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Pacing Mode (pacing + mode)

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Medical Sciences	100%

Selected Abstracts

Multicenter, Prospective, Randomized Safety and Efficacy Study of a New Atrial-Based Managed Ventricular Pacing Mode (MVP) in Dual Chamber ICDs

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2005
MICHAEL O. SWEENEY M.D.
Background: Ventricular desynchronization caused by right ventricular pacing may impair ventricular function and increase risk of heart failure (CHF), atrial fibrillation (AF), and death. Conventional DDD/R mode often results in high cumulative percentage ventricular pacing (Cum%VP). We hypothesized that a new managed ventricular pacing mode (MVP) would safely provide AAI/R pacing with ventricular monitoring and DDD/R during AV block (AVB) and reduce Cum%VP compared to DDD/R. Methods: MVP RAMware was downloaded in 181 patients with Marquis DR ICDs. Patients were initially randomized to either MVP or DDD/R for 1 month, then crossed over to the opposite mode for 1 month. ICD diagnostics were analyzed for cumulative percentage atrial pacing (Cum%AP), Cum%VP, and duration of DDD/R pacing for spontaneous AVB. Results: Baseline characteristics included age 66 ± 12 years, EF 36 ± 14%, and NYHA Class II,III 36%. Baseline PR interval was 190 ± 53 msec and programmed AV intervals (DDD/R) were 216 ± 50 (paced)/189 ± 53 (sensed) msec. Mean Cum%VP was significantly lower in MVP versus DDD/R (4.1 ± 16.3 vs 73.8 ± 32.5, P < 0.0001). The median absolute and relative reductions in Cum%VP during MVP were 85.0 and 99.9, respectively. Mean Cum%AP was not different between MVP versus DDD/R (48.7 ± 38.5 vs 47.3 ± 38.4, P = 0.83). During MVP overall time spent in AAI/R was 89.6% (intrinsic conduction), DDD/R 6.7% (intermittent AVB), and DDI/R 3.7% (AF). No adverse events were attributed to MVP. Conclusions: MVP safely achieves functional atrial pacing by limiting ventricular pacing to periods of intermittent AVB and AF in ICD patients, significantly reducing Cum%VP compared to DDD/R. MVP is a universal pacing mode that adapts to AVB and AF, providing both atrial pacing and ventricular pacing support when needed. [source]

Prevention of the Initiation of Atrial Fibrillation: Mechanism and Efficacy of Different Atrial Pacing Modes

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 3 2000
WEN-CHUNG YU
Several atrial pacing modes have been reported to be effective in the prevention of atrial fibrillation (AF); they included biatrial pacing, dual site right atrial pacing, Bachmann's bundle (BB) pacing, and coronary sinus pacing. However, the relative efficacy and electrophysiological mechanisms of these pacing modes in the prevention of AF are not clear. In 15 patients (age 54 ± 14 years) with paroxysmal AF, P wave duration, effective refractory period, and atrial conduction time were determined with six different atrial drive pacings, that were right atrial appendage (RAA), BB, right posterior interatrial septum (RPS), distal coronary sinus (DCS), RAA plus RPS simultaneously (DSA), and RAA plus DCS simultaneously (BiA). All these patients consistently had AF induced with early RAA extrastimulation coupling to RAA drive pacing. No patient had AF induced with RAA extrastimulation coupled to BB, RPS, or DCS drive pacing, but seven and eight patients had AF induced with RAA extrastimulation coupled to DSA and BiA drive pacing, respectively. The P wave duration was longest during RAA pacing, and became shorter during other atrial pacing modes. Analysis of electrophysiological change showed that early RAA extrastimulation coupled to RAA drive pacing caused the longest atrial conduction delay among these atrial pacing modes; BB, RPS, and DCS drive pacing caused a greater reduction of this conduction delay than DSA and BiA drive pacing. In addition, the effective refractory periods of RAA determined with BB, RPS, and DCS drive pacing were similar and longer than that determined with DSA and BiA drive pacing. In patients with paroxysmal AF, this arrhythmia was readily induced with RAA extrastimuli coupled to RAA drive pacing. BB, RPS, and DCS pacing were similar and more effective than DSA and BiA pacing in preventing AF. [source]

Short-Term Effects of Right Ventricular Pacing on Cardiorespiratory Function in Patients With a Biventricular Pacemaker

CONGESTIVE HEART FAILURE, Issue 6 2008
Stefan Toggweiler MD
The intention of this study was to evaluate the short-term effect of right ventricular (RV) pacing on cardiorespiratory function in patients with a biventricular pacemaker. A group of 26 patients with a biventricular pacemaker was enrolled in this cross-over, single-blind study. All patients underwent spiroergometry and electrocardiography in RV and biventricular pacing mode. Peak work capacity (102±32 W and 107±34 W for RV and biventricular pacing mode, respectively; P<.01) and peak oxygen consumption (21.4±6.7 mL/min/kg and 22.6±7.0 mL/min/kg for RV and biventricular pacing mode, respectively; P<.01) were significantly lower in the RV pacing mode. Heart rate at rest was significantly higher with active RV pacing. Short-term RV pacing in patients with a biventricular pacemaker resulted in a higher heart rate at rest, a lower peak work capacity, and a lower peak oxygen consumption compared with that in the biventricular pacing mode. [source]

Multicenter, Prospective, Randomized Safety and Efficacy Study of a New Atrial-Based Managed Ventricular Pacing Mode (MVP) in Dual Chamber ICDs

Autonomic Function during Closed Loop Stimulation and Fixed Rate Pacing: Heart Rate Variability Analysis from 24-Hour Holter Recordings

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 3 2010
RAFFAELE QUAGLIONE M.D.
Aim: Aim of this retrospective study was to analyze the effect of closed-loop stimulation (CLS) and DDD pacing mode on autonomic balance, and to evaluate heart rate variability (HRV) during CLS stimulation. Methods and Materials: Autonomic balance was estimated by a 24-hour HRV analysis of paced and spontaneous beats in patients implanted with a dual-chamber pacemaker (Inos2+ CLS,Biotronik GmbH, Berlin, Germany) and randomly assigned to CLS or DDD pacing mode. Patients underwent two 24-hour electrocardiogram Holter recordings at the end of each 3-month pacing mode period. Each Holter recording was automatically scanned to extract sequences of consecutive beats of the same type [atrial paced (Ap)-sequence and atrial spontaneous (As)-sequence], lasting at least 130 beats. Results: Eight hundred and ten sequences were extracted from 15 patients, and the following spectral parameters were evaluated during both CLS and DDD mode: the total power (variance), the absolute and percentage (relative to the total power) powers of the low frequency (LF, 0.04,0.15 Hz) and high frequency (HF, 0.15,0.4 Hz) components, as well as the LF/HF power ratio. Discussion: The two main findings of this study were: in all the patients, CLS seems to mimic short-term physiological HRV, although the variability (total power) was lower than that relative to the spontaneous beats; the HRV of the spontaneous beats had an higher LF/HF when the pacemaker was programmed as DDD respect to CLS, consistent with a shift toward sympathetic predominance. PACE 2010; 33:337,342) [source]

Overdrive Versus Conventional or Closed-Loop Rate Modulation Pacing in the Prevention of Atrial Tachyarrhythmias in Brady-Tachy Syndrome: On Behalf of the Burden II Study Group

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 11 2008
ANDREA PUGLISI M.D.
Background:Optimizing dual-chamber pacing to prevent recurrences of atrial tachyarrhythmias (AT) in sinus node dysfunction is still debated. Despite the large number of studies, efficacy of sophisticated preventive algorithms has never been proven. It is not clear whether this is due to imperfect study designs or to a substantial inefficacy of pacing therapies. Aim:To intraindividually compare AT burden between an atrial overdrive and two heart rate modulation approaches: a conventional accelerometric-sensor-based DDDR mode and a contractility-driven rate responsive closed loop (CLS) algorithm. Methods and Results:Four hundred fifty-one patients with Brady-Tachy syndrome (BTS), severe bradycardia, and a documented episode of atrial fibrillation were enrolled. One month after implant, each pacing therapy was activated for 3 months in random order. A simple log transformation was used to handle large and skew AT burden distributions. Estimates were adjusted for false-positive AT episodes and reported as geometric means (95% confidence interval). A significantly higher AT burden was observed during overdrive, 0.14% (0.09%, 0.23%) (adjusted, 0.12%[0.07%, 0.20%]). Both DDDR and CLS performed better: respectively, 0.11% (0.07%, 0.17%) (adjusted, 0.08%[0.05%, 0.14%]), 0.06% (0.03%, 0.09%) (adjusted, 0.04%[0.03%, 0.07%]). All the comparisons were statistically significant. During overdrive significantly more patients had AT episodes of duration between 1 minute and 1 hour. No significant differences were observed for longer episodes. Conclusions:Atrial overdrive showed the worst performance in terms of AT burden reduction and should not be preferred to heart rate modulation approaches that still have to be considered as a first-choice pacing mode in BTS. [source]

Evaluation of Atrial Thrombus Formation and Atrial Appendage Function in Patients with Pacemaker by Transesophageal Echocardiography

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 11 2006
ABOLFATH ALIZADEH M.D.
Background: Physiologic pacing is claimed to be superior to ventricular pacing in as much as it entails lower risk of atrial fibrillation, stroke, and atrial remodeling. There are few data on the relation between atrioventricular (AV) synchrony and atrial clot formation. Utilizing transesophageal echocardiography (TEE), this study sought to evaluate the effect of AV synchrony loss on left atrial physiology, atrial stasis, and clot formation. Methods: We conducted a cross-sectional study on patients with both AV and ventricular pacing with left ventricular ejection fraction (LVEF) >30%. TEE enabled us to explore atrial and pacing leads thrombi and measure left atrial appendage (LAA) flow velocity Results: A total 72 patients (mean age, 65 ± 11.7) were enrolled in the study. The pacing mode was VVI in 53% and AV sequential in 47% of patients. LVEF (mean ± SD; %) was 53.3 ± 6.2% in ventricular pacing mode and 52.2 ± 6.6 in physiologic pacing mode. Thrombus formation on pacing lead (<10 mm in 97% of patients) was observed in 32% of all the patients (23% in patients with AV sequential pacing mode and 39% with VVI mode). Left atrial appendage flow velocity (LAA-FV) was significantly higher among the patients with AV sequential pacing mode (49.44 ± 18 cm/s vs 40.94 ± 19.4 cm/s, P value = 0.02). LAA-FV >40 cm/s was detected in 60% of the patients, 60% of whom were in physiologic mode. Left atrial size was significantly larger among the patients with VVI pacing mode (42.3 ± 2.3 mm vs 37.79 ± 4.5 mm, P = 0.001). Multivariate analysis showed no relation between LAA-FV and age, hypertension, diabetes mellitus, left atrial size, and left ventricular function. Only one patient had right atrial clot. There was no thrombus in the ventricles and atrial appendage. Conclusion: Long-term loss of AV synchrony induced by VVI pacing is associated with the impairment of LAA contraction. Thrombus formation in the LAA is not increased by VVI pacing in patients with relatively good left ventricular (LV) function and sinus rhythm. [source]

Pacemaker Tachycardia in a Minute Ventilation Rate-Adaptive Pacemaker Induced by Electrocardiographic Monitoring

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 4 2006
WENDY LAU
Programmed upper rate pacing occurred in a patient with a rate-adaptive pacemaker when he was connected to a cardiac monitor in an emergency department. The tachycardia was mistakenly interpreted to be ventricular tachycardia and the patient received multiple DC shocks as well as intravenous amiodarone and sotalol, resulting in severe hemodynamic deterioration. It is important that physicians working in the hospital environment be familiar with this pacemaker-monitor interaction as the problem may be easily rectified by disconnecting the monitor or by reprogramming the pacemaker to a nonrate-adaptive pacing mode. [source]

AAIR Versus DDDR Pacing in the Bradycardia Tachycardia Syndrome: A Prospective, Randomized, Double-blind, Crossover Trial

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 11 2001
BERNHARD SCHWAAB
SCHWABB, B., et al.: AAIR Versus DDDR Pacing in the Bradycardia Tachycardia Syndrome: A Prospective, Randomized, Double-blind, Crossover Trial. In 19 patients paced and medicated for bradycardia tachycardia syndrome (BTS), AAIR and DDDR pacing were compared with regard to quality of life (QoL), atrial tachyarrhythmia (AFib), exercise tolerance, and left ventricular (LV) function. Patients had a PQ interval , 240 ms during sinus rhythm, no second or third degree AV block, no bundle branch block, or bifascicular block. In DDDR mode, AV delay was optimized using the aortic time velocity integral. After 3 months, QoL was assessed by questionnaires, patients were investigated by 24-hour Holter, cardiopulmonary exercise testing (CPX) was performed, and LV function was determined by echocardiography. QoL was similar in all dimensions, except dizziness, showing a significantly lower prevalence in AAIR mode. The incidence of AFib was 12 episodes in 2 patients with AAIR versus 22 episodes in 7 patients with DDDR pacing (P = 0.072). In AAIR mode, 164 events of second and third degree AV block were detected in 7 patients (37%) with pauses between 1 and 4 seconds. During CPX, exercise duration and work load were higher in AAIR than in DDDR mode (423 ± 127 vs 402 ± 102 s and 103 ± 31 vs 96 ± 27 Watt, P < 0.05). Oxygen consumption (VO2), was similar in both modes. During echocardiography, only deceleration of early diastolic flow velocity and early diastolic closure rate of the anterior mitral valve leaflet were higher in DDD than in AAI pacing (5.16 ± 1.35 vs 3.56 ± 0.95 m/s2 and 69.2 ± 23 vs 54.1 ± 26 mm/s, P < 0.05). As preferred pacing mode, 11 patients chose DDDR, 8 patients chose AAIR. Hence, AAIR and DDDR pacing seem to be equally effective in BTS patients. In view of a considerable rate of high degree AV block during AAIR pacing, DDDR mode should be preferred for safety reasons. [source]

Efficacy of Single Lead VDD Pacing in Patients with Impaired and Normal Left Ventricular Function

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2000
ANDREAS SCHUCHERT
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 m V). 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. [source]

Electrophysiologicai Characteristics of the Atrium in Sinus Node Dysfunction With and Without Postpacing Atrial Fihriliation

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 3 2000
ANTONIO DE SISTI
DE SISTI, A., ET AL.: Electrophysiologicai Characteristics of the Atrium in Sinus Node Dysfunction With and Without Postpacing Atrial Fibrillation . In patients with sinus node dysfunction (SND) with or without associated paroxysmal atrial fibrillation (AF), the effectiveness of atrial pacing in reducing the incidence of AF is not definitive. In addition, despite several studies involving large populations of implanted patients, little attention has been paid to the electrophysioiogicai (EP) atrial substrate and the effect of permanent atrial pacing. The aim of this study is to correlate EP data and the risk of AF after DDD device implantation. We reviewed FP data of 38 consecutive patients with SND. mean age 70 ± 8 years, who were investigated free of antiarrhythmic treatment, for the evaluation of the atrial substrate. We also considered as control group 25 subjects, mean age 63 ± 14 years, referred to our EP laboratory for unexplained syncope or various atrioventricular disturbances. Following pharmacological washout and at a drive cycle length of 600 ms. effective and functional refractory periods (ERP, FRP), Sl-Al and S2-A2 latency, Al and A2 conduction duration, and latent vulnerability index (EHP/A2) were measured. AF induction was tested with up to three extrastimuli at paced cycle lengths of 600 and 400 ms in 20 patients. Induction of sustained AF (> 30 seconds) was considered as the endpoint. P wave duration on the surface ECG in lead II/Vl was also measured. DDD pacing mode was chosen in all patients with the minimal atrial rate programmed between 60 and 75 beats/min (mean 64 ± 4 beats/min). After implantation, the patients were followed-up for 29 ± 17 months and clinically documented occurrence of AF was determined. When comparing patients with SND and subjects of the control group, we did not find any significant statistical differences in terms of ERP (237 ± 33 vs 250 ± 29 ms), FRP (276 ± 30 vs 280 ± 32 ms) and Sl-Al (39 ± 16 vs 33 ± 11 ms) and S2-A2 latency (69 ± 24 vs 63 ± 25 ms). In contrast, we observed significant differences regarding Al (55 ± 19 vs 39 ± 13 ms; P < 0.001), A2 (95 ± 34 vs 57 ± 18 ms; P < 0.001) and P wave duration (104 ± 18 vs 94 ± 15 ms; P < 0.05), and ERP/A2 (2.8 ± 1.2 vs 4.8 ± 1.6; P < 0.001). When comparing patients with (n = 11) or without (n =27) postpacing AF occurrence, we did not find any difference with reference to ERP, FRP. Sl-Al, S2-A2, Al duration, or follow-up duration. In patients with postpacing AF occurrence, A2 was longer (116 ± 41 vs 87 ± 27 ms; P < 0.01), FRP/A2 lower (2.1 ± 0.4 vs 3.1 ± 1.4; P < 0.05), P wave more prolonged (116 ± 22 vs 99 ± 14 ms; P < 0.01), and preexisting AF history predominant (6/11 vs 5/27 patients; P < 0.05). No difference was observed between patients with (n = 8) and without (n = 12) AF induction during the EP study. In patients with SND, the atrial refractoriness appears normal and the most important abnormality concerns conduction slowing disturbances. Persistence of AF despite pacing stresses the importance of mechanisms responsible for AF not entirely brady-dependent. In this setting, more prolonged atrial conduction disturbances, responsible for a low vulnerability index, and a preexisting history of AF enable us to identify a high risk patient group for AF in the follow-up. sinus node dysfunction, atrial fibrillation, electrophysiologicai study, atrial pacing [source]

The Effects of Rate-Adaptive Atrial Pacing Versus Ventricular Backup Pacing on Exercise Capacity in Patients with Left Ventricular Dysfunction

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2009
M.S.C.E., ROD PASSMAN M.D.
Background: Atrial rate-adaptive pacing may improve cardiopulmonary reserve in patients with left ventricular dysfunction. Methods: A randomized, blinded, single-crossover design enrolled dual-chamber implantable defibrillator recipients without pacing indications and an ejection fraction ,40% to undergo cardiopulmonary exercise treadmill stress testing in both atrial rate-adaptive pacing (AAIR) and ventricular demand pacing (VVI) pacing modes. The primary endpoint was change in peak oxygen consumption (VO2). Secondary endpoints were changes in anaerobic threshold, perceived exertion, exercise duration, and peak blood pressure. Results: Ten patients, nine males, eight with New York Heart Association class I, mean ejection fraction 24 ± 7%, were analyzed. Baseline VO2 was 3.6 ± 0.5 mL/kg/min. Heart rate at peak exercise was significantly higher during AAIR versus VVI pacing (142 ± 18 vs 130 ± 23 bpm; P = 0.05). However, there was no difference in peak VO2 (AAIR 23.7 ± 6.1 vs VVI 23.8 ± 6.3 mL/kg/min; P = 0.8), anaerobic threshold (AAIR 1.3 ± 0.3 vs VVI 1.2 ± 0.2 L/min; P = 0.11), rate of perceived exertion (AAIR 7.3 ± 1.5 vs VVI 7.8 ± 1.2; P = 0.46), exercise duration (AAIR 15 minutes, 46 seconds ± 2 minutes, 54 seconds vs VVI 16 minutes, 3 seconds ± 2 minutes, 48 seconds; P = 0.38), or peak systolic blood pressure (AAIR 155 ± 22 vs VVI 153 ± 21; P = 0.61) between the two pacing modes. Conclusion: In this study, AAIR pacing did not improve peak VO2, anaerobic threshold, rate of perceived exertion, or exercise duration compared to VVI backup pacing in patients with left ventricular dysfunction and no pacing indications. [source]

Mechanisms of Ventricular Fibrillation Initiation in MADIT II Patients with Implantable Cardioverter Defibrillators

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2008
RYAN ANTHONY M.D.
Background:The availability of stored intracardiac electrograms from implantable defibrillators (ICDs) has facilitated the study of the mechanisms of ventricular tachyarrhythmia onset. This study aimed to determine the patterns of initiation of ventricular fibrillation (VF) in Multicenter Automatic Defibrillator Implantation Trial (MADIT) II patients along with associated electrocardiogram (ECG) parameters and clinical characteristics. Methods:Examination of stored electrograms enabled us to evaluate the rhythm preceding each episode of VF and to calculate (intracardiac) ECG parameters including QT, QT peak (QTp), coupling interval, and prematurity index. Results:Sixty episodes of VF among 29 patients (mean age 64.4 ± 2.5 years) were identified. A single ventricular premature complex (VPC) initiated 46 (77%) episodes whereas a short-long-short (SLS) sequence accounted for 14 (23%) episodes. Of the 29 patients studied, 23 patients had VF episodes preceded by a VPC only, two patients with SLS only, and four patients with both VPC and SLS-initiated episodes. There were no significant differences between initiation patterns in regards to the measured ECG parameters; a faster heart rate with SLS initiation (mean RR prior to VF of 655 ± 104 ms for SLS and 744 ± 222 ms for VPC) approached significance (P = 0.06). The two patients with SLS only were not on ,-blockers compared to 83% of the VPC patients. Conclusion:Ventricular fibrillation is more commonly initiated by a VPC than by a SLS sequence among the MADIT II population. Current pacing modes designed to prevent bradycardia and pause-dependent arrhythmias are unlikely to decrease the incidence of VPC-initiated episodes of VF. [source]

Prevention of the Initiation of Atrial Fibrillation: Mechanism and Efficacy of Different Atrial Pacing Modes

Preserving Normal Ventricular Activation Versus Atrioventricular Delay Optimization During Pacing: The Role of Intrinsic Atrioventricular Conduction and Pacing Rate

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2000
IVAN ILIEV ILIEV
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 A V delay in the DDD mode and comparison between AAI and DDD with optimal A V delay for pacing rate 70/min and 90/min. Stimulus-R interval during AAI (AHI) was 282 ± 68 ms for rate 70/min and 330 ± 98 ms for rate 90/min (P < 0.01). The optimal A V delay was 159 ± 22 ms, A V 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 , 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 mP < 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. [source]