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  • 1
    Electronic Resource
    Electronic Resource
    Prevalence and Management of Inappropriate Detection and Therapies in Patients with First-Generation Biventricular Pacemaker-Defibrillators (2005)
    350 Main Street , Malden , MA 02148-5018 , USA and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Pacing and clinical electrophysiology 28 (2005), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: Tachycardia detection in first-generation biventricular pacemaker-implantable cardioverter defibrillators (BiV ICD) occurs through both the right ventricular (RV) and left ventricular (LV) leads, creating the potential for inappropriate detection and therapies. Little is known regarding the prevalence and management of patients with BiV ICDs and inappropriate detection. Methods and Results: A transvenous, first-generation BiV ICD was implanted in 77 consecutive patients (age 61 ± 11 years) for drug-refractory heart failure. The mean New York Heart Association class, QRS duration, and ejection fraction were 3.1 ± 0.4, 168 ± 24 ms, and 0.19 ± 0.07, respectively. Among the 77 patients, 17 (22%) experienced inappropriate detection at a mean of 154 ± 140 days after implantation. Fifteen of the 17 patients (88%) experienced inappropriate ICD therapy. In 16 of the 17 (94%) patients, the cause of inappropriate detection was double counting during sinus (8) or atrial rhythm (3), and nonsustained ventricular tachycardia (5). Despite reprogramming of the ICD, 9 patients (53%) required an additional procedure because of inappropriate therapies, including an upgrade to a dedicated BiV ICD (5), revision of the LV lead (2), ablation of the atrioventricular junction (1), and repeat defibrillation threshold testing (2). Conclusions: Inappropriate detection in patients with a first-generation BiV ICD is common and often results in inappropriate ICD therapy. The most common mechanism of inappropriate detection is double counting that often creates the need for additional procedures. Although devices in which tachycardia detection occurs only through the RV lead now are available, close follow-up of the many patients who received a first-generation BiV ICD is necessary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.2005.09499.x
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  • 2
    Electronic Resource
    Electronic Resource
    Mechanism of Immediate Recurrences of Atrial Fibrillation After Restoration of Sinus Rhythm (2004)
    350 Main Street , Malden , MA 02148-5018 , USA and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 27 (2004), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: An immediate recurrence of AF may occur after restoration of sinus rhythm. Although pulmonary vein (PV) isolation has been shown to prevent immediate recurrence of AF, the specific trigger for immediate recurrence of AF has not been described. In 89 consecutive patients (mean age 53 ± 11 years) who had sinus rhythm restored by spontaneous or transthoracic cardioversion in the course of a PV isolation procedure, electrograms recorded within a PV and in the adjacent left atrium were analyzed to determine the mechanism of initiation of immediate recurrence of AF. Immediate recurrence of AF was defined as a recurrence of AF within 90 seconds after restoration of sinus rhythm. There were 124 episodes of immediate recurrence of AF at a mean of 18 ± 23 seconds after cardioversion. Recordings within the PV that triggered the immediate recurrence of AF were available in 23 (19%) of the 124 immediate recurrence of AF episodes. Among these 23 episodes of immediate recurrence of AF, all (100%) were triggered by a burst of PV tachycardia (P 〈 0.001). The coupling interval and prematurity index (coupling interval/preceding sinus cycle length) of the premature depolarizations that did and did not trigger immediate recurrence of AF were 246 ± 67 ms and 0.30 ± 0.11 vs 378 ± 117 ms and 0.49 ± 0.16, respectively (P 〈 0.01). Immediate recurrence of AF was abolished by PV isolation. The mechanism of immediate recurrence of AF is a burst of PV tachycardia, not a single premature depolarization. Immediate recurrence of AF identifies patients with AF in whom the PVs may play a major role in the initiation of AF. (PACE 2004; 27:77–82)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.2004.00389.x
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  • 3
    Electronic Resource
    Electronic Resource
    Impact of Fusion Avoidance on Performance of the Automatic Threshold Tracking Feature in Dual Chamber Pacemakers: A Multicenter Prospective Randomized Study (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: CANDINAS, R., et al.: Impact of Fusion Avoidance on Performance of the Automatic Threshold Tracking Feature in Dual Chamber Pacemakers: A Multicenter Prospective Randomized Study. The Autocapture algorithm enables automatic capture verification on a beat-by-beat basis by recognizing the evoked response signal following each pacemaker stimulus. The algorithm intends to increase patient safety while decreasing energy consumption. However, the occurrence of fusion beats, particularly during dual chamber pacing, may limit the energy saving effect of Autocapture. The aim of this multicenter, prospective, randomized study was to evaluate the impact of the Fusion Avoidance (FA) algorithm on the incidence of fusion beats. Thirty-eight patients (mean age 69 ± 13 years) with intrinsic AV conduction who were implanted with an Affinity DR were studied. After programming a PV/AV delay of 120/190 ms, patients were randomized to FA On or Off. Each group was further randomized with respect to activation of the AutoIntrinsic Conduction Search (AICS) algorithm. The total number of beats, ventricular paced beats, fusion beats, backup pulses, and threshold searches were analyzed from 24-hour Holter recordings. The number of total beats was comparable in both FA groups. The number of total ventricular paced beats, fusion beats, backup pulses, and threshold searches were significantly reduced in the FA On group (% reduction: 68% P 〈 0.001, 75% P 〈 0.01, 95% P 〈 0.01, and 94% P 〈 0.05, respectively). The number of ventricular paced beats with full capture was significantly reduced when AICS was activated (P 〈 0.05). In conclusion, the FA algorithm substantially reduces the amount of ventricular paced beats, fusion beats, unnecessary backup pulses and threshold searches, and therefore, provides added benefits in energy saving obtained by Autocapture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2002.01540.x
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  • 4
    Electronic Resource
    Electronic Resource
    Incremental Value of Isolating the Right Inferior Pulmonary Vein During Pulmonary Vein Isolation Procedures in Patients With Paroxysmal Atrial Fibrillation (2004)
    350 Main Street , Malden , MA 02148-5018 , USA and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 27 (2004), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Electrical isolation of the left superior, left inferior, and right superior pulmonary veins (PVs) is often, but not always, effective in eliminating paroxysmal atrial fibrillation (PAF). The incremental clinical value of also isolating the right inferior PV has not been well defined. PV isolation by ostial applications of radiofrequency energy guided by PV potentials was performed in 176 consecutive patients (mean age 52 ± 11 years) with PAF. The left superior, left inferior, and right superior PVs were targeted in 106 patients, and all four PVs were targeted 70 patients. Successful isolation was achieved in 96% of targeted PVs. The mean duration of follow-up was 15 ± 7 months. At 1-year follow-up, 58% of patients in whom three PVs were isolated were free of recurrent PAF in the absence of antiarrhythmic drug therapy, compared to 73% of patients in whom all four PVs were isolated (P = 0.07). There is a trend towards a better outcome when all four PVs are isolated than when only the three major PVs are isolated. Whenever feasible, the right inferior PV should be isolated along with the other three PVs during the first ablation procedure in patients with PAF. (PACE 2004; 27:480–484)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.2004.00467.x
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  • 5
    Electronic Resource
    Electronic Resource
    Characteristics of Rapid Rhythms Recorded Within Pulmonary Veins During Atrial Fibrillation (2003)
    350 Main Street , Malden , MA 02148-5018 , U.S.A . : Blackwell Publishing
    Pacing and clinical electrophysiology 26 (2003), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Rapid rhythms often arise in the pulmonary veins during atrial fibrillation (AF). The activation patterns within pulmonary veins during these rapid rhythms are not well described. In 39 patients with paroxysmal AF, ostial recordings were obtained during AF in 110 pulmonary veins with a decapolar distal ring catheter. Pulmonary vein tachycardia (PVT) was defined as a pulmonary vein (PV) rhythm that had a cycle length shorter than at the adjacent left atrium. During AF, PVT was recorded in 93% of PV's, usually in the form of intermittent bursts that had a mean duration of 1,325 ± 647 ms and mean cycle length of 125 ± 20 ms. The mean cycle length of continuous PVT's (141 ± 25) was longer than the mean cycle length of intermittent bursts of PVT (P 〈 0.05). The intermittent PVT's were associated with a shorter left atrial cycle length than were the continuous PVT's. In 90% of PVTs, complex activation patterns attributable to simultaneous recordings from two or more overlapping fascicles were present at a segment of the pulmonary vein ostium, and the mean cycle length of these recordings was 80 ± 32 ms. PVT during AF is much more often intermittent than continuous. The relationship between PVT cycle length and left atrial cycle length suggests that PVT's influence the left atrium during AF. PVT must be distinguished from recordings within PV's that have a short cycle length as a result of simultaneous recordings from two or more overlapping fascicles. (PACE 2003; 26:1342–1347)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2003.t01-1-00192.x
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  • 6
    Electronic Resource
    Electronic Resource
    Rate-Dependent AV Delay Optimization in Cardiac Resynchronization Therapy (2005)
    350 Main Street , Malden , MA 02148-5018 , USA and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Pacing and clinical electrophysiology 28 (2005), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: During cardiac resynchronization therapy (CRT), cardiac performance is dependent on an optimized atrioventricular delay (AVD). However, the optimal AVD at different heart rates has not been defined yet during CRT. Method: The effects of an increase in heart rate by pacing or physical exercise on optimal AVD were studied in 36 patients with biventricular pacemakers/defibrillators. The velocity time integral (VTI) in the left ventricular outflow tract (LVOT) was measured with pulsed Doppler either at three different paced heart rates in the supine position or in seated position before and after physical exercise. Results: The baseline AVD was optimized to 99 ± 19 ms in the supine and 84 ± 22 ms in the seated position. When the heart rate was increased by DDD pacing, there was a positive linear relationship between an increase in heart rate, in AVD and in VTI (LVOT-VTI + 0.047 cm/s per 10 beats per minute (bpm) heart rate increase per 20 ms increase in AVD, P = 0.007). A similar but more pronounced relationship was found after physical exercise in the seated position (LVOT-VTI + 0.146 cm/s per 10 bpm heart rate increase per 20 ms increase of AVD, P = 0.013). This effect was observed in patients with and without AV block and mitral regurgitation. Conclusions: In conclusion, the systolic performance of the dilated ventricle, which depends on an elevated preload, is critically affected by the appropriate timing of the AVD during exercise. In contrast to normal pacemaker patients, in CRT the relatively short baseline AVD should be prolonged at increased heart rates. Further studies with other means of measuring exercise cardiac performance are needed to confirm these unexpected findings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.2005.40054.x
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  • 7
    Electronic Resource
    Electronic Resource
    Atrial Electrogram Amplitude and Efficacy of Cavotricuspid Isthmus Ablation for Atrial Flutter (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: Large atrial electrogram amplitudes recorded in the cavotricuspid isthmus (CTI) may reflect thick atrial musculature. For this reason, in patients with atrial flutter, the efficacy of an application of conventional radiofrequency energy may be related to the amplitude of the local atrial electrogram. In 100 consecutive patients (mean age 59 ± 13 years) with atrial flutter, contiguous applications of radiofrequency energy were delivered in the CTI. The criterion for complete CTI block was the presence of widely split double potentials (〉110 ms) along the entire ablation line during pacing from the coronary sinus and posterolateral right atrium. The atrial electrogram amplitude was measured before and after applications of radiofrequency energy at sites of gaps in the ablation line. Complete CTI block was achieved in 90 (90%) of the 100 patients. The mean atrial electrogram amplitudes at gap sites where an application of radiofrequency energy did and did not result in complete block were 0.36 ± 0.42 and 0.67 ± 0.62 mV, respectively (P 〈 0.01). The positive and negative predictive values (for complete block) of a ≥50% decrease in electrogram amplitude after an application of radiofrequency energy were 100% and 35%, respectively. The mean atrial electrogram amplitude is larger at CTI sites where complete isthmus block cannot be achieved with conventional radiofrequency energy. The efficacy of conventional radiofrequency ablation may be improved by identifying areas in the CTI where the voltage is relatively low. (PACE 2003; 26:1859–1863)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2003.t01-1-00281.x
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  • 8
    Electronic Resource
    Electronic Resource
    Anatomy of the Pulmonary Veins in Patients with Atrial Fibrillation and Effects of Segmental Ostial Ablation Analyzed by Computed Tomography (2003)
    350 Main Street , Malden , MA 02148 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 14 (2003), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Pulmonary Vein Anatomy. Introduction: The anatomic arrangement of pulmonary veins (PVs) is variable. No prior studies have quantitatively analyzed the effects of segmental ostial ablation on the PVs. The aim of this study was to determine the effect of segmental ostial radiofrequency ablation on PV anatomy in patients with atrial fibrillation (AF). Methods and Results: Three-dimensional models of the PVs were constructed from computed tomographic (CT) scans in 58 patients with AF undergoing segmental ostial ablation to isolate the PVs and in 10 control subjects without a history of AF. CT scans were repeated approximately 4 months later. PV and left atrial dimensions were measured with digital calipers. Four separate PV ostia were present in 47 subjects; 3 ostia were present in 2 subjects; and 5 ostia were present in 9 subjects. The superior PVs had a larger ostium than the inferior PVs. Patients with AF had a larger left atrial area between the PV ostia and larger ostial diameters than the controls. Segmental ostial ablation resulted in a 1.5 ± 3.2 mm narrowing of the ostial diameter. A 28% to 61% focal stenosis was present 7.6 ± 2.2 mm from the ostium in 3% of 128 isolated PVs. There were no instances of symptomatic PV stenosis during a mean follow-up of 245 ± 105 days. Conclusion: CT of the PVs allows identification of anatomic variants prior to catheter ablation procedures. Segmental ostial ablation results in a significant but small reduction in ostial diameter. Focal stenosis occurs infrequently and is attributable to delivery of radiofrequency energy within the PV. (J Cardiovasc Electrophysiol, Vol. 14, pp. 150-155, February 2003)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2003.02444.x
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  • 9
    Electronic Resource
    Electronic Resource
    Role of the Coronary Sinus in Maintenance of Atrial Fibrillation (2003)
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 14 (2003), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: Bursts of tachycardia arising in the pulmonary veins may play an important role in perpetuating atrial fibrillation (AF). However, the role of the coronary sinus (CS) in the perpetuation of AF has been unclear. The aim of this study was to determine whether the CS plays a role in perpetuation of AF. Methods and Results: Pulmonary vein isolation was performed by segmental ostial ablation with radiofrequency energy in 22 consecutive patients with paroxysmal AF. Bipolar and unipolar electrograms recorded in the left atrium and CS were analyzed during atrial pacing from the mitral annulus and during AF. There was a mean of 2.5 ± 0.5 electrical connections between the CS and the left atrium. The electrical connections between the left atrium and CS were ablated with a mean of 6.2 ± 2.7 minutes of radiofrequency energy applied along the atrial side of the inferior mitral annulus. During AF, episodes of intermittent tachycardia alternated between the left atrium and the CS. Among the 22 patients, sustained AF was still inducible in 9 after pulmonary vein isolation. After electrical disconnection of the CS from the left atrium, sustained AF was inducible in only 3 of these 9 patients. Conclusion: The CS may be a source of rapid repetitive electrical activity during AF. The lower probability of inducible sustained AF after electrical disconnection of the CS from the left atrium suggests that the CS may play a role in perpetuating AF. (J Cardiovasc Electrophysiol, Vol. 14, pp. 1329-1336, December 2003)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2003.03222.x
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  • 10
    Electronic Resource
    Electronic Resource
    Mechanistic Significance of Intermittent Pulmonary Vein Tachycardia in Patients with Atrial Fibrillation (2002)
    Oxford, UK : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 13 (2002), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Pulmonary Vein Tachycardia. Introduction: The significance of intermittent tachycardia within a pulmonary vein (PV) during an episode of atrial fibrillation (AF) is unclear. The aim of this study was to determine the role that intermittent PV tachycardias play in AF. Methods and Results: In 56 patients with AF, segmental ostial ablation guided by PV potentials was performed to isolate the PVs. The characteristics of intermittent PV tachycardias and the inducibility of AF before and after PV isolation were analyzed prospectively. During AF, a PV tachycardia (mean cycle length 130 ± 30 msec) with exit block to the left atrium was present in 93% of left superior, 80% of left inferior, 73% of right superior, and 7% of right inferior PVs. The site of shortest cycle length during AF alternated between the PVs and left atrium 1 to 13 times per minute. Complete isolation was achieved in 168 (94%) of 178 targeted PVs. In 99% of PVs, tachycardia resolved upon isolation. AF was persistent before and after PV isolation in 100% and 27% of patients, respectively (P 〈 0.001). Conclusion: Intermittent bursts of tachycardia are observed within multiple PVs during persistent AF in a majority of patients. After PV isolation, PV tachycardias almost always resolve, and AF is less likely to be inducible or persistent. These observations suggest a dynamic interplay between the atria and PVs, with intermittent bursts of PV tachycardia being dependent on left atrial input and with the probability of persistent AF diminishing when PV tachycardias are eliminated by PV isolation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2002.00645.x
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