Circadian Variation in Atrial Fibrillation in Patients with Frequent Paroxysms

Determinants of the duration of episodes of atrial fibrillation (AF) in patients with paroxysmal atrial fibrillation (PAF) are poorly understood. However, autonomic tone shows circadian variation and is known to affect atrial electrophysiology. We therefore compared the duration of episodes of AF with an onset during the day (08:00 - 22:00) to those with an onset during the night in a database of 24-hour ECG recordings in patients with frequent symptomatic PAF. The heart rate in the 30 seconds prior to AF onset was also compared. From 42 recordings, 296 episodes of AF > 30 seconds duration and preceded by > 60 seconds sinus rhythm were identified. The 165 nocturnal episodes tended to be shorter (median =1.15 min) than the 131 diurnal episodes (median =1.5 min) and the distribution of nocturnal and diurnal durations was significantly different (P = 0.007; Kolgomorov-Smirnov test). This was also true in recordings containing at least 1 diurnal and at least 1 nocturnal episode. The mean heart rate prior to AF onset was lower at night (62.2 ± 11.8 vs 75.6 ± 16.4 beats/min; P < 0.0001 Wilcoxon test). These findings suggest that in patients with frequent symptomatic PAF, autonomic influences affect the duration of episodes of AF and has pathphysiohgical and therapeutic implications.     

Reliability of a New Algorithm for Automatic Mode Switching from DDDR to DDIR Pacing Mode in Sinus Node Disease Patients with Chronotropic Incompetence and Recurrent Paroxysmal Atrial Fibrillation

To evaluate the safety and efficacy of a new algorithm for automatic mode switching (AMS) from DDD-DDDR to DDIR, 26 patients, 16 females and 10 males, mean age 73 ± 6 years of age, affected by sinus node disease, chronotropic incompetence, and recurrent paroxysmal atrial fibrillation (PAF) received the Medtronic Them DR pacemaker. The device continuously calculates, in ms, the running average of the intrinsic atrial rate (MAR) and compares the current atrial interval (CAI) with the stored MAR. When the CAI is greater than the MAR it increases by 8 ms, and when the CAI is less than the MAR, it decreases by 23 ms. When MAR ± 330 ms (182 beats/mm), tachycardia is detected and AMS is activated. All patients had clinical evaluation, 12-lead ECG, Holter monitoring, and exercise testing after implantation and every 3 months for 1 year. The results were compared with the data stored in the pacemaker memory: AMS episodes number; the histogram of the last 14 episodes; and atrial electrogram recording. Twenty-two Holier recordings in 13 patients showed PAF and in all of them AMS occurred simultaneously. AMS lasted between 10 seconds and 20 hours, and MAR ranged from 195–400 beats/mm. No episode of PAF and no AMS were recorded in 39 Holter recordings in 22 patients. Appropriate AMS was confirmed in five patients by stored atrial electrogram and in nine by 12-lead ECG and pacemaker event markers. Mean atrial sensing was 2.13 ± 1.04 mV during PAF and 3,18 ± 1.46 mV during sinus rhythm. No PAF episode and no AMS were recorded during exercise testing. In conclusion, this new algorithm was very reliable, sensitive, and specific.     

Exercise Chronotropy in Patients with Normal and Impaired Sinus Node Function After Cardiac Transplantation

The chronotropic response during graded, symptom limited exercise was investigoted in 32 cardiac transplant recipients a mean of 49 ± 18 days after transplantation. All patients had systematic evaluation of postoperative donor sinus node (SN) function and the cardioacceleratory response was compared according to the SN function. Twenty-one patients had normal postoperative SN studies (corrected SN recovery time < 520 msec, group I) while the SN function was impaired postoperatively in the remainder (n = 11, group II; corrected SN recovery time 4,149 ± 6,283 msec in 5 patients, junctionai escape rhythm in 6 patients). All patients had regained sinus rhythm at time of the exercise test Patients in group II had lower basal sinus rates at the beginning of exercise (91.5 ± 11 vs 101.4 ± 7 beats/min, P < 0.02). This lower chronotropy was maintained over every incremental step (F_{rato between groups}= 30, P = 0.0001, F_{rate vs workload}= 15, P = 0.0001 by two-way ANOVAJ and resulted in a significantly lower heart rate at individual peak exercise (108.3 ± 20 vs 124.2 ±13 beats/min, P < 0.02). A total of 14/16 patients in group I but only 2/16 patiejils in group 11 accomplished a peak heart rate ± 120 beats/min (P = 0.009). The workload achieved did not differ between the groups (107 ± 29 vs 102 ± 32 watts, P > 0.5). These data show a lower SN chronotropy during rest and at peak exercise in cardiac transplant recipients with postoperative SN deficiency and apparent normalization of SN fundion.     

Effect of right atrial overdrive pacing in the prevention of symptomatic paroxysmal atrial fibrillation: a multicenter randomized study,the PAF-PACE study

The aim of this study was to assess if right atrial overdrive pacing can suppress symptomatic episodes of paroxysmal atrial fibrillation (PAF) in patients without bradyarrhythmias. Forty-two patients with frequent and symptomatic PAF without other pacing indication had a pacemaker implanted after a 4-week run-in period, during which the frequency of symptomatic PAF episodes and the mean heart rate were objectively documented. Depending on the mean heart rate recorded during run-in, the pacemaker was programmed in random order to right atrial AAI pacing at 10-19 beats/min > mean heart rate (medium overdrive [MO]), at 20-29 beats/min > mean heart rate (high overdrive [HO]) and to no pacing (OAO mode) for 4-12 weeks each using a crossover design. In the 35 patients who completed the protocol, the number of symptomatic episodes of PAF (>30-second duration) per week was significantly lower during MO pacing (median 0.88, P = 0.001, n = 35) and during HO pacing (median 0.75, P = 0.002, n = 20) than during OAO (median 2.02 and 2.04, respectively). There was no difference between MO and HO pacing in the 20 patients paced at both rates (0.97 vs 0.75, P = 0.33). Seven patients did not complete the protocol due to persistent atrial fibrillation (n = 4), angina pectoris requiring surgery (n = 1), and unwillingness to continue the study due to improvement (n = 1) or worsening (n = 1) of symptoms during the study periods. Right atrial overdrive pacing can reduce the number of symptomatic PAF episodes in patients with frequent and drug refractory PAF but without bradyarrhythmias.     

Benefits and Limitations of Rate Adaptive Pacing Under Laboratory and Daily Life Conditions in Patients with Minute Ventilation Single Chamber Pacemakers

Rate adaptive pacing has been shown to improve hemodynamic performance and exercise tolerance during acute testing. However, there remain concerns about its benefit in daily life and possible complications incurred by unnecessary pacing. This double-blind crossover study compared the benefit of rate adaptive (SSIR) versus fixed rate (SSI) pacing under laboratory and daily life conditions in 20 rate incompetent patients with minute ventilation single chamber pacemakers (META II). The heart rate (HR) response during three different exercise tests (treadmill, bicycle ergomctry, walking test) was correlated with the Holler findings during daily life in either pacing mode. The maximal HR was significantly higher in the SSIR-mode compared to the SSI-mode, both during laboratory testing (treadmill: 123 ± 15 vs 93 ± 29 beats/min: ergometry: 118 ± 15 vs 89 ± 27 beats/min; walking test: 127 ± 9 vs 95 ± 26 beats/min, all P values < 0.01) as well as during daily life (Holter: 126 ± 13 vs 103 ± 24 beats/min, P < 0.01). On Holter, the average HR (71 ± 14 vs 71 ± 8 beats/min) and the percentage of paced rhythm (54 % vs 62%, SSI- vs SSIR-mode, P = NS) were not different in either mode. However, despite a 30% rate gain in the SSIR-mode, the exercise capacity remained unchanged, and only 38% of patients preferred the SSIR-mode. Minute ventilation pacemakers provide a physiological rate response to exercise. Irrespective of the protocol used, the findings of laboratory testing are comparable to those during daily life. However, patient selection for rate adaptive single chamber pacing should be made with caution, since the objective benefit of restoring normal chronotropy may subjectively be negligible for most patients.     

Relation between history of paroxysmal atrial fibrillation and electrophysiological abnormalities of atrial muscle

Although electrophysiological abnormalities of atrial muscle have been evaluated in patients with paroxysmal atrial fibrillation (PAF), no prior study has determined the contribution of the patient's history of PAF to electrophysiological abnormalities. The study population consisted of 108 patients (71 men; mean age, 57 ± 14 years) with symptomatic and idiopathic PAF who underwent electrophysiological study. Before electrophysiological study, histories of frequency, number of PAF episodes per month, and duration, a time interval from the first episode of PAF to electrophysiological study, were examined. At electrophysiological study, endocardial electrograms from 12 right atrial sites were recorded during sinus rhythm, and the right atrial effective refractory period was determined. Longest duration of atrial electrograms, maximal number of fragmented deflections, and number of abnormal atrial electrograms recorded at the right atrial sites were significantly greater in the frequent group (> 1 PAF episode per month, n = 57) than in the infrequent group (< 1 PAF episode per month, n = 51) (98 ± 18 ms vs 88 ± 16 ms, P < 0.005; 8.7 ± 2.6 vs 7.5 ± 2.6, P < 0.05; and 2.2 ± 2.2 vs 1.4 ± 1.6, P < 0.05, respectively). Indices of atrial vulnerability were also greater in the frequent group. Duration of PAF history was significantly correlated with longest duration r = 0.52, P < 0.0001), maximal number of fragmented deflections r = 0.51, P < 0.0001), and number of abnormal atrial electrograms r = 0.58, P < 0.0001). More frequent episodes and longer history of PAF significantly increased the electrophysiological abnormalities of the atrial muscle, suggesting that PAF results in gradual electrical remodeling of the atrial muscle.     

连续气道正压通气和高流量湿化氧疗方式下患者行纤维支气管镜诊疗的临床观察

目的探讨连续气道正压通气（CPAP）和高流量湿化氧疗（HFHCO）方式下患者行纤维支气管镜操作的临床效果。 方法选择2018年12月至2019年7月使用纤维支气管镜诊疗的26例留置人工气道患者,根据患者行纤维支气管镜的操作次数,将其分为CPAP组（32例次）和HFHCO组（32例次）。比较两组患者在纤维支气管镜诊疗操作前及诊疗操作过程中心率、呼吸频率、平均动脉压、外周动脉血氧饱和度（SaO₂）以及操作前后患者血液pH值、动脉血氧分压（PaO₂）、动脉血二氧化碳分压（PaCO₂）、脉搏血氧饱和度（SpO₂）。记录两组患者在行纤维支气管镜诊疗中的不良反应发生情况。 结果操作中,HFHCO组患者心率[（121 ± 3）次/ min vs.（130 ±3）次/ min]、呼吸频率[（21.3 ± 2.7）次/ min vs.（26.1 ± 2.3）次/ min]及平均动脉压[（99 ± 7）mmHg vs.（109 ± 8）mmHg]均较CPAP组患者显著降低（t = 5.232、5.164、6.424,P均< 0.001）。操作后,CPAP组和HFHCO组患者pH值[（7.45 ± 0.05）vs.（7.45 ± 0.07）]、PaO₂ [（86.5 ± 7.3）mmHg vs.（88.3 ±6.7）mmHg]、PaCO₂ [（40.1 ± 7.5）mmHg vs.（39.4 ± 6.8）mmHg]及SpO₂ [（93.9 ± 2.4）% vs.（94.1 ± 2.0）%]水平比较,差异均无统计学意义（t = 0.222、0.468、0.420、0.348,P = 0.731、0.670、0.684、0.697）。与同组操作前比较,CPAP组和HFHCO组患者操作中心率[（86 ± 4）次/ min vs.（130 ± 3）次/ min,（87 ± 4）次/ min vs.（121 ± 3）次/ min,t = 9.826、9.612,P均< 0.001]、呼吸频率[（17.8 ± 2.5）次/ min vs.（26.1 ± 2.3）次/ min,（16.7 ± 2.9）次/ min vs.（21.3 ± 2.7）次/ min,t = 8.488、5.837,P均< 0.001]及平均动脉压[（78 ± 7）mmHg vs.（109 ± 8）mmHg,（77 ± 7）mmHg vs.（99 ± 7）mmHg,t = 9.104、8.224,P均< 0.001]及操作后PaO₂ [（67.8 ± 2.6）mmHg vs.（86.5 ± 7.3）mmHg,（68.9 ± 4.0）mmHg vs.（88.3 ± 6.7）mmHg,t = 7.126、6.395,P均< 0.001]水平均显著升高。两组患者在进行纤维支气管镜诊疗操作过程中均未发生严重出血、恶性心律失常、气胸等事件。 结论对于留置气管插管或气管切开留置套管的患者,在应用CPAP或HFHCO给氧方式下行纤维支气管镜操作时均可改善患者气道通气,提高患者PaO₂,但是HFHCO给氧方式下患者的舒适度更好,减轻了患者呼吸、血流动力学体征的明显波动。     

Mechanism of Atrial Fibrillation:

Atrial fibrillation (AF) has been associated with premature beats and decreased atrial conduction velocity. This study examined a new index of dynamic inter-atrial conduction time (iaCT) in patients with paroxysmal AF (PAF). We compared 42 consecutive patients with paroxysmal AF (mean age = 52 ± 16 years) without structural heart disease with 39 age-matched patients (mean age = 49 ± 15 years) who underwent ablation of junctional tachycardias. Prior to investigation, all antiarrhythmic drugs were discontinued for an appropriate period of time. The following measurements were made: baseline iaCT (iaCTb) between high right atrium (HRA) and distal coronary sinus, iaCT during HRA pacing S1S1 600 ms (iaCTS1), maximum prolongation of iaCT during S2 and S3 delivery (iaCTS2, iaCTS3). We then derived the decremental index (DI), the maximum percent prolongation of iaCT = iaCT S3-iaCTS1/iaCTS1%. In patients with PAF, iaCTb was 81.3 ± 24 ms versus 59.5 ± 14 ms in controls (P = 0.0001). Atrial fibrillation was reproducibly and easily induced with a prominent increase in iaCT in 11 patients with AF. In this subgroup DI was 92 ± 17%, compared to 45 ± 21% in the other patients with AF (P = 0.0001) and 21 ± 15% in the control group (P = 0.0001). Spontaneous isolated or repetitive ectopic activity was observed in 11 patients with AF (26%), and decremental atrial conduction was observed in 76% of patients with AF. This study supports the role of dynamic inter-atrial conduction disturbances in patients with lone PAF. The DI may be a new index of vulnerability to paroxysmal AF.     

Safety of Antitachycardia Pacing in Patients with Implantable Cardioverter Defibrillators and Severely Depressed Left Ventricular Function

The purpose of this study was to investigate the efficacy and safety of antitachycardia pacing (ATP) in third-generation implantable Cardioverter defibrillators (ICDs) for terminating spontaneously occurring ventricular tachycardias (VTs) in patients with severely depressed left ventricular (LV) function. Ninety-one patients with active ATP were followed for 16 ± 13 months. During this period, 775 VT episodes occurring in 36 patients were treated by ATP. The patients were divided into two groups according to their LV ejection fraction (LVEF): group A with LVEF ± 30% (n = 20), and group B with LVEF ± 30% (n = 16). There were no differences between both groups in age, gender, underlying heart disease, indication for ICD therapy, or drug therapy. The VT rates were comparable (group A: 183 ± 16 beats/min; group B: 180 ± 21 beats/min; P = NS). Eighty-three percent of all episodes (n = 332) in group A and 93% of the VTs (n = 443) in group B were ATP terminated (P ± 0.01). Ten percent of VTs in group A were accelerated by ATP into the ventricular fibrillation zone versus 2% in group B (P ± 0.01). The individual termination rate and acceleration rate per patient were comparable in both groups. All VT episodes unresponsive to ATP were converted by backup shocks. The efficacy of first-shock therapy was similar in both groups (group A: 89%; group B: 97%; P = NS). The proportion of patients who needed at least one backup shock for unsuccessful ATP was comparable in both groups (group A: 65%; group B: 56%; P= NS). We conclude that ATP is effective and safe in patients with recurrent VTs and severely depressed LV function, and it can be safely programmed in this group of patients to minimize the use of shock therapy.     

Prevention of Atrial Arrhythmias during DDD Pacing by Atrial Overdrive

We evaluated the effect of atrial overdrive on the incidence of atrial arrhythmias (AA) in 22 patients (67 ± 9 years. 7 women, 15 men) with Chorus 6234 DDD pacemakers. Atrial overdrive was defined as a programmed paced rate 10 ppm faster than the mean ventricular rate stored for the last 24-hour period in the pacemaker memory. The protocol consisted of three phases of 1 month each. Phase I: observation after discontinuation of antiarrhythmic therapy. Phase II: arrhythmia analysis using the pacemaker memory after programming the lower rate to 55 ppm. The fallback function and histogram data were used to document the number and maximal duration of AA episodes as well as the total AA time in a month. Phase III: atrial overdrive. The mean ventricular heart rate was 65 ± 4 beats/min before atrial overdrive versus 75 ± 5 with atrial overdrive (P = 0.02). At the end of phase II, all patients presented with AA episodes (mean number per patient: 42 ± 78 in one month). In phase III (with atrial overdrive), 14 (64.6%) patients had no recorded AA (group A). In the other eight patients with persistent AA episodes in phase III (group B), there was a significant reduction in the number of AA episodes (90 ± 106 in phase II vs 38 ± 87 in phase III; P = 0.01), their total duration (166 ± 115 in phase II vs 92 ± 134 hours in phase HI; P = 0.03) and their maximal duration (121 ± 103 in phase II vs 85 ± 89 min; P = 0.04). Our short-term data suggest tliat atrial overdrive prevents or reduces A A episodes and demonstrate the feasibility and need of long-term studies to determine whether this benefit is sustained.     

Atrial and Ventricular Pressures in Atrial Flutter

The hemodynamic effects of atrial flutter (AF) are unknown. The purpose of the present study was to investigate the changes in atrial and ventricular pressures after induction of AF. In 23 patients with paroxysmal AF (age 59 ± 9 years), a hemodynamic study was performed both during sinus rhythm and after induction of the tachyarrhythmia. During AF, 13 patients showed a fixed 2:1 AV conduction and 10 patients showed variable conduction. Mean right and left atrial pressures increased (P < 0.001) and right and left ventricular end-diastolic pressures decreased (P < 0.001) after induction of AF. Roth the increase in mean atrial pressures and the decrease in ventricular end-diastolic pressures were present either in the patients with fixed 2:1 AV (heart rate: 133 ± 15 beats/min) or in those with variable conduction (heart rate 96 ± 15 beats/min), but were more marked in the former. AF produces an impairment of atrial function, as evidenced by the increase in mean atrial pressures and reduction in ventricular end-diastolic pressures in the absence of an elevated heart rate. The mechanisms responsible for the increase in mean atrial pressures are unknown; however, atrial contractions against closed AV valves seem to play an important role.     

Hemodynamics of Idiopathic Paroxysmal Atrial Fibrillation

The hemodynamics of induced atrial fibrillation (AF) was investigated in 15 patients (ages 58 ± 11 years) with paroxysmal AF presenting without organic heart disease or hypertension. A hemodynamic study was performed both during sinus rhythm and after the induction of AF. The mean heart rate increased from 73 ± 11 to 128 ± 18 beats/min (P < 0.001) after AF. Systolic and mean aortic pressures did not significantly change, and diastolic aortic pressure increased (78 ± 11 vs 89 ± 12 mmHg, P < 0.01). Left ventricular enddiastolic pressure decreased during AF (9 ± 3 vs 6 ± 2.6 mmHg, P < 0.005), whereas mean pulmonary wedge pressure increased (8 ± 2 vs 12 ± 4 mmHg, P < 0.001). Systolic pulmonary arterial pressure did not show significant variations, and there was a slight but statistically significant increase in the diastolic and mean pulmonary arterial pressures (P < 0.01). The right ventricular end-diastolic pressure decreased during AF (5.6 ± 2 vs 3.8 ± 2 mmHg, P < 0.01 j, whereas mean right atrial pressure showed a trend toward an increase. Stroke volume markedly decreased (P < 0.001) while the cardiac index did not significantly change. Systemic vascular resistance, pulmonary arteriolar resistance, and the arteriovenous O₂ difference showed no significant variations after the induction of AF. These results suggest that in subjects without organic heart disease, paroxysmal AF is well tolerated hemodynamicaily, and the rise in the atrial pressures during AF is not related to an increase in the ventricular end-diastolic pressure.     

The risk profile for obstructive sleep apnea does not affect the recurrence of atrial fibrillation

BACKGROUND: Obstructive sleep apnea (OSA) has been linked to increased prevalence and recurrence of atrial fibrillation (AF). We hypothesized that OSA may aggravate AF in patients with pacemakers implanted for sinus bradycardia who had documented paroxysmal AF. METHODS: Seventy-two patients (36 M, aged 77 +/- 6 years) completed the study. All patients received a dual-chamber pacemaker equipped with diagnostic and preventive functions for AF. OSA was diagnosed with the Berlin Questionnaire, which is validated to identify patients with OSA. Four-month continuous pacemaker recordings were collected for all patients. RESULTS: OSA was diagnosed in 28% of patients. Patients at high risk for OSA (HR group) and patients at low risk for OSA (LR group) were equivalent for gender, age, and body mass index. The rate of hypertension was higher in HR than in LR group (90% vs 44%, P < 0.01). The prevalence of paroxysmal AF during the study period was similar in HR and LR group (53% vs 44%, P = NS). Overall number of AF episodes per month was not significantly different between HR and LR group (7 +/- 13 vs 36 +/- 122, P = NS). Similarly, AF burden (AF%) was not significantly different between HR and LR group (0.3 +/- 0.6 vs 2.0 +/- 4.8, P = NS). Circadian distribution of AF episodes was similar in both groups. CONCLUSION: Long-term pacemaker recording of AF recurrence, AF burden, and its circadian distribution is similar in patients with paroxysmal AF at high risk for OSA and those at low risk for OSA.     

Clinical Study of a New Activity Sensor for Rate Adaptive Pacing Controlled by Electrical Signals Generated by the Kinetic Energy of a Moving Magnetic Ball

A new rate adaptive pacemaker (Sensorithm) controlled by an activity sensor providing electrical signals induced by a magnetic ball moving freely in an elliptical cavity surrounded by two copper coils, was implanted in ten patients; mean age of 75 years (range 64–89). Six patients had atrioventricular block and four had sinus node disease. In auto-set testing procedure during a 1-minute walk in the corridor, a slope resulting in a maximum rate of 95 beats/min was selected in every patient, and a medium reaction time was programmed. During graded treadmill exercise tests the heart rate increased 63 ± 7 beats/min to 135 ± 6 beats/min in rate adaptive pacing mode (VVIR), and 15 ± 6 beats/min (P < 0.0001) in ventricular pacing mode (VVI). The symptom-limited exercise time was 9.1 ± 1.1 minutes and 8.2 ±1.2 minutes (P = NS), and the exercise distance was 501 ± 95 meters and 428 ± 92 meters (P < 0.05) in VVIR and VVI pacing mode, respectively. The maximum oxygen uptake was 20.6 ± 2.6 mL/kg per minute in VVIR pacing and 18.1 ± 2.1 mL/kg per minute (P < 0.05) in VVI pacing. The delay time until the pacing rate increased 10% of the total rate increase at onset of treadmill exercise was 4.4 ± 0.7 seconds. Assuming a linear relation between metabolic workload and heart rate response from rest to the age predicted maximum heart rate, a deviation of heart rate ranging from 13.5 ± 11.2% to –1.6 ± 5.2% from the expected heart rate at mid-point and endpoint of each quartile of workload was observed during treadmill testing. Conclusions : By using a 1 -minute walk test for selecting an appropriate slope setting, Sensorithm provided a significant and proportional heart rate increase during exercise resulting in an improvement of exercise capacity during VVIR pacing compared to VVI pacing.     

Sinus and paced P wave duration and dispersion as predictors of atrial fibrillation after pacemaker implantation in patients with isolated sick sinus syndrome

The aim of this study was to prospectively evaluate the sinus and the paced P wave duration and dispersion as predictors of AF after pacemaker implantation in patients with isolated sick sinus syndrome (SSS). The study included 109 (69 women, mean age 72 +/- 11 years) patients with SSS, 59 with bradycardia-tachycardia syndrome (BTS). A 12-lead ECG was recorded before pacemaker implantation and during high right atrial and septal right atrial pacing at 70 and 100 beats/min. The ECGs were scanned into a computer and analyzed on screen. The patients were treated with AAIR (n = 52) or DDDR pacing. The P wave duration was measured in each lead and mean P wave duration and P wave dispersion were calculated for each ECG. AF during follow-up was defined as: AF in an ECG at or between follow-up visits; an atrial high rate episode with a rate of > or =220 beats/min for > or =5 minutes, atrial sensing with a rate of > or =170 beats/min in > or =5% of total counted beats, mode-switching in >/=5% of total time recorded, or a mode switching episode of > or =5 minutes recorded by the pacemaker telemetry. The ECG parameters were correlated to AF during follow-up. Mean follow-up was 1.5 +/- 0.9 years. None of the ECG parameters differed between patients with AF and patients without AF during follow-up, nor was there any difference between groups after correction for BTS and age. BTS was the strongest predictor of AF during follow-up (P < 0.001). P wave duration and dispersion measured before and during pacemaker implantation were not predictive of AF after pacemaker implantation in patients with isolated SSS.     

Preprocedural ventricular rate predicts subsequent sick sinus syndrome after ablation for long-standing persistent atrial fibrillation

Background: Concealed sick sinus syndrome may become manifest after restoration of sinus rhythm by ablation in patients with long-standing persistent atrial fibrillation (AF). The purpose of this study was to investigate the association between the preprocedural ventricular rate during AF and sinus node function in patients with long-standing persistent AF. Methods: Consecutive patients (n = 102) who underwent ablation for long-standing persistent AF were enrolled. We measured the ventricular rate during AF before ablation in the absence of antiarrhythmic drugs. Sinus node function was assessed by electrophysiological study and serial Holter recordings after ablation. Results: Patients in the lowest quartile of ventricular rate during AF had longer corrected sinus node recovery time (1.06 ± 1.39 seconds) than those in the other quartiles (0.54 ± 0.31 seconds; P = 0.006) and lower mean heart rate on 24-hour Holter recording 3 months after ablation (68 ± 9 beats/min vs 75 ± 10 beats/min, P = 0.01). During a mean follow-up of 23 ± 10 months, sick sinus syndrome necessitating permanent pacemaker implantation developed in five (5%) patients, and multivariate analysis revealed that a low ventricular rate during AF rate was an independent risk factor for sick sinus syndrome (odds ratio = 0.90 for a 1 beat/min increase in AF rate, P = 0.04). Conclusions: A low preprocedural ventricular rate during AF indicates the existence of sinus node dysfunction after restoration of sinus rhythm by ablation in patients with long-standing persistent AF. (PACE 2012; 35:1074-1080).     

Adequacy of Pacing Rate During Exercise in Rate Responsive Ventricular Pacing

Our objective was to determint; the adequate pacing rate during exercise in ventricular pacing by measuring exercise capacity, cardiac output, and sinus node activity. Eighteen patients with complete AV block and an implanted pacemaker underwent cardiopulmonary exercise tests under three randomized pacing rates: fixed rate pacing (VVJ) at 60 beats/min and ventricular rate-responsive pacing (VVIR) programmed to attain a heart rate of about 110 beats/min ar 130 beats/min (VVIR 110 and VVIR 130, respectively) at the end of exercise. Compared with VVI and VVIR 130, VVIR 110 was associated with an increased peak oxygen uptake(VVIR 110:20.3 ± 4.5 vs VVI: 16.9 ± 3.1; P < 0.01; and VVIR 130: 19.0 ± 4.1 mL/min per kg, respectively; P < 0.05) and a higher oxygen uptake at anaerobic threshold (15.3 ± 2.7, 12.7 ± 1.9; P < 0.01, and 14.6 ± 2.6 mL/min per kg; P < 0.05). The atrial rate during exercise expressed as a percentage of the expected maximal heart rate was lower in VVIR 110 than in VVI or VVIR 130 (VVIR 110: 75.9%± 14.6% vs VVI: 90.6%± 12.8%; P < 0.01; VVIR 110 vs VVIR 130: 89.1%± 23.1%; P < 0.05). There was no significant difference in cardiac output at peak exercise between VVIR 110 and VVIR 130. We conclude that a pacing rate for submaximal exercise of 110 beats/min may be preferable to that of 130 beats/min in respect to exercise capacity and sympathetic nerve activity.     

Enhanced specificity of a dual chamber ICD arrhythmia detection algorithm by rate stability criteria

Inappropriate therapy remains an important limitation of implantable cardioverter defibrillators (ICD). PARAD+ was developed to increase the specificity conferred by the original PARAD detection algorithm in the detection of atrial fibrillation (AF). To compare the performances of the two different algorithms, we retrospectively analyzed all spontaneous and sustained episodes of AF and ventricular tachycardia (VT) documented by state-of-the-art ICDs programmed with PARAD or PARAD+ at the physicians' discretion. The results were stratified according to tachycardia rates <150 versus > or =150 beats/min. The study included 329 men and 48 women (64 +/- 10 years of age). PARAD was programmed in 263, and PARAD+ in 84 devices. During a mean follow-up of 11 +/- 3 months, 1,019 VT and 315 AF episodes were documented among 338 devices. For tachycardias with ventricular rates <150 beats/min, the sensitivity of PARAD versus PARAD+ was 96% versus 99% (NS), specificity 80% versus 93% (P < 0.002), positive predictive value (PPV) 94% versus 91% (NS), and negative predictive value (NPV) 86% versus 99% (P < 0.0001). In contrast, in the fast VT zone, the specificity and PPV of PARAD (95% versus 84% and 100% versus 96%) were higher than those of PARAD+ (NS, P < 0.001). Among 23 AF episodes treated in 16 patients, 3 episodes triggered an inappropriate shock in 3 patients, all in the PARAD population. PARAD+ significantly increased the ICD algorithm diagnostic specificity and NPV for AF in the slow VT zone without compromising patient safety.     

A Randomized, Single-Blind Crossover Comparison of the Effects of Chronic DDD and Dual Sensor VVIR Pacing Mode on Quality-of- Life and Cardiopulmonary Performance in Complete Heart Block

The aim of this study was to compare DDD and dual sensor VVIR (activity and QT) pacing modes in complete AV block (CAVB). Eighteen patients (14 men and 4 women, aged 70 ± 6.5 years) implanted with a dual chamber, dual sensor pacemaker for CAVB with normal sinus node chronotropic function were studied. A quality-of-life and cardiovascular symptom questionnaire, and a treadmill exercise test were completed after a period of VVIR and a period of DDD pacing, each lasting 1 month. Overall quality-of-life and cardiovascular symptoms did not significantly differ, though three patients felt discomfort during VVIR mode. There was no significant statistical difference in Cardiopulmonary parameters. DDD and VVIR modes yielded the following respective data: maximum heart rate = 105.7 ± 21.8 beats/minute versus 107.6 ± 21.6 beats/minute (NS); maximum workload = 60 ± 33.4 W versus 59.3 ± 37.8 W (NS); treadmill duration = 10.1 ± 3.8 minute versus 10.1 ± 3.6 minute (NS); oxygen consumption at anaerobic threshold = 14.6 ± 4.1 ml/kg per minute versus 14.9 ± 4.6 mL/kg per minute (NS); maximum minute ventilation = 49.6 ± 9 L/min versus 46 ± 12 L/min (NS); and respiratory quotient = 1.08 ± 0.15 versus 1.08 ± 0.13 (NS). We conclude that, during a 1-month follow-up period, no difference was found between DDD and dual sensor VVIR (QT and activity) pacing modes in CAVB patients with regard to quality-of-life and Cardiopulmonary performance, though a trend toward an increased sense of well being was noted with the DDD mode.