Vibrational modes in partially optimized molecular systems

In this paper the authors develop a method to accurately calculate localized vibrational modes for partially optimized molecular structures or for structures containing link atoms. The method avoids artificially introduced imaginary frequencies and keeps track of the invariance under global translations and rotations. Only a subblock of the Hessian matrix has to be constructed and diagonalized, leading to a serious reduction of the computational time for the frequency analysis. The mobile block Hessian approach (MBH) proposed in this work can be regarded as an extension of the partial Hessian vibrational analysis approach proposed by Head [Int. J. Quantum Chem. 65, 827 (1997)]. Instead of giving the nonoptimized region of the system an infinite mass, it is allowed to move as a rigid body with respect to the optimized region of the system. The MBH approach is then extended to the case where several parts of the molecule can move as independent multiple rigid blocks in combination with single atoms. The merits of both models are extensively tested on ethanol and di-n-octyl-ether.

Calculating Reaction Rates with Partial Hessians: Validation of the Mobile Block Hessian Approach

In an earlier paper, the authors have developed a new method, the mobile block Hessian (MBH), to accurately calculate vibrational modes for partially optimized molecular structures [J. Chem. Phys. 2007, 126 (22), 224102]. The proposed procedure remedies the artifact of imaginary frequencies, occurring in standard frequency calculations, when parts of the molecular system are optimized at different levels of theory. Frequencies are an essential ingredient in predicting reaction rate coefficients due to their input in the vibrational partition functions. The question arises whether the MBH method is able to describe the chemical reaction kinetics in an accurate way in large molecular systems where a full quantum chemical treatment at a reasonably high level of theory is unfeasible due to computational constraints. In this work, such a validation is tested in depth. The MBH method opens a lot of perspectives in predicting accurate kinetic parameters in chemical reactions where the standard full Hessian procedure fails.

The role of the SCN5A-encoded channelopathy in irritable bowel syndrome and other gastrointestinal disorders

BACKGROUND

Gastrointestinal functional and motility disorders, like irritable bowel syndrome (IBS), have a high prevalence in the Western population and cause significant morbidity and loss of quality of life leading to considerable costs for health care. A decade ago, it has been demonstrated that interstitial cells of Cajal and intestinal smooth muscle cells, cells important for gastrointestinal motility, express the sodium channel alpha subunit Nav 1.5. In the heart, aberrant variants in this sodium channel, encoded by SCN5A, are linked to inherited arrhythmia syndromes, like the long-QT syndrome type 3 and Brugada syndrome. Mounting data show a possible contribution of SCN5A mutants to gastrointestinal functional and motility disorders. Two percent of IBS patients harbor SCN5A mutations with electrophysiological evidence of loss- and gain-of-function. In addition, gastrointestinal symptoms are more prevalent in cardiac SCN5A-mutation positive patients.

PURPOSE

This review firstly describes the Nav 1.5 channel and its physiological role in ventricular cardiomyocytes and gastrointestinal cells, then we focus on the involvement of mutant Nav 1.5 in gastrointestinal functional and motility disorders. Future research might uncover novel mutation-specific treatment strategies for SCN5A-encoded gastrointestinal channelopathies.

Dutch outcome in implantable cardioverter-defibrillator therapy (DO-IT): registry design and baseline characteristics of a prospective observational cohort study to predict appropriate indication for implantable cardioverter-defibrillator

BACKGROUND

Implantable cardioverter-defibrillators (ICDs) are widely used for the prevention of sudden cardiac death. At present, both clinical benefit and cost-effectiveness of ICD therapy in primary prevention patients are topics of discussion, as only a minority of these patients will eventually receive appropriate ICD therapy.

METHODS/DESIGN

The DO-IT Registry is a nationwide prospective cohort with a target enrolment of 1,500 primary prevention ICD patients with reduced left ventricular function in a setting of structural heart disease. The primary outcome measures are death and appropriate ICD therapy for ventricular tachyarrhythmias. Secondary outcome measures are inappropriate ICD therapy, death of any cause, hospitalisation for ICD related complications and for cardiovascular reasons. As of December 2016, data on demographic, clinical, and ICD characteristics of 1,468 patients have been collected. Follow-up will continue up to 24 months after inclusion of the last patient. During follow-up, clinical and ICD data are collected based on the normal follow-up of these patients, assuming ICD interrogations take place every six months and clinical follow-up is once a year. At baseline, the mean age was 66 (standard deviation [SD] 10) years and 27% were women.

CONCLUSION

The DO-IT Registry represents a real-world nationwide cohort of patients receiving ICDs for primary prevention of sudden cardiac death with reduced left ventricular function in a setting of structural heart disease. The registry investigates the efficacy of the current practice and aims to develop prediction rules to identify subgroups who will not (sufficiently) benefit from ICD implantation and to provide results regarding costs and budget impact of targeted supply of primary preventions ICDs.

Can the electronegativity equalization method predict spectroscopic properties?

The electronegativity equalization method is classically used as a method allowing the fast generation of atomic charges using a set of calibrated parameters and provided knowledge of the molecular structure. Recently, it has started being used for the calculation of other reactivity descriptors and for the development of polarizable and reactive force fields. For such applications, it is of interest to know whether the method, through the inclusion of the molecular geometry in the Taylor expansion of the energy, would also allow sufficiently accurate predictions of spectroscopic data. In this work, relevant quantities for IR spectroscopy are considered, namely the dipole derivatives and the Cartesian Hessian. Despite careful calibration of parameters for this specific task, it is shown that the current models yield insufficiently accurate results.

Implantable defibrillator therapy and mortality in patients with non-ischaemic dilated cardiomyopathy : An updated meta-analysis and effect on Dutch clinical practice by the Task Force of the Dutch Society of Cardiology

BACKGROUND

Primary prophylactic implantable cardioverter-defibrillators (ICDs) in patients with non-ischaemic cardiomyopathy (NICMP) remains controversial. This study sought to assess the benefit of ICD therapy with or without cardiac resynchronisation therapy (CRT) in patients with NICMP. In addition, data were compared with real-world clinical data to perform a risk/benefit analysis.

METHODS

Relevant randomised clinical trials (RCTs) published in meta-analyses since DANISH, and in PubMed, EMBASE and Cochrane databases from 2016 to 2020 were identified. The benefit of ICD therapy stratified by CRT use was assessed using random effects meta-analysis techniques.

RESULTS

Six RCTs were included in the meta-analysis. Among patients without CRT, ICD use was associated with a 24% reduction in mortality (hazard ratio [HR]: 0.76; 95% confidence interval [CI]: 0.62-0.93; P = 0.008). In contrast, among patients with CRT, a CRT-defibrillator was not associated with reduced mortality (HR: 0.74, 95% CI 0.47-1.16; P = 0.19). For ICD therapy without CRT, absolute risk reduction at 3‑years follow-up was 3.7% yielding a number needed to treat of 27.

CONCLUSION

ICD use significantly improved survival among patients with NICMP who are not eligible for CRT. Considering CRT, the addition of defibrillator therapy was not significantly associated with mortality benefit compared with CRT pacemaker.

P5023A mutation specific prediction model for ventricular arrhythmias in the phospholamban (PLN) p.Arg14del cardiomyopathy

Background/Introduction

The founder mutation p.Arg14del in the gene encoding phospholamban (PLN) is a known cause of arrhythmogenic cardiomyopathy (ACM) with distinct clinical features, such as microvoltages on the ECG and right or left ventricular dysfunction or both. At present, risk stratification for ICD implantation in carriers of this mutation is based on left ventricular ejection fraction and previous ventricular arrhythmia's, which are not specific risk factors for the PLN p.Arg14del cardiomyopathy.

Purpose

Our goal is to develop a mutation specific prediction model for incident malignant ventricular arrhythmia to guide ICD implantation.

Methods

Data were collected from p.Arg14del carriers with no history of malignant VA at baseline, identified between September 2009 and June 2018 in three Dutch university hospitals. Genetic analysis of PLN was performed in a clinical setting in index patients with clinical signs of DCM/ACM, or in family members of p.Arg14del carriers. We collected clinical data from the first cardiac evaluation and follow-ups. Malignant VAs were defined as sustained VA, appropriate ICD intervention or (aborted) sudden cardiac death. A prediction model was developed using Cox Proportional Hazard regression. Candidate baseline predictors were pre specified based on literature and clinical expertise. Age, sex, proband status, sudden cardiac death (SCD) in 1st degree relative, repolarization abnormalities, microvoltages, premature ventricular complexes (PVC) burden on 24hrs Holter monitoring, LVEF and non-sustained ventricular arrhythmias (NSVT) were considered. The multivariable model was fitted using stepwise backward selection based on Akaike's Information Criterion.

Results

We included 440 p.Arg14del carriers with a mean age of 41±18 years and 41% males. During a median follow-up of 4.7 years (IQR 1.7–7.3), 44 incident malignant VA occurred, 20 sustained VAs and 24 appropriate ICD therapies. The multivariable HR's of selected predictors were: 2.2 for minor and 4.5 for major repolarization abnormalities vs no abnormalities (p value respectively 0.06 and 0.01), 2.2 for LVEF <45% (p value 0,1) and 7.7 for >500PVC/24hrs (p value 0.003). Carriers with and without events could be accurately distinguished with this model, with an optimism corrected C-statistic of 0.81. The model calibrated well, with agreement of observed and predicted 5 year malignant VA risk. Risk groups were split into quintiles of predicted risk, figure 1 shows the Kaplan Meier curve of incident malignant VA per risk group. The 5 year risk of incident malignant VA in the lowest 3 quintiles was 0%, 9% in the 4th quintile and 25.2% in the highest quintile.

Conclusion

We created a PLN p.Arg14del mutation specific prediction model to estimate risk of incident malignant VA. With this model a clear distinction between high risk and low risk patients can be made and can be used to guide ICD implantation for primary prevention.

P4373Post systolic shortening in the apex of the left ventricular is a typical finding in patients with PLN mutation

Introduction

The p.Arg14del founder mutation in the gene encoding phospholamban (PLN) is associated with an increased risk of malignant ventricular arrhythmia and heart failure. Ejection fraction (EF) is the gold standard of systolic left ventricular (LV) function, however new technics using global longitudinal strain (GLS) are able to detect LV dysfunction early, e.g. in patients with chemotherapy. Moreover, strain analysis on post systolic shortening (PSS) can show distinct pattern in various diseases, e.g. patients with myocardial fibrosis and amyloid. The goal of this study was to investigate whether speckle tracking (GLS and PSS) of the LV can detect LV dysfunction in patients with PLN mutations and whether these patients have a specific PSS pattern.

Method

72 Patients (49 female, mean age 32 years) diagnosed with the genetic PLN mutation p.Arg14del and 21 controls (10 female, mean age 27 years) underwent complete Echocardiographic exam including LVEF, GLS and PSI of all LV segments. LVEF <50% was considered as LV dysfunction. The diagnostic characteristics of GLS and PSI were determined.

Results

Pearson correlation is in PLN patients between PSI apex and EF 0.677 (P <.0001) PSI apex and GLS 0.692 (P <.0001)

PLN patients appeared to have a typical pattern with a high PSI in the apical segments. An apical PSI >20 was the strongest diagnostic parameter indicating LV dysfunction.

Apical PSI >20 and LVEF <50% have a sensitivity and specificity of 78% and 85%.

Diagnostic characteristics PLN Controls P-value LVEF, % 55.2 59.3 0.033 GLS, % 15.5 17.3 0.163 PSI basal 8.5 10.1 0.326 PSI mid 5.6 2.9 0.070 PSI apical 15.6 2.1 0.01 LVEF, left ventricular ejection fraction; GLS, Global longitudinal strain; PSI, post systolic index.

PSI

Conclusion

PLN patients have a typical pattern of high PSI in the apex of the left ventricular which can be used as a diagnostic test to detect LV dysfunction.

Hospital utilisation and the costs associated with complications of ICD implantation in a contemporary primary prevention cohort

Introduction

Implantation of an implantable cardioverter defibrillator (ICD) is standard care for primary prevention of sudden cardiac death. However, ICD-related complications are increasing as the population of ICD recipients grows.

Methods

ICD-related complications in a national DO-IT Registry cohort of 1442 primary prevention ICD patients were assessed in terms of additional use of hospital care resources and costs.

Results

During a median follow-up of 28.7 months (IQR 25.2–33.7) one or more complications occurred in 13.5% of patients. A complication resulted in a surgical intervention in 53% of cases and required on average 3.65 additional hospital days. The additional hospital costs were €6,876 per complication or €8,110 per patient, to which clinical re-interventions and additional hospital days contributed most. Per category of complications, infections required most hospital utilisation and were most expensive at an average of €22,892. The mean costs were €5,800 for lead-related complications, €2,291 for pocket-related complications and €5,619 for complications due to other causes. We estimate that the total yearly incidence-based costs in the Netherlands for hospital management of ICD-related complications following ICD implantation for primary prevention are €2.7 million.

Conclusion

Complications following ICD implantation are related to a substantial additional need for hospital resources. When performing cost-effectiveness analyses of ICD implantation, including the costs associated with complications, one should be aware that real-world complication rates may deviate from trial data. Considering the economic implications, strategies to reduce the incidence of complications are encouraged.

A polymorphism in histidine-rich calcium binding protein as second hit in phospholamban cardiomyopathy

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Netherlands Cardio Vascular Research Initiative (CVON): the Dutch Heart Foundation, Dutch Federation of University Medical Center, the Netherlands Organization for Health Re-search and Development and the Royal Netherlands Academy of Sciences

Introduction

Sudden cardiac death (SCD) is one of the severe manifestations in carriers with a phospholamban (PLN p.Arg14del) cardiomyopathy. Prediction whether a patient with this pathogenic variant will be at risk for SCD is difficult. PLN has an important role in cardiac calcium homeostasis as regulator of the sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA). It has been shown that the p.Arg14del pathogenic variant leads to Ca2+ overload in cardiomyocytes. Recently, it was found that dilated cardiomyopathy (DCM) patients who have a polymorphism in histidine-rich calcium binding protein (HRC Ser96Ala, rs3745297), displayed an increased risk for malignant arrhythmias and SCD. HRC resides within the SR, where it acts as a regulator of Ca2+ homeostasis. This Ser96Ala gene variant is widespread, as 60% of the general population bears at least one copy of this allele.

Objective

To explore the effect of the HRC Ser96Ala polymorphism on ventricular arrhythmias and disease expression in PLN p.Arg14del pathogenic variant carriers.

Methods

337 p.Arg14del patients were included into the study; divided into wildtype (WT) (n=134, 24 index patients), heterozygous for Ser96Ala variant (n=142, 30 index patients) and homozygous for Ser96Ala variant (n=61, 11 index patients). The study was conducted according to the Declaration of Helsinki. Blood samples were genotyped on the Infinium® Global Screening Array-24 v3.0. Clinical data were subtracted from health records.

Results

In total 23% of PLN variant carriers were diagnosed with DCM while 11% of the variant carriers were diagnosed with arrhythmogenic cardiomyopathy. A significant difference in age of presentation (p=0.019) of p.Arg14del patients diagnosed with a DCM phenotype was found in homozygous HRC variant carriers (median 43 years, [36-47.3], n=8) compared to WT (median 49 years, [41-56.8], n=24) and heterozygous variant carriers (median 58.5 years, [51-66.5], n=22). No significant differences between the 3 groups were detected in manifestations of premature ventricular contractions (n=188, p=0.203), non-sustained ventricular tachycardia (n=248, p=0.314) and appropriate ICD shocks (n=308, p=0.901).

Conclusion

Although a significant difference in disease onset was found in PLN p.Arg14del patients with DCM who were homozygous for the HRC polymorphism, no correlations with arrhythmogenic parameters were found between patients with and without the HRC polymorphism. Therefore, we conclude that presence of the HRC polymorphism is not a discriminative predictor for arrhythmogenic events in PLN p.Arg14del.

A polymorphism in Histidine-Rich Calcium Binding Protein as second hit in Phospholamban Cardiomyopathy

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Netherlands Cardio Vascular Research Initiative (CVON): the Dutch Heart Foundation, Dutch Federation of University Medical Center, the Netherlands Organization for Health Re-search and Development and the Royal Netherlands Academy of Sciences

Introduction

Sudden cardiac death (SCD) is one of the severe manifestations in carriers with a phospholamban (PLN p.Arg14del) cardiomyopathy. Prediction whether a patient with this pathogenic variant will be at risk for SCD is difficult. PLN has an important role in cardiac calcium homeostasis as regulator of the sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA). It has been shown that the p.Arg14del pathogenic variant leads to Ca2+ overload in cardiomyocytes. Recently, it was found that dilated cardiomyopathy (DCM) patients who have a polymorphism in histidine-rich calcium binding protein (HRC Ser96Ala, rs3745297), displayed an increased risk for malignant arrhythmias and SCD. HRC resides within the SR, where it acts as a regulator of Ca2+ homeostasis. This Ser96Ala gene variant is widespread, as 60% of the general population bears at least one copy of this allele.

Objective

To explore the effect of the HRC Ser96Ala polymorphism on ventricular arrhythmias and disease expression in PLN p.Arg14del pathogenic variant carriers.

Methods

337 p.Arg14del patients were included into the study; divided into wildtype (WT) (n=134, 24 index patients), heterozygous for Ser96Ala variant (n=142, 30 index patients) and homozygous for Ser96Ala variant (n=61, 11 index patients). The study was conducted according to the Declaration of Helsinki. Blood samples were genotyped on the Infinium® Global Screening Array-24 v3.0. Clinical data were subtracted from health records.

Results

In total 23% of PLN variant carriers were diagnosed with DCM while 11% of the variant carriers were diagnosed with arrhythmogenic cardiomyopathy. A significant difference in age of presentation (p=0.019) of p.Arg14del patients diagnosed with a DCM phenotype was found in homozygous HRC variant carriers (median 43 years, [36-47.3], n=8) compared to WT (median 49 years, [41-56.8], n=24) and heterozygous variant carriers (median 58.5 years, [51-66.5], n=22). No significant differences between the 3 groups were detected in manifestations of premature ventricular contractions (n=188, p=0.203), non-sustained ventricular tachycardia (n=248, p=0.314) and appropriate ICD shocks (n=308, p=0.901).

Conclusion

Although a significant difference in disease onset was found in PLN p.Arg14del patients with DCM who were homozygous for the HRC polymorphism, no correlations with arrhythmogenic parameters were found between patients with and without the HRC polymorphism. Therefore, we conclude that presence of the HRC polymorphism is not a discriminative predictor for arrhythmogenic events in PLN p.Arg14del.

Longitudinal validation of the phospholamban (PLN) p.Arg14del risk model

Background/Introduction

Recently, a variant-specific prediction model for PLN p.Arg14del variant carriers was developed to predict individual malignant ventricular arrhythmia (VA) risk to inform decision-making for primary prevention implantable cardioverter defibrillator (ICD) implantation. This model predicts malignant VA risk from data at diagnosis, but iterative evaluation of malignant VA risk may be warranted considering that the risk factors for malignant VA are progressive.

Purpose

To evaluate the diagnostic performance of the PLN p.Arg14del risk model.

Methods/Results

Date were collected of 278 PLN p.Arg14del variant carriers at 3 year follow-up. This was considered the new baseline for the survival analysis. Patients with history of malignant VA at both baseline and during the first 3 years after baseline were excluded. At 3 year patients were aged 40.1±18.0 year and 40.7% was male. Median left ventricular ejection fraction (LVEF) was 53% and percentage with microvoltages was 10.3. During a median follow-up of 4 years (Interquartile range 1.8–6.5) 31 (11%) carriers experienced malignant VA, defined as sustained VA, appropriate ICD intervention, or (aborted) sudden cardiac death. Reevaluation of the predictors with the 3 year follow-up data revealed hazard rates that were similar to those in the original PLN p.Arg14del risk model; LVEF per 1% decrease (hazard ratio (HR) 1.10 [95% confidence interval (CI), 1.06–1.12]; p&lt;0.001), premature ventricular contraction count/24h (HR 1.51 [95% CI, 1.15–1.98]; p=0.003) and the presence of low-voltage electrocardiogram (HR 12.24 [95% CI, 5.21–28.8); p&lt;0.001). Negative T waves did not remain significant as a predictor. The 5-year malignant VA risk was calculated for each variant carrier, after multiple imputation for dealing with incomplete cases, by applying the PLN p.Arg14del risk model to the 3 year follow-up data. Afterwards the cohort was divided into tertiles of predicted risk. This clearly demonstrated the lowest risk tertile having a low malignant VA rate and the highest risk tertile having a high malignant VA rate, which resulted in an optimism-corrected C-statistic of 0.85 (95% CI 0.78–0.92).

Conclusion

The PLN p.Arg14del risk model is valid at 3 year follow-up in PLN p.Arg14del variant carriers with no history of malignant VA and can therefore be used to inform decision-making for primary prevention ICD implantation not merely at diagnosis, but also during follow-up and can be seen as a type of validation in a cohort where no other large cohort is present to perform external validation.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): 1. PSIDER: From pluripotent stem cells to prime editing gene therapy for inheritedcardiomyopathies. ZOn-MW.2. PREDICT2: Predicting sudden cardiac arrest. The Dutch Heart Foundation.