Clinical and hemodynamic comparison of VVI versus DDD pacing in patients with DDD pacemakers

To identify better those subgroups of pacemaker recipients who will benefit from dual chamber pacing, 19 patients with DDD pacemakers that were physiologically paced were entered into a blinded, randomized protocol comparing long-term VVI versus DDD pacing. Patients were evaluated in each of the pacing modes for exercise performance, cardiac chamber size, cardiac output, functional status and health perception. Eight patients (42%) insisted on early crossover, from VVI to DDD pacing, after only 1.8 +/- 1.4 weeks because of symptoms consistent with pacemaker syndrome. Overall, 12 patients preferred DDD pacing and no patient preferred VVI pacing (p = 0.001). Percent fractional shortening (30 +/- 8 vs 24 +/- 6%, p = 0.009) and cardiac output (6.3 +/- 2.6 vs 4.4 +/- 2.2 liters/min, p = 0.0001) where significantly greater in the DDD mode. Exercise duration was greater during DDD compared with VVI pacing (11.3 +/- 3.7 vs 10.1 +/- 3.7 minutes, p = 0.006). However, it was only in the crossover subgroup that DDD pacing resulted in significant improvement in exercise performance and health perception compared with VVI pacing. This subgroup of patients was characterized by an intrinsic sinus rate of less than 60 beats/min (4/8 vs 0/11, p = 0.006), ventriculoatrial (VA) conduction (4/8 vs 1/11, p = 0.048), greater increase in exercise peak systolic blood pressure from VVI to DDD mode (21 +/- 12 vs 4 +/- 13 mm Hg, p = 0.02) and greater improvement in exercise capacity from VVI to DDD pacing (2.2 +/- 1.2 vs 0.6 +/- 1.4 minutes, p = 0.03) compared with the other 11 patients.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of left ventricular filling profile on the effect of atrioventricular synchronous pacing.

We correlated the percentage of atrial contribution to left ventricular filling (percent AC) assessed by Doppler echocardiography with the hemodynamic benefit from atrioventricular synchronous pacing assessed by direct hemodynamic measurements. Subjects comprised 40 patients who underwent electrophysiologic catheterization because of unexplained syncope or bradycardia (< 40 beats/min). Femoral arterial and pulmonary capillary wedge pressure were recorded by catheterization, and cardiac output was measured by thermodilution during temporary atrioventricular synchronous (DDD, 70 beats/min with 150 ms of atrioventricular delay) and ventricular (VVI, 70 beats/min) pacing. Mitral inflow velocity by pulsed-wave Doppler echocardiography was recorded during DDD pacing and percent AC was obtained by calculating the ratio of mitral inflow velocity area during atrial systole to total mitral inflow velocity area during early diastole and atrial systole. The mean arterial pressure and the cardiac output increased significantly (99 +/- 16 mm Hg vs 90 +/- 15 mm Hg, p < 0.001; 4.6 +/- 1.0 L/min vs 3.9 +/- 0.9 L/min, p < 0.001), and the mean pulmonary capillary wedge pressure decreased (7 +/- 4 mm Hg vs 10 +/- 4 mm Hg, p < 0.001) during DDD compared with VVI pacing. A significant positive correlation was observed between the percent AC and the increase in cardiac output (r = 0.58, n = 40, p < 0.01) or the increase in mean arterial pressure (r = 0.62, n = 38, p < 0.01) during DDD pacing. The percent AC did not significantly correlate with the decrease in pulmonary capillary wedge pressure. In conclusion, patients with larger percent AC may receive major benefit from atrioventricular synchronous pacing.     

Effect of AV synchronization and rate increase on hemodynamics and on atrial natriuretic peptide in patients with total AV block

We studied nine patients (56 +/- 7 years) with complete AV-block and permanent dual-chamber pacemaker (DDD) under different pacing modes: ventricle pacing (VVI) 70 bpm, DDD 106 +/- 4 bpm, rate adaptive pacing (VVI-FA) 108 +/- 3 bpm. Exercise was performed supine on the bicycle ergometer at 50 watts for 5 min at each setting. DDD-paced patients showed significantly higher mixed venous oxygen saturation, being 45 +/- 2% after the fourth minute, (VVI 38 +/- 2%, p less than 0.01 and VVI-FA paced patients 40 +/- 1%, p less than 0.01). Pressures were normal under DDD pacing during exercise (RAP 7 +/- 2 mm Hg; PCP 14 +/- 3 mm Hg) and showed further increase to abnormal levels during VVI (RAP 13 +/- 2 mm Hg, p less than 0.01; PCP 21 +/- 3 mm Hg, p less than 0.02) and VVI-FA pacing (RAP 10 +/- 2 mm Hg, p less than 0.05; PCP 20 +/- 3 mm Hg, p less than 0.01). Stroke volume increased from 71 +/- 5 ml to 105 +/- 7 ml during VVI and from 64 +/- 7 ml to 81 +/- 7 ml during DDD pacing. Stroke volume remained unchanged (69 +/- 5 ml) during VVI-FA pacing. The peak levels of ANP during and after exercise were significantly higher under VVI (951 +/- 248 pg/ml) than under DDD pacing (650 +/- 140 pg/ml, p less than 0.01) and were not different between DDD and VVI-FA pacing (677 +/- 97 pg/ml). These results show that VVI pacing effects a more pronounced increase of ANP level than other pacing modes. Under moderate exercise, rate-responsive pacing compared to VVI pacing showed no differences in mixed venous oxygen saturation and in atrial pressures. Only DDD pacing showed higher oxygen saturation and a normalization of atrial pressures when compared to other types of single chamber pacing.     

BP and arterial distensibility in children with primary snoring

STUDY OBJECTIVE: While previous studies have suggested an association between obstructive sleep apnea and cardiovascular complications, the effects of primary snoring in children on daytime systemic BP and arterial distensibility remain unknown. Design and patients: To determine the effects of primary snoring on BP and peripheral conduit artery distensibility, 30 children with primary snoring were studied at an age of 9.5 +/- 2.8 years (mean +/- SD). Systemic BP was measured using an automated device, while brachioradial arterial distensibility was assessed by measuring pulse wave velocity (PWV), which is inversely related to the square root of distensibility. The results were compared to those of 30 healthy control subjects matched for age, sex, and body size. RESULTS: As compared to control subjects, children with primary snoring had significantly higher systolic BP (112 +/- 10 mm Hg vs 105 +/- 8 mm Hg, p = 0.001), diastolic BP (60 +/- 7 mm Hg vs 53 +/- 9 mm Hg, p = 0.004), and mean BP (81 +/- 7 mm Hg vs 71 +/- 8 mm Hg, p < 0.001). Likewise, those with primary snoring had significantly higher PWV (9.7 +/- 1.6 m/s vs 7.9 +/- 2.0 m/s, p = 0.001). Multiple regression identified age, body mass index (BMI), and primary snoring as significant determinants of systemic BP; however, primary snoring is the only significant determinant of PWV. Regardless of the BMI, systemic BP and PWV remained significantly higher in children with primary snoring. CONCLUSION: Children with primary snoring have increased daytime systemic BP and reduced arterial distensibility, which may jeopardize long-term cardiovascular health.     

Doppler ultrasound measurement of cardiac output in patients with physiologic pacemakers. Effects of left ventricular function and retrograde ventriculoatrial conduction

Dual-chamber cardiac pacing (DDD) offers obvious theoretical advantages over traditional ventricular demand (VVI) pacing. Nevertheless, no widely agreed upon criteria exist for the selection of patients for physiologic DDD pacemakers compared with the simpler VVI systems. Accordingly, a non-invasive method for measuring cardiac output (Doppler ultrasound) was used to identify candidates for pacing who would derive the greatest hemodynamic benefit from DDD vs VVI pacing. Among 29 patients studied at rest during VVI-mode pacing, the average cardiac output by Doppler ultrasound was 4.3 +/- 0.3 liters/min (mean +/- standard error of the mean). In the DDD mode, the average cardiac output was 5.0 +/- 0.3 liters/min (p less than 0.001). Baseline left ventricular ejection fraction did not identify a group that improved more with DDD pacing. Patients who showed either retrograde ventriculoatrial conduction or described symptoms consistent with the "pacemaker syndrome" during VVI pacing, however, showed greater increases in cardiac output during DDD pacing. In these patients, the mean improvement in cardiac output was 30.4 +/- 8.6% with DDD vs VVI pacing, as opposed to an average increase of only 14.4 +/- 3.4% in the remaining 20 patients (p = 0.02). Thus, Doppler ultrasound can be used to quantitate the change in cardiac output at rest that occurs with DDD vs VVI pacing. The change is independent of the level of left ventricular function but is substantially higher when there is evidence of ventriculoatrial conduction or the pacemaker syndrome.     

Beneficial effects of atrioventricular synchrony in dogs with right coronary artery embolization, and complete heart block

Complete heart block complicating right ventricular infarction frequently is accompanied by shock. Hemodynamic responses to different pacing modes were studied in six anesthetized, closed chest dogs following right coronary artery embolization with mercury and heart block induced by repetitive trans-septal DC shock. Hemodynamics were recorded at control, following right coronary artery embolization, during atrioventricular sequential pacing (DVI) and ventricular pacing (VVI). With respect to the hemodynamics recorded during VVI and DVI pacing; (1) The mean arterial pressure increased by 29.4% during DVI pacing (92.1 +/- 31.3 mm Hg vs 73.4 +/- 28.9 mm Hg p less than 0.005). This increase was primarily due to an augmentation in systolic arterial pressure. (2) The left ventricular end diastolic pressure increased by 35.8% during DVI pacing (16.3 +/- 5.3 mm Hg vs 12.0 +/- 4.3 mm Hg p less than 0.01). (3) Cardiac output improved by 33.8% during DVI pacing (2.34 +/- 0.75 L/min vs 1.76 +/- 0.59 L/min, p less than 0.0005). This was a consistent improvement in cardiac output with a narrow range of 27.1% to 39.0%. (4) There were no significant changes in right atrial, pulmonary, pulmonary capillary wedge pressures or in systemic vascular resistance. In dogs with right coronary artery occlusion and complete heart block DVI pacing is clearly superior to VVI pacing. This is probably because the atrial contribution to ventricular filling, in this model, is critically important to maintain an adequate cardiac output.     

Acute hemodynamic effects of right ventricular pacing site and pacing mode in patients with congestive heart failure secondary to either ischemic or idiopathic dilated cardiomyopathy

The hemodynamic effects of pacing in patients with congestive heart failure (CHF) remain controversial. Early studies reported that pacing from the right ventricular (RV) apex improved acute hemodynamic parameters in patients with left ventricular systolic dysfunction, but these findings were not confirmed in subsequent controlled studies. More recently, it has been proposed that pacing from the RV side of the ventricular septum improves hemodynamic function compared with intrinsic conduction or apical pacing. Either dual-chamber or ventricular pacing have been evaluated, again with inconsistent findings. To assess the effects of pacing site and mode on acute hemodynamic function, we evaluated 21 subjects with CHF and intrinsic conduction disease. Hemodynamics were compared in AAI, VVI, and DDD modes with pacing from the RV apex or high septum. The pacing rate was constant in each patient and the order of testing was randomized. In the absence of ventricular pacing (AAI mode), the mean systemic arterial pressure was 85 +/- 11 mm Hg, the right atrial pressure was 11 +/- 4 mm Hg, the pulmonary capillary wedge pressure was 18 +/- 8 mm Hg and the cardiac index was 2.4 +/- 0.7 L/min/m(2). Compared with AAI pacing, there were no improvements in any hemodynamic parameter with DDD pacing from either RV site. Hemodynamic function worsened with VVI pacing from both RV sites. Subgroup analyses of patients with dilated cardiomyopathy, with prolonged PR interval, or with significant mitral regurgitation also failed to demonstrate an improvement with pacing. We conclude that pacing mode but not RV pacing site affects acute hemodynamic function. Pacing in the DDD mode prevents the deleterious effects of VVI pacing in this patient population.     

高血压合并动脉粥样硬化与大动脉缓冲功能关系的研究

目的研究高血压病（EH）合并动脉粥样硬化患者大动脉缓冲功能的改变。方法选择313例EH患者,其中男性230例,女性83例,平均年龄（58.5±10.1）岁。应用脉搏波速度(pulse wave velocity,PWV)自动测量系统测定颈动脉-股动脉PWV作为反映大动脉节段扩张性的参数;B型超声对颈动脉进行扫查,动脉粥样硬化的定义为内膜-中层厚度≥1.3mm。颈动脉横断面顺应性和容积扩张性作为评价大动脉缓冲功能的指标。结果313例EH患者合并颈动脉粥样斑块者120例。与未合并颈动脉粥样硬化患者相比,EH合并颈动脉粥样硬化患者收缩压［（149.76±20.20）mmHg比（141.62±18.94）mmHg］、脉压［（61.72±18.94）mmHg比（52.84±14.58）mmHg］和PWV［（12.91±2.93）m/s比（10.78±2.02）m/s］显著升高(P均<0.001);颈动脉横断面顺应性［（64.68±40.52）10-3*mm2/mmHg比（81.55±63.45）10     

Relationship with plasma neurohormones and dyssynchrony detected by Doppler echocardiography in patients undergoing permanent pacemaker implantation

OBJECTIVE: To determine whether isovolumic relaxation flow (IRF) and isovolumic contraction flow (ICF) resulted from asynchrony and asynergy due to VVI and DDD pacemakers modulated neurohormones, we measured neurohormone levels in plasma and investigated the characteristics of IRF and ICF using Doppler echocardiography. METHODS AND RESULTS: We studied 11 patients with dual-chamber pacemakers (DDD) and 11 patients, with ventricular inhibiting mode (VVI). All patients underwent Doppler echocardiography of the left ventricle. Atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), renin and aldosteron were measured. The LV was scanned for the presence of intracavitary flow during the isovolumic relaxation and isovolumic contraction period. The plasma levels of BNP and ANP were significantly lower in DDD mode than in VVI mode (56 +/- 32 pg/ml vs. 94 +/- 32 pg/ml, p = 0.022 and 98 +/- 20 pg/ml vs. 134 +/- 17 pg/ml, p = 0.042, respectively). There were no significant differences in the plasma level of renin or aldosteron. VVI mode versus DDD mode increased isovolumic relaxation flow time (129 +/- 41 vs. 111 +/- 36 sec, p = 0.020) and isovolumic relaxation flow velocity (50 +/- 4 vs. 37 +/- 2 cm/s, p = 0.018). A strong relationship between blood ANP and BNP levels and IRF velocity was found in patients with a VVI pacemaker (r: 0.632, p: 0.028; r: 0.528, p: 0.024, respectively). CONCLUSION: VVI mode has a longer isovolumic relaxation time, isovolumic relaxation flow velocity and has higher ANP and BNP plasma levels than DDD mode. IRF resulting from asynergy and asynchrony in VVI mode pacemakers versus DDD mode pacemakers affects the plasma levels of ANP and BNP compared to renin and aldosteron.     

Bradycardia pacing-induced short-long-short sequences at the onset of ventricular tachyarrhythmias: a possible mechanism of proarrhythmia?

OBJECTIVES: The purpose of this study was to characterize interactions between normal pacing system operation and the initiating sequence of ventricular tachycardia (VT)/ventricular fibrillation (VF). BACKGROUND: Abrupt changes in ventricular cycle lengths (short-long-short, S-L-S) might initiate VT/VF. The S-L-S sequences might be passively permitted or actively facilitated by bradycardia pacing. METHODS: Initiating sequences of 1,356 VT/VF episodes in the PainFree Rx II (n = 634) and EnTrust Trial (n = 421) were analyzed with stored electrograms and by pacing mode (DDD/R, VVI/R, and Managed Ventricular Pacing [MVP]). Interactions between pacing and VT/VF initiation were classified as: non-pacing associated, pacing associated, pacing permitted, and pacing facilitated. RESULTS: Non-pacing associated (no pacing, no S-L-S) and pacing associated (ventricular pacing without S-L-S) onset accounted for 44.0% and 29.8% of all VT/VF, respectively. Pacing permitted (S-L-S sequences without ventricular pacing) episodes accounted for 6.4% (DDD/R), 20.0% (MVP), and 25.6% (VVI/R) of 1,356 VT/VF episodes. Pacing facilitated onset (S-L-S sequences actively facilitated by ventricular pacing including the terminal beat after a pause) accounted for 8.2% (MVP), 9.4% (VVI/R), and 14.8% (DDD/R) of 1,356 VT/VF episodes. Pacing facilitated S-L-S VT/VF occurred in 2.6% (MVP), 3.3% (VVI/R), and 5.2% (DDD/R) of patients with episodes and was the sole initiating sequence in approximately 1% of patients. Pause durations during pacing facilitated S-L-S differed between modes (DDD/R 793 +/- 172 ms vs. MVP 865 +/- 278 ms vs. VVI/R 1180 +/- 414 ms, p = 0.002). The majority of these episodes were monomorphic VT. CONCLUSIONS: Ventricular tachycardia/VF in some implantable cardioverter-defibrillator patients might be initiated by S-L-S sequences that are actively facilitated by bradycardia pacing operation and might constitute an important mechanism of ventricular proarrhythmia.     

Evaluation of maintenance of cardiac output during DDD and VVI pacing by exercise Doppler echocardiography]

To evaluate the efficacy of DDD pacing for cardiac reserve, we assessed increases in the stroke volume and cardiac output during randomized treadmill exercise in 16 patients by DDD and fixed-rate ventricular (VVI) pacing. The stroke volume index and cardiac index were determined using suprasternal Doppler measurements. Ten patients who showed sinus rhythm during exercise were excluded from this study. Compared with the findings during VVI pacing, those during DDD pacing showed: 1) a greater exercise-induced positive chronotropic response (mean maximum heart rate 122 +/- 22 beats/min vs 70 beats/min, p < 0.01), 2) a lesser increase in the stroke volume index (34 +/- 7 to 39 +/- 9 ml/m2 vs 31 +/- 7 to 49 +/- 11 ml/m2, p < 0.05), 3) a greater increase in the cardiac index (2.43 +/- 0.45 to 4.48 +/- 1.36 L/min/m2 vs 2.22 +/- 0.47 to 3.43 +/- 0.45 L/min/m2, p < 0.05), and 4) prolongation of exercise duration (6.35 +/- 2.00 min vs 5.97 +/- 1.81 min, NS). These findings indicated that VVI pacing promoted a greater stroke volume than DDD pacing, which provides a compensatory increase in contractility and the preload in cases without an increase in heart rate during exercise, however, the increase in cardiac output was insufficient due to the absence of a chronotropic response. In conclusion, a DDD pacemaker could effectively increase heart rate, causing a significant increase in cardiac output and extending exercise duration.     

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-chamber cardiac pacing with activity-initiated chronotropic response: evaluation by cardiopulmonary exercise testing

In this study, sequential cardiopulmonary exercise testing was used to assess the physiologic benefits of a single-chamber ventricular pacing system that utilizes a piezoceramic sensor to adjust heart rate by detecting "physical activity." An initial exercise test was conducted with the pacemaker programmed (based on a randomization table) to either the fixed rate (VVI, 70 beats/min) or rate-variable (VVI-Act) mode, and the results were compared with those obtained during a second exercise test in which the pacemaker was programmed to the alternate pacing mode. A 1.5 to 2 hr rest period was permitted between exercise tests, each of which consisted of a symptom-limited constant speed (3.0 mph) Balke protocol with 2 min stages commencing at 0.0% grade with increments of 2.5% at end of each stage. Compared with findings during fixed-rate VVI pacing, VVI-Act pacing was associated with greater exercise-induced positive chronotropic response (mean maximum heart rate VVI-Act 128 +/- 15.3 beats/min vs VVI 90 +/- 28.4 beats/min; p less than .01), prolongation of exercise duration (VVI-Act 10.2 +/- 3.8 min vs VVI 7.7 +/- 2.5 min; p less than .01), increased peak oxygen consumption (VVI-Act 1617 +/- 656 ml O2/min vs VVI 1325 +/- 451 ml O2/min; p less than .01), and onset of anaerobic threshold at a higher oxygen consumption (VVI-Act 1208 +/- 343 ml O2/min vs VVI 1064 +/- 377 ml O2/min: p less than .01). Additionally, of 44 comparable exercise stages tested in the two pacing modes, perceived exertion (assessed by a numerical grading system) was lower in 38 of 44 instances during VVI-Act compared with VVI pacing.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Total sympathetic activity and atrial natriuretic factor levels in VVI and DDD pacing with different atrioventricular delays during daily activity and exercise.

The purpose of the study was to assess at rest and during exercise total sympathetic activity, as expressed by plasma cyclic AMP (cAMP) blood levels and sinus node activity (SNA), as well as atrial natriuretic factor (ANF) blood levels in VVI and DDD pacing with long and short atrioventricular delays in DDD paced patients suffering from complete heart block. Clinical parameters, such as exercise time, and arterial blood pressure (ABP) were also taken into consideration. Thirteen patients (six males, mean age 65 +/- 2 years), were examined randomly in VVI and DDD pacing with 100 and 150 ms atrioventricular delays (AVD). Plasma cAMP and ANF were measured at rest, at peak exercise and 15 and 30 min after the test. The cAMP at rest remained unchanged whatever the pacing mode or the AVD, but 30 min after exercise, the cAMP levels were statistically lower in DDD pacing with short AVD (100 ms) than in DDD with long AVD (150 ms) or VVI pacing (cAMP DDD/100 ms: 16 +/- 0.8 pmol.ml-1, cAMP DDD/150 ms: 20 +/- 2 pmol.ml-1, P < 0.01, cAMP VVI: 29 pmol.ml-1, P < 0.001). ANF plasma levels at rest were significantly higher in VVI pacing than in DDD modes, with either long or short AVD (ANF DDD/100 ms: 93 +/- 10 pg.ml-1, ANF DDD/150 ms: 100 +/- 13 pg.ml-1, ANF VVI: 150 +/- 16 pg.ml-1, P < 0.001, P < 0.03 respectively compared to VVI).(ABSTRACT TRUNCATED AT 250 WORDS)     

Unterstützung der spontanen atrioventrukulären Überleitung bei Patienten mit DDD(R)-Schrittmachern Effektivität und Sicherheit

AIM: In a prospective and randomized multicenter study using a cross-over protocol we compared the efficacy and the safety of the ELA medical mode-switch algorithm (DDD/AMC = DDD to AAI) to conventional DDD stimulation in patients with spontaneous AV conduction. PATIENTS AND METHOD: Forty-eight patients with a mean age of 67 +/- 13 years were included. Underlying heart disease was present in 54%. Pacemaker indications were paroxysmal AV block (21%), sick-sinus syndrome (46%), paroxysmal AV block + sick-sinus syndrome (31%) and tachycardia-bradycardia syndrome (8%). Patients were excluded from the study in case of a permanent 1st to 3rd degree AV block, a right bundle-branch block with QRS > 120 ms, severe coronary heart disease or idiopathic cardiomyopathy. The programming of the pacemaker was randomized to either DDD/AMC or DDD and was crossed over after 1 month. The AV interval (AVI) which was programmed in conventional DDD pacing was calculated as AVI = PR (or AR) + 30 ms at rest or as AVI = PR (or AR) - 50 ms during exercise. When the DDD/AMC mode was programmed, the AV interval was calculated automatically. We analyzed the AV interval, the frequency of ventricular pacing, the number of pacemaker-induced tachycardias, the number of atrial tachyarrhythmias, and the final programming which was left to the physician's choice. RESULTS: The AV interval after conventional DDD stimulation was 201 +/- 38 ms vs 195 +/- 28 ms with DDD/AMC (p = ns). Ventricular stimulation was significantly less often in the DDD/AMC mode than in the DDD mode (15 +/- 17% vs 48 +/- 37%, p < 0.001). Thereby the DDD/AMC algorithm led to a 69% reduction of ventricular pacing which means an approximately 5.5 months prolongation of the battery lifetime. There was no significant difference in the incidence of pacemaker-induced tachycardias. At the end of the study 77% of the physicians programmed the DDD/AMC mode. CONCLUSION: The analyzed DDD/AMC mode-switch algorithm leads to a significant reduction of ventricular pacing in patients with spontaneous AV conduction or with only paroxysmal AV block. Thereby the battery lifetime is prolonged and the incidence of complications due to ventricular pacing can be reduced.     

Non-invasive evaluation of left ventricular function (systolic time interval) in patients using double-chamber pacemakers programmed on DDD and VVI

OBJECTIVE: To evaluate changes on left ventricular function as assessed by systolic time intervals (STI), by programming "physiological" pacemakers either on VVI or DDD mode. STUDY DESIGN: Comparison of STI values--electromechanical systole (QS2); left ventricular ejection time (LVET); pre-ejection period (PEP); PEP/LVET--in patients submitted to double chamber pacing programmed in DDD or VVI mode. SETTING: Cardiac Pacing Center in a Department of Cardiology at a University Hospital. PATIENTS: We have studied 12 patients (3 men, 9 women), mean age 56.16 years (range 25-76 years) treated with double chamber pacing. INTERVENTIONS: Initial measurements of STI in DDD or one week in VVI mode, and again after one week in DDD mode. RESULTS: Significant changes were found after the first week in VVI pacing, versus baseline determination in DDD pacing, for LVET, PEP, and PEP/LVET (p less than 0.05). At the end of the second week (DDD pacing), there were also statistically significant differences for QS2 (P less than 0.05), LVET (P less than 0.01) and PEP/LVET (P less than 0.05) values when compared with the ones obtained in VVI pacing, at the end of the preceding week. No significant changes were found between the initial and the final STI determinations (both in DDD pacing). CONCLUSION: We concluded for a better performance of the left ventricle at rest when "physiological" pacing is compared with VVI pacing.     

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.     

Comparison of the effects of VVI versus DDD pacing on cardiac baroreflex function

INTRODUCTION: Conventional baroreceptor-heart rate (HR) reflex sensitivity cannot be examined in chronotropically incompetent patients or in pacemaker recipients. However, cardiac baroreceptor reflex sensitivity (BRS)-stroke volume (SV), which is closely and linearly correlated with BRS-HR, may be an alternative in that population. The aim of this study was to compare the BRS-SV in pacemaker recipients with a fixed HR paced in VVI versus DDD modes in the supine and upright positions. METHODS: The pacing mode was set randomly to DDD or VVI with complete atrial and/or ventricular capture, then crossed over to the alternate mode in 9 recipients of dual-chamber pacemakers with atrioventricular (AV) block. Beat-to-beat mean blood pressure and SV were measured in the supine and upright positions, using a tilt table. The BRS-SV, expressed in %/mmHg, was the ratio of low-frequency (LF) power to total power (TP) of SV variability, measured by spectral analysis of spontaneous variations in mean blood pressure and SV. RESULTS: BRS-SV was significantly lower in the VVI than in the DDD mode in the supine (37.2 +/- 26.7 vs 14.5 +/- 7.7%/mmHg) and upright (22.9 +/- 16.9 vs 10.6 +/- 6.6%/mmHg) positions (P < 0.05 for both comparisons). CONCLUSIONS: VVI pacing is adverse from the standpoint of cardiac autonomic baroreflex function. A decreased BRS-SV may be one of the factors involved in the hemodynamic intolerance associated with VVI pacing.     

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.