Alexander H Maass

University of Groningen, Groningen, Groningen, Netherlands

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Publications (74)429.06 Total impact

  • No preview · Article · Dec 2015 · Europace

  • No preview · Article · Dec 2015 · Cardiac electrophysiology clinics
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    ABSTRACT: -The recent advent of subcutaneous implantable cardioverter defibrillators (S-ICDs) has provided investigators with a safe and effective new therapy in patients at risk of sudden cardiac death. At present, no data are available with regard to the longevity of these new devices. This study evaluated the longevity of the S-ICD system. -All patients enrolled in the European Regulatory Trial were included in the analysis. During follow-up, time and causes of device replacement or explantation were assessed and categorized. Device longevity was estimated using Kaplan-Meier analysis. Fifty-five patients were followed for a median of 5.8 years. During follow-up, 26 (47%) patients underwent device replacement and 5 (9%) device explantation. Median time to replacement was 5.0 years (Q1-Q3, 4.4 - 5.6 years). Replacement was caused by battery depletion in 25 patients (92%), of which 5 within 1.5 years due to premature battery depletion, and by infection in 1 patient (2%). Replacement for a transvenous ICD system was required in 4 patients (7%), due to ineffective defibrillation in 1 (0,003 per patient-year), need for resynchronization therapy in 2 (0.01 per patient-year) and for anti-bradycardia pacing in 1 (0.003 per patient-year). At 5 years follow-up, 71% of devices were still in service. -This study provides the first estimate of S-ICD system longevity since its introduction in clinical practice. Median longevity of the first generation S-ICD system was 5.0 years. The majority of devices were replaced due to battery depletion. Clinical Trial Registration- Unique identifier: NCT01117792.
    No preview · Article · Jul 2015 · Circulation Arrhythmia and Electrophysiology
  • Alexander H Maass · B Daan Westenbrink

    No preview · Article · Mar 2015 · European Journal of Heart Failure
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    A H Maass

    Preview · Article · Sep 2014 · Netherlands heart journal: monthly journal of the Netherlands Society of Cardiology and the Netherlands Heart Foundation
  • Alexander H Maass · Isabelle C Van Gelder

    No preview · Article · May 2014 · Europace
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    Full-text · Article · May 2014 · European Journal of Heart Failure
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    ABSTRACT: Cardiac resynchronization therapy is one of the cornerstones of heart failure treatment. Inability to access the coronary sinus or one of its sidebranches is one of the most common causes of therapeutic failure. We describe a technique using video-assisted thoracic surgery for epicardial placement of the left ventricular lead and use an intrathoracic route to connect the lead to the device.
    No preview · Article · Dec 2013 · Journal of Cardiac Surgery
  • A H Maass · D J van Veldhuisen
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    ABSTRACT: Devices have become a cornerstone of heart failure (HF) therapy. Implantable cardioverter-defibrillators (ICDs) decrease mortality, and cardiac resynchronization therapy (CRT) improves symptoms and mortality. Most data have been collected in patients with systolic dysfunction. Data in patients with preserved systolic function are scarce, but interesting therapeutic concepts are evolving. Besides therapeutic functions, devices can have add-on diagnostic features such as early detection of fluid overload. In addition, stand-alone diagnostic devices are now also being developed for HF.
    No preview · Article · Oct 2013 · Clinical Pharmacology &#38 Therapeutics
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    ABSTRACT: Atrial fibrillation (AF) is often preceded by underlying cardiac diseases causing ventricular pressure overload. It was our aim to investigate the progression of atrial remodeling in a small animal model of ventricular pressure overload and its association with induction of AF. Male mice were subjected to transverse aortic constriction (TAC) or sham operation. After four or eight weeks, echocardiographic measurements and hemodynamic measurements were made and AF induction was tested. The hearts were either fixed in formalin or ventricles and atria were separated, weighed and snap-frozen for RNA analysis. Four weeks of pressure overload induced ventricular hypertrophy and minor changes in the atria. After eight weeks a significant reduction in left ventricular function occurred, associated with significant atrial remodeling including increased atrial weight, a trend towards an increased left atrial cell diameter, atrial dilatation and increased expression of markers of hypertrophy and inflammation. Histologically, no fibrosis was found in the left atrium. But atrial gene expression related to fibrosis was increased. Minor changes related to electrical remodeling were observed. AF inducibility was not different between the groups. Left ventricular end diastolic pressures were increased and correlated with the severity of atrial remodeling but not with AF induction. Permanent ventricular pressure overload by TAC induced atrial remodeling, including hypertrophy, dilatation and inflammation. The extent of atrial remodeling was directly related to LVEDP and not duration of TAC per se.
    Full-text · Article · Sep 2013 · PLoS ONE
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    ABSTRACT: Voltage-gated sodium channels composed of a pore-forming α subunit and auxiliary β subunits are responsible for the upstroke of the action potential in cardiac muscle. However, their localization and expression patterns in human myocardium have not yet been clearly defined. We used immunohistochemical methods to define the level of expression and the subcellular localization of sodium channel α and β subunits in human atrial myocytes. Nav1.2 channels are located in highest density at intercalated disks where β1 and β3 subunits are also expressed. Nav1.4 and the predominant Nav1.5 channels are located in a striated pattern on the cell surface at the z-lines together with β2 subunits. Nav1.1, Nav1.3, Nav1.6 channels are located in scattered puncta on the cell surface in a pattern similar to β3 and β4 subunits. Nav1.5 comprised approximately 88% of the total sodium channel staining, as assessed by quantitative immunohistochemistry. Functional studies using whole cell patch-clamp recording and measurements of contractility in human atrial cells and tissue showed that TTX-sensitive (non-NaV1.5) α subunit isoforms account for up to 27% of total sodium current in human atrium and are required for maximal contractility. Overall, our results show that multiple sodium channel α and β subunits are differentially localized in subcellular compartments in human atrial myocytes, suggesting that they play distinct roles in initiation and conduction of the action potential and in excitation-contraction coupling. TTX-sensitive sodium channel isoforms, even though expressed at low levels relative to TTX-sensitive NaV1.5, contribute substantially to total cardiac sodium current and are required for normal contractility.
    Full-text · Article · May 2013 · Journal of Molecular and Cellular Cardiology
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    ABSTRACT: Atrial fibrillation (AF) often occurs in the presence of an underlying disease. These underlying diseases cause atrial remodelling, which make the atria more susceptible to AF. Stretch is an important mediator in the remodelling process. The aim of this study was to develop an atrial cell culture model mimicking remodelling due to atrial pressure overload. Neonatal rat atrial cardiomyocytes (NRAM) were cultured and subjected to cyclical stretch on elastic membranes. Stretching with 1 Hz and 15% elongation for 30 min. resulted in increased expression of immediate early genes and phosphorylation of Erk and p38. A 24-hr stretch period resulted in hypertrophy-related changes including increased cell diameter, reinduction of the foetal gene program and cell death. No evidence of apoptosis was observed. Expression of atrial natriuretic peptide, brain natriuretic peptide and growth differentiation factor-15 was increased, and calcineurin signalling was activated. Expression of several potassium channels was decreased, suggesting electrical remodelling. Atrial stretch-induced change in skeletal α-actin expression was inhibited by pravastatin, but not by eplerenone or losartan. Stretch of NRAM results in elevation of stress markers, changes related to hypertrophy and dedifferentiation, electrical remodelling and cell death. This model can contribute to investigating the mechanisms involved in the remodelling process caused by stretch and to the testing of pharmaceutical agents.
    Full-text · Article · Apr 2013 · Journal of Cellular and Molecular Medicine
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    A H Maass

    Preview · Article · Mar 2013 · Netherlands heart journal: monthly journal of the Netherlands Society of Cardiology and the Netherlands Heart Foundation
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    ABSTRACT: OBJECTIVES: The purpose of the study was to evaluate the efficacy and safety of the entirely subcutaneous implantable cardioverter-defibrillator (S-ICD). BACKGROUND: A new entirely S-ICD has been introduced, that does not require lead placement in or on the heart. The authors report the largest multicenter experience to date with the S-ICD with a minimum of 1-year follow-up in the first 118 Dutch patients who were implanted with this device. METHODS: Patients were selected if they had a class I or IIa indication for primary or secondary prevention of sudden cardiac death. All consecutive patients from 4 high-volume centers in the Netherlands with an S-ICD implanted between December 2008 and April 2011 were included. RESULTS: A total of 118 patients (75% males, mean age 50 years) received the S-ICD. After 18 months of follow-up, 8 patients experienced 45 successful appropriate shocks (98% first shock conversion efficacy). No sudden deaths occurred. Fifteen patients (13%) received inappropriate shocks, mainly due to T-wave oversensing, which was mostly solved by a software upgrade and changing the sensing vector of the S-ICD. Sixteen patients (14%) experienced complications. Adverse events were more frequent in the first 15 implantations per center compared with subsequent implantations (inappropriate shocks 19% vs. 6.7%, p = 0.03; complications 17% vs. 10%, p = 0.10). CONCLUSIONS: This study demonstrates that the S-ICD is effective in terminating ventricular arrhythmias. There is, however, a considerable percentage of ICD related adverse events, which decreases as the therapy evolves and experience increases.
    Full-text · Article · Sep 2012 · Journal of the American College of Cardiology
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    ABSTRACT: Heart failure (HF) remains a major medical problem, and the European Journal of Heart Failure is dedicated to publishing research further investigating its pathophysiology and diagnosis in order to help clinicians alleviate symptoms and improve patient outcomes.( 1) This review reports on important studies in the field of HF published in 2011. All research areas are addressed, including experimental studies, biomarkers, clinical trials, arrhythmias, and new insights into the role of device therapy.
    No preview · Article · Aug 2012 · European Journal of Heart Failure
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    ABSTRACT: Atrial fibrillation (AF) and heart failure often co-exist. It is unknown whether the sequence in which AF and heart failure develop is of significance regarding prognosis. We assessed the prognosis of AF patients hospitalized for heart failure based on the timing of AF and heart failure development. Consecutive AF patients hospitalized for heart failure were included. Patients who had developed AF before or consecutively with heart failure ('AF first') were compared with patients who had developed heart failure before AF ('heart failure first'). The primary endpoint was a composite of cardiovascular hospitalization or all-cause mortality. The majority of patients hospitalized for AF and heart failure consisted of patients who had developed AF first (137 of 182 patients, 75%, vs. 45 of 182 patients, 25%). The two groups were similar regarding age and gender, but patients with AF first less often had coronary artery disease and had higher ejection fractions than patients with heart failure first (39 ± 14% vs. 32 ± 13%, P = 0.004). During 16 ± 11 months follow-up, the primary composite endpoint occurred less often in patients with AF first than in patients with heart failure first (49.6% vs. 77.7% of patients, P = 0.001). Development of AF first remained beneficial regarding the primary endpoint on multivariable analysis (adjusted hazard ratio 0.50, 95% confidence interval 0.29-0.86, P = 0.01). The majority of patients hospitalized for AF and heart failure consisted of patients who had developed AF first. Prognosis in these patients was relatively benign as compared with those who had developed heart failure first.
    No preview · Article · Jun 2012 · European Journal of Heart Failure
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    Dirk J van Veldhuisen · Alexander H Maass
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    ABSTRACT: Heart failure (HF) remains a large medical problem, and prevention of decompensation and HF-related hospitalizations is important, not only for the patient, but also from an economic point of view. Close monitoring is crucial, and can be done through a whole spectrum of modalities. This ranges from a (nurse-based) disease management program, to structured telephone support, to remote or telemonitoring with or without the use of an implantable device(1-3). (SELECT FULL TEXT TO CONTINUE).
    Preview · Article · May 2012 · Circulation
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    ABSTRACT: Implantable cardioverter-defibrillators (ICDs) are widely used to prevent fatal outcomes associated with life-threatening arrhythmic episodes in a variety of cardiac diseases. These ICDs rely on transvenous leads for cardiac sensing and defibrillation. A new entirely subcutaneous ICD overcomes problems associated with transvenous leads. However, the role of the subcutaneous ICD as an adjunctive or primary therapy in patients at risk for sudden cardiac death is unclear. The PRAETORIAN trial is an investigator-initiated, randomized, controlled, multicenter, prospective 2-arm trial that outlines the advantages and disadvantages of the subcutaneous ICD. Patients with a class I or IIa indication for ICD therapy without an indication for bradypacing or tachypacing are included. A total of 700 patients are randomized to either the subcutaneous or transvenous ICD (1:1). The study is powered to claim noninferiority of the subcutaneous ICD with respect to the composite primary endpoint of inappropriate shocks and ICD-related complications. After noninferiority is established, statistical analysis is done for potential superiority. Secondary endpoint comparisons of shock efficacy and patient mortality are also made. The PRAETORIAN trial is a randomized trial that aims to gain scientific evidence for the use of the subcutaneous ICD compared with the transvenous ICD in a population of patients with conventional ICD with respect to major ICD-related adverse events. This trial is registered at with trial ID NCT01296022.
    Full-text · Article · May 2012 · American heart journal
  • Marcus J Hof · Alexander H Maass

    No preview · Article · Apr 2012 · European Journal of Heart Failure
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    ABSTRACT: Fibroblast growth factors (FGFs) and their receptors play an important role during embryonic induction and patterning, as well as in modulating proliferative and hypertrophic growth in fetal and adult organs. Exogenous FGF2 (also known as basic FGF) was found to be able to induce proliferation of chick embryonic and fetal cardiac myocytes in vivo and is also important for vascular development. The aim of this study was to assess the effect of FGF2 signaling on growth of chick embryonic ventricular wall and its vascularization. Methods In the first set of experiments, left ventricular wall of E7 chick embryos was injected with either GFP-expressing replication-deficient adenovirus alone or in combination with adenoviral vector encoding human FGF-2 gene. In the second set of experiments, FGF signaling was blocked in E8 chick embryos using FGF receptor tyrosine kinase inhibitor SU 5402. Hearts were sampled at ED9 for both protocols. In the third set of experiments we tested whether FGF2 signaling is involved in transmission of mechanical stretch to myocyte growth in vivo using an established pressure overload model.
    Full-text · Article · Mar 2012 · Cardiovascular Research

Publication Stats

1k Citations
429.06 Total Impact Points


  • 2007-2015
    • University of Groningen
      • • Department of Cardiology
      • • Department of Genetics
      Groningen, Groningen, Netherlands
  • 2002-2009
    • University of Wuerzburg
      • Department of Internal Medicine I
      Würzburg, Bavaria, Germany
  • 2005
    • University of Texas at Dallas
      • Molecular Biology
      Richardson, Texas, United States
  • 2004
    • University of Washington Seattle
      Seattle, Washington, United States
  • 2000-2001
    • University of Colorado at Boulder
      • Department of Molecular, Cellular, and Developmental Biology (MCDB)
      Boulder, CO, United States