Proposed diagnostic criteria for arrhythmogenic cardiomyopathy: European Task Force consensus report

Arrhythmogenic cardiomyopathy (ACM) is a heart muscle disease characterized by prominent "non-ischemic" myocardial scarring predisposing to ventricular electrical instability. Diagnostic criteria for the original phenotype, arrhythmogenic right ventricular cardiomyopathy (ARVC), were first proposed in 1994 and revised in 2010 by an international Task Force (TF). A 2019 International Expert report appraised these previous criteria, finding good accuracy for diagnosis of ARVC but a lack of sensitivity for identification of the expanding phenotypic disease spectrum, which includes left-sided variants, i.e., biventricular (ABVC) and arrhythmogenic left ventricular cardiomyopathy (ALVC). The ARVC phenotype together with these left-sided variants are now more appropriately named ACM. The lack of diagnostic criteria for the left ventricular (LV) phenotype has resulted in clinical under-recognition of ACM patients over the 4 decades since the disease discovery. In 2020, the "Padua criteria" were proposed for both right- and left-sided ACM phenotypes. The presently proposed criteria represent a refinement of the 2020 Padua criteria and have been developed by an expert European TF to improve the diagnosis of ACM with upgraded and internationally recognized criteria. The growing recognition of the diagnostic role of CMR has led to the incorporation of myocardial tissue characterization findings for detection of myocardial scar using the late‑gadolinium enhancement (LGE) technique to more fully characterize right, biventricular and left disease variants, whether genetic or acquired (phenocopies), and to exclude other "non-scarring" myocardial disease. The "ring-like' pattern of myocardial LGE/scar is now a recognized diagnostic hallmark of ALVC. Additional diagnostic criteria regarding LV depolarization and repolarization ECG abnormalities and ventricular arrhythmias of LV origin are also provided. These proposed upgrading of diagnostic criteria represents a working framework to improve management of ACM patients.

Pregnancy in arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy (AC) is a rare heart muscle disease with a genetic background and autosomal dominant mode of transmission. The clinical manifestation is characterized by ventricular arrhythmias (VA), heart failure (HF) and the risk of sudden cardiac death (SCD). Pregnancy in young female patients with AC represents a challenging condition for the life and family planning of young affected women. In addition to genetic mechanisms that influence the complex pathophysiology of AC, experimental and clinical data have confirmed the pathogenetic role of strenuous exercise and competitive sports in the early onset and rapid progression of AC symptoms and complications. Pregnancy and exercise share a number of physiological aspects of adaptation. In AC, both result in ventricular volume overload and myocardial stretch. Therefore, pregnancy has been postulated as a potential risk factor for HF, VA, SCD, and pregnancy-related obstetric complications in patients with AC. However, the available evidence on pregnancy in AC does not confirm this hypothesis. In most women with AC, pregnancies are well tolerated, uneventful, and follow a benign course. Pregnancy-related symptoms (VA, syncope, HF) and mortality, as well as obstetric complications, are uncommon in AC patients and range in the order of background populations and cohorts with AC and no pregnancy. The number of completed pregnancies is not associated with an acceleration of AC pathology or an increased risk of VA or HF during pregnancy and follow-up. Accordingly, there is no medical indication to advise against pregnancy in patients with AC. Preconditions include stability of rhythm and hemodynamics at baseline, as well as clinical follow-ups and the availability of multidisciplinary expert consultation during pregnancy and postpartum. Genetic counseling is recommended prior to pregnancy for all couples and their families affected by AC.

Genome-wide association analysis in dilated cardiomyopathy reveals two new players in systolic heart failure on chromosomes 3p25.1 and 22q11.23

AIMS

Our objective was to better understand the genetic bases of dilated cardiomyopathy (DCM), a leading cause of systolic heart failure.

METHODS AND RESULTS

We conducted the largest genome-wide association study performed so far in DCM, with 2719 cases and 4440 controls in the discovery population. We identified and replicated two new DCM-associated loci on chromosome 3p25.1 [lead single-nucleotide polymorphism (SNP) rs62232870, P = 8.7 × 10-11 and 7.7 × 10-4 in the discovery and replication steps, respectively] and chromosome 22q11.23 (lead SNP rs7284877, P = 3.3 × 10-8 and 1.4 × 10-3 in the discovery and replication steps, respectively), while confirming two previously identified DCM loci on chromosomes 10 and 1, BAG3 and HSPB7. A genetic risk score constructed from the number of risk alleles at these four DCM loci revealed a 3-fold increased risk of DCM for individuals with 8 risk alleles compared to individuals with 5 risk alleles (median of the referral population). In silico annotation and functional 4C-sequencing analyses on iPSC-derived cardiomyocytes identify SLC6A6 as the most likely DCM gene at the 3p25.1 locus. This gene encodes a taurine transporter whose involvement in myocardial dysfunction and DCM is supported by numerous observations in humans and animals. At the 22q11.23 locus, in silico and data mining annotations, and to a lesser extent functional analysis, strongly suggest SMARCB1 as the candidate culprit gene.

CONCLUSION

This study provides a better understanding of the genetic architecture of DCM and sheds light on novel biological pathways underlying heart failure.

Mid-regional proatrial natriuretic peptide for predicting prognosis in hypertrophic cardiomyopathy

OBJECTIVES

N-terminal probrain natriuretic peptide (NT-proBNP) predicts mortality and the development of heart failure in hypertrophic cardiomyopathy (HCM). Mid-regional proatrial natriuretic peptide (MR-proANP) is a stable by-product of production of atrial natriuretic peptide. We sought to compare the prognostic value of MR-proANP and NT-proBNP in HCM.

METHODS

We prospectively enrolled a cohort of patients with HCM from different European centres and followed them. All patients had clinical, ECG and echocardiographic evaluation and measurement of MR-proANP and NT-proBNP at inclusion.

RESULTS

Of 357 patients enrolled, the median age was 52 (IQR: 36-65) years. MR-proANP and NT-proBNP were both independently associated with age, weight, New York Heart Association (NYHA) class, left ventricular ejection fraction (LVEF), wall thickness and left atrial dimension. During a median follow-up of 23 months, 32 patients had a primary end point defined as death (n=6), heart transplantation (n=8), left ventricular assist device implantation (n=1) or heart failure hospitalisation (n=17). Both NT-proBNP and MR-proANP (p<10^-4) were strongly associated with the primary endpoint, and the areas under the receiver operating characteristic (ROC) curves for both peptides were not significantly different. However, in a multiple stepwise regression analysis, the best model for predicting outcome was NYHA 1-2 vs 3-4 (HR=0.35, 95% CI 0.16 to 0.77, p<0.01), LVEF (HR=0.96, 95% CI 0.94 to 0.98, p=0.0005) and MR-proANP (HR=3.77, 95% CI 2.01 to 7.08, p<0.0001).

CONCLUSIONS

MR-proANP emerges as a valuable biomarker for the prediction of death and heart failure related events in patients with HCM.

Radioligands for imaging myocardial α- and β-adrenoceptors

Alpha- and beta-adrenoceptors play an important role in the control of heart function. According to their molecular, biological, and pharmacological characteristics, they are subdivided into α1-, α2- and β1-, β2-, β3-, β4-adrenoceptors. In cardiac disease, there is often a selective downregulation of β1-adrenoceptors associated with a relative increase in β2- and α1-adrenoceptors. Functional imaging techniques like single-photon emission tomography (SPECT) and positron emission tomography (PET) provide the unique capability for non-invasive assessment of cardiac adrenoceptors. Radioligands with high specific binding to cardiac α- and β-adrenoceptors suitable for radiolabelling are required for clinical studies. The non-selective β-adrenoceptor antagonist [11C]CGP-12177 was used to quantify β-adrenoceptor density using PET in patients with heart disease. New non-selective ligands (e. g. [11C]CGP-12388, [18F]CGP-12388, [11C]carazolol and [18F]fluorocarazolol) are currently evaluated; β1-selective radioligands (e. g. [11C]CGP-26505, [11C]bisoprolol, [11C]HX-CH 44) and β2-selective radioligands (e. g. [11C]formoterol, [11C]ICI-118551) were assessed in animals. None of them turned out as suitable for cardiac PET.

Potential radioligands for imaging cardiac α1-adrenoceptors are based on prazosin. Whereas [11C]prazosin shows low specific binding to myocardium, its derivative [11C]GB67 looks more promising. The putative α2-adrenoceptor radioligand [11C]MK-912 shows high uptake in rodent myocardium but has not yet been evaluated in man.

A number of radioligands were evaluated for assessing cardiac adrenoceptors using PET. New radioligands are needed to provide more insight into cardiac pathophysiology which may influence the therapeutic management of patients with cardiovascular disease.

Closure of Left Atrial Appendage With Persistent Distal Thrombus Using an Amplatzer Amulet Occluder

A 73-year-old patient with permanent atrial fibrillation presented for left atrial appendage (LAA) occlusion. Transesophageal echocardiography demonstrated a thrombus in the distal LAA. This image series illustrates a "no touch" technique that was used to ensure successful implantation of an Amplatzer Amulet LAA occlusion device without the use of an embolization protection system.

Sex differences in absolute myocardial perfusion. Non-invasive H2(15)O-PET in young healthy adults

AIM

To investigate sex differences in myocardial perfusion especially in healthy individuals since former studies are rare and findings are controversial. Participants, methods: 26 subjects were enrolled: 16 healthy women (age: 34 ±7 years) were compared with 10 healthy men (age: 34 ± 3 years; p = ns). Myocardial blood flow (MBF) and coronary vascular resistance (CVR) were quantified at rest, during adenosine infusion and cold-pressor-testing, using positron emission tomography and radioactive-labelled water (H2(15)O-PET).

RESULTS

Women showed higher MBF than men at rest (1.10 ± 0.18 vs. 0.85 ± 0.20 ml/min/ml; p = 0.003) and cold-stress (1.39 ± 0.38 vs. 1.06 ± 0.28 ml/min/ml; p = 0.026). Corrected for rate-pressure-product, baseline findings maintained significance (1.41 ± 0.33 vs. 1.16 ± 0.19 ml/min/ml; p = 0.024). CVR was lower in women at baseline (81 ± 14 vs. 107 ± 22 mmHg*ml(-1)*min*ml; p = 0.006) and during cold-pressor-testing (71 ± 17 vs. 91 ± 20 mmHg*ml(-1)*min*ml; p = 0.013). Under adenosine neither maximal MBF (4.06 ± 1.0 vs. 3.91 ± 0.88 ml/min/ml; p = ns) nor coronary flow reserve (3.07 ± 1.12 vs. 3.44 ± 0.92; p = ns) nor CVR (24 ± 8 vs. 24 ± 6 mmHg*ml(-1)*min*ml; p = ns) showed sex-related differences.

CONCLUSION

Women show higher myocardial perfusion and lower coronary vascular resistance than men in physiologic states. Maximum perfusion and vasodilation under adenosine are not sex-specific.

Treatment of Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia: An International Task Force Consensus Statement

Supplemental Digital Content is available in the text.

Biventricular myocardial strain analysis in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) using cardiovascular magnetic resonance feature tracking

BACKGROUND

Fibrofatty degeneration of myocardium in ARVC is associated with wall motion abnormalities. The aim of this study was to examine whether Cardiovascular Magnetic Resonance (CMR) based strain analysis using feature tracking (FT) can serve as a quantifiable measure to confirm global and regional ventricular dysfunction in ARVC patients and support the early detection of ARVC.

METHODS

We enrolled 20 patients with ARVC, 30 with borderline ARVC and 22 subjects with a positive family history but no clinical signs of a manifest ARVC. 10 healthy volunteers (HV) served as controls. 15 ARVC patients received genotyping for Plakophilin-2 mutation (PKP-2), of which 7 were found to be positive. Cine MR datasets of all subjects were assessed for myocardial strain using FT (TomTec Diogenes Software). Global strain and strain rate in radial, circumferential and longitudinal mode were assessed for the right and left ventricle. In addition strain analysis at a segmental level was performed for the right ventricular free wall.

RESULTS

RV global longitudinal strain rates in ARVC (-0.68 ± 0.36 sec⁻¹) and borderline ARVC (-0.85 ± 0.36 sec⁻¹) were significantly reduced in comparison with HV (-1.38 ± 0.52 sec⁻¹, p ≤ 0.05). Furthermore, in ARVC patients RV global circumferential strain and strain rates at the basal level were significantly reduced compared with HV (strain: -5.1 ± 2.7 vs. -9.2 ± 3.6%; strain rate: -0.31 ± 0.13 sec(-1) vs. -0.61 ± 0.21 sec⁻¹). Even for patients with ARVC or borderline ARVC and normal RV ejection fraction (n=30) global longitudinal strain rate proved to be significantly reduced compared with HV (-0.9 ± 0.3 vs. -1.4 ± 0.5 sec(-1); p < 0.005). In ARVC patients with PKP-2 mutation there was a clear trend towards a more pronounced impairment in RV global longitudinal strain rate. On ROC analysis RV global longitudinal strain rate and circumferential strain rate at the basal level proved to be the best discriminators between ARVC patients and HV (AUC: 0.9 and 0.92, respectively).

CONCLUSION

CMR based strain analysis using FT is an objective and useful measure for quantification of wall motion abnormalities in ARVC. It allows differentiation between manifest or borderline ARVC and HV, even if ejection fraction is still normal.

Autonomic dysfunction in patients with arrhythmogenic right ventricular cardiomyopathy: biochemical evidence of altered signaling pathways

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an important cause of sudden cardiac death especially in times of increased sympathetic tone, for example, during sports, which have been confirmed by nuclear imaging studies. However, the underlying biochemical pathways remain to be delineated. Therefore, we investigated the expression levels of proteins of the signaling cascade in patients with ARVC.

METHODS

During diagnostic work-up, right ventricular endomyocardial biopsies (EMBs) were sampled from 15 consecutive male ARVC patients (52 ± 14 years). Tissue levels of key proteins of the signaling cascade were analyzed. Results were compared to those obtained from EMBs of 10 patients with idiopathic right ventricular outflow-tract tachycardia (RVOT; 41 ± 14 years) and of five control subjects without identifiable structural heart disease (42 ± 13 years; P = ns).

RESULTS

Among the proteins analyzed, only tissue levels of norepinephrine (NE; P < 0.04) and cyclic adenosine-3´,5´-monophospate (cAMP; P < 0.01) were significantly lower in ARVC when compared to RVOT patients. When compared to controls, mean cAMP levels were lower in patients with ARVC but did not reach statistical significance. No differences in cAMP were observed between RVOT and controls.

CONCLUSIONS

The current findings confirm and expand the concept of adrenergic dysfunction in ARVC: the reduction of NE in ARVC could lead to an impaired stimulation of β-adrenoceptor subsequent signaling pathways with potential implication for cardiac fibrosis and arrhythmogenesis.

The identification of right-to-left shunts using contrast transcranial Doppler ultrasound: performance and interpretation modalities, and absence of a significant side difference of cardiac micro-emboli

Cardiac and extracardiac right-to-left shunts can be identified by transesophageal echocardiography (TEE) as well as by transcranial Doppler ultrasound (TCD) using contrast agents that do not pass the lungs. Currently, the appropriate performance of a Valsalva manoeuvre (VM) to provoke the shunt, the use of different contrast agents and the classification of the TCD results are still under debate. In this study, we looked also at possible side effects of provoked cardiac micro-emboli in the left and right hemisphere. Seventy-one patients were investigated by both TEE and bilateral TCD of the middle cerebral arteries. The following protocol was applied in a randomized way: (1) Echovist-300 without VM; (2) Echovist-300, VM for 5 seconds starting 5 seconds after the beginning of contrast injection; (3) repetitive short VMs in between 2 and 13 seconds after the beginning of Echovist-300 injection; and (4) repetitive short VMs in between 2 and 13 seconds after the beginning of agitated saline injection. Only if one of the tests (2-4) was negative, this particular negative test was repeated. Use of Echovist-300, but not of saline yielded 100% sensitivity in the detection of TEE-proven shunts. The repetitive VM was slightly superior to the conventional VM. Introduction of a threshold of two or even three microbubbles produced less falsely positive TCD results in comparison to the TEE. There was no difference in microbubbles. TCD using Echovist-300 is a sensitive method to identify TEE-proven cardiac right-to-left shunts. Repetitive VM is an alternative to conventional VM.

Electrophysiological characteristics of ventricular tachyarrhythmias in cardiac sarcoidosis versus arrhythmogenic right ventricular cardiomyopathy

BACKGROUND

Recent evidence suggests that cardiac sarcoidosis (CS) and arrhythmogenic right ventricular cardiomyopathy (ARVC) can manifest very similarly.

OBJECTIVE

To investigate whether there are significant demographic and electrophysiological differences between patients with CS and ARVC.

METHODS

We prospectively compared patients with proven CS or ARVC who underwent radiofrequency catheter ablation of ventricular tachycardias by using 3-dimensional electroanatomical mapping. Furthermore, we evaluated whether the diagnostic criteria for ARVC would have excluded ARVC in patients with CS.

RESULTS

Eighteen patients (13 men; mean age 44.9 years) were included. All 18 patients had mild to moderately reduced right ventricular ejection fraction. Patients with cardiac sarcoidosis (n = 8) had a significantly lower mean left ventricular ejection fraction (35.6±19.3 vs 60.6±9.4; P = .002). Patients with CS had a significantly wider QRS (0.146 vs 0.110s; P = .004). Five of 8 (63%) patients with CS fulfilled the diagnostic ARVC criteria. Ventricular tachycardias (VTs) with a left bundle branch block pattern were documented in all but one patient (with CS). Programmed ventricular stimulation induced an average of 3.7 different monomorphic VTs in patients with CS vs 1.8 in patients with ARVC (P = .01). VT significantly more often originated in the apical region of the right ventricle in CS vs ARVC (P = .001), with no other predilection sites. Ablation success and other electrophysiological parameters were not different.

CONCLUSIONS

The current diagnostic ARVC guidelines do not reliably exclude patients with CS. Clinical and electrophysiological parameters that were characteristic of CS in our patients include reduced left ventricular ejection fraction, a significantly wider QRS, right-sided apical VT, and more inducible forms of monomorphic VT.

Arrhythmogenic right ventricular cardiomyopathy: an update on pathophysiology, genetics, diagnosis, and risk stratification

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiomyopathy accounting for life-threatening ventricular tachyarrhythmias and sudden death in young individuals and athletes. Over the past years, mutations in desmosomal genes have been identified as disease-causative. However, genetic heterogeneity and variable phenotypic expression alongside with diverse disease progression still render the evaluation of its prognostic implication difficult. ARVC was initially entered into the canon of cardiomyopathies of the World Health Organization in 1995, and international efforts have resulted in the 2010 modified diagnostic criteria for ARVC. Despite all additional insights into pathophysiology, clinical management, and modern risk stratification, under-/misdiagnosing of ARVC remains a problem and hampers reliable statements on the incidence, prevalence, and natural course of the disease.This review provides a comprehensive overview of the current literature on the pathogenesis, diagnosis, treatment, and prognosis of ARVC and sheds some light on potential new developments in these areas.

Evidence for FHL1 as a novel disease gene for isolated hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is characterized by asymmetric left ventricular hypertrophy, diastolic dysfunction and myocardial disarray. HCM is caused by mutations in sarcomeric genes, but in >40% of patients, the mutation is not yet identified. We hypothesized that FHL1, encoding four-and-a-half-LIM domains 1, could be another disease gene since it has been shown to cause distinct myopathies, sometimes associated with cardiomyopathy. We evaluated 121 HCM patients, devoid of a mutation in known disease genes. We identified three novel variants in FHL1 (c.134delA/K45Sfs, c.459C>A/C153X and c.827G>C/C276S). Whereas the c.459C>A variant was associated with muscle weakness in some patients, the c.134delA and c.827G>C variants were associated with isolated HCM. Gene transfer of the latter variants in C2C12 myoblasts and cardiac myocytes revealed reduced levels of FHL1 mutant proteins, which could be rescued by proteasome inhibition. Contractility measurements after adeno-associated virus transduction in rat-engineered heart tissue (EHT) showed: (i) higher and lower forces of contraction with K45Sfs and C276S, respectively, and (ii) prolonged contraction and relaxation with both mutants. All mutants except one activated the fetal hypertrophic gene program in EHT. In conclusion, this study provides evidence for FHL1 to be a novel gene for isolated HCM. These data, together with previous findings of proteasome impairment in HCM, suggest that FHL1 mutant proteins may act as poison peptides, leading to hypertrophy, diastolic dysfunction and/or altered contractility, all features of HCM.

Load-reducing therapy prevents development of arrhythmogenic right ventricular cardiomyopathy in plakoglobin-deficient mice

OBJECTIVES

We used a murine model of arrhythmogenic right ventricular cardiomyopathy (ARVC) to test whether reducing ventricular load prevents or slows development of this cardiomyopathy.

BACKGROUND

At present, no therapy exists to slow progression of ARVC. Genetically conferred dysfunction of the mechanical cell-cell connections, often associated with reduced expression of plakoglobin, is thought to cause ARVC.

METHODS

Littermate pairs of heterozygous plakoglobin-deficient mice (plako(+/-)) and wild-type (WT) littermates underwent 7 weeks of endurance training (daily swimming). Mice were randomized to blinded load-reducing therapy (furosemide and nitrates) or placebo.

RESULTS

Therapy prevented training-induced right ventricular (RV) enlargement in plako(+/-) mice (RV volume: untreated plako(+/-) 136 ± 5 μl; treated plako(+/-) 78 ± 5 μl; WT 81 ± 5 μl; p < 0.01 for untreated vs. WT and untreated vs. treated; mean ± SEM). In isolated, Langendorff-perfused hearts, ventricular tachycardias (VTs) were more often induced in untreated plako(+/-) hearts (15 of 25), than in treated plako(+/-) hearts (5 of 19) or in WT hearts (6 of 21, both p < 0.05). Epicardial mapping of the RV identified macro-re-entry as the mechanism of ventricular tachycardia. The RV longitudinal conduction velocity was reduced in untreated but not in treated plako(+/-) mice (p < 0.01 for untreated vs. WT and untreated vs. treated). Myocardial concentration of phosphorylated connexin43 was lower in plako(+/-) hearts with VTs compared with hearts without VTs and was reduced in untreated plako(+/-) compared with WT (both p < 0.05). Plako(+/-) hearts showed reduced myocardial plakoglobin concentration, whereas β-catenin and N-cadherin concentration was not changed.

CONCLUSIONS

Load-reducing therapy prevents training-induced development of ARVC in plako(+/-) mice.

Cardiac sympathetic dysfunction in genotyped patients with arrhythmogenic right ventricular cardiomyopathy and risk of recurrent ventricular tachyarrhythmias

Patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) typically present with ventricular tachyarrhythmias preferentially triggered by an elevated sympathetic tone. Previous studies demonstrated an impairment of the presynaptic catecholamine reuptake as assessed by (123)I-labeled norepinephrine analog on metaiodobenzylguanidine ((123)I-MIBG) SPECT. Mutations in the gene encoding for plakophilin-2 (PKP-2) are the most common cause of autosomal dominant ARVC (ARVC-9). In this study, we investigated the potential role of adrenergic dysfunction on the arrhythmia profile in patients with ARVC and correlated these findings with the causative genotype.

METHODS

(123)I-MIBG SPECT was performed for 42 patients with definite ARVC (10 women, 32 men; mean age ± SD, 43 ± 14 y). Images were acquired at 4 h after injection and analyzed for regional (123)I-MIBG uptake in a standardized 33-segment polar map. Results were compared with those obtained from 10 control subjects (5 women, 5 men; mean age ± SD, 43 ± 12 y).

RESULTS

An abnormal tracer uptake was detected in 25 patients with ARVC (59%). The extents of right ventricular dilation and regional wall motion abnormalities as well as electrocardiographic markers of de- or repolarization were not significantly different between patients with normal and abnormal (123)I-MIBG SPECT findings. However, during long-term follow-up of 11.9 ± 4.1 y, patients with abnormal (123)I-MIBG SPECT findings experienced life-threatening ventricular tachyarrhythmias significantly more often (22/25 patients [88%]) and independent of the extent of right ventricular dysfunction than those with a normal sympathetic innervation (6/17 patients [35%]; P < 0.0005). Mutations in PKP-2 were identified in 17 patients (40%) but were not correlated with the degree of adrenergic dysfunction.

CONCLUSION

In patients with ARVC, an impairment of adrenergic innervation independent of the underlying genotype is associated with a higher incidence for future recurrences of ventricular tachyarrhythmias. This finding may suggest a potential role of (123)I-MIBG SPECT for individualized risk stratification in ARVC patients and asymptomatic PKP-2 mutation carriers alike.

Autonomic dysfunction in patients with Brugada syndrome: further biochemical evidence of altered signaling pathways

BACKGROUND

In patients with Brugada syndrome (BrS), life-threatening ventricular tachyarrhythmias predominantly occur during vagal stimulation at rest or during sleep. Previous imaging studies displayed an impaired autonomic function in BrS patients. However, it remains unclear whether these alterations primarily stem from a reduction of synaptic release of norepinephrine (NE) or an enhanced presynaptic reuptake. Both conditions could lead to reduced NE concentrations in the synaptic cleft. Therefore, we analyzed key components of the sympathoadrenergic signaling pathways in patients with BrS.

METHODS AND RESULTS

Endomyocardial biopsies were obtained from eight BrS patients (seven male; age 49 ± 15 years) and five controls (three male; age 43 ± 13 years; P = ns). The concentrations of NE, epinephrine (Epi), NE transport (NET) carrier protein, cyclic adenosine 5'monophosphate (cyclic adenosine monophosphate [cAMP]), inhibitory G-proteins (G(i1,2) α), troponin-I (TNI), and phosphorylated TNI were analyzed. Levels of NET, G(i1,2) α, TNI, Epi, and phosphorylated TNI were comparable between the groups. Compared to controls, patients with BrS showed reduced cAMP and NE concentrations.

CONCLUSIONS

The current findings expand the concept of adrenergic dysfunction in BrS: the reduction of NE in BrS could lead to an impaired stimulation of β-adrenoceptors resulting in a reduction of cAMP and alterations of the subsequent signaling pathway with potential implication for arrhythmogenesis.

A genome-wide association study identifies two loci associated with heart failure due to dilated cardiomyopathy

AIMS

Dilated cardiomyopathy (DCM) is a major cause of heart failure with a high familial recurrence risk. So far, the genetics of DCM remains largely unresolved. We conducted the first genome-wide association study (GWAS) to identify loci contributing to sporadic DCM.

METHODS AND RESULTS

One thousand one hundred and seventy-nine DCM patients and 1108 controls contributed to the discovery phase. Pools of DNA stratified on disease status, population, age, and gender were constituted and used for testing association of DCM with 517 382 single nucleotide polymorphisms (SNPs). Three DCM-associated SNPs were confirmed by individual genotyping (P < 5.0 10(-7)), and two of them, rs10927875 and rs2234962, were replicated in independent samples (1165 DCM patients and 1302 controls), with P-values of 0.002 and 0.009, respectively. rs10927875 maps to a region on chromosome 1p36.13 which encompasses several genes among which HSPB7 has been formerly suggested to be implicated in DCM. The second identified locus involves rs2234962, a non-synonymous SNP (c.T757C, p. C151R) located within the sequence of BAG3 on chromosome 10q26. To assess whether coding mutations of BAG3 might cause monogenic forms of the disease, we sequenced BAG3 exons in 168 independent index cases diagnosed with familial DCM and identified four truncating and two missense mutations. Each mutation was heterozygous, present in all genotyped relatives affected by the disease and absent in a control group of 347 healthy individuals, strongly suggesting that these mutations are causing the disease.

CONCLUSION

This GWAS identified two loci involved in sporadic DCM, one of them probably implicates BAG3. Our results show that rare mutations in BAG3 contribute to monogenic forms of the disease, while common variant(s) in the same gene are implicated in sporadic DCM.

Prophylactic implantable defibrillator in patients with arrhythmogenic right ventricular cardiomyopathy/dysplasia and no prior ventricular fibrillation or sustained ventricular tachycardia

BACKGROUND

The role of implantable cardioverter-defibrillator (ICD) in patients with arrhythmogenic right ventricular cardiomyopathy/dysplasia and no prior ventricular fibrillation (VF) or sustained ventricular tachycardia is an unsolved issue.

METHODS AND RESULTS

We studied 106 consecutive patients (62 men and 44 women; age, 35.6±18 years) with arrhythmogenic right ventricular cardiomyopathy/dysplasia who received an ICD based on 1 or more arrhythmic risk factors such as syncope, nonsustained ventricular tachycardia, familial sudden death, and inducibility at programmed ventricular stimulation. During follow-up of 58±35 months, 25 patients (24%) had appropriate ICD interventions and 17 (16%) had shocks for life-threatening VF or ventricular flutter. At 48 months, the actual survival rate was 100% compared with the VF/ventricular flutter-free survival rate of 77% (log-rank P=0.01). Syncope significantly predicted any appropriate ICD interventions (hazard ratio, 2.94; 95% confidence interval, 1.83 to 4.67; P=0.013) and shocks for VF/ventricular flutter (hazard ratio, 3.16; 95% confidence interval, 1.39 to 5.63; P=0.005). The positive predictive value of programmed ventricular stimulation was 35% for any appropriate ICD intervention and 20% for shocks for VF/ventricular flutter, with a negative predictive value of 70% and 74%. None of the 27 asymptomatic patients with isolated familial sudden death had appropriate ICD therapy. Twenty patients (19%) had inappropriate ICD interventions, and 18 (17%) had device-related complications.

CONCLUSIONS

One fourth of patients with arrhythmogenic right ventricular cardiomyopathy/dysplasia and no prior sustained ventricular tachycardia or VF had appropriate ICD interventions. Syncope was an important predictor of life-saving ICD intervention and is an indication for ICD. Prophylactic ICD may not be indicated in asymptomatic patients because of their low arrhythmic risk regardless of familial sudden death and programmed ventricular stimulation findings. Programmed ventricular stimulation had a low predictive accuracy for ICD therapy.

Diagnosis of arrhythmogenic right ventricular cardiomyopathy/dysplasia: proposed modification of the task force criteria

BACKGROUND

In 1994, an International Task Force proposed criteria for the clinical diagnosis of arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) that facilitated recognition and interpretation of the frequently nonspecific clinical features of ARVC/D. This enabled confirmatory clinical diagnosis in index cases through exclusion of phenocopies and provided a standard on which clinical research and genetic studies could be based. Structural, histological, electrocardiographic, arrhythmic, and familial features of the disease were incorporated into the criteria, subdivided into major and minor categories according to the specificity of their association with ARVC/D. At that time, clinical experience with ARVC/D was dominated by symptomatic index cases and sudden cardiac death victims-the overt or severe end of the disease spectrum. Consequently, the 1994 criteria were highly specific but lacked sensitivity for early and familial disease.

METHODS AND RESULTS

Revision of the diagnostic criteria provides guidance on the role of emerging diagnostic modalities and advances in the genetics of ARVC/D. The criteria have been modified to incorporate new knowledge and technology to improve diagnostic sensitivity, but with the important requisite of maintaining diagnostic specificity. The approach of classifying structural, histological, electrocardiographic, arrhythmic, and genetic features of the disease as major and minor criteria has been maintained. In this modification of the Task Force criteria, quantitative criteria are proposed and abnormalities are defined on the basis of comparison with normal subject data.

CONCLUSIONS

The present modifications of the Task Force Criteria represent a working framework to improve the diagnosis and management of this condition.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00024505.

Diagnosis of arrhythmogenic right ventricular cardiomyopathy/dysplasia: proposed modification of the Task Force Criteria

BACKGROUND

In 1994, an International Task Force proposed criteria for the clinical diagnosis of arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) that facilitated recognition and interpretation of the frequently nonspecific clinical features of ARVC/D. This enabled confirmatory clinical diagnosis in index cases through exclusion of phenocopies and provided a standard on which clinical research and genetic studies could be based. Structural, histological, electrocardiographic, arrhythmic, and familial features of the disease were incorporated into the criteria, subdivided into major and minor categories according to the specificity of their association with ARVC/D. At that time, clinical experience with ARVC/D was dominated by symptomatic index cases and sudden cardiac death victims-the overt or severe end of the disease spectrum. Consequently, the 1994 criteria were highly specific but lacked sensitivity for early and familial disease.

METHODS AND RESULTS

Revision of the diagnostic criteria provides guidance on the role of emerging diagnostic modalities and advances in the genetics of ARVC/D. The criteria have been modified to incorporate new knowledge and technology to improve diagnostic sensitivity, but with the important requisite of maintaining diagnostic specificity. The approach of classifying structural, histological, electrocardiographic, arrhythmic, and genetic features of the disease as major and minor criteria has been maintained. In this modification of the Task Force criteria, quantitative criteria are proposed and abnormalities are defined on the basis of comparison with normal subject data.

CONCLUSIONS

The present modifications of the Task Force Criteria represent a working framework to improve the diagnosis and management of this condition. Clinical Trial Registration clinicaltrials.gov Identifier: NCT00024505.

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.

Transcriptional profiling of ion channel genes in Brugada syndrome and other right ventricular arrhythmogenic diseases

AIMS

Brugada syndrome is an inherited sudden-death arrhythmia syndrome. Na(+)-current dysfunction is central, but mutations in the SCN5A gene (encoding the cardiac Na(+)-channel Nav1.5) are present in only 20% of probands. This study addressed the possibility that Brugada patients display specific expression patterns for ion-channels regulating cardiac conduction, excitability, and repolarization.

METHODS AND RESULTS

Transcriptional profiling was performed on right-ventricular endomyocardial biopsies from 10 unrelated Brugada probands, 11 non-diseased organ-donors, seven heart-transplant recipients, 10 with arrhythmogenic right-ventricular cardiomyopathy, and nine with idiopathic right-ventricular outflow-tract tachycardia. Brugada patients showed distinct clustering differences vs. the two control and two other ventricular-tachyarrhythmia groups, including 14 of 77 genes encoding important ion-channel/ion-transporter subunits. Nav1.5 and K(+)-channels Kv4.3 and Kir3.4 were more weakly expressed, whereas the Na(+)-channel Nav2.1 and the K(+)-channel TWIK1 were more strongly expressed, in Brugada syndrome. Differences were also seen in Ca(2+)-homeostasis transcripts, including stronger expression of RYR2 and NCX1. The molecular profile of Brugada patients with SCN5A mutations did not differ from Brugada patients without SCN5A mutations.

CONCLUSION

Brugada patients exhibit a common ion-channel molecular expression signature, irrespective of the culprit gene. This finding has potentially important implications for our understanding of the pathophysiology of Brugada syndrome, with possible therapeutic and diagnostic consequences.

A novel dominant mutation in plakoglobin causes arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited disorder associated with arrhythmias and sudden death. A recessive mutation in the gene encoding plakoglobin has been shown to cause Naxos disease, a cardiocutaneous syndrome characterized by ARVC and abnormalities of hair and skin. Here, we report, for the first time, a dominant mutation in the gene encoding plakoglobin in a German family with ARVC but no cutaneous abnormalities. The mutation (S39_K40insS) is predicted to insert an extra serine residue at position 39 in the N-terminus of plakoglobin. Analysis of a biopsy sample of the right ventricle from the proband showed markedly decreased localization of plakoglobin, desmoplakin, and connexin43 at intercalated discs in cardiac myocytes. A yeast-two-hybrid screen revealed that the mutant protein established novel interactions with histidine-rich calcium-binding protein and TGF beta induced apoptosis protein 2. Immunoblotting and confocal microscopy in human embryonic kidney 293 (HEK293) cell lines transfected to stably express either wild-type or mutant plakoglobin protein showed that the mutant protein was apparently ubiquitylated and was preferentially located in the cytoplasm, suggesting that the S39_K40insS mutation may increase plakoglobin turnover via proteasomal degradation. HEK293 cells expressing mutant plakoglobin also showed higher rates of proliferation and lower rates of apoptosis than did cells expressing the wild-type protein. Electron microscopy showed smaller and fewer desmosomes in cells expressing mutant plakoglobin. Taken together, these observations suggest that the S39_K40insS mutation affects the structure and distribution of mechanical and electrical cell junctions and could interfere with regulatory mechanisms mediated by Wnt-signaling pathways. These results implicate novel molecular mechanisms in the pathogenesis of ARVC.

Quantitative assessment of angiographic right ventricular wall motion in arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C)

INTRODUCTION

Angiography of the right ventricle (RV) is a standard, reference technique to diagnose wall motion abnormalities in arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C). RV wall motion is usually assessed by qualitative, visual impression, and has lacked a quantitative basis for defining abnormalities. Since the normal RV has a markedly asymmetric movement, angiographic interpretation can differ, even among experienced clinicians. The purpose of this study was to quantify RV wall motion based on contrast ventriculography in patients with ARVD/C and to specify the severity and location of wall motion abnormalities, as compared with normal subjects.

METHODS AND RESULTS

We analyzed the angiographic contours of the RV in three views from 19 normal subjects and 23 subjects with ARVD/C. Contour area movement during contraction was calculated circumferentially and further analyzed in nine zones. RV ejection fraction was also computed. Wall motion in ARVD/C was depressed by more than 30% at the tricuspid valve and inferior wall regions (P < 0.001) and significantly reduced at the apex (P = 0.003). However, the RVOT and anterior wall motion were not significantly reduced. RV ejection fraction was depressed from 60 +/- 11% in normal subjects to 41 +/- 12% in ARVD/C patients (P < 0.001).

CONCLUSION

Wall motion abnormalities in ARVD/C can be quantified and compared with normal controls, showing primarily reduced movement in the tricuspid and inferior wall regions. This study delineates objective measurements that can be used to aid in the diagnosis of ARVD/C. In addition, they may be incorporated in future refinements of criteria to diagnose ARVD/C.

Diagnostic usefulness and prognostic implications of the mitral E/E' ratio in patients with heart failure and severe secondary mitral regurgitation

In patients with chronic heart failure (CHF) and severe secondary mitral regurgitation (MR), the diagnostic usefulness and prognostic impact of tissue Doppler imaging (TDI) is unknown. This prospective study enrolled 370 patients with stable CHF. Severe secondary MR, defined as effective regurgitant orifice area >/=0.20 cm(2), was present in 92 patients (25%). Echo measurements comprised left ventricular volumes, ejection fraction, mitral E/A ratio, deceleration time, and TDI-derived mitral annular velocities (e.g., S', E', A', E/E'). During a follow-up of 790 +/- 450 days, all-cause mortality and rehospitalization data were analyzed. Patients with or without MR did not differ with respect to age or ejection fraction, but patients with MR were in a poorer New York Heart Association functional class and had a higher mitral E/E' ratio. During follow-up, 70 patients (18%) died and 134 patients (36%) were rehospitalized for worsening heart failure. Mortality rate was significantly higher in patients with versus without severe MR (33% vs 14%, p <0.001). In the MR group, the mitral E/E' ratio independently predicted all-cause mortality and was also significantly associated with rehospitalization for worsening heart failure. In patients with MR with an E/E' ratio >13.5, outcome was markedly worse compared with patients with an E/E' ratio </=13.5 (event-free survival rate, 64% vs 31%, p <0.001). In conclusion, in patients with CHF and severe secondary MR, a higher mitral E/E' ratio is associated with increased morbidity and an adverse outcome. TDI appears to be a useful adjunct in the diagnostic workup and risk stratification of such patients.

Effective Methods to Correct Contrast Agent-Induced Errors in PET Quantification in Cardiac PET/CT

In combined PET/CT studies, x-ray attenuation information from the CT scan is generally used for PET attenuation correction. Iodine-containing contrast agents may induce artifacts in the CT-generated attenuation map and lead to an erroneous radioactivity distribution on the corrected PET images. This study evaluated 2 methods of thresholding the CT data to correct these contrast agent-related artifacts.

METHODS

PET emission and attenuation data (acquired with and without a contrast agent) were simulated using a cardiac torso software phantom and were obtained from patients. Seven patients with known coronary artery disease underwent 2 electrocardiography-gated CT scans of the heart, the first without a contrast agent and the second with intravenous injection of an iodine-containing contrast agent. A 20-min PET scan (single bed position) covering the same axial range as the CT scans was then obtained 1 h after intravenous injection of (18)F-FDG. For both the simulated data and the patient data, the unenhanced and contrast-enhanced attenuation datasets were used for attenuation correction of the PET data. Additionally, 2 threshold methods (one requiring user interaction) aimed at compensating for the effect of the contrast agent were applied to the contrast-enhanced attenuation data before PET attenuation correction. All PET images were compared by quantitative analysis.

RESULTS

Regional radioactivity values in the heart were overestimated when the contrast-enhanced data were used for attenuation correction. For patients, the mean decrease in the left ventricular wall was 23%. Use of either of the proposed compensation methods reduced the quantification error to less than 5%. The required time for postprocessing was minimal for the user-independent method.

CONCLUSION

The use of contrast-enhanced CT images for attenuation correction in cardiac PET/CT significantly impairs PET quantification of tracer uptake. The proposed CT correction methods markedly reduced these artifacts; additionally, the user-independent method was time-efficient.

Impaired myocardial perfusion and perfusion reserve associated with increased coronary resistance in persistent idiopathic atrial fibrillation

AIMS

Patients with atrial fibrillation (AF) present with symptoms of myocardial ischaemia despite exclusion of coronary artery disease. A small vessel disease has been suggested. We quantified myocardial perfusion, perfusion reserve, and coronary vascular resistance (CVR) in AF patients using positron emission tomography (PET).

METHODS AND RESULTS

Twenty-five male patients (age: 58 +/- 13 years) with persistent idiopathic AF were compared with 13 age- and risk-matched male controls (age: 56 +/- 8 years). Using H(2)(15)O-PET, myocardial blood flow (MBF) was quantified at rest, at hyperaemia (adenosine), and during cold-pressor-testing (CPT). Scans were repeated 4.1 +/- 2.3 months after cardioversion in 10 AF patients. In AF, resting MBF (0.95 +/- 0.19 vs. 1.14 +/- 0.22 mL/min/mL; P = 0.009), hyperaemic MBF (2.07 +/- 0.80 vs. 3.33 +/- 0.78 mL/min/mL; P < 0.001), and MBF under CPT (0.90 +/- 0.25 vs. 1.14 +/- 0.25 mL/min/mL; P < 0.014) were significantly reduced compared with matched controls. Hyperaemic CVR was increased in AF (47 +/- 21 vs. 29 +/- 7 mmHg x mL/min/mL; P = 0.012) but unchanged at rest and under CPT. After cardioversion, resting MBF and MBF under CPT in AF were similar to matched controls, however, hyperaemic MBF and CVR were not recovered.

CONCLUSION

In AF, MBF at baseline, at hyperaemia, and at CPT is reduced, whereas CVR under hyperaemic conditions is increased. Following electrical cardioversion, these findings are partly reversible and therefore most likely secondary to the arrhythmia.