Cost-effectiveness of dual-chamber pacemaker therapy: does single lead VDD pacing reduce treatment costs of atrioventricular block?

AIMS: Implantation of single-lead VDD pacemakers is an established alternative to DDD pacing in patients with atrioventricular block. This study compares the long-term costs of both systems. METHODS AND RESULTS: Three hundred and sixty patients with atrioventricular block received VDD or DDD pacemakers in alternating order. Primary costs of implantation included: devices, leads and operation material, surgeons, nurses, medical technicians, and hospitalization. The mean cost of an uncomplicated DDD pacemaker implantation was defined as 1000 virtual cost-units (CU). Costs of pacemaker related complications or re-operations as well as upgrades from VDD to DDD devices were considered secondary costs and assessed during a mean follow-up period of 42+/-15 months. Pacing efficacy was assessed by event-free survival with maintained atrioventricular synchronized pacing mode. Costs of pacemaker devices were not different (639+/-26 CU in VDD vs 641+/-32 CU in DDD, ns). However, due to lower costs of lead hardware (102+/-10 CU in VDD vs 133+/-14 CU in DDD, P<0.001) and shorter implantation procedures (44.3+/-5.1 min vs 74.4+/-13.5 min, P<0.001), costs of an uncomplicated implantation were 8.9% lower in the VDD group (911+/-35 CU vs 1000+/-39 CU, P<0.001). A smaller complication rate in the VDD group led to a 16.1% reduction of secondary costs (26+/-17 CU year(-1)vs 31+/- 25 CU year(-1), P=0.024). Event-free survival did not differ between groups (83.4% in VDD vs 84.9% in DDD, ns). CONCLUSION: Use of single-lead VDD pacemakers achieves significant reduction of implantation and follow-up costs without loss of therapeutic efficacy compared to conventional DDD systems.     

DDD and single-lead VDD pacing: evaluation of atrial signal dynamic changes

BACKGROUND: Single-lead VDD pacing systems are an alternative to conventional DDD pacemakers in patients with atrioventricular (AV) block and normal sinus function. HYPOTHESIS: The aim of this study was to assess changes of P-wave amplitude occurring in dynamic conditions in two groups of patients with a single-lead VDD and with a DDD pacing system, respectively. METHODS: Twenty-eight patients with second- or third-degree AV block and normal sinus function were enrolled prospectively into the study. Seventeen patients were implanted with a single-lead VDD pacing system and 11 with a DDD pacemaker. Patients were evaluated at 3 months (all patients) and at 6 months (26 patients) at supine and in dynamic conditions (postural changes, hyperventilation, and during exercise). RESULTS: Mean P-wave values at supine were 1.92 +/- 1.10 mV at 3 months and 1.76 +/- 1.01 mV at 6 months for VDD systems, and 4.63 +/- 2.18 mV at 3 months and 4.58 +/- 2.80 mV at 6 months for DDD pacemakers. In dynamic conditions, P-wave amplitude changes compared with supine condition ranged between -74 and +226% in VDD, and between -53 and +138% in DDD; however P-wave amplitudes showed no significant changes compared with baseline. Moreover, changes in atrial signal amplitudes did not occur randomly, and in both systems P-wave amplitudes remained significantly correlated with supine values. CONCLUSIONS: A wide range of P-wave amplitude variations occurs in different postural conditions or during exercise, both with single-lead VDD and DDD pacing systems. However, with appropriate programming of atrial sensitivity based on supine values, constant atrial tracking can be maintained.     

Influence of Cardiac Pacing Mode on Left Atrial Appendage Flow Velocity: Implication to Systemic Embolism During VVI Pacing

Previous studies have shown that the incidence of thromboembolism is higher in patients with single-chamber ventricular demand (VVI) pacemakers than in patients with dual-chamber (DDD) pacemakers. However, data on left atrial appendage flow velocity in pacing patients are limited. To investigate the influence of the pacing mode on the left atrial appendage flow velocity, we studied 19 patients with permanent DDD pacemakers and measured the left atrial appendage flow velocity by transesophageal echocardiography at baseline (during DDD pacing) and after switching to VVI pacing. The indications for pacemaker implantation were second- and third-degree atrioventricular block (AVB group, n = 11) and sick sinus syndrome (SSS group, n = 8). Compared with the DDD pacing mode, there was a significant decrease in the left atrial appendage flow velocity during VVI pacing in both the SSS group (43 ± 14 vs 23 ± 7 cm / sec, P < 0.05) and the AVB group (59 ± 18 vs 41 ± 18 cm / sec, P < 0.05). In eight patients with persistent retrograde ventriculoatrial conduction during VVI pacing, the left atrial appendage flow velocity was markedly decreased (from 43 ± 16 to 25 ± 9 cm / sec, P < 0.05). In five (63%) of the eight patients, left atrial appendage flow velocity was less than 25 cm/sec. A reduction in left atrial appendage flow velocity when switching from DDD to VVI pacing may account for an increased risk of thrombus formation in the left atrial appendage (an increased thromboembolic risk in patients in sinus rhythm with VVI pacemakers).     

Atrial tracking (synchronous) pacing in a pediatric and young adult population

One hundred pediatric and young adult patients underwent implantation of an atrial tracking pacemaker. Seventy-four pacemakers paced in an atrioventricular (AV) sequential mode at the lower rate limit (DDD) while 26 paced in a ventricular demand mode at the lower rate limit (VDD). Five patients required reoperation during follow-up of 1 month to 2.5 years (mean 1.5 years). Six additional patients required programming to ventricular demand (3) or AV sequential (3) pacing, because of development of sinus bradycardia (2), atrial sensing problems (1) or pacemaker-mediated tachycardia (3). Pulse generators that could sense atrial signals less than 1.0 mV and had a programmable atrial refractory period did not require reprogramming out of the atrial tracking mode. No patient developed atrial flutter or fibrillation. Sensing problems during exercise occurred in 37% of the first 60 pacemakers but in none of the last 40, which had improved electronic components. Atrial tracking pacing is feasible in pediatric and young adult patients.     

Feasibility of dual-chamber (DDD) pacing via a single-pass (VDD) pacing lead employing a floating atrial ring (dipole): case series, future considerations, and refinements

The objective of this study was to assess the feasibility of DDD pacing from a standard single-pass VDD pacemaker system. Over the past 2 decades significant advances have been made in the development of single-pass VDD pacing systems. These have been shown in long-term prospective studies to effectively preserve atrioventricular (AV)synchrony in patients with AV block and normal sinus node function. What remains problematic is the development of a single-pass pacing system capable of DDD pacing. Such a lead configuration would be useful in those patients with peripheral venous anomalies and in younger patients with congenital anomalies, which may require lead revisions in the future. In addition, with the increased use of resynchronization (biventricular pacing) therapy, the availability of a reliable single-pass lead will minimize operative time, enhance patient safety, and minimize the amount of hardware within the heart. The feasibility of DDD pacing via a Medtronic Capsure VDD-2 (Model #5038) pacing lead was evaluated. Twenty patients who presented with AV block and normal sinus node function were recruited for this study. Atrial pacing thresholds and sensitivities were assessed intraoperatively in the supine position with various respiratory maneuvers. Five patients who agreed to participate in long-term follow-up received a dual-chamber generator and were evaluated periodically over a 12-month period. Mean atrial sensitivity was 2.35 +/- 0.83 mV at the time of implantation. Effective atrial stimulation was possible in all patients at the time of implantation (mean stimulation threshold 3.08 +/- 1.04 V at 0.5 ms [bipolar], 3.34 +/- 0.95 V at 0.5 ms [unipolar]). Five of the 20 patients received a Kappa KDR701 generator, and atrial electrical properties were followed up over a 1-year period. There was no significant change in atrial pacing threshold or incidence of phrenic nerve stimulation over the 1-year follow-up. A standard single-pass VDD pacing lead system was capable of DDD pacing intraoperatively and during long-term follow-up. Despite higher than usual thresholds via the atrial dipole, pacemaker telemetry revealed < 10% use of atrial pacing dipole over a 12-month period, which would minimally deplete the pacemaker's battery. In addition, the telemetry confirmed appropriate sensing and pacing of the atrial dipole throughout the study period. At this time such systems can serve as back-up DDD pacing systems with further refinements required to optimize atrial thresholds in all patients.     

Long-term clinical performance of AAI pacing in patients with sick sinus syndrome: a comparison with dual-chamber pacing.

AIMS: In this clinical study, we compared two groups of age-matched patients, AAI and DDD, to evaluate the clinical benefits of AAI pacing in patients with sick sinus syndrome (SSS) and normal atrioventricular (AV) conduction. METHODS AND RESULTS: Ninety-five patients with SSS implanted with AAI pacemakers were compared with 101 SSS patients implanted with DDD pacemakers. Mortality, chronic atrial fibrillation, lead survival rates, and reoperation rates were compared by Kaplan-Meier analysis. Eight AAI devices were switched to DDD due to high-degree (grade 2-3) AV block. The incidence of high-degree AV block was 1.104%/year, with a freedom rate of 88.6% at 10 years. There were no significant differences between the two groups in survival rates (87.8% in AAI vs. 93.4% in DDD at 10 years), freedom from atrial fibrillation (93.6% vs. 90.6%), or freedom from reoperation (71.3% vs. 76.3%). On the other hand, lead failure was twice as frequent in the DDD group than in the AAI group (relative risk=2.045, P=0.0382). CONCLUSION: AAI pacing, a simple system using a single lead and single-chamber pacemaker, can achieve a clinical outcome similar to that of the DDD mode in patients with SSS and normal AV conduction.     

Immediate impairment of left ventricular mechanical performance and force-frequency relation by rate-responsive dual-chamber, but not atrial pacing: Implications from intraventricular isovolumic relaxation flow

BACKGROUND: Despite the maintenance of atrioventricular (AV) synchrony, the detrimental effect of left ventricular asynchronization on mechanical performance and intraventricular flow by nonphysiologic right ventricular apical pacing in dual-chamber pacing, with and without rate adaptation, is not clear. METHOD: Twenty-seven consecutive patients receiving permanent pacemakers for symptomatic bradyarrhythmias (18 with DDD and 9 with AAI mode pacemakers) were evaluated with standard and tissue Doppler echocardiography before and 24 h after pacemaker implantation. The rate-response effect of pacing was studied by programmed rate with increments of 20, from 60 to 100/min. RESULTS: Color M-mode echocardiography demonstrated that much more DDD patients developed new biphasic intraventricular flow during isovolumic relaxation period than AAI patients (13/18 versus 0/9, P<0.001). In DDD patients, the ventricular relaxation represented by mitral annulus velocity in early diastole significantly attenuated (before vs. after DDDR, 8.5+/-2.8 vs. 5.2+/-1.2 cm/s, P<0.05), and also the mitral flow propagation velocity (33+/-11 vs. 25+/-5 cm/s, P<0.01). The myocardial performance index increased after DDD (0.70+/-0.15 vs. 0.79+/-0.24, P<0.05) but not after AAI (0.61+/-0.1 vs. 0.59+/-0.08, P=NS). For both pacing groups, the accelerated pacing rate prolonged the isovolumic relaxation time and shortened the diastole period (P<0.001). However, only DDD patients had a decreased mitral flow propagation velocity (P=0.026) and an attenuated force-frequency relation in programmed rate acceleration. CONCLUSION: Despite the AV synchrony, right ventricular apical pacing immediately attenuates the left ventricular contraction and relaxation performance, which deteriorated further and suppressed the physiologically positive force-frequency relation after accelerated pacing rate.     

Atrial pacing for prevention of atrial fibrillation: assessment of simultaneously implemented algorithms.

AIMS: Several preliminary studies indicated that right atrial pacing could prevent atrial tachyarrhythmias (ATA). We sought to compare the safety and the efficacy of atrial-based pacing supplemented by dedicated combined algorithms with conventional atrial pacing in the prevention of ATA. METHODS: Fifty-five patients with a history of recurrent paroxysmal ATA implanted with a dual-chamber pacemaker were studied during two randomized cross-over pacing periods (conventional DDD and DDD with ATA prevention algorithms) of 6 months duration. The primary endpoint was the burden of ATA episodes recorded by the device mode switch algorithm. RESULTS: The cross-over analysis did not demonstrate any significant difference between the two pacing modes: 254+/-533 h of ATA during the control period versus 238+/-518 h during the ATA prevention period. Analysis of a subgroup of patients found that those with the lower percentage of ventricular pacing benefited from ATA prevention algorithms (120+/-182 h versus 225+/-350 h during the control period; P < 0.04). CONCLUSION: When compared with DDD pacing at 70 bpm, ATA prevention algorithms have not demonstrated significant efficacy. However, a subgroup of patients with preserved native AV conduction (low percentage of ventricular pacing) responded to ATA prevention algorithms.     

Sustained improvement in exercise tolerance following physiological cardiac pacing

Fifty-three patients have received ‘physiological’pacemakers,37 with atrioventricular (AV) block having atrial synchronousunits (VAT or VDD) implanted and the remaining 16 patients withboth AV block and sick sinus syndrome having ‘universal’(DDD) pacemakers. Effort tolerance was assessed by serial bicycleergometry and in 16 patients direct comparisons between ventricularpacing and atrial synchronous pacing could be made acutely.Physiological pacemakers were found to increase maximum efforttolerance by 43% compared to pre-pacing values (P<0.01).The increase was sustained over a mean of 33 months post pacing.The atrial synchronous mode increased maximum effort toleranceby 34% acutely compared to ventricular inhibited pacing. Dualchambered ‘physiological’ pacemakers represent asignificant therapeutic advance over standard ventricular inhibitedpacemakers.     

The Impact of the Distance between the Atrial Electrode and the Atrial Wall on Atrial Undersensing in Patients with VDD Pacemakers: Long‐Term Follow‐Up

Aim: Atrial undersensing (AUS) in single‐lead VDD pacemakers may be due to diminished P‐wave amplitude secondary to local inflammation beneath the electrodes closer to atrial wall. The aim of this study was to assess the potential effect of distance between atrial electrode and atrial wall on immediate and long‐term atrial sensing stability in VDD systems. Methods: A total of 275 patients with normal sinus node function who received VDD pacemakers were enrolled into the study and were followed up for a median duration of 33 months. During each control visit, a standard 12‐lead electrocardiogram (ECG) was obtained and standard pacemaker function assessment was performed including testing for pacing threshold and atrioventricular synchrony. The distance between atrial electrode and atrial wall was measured from chest X‐ray. Results: Of the 275 patients, AUS was detected in 59 patients. Univariate predictors of AUS were use of closely spaced bipolar ring atrial electrode (CSBR) (P = 0.01), wider atrial ring‐spacing (P = 0.03), and atrial sensitivity programmed to a higher level (P = 0.001). Use of CSBR (P = 0.04) and atrial sensitivity ≥0.3 mV (P = 0.02) were observed to be the independent predictors for AUS. When the distance between atrial electrode and atrial wall was <7 mm, AUS was less with diagonally arranged bipolar ring electrodes (DABR) than it was with CSBRs (P = 0.02). Conclusions: The distance between atrial electrode and atrial wall does not appear to affect AUS incidence in VDD pacemakers. For VDD electrodes closer to atrial wall, AUS was significantly less likely in DABR‐type electrodes.     

Inducibility of atrial fibrillation during atrioventricular pacing with varying intervals: role of atrial electrophysiology and the autonomic nervous system

INTRODUCTION: Patients receiving VVI pacemakers have a higher incidence of paroxysmal atrial fibrillation (AF) than those receiving DDD pacemakers. However, the mechanism behind the difference is not clear. The purpose of this study was to investigate whether atrial electrophysiology and the autonomic nervous system play a role in the occurrence of AF during AV pacing. METHODS AND RESULTS: The study population consisted of 28 patients who had (group I, n = 15) or did not have (group II, n = 13) AF induced by a single extrastimulus during pacing with different AV intervals. Atrial pressure, atrial size, atrial effective refractory periods, and atrial dispersion were evaluated during pacing with different AV intervals. Twenty-four-hour heart rate variability and baroreflex sensitivity also were examined. Atrial pressure, atrial size, effective refractory periods in the right posterolateral atrium and distal coronary sinus, and atrial dispersion increased as the AV interval shortened from 160 to 0 msec. During AV pacing, group I patients had greater minimal (52+/-17 vs 25+/-7 msec; P < 0.005) and maximal (76+/-16 vs 36+/-9 msec; P < 0.005) atrial dispersion than group II patients. The differences in atrial size and atrial dispersion among different AV intervals were greater in patients with AF than in those without AF. Baroreflex sensitivity (6.6+/-1.7 vs 3.9+/-1.0; P < 0.00005), but not heart rate variability, was higher in patients with AF than in those without AF. CONCLUSION: Abnormal atrial electrophysiology and higher vagal reflex activity can play important roles in the genesis of AF in patients receiving pacemakers.     

Development of sinus node disease in patients with AV block: implications for single lead VDD pacing

OBJECTIVE: To investigate the incidence of sinus node disease after pacemaker implantation for exclusive atrioventricular (AV) block. DESIGN: 441 patients were followed after VDD (n = 219) or DDD pacemaker (n = 222) implantation for AV block over a mean period of 37 months. Sinus node disease and atrial arrhythmias had been excluded by Holter monitoring and treadmill exercise preoperatively in 286 patients (group A). In 155 patients with complete AV block, a sinus rate above 70 beats/min was required for inclusion in the study (group B). Holter monitoring and treadmill exercise were performed two weeks, three months, and every six months after implantation. Sinus bradycardia below 40 beats/min, sinoatrial block, sinus arrest, or subnormal increase of heart rate during treadmill exercise were defined as sinus node dysfunction. RESULTS: Cumulative incidence of sinus node disease was 0.65% per year without differences between groups. Clinical indicators of sinus node dysfunction were sinus bradycardia below 40 beats/min in six patients (1.4%), intermittent sinoatrial block in two (0.5%), and chronotropic incompetence in five patients (1.1%). Only one of these patients (0.2%) was symptomatic. Cumulative incidence of atrial fibrillation was 2.0% per year, independent of the method used for the assessment of sinus node function and of the implanted device. CONCLUSIONS: In patients undergoing pacemaker implantation for isolated AV block, sinus node syndrome rarely occurs during follow up. Thus single lead VDD pacing can safely be performed in these patients.     

Right atrial pacing impairs cardiac function during resynchronization therapy: acute effects of DDD pacing compared to VDD pacing

OBJECTIVES: We aimed to compare the hemodynamic effects of right-atrial-paced (DDD) and right-atrial-sensed (VDD) biventricular paced rhythm on cardiac resynchronization therapy (CRT). BACKGROUND: Cardiac resynchronization therapy improves hemodynamics in patients with severe heart failure and left ventricular (LV) dyssynchrony. However, the impact of active right atrial pacing on resynchronization therapy is unknown. METHODS: Seventeen CRT patients were studied 10 months (range: 1 to 46 months) after implantation. At baseline, the programmed atrioventricular delay was optimized by timing LV contraction properly at the end of atrial contraction. In both modes the acute hemodynamic effects were assessed by multiple Doppler echocardiographic parameters. RESULTS: Compared to DDD pacing, VDD pacing resulted in much better improvement of intraventricular dyssynchrony assessed by the septal-to-posterior wall motion delay (VDD 106 +/- 83 ms vs. DDD 145 +/- 95 ms; p = 0.001), whereas the interventricular mechanical delay (difference between onset of pulmonary and aortic outflow) did not differ (VDD 20 +/- 21 ms vs. DDD 18 +/- 17 ms; p = NS). Furthermore, VDD pacing significantly prolonged the rate-corrected LV filling period (VDD 458 +/- 123 ms vs. DDD 371 +/- 94 ms; p = 0.0001) and improved the myocardial performance index (VDD 0.60 +/- 0.18 vs. DDD 0.71 +/- 0.23; p < 0.01). CONCLUSIONS: Our findings suggest that avoidance of right atrial pacing results in a higher degree of LV resynchronization, in a substantial prolongation of the LV filling period, and in an improved myocardial performance. Thus, the VDD mode seems to be superior to the DDD mode in CRT patients.     

The Atrial Pacing Peri-ablation for Paroxysmal Atrial Fibrillation (PA3) Study: rationale and study design.

The Canadian Atrial Pacing Peri-Ablation for Paroxysmal Atrial Fibrillation Study tested the hypotheses that atrial pacing prevents paroxysmal atrial fibrillation (PAF) in patients without symptomatic bradycardia and that DDDR pacing is more likely to prevent PAF following total atrioventricular (AV) node ablation compared to VDD pacing. Patients with PAF who were refractory to or intolerant of antiarrhythmic drug therapy received a Medtronic Thera DR pacemaker 3 months prior to a planned total AV node ablation. Patients were randomized to atrial pacing or no pacing therapy. The time to first recurrence of sustained PAF was the primary study outcome event. Following AV node ablation, patients were randomized to the DDDR or VDD mode in a crossover study design. Patients were followed in each mode for 6 months. The time course of PAF recurrence was compared for each pacing mode.     

VDD-pacemaker in children--a long-term therapy?

AIMS: Transvenous AV-synchronous pacing in children started with the invention of smaller sized VDD leads and miniaturization of pacemakers. Whether or not this is a favourable long-term therapy was retrospectively investigated by us based on data from our records. METHODS: From May 1977 to July 2001 we implanted pacemakers in 104 children younger than 15 years of age. In 55 patients transvenous leads were implanted. Twelve of these (21.8 %) received a VDD pacemaker for hemodynamic reasons. RESULTS: Ages ranged from 11 months to 14.5 years (mean 7.7 +/- 4.3 y). Sizes of the children ranged from 67 to 141 cm (mean 105.9 +/- 15.5 cm) and body weight ranged from 5.3 to 62.0 kg (mean 22.5 +/- 9.8 kg). The mean follow-up period was 47.5 +/- 15.1 months. In 86.3 % of the time during follow-up pacemakers of which we obtained data were working in the VDD mode. Five of the twelve VDD patients (41.7 %) had to be reoperated because of severe traction on the leads. In all five patients the VDD systems were explanted and the patients changed to dual chamber pacemakers. The period of time between implantation and VDD lead explantation ranged from 24 to 74 months (48.6 +/- 18.5). CONCLUSIONS: VDD pacemakers can be implanted safely even in children with a low complication rate perioperatively. 41.7 % of our VDD patients had to be reoperated within the surveillance time because of severe lead tension due to thoracic growth. In our experience VDD pacemakers in smaller children seem to be a temporary solution to bridge AV-synchrony from a young age to DDD pacing in young adulthood.     

Noninvasive measurement of atrial contribution to the cardiac output in children and adolescents with congenital complete atrioventricular block treated with dual-chamber pacemakers

The contribution of atrial contraction to cardiac output (CO) has been the subject of extensive research but has yet to be quantified adequately in children and adolescents. Patients with third-degree atrioventricular (AV) block treated with pacemakers (PMs) are ideal candidates to assess the atrial contribution to CO by repeated measurements in single-chamber pacing mode (VVIR) and dual-chamber pacing mode (DDD/VDD). Hemodynamic measurements in children are often complicated by technical restrictions, but more recently a noninvasive method involving inert gas rebreathing has become available, which is an excellent tool for this age group. We examined 10 patients (6 female patients, mean age 14.5 ± 2.5 years, range 11 to 18) with congenital complete AV block treated with dual-chamber PM. Using an inert gas rebreathing device (Innocor) we measured CO in DDD/VDD with optimized AV delays. Devices were subsequently set to VVIR with matched heart rates and after 20 minutes the CO measurement was repeated. Mean CO of 6.4 ± 1.8 L/min was significantly higher in DDD/VDD than in VVIR, where it averaged 5.2 ± 1.4 L/min (p <0.001). Fractional increase of CO gained through sequential ventricular contraction was 18% (p <0.001). In VVIR, 8 patients reported PM-related symptoms. In conclusion, our data strongly suggest that pediatric patients with congenital complete AV block may benefit from AV synchrony with respect to hemodynamics and tolerability. Therefore, preferred use of DDD/VDD with optimized AV conduction delays should be considered.     

Relative importance of activation sequence compared to atrioventricular synchrony in left ventricular function

This study evaluated the relative hemodynamic importance of a normal left ventricular (LV) activation sequence compared to atrioventricular (AV) synchrony with respect to systolic and diastolic function. Twelve patients with intact AV conduction and AV sequential pacemakers underwent radionuclide studies at rest and Doppler echocardiographic studies at rest and during submaximal exercise, comparing atrial demand pacing (AAI) to sequential AV sensing pacing (DDD) and ventricular demand pacing (VVI). Studies at rest were performed at a constant heart rate between pacing modes, and the exercise study was performed at a constant heart rate and work load. Cardiac output was higher during AAI than during both DDD and VVI (6.2 +/- 1 vs 5.6 +/- 1 and 5.3 +/- 1 liters/min, p less than 0.05). LV ejection fraction was likewise higher during AAI (55 +/- 12 vs 49 +/- 11 vs 51 +/- 13, p less than 0.05). VVI with or without AV synchrony was associated with a paradoxical septal motion pattern, resulting in a 25% impairment of regional septal ejection fraction. In addition, LV contraction duration was more homogenous during AAI. Peak filling rate during AAI and VVI was higher than during DDD (2.86 +/- 1 and 2.95 +/- 1 vs 2.25 +/- 1 end-diastolic volume/s; p less than 0.05). During VVI, the time to peak filling was significantly shorter than during both AAI and DDD (165 +/- 34 vs 239 +/- 99 and 224 +/- 99 ms; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Single-pass lead VDD pacing system in children and adolescents: report of twenty-four patients

The dual-chamber pacing systems allow for AV synchrony, but generally require the placement of two separate transvenous leads. Single-lead atrioventricular synchronous pacing system (VDD) using single-pass leads has been accepted as therapeutic alternative for atrioventricular block with normal sinus node function. The aim of this study is to evaluate clinical performance of single-pass lead VDD pacing systems in 24 consecutive patients in a ten-year period. The study group includes 17 (70.8%) male and 7 (28.8%) female patients.The mean age and mean weight during pacemaker implantation was 10.4 +/- 3.8 years (4-17 years) and 30 +/- I I kg (13.5-55 kg), respectively. The patients have been followed for 7-84 months (median 42 months). The percentage of atrial sensing-ventricular pacing changed from 75 to 99.9% at the last control. During the follow-up period, pacing mode was changed to VVIR due to complete loss of AV synchrony in five patients (21%). Four of them had underlying cardiac disease. In these patients loss of AV synchrony might be related to cardiac enlargement/abnormal cardiac anatomy or small atrial dipole-ventricular tip length. Despite the loss of AV synchrony in post surgical AV block or dilated cardiomyopathy, single-lead VDD pacing systems can be successfully used in children with complete AV block and normal sinus node function. Patients and lead selection should be taken into consideration for the maintenance of AV synchrony.     

Single-chamber ventricular pacing increases markers of left ventricular dysfunction compared with dual-chamber pacing.

AIMS: Large randomized trials comparing DDD with VVI pacing have shown no differences in mortality, but conflicting evidence exists in regard to heart failure endpoints. Here we evaluated the effect of pacing mode on serum levels of brain natriuretic peptide (BNP) and amino-terminal-proBNP (NT-proBNP). Methods Forty-one patients (age 73 +/- 10 years) with dual-chamber pacemakers were included in a prospective, single-blind, randomized crossover study evaluating the impact of DDD(R)/VDD versus VVI(R) mode on objective and functional parameters. Data were collected after a 2-week run-in phase and after 2 weeks each of VVI(R) and DDD(R)/VDD pacing or vice versa. Results BNP and NT-proBNP levels during DDD(R)/VDD stimulation (151 +/- 131 and 547 +/- 598 pg/mL) showed no change compared with baseline (154 +/- 130 and 565 +/- 555 pg/mL), but a significant 2.4-fold increase was observed during VVI(R) mode [360 +/- 221 and 1298 +/- 1032 pg/mL; P < 0.001 compared with DDD(R)/VDD]. The assessment of functional class, the presence of pacemaker syndrome [49% in VVI(R) mode] and the patients' preferred pacing mode showed significant differences in favour of DDD(R)/VDD pacing. CONCLUSION: Patients can differentiate between DDD(R)/VDD and VVI(R) pacing, and prefer the former. Compared with DDD(R)/VDD pacing, VVI(R) stimulation induces a two- to three-fold increase in serum BNP and NT-proBNP levels.     

Upgrade to dual chamber pacing after long-term ventricular stimulation: feasibility and intermediate term follow-up.

AIMS: To evaluate the feasibility and follow-up results of atrial lead implantation and a change to dual chamber pacing following long-term treatment with single chamber ventricular stimulation. METHODS AND RESULTS: During a 30-month period, 70 consecutive patients with ventricular pacemakers were referred for pulse generator exchange or lead reoperation. Using defined criteria, an upgrade procedure was considered indicated in 34 of the cases (49%); these patients had a mean age of 74.8+/-8.8 years, and had been treated with VVI or VVIR pacing for a mean time of 7.8+/-3.8 years (range 1.8-17). An atrial lead was successfully implanted via ipsilateral subclavian venipuncture through the existing pectoral pacemaker pocket in 33 of the 34 cases (97% of the attempts). Postoperatively, one atrial lead dislodgement was seen, and another patient required atrial lead adjustment due to P wave undersensing. The mean follow-up period was 14+/-10 months. During this time, four patients developed permanent atrial fibrillation (annual incidence 11%. In 82% of the patients in whom an upgrade procedure was attempted, dual chamber pacing was maintained at the end of follow-up. CONCLUSION: Restoration of AV synchrony is possible in a substantial proportion of patients treated with long-term ventricular stimulation. Atrial lead placement through ipsilateral subclavian venipuncture is generally feasible, and the vast majority of cases remain in dual chamber pacing with normal function during intermediate term follow-up.