADIT-CRT Long-Term International Follow-Up Registry - Europe, NCT02060110).

Cardiovascular function and ozone exposure: The Multicenter Ozone Study in oldEr Subjects (MOSES)

BACKGROUND

To date, there have been relatively few studies of acute cardiovascular responses to controlled ozone inhalation, although a number of observational studies have reported significant positive associations between both ambient ozone levels and acute cardiovascular events and long-term ozone exposure and cardiovascular mortality.

OBJECTIVES

We hypothesized that short-term controlled exposure to low levels of ozone in filtered air would induce autonomic imbalance, repolarization abnormalities, arrhythmia, and vascular dysfunction.

METHODS

This randomized crossover study of 87 healthy volunteers 55-70 years of age was conducted at three sites using a common protocol, from June 2012 to April 2015. Subjects were exposed for 3 h in random order to 0 ppb (filtered air), 70 ppb ozone, and 120 ppb ozone, alternating 15 min of moderate exercise with 15 min of rest. A suite of cardiovascular endpoints was measured the day before, the day of, and up to 22 h after each exposure. Mixed effect linear and logit models evaluated the impact of exposure to ozone on pre-specified primary and secondary outcomes. Site and time were included in the models.

RESULTS

We found no significant effects of ozone exposure on any of the primary or secondary measures of autonomic function, repolarization, ST segment change, arrhythmia, or vascular function (systolic blood pressure and flow-mediated dilation).

CONCLUSIONS

In this multicenter study of older healthy women and men, there was no convincing evidence for acute effects of 3-h, relatively low-level ozone exposures on cardiovascular function. However, we cannot exclude the possibility of effects with higher ozone concentrations, more prolonged exposure, or in subjects with underlying cardiovascular disease. Further, we cannot exclude the possibility that exposure to ambient ozone and other pollutants in the days before the experimental exposures obscured or blunted cardiovascular biomarker response to the controlled ozone exposures.