Henri Sunthorn

Reducing unnecessary right ventricular pacing with the managed ventricular pacing mode in patients with sinus node disease and AV block.

Background: Frequent and unnecessary right ventricular apical pacing increases the risk of atrial fibrillation or congestive heart failure. We evaluated a new pacing algorithm, managed ventricular pacing (MVP) which automatically changes modes between AAI/R and DDD/R in patients receiving pacemakers for symptomatic bradycardia.

Improvement in cardiac sympathetic nerve activity in responders to resynchronization therapy

AIMS To assess changes in cardiac adrenergic activity with cardiac resynchronization therapy (CRT), and to investigate whether these changes are related to improvement in left ventricular ejection fraction (LVEF). METHODS AND RESULTS Sixteen patients (13 males, age 66 +/- 7 years) were studied at baseline and after > or =6 months of CRT (mean follow-up 9.2 +/- 3.2 months). LVEF was assessed by nuclear angiography. Responders were defined as patients showing > or =5% absolute increase in LVEF + improvement in > or =1 NYHA class + absence of heart failure hospitalization. Cardiac sympathetic nerve activity was studied by (123)I-metaiodobenzyl-guanidine ((123)I-MIBG) scintigraphy. Responders (n = 8) showed lower (123)I-MIBG washout at follow-up when compared with non-responders (P = 0.002), indicating lower cardiac sympathetic nerve activity. The decrease in (123)I-MIBG washout at follow-up when compared with baseline was only seen in the responder group (P = 0.036). There was a moderate correlation between increase in LVEF and decrease in (123)I-MIBG washout (r = 0.52, P = 0.04). CONCLUSION CRT induces a reduction in cardiac sympathetic nerve activity in responders, that parallels an improvement in LVEF, whereas non-responders do not show any significant changes.

Optimization of Device Programming for Cardiac Resynchronization Therapy

Cardiac resynchronization therapy may lead to remarkable improvement in clinical status in selected patients with heart failure. However, approximately 20–30% of patients may not respond to this treatment. One of the reasons for this may be suboptimal programming of the device, which has particular considerations as compared to standard pacemakers. Hemodynamic response to pacing may be affected by timing of the atrioventricular (AV) interval, affecting synchronicity of atrial and ventricular contraction. In addition current biventricular devices have separate right and left ventricular channels that allow programming of an interventricular (VV) interval with right or left ventricular preexcitation. This article focuses on the parameters that may be optimized for biventricular pacing, and reviews the different techniques currently available for this application, with special emphasis paid to echocardiography.

Prospective study of axillary vein puncture with or without contrast venography for pacemaker and defibrillator lead implantation.

Axillary vein puncture may be used to implant pacemaker (PM) or cardioverter defibrillator leads, though usually requires venography. We prospectively compared punctures guided by venography versus a new radiological landmark. In 232 patients, the puncture was guided by injecting diluted contrast material via an ipsilateral peripheral vein (group A, n = 142), or without venography using the intersection of the lateral borders of the second and third rib as a radiological landmark, followed by contrast injection in case of failure (group B, n = 90). We implantated 1–3 leads per patient. In group A, implantation was successful in 135 patients (95%) and in group B in 55 patients (61%, P < 0.001 vs group A). Subsequent contrast injection allowed successful implantations in 34 of 35 patients, with an success rate of 97% for the overall study population of 224 patients. Venous access was achieved after a mean of 10.4 ± 3.2 minutes of skin incision in group A versus 9.4 ± 3.0 minutes in group B (ns). Pneumothorax occurred in two patients (1% overall). Thus non‐contrast guided puncture using a new radiological landmark was successful in a majority of patients. This technique may be useful in absence of ipsilateral peripheral vein access, or presence of contrast allergy.

Thresholds and complications with right ventricular septal pacing compared to apical pacing

Background: Right ventricular septal pacing has been proposed as an alternative to apical pacing. However, data concerning thresholds and requirement for lead repositioning with this technique are scant.

Pacing of the interventricular septum versus the right ventricular apex: a prospective, randomized study.

BACKGROUND Left ventricular (LV) function may be impaired by right ventricular (RV) apical pacing. The interventricular septum is an alternative pacing site, but randomized data are limited. Our aim was to compare ejection fraction (EF) resulting from pacing the interventricular septum versus the RV apex. METHODS RV lead implantation was randomized to the apex or the mid-septum. LVEF and RVEF were determined at baseline and after 1 and 4 years by radionuclide angiography. RESULTS We enrolled 59 patients, of whom 28 were randomized to the apical group and 31 to the septal group, with follow-up available in 47 patients at 1 year and 33 patients at 4 years. LVEF in the apical and in the septal groups was 55 ± 8% vs. 46 ± 15% (p=0.021) at 1 year and 53 ± 12% vs. 47 ± 15% (p=0.20) at 4 years. Echocardiography confirmed a mid-septal lead position in only 54% of patients in the septal group, with an anterior position in the remaining patients. In the septal group, LVEF decreased significantly in patients with an anterior RV lead (-10.0 ± 7.7%, p=0.003 at 1 year and -8.0 ± 9.5%, p=0.035 at 4 years), but not in patients who had a mid-septal lead. Left intraventricular dyssynchrony was significantly increased in case of an anterior RV lead. RVEF was not significantly impaired by RV pacing, regardless of RV lead position. CONCLUSIONS Pacing at the RV septum confers no advantage in terms of ventricular function compared to the apex. Furthermore, inadvertent placement of the RV lead in an anterior position instead of the mid-septum results in reduced LV function.

Utility of the surface electrocardiogram for confirming right ventricular septal pacing: validation using electroanatomical mapping

AIMS When targeting the interventricular septum during pacemaker implantation, the lead may inadvertently be positioned on the anterior wall due to imprecise fluoroscopic landmarks. Surface electrocardiogram (ECG) criteria of the paced QRS complex (e.g. negativity in lead I) have been proposed to confirm a septal position, but these criteria have not been properly validated. Our aim was to investigate whether the paced QRS complex may be used to confirm septal lead position. METHODS Anatomical reconstruction of the right ventricle was performed using a NavX® system in 31 patients (70 ± 11 years, 26 males) to validate pacing sites. Surface 12-lead ECGs were analysed by digital callipers and compared while pacing from a para-Hissian position, from the mid-septum, and from the anterior free wall. RESULTS Duration of the QRS complex was not significantly shorter when pacing from the mid-septum compared with the other sites. QRS axis was significantly less vertical during mid-septal pacing (18 ± 51°) compared with para-Hissian (38 ± 37°, P = 0.028) and anterior (53 ± 55°, P = 0.003) pacing, and QRS transition was intermediate (4.8 ± 1.3 vs. 3.8 ± 1.3, P < 0.001, and vs. 5.4 ± 0.9, P = 0.045, respectively), although no cut-offs could reliably distinguish sites. A negative QRS or the presence of a q-wave in lead I tended to be more frequent with anterior than with mid-septal pacing (9/31 vs. 3/31, P = 0.2 and 8/31 vs. 1/31, P = 1.0, respectively). CONCLUSION No single ECG criterion could reliably distinguish pacing the mid-septum from the anterior wall. In particular, a negative QRS complex in lead I is an inaccurate criterion for validating septal pacing.

Evaluation of an individualized strategy of cavotricuspid isthmus ablation as an adjunct to atrial fibrillation ablation.

Objectives: To evaluate supplementary cavotricuspid isthmus (CTI) ablation as an adjunct to atrial fibrillation (AF) ablation in selected patients.

Comparison of tools and techniques for implanting pacemaker leads on the ventricular mid-septum.

INTRODUCTION Many physicians target the interventricular septum for pacemaker implantation, but the lead may inadvertently end up in an anterior position. AIMS We sought to compare two stylet shapes to achieve mid-septal lead placement, as well as the utility of a novel right anterior oblique (RAO) fluoroscopic landmark. METHODS AND RESULTS Patients undergoing pacemaker implantation were enrolled into four consecutive groups according to stylet shape: a standard curve [two-dimensional (2D) stylet] or with an additional distal posterior curve [three-dimensional (3D) stylet], and whether RAO fluoroscopy was used. Left oblique anterior (LAO) and postero-anterior (PA) fluoroscopic views were used in all cases. After implantation, validation of right ventricular lead position (septal vs. anterior) was performed by echocardiography. A total of 113 patients were included, of whom lead position could be validated in 106 patients. Septal position was achieved in only 10 of 22 (45%) patients in the 2D stylet group and in 17 of 23 (74%) patients in the 3D stylet group (P = 0.07) when only PA and LAO fluoroscopy were used. Results were significantly improved by additional use of RAO fluoroscopy, with successful septal placement in 25 of 28 (89%) patients in the 2D stylet + RAO group (P = 0.001) and 32 of 33 (97%) patients in the 3D stylet + RAO group (P = 0.015). CONCLUSIONS A septal lead position was obtained in only about half of the patients when a 2D stylet was used with only LAO and PA fluoroscopic views. A 3D stylet was useful to attain the target position, and additional RAO fluoroscopy significantly improved success rate with both stylet shapes.

Biatrial pacing improves atrial haemodynamics and atrioventricular timing compared with pacing from the right atrial appendage.

AIMS Patients with interatrial conduction delay may have suboptimal left atrioventricular (AV) timing due to delayed contraction of the left atrium with foreshortening of ventricular filling. This may be an issue in pacemaker patients, especially those requiring resychronization therapy. Pacing from the high interatrial septum (IAS) or the distal or proximal coronary sinus (CSD and CSP) may improve left AV synchrony compared with pacing from the right atrial appendage (RAA). Our aim was to compare haemodynamics of these pacing sites. METHODS AND RESULTS A total of 24 patients undergoing radiofrequency ablation for paroxysmal atrial fibrillation were studied. Left atrial pressures were recorded in sinus rhythm, and during pacing from the RAA, IAS, CSD, CSP, and with biatrial (BiA) pacing from the IAS + CSD. Amplitudes, +dP/dT(max), and timing of the a-wave were compared between recordings. Left atrial contractility, measured by +dP/dT(max), was greatest during BiA pacing (P ≤ 0.03 for all comparisons). There was a marked reduction in delay to peak a-wave when pacing from all sites compared with the RAA, with BiA pacing yielding the shortest delay (P ≤ 0.001). However, AV conduction was shortened by all alternative pacing sites, which mitigated the anticipation of left atrial contraction with respect to ventricular activation, except for BiA pacing (P < 0.001). Pacing of the IAS did not result in any improvement in haemodynamics or AV synchrony. CONCLUSION Multisite atrial pacing results in favourable acute atrial haemodynamics and left AV synchrony. This may be a solution in pacemaker patients with interatrial conduction delay.