Long-term complication rates in ventricular, single lead VDD, and dual chamber pacing

A higher incidence of pacemaker related complications has been reported in DDD systems as compared to VVI devices. The implantation of single lead VDD pacemakers might reduce the complication rate of physiological pacing in patients with AV block. In a retrospective study, the data records of 1,214 consecutive patients with pacemaker implantation for AV block between 1990 and 2001 (VVI 36.5%, DDD 32.9%, VDD 30.6%) were analyzed. Complications requiring surgical interventions were compared during a follow-up period of 64 +/- 31 months. Operation and fluoroscopic times were longer in DDD pacemaker implantation compared to VDD and VVI devices:58 +/- 23 versus 39 +/- 10 and 37 +/- 13 minutes (P<0.001), 9.2 +/- 5.2 versus 4.1 +/- 2.4 and 3.5 +/- 2.3 minutes, respectively. Differences remained significant after correction for covariates. In a multivariate Cox regression model, the corrected complication hazard of a DDD pacemaker implantation was increased by 3.9 (1.4-11.3) compared to VVI and increased by 2.3 (1.1-4.5) compared to VDD pacing. Higher complication rates in DDD pacing were mainly due to a higher incidence of early reoperation for atrial lead dysfunction, whereas the long-term complication rate was not different from VDD or VVI pacing. Early and long-term complication rates did not differ between VDD and VVI pacemaker systems. In conclusion, operation time and complication rates of physiological pacing are reduced by VDD pacemaker implantation achieving values comparable to VVI pacing. Thus, single lead VDD pacing can be recommended for patients with AV block.     

Optimal pacing for symptomatic AV block: a comparison of VDD and DDD pacing

VDD pacing provides the physiological benefits of atrioventricular synchronous pacing with the convenience of a single lead system, but is hampered by uncertainty regarding long-term atrial sensing and potential development of sinus node disease. To examine the long-term reliability and complication rates of VDD pacing, we compared the outcome of 112 consecutive patients (age 70 +/- 13 years, 59% male) with symptomatic AV block who received a single pass bipolar VDD system to 80 patients (age 63 +/- 16 years, 70% male) who received DDD pacing for the same indication. All patients were judged to have intact sinus node function based on submitted ECGs and monitoring results at the time of implant. Implant time was reduced in VDD patients compared to DDD patients (63 +/- 20 vs 97 +/- 36 minutes, P < 0.0001). Implant complications occurred in 5 (6%) DDD patients compared to 3 (3%) VDD patients (P = 0.15). The implant P wave was lower with VDD pacing compared to DDD patients (2.91 +/- 1.48 vs 4.0 +/- 1.7 mV, P < 0.0001), but remained stable during long-term follow-up in both groups. During 17.7 +/- 10.0 months of follow-up in the VDD group, only 2 VDD patients were reprogrammed to VVIR mode, compared to 3 DDD patients. Physiological atrioventricular activation was maintained in 94%-99% of beats throughout the follow-up period in the VDD group. VDD pacing is an excellent strategy for treatment of patients with symptomatic AV block. The lower cost, high reliability, and abbreviated implantation time suggest that VDD pacing is a viable alternative to DDD pacing in patients with high-degree AV block and normal sinus node function.     

Optimal pacing for symptomatic AV block: a comparison of VDD and DDD pacing

VDD pacing provides the physiological benefits of atrioventricular synchronous pacing with the convenience of a single lead system, but is hampered by uncertainty regarding long term atrial sensing and potential development of sinus node disease. To examine the long-term reliability and complication rates of VDD pacing, we compared the outcome of 112 consecutive patients (age 70 +/- 13 years, 59% men) with symptomatic AV block who received a single pass bipolar VDD system, to 80 patients (age 63 +/- 16 years, 70% men) who received DDD pacing for the same indication. All patients were judged to have intact sinus node function based on submitted ECGs and monitoring results at the time of implant. Implant time was reduced in VDD patients compared to DDD patients (63 +/- 20 vs 97 +/- 36 minutes, P < 0.0001). Implant complications occurred in 5 (6%) DDD patients compared to 3 (3%) VDD patients (P = 0.15). The implant P wave was lower with VDD pacing compared to DDD patients (2.91 +/- 1.48 vs 4.0 +/- 1.7 mv, P < 0.0001), but remained stable during long-term follow-up in both groups. During 17.7 +/- 10.0 months of follow-up in the VDD group, only two VDD patients were reprogrammed to VVIR mode, compared to three DDD patients. Physiological atrioventricular activation was maintained in 94%-99% of beats throughout the follow-up period in the VDD group. VDD pacing is an excellent strategy for treatment of patients with symptomatic AV block. The lower cost, high reliability, and abbreviated implantation time suggest that VDD pacing is a viable alternative to DDD pacing in patients with high degree AV block and normal sinus node function.     

The acute effect of cardiac pacing mode on endothelial vasodilation: prospective, double-blind, cross-over, comparative clinical study

Background: Compared to atrioventricular sequential pacing, ventricular demand pacing is known to have somewhat more deleterious hemodynamic effects, which probably arise from increased sympathetic tonus and inappropriate baroreceptor activation. Endothelial function is affected by various local and systemic factors including baroreceptor activity. The aim of this study was to explore whether cardiac pacing would have any effect on endothelial functions.
Methods: Twelve patients (six male, mean age: 75 ± 9 years) with previously implanted DDD or VDD cardiac pacemakers were included. All patients had stable atrial rhythms during the study. Patients were randomized to either atrial-based pacing mode (VDD or DDD) or ventricular demand pacing mode (VVI) first, and then cross-over was performed with the other pacing mode. Endothelial function was assessed by brachial artery ultrasonography. Basal diameter of the brachial artery, and both flow-mediated dilation (FMD) and endothelium-independent vasodilation with nitroglycerin were measured 1 hour after each pacing mode.
Results: Compared to atrial-based pacing mode, ventricular demand pacing was associated with a significantly worse FMD both as absolute and percentage values (0.17 ± 0.09 mm vs 0.28 ± 0.11 mm, P = 0.015 and 4.84 ± 2.37 % vs 7.00 ± 2.88 %, P = 0.028, respectively). However, there was no significant difference in nitroglycerin-mediated vasodilation values between the two pacing sessions.
Conclusions: Acute ventricular demand pacing (VVI pacing) is clearly associated with attenuation of FMD in patients with atrial-based pacing systems. The attenuation of endothelial vasodilation might have a role in hemodynamic and clinical deterioration in patients with VVI pacemakers.     

Complications of Single Lead VDD Pacing in 35 Patients with AV Block

The implantation of a VDD system is comparable to that of a VVI system, but its management is associated with typical complications of dual chamber pacing. In 35 patients with symptomatic AV block and normal sinus node function, two different VDD pacing systems were implanted. Most of the complications described and their mode of resolution were common to VDD and DDD pacing; however, the VDD system eliminated the need for two separate leads. We, therefore, favor single lead VDD pacing in the treatment of complete AV block with normal sinus node function.     

Preserving normal ventricular activation versus atrioventricular delay optimization during pacing: the role of intrinsic atrioventricular conduction and pacing rate

The purpose of the study was to compare the effects of DDD pacing with optimal AV delay and AAI pacing on the systolic and diastolic performance at rest in patients with prolonged intrinsic AV conduction (first-degree AV block). We studied 17 patients (8 men, aged 69 +/- 9 years) with dual chamber pacemakers implanted for sick sinus syndrome in 15 patients and paroxysmal high degree AV block in 2 patients. Aortic flow and mitral flow were evaluated using Doppler echocardiography. Study protocol included the determination of the optimal AV delay in the DDD mode and comparison between AAI and DDD with optimal AV delay for pacing rate 70/min and 90/min. Stimulus-R interval during AAI (ARI) was 282 +/- 68 ms for rate 70/min and 330 +/- 98 ms for rate 90/min (P < 0.01). The optimal AV delay was 159 +/- 22 ms. AV delay optimization resulted in an increase of an aortic flow time velocity integral (AFTVI) of 16% +/- 9%. At rate 70/min the patients with ARI < or = 270 ms had higher AFTVI in AAI than in DDD (0.214 +/- 0.05 m vs 0.196 +/- 0.05 m, P < 0.01), while the patients with ARI > 270 ms demonstrated greater AFTVI under DDD compared to AAI (0.192 +/- 0.03 m vs 0.166 +/- 0.02 m, P < 0.01). At rate 90/min AFTVI was higher during DDD than AAI (0.183 +/- 0.03 m vs 0.162 +/- 0.03 m, P < 0.01). Mitral flow time velocity integral (MFTVI) at rate 70/min was higher in DDD than in AAI (0.189 +/- 0.05 m vs 0.173 +/- 0.05 m, P < 0.01), while at rate 90/min the difference was not significant in favor of DDD (0.149 +/- 0.05 m vs 0.158 +/- 0.04 m). The results suggest that in patients with first-degree AV block the relative impact of DDD and AAI pacing modes on the systolic performance depends on the intrinsic AV conduction time and on pacing rate.     

心电图P波宽度在优化双腔起搏器房室间期中的价值

目的:探索以心电图P波宽度优化双腔起搏器房室间期(AV间期)的方法,以期获得良好的血流动力学效果。方法:选择63例因Ⅲ度或高度房室传导阻滞植入Medtronic双腔起搏器的患者,测量其心电图自身P波宽度,或从心房起搏脉冲至起搏P波末端的宽度,在此测量值上加100ms,设定为双腔起搏器的感知AV间期(SAV)和起搏AV间期(PAV)。每例患者分别在出厂常规设置的AV间期和根据心电图优化的AV间期设定值下进行超声心动图检查,比较即刻血流动力学参数。结果:经心电图优化AV间期后,患者左室舒张末容积(LVEDV)、左室收缩末期容积(LVESV)和左室射血分数(LVEF)均较常规出厂设置的AV间期有显著改善(69.5±11.2比72.3±12.7;29.5±9.5比27.88±10.07;63.6±5.3比67.2±6.2,P<0.05)。结论:根据心电图P波宽度优化双腔起搏器AV间期,可获得良好的血流动力学效果,左室充盈改善,LVEF上升;且该法简单易行,具广泛的临床实用价值。     

Diagnosis of Atrial Undersensing in Dual Chamber Pacemakers: Impact of Autodiagnostic Features

Atrial undersensing occurs in a considerable number of patients, both with single lead VDD pacemakers and with DDD devices. The aim of this study was to investigate the diagnostic efficacy of electrocardiographic methods and autodiagnostic pacemaker features to detect atrial sensing dysfunction. Two hundred and thirty-one patients with AV block received single lead VDD pacemakers or DDD devices. Atrial sensitivity was programmed to 0.1 or 0.18 in VDD devices and to 0.5 mV in DDD devices; the rate limits were set to 40 and 160 beats/min. Twelve-lead ECG recording for 1 minute during deep respiration and change of body position, 24-hour Holter ECG recording, and treadmill exercise were performed 2 weeks and 15 months after pacemaker implantation. AV synchrony and, if available, P wave amplitude histogram were sampled by autodiagnostic pacemaker features and compared to electrocardiographic findings. Atrial undersensing was assumed, if AV synchrony was below 100% or if minimal P wave amplitude (PWA) was equal to the programmed atrial sensitivity. Intermittent atrial undersensing occurred in 20.7% of patients. The diagnostic sensitivities of the various methods used to detect atrial sensing failures were: 24-hour Holter monitoring 97.5%, P wave amplitude histogram 90.0%, stored AV synchrony 68.0% without significant difference between the various devices, treadmill exercise testing 58.8%, and 12-lead ECG recording 21.3%. In one patient, atrial undersensing was exclusively detected by exercise testing. In conclusion, autodiagnostic pacemaker features facilitate the evaluation of atrial sensing performance. However, to exclude intermittent atrial malsensing, routine Holter monitoring and treadmill exercise are still needed .     

Incidence of Atrial Fibrillation in Patients with Different Mode of Pacing. Long-term Follow-up

We evaluated the incidence of atrial fibrillation in 189 patients (92males, 97females, mean age 75 ± 12yrs, range 41–100yrs) with pacemaker, during a mean follow-up of 5.5yrs (range 1–24yrs). The indications for implant were: complete AV block (115pts), second degree Möbilz 2 AV block (51pts). bifascicular block (5pts). sick sinus syndrome (14pts), symptomatic bradycardia (4pts). The mode of stimulation considered were VVI (105pt), VVI rate responsive (21pts), single lead VDD (43pts), DDD (20pts). The occurrence of retrograde VA conduction in patients with VVI or VVI rate responsive pacing was also evaluated. Atrial fibrillation occurred in 40 pts (21%). The highest incidence was evidenced in patients with sick sinus syndrome (9pts, 64%), and in patients with VVI stimulation (28pts, 27%). On the contrary, the lowest incidence was found in single lead VDD stimulation (4pts, 9%). The patients with dual chamber pacing showed a relatively high incidence of the arrhythmia (5pts, 25%). Atrial fibrillation occurred in 9 out of 32 patients with retrograde VA conduction, and in 22 out of 94 patients without retrograde conduction (28% versus 23%, p=NS). In conclusion, it is confirmed that patients with sick sinus syndrome are at high risk for atrial fibrillation. Single lead VDD stimulation seems to be the better mode of pacing in preventing atrial fibrillation, while dual chamber pacing showed minor efficacy. The presence of retrograde VA conduction could not predict the occurrence of the arrhythmia.     

Efficacy of single lead VDD pacing in patients with impaired and normal left ventricular function

Atrial synchronous ventricular pacing seems to be the best pacing mode for patients with advanced AV block and impaired LV function. The long-term follow-up of single lead VDD pacing was studied in 33 patients with impaired LV function and compared to 42 patients with normal LV function. All patients received the same VDD lead and VDDR pacemaker. The lead model with 13-cm AV spacing between the atrial and ventricular electrode was implanted in 89% of the patients. Follow-ups were 1, 3, 6, and 12 months after implantation. The percentage of atrial sensing and the P wave amplitude were determined at each follow-up. Minimal P wave amplitude at implantation was 2.0 +/- 1.4 mV in patients with impaired and 1.7 +/- 0.9 mV with normal LV function (not significant). At the 12-month follow-up, 33 patients with normal and 23 patients with depressed LV function remained paced in the VDD mode. The remaining patients died in five (impaired LV function) and seven cases (normal LV function) or their pacemakers were programmed to the VVI/VVIR pacing mode in four (impaired LV function) and three cases (normal LV function). P wave amplitude did not differ in the two groups (e.g., at month 12: impaired: 1.17 +/- 0.42 mV; normal: 1.09 +/- 0.49 mV). The atrial sensitivity was programmed in most patients to sensitive settings with no differences between the two groups (e.g., at month 12: impaired: 0.13 +/- 0.06 mV; normal: 0.13 +/- 0.05 mV). The diagnostic counters indicated nearly permanent atrial sensing (e.g., at month 12: impaired: 99.3 +/- 2.2%; normal: 99.0 +/- 1.0 mV). In conclusions, single lead VDD pacing restored AV synchronous ventricular pacing in patients with normal and with impaired LV function indicating that it could be an alternative to DDD pacemakers, but not to dual-chamber pacing.     

Inhibition of ventricular stimulation in patients with dual chamber pacemakers and prolonged AV conduction

Episodes of repetitive P wave undersensing have been described in dual chamber pacemakers due to automatic extension of the postventricular atrial refractory period (PVARP). Pacemaker stimulation was completely inhibited despite the presence of adequate P waves. This study sought to determine whether cycles of repetitive P wave undersensing occur even in the absence of PVARP extension. Two-hundred fifty-five patients were investigated after DDD or VDD pacemaker implantation for intermittent atrioventricular (AV) block. Forty-six episodes of repetitive atrial undersensing were found during 24-hour Holter ECG in nine patients. Pacemaker syndrome-like symptoms occurred. Episodes were elicited by atrial or ventricular premature contractions when (1) native AV conduction was present but considerably prolonged, (2) intrinsic sinus rate exceeded pacemaker intervention rate, and (3) native AV interval plus PVARP exceeded sinus cycle length. Programming of a particularly short AV interval and PVARP helped to reduce the incidence of repetitive P wave undersensing. Patients with dual chamber devices and prolonged native AV conduction are prone to develop episodes of output inhibition. Standard timing cycles may be inappropriate in these patients.     

Comparative Evaluation of Bipolar Atrial Electrogram Amplitude During Everyday Activities: Atrial Active Fixation Versus Two Types of Single Pass VDD/R Leads

Endocardial P wave amplitude (PWA) is an important determinant of the atrial sensing capabilities of an atrial-based pacing system. Although changes in PWA during physical activities are known to occur in DDD/R pacing, there is little information on the P wave stability in single pass lead VDD/R pacemakers using floating P wave sensing. We investigated the variation of PWA during daily life activities using telemetry recorded atrial electrograms in 21 patients with DDDR pacemakers (Relay or Elite) and 29 patients with single lead VDD/ R pacemakers (Unity or Thera). Physical activities resulted in marked individual variability of PWA but, as a group, there was no significant difference between PWA during sitting, standing, lying down, and coughing in both DDDR and VDD/R pacing. In the Elite II pacemaker, walking at 2 miles per hour resulted in significant reduction of PWA (11.6% compared with sitting, P < 0.05). The most consistent reduction in PWA occurred in the relaxation phase of the Valsalva maneuver (VM), with all pacemakers showing a reduction in PWA (mean reduction in PWA compared with sitting in DDDR and VDD/R were 16.6% and 12.8%, respectively). Two patients with DDDR pacemakers (Relay) and three patients with VDD/R pacemakers (1 Unity and 2 Thera) had atrial sensing failure during VM or walking. In conclusion, large variation in PWA occurs during daily life activities. The extent of variation is dependent on the patients, types of atrial lead, and the maneuvers performed. A twice sensing threshold may be insufficient to ensure adequate atrial sensing during these activities. The VM, which effects a consistent change in intracardiac volume, is the most reliable method for bedside evaluation of the lower end of sensitivity margin.     

Lack of Influence of Atrioventricular Delay on Stroke Volume at Rest in Patients with Complete Atrioventricular Block and Dual Chamber Pacing

Dual chamber pacing (DDD) maintains atrioventricular (AV) sequence; AV delay programmability modifies the relationship between atrial and ventricular contraction. To evaluate the hemodynamic effects of such a modification, ten patients with a DDD unit for complete AV block were studied by time-motion (M-mode) and Doppler echocardiography during inhibited ventricular pacing (VVI), atrial-triggered ventricular pacing (VDD) and atrioventricular sequential pacing (DVI) at different AV delay (90, 140, 190, 240 msec). A significant improvement in stroke volume (SV) (15%-20%, P less than 0.05) was seen during DDD versus VVI pacing; no changes, however, were observed in the same patient with different AV delay or during DVI versus VDD pacing. These data suggest that programming of AV delay does not affect systolic performance at rest; longer diastolic filling times recorded during DDD pacing with "short" AV delay (90-140 msec) do not seem to be a hemodynamically relevant epi-phenomenon of PM programming.     

Diastolic Mitral Regurgitation in Patients with First-Degree Atrioventricular Block

Diastolic mitral regurgitation has been observed in patients with DDD pacemakers when the atrioventricular (AV) delay was prolonged. However, diastolic mitral regurgitation associated with first-degree AV block has not been fully studied. We examined transmitral blood flow in 24 patients with first-degree AV block and normal cardiac function (ages 35.3 ± 17.4 years), and in nine patients with DDD pacemakers and normal cardiac function (ages 73.1 ± 8.1 years), using pulsed Doppler echocardiography. Diastolic mitral regurgitation was observed in 19 of 24 patients with first-degree AV block. Although PQ interval was shortened from 0.32 ± 0.06 to 0.20 ± 0.05 seconds (P < 0.01) after 1 mg atropine sulfate IV, the interval between P wave (ECG) and the beginning of diastolic mitral regurgitation did not change, while the duration of diastolic mitral regurgitation was shortened from 0.15 ± 0.03 to 0.05 ± 0.03 seconds (P < 0.01). There was a significant correlation between changes in PQ interval and changes in the duration of diastolic mitral regurgifation (r = 0.92, P < 0.001). Although cardiac output (3.9 ± 0.05 L/min) and pulmonary capillary wedge pressure (5.1 ± 1.5 mmHg) were normal in all patients with pacemakers, diastolic mitral regurgitation was observed when the AV delay was prolonged. The critical PQ interval for the appearance of diastolic mitral regurgitation was 0.23 ± 0.01 seconds. In patients with prolonged PQ intervals, delayed ventricular contraction following atrial contraction may be associated with mitral regurgitation in the presence of a reversed AV pressure gradient. The results of this study suggest that diastolic mitral regurgitation occurs not only in patients with DDD pacemakers, but also with AAIR pacemakers when the PQ interval is prolonged. The occurrence of diastolic mitral regurgitation is associated with the pacing mode or the setting of AV delay.     

Reduction of right ventricular pacing in patients with sinus node dysfunction through programming a long atrioventricular delay along with the DDIR mode

Background  

Right ventricular (RV) pacing increases the incidence of atrial fibrillation (AF) and hospitalization rate for heart failure. Many patients with sinus node dysfunction (SND) are implanted with a DDDR pacemaker to ensure the treatment of slowly conducted atrial fibrillation and atrioventricular (AV) block. Many pacemakers are never reprogrammed after implantation. This study aims to evaluate the effectiveness of programming DDIR with a long AV delay in patients with SND and preserved AV conduction as a possible strategy to reduce RV pacing in comparison with a nominal DDDR setting including an AV search hysteresis.     

Long-Term Survival of Chosen Atrial-Based Pacing Modalities

Atrial-based cardiac pacing modalities were chosen in 341 of 684 (50%) patients selected for permanent cardiac pacing at the Grey Nuns Community Health Center between 1989 and 1995. There were 183 males and 158 females. Mean age was 70 years (range 8–97 years). The indications for atrial-based pacing were: advanced atri- oventricular (AV) block (n = 166) 49%; sick sinus syndrome (n = 153) 45%; hypersensitive carotid sinus syndrome (n = 11) 3%; neurocardiac syncope (n = 10) 2.9%; and hypertrophic cardiomyopathy (n = 1) 0.3%. Forty-eight patients had a known history of paroxysmal atrial arrhythmias. All patients had routine follow-up performed at 24 hours, 7 days, 6 weeks, 3 months, and then 6 biannuallv. Mean follow-up was 6.5 years (range 1 month to 12 years). Observed survival of the programmed atrial-based modality was compared to the original mode chosen at the time of implantation. Thirty-five of 37 (95%) chosen for AAIR modes remain programmed AAIR. Twenty-two of 24 (92%) chosen for VDDR modes remain programmed VDDR. Two hundred and fifty-five of 280 (91 %) chosen for DDD or DDDR modes remain programmed DDDR. Two of 37 (5%) patients originally implanted with AAI pacing systems were upgraded to DDDR mode due to new onset AV block. One of 24 (4%) patients originally implanted with a VDDR pacing system was upgraded to DDDR due to loss of atrial sensing of the single pass lead. Twenty-six of 304 (8.5%) patients originally implanted with DDD/DDDR (n - 25) and VDDR (n = 1) pacing systems were reprogrammed to VVI or WIR: 16 (62%) due to sustained refractory atrial arrhythmias; 5 (19%) due to atrial lead malfunction; and 5 (19%) due to reasons unrelated to the pacing system. With careful review of the patients' conduction disorder and appropriate selection of pacing modality, the observed survival of long-term atrial-based pacing remains at 92% when compared to the chosen modality at the time of implantation. Atrial-based pacing may be used to reduce the incidence of atrial dysrhythmia with careful programming of the base atrial pacing rates.     

A New Dual-Chamber Pacing Mode to Minimize Ventricular Pacing

Despite the low long-term incidence of high-degree atrioventricular (AV) block and the known negative effects of ventricular pacing, programming of the AAI mode in patients with sinus node dysfunction (SND) remains exceptional. A new pacing mode was, therefore, designed to combine the advantages of AAI with the safety of DDD pacing. AAIsafeR behaves like the AAI mode in absence of AV block. First- and second-degree AV blocks are tolerated up to a predetermined, programmable limit, and conversion to DDD takes place in case of high-degree AV block. From DDD, the device may switch back to AAI, provided AV conduction has returned. The safety of AAIsafeR was examined in 43 recipients (70 ± 12-year old, 24 men) of dual chamber pacemakers implanted for SND or paroxysmal AV block. All patients underwent 24-hour ambulatory electrocardiographic recordings before hospital discharge and at 1 month of follow-up with the AAIsafeR mode activated. No AAIsafeR-related adverse event was observed. At 1 month, the device was functioning in AAIsafeR in 28 patients (65%), and the mean rate of ventricular pacing was 0.2%± 0.4%. Appropriate switches to DDD occurred in 15 patients (35%) for frequent, unexpected AV block. AAIsafeR mode was safe and preserved ventricular function during paroxysmal AV block, while maintaining a very low rate of ventricular pacing. The performance of this new pacing mode in the prevention of atrial fibrillation will be examined in a large, controlled study.     

Single versus dual chamber pacing in the young: noninvasive comparative evaluation of cardiac function

The advantages of atrial synchrony over asynchronous ventricular pacing remain unclear in the young, chronically right ventricular (RV) - paced patient. This is in contrast to the older patient with inherent diastolic dysfunction who has been shown to benefit from atrial synchrony with dual chamber (DDD,R/VDD), over single chamber rate response (VVI,R) ventricular pacing. The goal of this study was to noninvasively assess cardiac function in a group of young, RV-paced patients before and after establishment of atrial synchrony. Echocardiographic data were retrospectively analyzed from 10 patients with congenital or acquired complete AV block, who were VVI,R paced for 10.2 +/- 2 years (mean age at study 19.2 +/- 8.9 years), and were subsequently converted to DDD,R/VDD pacing (mean age at study 20.7 +/- 9.5 years). Paired t-test analysis of left ventricular (LV) systolic and diastolic function during VVI,R versus DDD,R/VDD pacing did not result in any short-term difference in LV short axis fractional area of change or FAC (53% +/- 7.5% vs 56.8% +/- 8.7%) or mitral maximal velocity (E) normalized to mitral flow velocity time integral (VTI) (5.2/s +/- 1.5 vs 4.4/s +/- 1.5). A decrease in mitral flow E/A ratio was observed after short-term DDD,R/VDD pacing (2.2 +/- 0.5 vs 1.9 +/- 0.3). Atrial synchronous dual chamber pacing in young patients with complete AV block does not lead to any appreciable early change in global LV function over single-site RV pacing. Therefore, early establishment of atrial synchrony in the young asymptomatic VVI,R-paced patient with normal intrinsic ventricular function may not be warranted.     

Near elimination of ventricular pacing in SafeR mode compared to DDD modes: a randomized study of 422 patients

Aims: SafeR performance versus DDD/automatic mode conversion (DDD/AMC) and DDD with a 250‐ms atrioventricular (AV) delay (DDD/LD) modes was assessed toward ventricular pacing (Vp) reduction. Methods: After a 1‐month run‐in phase, recipients of dual‐chamber pacemakers without persistent AV block and persistent atrial fibrillation (AF) were randomly assigned to SafeR, DDD/AMC, or DDD/LD in a 1:1:1 design. The main endpoint was the percentage of Vp (%Vp) at 2 months and 1 year after randomization, ascertained from device memories. Secondary endpoints include %Vp at 1 year according to pacing indication and 1‐year AF incidence based on automatic mode switch device stored episodes. Results: Among 422 randomized patients (73.2 ± 10.6 years, 50% men, sinus node dysfunction 47.4%, paroxysmal AV block 30.3%, bradycardia‐tachycardia syndrome 21.8%), 141 were assigned to SafeR versus 146 to DDD/AMC and 135 to DDD/LD modes. Mean %Vp at 2 months was 3.4 ± 12.6% in SafeR versus 33.6 ± 34.7% and 14.0 ± 26.0% in DDD/AMC and DDD/LD modes, respectively (P < 0.0001 for both). At 1 year, mean %Vp in SafeR was 4.5 ± 15.3% versus 37.9 ± 34.4% and 16.7 ± 28.0% in DDD/AMC and DDD/LD modes, respectively (P < 0.0001 for both). The proportion of patients in whom Vp was completely eliminated was significantly higher in SafeR (69%) versus DDD/AMC (15%) and DDD/LD (45%) modes (P < 0.0001 for both), regardless of pacing indication. The absolute risk of developing permanent AF or of remaining in AF for >30% of the time was 5.4% lower in SafeR than in the DDD pacing group (ns). Conclusions: In this selected patient population, SafeR markedly suppressed unnecessary Vp compared with DDD modes. PACE 2012; 35:392–402)     

Single Lead VDD Pacing: Multicenter Study

Optimal treatment for patients with AV block and normal sinoatrial node (SA) function entails atrial sensing and ventricular pacing (VDD mode). Single-lead VDD pacing preserves AV synchrony, precludes the need to insert two leads, and makes the implanter's work simpler and quicker. Our objectives were to verify the performance of the Thera(tm) VDD pacing system (Medtronic, Inc., Minneapolis, MN, USA), and evaluate the effectiveness of its atrial sensing and its ventricular sensing and pacing. In 165 patients, 150 adults (mean age 62 ± 18 years) and 15 children (mean age 7 ± 5 years) with 1°–3° AV block and normal SA node function, a Thera VDD system (Models 8948 or 8968) was implanted. Intraoperative ventricular electrical measurements were not significantly different from those of VVI pacemakers. The mean amplitude of the atrial signal during implantation was 4.1 ± 1.9 mV. Optimal atrial signals during implantation were usually obtained in the mid or lower part of the right atrium by using a special technique. Adequate atrial measurements remained stable throughout 24 months. There was no difference between serial measurements of atrial signal amplitudes at predischarge and during follow-up visits. Reposition of the lead was done in 2 patients (1.4%), and reprogramming to VVI in 7 patients: due to atrial fibrillation in 3 (1.8%) and due to atrial undersensing in 4 patients (2.4%). Thera VDD pacing is reliable and easy to manage with dependable atrial sensing and ventricular pacing. The survival rate of VDD pacing at 2 years was 96%.