T-wave alternans poorly prognostic in primary prophylactic ICD patients: a prospective EU-CERT-ICD study

Background

New methods to identify patients who truly benefit from primary prophylactic implantable cardioverter defibrillation (ICD) are urgently needed. T-wave alternans (TWA) represents a beat-to-beat fluctuation in the morphology of the ST-segment and T-wave. It has been shown to associate with arrhythmogenesis of heart and sudden cardiac death [1]. We hypothised that TWA might associate with benefit from ICD implantation in primary prevention.

Methods

In EU-CERT-ICD study, we prospectively enrolled 2327 primary prophylactic ICD candidates from 15 European countries. A 24-hours Holter-monitoring was taken from all recruited patients at enrolment. TWA was assessed from Holter-monitoring using MMA method with Getemed Cardioday software. To assess the benefit from ICD treatment, we used outcomes all-cause mortality, appropriate shock and survival benefit. We conducted Cox regression model, competing risk regression model and propensity score adjusted Cox regression model. TWA was assessed both as contiguous variable and with cut-off points <47 μV and <60 μV.

Results

Final cohort included 1,734 valid T-wave alternans samples, 1,211 patients with ICD and 523 control patients with conservative treatment, with mean follow-up time 2.3 years. TWA <60 μV predicted lower all-cause mortality in ICD patients in univariate cox regression model (HR 1.484, 95% CI 1.024–2.151, p=0.0374). In multivariate models, TWA did not predict death or appropriate shocks in ICD patients. In addition, TWA did not predict death in control patients. In propensity score adjusted Cox regression model, TWA did not predict ICD benefit.

Conclusion

T-wave alternans is poorly prognostic in primary prophylactic ICD patients. Altough it may predict life-threatening arrhythmias and sudden cardiac death in several patient populations, it cannot be used in assessing benefit from implantable cardioverter defibrillator in primary prevention among patients with ejection fraction ≤35%.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Community's 7th Framework Program FP7/2007-2013

PI3K/mTOR inhibitor omipalisib prolongs cardiac repolarization along with a mild proarrhythmic outcome in the AV block dog model

Background

The phosphoinositide 3-kinase (PI3K) signaling pathway is an interesting target in cancer treatment. The awareness of the proarrhythmic risk of PI3K inhibitors was raised because PI3K is also involved in regulating signaling toward cardiac ion channels. Canine cardiomyocytes treated with PI3K inhibitors show an increased action potential duration and reduced cardiac repolarizing currents. Now, the potential proarrhythmic effect of chronic treatment of PI3K/mTOR inhibitor GSK2126458 (omipalisib) was investigated in the atrioventricular (AV) block dog model.

Methods

Purpose-bred Mongrel dogs received complete AV block by ablation of the bundle of His and their hearts were paced in the right ventricular apex at VDD-mode (RVA-VDD). In this way, sinus rhythm was maintained for 15 ± 1 days and thereby bradycardia-induced cardiac remodeling was prevented. Dogs received 1 mg/kg omipalisib once (n = 3) or twice (n = 10) a day via oral administration for 7 days. Under standardized conditions (anesthesia, bradycardia at 60 beats/min, and a dofetilide challenge), potential proarrhythmic effects of omipalisib were investigated.

Results

Twice daily dosing of omipalisib increased accumulative plasma levels compared to once daily dosing accompanied with adverse events. Omipalisib prolonged the QT interval at baseline and more strongly after the dofetilide challenge (490 ± 37 to 607 ± 48 ms). The arrhythmic outcome after omipalisib resulted in single ectopic beats in 30% of dogs perpetuating in multiple ectopic beats and TdP arrhythmia in 20% of dogs. Isolated ventricular cardiomyocytes from omipalisib-treated dogs showed a diminished I_Ks current density.

Conclusion

Chronic treatment of PI3K/mTOR inhibitor omipalisib prolonged the QT interval in a preclinical model under standardized proarrhythmic conditions. Furthermore, this study showed that electrical remodeling induced by omipalisib had a mild proarrhythmic outcome.

Buccal mucosa cells as a potential diagnostic tool to study onset and progression of arrhythmogenic cardiomyopathy

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Netherlands Cardio Vascular Research Initiative (CVON) and 'Stichting Vriendenloterij'

Background

Arrhythmogenic cardiomyopathy (ACM) is predominantly caused by pathogenic variants in genes encoding desmosomal proteins (most often plakophilin-2). However, such variants are also found in genes encoding non-desmosomal proteins, such as phospholamban (PLN, p.Arg14del variant). Previous research showed that plakoglobin protein levels and localization in cardiac tissue of ACM patients, and p.Arg14del patients diagnosed with an ACM phenotype, are disturbed and this could be an additional tool to identify variant carriers at risk of developing ACM. Information about plakoglobin status can only be obtained via endocardial biopsies, however, this technique has major drawbacks, and therefore an alternative is needed. A promising new non-invasive tool is the use of buccal mucosa cells (BMC), as it has been reported that effects of pathogenic variants in desmosomal genes are reflected in non-cardiac tissues like BMC smears that also express those genes.

Purpose

To investigate the clinical usability of BMC as a tool to classify patients at risk of developing ACM by comparing controls with preclinical variant carriers and symptomatic ACM patients, and patients carrying the PLN p.Arg14del variant being preclinical, diagnosed with ACM or dilated cardiomyopathy (DCM).

Methods

BMC of 33 ACM patients (19 males, 28 with a PKP2 mutation), 17 PLN p.Arg14del patients (6 males, 3 diagnosed with ACM, 7 DCM and 7 preclinical carriers) and 34 controls (14 males), were collected on glass slides, fixed and labelled with anti-plakoglobin antibodies diluted 1:5.000, 1:10.000, 1:20.000 and 1:40.000, and scored for their membrane labelling.

Results

Data revealed that for each dilution, plakoglobin protein levels at the membrane were significantly reduced in BMC obtained from ACM patients (both in symptomatic patients and in preclinical variant carriers) when compared to controls. This effect was independent from age and sex of the patients. Dilutions 1:5.000 and 1:10.000 showed a moderate to strong correlation with the revised 2010 Task Force Criteria Score (TFC) which is commonly used for ACM diagnosis (rs  = -0.67, n=64, p<0.0001 and rs = -0.71, n=64, p<0.0001 resp.). In contrast, plakoglobin scores of PLN p.Arg14del patients were comparable to controls (p>0.209).

Conclusion

There is a significant reduction of plakoglobin protein in BMC of ACM patients and carriers with variants predisposing to ACM, but not for patients carrying the PLN p.Arg14del variant when compared to controls. However, for clinical diagnosis of the individual ACM patient, this method is not discriminative enough to distinguish true patients from preclinical variant carriers and controls, because of high interindividual variability.

Determining the role of uremic toxins on cardiac electrophysiology and pro-arrhythmia during chronic kidney disease

Funding Acknowledgements

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Young Talent Programme, CVON RECONNECT

Introduction

Chronic kidney disease (CKD) is represented by a diminished filtration capacity of the kidneys. End stage renal disease patients need dialysis treatment to remove waste and toxins from the circulation. However, endogenously produced uremic toxins (UTs) cannot always be filtered during dialysis. UTs are one of the CKD-related factors already linked to maladaptive and pathophysiological remodeling of the heart. Importantly, 50% of the deaths in dialysis patients is cardiovascular related, with sudden cardiac death predominating. However, the mechanisms responsible still remain poorly understood.

Purpose

To assess the potentially increased pro-arrhythmic risk of pre-identified UTs at clinically relevant concentrations: 1) acutely in isolated adult dog ventricular cardiomyocytes (ADCMs) and human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs), 2) chronically in iPSC-CMs and 3) both conditions in human embryonic kidney (HEK) cells transfected with constructs that generate different ion channels, using optical and manual electrophysiological in vitro approaches.

Methods and results

Using the voltage sensitive membrane dye FluoVolt and manual patch clamp, action potential duration (APD) prolongation, considered as a pro-arrhythmic parameter, was assessed in ADCMs and iPSC-CMs. Acute exposure of indoxyl sulfate (IS), kynurenine (KYN) or kynurenic acid (KYNA) induced no alterations in APD in ADCMs and iPSC-CMs. iPSC-CMs, although having rather immature electrophysiological characteristics, showed significant APD prolongation when exposed chronically (48h) to those UTs.

Manual patch clamp on HEK293 cells was performed to investigate individual ion currents to reveal underlying mechanisms. The repolarizing current IKr, often most sensitive and responsible for APD alterations, was not acutely affected by IS, KYN, or KYNA. However, chronic exposure (48h) to IS or KYNA significantly decreased IKr at clinically relevant concentrations.

Finally, the protein level of the ion channel conducting IKr was determined in HEK293 cells, to further unveil the mechanism behind the effects of UTs on channels conducting IKr. Chronic exposure (48-72h) of the three UTs decreased total ion channel expression at pathological concentrations, which could be responsible for the decreased IKr and prolonged APD.

Conclusion

The results show the proof of concept to identify potentially pro-arrhythmogenic UTs and their mode of action, allowing the provision of a clinically relevant overview of (patho)physiological concentrations of UTs in both acute and chronic exposure.

Dg-mapping as a tool to determine the spatial distribution of the focal sources and the number of reentries during torsade de pointes in the cavb dog model

Funding Acknowledgements

Type of funding sources: None.

Background

Torsade de Pointes (TdP) is a ventricular tachycardia that is still incompletely understood. While the origin of the arrhythmia is generally accepted to be caused by triggered activity, the perpetuation of such an episode is still under debate.

Purpose

We compare the difference in reentrant activity between self- and non-terminating(ST and NT) TdP episodes. In addition, we analyzed the distribution of the triggered activity for preferred locations.

Methods

A total of 5 dogs with Chronic Atrioventricular Block developed 54 episodes of TdP. These episodes were examined for reentry loops and focal sources. First, to detect loops, we used Directed Graph Mapping, a novel mapping technique based on principles from network theory. Subsequently, the number of simultaneous loops and the presence of (bi-)ventricular reentry was compared between the ST and NT groups. Second, focal sources were accumulated into heatmaps. The distribution of sources was compared to a randomly distributed model for the detection of preferred locations.

Results

Concerning reentry, during the time at which loops are present, a typical ST episode shows an average of 1.33(±0.66) reentry loops present at one time compared to an average of 2.72(±1.48) for a typical NT episode. Looking at the (bi-)ventricular reentry, only 1 of the 4 ST episodes (25%) shows the presence of this type of reentry and only 7.12 % of the total reentry duration, while all 9 NT episodes (100%) develop (bi-)ventricular reentry to a greater degree than in the one ST episode (Between 10.10% and 69.62% of their total reentry duration). Regarding the triggered activity, we see locations in the heatmaps containing up to 23% of all detected focal sources in the entire system. Compared to a random distribution of focal sources, the chances to get as many sources in one location as shown in the data are close to 0%.

Conclusion

Reentry in NT TdP differentiates itself from the reentry in ST cases on the basis of the number of simultaneous loops in the system and the presence of (bi-)ventricular reentry. Triggered activity in CAVB dogs occurs at preferred locations in the ventricles. Therefore, ablating these preferred regions could be a possible strategy to prevent TdP.

Determining the role of uremic toxins on cardiac electrophysiology and pro-arrhythmia during chronic kidney disease

Funding Acknowledgements

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Young Talent Programme, CVON

Introduction

Chronic kidney disease (CKD) is represented by a diminished filtration capacity of the kidneys. End stage renal disease patients need dialysis treatment to remove waste and toxins from the circulation. However, endogenously produced uremic toxins (UTs) cannot always be filtered during dialysis. UTs are one of the CKD-related factors already linked to maladaptive and pathophysiological remodeling of the heart. Importantly, 50% of the deaths in dialysis patients is cardiovascular related, with sudden cardiac death predominating. However, the mechanisms responsible still remain poorly understood.

Purpose

To assess the potentially increased pro-arrhythmic risk of pre-identified UTs at clinically relevant concentrations: 1) acutely in isolated adult dog ventricular cardiomyocytes (ADCMs) and human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs), 2) chronically in iPSC-CMs and 3) both conditions in human embryonic kidney (HEK) cells transfected with constructs that generate different ion channels, using optical and manual electrophysiological in vitro approaches.

Methods and results

Using the voltage sensitive membrane dye FluoVolt and manual patch clamp, action potential duration (APD) prolongation, considered as a pro-arrhythmic parameter, was assessed in ADCMs and iPSC-CMs. Acute exposure of indoxyl sulfate (IS), kynurenine (KYN) or kynurenic acid (KYNA) induced no alterations in APD in ADCMs and iPSC-CMs. iPSC-CMs, although having rather immature electrophysiological characteristics, showed significant APD prolongation when exposed chronically (48h) to those UTs.

Manual patch clamp on HEK293 cells was performed to investigate individual ion currents to reveal underlying mechanisms. The repolarizing current IKr, often most sensitive and responsible for APD alterations, was not acutely affected by IS, KYN, or KYNA. However, chronic exposure (48h) to IS or KYNA significantly decreased IKr at clinically relevant concentrations.

Finally, the protein level of the ion channel conducting IKr was determined in HEK293 cells, to further unveil the mechanism behind the effects of UTs on channels conducting IKr. Chronic exposure (48-72h) of the three UTs decreased total ion channel expression at pathological concentrations, which could be responsible for the decreased IKr and prolonged APD.

Conclusion

The results show the proof of concept to identify potentially pro-arrhythmogenic UTs and their mode of action, allowing the provision of a clinically relevant overview of (patho)physiological concentrations of UTs in both acute and chronic exposure.

QRS duration as an independent risk factor for appropriate shocks and mortality in patients with prophylactic implantable cardioverter-defibrillator

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Community’s 7th Framework Programme FP7/2007-2013

Background

The implantable cardioverter defibrillator (ICD) is an established therapy for the prevention of sudden cardiac death (SCD) in high-risk heart failure patients. However, improvements in risk stratification are necessary to increase the efficiency of ICD use. We performed an analysis of the retrospective EU-CERT-ICD registry with respect to QRS duration and effects of cardiac resynchronisation therapy (CRT) on outcomes.

Methods/Results

A total of 5033 patients (81% males) from 14 European centres had an ICD implanted for primary prophylaxis. Mean age at the time of ICD implantation was 64±11 years and ischemic cardiomyopathy was the underlying pathology in 65% of patients. CRT was used in 43% of the patients. The median follow-up was 2.7 years (IQR 1.4-4.6 years). Predefined primary endpoints were all-cause mortality, first appropriate and first inappropriate shocks. The effect of covariates on the cumulative primary endpoints were assessed through hazard ratios in the Fine and Gray subdistributional hazard models (accounting for the competing risks) stratified by centres.

Because of resynchronization by the device, the analysis considered a different influence of QRS on outcomes in the CRT-D and the ICD groups. We observed an increase in the cumulative incidence of the first appropriate shock with increasing QRS values for patients implanted with only an ICD (HR 1.12 per 10ms increase, p<0.001). In patients with CRT-D, increasing QRS values related to a (statistically non-significant) decrease in the cumulative incidence of the first appropriate shocks (HR 0.96 per 10ms, p=0.299).

Since a wide QRS is an indication for CRT-D therapy, high QRS values cluster among those patients with implanted CRT-D, while among patients with QRS under 130ms standard ICD implantations are more frequent. This can explain the observed increase in the cumulative incidence of the first appropriate shocks for increasing QRS values up to 130ms in the ICD-group and its decrease for increasing QRS values over 130ms in the CRT-D group.

Regarding all-cause mortality, hazard ratios for age, LVEF, NYHA, ICM, AF, diabetes and sex category agreed with the results obtained in previously published meta-analyses.

Increased QRS values are associated with higher mortality in the ICD group (HR 1.09 per 10ms increase, p<0.001), but not in the CRT-D group (HR 0.99 per 10ms increase, p=0.695).

Conclusion

In our study, we confirmed QRS duration as an independent risk factor for appropriate ICD shocks and all-cause mortality in patients with ICD for primary prophylaxis. However, this was only observed in patients with single- or dual-chamber ICD, while there was no correlation in CRT-D patients. The findings suggest that CRT-D exerts a protective effect regarding the occurrence of first appropriate shock and all-cause mortality for patients with QRS values higher than 130 ms and indication for resynchronization.

Istaroxime treatment ameliorates calcium dysregulation in a zebrafish model of phospholamban R14del cardiomyopathy

The heterozygous Phospholamban p.Arg14del mutation is found in patients with dilated or arrhythmogenic cardiomyopathy. This mutation triggers cardiac contractile dysfunction and arrhythmogenesis by affecting intracellular Ca2+ dynamics. Little is known about the physiological processes preceding induced cardiomyopathy, which is characterized by sub-epicardial accumulation of fibrofatty tissue, and a specific drug treatment is currently lacking. Here, we address these issues using a knock-in Phospholamban p.Arg14del zebrafish model. Hearts from adult zebrafish with this mutation display age-related remodeling with sub-epicardial inflammation and fibrosis. Echocardiography reveals contractile variations before overt structural changes occur, which correlates at the cellular level with action potential duration alternans. These functional alterations are preceded by diminished Ca2+ transient amplitudes in embryonic hearts as well as an increase in diastolic Ca2+ level, slower Ca2+ transient decay and longer Ca2+ transients in cells of adult hearts. We find that istaroxime treatment ameliorates the in vivo Ca2+ dysregulation, rescues the cellular action potential duration alternans, while it improves cardiac relaxation. Thus, we present insight into the pathophysiology of Phospholamban p.Arg14del cardiomyopathy.

Short-term variability of repolarization is equally modulated by atrial and (bi)ventricular high rate pacing in patients with an indication for an implantable cardioverter defibrillator

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Dutch Heart Foundation

Background

 An increase in temporal dispersion of repolarization, quantified as short-term variability of the QT-interval (STV-QT), precedes ventricular arrhythmias and has therefore been proposed as a marker for monitoring of imminent arrhythmic risk. A reversal of an increased STV by high rate pacing at 100 bpm was anti-arrhythmic in the chronic atrioventricular block dog model susceptible to Torsade de Pointes arrhythmias upon challenge with an IKr-blocker. The objective of the current study was to investigate the physiological modulation of STV by pacing in patients with an indication for an implantable cardioverter defibrillator (ICD), and to compare atrial and ventricular pacing.

Methods

 ECG recordings were obtained with a sampling frequency of 1200 Hz in 10 dual chamber ICD patients and 10 patients with cardiac resynchronization therapy with defibrillation function (CRT-D) during the implantation or replacement. One-minute recordings were made during sinus rhythm (SR), and during pacing at 80 and 100 beats per minute (bpm) from the atrium (AAI), atrium and right ventricle (DDD RVp), and during atrio-biventricular pacing (DDD BiVp). The QT-interval was determined offline with fiducial segment averaging at one minute of each pacing rate, and 31 consecutive beats were used to calculate STV-QT with the following formula: ∑|D(n + 1)-Dn |/(N×√2), where D represents the determinant of repolarization (in this case the QT interval), and N represents the number of beats taken into account minus 1.

Results

 In the patients overall, STV-QT decreased from 1.27 ± 0.38 ms in SR (±58 bpm) to 0.86 ± 0.26 ms* during AAI80, and to 0.68 ± 0.22 ms*† during AAI100 (*p < 0.05 compared to SR, †p < 0.05 compared to 80 bpm). The same decrease was seen during DDD80 RVp (0.81 ± 0.28 ms*) and during DDD100 RVp (0.66 ± 0.22 ms*†) (fig. 1). Additionally, DDD BiVp decreased STV-QT to 0.78 ± 0.20 ms* at 80 bpm and to 0.62 ± 0.19 ms* at 100 bpm in CRT-D patients (fig. 2).

Conclusion

 Pacing at 80 and 100 bpm decreases STV-QT compared to sinus rhythm both in dual chamber ICD patients and CRT-D patients. The modulation of STV-QT is similar during atrial, and atrio- right ventricular and atrio-biventricular pacing. Abstract Figure. Modulation of STV-QT by AAI and DDD RVp

Fibrosis biomarkers as a predictive tool for clinical outcome in PLNR14Del patients

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): Netherlands Cardio Vascular Research Initiative (CVON): the Dutch heart foundation

Background

Mutations in phospholamban (PLN, most often PLNR14Del), a protein that regulates Ca2+ homeostasis in cardiomyocytes, are found in patients diagnosed with arrhythmogenic (ACM) and dilated cardiomyopathy (DCM). Fibrosis formation in the heart is one of the hallmarks in PLN patients, which compromises cardiac contractility and predisposes to arrhythmogenicity. Collagen type I is the most abundant type of collagen in the heart (85%). During continuous collagen synthesis propeptides, like procollagen type I carboxy-terminal propeptide (PICP) and during collagen breakdown, C-terminal telopeptide collagen type I (ICTP), are released into the circulation. Clinically, detection of fibrosis occurs via echo or MRI, however difficulties arise when patchy fibrosis has to be detected.

Purpose

To investigate if PICP and ICTP levels in blood are useful predictive biomarkers for clinical outcome in PLN patients.

Methods

78 serum and EDTA blood samples were collected on the same day from ACM diagnosed (n = 12), DCM diagnosed (n = 14) or non-classified (n = 52) PLN patients. PICP levels were measured with an ELISA assay and ICTP with a RIA. Clinical data were subtracted two years around blood collection from Redcap, a Dutch database with medical records from PLN patients. Data were not normally distributed, so Spearman’s correlation coefficient and Mann-Whitney test were used.

Results

Gender, age and PICP/ICTP ratios were similarly distributed between the subgroups. First, we checked if clinical data subtracted two years around blood collection provided reliable results regarding clinical outcome. Patients who underwent clinical testing  5.5 weeks around blood collection revealed that clinical data were in line with the best-fitted line of the linear regression and therefore provide reliable results. Next, the potential correlation of fibrosis biomarkers with electrical parameters was assessed. Increased PICP/ICTP ratios suggest a higher collagen deposition. Although there was no correlation with prolonged QRS duration (Rs 0.13, n = 62, ns), subgroup analysis showed a significant weak correlation for non-classified patients (Rs 0.32, n = 38, p = 0.05). No significant correlation was found for ACM or DCM patients; however, groups were rather small. PICP/ICTP ratio was significantly higher in patients with T wave inversion and premature ventricular contractions (PVCs) during an exercise tolerance test. A weak inverted correlation was found with left ventricular ejection fraction and PICP/ICTP (Rs -0.28, n = 23, ns), while moderate correlations between the ratio and end diastolic volume, and end systolic volume exist (both Rs 0.40, n = 23, p = 0.06).

Conclusion

High PICP/ICTP ratios correlate with clinical outcome in PLN patients, such as T wave inversion and PVCs. However, the size and heterogeneity of the patient group resulted in weak to moderate correlation coefficients and might therefore currently precludes to use PICP and ICTP levels as biomarker.

Buccal mucosa cells as a diagnostic tool in patients with arrhythmogenic cardiomyopathy

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): Netherlands Cardio Vascular Research Initiative (CVON): the Dutch heart foundation

Background

Arrhythmogenic cardiomyopathy (ACM) is predominantly caused by mutations in genes encoding desmosomal proteins (most often multiple different mutations in plakophilin-2), however also mutations in non-desmosomal proteins like phospholamban (PLN, PLNR14Del) are found. Previous investigations showed that plakoglobin protein levels and localization in cardiac tissue of ACM patients is disturbed and this could be a valuable additional tool to discriminate between non-affected family members and those being at risk during progression of the disease. Information about cardiac plakoglobin status can only be obtained via endocardial biopsies, however, this technique has major draw-backs and risks, and therefore an alternative is needed. A promising new non-invasive tool is the use of buccal mucosa cells (BMC), as it has been reported that effects of mutations in desmosomal proteins are additionally reflected in non-cardiac tissues like buccal mucosa smears that do also express those desmosomal genes.

Purpose

To investigate the clinical usability of BMC as tool to classify patients at risk of developing ACM by comparing healthy controls with asymptomatic and symptomatic classical ACM patients, and patients carrying a PLNR14Del mutation.

Methods and results

BMC of 84 human subjects, 33 ACM patients (19 males, 28 with a PKP2 mutation), 17 PLN patients (6 males) and 34 healthy controls (14 males), were collected on glass slides, fixed and labelled with anti-plakoglobin antibodies diluted 1:5.000, 1:10.000, 1:20.000 and 1:40.000, and scored for their membrane labelling. Data revealed that for each applied dilution, plakoglobin protein levels at the membrane were significantly reduced in BMC obtained from ACM patients compared to healthy controls. This effect appeared independent from age and sex of the patients. Furthermore, dilutions 1:5.000 and 1:10.000 showed a moderate correlation with the revised 2010 Task Force Criteria Score (TFC) which are commonly used for ACM diagnosis (Rs -0.67, n = 64, p <0.0001 and Rs -0.71, n = 64, p < 0.0001 resp.) In contrast, plakoglobin scores of PLN patients were similar to controls.

Conclusion

On the population level, there is a significant reduction of plakoglobin protein in BMC membranes of ACM patients but not for patients bearing the PLNR14Del mutation when compared to healthy controls. However, for clinical diagnosis of the individual patient, this method is most likely not discriminative enough to distinguish patients from healthy controls, because of the high interindividual variability.

The risk of ventricular arrhythmias in a Dutch CRT population: CRT-defibrillator versus CRT-pacemaker

Background

Patients eligible for cardiac resynchronisation therapy (CRT) have an indication for primary prophylactic implantable cardioverter defibrillator (ICD) therapy. However, response to CRT might influence processes involved in arrhythmogenesis and therefore change the necessity of ICD therapy in certain patients.

Method

In 202 CRT-defibrillator patients, the association between baseline variables, 6-month echocardiographic outcome (volume response: left ventricular end-systolic volume decrease < ≥15 % and left ventricular ejection fraction (LVEF) ≤ >35 %) and the risk of first appropriate ICD therapy was analysed retrospectively.

Results

Fifty (25 %) patients received appropriate ICD therapy during a median follow-up of 37 (23–52) months. At baseline ischaemic cardiomyopathy (hazard ratio (HR) 2.0, p = 0.019) and a B-type natriuretic peptide level > 163 pmol/l (HR 3.8, p < 0.001) were significantly associated with the risk of appropriate ICD therapy. After 6 months, 105 (52 %) patients showed volume response and 51 (25 %) reached an LVEF > 35 %. Three (6 %) patients with an LVEF > 35 % received appropriate ICD therapy following echocardiography at ± 6 months compared with 43 patients (29 %) with an LVEF ≤ 35 % (p = 0.001). LVEF post-CRT was more strongly associated to the risk of ventricular arrhythmias than volume response (LVEF > 35 %, HR 0.23, p = 0.020).

Conclusion

Assessing the necessity of an ICD in patients eligible for CRT remains a challenge. Six months post-CRT an LVEF > 35 % identified patients at low risk of ventricular arrhythmias. LVEF might be used at the time of generator replacement to identify patients suitable for downgrading to a CRT-pacemaker.

T-Wave Alternans Is Linked to Microvascular Obstruction and to Recurrent Coronary Ischemia After Myocardial Infarction

The purpose of this study is to investigate the relationship between T-wave alternans (TWA), infarct size and microvascular obstruction (MVO) and recurrent cardiac morbidity after ST elevation myocardial infarction (STEMI). One hundred six patients underwent TWA testing 1-12 months and 57 patients underwent cardiac magnetic resonance imaging (MRI) in the first 2-4 days after STEMI. During follow-up (3.5 ± 0.5 years), death (n = 2), ventricular tachycardia (n = 3), supraventricular tachycardia (n = 4), heart failure (n = 3) and recurrent coronary ischemia (n = 25) were observed. After multivariate analysis, positive TWA (HR2.59, CI1.10-6.11, p0.024) and larger MVO (HR1.08, CI1.01-1.16, p0.034) were associated with recurrent angina or ACS. Presence of MVO was correlated with TWA (Spearman rho 0.404, p0.002) and the impairment of LVEF (-0.524, p < 0.001). Patients after STEMI remain at a high risk of symptoms of coronary ischemia. The presence of MVO and TWA 1-12 months after STEMI is related to each other and to recurrent angina or ACS.

The electromechanical window is no better than QT prolongation to assess risk of Torsade de Pointes in the complete atrioventricular block model in dogs

BACKGROUND AND PURPOSE

The electromechanical window (EMW), the interval between the end of the T-wave and the end of the left ventricular pressure (LVP) curve, has recently been proposed as a predictor of risk of Torsade de Pointes (TdP) in healthy animals, whereby a negative EMW (mechanical relaxation earlier than repolarization) after drug administration indicates an increased TdP risk. The aims of this study were to assess (i) the effect of the ventricular remodelling in the canine chronic, complete atrioventricular block (CAVB) model on EMW; (ii) the effect of the I(Kr) -blocker dofetilide on EMW; and (iii) the correlation of EMW with TdP inducibility.

EXPERIMENTAL APPROACH

Our 11 year database of experiments of CAVB in dogs under general anaesthesia was reviewed and experiments included if ECG and LVP were recorded simultaneously at spontaneous rhythm. In total, 89 experiments in 44 dogs were appropriate and were analysed.

KEY RESULTS

During normally conducted sinus rhythm or acute atrioventricular block, EMW was positive. During CAVB, EMW was decreased to negative values. Dofetilide further reduced EMW before inducing repetitive TdP in 82% of the experiments. However, subclassification into inducible and non-inducible dogs revealed no difference in EMW. Analysis of the components of EMW revealed that the observed changes in EMW were solely caused by QT prolongation.

CONCLUSIONS AND IMPLICATIONS

In the canine CAVB model, ventricular remodelling and I(Kr) block by dofetilide are associated with negative EMW values, but this reflects QT prolongation, and implies that the EMW lacks specificity to predict dofetilide-induced TdP.

Structure-activity relationships of pentamidine-affected ion channel trafficking and dofetilide mediated rescue

BACKGROUND AND PURPOSE

Drug interference with normal hERG protein trafficking substantially reduces the channel density in the plasma membrane and thereby poses an arrhythmic threat. The chemical substructures important for hERG trafficking inhibition were investigated using pentamidine as a model drug. Furthermore, the relationship between acute ion channel block and correction of trafficking by dofetilide was studied.

EXPERIMENTAL APPROACH

hERG and K(IR)2.1 trafficking in HEK293 cells was evaluated by Western blot and immunofluorescence microscopy after treatment with pentamidine and six pentamidine analogues, and correction with dofetilide and four dofetilide analogues that displayed different abilities to inhibit IKr . Molecular dynamics simulations were used to address mode, number and type of interactions between hERG and dofetilide analogues.

KEY RESULTS

Structural modifications of pentamidine differentially affected plasma membrane levels of hERG and K(IR)2.1. Modification of the phenyl ring or substituents directly attached to it had the largest effect, affirming the importance of these chemical residues in ion channel binding. PA-4 had the mildest effects on both ion channels. Dofetilide corrected pentamidine-induced hERG, but not K(IR)2.1 trafficking defects. Dofetilide analogues that displayed high channel affinity, mediated by pi-pi stacks and hydrophobic interactions, also restored hERG protein levels, whereas analogues with low affinity were ineffective.

CONCLUSIONS AND IMPLICATIONS

Drug-induced trafficking defects can be minimized if certain chemical features are avoided or 'synthesized out'; this could influence the design and development of future drugs. Further analysis of such features in hERG trafficking correctors may facilitate the design of a non-blocking corrector for trafficking defective hERG proteins in both congenital and acquired LQTS.

New antiarrhythmic targets to control intracellular calcium handling

Sudden cardiac death due to ventricular arrhythmias is a major problem. Drug therapies to prevent SCD do not provide satisfying results, leading to the demand for new antiarrhythmic strategies. New targets include Ca²⁺/Calmodulin-dependent protein kinase II (CaMKII), the Na/Ca exchanger (NCX), the Ryanodine receptor (RyR, and its associated protein FKBP12.6 (Calstabin)) and the late component of the sodium current (I_Na-Late), all related to intracellular calcium (Ca²⁺) handling. In this review, drugs interfering with these targets (SEA-0400, K201, KN-93, W7, ranolazine, sophocarpine, and GS-967) are evaluated and their future as clinical compounds is considered. These new targets prove to be interesting; however more insight into long-term drug effects is necessary before clinical applicability becomes reality.

Implementation of guidelines for implantable cardioverter-defibrillator therapy in clinical practice: Which patients do benefit?

PURPOSE

Based on multiple large clinical trials conducted over the last decades guidelines for implantable cardioverter-defibrillator (ICD) implantations have been evolving. The increase in primary prophylactic ICD implantations challenges us to be critical towards the indications in certain patient populations.

METHODS

We retrospectively collected patient characteristics and rates of appropriate and inappropriate ICD therapy, appropriate and inappropriate ICD shock and mortality of all patients who received an ICD in the University Medical Center Utrecht (UMCU) over the years 2006-2011.

RESULTS

A total of 1075 patients were included in this analysis (74 % male, mean age 61 ± 13 years, left ventricular ejection fraction 30 ± 13 %); 61 % had a primary indication and 58 % had ischaemic heart disease. During a mean follow-up period of 31 ± 17 months, 227 of the patients (21 %) received appropriate ICD therapy (149 (14 %) patients received an appropriate ICD shock). Females, patients with a primary prophylactic indication and patients with non-ischaemic heart disease experienced significantly less ICD therapy. Only a few patients (54, 5 %) received inappropriate ICD therapy; 33 (3 %) patients received an inappropriate ICD shock. Fifty-five patients died within one year after ICD implantation and were therefore, in retrospect, not eligible for ICD implantation.

CONCLUSION

Our study confirms the benefit of ICD implantation in clinical practice. Nevertheless, certain patients experience less benefit than others. A more patient-tailored risk stratification based on electrophysiological parameters would be lucrative to improve clinical benefit and cost-effectiveness.

JTV519 (K201) reduces sarcoplasmic reticulum Ca²⁺ leak and improves diastolic function in vitro in murine and human non-failing myocardium

BACKGROUND AND PURPOSE

Ca²⁺ leak from the sarcoplasmic reticulum (SR) via ryanodine receptors (RyR2s) contributes to cardiomyocyte dysfunction. RyR2 Ca²⁺ leak has been related to RyR2 phosphorylation. In these conditions, JTV519 (K201), a 1,4-benzothiazepine derivative and multi-channel blocker, stabilizes RyR2s and decrease SR Ca²⁺ leak. We investigated whether JTV519 stabilizes RyR2s without increasing RyR2 phosphorylation in mice and in non-failing human myocardium and explored underlying mechanisms.

EXPERIMENTAL APPROACH

SR Ca²⁺ leak was induced by ouabain in murine cardiomyocytes. [Ca²⁺]-transients, SR Ca²⁺ load and RyR2-mediated Ca²⁺ leak (sparks/waves) were quantified, with or without JTV519 (1 µmol·L⁻¹). Contribution of Ca²⁺ -/calmodulin-dependent kinase II (CaMKII) was assessed by KN-93 and Western blot (RyR2-Ser(2814) phosphorylation). Effects of JTV519 on contractile force were investigated in non-failing human ventricular trabeculae.

KEY RESULTS

Ouabain increased systolic and diastolic cytosolic [Ca²⁺](i) , SR [Ca²⁺], and SR Ca²⁺ leak (Ca²⁺ spark (SparkF) and Ca²⁺ wave frequency), independently of CaMKII and RyR-Ser(2814) phosphorylation. JTV519 decreased SparkF but also SR Ca²⁺ load. At matched SR [Ca²⁺], Ca²⁺ leak was significantly reduced by JTV519, but it had no effect on fractional Ca²⁺ release or Ca²⁺ wave propagation velocity. In human muscle, JTV519 was negatively inotropic at baseline but significantly enhanced ouabain-induced force and reduced its deleterious effects on diastolic function.

CONCLUSIONS AND IMPLICATIONS

JTV519 was effective in reducing SR Ca²⁺ leak by specifically regulating RyR2 opening at diastolic [Ca²⁺](i) in the absence of increased RyR2 phosphorylation at Ser(2814) , extending the potential use of JTV519 to conditions of acute cellular Ca²⁺ overload.

Comparison of the IKr blockers moxifloxacin, dofetilide and E-4031 in five screening models of pro-arrhythmia reveals lack of specificity of isolated cardiomyocytes

BACKGROUND AND PURPOSE

Drug development requires the testing of new chemical entities for adverse effects. For cardiac safety screening, improved assays are urgently needed. Isolated adult cardiomyocytes (CM) and human embryonic stem cell-derived cardiomyocytes (hESC-CM) could be used to identify pro-arrhythmic compounds. In the present study, five assays were employed to investigate their sensitivity and specificity for evaluating the pro-arrhythmic properties of I(Kr) blockers, using moxifloxacin (safe compound) and dofetilide or E-4031 (unsafe compounds).

EXPERIMENTAL APPROACH

Assays included the anaesthetized remodelled chronic complete AV block (CAVB) dog, the anaesthetized methoxamine-sensitized unremodelled rabbit, multi-cellular hESC-CM clusters, isolated CM obtained from CAVB dogs and isolated CM obtained from the normal rabbit. Arrhythmic outcome was defined as Torsade de Pointes (TdP) in the animal models and early afterdepolarizations (EADs) in the cell models.

KEY RESULTS

At clinically relevant concentrations (5-12 µM), moxifloxacin was free of pro-arrhythmic properties in all assays with the exception of the isolated CM, in which 10 µM induced EADs in 35% of the CAVB CM and in 23% of the rabbit CM. At supra-therapeutic concentrations (≥100 µM), moxifloxacin was pro-arrhythmic in the isolated rabbit CM (33%), in the hESC-CM clusters (18%), and in the methoxamine rabbit (17%). Dofetilide and E-4031 induced EADs or TdP in all assays (50-83%), and the induction correlated with a significant increase in beat-to-beat variability of repolarization.

CONCLUSION AND IMPLICATIONS

Isolated cardiomyocytes lack specificity to discriminate between TdP liability of the I(Kr) blocking drugs moxifloxacin and dofetilide or E4031.

Robust anti-arrhythmic efficacy of verapamil and flunarizine against dofetilide-induced TdP arrhythmias is based upon a shared and a different mode of action

BACKGROUND AND PURPOSE

The high predisposition to Torsade de Pointes (TdP) in dogs with chronic AV-block (CAVB) is well documented. The anti-arrhythmic efficacy and mode of action of Ca(2+) channel antagonists, flunarizine and verapamil against TdP were investigated.

EXPERIMENTAL APPROACH

Mongrel dogs with CAVB were selected based on the inducibility of TdP with dofetilide. The effects of flunarizine and verapamil were assessed after TdP and in different experiments to prevent dofetilide-induced TdP. Electrocardiogram and ventricular monophasic action potentials were recorded. Electrophysiological parameters and short-term variability of repolarization (STV) were determined. In vitro, flunarizine and verapamil were added to determine their effect on (i) dofetilide-induced early after depolarizations (EADs) in canine ventricular myocytes (VM); (ii) diastolic Ca(2+) sparks in RyR2(R4496+/+) mouse myocytes; and (iii) peak and late I(Na) in SCN5A-HEK 293 cells.

KEY RESULTS

Dofetilide increased STV prior to TdP and in VM prior to EADs. Both flunarizine and verapamil completely suppressed TdP and reversed STV to baseline values. Complete prevention of TdP was achieved with both drugs, accompanied by the prevention of an increase in STV. Suppression of EADs was confirmed after flunarizine. Only flunarizine blocked late I(Na). Ca(2+) sparks were reduced with verapamil.

CONCLUSIONS AND IMPLICATIONS

Robust anti-arrhythmic efficacy was seen with both Ca(2+) channel antagonists. Their divergent electrophysiological actions may be related to different additional effects of the two drugs.

The anti-protozoal drug pentamidine blocks KIR2.x-mediated inward rectifier current by entering the cytoplasmic pore region of the channel

BACKGROUND AND PURPOSE

Pentamidine is a drug used in treatment of protozoal infections. Pentamidine treatment may cause sudden cardiac death by provoking cardiac arrhythmias associated with QTc prolongation and U-wave alterations. This proarrhythmic effect was linked to inhibition of hERG trafficking, but not to acute block of ion channels contributing to the action potential. Because the U-wave has been linked to the cardiac inward rectifier current (I(K1)), we examined the action and mechanism of pentamidine-mediated I(K1) block.

EXPERIMENTAL APPROACH

Patch clamp measurements of I(K1) were made on cultured adult canine ventricular cardiomyocytes, K(IR)2.1-HEK293 cells and K(IR)2.x inside-out patches. Pentamidine binding to cytoplasmic amino acid residues of K(IR)2.1 channels was studied by molecular modelling.

KEY RESULTS

Pentamidine application (24 h) decreased I(K1) in cultured canine cardiomyocytes and K(IR)2.1-HEK293 cells under whole cell clamp conditions. Pentamidine inhibited I(K1) in K(IR)2.1-HEK293 cells 10 min after application. When applied to the cytoplasmic side under inside-out patch clamp conditions, pentamidine block of I(K1) was acute (IC(50)= 0.17 microM). Molecular modelling predicted pentamidine-channel interactions in the cytoplasmic pore region of K(IR)2.1 at amino acids E224, D259 and E299. Mutation of these conserved residues to alanine reduced pentamidine block of I(K1). Block was independent of the presence of spermine. K(IR)2.2, and K(IR)2.3 based I(K1) was also sensitive to pentamidine blockade.

CONCLUSIONS AND IMPLICATIONS

Pentamidine inhibits cardiac I(K1) by interacting with three negatively charged amino acids in the cytoplasmic pore region. Our findings may provide new insights for development of specific I(K1) blocking compounds.

Literature-based evaluation of four 'hard endpoint' models for assessing drug-induced torsades de pointes liability

In safety pharmacology, a number of preclinical models for detecting drug-induced proarrhythmia liability have been recently introduced that utilize hard endpoints: early after depolarziations (EADs), torsades de pointes (TdP) or both as the principal biomarker. To explore the validity of four of the most common of these models, (the isolated canine/rabbit left ventricular wedge preparation, the isolated rabbit heart, the methoxamine-pretreated anaesthetized rabbit and the complete, chronic AV-blocked (CAVB) dog (conscious and anaesthetized), the present article reviews published data sets for three drugs with recognized and different human TdP liabilities (cisparide, terfenadine and moxifloxacinin). Finally, this review considers the value of inclusion of analysis of beat-to-beat variability of repolarization (BVR) in TdP liability testing to improve sensitivity and specificity.

International Life Sciences Institute (Health and Environmental Sciences Institute, HESI) initiative on moving towards better predictors of drug-induced torsades de pointes

Knowledge of the cardiac safety of emerging new drugs is an important aspect of assuring the expeditious advancement of the best candidates targeted at unmet medical needs while also assuring the safety of clinical trial subjects or patients. Present methodologies for assessing drug-induced torsades de pointes (TdP) are woefully inadequate in terms of their specificity to select pharmaceutical agents, which are human arrhythmia toxicants. Thus, the critical challenge in the pharmaceutical industry today is to identify experimental models, composite strategies, or biomarkers of cardiac risk that can distinguish a drug, which prolongs cardiac ventricular repolarization, but is not proarrhythmic, from one that prolongs the QT interval and leads to TdP. To that end, the HESI Proarrhythmia Models Project Committee recognized that there was little practical understanding of the relationship between drug effects on cardiac ventricular repolarization and the rare clinical event of TdP. It was on that basis that a workshop was convened in Virginia, USA at which four topics were introduced by invited subject matter experts in the following fields: Molecular and Cellular Biology Underlying TdP, Dynamics of Periodicity, Models of TdP Proarrhythmia, and Key Considerations for Demonstrating Utility of Pre-Clinical Models. Contained in this special issue of the British Journal of Pharmacology are reports from each of the presenters that set out the background and key areas of discussion in each of these topic areas. Based on this information, the scientific community is encouraged to consider the ideas advanced in this workshop and to contribute to these important areas of investigations over the next several years.

No proarrhythmic properties of the antibiotics Moxifloxacin or Azithromycin in anaesthetized dogs with chronic-AV block

BACKGROUND & PURPOSE

The therapeutically available quinolone antibiotic moxifloxacin has been used as a positive control for prolonging the QT interval in both clinical and non-clinical studies designed to assess the potential of new drugs to delay cardiac repolarization. Despite moxifloxacin prolonging QT, it has not been shown to cause torsades de pointes arrhythmias (TdP). Azithromycin is a macrolide antibiotic that has rarely been associated, clinically, with cases of proarrhythmia. As there is a lack of clinical data available, the cardiac safety of these drugs was assessed in a TdP-susceptible animal model by evaluating their repolarization and proarrhythmia effects.

EXPERIMENTAL APPROACH & KEY RESULTS

In transfected HEK cells, the IC(50)s for I (hERG) were 45+/-6 and 856+/-259 microg ml(-1) for moxifloxacin and azithromycin, respectively. Intravenous administration of 2 and 8 mg kg(-1) moxifloxacin (total peak-plasma concentrations 4.6+/-1.5 and 22.9+/-6.8 microg ml(-1)) prolonged the QT(c) in 6 anaesthetized dogs with chronic AV block by 7+/-3 and 21+/-19%, respectively. Similar intravenous doses of azithromycin (total peak-plasma concentrations 5.4+/-1.3 and 20.8+/-4.9 microg ml(-1)) had no electrophysiological effects in the same dogs. The reference compound, dofetilide (25 microg kg(-1) i.v.) caused QT(c) prolongation (29+/-15%) and TdP in all dogs. Beat-to-beat variability of repolarization (BVR), quantified as short-term variability of the left ventricular monophasic action potential duration, was only increased after dofetilide (1.8+/-0.7 to 3.8+/-1.5 ms; P<0.05).

CONCLUSION & IMPLICATIONS

As neither moxifloxacin nor azithromycin caused TdP or an increase in the BVR, we conclude that both drugs can be used safely in clinical situations.

End–diastolic myofiber stress and ejection strain increase with ventricular volume overload

BACKGROUND

Myocardial stress and strain are considered primary mechanical stimuli for hypertrophic remodeling. Their values and significance in the intact beating heart during chronic overload remain poorly characterized.

METHODS AND RESULTS

Left-ventricular (LV) dimensions (echocardiography) and pressure (invasive) were simultaneously recorded in anesthetized dogs at sinus rhythm (SR), acute and 1, 2, 6, 12 weeks of atrioventricular block (AVB), leading to structural, electrical and contractile remodeling. Mechanical load of the myocardium was quantified as myofiber stress (sigma(f)), being force along myofiber orientation per cross-sectional area, and natural myofiber strain (e(f)), being change in natural logarithm of myofiber length (l) divided by its reference length: e(f) = ln(l/l(ref)). Time courses of sigma(f) and e(f) were calculated from LV pressure and dimensions, using a validated mathematical model of cardiac mechanics. End-diastolic sigmaf increased from 2.0 +/- 0.1 kPa at SR to 3.4 +/- 0.3 kPa at acute AVB, remaining elevated for > 6 weeks. Systolic sigma(f) was not affected by AVB. Ejection strain rose instantly upon AVB, reaching a maximum at 2 weeks: 0.24 +/- 0.02 vs. 0.10 +/- 0.01 at SR. The increase of myofiber stroke work (sigma(f)-e(f) loop area) from 3.1 +/- 0.3 at SR to 6.0 +/- 0.5 kJ/m(3)/beat at 1 week AVB was attributed mainly to an increase of strain during ejection. Stroke work and ejection strain remained elevated up to 12 weeks. The rate of LV-mass increase was maximal (2.2 +/- 0.4 g/day) at 1 week AVB.

CONCLUSIONS

Serial mechanical phenotyping is feasible in the intact anesthetized dog with chronic ventricular overload. Our new approach yields values of mechanical load that are comparable to those found in isolated myocardium by others. In chronic AVB, both end-diastolic myofiber stress and ejection strain are increased. Early increases of both parameters coincide with peak hypertrophic growth, suggesting their important role for mechanotransduction. Peak systolic sigmaf is likely not important for hypertrophy in this model, since it does not change throughout the experiment.

Should class III drugs be initiated in hospital to prevent drug-induced torsade de pointes arrhythmias?

OBJECTIVES

In the US, the FDA requires in-hospital institution of class III drugs. This study retrospectively assessed whether these criteria, which differ markedly from the Dutch exclusion criteria, could predict sotalol-induced torsade de pointes arrhythmias (TdP).

METHOD

Oral sotalol effect in a control group (50 patients, 62±12 years, 23 men, 27 women) was compared with five patients developing TdP (75±5years, all women), using known and new (JTU area measured in lead V2) risk parameters. Paroxysmal atrial fibrillation was the most common indication for sotalol treatment.

RESULTS

At baseline the strict US regulations would have identified four of five TdP patients on the basis of individual K⁺ levels, creatinine clearance and QT_c. However, 7 of 49 controls would also have been excluded, although they did not develop documented TdP in the >2 years follow-up. Sotalol slightly increased QT_c (361±34 to 387±33ms) in controls, due to heart rate reduction. In the TdP group, sotalol dramatically increased QT_c (467±33 to 626±52 ms, +35%, p<0.05) accompanied by deep negative TU waves and an increased JTU area and all could be identified as risk patients.

CONCLUSION

Patients developing TdP on oral sotalol can be identified using the FDA risk criteria and hospitalisation may therefore be appropriate. A European prospective study is required to investigate the costs, sensitivity and specificity of this strategy.