Atrioverter: an implantable device for the treatment of atrial fibrillation

BACKGROUND: During atrial fibrillation, electrophysiological changes occur in atrial tissue that favor the maintenance of the arrhythmia and facilitate recurrence after conversion to sinus rhythm. An implantable defibrillator connected to right atrial and coronary sinus defibrillation leads allows prompt restoration of sinus rhythm by a low-energy shock. The safety and efficacy of this system, called the Atrioverter, were evaluated in a prospective, multicenter study. METHODS AND RESULTS: The study included 51 patients with recurrent atrial fibrillation who had not responded to antiarrhythmic drugs, were in New York Heart Association Heart failure class I or II, and were at low risk for ventricular arrhythmias. The atrial defibrillation threshold had to be 相似文献   

Monetary compensation for plasma donors: a record of safety

BACKGROUND: Atrial fibrillation (AF) is the most common arrhythmia after open heart surgery. Traditional treatment with a range of antiarrhythmic drugs and electrical cardioversion is associated with considerable side effects. The aim of this study was to examine the feasibility and efficacy of low-energy atrial defibrillation with temporary epicardial defibrillation wire electrodes. METHODS AND RESULTS: Epicardial defibrillation wire electrodes were placed at the left and right atria during open heart surgery in 100 consecutive patients (age 65+/-9 years; male to female ratio 67:23). Electrophysiological studies performed postoperatively revealed a test shock (0.3 J) impedance of 96+/-12 omega (monophasic) and 97+/-13 omega (biphasic). During their hospital stay, AF occurred in 23 patients (23%) at 2.1+/-1.3 days postoperatively. Internal atrial defibrillation was performed in 20 patients. Of these patients, 80% (16/20) were successfully cardioverted with a mean energy of 5.2+/-3 J. Early recurrence of AF (< or =60 seconds after defibrillation) developed in 8 patients. Five patients had multiple episodes of AF. In total, 35 episodes of AF were treated, with an 88% success rate. Only 6 patients (30%) required sedation. No complications were observed with shock application or with lead extraction. CONCLUSIONS: Atrial defibrillation with temporary epicardial wire electrodes can be performed safely and effectively in patients after cardiac operations. The shock energy required to restore sinus rhythm is low. Thus, patients can be cardioverted without anesthesia.     

Clinical shock tolerability and effect of different right atrial electrode locations on efficacy of low energy human transvenous atrial defibrillation using an implantable lead system

OBJECTIVES: The objectives of this study were 1) to evaluate the effect of different right atrial electrode locations on the efficacy of low energy transvenous defibrillation with an implantable lead system; and 2) to qualitate and quantify the discomfort from atrial defibrillation shocks delivered by a clinically relevant method. BACKGROUND: Biatrial shocks result in the lowest thresholds for transvenous atrial defibrillation, but the optimal right atrial and coronary sinus electrode locations for defibrillation efficacy in humans have not been defined. METHODS: Twenty-eight patients (17 men, 11 women) with chronic atrial fibrillation (AF) (lasting > or = 1 month) were studied. Transvenous atrial defibrillation was performed by delivering R wave-synchronized biphasic shocks with incremental shock levels (from 180 to 400 V in steps of 40 V). Different electrode location combinations were used and tested randomly: the anterolateral, inferomedial right atrium or high right atrial appendage to the distal coronary sinus. Defibrillation thresholds were defined in duplicate by using the step-up protocol. Pain perception of shock delivery was assessed by using a purpose-designed questionnaire; sedation was given when the shock level was unacceptable (tolerability threshold). RESULTS: Sinus rhythm was restored in 26 of 28 patients by using at least one of the right atrial electrode locations tested. The conversion rate with the anterolateral right atrial location (21 [81%] of 26) was higher than that with the inferomedial right atrial location (8 [50%] of 16, p < 0.05) but similar to that with the high right atrial appendage location (16 [89%] of 18, p > 0.05). The mean defibrillation thresholds for the high right atrial appendage, anterolateral right atrium and inferomedial right atrium were all significantly different with respect to energy (3.9 +/- 1.8 J vs. 4.6 +/- 1.8 J vs. 6.0 +/- 1.7 J, respectively, p < 0.05) and voltage (317 +/- 77 V vs. 348 +/- 70 V vs. 396 +/- 66 V, respectively, p < 0.05). Patients tolerated a mean of 3.4 +/- 2 shocks with a tolerability threshold of 255 +/- 60 V, 2.5 +/- 1.3 J. CONCLUSIONS: Low energy transvenous defibrillation with an implantable defibrillation lead system is an effective treatment for AF. Most patients can tolerate two to three shocks, and, when the starting shock level (180 V) is close to the defibrillation threshold, they can tolerate on average a shock level of 260 V without sedation. Electrodes should be positioned in the distal coronary sinus and in the high right atrial appendage to achieve the lowest defibrillation threshold, although other locations may be suitable for certain patients.     

Radiofrequency catheter ablation in type I atrial flutter: preliminary experience of 10 cases

Common atrial flutter results from macroreentry in the right atrium. Catheter ablation of slow conduction, between tricuspid annulus and inferior vena cava (TA-IVC) or tricuspid annulus and coronary sinus ostium (TA-CS os) has been reported to terminate and prevent recurrence of this arrhythmia. We reported 10 consecutive patients, 7 men and 3 women, who underwent radiofrequency catheter ablation of common atrial flutter. The mean age was 59.4 +/- 11.2 years (range 42-82 years). During the paroxysmal atrial flutter, all patients had palpitation, 4 had dyspnea on exertion, 3 patients had syncope and 1 patient had presyncope. The mean duration of symptoms was 5.7 +/- 4.9 years (range 0.5-13 years). Two patients had dilated cardiomyopathy, 1 Ebstein's anomaly and 1 chronic obstructive pulmonary disease. Four patients (40%) had history of atrial fibrillation (AF) before ablation. The mean cycle length of atrial rhythm was 257.2 +/- 36.6 ms. Ablation was done by anatomical approach and could terminate arrhythmia in 9 patients (90%), 7 from TA-IVC, 2 from TA-CS os without major complication. The mean number of applications was 20.4 +/- 16.9 and turned atrial flutter to normal sinus rhythm in 13.5 +/- 10.7 seconds. Fluoroscopic and procedure times were 38.4 +/- 31.4 and 157.2 +/- 68.8 minutes, respectively. During the follow-up period of 24.0 +/- 28.7 weeks, 2 patients had recurrent atrial arrhythmia, 1 atrial fibrillation and 1 atrial flutter type I, giving the final success rate of 70 per cent. All patients who had recurrence or failure had a history of paroxysmal AF before ablation. In conclusion, radiofrequency catheter ablation in atrial flutter type I, using anatomical approach, is an effective treatment to terminate and prevent this arrhythmia in short term follow-up. It may be considered as an alternative treatment in patients with atrial flutter who were refractory to antiarrhythmic agents.     

An Italian experience of radiofrequency transcatheter ablation in type-I atrial flutter: the results and follow-up

BACKGROUND: Type I atrial flutter (AF) is a supraventricular tachycardia that is notoriously disabling and resistant to antiarrhythmic drugs. The introduction of an effective non-pharmacologic technique, such as radiofrequency catheter ablation (RF), opened new therapeutic prospects for the management of this arrhythmia. The aim of our study was to evaluate the long-term efficacy of atrial flutter RF using a successful procedure marker of bi-directional conduction block in the isthmus. METHODS: In the last consecutive 50 patients (pts) who underwent RF procedure for AF at our Center (46 pts during spontaneous or induced AF and 4 in sinus rhythm) after the successful interruption of AF we performed the usual reinduction attempts and well atrial pacing from 2 sites in the right atrium (in 18 pts before and after RF and in 32 only after RF). The sites of pacing were site 1: low lateral right atrium (LRA); site 2: proximal coronary sinus (PCS). The 50 pts consisted of 13 females, 37 males with a mean age of 62.5 +/- 9.7 years (35-83). The end-point for the procedure was: 1) abrupt interruption of AF; 2) inability to reinduce AF; 3) recognition of atrial activation sequence during pacing in LRA and in PCS compatible with conduction block in the isthmus. RESULTS: The RF was successful in terminating AF in all pts after 11 +/- 7 applications of energy. After ablation, sustained AF was no longer inducible by atrial pacing. After RF, during pacing in sinus rhythm from LRA, the lower septum and PCS presented a delayed activation after the His region. Similarly, during pacing from PCS after ablation, the atrial activation sequence was modified: the low lateral right atrium was now activated by a single front after the high lateral atrium. No acute complications were noted in any pts during or after procedure. AF recurred in 9 pts. Four pts now present chronic atrial fibrillation. The mean follow-up period is 14.8 +/- 8 months. All the patients were discharged without antiarrhythmic therapy. CONCLUSIONS: The mechanism of successful ablation is the bi-directional conduction block in the isthmus with the evidence of the changes in the right atrial activation sequence during atrial pacing in sinus rhythm in LRA and in PCS before and after RF.     

Implantable atrial defibrillator for atrial fibrillation

Atrial fibrillation is a common problem. Pharmacological and nonpharmacological approaches have limited therapeutic efficacy in many patients. Low energy transvenous atrial defibrillation using catheters positioned inside the right atrium and cornonary sinus has been shown to be efficacious in converting atrial fibrillation to sinus rhythm. We report the successful use of this technology in an implantable form in a patient with symptomatic atrial fibrillation. The patient could be kept in sinus rhythm using an implanted atrial defibrillator.     

Effects of left atrial dilatation on the endocardial atrial defibrillation threshold: a study in an ovine model of pacing induced dilated cardiomyopathy

Left atrial (LA) dilation is a common finding in patients with chronic atrial fibrillation (AF). Progressive dilatation may alter the atrial defibrillation threshold (ADFT). In our study, epicardial electrodes were implanted on the LA free wall and right ventricular apex of eight adult sheep. Large surface area, coiled endocardial electrodes were positioned in the coronary sinus and right atrium (RA). LA dilatation was induced by rapid ventricular pacing (190 beats/min) for 6 weeks and echocardiographically assessed weekly along with the ADFT (under propofol anesthesia). LA effective refractory period (ERP) was measured every 2-3 days using a standard extra stimulus technique and 400 ms drive. The AF cycle length (AFCL) was assessed from LA electrograms. During the 6 weeks of pacing the mean LA area increased from 6.1 +/- 1.5 to 21.3 +/- 2.4 cm2. There were no significant changes in the mean ADFT (122 +/- 15 V), circuit impedance (46 +/- 5 omega), or LA AFCL (136 +/- 23 ms). There was a significant increase in the mean LA ERP (106 +/- 10 ms at day 0, and 120 +/- 13 ms at day 42 of pacing). In this study, using chronically implanted defibrillation leads, the minimal energy requirements for successful AF were not significantly altered by ongoing left atrial dilatation. This finding is a further endorsement of the efficiency of the coronary sinus/RA shock vector. Furthermore, the apparent stability of the AF present may be a further indication of a link between the type of AF and the ADFT.     

Power spectral analysis of heart period variability of preceding sinus rhythm before initiation of paroxysmal atrial fibrillation

Time domain analysis of heart period variability in patients without structural heart disease demonstrated increased parasympathetic modulation before paroxysmal atrial fibrillation (AF) occurring predominantly at night. However, diurnal differences in autonomic activity preceding AF episodes in a diverse patient population have not been assessed. Accordingly, we performed spectral analysis of heart period variability on Holter recordings during sinus rhythm preceding AF in 29 patients, 17 with night and 12 with day episodes. Samples taken 5, 10, and 20 minutes before AF onset were compared. Normalized high-frequency (HF) spectral power change was greater when comparing the interval 10 to 5 minutes with 20 to 10 minutes preceding AF in 26 of 29 patients (0.09 +/- 0.07 vs 0.03 +/- 0.02; p < 0.0001). HF spectral power increased before 3 of 12 AF episodes during the day compared with 15 of 17 AF episodes during the night (p = 0.001). Nocturnal AF episodes were preceded by increased HF spectral power in the 5- versus the 20-minute sample expressed as natural logarithm-transformed values (5.6 +/- 4.8 vs 4.2 +/- 4.0; p < 0.005) and normalized values (0.19 +/- 0.09 vs 0.10 +/- 0.07; p < 0.02), a decrease in low-frequency/HF ratio (1.05 +/- 0.61 vs 2.21 +/- 1.75; p < 0.05) and heart rate (60 +/- 13 vs 71 +/- 13 beats/min; p = 0.06). Structural heart disease was more common with daytime than nocturnal AF episodes (58% vs 18%, p < 0.05). In conclusion, HF spectral power change was increased preceding most AF episodes. However, diurnal differences were demonstrated. Contrary to daytime AF, increased parasympathetic activity preceded predominantly nocturnal AF, mostly in younger patients with structurally normal hearts.     

Atrial vulnerability in patients with paroxysmal "lone" atrial fibrillation

Little is known about the electrophysiological properties of the atrium predisposing to paroxysmal atrial fibrillation (AF), especially in patients without structural heart disease. This study was conducted to analyze intraatrial conduction, atrial refractoriness, and arrhythmia inducibility in patients with lone paroxysmal AF. An electrophysiological study was performed in 24 patients with a documented history of lone paroxysmal AF but in sinus rhythm at the time of the electrophysiological study. Twelve patients without any history of atrial arrhythmias served as controls. The patients with lone paroxysmal AF showed a significant prolonged local conduction time S1A1 (70 +/- 21 ms vs 36 +/- 12 ms, P < 0.0001), a lack of rate adaptation of the functional refractory period (FRP changes/cycle length changes < 10% in 15 of 24 patients with lone paroxysmal AF vs 1/12 controls, P = 0.002) and a higher incidence of inducible AF with only one extrastimulus (13/24 vs 0/12, P = 0.0014). The total P wave duration in the surface ECG (89 +/- 14 ms vs 83 +/- 8 ms, P = 0.15), the intraatrial conduction time (36 +/- 14 ms vs 28 +/- 8 ms, P = 0.07), the presence of a fragmented atrial electrogram (16/24 vs 7/12, P = 0.62), the absolute value of the effective refractory period (204 +/- 28 ms vs 212 +/- 23 ms, P = 0.42), and the vulnerability index (3.0 +/- 1.5 vs 3.6 +/- 1.5, P = 0.26) were not statistically different between the two groups. The presence of a prolonged (> 50 ms) S1A1 and/or the presence of a lack of rate adaptation of the FRP and/or the presence of inducible AF identified patients with spontaneous lone paroxysmal AF with a sensitivity of 96%, a specificity of 67%, a positive predictive value of 85%, and a negative predictive value of 89%. In patients with lone paroxysmal AF, the electrophysiological study using conventional techniques allows not only to detect AF inducibility using a nonaggressive protocol, but also to reveal several electrophysiological abnormalities related to the atrial substrate itself. This atrial vulnerability may explain the high incidence of recurrences in patients with lone paroxysmal AF.     

Electrophysiological properties in patients undergoing atrial compartment operation for chronic atrial fibrillation with mitral valve disease

AIMS: Surgical treatment for atrial fibrillation is now feasible in selective cases. The aim of this study was to assess the electrophysiological properties of patients undergoing atrial compartment operation for chronic atrial fibrillation. METHODS AND RESULTS: Electrophysiological studies were performed in 20 mitral valve patients with atrial fibrillation who had been maintained in sinus rhythm for more than 1 year after atrial compartment operation. Intra-cardiac recording and programmed electrical stimulation were performed in various atrial compartments. The parameters studied included sinus node function, atrial conduction and refractoriness, atrioventricular conduction function and inducible arrhythmias if any. Intra-cardiac recordings showed that the rhythm was of sinus origin in all cases, with the earliest atrial activity located in the high right atrium. The mean sinus cycle length was 750 +/- 110 ms, AH time 106 +/- 29 ms, and HV time 53 +/- 7 ms. The sinus node function was normal in 18 patients (90%), and only two patients had prolonged sinus node recovery and sino-atrial conduction. The right atrial appendage compartment was driven by the sinus node in all patients. However, the conduction time from the high right atrium to the right atrial appendage compartment was markedly prolonged in 12 of 15 patients (80%) undergoing the three-compartment operation in which an incision was placed between the high right atrium and right atrial appendage compartments. On the other hand, the electrical activities in the left atrial compartment were much more varied. In 13 of 20 patients (65%), the left atrial compartment was driven by the sinus node; 11 of the 13 patients had a normal or mildly prolonged conduction time (ranged 75 to 146 ms), whereas two patients had a marked delay in conduction (200 ms and 266 ms, respectively). In the remaining seven patients, the left atrial compartments were dissociated from the rest of the heart; five of them had a quiescent left atrium, one a fluttering left atrial rhythm, and one a slow left atrial rhythm. The effective refractory period was longer in the left atrial compartment (242 +/- 47 ms) as compared to that of the high right atrium (224 +/- 26 ms, P < 0.01) and right atrial appendage compartments (219 +/- 25 ms, P < 0.01). Programmed electrical stimulation could not induce atrial fibrillation in any patient, whereas two patients had inducible atrial flutter and three repetitive atrial responses. CONCLUSIONS: (1) Atrial compartment operation does not impair sinus node function in most cases. (2) Elimination of atrial fibrillation while maintaining the electrical connection between different atrial compartments is feasible.     

Direct conversion of atrial flutter to sinus rhythm with low-output, short-duration transesophageal atrial pacing

BACKGROUND AND HYPOTHESIS: Transesophageal atrial pacing (TAP) is useful for terminating paroxysmal non-self terminating atrial flutter (PAF); however, high output pacing of long stimulus duration causes severe symptoms such as chest pain. The objective of this study was to investigate the effect of low-output, short-duration TAP on the conversion of PAF. METHODS: We applied low-output (within 15 mA with a pulse duration of 10 ms), short-duration (within 4 s) TAP in 31 patients (50 +/- 19 years) with PAF. Transesophageal pacing was delivered with 10 pulses of burst pacing at intervals that were 20 ms shorter than those of the flutter wave length. When the conversion was unsuccessful, we delivered 20 pulses of burst pacing. RESULTS: Sixteen patients (52%) were converted directly to sinus rhythm and 12 (38%) to atrial fibrillation. Transesophageal pacing was ineffective in 3 (10%) patients. The duration of atrial flutter, maximum flutter wave amplitude, effective pacing intervals, underlying heart diseases, and cardiac function were not different between patients who had direct conversion to sinus rhythm and those converted to atrial fibrillation. The patients who had direct conversion to sinus rhythm had longer flutter wave cycle lengths than those converted to atrial fibrillation (248 vs. 221 ms, p < 0.005). No patient had complications and complained of any symptoms. CONCLUSION: Low-output, short-duration TAP was useful to convert PAF directly to sinus rhythm without side effects.     

Tachycardia-induced change of atrial refractory period in humans: rate dependency and effects of antiarrhythmic drugs

BACKGROUND: Atrial fibrillation (AF) has been shown to shorten the atrial effective refractory period (ERP) and make the atrium more vulnerable to AF. This study investigated the effect of atrial rate and antiarrhythmic drugs on ERP shortening induced by tachycardia. METHODS AND RESULTS: Seventy adult patients without structural heart disease were included. For the first part of the study, right atrial ERP was measured with a drive cycle length of 500 ms before and after 10 minutes of rapid atrial pacing using five pacing cycle lengths (450, 400, 350, 300, and 250 ms) in 10 patients. For the second part of the study, the remaining 60 patients were included to study the effects of antiarrhythmic drugs on changes in atrial ERP induced by AF. Atrial ERP was measured with a drive cycle of 500 ms before and after an episode of pacing-induced AF. After the patients were randomized to receive one of six antiarrhythmic drugs (procainamide, propafenone, propranolol, dl-sotalol, amiodarone, and verapamil), atrial ERP was measured before and after another episode of pacing-induced AF. In the first part of the study, atrial ERP shortened significantly after 10 minutes of rapid atrial pacing, and the degree of shortening was correlated with pacing cycle length. The second part of the study showed that atrial ERP shortened after conversion of AF (172+/-15 versus 202+/-14 ms, P<0.0001) and that ERP shortening was attenuated after verapamil infusion (-4.6+/-1.2% versus -15.1+/-3.4%, P<0.001) but was unchanged after infusion of the other antiarrhythmic drugs. Furthermore, all of these antiarrhythmic drugs could decrease the incidence and duration of secondary AF. CONCLUSIONS: The atrial ERP shortening induced by tachycardia was a rate-dependent response. Verapamil, but not other antiarrhythmic drugs, could markedly attenuate this effect. However, verapamil and the other drugs could decrease the incidence and duration of secondary AF.     

Actinic superficial folliculitis

BACKGROUND: The maze operation is effective for the restoration of sinus rhythm; however, restoration of atrial mechanical function has not been demonstrated in all patients. METHODS: Maze operations were performed in 32 patients (13 men, 19 women; mean age 47.1 +/- 9.0 years) combined with valvular surgery (n = 25), coronary artery bypass graft (CABG) (n = 3), and others (n = 4). At 1 week, 3 months, 6 months, and 1 year after the operation, prospective serial Doppler echocardiographic examination was carried out to determine the presence of atrial mechanical function. RESULTS: Sinus rhythm was restored and maintained during the follow-up period in 26 (81%) patients; in 22 patients this was due solely to the operation, whereas in four patients an antiarrhythmic agent was needed to maintain sinus rhythm. Another four patients showed paroxysmal atrial fibrillation (AF) despite treatment with an antiarrhythmic agent. Right atrial mechanical function was restored in all 30 patients with sinus rhythm or paroxysmal AF; in 19 (63%) of these, left atrial mechanical function was restored. In patients with restored left atrial mechanical function, peak A velocity (A) and A/E ratio (A/E) of mitral inflow were significantly lower than in the 16 postoperative control patients (A: 0.46 +/- 0.14 m/sec vs 0. 75 +/- 0.29 m/sec, p < 0.01; A/E: 0.40 vs 0.80, p < 0.01). In patients with left atrial mechanical function, the duration of AF was significantly shorter than in patients without left atrial mechanical function (1.9 +/- 2.9 years vs 7.1 +/- 3.0 years, p < 0. 01), but there were no significant differences in left atrial size and volume. CONCLUSIONS: The maze operation could be safely added to standard open heart surgery for the correction of underlying structural heart disease. The rate of conversion to sinus rhythm resulting solely from the operation might be lower than the rates previously reported with only the duration of AF adversely affecting the restoration of left atrial mechanical function. Considering the fact that not all patients converted to sinus rhythm show atrial mechanical function, the role of the maze operation in the prevention of systemic embolism, with subsequent improvement in survival, requires further study.     

Electrocardiographic and clinical predictors of torsades de pointes induced by almokalant infusion in patients with chronic atrial fibrillation or flutter: a prospective study

The aim of this study was to identify predictors of torsades de pointes (TdP) in patients with atrial fibrillation (AF) or flutter exposed to the Class III antiarrhythmic drug almokalant. TdP can be caused by drugs that prolong myocardial repolarization. One hundred patients received almokalant infusion during AF (infusion 1) and 62 of the patients during sinus rhythm (SR) on the following day (infusion 2). Thirty-two patients converted to SR. Six patients developed TdP. During AF, T wave alternans was more common prior to infusion (baseline) in patients developing TdP (50% vs 4%, P < 0.01). After 30 minutes of infusion 1, the TdP patients exhibited a longer QT interval (493 +/- 114 vs 443 +/- 54 ms [mean +/- SD], P < 0.01), a larger precordial QT dispersion (50 +/- 74 vs 27 +/- 26 ms, P < 0.05), and a lower T wave amplitude (0.12 +/- 0.21 vs 0.24 +/- 0.16 mV, P < 0.01). After 30 minutes of infusion 2, they exhibited a longer QT interval (672 +/- 26 vs 489 +/- 74 ms, P < 0.001), a larger QT dispersion in precordial (82 +/- 7 vs 54 +/- 52 ms, P < 0.01) and extremity leads (163 +/- 0 vs 40 +/- 34 ms, P < 0.001), and T wave alternans was more common (100% vs 0%, P < 0.001). Risk factors for development of TdP were at baseline: female gender, ventricular extrasystoles, and treatment with diuretics; and, after 30 minutes of infusion: sequential bilateral bundle branch block, ventricular extrasystoles in bigeminy, and a biphasic T wave. Patients developing TdP exhibited early during almokalant infusion a pronounced QT prolongation, increased QT dispersion, and marked morphological T wave changes.     

Optimization of shocking lead configuration for transvenous atrial defibrillation

INTRODUCTION: High atrial defibrillation energy requirements (ADER) in patients with chronic atrial fibrillation (AF) may limit the acceptance of transvenous atrial defibrillation. We evaluated an optimized defibrillation electrode configuration that could help to reduce the ADER in patients with AF. METHODS AND RESULTS: We tested ten different configurations in nine dogs with AF (3.33+/-2.92 days) induced by rapid atrial pacing. The configurations were: right atrial (RA) appendage as anode and coronary sinus (CS) as cathode; RA and innominate vein (I) as anode to CS (cathode); RA-CS (anode) to I (cathode); I-CS (anode) to RA (cathode); RA and left lateral subcutaneous patch (P) as anode to CS (cathode); RA-CS (anode) to P (cathode); P-CS (anode) to RA (cathode); superior vena cava (SVC) and CS (anode) to RA (cathode); RA-CS (anode) to SVC (cathode); and RA-SVC (anode) to CS (cathode). ADER was defined as the voltage needed to defibrillate the atria in 10% to 90% of 20 consecutive shocks. Three lead systems had ADER lower than the RA (anode) to CS (cathode) configuration, which required a mean of 143+/-58 volts. These three were: RA-SVC (anode) to CS (cathode) 103+/-29 V; I-CS (anode) to RA (cathode) 129+/-39 V; and P-CS (anode) to RA (cathode) 130+/-38 V. The remaining configurations had ADER higher than the RA (anode) to CS (cathode) configuration. CONCLUSION: Adding an additional shocking electrode may reduce ADER when compared with the RA (anode) to CS (cathode) configuration. This concept could be incorporated into future implantable atrial defibrillators or used for refractory patients undergoing temporary transvenous cardioversion.     

Omental delivery of prostaglandin E1 effectively increases portal venous blood flow in 66%-hepatectomized rats

BACKGROUND: Contraction-excitation feedback, that is, electrophysiologic changes that are caused or preceded by mechanical changes of the myocardium, has been extensively studied in the ventricles. The role of contraction-excitation feedback in the atria, and more particularly in the genesis and maintenance of atrial fibrillation, has been less adequately investigated. HYPOTHESIS: The aim of the present study was to determine whether increased right atrial pressure (RAP) facilitates the induction of atrial fibrillation (AF) in patients with a history of lone AF. METHODS: Sixteen patients with a history of paroxysmal AF but without structural heart disease were included in the study. All patients underwent electrophysiologic study at both a lower (3.1 +/- 2.0 mmHg) and (in 13 cases) a higher (6.4 +/- 2.5 mmHg) RAP. "Higher" was considered the pressure following rapid (in about 30 min) intravenous administration of normal saline or before the administration of a diuretic. RESULTS: Rapid atrial pacing induced AF in 19 of 29 attempts. At a lower pressure, rapid pacing induced brief (3 s to 3 min) AF in 3 of 16 patients, long-lasting (> 3 min) AF in 3 of 16 patients, and no AF in 10 of 16 patients. At a higher pressure, brief AF was induced in 3 of 10 patients in whom no AF could be induced at a lower pressure, and long-lasting AF in 10 patients in whom either brief AF (3 cases) or no AF (7 cases) was induced at a lower pressure. In 11 patients, in whom Wenckebach periodicity was determined at both higher and lower pressure, the critical cycle length at which atrioventricular block appeared was significantly (p < 0.001, paired t-test) longer (349.1 +/- 44.4 ms, i.e., +15.5 +/- 11.3 ms) at higher than at lower atrial pressure (333.6 +/- 41.0 ms). In nine patients, in whom Wenckebach periodicity was determined and two rhythms occurred at different pressures, the critical cycle length was 332.2 +/- 45.8 ms when associated with sinus rhythm, and significantly (p < 0.01) longer (344.4 +/- 48.0 ms, i.e., +12.2 +/- 8.3 ms) when associated with induction of AF. CONCLUSION: In patients with lone atrial fibrillation, modest increases in atrial pressure may facilitate the induction of atrial fibrillation.     

Effect of flecainide on atrial and ventricular refractoriness and conduction in patients with normal left ventricle. Implications for possible antiarrhythmic and proarrhythmic mechanisms

We studied the effects of intravenous flecainide (2 mg.kg-1) on atrial and ventricular refractoriness and conduction during sinus rhythm, induced atrial fibrillation and atrial pacing at rates of 100, 120 and 150 ppm, in 14 patients with normal left ventricle. Flecainide caused a significant increase in QRS duration during sinus rhythm (mean +/- SD: 87.2 +/- 8.4 ms vs 102.8 +/- 9.1 ms, P < 0.001), atrial fibrillation (87.8 +/- 10.0 ms vs 108.8 +/- 13.7 ms, P < 0.001) and at all paced rates. The duration of the atrial electrogram was significantly increased during sinus rhythm (54.9 +/- 13.2 ms vs 64.8 +/- 16.6 ms, P = 0.003) and at all pacing rates. The PA interval was also significantly prolonged, as was the pacing stimulus-to-atrial-electrogram interval at all pacing rates. There was increased QRS duration and atrial electrogram prolongation at higher pacing rates. Atrial refractoriness was prolonged during sinus rhythm (216.4 +/- 28.2 vs 228.6 +/- 36.1, P = 0.02), but not during atrial pacing at any rate. The QT interval, but not the JT interval or ventricular refractoriness, was significantly prolonged during sinus rhythm and at all pacing rates. Flecainide slows atrial conduction in a use dependent manner and increases atrial refractoriness during sinus rhythm but not during faster atrial pacing, thus not displaying a use-dependent effect. QRS duration is prolonged in a use-dependent manner without a commensurate increase in ventricular refractoriness. In the presence of rapidly conducted atrial fibrillation, which was not found to be slowed by flecainide, this effect may constitute a proarrhythmic mechanism even in patients with no apparent myocardial abnormality.     

Prevention of recurrent atrial fibrillation with chronic dual-site right atrial pacing

OBJECTIVES: We investigated 1) the feasibility, safety and efficacy of multisite right atrial pacing for prevention of atrial fibrillation (AF); and 2) the ability of atrial pacing in single- and dual-site modes to increase arrhythmia-free intervals in patients with drug-refractory AF. BACKGROUND: We recently developed and applied a novel technique of dual-site right atrial pacing in an unselected group of consecutive patients with AF requiring demand pacing. A prospective crossover study design was used to evaluate single- and dual-site right atrial pacing modes. METHODS: The frequency of AF during the 3 months before pacemaker implantation was analyzed. Consecutive consenting patients underwent insertion of two atrial leads and one ventricular lead with a DDDR pulse generator. Patients were placed in a dual-site pacing mode for the first 3 months and subsequently mode switched to single site pacing for 3 months. Mode switching was repeated at 6-month intervals thereafter. RESULTS: Atrial pacing resulted in a marked decline in AF recurrences (p < 0.001). During dual-site pacing with an optimal drug regimen, there was no AF recurrence in any patient compared with five recurrences in 12 patients during single-site pacing (p = 0.03). The mean (+/-SD) arrhythmia-free interval before pacing (14 +/- 14 days) was prolonged with dual- (89 +/- 7 days, p < 0.0001) and single-site pacing (76 +/- 27 days, p < 0.0001). Symptomatic AF episodes showed a declining trend during dual- and single-site pacing compared with those during the preimplantation period (p = 0.10). Mean antiarrhythmic drug use for all classes declined from 4 +/- 1.9 drugs before implantation to 1.5 +/- 0.5 (p < 0.01) drugs after implantation. Twelve (80%) of 15 patients remained in atrial paced rhythm at 13 +/- 3 months. CONCLUSIONS: We conclude that multisite right atrial pacing is feasible, effective and safe for long-term application. Atrial pacing significantly prolongs arrhythmia-free intervals in patients with drug-refractory paroxysmal AF. Dual-site right atrial pacing may offer additional benefits and should be considered either as the primary mode or in patients unresponsive to single-site pacing.     

Electrophysiological characteristics of the human atria after cardioversion of persistent atrial fibrillation

BACKGROUND: In animal models, induced atrial fibrillation shortens the atrial effective refractory period (ERP) and reverses its physiological adaptation to rate. It is not clear whether this process, known as "electrical remodeling," occurs in humans. METHODS AND RESULTS: We determined the ERPs, at 5 pacing cycle lengths (300 to 700 ms) and in 5 right atrial sites, after internal cardioversion of chronic atrial fibrillation in 25 patients (14 in pharmacological washout and 11 on amiodarone). The ERPs were 195.5+/-18.8 ms in the washout and 206.3+/-17.9 ms in the amiodarone patients (P<0.0001). ERPs were closely correlated with the stimulation rates (r=0.95 in the washout and r=0.94 in the amiodarone group), and slope values indicating a normal (>/=0.07) or nearly normal (0.05 to 0.06) adaptation of ERP to rate were found in 77% of the 84 paced sites. The mean ERP was shorter in the lateral wall (198.1+/-17.9 ms) than in the atrial roof (203.3+/-21.5 ms) and in the septum (210.5+/-20.0 ms) (P<0.03). After 4 weeks of sinus rhythm, the mean ERP, determined again in 8 patients (4 in wash-out and 4 on amiodarone), was significantly increased compared with the basal study (221. 4+/-21.4 versus 197.8+/-18.3 ms, P<0.0001). CONCLUSIONS: After cardioversion of chronic atrial fibrillation, (1) atrial ERP adaptation to rate was normal or nearly normal in the majority of the cases, (2) a significant dispersion of refractoriness between different right atrial sites was present, and (3) ERPs were significantly increased after 4 weeks of sinus rhythm in both washout and amiodarone patients.     

Unexpected instant death following successful coronary artery bypass graft surgery (and other clinical settings): atrial fibrillation, quinidine, procainamide, et cetera, and instant death

Primum non nocere. Atrial fibrillation (AF) occurs commonly following coronary artery bypass graft surgery, although new onset atrial fibrillation in this setting is usually transient. When AF reverts or is converted to sinus rhythm it is unlikely to recur, whether or not the patient takes preventive medication. As no benefit (and sometimes increased risk) associated with reduced mortality or morbidity in this setting has been reported for antiarrhythmic agents, standard treatment should consist of observation or control of ventricular response with an appropriate agent until AF relapses to sinus rhythm. If an antiarrhythmic agent, especially a class I agent, is used because of persistent or recurrent AF in the early postoperative period, heart rhythm should be monitored as long as the class I agent is administered and treatment initiated if an undersirable rhythm develops. Atrial fibrillation in other clinical settings in patients with structural heart disease presents a more difficult management problem. Class I agents are reported to be associated with an increased risk of death, despite an efficacious effect of maintaining sinus rhythm. Amiodarone is reported to be well tolerated with respect to the cardiovascular system, but unacceptable noncardiac effects are reported. A safe amiodarone-like agent is greatly needed. Atrial fibrillation in patients with no structural heart disease is not discussed in this presentation.