A Relationship Between Fluctuations in Heart Rate and The Duration of Subsequent Episodes of Atrial Fibrillation

A relationship between autonomic tone and the onset of paroxysmal atrial fibrillation in some patients is recognised Episodes of PAF may vary enormously in duration, however, from a few beats to many hours. Whether autonomic tone influences the duration of ihe episodes has been less well investigated.
From a database of Holter recording taken from patients with symptomatic PAF, we identified all episodes of at least 30 seconds duration which were preceded by noise free sinus rhythm. This study examined the heart rate prior to AF onset, the change in heart rate over the final minute of sinus rhythm and the time of AF onset, and compared the data from those episodes of AF of more than 5 minutes duration to the shorter ones. Heart rate was slower before long episodes of AF, but this was found to predominantly represent data from separate recordings. A highly significant rise in heart rate was detected prior to long AF episodes compared to shorter ones. Daytime AF episodes were slightly longer than nocturnal ones.
The most important finding was that longer AF episodes were typified by a heart rate acceleration. This suggests that, regardless of underlying aetiology, and increase in sympathetic tone may be important in the sustenance of episodes of PAF.     

Age and Gender Influences on Rate and Duration of Paroxysmal Atrial Fibrillation

The influence of age and gender on the character of paroxysmal atrial fibrillation (PAF) has not been described. Methods: The heart rate (HR) during PAF in patients receiving placebo or antiarrhythmic therapy was analyzed. Data from 177 24-hour Holter recordings were analyzed to mark the onset and termination of PAF and converted into RR interval files. PAF episodes lasting at least 2 minutes and containing ± 20% noise were included. HR during the first 30-second segment versus during the remainder of the episode, and the duration of PAF episodes were compared among groups of different ages and sex (Wilcoxon test). Results: 236 episodes from 55 recordings in 32 patients (all patients: 61.4 ± 12.8 years; men (19): 58.5 ± 12.6 years; women (13) 65.5 ± 12.4 years, P = ns for difference in age) fulfilled the inclusion criteria. Women had a higher mean heart rate at AF onset (123 ± 35 beats/min vs 115 ± 20 beats/min, P = 0.02) and during the remainder of the episode (120 ± 25 beats/min vs 112 ± 22 beats/min at the start, P = 0.01, and 116 ± 26 beats/min vs 108 ± 18 beats/min subsequently, P = 0.01). Episodes tended to be longer in women (mean 89.8 min vs 50.5 min, P = NS) and in the aged (mean 83.8 min vs 46.9 min, P = NS). Conclusion: PAF episodes are associated with faster heart rates and last longer in women, which may reflect differing autonomic responses to AF. A slower ventricular rate during PAF in older patients probably reflects an increasing prevalence of impaired atrioventricular conduction.     

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.     

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.     

Electrical Atrial Remodeling Assessed by Monophasic Action Potential and Atrial Refractoriness in Patients with Structural Heart Disease

The present study was performed to assess the effect of induced atrial fibrillation (AF) on atrial monophasic action potentials (MAPs) and atrial refractory period (ERP) in patients with structural heart disease. An electrode MAP catheter was placed in the right atrium to continuously measure atrial potential duration (APD₉₀) in 13 patients (coronary artery disease, 10 patients; dilated cardiomyopathy, 2 patients; hypertrophic cardiomyopathy, 1 patient) without spontaneous AF episodes. AF was induced by rapid atrial stimulation (300–1500/min). If sinus rhythm returned within 10 minutes, AF was reinduced. The atrial ERP was measured during atrial pacing at a basic cycle length of 550 ms before AF induction and after its conversion. Results: The mean atrial ERP and the atrial APD₉₀ before AF was 242 ± 34 ms and 256 ± 23 ms, respectively. ERP and APD_go shortening was observed after 3 minutes of AF. After 11 ± 0.5 min (10 min 20 s-13 min 10 s) of AF, ERP and APD₉₀ reached their minimal values of 72%± 13% and 71%± 10% of baseline, respectively. ERP and APD₉₀ returned to their initial values within 10 minutes after conversion of AF. A tendency toward longer duration of consecutive AF episodes and facilitation of their induction was observed. Conclusion: The present study confirms that short episodes of AF modify the electrophysiological properties of the atria in humans. In patients with structural heart disease, induced atrial fibrillation shortens the atrial ERP as well as the atrial APD₉₀. The changes were reversible within 10 minutes after arrhythmia termination.     

Paroxysmal atrial fibrillation: ectopic atrial activity and prevalence of severely symptomatic patients

Catheter ablation is a promising approach in severely symptomatic patients with paroxysmal atrial fibrillation (PAF). Until this time it has only been performed in highly selected patients with weekly episodes and frequent premature atrial contractions (PACs). The aim of the present study was to estimate the prevalence of severely symptomatic patients with PAF and to evaluate the significance of PACs. The files of 7,447 consecutive patients were screened and 1,357 PAF patients identified. Holter recordings were performed in 108 patients with >/=2 spontaneous AF episodes. Despite antiarrhythmic treatment, 6.5% (1.8-11.1%) had a history of weekly PAF episodes. 29.2% of patients and 10% of healthy, age-matched controls had more than 700 PACs. The number of PACs was inversely related to the reported numbers of previous episodes and directly related to age and size of left atrium. We estimate that about 6.5% of patients with PAF are severely symptomatic and might benefit from catheter ablation. Our data suggest that the number of PACs should not be used as a selection criterion for catheter ablation. Frequent PACs are seen in a substantial proportion of elderly healthy individuals.     

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.     

Circadian variation in ventricular tachycardia and atrial fibrillation in a medical-cardiological ICU

OBJECTIVE: To assess the diurnal distribution of ventricular tachycardia (VT) and atrial fibrillation (AF) in critically ill patients. DESIGN AND SETTING: Prospective observational study (episode-based design) in an eight-bed medical/cardiological ICU at a university hospital that also admits postoperative patients. PATIENTS: 98 consecutive patients with AF ( n=55) or ventricular tachycardia ( n=43). MEASUREMENTS AND RESULTS: There were a total of 218 arrhythmia episodes (83 AF, 136 VT). The time of arrhythmia onset was not evenly distributed. Circadian variation in VT but not AF onset was well represented by a sine wave function. Both VT and AF fibrillation showed a trough during the night. The distribution of VT and AF episodes did not differ significantly with or without analgosedation. CONCLUSIONS: In critically ill patients the onset of VT and AF over 24-h is nonuniformly distributed. In VT this circadian pattern of occurrence is well modeled by a sine wave function peaking between noon and 2 p.m. The circadian pattern is less clear for AF. The circadian variation is seen irrespective of the presence of absence of analgosedation for both arrhythmias.     

Electrophysiological differences of the spontaneous onset of paroxysmal and persistent atrial fibrillation

BACKGROUND: Information about the spatiotemporal organization of atrial activity at the onset of atrial fibrillation (AF) is still limited. METHODS: AF mapping was performed in 30 patients with AF (mean age 53 +/- 9 years, 26 males) by deploying a noncontact mapping balloon in the left atrium (LA). Twenty-four patients had paroxysmal AF and six patients had persistent AF. Three types of AF episodes were analyzed: nonsustained AF (lasting 30 seconds, with spontaneous conversion or requiring internal cardioversion and subsequent stable sinus rhythm), and persistent AF episodes (stable sinus rhythm lasting 相似文献   

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.     

Acute sleep deprivation is associated with increased electrocardiographic P-wave dispersion in healthy young men and women

Background: Sleep deprivation (SD) is associated with worse cardiovascular outcome including mortality. Prolonged P-wave duration and P-wave dispersion (Pd) are known to represent inhomogeneous conduction of sinus impulses and are known to be electrophysiologic predictors of atrial fibrillation. Pd in normal subjects has been reported to be influenced by the autonomic tone. Because autonomic tone is affected by sleep and sleep duration, we evaluated the effect of acute SD on P-wave duration and Pd in healthy young adults and whether the effect was gender selective.
Methods : We obtained electrocardiograms of 37 healthy young volunteers (age: 28.45 ± 7.97; 11 women) after a night of regular sleep and repeated after a night with sleep debt. We measured minimum and maximum P-wave durations (Pmin, Pmax) and Pd in milliseconds.
Results : Average sleep time of the subjects were 7.7 ± 0.8 hours during regular sleep and 1.7 ± 1.6 hours during a night of sleep debt (P < 0.001). Subjects had significantly lower values of Pmin in milliseconds after a night of sleep debt when compared to regular sleep (65.13 ± 8.03 vs 74.86 ± 10.95; P < 0.001), whereas they had significantly higher values of Pmax and Pd (102.16 ± 9.46 vs 95.13 ± 11.21; P < 0.001 and 37.02 ± 8.11 vs 20.27 ± 11.42; P < 0.001, respectively). In Pearson's correlation analysis Pmin was positively and Pmax and Pd were negatively correlated with sleep time (P < 0.001, r = 0.465; P = 0.003, r =−0.336 and P < 0.001, r =–0.698 respectively). Effect of SD on P-wave duration and Pd was similar for both men and women.
Conclusions : In conclusion, prolongation of Pmax and Pd in acute SD suggests that acute SD might contribute to development and/or recurrence of atrial fibrillation.     

Mode Switch Despite Undersensing of Atrial Fibrillation in ODD Pacing

Mode switching algorithms are commonly used to protect the ventricles against high rates induced by atrial tachycardia. In the case of atrial fibrillation (AF), the response of these algorithms depends on the quality of atrial sensing. The Chorum 7234 DDDR pacemaker uses a new mode switching algorithm, based on a statistical analysis of the atrial rhythm. It includes two criteria of diagnosis: "high" if more than 28 of 32 cycles are abnormally accelerated; and "low" if more than 36 of 64 cycles are abnormally accelerated. Methods: From a taped database of electrophysiological studies, episodes of AF lasting more than 2 minutes were selected. A tape recorder replayed the atrial signals into an external Chorum device. Each episode was replayed eight times with a programmed atrial sensitivity increasing from 0.4 –2.0 mV. For each criterion of diagnosis and each programmed sensitivity, the percentage of atrial sensing, the time to switching, and the mean ventricular rate were measured. Ten episodes of AF from 10 patients (9 men and 1 woman; ages 62 ± 16 years) were included: 1.95 ± 0.97 mV and 196 ± 64 ms. The sensitivity of the algorithm to diagnose atrial tachycardia reached 100%, for an atrial sensitivity set between 0.4 and 1.0 mV. The mean percentages of atrial sensed events were 74%± 18% and 46%± 9% for the "high" and "low" criteria, respectively. The mean diagnostic times were 28 ± 26 seconds and 68 ± 27 seconds, respectively. Sensing of < 23% of AF events resulted in failure to diagnose the arrhythmias by both algorithms. In the event of diagnostic failure, the mean ventricular pacing rate was 79 ± 9 ppm. Conclusion: Up to an atrial sensitivity of 1 mV, 100% of AF episodes were diagnosed. The Chorum mode switching algorithms are 100% reliable if > 45% of the AF waves are sensed. In the event of switching failure, the ventricle is protected by an average rate remaining below 80 ppm. (PACE 1996;     

Impact of premature atrial contractions in atrial fibrillation

In spite of the increasing knowledge about paroxysmal atrial fibrillation (PAF), details on mode of initiation in unselected patients are scarce. This paper focuses on trigger mechanisms of spontaneous onset of AF in consecutive patients with PAF. One hundred eight consecutive patients with two or more ECG documented AF episodes within the previous year had a 24-hours Holter recording performed. All AF episodes (n = 157) were reviewed and, within the last 10 beats prior to AF initiation. PP intervals were measured on 25 mm/s paper printouts and premature atrial contractions (PACs) were counted. Additionally, randomly selected coupling intervals (PP') for PACs not triggering AF were measured and compared to AF triggering intervals and to PP' intervals from healthy controls. PACs preceded all AF episodes. AF initiation displayed a wide variety in terms of PP coupling intervals and number of PACs prior to initiation within and between subjects. In episodes with PACs within the last 10 beats prior to initiation, we observed a long-short PP sequence at the time of initiation. Mean PP' interval (+/- SE) for AF triggering PACs was 403 +/- 9 ms, significantly shorter, P < 0.0001, than PP' for nontriggering PACs (584 +/- 8 ms) and PACs in healthy controls (589 +/- 6 ms). However, a large proportion of nontriggering PACs had short PP' coupling intervals without triggering AF. These observations highlight the importance of other factors than the trigger per se, such as the arrhythmogenic substrate, and suggest that therapeutic maneuvers aimed at curing PAF should target these as well as the trigger mechanisms.     

Long-Term Follow-Up After Right Atrial Radiofrequency Catheter Treatment of Paroxysmal Atrial Fibrillation

Catheter ablation of paroxysmal atrial fibrillation using long linear lesions in the right atrium is still under investigation, and its long-term follow-up is unknown. Methods: Thirty-six men and nine women (aged 51 ± 12 years) with symptomatic daily episodes of AF for 6 ± 5 years despite the use of 4.7 ± 1.5 antiarrhythmic drugs were studied between July 1994 and January 1996. Progressively longer ablation lines were performed in 3 groups of 15 consecutive patients each, using a 14-electrode catheter or a single-electrode dragging technique. Success was defined as atrial fibrillation elimination or recurrence for no longer than 6 hours over 3 months of observation. Patients who had fewer than 6 hours of atrial fibrillation per month were considered "improved." Medium- (11 ± 4 months) and long-term (26 ± 5 months) results were assessed clinically from a patient's diary and from Holter recordings. Results: After a follow-up of 11 months, 24 patients had a favorable result of the ablation procedure with or without additional antiarrhythmic drug therapy, representing 53% of the original cohort. After 26 ± 5 months of follow-up, these successful results were reduced to 17 patients (37%). Conclusions: After linear atrial ablation, a significant long-term attrition of arrhythmia-free patients was observed. This may be due to a combination of disease progression, incomplete linear block, and ineffective ablation of arrhythmogenic triggers.     

Observations From Intraatrial Recordings on the Termination of Electrically Induced Atrial Fibrillation in Humans

Background: The circulating wavelet hypothesis suggests that atrial fibrillation could terminate by either progressive fusion or simultaneous block of all wavelets. Methods: Intraatrial recordings from the right atrial free wall were made during procainamide induced (n = 8) or spontaneous (n = 7) termination of electrically induced atrial fibrillation in 14 patients. Atrial rate, mean magnitude squared coherence, and direction of activation during sequential electrograms were measured. Rate and coherence were calculated from the earliest point within 5 minutes prior to termination as well as from the 4-second interval just prior to termination. Results: Termination was directly to sinus rhythm (13 episodes) or to atrial flutter (2 episodes). For the eight procainamide induced terminations, rate decreased between the first measurement and the measurement just prior to termination, from 443 ±127 beats/ min to 322 ± 119 beats/min. For the seven spontaneous terminations, rate also decreased from 373 ± 119 beats/min to 323 ± 88 beats/min; however, a slight increase in atrial rate prior to termination was observed in three episodes. No specific patterns of atrial cycle lengths were seen during the final few seconds of fibrillation. No increase in coherence was observed. In seven episodes, recordings were made using orthogonal bipoles in the x, y, and z directions, allowing direction of activation of wavefronts to be measured. Three episodes showed multiple instances where direction of activation remained similar over several electrograms as we have previously reported for chronic fibrillation. However, no such instances precipitated termination in any of the seven episodes. Conclusions: Atrial fibrillation usually terminates directly to sinus rhythm and does so abruptly and without forewarning. While we and others have previously reported that the rate of atrial fibrillation decreases with procainamide infusion, a decrease in the rate of atrial fibrillation is not required for the rhythm to terminate and consequently may not be a part of the termination process at all. Coherence does not demonstrate a progressive increase in the organization of atrial fibrillation prior to termination. Lack of stabilization in the direction of activation of wavefronts in the final few seconds also fails to support fusion of wavefronts as the mechanism of termination of atrial fibrillation. Simultaneous block of all wavelets is consistent with, but not proven by our observations.     

Spontaneous Reinitiation of Atrial Fibrillation Following Transvenous Atrial Defibrillation

Spontaneous reinitiation of atrial fibrillation (AF) has not been systematically looked at in patients undergoing transvenous AF. This study involved 11 patients, the mean age 60 ± 8 years. 3 male and 8 female, in whom transvenous atrial defibrillation successfully converted AF to sinus rhythm. Eight patients had paroxysmal AF and three patients had chronic persistent AF for 4 weeks or more. Four patients were taking antiarrhythmic medications at the time of testing. Multipolar transvenous catheters were positioned inside the coronary sinus, right atrium, and the right ventricle. Atrial defibrillation testing was performed using the METRIX atrial defibrillation system in nine patients and the Ventritex HVSO2 in the remaining two patients. A total of 64 therapeutic shocks (range 3–11) were delivered in the 11 patients, and 31 of these successfully converted AF to sinus rhythm. In four patients spontaneous AF was reinitiated following 12 successful transvenous atrial defibrillation episodes. The mean time to reinitiation of AF following shock delivery and restoration of sinus rhythm was 8.26 ± 5.25 seconds, range 1.8–19.9 seconds. All 12 episodes of spontaneous AF were preceded by a spontaneous premature atrial complex. The coupling interval of the premature atrial complexes was 443 ± 43 ms, range 390–510 ms. None of the patients taking antiarrhythmic medications or those demonstrating no premature atrial complexes had spontaneous reinitiation of AF. In conclusion, spontaneous reinitiation of AF can occur in a significant proportion of patients with AE undergoing transvenous atrial defibrillation. This phenomenon is preceded by the occurrence of atrial premature complex. Findings of this study may have significant clinical implications.(PACE 1998; 21:1105–1110)     

Frequent and prolonged asymptomatic episodes of paroxysmal atrial fibrillation revealed by automatic long-term event recorders in patients with a negative 24-hour Holter

The presence, frequency, and duration of episodes of paroxysmal atrial fibrillation (PAF) is difficult to establish. This is caused by the limited duration of standard Holter recordings and to the unsatisfactory yield of patient-triggered event recorders, because of asymptomatic events and of an inconsistent use of the patient dependent triggering function. A prospective cohort of 65 consecutive patients with recurrent palpitations and a negative 24-hour ECG Holter was investigated by means of a cardiac event recorder bearing continuous automatic arrhythmia analysis and storage. Over a mean duration of 77 +/- 36 hours, episodes of PAF were diagnosed in 20 (31%) patients, who had a total of 37 episodes; mean duration of PAF episodes was 7 hours 50 minutes +/- 8/hours 45 minutes (minimum 45 minutes, maximum 28 hours). Eleven (55%) of these 20 patients were asymptomatic and would have remained undiagnosed without the automatic mode of the event recorder. Asymptomatic PAF episodes were longer than symptomatic ones (10 hours 30 minutes +/- 6 hours 30 minutes vs 4 hours 50 minutes +/- 4 hours, P < 0.05). In addition, episodes of sustained paroxysmal supraventricular tachycardia (PSVT) were diagnosed in 39 (57%) patients, of whom 34 (87%) were symptomatic. In this prospective cohort, a second standard 24-hour monitoring would have missed 44% of the patients with PAF or PSVT and a classical patient-triggered event recorder 13%. In patients still complaining of palpitations after one negative 24-hour Holter, numerous, prolonged, and often asymptomatic episodes of PAF can be revealed by long-term automatic event recorders. These devices should help clarify the clinical consequences of such episodes.     

Impact of the Preprocedural Frequency of Paroxysmal Atrial Fibrillation on the Clinical Outcome after Catheter Ablation

Background: Pulmonary vein antral isolation (PVAI) is a recommended treatment for symptomatic drug‐refractory paroxysmal atrial fibrillation (PAF). PAF naturally progresses toward persistent AF with an increase in the frequency and duration of AF. The objective of this study was to evaluate whether the preprocedural AF frequency had an impact on the AF recurrence after PVAI in patients with symptomatic PAF. Methods and Results: A total of 362 consecutive patients (61.0 ± 9.8 years; 274 males) with drug‐refractory PAF who underwent PVAI were included. The preprocedural frequency of PAF was daily, weekly, monthly, and yearly in 145 (40.1%), 112 (30.9%), 90 (24.9%), and 15 (4.1%) patients, respectively. There were no significant differences in any of the preprocedural variables between the four groups, except for the number of ineffective antiarrhythmic drugs (AADs). PVAI was successfully performed in all patients. At 12 months after the initial procedure, 63.5% of the entire group of patients were free of AF recurrences without any AADs, respectively. A Cox regression multivariate analysis of the variables including the AF frequency, age, gender, duration of AF, presence of hypertension or structural heart disease, left atrial size, left ventricular ejection fraction, and body mass index demonstrated that the AF frequency was not an independent predictor of AF recurrence after a single ablation procedure (P = 0.194). Conclusions: This study demonstrated that the preprocedural AF frequency did not predict AF recurrence after PVAI in patients with PAF. From the clinical point of view, an additional AF classification based on the preprocedural AF frequency might not be valuable in patients undergoing PVAI. (PACE 2012; 35:1236–1241)     

Maintenance of Atrial Fibrillation in Anesthetized and Unanesthetized Sheep Using Cholinergic Drive

Atrial fibrillation (AF) was induced electrically and the duration of AF was measured in six isoflurane-anesthetized sheep (weight range 54.5–72.7 kg), and in five Unanesthetized sheep (weight range 60–75 kg). In the anesthetized sheep, AF was induced by direct electrical stimulation of the right atrium with a catheter electrode and the duration of AF was determined. Intravenous neostig- mine (10 fig/kg IV) was administered and the duration of AF was again measured. Then cholinergic drive was increased by bilateral electrical vagal stimulation; AF was induced and the duration of AF was measured. In the anesthetized animals with no neostigmine or vagal stimulation, 34% of the episodes of AF lasted 10 seconds, 11% lasted 20 seconds, and only 1 % lasted 200 seconds. However, in one anesthetized animal AF was sustained for 4,800 seconds with no drug or vagal support. The administration of neostigmine alone in 3 anesthetized animals more than doubled the average duration of AF. In the animals with vagal stimulation (after neostigmine), AF persisted throughout stimulation, but ceased shortly after vagal stimulation was terminated at 2,220, 4,500, and 3,840 seconds. The AF frequency ranged from 325–750/min. The Unanesthetized sheep were lightly sedated with a small dose (200 fig/kg IM) of xylazine to make them less sensitive to environmental noise; then AF was induced and its duration was timed. After these measurements, neostigmine was administered (30 μg/kg IM) and cholinergic drive was produced reflexly by intravenous injection of 60–2,000 fig of phenylephrine. AF was electrically induced at the time of maximum reflex slowing in heart rate. For the control (no drug! studies, 64% of the AF episodes lasted 10 seconds, 20% lasted 20 seconds, and only 2% of the episodes lasted as long as 140 seconds. When phenylephrine was injected after neostigmine to provide increased cholinergic drive, the duration of fibrillation depended on the dose of phenylephrine. In a 60-kg sheep, the duration of AF increased from 1 second with an intravenous dose of 60 μg to 700 seconds with an intravenous dose of 2,000 μg. However, there was a considerable range in responsiveness to the reflex cholinergic drive provided by the intravenous phenylephrine; for example a single intravenous 500-μg dose produced AF ranging from 190–540 seconds among the sheep. The duration of AF was most controllable in the anesthetized sheep, following neostigmine administration and with bilateral vagal stimulation. In the Unanesthetized sheep, AF could generally be sustained for more than the duration of the half-life (about 4 minutes) of phenylephrine following neostigmine. However, there was a large variation in the duration of AF among the animals for the same dose of phenylephrine. This study identifies two methods (direct vagal stimulation and reflex vagal stimulation) for providing the cholinergic drive needed to sustain AF in the adult sheep. The duration of AF is sufficiently long to enable the measurement of electrical atrial defibriilation threshold.