BACKGROUND: Transient VA block can be created in the AV node (AVN) when an atrial extrastimulus is delivered at the AVN effective refractory period (ERP) due to anterograde concealed conduction. OBJECTIVE: We hypothesized that ventricular stimulation during pacing-induced AVN refractoriness could identify concealed accessory pathways (APs) that remain hidden with ...

BACKGROUND: Ventricular arrhythmias (VAs) may arise from the aortic sinuses and have electrocardiographic and electrophysiological characteristics that suggest a left (LCC) or right coronary cusp (RCC) origin. However, VAs that arise near the junction of those two cusps (L-RCC) may have unusual features. OBJECTIVES: The purpose of this study was ...

Experimental studies have linked alternans, an abnormal beat-to-beat alternation of cardiac action potential duration, to the genesis of lethal arrhythmias such as ventricular fibrillation. Prior studies have considered various closed-loop feedback control algorithms for perturbing interstimulus intervals in such a way that alternans is suppressed. However, some experimental cases are ...

Although transvenous access to the coronary veins has considerably simplified left ventricular (LV) pacing, it can remain a time consuming and arduous task achieving satisfactory pacing positions for the LV electrode. Common problems include negotiating small veins with adequate guide catheter stability, pacing electrode stability once positioned, and phrenic nerve ...

BACKGROUND: Dilated cardiomyopathy is a naturally occurring disease in humans and dogs. Human studies have shown increased levels of myosin heavy chain (MHC)-beta in failing ventricles and the left atria (LA) and of ventricular light chain (VLC)-2 in the right atria in dilated cardiomyopathy. METHODS AND RESULTS: This study evaluates ...

BACKGROUND: Chronic right ventricular apical (RVA) pacing can lead to an increased risk of heart failure. However, assessment of left ventricular mechanical dyssynchrony in the whole left ventricle simultaneously with acute RVA pacing has never been investigated. METHODS AND RESULTS: This study included 35 patients with sick sinus syndrome and ...

BACKGROUND: Cardiac memory is a change in T-wave morphology induced by ventricular pacing or arrhythmias that persist after resumption of normal AV conduction. Changing the pacemaker site from atrium to ventricle alters ventricular activation and the mechanical pattern of ventricular contraction. Either or both alterations affect T-wave configuration. OBJECTIVE: The ...

This report deals with a patient with single-lead VDD pacemaker and intermittent atrial sensing failure. At first glance, the electrocardiogram suggested a VVI mechanism of pacing, being paced QRS complexes dissociated from sinus P waves: this revealed that intracardiac atrial electrograms were too small to reach the sensing threshold. At ...

BACKGROUND: Conventional dual-chamber pacing maintains atrioventricular synchrony but results in high percentages of ventricular pacing, which causes ventricular desynchronization and has been linked to an increased risk of atrial fibrillation in patients with sinus-node disease. METHODS: We randomly assigned 1065 patients with sinus-node disease, intact atrioventricular conduction, and a normal ...

OBJECTIVES: Biventricular pacing is important therapy for congestive heart failure, reversing left ventricular dysfunction in dilated cardiomyopathy. Although left ventricular lead location and right ventricular-left ventricular delay are believed to be critical in biventricular pacing, there is no established technique for optimizing pacing site and timing. METHODS: After median sternotomy ...

Physiologic pacing is an evolving term used to describe different concepts and technologic developments in implantable devices (including pacemakers and defibrillators) over the past several decades. Currently much of the discussion about optimal physiologic pacing involves fairly recently appreciated deleterious effects of traditional right ventricular pacing. Technologic solutions to the ...

INTRODUCTION: Pacing site is known to influence the contractile state of the ventricle. Non-physiologic pacing sites such as the right ventricular apex (RVA) or left ventricular freewall (LVFW) have been shown to decrease the contractile state of normal myocardium, due to abnormal electrical propagation. The impact of pacing at these ...

We report on a 32-year-old man with tricuspid atresia, pulmonary stenosis and hypoplastic right ventricle. He had received a Fontan-Kreutzer procedure (anastomosis between the right atrial appendage and the pulmonary artery) at the age of 14 years. At the age of 2 years, an abdominal VVI-pacemaker with an epicardial ventricular ...

BACKGROUND: Myocardial infarction modifies the distribution of stress within the heart, increasing wall stress in ischemic and surrounding tissue, which often leads to adverse left ventricular remodeling. Electrical preexcitation pacing with appropriate timing of high-stress regions can reduce local strain and may attenuate global remodeling. METHODS AND RESULTS: Myocardial infarction ...

AIMS: Permanent ventricular pacing in children is associated with ventricular dysfunction due to asynchronous activation. It is unclear whether paced QRS intervals increase disproportionately over time, which could potentially cause ventricular dysfunction. METHODS: A total of 52 children, with bipolar steroideluting epicardial leads implanted at a median age of 5.6 ...

OBJECTIVES: The purpose of this study was to evaluate the feasibility and safety of a novel technology that uses energy transfer from an ultrasound transmitter to achieve cardiac stimulation without the use of a pacing lead in humans. BACKGROUND: To overcome the limitations of pacemaker leads, a new technology enabling ...

BACKGROUND: Right ventricular apical (RVA) pacing induces electrophysiological and structural remodeling. Cardiac memory (CM) evolves during the course of pacing and is readily apparent on electrocardiography (ECG) or vectorcardiography (VCG) when normal ventricular activation resumes. OBJECTIVE: This study sought to assess ventricular repolarization (VR) changes during pacing and intermittent normal ...

AIMS: Biventricular (BiV) pacing and left univentricular (LUV) pacing can each produce clinical benefits in heart failure. The impact of modern refinements in pacing optimization on the relative benefits of these two modes is unknown. We aimed to compare these two modes in patients with heart failure, using Echo-based optimization ...

Coronary sinus (CS) dissection during biventricular pacing electrode implantation is a complication that rarely develops. A 71-year-old female with recurrent ventricular tachycardia, heart decompensation, and poor left ventricular function because of dilated cardiomyopathy was admitted for the implantation of a cardioverter-defibrillator for biventricular pacing. During the operation, we experienced a ...

A 53-year-old woman with sinus node dysfunction underwent dual-chamber pacemaker implantation through a persistent left superior vena cava draining into the coronary sinus, which was detected at the time of implantation. We managed to fix the ventricular lead in the right ventricular (RV) apex by forming a clockwise loop in ...

OBJECTIVES: The purpose of this study was to characterize interactions between normal pacing system operation and the initiating sequence of ventricular tachycardia (VT)/ventricular fibrillation (VF). BACKGROUND: Abrupt changes in ventricular cycle lengths (short-long-short, S-L-S) might initiate VT/VF. The S-L-S sequences might be passively permitted or actively facilitated by bradycardia pacing. ...

BACKGROUND: Right ventricular (RV) pacing restores ventricular systole in patients with atrioventricular (AV) block, yet recent studies have suggested that in patients with AV block and left ventricular (LV) dysfunction, RV pacing may exacerbate the progression to heart failure (HF). BLOCK HF is a prospective, multi-center, randomized, double-blind, controlled trial ...

A new technique for the placement of left ventricular pacing leads in the tributaries of the coronary sinus (CS) is described. Antegrade visualization of the CS is accomplished by selective coronary angiography, and a hydrophilic 0.032 in. wire is advanced along the CS. This facilitates the advancement of a CS ...

This article provides information and a commentary on trials relevant to the pathophysiology, prevention and treatment of heart failure, presented at Heart Rhythm 2007 organised by the Heart Rhythm Society which was held in Denver, USA and Heart Failure 2007 organised by the Heart Failure Association of the European Society ...

OBJECTIVE: Pulmonary veins (PVs) are important sources of paroxysmal atrial fibrillation (AF). Rapid atrial pacing changes atrial electrophysiology, and facilitates the induction and maintenance of AF. The purpose of our study was to evaluate the changes in atrial effective refractory period (AERP) proprieties and in ionic currents in PVs myocytes ...

An infant with a congenital auriculoventricular block (CAVB) of immunological origin was diagnosed prenatally. The mother had Gougerot-Sjögren disease with positive anti-Sjogren's Syndrome A (SSA) and Sjogren's Syndrome B (SSB) serologies. Cardiac pacing was necessary and the epicardial route was chosen. Considering the left ventricular (LV) dilatation, bi-ventricular (BiV) stimulation ...

BACKGROUND: Normalization of heart rate post-pacing stress echocardiography (PASE) could enable evaluation of effect of ischemia on diastolic function. METHODS: We examined the effect of pacing on left ventricular (LV) filling in 55 patients who underwent a transesophageal PASE. Pulse wave Doppler of mitral inflow was obtained at baseline and ...

We investigated left ventricular ejection fraction and new left ventricular wall motion abnormality before pacemaker implantation and at follow-up and mortality at long-term follow-up in 81 patients with implantable cardioverter defibrillators treated with biventricular pacing and in 80 patients with implantable cardioverter defibrillators treated with DDDR-70 right ventricular pacing. At ...

OBJECTIVE: This study was planned to investigate ventricular myocardial excitation in birds in which Purkinje fibres penetrate into the ventricular wall and reach the epicardium to advance our knowledge about the evolution of the ventricular activation process in vertebrates. METHODS: A depolarization pattern of the left ventricular free wall in ...

BACKGROUND: Altered electrical activation of the heart by pacing or disease induces profound ventricular electrical remodeling (VER), manifested electrocardiographically as T-wave memory and ultimately as deleterious mechanical remodeling from heterogeneous strain. Although T-wave memory is associated with altered expression of sarcolemmal ion channels, the biophysical mechanisms responsible for triggering remodeling ...

BACKGROUND: Intracardiac electrodes create an "antenna" capable of unintentionally recording and stimulating tissue beyond the chamber in which they are positioned, resulting in far-field R wave oversensing in pacemakers and inappropriate detection in defibrillators. This feasibility study sought to determine whether a specially constructed lead with two distal totally intramyocardial ...

PURPOSE: Fast swim times in morning rounds are essential to ensure qualification in evening finals. A significant time-of-day effect in swimming performance has consistently been observed, although physical activity early in the day has been postulated to reduce this effect. The aim of this study was to compare intradaily variation ...

BACKGROUND: Although the right atrial appendage (RAA) is typically used for atrial pacing lead implant, recent studies have shown benefits of alternate site atrial pacing (ASAP) in the elderly. However, comparable studies in the young are lacking. METHODS: To investigate effects of ASAP on cardiac function and atrioventricular mechanical interactions ...

BACKGROUND: Deleterious effect on left ventricular (LV) function was observed with conventional right ventricular apical (RVA) pacing. Preliminary data suggested that biventricular pacing (BiV) may be superior to RVA pacing in patients with LV systolic dysfunction. However, the optimal pacing mode and site(s) for patients with normal LV systolic function ...

INTRODUCTION: This study examines the consequences of a large transmural apical infarct on the epicardial electrical activity in isolated rabbit hearts. METHODS AND RESULTS: Hearts were isolated 8 weeks after coronary artery ligation. Membrane voltage from the epicardial surface of the left ventricle (LV) including the infarct was monitored using ...

Urocortin 1 (Ucn1) may be involved in the pathophysiology of heart failure (HF), but the impact of Ucn1 administration on progression of the disease is unknown. The aim of this study was to investigate the effects of Ucn1 in sheep from the onset of cardiac overload and during the subsequent ...

AIMS: We investigated whether biventricular (BiV) pacing favourably affects cardiac sympathetic activity in heart failure (HF). METHODS AND RESULTS: In 10 HF patients treated with BiV pacing, we assessed cardiac sympathetic activity by metaiodobenzylguanidine ((123)I-MIBG) imaging. Patients were randomized in a double-blinded crossover fashion, for two weeks of either inactivation ...

AIMS: To compare both short- and long-term stability and pacing parameters of CS leads. Long-term maintenance of coronary sinus (CS) pacing lead position has not yet been assessed by serial X-ray digital imaging. METHODS AND RESULTS: Using X-ray digital imaging in anteroposterior and left lateral views, we performed analysis of ...

BACKGROUND: The complications and limitations of biventricular pacing largely relate to left ventricular (LV) pacing. An alternative approach was tested of simultaneously pacing the right ventricular (RV) apex and outflow tract (RVOT) or using bifocal right ventricular pacing (BRVP) to provide cardiac resynchronisation. METHODS: 21 consecutive patients with heart failure ...

To quantify cardiac apex rotation (CAR), the authors recently proposed the use of a Coriolis force sensor (gyroscope) as an alternative to other complex techniques. The aim of this study was to evaluate the effects of right ventricular (RV) pacing on CAR. A sheep heart was initially paced from the ...

BACKGROUND: Heart rate can affect cardiac function, but the importance of rates lower than 100 paced beats per minute is unknown. We therefore sought to evaluate the impact of different heart rates on ejection fraction, 6-minute walk, and peak oxygen consumption (VO2) in heart failure patients. METHODS AND RESULTS: We ...

AIMS: Right ventricular (RV) pacing has been shown to cause heart failure symptoms in patients with and without previous systolic left ventricular (LV) dysfunction. The aim here was to evaluate the preventive effect of biventricular pacing vs. RV apical pacing in patients with indication for permanent ventricular pacing. Methods PREVENT-HF ...

AIMS: Endocardial (ENDO) or epicardial (EPI) pacing systems are implanted in infants but it remains unclear which system should be preferred. METHODS AND RESULTS: We evaluated the results of children <or=1 year who underwent pacemaker (PM) implantation at our centre with a retrospective analysis. Between 1992 and 2004, 56 patients, ...

OBJECTIVE: To investigate whether transoesophageal cardiac pacing can induce ventricular fibrillation (VF) and how long the cardiac pacing has to be sustained to prevent the reversion of the VF induced. METHODS: A pacing electrode was inserted orally into the oesophagus and high-frequency ventricular pacing was performed so as to elicit ...

Abnormal electrical activation of the left ventricle results in mechanical dyssynchrony, which is in part characterized by early stretch of late-activated myofibers. To describe the pattern of deformation during "prestretch" and gain insight into its causes and sequelae, we implanted midwall and transmural arrays of radiopaque markers into the left ...

INTRODUCTION: The purpose of this study was to examine BiV pacing-dependent changes in QT interval and the related potential for proarrhythmia. Biventricular (BiV) pacing has emerged as a promising therapy for patients with advanced congestive heart failure (CHF) and bundle branch block (BBB). METHODS AND RESULTS: One hundred and seventy-six ...

Cardiac memory is usually observed after right ventricular apical pacing and considered to be related to alter asynchronous activation by apical pacing. However, it is not known whether it occurs by unaltered high to low synchronous ventricular activation by right ventricular outflow tract (RVOT) pacing. We present here a case ...

OBJECTIVES: Considering the recent discovery of postconditioning, we investigated whether intermittent dyssynchrony immediately upon reperfusion induces cardioprotection as well. BACKGROUND: Intermittent dyssynchrony, induced by ventricular pacing, preconditions myocardium. METHODS: Isolated ejecting rabbit hearts were subjected to 30-min coronary occlusion and 2-h reperfusion. Control, left ventricular (LV) pacing preconditioning (LVPpreC) (3 ...

BACKGROUND: Although several randomized trials have detected no reduction in major cardiovascular events with the routine use of dual-chamber as opposed to ventricular pacemakers, many individuals continue to advocate their use as a means of improving exercise capacity. METHODS: The Canadian Trial of Physiological Pacing (CTOPP) trial is the largest ...

Although the overall need for emergency pacing following AMI has reduced with the wide spread use of thrombolysis the availability of transcutaneous pacing offers an emergency non-invasive strategy to optimise circulation following CHB or ventricular standstill. Transcutaneous pacing also facilitates the safe instigation of thrombolytic therapy to achieve reperfusion of ...