Claus Graff

Claus Graff
Aalborg University · Department of Health Science and Technology

M.Sc. BME, PhD

About

205
Publications
21,906
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3,053
Citations
Citations since 2017
115 Research Items
2172 Citations
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Introduction
Claus Graff currently works at the Department of Health Science and Technology, Aalborg University.

Publications

Publications (205)
Article
Background: As new heart rhythm monitoring technologies emerge, subclinical atrial fibrillation (AF) signifies a future challenge to health care systems. The pathological characteristics of this condition are largely unknown. Objectives: This study sought to characterize the natural history of subclinical AF in at-risk patients from the general...
Article
Background: Stroke is an increasing health problem world-wide. Atrial fibrillation (AF) is a major risk factor for stroke, and the attention towards AF screening is rising, while new monitoring-technologies emerge. We aimed to evaluate the performance of a large panel of screening strategies and to assess population characteristics associated with...
Article
Background It is unknown whether screening for atrial fibrillation and subsequent treatment with anticoagulants if atrial fibrillation is detected can prevent stroke. Continuous electrocardiographic monitoring using an implantable loop recorder (ILR) can facilitate detection of asymptomatic atrial fibrillation episodes. We aimed to investigate whet...
Article
Full-text available
Aims The aim of this study was to investigate the association between within-individual changes in physical activity and onset of atrial fibrillation (AF). Methods and results A total of 1410 participants from the general population (46.2% women, mean age 74.7 ± 4.1 years) with risk factors but with no prior AF diagnosis underwent continuous mon...
Article
Background: Recent studies have suggested a high prevalence of subclinical atrial fibrillation (AF) in various patient populations, and interest in AF screening has increased. However, knowledge about episode duration is scarce, and risk factors for short or long subclinical AF episodes have yet to be recognized. The aim of the study was to assess...
Article
Full-text available
Prospective studies applying fluoroscopy for assessment of right ventricular (RV) lead position have failed to show clear benefits from RV septal pacing. We investigated the impact of different RV lead positions verified by computed tomography (CT) on the risk of pacing-induced cardiomyopathy (PICM). We retrospectively included 153 patients who und...
Article
BACKGROUND ECG marker P Terminal Force V1 (PTFV1) is generally perceived as a marker of left atrial pathology and has been associated with atrial fibrillation or flutter (AF). OBJECTIVE To determine the association between PTFV1 components (duration and amplitude) and incident AF and stroke/TIA. METHODS We included patients with an ECG recorded i...
Article
Background An evidence-based approach for risk stratification of subclinical atrial fibrillation (AF) and hereby AF screening is lacking. This study aimed to investigate whether established cardiovascular diseases (CVD) could help to identify the population more likely to benefit from AF screening. Methods The LOOP Study randomized AF-naïve indivi...
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Objectives. New-onset postoperative atrial fibrillation (POAF) is a common complication after cardiac surgery. The arrhythmia often entails a longer hospital stay, greater risk of other complications, and higher mortality both short- and long-term. An investigation of the use of early atrial electrograms in predicting POAF in cardiac surgery was pe...
Article
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 continu...
Article
Background Right ventricular (RV) pacing may induce significant left ventricular (LV) dyssynchrony resulting in pacing-induced cardiomyopathy (PICM). LV activation sequence is affected by RV pacing site and previous studies suggest that RV septal pacing may be superior compared to traditional RV apical pacing. However, results are conflicting and r...
Article
Background COVID‐19 infection has been hypothesized to affect left ventricular function; however, the underlying mechanisms and the association to clinical outcome are not understood. The global work index (GWI) is a novel echocardiographic measure of systolic function that may offer insights on cardiac dysfunction in COVID‐19. We hypothesized that...
Article
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Background: Cardiac resynchronization therapy (CRT) is a treatment for patients with heart failure and electrical dyssynchrony, i.e., left bundle branch block (LBBB) ECG pattern. CRT resynchronizes ventricular contraction with a right ventricle (RV) and a left ventricle (LV) pacemaker lead. Positioning the LV lead in the latest electrically activat...
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Full-text available
Objectives To determine whether electrocardiogram (ECG) markers are associated with incident non-Alzheimer's dementia (non-AD) and whether these markers also improve risk prediction for non-AD. Materials and methods We retrospectively included 170,605 primary care patients aged 60 years or older referred for an ECG by their general practitioner an...
Article
Full-text available
The QT interval is an electrocardiographic measure representing the sum of ventricular depolarization and repolarization, estimated by QRS duration and JT interval, respectively. QT interval abnormalities are associated with potentially fatal ventricular arrhythmia. Using genome-wide multi-ancestry analyses (>250,000 individuals) we identify 177, 1...
Article
Importance: Atrial fibrillation (AF) screening trials have failed to demonstrate a significant reduction in stroke risk. The impact on stroke severity and the importance of prior strokes are unknown. Objective: To assess stroke characteristics in patients undergoing implantable loop recorder (ILR) screening for AF vs usual care and assess the im...
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Background: Hypertension is a well-known risk factor for atrial fibrillation (AF), but data on the interaction between systolic blood pressure (SBP) and effects of continuous AF screening are lacking. Methods: The LOOP Study randomized AF-naive individuals aged 70 to 90 years with additional stroke risk factor to either screening with implantabl...
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Background Elderly individuals occupy an increasing part of the general population. Conventional and speckle-tracking transthoracic echocardiography may help guide risk stratification in these individuals. The purpose of this study was to evaluate the potential utility of conventional and speckle-tracking echocardiography in the screening of cardia...
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Four-dimensional (4D) echocardiography may provide more accurate estimations of left atrial (LA) volumes than 2-dimensional (2D) measures. We sought to compare the concordance of a novel 4D LA quantification software versus 2D echocardiography against cardiac magnetic resonance (CMR). This was a multimodality imaging substudy of a randomized clinic...
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Background Patients with Type 1 diabetes mellitus have been shown to be at a two to ten-fold higher risk of sudden cardiac death (SCD) (Svane et al., Curr Cardiol 2020; 22:112) than the general population, but the underlying mechanism is unclear. Hyperglycaemia is a recognised cause of QTc prolongation; a state patients with type 1 diabetes are mor...
Article
Funding Acknowledgements Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Svend Andersens Foundation Karl G Andersens Foundation Helsefonden Background Right ventricular (RV) pacing may induce electrical and mechanical dyssynchrony which may lead to heart failure. Often, the physician aims for lead implantation...
Article
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...
Article
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 fibrillatio...
Article
Left atrial enlargement (LAE) is associated with hypertension and an increased risk of cardiovascular morbidity and mortality. Guidelines for hypertension recommend LAE evaluation. We aimed to estimate the agreement of LAE as assessed by 12-lead electrocardiogram (ECG) and cardiac computed tomography (CT) in both the general population and hyperten...
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Full-text available
Purpose The cardiac T-wave peak-to-end interval (Tpe) is thought to reflect dispersion in ventricular repolarisation, with abnormalities in Tpe associated with increased risk of arrhythmia. Extracellular K⁺ modulates cardiac repolarisation, and since arterial plasma K⁺ concentration ([K⁺]) rapidly increases during and declines following exercise, w...
Article
Aims: Left atrial (LA) fibrosis is a hallmark of atrial cardiomyopathy, and non-invasive surrogate measures of LA fibrosis are therefore needed. We investigated the association between four-dimensional (4D) echocardiographic LA measures and LA fibrosis. Methods and results: A multimodality imaging substudy was performed in a randomized clinical...
Article
Background: Atrial remodeling is associated with future atrial fibrillation (AF) and stroke. AF has been associated with cognitive impairment and cerebral white matter lesions. We wished to investigate the possible direct association between atrial remodeling and cerebrovascular disease in patients with and without AF documented by implantable loo...
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Full-text available
Recent global developments underscore the prominent role big data have in modern medical science. But privacy issues constitute a prevalent problem for collecting and sharing data between researchers. However, synthetic data generated to represent real data carrying similar information and distribution may alleviate the privacy issue. In this study...
Preprint
The QT interval is an electrocardiographic measure representing the sum of ventricular depolarization (QRS duration) and repolarization (JT interval). Abnormalities of the QT interval are associated with potentially fatal ventricular arrhythmia. We conducted genome-wide multi-ancestry analyses in >250,000 individuals and identified 177, 156 and 121...
Article
Full-text available
Persons living with HIV (PLWH) may have increased incidence of cardiovascular events and longer QTc intervals than uninfected persons. We aimed to investigate the incidence and risk factors of de novo major electrocardiogram (ECG) abnormalities and QTc prolongation in well-treated PLWH. We included virologically suppressed PLWH without major ECG ab...
Article
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 im...
Article
Background Fascicular heart blocks can progress to complete heart blocks, but this risk has not been evaluated in a large general population. Objective To investigate the association between various types of fascicular blocks diagnosed by electrocardiogram (ECG) readings and the risk of incident higher degree atrioventricular block (AVB), syncope,...
Article
Background Patients with severe mental illness (SMI) including schizophrenia, bipolar disorder, and severe depression have earlier onset of cardiovascular risk factors, predisposing to worse future heart failure (HF) compared with the general population. We investigated associations between the presence/absence of SMI and long-term HF outcomes. Me...
Article
Background QRS duration and morphology including left bundle branch block (LBBB) are the most widely used electrocardiogram (ECG) markers for assessing ventricular dyssynchrony and predicting heart failure (HF). However, the vectorcardiographic QRS area may more accurately identify delayed left ventricular activation and HF development. Objective...
Article
Full-text available
Background In long QT syndrome (LQTS), beta blockers prevent arrhythmias. As a supplement, means to increase potassium has been suggested. We set to investigate the effect of moderate potassium elevation on cardiac repolarisation. Methods Patients with LQTS with a disease-causing KCNQ1 or KCNH2 variant were included. In addition to usual beta-bloc...
Article
Aims To study the relationship between subclinical atrial fibrillation (AF) and changes in cognitive function in a large cohort of individuals with stroke risk factors. Methods : Individuals with no prior AF diagnosis but with risk factors for stroke were recruited to undergo annual cognitive assessment with the Montreal Cognitive Assessment (MoCA...
Article
Objective: With hepatic steatosis (HS) being an established risk factor for CVD in the general population, it may also be a predictor of CVD in patients with schizophrenia. The aim of the present study was to investigate if time since schizophrenia diagnosis, body mass index (BMI), sex, metabolic syndrome, alcohol use, smoking, alanine transaminas...
Article
Background Targeted temperature management (TTM) following out-of-hospital cardiac arrest (OHCA) prolongs the QT-interval but our knowledge of different temperatures and risk of arrhythmia is incomplete. Objective To assess whether the QTc, QT-peak (QTp) and T-peak to T-end interval (TpTe) may be useful markers of ventricular arrhythmia in contemp...
Article
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Introduction: Hydroxychloroquine has been suggested as possible treatment for Severe Acute Respiratory Syndrome-coronavirus-2 (SARS-CoV-2). Studies reported an increased risk of QTcF-prolongation after treatment with hydroxychloroquine. The aim of this study was to analyze the concentration-dependent effects of hydroxychloroquine on the ventricula...
Article
Full-text available
EQ-5D is a generic instrument to measure health-related quality of life. In 2009, a new version, EQ-5D-5L, was introduced as an attempt to reduce ceiling effects and improve sensitivity to small changes over time. The objective of this study was to assess the measurement properties of the EQ-5D-5L instrument compared to the EQ-5D-3L instrument in a...
Article
Full-text available
Deep learning-based tools may annotate and interpret medical data more quickly, consistently, and accurately than medical doctors. However, as medical doctors are ultimately responsible for clinical decision-making, any deep learning-based prediction should be accompanied by an explanation that a human can understand. We present an approach called...
Article
Full-text available
Cortexolone 17α-propionate, also known as clascoterone, is a potent androgen receptor inhibitor intended for the topical treatment of skin diseases associated with androgenic pathway alterations. In nonclinical studies, cortexolone 17α-propionate was found to have a weak inhibitory effect on human Ether-à-go-go-Related Gene (hERG) potassium channel...
Preprint
Full-text available
Big data is needed to implement personalized medicine, but privacy issues are a prevalent problem for collecting data and sharing them between researchers. A solution is synthetic data generated to represent real dataset carrying similar information. Here, we present generative adversarial networks (GANs) capable of generating realistic synthetic D...
Article
Full-text available
In clinical trials, traditionally only a limited number of 12‐lead resting electrocardiograms (ECGs) can be recorded and, thus, long intervals may elapse between assessment timepoints and valuable information may be missed during times when patients' cardiac electrical activity is not being monitored. These limitations have led to the increasing us...
Article
Full-text available
Aim Left bundle branch block (LBBB) is associated with an increased risk of heart failure (HF). We assessed the impact of common ECG parameters on this association using large-scale data. Methods and results Using ECGs recorded in a large primary care population from 2001 to 2011, we identified HF-naive patients with a first-time LBBB ECG. We obta...
Article
Background ECG abnormalities are associated with adverse outcomes in the general population, but their prognostic significance in severe mental illness (SMI) remains unexplored. We investigated associations between no, minor, and major ECG abnormalities and fatal cardiovascular disease (CVD) among patients with SMI compared with controls without me...
Preprint
Full-text available
Deep learning-based tools may annotate and interpret medical tests more quickly, consistently, and accurately than medical doctors. However, as medical doctors remain ultimately responsible for clinical decision-making, any deep learning-based prediction must necessarily be accompanied by an explanation that can be interpreted by a human. In this s...
Article
Background Electrocardiographic T-wave morphology is used in drug safety studies as an adjunct to the QTc interval, but few measurements of T-wave morphology can be interpreted in clinical practice. Morphology combination score (MCS) is a combination of T-wave flatness/peakedness, asymmetry, and notching, enabling easy visual assessment of T-wave m...
Article
Full-text available
Background Left atrial late gadolinium enhancement (LA LGE) measured with cardiac magnetic resonance (CMR) imaging is emerging as a marker of atrial fibrosis and has been associated with worse outcomes in AF ablation procedures. However, the prognostic value of LA LGE for incident AF remains unknown. Methods CMR including measurement of left ventr...
Article
Full-text available
Aims The present study had two aims: (i) compare echocardiographic parameters in COVID‐19 patients with matched controls and (2) assess the prognostic value of measures of left (LV) and right ventricular (RV) function in relation to COVID‐19 related death. Methods and results In this prospective multicentre cohort study, 214 consecutive hospitaliz...
Article
Background: Biventricular (BiV) pacing increases transmural repolarization heterogeneity due to epicardial to endocardial conduction from the left ventricular (LV) lead. However, limited evidence is available on concomitant changes in ventricular depolarization and repolarization and long-term outcomes of BiV pacing. Therefore, we investigated ass...
Article
Full-text available
Background Women appear to derive more benefit from cardiac resynchronization therapy(CRT) than men, even after accounting for the higher burden of risk factors for non-response often observed in men. Objective To assess for sex-specific differences in left ventricular(LV) electrical dyssynchrony as a contributing electrophysiological explanation...
Article
Background In patients with long QT syndrome (LQTS), swimming and loud noises have been identified as genotype-specific arrhythmic triggers in LQTS type 1 and LQTS type 2, respectively. Objective To compare LQTS groups’ responses to arrhythmic triggers. Methods LQTS1 and LQTS2 patients were included. Before and after beta blocker intake, electroc...
Article
Background: Thyroid hormones within the euthyroid range have been linked to mortality and differences in heart rate. However, some relations between thyroid hormone concentration and various electrocardiographic measurements remain unassessed. We aimed to investigate the association between thyroid hormone concentrations within the euthyroid range...
Article
Objectives We hypothesized that left atrial (LA) fibrosis was associated with incident atrial fibrillation (AF) as detected by continuous long-term monitoring in an at-risk population. Background LA late gadolinium enhancement (LGE) measured with cardiac magnetic resonance is emerging as a marker of atrial fibrosis and has been associated with wor...
Article
Background A low electrocardiogram (ECG) Lead One Ratio (LOR) of the maximum positive/negative QRS amplitudes is associated with lower left ventricular ejection fraction (LVEF) and worse outcomes in left bundle branch block (LBBB); however, the impact of LOR on CRT outcomes is unknown. We compared clinical outcomes and echocardiographic changes aft...
Article
Aims: We aimed to investigate whether left atrial (LA) markers from cardiovascular magnetic resonance (CMR) were able to predict atrial fibrillation (AF) in elderly patients with risk factors for stroke. Methods and results: At baseline, 203 participants with stroke risk factors but without history of AF underwent advanced CMR and received an im...
Article
Background QRS morphology including left bundle branch block (LBBB) and duration remain the most widely used surrogate markers in the 12-lead electrocardiogram (ECG) for assessing ventricular dyssynchrony and predicting future burden of heart failure (HF) and cardiovascular mortality. However, the vectorcardiographic QRS area has recently been prop...
Conference Paper
Aims Potassium disturbances are common and associated with increased morbidity and mortality, even in patients without prior cardiovascular disease. We examined six electrocardiographic (ECG) measures and their association to serum potassium levels. Methods and results From the Copenhagen General Practitioners' Laboratory, we identified 163,547 in...
Article
Background: The Fourth Universal Definition of Myocardial Infarction defines electrocardiographic (ECG) Q waves as duration ≥30ms and amplitude ≥1mm or QS complex in two contiguous leads. However, current taskforce criteria may be overly restrictive. Therefore, we investigated the association of isolated, lenient, or strict Q waves with long-term...
Article
Aims: Potassium disturbances are common and associated with increased morbidity and mortality, even in patients without prior cardiovascular disease. We examined six electrocardiographic (ECG) measures and their association to serum potassium levels. Methods and results: From the Copenhagen General Practitioners' Laboratory, we identified 163,54...
Article
Background: PR interval prolongation is associated with poor outcome after cardiac resynchronization therapy (CRT) among patients with left bundle branch block (LBBB) but the mechanisms are unknown. We investigated clinical outcomes, electrocardiogram (ECG) and echocardiogram changes after CRT by PR interval. Methods: This is a retrospective stu...
Article
Background: Changes in left ventricular (LV) activation after cardiac resynchronization therapy (CRT) influence survival but are difficult to quantify non-invasively. Methods and results: We studied 527 CRT patients to assess whether non-invasive quantification of changes in LV activation, defined by change (Δ) in QRS area(QRSA), can predict out...
Article
: Abnormal electrocardiograms (ECG) are associated with increased risk of arrhythmias and sudden cardiac death. We aimed to investigate the prevalence and associated risk factors of prolonged QTc and major ECG abnormalities, in persons living with HIV (PLWH) and uninfected controls. Design: PLWH aged ≥40 were recruited from the Copenhagen comorbi...