1,721,095 research outputs found
When to choose cardiac resynchronization therapy in chronic heart failure: Type and duration of the conduction delay
No full textCardiac resynchronization therapy (CRT) is an established treatment for patients with heart failure (HF), impaired left ventricular (LV) function, and wide QRS complex. The initial randomized clinical trials, which led to the widespread use of CRT, selected patients on the basis of QRS duration, not focusing on QRS morphology. However, recent evidences emphasized the role of left bundle branch block morphology in patients that underwent CRT in order to predict better response to therapy. Moreover, conventional right ventricular apical pacing might have long-term detrimental effects on cardiac structure and LV function, possibly leading to the development of HF. Therefore, current guidelines recommend upgrade from conventional pacemaker or implantable cardioverter-defibrillator to CRT or de novo CRT in patients with high (or expected high) percentage of ventricular pacing and reduced EF. We reviewed current knowledge on candidates' selection for CRT based on conduction delays that lead to electrical and mechanical dyssynchrony of the left ventricle
Electrophysiological study and catheter ablation of a Mahaim fibre located at the mitral annulus-aorta junction
No full textAccessory pathways with slow and anterograde decremental conduction (Mahaim fibres) are responsible for a minority of atrioventricular reentrant tachycardias. While usually located along the tricuspid annulus, left-sided Mahaim fibres have been occasionally reported. We here report on a unique case of radiofrequency catheter ablation of a Mahaim pathway located at the supero-septal aspect of the mitral annulus, in a region known as mitral annulus– aorta junction, between the right and left fibrous trigons. Electrophysiological properties and embryological implica- tions of this unusual accessory pathway are discussed
Complex electrocardiographic findings ia a neonate with Long QT syndrome
No full textA case of long QT syndrome diagnosed in the early neonatal period is described. A full-term male baby was delivered by cesarean section at 38 weeks of gestation. The indication to cesarean section was sudden marked fetal bradycardia. At birth, he presented the following rhythm disorders: a) an ectopic atrial rhythm with T wave alternans, and b) atrioventricular conduction disorders. Sinus rhythm, with a prolonged QT interval and T wave alternans, was recovered soon after birth, before starting beta-blocker therapy. The family history was negative for the long QT syndrome: sudden unexpected death and/or syncopal episodes and cases of congenital deafness have not been reported. Molecular screening of the five long QT syndrome-related genes did not reveal the presence of any mutation. At 3 years of follow-up, the child is well and he did not present with symptoms or arrhythmias during this period
Efficacy and safety of rivaroxaban compared with vitamin K antagonists for peri-procedural anticoagulation in catheter ablation of atrial fibrillation: a systematic review and meta-analysis
No full textDevelopment of an entirely subcutaneous implantable cardioverter-defibrillator.
No full textThe recent advent of an entirely subcutaneous implantable defibrillator (ICD) has provided a
relevant contribution to the debate concerning the use of ICD therapy in patients at high risk for
death. Although conventional transvenous ICDs have proven very effective during the past 23
years, they still appear to be limited by nontrivial acute and long-term complications. This study
delineates some of the historical and current issues characterizing the advent of the
subcutaneous ICD system in daily clinical practice. Subcutaneous ICDs have proven effective
in more than 1100 patients worldwide and appear to be competitive with transvenous ICD in all
clinical conditions not requiring antibradycardia, antitachycardia, or cardiac resynchronization
pacing. (Prog Cardiovasc Dis 2012;54:493-497
An unusual pattern of Para-Hisian pacing. The role of infra-Hisian conduction delay
No full textA 26-year-old male athlete with a history of palpitations and intermittent preexcitation was referred to our center. The echocardiogram did not reveal any relevant abnormalities, while his basal 12-lead electrocardiogram showed sinus rhythm and incomplete left bundle branch block (LBBB).
An electrophysiological study was performed, and multipolar diagnostic catheters were positioned at the His bundle (HB) region and coronary sinus. The AH and HV intervals were 60 milliseconds and 45 milliseconds, respectively. Retrograde conduction was concentric and decremental. During Para-Hisian pacing (PHP) maneuver, an interesting phenomenon was observed (Figure 1A). The loss of direct HB capture at a lower pacing-output led to delayed retrograde HB activation, with a subsequent significant and homogenous delay in atrial activation, consistent with a nodal response (beat 2, Figure 1A). The H-A interval was slightly shorter (∼10 milliseconds) at beat 2, likely because the loss of HB capture caused a marked prolongation of the H-H interval compared to the basal pacing cycle length favoring faster retrograde conduction over the AV node (ie, decremental conduction).
However, the typical QRS widening was absent, and there was only a slight change in QRS morphology (earlier R/S transition in chest leads), while QRS duration remained nearly unchanged (∼120 milliseconds). Notably, the basal incomplete LBBB was observed to be more evident either spontaneously (Figure 1B), or at slightly faster rates of atrial pacing. Typically, direct HB capture at high pacing-output
produces a narrower QRS because of the support of His-Purkinje system providing faster and more synchronous activation of both ventricles. In particular, the LBB should play a dominant role in this scenery since it supports the activation of the left ventricle (LV) that is far from the pacing site. In our case, the status of HB capture during PHP (direct capture vs. delayed retrograde activation) did not affect LV timing nor had a major effect on ventricular activation time (QRS duration), likely due to the basal conduction defect at the LBB level. In this study, no inducible tachycardia or accessory pathways were observed even at high-dose Isoproterenol and ablation was not performed.
This case highlights an additional potential pitfall during PHP maneuver and how basal infra-Hisian conduction delay may affect the typical QRS changes that are essential criteria to recognize the status of HB capture. Multipolar HB recordings and the ability to detect retrograde HB potential, rather than relying on QRS changes, are the key for correct interpretation in such cases
Premature ventricular extrastimulus without His or ventricular capture. An unexpected response during AV nodal reentrant tachycardia
No full textA 52-year-old male was referred to our center for catheter ablation of recurrent episodes of paroxysmal supraventricular tachycardia. No relevant abnormalities were observed at his basal ECG and echocar- diogram. Electrophysiological study was performed, and multipolar diagnostic catheters were introduced via the femoral veins. Typical atrioventricular (AV) nodal reentrant tachycardia with a medium rate of 200 bpm was reproducibly induced and diagnosed according to the standard criteria. During ventricular resetting maneuver using the His catheter, an expected phenomenon was observed after applying an early premature ventricular extrastimulus (PVE) (Figure 1). At a first look, the stimulus occurred during the ventricular refractory period without any capture. However, a phase of right bundle branch block (RBBB) occurred immediately after this apparently noncapturing PVE and without any subsequent change in the tachycardia cycle length making rate-dependent RBBB unlikely as a mechanism. The PVE did not capture ventricular myocardium, nor the His bundle (H-H intervals remained unchanged), and the tachycardia was not reset (Figure 1A). The induced RBBB was likely due to local concealed capture of the proximal RBB during its relative refractory period by the applied PVE. The stimulus could generate only an attenuated action potential with slow conduction in the RBB (the asterisk, Figure 1B) unable to
advance the next QRS. Nevertheless, the local capture of proximal RBB rendered it unexcitable by the antegrade activation of the ongoing tachycardia. Another possible mechanism is local electrotonus after PVE causing local loss of membrane potential adjacent to the distal RBB and resulting in conduction block of the advancing wave coming down the RBB. Subsequently, RBBB was likely maintained through a linking effect and repetitive retrograde penetration of the RBB by impulses propagating antegradely over the contralateral left bundle (Figure 1C).
This case highlights intriguing electrophysiological phenomena that can still be observed during a classical pacing maneuver of a common reentry circuit including concealed capture of the His-Purkinje system, electrotonus, linking effect, and functional aberrancy
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
