Pathophysiology and prevention of atrial fibrillation

Myocardial sleeves of pulmonary veins and atrial fibrillation: a postmortem histopathological study of 100 subjects

Atrial fibrillation (AF) is triggered by ectopic beats originating from extensions of the left atrial myocardium over the pulmonary veins (PVs), so-called myocardial sleeves. A total of 100 hearts (393 PVs) obtained at autopsy were studied. Of these, 50 were from patients with chronic AF and 50 from controls in sinus rhythm. Out of a total of 393 PVs studied, a sleeve was present in 349 PVs (88.8%). The myocardial sleeves frequently harboured senile atrial amyloid and scarring. These two changes were evaluated semi-quantitatively (grade 0-3). Amyloidosis was found in 68% of all hearts and in 55% of all sleeves. It was more frequent in patients with AF (58.5%) than in those without (51.7%), however, without statistical significance (p values 0.948, 0.306, 0.166 and 1). Scarring was present in all 349 sleeves studied. It was significantly more severe in patients with AF (average grade 2.44) than in those without (average grade 2.00) (p values <0.001, <0.1, <0.05 and <0.01). In conclusion, amyloidosis and particularly scarring of the myocardial sleeves of the pulmonary veins, appear to be common in the elderly population as an arrhythmogenic substrate for AF.

High-sensitivity C-reactive protein is predictive of successful cardioversion for atrial fibrillation and maintenance of sinus rhythm after conversion

BACKGROUND

Cardioversion for atrial fibrillation (AF) is the most effective treatment for the restoration of sinus rhythm (SR). Recently, an elevated level of hs-CRP has been shown to be associated with AF burden, suggesting that inflammation increases the propensity for persistence of AF. We examined whether the level of high-sensitivity C-reactive protein (hs-CRP) was predictive of the outcome of cardioversion for AF.

METHODS AND RESULTS

One hundred and six patients with a history of symptomatic AF lasting > or =1 day (age 63+/-14 years, mean+/-S.D.) underwent cardioversion. Echocardiography and hs-CRP assay were performed immediately prior to cardioversion. SR was restored in 84 patients (79%). By using selected cutoff values, multiple discriminant analysis revealed significant associations between successful cardioversion and a shorter duration of AF (AF duration< or =36 days, odds ratio (OR), 0.98; 95% confidence interval (CI), 0.97-0.99), smaller left atrial diameter (left atrial diameter< or =40 mm, OR 0.82, 95% CI 0.71-0.94), better-preserved left ventricular ejection fraction (left ventricular ejection fraction> or =60%, OR 0.92, 95% CI 0.86-0.99), and lower hs-CRP level (hs-CRP< or =0.12 mg/dL, OR 0.33, 95% CI 0.21-0.51). During a follow-up period of 140+/-144 days, AF recurred in 64 patients (76%). By using a cutoff value of hs-CRP> or =0.06 mg/dL, Cox proportional-hazards regression model found that only hs-CRP level was an independent predictor of AF recurrence (OR 5.30, 95% CI 2.46-11.5) after adjustment for coexisting cardiovascular risks. When patients were divided by the hs-CRP level of 0.06 mg/dL, percentage of maintenance of SR below and above the cutoff was 53% and 4%, respectively (log-rank test, p<0.0001).

CONCLUSIONS

hs-CRP level determined prior to cardioversion represents an independent predictor of both successful cardioversion for AF and the maintenance of SR after conversion.

Electrophysiologic characteristics of atria in patients without heart disease

BACKGROUND

The significance of atrial fibrillation or tachycardia (AF) induction remains debatable. Some believe that the presence of heart disease (HD) increases the sensitivity and decreases the specificity of programmed atrial stimulation (PAS). There are few data in patients without HD. The purpose of the study was to evaluate the results of PAS in asymptomatic patients without HD and in those with documented spontaneous AF, but without HD, to know the diagnosis value of the technique.

METHODS

A total of 4,900 PAS were consecutively performed. The control group (I, N=67) was defined by the absence of preexcitation syndrome, dizziness/syncope, hypertension, history of tachycardia, or other documented HD together with a normal 2D echocardiogram and 24-hour Holter monitoring. They were compared to a group (II) of 54 patients with documented paroxysmal AF and without HD. PAS used one and two extrastimuli, delivered during sinus rhythm and two drive rates (600, 400 ms). Atrial-effective refractory periods (ARP), their adaptation to cycle length, and conduction times were noted. AF induction was defined as the induction of AF lasting more than 1 minute.

RESULTS

Group I patients (1.4% of 4,900) were younger than group II (51 +/- 17 vs 65 +/- 11 years, P < 0.001). A single extrastimulus never induced sustained AF in group I, but did so in 11 group II patients (20%); sustained AF was induced by two extrastimuli in 15 group I patients (22%) and in 31 group II patients (57%) (P < 0.001). There were no ARP and conduction time differences in group I patients with and without inducible AF, but there was a longer sinus cycle length in patients with inducible AF (977 +/- 164 vs 838 +/- 141 ms, P < 0.02). There were no electrophysiological differences in group II patients with and without inducible AF. No group I patient developed spontaneous AF (follow-up 4 +/- 2 years). The sensitivity of PAS with one extrastimulus was 20% and the specificity 100%; the sensitivity of PAS with two extrastimuli was 57% and the specificity 78%.

CONCLUSION

Sustained AF was not induced by one extrastimulus in control patients without symptoms, nor heart disease, but sustained AF was induced by two extrastimuli in 22% of these patients. The induction of a sustained AF by two extrastimuli should be interpreted cautiously, particularly in patients with a relative sinus bradycardia. However, the sensitivity of PAS with one extrastimulus was very low and two extrastimuli were required in patients with spontaneous AF to induce the tachycardia. Other electrophysiological parameters were not useful to differentiate patients with and without inducible AF.

Onset mechanism of paroxysmal atrial fibrillation detected by ambulatory Holter monitoring

AIMS

The aim of this study was to evaluate the mechanisms of induction of paroxysmal atrial fibrillation (PAF) by analysis of its onset recorded on Holter monitoring (HM).

METHODS AND RESULTS

One hundred and seven HM were evaluated in 90 patients (mean age 67.7, cardiac disease in 31.1%), with one or more self-terminating episodes of PAF, lasting >or=30 s. Two hundred and thirty-three episodes of PAF were detected. A triggering premature atrial complex (PAC) was present in 222/233 episodes (95.3%); 118/233 episodes were preceded by a bradyarrhythmic event (BE) or a post-extrasystolic pause (50.6%). According to the polarity of the ectopic P-wave, triggering PACs were left atrial origin in 74.3%, right atrial in 15.3%, not determined in 10.4% of cases. Coupling interval (CI) of triggering PACs was shorter in episodes preceded by BEs; it was shorter than that of non-triggering PACs. Frequency of PACs was significantly higher in the hour preceding the onset of PAF. During the day, three periods of higher frequency of PAF onsets were found from noon to 2 p.m., 6 p.m. to 2 a.m., and 4 a.m. to 6 a.m. Heart rate variability analysis showed a vagal prevalence in the 5 min preceding the onset of arrhythmia, both in the time and in the frequency domain.

CONCLUSION

Paroxysmal atrial fibrillation is generally triggered by a PAC, with left atrial origin in two-thirds of cases: CI and neuroendocrine balance are factors affecting the induction of the arrhythmia.

Angiotensin II-induced changes of calcium sparks and ionic currents in human atrial myocytes: potential role for early remodeling in atrial fibrillation

AIMS

Atrial angiotensin II (ANG II) levels have been shown to be increased in atrial fibrillation (AF). The purpose of the study was to evaluate a potential role of ANG II in the early remodeling and susceptibility to chronicization of AF.

METHODS AND RESULTS

Isolated human atrial myocytes were incubated in ANG II and/or angiotensin type 1 receptor blocker candesartan. ANG II markedly increased the frequency of spontaneous Ca(2+) sparks, spark full duration, time to peak Ca(2+) fluorescence and decay time measured by confocal imaging. Sarcoplasmic reticulum calcium content estimated by caffeine-evoked calcium release did not differ between ANG II-treated cells and controls. Patch-clamp recordings revealed that ANG II significantly decreased I(to) and increased I(Ca,L) current densities. Candesartan blocked these ANG II-mediated alterations. ANG II exhibited no effect on I(K1), I(Kur) and I(f) current size. Expression of connexin 40 and connexin 43 was not significantly changed by ANG II as assessed by immunohistochemistry and Western blot analysis.

CONCLUSION

ANG II-induced alterations of calcium handling and electrophysiological changes in human atrial cells similar to those previously observed in the onset of AF. Prevention of these alterations by candesartan might constitute a useful pharmacological strategy for the treatment of AF.

The role of pacing mode in the development of atrial fibrillation

Asynchronous ventricular pacing has been shown to increase the risk of development of atrial fibrillation (AF) because of various mechanisms: retrograde atrioventricular (AV) conduction with increase in atrial pressure causing acute atrial stretch and reverse flow in the pulmonary veins, mitral regurgitation, reduced coronary blood flow, adverse neuroendocrine reactions, etc. Dual-chamber pacing preserves atrioventricular synchrony. However, in randomized multicentre trials comparing VVI(R) with DDD(R) pacing, AF is only slightly less frequent in the dual-chamber mode. This is most likely due to unnecessary ventricular pacing, which is frequent in dual-chamber pacing. At nominal values, dual-chamber devices usually do not permit intrinsic AV conduction but promote delivery of the ventricular stimulus at an inappropriate time in an inappropriate place. Programming of long AV delays facilitates spontaneous AV conduction but usually cannot completely avoid unnecessary ventricular pacing and causes other problems in the dual-chamber mode. Atrial septal lead placement can improve left-sided AV synchrony and promote spontaneous AV conduction. Programming of the AAI(R) mode is superior to the dual-chamber mode but cannot be used if AV conduction is impaired intermittently or permanently. Therefore, dedicated algorithms enhancing spontaneous AV conduction in the dual-chamber mode are desirable for a large proportion of pacemaker patients.

Inter-atrial conduction time shortens after blood pressure control in hypertensive patients with left ventricular hypertrophy

Assuming that blood pressure control could induce a shortening of the inter-atrial conduction time and prevent atrial fibrillation occurrence, we studied the inter-atrial conduction time in hypertensive patients with left ventricular hypertrophy.

METHODS

Sixty-eight (26 male) 58.34+/-8.08-year-old patient participated in the study. All were in sinus rhythm and had abnormal blood pressure (163+/-18/95+/-9 mm Hg). Their cardiac mass index was increased (151+/-43 g/m(2) SC) and their left atrial dimension was normal (3.67+/-0.54 cm). The inter-atrial conduction time was measured in the echocardiogram from the beginning of the electrocardiographic P wave to the beginning of the A wave in the mitral Doppler signal and was corrected for heart rate. Heart rhythm disturbances were monitored clinically and by means of a Holter. Most patients were treated with angiotensin antagonists.

RESULTS

It was found that arterial blood pressure decreased significantly after treatment and that the P-A interval was significantly reduced (71.4+/-14.5 vs. 63.9+/-11.5 ms). During the follow-up, no patient complained of arrhythmia symptoms or exhibited atrial fibrillation in the Holter recording.

CONCLUSION

In this selected group of patients with hypertensive heart disease (left ventricular hypertrophy), an effective blood pressure control was accompanied by a significant decrease in the inter-atrial conduction time. It is possible that these effects prevent atrial fibrillation.

Sodium calcium exchange as a target for antiarrhythmic therapy

In search of better antiarrhythmic therapy, targeting the Na/Ca exchanger is an option to be explored. The rationale is that increased activity of the Na/Ca exchanger has been implicated in arrhythmogenesis in a number of conditions. The evidence is strong for triggered arrhythmias related to Ca2+ overload, due to increased Na+ load or during adrenergic stimulation; the Na/Ca exchanger may be important in triggered arrhythmias in heart failure and in atrial fibrillation. There is also evidence for a less direct role of the Na/Ca exchanger in contributing to remodelling processes. In this chapter, we review this evidence and discuss the consequences of inhibition of Na/Ca exchange in the perspective of its physiological role in Ca2+ homeostasis. We summarize the current data on the use of available blockers of Na/Ca exchange and propose a framework for further study and development of such drugs. Very selective agents have great potential as tools for further study of the role the Na/Ca exchanger plays in arrhythmogenesis. For therapy, they may have their specific indications, but they carry the risk of increasing Ca2+ load of the cell. Agents with a broader action that includes Ca2+ channel block may have advantages in other conditions, e.g. with Ca2+ overload. Additional actions such as block of K+ channels, which may be unwanted in e.g. heart failure, may be used to advantage as well.

Targets and endpoints in ablation therapy for atrial fibrillation in the light of pathophysiological mechanisms

Atrial fibrillation (AF), an important public health problem is a complex and multifactorial arrhythmia. Non-pharmacological treatment for symptomatic patients is of increasing importance. The different catheter ablation techniques in AF treatment developed during recent years, all based on different pathophysiological insights, are discussed. The non-standardized use of different follow-up methods after ablation make interpretation and comparison of results difficult.

Statin use is associated with a reduction in atrial fibrillation after noncardiac thoracic surgery independent of C-reactive protein

STUDY OBJECTIVES

The level of C-reactive protein (CRP) has been shown to be elevated in patients with atrial fibrillation/flutter (AF) unrelated to surgery, and statins are known to lower the CRP level. To determine whether an elevated CRP level predisposes the patient to postoperative AF and whether statin use is associated with a reduced AF incidence, we studied a consecutive group of patients who were at risk for AF after undergoing thoracic surgery (age, > or = 60 years).

DESIGN AND SETTING

A prospective study in a tertiary care cancer center of 131 patients (mean [+/- SD] age, 73 +/- 6 years) who had undergone major lung or esophageal resection. High-sensitivity CRP and interleukin (IL)-6 levels were measured before surgery, on arrival at the postanesthesia care unit, and on the first morning after surgery. Continuous telemetry was used for 72 to 96 h to detect AF.

RESULTS

AF occurred in 38 of 131 patients (29%) at a median time after surgery of 3 days. Although CRP and IL-6 levels increased significantly (p < 0.001) in response to surgery, patients with or without AF did not differ in perioperative values. In a stepwise logistic regression, statin use was associated with a threefold decrease in the odds of developing AF (odds ratio [OR], 0.26; 95% confidence interval [CI], 0.08 to 0.82; p = 0.022) and a greater PR interval (OR, 1.11 per 5-ms increments; 95% CI, 1.01 to 1.22; p = 0.027) predicted an increase in the risk of AF.

CONCLUSIONS

The preoperative use of statins was associated with a protective effect against postoperative AF independent of CRP levels. In contrast to AF in the general population, early markers of inflammation did not predict the postoperative occurrence of AF.

Prevention of atrial fibrillation

PURPOSE OF REVIEW

This review summarizes current concepts on the pathophysiology of atrial fibrillation, identifying predisposing factors to guide primary and secondary preventive approaches.

RECENT FINDINGS

Many factors contribute to the development and progression of atrial fibrillation, including cardiovascular diseases, age, neurohormones, genetics, diet, autonomic influences, and inflammation. Therapeutic efforts have been directed to modify this altered milieu and prevent the development of atrial electrical and structural remodeling. This nonconventional antiarrhythmic management appears to have an important role also in secondary prevention of atrial fibrillation; the indications for conventional antiarrhythmic agents are decreasing because of side effects and limited efficacy. Interventional electrophysiology techniques have been developed to target the arrhythmia substrate responsible for the initiation or maintenance of atrial fibrillation, achieving high success rates.

SUMMARY

Atrial fibrillation is the most commonly treated arrhythmia and its incidence is predicted to increase. It is associated with significant morbidity and mortality. Preventive efforts should be initiated early and include diversified interventions to correct predisposing factors and modify the altered atrial substrate.

Atrial fibrillation: public health implications

BACKGROUND

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in the United States, affecting 2.3 million Americans. AF is associated with significant morbidity, mortality, and poor quality of life. AF and its treatments result in high healthcare resource use and costs.

OBJECTIVE

To develop a framework for public health action for the prevention, detection, and control of AF.

METHODS

A literature search was conducted via MEDLINE and CINAHL for the 1990-2004 period. Key words included atrial fibrillation, epidemiology, prevention, detection, treatment, and public health.

RESULTS

Published data predict a substantial increase in the prevalence of AF due to improved survival of people with coronary heart disease; increasing prevalence of hypertension, heart failure, and diabetes; and the aging of the American population. Low public awareness of AF and quality-of-care issues related to detection, control, and management are evident.

CONCLUSIONS

Awareness, early detection and treatment, improved patient self-management, and attention by public health programs are essential to reduce the burden of AF. Partnerships among professional nursing and medical organizations, the Centers for Disease Control and Prevention, and patient advocacy groups represent another important approach to improving public health outcomes for AF. Hospitalizations for AF and controversies over optimal treatment strategies (e.g., rate vs rhythm control) underscore the need for both public health and applied research.

Prevalence of atrial fibrillation and associated factors in a population of long-term hemodialysis patients

BACKGROUND

Hemodialysis (HD) is associated with cardiovascular structural modifications; moreover, during HD, rapid electrolytic changes occur. Both factors may favor the onset of atrial fibrillation.

METHODS

To define the prevalence of atrial fibrillation and identify associated factors, 488 patients on long-term HD therapy (age, 66.6 +/- 13.4 years; men, 58.0%; duration of HD, 76.5 +/- 84.3 months) were studied.

RESULTS

Atrial fibrillation was reported in 27.0% of patients; paroxysmal in 3.5%, persistent in 9.6%, and permanent in 13.9%. Clinical and echocardiographic variables were considered: patients with atrial fibrillation were older (71.8 +/- 9.3 versus 64.7 +/- 14.2 years; P < 0.01), and its prevalence increased with age. Patients with arrhythmia had a longer duration of dialysis therapy (93.2 +/- 100.5 versus 70.2 +/- 76.7 months; P = 0.02). Atrial fibrillation was associated significantly with ischemic heart disease (P < 0.01), dilated cardiomyopathy (P < 0.01), acute pulmonary edema (P < 0.05), valvular disease (P < 0.05), cerebrovascular accidents (P < 0.05), and predialytic hyperkalemia (P < 0.05). Patients with atrial fibrillation more frequently showed left atrial dilatation (59.8% versus 34.5%; P < 0.0001), and in these subjects, left ventricular ejection fraction was significantly lower (53.9% versus 57.4%; P = 0.029). No association was found between arrhythmia and hypertension or diabetes. Multivariate analysis confirmed that patient age (P < 0.001), duration of HD therapy (P = 0.001), and left atrial dilatation (P < 0.001) were associated with atrial fibrillation.

CONCLUSION

Atrial fibrillation is much more frequent in HD patients than in the general population; age, duration of HD history, presence of some heart diseases, and left atrial dilatation are associated with the arrhythmia.

Role of angiotensin system and effects of its inhibition in atrial fibrillation: clinical and experimental evidence

Atrial fibrillation (AF) is a common arrhythmia that is difficult to treat. Anti-arrhythmic drug therapy, to maintain sinus-rhythm, is limited by inadequate efficacy and potentially serious adverse effects. There is increasing interest in novel therapeutic approaches that target AF-substrate development. Recent trials suggest that angiotensin converting-enzyme (ACE)-inhibitors and angiotensin-receptor blockers (ARBs) may be useful, particularly in patients with left ventricular hypertrophy or failure. The clinical potential and mechanisms of this approach are under active investigation. Angiotensin-II is involved in remodelling and may have direct electrophysiological actions. Experimental studies show protection from atrial structural and possibly electrical remodelling with ACE-inhibitors and ARBs, as well as potential effects on cardiac ion-channels. This article reviews information pertaining to the clinical use and mechanism of action of ACE-inhibitors and ARBs in AF. A lack of prospective randomized double-blind trials data limits their application in AF patients without another indication for their use, but studies under way may alter this in the near future. This exciting field of investigation may lead to significant improvements in therapeutic options for AF patients.

A retrospective evaluation of transthoracic biphasic electrical cardioversion for atrial fibrillation in dogs

OBJECTIVES

To evaluate safety, efficacy, and clinical usefulness of biphasic transthoracic cardioversion for management of dogs with atrial fibrillation (AF).

BACKGROUND

In dogs AF is usually managed with heart rate control rather than by restoration of sinus rhythm (SR). However, restoration of SR has potential advantages of improving cardiac output and reducing ventricular filling pressures, and biphasic cardioversion provides an improved benefit/risk ratio compared to traditional monophasic cardioversion.

ANIMALS, MATERIALS AND METHODS

Retrospective analysis of data from 39 dogs with spontaneous AF managed with biphasic transthoracic cardioversion was done. Conversion characteristics, adverse effects, and duration of SR were evaluated. Effects of heart disease and pretreatment with amiodarone on success of cardioversion and on duration of SR were also evaluated.

RESULTS

Restoration of SR was achieved in 36 of 39 dogs (92.3%). Presence of heart disease or atrial enlargement had no effect on cardioversion characteristics or ability to restore SR. Median duration of SR following cardioversion and treatment with amiodarone was 120 days. Dogs with lone AF remained in SR longer than those with heart disease.

CONCLUSIONS

Biphasic cardioversion is safe and effective. Although duration of SR varied, a majority of dogs remained in SR long enough to benefit.

Targeting the renin-angiotensin-aldosterone-system in atrial fibrillation: a shift from electrical to structural therapy?

Despite its increasing incidence and prevalence, treatment options in atrial fibrillation (AF) are far from ideal and often limited. After decades of focus on the electrical aspects of AF with unsatisfactory results, recent research is focusing increasingly on the atrial structural remodelling that underlies the development of AF in different pathological conditions, such as hypertension, heart failure, diabetes mellitus and coronary artery disease. The aim of this review is to provide a comprehensive overview of the role of the renin-angiotensin-aldosterone-system in AF and to highlight the clinical evidence on renin-angiotensin-aldosterone-system blockade as a therapeutic option in AF.

Myocyte changes and their left atrial distribution in patients with chronic atrial fibrillation related to mitral valve disease

It has been found that the pulmonary veins and adjacent left atrial posterior wall (LAPW) are deeply involved in both the initiation and maintenance of atrial fibrillation (AF), and the identification of these high-risk sites has aroused great interest in investigating their histopathologic substrate. We used light and conventional electron microscopy to evaluate the differential myocyte and interstitial changes in LAPW and left atrial appendage (LAA) samples from 28 patients with chronic AF undergoing mitral valve surgery and from 12 autoptic controls. There were always more myocytes with loss of sarcomeres in the LAPW than in the LAA (19.9% +/- 7.7% versus 8.2% +/- 5.0%; P < .0001), and the LAPW showed more marked immunohistochemical evidence of dedifferentiation, characterized by the reexpression of smooth muscle actin. In pathological left atria, myocyte diameter in the LAPW and LAA was comparable (19.0 +/- 1.5 versus 18.5 +/- 2.0 microm; not significant) but larger than in the controls (11.9 +/- 0.8 and 12.1 +/- 1.3 microm, respectively; P < .0001). A terminal deoxynucleotidyltransferase assay did not reveal any myocyte apoptosis. The LAPW also showed more interstitial fibrosis than the LAA (7.49% +/- 3.34% versus 2.80% +/- 1.35%; P < .0001). Ultrastructural examination confirmed the presence of myocyte myocytolysis in the perinuclear area and showed changes in mitochondrial shape. In conclusion, the LAPW in patients with chronic AF related to mitral valve disease seems to be a particular anatomical site in which major myocyte and interstitial changes are concentrated, whereas the LAA is more protected. This remodeling may increase the heterogeneity of LAPW electrical conduction, thus confirming this location as an elective target for the ablation treatment of AF.

Economic burden and co-morbidities of atrial fibrillation in a privately insured population

OBJECTIVE

This study assesses the direct (medical and drugs) and indirect (work loss) annual costs associated with Atrial Fibrillation (AFIB) in a privately insured population.

BACKGROUND

AFIB is the most common sustained rhythm disturbance, affecting 2.3 million people in the United States.

METHODS

Cost and co-morbidity measures for AFIB patients were compared to matched controls using a privately insured administrative database (including medical, drug, and disability claims) for 2 million enrollees, 1999-2002 from 16 employers across the United States. Patients with an AFIB diagnosis on at least two occasions were included in the co-morbidity analysis (n = 3944). A non-AFIB control sample was randomly selected with a 1:1 ratio, with characteristics (i.e., age, gender, health plan) matched to AFIB patients. Excess medical costs (i.e., employer payments) were estimated for AFIB patients, defined as the difference in average annual costs between AFIB and control patients (n = 3944); excess work-loss costs were defined similarly for employees with available work-loss data (n = 603). Statistical significance in the descriptive analysis was measured by paired t-tests for cost, or Chi-square tests for co-morbidity comparisons. A two-part multivariate model of excess cost was further estimated to control for co-existing conditions and other patient characteristics. The excess costs of AFIB patients were estimated as the difference between the observed costs of AFIB patients and their estimated costs, assuming they did not have AFIB.

RESULTS

The multivariate analysis found that the excess annual direct cost of AFIB was $12,349 (p < 0.01), with AFIB patients approximately 5 times as costly as non-AFIB individuals ($15,553 versus $3204, respectively). The excess annual total cost was $14,875 (p < 0.01), with AFIB patients again approximately 5 times as costly as non-AFIB individuals ($18,454 versus $3,579, respectively). AFIB was associated with increased incidence of atrial flutter (p < 0.01), heart failure (Relative Risk (RR) = 29, p < 0.01), other arrhythmias/conduction disorders (RR = 16, p < 0.01), heart attack (RR = 8, p < 0.01), and stroke (RR = 6, p < 0.01).

CONCLUSIONS

AFIB is a costly disease and one for which more definitive therapies might offer some potential for reducing, not only the clinical impact, but also the economic burden of the disease.

Pulmonary Vein Isolation as an End Point for Left Atrial Circumferential Ablation of Atrial Fibrillation

OBJECTIVES

We sought to determine whether elimination of pulmonary vein (PV) arrhythmogenicity is necessary for the efficacy of left atrial circumferential ablation (LACA) for atrial fibrillation (AF).

BACKGROUND

The PVs often provide triggers or drivers of AF. It has been shown that LACA is more effective than PV isolation in eliminating paroxysmal AF. However, it is not clear whether complete PV isolation is necessary for the efficacy of LACA.

METHODS

In 60 consecutive patients with paroxysmal (n = 39) or chronic (n = 21) AF (mean age 53 +/- 12 years), LACA to encircle the left- and right-sided PVs, with additional lines in the posterior left atrium and along the mitral isthmus, was performed under the guidance of an electroanatomic navigation system. The PVs were mapped with a decapolar ring catheter before and after LACA. If PV isolation was incomplete, no attempts at complete isolation were made.

RESULTS

After LACA, there was incomplete electrical isolation of one or more PVs in 48 (80%) of the 60 patients. The prevalence of PV tachycardias was 82% before and 8% after LACA (p < 0.001). At 11 +/- 1 months of follow-up, 10 (83%) of the 12 patients with complete and 39 (81%) of 48 patients with incomplete PV isolation were free from recurrent AF without antiarrhythmic drug therapy (p = 1.0). A successful outcome was not related to the number of completely isolated PVs per patient (p = 0.6).

CONCLUSIONS

Left atrial circumferential ablation modifies the arrhythmogenic substrate within the PVs. Complete electrical isolation of the PVs is not a requirement for a successful outcome after LACA.

Curative catheter ablation for atrial fibrillation

With the recent advances in the understanding of the mechanisms of atrial fibrillation, radiofrequency catheter ablation has emerged as an effective therapeutic modality for patients with atrial fibrillation. Techniques for catheter ablation evolved from elimination of triggers that often originate within the pulmonary veins and initiate atrial fibrillation, to additional left atrial ablation using a variety of approaches to also eliminate the mechanisms that play a role in perpetuation of atrial fibrillation. With the current ablation strategies, atrial fibrillation can be eliminated in approximately 85% of patients with paroxysmal, and in approximately 70% of patients with chronic, atrial fibrillation with a low incidence of significant complications. In symptomatic patients with paroxysmal or chronic atrial fibrillation who have failed antiarrhythmic drug therapy, catheter ablation is an effective treatment strategy for maintenance of sinus rhythm.

Critical mass hypothesis revisited: role of dynamical wave stability in spontaneous termination of cardiac fibrillation

The tendency of atrial or ventricular fibrillation to terminate spontaneously in finite-sized tissue is known as the critical mass hypothesis. Previous studies have shown that dynamical instabilities play an important role in creating new wave breaks that maintain cardiac fibrillation, but its role in self-termination, in relation to tissue size and geometry, is not well understood. This study used computer simulations of two- and three-dimensional tissue models to investigate qualitatively how, in relation to tissue size and geometry, dynamical instability affects the spontaneous termination of cardiac fibrillation. The major findings are as follows: 1) Dynamical instability promotes wave breaks, maintaining fibrillation, but it also causes the waves to extinguish, facilitating spontaneous termination of fibrillation. The latter effect predominates as dynamical instability increases, so that fibrillation is more likely to self-terminate in a finite-sized tissue. 2) In two-dimensional tissue, the average duration of fibrillation increases exponentially as tissue area increases. In three-dimensional tissue, the average duration of fibrillation decreases initially as tissue thickness increases as a result of thickness-induced instability but then increases after a critical thickness is reached. Therefore, in addition to tissue mass and geometry, dynamical instability is an important factor influencing the maintenance of cardiac fibrillation.

Mechanisms of Atrial Fibrillation: Lessons From Studies in Patients

Recent clinical studies performed in human subjects have provided important clues that improved our understanding of the mechanisms of atrial fibrillation (AF) and facilitated development of new treatment strategies. When analyzed together, these studies confirm the complexity and multifactorial nature of AF. Because a variety of mechanisms such as focal drivers within the thoracic veins, rotors in the left atrium, multiple reentrant circuits, and autonomic innervation may play a role in the initiation and maintenance of AF alone or in combination, the best strategy to eliminate AF may be the accurate identification of one or more of the mechanisms critical to the genesis of AF and to target the specific mechanism(s).

Mechanisms of Atrial Fibrillation: Lessons From Animal Models

Studies in animal models have provided extremely important insights about atrial fibrillation (AF). The classic mechanisms that still form the framework for our understanding of AF (focal activity, single-circuit or "mother wave" reentry, and multiple circuit reentry) were established based on animal studies almost 100 years ago. The past 10 years have witnessed a tremendous acceleration of animal work in this area, including the development of a range of AF models in clinically relevant pathological substrates (eg, atrial tachycardia remodeling, congestive heart failure, pericarditis, ischemic heart disease, mitral valve disease, volume overload states, respiratory failure) and the establishment of an increasing number of genetically defined transgenic mouse models. This article reviews the contribution of animal models to our knowledge about AF mechanisms and to clinical management, dealing with such issues as the theory of reentry; the specific applications of various animal models and their contribution to our understanding of electrophysiologic, ionic, and molecular mechanisms; the role of the autonomic nervous system and regional factors; and the development of novel therapeutic approaches. The complementary nature of animal research and clinical investigation is emphasized and the clinical relevance of findings in experimental models is highlighted.

Inhibition of angiotensin II signaling and recurrence of atrial fibrillation in AFFIRM

OBJECTIVES

We investigated whether inhibition of endogenous angiotensin II signaling reduces the recurrence rate of atrial fibrillation (AF) in patients enrolled in the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study.

BACKGROUND

Structural and electrical remodeling contribute to AF. Previous experimental studies have implicated the angiotensin II signaling pathway in this process, and recent clinical evidence supports a beneficial effect of inhibiting angiotensin II activity.

METHODS

Using the AFFIRM database, we retrospectively identified a cohort of patients randomized to the rhythm-control arm who were in sinus rhythm. Exposure to angiotensin II receptor blockers or angiotensin-converting enzyme inhibitors (ANGI) was determined, and the time to first recurrence of AF was compared between ANGI users and nonusers.

RESULTS

The study cohort included 732 patients not taking ANGI through the initial 2-month follow-up and 421 patients taking ANGI during this time. Patients in the ANGI group more likely had hypertension, diabetes, coronary artery disease, and congestive heart failure compared to patients not taking ANGI. Risk of AF recurrence in the ANGI treatment group did not differ from the risk observed in patients not taking the drugs (hazard ratio [HR] = 0.91, 95% confidence interval [CI] = 0.77-1.09). However, in patients with congestive heart failure or impaired left ventricular function, ANGI use was associated with a lower risk of AF recurrence.

CONCLUSIONS

This analysis provides evidence that ANGI use may be beneficial in some patient subgroups with AF and underscores the need for randomized clinical trials defining more fully the role of angiotensin II inhibition in treating AF.

Antiadrenergic therapy in the control of atrial fibrillation

Atrial fibrillation (AF) in heart failure develops commonly in older individuals and its prevalence increases as heart failure severity progresses. Because of deteriorating hemodynamics, patients with heart failure are at increased risk for developing AF and, conversely, AF in heart failure patients is associated with adverse hemodynamic changes. AF is believed to increase the mortality risk in heart failure, which may be minimized by treatment that includes the control of ventricular rate, prevention of thrombotic events, and conversion to normal sinus rhythm. Clinical guidelines recommend amiodarone or dofetilide in heart failure patients, but these drugs have certain drawbacks, such as an increased risk for bradyarrhythmias with amiodarone and proarrhythmic reaction with dofetilide. Some but not all clinical trials have suggested that rate control should be the primary therapeutic goal in high-risk heart failure patients with AF and, if unsuccessful, followed by rhythm control. The former is effectively achieved with rate-lowering beta-blockers alone or in combination with digoxin. Recent studies evaluating the effects of combination carvedilol/digoxin therapy demonstrate synergistic effects between the two drugs. This combination therapy decreased heart failure symptoms, effectively reduced ventricular rate, and improved ventricular function to a greater extent compared with that produced by either drug alone. Although digoxin alone is an effective heart failure treatment, its use as a single rate-control therapy is often ineffective in heart failure patients with AF associated with rapid ventricular response. Carvedilol is effective, alone or in combination, with digoxin in such heart failure patients with AF, and has been shown to reduce mortality risk in patients with chronic heart failure during prolonged therapy.

Mechanisms of recurrent atrial fibrillation after pulmonary vein isolation by segmental ostial ablation

OBJECTIVES

The aim of this study was to determine the mechanisms responsible for recurrent atrial fibrillation (AF) after pulmonary vein isolation (PV) by segmental ostial ablation.

BACKGROUND

Recovery of conduction into a previously isolated PV is a common observation when there is recurrent AF soon after segmental ostial ablation. However, the mechanisms of recurrent AF have been unclear.

METHODS

A repeat ablation procedure was performed in 50 patients who had recurrent paroxysmal AF at a mean of 7 +/- 6 months after segmental ostial ablation to isolate the PVs. During the repeat procedure, a ring catheter was inserted into each PV during sinus rhythm and AF to determine whether the veins were still isolated and, if not, whether there were PV tachycardias with a cycle length shorter than in the adjacent left atrium during AF.

RESULTS

There was recovery of conduction over a previously ablated muscle fascicle in >/=1 PV in 49 patients (98%). There were 10 +/- 2 episodes of PV tachycardia per minute in 36 (72%) of the 50 patients during AF. Repeat ablation was performed by segmental ostial ablation (23 patients) or by left atrial catheter ablation to encircle the left- and right-sided PVs 1 to 2 cm from the ostia, with additional ablation lines in the posterior left atrium and mitral isthmus (27 patients). At 6-month follow-up, among 23 patients who underwent repeat ablation by segmental ostial ablation, AF recurred in 4 (21%) of the 19 patients who had PV tachycardias and in 3 (75%) of the 4 patients who did not (P = .03). Among the 27 patients who underwent left atrial ablation, AF recurred in 2 (12%) of the 17 patients who had PV tachycardias and in 1 (10%) of the 10 patients who did not (P = 0.7).

CONCLUSIONS

Recovery of conduction in previously ablated muscle fascicles is a common finding in patients with recurrent AF after segmental ostial ablation. The efficacy of repeat segmental ostial ablation depends on the presence of PV tachycardias, whereas left atrial ablation is effective regardless of whether PV tachycardias are present or not during AF.

Mechanism of atrial fibrillation: decremental conduction, fragmentation, and ectopic activity in patients with drug resistance paroxysmal atrial fibrillation and structurally normal heart

Atrial fibrillation (AF) has been associated with premature beats and decreased atrial conduction velocity. This study examined a new index of dynamic inter-atrial conduction time (iaCT) in patients with paroxysmal AF (PAF). We compared 42 consecutive patients with paroxysmal AF (mean age = 52 +/- 16 years) without structural heart disease with 39 age-matched patients (mean age = 49 +/- 15 years) who underwent ablation of junctional tachycardias. Prior to investigation, all antiarrhythmic drugs were discontinued for an appropriate period of time. The following measurements were made: baseline iaCT (iaCTb) between high right atrium (HRA) and distal coronary sinus, iaCT during HRA pacing S1S1 600 ms (iaCTS1), maximum prolongation of iaCT during S2 and S3 delivery (iaCTS2, iaCTS3). We then derived the decremental index (DI), the maximum percent prolongation of iaCT = iaCT S3-iaCTS1/iaCTS1%. In patients with PAF, iaCTb was 81.3 +/- 24 ms versus 59.5 +/- 14 ms in controls (P = 0.0001). Atrial fibrillation was reproducibly and easily induced with a prominent increase in iaCT in 11 patients with AF. In this subgroup DI was 92 +/- 17%, compared to 45 +/- 21% in the other patients with AF (P = 0.0001) and 21 +/- 15% in the control group (P = 0.0001). Spontaneous isolated or repetitive ectopic activity was observed in 11 patients with AF (26%), and decremental atrial conduction was observed in 76% of patients with AF. This study supports the role of dynamic inter-atrial conduction disturbances in patients with lone PAF. The DI may be a new index of vulnerability to paroxysmal AF.

C reactive protein concentration and recurrence of atrial fibrillation after electrical cardioversion

BACKGROUND

To test the hypothesis that a high C reactive protein (CRP) concentration would predict recurrence of atrial fibrillation (AF) after cardioversion in patients taking antiarrhythmic drugs.

METHODS

111 patients who underwent direct current cardioversion for symptomatic AF were enrolled. Blood was drawn for CRP determination before cardioversion on the same day. All patients were taking antiarrhythmic drugs before and after electrical cardioversion.

RESULTS

After a mean follow up of 76 days, 75 patients had recurrence of AF. In univariate analysis, the median CRP concentration was significantly higher in patients with AF recurrence (3.95 mg/l v 1.81 mg/l, p = 0.002). Among the 55 patients with CRP in the upper 50th centile, 44 (80%) experienced recurrence of AF over a total follow up of 8.98 patient years, whereas among the 56 patients with CRP in the lower 50th centile, 31 (55%) experienced recurrence of AF over a total follow up of 14.3 patient years (p < 0.001). The adjusted hazard ratio comparing the upper 50th centile of CRP with the lower 50th centile of CRP was 2.0 (95% confidence interval 1.2 to 3.2, p = 0.007).

CONCLUSIONS

CRP is independently associated with recurrence of AF after electrical cardioversion among patients taking antiarrhythmic drugs. These results suggest that inflammation may have a role in the pathogenesis of AF resistant to antiarrhythmic drugs.

Atrial fibrillation after cardiac surgery: an evidence-based approach to prevention

A number of advances in surgical and anesthetic techniques have reduced the risk for patients undergoing cardiac surgery. However, postoperative atrial fibrillation remains common, with an incidence ranging between 25% and 40%. It is associated with an increased incidence of congestive heart failure, renal insufficiency, and stroke that prolongs hospitalization and increases rates of readmission after discharge. Consequently, there has been great interest in strategies to prevent this arrhythmia. When both safety and efficacy are considered, the available evidence to date suggests that only beta-blockers can be recommended for the prevention of atrial fibrillation after cardiac surgery. Other treatments might be considered on an individual basis after careful consideration of the patient's potential for side effects.

Atrial fibrillation: profit from cardiac pacing?

The impact of cardiac pacing on the prevention of atrial fibrillation is under scientific investigation. Several prospective randomised clinical trials have reported that atrial-based "physiologic" AAI(R)- or DDD(R)-pacing is associated with a lower incidence of paroxysmal and permanent atrial fibrillation than single-chamber ventricular pacing in patients with a conventional pacemaker indication. However, it is still uncertain whether atrial pacing itself has independent antiarrhythmic properties. In contrast, right ventricular pacing is considered to promote atrial fibrillation, even in preserved AV synchrony during dual-chamber pacing. The electrical secondary prevention of atrial fibrillation is mainly based on variations of the atrial pacing site and sophisticated preventive pacing algorithms incorporated in the pacemaker software. Dual-site right atrial and biatrial pacing were reported to exhibit modest to no benefit for the prevention of atrial fibrillation, whereas septal pacing and specific preventive pacing algorithms have been demonstrated to reduce the incidence of atrial fibrillation in a number of clinical trials. However, the role of septal pacing and preventive pacing algorithms still has to be clarified since, overall, study results have been inconsistent so far. One of the main goals of future investigations should be the identification of responder groups of preventive pacing concepts. In clinical practice, the efficacy of pacing algorithms and septal pacing has to be determined in the individual case. These options should be taken into account in patients with symptomatic bradycardia as the indication for cardiac pacing and, in addition, symptomatic atrial fibrillation.

Catheter Ablation of Paroxysmal Atrial Fibrillation

In the recent years, many investigators have proved the efficacy and safety of catheter ablation in patients with paroxysmal atrial fibrillation. Further studies would be necessary to decrease the recurrence rate and complication rate, and make the procedure more simple.

Paroxysmal Atrial Fibrillation Coincident With Cardiac Decompensation is a Predictor of Poor Prognosis in Chronic Heart Failure

BACKGROUND

The prognostic significance of atrial fibrillation (AF) in chronic heart failure (CHF) remains poorly understood.

METHODS AND RESULTS

Death and rehospitalizaion for CHF exacerbation for 427 consecutive patients hospitalized from 1996 to 2002 were retrospectively analyzed in relation to cardiac rhythm: sinus rhythm (SR; n=239) or AF (n=188). The AF group was classified according to an Intervention (n=57) or Non-Intervention (n=131) group for defibrillating AF. During the follow-up of 34+/-23 months, there was no significant difference of mortality or morbidity between the SR and AF groups, or between the Intervention and Non-Intervention groups, respectively. However, the Non-Intervention group consisted of 28 patients with paroxysmal AF (PAF), which spontaneously converted to SR during hospitalization, and 103 with chronic AF (CAF). The rehospitalization for CHF exacerbation was significantly higher in PAF than that in CAF and SR (p=0.00005 and 0.002, respectively). Multivariate Cox analysis demonstrated that, PAF, but not CAF, was a predictor of readmission (relative risk 2.30, p=0.004, 95% confidence interval 1.30 to 4.05).

CONCLUSIONS

The present data implied that PAF coincident with cardiac decompensation could be a new predictor of prognosis for CHF. The management strategies of AF in CHF should be discussed according to the phenotype of AF.

Effects of amiodarone and thoracic epidural analgesia on atrial fibrillation after coronary artery bypass grafting

OBJECTIVE

This study was designed to assess the effects of a perioperative dosing regimen of amiodarone administration, high thoracic epidural anesthesia (TEA), or a combination of the 2 regimens on atrial fibrillation (AF) after coronary artery bypass grafting (CABG).

DESIGN AND SETTING

The study was prospective, controlled, and randomized and was performed in a tertiary health care center associated with a university.

PARTICIPANTS

One hundred sixty-three patients scheduled for coronary artery bypass graft surgery.

INTERVENTIONS

In this 2 x 2 factorial-designed study the patients were randomized to 1 of 4 regimens in which group E had perioperative TEA, group E+A had TEA and amiodarone, group A had amiodarone, and group C served as control. The epidural catheter was inserted at T1-3 the day before surgery. TEA groups received TEA for 96 hours. The amiodarone regimen consisted of a single loading dose of 1,800 mg of amiodarone orally. Intravenous infusion of amiodarone was started after induction of anesthesia and was administered at 900 mg over 24 hours for the subsequent 3 days.

MEASUREMENTS AND MAIN RESULTS

AF was documented using Holter monitoring. In group E 22 of 44 (50%), in group E+A 10 of 35 (28.6%), in group A 10 of 36 (27.8%), and in the control group 20 of 48 (41.7%) patients developed AF (odds ratio amiodarone/nonamiodarone 0.47 [0.24-0.90]; P = 0.02).

CONCLUSIONS

The perioperative amiodarone regimen used in this study was effective in reducing the incidence of AF after CABG while TEA was not.

Strategies for perioperative arrhythmias

Rapid atrial arrhythmias affect close to one million elderly Americans who undergo cardiac or non-cardiac operations annually and have been associated with prolonged hospital stays. In contrast, bradyarrhythmias or ventricular arrhythmias severe enough to require treatment occur in less than 1% of patients who undergo all types of surgery, including cardiac. This article focuses on new issues leading to the improved understanding of the pathophysiology and mechanisms of post-operative atrial arrhythmias. New approaches directed at prophylaxis and acute therapy of atrial arrhythmias are discussed, as are recommendations to prevent thromboembolic events. Practice and research agenda are proposed.

Prolonged signal-averaged P wave duration after elective cardioversion increases the risk of recurrent atrial fibrillation

OBJECTIVE

To assess the risk of atrial fibrillation (AF) recurrence after elective cardioversion of AF in relation to the signal-averaged P wave duration (SAPWD), clinical characteristics of the patient, and the duration of the AF disease.

DESIGN

We studied 131 consecutive patients (88 men, 43 women), median age 67 years (range 29-87 years), after elective cardioversion of AF into sinus rhythm. The SAPWD was measured on inclusion, and the follow-up period was 1 month. Recurrent AF within the first month after cardioversion was regarded as endpoint.

RESULTS

AF recurred in 73 patients (56%). Multiple logistic regression analysis showed that prolonged SAPWD above 160 ms was the only significant risk factor for recurrent AF, OR=2.22 (95% CI 1.07-4.60), p=0.03. There was no significant effect of age, diagnosed hypertension, diagnosed congestive heart failure, dilated left atrium, or long duration of AF on the risk of AF relapse.

CONCLUSION

Prolonged SAPWD above 160 ms is a risk factor for recurrent AF after elective cardioversion of persistent AF.

Electrical remodeling of the canine superior vena cava after chronic rapid atrial pacing

BACKGROUND

The superior vena cava (SVC) might serve as the trigger and/or substrate for paroxysmal atrial fibrillation (AF). However, the electrophysiological properties of the SVC with chronic AF are unknown. The purposes of this study were to investigate the electrophysiological properties of the SVC and the electropharmacological effects of intravenous dl-sotalol on the canine SVC after chronic rapid atrial pacing (RAP).

METHODS AND RESULTS

In the control group, the effective refractory period (ERP), conduction velocity, and AF inducibility of the SVC were assessed in 6 normal dogs before and after an infusion of dl-sotalol. In the experimental group, the ERP, conduction velocity, and AF inducibility of the SVC were assessed before and after dl-sotalol administration in 10 dogs after 8 weeks of RAP. The SVC showed a shorter ERP, decreased slope of rate-adaptation of the ERP, increased ERP dispersion, a decreased conduction velocity, and increased inducibility and duration of AF initiated from the SVC in the RAP dogs. In the RAP dogs, intravenous dl-sotalol significantly increased the ERP, but dl-sotalol did not change the slope of rate-adaptation of the ERP, dispersion of the ERP, conduction velocity, inducibility, or duration of AF initiated from the SVC.

CONCLUSIONS

The present study demonstrates that the canine SVC shows significant electrical remodeling and increased AF vulnerability after chronic RAP. Intravenous dl-sotalol was unable to decrease the inducibility or duration of AF initiated from the SVC.

Down-regulation of sarcolipin mRNA expression in chronic atrial fibrillation

BACKGROUND

Abnormal intracellular Ca2+ homeostasis is an important modulator of chronic atrial fibrillation. Sarcolipin, a homologue of phospholamban, is specifically expressed in the atria, and may play an important role in modulating intracellular Ca2+ homeostasis in the atria. The aim of this study was to investigate the expression of sarcolipin mRNA in the atrial myocardium of patients with chronic atrial fibrillation.

METHODS

We analyzed the expression of sarcolipin, phospholamban, cardiac calsequestrin and sodium calcium exchanger mRNAs in the right atrial myocardium from nine patients with mitral valvular disease with atrial fibrillation (MVD/AF), nine patients with MVD who had normal sinus rhythm (MVD/NSR), and 10 control patients with normal sinus rhythm who received open heart surgery (controls). The expression of mRNA was measured using the ABI PRISM 7700 Sequence Detection System (Applied Biosystems, Foster City, CA).

RESULTS

Relative expression levels of sarcolipin mRNA were significantly lower in MVD/AF (0.60 +/- 0.11) than in either MVD/NSR (1.28 +/- 0.17, P < 0.01) or controls (1.10 +/- 0.10, P < 0.05). The expression levels of sarcolipin mRNA were significantly lower in the group with high values for right atrial pressure. The expression levels of phospholamban, cardiac calsequestrin and sodium calcium exchanger mRNAs were comparable among all three groups.

CONCLUSIONS

Chronic electrical and mechanical overload decreased the expression of sarcolipin mRNA in the right atrial myocardium in patients with chronic atrial fibrillation. Down-regulation of sarcolipin mRNA may be part of atrial fibrillation-induced atrial remodelling.

Clinical prediction rule for atrial fibrillation after coronary artery bypass grafting

OBJECTIVES

This study was designed to devise and validate a practical prediction rule for atrial fibrillation/atrial flutter (AF) after coronary artery bypass grafting (CABG) using easily available clinical and standard electrocardiographic (ECG) criteria.

BACKGROUND

Reported prediction rules for postoperative AF have suffered from inconsistent results and controversy surrounding the added predictive value of a prolonged P-wave duration.

METHODS

In 1,851 consecutive patients undergoing CABG with cardiopulmonary bypass, preoperative clinical characteristics and standard 12-lead ECG data were examined. Patients were continuously monitored for the occurrence of sustained postoperative AF while hospitalized. Multiple logistic regression was used to determine significant predictors of AF and to develop a prediction rule that was evaluated through jackknifing.

RESULTS

Atrial fibrillation occurred in 508 of 1,553 patients (33%). Multivariate analysis showed that greater age (odds ratio [OR] 1.1 per year [95% confidence intervals (CI) 1.0 to 1.1], p < 0.0001), prior history of AF (OR 3.7 [95% CI 2.3 to 6.0], p < 0.0001), P-wave duration >110 ms (OR 1.3 [95% CI 1.1 to 1.7], p = 0.02), and postoperative low cardiac output (OR 3.0 [95% CI 1.7 to 5.2], p = 0.0001) were independently associated with AF risk. Using the prediction rule we defined three risk categories for AF: <60 points, 61 of 446 (14%); 60 to 79 points, 330 of 908 (36%); and >or=80 points, 117 of 199 (59%). The area under the receiver-operator characteristic curve for the model was 0.69.

CONCLUSIONS

These data show that post-CABG AF can be predicted with moderate accuracy using easily available patient characteristics and may prove useful in prognostic and risk stratification of patients after CABG. The presence of intraatrial conduction delay on ECG contributed least to the prediction model.

Prevalence of Asymptomatic Recurrences of Atrial Fibrillation After Successful Radiofrequency Catheter Ablation

INTRODUCTION

The long-term efficacy of radiofrequency catheter ablation of atrial fibrillation (AF) has been based on patient-reported symptoms suggestive of AF. However, asymptomatic recurrences of AF may remain undetected. The aim of this study was to determine the prevalence of asymptomatic recurrences of AF after an apparently successful catheter ablation procedure for AF.

METHODS AND RESULTS

Among 244 consecutive patients (mean age 53 +/- 11 years) who underwent a pulmonary vein isolation procedure for symptomatic paroxysmal AF and who reported no symptoms of recurrent AF at > or =6 months after the procedure, 60 patients with a history of > or =1 episode of AF per week were asked to participate in this study. Preablation, these patients had experienced 19 +/- 13 episodes of AF per month. The patients were provided with a patient-activated transtelephonic event recorder for 30 days, a mean of 642 +/- 195 days after the ablation procedure, and were asked to record and transmit recordings on a daily basis and whenever they felt palpitations. Seven patients (12%) felt palpitations during the study, although they had not experienced symptoms previously. Each of these 7 patients had an episode of AF documented with the event monitor during symptoms. In these 7 patients, the mean number of episodes per month decreased from 19 +/- 14 preablation to 3 +/- 1 postablation (P < 0.001). Among the 53 asymptomatic patients, an episode of AF was captured in 1 (2%) patient during the study period.

CONCLUSION

Asymptomatic recurrences of AF after an apparently successful catheter ablation procedure for symptomatic paroxysmal AF are infrequent.

Conduction Characteristics at the Crista Terminalis During Onset of Pulmonary Vein Atrial Fibrillation

INTRODUCTION

Focal atrial fibrillation (AF) may initiate with an irregular rapid burst of atrial ectopic (AE) activity from a pulmonary vein (PV) focus, but how AF is maintained it is not known. The crista terminalis (CT) is an important line of block in atrial flutter (AFL), but its role in AF has not been determined. The aim of this study was to examine the conduction properties of the CT during onset of AF.

METHODS AND RESULTS

In 10 patients (mean age 38 +/- 8 years), we analyzed conduction across the CT during onset of focal AF from an arrhythmogenic PV and during pacing from the same PV at cycle lengths of 700 and 300 ms. A 20-pole catheter was positioned on the CT using intracardiac echocardiography. In 10 control patients with no history of AF, we analyzed conduction across the CT during pacing from the distal coronary sinus at 700 and 300 ms. In all 10 AF patients, AF was initiated with 1 to 9 AE beats (median 5) from a PV. During sinus rhythm, there were no split components (SC) recorded on the CT. During PV AE activity, discrete SC were recorded on the CT in all patients over 6.3 +/- 0.9 bipoles (3.7 +/- 0.3 cm). Maximal splitting of SC was 66 +/- 31 ms (37-139). There was an inverse relationship between AE coupling intervals and the degree of splitting between SC in all patients. Degeneration to AF was preceded by progressive decrement across the CT. SC were recorded during PV pacing at 700 and 300 ms (maximal distance between SC of 24 +/- 3 ms and 43 +/- 5 ms, respectively, P < 0.001). Maximum SC at CT in controls was 13 +/- 8 ms at 700 ms (P = 0.06 vs AF patients) and 16 +/- 9 ms at 300 ms (P < 0.01 vs AF patients).

CONCLUSION

(1) These observations provide evidence of anisotropic, decremental conduction across the CT during onset of focal AF and during pacing from the same PV. A line of functional conduction block develops along this anatomic structure (CT). Whether this line of block acts as an initiator of AF or simply contributes passively to nonuniform fibrillatory conduction is unknown. (2) In some patients with focal AF, development of conduction block along the CT may provide a substrate for typical AFL.

Arrhythmia-provoking factors and symptoms at the onset of paroxysmal atrial fibrillation: a study based on interviews with 100 patients seeking hospital assistance

Background

Surprisingly little information on symptoms of paroxysmal atrial fibrillation is available in scientific literature. Using questionnaires, we have analyzed the symptoms associated with arrhythmia attacks.

Methods

One hundred randomly-selected patients with idiopathic paroxysmal atrial fibrillation filled in a structured questionnaire.

Results

Psychic stress was the most common factor triggering arrhythmia (54%), followed by physical exertion (42%), tiredness (41%) coffee (25%) and infections (22%). Thirty-four patients cited alcohol, 26 in the form of red wine, 16 as white wine and 26 as spirits. Among these 34, red wine and spirits produced significantly more episodes of arrhythmia than white wine (p = 0.01 and 0.005 respectively).

Symptoms during arrhythmia were palpitations while exerting (88%), reduced physical ability (87%), palpitations at rest (86%), shortage of breath during exertion (70%) and anxiety (59%). Significant differences between sexes were noted regarding swollen legs (women 21%, men 6%, p = 0.027), nausea (women 36%, men 13%, p = 0.012) and anxiety (females 79%, males 51%, p = 0.014).

Conclusion

Psychic stress was the commonest triggering factor in hospitalized patients with paroxysmal atrial fibrillation. Red wine and spirits were more proarrhythmic than white wine. Symptoms in women in connection with attacks of arrhythmia vary somewhat from those in men.

Age- and sex-related atrial electrophysiologic and structural changes

Age and gender dependence of the 3 major variables--left atrial (LA) dimension, effective refractory period (ERP), and atrial conduction--that govern the development of atrial fibrillation (AF) were examined in 76 women and 39 men without structural heart disease. A significant positive correlation was found between age and LA dimension, mainly because of a strongly positive correlation in women not taking hormone replacement therapy but not in women on hormone replacement therapy. Men had a significantly greater average LA dimension than women. Neither ERP nor atrial conduction estimated by normalized P-wave duration demonstrated any significant correlation with either age or gender. It was concluded that LA size is greater in the elderly and in men, which may increase their risk for AF.

Influence of age on atrial fibrillation inducibility

The prevalence of AF is known to increase in the elderly. Some electrophysiological changes were reported in these patients, but the effects of age on AF inducibility and other electrophysiological signs associated with atrial vulnerability are unknown. The purpose of the study was to evaluate the effects of age on atrial vulnerability and AF induction. The study consisted of 734 patients (age 16-85 years, mean 61 +/- 15 years) without spontaneous AF who were admitted for electrophysiological study. Study was indicated for dizziness or ventricular tachyarrhythmia. Programmed atrial stimulation was systematically performed. One and two extrastimuli were delivered in sinus rhythm and atrial driven rhythms (600, 400 ms). Univariate and multivariate analysis of several clinical and electrophysiological data were performed. AF inducibility, defined as the induction of an AF lasting > 1 minute, was paradoxically and significantly decreased in elderly (> 70 years) patients compared to younger patients (< 70 years) (P < 0.01). AF inducibility was present in 40% of 62 patients < 40 years, 39% of 99 patients age 40-50 years, 37% of 130 patients age 50-60 years, 38% of 222 patients age 60-70 years, and only 28% of 221 patients > 70 years. There was no significant correlation with the sex, the presence of dizziness, the presence or not of an underlying heart disease, the left ventricular ejection fraction, and the presence of salvos of atrial premature beats on 24-hour Holter monitoring. There was a significant correlation with a longer atrial effective refractory period in the elderly (226 +/- 41 ms) than in younger patients (208 +/- 31 ms) (P < 0.001). Other electrophysiological parameters of atrial vulnerability did not change significantly. Increased atrial refractory period and age >70 years were independent factors of decreased AF inducibility. Programmed atrial stimulation should be interpreted cautiously before the age of 70 years. AF induction is facilitated by the presence of a short atrial refractory period in these patients. Surprisingly, AF inducibility decreases in patients > 70 years because their atrial refractory period increases. Therefore, increased AF prevalence in these patients should be explained by nonelectrophysiological causes.

Postoperative atrial fibrillation: new directions in prevention and treatment

Postoperative atrial fibrillation (POAF) is the most common and vexing complication of cardiac surgeries in adults. The consequences of this dysrhythmia are numerous and include hemodynamic instability, increased risk for embolic stroke, increased length of hospital stay, increased cost of hospitalization, significant resource utilization, and decreased long-term survival. While some progress has been made in prevention of POAF, the multiple mechanisms involved in its genesis are yet to be elucidated. This article reviews our current understanding of these mechanisms, predictors of POAF, drug therapy for prevention and treatment, and new uses for pacing and internal cardioversion for the prevention and treatment of POAF.