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  • 1
    Electronic Resource
    Electronic Resource
    Capture Window in Human Atrial Fibrillation (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 10 (1999), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Capture Window in Human AF. Introduction: Local capture of atrial fibrillation (AF) was shown in animal experiments for a wide range of pacing rates, thus demonstrating the existence of an excitable gap. The aim of this study was to assess the existence of an excitable gap in human AF by studying the mechanism of local control and acceleration of AF over a wide range of pacing rates and by evaluating the time window of capture. Methods and Results: Recording and stimulation of electrical activity in the right atrium during AF was performed by a monophasic action potential (MAP) contact electrode catheter in 17 patients with lone AF during electrophysiologic study. Stimulation was started at pacing intervals close to the mean AF interval, and the time window of capture was estimated by lengthening or shortening the pacing interval until capture was lost. Pacing intervals shorter than the minimum cycle length for capture were also tested. Beat-to-beat measurements of AF intervals during pacing were performed. Atrial MAP signal showed rapid irregular activity with an average AF interval of 151.3 ± 16.1 msec and SD of 21.3 ± 5.2 msec. Rapid pacing with a cycle length slightly shorter or longer than the mean AF interval resulted in local capture of AF. The width of time window of capture ranged from 22 to 36 msec, with a mean value of 28.8 ± 4.9 msec. The average minimum pacing interval of stable capture was 129.2 ± 19.5 msec, while the maximum was 158.1 ± 18.7 msec, corresponding to 85% and 104% of mean AF cycle length, respectively. Pacing too rapidly resulted in a transient acceleration of AF, with an average shortening of fibrillation interval from 149.8 ± 16.6 to 123.2 ± 15.1 msec (P 〈 0.01). Conclusion: Local capture is feasible during AF in humans over a wide range of pacing rates, indicating the possibility of regional control of the fibrillatory process. This result demonstrates the presence of an excitable gap during AF in human atria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1999.tb00678.x
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  • 2
    Electronic Resource
    Electronic Resource
    Far-Field R Wave Oversensing in Dual Chamber Pacemakers Designed for Atrial Arrhythmia Management: (2004)
    350 Main Street , Malden , MA 02148-5018 , USA and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Pacing and clinical electrophysiology 27 (2004), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The aim of the study was to determine the incidence and practical implications of far-field R wave oversensing (FFRWO) and its association with pacing site and lead tip to ring spacing (TTRS) in implantable devices designed to diagnose and treat atrial tachyarrhythmias and programmed with a fixed and short postventricular blanking period. The study included 395 patients who were implanted with a DDDRP pacemaker and prospectively followed. At implant and follow-up visits FFRWO was assessed by analyzing lead electrical measures and atrial tachyarrhythmic episodes collected in the device diagnostics. During a median follow-up of 12 months 11 (2.8%) of 395 patients showed a clinically significant FFRWO that induced inappropriate detection or pacemaker malfunctioning. The atrial pacing site of these 11 patients was right atrium appendage (RAA) for 3 patients, representing 1.1% of 254 RAA patients, coronary sinus ostium (CSO) for 7 patients, representing 7.4% of 94 CSO patients (P 〈 0.005 vs RAA), and lateral wall (LW) for 1 (2.9%) of 34 LW patients. The minimal value of the FFRWO to P wave ratio, measured at implant, associated with a clinically significant FFRWO was 0.6; therefore, a value of 0.5 was used as a cutoff to identify patients at risk of undesirable device behavior induced by FFRWO: there were 11 (9.6%) of 114 of RAA patients with short (≤ 10 mm) TTRS, 22 (18.8%) of 117 of RAA patients with long (≥ 17 mm) TTRS (P 〈 0.05 vs short TTRS), 21 (30.6%) of 64 of CSO patients short TTRS (P 〈 0.001 vs RAA patients with short TTRS) and 3 (30%) of 10 of CSO patients with long TTRS. The analysis showed that, despite the short postventricular blanking time, FFRWO inducing undesired functioning in AT500 pacemakers is infrequent (2.8% of patients). Compared to RAA, the CSO lead position was more frequently associated with FFRWO.TTRS 〈 10 mm was associated with lower risk of clinically significant FFRWO in RAA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.2004.00613.x
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  • 3
    Electronic Resource
    Electronic Resource
    Conversion of Recent-Onset Atrial Fibrillation to Sinus Rhythm: Effects of Different Drug Protocols (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 21 (1998), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In a population of 417 hospitalized patients, the efficacy and safety of different drug regimens administered to convert atrial fibrillation (AF) of recent anset (≤ 7 days duration) to sinus rhythm were evaluated. All patients were in NYHA Class ≤ 2, and free of heart failure. They were randomly allocated to treatment with placebo in 121 patients; IV amiodarone, 5 mg/kg bolus, followed by 1.8 g/24 hours in 51 patients; IV propafenone, 2 mg/kg bolus, followed by 0.0078 mg/kg/min in 57 patients; p.o. propafenone, 600 mg p.o. in a single dose in 119 patients; and p.o. flecainide, 300 mg p.o. in a single dose in 69 patients. All patients were continuously monitored by Holter ECG, and the number of conversions to sinus rhythm was measured at 1, 3, and 8 hours. Results: (1) IV propafenone resulted in a higher conversion rate within 1 hour compared with the oral loading regimens of propafenone or flecainide, but the conversion rates at 3 and 8 hours were comparable, approximately 75% at 8 hours; 2) IV amiodarone was not different from placebo until 8 hours when it was associated with 57% of conversions; (3) conversion to sinus rhythm at 8 hours was observed in 37% of the placebo treated patients. Serious adverse effects occurred in few patients: two patients treated with flecainide and one treated with IV propafenone experienced left ventricular decompensation; one patient treated with placebo and two treated with flecainide had atrial flutter with rapid ventricular response. In conclusion, single-dose, oral loading with propafenone or flecainide are acceptable alternatives to conventional drug regimens in selected hospitalized patients. In addition, the measure of a placebo effect is mandatory in studies of recent-onset AF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1998.tb01203.x
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  • 4
    Electronic Resource
    Electronic Resource
    Steroid-Eluting Electrodes Prevent Chronic Pacing Threshold Rise in the Atrial Chamher After Oral Propafenone Administration (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 20 (1997), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The aim of the study was to evaluate chronic atrial pacing threshold increase after oral propafenone therapy. Fifty patients affected by advanced AV block and sick sinus syndrome were studied at least 6 months after pacemaker implantation, before and after oral propafenone therapy (450–900 mg/day based on body weight). The patients were subdivided into three groups as to the type of electrode implanted, all three unipolar: group I (20 patients) Medtronic CapSure 4003, group II (13 patients) Medtronic Target Tip 4011, group III (17 patients) Medtronic 4057 screw-in leads. In all cases, Medtronic unipolar pacemakers were implanted with the same noninvasive autothreshold measurement method. Propafenone and 5-OH-propafenone blood levels were measured 3–5 hours after drug administration. The pacing autothreshold was measured at 0.8, 1.6, and 2.5 V by reducing the pulse width. After propafenone. groups II and III showed a statistically significant threshold rise (P ranging from 〈 0.01 to 〈0.05), whereas no significant difference was found in group I. Propafenone and 5-OH-propafenone blood levels did not show any significant difference among the three groups. Strength-durution curves were drawn for the three groups before und after propafenone: at baseline the curves shifted to the left with the steep part above the knee, clearly favoring CapSure over the other two groups. After propafenone, the curves shifted to the right, with the flat part progressively more evident in groups II and III. In the atrial chamber, steroid-eluting leads prevented threshold increase after propafenone therapy, in contrast with a significant threshold rise with conventional porous and screw-in leads.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1997.tb06167.x
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  • 5
    Electronic Resource
    Electronic Resource
    Predictors of Atrial Antitachycardia Pacing Efficacy in Patients Affected by Brady-Tachy Form of Sick Sinus Syndrome and Implanted with a DDDRP Device (2005)
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 16 (2005), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: Recent options to treat atrial tachyarrhythmias (ATA) include implantable devices delivering antitachycardia pacing therapies (ATP). No prospective study selected patients with higher chances of episode termination by ATP or indicated the most effective ATP use. Our aim was to study ATP efficacy in patients with brady-tachy form of sinus node disease (SND), identifying clinical factors, ATA characteristics, and device features predicting ATP efficacy. Methods and Results: Three hundred and sixteen patients (105 M, aged 71.1 ± 8.8 years) received a DDDRP pacemaker and were prospectively followed. Median follow-up was 18 months: 37,125 ATA episodes occurred in 217 patients; ATP treated 5,536 of them. Overall, ATP efficacy was 50.0%. A multivariate analysis identified longer arrhythmia cycle lengths (OR = 1.25; CI = 1.07-1.47) and shorter delays to ATP delivery (OR = 0.15; CI = 0.10-0.22) as independent predictors of ATP efficacy for episodes preceded by ≥5 minutes of sinus rhythm. Additionally, ATP efficacy for all treated episodes was predicted by lower New York Heart Association (NYHA) class (OR = 0.64; CI = 0.42-0.98), episode classification as nonimmediate recurrence of ATA (non-IRAT) (OR = 0.07; CI = 0.02-0.33), absence of overlap in the device detection windows (OR = 0.54; CI = 0.32-0.91), and flecainide treatment (OR = 2.22; CI = 1.04-4.71). Conclusions: In patients paced for SND, multivariate analysis shows that ATP efficacy is associated to longer arrhythmia cycle lengths, shorter ATP delivery delays, NYHA class I, episode classification as non-IRAT, absence of overlap in the atrial arrhythmia device detection windows, and flecainide treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.2005.40716.x
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  • 6
    Electronic Resource
    Electronic Resource
    Capture of Atrial Fibrillation Reduces the Atrial Defibrillation Threshold (2002)
    Oxford, UK : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 25 (2002), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: VILLANI, G.Q., et al.: Capture of Atrial Fibrillation Reduces the Atrial Defibrillation Threshold. The effect of the atrial activity synchronization by single site right atrial pacing on atrial defibrillation threshold (ADFT) was investigated in patients with AF. Two series of randomized incremental cardioversion tests, with increasing energy levels from 0.5 to 10 J, were performed in 15 patients with recurrent episodes of idiopathic paroxysmal AF using two 7 Fr “single coil” catheters for internal cardioversion. After induction of sustained AF (〉 10 minutes), shocks were delivered, preceded or not by 10 seconds of overdrive local atrial pacing, according to the randomization, using an external cardioverter defibrillator. A total of 187 shocks was delivered to the study population. ADFT was reduced when overdrive atrial stimulation preceded the cardioversion (3.6 ± 1.6 vs 2.9 ± 1.7 J, P = 0.02). Local atrial capture was considered on the basis of 1:1 phase locking between stimulus and atrial activation wave, and constant morphology of atrial wave criteria. Effective atrial capture was obtained in 8 of 15 patients. There was not significant difference in the mean of FF intervals of patients in which atrial capture was or was not stable (209 ± 22 vs 208 ± 28 ms). Patients were then considered according to the outcome of atrial pacing before direct current shock. A marked ADFT reduction was observed in patients with stable capture (3.8 ± 1.7 vs 2.5 ± 1.7 J, P = 0.0003), while no significant difference in ADFT was found when capture was not achieved (3.4 ± 1.6 vs 3.6 ± 1.5 J, P = NS). In conclusion, regularization of atrial electrical activity by atrial capture reduces the ADFT. A constant pacing entrainment seems to lower the energy required for electrical cardioversion by reducing the amount of fibrillating tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2002.01159.x
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  • 7
    Electronic Resource
    Electronic Resource
    Atrial Tachyarrhythmia Recurrence Temporal Patterns in Bradycardia Patients Implanted with Antitachycardia Pacemakers (2004)
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 15 (2004), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: New-generation pacemakers allow continuous atrial tachyarrhythmia (AT) monitoring that provides accurate information about AT type, frequency, burden, and temporary evolution. Methods and Results: We performed a prospective multicenter study to describe AT temporal patterns in patients with sinus bradycardia and AT. Two hundred forty patients (123 men; age 71 ± 8 years) were implanted with a DDDRP pacemaker (model AT500, Medtronic Inc.). All patients were followed for 13 months. The first-month stabilization period of all patients was discarded from analysis. Seventy percent of patients had AT recurrences. Mean time to first AT recurrence (48.2 days, 95% confidence interval [CI] 37.0–59.5 days) was significantly longer than the time between first and second AT episode (10.3 days, 95% CI 6.7–13.9 days, P 〈 0.01). A minority of patients had a uniform time distribution of AT recurrences: 〈25% of patients had AT episodes in more than 6 of the 12 months considered in the study. The probability density function of consecutive sinus rhythm days between AT episodes was calculated for each of 40 patients who experienced 〉25 AT episodes and fitted by power law and exponential functions. The best fit was obtained by power law function in 60% of patients, by exponential function in 10%, and the two models gave comparable results in 30% of patients. Conclusion: In our population of patients with a history of sinus bradycardia and AT who were implanted with a new device equipped with atrial pacing therapies, 30% did not experience AT recurrences in the 12-month study period. Analysis of interevent time showed that in 60% of patients AT recurrences do not follow a uniform or random distribution. These findings bring into question the use of cross-over design and time to first AT recurrence as a clinical outcome in trials for AT therapy in this patient population. (J Cardiovasc Electrophysiol, Vol. 15, pp. 44-51, January 2004)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2004.03317.x
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  • 8
    Electronic Resource
    Electronic Resource
    Endocardial Defibrillation Lead Extraction: (2003)
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 26 (2003), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Spurious discharges due to late insulation break in an IS-1 pacing/sensing connector prompted ICD lead removal in 65-year-old man. The tip of the lead was easily freed and pulled back into the SVC by the superior approach. After that, the lead became trapped. The distal part of the lead was caught and easily withdrawn by inferior approach. Superior venous angiography showed extravascular location of the entrapped part of the lead due to the unintentional percutaneous puncture of the innominate vein after piercing the subclavian vein. It may be desirable to use contrast venography before intervention of extraction to ensure venous patency and lead location. (PACE 2003; 26:2036–2038)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2003.00314.x
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  • 9
    Electronic Resource
    Electronic Resource
    Oral Loading with Propafenone: A Placebo-Controlled Study in Elderly and Nonelderly Patients with Recent Onset Atrial Fibrillation (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 21 (1998), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The efficacy and safety of propafenone as an oral loading dose (600-mg single oral dose) in converting recent-onset atrial fibrillation (≤ 7 days duration) to sinus rhythm were evaluated in a single-blind, placebo-controlled study according to patients' age. Overall, 240 hospitalized patients, NYHA Class ≤ 2 without signs or symptoms of heart failure were enrolled: among patients aged ≤ 60 years, 55 were allocated to propafenone treatment and 59 to placebo, respectively, and among patients aged 〉 60 years, 64 were allocated to propafenone treatment and 62 to placebo, respectively. Results: In each age group, the likelihood of conversion to sinus rhythm was significantly greater after propafenone compared with plocebo at 3 and 8 hours. For patients aged ≤ 60 years, corresponding odd ratios were 3.78 (95% CI = 1.80–7.92, P = 0.04) at 3 hours and 4.74 (95% CI = 2.12–10.54, P = 0.02) at 8 hours; for patients aged 〉 60 years odd ratios were 5.03 (95% CI = 2.08–12.12, P = 0.02) at 3 hours and 6.75 (95% CI = 3.28–73.86, P = 0.01) at 8 hours, respectively. Logistic regression analysis showed that conversion to sinus rhythm within 3 hours was predicted by age ≤ 60 years (P = 0.0064) and by propafenone treatment (P 〈 0.0001), and conversion to sinus rhythm within 8 hours was predicted by age ≤ 60 years (P = 0.0467) and by propafenone treatment (P 〈 0.0001). The occurrence of adverse effects was observed in 14%-16% of propafenone treated patients and in 8% of placebo treated patients without significant differences according to age. In conclusion, in patients with recent-onset atrial fibrillation without signs of heart failure, propafenone as a single oral loading dose is effective. It is also effective in selected elderly subjects with a favorable safety profile. Moreover, spontaneous conversion to sinus rhythm appears to occur less frequently in elderly patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1998.tb01202.x
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  • 10
    Electronic Resource
    Electronic Resource
    Risk of Complications of Atrial Fibrillation (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 20 (1997), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Atrial fibrillation is associated with three major risk of complications: thromboembolism, hemodynamic compromise, and arrhythmogenesis. In patients with chronic atrial fibrillation the incidence of embolization is about 5% per year. The risk of embolism and in particular of stroke can be reduced by warfarine anticoagulation. Aspirin is generally less effective than warfarin, although it is probably more effective than placebo. The hemodynamic complications which may occur during atrial fibrillation are mainly due to the loss of effective atrial contraction, the irregular ventricular rhythm, and the possible excessively rapid ventricular rate. Sudden death is a recognized manifestation of Wolff-Parkinson-White syndrome and is considered to be precipitated by atrial fibrillation in the majority of patients. Torsades de pointes is perhaps the most widely recognized proarrhythmia associated with treatment of atrial fibrillation, especially with 1A antiarrhythmic drugs and sotalol. The chronic treatment with type 1C drugs in 3.5%–5% of patients may induce atrial flutter with 1:1 conduction with significant hemodynamic compromise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1997.tb06117.x
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