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New Bayesian Discriminator for Detection of Atrial Tachyarrhythmias
- Weichao Xu,
- Hung-Fat Tse,
- Francis H.Y. Chan,
- Peter Chin Wan Fung,
- Kathy Lai-Fun Lee and
- Chu-Pak Lau
Circulation Volume 105, Issue 1226 March 2002

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Background— Accurate, rapid detection of atrial tachyarrhythmias has important implications in the use of implantable devices for treatment of cardiac arrhythmia. Currently available detection algorithms for atrial tachyarrhythmias, which use the single-index method, have limited sensitivity and specificity.Methods and Results— In this study, we evaluated the performance of a new Bayesian discriminator algorithm in the detection of atrial fibrillation (AF), atrial flutter (AFL), and sinus rhythm (SR). Bipolar recording of 364 rhythms (AF=156, AFL=88, SR=120) at the high right atrium were collected from 20 patients who underwent electrophysiological procedures. After initial signal processing, a column vector of 5 features for each rhythm were established, based on the regularity, rate, energy distribution, percent time of quiet interval, and baseline reaching of the rectified autocorrelation coefficient functions. Rhythm identification was obtained by use of Bayes decision rule and assumption of Gaussian distribution. For the new Bayesian discriminator, the overall sensitivity for detection of SR, AF, and AFL was 97%, 97%, and 94%, respectively; and the overall specificity for detection of SR, AF, and AFL was 98%, 98%, and 99%, respectively. The overall accuracy of detection of SR, AF, and AFL was 98%, 97% and 98%, respectively. Furthermore, sensitivity, specificity, and accuracy of this algorithm were not affected by a range of white Gaussian noises with different intensities.Conclusions— This new Bayesian discriminator algorithm, based on Bayes decision of multiple features of atrial electrograms, allows rapid on-line and accurate (98%) detection of AF with robust anti-noise performance.
Primary Prevention of Sudden Cardiac Death in Idiopathic Dilated Cardiomyopathy: The Cardiomyopathy Trial (CAT)
- Dietmar Bänsch,
- Matthias Antz,
- Sigrid Boczor,
- Marius Volkmer,
- Jürgen Tebbenjohanns,
- Karlheinz Seidl,
- Michael Block,
- Frank Gietzen,
- Jürgen Berger,
- Karl Heinz Kuck
Circulation Volume 105, Issue 1226 March 2002

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Background— Patients with idiopathic dilated cardiomyopathy (DCM) and impaired left ventricular ejection fraction have an increased risk of dying suddenly.Methods and Results— Patients with recent onset of DCM (≤9 months) and an ejection fraction ≤30% were randomly assigned to the implantation of an implantable cardioverter-defibrillator (ICD) or control. The primary end point of the trial was all-cause mortality at 1 year of follow-up. The trial was terminated after the inclusion of 104 patients because the all-cause mortality rate at 1 year did not reach the expected 30% in the control group. In August 2000, the vital status of all patients was updated by contacting patients, relatives, or local registration offices. One hundred four patients were enrolled in the trial: Fifty were assigned to ICD therapy and 54 to the control group. Mean follow-up was 22.8±4.3 months, on the basis of investigators’ follow-up. After 1 year, 6 patients were dead (4 in the ICD group and 2 in the control group). No sudden death occurred during the first and second years of follow-up. In August 2000, after a mean follow-up of 5.5±2.2 years, 30 deaths had occurred (13 in the ICD group and 17 in the control group). Cumulative survival was not significantly different between the two groups (93% and 80% in the control group versus 92% and 86% in the ICD group after 2 and 4 years, respectively).Conclusions— This trial did not provide evidence in favor of prophylactic ICD implantation in patients with DCM of recent onset and impaired left ventricular ejection fraction.
On the Reanalysis of the GISSI-Prevenzione
- Alexander Leaf
Circulation Volume 105, Issue 1623 April 2002

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Electrical Conduction in Canine Pulmonary Veins: Electrophysiological and Anatomic Correlation
- Mélèze Hocini,
- Siew Y. Ho,
- Tokuhiro Kawara,
- André C. Linnenbank,
- Mark Potse,
- Dipen Shah,
- Pierre Jaïs,
- Michiel J. Janse,
- Michel Haïssaguerre and
- Jacques M.T. de Bakker
Circulation Volume 105, Issue 2021 May 2002

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Background— Paroxysmal atrial fibrillation in patients is often initiated by foci in the pulmonary veins. The mechanism of these initiating arrhythmias is unknown. The aim of this study was to determine electrophysiological characteristics of canine pulmonary veins that may predispose to initiating arrhythmias.Methods and Results— Extracellular recordings were obtained from the luminal side of 9 pulmonary veins in 6 Langendorff-perfused dog hearts after the veins were incised from the severed end to the ostium. Pulmonary veins were paced at the distal end, the ostium, and an intermediate site. During basic and premature stimulation, extracellular electrical activity was recorded with a grid electrode that harbored 247 electrode terminals. In 4 hearts, intracellular electrograms were recorded with microelectrodes. Myocyte arrangement immediately beneath the venous walls was determined by histological analysis in 3 hearts. Extracellular mapping revealed slow and complex conduction in all pulmonary veins. Activation delay after premature stimulation could be as long as 96 ms over a distance of 3 mm. Action potential duration was shorter at the distal end of the veins than at the orifice. No evidence for automaticity or triggered activity was found. Histological investigation revealed complex arrangements of myocardial fibers that often showed abrupt changes in fiber direction and short fibers arranged in mixed direction.Conclusions— Zones of activation delay were observed in canine pulmonary veins and correlated with abrupt changes in fascicle orientation. This architecture of muscular sleeves in the pulmonary veins may facilitate reentry and arrhythmias associated with ectopic activity.
Impact of Myocardial Ischemia and Reperfusion on Ventricular Defibrillation Patterns, Energy Requirements, and Detection of Recovery
- Hao Qin,
- Gregory P. Walcott,
- Cheryl R. Killingsworth,
- Dennis L. Rollins,
- William M. Smith and
- Raymond E. Ideker
Circulation Volume 105, Issue 2128 May 2002

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Background— Shocks that have defibrillated spontaneous ventricular fibrillation (VF) during acute ischemia or reperfusion may seem to have failed if VF recurs before the ECG amplifier recovers after shock. This could explain why the defibrillation threshold (DFT) for spontaneous VF appears markedly higher than for electrically induced VF.Methods and Results— The DFT for electrically induced VF (E-DFT) was determined in 15 pigs before ischemia, followed by left anterior ascending or left circumflex artery occlusion. VF was electrically induced 20 minutes after occlusion, followed 5 minutes later by reperfusion. Whether spontaneous or electrically induced, VF during occlusion or reperfusion was treated with up to 3 shocks at 1.5×E-DFT. If all 3 shocks failed, shock strength was increased. Thirty minutes after reperfusion, the other artery was occluded and the protocol was repeated. Defibrillation was considered successful if postshock sinus/idioventricular rhythm was present for ≥30 seconds. VF recurring within 30 seconds after the shock was considered immediate or delayed if the first postshock activation complex in a rapidly restored ECG recording was VF or sinus/idioventricular rhythm, respectively. Defibrillation efficacy at 1.5×E-DFT was significantly higher for electrically induced ischemic VF (76%) than for spontaneous VF (31%). The incidence of delayed recurrence after electrically induced nonischemic (3%) or ischemic (20%) VF was significantly lower than after spontaneous VF (75%). Mean VF recurrence time after spontaneous VF was 4.6±5.3 seconds.Conclusions— Spontaneous VF can be halted by a shock but then quickly restart before a standard ECG amplifier has recovered from postshock saturation, making it appear that the shock failed.
Electrophysiology and Arrhythmogenic Activity of Single Cardiomyocytes From Canine Superior Vena Cava
- Yi-Jen Chen,
- Yao-Chang Chen,
- Hung-I Yeh,
- Cheng-I Lin and
- Shih-Ann Chen
Circulation Volume 105, Issue 224 June 2002

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Background— The superior vena cava (SVC) has been proved to be a focal point in the initiation of paroxysmal atrial fibrillation. The autonomic nervous system plays an important role in the genesis of atrial fibrillation. However, the arrhythmogenic potentials of SVC and its responses to autonomic agents are not clear. The purpose of this study was to isolate single SVC cardiomyocytes and to investigate their electrophysiological characteristics, as well as the direct effects of autonomic agents.Methods and Results— Canine SVC cardiomyocytes were isolated by perfusion with digestive enzymes. The action potentials and ionic currents were investigated in single SVC cardiomyocytes using the whole-cell clamp technique. Dissociation of the SVC yielded rod-shaped single cardiomyocytes with (n=74, 51%) or without (n=71, 49%) pacemaker activities. There were similar densities of inward Ca²⁺, delayed rectifier K⁺, transient inward, inward rectifier K⁺, and pacemaker currents between SVC cardiomyocytes with and without pacemaker activity. SVC cardiomyocytes with pacemaker activity have, however, greater transient outward currents than those without pacemaker activity. In SVC cardiomyocytes, acetylcholine (5.5 μmol/L) abolished the spontaneous activities, but isoproterenol (10 nmol/L), atropine (10 μmol/L), and phenylephrine (10 μmol/L) accelerated the spontaneous activity and induced the occurrences of early or delayed afterdepolarizations.Conclusions— These findings suggest that SVC cardiomyocytes have distinct action potentials and ionic current profiles that may be responsible for the arrhythmogenic activity of the SVC.
Autonomic Tone Variations Before the Onset of Paroxysmal Atrial Fibrillation
- Marco Bettoni and
- Marc Zimmermann
Circulation Volume 105, Issue 2311 June 2002

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Background— Mechanisms favoring the occurrence of paroxysmal atrial fibrillation (PAF) are complex and poorly defined. This study was designed to analyze dynamic changes in autonomic tone preceding the onset of PAF in a large group of patients.Methods and Results— Holter tapes from 77 unselected consecutive patients (63 men and 14 women aged 58±12 years) with PAF were analyzed. A total of 147 episodes of sustained AF (>30 minutes) were recorded and submitted to time-domain and frequency-domain heart rate variability analyses; 6 periods were studied using repeated measures ANOVA: the 24-hour period, the hour preceding PAF, and the 20 minutes before PAF divided into four 5-minute periods. In the time-domain analyses, a linear decrease in mean RR interval from 925±16 to 906±16 ms (P<0.0002) was observed before the onset of PAF, together with a significant increase in the standard deviation of NN intervals from 65±4 to 70±4 ms (P<0.02). In the frequency-domain analyses, a significant increase in high-frequency (HF, HF-NU) components was observed before PAF (P<0.001 and P<0.0001, respectively), together with a progressive decrease in low-frequency components (LF, LF-NU) (P<0.0001 and P<0.004, respectively). The low/high frequency ratio showed a linear increase until 10 minutes before PAF, followed by a sharp decrease immediately before PAF, suggesting a primary increase in adrenergic tone followed by a marked modulation toward vagal predominance. No difference was observed in these heart rate variability changes between patients with “lone” PAF and patients with structural heart disease.Conclusions— The occurrence of PAF greatly depends on variations of the autonomic tone, with a primary increase in adrenergic tone followed by an abrupt shift toward vagal predominance.
Electrical Connections Between Pulmonary Veins: Implication for Ostial Ablation of Pulmonary Veins in Patients With Paroxysmal Atrial Fibrillation
- Atsushi Takahashi,
- Yoshito Iesaka,
- Yoshihide Takahashi,
- Ryoko Takahashi,
- Kenzaburo Kobayashi,
- Katsumasa Takagi,
- Osamu Kuboyama,
- Takeo Nishimori,
- Hidenobu Takei,
- Hiroshi Amemiya,
- Hideomi Fujiwara and
- Masayasu Hiraoka
Circulation Volume 105, Issue 2525 June 2002

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Background— Electrical disconnection of the myocardial extensions into arrhythmogenic pulmonary veins (PVs) is recognized as a curative technique for paroxysmal atrial fibrillation (AF). However, the presence of electrical connections between the PVs, which may make achievement of PV disconnection difficult, has not been systematically evaluated.Methods and Results— Forty-nine consecutive patients with drug-resistant AF underwent ostial radiofrequency (RF) catheter ablation of arrhythmogenic PVs with foci triggering AF. Pacing from inside the targeted PV was performed after each RF delivery to identify the left atrial exit site of the residual venoatrial conduction. Successful PV disconnection was defined as achieving elimination of the PV potentials during sinus rhythm or left atrial pacing, and the loss of left atrial conduction during intra-PV pacing. A total of 112 arrhythmogenic PVs were identified. PV disconnection was achieved with 10±6.1 minutes of RF delivery to the ostia of 101 targeted PVs. In 7 left superior (LS) PVs from 7 patients (14%), the earliest atrial activity was recorded from the left inferior (LI) PV ostium during intra-LSPV pacing after 11±4.7 minutes of RF delivery to the LSPV ostium. Disconnection of these LSPVs was achieved by LIPV disconnection. In the remaining 4 PVs from 4 patients, PV disconnection could not be achieved.Conclusions— Fourteen percent of the patients had electrical connections between contiguous PVs. In these patients, ostial ablation of an untargeted PV was required for successful targeted PV disconnection.
Interventions on Prevention of Postoperative Atrial Fibrillation in Patients Undergoing Heart Surgery: A Meta-Analysis
- Eugene Crystal,
- Stuart J. Connolly,
- Khaled Sleik,
- Tracy J. Ginger and
- Salim Yusuf
Circulation Volume 106, Issue 12 July 2002

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Background— Postoperative atrial fibrillation (AF) is a common complication of cardiac surgery and has been associated with increased incidence of other complications and increased hospital length of stay (LOS). Prevention of AF is a reasonable clinical goal, and, consequently, many randomized trials have evaluated the effectiveness of pharmacological and nonpharmacological interventions for prevention of AF. To better understand the role of various prophylactic therapies against postoperative AF, a systematic review of evidence from randomized trials was performed.Methods and Results— Fifty-two randomized trials (controlled by placebo or routine treatment) of β-blockers, sotalol, amiodarone, or pacing were identified by systematic literature search. The 3 drug treatments each prevented AF with the following odds ratios (ORs): β-blockers, 0.39 (95% CI, 0.28 to 0.52); sotalol, 0.35 (95% CI, 0.26 to 0.49); and amiodarone, 0.48 (95% CI, 0.37 to 0.61). Pacing was also effective; for biatrial pacing, the OR was 0.46 (95% CI, 0.30 to 0.71). The influence of pharmacological interventions on LOS was as follows: −0.66 day (95% CI, 2.04 to 0.72) for β-blockers; −0.40 day (95% CI, 0.87 to 0.08) for sotalol; and −0.91 day (95% CI, 1.59 to −0.23) for amiodarone. The influence for biatrial pacing was −1.54 day (95% CI, −2.85 to −0.24). The incidence of stroke was 1.2% in all the treatment groups combined and 1.4% in controls (OR, 0.90; 95% CI, 0.46 to 1.74).Conclusions— β-Blockers, sotalol, and amiodarone all reduce risk of postoperative AF with no marked difference between them. There is evidence that use of these drugs will reduce LOS. Biatrial pacing is a promising new treatment opportunity. There was no evidence that reducing postoperative AF reduces stroke; however, data on stroke are incomplete.
Adverse Outcomes of Interrupted Precordial Compression During Automated Defibrillation
- Ting Yu,
- Max Harry Weil,
- Wanchun Tang,
- Shijie Sun,
- Kada Klouche,
- Heitor Povoas and
- Joe Bisera
Circulation Volume 106, Issue 316 July 2002

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Background— Current versions of automated external defibrillators (AEDs) require frequent stopping of chest compression for rhythm analyses and capacity charging. The present study was undertaken to evaluate the effects of these interruptions during the operation of AEDs.Methods and Results— Ventricular fibrillation was electrically induced in 20 male domestic swine weighing between 37.5 and 43 kg that were untreated for 7 minutes before CPR was started. Defibrillation was attempted with up to 3 sequential 150-J biphasic shocks, but each was preceded by 3-, 10-, 15-, or 20-second interruptions of chest compression. The interruptions corresponded to those that were mandated by commercially marketed AEDs for rhythm analyses and capacitor charge. The sequence of up to 3 electrical shocks and delays were repeated at 1-minute intervals until the animals were successfully resuscitated or for a total of 15 minutes. Spontaneous circulation was restored in each of 5 animals in which precordial compression was delayed for 3 seconds before the delivery of the first and subsequent shocks but in none of the animals in which the delay was >15 seconds before the delivery of the first and subsequent shocks. Longer intervals of CPR interventions were required, and there was correspondingly greater failure of resuscitation in close relationship to increasing delays. The durations of interruptions were inversely related to the durations of subthreshold levels of coronary perfusion pressure. Postresuscitation arterial pressure and left ventricular ejection fraction were more severely impaired with increasing delays.Conclusions— Interruptions of precordial compression for rhythm analyses that exceed 15 seconds before each shock compromise the outcome of CPR and increase the severity of postresuscitation myocardial dysfunction.
Left Atrial Appendage Activity Masquerading as Pulmonary Vein Potentials
- Dipen Shah,
- Michel Haissaguerre,
- Pierre Jais,
- Meleze Hocini,
- Teiichi Yamane,
- Laurent Macle,
- Kee Joon Choi and
- Jacques Clementy
Circulation Volume 105, Issue 2418 June 2002

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Background— Despite extensive proximal ablation, all potentials frequently cannot be eliminated from the left pulmonary veins (PV).Methods and Results— PV electrograms were analyzed during sinus rhythm, coronary sinus, and left atrial appendage (LAA) pacing, and PV and LAA angiography performed. During pacing, an initial low-amplitude slow potential was recorded on the anterior aspect of the left superior PV and anticipated with shortest activation time by LAA pacing. Its timing coincided with posterior LAA activation, shown to be immediately adjacent to the left superior PV by angiography. In the left inferior PV, the first potential was smaller and less sharp, coinciding with adjacent low LA activation. Angiographically, the LAA was at least 15 mm from the left inferior PV. The second sharper potential in both left PVs was eliminated by proximal ablation.Conclusion— Far field LAA activity consistently adds to PV myocardial electrograms in the left superior PV whereas lower, less sharp extravenous potentials in the left inferior PV originate from the inferior LA. They can be identified by LAA and coronary sinus pacing.
Use of Irbesartan to Maintain Sinus Rhythm in Patients With Long-Lasting Persistent Atrial Fibrillation: A Prospective and Randomized Study
- Antonio H. Madrid,
- Manuel G. Bueno,
- Jose M.G. Rebollo,
- Irene Marín,
- Gonzalo Peña,
- Enrique Bernal,
- Aníbal Rodriguez,
- Lucas Cano,
- José M. Cano,
- Pedro Cabeza and
- Concepción Moro
Circulation Volume 106, Issue 316 July 2002

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Background— Data from studies of angiotensin-converting enzyme inhibitors provide evidence that the renin-angiotensin-aldosterone system plays a role as a mediator of atrial remodeling in atrial fibrillation. The present study has evaluated the effect of treatment with the angiotensin I type 1 receptor blocker irbesartan on maintaining sinus rhythm after conversion from persistent atrial fibrillation.Methods and Results— To be included in the present study, patients must have had an episode of persistent atrial fibrillation for >7 days. The patients were then randomized and scheduled for electrical cardioversion. Two groups of patients were compared: Group I was treated with amiodarone, and group II was treated with amiodarone plus irbesartan. The primary end point was the length of time to a first recurrence of atrial fibrillation. From a total of 186 patients assessed in the study, 154 were analyzed with the use of intention-to-treat analysis. Seventy-five patients were randomly allocated to group I and 79 to group II. After 2 months of follow-up in the intention-to-treat analysis, the group treated with irbesartan had fewer patients with recurrent atrial fibrillation (Kaplan-Meier analysis, 84.79% versus 63.16%, P=0.008). The Kaplan-Meier analysis of time to first recurrence during the follow-up period (median time, 254 days [range, 60 to 710]) also showed that patients treated with irbesartan had a greater probability of remaining free of atrial fibrillation (79.52% versus 55.91%, P=0.007).Conclusions— Patients treated with amiodarone plus irbesartan had a lower rate of recurrence of atrial fibrillation than did patients treated with amiodarone alone.
Sustained Ventricular Arrhythmias Among Patients With Acute Coronary Syndromes With No ST-Segment Elevation: Incidence, Predictors, and Outcomes
- Sana M. Al-Khatib,
- Christopher B. Granger,
- Yao Huang,
- Kerry L. Lee,
- Robert M. Califf,
- Maarten L. Simoons,
- Paul W. Armstrong,
- Frans Van de Werf,
- Harvey D. White,
- R. John Simes,
- David J. Moliterno,
- Eric J. Topol and
- Robert A. Harrington
Circulation Volume 106, Issue 316 July 2002

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Background— The prognosis of ventricular arrhythmias among patients with non–ST-elevation acute coronary syndromes is unknown. We studied the incidence, predictors, and outcomes of sustained ventricular arrhythmias in 4 large randomized trials of such patients.Methods and Results— We pooled the datasets of the Global Use of Streptokinase and tPA for Occluded Arteries (GUSTO)-IIb, Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy (PURSUIT), Platelet IIb/IIIa Antagonism for the Reduction of Acute Coronary Syndrome Events in a Global Organization Network (PARAGON)-A, and PARAGON-B trials (n=26 416). We identified independent predictors of ventricular fibrillation (VF) and ventricular tachycardia (VT) and compared the 30-day and 6-month mortality rates of patients who did (n=552) and did not (n=25 864) develop these arrhythmias during the index hospitalization. Independent predictors of in-hospital VF included prior hypertension, chronic obstructive pulmonary disease, prior myocardial infarction, and ST-segment changes at presentation. Except for hypertension, these variables also independently predicted in-hospital VT. In Cox proportional-hazards modeling, in-hospital VF and VT were independently associated with 30-day mortality (hazard ratio [HR], 23.2 [95% CI, 18.1 to 29.8] for VF and HR, 7.6 [95% CI, 5.5 to 10.4] for VT) and 6-month mortality (HR, 14.8 [95% CI, 12.1 to 18.3] for VF and HR, 5.0 [95% CI, 3.8 to 6.5] for VT). These differences remained significant after excluding patients with heart failure or cardiogenic shock and those who died <24 hours after enrollment.Conclusions— Despite the use of effective therapies for non–ST-elevation acute coronary syndromes, ventricular arrhythmias in this setting are associated with increased 30-day and 6-month mortality. More effective therapies are needed to improve the survival of patients with these arrhythmias.
Mapping and Ablation of Idiopathic Ventricular Fibrillation
- Michel Haïssaguerre,
- Morio Shoda,
- Pierre Jaïs,
- Akihiko Nogami,
- Dipen C. Shah,
- Josef Kautzner,
- Thomas Arentz,
- Dietrich Kalushe,
- Dominique Lamaison,
- Mike Griffith,
- Fernando Cruz,
- Angelo de Paola,
- Fiorenzo Gaïta,
- Mélèze Hocini,
- Stéphane Garrigue,
- Laurent Macle,
- Rukshen Weerasooriya and
- Jacques Clémenty
Circulation Volume 106, Issue 820 August 2002

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Background— Ventricular fibrillation is the main mechanism of sudden cardiac death. The feasibility of eliminating recurrent episodes by catheter ablation has not been reported.Methods and Results— Twenty-seven patients without known heart disease (13 men, 14 women, 41±14 years of age) were studied after being resuscitated from recurrent (10±12) episodes of primary idiopathic ventricular fibrillation; 23 had received a defibrillator. The first initiating beat of ventricular fibrillation had an identical electrocardiographic morphology and coupling interval (297±41 ms) to preceding isolated premature beats typically noted in the aftermath of resuscitation. These triggers were localized by mapping the earliest electrical activity and ablated by local radiofrequency delivery. Outcome was assessed by Holter and defibrillator memory interrogation. Premature beats were elicited from the Purkinje conducting system in 23 patients: from the left ventricular septum in 10, from the anterior right ventricle in 9, and from both in 4. The interval from the Purkinje potential to the following myocardial activation varied from 10 to 150 ms during premature beat but was 11±5 ms during sinus rhythm, indicating location at peripheral Purkinje arborization. The premature beats originated from the right ventricular outflow tract muscle in 4 patients. The accuracy of mapping was confirmed by acute elimination of premature beats during local radiofrequency delivery. During a follow-up of 24±28 months, 24 patients (89%) had no recurrence of ventricular fibrillation without drug.Conclusions— Primary idiopathic ventricular fibrillation is a syndrome characterized by dominant triggers from the distal Purkinje system. These sources can be eliminated by focal energy delivery.
Segmental Ostial Ablation to Isolate the Pulmonary Veins During Atrial Fibrillation: Feasibility and Mechanistic Insights
- Hakan Oral,
- Bradley P. Knight,
- Mehmet Özaydın,
- Aman Chugh,
- Steve W.K. Lai,
- Christoph Scharf,
- Sohail Hassan,
- Radmira Greenstein,
- Jihn D. Han,
- Frank Pelosi,
- S. Adam Strickberger and
- Fred Morady
Circulation Volume 106, Issue 103 September 2002

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Background— The purpose of this study was to determine the feasibility and mechanistic implications of segmental pulmonary vein (PV) ostial ablation during atrial fibrillation (AF).Methods and Results— Forty consecutive patients underwent PV isolation for AF. Among 125 PVs targeted for isolation, ablation was performed during AF in 70 veins and during sinus rhythm in 55 veins. A decapolar Lasso catheter was positioned near the ostium. During AF, ostial ablation was performed near the Lasso catheter electrodes that recorded a tachycardia with a cycle length shorter than in the adjacent left atrium. During sinus rhythm, ostial ablation was guided by PV potentials. Complete PV isolation was achieved in 70 PVs (100%) ablated during AF and in 53 PVs (96%) ablated during sinus rhythm (P=0.4). The mean durations of radiofrequency energy needed for isolation were 7.4±4.4 and 5.2±3.9 minutes during AF and sinus rhythm, respectively (P<0.01). Before ablation, an immediate recurrence of AF (IRAF), occurred after cardioversion in 18 of 40 patients, and IRAF was consistently abolished by PV isolation. The probability of AF termination during isolation of a PV was directly related to the extent of tachycardia in that vein. As more PVs were isolated, induction of persistent AF by rapid pacing became less likely.Conclusions— Segmental ostial ablation guided by PV tachycardia during AF is feasible and as efficacious as during sinus rhythm. The responses to cardioversion, ablation, and rapid pacing observed in this study imply that IRAF is triggered by the PVs and that PV tachycardias may play an important role in the perpetuation of AF.
KB-R7943 Prevents Acute, Atrial Fibrillation–Induced Shortening of Atrial Refractoriness in Anesthetized Dogs
- Akira Miyata,
- Douglas P. Zipes,
- Stephen Hall and
- Michael Rubart
Circulation Volume 106, Issue 1110 September 2002

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Background— To test the hypothesis that Ca²⁺ influx via Na⁺/Ca²⁺ exchange (NCX) underlies atrial fibrillation (AF)–induced shortening of atrial effective refractory period (AERP), we examined the potential of KB-R7943 (KB), a selective inhibitor of Ca²⁺-influx mode NCX, to attenuate this effect.Methods and Results— Studies were performed in 41 isoflurane-anesthetized dogs. In sinus rhythm dogs, peak AERP changes resulting from intravenous KB infusion ranged from (mean±SEM) 4.4±0.4% (1 mg/kg) to 14.8±2.6% (5 mg/kg; ED₅₀=1.9 mg/kg). AERP was maximally prolonged between 5 and 10 minutes after beginning of KB infusion and returned to baseline values within 30 minutes thereafter. Rapid atrial pacing–induced AF reversibly shortened AERP (P<0.001) in 5 dogs, averaging 14.9±2.1% after 90 minutes of AF. Both the time course and magnitude of mean AERP changes in 5 AF dogs receiving 5 mg/kg KB were indistinguishable from those in 5 sinus rhythm dogs receiving an equivalent KB dose (P>0.05). We measured cardiac tissue and arterial plasma KB concentrations produced by intravenous infusion (1 mg · kg⁻¹ · min⁻¹) of 5 mg/kg KB. Plasma drug concentration peaked at the end of KB infusions (30.86±3.26 nmol/L; n=4 dogs) and declined to 0.56±0.19 nmol/L after 100 minutes. The cardiac tissue-to-plasma drug concentration gradient averaged ≈40 at 100 minutes after start of KB infusion. KB at concentrations achieved in vivo irreversibly blocked NCX-mediated Ca²⁺ influx in isolated canine right atrial myocytes by ≈60%, but had no significant effect on NCX-dependent Ca²⁺ extrusion.Conclusion— NCX-mediated Ca²⁺ influx plays an important role in acute, AF-induced AERP shortening.
Two Types of Ventricular Fibrillation in Isolated Rabbit Hearts: Importance of Excitability and Action Potential Duration Restitution
- Tsu-Juey Wu,
- Shien-Fong Lin,
- James N. Weiss,
- Chih-Tai Ting and
- Peng-Sheng Chen
Circulation Volume 106, Issue 141 October 2002

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Background— The combined effects of excitability and action potential duration (APD) restitution on wavefront dynamics remain unclear.Methods and Results— We used optical mapping techniques to study Langendorff-perfused rabbit hearts. In protocol IA (n=10), D600 at increasing concentrations was infused during ventricular fibrillation (VF). With concentration increased to 0.5 mg/L, fast VF (dominant frequency, 19.1±1.8 Hz) was consistently converted to ventricular tachycardia (VT). However, increasing D600 further to 2.5 or 5.0 mg/L converted VT to slow VF (11.9±2.3 Hz, P=0.0011). In an additional 4 hearts (protocol IB), tetrodotoxin converted a preexisting VT to slow VF (11.0±1.4 Hz). Optical maps show wandering wavelets in fast VF, organized reentry in VT, and spatiotemporal periodicity in slow VF. In protocol II, we determined APD and conduction time⁻¹ (CT⁻¹) restitutions during D600 infusion. CT⁻¹ was used as an estimate of excitability. At 0.1 mg/L, APD and CT⁻¹ restitutions were steep and flat, respectively. APD restitution became flattened when D600 increased to 0.5 mg/L, converting fast VF to VT. Further increasing D600 to 2.5 or 5.0 mg/L steepened CT⁻¹ restitution and widened the range of S₁ pacing cycle lengths over which CT⁻¹ decreased, converting VT to slow VF.Conclusions— Two types of VF exist in isolated rabbit hearts. Fast (type I) VF is associated with a steep APD restitution, a flat CT⁻¹ restitution, and wandering wavelets. Slow (type II) VF is associated with a flat APD restitution, a steep CT⁻¹ restitution, and spatiotemporal periodicity. Both excitability and APD restitution are important in VF maintenance.
Ventricular Rate Control by Selective Vagal Stimulation Is Superior to Rhythm Regularization by Atrioventricular Nodal Ablation and Pacing During Atrial Fibrillation
- Shaowei Zhuang,
- Youhua Zhang,
- Kent A. Mowrey,
- Jianbo Li,
- Tomotsugu Tabata,
- Don W. Wallick,
- Zoran B. Popović,
- Richard A. Grimm,
- Andrea Natale and
- Todor N. Mazgalev
Circulation Volume 106, Issue 141 October 2002

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Background— Selective atrioventricular nodal (AVN) vagal stimulation (AVN-VS) has emerged as a novel strategy for ventricular rate (VR) control in atrial fibrillation (AF). Although AVN-VS preserves the physiological ventricular activation sequence, the resulting rate is slow but irregular. In contrast, AVN ablation with pacemaker implantation produces retrograde activation (starting at the apex), with regular ventricular rhythm. We tested the hypothesis that, at comparable levels of VR slowing, AVN-VS provides hemodynamic benefits similar to those of ablation with pacemaker implantation.Methods and Results— AVN-VS was delivered to the epicardial fat pad that projects parasympathetic nerve fibers to the AVN in 12 dogs during AF. A computer-controlled algorithm adjusted AVN-VS beat by beat to achieve a mean ventricular RR interval of 75%, 100%, 125%, or 150% of spontaneous sinus cycle length. The AVN was then ablated, and the right ventricular (RV) apex was paced either irregularly (i-RVP) using the RR intervals collected during AVN-VS or regularly (r-RVP) at the corresponding mean RR. The results indicated that all 3 strategies improved hemodynamics compared with AF. However, AVN-VS resulted in significantly better responses than either r-RVP or i-RVP. i-RVP resulted in worse hemodynamic responses than r-RVP. The differences among these modes became less significant when mean VR was slowed to 150% of sinus cycle length.Conclusions— AVN-VS can produce graded slowing of the VR during AF without destroying the AVN. It was hemodynamically superior to AVN ablation with either r-RVP or i-RVP, indicating that the benefits of preserving the physiological antegrade ventricular activation sequence outweigh the detrimental effect of irregularity.
Selective Vagal Stimulation for Rate Control in Atrial Fibrillation
- John P. DiMarco
Circulation Volume 106, Issue 141 October 2002

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Electroanatomic Mapping and Catheter Ablation of Breakthroughs From the Right Atrium to the Superior Vena Cava in Patients With Atrial Fibrillation
- Masahiko Goya,
- Feifan Ouyang,
- Sabine Ernst,
- Marius Volkmer,
- Matthias Antz and
- Karl-Heinz Kuck
Circulation Volume 106, Issue 1110 September 2002

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Background— The superior vena cava (SVC) is one of the sources of ectopies that can initiate atrial fibrillation (AF). We investigated by radiofrequency ablation the electrophysiological characteristics of the junction of the right atrium (RA) and the SVC and the feasibility of electrical disconnection of the SVC from the RA.Methods and Results— Sixteen patients with paroxysmal AF after pulmonary vein isolation underwent electroanatomic mapping at the RA–SVC junction during sinus rhythm. Mapping showed sharp potentials (SVC potentials) inside the SVC. Activation spread from the earliest SVC potential (breakthrough) to the rest of the SVC. SVC potentials were found over a large amount of the circumference, suggesting widespread muscle coverage of the SVC. Breakthroughs from the RA to SVC were located anteriorly, laterally, posteriorly, and septally in 3, 4, 10, and 6 patients, respectively. The number of breakthroughs was 1.4±0.5 per patient. Radiofrequency energy was applied with the end point of electrical disconnection. All breakthroughs were eliminated with 3.1±1.7 applications per breakthrough without complications.Conclusions— SVC potentials can be recorded inside the SVC. There are specific breakthroughs from the RA to the SVC that can be identified by electroanatomic mapping. The electrical disconnection of the SVC from the RA is feasible.

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