Influence of structural heart disease on characteristics of atrial fibrillation recurrence in patients with dual-chamber pacemakers

Aims

The aim of the study was to prospectively examine the influence of structural heart disease (SHD) and sinus node dysfunction (SND) on the frequency and duration of atrial fibrillation (AF) episodes in patients with implanted pacemakers.

Methods

We examined episodes of AF in 207 patients (93 with SHD; 165 with SND) with known or suspected paroxysmal AF who underwent dual-chamber pacing.

Results

Seventy-one percent of all patients experienced at least one episode of AF during follow-up, with a mean burden of 3.3 ± 6.4 h/d (median, 0.2 hours) and a mean frequency of 11.7 ± 26.0 episodes per day (median, 1.4). The proportion of episodes longer than 6 hours was greater in patients with SHD when compared to patients without SHD. In a logistic regression model adjusted for SND, gender, and the 2-way interactions of SND, sex, and SHD, SHD was a significant factor (P = .0188) with the odds ratio of having an episode longer than 6 hours 3.4 times higher for patients with SHD than for patients without SHD. Older patients with SHD had less frequent but longer episodes compared to younger patients. In patients without SHD, there was no comparable age difference. Burden, frequency, and average episode length were not influenced by the presence or absence of SND.

Conclusions

Patients with SHD have longer episodes of AF supporting the concept that SHD influences the underlying substrate to favor perpetuation.     

Novel electrophysiologic parameter of dispersion of atrial repolarization: comparison of different atrial pacing methods

INTRODUCTION: Heterogeneity of ventricular repolarization plays a major role in reentrant tachyarrhythmias in cardiac tissue. However, the role of atrial repolarization added activation time (AT) to refractoriness in atrial vulnerability has not been investigated in detail. METHODS AND RESULTS: The study population consisted of 34 patients: 18 with atrial fibrillation (AF) and 16 without AF (control group). The effective refractory periods (ERPs) in the right atrial appendage, low lateral right atrium, high right septum, and distal coronary sinus, and ATs from P wave onset to each electrogram during sinus rhythm and right atrial appendage, low lateral right atrial, high right septal, distal coronary sinus, and biatrial pacing were measured. Atrial recovery time, defined as the sum of AT and ERP, and its dispersions during sinus rhythm, right atrial appendage, low lateral right atrial, high right septal, distal coronary sinus, and biatrial pacing were calculated. Both ERP dispersion and atrial recovery time dispersion during sinus rhythm were significantly greater in the AF group than in the control group. Atrial recovery time dispersion during distal coronary sinus, high right septal, or biatrial pacing was significantly smaller than that during right atrial appendage or low lateral right atrial pacing in each group. In particular, atrial recovery time dispersion during distal coronary sinus pacing was the smallest of the five pacing methods in the AF group. P wave duration during biatrial or high right septal pacing was significantly shorter than during right atrial appendage, low lateral right atrial, or distal coronary sinus pacing in each group. CONCLUSION: Atrial recovery time dispersion is suitable as an electrophysiologic parameter of atrial vulnerability. Distal coronary sinus pacing may prevent AF by increasing homogeneity of atrial repolarization, whereas biatrial and high right septal pacing contribute not only homogeneity of atrial repolarization but also improvement of atrial depolarization.     

Right ventricular apical lead position is associated with prolonged signal-averaged P-wave duration

Aim

The study aimed to determine if right ventricular apical pacing is associated with adverse change in atrial substrate compared with right ventricular septal pacing.

Methods

Patients with septal leads and dual-chamber devices with more than 3 months of follow-up and 70% or higher cumulative percentage of ventricular pacing were compared with a matched group of apically implanted leads with a cumulative percentage ventricular pacing of 70% or higher. Device parameters were recorded, and high-resolution recordings were obtained for signal-averaged P-wave (SAPW) analysis. Previously obtained SAPW recordings taken from 49 healthy patients and 73 patients with paroxysmal atrial fibrillation were used as negative and positive controls, respectively.

Results

Ten patients with septal leads (mean age, 71.9 ± 12.1 years; mean months implanted, 10.5 ± 3.2 months) and 9 patients with apical leads (mean age, 71.9 ± 5.7 years; mean months implanted, 11.4 ± 6.4 months) were enrolled. The SAPW duration was longer in the apical cohort compared with the septal cohort (144.8 ± 6.9 and 133.0 ± 5.5 milliseconds, respectively; P = .001), whereas there was no significant difference between septal and normal cohorts (133.0 ± 5.5 and 129.3 ± 7.1 milliseconds, respectively; P = .08).

Conclusions

Apical pacing is associated with prolonged P-wave duration relative to septal pacing and controls: this may manifest as increased risk of atrial tachycardias and presents a potentially novel benefit of septal pacing.     

Effects of Cilazapril on atrial electrical, structural and functional remodeling in atrial fibrillation dogs

Background and purpose

The effects of angiotensin-converting enzyme inhibitor on long-term atrial electrophysiologic and structural remodeling are still unclear. The purpose of this study is to investigate the effects of Cilazapril on atrial electrical, structural, and functional remodeling in atrial fibrillation (AF) dogs induced by chronic rapid atrial pacing.

Methods

Twenty dogs were randomly divided into sham-operated group (n = 6), control group (n = 7), and Cilazapril group (n = 7). One thin silicon plaque containing 4 pairs of electrodes was sutured to each atrium. A pacemaker was implanted in a subcutaneous pocket and attached to a screw-in epicardial lead in the right atrial appendage. The dogs in control group and Cilazapril group were paced at 400 beats per minute for 6 weeks. The dogs in Cilazapril group received Cilazapril (0.5 mg•kg⁻¹•d⁻¹) 1 week before rapid atrial pacing until pacing stop. Before and after 6-week rapid atrial pacing, atrial effective refractory period (AERP) at 8 sites, AERP dispersion, intraatrium conduction time, inducibility, and duration of AF were measured. Transthoracic and transesophageal echocardiographic examinations included left atrium (LA) maximal volume, LA minimal volume, LA ejection fraction, left atrial appendage (LAA) maximal volume, LAA minimal volume, LAA ejection fraction, LAA maximal forward flow velocity, and LAA minimal backward flow velocity were performed. Atrial collagen volume fraction was analyzed by Masson staining.

Results

After 6-week rapid atrial pacing, although there was no significant difference in AERP shortening and AERP rate adaptation reduction between the control group and the Cilazapril group, the inducibility and duration of AF were found to be dramatically lower in the Cilazapril group than those in the control group (AF inducibility, 65.7% vs 95.7%, P < .05; AF duration, 531.5 ± 301.2 vs 1432.2 ± 526.5 s, P < .01).The post-tachycardia intraatrium conduction times after 6 weeks with Cilazapril were significantly shorter than those in the control group. Cliazapril could partially prevent AERP dispersion increase induced by chronic rapid atrial pacing. Compared with the control group, the LA and LAA volumes were significantly smaller; LA ejection fraction, LAA ejection fraction, LAA maximal forward flow velocity, and LAA minimal backward flow velocity were dramatically higher in the Cilazapril group. The Cilazapril group had a significantly lower percentage of interstitial fibrosis than the control group.

Conclusions

Cilazapril can suppress structural and functional remodeling and prevent the induction and promotion of AF in chronic rapid atrial pacing dogs.     

Comparison of the acute effects of pacing the atrial septum, right atrial appendage, coronary sinus os, and the latter two sites simultaneously on the duration of atrial activation

OBJECTIVE—To compare the acute effects of right atrial appendage, atrial septal, coronary sinus os, and dual site pacing on the duration of atrial activation.
METHODS—20 patients with a variety of cardiac conditions underwent an intracardiac electrophysiological study. Electrograms were recorded from the right atrial appendage and at multiple sites within the coronary sinus. The duration of atrial activation was measured during pacing at the right atrial appendage, atrial septum, and coronary sinus os, and also during dual site stimulation.
RESULTS—The duration of atrial activation with atrial appendage pacing was notably longer (p < 0.001) than with dual site, septal, or coronary sinus os pacing, but there were no significant differences in atrial activation times between these latter three pacing modes. When stimulating the atria at a cycle length of 500 ms, the mean (SD) duration of atrial activation was 145 (37) ms for right atrial appendage pacing, 93 (26) ms for dual site pacing, 96 (28) ms for septal pacing, and 98 (28) ms for coronary sinus os pacing.
CONCLUSIONS—Assuming that the duration of atrial activation is an important determinant of predisposition to paroxysmal atrial fibrillation, atrial septal pacing or coronary sinus os pacing would appear to offer the same advantage as dual site pacing without the additional complexities associated with the latter pacing mode.


Keywords: atrial septal pacing; dual site pacing; atrial activation; atrial fibrillation     

房间隔起搏对阵发性心房颤动患者最大P波时限和P波离散度的影响

观察房间隔起搏对阵发性心房颤动 (AF)患者最大P波时限 (Pmax)及P波离散度 (Pd)的影响 ,探悉房间隔起搏防治AF发作的电生理机制。对 2 1例阵发性AF患者和 2 6例室上性心动过速行射频消融术无阵发性AF患者 ,分别进行右心耳和房间隔起搏 ,比较不同部位起搏对阵发性AF和无阵发性AF患者的Pmax和Pd影响。结果 :阵发性AF患者较无阵发性AF患者Pmax和Pd值明显大 (分别为 1 35± 1 5vs 1 1 9± 1 4ms ,P <0 .0 5 ;36 .5± 9.2vs 1 9.7± 7.1ms ,P <0 .0 1 ) ;房间隔起搏使阵发性AF患者Pd、Pmax显著下降 (分别为 2 3 .4± 8vs 36 .5± 9.2ms ,1 2 0± 1 1vs1 35± 1 5ms,P均 <0 .0 5) ;右心耳起搏使无阵发性AF患者Pmax和Pd明显增加 (分别为 1 32± 1 2vs 1 1 9± 1 4ms,2 5 .5± 8.5vs 1 9.7± 7.1ms ,P均 <0 .0 5)。结论 :右心耳起搏能够使无阵发性AF患者Pmax和Pd值增加。房间隔起搏能够明显降低阵发性AF患者Pmax、Pd ,纠正房内或房间传导延缓 ,改善心房内电活动的各向异性 ,防治AF发作     

Effect of an implantable cardioverter defibrillator with atrial detection and shock therapies on patient-perceived,health-related quality of life

Background

This study used a device (DDD implantable cardioverter defibrillator [ICD]) capable of delivering pacing and shock therapies to restore normal sinus rhythm in patients with atrial tachycardias or atrial fibrillation (AF). The purpose of this study was to assess the effect of the device on patient-perceived, health-related quality of life (QOL).

Methods

The DDD ICD was implanted in 267 patients with drug refractory, symptomatic AF from 45 centers across Europe, the United States, and Canada. Patients completed self-reported, validated QOL assessments at baseline and at 3- and 6-month follow-up visits (The Medical Outcomes Short Form 36 [SF-36] and the Symptom Checklist [SCL]).

Results

The mean age of the study group was 62 ± 12 years, and 73% of the patients were male. A total of 150 patients completed SF-36 assessments, and 138 patients completed SCL assessments at all 3 times. Baseline scores were more impaired (P < .05) on most SF-36 scales compared with norms for a general population, but were similar to a comparison group of patients with AF who were referred to tertiary care centers. The role-physical, physical functioning, vitality, mental health, and social functioning scales all improved significantly with time (all P < .04). Similarly, symptom frequency and severity (SCL) also improved significantly from baseline to 6 months (both P < .01). Shock therapy was delivered in 86 of the 150 patients (57%) with complete SF-36 evaluations. There was no evidence that receiving shocks decreased the relative improvement in QOL associated with implantation of the device.

Conclusions

In a 6-month period, QOL improves after implantation of a DDD ICD with atrial shock and pacing therapies. These improvements were not attenuated by receipt of shocks.     

低位房间隔起搏与右心耳起搏的临床对比研究

目的 探讨低位房间隔起搏与右心耳起搏在植入操作时间、起搏参数方面的差异.方法 选取40例因窦房结功能障碍或成人获得性房室传导阻滞导致的缓慢型心律失常行起搏治疗的患者分为两组.其中,房间隔组20例,采用主动固定螺旋电极行低位房间隔起搏;右心耳组20例,采用被动固定翼状电极行右心耳起搏.对比两组电极植入操作时间,电极植入时、术后1个月、3个月的起搏参数（阈值和阻抗）.结果 房间隔组与右心耳组比较,心房电极植入操作时间和起搏参数在术中、术后1个月、3个月差异均无统计学意义（P＞0.05）.结论 低位房间隔起搏与右心耳起搏具有相似的电极植入操作时间以及相同的起搏参数,为临床起搏治疗的有效部位.     

Do baseline atrial electrocardiographic and infarction patterns predict new-onset atrial fibrillation after ST-elevation myocardial infarction? Insights from the Assessment of Pexelizumab in Acute Myocardial Infarction Trial

Background

Atrial infarction reportedly occurs in 0.7% to 52% of ST-elevation myocardial infarctions (STEMIs), up to two thirds of whom develop atrial fibrillation and flutter (AF). Prospective validation of electrocardiographic atrial infarction patterns is lacking. Hence, in STEMI patients treated with primary percutaneous coronary intervention, we examined whether baseline atrial electrocardiographic changes or atrial infarction patterns predicted new AF or mortality.

Methods

Within the Assessment of Pexelizumab in Acute Myocardial Infarction trial, a nested case-control study was conducted. Patients with new AF were matched 1:1 with controls, and baseline atrial electrocardiographic variables were examined.

Results

Abnormal P wave morphology (Liu minor criterion for atrial infarction) was significantly associated with new AF (adjusted odds ratio, 1.68; 1.03-2.73). This was also independently associated with 90-day mortality in the overall case-control cohort (adjusted hazard rate, 1.90; 1.04-3.46) and among patient with new-onset AF (adjusted hazard rate, 2.43; 1.22-4.84).

Conclusions

Abnormal P wave morphology significantly predicted new AF and 90-day mortality in STEMI patients.     

Electrocardiographic alterations after chronic right ventricular apical pacing in patients with sinus node dysfunction

Objective

The purpose of this study is to investigate the potential to induce electrical remodeling by chronic right ventricular apical (RVA) in patients with sinus node dysfunction.

Methods

Ninety-two patients with sinus node dysfunction who underwent initial pacemaker implantation were included in the study. During routine clinic visits, electrocardiograms and echocardiograms were recorded. Forty-five patients were also studied as controls.

Results

During a mean follow-up time of 3.3 ± 0.5 years, the intrinsic QRS duration increased from 87 ± 9 milliseconds before device implantation to 94 ± 10 milliseconds (P < .001). The left ventricular end-diastolic diameter increased from 46 ± 3 to 50 ± 4 mm (P < .001), and the left ventricular ejection fraction decreased from 63% ± 4% to 57% ± 5% (P < .001). Logistic regression analysis revealed that elderly age at the time of pacemaker implantation (odds ratio [OR], 3.41; 95% confidence interval [CI], 1.07-10.90; P = .04), RVA pacing (OR, 3.91; 95% CI, 1.10-13.89; P = .03), and coronary artery disease (OR, 7.33; 95% CI, 1.09-50.29; P = .04) were independent predictors of the prolongation of intrinsic QRS duration.

Conclusions

The present study indicated that chronic RVA pacing may lead to a prolongation of intrinsic QRS duration, which could be independently predicted by elderly age, chronic RVA pacing, and the presence of coronary artery disease.     

Angiotensin-converting enzyme inhibitors as adjunctive therapy in patients with persistent atrial fibrillation

Objectives

The purpose of the current study was to assess the effect of angiotensin-converting enzyme inhibitor (ACEI) therapy in facilitating cardioversion from persistent atrial fibrillation (AF) and maintaining sinus rhythm.

Background

Pharmacologic therapy and electrical cardioversion for AF are often unsuccessful in maintaining long-term sinus rhythm.

Methods

The current study, a 1-year, prospective follow-up, comprised 47 patients with persistent AF undergoing electrical cardioversion. Patients receiving ACEI were compared with those receiving other medications. The study end point was the number of defibrillation attempts required for atrial defibrillation and the number of hospital admissions. A secondary end point was change in signal-averaged P-wave duration (SAPD) 1 year after successful electrical cardioversion.

Results

Of those admitted and requiring electrical defibrillation, the number of defibrillation attempts required for successful cardioversion was significantly less in the ACEI group (P < .001). The incidence rate ratio for admissions comparing recipients of ACEI with others was 0.14 (P = .03). Patients receiving ACEI therapy had significantly lower SAPD at 1 year when compared with the no-ACEI group (135 ms ± 3 vs 150 ms ± 2, P = .002).

Conclusions

The use of long-term ACEI therapy facilitated electrical defibrillation in patients with persistent AF. ACEI therapy also reduced SAPD, suggesting amelioration of the arrhythmogenic substrate. Furthermore, we confirmed that SAPD is prolonged in patients with persistent AF.     

Fibrillation atriale, description de la prise en charge par les cardiologues, étude observationnelle. Résultats de l’étude Factuel

Objectives

To describe the management of patients with atrial fibrillation (AF) and to study consistency with guidelines on management of AF.

Patients and methods

Observational study on a random sample of cardiologists from a French national database. Each cardiologist had to recruit the first five patients meeting inclusion criteria (patients diagnosed with AF between January 2004 and one month before inclusion and accepting the collection of their medical data).

Results

Between December 2006 and January 2207, 1789 patients aged 71 on average have been recruited by 481 cardiologists. Fifty-one percent were diagnosed with paroxysmal, 15% with persistent and 33% with permanent AF. Restoration of sinus rhythm was preferred in forms considered as paroxysmal or persistent forms whereas control of the ventricular rate was more frequent in AF considered as permanent. Overall, therapeutic guidelines are applied in practice, despite a frequent use of amiodarone in patients with no associated heart disease. Prevention of thromboembolism was observed in 88% of the patients.

Conclusions

FACTUEL is the biggest observational study on AF ever conducted in France. The therapeutic strategies used by the cardiologists are consistent with the objectives of preventing thromboembolism and controlling heart rhythm and/or rate. In most cases, the treatment used is consistent with the therapeutic guidelines.     

Association of rate-controlled persistent atrial fibrillation with clinical outcome and ventricular remodelling in recipients of cardiac resynchronization therapy

Background

Whether patients with persistent atrial fibrillation (AF) obtain the same degree of benefit with cardiac resynchronization therapy (CRT) as those in sinus rhythm remains unclear.

Methods

We enrolled 93 patients undergoing CRT implantation, 20 (22%) of whom had rate-controlled persistent AF. The primary endpoint was CRT response defined as 1 class improvement in Specific Activity Scale and 15% reduction in left ventricular end-systolic volume (LVESV) during 12 months. Other endpoints included changes in 6-minute walk distance, quality of life, B-type natriuretic peptide, and survival.

Results

Baseline characteristics were similar in those with and without AF. Response to CRT was observed in 42% vs 54% of those with and without AF, respectively (P = 0.3). Both groups had significant improvements in 6-minute walk distance, quality of life, and LVESV, but the improvement in LVESV was smaller in those with AF (13.7% ± 14.9% vs 27.7% ± 23.7%; P = 0.02). During 2.8 ± 1.4 years of follow-up, AF was associated with a 2.2-fold increased risk of death or transplantation (95% confidence interval, 1.2-3.9; P = 0.01).

Conclusions

Compared with patients without rate-controlled persistent AF, those with rate-controlled persistent AF had similar rates of clinical improvement but less left ventricular reverse remodelling in the first year after CRT. AF was associated with a markedly higher risk of death or transplantation in long-term follow-up. Given these findings, randomized studies assessing CRT efficacy in those with AF are warranted.     

Spatial characteristics of atrial fibrillation electrocardiograms

Background

The present study investigates spatial properties of atrial fibrillation (AF) by analyzing vectorcardiogram loops synthesized from 12-lead electrocardiograms (ECGs).

Methods

After atrial signal extraction, spatial properties are characterized through analysis of successive, fixed-length signal segments and expressed in loop orientation, that is, azimuth and elevation, as well as in loop morphology, that is, planarity and planar geometry. It is hypothesized that more organized AF, expressed by a lower AF frequency, is associated with decreased variability in loop morphology. Atrial fibrillation frequency is determined using spectral analysis.

Results

Twenty-six patients with chronic AF were analyzed using 60-second ECG recordings. Loop orientation was similar when determined from either entire 60- or 1-second segments. For 1-second segments, the correlation between AF frequency and the parameters planarity and planar geometry were 0.608 (P < .001) and 0.543 (P < .005), respectively.

Conclusions

Quantification of AF organization based on AF frequency and spatial characteristics from the ECG is possible. The results suggested a relatively weak coupling between loop morphology and AF frequency when determined from the surface ECG.     

Evaluation of atrial refractoriness immediately after percutaneous mitral balloon commissurotomy in patients with mitral stenosis and sinus rhythm

Background

Chronic atrial stretch and rheumatic inflammatory activity leads to atrial dilatation and conduction slowing, and this increases the susceptibility to atrial fibrillation (AF). The aim of this study was to examine the effects of changes in the chronic atrial stretch on atrial refractoriness in the early period after percutaneous mitral balloon commissurotomy (PMBC) in patients with mitral stenosis and sinus rhythm.

Methods

Twenty-five patients undergoing PMBC were enrolled in this study. We evaluated the changes in pulmonary arterial pressure (PAP), left atrial (LA) pressure, mean mitral diastolic gradient, and mitral valve area in addition to the changes in atrial effective refractory periods (AERPs), AERP dispersion, and intra-atrial and interatrial conduction times after PMBC.

Results

There were significant decreases in mean diastolic gradient, PAP, mean LA pressure, and LA size after PMBC. Accompanying these acute hemodynamic changes after PMBC, AERPs in high right atrium (HRA), distal coronary sinus (DCS), and right posterolateral (RPL) were found to be increased (P <.001), and AERP dispersion, PA_HIS (an interval between P wave on the surface electrocardiogram and atrial electrogram at the His bundle site), and HRA-DCS intervals were significantly reduced after PMBC (P <.001). It was revealed with linear regression and correlation analysis that only the changes in AERP dispersion were correlated with changes in LA pressure.

Conclusions

Relief of chronic atrial stretch results in an increase in AERPs and decrease in AERP dispersion, suggesting the potential reversibility of the electrophysiological features of chronic atrial dilatation. Our study emphasizes that an acute reduction of chronic atrial stretch in mitral stenosis resulted in favorable effects on atrial electrophysiological characteristics, and our results provide the first detailed insights into the electrophysiological changes after PMBC in patients with sinus rhythm.     

Causes of errors in the electrocardiographic diagnosis of atrial fibrillation by physicians

Background

The emphasis of most large studies has been placed on the treatment and prevention of atrial fibrillation (AF) and its complications. Little is known about the accuracy of physicians in the electrocardiographic (ECG) diagnosis of AF and the possible causes of the diagnostic errors.

Methods

Over a period of 10 months, a total of 35 508 ECGs (28 356 patients) were overread in a 385-bed community hospital within 24 hours of the initial reading. Corrected ECGs were returned to the patient file. The gold standard for the final diagnosis was based on the consensus by the cardiologist readers.

Results

In all, 35 508 ECGs were reviewed. A total of 2809 cases of AF were studied. Incorrect diagnoses related to AF were found in 219 cases. Type I errors (overdiagnosis) occurred in 137 cases. Rhythms with irregular R-R intervals (sinus rhythm with premature atrial contractions and atrial tachycardia or flutter with variable atrioventricular conduction) were misdiagnosed as AF. The presence of low-amplitude atrial activity and/or baseline artifact significantly increased the likelihood of the erroneous diagnosis, whereas ventricular rates of 130 beats/min did not influence the rate of error. Type II errors (missed AF) occurred in 82 cases where AF was either missed or confused with atrial tachycardia/flutter. Finally, ventricular pacing significantly increased the likelihood of type II errors.

Conclusions

In our institution, about 900 ECGs are read each week and 5 of them carry a wrong interpretation related to AF. More attention to common sources of errors as reinforced by an ongoing quality improvement program may reduce the rate of mistakes and thus prevent serious consequences.     

Vectorcardiographic lead systems for the characterization of atrial fibrillation

Objective

The aim of the study was to design a vectorcardiographic lead system dedicated to the analysis of atrial fibrillation (AF).

Methods

Body surface potentials during AF were simulated by using a biophysical model of the human atria and thorax. The XYZ components of the equivalent dipole were derived from the Gabor-Nelson equations. These served as the gold standard while searching for an optimal orthogonal lead system for the estimation of the heart vector while using a limited number of electrode positions. Six electrode configurations and their dedicated transfer matrices were tested by using 10 different episodes of simulated AF and 25 different thorax geometries.

Results

Root-mean-square-based relative estimation error of the vectorcardiogram using the Frank electrodes was 0.39. An adaptation of 4 of the 9 electrode locations of the standard electrocardiogram, with 1 electrode moved to the back, reduced the error to 0.24.

Conclusion

The Frank lead system is suboptimal for estimating the equivalent dipole components (VCG) during AF. Alternative electrode configurations should include at least 1 electrode on the back.     

Arrhythmogenic consequences of action potential duration gradients in the atria

Background

Atrial action potential duration (APD) has been shown to decrease with increasing distance from the sinoatrial node in several species, including humans. This gradient has been postulated to be cardioprotective by reducing repolarization gradients.

Objectives

This study tests the effect of the APD gradient on reentry initiation and characteristics.

Methods

This study used a geometrically accurate atrial computer model to examine arrhythmogenic consequences of an APD gradient on reentry initiation by ectopic beats applied at several locations. As well, dominant frequency maps of any ensuing reentries were analyzed to determine how APD gradients affected rotor behaviour.

Results

When the APD gradient was increased, anatomic reentry that used the coronary sinus as a critical pathway was prevented, but initiation of functional reentry was unaffected. If a rotor did form, APD gradients led to more disorganized behaviour. For rotors circulating around the pulmonary veins, discrete interatrial coupling accounted for left atrium-right atrium frequency gradients, irrespective of an APD gradient.

Conclusions

Gradients are protective against anatomic reentry but also increase the complexity of arrhythmias that arise.     

Factors related to the early and late success of direct current cardioversion of chronic nonrheumatic atrial fibrillation: An echocardiographic study

OBJECTIVES:

To assess factors related to the success of restoration and one-year maintenance of sinus rhythm in chronic (more than 48 h) nonrheumatic atrial fibrillation (AF).

METHODS AND RESULTS:

One hundred and fifty consecutive patients aged 62±9 years with AF lasting 123±254 days were evaluated clinically with transthoracic and transesophageal echocardiography before elective direct current cardioversion. Heart chamber dimensions and left ventricular ejection fraction were measured. The presence of left atrial thrombi and spontaneous echocardiographic contrast as well as flow velocities in the left atrial appendage were assessed. The first cardioversion was followed by standardized two-step antiarrhythmic treatment including a second cardioversion, if necessary. Twenty patients (13%) spontaneously reverted to sinus rhythm (S) during anticoagulation preceding cardioversion, 81 (54%) were successfully cardioverted (Y), and in 49 (33%) cardioversion failed initially (N). No differences were noted between the two latter groups. However, S patients had smaller left atria measured in the short and long axes (42±4 mm, P=0.05, and 53±7 mm, P=0.005, respectively) than both the Y (45±4 and 61±8 mm) and the N patients (46±4 and 61±8 mm). One-year follow-up was obtained in 95 patients: 64 (67%) were in sinus rhythm while 31 (33%) had AF. Again, no initial differences predicting the maintenance of sinus rhythm were found.

CONCLUSIONS:

Spontaneous reversion of AF seems more likely with smaller left atria. Echocardiography, including trans-esophageal echocardiography, is unlikely to identify patients in whom attempts to restore and maintain sinus rhythm will fail or succeed.     

Transesophageal echocardiography before cardioversion of recurrent atrial fibrillation: does absence of previous atrial thrombi preclude the need of a repeat test?

Background

Atrial fibrillation (AF) is a recurrent problem that frequently requires repeat cardioversion. Transesophageal echocardiography (TEE) is indicated before cardioversion in patients who are underanticoagulated (warfarin therapy <3 weeks or international normalized ratio [INR] <2.0). It remains uncertain if TEE should be repeated in underanticoagulated patients who had no atrial thrombi detected by previous TEE.

Methods and results

From January 1996 to June 2001, 76 patients (43 men, 33 women; mean age, 68.8 ± 10.4 years) who were underanticoagulated and had no atrial thrombi in previous TEE underwent repeat TEE before cardioversion of recurrent AF. The duration of recurrent AF at the time of the second TEE was 5.1 ± 9.3 months (1 day to 4 years). The underlying diseases included coronary artery disease (n = 30), hypertension (n = 22), valvular heart diseases (n = 8), dilated cardiomyopathy (n = 4), hypertrophic cardiomyopathy (n = 2), and others (n = 10). Eight (10.5%) patients (2 men, 6 women; mean age, 68.6 ± 6.6 years) were found to have intra-atrial thrombi on the second TEE. Of these 8 patients, 3 had coronary artery disease, 1 had hypertension, 2 had dilated cardiomyopathy, 1 had hypertrophic cardiomyopathy, and 1 had AF of unknown cause. The duration of recurrent AF in patients with and without thrombi was not significantly different (3.6 ± 4.7 versus 5.3 ± 9.7 months, P = .22). Of the 8 patients with intra-atrial thrombi on the second TEE, 5 had been taking warfarin for 3 to 4 weeks but had subtherapeutic INR and 3 were taking aspirin only. Compared with patients without intra-atrial thrombi, patients with intra-atrial thrombi had lower ejection fraction (32.5% ± 18.1% versus 49.9% ± 14.1%, P = .015), slower left atrial appendage empty velocity (0.22 ± 0.08 versus 0.41 ± 0.17 m/s, P < .01), and higher prevalence of spontaneous echo contrast (87.5%) than in patients without intra-atrial thrombi (19.1%, P < .05) but similar left atrial size (49.5 ± 5.3 versus 47.3 ± 7.1 mm, P = .15). Cardioversion was cancelled in all patients with atrial thrombi.

Conclusions

In underanticoagulated patients, repeat TEE is necessary before cardioversion of recurrent AF even if the previous TEE showed no atrial thrombi.