Direct His Research Articles

Direct his-Bundle Pacing: Acute Echocardiographic Evaluation

Right ventricular apical pacing alters impulse conduction producing an intraventricular desynchronization that could be detrimental for LV function. Direct His bundle pacing (DHBP) represents a novel approach to cardiac pacing in pts with normal His-Purkinje activation because it maintains or restores the physiological activation of the ventricular muscle during cardiac pacing. 13 pts (mean age 76±3 years; 2 females; QRS duration 118±24 ms; LV EF% 60±11; LV end-diastolic volume 61±22 ml/m2) have been investigated. At baseline and after DHBP Tissue Doppler Imaging was performed to evaluate the intraventricular dyssynchrony [defined as the interval between the earliest LV wall motion and the latest (intra LV delay) or as standard deviation (SD, modified Yu index) of all time intervals]. Tei index, E/A ratio, dP/dT, MR (mitral regurgitation-diameter of vena contracta) were also obtained. Baseline intra-LV desynchronization (intra-LV delay above 40 ms) was observed in 2 pts with normal QRS and in all 4 pts who had intraventricular conduction delay (QRS > 120 ms). in table are displayed the values at baseline and after DHBP: After DHBP only one pt with baseline QRS >120 ms maintained an intra-LV desynchronization. Moreover both Tei index and dP/dT improved but not significantly. Conclusion: DHBP maintains the normal activation and contraction of ventricular myocardium.

527 A novel technique for direct His bundle pacing

527 A novel technique for direct His bundle pacing

24 Permanent direct His bundle pacing does not induce ventricular dyssynchrony as opposed to conventional right ventricular apical DDD pacing

24 Permanent direct His bundle pacing does not induce ventricular dyssynchrony as opposed to conventional right ventricular apical DDD pacing

Where to pace and where not to pace?

Where to pace and where not to pace?

679 Acute haemodynamic effects of permanent, direct His bundle pacing

679 Acute haemodynamic effects of permanent, direct His bundle pacing

527 A novel technique for direct His bundle pacing

527 A novel technique for direct His bundle pacing

679 Acute haemodynamic effects of permanent, direct His bundle pacing

679 Acute haemodynamic effects of permanent, direct His bundle pacing

24 Permanent direct His bundle pacing does not induce ventricular dyssynchrony as opposed to conventional right ventricular apical DDD pacing

24 Permanent direct His bundle pacing does not induce ventricular dyssynchrony as opposed to conventional right ventricular apical DDD pacing

Commentary on the abstracts for Cardiostim 2005 Pacing and Haemodynamics: Art of Timing Budapest, Hungary, April 6–8, 2005

The Cardiostim team and Prof. Aladar Ronaszeki organised an educational meeting in Budapest from April 6 to 8 entitled “Pacing and Haemodynamics: Art of Timing”. This European congress has been an opportunity to discuss the haemodynamic effects of the various modes of pacing available, and more specifically Cardiac Resynchronisation Therapy (CRT) for heart failure patients. The reader will find below the 101 abstracts selected among the 156 received, printed in three different sections: conventional pacing, CRT, and a small set of abstracts on ablation techniques, which will not receive comment. Many investigations have demonstrated the deleterious effects of right ventricular (RV) apical pacing. Padeletti et al. (for the WHERE study) elegantly show the benefit of preserving spontaneous AV conduction in comparison with RV apical pacing, in DDD paced patients, via PEA measurements. PEA, which has been demonstrated to be closely correlated with LV d P /d t , significantly increases when patients are not RV paced, and decreases when they are RV paced. PEA variations parallel clinical outcomes and echo parameter values. When pacing is necessary, there is still controversy about the optimal RV pacing site. Direct His bundle pacing is feasible and safe (Catanzariti et al.), but requires normal function of the bundle branches and Purkinje system. Implantation is also difficult to perform. Long term reliability of His pacing is unknown. For Kutarski et al., RV outflow tract (RVOT) pacing is preferable to RV apical pacing. But for van Gelder, RV apical pacing is preferred for CRT patients. In our experience, RVOT and RV apical pacing provide similar haemodynamic results on average, but may induce significant individual differences. To help to understand individual requirements, one of the main targets for manufacturers is to propose haemodynamic sensors that could evaluate and guide the benefits of various pacing sites, such as …

Thermodynamics of metal ion binding. 2. Metal ion binding by carbonic anhydrase variants.

The ability to construct molecular motifs with predictable properties in aqueous solution requires an extensive knowledge of the relationships between structure and energetics. The design of metal binding motifs is currently an area of intense interest in the bioorganic community. To date synthetic motifs designed to bind metal ions lack the remarkable affinities observed in biological systems. To better understand the structural basis of metal ion affinity, we report here the thermodynamics of binding of divalent zinc ions to wild-type and mutant carbonic anhydrases and the interpretation of these parameters in terms of structure. Mutations were made both to the direct His ligand at position 94 and to indirect, or second-shell, ligands Gln-92, Glu-117, and Thr-199. The thermodynamics of ligand binding by several mutant proteins is complicated by the development of a second zinc binding site on mutation; such effects must be considered carefully in the interpretation of thermodynamic data. In all instances modification of the protein produces a complex series of changes in both the enthalpy and entropy of ligand binding. In most cases these effects are most readily rationalized in terms of ligand and protein desolvation, rather than in terms of changes in the direct interactions of ligand and protein. Alteration of second-shell ligands, thought to function primarily by orienting the direct ligands, produces profoundly different effects on the enthalpy of binding, depending on the nature of the residue. These results suggest a range of activities for these ligands, contributing both enthalpic and entropic effects to the overall thermodynamics of binding. Together, our results demonstrate the importance of understanding relationships between structure and hydration in the construction of novel ligands and biological polymers.

Estimulación permanente del haz de His tras ablación mediante radiofrecuencia del nodo auriculoventricular en pacientes con trastorno de la conducción suprahisiano

The asynchronic contraction of the left ventricle due to left bundle branch block or right ventricular pacing is inferior from a hemodynamic point of view to the synchronic contraction through the conduction system. Several authors have reported some cases of pump failure and deterioration of mitral regurgitation after AV nodal ablation. Alternative sites of pacing such as the right ventricular outflow tract pacing have been proposed in order to avoid these complications. Direct His bundle pacing might be a new alternative for permanent pacing, however, it has not been extensively evaluated in humans yet. Our aim is to prove the feasibility of permanent His pacing in terms of stability, thresholds and pump function. patients without structural heart disease, selected for AV nodal ablation due to uncontrolled paroxysmal atrial fibrillation, or for pacemaker implantation due to supraHis conduction disturbance, with normal conduction system. An active fixation permanent lead was placed in His position using an steering guidewire and a diagnostic catheter as an anatomical reference. We also implanted a lead in the right atrial appendage and both were connected to a DDDR generator. Pacing thresholds and ecocardiographic ventricular function parameters were evaluated (ejection fraction, cavity size, mitral regurgitation). 12 patients met the inclusion criteria. Successful His pacing was achieved in 8 out of 12 cases (66%) with acceptable thresholds at implantation (1.24 +/- 0.13 volts at 0.5 ms) and during follow up at 3 months (1.31 +/- 0.20 volts at 0.5 ms). Neither a significant change in the ecocardiographic parameters not a deterioration in the clinical status caused by ablation or stimulation was evidenced. The His bundle may be the site of choice for long term pacing in patients with AV block and normal infraHis conduction system.

Catheter ablation of the atrioventricular junction: a report of the percutaneous mapping and ablation registry.

An international registry was formed to collate data for patients undergoing attempted catheter ablation of the atrioventricular (AV) junction and insertion of a permanent pacemaker. Over the past 2 years, data was submitted for 127 patients who were followed for a mean of 9.9 +/- 8.2 months. The most common arrhythmia treated was chronic or paroxysmal atrial fibrillation or flutter (78 patients, 61%); the remainder had supraventricular tachycardia due to AV node reentry, ectopic atrial tachycardia, or incorporated an accessory pathway. A single shock of 150 to 400 J was effective in producing chronic third-degree AV block in 45 patients while two or more shocks were used in an additional 45 patients. There was no significant difference in the total cumulative energy used in successful and unsuccessful procedures. Immediate complications related to the shock included ventricular fibrillation (one patient), pericardial tamponade (one patient), and transient hypotension (one patient). No chronic sequelae occurred as a result of these complications. Late complications (1 day to 1 month) included ventricular tachycardia (three patients), sepsis involving the pacemaker pocket (two patients), staphylococcal sepsis from temporary pacing catheter (one patient), thrombophlebitis (one patient), thrombosis of the left subclavian vein (one patient), and hemothorax (one patient). Follow-up evaluation revealed chronic third degree AV block in 90 (71%) and AV conduction resumed but no drugs were required for arrhythmia control in eight (6.5%) and arrhythmia control was achieved with previously ineffective drugs in 16 (13%). Thirteen patients (10%) had no improvement and five of these patients underwent cardiac electrosurgery for direct His bundle ablation.(ABSTRACT TRUNCATED AT 250 WORDS)