Efficacy on resynchronization and longitudinal contractile function comparing His-bundle pacing with conventional biventricular pacing: a substudy to the His-alternative study

AIMS

His-bundle pacing has emerged as a novel method to deliver cardiac resynchronization therapy (CRT). However, there are no data comparing conventional biventricular (BiV)-CRT with His-CRT with regard to effects on mechanical dyssynchrony and longitudinal contractile function.

METHODS AND RESULTS

Patients with symptomatic heart failure, left ventricular ejection fraction ≤ 35%, and left bundle branch block (LBBB) by strict ECG criteria were randomized 1:1 to His-CRT or BiV-CRT. Two-dimensional strain echocardiography was performed prior to CRT implantation and at 6 months after implantation. Differences in changes in mechanical dyssynchrony (standard deviation of time-to-peak in 12 midventricular and basal segments) and regional longitudinal strain in the six left ventricular walls were compared between the BiV-CRT and His-CRT groups.In the on-treatment analysis, 31 received BiV-CRT and 19 His-CRT. In both groups, mechanical dyssynchrony was significantly reduced after 6 months [BiV group from 120 ms (±45) to 63 ms (±22), P < 0.001, and His group from 116 ms (±54) to 49 ms (±11), P < 0.001] but no significant differences in changes could be demonstrated between groups [-9.0 ms (-36; 18), P = 0.50]. Global longitudinal strain (GLS) improved in both groups [BiV group from -9.1% (±2.7) to -10.7% (±2.6), P = 0.02, and His group from -8.6% (±2.1) to -11.1% (±2.0), P < 0.001], but no significant differences in changes could be demonstrated from baseline to follow-up [-0.9% (-2.4; -0.6), P = 0.25] between groups. There were no regional differences between groups.

CONCLUSION

In heart failure, patients with LBBB, BiV-CRT, and His-CRT have comparable effects with regard to improvements in mechanical dyssynchrony and longitudinal contractile function.

Behavioural digital biomarkers enable real-time monitoring of patient-reported outcomes: a substudy of the multicenter, prospective observational SafeHeart study

INTRODUCTION

Patient-reported outcome measures (PROMs) serve multiple purposes, including shared decision-making and patient communication, treatment monitoring and health-technology assessment. Patient monitoring using PROMs is constrained by recall and non-response bias, respondent burden and missing data. We evaluated the potential of behavioural digital biomarkers obtained from a wearable accelerometer to achieve personalised predictions of PROMs.

METHODS

Data from the multicenter, prospective SafeHeart study conducted at Amsterdam University Medical Center in the Netherlands and Copenhagen University Hospital, Rigshospitalet in Copenhagen, Denmark, was used. The study enrolled patients with an implantable cardioverter defibrillator (ICD) between May 2021 and September 2022 who then wore wearable devices with raw acceleration output to capture digital biomarkers reflecting physical behaviour. To collect PROMs, patients received the KCCQ and EQ5D-5 L questionnaire at two instances; baseline and after 6 months. Multivariable Tobit regression models were used to explore associations between digital biomarkers and PROMs, specifically whether digital biomarkers could enable PROM prediction.

RESULTS

The study population consisted of 303 patients (mean age 62.9 ± 10.9 years, 81.2% male). Digital biomarkers showed significant correlations to patient-reported physical and social limitations, severity and frequency of symptoms and quality of life. Prospective validation of the Tobit models indicated moderate correlations between the observed and predicted scores for KCCQ (concordance correlation coefficient (CCC) = 0.49, mean difference: 1.07 points) and EQ5D-5 L (CCC = 0.38, mean difference 0.02 points).

CONCLUSION

Wearable digital biomarkers correlate with PROMs, and may be leveraged for real-time prediction. These findings hold promise for monitoring of PROMs through wearable accelerometers.

Loss-of-function variants in founder population highlight atrial myopathy as susceptibility to atrial fibrillation

Background

Atrial fibrillation (AF) is the most common cardiac arrhythmia, and it's associated with genes responsible for cardiac conduction, cardiogenesis, and cardiac structure. The Finnish population has evolved in relative isolation and undergone several bottlenecks, resulting in enrichment of deleterious variants. This facilitates identification of possible causal genes through protein-truncating variants that likely would not have been identified in other populations.

Purpose

To identify novel genetic associations with large effect on AF risk.

Methods

We accessed publicly available summary statistics on AF (ICD-10 code I48) from the FinnGen project R6, containing 28,670 AF cases and 135,821 controls. Then, we annotated all variants in the summary statistics and extracted variants that were predicted with a high effect impact (n=7,113). To account for multiple testing, a false discovery rate cutoff &lt;10% was applied. The UK Biobank was assessed for comparison of allele frequencies. Afterwards, we investigated protein and single-cell RNA expression of the genes of interest in human atrial tissue. Human atrial tissue was obtained by us from 7 individuals and used for mass spectrometry-based proteomics, while single-nucleus RNA sequencing (snRNAseq) data from human hearts was acquired by Tucker [1].

Results

In a genome-wide association study (GWAS) focusing on loss-of function (LOF) variation, we report two LOF variants in the structural genes SYNPO2L and CTNNA3 with much higher allele frequencies compared to non-Finnish Europeans (85-fold and 80-fold enrichment, respectively). The variants increase the risk of AF considerably, which is emphasized as the two variants show the highest effect sizes of all GWAS variants ever associated with AF (SYNPO2L; odds ratio [OR] = 2.79, P-value = 1.32x10–8 and CTNNA3; OR = 2.43, P-value = 9.40x10–7), exceeding that of most clinical risk factors. We accessed phenome-wide association study (PheWAS) results on both variants. There was no association with other phenotypes for the SYNPO2L variant whereas the CTNNA3 variant showed suggestive association with valvular heart disease (P-value = 2.95x10–5). SYNPO2L and CTNNA3 exhibited high protein and RNA expression levels in atrial tissue and were predominantly expressed in cardiomyocytes (Fig. 1).

Conclusion

We identified novel associations between LOF variation in the structural genes SYNPO2L and CTNNA3 and AF. Our study showed how genetic examination of a European subpopulation facilitates discovery of genetic variants and pathophysiological understanding. The results underline the importance of thoroughly investigating subpopulations as unique variants with large effect sizes can be identified.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): This work was supported by the Research Foundation at Rigshospitalet and the Hallas-Møller Emerging Investigator Novo Nordisk.

His-pacing and biventricular pacing show similar efficiency in resynchronization and improvements in longitudinal contractile function

Background

The clinical role for HIS-pacing in cardiac resynchronization therapy (HIS-CRT) is promising but is yet to be established. The randomised His-alternative study showed better remodelling with HIS-CRT compared to patients receiving conventional biventricular pacing (BIV-CRT) in the per-protocol-analysis.

Purpose

In this substudy we investigated whether HIS-pacing was more efficient compared to BIV-CRT in improving mechanical synchrony and longitudinal contractile function.

Methods

In the His-Alternative study 50 patients with symptomatic heart failure, left ventricular ejection fraction (LVEF) ≤35% and Left bundle branch block were randomized 1:1 to His-CRT or BiV-CRT and followed for 6 months. At implantation, 7 patients crossed over from His-pacing to LV-pacing in the His-CRT group and 1 patient crossed over from LV-pacing to His-pacing in the BiV-CRT group. All patients had echocardiography performed including 2D-strain echocardiography to asses global systolic longitudinal deformation (GLS) at baseline and 6 months. Mechanical dyssynchrony was measured as SD of time-to-peak in all 12 segments of the left ventricle (TPS-SD).

Results

There were no significant differences in baseline characteristics between patients receiving HIS-CRT and BIV-CRT with regard to dyssynchrony and longitudinal systolic strain. LVEF was significantly higher at 6 months (48±8% vs. 42±8%; p&lt;0.05) in the HIS-CRT group. However, GLS did not significantly improve more with HIS-CRT compared to BIV-CRT, (−8.7ms ± 2.0 to −11.1 ms ± 2.0 vs −9.1 ms ± 2.7 to −10.8±2.5 ms ± 2.8, P = ns for difference) and regarding resynchronization measured as TPS-SD there was no significant difference either (110 ms ± 51 to 47 ms ± 10 vs. 115 ms ± 42 to 60 ms ± 21, P = ns for difference).

Conclusion

In this substudy, HIS-pacing did not prove more efficient than BIV-CRT in resynchronizing the left ventricle, nor did the observed improvement in longitudinal function differ significantly between methods. However, the number of included patients was rather small and larger studies are needed to fully assess the possible benefits of HIS-CRT.

Funding Acknowledgement

Type of funding sources: None.

Risk stratification parameters as assessed by continuous long-term cardiac monitoring in pulmonary hypertension – heart rate variability, heart rate, and physical activity

Background

Pulmonary hypertension (PH) is a progressive disease affecting both the pulmonary vasculature and the heart. In the current ESC/ERS guidelines nine variables are used in PH risk assessment, and have been proven to be independent predictors of survival in PH. The risk assessment parameters include clinical symptoms, exercise capacity and imaging. The present study is the first to assess continuous 24/7 heart rate variability (HRV), heart rate (HR) and physical activity monitoring in patients with PH.

Purpose

To identify risk stratification parameters by continuous cardiac monitoring in PH.

Methods

Patients diagnosed with PH were included in this prospective single-centre study. Patients had a Reveal LINQ insertable cardiac monitor implanted to continuously monitor heart rate variability (HRV), heart rate at day and night and physical activity. HRV was expressed as the mean HRV in sinus rhythm during each full day (SDANN method). Pearson and Spearman correlations between the loop recorder variables and ESC/ERS risk stratification variables were calculated and compared with the loop recorder data in 30-days intervals.

Results

A total of 41 patients were prospectively enrolled, 27 patients with pulmonary arterial hypertension (PAH) and 14 patients with chronic thromboembolic pulmonary hypertension (CTPEH). The patients were monitored continuously in a total of 82 patient-years, had a mean age of 58 years and were primarily in a stable disease phase with a mean WHO functional class (FC) of 2.2. HRV and physical activity divided by heart rate at daytime showed the highest correlations respectively with current risk parameters. In particular, high correlations were found between HRV and NT-proBNP (R=−0,69 p≤2.2e-16), WHO FC (R=−0,65 p=2.4e-5), RVEF (R=0,61 p=0,00012) and right atrial pressure (RAP) (R=−0.67 p=0.0023) (Figure 1).

Conclusion

This study demonstrates the potential of HRV, and physical activity divided by heart rate daytime as risk parameters in pulmonary hypertension. Progression of symptoms in PH are often delayed compared with pathophysiological changes, and continuous monitoring offers a potential to early recognition of disease progression and optimization of PAH therapy.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): The study was supported by the Heart Centre Research Council,Rigshospitalet and an investigator initiated study research grant fromJansson Pharmaceuticals.

Screening for atrial fibrillation to prevent stroke in elderly individuals with or without preexisting cardiovascular disease

Background

Previous research has showed that various cardiovascular diseases (CVD) are associated with increased risks of atrial fibrillation (AF) and stroke. However, data on the interaction between CVD and AF screening efficacy are lacking.

Purpose

To evaluate the influence of preexisting CVD on the effects of AF screening with long-term continuous monitoring.

Methods

The LOOP Study (Atrial Fibrillation detected by Continuous ECG Monitoring using Implantable Loop Recorder to prevent Stroke in High-risk Individuals) randomized AF-naïve individuals aged ≥70 years and with additional stroke risk factors to either long-term screening with implantable loop recorder (ILR) and subsequent anticoagulation initiation upon detection of AF episodes ≥6 minutes, or usual care (the control group). In the current study, all participants from the LOOP Study were divided into two risk groups according to the presence of CVD (defined as ischemic heart disease, heart failure, previous stroke, valvular heart disease, or peripheral artery disease). The relative risks of outcomes in groupwise comparisons, as indicated by hazard ratio (HR), were assessed in the cause-specific Cox proportional-hazards model with death as competing risk.

Results

Of 6004 participants included, 1997 (33.3%) had ≥1 CVD at baseline. Compared with no CVD, the presence of CVD was associated with increased risks of AF diagnosis in the ILR group (adjusted HR 1.32 [1.09–1.59]) and of stroke or systemic arterial embolism in the entire study cohort (adjusted HR 1.34 [1.06–1.69]). For ILR screening versus usual care, there was no decrease in stroke or systemic arterial embolism among participants with preexisting CVD (adjusted HR 1.13 [0.76–1.68]), whereas a significant risk reduction was obtained by screening among those without CVD (adjusted HR 0.64 [0.44–0.93]). The interaction was significant (adjusted p-value for interaction 0.041).

Conclusions

In an elderly, high-risk population, ILR screening did not prevent stroke significantly in individuals with preexisting CVD, but it was associated with an approximately 40% risk reduction among those without CVD.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): The LOOP Study was funded by Innovation Fund Denmark [grant number 12-1352259], The Research Foundation for the Capital Region of Denmark, The Danish Heart Foundation [grant number 11-04-R83-A3363-22625], Aalborg University Talent Management Program, Arvid Nilssons Fond, Skibsreder Per Henriksen, R og Hustrus Fond, the European Union's Horizon 2020 program [grant number 847770], Læge Sophus Carl Emil Friis og hustru Olga Doris Friis' Legat, and an unrestricted grant from Medtronic.

Genome-wide association study on cerebral white-matter hyperintensities in 36,577 individuals

Background/Introduction

A quarter of all strokes are caused by cerebral small vessel disease (CSVD), which is also the most common pathology underlying vascular dementia. [1] White matter hyperintensities (WMH), a radiological marker detectable on magnetic resonance imaging (MRI), can serve as a proxy for CSVD. WMH is associated with stroke, increased risk of dementia and functional decline in older age. [2,3]

Purpose

We aimed at investigating the genetic architecture of WMH using cerebral MRI data.

Methods

We used imaging data ∼40,000 individuals from the UK Biobank, a large population-based, prospective cohort study. We selected individuals with available total volume of WMH from T1 and T2_FLAIR images.

We performed a genome-wide association study (GWAS) on autosomal genetic variants assuming an additive model based on genotype dosages with BOLT-LMM treating WMH as outcome.

We applied LD score regression (LDSC software) to estimate the genetic correlation between WMH traits and traits selected based on availability and relevance for cardiovascular disease.

Results

We included a total of 36,577 individuals with available quality controlled cerebral MRI data.

Genome-wide analysis identified 20 loci of statistical significance, six of which are not previously reported (Fig. 1). Within these novel loci, the following genes are located in proximity to lead variants: EHBP1, OTX1, WDPCP, VCAN, WNT16, FAM3C, ERI1, PRAG1, CACNB2, MTHFSD, FOXL1, FOXC2. Using BOLT, we found the heritability of WMH to be 37%.

We investigated genetic correlation between WMH and multiple phenotypes (Fig. 2). We observed the highest correlation with small vessel stroke (rg=0.56, P=3.9x10–4) Interestingly, WMH was genetically correlated with left atrial volume (rg=0.24, P=2.8x10–3).

Conclusion

In a GWAS on WMH acquired from cerebral MRI, we identified 20 significant loci, of which six are novel. This genetic study provides insights on the biological understanding and epidemiology of CSVD.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): John and Birthe Meyer FoundationThe Hallas-Møller Emerging Investigator Novo Nordisk

High prevalence of deleterious variants in cardiomyopathy genes in patients with early onset atrial fibrillation

Background

Atrial Fibrillation (AF) is a common cardiac arrhythmia associated with increased morbidity and mortality. AF has a significant heritable component and genome-wide association studies have associated numerous loci in the human genome with AF. The arrhythmia is relatively rare in younger individuals, but studies have shown that individuals with early-onset AF may harbour a considerable burden of pathogenic genetic variants.

In recent years, the concept of atrial cardiomyopathy has emerged as a mechanism involved in AF pathogenesis. Genes well-known to be related to ventricular structure, including cardiomyopathies have now also been associated with AF.

Purpose

Using targeted genetic sequencing, this study aimed to elucidate the role of deleterious genetic variants in cardiomyopathy genes in early-onset AF, and provide new insights into AF pathogenesis.

Methods

We performed targeted genetic sequencing of 445 Danish individuals with onset of AF before age 40 years and no other cardiovascular co-morbidities, and of 387 controls with no history of AF. Based on guidelines for genetic testing for clinical use, we focused on 30 genes with well-established associations with dilated cardiomyopathy, hypertrophic cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy. We examined the prevalence of loss-of-function variants (defined as variants leading to premature stop-codon, frameshift or splice-site variants), as these are most likely to be disease-causing. We filtered for rare variants using a minor allele frequency &lt;0.1%. The difference in prevalence in the two groups was analyzed using a logistic regression model.

Results

We found that 38 of the 445 early-onset AF patients carried loss-of-function variants in well-established cardiomyopathy genes. The prevalence of rare, loss-of-function variants was enriched in cases compared with controls (8.5%. vs. 1.0%, P=8.27x10–7). The variants were identified in eight different genes, with most rare variants found in the TTN gene (Table 1). In sensitivity analyses excluding TTN variants, we found that 12 individuals (∼2.7%) with AF harbored deleterious loss-of-function variants (P=0.0396).

Conclusions

Individuals with early onset of AF have a considerable burden of rare, deleterious variants in established cardiomyopathy genes. These new insights could help inform future recommendations for genetic testing and follow-up to detect early cardiomyopathy manifestations to prevent adverse outcomes in patients with early onset of AF. These findings support the presence of atrial cardiomyopathy.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Hallas-Møller emerging investigator grant, The Novo Nordisk Foundation (NNF: NNF17OC0031204)The John and Birthe Meyer Foundation

Genome-wide multi-trait analysis on cardioembolic stroke identifies 47 novel loci

Background

Ischemic stroke is one of the leading causes of death and disability-adjusted life-years worldwide. It has several subtypes and cardioembolic stroke (CES) accounts for 15–30% of ischemic strokes. Atrial fibrillation (AF) is the most important risk factor for CES. AF increases the risk of stroke up to 5-fold and there is a substantial overlap in the aetiology of AF and CES. Large genome-wide association studies (GWAS) on AF have identified more than 150 common and rare genetic variants. However, the difficulty in acquiring large sample sizes of CES cohorts has hindered the genetic description of the disease.

Purpose

In this study, we mapped the genetics of CES to increase our understanding of the molecular biology driving the disease. By leveraging the large genetic cohorts of AF through a multi-trait analysis of AF and CES, we aimed to bypass the lack of statistical power for studying the genetics of CES.

Methods

First, we obtained the largest possible sample size of AF GWAS by conducting a meta-analysis on publicly available summary statistics from the FinnGen study (v5) and the largest multi-ethnic meta-analysis on AF to date. Summary statistics for stroke were obtained from the largest multi-ancestry GWAS on stroke to date, MEGASTROKE, which examined different ancestries and stroke subtypes. Multi-trait analysis requires a high genetic correlation. Genetic correlations between the different stroke summary statistics and the AF meta-analysis were assessed with LD Score Regression.

Second, we performed a joint meta-analysis of CES with MTAG using the CES summary statistics from MEGASTROKE and the AF GWAS meta-analysis. MTAG recalculates p-values and effect sizes for each trait separately by leveraging the covariation for correlated traits. The MTAG-computed summary statistics for CES and AF were subjected to genomic loci characterisation, with functional and annotation analysis carried out by FUMA.

Results

We show a high genetic correlation between CES and AF (rg = 0.88). Using MTAG, the GWAS meta-analysis of CES increased the effective sample size by almost 3 folds (n=24,639, Table 1). We discovered 50 CES loci whereof 47 are novel (Fig. 1). We mapped 101 genes to CES MTAG computed summary statistics, obtaining enrichment in gene sets involved in cardiac conduction and contraction, cardiac tissue development and cranial skeleton morphogenesis.

Conclusion

In conclusion, we identified 47 novel CES loci and demonstrated a substantial shared genetic variation with AF. We furthermore mapped 98 genes not previously linked to CES by AF. These results represent findings that potentially could be used for antithrombotic drug discovery and are a major advance in our understanding of the genetic underpinnings of CES

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): John and Birthe Meyer Foundation, the Research Foundation of the Heart Centre, Rigshospitalet, the Research Council at Rigshospitalet.The Hallas-Møller Emerging Investigator Novo Nordisk (NNF17OC0031204), Arvid Nilsson Foundation

Arrhythmogenic right ventricular cardiomyopathy – evolution of electrocardiographic markers during long-term follow-up prior to ascertainment of diagnosis

Background

Depolarization and repolarization abnormalities are part of the diagnostic Task Force Criteria of 2010 (TFC2010) for arrhythmogenic right ventricular cardiomyopathy (ARVC). These abnormalities are thought to be progressive but have also been described as dynamic and sometimes reversible. Evolution of ECG abnormalities prior to clinical ARVC diagnosis is poorly studied.

Objective

To assess the evolution of ECG depolarization and repolarization characteristics in patients with ARVC prior to diagnosis and to identify markers of disease progression at a preclinical stage.

Methods

353 patients with definite ARVC from Sweden, Denmark, the Netherlands and Canada with at least one 12-lead digital ECG (65% males, 67% probands, 56% mutation carriers, median age at diagnosis 42 [IQR 29–53] years and median age at first ECG 44 [30–55] years) were included. Digital ECGs were extracted from regional ECG archives. ECGs with left bundle branch block, ventricular pacing or recorded either prior to 15 years of age or after heart transplantation were excluded. Remaining 6,871 ECGs were digitally processed and automatically analysed using the Glasgow algorithm. Median values for overall QRS duration, terminal activation delay (TAD) in lead V1 as well as amplitudes of QRS-T-components in precordial leads per patient per year were used for analyses and graphically represented using Lowess smoothing with cubic splines (Figure 1). Blue lines indicate smoothed conditional mean with 95% confidence interval (shadow). Time “0” (red line) indicates the time when TFC2010 were fulfilled for definite diagnosis.

A database of 18,564 anonymized digital ECGs (58% males, median age at latest ECG 41 years [IQR 32–52]) who were in contact with health care during 2020–2021 was processed using the same exclusion criteria and signal-processing methodology as in the ARVC group and used as a reference (black line).

Results

TAD in lead V1 and overall QRS duration demonstrated a significant increase years before ARVC diagnosis, and significant reductions were seen in QRS-T voltages measured as R wave amplitude, QRS amplitude (the absolute sum of R wave and S wave), and T wave amplitude (Table 1 and Figure 1). The changes were seen in all precordial leads, not only the right-sided, and visually diverging from the controls.

Conclusion

Development of the ARVC ECG phenotype started several years before diagnosis and continued afterwards. QRS duration and TAD increased, QRS voltages decrease, and T wave amplitude decreased eventually leading to T wave inversion. These changes might be visually assessed but also measured with available ECG software. These findings may be clinically useful in the screening and follow-up of ARVC relatives.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Governmental funding of clinical research (ALF), Region Ostergotland, Sweden.The Swedish Heart-Lung Foundation.

Cardiac resynchronisation therapy and implantable cardioverter-defibrillator in non-ischaemic systolic heart failure: extended follow-up of the DANISH trial

Background

In the Danish Study to Assess the Efficacy of Implantable Cardioverter-Defibrillators [ICDs] in Patients with Non-ischaemic Systolic Heart Failure on Mortality (DANISH) trial, ICD implantation did not provide an overall survival benefit in patients with non-ischaemic systolic heart failure. A high proportion of patients in the DANISH trial received a cardiac resynchronisation therapy (CRT) device, which improves the prognosis in patients with heart failure. Therefore, it is of interest to examine whether the effect of ICD implantation in patients with non-ischaemic systolic heart failure is modified by CRT.

Purpose

Adding 4 years of additional follow-up to the DANISH trial, we examined the effect of ICD implantation according to status with respect to CRT implantation at baseline.

Methods

In the DANISH trial, 556 patients with non-ischaemic systolic heart failure were randomised to receive an ICD and 560 to receive usual clinical care (control). Patients fulfilling indications for a CRT device received a CRT-defibrillator (if randomised to ICD arm) or CRT-pacemaker (if randomised to control arm). In the ICD group, 322 patients (57.9%) received a CRT device; in the control group, 323 patients (57.7%) received a CRT device. In this extended follow-up study, patients were followed until May 18, 2020. The primary outcome was death from any cause; secondary outcomes were cardiovascular death and sudden cardiovascular death.

Results

During a median follow-up of 9.5 years, the ICD group did not have significantly lower all-cause mortality compared with the control group (hazard ratio [HR] 0.89 [95% CI, 0.74–1.08]). The results were independent of whether the patient received a CRT device at randomisation (patients with a CRT device: HR 0.92 [95% CI, 0.72–1.18]; patients without a CRT device: HR 0.86 [95% CI, 0.64–1.14]; P for interaction, 0.72). Similarly, ICD implantation did not reduce rates of cardiovascular death overall (HR 0.87 [95% CI, 0.70–1.09]), and this association was not modified by CRT (patients with a CRT device: HR 0.89 [95% CI, 0.66–1.19]; patients without a CRT device: HR 0.85 [95% CI, 0.60–1.20]; P for interaction, 0.86). The ICD group had significantly lower rates of sudden cardiovascular death in the overall population (HR, 0.60 [95% CI, 0.40–0.92]), and this association was not modified by CRT (patients with a CRT device: HR 0.69 [95% CI, 0.40–1.21]; patients without a CRT device: HR 0.51 [95% CI, 0.26–0.97]; P for interaction, 0.47). See Figure 1 for all results.

Conclusions

In this extended follow-up study of the DANISH trial, the effect of ICD implantation in patients with non-ischaemic systolic heart failure was not modified by CRT.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): The DANISH trial was supported by unrestricted grants from Medtronic, St Jude Medical, Tryg Fonden, and the Danish Heart Foundation. No further funding was obtained for this follow-up study.

Accidental diagnosis of bradyarrhythmia in patients monitored for atrial fibrillation

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): The study was supported by The Innovation Fund Denmark [12-135225], The Research Foundation for the Capital Region of Denmark [no grant number], The Danish Heart Foundation [11-04-R83-A3363-22625], Aalborg University Talent Management Programme [no grant number], Arvid Nilssons Fond [no grant number], Skibsreder Per Henriksen, R. og Hustrus Fond [no grant number], Medtronic [no grant number], and the AFFECT-EU consortium which has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 847770.

Background

The interest in heart rhythm monitoring and technologies to detect arrhythmia is increasing. The prevalence and prognostic significance of subclinical bradyarrhythmias is unknown.

Objectives

To assess the accidental diagnosis of bradyarrhythmia and its subsequent treatment and prognostic impact in persons screened for atrial fibrillation compared to unscreened persons.

Methods

We utilized a randomized trial of ≥70-year-olds with cardiovascular risk factors recruited outside the hospital setting to receive implantable loop recorder screening for atrial fibrillation (ILR group) vs. usual care (Control group). Time-to-event analyses were performed for bradyarrhythmia, pacemaker implantation, syncope, and sudden cardiovascular death.

Results

A total of 6004 participants were randomized (mean age 75 years, 47% women, 91% with hypertension, 20% with prior syncope), 4503 to Control and 1501 to ILR. The median follow-up period was 64.5 [59.3, 69.8] months. A total of 675 deaths occurred with an overall rate of 2.16 (2.00-2.33) per 100 person-years, and 67 sudden cardiovascular deaths occurred with a rate of 0.21 (0.15-0.28) for the Control group and 0.23 (0.14-0.37) for the ILR group (hazard ratio (HR) 1.11 (0.64-1.90), p=0.71)).

The overall rate of incident bradyarrhythmia was 1.63 (1.49-1.79) per 100 person-years, and bradyarrhythmia was diagnosed in 172 (3.82%) and 312 (20.8%) participants in the Control and ILR group, respectively (HR 6.21 (5.15-7.48), p&lt;0.0001) (Figure 1). The most common bradyarrhythmia was sinus node dysfunction (SND) which was diagnosed in 68 participants in the Control group (1.51%) and 214 in the ILR group (14.26%). In the Control group, 57.35% of diagnoses of sinus node dysfunction resulted in pacemaker implantation, compared to 12.15% in the ILR group where the majority was treated conservatively (Figure 2). The second-most common type of bradyarrhythmia was high-grade atrioventricular block (AVB) which was diagnosed in 86 participants in the Control group (1.91%) and 54 in the ILR group (3.60%). In both groups, the majority of high-grade AVB was treated with pacemaker, although 29.63% in the ILR group were treated conservatively. Risk factors for bradyarrhythmia included higher age, male sex, and prior syncope.

Overall, a pacemaker was implanted in 132 (2.93%) and 66 (4.40%) participants (HR 1.53 (1.14-2.06), p&lt;0.0001), syncope occurred in 120 (2.66%) and 33 (2.20%) participants (HR 0.83 (0.56-1.22), p=0.34), and sudden cardiovascular death occurred in 49 (1.09%) and 18 (1.20%) participants (HR 1.11 (0.64-1.90), p=0.71) in the Control and ILR group, respectively.

Conclusions

Bradyarrhythmias are highly common in ≥70-year-olds with cardiovascular risk factors. Compared to Control, ILR monitoring led to a six-fold increase in diagnosis of bradyarrhythmia and a significant increase in pacemaker implantations, but no change in the risk of syncope or sudden death.

Adherence to wearables in implantable cardioverter-defibrillator patients: Preliminary results from the prospective, multicenter SafeHeart-study

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Horizon2020

Introduction

Wearable devices are gaining interest in the clinical assessment of physical behavior as a marker of disease severity. With the increased use, patient willingness and adherence will be increasingly important. As part of the SafeHeart study, examining the potential of physical behavior as an identifier of clinical deterioration in patients with an implantable cardioverter defibrillator (ICD), we present preliminary results on adherence to a wrist-worn wearable used for physical behavior assessment.

Purpose

Define the willingness to participate and long-term adherence to wearables in an ICD population.

Methods

This is a preliminary analysis of the ongoing multicenter, prospective, observational SafeHeart study. SafeHeart is aimed to construct a personalized prediction engine for ICD therapy using wearable-assessed physical behavior, remote ICD monitoring, electronic health records, and patient-reported data. The study will enroll 400 participants with an ICD with or without cardiac resynchronization therapy (CRT-D). In this preliminary analysis, wearable data was analyzed for the first 50 participants, where inclusion required a minimum of 1 month of follow up data. No data from the wearables were provided to the participants. The wrist-worn wearables were used continuously (day and night) for up to 12 months of follow-up. Adherence to the wearable was measured through patient-reported (subjective) adherence and wearable-measured (objective) adherence. Data were extracted from the wearables and non-wear time was detected via open source algorithms. A valid day was set to 22 hours of available wear time with 24-hour periods assessed from 3pm to 3pm for sleep metric capture. The willingness to participate and dropout rates were calculated for the same first 50 patients of the study.

Results

A total of 50 ICD participants were included in this study. The mean age was 65.1 years, 82 % male, with a mean follow up of 7 weeks, generating 326 patient weeks of data. Regarding patient-reported adherence, participants reported 81.4% full adherence and 18.6 % of participants reported very brief non-wear due to e.g. sauna or surgery. Of those reporting non-wear, 62.5% described one episode only of non-wear lasting 15-75 minutes. Regarding objectively measured adherence from wearable data, full adherence was shown in 91.7% of days. The mean number of valid days per participant was 41.3. Recruitment rates showed a willingness to participate of 50% (50/100) out of eligible subjects invited. No participants were lost to follow

Conclusion

Results show high adherence and reasonable willingness to participate without wearable adherence dropping over time. Comparison of objectively measured and patient-reported adherence showed similar values.

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&lt;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&lt;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.

Systolic blood pressure and effects of screening for atrial fibrillation with long-term continuous monitoring

Funding Acknowledgements

Type of funding sources: Other. Main funding source(s): The LOOP Study was supported by Innovation Fund Denmark [grant number 12-1352259], The Research Foundation for the Capital Region of Denmark, The Danish Heart Foundation [grant number 11-04-R83-A3363-22625], Aalborg University Talent Management Program, Arvid Nilssons Fond, Skibsreder Per Henriksen, R og Hustrus Fond, the European Union’s Horizon 2020 program [grant number 847770 to the AFFECT-EU consortium], Læge Sophus Carl Emil Friis og hustru Olga Doris Friis’ Legat, and an unrestricted grant from Medtronic.

Background

The recently published LOOP Study was a randomized controlled clinical trial to evaluate systematic atrial fibrillation (AF) screening with long-term continuous monitoring in an elderly population at risk and found no significant reduction in stroke. However, the screening effects seemed to differ across levels of systolic blood pressure (SBP). It is well-known that hypertension constitutes a prominent risk factor for clinical AF and stroke alike, but data on the impacts of SBP on subclinical AF and hereby AF screening efficacy are lacking.

Purpose

With this post hoc analysis of the LOOP Study, we aimed to provide insights into the interaction between SBP and benefits of systematic AF screening.

Methods

The LOOP Study randomized individuals aged 70-90 years with ≥1 stroke risk factor (hypertension, diabetes, heart failure, or previous stroke) and without prior AF to either monitoring with implantable loop recorder (ILR) and initiation of oral anticoagulation upon detection of new-onset AF episodes lasting ≥6 minutes, or usual care (control group). In total, 5997 participants with available SBP measurements at enrolment were included in the present analysis. The interaction between SBP and ILR screening efficacy on stroke or systemic arterial embolism (SAE), as indicated by hazard ratio (HR) for ILR versus control, was assessed with polynomial moving-average regression. The lowest SBP threshold with significant screening benefits was further determined and used to examine clinical outcomes and the occurrence of AF with respect to dichotomized SBP. Additionally, penalized spline models were employed to assess AF occurrence by SBP as a continuous variable.

Results

HR of stroke/SAE for ILR versus control decreased with increasing SBP and the lowest threshold for significant screening benefits was at SBP ≥150 mmHg. ILR screening of participants with SBP ≥150 mmHg yielded a 45% risk reduction of stroke/SAE (HR 0.55 [0.37-0.82]). Within the ILR group, SBP ≥150 mmHg was associated with an increased risk of AF episodes ≥24 hours as compared to lower SBP (HR 1.57 [1.01-2.45]), but not with the overall occurrence of AF (HR 1.14 [0.95-1.36]). No significant association between SBP and AF occurrence in the ILR group was reported in penalized spline models either (p-value: 0.73).

Conclusions

The benefits of ILR screening for AF on stroke/SAE increased with increasing blood pressure. SBP ≥150 mmHg was associated with a 1.5-fold increased risk of AF episodes ≥24 hours, along with an almost 50% risk reduction of stroke/SAE by ILR screening.

Reduced longitudinal strain in the left ventricular inferior wall predicts malignant arrhythmia in non-ischemic heart failure. A DANISH substudy

Funding Acknowledgements

Type of funding sources: None.

BACKGROUND

Small studies have suggested that poor regional myocardial function may be associated with malignant arrhythmias, in particular around the inferior-posterior region. We tested this hypothesis in a subgroup of patients from the DANISH trial.

METHODS

From two centers, 317 patients with non-ischemic heart failure (LVEF &lt; 35%) from the DANISH trial were evaluated by 2D-strain echocardiography. Regional strain was calculated as the average longitudinal strain in basal-, midventricular- and apical segments in each of the six left ventricular walls. Reduced regional function was defined as below-median regional strain. The endpoint was a composite of sudden cardiac death (SCD), sustained VT, admission with ventricular arrhythmia, and appropriate therapy from a primary prophylactic ICD. Time-to-first-event analysis was performed using Cox models.

RESULTS

Mean age at inclusion was 62 years (72% male), median LVEF was 25% (IQR 20-30) median inferior strain was -8.7% (IQR -12.3; -4.9). After a five-year follow-up, 43 events were observed. Reduced inferior strain was associated with the composite endpoint in univariate analysis with a HR 2.08(95% CI 1.11-3.90), P = 0.021. After multivariate adjustment for clinical and echocardiographic parameters, inferior strain remained an independent predictor with a HR 2.78(95% CI 1.39–5.56), P = 0.004. Strain measurements in no other region were associated with the endpoint in the multivariate analysis. In subgroup analysis of patients in the two lower age tertiles (&lt;68 of age) we found that reduced inferior- and posterior strain were associated with development of the composite endpoint after multivariate adjustment with HRs of 3.25(95% CI 1.41-7.53), P = 0.006 and 2.51(95% CI 1.14-5.53), P = 0.022.

CONCLUSIONS

Low inferior-posterior strain was associated with a 2-3-fold increase in risk of malignant arrhythmia and SCD in patients with non-ischemic heart failure. Abstract Figure.

Heart rate variability in patients with pulmonary hypertension as assessed with long-term continuous cardiac monitoring correlates with other established risk assessment parameters

Background

A few short-term monitoring studies (10 minutes–24 hours) have revealed lower heart rate variability (HRV) in patients with pulmonary hypertension (PH). This is the first study to apply continuous heart rate variability monitoring in pulmonary hypertension.

Purpose

Assessment of HRV as a non-invasive risk marker in pulmonary hypertension (PH) using long-term continuous monitoring.

Methods

Patients diagnosed with PH according to international guidelines were included in this prospective single-centre study. Patients were implanted with a Reveal LINQ (Medtronic) insertable cardiac monitor to record HRV. HRV was expressed as the mean of HRV in sinus rhythm during the full day for all days per patient (SDANN method). Pearson and Spearman correlations between HRV and established risk determinants were estimated.

Results

Thirty-two patients with PH were included. Twenty-two patients had pulmonary arterial hypertension (PAH) and 10 had chronic thromboembolic PH. During 50 patient-years of continuous monitoring (median: 654 (range: 394–714) days per patient), HRV was significantly correlated to the following risk determinants in PH (variable 1–3) in addition to other variables (variable 4–8): (1) WHO functional class (FC) (r=−0.55, p = &lt;0.001) (Figure 1), (2) NT-proBNP (r=−0.5, p=0.003), (3) cardiac index (r=−0.45, p=0.03), (4) heart rate at night time (0 am–4 am) (r=−0.68, p=&lt;0.001) (Figure 1), (5) TAPSE (r=0.41, p=0.025), (6) right ventricle ejection fraction (r=−0.37, p=0.014), (7) tricuspid regurgitation gradient (r=−0.38, p=0.045) and (8) right ventricle end diastolic volume (ml) (r=−0.37, p=0.035).

Conclusions

This is the first study to apply continuous monitoring of HRV in patients with PH. HRV was significantly correlated with several variables already being used in risk stratification. HRV may be an additional non-invasive variable in risk assessment in PH aiding in optimization of treatment.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Janssen

Integration of Scandinavian genetic data with UK biobank data implicates the RBM20 gene with atrial fibrillation pathogenesis

Purpose

Atrial fibrillation (AF) is the most common sustained arrhythmia. It carries a large healthcare burden and is associated with serious complications. The arrhythmia has a substantial genetic component and is associated with several structural genes, including the gene TTN. A recent large genome-wide association study on AF found an association to RBM20. The RBM20 gene is a splicing factor targeting TTN, RYR2 and CAMK2D among other cardiac genes. Using Next-Generation Sequencing and data derived from the UK Biobank, we aimed to reveal the role of RBM20 in AF.

Methods and results

We examined the burden of rare (Minor allele frequency (MAF)&lt;0.01%) RBM20 loss-of-function (LOF) variants in whole-exome sequencing data from the UK Biobank (n=175,280). AF was defined by ICD9/10, while individuals without AF were used as controls. Association tests aggregating rare variants in RBM20 using the Efficient Variant-Set Mixed Model Association Test (SMMAT) were performed to assess the effect of LOF RBM20 variants, adjusted for age, sex and principal components. We identified 33 LOF variants in RBM20, which were significantly enriched in AF (P=0.0087).

To examine the effect of rare missense RBM20 variants in the splicing of TTN, we screened an in-house cohort of 531 Scandinavian early-onset AF patients using targeted sequencing. We filtered for rare (MAF&lt;0.1%) and deleterious (defined as combined annotation dependent depletion score &gt;20) variants and identified nine missense variants and three novel LOF variants in RBM20. To evaluate the effect of these RBM20 variants, we constructed a series of human RBM20 single nucleotide base exchange mutants. The splicing activity of the variants was measured with RT-qPCR on HEK293 cells transfected with a TTN241–3 splicing reporter. Four of these variants resulted in a significantly altered splicing activity in TTN, with the largest effect observed for LOF variants.

In order to examine the biological effect of RBM20 variants on structural changes in atrial tissue, we used a Norwegian Brown rat animal model with loss of RBM20. In this model, Transmission Electron Microscopy revealed altered sarcomere and mitochondrial structure in its atrial cardiomyocytes. Furthermore, nanopore RNA sequencing of atrial tissue from the aforementioned animal model indicated altered expression in several key cardiac genes, including TTN and PITX2.

Conclusion

Rare RBM20 LOF variants are significantly enriched in AF cases, seen in a large population of 175,000 individuals. We demonstrated that the effect of LOF RBM20 on alternative TTN splicing can be detected on an individual level in patients with AF. Studies using an animal model indicates that LOF in RBM20 may affect atrial function through altered expression of several genes in the atria, and may cause structural changes in the atrial cardiomyocytes. This suggests that RBM20 may be involved in AF pathogenesis mediated through an atrial cardiomyopathy.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Novo Nordisk Foundation Pre-Graduate Scholarships (NNF18OC0053094)The Hallas Møller Emerging Investigator grant (Novo Nordisk Foundation (NNF17OC0031204))

Left atrial remodeling and cerebrovascular disease assessed by magnetic resonance imaging in patients undergoing continuous heart rhythm monitoring

Background

Atrial remodeling and atrial fibrillation (AF) have both been associated with cerebrovascular lesions. We wished to investigate the possible direct association between atrial remodeling and cerebrovascular disease including white matter lesions and lacunar infarcts in patients with and without atrial fibrillation (AF) as documented by implantable loop recorder (ILR).

Methods

Cardiac and cerebral MRI scans were acquired in a cross-sectional study including participants ≥70 years of age with stroke risk factors (history of hypertension, diabetes mellitus, congestive heart failure and/or previous stroke) but without known AF. Cerebrovascular disease was visually rated using the Fazekas scale and number of lacunar strokes. Left atrial (LA) (see figure) and ventricular volumes and function were analyzed, and associations between atrial remodeling and cerebrovascular disease were assessed with logistic regression models. Multivariable models were adjusted for sex, age, diabetes, hypertension, heart failure and history of stroke/transient ischemic attack. The analyses were stratified according to sinus rhythm or any AF during three months of continuous ILR monitoring to account for subclinical AF.

Results

Of 200 participants investigated, 87% had a Fazekas score≥1 and 45% had ≥1 lacunar infarct. Within three months of ILR implantation, AF was detected in 28 (14%) participants, while 172 (86%) had sinus rhythm only. Results are summarized in table. For participants with sinus rhythm, lower LA passive emptying fraction was associated with Fazekas score after multivariable adjustment, while LA total emptying fraction was borderline significant, and increased LA maximum and minimum volumes were associated with lacunar infarcts. There were no significant associations in patients with AF.

Sensitivity analyses showed similar results with longer screening periods for AF.

Conclusions

In patients free from AF as documented by ILR monitoring, we found an independent association between LA passive emptying and Fazekas score, and between atrial volumes and lacunar infarcts. This supports that atrial remodeling alone without AF is associated with an increased risk of cerebrovascular lesions.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): The Innovation Fund, DenmarkThe Research Foundation for the Capital Region of Denmark

Genome-wide association study of atrial fibrillation in 114,539 Finnish individuals reveals novel locus associated with cardiac remodelling

Background/Introduction

Atrial fibrillation (AF) is the most common cardiac arrhythmia and it is associated with serious complications, such as stroke, heart failure, and premature death. Previous genome-wide association studies (GWAS) have associated more than 140 genomic loci with AF; however, these studies predominantly include subjects of European ancestry. Although, the Finnish population is European, it is genetically considered different from other European populations as it has been isolated and developed through multiple bottlenecks followed by population growth. Therefore, pathogenic variants are more easily discovered and heritably diseases are more prevalent.

Methods

We accessed summary statistics on atrial fibrillation and flutter (I48) from the Finngen project. Loci were defined as 1 megabase regions around lead SNPs, and loci were considered novel when the SNPs had P-values &lt;5x10–8 after conditional analysis, and no previously reported SNPs were within the loci. FINEMAP was done with a Finnish LD reference panel, and colocalization of GWAS and eQTL signals were analysed with MetaXcan.

Results

A GWAS on 17,325 Finnish AF cases and 97,214 controls confirms 16 previous identified loci and reveals one novel locus on chromosome 19. The novel lead SNP, rs190065070 (odds ratio [OR] = 1.44, 95% confidence interval [CI] = 1.29–1.61, P-value = 5.96x10–11), is close to the gene EMC10, which encodes the endoplasmic reticulum membrane protein complex subunit 10. While the locus harbours other genes, our MetaXcan analysis could not provide conclusive evidence for other plausible genes. The EMC complex consists of 10 subunits and is a chaperone in endoplasmic reticulum-resident membrane proteins. Previous mouse studies have shown EMC10 to be important in angiogenesis after myocardial infarction, and it has recently been associated with a novel neurodevelopment syndrome. The EMC1 subunit has been associated with congenital heart disease.

Conclusion

We present a novel susceptibility locus associated with AF in the Finnish population. The locus is in proximity to the gene EMC10, which is involved in structural remodelling of the heart after myocardial infarction. These results propose a potentially novel pathophysiological pathway in AF.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): The Research Foundation RigshospitaletThe John and Birthe Meyer Foundation

Accelerometry-assessed physical behaviour and the association with clinical outcomes in implantable cardioverter-defibrillator recipients: a systematic review

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Eurostars

Introduction

Patients at a high risk of sudden cardiac death (SCD) benefit from an implantable cardioverter defibrillator (ICD). However, they remain at a high risk of (inappropriate) shocks, heart failure, mortality and psychological distress. Consumer-level wearable accelerometry as method for recording physical behaviour (PB) has gained popularity over the past years, but so far the clinical potential is largely underinvestigated. The identification of patterns in PB and the association with clinical outcomes may provide a means to improve ICD therapy.

Purpose

This review addresses the evidence concerning PB in ICD patients and aims to characterise PB patterns associated with clinical outcomes.

Methods

A systematic review of studies focussing on accelerometer-assessed PB in patients older than 18 years equipped with an ICD, or patients at a high risk of SCD (e.g. advanced heart failure) was performed. PB could be assessed using a wearable accelerometer or an embedded accelerometer in the ICD (i.e. device-measured physical activity (D-PA)). Papers presenting quantitative data in English language peer reviewed journals published between January 2000 and September 2020 were identified via the OVID MEDLINE and OVID EMBASE databases. A study protocol describing study selection, data charting and summarisation of results was developed apriori. Study selection was conducted by two independent reviewers and a third reviewer in case of disagreement.

Results

A total of 4219 studies were identified, of which 51 were deemed appropriate for this review. Of these studies, 29 examined D-PA (n = 169.742 patients), 19 examined wearable accelerometery (n = 1.601) and 3 validated wearable accelerometry against D-PA (n = 106). The main findings were that (i) a low level of physical activity (PA) after implantation of the ICD and (ii) a decline in physical activity were both associated with an increased risk of ICD shocks, hospitalization and mortality. Second, PB was affected by cardiac factors (e.g. onset of atrial arrhythmias, ICD shocks) and non-cardiac factors (e.g. seasonal differences, pandemic lockdown). Third, PB was related to left ventricular ejection fraction, physical and cognitive function and quality of life. The evidence regarding wearable accelerometry compared to D-PA was scarce and heterogeneous.

Conclusion

This review demonstrated the potential of PB as an identifier of clinical deterioration in an ICD population. Accelerometer-assessed PB data could improve early warning systems and facilitate preventive and pro-active strategies, especially considering the nature of PB as modifiable risk factor. We suggest two directions for future research: (i) prospective collection of wearable accelerometry data in an ICD population to identify the most clinically relevant behavioural metrics (ii) investigation of preventive measures that can be undertaken once changes in PB are observed. Abstract Figure. Accelerometry-derived physical behaviour

Relationship between natriuretic peptides and left atrial mechanics and their relation to recurrence of atrial fibrillation following catheter ablation

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): The Danish Heart Foundation (grant no.: 09-04-R72-A2408-22545, 10-04-R78-A2929-22588, 11-04-R84-A3230-22650, and 18-R125-A8534-22083), and the Heart Centre Research Committee at Rigshospitalet, Copenhagen.

Background

The relationship between natriuretic peptides and atrial distension is not completely understood. Furthermore, how they can be used together clinically has not been fully explored.

Purpose

We sought to examine their interrelationship and how they relate to atrial fibrillation (AF) recurrence following catheter ablation.

Methods

Patients scheduled for catheter ablation as part of a randomized controlled clinical trial were included. Patients who underwent pre-operative echocardiography and had natriuretic peptide measurements performed, specifically mid-regional proANP (MR-proANP) and N-terminal proBNP (NT-proBNP), were included in this analysis. Echocardiography included assessment of atrial distension by left atrial strain.

The outcome was AF recurrence at 6 months after a 3-month blanking period. Logistic regression was performed to assess the association between log-transformed natriuretic peptides and AF. Multivariable adjustments were made for age, gender, randomization, and LVEF.

Results

Out of 99 patients 44 developed AF. No differences in natriuretic peptides nor echocardiographic measures were observed between the outcome groups.

Neither MR-proANP nor NT-proBNP were univariable predictors of AF recurrence (MR-proANP: OR = 1.06 (0.99-1.14), p = 0.09, per 10% increase; NT-proBNP: OR = 1.01 (0.98-1.05), p = 0.38, per 10% increase). These findings were unchanged after multivariable adjustments. However, atrial strain significantly modified the association between MR-proANP and AF (p for interaction = 0.009) such that MR-proANP was a significant predictor of AF in patients with high atrial strain values (OR = 1.24 (1.06-1.46), p = 0.008, per 10% increase) but not in patients with low atrial strain values. Among patients with high atrial strain values, an MR-proANP &gt; 116pmol/L was associated with a 10-fold increased risk of AF (OR = 9.78 (2.21-43.33), p = 0.003). figure.

Conclusion

Atrial natriuretic peptide predicts AF recurrence in patients with preserved atrial distension. Assessing atrial distension by echocardiography may assist the clinical interpretation of atrial natriuretic peptide concentration.

Abstract Figure.

Left atrial strain predicts subclinical atrial fibrillation detected by long-term continuous rhythm monitoring in elderly high-risk individuals

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): he Innovation Fund Denmark (grant no.: 12-135225), The Research Foundation for the Capital Region of Denmark, The Danish Heart Foundation (grant no.: 11-04-R83-A3363-22625 and 18-R125-A8534-22083), Aalborg University Talent Management Programme, Arvid Nilssons Fond, Skibsreder Per Henriksen, R. og Hustrus Fond, and Medtronic

Background

Left atrial (LA) speckle tracking is a novel technique that provides detailed information on atrial function. Its utility for predicting subclinical atrial fibrillation (SCAF) is, however, not well-established.

Purpose

To investigate whether LA speckle tracking measures are associated with SCAF as detected by long-term continuous rhythm monitoring.

Methods

This was an echocardiographic substudy of a randomized controlled clinical trial that enrolled elderly individuals (≥70 years) with a CHADS2-score≥2 to either no intervention or implantation of a loop recorder (Reveal LINQ) to detect SCAF (≥6 minutes). A subset of the participants receiving a loop recorder was included in this analysis. An echocardiographic examination was performed, which included conventional measurements and LA speckle tracking. LA speckle tracking allowed for assessment of reservoir, conduit, and contraction strain. Multivariable proportional hazards Cox regression was applied to adjust for the clinical risk score (CHARGE-AF) and net reclassification index (NRI) was used to assess prognostic improvement of this score. Incidence rate curves were constructed using Poisson models.

Results

Overall, 976 participants were eligible for analysis. Median follow-up time was 3 years (interquartile range: 1.7-4.0 years), during which 284 (29%) were diagnosed with SCAF. The mean age was 74 years, 56% were male, median CHA2DS2-VASc-score was 4. A dilated LA (LA volume≥34ml/m2) was observed in 152 (16%).

LA speckle tracking revealed that both LA reservoir strain and contraction strain were univariable predictors of SCAF (HR = 1.05 (1.03-1.06) and HR = 1.07 (1.05-1.10), p &lt; 0.001, per 1% decrease), such that decreasing reservoir and contraction strain were linearly associated with an increased risk of SCAF (figure). LA conduit strain was not a predictor of SCAF. These findings were unchanged after adjusting for the CHARGE-AF score, and both LA strain measures significantly improved the NRI when added to the CHARGE-AF score by 23% and 33%, respectively.

Even in participants with normal LA size, both reservoir and contraction strain were independent predictors of SCAF after multivariable adjustment (HR = 1.03 (1.01-1.05), p = 0.001 and HR = 1.06 (1.04-1.09), p &lt; 0.001, per 1% decrease).

Conclusion

Decreasing left atrial reservoir and contraction strain are independently associated with an increased risk of SCAF as detected by long-term continuous monitoring and provide incremental prognostic value in addition to clinical risk score.

Abstract Figure.

4259Discovery of the first genome-wide significant risk loci for syncope and collapse

Background

Syncope is a common condition in the general population causing frequent hospitalisation and visits to the emergency department. Family aggregation and twin studies have previously indicated that syncope and collapse has a heritable component.

Purpose

We investigated whether common genetic variants predispose to syncope and collapse.

Methods

We used genome-wide association data on syncope and collapse for 408,961 individuals with European ancestry from the UK Biobank study. In a replication study, the Integrative Psychiatric Research Consortium (iPSYCH) cohort (n=86,189) was used to investigate the risk of incident syncope stratified by genotype carrier status.

Results

We report on a genome-wide significant locus on chromosome 2q32.1 with the lead SNP rs12465214 (odds ratio [OR] = 1.13, 95% confidence interval [CI] = 1.10–1.17, P=5.8x10–15; Figure 1a). This association was replicated in the iPSYCH cohort, where homozygous carriers of the C allele conferred an increased hazard ratio (HR=1.30, CI: 1.15–1.46, P=1.68x10–5; Figure 1b). LD score regression demonstrated a significant genetic correlation (rg) with coronary artery disease (rg=0.41, P=6.99x10–15) and related phenotypes such as angina and hypertension (Figure 1c). Analyses of eQTL (P=4x10–8) and epigenetic chromatin states revealed that variation in this locus likely affects expression of the gene ZNF804A, which resides in its proximity (Figure 1d). A qPCR analysis showed that ZNF804A was mostly expressed in the brain. A lower level of ZNF804A expression was also detected in the cerebral arteries. ZNF804A was not expressed in heart tissue.

Figure 1

Conclusion

rs12465214 is associated with syncope and collapse. Variation in this locus likely modulates the expression of the nearby gene ZNF804A through eQTLs and chromatin interactions. ZNF804A is mainly expressed in the brain and cerebral arteries. However, the precise function of ZNF804A is unknown. Furthermore, syncope and collapse is a polygenetic trait and share a significant genetic overlap with coronary artery disease, angina and hypertension.

Acknowledgement/Funding

This work was supported by grants from The John and Birthe Meyer Foundation, The Research Foundation of the Heart Centre, Rigshospitalet, The Research

P5653Atrial fibrillation in arrhythmogenic right ventricular cardiomyopathy and its association with left atrial volume index

Background

Recent studies in arrhythmogenic right ventricular cardiomyopathy (ARVC) support atrial involvement in the disease progression and consider atrial fibrillation (AF) as one of the primary manifestations of ARVC. We aimed to assess clinical factors, components of 2010 Task Force criteria (TFC2010) and echocardiographic characteristics of atria associated with AF in the Scandinavian cohort of ARVC patients.

Methods

Study sample comprised of 106 definite ARVC patients by TFC2010 from three tertiary care centers participating in the Nordic ARVC Registry (33% females, median age at ARVC diagnosis 41 years [IQR 30–54 years]). No concomitant diseases were observed in 90 patients (85%) while 16 patients had one or more comorbidities: hypertension (n=6), diabetes mellitus (n=5), coronary artery disease (n=5) or congestive heart failure (n=9). AF was included in the registry protocol as a pre-specified clinical event and verified by processing of the electronic ECG databases which contains all ECG recordings from the involved hospitals catchment areas (earliest ECG from 1988). Left (LA) and right atrial (RA) dimensions were obtained by revisiting cardiac ultrasound examinations performed at the time of ARVC diagnosis. Association between AF and clinical characteristics was assessed using multivariable logistic regression analysis adjusted for age and gender.

Results

AF was diagnosed in 29 patients (27%) at a median age of 53 (IQR 38–63) years, 7 females (24%). Median time from ARVC diagnosis to AF onset was 8 (IQR 2–12) years. AF was univariately associated with right ventricular structural abnormalities meeting the definition of major imaging criterion by 2010TFC, ventricular tachycardia (VT) with superior axis (major criterion) and LA volume index. Significantly associated variables were included in a multivariate model, in which LA volume index (OR=1.07, 95% CI 1.01–1.14, p=0.021) and superior axis VT (OR=7.45, 95% CI 1.82–30.55, p=0.005) remained independently associated with AF. In receiver operating characteristic (ROC) curve analysis, LA volume index was significantly associated with AF (AUC=0.703, p=0.005) and with superior axis VT (AUC=0.703, p=0.021). AF was not associated with either RA volume index (univariate OR=1.03, 95% CI 0.99–1.06, p=0.203) or left ventricular ejection fraction (OR=0.97, 95% CI 0.92–1.03, p=0.299).

Conclusion

In patients with ARVC,AF is primarily associated with LA structural abnormalities without indication of RA involvement and is strongly associated with ventricular arrhythmias thus indicating parallel development of atrial and ventricular arrhythmic substrate.

P2627Diffuse coronary artery disease and effect of implantable cardioverter-defibrillators in patients with non-ischaemic systolic heart failure

Background

Implantable defibrillators reduce mortality in patients with ischaemic heart failure. The recent Danish Study to Assess the Efficacy of Implantable Cardioverter Defibrillators in Patients With Non-Ischaemic Systolic Heart Failure on Mortality (DANISH) found no overall effect on all-cause mortality with ICD implantation. Coronary artery disease (CAD) as the cause of heart failure had to be ruled out prior to inclusion into DANISH, but patients could have diffuse atherosclerosis, one- or two-vessel disease on the qualifying coronary angiogram if the investigator did not find that the degree of CAD could explain the severely reduced left ventricular ejection fraction. It is unknown if concomitant coronary atherosclerosis is related to outcome in patients with non-ischaemic cardiomyopathy and whether the effect of implanting an ICD is different in patients with non-ischaemic cardiomyopathy and coronary atherosclerosis.

Purpose

The aim of this study was to investigate the association between coronary atherosclerosis and all-cause mortality in patients with non-ischaemic systolic heart failure and the effect of ICD implantation in these patients.

Methods

Of the 1116 patients from the DANISH study, 838 patients with available coronary angiography data were included in this subgroup analysis. Patients were considered to have coronary atherosclerosis if the invasive cardiologist described diffuse atherosclerosis or coronary stenosis. We used cox regression to assess the relationship between coronary atherosclerosis and mortality and between ICD implantation and mortality in patients with and without coronary atherosclerosis. Data are presented as hazard ratios with 95% confidence intervals.

Results

Of the 838 patients, 266 (32%) had coronary atherosclerosis, 216 (81%) of whom were reported as having atherosclerosis without stenoses. Patients with coronary atherosclerosis were significantly older (median age 67 years vs 61 years), more often male (77% vs 70%) and had a higher prevalence of diabetes (30% vs 17%).

In univariable analysis, coronary atherosclerosis was a significant predictor of all-cause mortality (HR, 1.41; 95% CI, 1.04–1.91; P=0.03). However, the association between coronary atherosclerosis and all-cause mortality disappeared when adjusting for age, gender and diabetes (HR 1.02, 0.75–1.41, P=0.88). Adjusted hazard ratios are shown in Figure 1.

There was no association between ICD treatment and all-cause mortality in patients with or without coronary atherosclerosis (HR 0.94; 0.58–1.52; P=0.79 vs HR 0.82; 0.56–1.20; P=0.30), P for interaction=0.67.

Figure 1

Conclusions

In patients with non-ischaemic systolic heart failure, the concomitant presence of coronary atherosclerosis was associated with increased mortality. However, this association was not independent of other risk factors. ICD implantation was not associated with mortality risk in patients either with or without concomitant coronary atherosclerosis.

Acknowledgement/Funding

TrygFonden (Copenhagen, DK), Medtronic (US) and St. Jude Medical (US)

P4533Duration of heart failure and effect of defibrillator implantation in patients with non-ischemic systolic heart failure

Introduction

Patients with non-ischemic systolic heart failure have increased risk of sudden cardiac death (SCD) and death from progressive pump failure. Whether the risk of SCD changes over time is unknown. We seek to investigate the relationship between duration of heart failure, mode of death, and effect of implantable cardioverter defibrillator (ICD) implantation.

Methods

We examined the risk of all-cause death and SCD according to the duration of heart failure among patients with non-ischemic systolic heart failure enrolled in the Danish Study to Assess the Efficacy of ICDs in Patients with Non-ischemic Systolic Heart Failure on Mortality (DANISH) trial. Patients were divided according to quartiles of heart failure duration (Q1 ≤8 months, Q2 9 ≤18 months, Q3 19 ≤65 months, Q4 ≥66 months).

Results

A total number of 1116 patients were included. Patients with the longest duration of heart failure were older, more often men, had more comorbidity, and more often received cardiac resynchronizing therapy device. Doubling of heart failure duration was an independent predictor of both all-cause mortality (HR 1.26 95% CI 1.17–1.37, p<0.0001), and SCD (HR 1.29 95% CI 1.11–1.49, p=0.0009). The proportion of deaths caused by SCD was not different between heart failure quartiles (p=0.91), and the effect of ICD implantation on all-cause mortality was not modified by the duration of heart failure (p=0.59).

Duration of heart failure and death

Conclusions

Duration of heart failure predicted both all-cause mortality and risk of SCD independently of other risk indicators. However, the proportion of death caused by SCD did not change with longer duration of heart failure and the effect of ICD was not modified by the duration of heart failure.

Acknowledgement/Funding

The work was sponsored by The Danish Heart Foundation (Hjerteforeningen) and the Lundbeck Foundation (Lundbeckfonden). The DANISH trial was supported

P2247Pregnancies and childbirth in women with arrhythmogenic right ventricular cardiomyopathy are associated with low risk of ventricular arrhythmias

Background

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is associated with a risk of ventricular arrhythmias (VA) and sudden cardiac death (SCD). Even though female patients with ARVC are considered to be at lower risk of VA, the impact of pregnancy and child birth on the arrhythmic risk and development of arrhythmic substrate in the context of ARVC remains insufficiently studied.

Objective

To assess the risk of VA in relation to childbirth in women with ARVC and the impact of multiple pregnancies on progression of arrhythmic manifestations of the disease.

Methods

The study included 186 females with definite ARVC (n=107, 70 probands) or unaffected mutation-carriers (n=79) with median age at the end of follow up of 48 (IQR 34–60) years. Seventeen women had 1, 59 had 2 and 29 had ≥3 child births by the age of 40 years. VA was defined as ventricular tachycardia, appropriate ICD therapy, aborted cardiac arrest or SCD. Proportions of patients who experienced VA by the age of 40 years were compared between nulliparous women (n=81) and those with reported child births (n=105). VA-free survival after accomplished pregnancies was assessed for women ≥40 years of age (n=119). Cumulative probability of VA for each pregnancy (n=230) was assessed from conception through 2 years after child birth and compared between those that occurred before ARVC diagnosis (Pre-Ds, n=164), after it (Post-Ds, n=11) and in unaffected mutation carriers (No-Ds, n=55).

Results

The nulliparous women had lower age at ARVC diagnosis (37 vs 44, p=0.023) and more often had VA before the age of 40 (31% vs 13%, p=0.003) while the number of child births was not related to the prevalence of VA (18% among women with 1 childbirth, 12% in those with 2 and 14% in those with 3 or more, ns). Three women suffered SCD before the age of 40. VA-free survival after 40 years did not differ between nulliparous and those who gave birth (Figure A). Only four pregnancy-related events were documented (Figure B): 1 in the Post-Ds group and three in the Pre-Ds group. No pregnancy-related events were reported in the unaffected mutation carriers.

Conclusion

In this Scandinavian cohort of women with ARVC we observed no indication of an increased VA risk either associated with pregnancies or during long-term follow up after the last child birth.

P992Incidence, predictors, and success of ventricular tachycardia catheter ablation in arrhythmogenic right ventricular cardiomyopathy (ARVC): A long-term cohort study from the Nordic ARVC registry

Background

Catheter ablation may reduce ventricular tachycardia (VT) burden in arrhythmogenic right ventricular cardiomyopathy (ARVC) patients. However, little is known about factors predicting need for ablation and various outcomes have been reported.

Purpose

We sought to investigate predictors and use of VT ablation and to evaluate the post-procedural outcome in ARVC patients.

Methods

We studied 435 patients from the Nordic ARVC registry including 220 probands with definite ARVC according to the 2010 task force criteria and 215 mutation-carrying relatives identified through cascade screening. Patients were followed until first-time VT ablation, death, heart transplantation, or January 1st 2018. Additionally, patients undergoing VT ablation were further followed from the time of ablation for recurrent ventricular arrhythmias.

Results

Cumulative use of VT ablation was 4% (95% CI 3%-6%) and 11% (95% CI 8%-15%) after 1 and 10 years. All procedures were performed in probands in whom the cumulative use was 8% (95% CI 5%-12%) and 20% (95% CI 15%-26%). In adjusted analyses restricted to probands, only young age predicted need for ablation. In patients undergoing ablation, risk of recurrent arrhythmias was 59% (95% CI 44%-71%) and 74% (95% CI 59%-84%) 1 and 5 years after the procedure. Despite high recurrence rates, the burden of ventricular arrhythmias was reduced after ablation (p=0.0042). Young age, use of several antiarrhythmic drugs and inducibility to VT immediately after ablation were associated with an unfavorable outcome.

Conclusions

Twenty percent of ARVC probands developed a clinical indication for VT ablation within 10 years after diagnosis whereas mutation-carrying relatives were without such need. Although the burden of ventricular arrhythmias decreased after ablation, risk of recurrence was substantial.

P1231Loss of function in cytoskeletal genes associates with early onset atrial fibrillation

Introduction

Atrial fibrillation (AF) is the most common cardiac arrhythmia. It carries an increased risk of serious complications and an increased mortality. Genome Wide Association Studies have demonstrated that variants in several structural genes are associated with AF, and recently two landmark papers have implicated loss of function (LoF) variants in titin (TTN), a gene associated with dilated cardiomyopathy (DCM), in patients with early onset AF. An atrial cardiomyopathy syndrome has been proposed as a mechanism in the development of AF.

Purpose

We hypothesized that genes encoding structural proteins that were associated with DCM, could also be involved in atrial cardiomyopathy and contribute to AF.

Materials and methods

We performed targeted deep sequencing of structural genes associated with DCM. The genes were grouped by cellular function, and the burden of LoF variants was examined in a cohort of 540 early onset AF patients and compared to a control group (n=383). The patients were below age 49 with normal echo, and no other cardiovascular disease at onset of AF. Patient inclusion in the cohort is still ongoing, and we are working on obtaining a CRISPR/CAS9 modified zebra fish model with LoF variants in cytoskeletal proteins.

Results

We identified a total of 6 carriers of LoF variants in 3 genes thought to encode cytoskeletal proteins (DMD, PDLIM3 and FKTN). The burden of variants in cytoskeletal genes was significantly increased in patients with early onset AF compared with controls (p=0.0385). Four carriers had LoF variants in the dystrophin gene (DMD), while there was 1 carrier of LoF variants in PDLIM3 and FKTN respectively. All carriers with LoF variants in DMD developed persistent AF before age 30.

Conclusion

Our data suggest that rare mutations in cytoskeletal genes previously associated with DCM, may also play a role in the development of early onset AF. The data supports that AF is a part of an atrial cardiomyopathy syndrome.

Acknowledgement/Funding

Novo Nordisk Fonden Pre-Graduate Scholarships

Integration of 60,000 exomes and ACMG guidelines question the role of Catecholaminergic Polymorphic Ventricular Tachycardia-associated variants

Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) is a highly lethal cardiac arrhythmia disease occurring during exercise or psychological stress. CPVT has an estimated prevalence of 1:10,000 and has mainly been associated with variants in calcium-regulating genes. Identification of potential false-positive pathogenic variants was conducted by searching the Exome Aggregation Consortium (ExAC) database (n = 60,706) for variants reported to be associated with CPVT. The pathogenicity of the interrogated variants was assessed using guidelines from the American College of Medical Genetics and Genomics (ACMG) and in silico prediction tools. Of 246 variants 38 (15%) variants previously associated with CPVT were identified in the ExAC database. We predicted the CPVT prevalence to be 1:132. The ACMG standards classified 29% of ExAC variants as pathogenic or likely pathogenic. The in silico predictions showed a reduced probability of disease-causing effect for the variants identified in the exome database (p < 0.001). We have observed a large overrepresentation of previously CPVT-associated variants in a large exome database. Based on the frequency of CPVT in the general population, it is less likely that the previously proposed variants are associated with a highly penetrant monogenic form of the disease.

Non-Invasive Measurement of Stroke Volume and Left Ventricular Ejection Fraction

The stroke volume (SV) was determined by first passage radionuclide cardiography and the left ventricular ejection fraction (LVEF) by multigated radionuclide cardiography in 20 patients with ischemic heart disease. The results were evaluated against those obtained by the invasive dye dilution or thermodilution and left ventricular cardioangiographic techniques. In a paired comparison the mean difference between the invasive and radionuclide SV was −1 ml (SED 3.1) with a correlation coefficient of 0.83 (p<0.01). Radionuclide LVEF values also correlated well with cardioangiographic measurements, r=0.93 (p<0.001). LVEF determined by multigated radionuclide cardiography was, however, significantly lower than when measured by cardioangiography, the mean difference being 6 per cent (p<0.001). These findings suggest that radionuclide determinations of SV and LVEF are reliable. The discrepancy between the non-invasive and invasive LVEF values raises the question, whether LVEF is overestimated by cardioangiography or underestimated by radionuclide cardiography.

Maximal heart rate does not limit cardiovascular capacity in healthy humans: insight from right atrial pacing during maximal exercise

In humans, maximal aerobic power (VO2 max ) is associated with a plateau in cardiac output (Q), but the mechanisms regulating the interplay between maximal heart rate (HRmax) and stroke volume (SV) are unclear. To evaluate the effect of tachycardia and elevations in HRmax on cardiovascular function and capacity during maximal exercise in healthy humans, 12 young male cyclists performed incremental cycling and one-legged knee-extensor exercise (KEE) to exhaustion with and without right atrial pacing to increase HR. During control cycling, Q and leg blood flow increased up to 85% of maximal workload (WLmax) and remained unchanged until exhaustion. SV initially increased, plateaued and then decreased before exhaustion (P < 0.05) despite an increase in right atrial pressure (RAP) and a tendency (P = 0.056) for a reduction in left ventricular transmural filling pressure (LVFP). Atrial pacing increased HRmax from 184 ± 2 to 206 ± 3 beats min(-1) (P < 0.05), but Q remained similar to the control condition at all intensities because of a lower SV and LVFP (P < 0.05). No differences in arterial pressure, peripheral haemodynamics, catecholamines or VO2 were observed, but pacing increased the rate pressure product and RAP (P < 0.05). Atrial pacing had a similar effect on haemodynamics during KEE, except that pacing decreased RAP. In conclusion, the human heart can be paced to a higher HR than observed during maximal exercise, suggesting that HRmax and myocardial work capacity do not limit VO2 max in healthy individuals. A limited left ventricular filling and possibly altered contractility reduce SV during atrial pacing, whereas a plateau in LVFP appears to restrict Q close to VO2 max .