International Journal of Cardiology 191 (2015) 90–96

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Prolonged right ventricular ejection delay identifies high risk patients and gender differences in Brugada syndrome☆,☆☆ Sophie C.H. Van Malderen a,e,⁎, Dirk Kerkhove b, Dominic A.M.J. Theuns e, Caroline Weytjens b, Steven Droogmans b, Kaoru Tanaka c, Dorien Daneels d, Sonia Van Dooren d, Marije Meuwissen d, Maryse Bonduelle d, Pedro Brugada a, Guy Van Camp b a

Department of Electrophysiology (Heart Rhythm Management Centre), Vrije Universiteit Brussel (VUB), UZ Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium Department of Non-invasive Cardiology, Vrije Universiteit Brussel (VUB), UZ Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium c Department of Cardiac Radiology, Vrije Universiteit Brussel (VUB), UZ Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium d Centre for Medical Genetics, Reproduction and Genetics, Reproduction Genetics and Regenerative Medicine, Vrije Universiteit Brussel (VUB), UZ Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium e Department of Electrophysiology, Thoraxcenter, Erasmus MC, 's Gravendijkwal 230, 3015 CE Rotterdam, The Netherlands. b

a r t i c l e

i n f o

Article history: Received 14 December 2014 Received in revised form 6 April 2015 Accepted 30 April 2015 Available online 1 May 2015 Keywords: Brugada Syndrome Tissue Velocity Imaging Gender Conduction delay Syncope SCN5A

a b s t r a c t Background and objectives: Right ventricular (RV) conduction delay has been suggested as an underlying pathophysiological mechanism in Brugada syndrome (BS). In this cross-sectional study we non-invasively assessed the value of echocardiographic markers reflecting ventricular ejection delay to further assess electromechanical abnormalities in BS and to identify patients at risk for life-threatening arrhythmic events. Furthermore, we sought to assess differences in ejection delays between genders because male BS patients demonstrate a more malignant clinical phenotype. Methods: 124 BS patients (57.3% males) and 62 controls (CTR) (48.4% males) were included. Using Tissue Velocity Imaging, the ejection delay, determined as the time from QRS onset to the onset of the sustained systolic contraction, was measured for both RV free wall (RVED) and lateral LV wall (LVED). From these parameters, the interventricular ejection delay between both walls (IVED) was calculated. Results: BS patients had longer RVEDs and IVEDs compared to the CTR. BS patients with a previous history of syncope or spontaneous ventricular arrhythmia showed the longest RVEDs and IVEDs. Male BS patients demonstrated longer RVEDs and IVEDs than females. Male BS patients with malignant events had the longest delays. No significant differences regarding LVED were observed between BS patients and CTR. Conclusions: We demonstrated that a previous history of malignant events was associated with longer RVEDs. Our findings supported the RV conduction delay mechanism behind BS and demonstrated for the first time that the predominant malignant male Brugada phenotype might also be the result of a more delayed RV conduction in males. © 2015 Elsevier Ireland Ltd. All rights reserved.

1. Background Brugada syndrome (BS) defines the association between specific Jwave and ST-segment elevations in the right precordial leads (V1–V3) of the Brugada ECG [1,2] and the development of syncope, life threatening ventricular arrhythmias (VA) [3] and sudden cardiac death (SCD). The genetic predisposition for BS became evident following the detection of mutations in the SCN5A gene encoding for the Nav1.5 voltage☆ All authors take responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation. ☆☆ There are no conflicting relationships with the industry, and no grants, contracts or other forms of financial support in connection with this study. ⁎ Corresponding author at: Erasmus MC, Thoraxcenter, Department of Cardiologie, Clinical Electrophysiology's Gravendijkwal 230, 3015CE Rotterdam, The Netherlands. E-mail address: [email protected] (S.C.H. Van Malderen).

http://dx.doi.org/10.1016/j.ijcard.2015.04.243 0167-5273/© 2015 Elsevier Ireland Ltd. All rights reserved.

gated sodium channel [4,5], which are identified in 20–30% of BS patients. There has been an extensive debate on the precise pathophysiological mechanism in BS [6,7]. Two hypotheses currently receive the widest support. The repolarization hypothesis describes the transmural dispersion of repolarization between the right ventricle (RV) and right ventricular outflow tract (RVOT) endocardium and epicardium, creating a vulnerable window for phase 2 re-entry and initiation of VA [6,8–10]. The depolarization hypothesis is based on a conduction delay of the RV action potential (AP) towards the RVOT, in combination with subtle structural derangements, potentially leading to functional block which facilitates re-entry [6,7,11]. Although both theories seem opposing, they're probably not mutually exclusive: an overlap or a variable contribution of each mechanism to the phenotype of individual BS patients [7, 12] is likely, equally depending on gender, age, genetic background

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(including polymorphisms), and other modulating factors such as vagal tone and high fever [1]. BS was initially considered to be a primary electrical cardiac disease in an otherwise structurally normal heart [13,14]. However, subtle structural abnormalities, particularly in the right ventricle (RV) and the right ventricular outflow tract (RVOT) have been identified on computed tomography (CT) [15,16], cardiac magnetic resonance (CMR) [17–19], echocardiography [20–22] and biopsies [23,24]. Furthermore, studies confirmed that BS is a RV disease and consented that the anterior RVOT epicardium is likely to be the primary arrhythmogenic area in BS [8,9,25–31]. Since current risk stratification of asymptomatic BS patients still fails, the identification of a reliable and preferably non-invasive parameter to further quantify the severity of the pathological electromechanical coupling within different risk groups, could create new opportunities to predict the occurrence of VA. Therefore, besides previous findings in BS regarding a more pronounced delay between RV and left ventricular (LV) ejection onset at baseline and during flecainide provocation [22], it is essential to analyze additional electromechanical parameters in the absence of sodium channel blockers. Despite equal genetic transmission, the male gender is associated with a more prevalent and malignant clinical phenotype [32–34]. This has only been explained within the ‘repolarization hypothesis’ [6,8,35] and gender differences regarding conduction delay (‘depolarization hypothesis’) have not been determined. This study aims to further elucidate the complex relation between electrocardiographic and contractile abnormalities of the myocardium by studying timing of RV and LV ejection using Tissue Velocity Imaging (TVI). Next to this, TVI-parameters were correlated with the severity of the underlying electrical dysfunction and the clinical phenotype as a first step to identify potential non-invasive parameters for future risk stratification. Finally, a subgroup analysis was performed to determine gender-based electromechanical differences. 2. Methods This cross-sectional study was performed in accordance with the Declaration of Helsinki and approved by the UZ Brussel Ethical Committee. Written informed consent was obtained from all patients and controls. 2.1. Study population Patients with BS and controls (CTR) were recruited between May 2011 and May 2014 at the outpatient clinic of the UZ Brussel. The diagnosis of BS was confirmed if patients previously had either a spontaneous or a drug induced ST-segment elevation with a type 1 morphology of N2 mm in N 1 lead among the right precordial leads (V1 to V3) [1,2]. CTR were healthy age/gender-matched volunteers. Patients with BS and CTR were eligible for inclusion if they met all of the following criteria: N18 years old; absence of pericarditis, ischemic heart disease, any known cardiomyopathy, structural heart disease or another channelopathy; absence of atrial fibrillation or pacing during echocardiography; and no intake of beta-blockers or antiarrhythmic drugs. 2.2. Transthoracic echocardiography (TTE) A TTE (Vivid 9, GE-Vingmed, Horten, Norway) was performed at a median of 60 months (IQR 15–99 months) after diagnosis of BS. LV ejection fraction (LVEF, Teichholz method), tricuspid annular plane systolic excursion (TAPSE), maximal proximal (anterior) RVOT diameter (mm), basal RV diameter (RVD) (RVD1), mid cavity RVD (RVD2) and longitudinal RVD from apex to base (RVD3) were assessed on conventional 2D-grayscale images in the apical 4-chamber, the parasternal short and long axis views [36]. Color Doppler myocardial images were recorded in the apical 4-chamber view with a median frame rate of 139 fps

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(IQR 98–163 fps). Lead II was used for the ECG recording. Images and loops were digitally stored for offline analysis (EchoPac, GE Vingmed Ultrasound, version 112). 2.3. Offline analysis and reproducibility of measurements In the color TDI-coded apical 4-chamber view, a sample area was placed at the basal portions of the RV free wall and the lateral LV wall. A 30 ms temporal smoothing filter was applied. QRS gain was increased to ensure correct assessment of the beginning of the QRS. If a Q-wave was absent, the QRS onset was determined at the beginning of the Rwave. The RV and LV ejection delay (RVED, LVED) were measured as the time from QRS onset to the onset of the systolic ejection wave at the end of the isovolumetric contraction (IVC) (Fig. 1). Because septal motion is multiphasic and influenced by both LV and RV movements, we assessed the LVED at the lateral LV wall. The interventricular ejection delay (IVED) was calculated as the difference between the RVED and the LVED. These ejection delays represent both the conduction delay and the electromechanical coupling for each wall. All timings were corrected for heart frequency (HF) using Bazett's formula. All TTE analysis were performed separately and blinded to other patient data. Variability was evaluated for RVED and LVED. Intra- and interobserver variability was assessed by analyzing color TVI images from 20 BS patients and 10 CTR by two independent observers and by the same observer with an interval of 2 months. Both observers were experienced in clinical echocardiography and tissue velocity analysis. 2.4. Electrocardiography Before TTE, a routine 12-lead electrocardiogram (ECG) was acquired using a GE Healthcare-MAC 5500 ECG Diagnosis System. The data assessed on the ECG was maximum ST segment elevation in leads V1, V2 or V3 and the type of BS-repolarization pattern based on the second consensus document published in 2005 [1]. ST segment elevation was measured 80 ms after the J point or at the nadir of the ST segment in case of a type 1 ECG. ECG evaluation was blinded. 2.5. Genetic analysis SCN5A mutation analysis of all 28 exons and flanking intron-exon boundaries was performed by High Resolution Melting Curve Analysis (HRMCA) as a first line mutation detection assay using a Lightcycler 480 RT-PCR instrument (Roche Applied Science). In regions with aberrant HRMCA profiles, the exons and flanking intronic sequences were PCR amplified and Sanger sequenced on an ABI 3130xl DNA Sequence Detection System (Applied Biosystems). 3. Statistics Normality of distribution was assessed using the Kolmogorov– Smirnov test. Descriptive statistics are presented as mean ± SD for continuous variables if normally distributed, otherwise by median and interquartile range (IQR). Where appropriate, continuous data was compared using One-way ANOVA, Kruskal–Wallis test, Mann–Whitney test and the independent t test. Categorical data was expressed as percentages and compared using the Chi-square test. For the analysis of intra- and interobserver variability, we calculated the intraclass correlation coefficient (ICC) for continuous echocardiographic parameters. The data was considered reproducible if the ICC was N 0.60; in particular, reproducibility was considered almost perfect if it was between 0.80 and 1.00. The Pearson correlation coefficient was calculated to assess the association between continuous variables. Receiver operating characteristic (ROC) curves, the area under the curve (AUC) of the ROC, sensitivity and specificity were calculated to determine the value of RVED that best differentiates BS patients from CTR and HR from LR BS patients. Analyses

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Fig. 1. Myocardial velocities measured by color Tissue Velocity Imaging in a control subject (A) and a high risk BS patient (B). Color doppler sample areas were placed at the basal portions of the lateral LV wall (blue sample/curve) and the free RV wall (yellow sample/curve). QRS onset (red arrowhead) was determined at the beginning of the R-wave if a Q-wave was absent (B). The ejection delay of the RV and the LV (RVED, LVED) were measured as the time of the QRS onset to the onset of the systolic ejection wave (open blue/yellow arrows) at the end of the isovolumetric contraction (asterisks). These ejection delays represent both the electromechanical coupling and the conduction delay at each wall. Note the longer RVED in the high risk BS patient compared to the control.

were performed using SPSS software (version 21, IBM) and a two-sided probability value of P b 0.05 was considered statistically significant. 4. Results 4.1. Patient characteristics and clinical presentation 124 patients with BS (mean age 45.5 ± 14.2 years, 57.3% males) and 62 CTR (mean age 44.2 ± 11.1 years, 48.4% males) were enrolled in this

cross-sectional study. Based on current controversy in literature regarding the role of electrophysiology studies (EPS) in risk stratification [37], patients with BS were divided into 3 groups: high risk (HR) BS patients (n = 48) with a previous history of syncope, spontaneous sustained ventricular arrhythmia (VA) or aborted cardiac arrest (ACA); low risk (LR) asymptomatic BS patients (n = 71) with a negative EPS; and asymptomatic but inducible (AI) BS patients (n = 5) with a positive EPS. An EPS, using up to 2 ventricular extrastimuli, was considered positive if a sustained VA was induced. LV ejection fraction and TAPSE were

Table 1 Patient characteristics and clinical presentation. All BS (n = 124) Male, n (%) 71 (57.3%) Age (y) 48 [33–56] 24.6 ± 3.3 BMI (kg/m2) BPs (mm Hg) 120 [110–130] BPd (mm Hg) 78 [70–80] HF (bpm) 67.0 ± 10.1 Ethnic group, n (%) Caucasian 120 (96.8%) African descent 3 (2.4%) Asian 1 (0.8%) Clinical presentation, n (%) Syncope 43 (34.7%) Spont. VT 9 (7.3%) Spont. VF 7 (5.6%) ACA 8 (6.5%) EPS performed 116 (93.5%) EPS + 16 (12.9%) ICD 49 (39.5%) ECG features Max ST (μV) 142 [88–246] Type 1 at TTE 9 (7.3%) Intermit.Type 1 29 (23.4%) Dynamic ECG 38 (30.6%) Genetic analysis SCN5A analyzed 114 (91.9%) SCN5Am 31 (27.2%)

HR BS (n = 48)

LR BS (n = 71)

AI BS (n = 5)

CTR (n = 62)

All BS vs CTR (p-value)

HR BS vs LR BS (p-value)

HR BS vs CTR (p-value)

LR BS vs CTR (p-value)

32 (66.7%) 48 [37–58] 24.9 ± 3.3 120 [110–138] 77 [70–80] 66.2 ± 8.8

36 (50.7%) 46 [32–55] 24.2 ± 3.1 120 [110–124] 75 [70–80] 67.5 ± 11.1

3 (60.0%) 53 [47–61] 26.9 ± 4.6 130 [118–140] 80 [75–85] 68.8 ± 8.1

30 (48.4%) 48.0 [35–53] 24.0 ± 2.8 120 [110–130] 80 [70–80] 67.2 ± 10.6

NS NS NS NS NS NS

NS NS NS NS NS NS

NS NS NS NS NS NS

NS NS NS NS NS NS

46 (95.8%) 1 (2.1%) 1 (2.1%)

69 (97.2%) 2 (2.8%) 0 (0.0%)

5 (100.0%) 0 (0.0%) 0 (0.0%)

60 (96.8%) 2 (3.2%) 0 (0.0%)

NS NS NS

NS NS NS

NS NS NS

NS NS NS

43 (89.6%) 9 (18.8%) 7 (14.6%) 8 (16.7%) 47 (97.9%) 11 (22.9%) 40 (83.3%)

0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 64 (90.1%) 0 (0.0%) 4 (5.6%)

0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 5 (100.0%) 5 (100.0%) 5 (100.0%)

0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%)

b0.001 0.030 NS 0.041 b0.001 b0.001

b0.001 b0.001 0.001 b0.001 NS b0.001 b0.001

b0.001 b0.001 0.002 0.001 b0.001 b0.001

b0.001 NS

154 [82–260] 6 (12.5%) 16 (33.3%) 22 (45.8%)

137 [88–223] 2 (2.8%) 9 (12.7%) 15 (21.1%)

142 [98–166] 1 (20.0%) 4 (80.0%) 1 (20.0%)

117 [68–200] 0 (0.0%) 0 (0.0%) 0 (0.0%)

NS 0.036 b0.001 b0.001

NS 0.040 0.007 0.020

NS 0.006 b0.001 b0.001

NS NS 0.008 b0.001

45 (93.8%) 13 (28.9%)

65 (91.5%) 16 (24,6%)

4 (80.0%) 2 (50.0%)

0 (0.0%) -

b0.001 b0.001

NS NS

b0.001 b0.001

b0.001 b0.001

BS pts indicates patients with Brugada syndrome; HR, high risk; LR, low risk; AI, asymptomatic inducible; CTR, controls; vs, versus; diagn., diagnosis; y, years; m, months; BSA, body surface area; BMI, body mass index; BPs, systolic blood pressure; BPd, diastolic blood pressure; MP, mean blood pressure; Spont., spontaneous; HF, heart frequency; VT, ventricular tachycardia; VF, ventricular fibrillation; ACA: aborted cardiac arrest; EPS, electrophysiology study; EPS +, positive EPS with inducible sustained VT or VF; ICD, implantable cardioverter defibrillator; Max ST, maximal ST segment elevation; ECG, electrocardiogram; TTE, transthoracic echocardiography; Intermit., intermittent; SCN5Am, mutation in SCN5A gene. Values of variables with a normal and abnormal distribution are presented as mean ± SD and median [IQR], respectively.

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normal in all groups and did not differ significantly between BS patients and CTR. HR BS patients had a larger RVD1, RVD2 and RVOT when compared to CTR, whereas LR BS patients did not (Table 2). Genetic analysis was performed after consent in 114 BS patients from 70 families. 28.9% (13/45) of screened HR patients and 24.6% (16/65) of screened LR BS patients had an SCN5A mutation (SCN5Am). Clinical characteristics of these groups are shown in Table 1.

patients with previous spontaneous sustained VA (n = 16, 12.9%) also had a significantly longer RVED (138.5 ± 19.9 ms) compared to those without previous spontaneous VA (n = 108, 128.0 ± 16.1 ms, P = 0.033) and CTR (n = 62, P = 0.005) (Fig. 2b). Because only 8 BS patients (6.5%) had a previous ACA and all of them also had a previous history of syncope or VA, this subgroup was not compared with subjects without a previous ACA.

4.2. RV ejection delay

4.4. Males versus females

The mean RVED for all BS patients was significantly longer compared to CTR (128.9 ± 16.6 vs 120.3 ± 16.4 ms, P = 0,001) (Fig. 1, Table 2). Subgroup analysis confirmed significantly longer RVED for HR versus LR BS patients (132.7 ± 15.5 vs 126.4 ± 16.7 ms, P = 0.041), HR BS patients versus CTR (P b 0.001), and LR BS patients versus CTR (P = 0.035) (Table 2). In all BS patients, systolic RV ejection started on average 37.6 ± 17.1 ms later than LV ejection. This prolonged IVED was mainly explained by the longer RVED and IVED in HR BS patients (132.7 ± 15.5 and 41.1 ± 16.1 ms, respectively) and appeared to be significantly shorter in CTR (31.3 ± 13.6 ms, P = 0.013) (Fig. 1, Table 2). No significant differences were observed in LVED between risk groups and CTR (Table 2). BS patients with a SCN5Am were equally distributed between HR and LR groups (Table 1) and did not have a longer RVED or IVED compared to non-carriers. By ROC analysis, a RVED N125.0 ms had a 62.9% specificity and a 62.1% sensitivity in separating BS patients from CTR (AUC 0.642, 95% CI 0.558–0.726, P = 0.002), with a NPV of 45.3% and a PPV of 77.0%. No significant cut-off value could be determined to separate HR from LR patients. We found no association between RVED or IVED and the presence of a type 1 ECG (before TTE or during follow-up), neither with maximal ST-segment elevation nor with the inducibility of VT/VF during an EPS. The intra- and interobserver variabilities of RVED measurements demonstrated an excellent intraclass correlation coefficient of 0.93 (95% CI 0.85–0.97, r = 0.86) and 0.89 (95% CI 0.73–0.95, r = 0.84), respectively, and for LVED of 0.97 (95% CI 0.93–0.98, r = 0.93) and 0.93 (95% CI 0.81–0.97, r = 0.89), respectively.

Subgroup analysis was performed to evaluate the impact of gender on mechanical timing abnormalities in BS (Fig. 3). HR male BS patients had the longest RVED (137.0 ± 16.5 ms) and IVED (43.0 ± 18.0 ms), and these delays differed significantly from male CTR (120.0 ± 15.8 and 33.5 ± 13.4 ms; P b 0.001 and P = 0.021, respectively). LR male BS patients also had a longer RVED (129.3 ± 17.3 ms) when compared to male CTR (P = 0.027) and a similar IVED. LVED was not significantly different between male groups. In contrast, no significant difference in any timing parameter was observed between female groups. When comparing males and females in the entire BS population, RVED and IVED differed significantly (132.2 ± 17.3 vs 124.6 ± 14.7 ms, P = 0.010; and 40.3 ± 18.6 vs 33.9 ± 14.3 ms, P = 0.041, respectively). In HR BS patients, only RVED differed significantly between both genders (137.0 ± 16.5 vs 124 ± 8.6 ms, P = 0.005). In LR BS patients and CTR, delays were similar between both genders (Fig. 3). When looking only at males, a RVED of N124.9 ms had a 73.3% specificity and a 70.8% sensitivity in separating male BS patients from male CTR (AUC 0.711, 95% CI 0.599–0.823, P = 0.001), with a NPV of 52.4% and a PPV of 88.4%. No significant RVED cut-off value could be determined in females.

4.3. Impact of syncope and spontaneous sustained VA on RVED Subgroup analysis was performed to determine whether a significant difference in RVED alone could discriminate between subjects with and without a history of either syncope or spontaneous sustained VA. BS patients who experienced syncopes in the past (n = 43, 34.7%), had a significantly longer RVED (133.6 ± 16.9 ms) compared to BS patients without previous syncopes (n = 81, 126.8 ± 16.6 ms, P = 0.033) and CTR (n = 62, 120.3 ± 16.4 ms, P b 0.001) (Fig. 2a). BS

5. Discussion 5.1. RV ejection delay The present study supports previous findings of RV involvement in BS [8,15–31,38]. Besides known structural RV abnormalities [15, 17–19] (Table 2), our data demonstrated delays in the right (RVED) and the interventricular (IVED) conduction (Fig. 1, Table 2), which is in line with the depolarisation hypothesis [6,7]. Only one study [22] used TVI to analyze the timing of RV and LV mechanics before and during flecainide challenge in a relatively low number of BS patients (n = 16). A larger delay between the onset of RV and LV ejection could be observed at baseline and upon the pharmacological induction of a type 1 ECG [22]. The data from our larger cohort (n = 124) confirmed the larger baseline IVED in BS patients and provided additional information on merely the RVED and the LVED within different BS subpopulations

Table 2 Ventricular function, dimensions and TDI-derived time intervals. All BS (n = 124) Ventricular function and dimensions LVEF (%) 73.3 ± 6.7 TAPSE (mm) 24.3 ± 5.1 RVD1 (mm) 29.9 ± 5.7 RVD2 (mm) 25.3 ± 5.5 RVD3 (mm) 68.7 ± 8.2 RVOT (mm) 37.5 ± 5.8 TDI-derived time intervals RVED (ms) 128.9 ± 16.6 LVED (ms) 91.4 ± 16.2 IVED (ms) 37.6 ± 17.1

HR BS (n = 48)

LR BS (n = 71)

AI BS (n = 5)

CTR (n = 62)

74.6 ± 6.4 24.7 ± 4.7 30.8 ± 5.8 26.4 ± 5.6 68.2 ± 8.6 37.5 ± 5.2

72.3 ± 6.8 24.2 ± 5.4 29.2 ± 5.3 24.5 ± 5.4 68.8 ± 8.0 37.6 ± 6.4

73.4 ± 6.3 22.9 ± 1.9 32.1 ± 9.2 27.4 ± 4.8 70.5 ± 6.5 36.9 ± 4.3

72.4 ± 7.2 25.6 ± 3.9 28.6 ± 4.5 24.7 ± 5.5 71.1 ± 8.6 33.2 ± 5.7

132.7 ± 15.5 91.6 ± 16.9 41.1 ± 16.1

126.4 ± 16.7 90.8 ± 16.1 35.7 ± 17.8

128.8 ± 23.0 98.1 ± 10.9 30.7 ± 12.8

120.3 ± 16.4 89.0 ± 13.5 31.3 ± 13.6

All BS vs CTR (p-value)

HR BS vs LR BS (p-value)

HR BS vs CTR (p-value)

LR BS vs CTR (p-value)

NS NS NS 0.033 NS b0.001

NS NS NS NS NS NS

NS NS 0.031 0.007 NS b0.001

NS NS NS NS NS NS

0,001 NS 0.013

0.041 NS NS

b0.001 NS 0,001

0,035 NS NS

BS indicates patients with Brugada syndrome; HR, high risk; LR, low risk, AI, asymptomatic inducible, CTR, controls; vs, versus; LVEF, left ventricular ejection fraction (Teichholdz method); TAPSE, tricuspid annular plane systolic excursion; RVD, right ventricular diameter; RVD1, basal RVD; RVD2, mid cavity RVD; RVD3, longitudinal RVD from apex to base; RVOT, maximal diameter of the proximal (anterior) right ventricular outflow tract; RVED, right ventriclular ejection delay; LVED, left ventricular ejection delay; IVED, interventricular ejection delay. All timings were corrected for HF by using Bazett's formula. All data follow a normal distribution and are presented as mean ± SD.

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[40] and may provide an additional explanation for the demonstrated ventricular delays in BS patients. Lack of difference between BS and CTR regarding LVED values could in part be due to a lesser amount or even the absence of fibrosis in the LV of BS patients [23]. In this study BS patients with an SCN5Am, encoding for Nav1.5 channels, did not demonstrate longer RVEDs compared to non-carriers. Nevertheless, different types of SCN5A mutations have been shown to result in different amounts of INa reduction and variable phenotypic expressions [45]. Consequently, RVED values might differ between carriers of different SCN5Am types. Further research on this topic is required but lies beyond the scope of this paper. 5.2. Gender-based differences Most imaging studies in BS analyzed mainly [17,18,21,22] or only male patients [15,16]. Since 42.7% of the patients were female, our data provides the opportunity to evaluate a possible gender-related effect on the phenotype in BS. An intriguing finding is that male BS patients had longer RVEDs and IVEDs compared to female BS patients. Notably, male HR BS patients had the longest RVEDs and IVEDs (Fig. 3). As ejection delay represents conduction delay, these findings suggest that the predominance of the malignant Brugada phenotype in males [32–34] is also the result of a longer RV conduction delay. The reason for this gender based difference could be a reduced Cx43 expression and the increased RV fibrosis, as described in male heterozygous SCN5A-mice [46,47]. However, these preclinical findings cannot be translated to patients directly and need confirmation in clinical studies. 5.3. Risk stratification and future perspectives

Fig. 2. Right ventricular ejection delay (RVED) determined either by syncope (A) or spontaneous sustained ventricular arrhythmia (B). BS indicates Brugada syndrome; CTR, controls; VA, sustained ventricular arrhythmia. Values are mean ± SD. *P b 0,050 vs BS patients with a previous history of either syncope or VA.

(Fig. 1, Table 2). The prolonged RVED and IVED in all BS patients were mainly driven by the larger delays in the HR group. In addition, we showed that both BS patients with a previous history of either syncope or spontaneous VA had significantly longer RVEDs compared to CTR and BS patients who did not experience syncope or VA (Fig. 2). The basis for a delayed conduction in the RV and the RVOT in BS is largely unknown but has been attributed to a reduced net depolarization force, structural abnormalities and fibrosis [23,24,39,40]. The net depolarization current depends on the availability of both Nav1.5 channels and the intercellular electrical coupling by gap junctions [41,42]. Connexin 43 (Cx43), the main connexin in gap junctions of the ventricular myocardium, interacts with Nav1.5 at the intercalated disc [43]. Severe loss of Cx43 expression leads to a decreased Nav1.5 expression and amplitude of sodium current (INa), resulting in a slowed and dispersed conduction with a consequent propensity to develop VA [41,44]. Altered Cx43 expression has been demonstrated in heterozygous SCN5A-mice

Ideally, risk stratification should be improved by non-invasive assessment of the underlying electromechanical dysfunction. Although BS patients with a previous history of either syncope or spontaneous VA have longer RVEDs (Fig. 2), this color TVI parameter should be prospectively studied in a larger study population with a long-term clinical follow-up in order to support RVED as a future risk marker, as well as to elucidate any form of disease progression (‘Brugada cardiomyopathy’). If BS would indeed be a progressive disease, a potential bias for the interpretation of our cross-sectional results could be the heterogeneity in the stage of the disease that is affecting the measured delays. Therefore future studies with longterm follow-up should address the question on whether progressive changes in RVED, as well as syncope or spontaneous VA, represent a more advanced stage of BS or not. As a RVED cut-off of 124.9 ms yields a PPV of 88.4% and a NPV of 52.4%, further confirmation in prospective and larger data is needed to determine whether this parameter could be a useful additional screening tool to identify BS patients in males. For the time being, we recommend systematic and serial follow-up of this TVI parameter for any BS patient, either with or without malignant events. 6. Conclusions Our findings show that HR BS patients with a history of syncope or spontaneously sustained VA have significantly longer RVEDs and IVEDs, compared to asymptomatic BS patients and CTR. Given that these ejection delays represent conduction delay, this study provides new and additional evidence to further support the depolarization hypothesis in BS. The observed gender differences in RVEDs and IVEDs suggest that the predominant male malignant Brugada phenotype might also be the result of a more delayed RV conduction when compared to females. Moreover, the used TVI-method non-invasively couples the electrical delay directly to mechanical delay, thereby confirming the universality of the electromechanical coupling principle.

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Fig. 3. Gender differences in right ventricular ejection delay (RVED). BS indicates Brugada syndrome; HR, high risk; LR, low risk; IA, inducible asymptomatic; CTR, controls. Values are mean ± SD. *P b 0.050 vs CTR. **P b 0.050 between HR and LR BS patients. †P b 0,050 between genders in each subgroup.

7. Limitations Values measured in the AI BS group are based on only 5 patients and are therefore not representative for a larger population of asymptomatic BS patients with a positive EPS. Authors therefore decided not to determine whether RVED values in the AI BS group are either similar to those of the HR or the LR BS patients (Table 2). Due to the design of this study, the size of our patient group and the absence of follow-up, this study is not suitable to determine the value of RVED as a possible risk stratification marker. For the same reason no information can be provided on whether the RVED changes progressively with the natural evolution of the disease.

Conflict of interest There were no conflicts of interest related to this study.

Acknowledgments We kindly thank Richard Alloway and Orville Small, both native English speakers, for revising the manuscript.

References [1] C. Antzelevitch, P. Brugada, M. Borggrefe, J. Brugada, R. Brugada, D. Corrado, et al., Brugada syndrome: report of the second consensus conference: endorsed by the Heart Rhythm Society and the European Heart Rhythm Association, Circulation 111 (2005) 659–670. [2] S.G. Priori, A. a Wilde, M. Horie, Y. Cho, E.R. Behr, C. Berul, et al., Executive summary: HRS/EHRA/APHRS expert consensus statement on the diagnosis and management of patients with inherited primary arrhythmia syndromes, Europace 15 (2013) 1389–1406. [3] S. Viskin, R. Fish, M. Eldar, D. Zeltser, M.D. Lesh, A. Glick, et al., Prevalence of the Brugada sign in idiopathic ventricular fibrillation and healthy controls, Heart 84 (2000) 31–36. [4] Q. Chen, G.E. Kirsch, D. Zhang, R. Brugada, J. Brugada, P. Brugada, et al., Genetic basis and molecular mechanism for idiopathic ventricular fibrillation, Nature 392 (1998) 293–296. [5] J.D. Kapplinger, D.J. Tester, M. Alders, B. Benito, M. Berthet, J. Brugada, et al., An international compendium of mutations in the SCN5A-encoded cardiac sodium channel in patients referred for Brugada syndrome genetic testing, Heart Rhythm. 7 (2010) 33–46. [6] P.G. Meregalli, A.A.M. Wilde, H.L. Tan, Pathophysiological mechanisms of Brugada syndrome: depolarization disorder, repolarization disorder, or more? Cardiovasc. Res. 67 (2005) 367–378. [7] A.A.M. Wilde, P.G. Postema, J.M. Di Diego, S. Viskin, H. Morita, J.M. Fish, et al., The pathophysiological mechanism underlying Brugada syndrome: depolarization versus repolarization, J. Mol. Cell. Cardiol. 49 (2010) 543–553. [8] G.-X. Yan, C. Antzelevitch, Cellular basis for the Brugada syndrome and other mechanisms of arrhythmogenesis associated with ST-segment elevation, Circulation 100 (1999) 1660–1666.

[9] J.M. Di Diego, Z.Q. Sun, C. Antzelevitch, I(to) and action potential notch are smaller in left vs. right canine ventricular epicardium, Am. J. Physiol. 271 (1996) H548–H561. [10] C. Antzelevitch, S. Sicouri, S.H. Litovsky, a. Lukas, S.C. Krishnan, J.M. Di Diego, et al., Heterogeneity within the ventricular wall. Electrophysiology and pharmacology of epicardial, endocardial, and M cells, Circ. Res. 69 (1991) 1427–1449. [11] F. Sacher, L. Jesel, P. Jais, M. Haïssaguerre, Insight into the mechanism of Brugada syndrome: epicardial substrate and modification during ajmaline testing, Heart Rhythm. 11 (2013) 732–734. [12] J. Bhar-Amato, L. Nunn, P. Lambiase, A review of the mechanisms of ventricular arrhythmia in Brugada syndrome, Indian Pacing Electrophysiol. J. 10 (2010) 410–425. [13] J. Brugada, R. Brugada, P. Brugada, Right bundle-branch block and ST-segment elevation in leads V1 through V3: a marker for sudden death in patients without demonstrable structural heart disease, Circulation 97 (1998) 457–460. [14] P. Brugada, J. Brugada, Right bundle branch block, persistent ST segment elevation and sudden cardiac death: a distinct clinical and electrocardiographic syndrome. A multicenter report, J. Am. Coll. Cardiol. 20 (1992) 1391–1396. [15] M. Takagi, N. Aihara, S. Kuribayashi, a Taguchi, W. Shimizu, T. Kurita, et al., Localized right ventricular morphological abnormalities detected by electron-beam computed tomography represent arrhythmogenic substrates in patients with the Brugada syndrome, Eur. Heart J. 22 (2001) 1032–1041. [16] M. Takagi, N. Aihara, S. Kuribayashi, A. Taguchi, T. Kurita, K. Suyama, et al., Abnormal response to sodium channel blockers in patients with Brugada syndrome: augmented localised wall motion abnormalities in the right ventricular outflow tract region detected by electron beam computed tomography, Heart 89 (2003) 169–174. [17] O. Catalano, S. Antonaci, G. Moro, M. Mussida, M. Frascaroli, M. Baldi, et al., Magnetic resonance investigations in Brugada syndrome reveal unexpectedly high rate of structural abnormalities, Eur. Heart J. 30 (2009) 2241–2248. [18] T. Papavassiliu, C. Wolpert, S. Flüchter, R. Schimpf, W. Neff, K.K. Haase, et al., Magnetic resonance imaging findings in patients with Brugada syndrome, J. Cardiovasc. Electrophysiol. 15 (2004) 1133–1138. [19] F. Van Hoorn, M.E. Campian, A. Spijkerboer, M.T. Blom, R.N. Planken, A.C. van Rossum, et al., SCN5A mutations in Brugada syndrome are associated with increased cardiac dimensions and reduced contractility, PLoS One 7 (2012) e42037. [20] Z. Huang, L. Chen, W. Li, Q. Tang, C. Huang, Q. Xie, et al., Interventricular septum motion abnormalities: unexpected echocardiographic changes of Brugada syndrome, Chin. Med. J. (Engl.) 120 (2007) 1898–1901. [21] M. Iacoviello, C. Forleo, A. Puzzovivo, I. Nalin, P. Guida, M. Anaclerio, et al., Altered two-dimensional strain measures of the right ventricle in patients with Brugada syndrome and arrhythmogenic right ventricular dysplasia/cardiomyopathy, Eur. J. Echocardiogr. 12 (2011) 773–781. [22] R. Tukkie, P. Sogaard, J. Vleugels, I.K.L.M. de Groot, A. a M. Wilde, H.L. Tan, Delay in right ventricular activation contributes to Brugada syndrome, Circulation 109 (2004) 1272–1277. [23] R. Coronel, S. Casini, T.T. Koopmann, F.J.G. Wilms-Schopman, A.O. Verkerk, J.R. de Groot, et al., Right ventricular fibrosis and conduction delay in a patient with clinical signs of Brugada syndrome: a combined electrophysiological, genetic, histopathologic, and computational study, Circulation 112 (2005) 2769–2777. [24] A. Frustaci, S.G. Priori, M. Pieroni, C. Chimenti, C. Napolitano, I. Rivolta, et al., Cardiac histological substrate in patients with clinical phenotype of Brugada syndrome, Circulation 112 (2005) 3680–3687. [25] K. Nademanee, G. Veerakul, P. Chandanamattha, L. Chaothawee, A. Ariyachaipanich, K. Jirasirirojanakorn, et al., Prevention of ventricular fibrillation episodes in Brugada syndrome by catheter ablation over the anterior right ventricular outflow tract epicardium, Circulation 123 (2011) 1270–1279. [26] P.G. Postema, P.F.H.M. van Dessel, J.M.T. de Bakker, L.R.C. Dekker, A.C. Linnenbank, M.G. Hoogendijk, et al., Slow and discontinuous conduction conspire in Brugada syndrome: a right ventricular mapping and stimulation study, Circ. Arrhythm. Electrophysiol. 1 (2008) 379–386. [27] L. Eckardt, P. Kirchhof, E. Schulze-Bahr, S. Rolf, M. Ribbing, P. Loh, et al., Electrophysiologic investigation in Brugada syndrome; yield of programmed ventricular

96

[28]

[29]

[30]

[31]

[32]

[33] [34]

[35] [36]

[37]

S.C.H. Van Malderen et al. / International Journal of Cardiology 191 (2015) 90–96 stimulation at two ventricular sites with up to three premature beats, Eur. Heart J. 23 (2002) 1394–1401. H. Morita, K. Fukushima-Kusano, S. Nagase, S. Takenaka-Morita, N. Nishii, M. Kakishita, et al., Site-specific arrhythmogenesis in patients with Brugada syndrome, J. Cardiovasc. Electrophysiol. 14 (2003) 373–379. M. Haïssaguerre, F. Extramiana, M. Hocini, B. Cauchemez, P. Jaïs, J.A. Cabrera, et al., Mapping and ablation of ventricular fibrillation associated with long-QT and Brugada syndromes, Circulation 108 (2003) 925–928. F. Rouzet, V. Algalarrondo, S. Burg, P. Nassar, L. Sarda-Mantel, P. Aouate, et al., Contraction delay of the RV outflow tract in patients with Brugada syndrome is dependent on the spontaneous ST-segment elevation pattern, Heart Rhythm. 8 (2011) 1905–1912. P.D. Lambiase, A.K. Ahmed, E.J. Ciaccio, R. Brugada, E. Lizotte, S. Chaubey, et al., Highdensity substrate mapping in Brugada syndrome: combined role of conduction and repolarization heterogeneities in arrhythmogenesis, Circulation 120 (2009) 106–117. A.K. Gehi, T.D. Duong, L.D. Metz, J.A. Gomes, D. Mehta, Risk stratification of individuals with the Brugada electrocardiogram: a meta-analysis, J. Cardiovasc. Electrophysiol. 17 (2006) 577–583. L. Eckardt, Gender differences in Brugada syndrome, J. Cardiovasc. Electrophysiol. 18 (2007) 422–424. J.M. Di Diego, J.M. Cordeiro, R.J. Goodrow, J.M. Fish, A.C. Zygmunt, G.J. Pérez, et al., Ionic and cellular basis for the predominance of the Brugada syndrome phenotype in males, Circulation 106 (2002) 2004–2011. J.M. Di Diego, Ionic and cellular basis for the predominance of the Brugada syndrome phenotype in males, Circulation 106 (2002) 2004–2011. L.G. Rudski, W.W. Lai, J. Afilalo, L. Hua, M.D. Handschumacher, K. Chandrasekaran, et al., Guidelines for the echocardiographic assessment of the right heart in adults: a report from the American Society of Echocardiography endorsed by the European Association of Echocardiography, a registered branch of the European Society of Cardiology, and t, J. Am. Soc. Echocardiogr. 23 (2010) 685–713. S.G. Priori, C. Napolitano, Should patients with an asymptomatic Brugada electrocardiogram undergo pharmacological and electrophysiological testing? Circulation 112 (2005) 279–292.

[38] T. Szél, C. Antzelevitch, Abnormal repolarization as the basis for late potentials and fractionated electrograms recorded from epicardium in experimental models of Brugada syndrome, J. Am. Coll. Cardiol. 63 (2014) 2037–2045. [39] M.G. Hoogendijk, M. Potse, A.C. Linnenbank, A.O. Verkerk, H.M. den Ruijter, S.C.M. van Amersfoorth, et al., Mechanism of right precordial ST-segment elevation in structural heart disease: excitation failure by current-to-load mismatch, Heart Rhythm. 7 (2010) 238–248. [40] T.A.B. Van Veen, M. Stein, A. Royer, K. Le Quang, F. Charpentier, W.H. Colledge, et al., Impaired impulse propagation in Scn5a-knockout mice: combined contribution of excitability, connexin expression, and tissue architecture in relation to aging, Circulation 112 (2005) 1927–1935. [41] J.A. Jansen, M. Noorman, H. Musa, M. Stein, S. de Jong, R. van der Nagel, et al., Reduced heterogeneous expression of Cx43 results in decreased Nav1.5 expression and reduced sodium current that accounts for arrhythmia vulnerability in conditional Cx43 knockout mice, Heart Rhythm. 9 (2012) 600–607. [42] J.P.P. Smits, L. Eckardt, V. Probst, C.R. Bezzina, J.J. Schott, C.A. Remme, et al., Genotype-phenotype relationship in Brugada syndrome: electrocardiographic features differentiate SCN5A-related patients from non-SCN5A-related patients, J. Am. Coll. Cardiol. 40 (2002) 350–356. [43] J.M. Rhett, E.L. Ongstad, J. Jourdan, R.G. Gourdie, Cx43 associates with Na(v)1.5 in the cardiomyocyte perinexus, J. Membr. Biol. 245 (2012) 411–422. [44] H.V.M. Van Rijen, D. Eckardt, J. Degen, M. Theis, T. Ott, K. Willecke, et al., Slow conduction and enhanced anisotropy increase the propensity for ventricular tachyarrhythmias in adult mice with induced deletion of connexin43, Circulation 109 (2004) 1048–1055. [45] P.G. Meregalli, H.L. Tan, V. Probst, T.T. Koopmann, M.W. Tanck, Z.A. Bhuiyan, et al., Type of SCN5A mutation determines clinical severity and degree of conduction slowing in loss-of-function sodium channelopathies, Heart Rhythm. 6 (2009) 341–348. [46] N.M. Thomas, J.F. Jasmin, M.P. Lisanti, D.A. Iacobas, Sex differences in expression and subcellular localization of heart rhythm determinant proteins, Biochem. Biophys. Res. Commun. 406 (2011) 117–122. [47] K. Jeevaratnam, R. Rewbury, Y. Zhang, L. Guzadhur, A.A. Grace, M. Lei, et al., Frequency distribution analysis of activation times and regional fibrosis in murine Scn5a +/− hearts: the effects of ageing and sex, Mech. Ageing Dev. 133 (2012) 591–599.