Low Atrial Pacing Research Articles

Atrial Pacing Affects Left Atrial Morphological and Functional Parameters Early after Pacemaker Implantation.

Background and Objectives: Chronic atrial stimulation might impair left atrial (LA) function. We aimed to assess the impact of atrial pacing burden on LA volumetric and functional parameters after implantation of a dual-chamber pacemaker. Materials and Methods: The prospective study included 121 subjects with sinus node disease (SND) or atrioventricular block (AVB) that received a dual-chamber pacemaker. After device implantation, the subjects were divided into three groups: (1) SND with a lower rate (LR) set to 60 bpm and rate response enabled; (2) AVB with an LR set to 60 bpm and no rate response; and (3) AVB with an LR set to 40 bpm and no rate response. Subjects were followed at one and three months. Two subsets of patients with high and low atrial pacing burdens accompanied by low ventricular pacing percentage were analyzed. LA function was evaluated with volumetric and strain parameters from transthoracic echocardiography. Results: The high atrial low ventricular pacing group consisted of 38 subjects, and the low atrial low ventricular group consisted of 22 subjects. When looking at the change in volumetric parameters, we observed a tendency for volumes to increase in both groups; however, only minimal LA volume reached statistical significance at three months in the high atrial pacing group. A trend towards the lowering of an active emptying fraction at one month (p = 0.076) became significant at three months (p = 0.043), and was also only observed in the same group. Moreover, a decrease in the tendency to reach statistical significance at three months for reservoir and contractile strain parameters and stiffness index was only observed in the high atrial pacing group. Meanwhile, in the low atrial pacing burden group, all parameters remained significantly unchanged. Conclusions: The burden of right atrial pacing in patients with preserved left ventricular function negatively influences functional and morphologic LA parameters. Moreover, negative effects take place soon after pacemaker implantation and appear to be sustained.

PO-688-04 LOW RIGHT ATRIAL PACING USAGE IN CARDIAC RESYNCHRONIZATION THERAPY POPULATION - DESCRIPTIVE STUDY FROM THE CERTITUDE REGISTRY

Two-lead cardiac resynchronization therapy with DX technology (CRT-DX) has been demonstrated to provide adequate resynchronization therapy equivalent to conventional three-lead CRT-D systems with fewer complications. We performed a retrospective review of right atrial (RA) lead pacing usage in our CRT-D population to identify potential patients with low atrial pacing percentage (Ap%) that may benefit from a two-lead CRT-DX system. We identified and characterized CRT-D and CRT-DX systems with at least 3-months of follow-up duration from the CERTITUDE registry, a de-identified database containing qualified US BIOTRONIK devices registered with Home Monitoring®. CRT-D generators with an implanted RA pacing lead and right ventricular ICD lead were classified as CRT-D systems. CRT-DX systems were classified as having DX technology with a DX ICD lead and no RA lead implanted. All Ap% and p-wave sensing values from daily remote monitoring transmissions were analyzed from these groups. We defined Low Ap Usage as a mean Ap% ≤5% and no presence of daily Ap% ≥9% with the understanding that defining the true need for atrial pacing would require consideration of individual programmed parameters, diurnal variation, dependency status, etc. A total of 4,903 systems (4,516 CRT-Ds, 387 CRT-DXs) were identified for analysis with a mean follow-up duration of 954.7 days (SD: ±466.4). Of the 4,516 CRT-D systems analyzed, 902 (20.0%) had Low Ap Usage. Of the 387 CRT-DX systems analyzed, 8 systems (2.1%) subsequently required a right atrial lead implant with a mean time to RA implant of 601.4 days (SD: ±431.3). Mean sensing values were higher in the CRT-DX group with p-wave amplitude of 3.42 mV compared to 3.11 mV (p-value<0.001) in the CRT-D group. In this descriptive analysis from the CERTITUDE registry, we identified 20.0% of the CRT-D patients with low right atrial pacing usage, which highlights a proportion of CRT subjects that could be good candidates for a CRT-DX system. Additionally, the need for atrial pacing in CRT-DX patients was uncommon. Lastly, atrial sensing parameters with CRT-DX were superior as compared to the CRT-D group.

Dual-chamber cardiac pacing effect on left and right atria morphometric parameters and function

Abstract Background Dual-chamber pacemaker implantation is a standard interventional treatment strategy for atrioventricular block (AVB) and sick sinus syndrome (SSS). It has been proven that a high percentage of right ventricular pacing might have detrimental effects on cardiac function. However, there is a lack of data on atrial pacing effect on left (LA) and right (RA) atria function. Purpose To assess the impact atrial pacing on left and right atria morphologic and functional parameters in patients after dual-chamber pacemaker implantation. Methods We conducted a prospective study that included patients who received a dual-chamber pacemaker for an indication of AVB or SSS. After signing of the informed consent pacemaker was programmed for base rate of 40 bpm and no rate response in case of clear AVB indication or for base rate of 60 bpm and rate response if indication was SSS. An transthoracic echocardiography was done the next day after pacemaker implantation and after one month at follow up (FU). During the FU the atrial pacing (AP) and ventricular pacing (VP) percentage were captured. To exclude the impact of right ventricular pacing, patients with high VP percentage (&amp;gt;40%) were excluded from analysis. Patients were divided into two groups – group A with high AP (&amp;gt;50%), and group B – low AP (&amp;lt;50%). LA expansion fraction reflecting reservoir function, emptying – reflecting conduit, and active emptying reflecting “atrial kick” were analysed. To compare means the Mann Whitney U test, and for categorical variables – X2 test were used. Results A total of n=100 patients underwent dual-chamber implantation and signed informed consent. Due to significant structural heart disease or reduced ejection fraction (&amp;lt;50%) 11 patients were excluded. Out of those, n=30 were excluded due to a high VP percentage. Group consisted of n=28 and group B of – n=31 patients. Average AP in group A was 66.2% and 5.0% in group B. The mean age (group A 73.6 SD 8.8 years vs group B 79.2 SD 7.3 years, p=0.197), gender distribution (group A males 45.5% vs group B 50.0%, p=0.773), and mean BMI (group A 26.5 SD 4.7 kg/m2 vs group B 29.2 SD 3.3 kg/m2, p=0.191) did not differ significantly between the two groups. The baseline LA and RA morphometric and functional parameters presented in figure 1 and did not differ significantly between the two groups. The change in LA and RA functional parameters presented in figure 2. Even though it did not reach statistical significance, a tendency for lower LA expansion fraction, active emptying fraction and LA ejection fraction were observed in group A. RA morphometric parameters did not change significantly between the two groups at FU. Conclusion A higher percentage of atrial pacing in dual-chamber pacemaker population could lead to impaired LA function over time. Though, longer observational period is needed. Funding Acknowledgement Type of funding sources: None. Figure 1Figure 2

The Detrimental Effect of RA Pacing on LA Function and Clinical Outcome in Cardiac Resynchronization Therapy

ObjectivesThis study assessed the impact of right-atrial (RA) pacing on left-atrial (LA) physiology and clinical outcome. BackgroundData for the effects of RA pacing on LA synchronicity, function, and structure after cardiac resynchronization therapy (CRT) are scarce. MethodsThe effect of RA pacing on LA function, morphology, and synchronicity was assessed in a prospective imaging cohort of heart failure (HF) patients in sinus rhythm with a guideline-based indication for CRT. Additionally, in a retrospective outcome cohort of consecutive HF patients undergoing CRT implantation, the relationship to RA pacing was assessed using various outcome endpoints. High versus low atrial pacing burden was defined as atrial pacing above or below 50% in both cohorts. ResultsA total of 36 patients were included in the imaging cohort (68 ± 11 years of age). Six months after CRT, patients with high RA pacing burden showed less improvement in LA maximum and minimum volumes and total emptying fraction (p < 0.05). Peak atrial longitudinal strain and reservoir and booster strain rates but not conduit strain rate improved after CRT in patients with low RA pacing burden but worsened in patients with high RA pacing burden (p < 0.05 for all). A high RA pacing burden induced significant intra-atrial dyssynchrony (maximum opposing wall delay: 44 ± 13 ms vs. 97 ± 17 ms, respectively; p = 0.022). A total of 569 patients were included in the outcome cohort. After covariate adjustments were made, a high RA pacing burden was associated with reduced LV reverse remodeling (β = 8.738; 95% confidence interval [CI]: 3.101 to 14.374; p = 0.002) and new-onset or recurrent atrial fibrillation (41% vs. 22%, respectively, at a median of 31 months [range 22 to 44 months follow-up]; p < 0.001). There were no differences in time to first HF hospitalization or all-cause mortality (p = 0.185) after covariate adjustment. However, in a recurrent event analysis, HF readmissions were more common in patients exposed to a high RA pacing burden (p = 0.003). ConclusionsRA pacing in CRT patients negatively influences LA morphology, function, and synchronicity, which is associated with worse clinical outcome, including diminished LV reverse remodeling, increased risk for new-onset or recurrent AF and heart failure readmission. Strategies reducing RA pacing burden may be warranted.

Impact of high-grade atrioventricular block and cumulative frequent pacing on atrial arrhythmias.

The relationship between high-grade atrioventricular block (HGAVB) with cumulative frequent pacing and risk of atrial arrhythmias (AAs) has not been well characterized. We hypothesized HGAVB and pacing may have significant impact on incidence and prevalence of AAs by modulating atrial substrate. To determine impact of HGAVB and pacing on AAs including atrial fibrillation (AF), atrial flutter (AFL), and atrial tachycardia (AT). All consecutive patients who underwent dual-chamber pacemaker implantation for HGAVB from 2005 to 2011 at the University of Chicago were included. AAs and percent of pacing were detected through device interrogation. Patients' data were collected from electronic medical records and clinic visits. A total of 166 patients (mean age 71±15years; 54% female, 56% African American) were studied. AF was documented in 27% of patients before pacemaker implantation. During a mean 5.8±2.2years of follow-up, 47% had device-detected AF, 10% AFL, and 26% AT. New-onset AF was documented in 40 of the 122 patients without prior AF (33%). Continuous (≥ 99%) right ventricular pacing was associated with significantly decreased AF prevalence (34%vs 59%, P=0.005), and correlated with lower incidence (26%vs 41%, P=0.22). Pacing suppressed AF in 14% of patients with baseline AF; those patients had lower atrial pacing (3.2%vs 45%, P<0.0001). Left atrial dilation was the only independent predictor of AF with frequent pacing (P=0.009). HGAVB is associated with high incidence and prevalence of AAs with and without pacing. Cumulative frequent (≥99%) ventricular pacing reduces risk of AF in patients with HGAVB.

Abstract 18656: A Decade of Follow-up with Excellent Transmural Atrial Lead Performance in Complex Congenital Heart Patients

Background: Many patients (pts) with postoperative congenital heart disease require permanent pacing for rhythm management and cannot undergo transvenous atrial leads. Extensive epicardial scar can prohibit adequate acute and chronic pacing and sensing thresholds. We described transmural atrial lead (TMA, epicardial to endocardial) pacing previously and now report long-term lead performance. Methods: A bipolar, steroid eluting transvenous lead is placed from the epicardial surface via purse-string and affixed to position the lead against the atrial endocardium. 52 patients underwent TMA placement between 1998 and 2004. Records were reviewed for lead characteristics and acute and long term performance. Follow up data was available for 51 patients. TMAs were placed in the right atrial appendage, the lateral right atrial wall, left atrium, and dome of the left atrium. Medtronic 5072 (n=43), Guidant 4469 (n=6) or other (n=3) leads were used. Results: 52 pts underwent TMA at an avg age of 13.4 yrs; 19 to replace existing leads and 36 as part of a larger surgery. Pre-op, 25 pts had atrial tachycardia (AT). 22 pts had Fontan/revision. Acute TMA pace threshold was 0.87V @ 0.5msec. 43/52 leads remain active at an avg follow-up of 10.2 yrs. Chronic pace threshold avg is 0.96V @ 0.3-0.5msec; atrial electrogram is 2.97mV in 30/43 pts with intrinsic P waves. Atrial overdrive of AT using TMA was successful in 8/9 pts. No clots were oberved in any pt in follow-up. 3 pts died (one awaiting transplant, one sudden, one stroke (TMA on Fontan side, no fenestration). There were 2 TMA fractures, 3 removed for non-TMA reasons. Conclusions: TMAs show excellent late functional properties as an alternative to epicardial leads in complex pts, maintaining low atrial pacing thresholds, consistent sensing and the benefit of effective overdrive pacing of ATs. TMAs exhibit superior long term performance in complex Fontan and atrial switch patients.

Non-physiological increase of AV conduction time in sinus disease patients programmed in AAIR-based pacing mode

The EVOCAV(DS) trial aimed to quantify the paradoxal atrioventricular (AV) conduction time lengthening in sinus node (SD) patients (pts) paced in AAIR-based pacing mode. SD pts, implanted with dual-chamber pacemaker programmed in AAIR-based pacing mode, were randomized in two arms for a 1-month period: the low atrial pacing (LAP; basic rate at 60 bpm, dual sensor with minimal slope) and the high atrial pacing (HAP; basic rate at 70 bpm, dual sensor with optimized slope, overdrive pacing) arm. At 1 month, crossover was performed for an additional 1-month period. AV conduction time, AV block occurrence and AV conduction time adaptation during exercise were ascertained from device memories at each follow-up. Seventy-nine pts participated to the analysis (75 ± 8 years; 32 male; PR = 184 ± 38 ms; bundle branch block n = 12; AF history n = 36; antiarrhythmic treatment n = 53; beta-blockers n = 27; class III/Ic n = 18; both n = 8). The mean AV conduction time was significantly greater during the HAP (275 ± 51 ms) vs. LAP (263 ± 49 ms) period (p < 0.0001). Class III/Ic drugs were the only predictors of this abnormal behaviour. Degree II/III AV blocks occurred in 49 % of pts in the HAP vs. 19 % in the LAP period (p < 0.0001). Fifty-two patients (66 %) presented a lengthening of AV conduction time during exercise. AAIR-based pacing in SD pts may induce a significant lengthening of pts' AV conduction time, including frequent abnormal adaptation of AV conduction time during exercise.

Atrial Pacing Percentage and Its Effect on Mortality in ICD and CRT-D Patients

Background: Few studies have evaluated the effects of atrial pacing (AP) on mortality in device patients. We hypothesize that increased AP impacts mortality in patients implanted with ICDs and CRT-Ds. Methods: Data were collected from a prospective 2-year study (ACT registry) that included dual-chamber ICD and CRT-D patients. The association between AP (5 brackets: 80%) and all-cause mortality was analyzed using Cox proportional hazards regression models adjusting for age, LVEF, and %AMS. Results: This analysis includes 1283 patients (baseline demographics: 77% male, 69±11 yrs, LVEF 28±11%, QRS 133±33 ms, %AMS 5±16%). The average follow-up time was 19.1±6.7 months. Seventy percent of patients were either AP 50% representing sinus node disease. CRT-D patients that were AP 51–80%, had higher mortality (p=0.03) as compared to the low AP group (<10%). Otherwise, no other significant differences (p<0.05) in all-cause mortality were observed for the different AP brackets for both ICD and CRT-D groups as compared to the low AP bracket. Conclusion: AP does not worsen mortality in ICD and CRT-D patients that are paced a higher amount of time compared to patients that have intrinsic sinus conduction.

Angiotensin‐(1‐7) stimulates high atrial pacing‐induced ANP secretion

Angiotensin‐(1‐7) [Ang‐(1‐7)] has many beneficial roles in cardiovascular physiology, counterbalancing Angiotensin II functions. It is considered as one of the theurapeutic agent for cardiovascular diseases in the future. The aim of the present study is to elucidate the modulatory role of Ang‐(1‐7) in atrial natriuretic peptide (ANP) secretion using isolated perfused beating rat atria and cardiac hypertrophied rat model. Ang‐(1‐7) (10−8, 10−7, and 10−6M) increased the ANP secretion and ANP concentration in a dose‐dependent manner at high atrial pacing (6.0 Hz) with an increased cGMP amount. However, Ang‐(1‐7) did not cause any changes in atrial parameters at low atrial pacing (1.2 Hz). An antagonist of Mas receptor or inhibitors of phosphoinositide 3‐kinase (PI3K), protein kinase B (Akt), or nitric oxide synthase pretreatment blocked the increase of high atrial pacing‐induced ANP secretion by Ang‐(1‐7). The inhibition of Na+/H+ exchanger‐1 (NHE‐1) and calcium/calmodulin‐dependent kinase II (CaMKII) showed the similar result. Ang‐(1‐7) did not show any changes in intracellular calcium concentration in quiescent atrial myocytes. However, Ang‐(1‐7) attenuated an increase of intracellular calcium concentration induced by angiotensin II. Intravenous infusion of Ang‐(1‐7) increased the plasma concentration of ANP by 2‐fold without changes in blood pressure and heart rate in isoproterenol‐treated rats but not in control rats. Ang‐(1‐7) attenuated cardiac hypertrophy induced by isoproterenol. These results suggest that Ang‐(1‐7) increased the ANP secretion at high atrial pacing via Mas/PI3K/Akt pathway and the activation of NHE‐1 and CaMKII.Supported by the KOSEF (R13‐2008‐005‐00000‐0).

Angiotensin-(1–7) stimulates high atrial pacing-induced ANP secretion via Mas/PI3-kinase/Akt axis and Na+/H+ exchanger

Angiotensin-(1-7) [ANG-(1-7)], one of the bioactive peptides produced in the renin-angiotensin system, plays a pivotal role in cardiovascular physiology by providing a counterbalance to the function of ANG II. Recently, it has been considered as a potential candidate for therapeutic use in the treatment of various types of cardiovascular diseases. The aim of the present study is to explain the modulatory role of ANG-(1-7) in atrial natriuretic peptide (ANP) secretion and investigate the functional relationship between two peptides to induce cardiovascular effects using isolated perfused beating rat atria and a cardiac hypertrophied rat model. ANG-(1-7) (0.01, 0.1, and 1 muM) increased ANP secretion and ANP concentration in a dose-dependent manner at high atrial pacing (6.0 Hz) with increased cGMP production. However, at low atrial pacing (1.2 Hz), ANG-(1-7) did not cause changes in atrial parameters. Pretreatment with an antagonist of the Mas receptor or with inhibitors of phosphatidylinositol 3-kinase (PI3K), protein kinase B (Akt), or nitric oxide synthase blocked the augmentation of high atrial pacing-induced ANP secretion by ANG-(1-7). A similar result was observed with the inhibition of the Na(+)/H(+) exchanger-1 and Ca(2+)/calmodulin-dependent kinase II (CaMKII). ANG-(1-7) did not show basal intracellular Ca(2+) signaling in quiescent atrial myocytes. In an in vivo study using an isoproterenol-induced cardiac hypertrophy animal model, an acute infusion of ANG-(1-7) increased the plasma concentration of ANP by twofold without changes in blood pressure and heart rate. A chronic administration of ANG-(1-7) increased the plasma ANP level and attenuated isoproterenol-induced cardiac hypertrophy. The antihypertrophic effect was abrogated by a cotreatment with the natriuretic peptide receptor-A antagonist. These results suggest that 1) ANG-(1-7) increased ANP secretion at high atrial pacing via the Mas/PI3K/Akt pathway and the activation of Na(+)/H(+) exchanger-1 and CaMKII and 2) ANG-(1-7) decreased cardiac hypertrophy which might be mediated by ANP.

Right ventricular pacing to assess transisthmus conduction in patients undergoing isthmus-dependent atrial flutter ablation: A new useful technique?

Successful radiofrequency (RF) ablation of typical, isthmus-dependent atrial flutter requires establishment and confirmation of bidirectional conduction block across the cavotricuspid isthmus. Low atrial pacing usually is performed from the bipoles of the 20-pole Halo catheter, septal and lateral to the cavotricuspid isthmus ablation line. However, occasionally this is difficult because of high pacing thresholds and/or saturation of the atrial electrograms recorded near the pacing catheter. The purpose of this study was to assess if right ventricular (RV) pacing and resulting retrograde atrial activation can be used to assess conduction block from the septum to the lateral wall in a clockwise direction. Thirty-five consecutive male patients (mean age 64 +/- 10 years; mean ejection fraction 42 +/- 13%; mean left atrial dimension 44 +/- 6 mm) with typical isthmus-dependent atrial flutter were studied. The following electrophysiology catheters were used: 20-pole catheter along the tricuspid annulus, quadripolar catheters at the His and/or RV apex, and 8-mm ablation catheter. Following RF ablation of the cavotricuspid isthmus, bidirectional conduction block was confirmed in all 35 patients by pacing at a cycle length of 600 ms from bipoles septal and lateral to the cavotricuspid isthmus ablation line. Conduction times from pacing artifact to adjacent bipolar atrial electrograms and reversal of atrial activation pattern were analyzed. RV pacing was performed and retrograde atrial activation pattern assessed. If retrograde AV nodal conduction was absent, isoproterenol was infused intravenously at 2 microg/min, and RV pacing was repeated. The conduction time between the double potentials across the cavotricuspid isthmus ablation line was measured. Mean conduction times across the isthmus during septal (S), lateral (L), and RV pacing were 145 +/- 21 ms, 144 +/- 24 ms, and 129 +/- 20 ms, respectively. Retrograde AV nodal conduction was present in 34 of 35 patients (isoproterenol 8 patients). Evidence of conduction block by a clear change in activation pattern across the isthmus was seen during RV pacing in 33 of 35 patients with bidirectional conduction block. RV pacing is a simple and easy maneuver that can be performed to assess isthmus conduction in most patients.

Treatment of tachyarrhythmias in a patient with the long QT syndrome by autotransplantation of the heart and sinus node-triggered atrial pacing

The case history of a 37-year-old woman with the long QT syndrome and drug-refractory paroxysmal ventricular tachyarrhythmias is reported. She was resuscitated eight times between 1980 and 1987. The duration of these attacks increased from a few minutes to 8 hours and the interval between them decreased from 2 years to 4 weeks. An autotransplantation was performed of the anatomically and hemodynamically normal heart. She has had normal QT intervals and has been free of tachyarrhythmias since the operation in June 1987. Because of a slow escape low atrial rhythm, she was treated with a dual-chamber pacemaker programmed in the VDD mode with a coupling interval of 15 msec. The pacemaker wires were connected to the nontransplanted atrial cuff ("atrial" wire) and the transplanted atrium ("ventricular" wire). The hemodynamic effect of the resultant sinus node-driven low atrial pacing was restoration of normal values. This is the first report of successful autotransplantation of the heart for ventricular tachyarrhythmias caused by the long QT syndrome.

Pacemaker Syndrome with AAI Rate Variable Pacing: Importance of Atrioventricular Conduction Properties, Medication, and Pacemaker Programmability

A patient who received an AAI Activitrax rate variable pacemaker for treatment of symptomatic sinus bradycardia is described. disopyramide prolonged the anterograde effective refractory period of the fast conducting atrioventricular (AV) nodal pathway to such an extent, that conduction switched to the slow AV nodal pathway at low atrial pacing rates. This gave rise to symptoms of the pacemaker syndrome during moderate exercise because the paced atrial event was conducted with a long, spike to Q interval with occurrence of the paced atrial event just after the preceding QRS complex. A change of medication solved this problem. Programming a bipolar electrode configuration avoided sensing of far-field QRS signals with the associated problems of resetting the basic pacing interval as well as the upper rate interval. AAI rate variable pacing requires careful evaluation of AV conduction properties, AV conduction intervals as well as the influence of medication to be given. The use of multiprogrammable pacemakers with marker channel capability will significantly facilitate the understanding and resolution of anomalous behavior.

Selective versus non-selective His bundle pacing.

His bundle pacing was achieved in 10 anaesthetized open chest dogs by stimulation from bipolar electrode catheters positioned in the aortic root and right heart. Recordings were taken directly through plunge wires from the right atrium, high ventricular septum, and epicardial sites on the right and left ventricles. Six types of response were seen during A-V junctional stimulation: (1) low atrial pacing; (2) combined atrial and His bundle pacing; (3) His bundle pacing; (4) combined atrial, ventricular septal, and His bundle pacing; (5) combined septal and His bundle pacing; and (6) ventricular pacing. Pacing of the His bundle in combination with the atrium and/or ventricular septum is designated as non-selective, whereas stimulation of the His bundle alone is considered selective pacing. Non-selective His bundle pacing can be recognized from the surface leads by changes in onset and amplitude of the QRS with appreciable T-wave alterations. Although electrode position was an important determinant of the type of pacing achieved, a variety of patterns of stimulation resulted from variation in the modalities of the pacing stimulus, ie, polarity, intensity, and duration. Unless these factors are considered, selective His bundle pacing may not be achieved.