Return of atrial mechanical function following electrical conversion of atrial dysrhythmias

Risk Factors and Prognostic Implications of New-Onset Paroxysmal Atrial Fibrillation in Patients Hospitalized with Intracerebral Hemorrhage

Objective

We aimed to assess the prevalence and risk factors of new-onset paroxysmal atrial fibrillation (PAF) in patients hospitalized with ICH and determine whether the new-onset PAF had influenced functional outcomes.

Methods

We analyzed a database of all consecutive patients with ICH from October 2013 to May 2022. Univariate and multivariable regression analyses were performed to identify risk factors for new-onset PAF in patients with ICH. Multivariate models were also constructed to assess whether the new-onset PAF was an independent predictor of poor functional outcome, as measured using the modified Rankin scale.

Results

This study included 650 patients with ICH, among whom 24 patients had new-onset PAF. In the multivariable model, older age (OR per 10-y increase, 2.26 [95% CI, 1.52-3.35]; P<0.001), hematoma volume (OR per 10-mL increase, 1.80 [95% CI, 1.26-2.57]; P=0.001), and heart failure (OR, 21.77 [95% CI, 5.52-85.91]; P<0.001) were independent risk factors for new-onset PAF. In a sensitivity analysis restricted to 428 patients with N-terminal pro-B-type natriuretic peptide (NT-proBNP), older age, larger hematoma volume, heart failure, and increased NT-proBNP were associated with new-onset PAF. After adjusting for baseline variables, new-onset PAF was an independent predictor of poor functional outcome (OR, 10.35 [95% CI, 1.08-98.80]; P=0.042).

Conclusion

Older age, larger hematoma volume, and heart failure were independent risk factors for new-onset PAF after ICH. Increased NT-proBNP is correlated with higher risks for new-onset PAF when their information is available at admission. Furthermore, new-onset PAF is a significant predictor of poor functional outcome.

The risk and timing of acute ischemic stroke after electrical cardioversion for atrial fibrillation in Taiwan: A nationwide population-based cohort study

BACKGROUND

There is a positive association between electrical cardioversion (ECV) and acute ischemic stroke (AIS). Although 4 weeks of anticoagulation therapy after ECV in atrial fibrillation (AF) patients is generally suggested by current guidelines to reduce the risk of AIS, limited studies have been conducted in Asian populations to determine the risk and timing of AIS after ECV for AF in recent years. Therefore, we aim to use the National Health Insurance Research Database (NHIRD) in Taiwan to determine the risk and timing of AIS after ECV for AF.

METHODS

The data analyzed in this nationwide population-based retrospective cohort study were obtained from the NHIRD in Taiwan. The outcome in this study was the cumulative incidence of AIS in patients with AF during 7-day and 30-day follow-up periods after the patients underwent ECV.

RESULTS

Our analysis included 39,697 patients with AF, of whom 5723 received ECV and 5723 were propensity score-matched controls. Compared to the controls, patients who received ECV exhibited a significantly increased incidence of 7-day AIS development (adjusted hazard ratio [HR] = 1.524, p = 0.003). In contrast, the incidence of 30-day AIS development showed no significant increase (adjusted HR = 1.301, p = 0.426).

CONCLUSIONS

AF patients who underwent ECV had a higher incidence of 7-day AIS development but not 30-day AIS development. Considering the timing of AIS development after ECV in AF patients, the optimal duration of antithrombotic therapy after ECV deserves further investigation.

Improvement in Sleep-Disordered Breathing Indices Downloaded From a Positive Airway Pressure Machine Following Conversion of Atrial Fibrillation to Sinus Rhythm

ABSTRACT

Sleep-disordered breathing (SDB) is a contributor to atrial fibrillation (AF) and treatment of obstructive sleep apnea can reduce the recurrence of AF following catheter ablation. However, the effect of AF therapies on measures of SDB severity is less robustly described. We present the case of a middle-aged man with SDB and persistent AF who exhibited improvement in SDB metrics, as characterized by data downloaded from his auto-titrating continuous positive airway pressure (AutoCPAP) machine, very shortly following procedures that restored sinus rhythm. Between procedures, when his rhythm reverted to AF, the downloaded parameters suggested more SDB events. After catheter ablation, the patient maintained sinus rhythm and the improvement in SDB metrics was sustained as well. This case provides support in favor of a bidirectional relationship between SDB and AF and suggests that data available from PAP machines may be useful in serial assessment of SDB status relative to heart rhythm.

Atrial fibrillation

Atrial fibrillation is the most common arrhythmia affecting patients today. Disease prevalence is increasing at an alarming rate worldwide, and is associated with often catastrophic and costly consequences, including heart failure, syncope, dementia, and stroke. Therapies including anticoagulants, anti-arrhythmic medications, devices, and non-pharmacologic procedures in the last 30 years have improved patients' functionality with the disease. Nonetheless, it remains imperative that further research into AF epidemiology, genetics, detection, and treatments continues to push forward rapidly as the worldwide population ages dramatically over the next 20 years.

Canadian Cardiovascular Society atrial fibrillation guidelines 2010: prevention of stroke and systemic thromboembolism in atrial fibrillation and flutter

The stroke rate in atrial fibrillation is 4.5% per year, with death or permanent disability in over half. The risk of stroke varies from under 1% to over 20% per year, related to the risk factors of congestive heart failure, hypertension, age, diabetes, and prior stroke or transient ischemic attack (TIA). Major bleeding with vitamin K antagonists varies from about 1% to over 12% per year and is related to a number of risk factors. The CHADS(2) index and the HAS-BLED score are useful schemata for the prediction of stroke and bleeding risks. Vitamin K antagonists reduce the risk of stroke by 64%, aspirin reduces it by 19%, and vitamin K antagonists reduce the risk of stroke by 39% when directly compared with aspirin. Dabigatran is superior to warfarin for stroke prevention and causes no increase in major bleeding. We recommend that all patients with atrial fibrillation or atrial flutter, whether paroxysmal, persistent, or permanent, should be stratified for the risk of stroke and for the risk of bleeding and that most should receive antithrombotic therapy. We make detailed recommendations as to the preferred agents in various types of patients and for the management of antithrombotic therapies in the common clinical settings of cardioversion, concomitant coronary artery disease, surgical or diagnostic procedures with a risk of major bleeding, and the occurrence of stroke or major bleeding. Alternatives to antithrombotic therapies are briefly discussed.

Electrical and pharmacologic cardioversion for atrial fibrillation

In this article, electrical and pharmacologic cardioversion for atrial fibrillation is described in detail. Indications for cardioversion and management of pericardioversion anticoagulation also are discussed. Finally, management strategies for immediate recurrence of atrial fibrillation and cardioversion failure are offered.

Acute anticoagulation adjustment in patients with atrial fibrillation at risk for stroke: approaches, strategies, risks and benefits

The acute management of anticoagulation in patients with atrial fibrillation to prevent stroke and other thromboembolic complications includes the use of individualized strategies tailored to the patient and based on the situation (cardioversion, surgeries, dental procedures, cardiac interventions, other invasive procedures and initiation of, or adjustment to, warfarin dosing). The vast range of choices can cause confusion and few randomized controlled clinical trials in this area provide adequate guidance. Chronic anticoagulation management is more straightforward since clinical evidence is ample, randomized clinical trial data provides cogent informaiton and guidelines have been established. Acute management of anticoagulation in patients with atrial fibrillation to prevent thromboembolic complications is often unrecognized but is emerging as a crucial, but challenging, and increasingly complex aspect of the care of patients with atrial fibrillation. This review addresses issues regarding such patients who may be at risk for stroke and require acute adjustments of anticoagulation (in light of, or in lieu of, chronic anticoagulation). Several promising new strategies are considered in light of established medical care. This analysis provides practical recommendations based on available data and presents results from recent investigations that may provide insight into future strategies.

Antithrombotic Therapy in Atrial Fibrillation

This chapter about antithrombotic therapy in atrial fibrillation (AF) is part of the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this chapter are the following (all vitamin K antagonist [VKA] recommendations have a target international normalized ratio [INR] of 2.5; range, 2.0 to 3.0): In patients with persistent or paroxysmal AF (PAF) [intermittent AF] at high risk of stroke (ie, having any of the following features: prior ischemic stroke, transient ischemic attack, or systemic embolism, age > 75 years, moderately or severely impaired left ventricular systolic function and/or congestive heart failure, history of hypertension, or diabetes mellitus), we recommend anticoagulation with an oral VKA, such as warfarin (Grade 1A). In patients with persistent AF or PAF, age 65 to 75 years, in the absence of other risk factors, we recommend antithrombotic therapy with either an oral VKA or aspirin, 325 mg/d, in this group of patients who are at intermediate risk of stroke (Grade 1A). In patients with persistent AF or PAF < 65 years old and with no other risk factors, we recommend aspirin, 325 mg/d (Grade 1B). For patients with AF and mitral stenosis, we recommend anticoagulation with an oral VKA (Grade 1C+). For patients with AF and prosthetic heart valves, we recommend anticoagulation with an oral VKA (Grade 1C+); the target INR may be increased and aspirin added depending on valve type and position, and on patient factors. For patients with AF of > or = 48 h or of unknown duration for whom pharmacologic or electrical cardioversion is planned, we recommend anticoagulation with an oral VKA for 3 weeks before and for at least 4 weeks after successful cardioversion (Grade 1C+). For patients with AF of > or = 48 h or of unknown duration undergoing pharmacologic or electrical cardioversion, an alternative strategy is anticoagulation and screening multiplane transesophageal echocardiography (Grade 1B). If no thrombus is seen and cardioversion is successful, we recommend anticoagulation for at least 4 weeks (Grade 1B). For patients with AF of known duration < 48 h, we suggest cardioversion without anticoagulation (Grade 2C). However, in patients without contraindications to anticoagulation, we suggest beginning IV heparin or low molecular weight heparin at presentation (Grade 2C).

Anticoagulant use in nonvalvular atrial fibrillation. Determining risk and choosing the safest course

Previous TIA or stroke, diabetes, advanced age, impaired left ventricular function, and a history of hypertension are strong risk factors in patients with nonvalvular AF. When none of these factors is present, aspirin in a dose of 325 mg offers effective protection against future stroke. When any of these factors are present, warfarin adjusted to an INR of 2.0 to 3.0 offers greater protection against future stroke than aspirin alone or aspirin and fixed-dose warfarin (INR 1.2-1.5). More data are needed before newer anticoagulants can be recommended for treatment.

Cardioversion of atrial fibrillation and its effect on right ventricular function as assessed by tricuspid annular motion

In patients with atrial fibrillation, the reduced right ventricular function determined by tricuspid annular motion before cardioversion returns to normal 1 month after successful cardioversion to sinus rhythm. The simplicity of recording the tricuspid annular motion provides an easy opportunity to assess right ventricular function following electroconversion of atrial fibrillation to sinus rhythm.

Atrial ejection force in patients with atrial fibrillation: comparison between DC shock and pharmacological cardioversion

It is well known that the restoration of sinus rhythm is not always associated with the return of effective atrial contraction. Atrial ejection force (AEF) is a noninvasive Doppler derived parameter that measures the strength of the atrial contraction. The aim of the present study was to use pulsed-Doppler echocardiography to determine if different modalities of cardioversion influence the delay in the return of effective atrial contraction after cardioversion. DC shock and pharmacological therapy were compared. Sixty-eight patients were randomly cardioverted, either using DC shock or i.v. procainamide. The patients who were restored to a sinus rhythm had a complete Doppler echocardiographic examination within 1 hour after the restoration, after 24 hours, after 1 month, and after 3 months. AEF was measured and compared in the two groups of patients and within the same group. AEF was greater immediately and at 24 hours after cardioversion in patients who underwent pharmacological therapy compared to patients treated with DC shock (peak A wave, 60 +/- 9 vs 31 +/- 8 msec, P < 0.001; AEF 11.3 +/- 3 vs 5 +/- 2.9 dynes, P < 0.001). In both groups, AEF increases over time. In conclusion, AEF is a noninvasive parameter that can be easily measured after cardioversion and can give accurate information about the recovery of left atrial mechanical function. This finding may have important implications for guiding the anticoagulant therapy after cardioversion.

Timing of thromboembolic events after electrical cardioversion of atrial fibrillation or flutter: a retrospective analysis

Pooled data from 32 studies were reviewed to assess the timing of thrombolic complications after cardioversion of atrial fibrillation or flutter. We found that 98% of embolic episodes occurred within 10 days of cardioversion.

"Stunning" of the left atrium after spontaneous conversion of atrial fibrillation to sinus rhythm: demonstration by transesophageal Doppler techniques in a canine model

OBJECTIVES

This study compared left atrial and left atrial appendage contraction velocities in sinus rhythm before and after a brief period of atrial fibrillation in a canine model.

BACKGROUND

In patients, left atrial appendage contraction velocities measured during sinus rhythm after cardioversion from atrial fibrillation are depressed relative to left atrial appendage emptying velocities measured during atrial fibrillation, suggesting that the left atrial appendage is mechanically "stunned."

METHODS

This phenomenon was studied in a canine model of acute (60 min) pacing-induced atrial fibrillation followed by spontaneous reversion to sinus rhythm using epicardial and transesophageal pulsed wave Doppler. Unique features of the model include: 1) comparison of left atrial function postconversion to baseline sinus rhythm rather than to measurements during atrial fibrillation, 2) control of the duration of atrial fibrillation and 3) elimination of the extraneous influences of direct current shock and antiarrhythmic agents, which may independently depress left atrial function.

RESULTS

Hemodynamic conditions (heart rate, mean arterial pressure, cardiac output, mean pulmonary artery pressure, mean right atrial pressure and mean left atrial pressure) at baseline, during 60 min of atrial fibrillation and after reversion to sinus rhythm were constant throughout the study period. Peak left atrial contraction velocities (measured from the transmitral flow velocity profile) were significantly (p < 0.02) reduced to 64+/-22% of baseline values upon spontaneous conversion of atrial fibrillation to sinus rhythm and recovered to basal values by 20 min after resumption of sinus rhythm. Peak left atrial appendage contraction velocities were significantly (p < 0.001) reduced to 49+/-24% of baseline values upon spontaneous conversion of atrial fibrillation to sinus rhythm and recovered to basal values by 40 min after reversion to sinus rhythm.

CONCLUSIONS

Even brief (60 min) periods of atrial fibrillation in normal canine hearts result in marked depression of global left atrial systolic function and regional left atrial (left atrial appendage) systolic function upon resumption of sinus rhythm. This "mechanical stunning" of left atrial systolic function appears to be more profound and of longer duration for the left atrial appendage compared with the left atrium as a whole, which may predispose the appendage to blood stasis and thrombus formation. Chronic models of atrial fibrillation need to be developed to examine the impact of longer periods of atrial fibrillation upon the magnitude and duration of postconversion left atrial "stunning."

The peri-operative management of atrial fibrillation

Atrial fibrillation is a common arrhythmia frequently seen in surgical patients. The onset of new atrial fibrillation during the peri-operative period is less common. There are many possible precipitating factors, although volatile agents themselves may have an antifibrillatory action. The management of atrial fibrillation includes removal of any precipitating factors and treatment of the arrhythmia itself. Immediate management of acute-onset atrial fibrillation is usually direct current cardioversion. Alternatively, anti-arrhythmic drugs can be used to achieve cardioversion. In patients with rapid, chronic atrial fibrillation or those refractory to cardioversion, priority is given to control of the ventricular rate. Thrombo-embolism is a significant risk if atrial fibrillation is paroxysmal or persists for more than 48 h.

Thromboembolism in chronic atrial flutter: is the risk underestimated?

OBJECTIVES

We sought to evaluate the risk of thromboembolic events in the presence of chronic atrial flutter and to determine the impact of anticoagulation therapy, if any, on this risk.

BACKGROUND

Thromboembolic events are thought to be rare after cardioversion of atrial flutter.

METHODS

This study was a retrospective analysis of 110 consecutive patients referred to the electrophysiology laboratory for cardioversion of chronic atrial flutter from 1986 to 1996. Atrial flutter was present for at least 6 months. Of the 110 patients reviewed, 100 had adequate information available regarding the effectiveness of anticoagulation (mean age 64 years, range 27 to 86; 75 men, 25 women; mean left ventricular ejection fraction 42%).

RESULTS

Thirteen patients (13%) had a thromboembolic event. Of these, seven were attributable to causes other than atrial flutter. In the remaining six patients (6%), thromboembolic events occurred during a rhythm of atrial flutter or after cardioversion to sinus rhythm. Other causes of thromboembolism were excluded. Effective anticoagulation was associated with a decreased risk of thromboembolism (p = 0.026).

CONCLUSIONS

Patients with chronic atrial flutter are at an increased risk of thromboembolic events. Effective anticoagulation may decrease this risk.

The medical management of atrial fibrillation

Atrial fibrillation is an extremely common arrhythmia that is associated with significant sequelae. Certain aspects of therapy, such as anticoagulation, are studied in well-constructed randomized trials. Other therapy, such as the maintenance of sinus rhythm with antiarrhythmic agents, is supported by limited evidence. This article reviews the epidemiology and medical treatment of this arrhythmia, addressing anticoagulation, ventricular rate control, and restoration and maintenance of sinus rhythm. Randomized trials in progress that attempt to answer important questions in the management of atrial fibrillation are also discussed.

Recovery of atrial systolic function after pharmacological conversion of chronic atrial fibrillation to sinus rhythm: a Doppler echocardiographic study

OBJECTIVE

To evaluate the time course of the recovery of atrial mechanical function after pharmacological cardioversion of chronic atrial fibrillation to sinus rhythm.

PATIENTS AND METHODS

21 patients (12 male, 9 female, aged 37-77 years) with chronic atrial fibrillation (< 6 months) were followed up by serial transmitral pulsed Doppler echocardiography. Echocardiographic studies were performed within the first 24 hours and on day 8, 15, and 30 after cardioversion.

RESULTS

There was a significant increase (mean (SD)) in the peak A-wave velocity (from 0.35 (0.10) on day 1 to 0.50 (1.73) on day 8, and thereafter a gradual increase to 0.61 (0.14) m/s on day 30). Similarly, integrated late atrial velocities increased from 4.50 (1.46) on day 1 to 5.61 (1.73) on day 8 and 5.97 (1.47) cm/s2 on day 30. The atrial contribution to total transmitral flow increased significantly from 26 (7)% immediately after conversion of atrial fibrillation to sinus rhythm to 34 (7)% on day 30, indicating the haemodynamic benefit of the restoration of sinus rhythm. Left atrial diameter decreased but not significantly, from 4.11 (0.37) to 3.98 (0.34) cm (P < 0.005).

CONCLUSIONS

These results suggest that restoration of atrial mechanical function after pharmacological cardioversion in patients with chronic atrial fibrillation is slow and gradual, as it is after electrical DC restoration of sinus rhythm. This time course may have important implications for determining how long treatment with anticoagulants and antiarrhythmic agents needs to continue in individual patients. It will also influence the clinical assessment of the haemodynamic benefit of restoring sinus rhythm in patients with chronic atrial fibrillation.

Transesophageal echocardiography

This article presents an overview of the benefits and efficacy of transesophageal echocardiography (TEE) in the critically ill patient. The echocardiographic evaluation of ventricular function both regional and global, is discussed with special emphasis on ischemic heart disease; assessment of preload, interrogation of valvular heart disease (prosthetic and native) and its complications; endocarditis and its complications; intracardiac and extracardiac masses, including pulmonary embolism; aortic diseases (e.g., aneurysan, dissection, and traumatic tears); evaluation of patent foramen ovale and its association with central and peripheral embolic events; advancements in computer technology; and finally, the effect of TEE on critical care.

Transesophageal echocardiographic assessment of embolic sources: intracardiac and extracardiac masses and aortic degenerative disease

The increased sensitivity of transesophageal echocardiography (TEE) makes it complementary and, in many cases, superior to transthoracic echocardiography in the detection of various sources of embolism. These sources include intracardiac thrombus, tumors, spontaneous echocardiographic contrast, and others. TEE is also helpful as an adjunctive test for the diagnosis of pulmonary embolisms.

Physician variation in the management of patients with atrial fibrillation

OBJECTIVE

To investigate variations in the management of patients with atrial fibrillation among consultant physicians.

DESIGN

Questionnaire survey.

SUBJECTS

Consultant physicians in England, Wales, and Scotland.

RESULTS

214 consultant physicians (88 cardiologists and 126 non-cardiologists) were surveyed between May and July 1994. Most physicians (47.7%) reported that they saw one to five patients with atrial fibrillation weekly. Some 52% of cardiologists and 40% of non-cardiologists considered that the main factor influencing their decision of whether or not to anticoagulate was the clinical history--that is, heart failure, valve disease, or stroke. When encountering a patient admitted acutely with new onset atrial fibrillation, significantly more cardiologists (66% v 52%, chi 2 = 6.89, P = 0.03) would immediately start anticoagulant treatment, most favouring intravenous heparin. Most physicians would also introduce antiarrhythmic treatment or digoxin, but more cardiologists would attempt immediate pharmacological (39% v 18% of non-cardiologists, P < 0.001) or later electrical (86% v 69%, chi 2 = 11.7, P = 0.003) cardioversion to sinus rhythm, while non-cardiologists tended to prefer "rate control" with digoxin. Although many physicians would not continue antiarrhythmic treatment post-cardioversion, more cardiologists than non-cardiologists would do so (the commonest choice being class III agents) (31% v 17%, P = 0.04). Fewer non-cardiologists would continue anticoagulant treatment post-cardioversion (27% v 69% of cardiologists, chi 2 = 39.8, P < 0.0001). When treating patients with atrial fibrillation, decisions about anticoagulation were usually related to the perceived relative risk of thromboembolism versus haemorrhage derived for each of six case management scenarios in the questionnaire. There was, however, general agreement between cardiologists and non-cardiologists in the use of antithrombotic treatment in the management of lone atrial fibrillation, paroxysmal atrial fibrillation, and patients with atrial fibrillation and mitral valve disease or thyrotoxicosis.

CONCLUSION

There is considerable variation in the management of atrial fibrillation, with more cardiologists than non-cardiologists considering cardioversion to sinus rhythm (and the use of antiarrhythmic and anticoagulant treatment post-cardioversion) and thrombo-prophylaxis with anticoagulation. Guidelines on the management of this common arrhythmia are clearly required.

Cardioversion of atrial fibrillation

Cardioversion to sinus rhythm should be considered for all patients in atrial fibrillation in order to improve cardiac performance and perhaps to reduce the long-term risk of thromboembolic complications. Different methods of cardioversion, whether electrical or pharmacological, exist and there is often uncertainty about performing the procedure. In particular, there is often confusion about the use of anti-arrhythmic drugs and the suitable length of anticoagulant therapy required pre- and post-cardioversion. This review discusses the current understanding of electrical and pharmacological cardioversion of atrial fibrillation, the clinical effects and the role of prophylactic anti-arrhythmic and anticoagulant therapy in this procedure.

Hemodynamics of idiopathic paroxysmal atrial fibrillation

The hemodynamics of induced atrial fibrillation (AF) was investigated in 15 patients (ages 58 +/- 11 years) with paroxysmal AF presenting without organic heart disease or hypertension. A hemodynamic study was performed both during sinus rhythm and after the induction of AF. The mean heart rate increased from 73 +/- 11 to 128 +/- 18 beats/min (P < 0.001) after AF. Systolic and mean aortic pressures did not significantly change, and diastolic aortic pressure increased (78 +/- 11 vs 89 +/- 12 mmHg, P < 0.01). Left ventricular end-diastolic pressure decreased during AF (9 +/- 3 vs 6 +/- 2.6 mmHg, P < 0.005), whereas mean pulmonary wedge pressure increased (8 +/- 2 vs 12 +/- 4 mmHg, P < 0.001). Systolic pulmonary arterial pressure did not show significant variations, and there was a slight but statistically significant increase in the diastolic and mean pulmonary arterial pressures (P < 0.01). The right ventricular end-diastolic pressure decreased during AF (5.6 +/- 2 vs 3.8 +/- 2 mmHg, P < 0.01), whereas mean right atrial pressure showed a trend toward an increase. Stroke volume markedly decreased (P < 0.001) while the cardiac index did not significantly change. Systemic vascular resistance, pulmonary arteriolar resistance, and the arteriovenous O2 difference showed no significant variations after the induction of AF. These results suggest that in subjects without organic heart disease, paroxysmal AF is well tolerated hemodynamically, and the rise in the atrial pressures during AF is not related to an increase in the ventricular end-diastolic pressure.

Left atrial appendage contractile function in atrial fibrillation. Influence of heart rate and cardioversion to sinus rhythm

BACKGROUND

A high incidence of embolic phenomena is associated with atrial fibrillation (AF) and the left atrial appendage (LAA) is frequently the source of the emboli. Thrombus formation may be due to stasis within the fibrillating and inadequately emptying LAA. Because LAA emptying in AF may be the result of mechanical compression by the adjacent left ventricle, it is possible that left ventricular diastolic filling duration will importantly influence passive emptying of the LAA. We hypothesized that the magnitude of emptying of the LAA in AF is related to the duration of left ventricular diastolic filling which is determined by the ventricular response rate in AF.

OBJECTIVE

The objective of our study was to determine the relationship of ventricular response rate in AF to LAA emptying and to assess the influence of sinus rhythm and heart rate on LAA emptying immediately after direct current cardioversion to sinus rhythm.

METHODS

To study this, we used transesophageal echocardiography to measure LAA ejection fraction ([LAAmax-LAAmin]/LAAmax x 100%) and evaluated its relationship to left ventricular response rate (VRR) in 26 patients with AF (mean age, 65 +/- 7 [1 SD] years).

RESULTS

There was a strong inverse relationship between LAA ejection fraction and VRR in AF (r = -0.73; p < 0.001). LAA ejection fraction during AF was 26 +/- 10%, and immediately after successful cardioversion, it increased to 46 +/- 12% (p < 0.001). However, during sinus rhythm there was no relationship between LAA ejection fraction and VRR (r = 0.06; p = NS) in the subgroup of patients who were successfully converted to sinus rhythm. There were poor relationships between LAA ejection fraction and peak transmitral flow velocity (r = -0.41; p = NS) or pulmonary venous flow velocity (r = -0.03; p = NS) in AF.

CONCLUSION

These results indicate that the magnitude of LAA emptying in AF is strongly and inversely influenced by ventricular rate. Direct current cardioversion to sinus rhythm is associated with an increase in the magnitude of LAA emptying that is not influenced by heart rate. The magnitude of LAA emptying may be an important factor in the formation of thromboemboli in AF. The extent to which controlling the VRR in chronic AF will prevent stasis and LAA thrombus formation remains to be determined.

Recovery of atrial function after atrial compartment operation for chronic atrial fibrillation in mitral valve disease

OBJECTIVES

We prospectively studied the recovery of atrial function after atrial compartment operation and mitral valve surgery in patients with chronic atrial fibrillation caused by mitral valve disease.

BACKGROUND

Chronic atrial fibrillation is the most common arrhythmia in mitral valve disease. This arrhythmia is associated with excessive morbidity and mortality. Mitral valve surgery alone rarely eliminates it.

METHODS

Twenty-two patients underwent mitral valve surgery and a new surgical method, atrial compartment operation. Doppler echocardiography was performed in all patients before operation and at 1 week and 2 and 6 months after operation in the successful cardioversion group. Peak early diastolic (E) and atrial (A) filling velocities, peak A/E velocity ratio and A/E integral ratio of the mitral and tricuspid valves were measured.

RESULTS

Sinus rhythm was restored immediately after operation in 91% of patients and was maintained for > 1 week in 15 (68%) of 22 patients and > 6 months in 14 (64%) of 22. Eleven of 15 patients had left atrial paralysis (A/E integral ratio 0) at 1 week and 6 of 14 patients at 2 months. Nine of 15 patients had right atrial paralysis (A/E integral ratio 0) at 1 week and 1 of 14 patients at 2 months. Both left and right atrial contractile function (presence of an A wave on Doppler findings) was detected at 6 months in 14 patients. Mean (+/- SD) peak atrial filling velocity of the mitral valve was 15 +/- 26 cm/s at 1 week, 38 +/- 39 cm/s at 2 months and 93 +/- 32 cm/s at 6 months (p < 0.001). Mean peak atrial filling velocity of the tricuspid valve was 14 +/- 19 cm/s at 1 week, 33 +/- 19 cm/s at 2 months and 50 +/- 19 cm/s at 6 months (p < 0.001). Peak early diastolic and atrial filling velocities, peak A/E velocity ratio and A/E integral ratio of the mitral and tricuspid valves increased significantly from 1 week to 6 months.

CONCLUSIONS

Chronic atrial fibrillation in mitral valve disease can often be eliminated by atrial compartment operation. No surgical mortality or significant complications were encountered. Both left and right atrial function, as manifested by Doppler findings, recover after compartment operation and improve over time. The mechanical function of the right atrium recovers earlier than that of the left.

Should all patients undergo transesophageal echocardiography before electrical cardioversion of atrial fibrillation?

The management of anticoagulant therapy in patients with atrial fibrillation undergoing electrical cardioversion remains controversial, largely because of inadequate studies demonstrating risk or benefit, a relatively inconvenient anticoagulation management strategy and the increasing use of transesophageal echocardiography. Recent investigations into the potential mechanisms involved in the development of thrombus and systemic embolism in patients undergoing electrical cardioversion of atrial fibrillation may provide insight into underlying predisposing factors, with subsequent modification of management strategies. Conventional wisdom suggests that preexisting thrombus is responsible for thromboembolic events after cardioversion. However, development of a thrombogenic milieu after cardioversion, particularly in the left atrial appendage, may also be an important predisposing factor. To protect against both potential mechanisms of embolization, these data support therapeutic anticoagulation for all patients with atrial fibrillation of > 2 days in duration from the time of, as well as after cardioversion for a total of 4 weeks, undergoing cardioversion, even in the absence of thrombus on echocardiography. Therefore, the role of transesophageal echocardiography in this setting should be to enable early cardioversion if atrial thrombus is excluded and to identify high risk patients with atrial thrombi so as to postpone cardioversion and avoid the risk of embolization. Ultimately, however, a controlled, randomized and prospective clinical trial will be required to compare conventional management with a transesophageal echocardiography-guided strategy.

Transesophageal echocardiography before and during direct current cardioversion of atrial fibrillation: evidence for "atrial stunning" as a mechanism of thromboembolic complications

OBJECTIVES

The purpose of this study was to evaluate the usefulness of transesophageal echocardiography before electrical cardioversion in patients with atrial fibrillation and to determine the mechanism of thromboembolism after cardioversion.

BACKGROUND

Thromboembolic complications after electrical cardioversion of atrial fibrillation have been attributed to the dislodgment of preexistent left atrial thrombus during the resumption of atrial contraction. Transesophageal echocardiography has been proposed as a method of screening patients for left atrial thrombus before cardioversion.

METHODS

Seventy transesophageal echocardiographic studies were performed in 66 patients, predominantly with nonvalvular atrial fibrillation, before direct current cardioversion. In addition, transesophageal echocardiography was performed during the cardioversion procedure in 15 patients and immediately after in 1 patient.

RESULTS

Left atrial thrombus was detected in one patient (1.4%), and cardioversion was cancelled. Thromboembolic complications occurred in 4 patients, none of whom had evidence of left atrial thrombus before cardioversion. Within 10 s of successful cardioversion, left atrial spontaneous echo contrast appeared in five patients, increased in one patient and was unchanged in nine patients. Patients with new or increased spontaneous echo contrast had more impaired atrial contraction and slower initial heart rates after cardioversion than those without. Left ventricular contraction was also impaired transiently by cardioversion.

CONCLUSIONS

Transesophageal echocardiographic detection of left atrial thrombus before direct current cardioversion is important but infrequent in patients with predominantly nonvalvular atrial fibrillation. The occurrence of thromboembolic complications in the absence of demonstrable left atrial thrombus and the new development of spontaneous echo contrast in association with the transient atrial dysfunction ("stunning") caused by cardioversion suggest that cardioversion may promote new thrombus formation, in which case all patients should receive full anticoagulant therapy at the time of cardioversion.

Heterogeneity and time course of improvement in cardiac function after cardioversion of chronic atrial fibrillation: assessment of serial echocardiographic indices

OBJECTIVE

To assess the clinical characteristics of patients in whom cardiac function improved after cardioversion of atrial fibrillation and the time course of the improvement.

DESIGN

A prospective serial study of echocardiograms recorded before cardioversion and one day, seven days, one month, and three months after cardioversion.

SETTING

Echocardiography laboratory of a university hospital.

PATIENTS

23 patients with chronic atrial fibrillation in whom cardioversion was successful.

MAIN OUTCOME MEASURES

M mode indices of the left ventricular wall motion and pulsed Doppler indices of the left ventricular inflow.

RESULTS

Three months after cardioversion percentage fractional shortening had increased by more than 5% in 14 patients (improved group) and by less than 5% in nine patients (non-improved group). Those in whom cardiac function improved had significantly higher heart rates and a greater reduction in ventricular filling during atrial fibrillation and a more prominent atrial filling wave three months after cardioversion than those patients in the non-improved group. Over the three months of follow up the mean (1SD) percentage fractional shortening increased from 22 (3)% to 30 (4)% in the improved group and in this group heart rate fell one day after cardioversion. A month after cardioversion the percentage fractional shortening had increased to 35 (5)% and the atrial systolic contribution to left ventricular filling increased from 30 (9)% on day 1 to 47 (12)%.

CONCLUSIONS

Cardioversion improved cardiac function in patients with tachycardia and reduced ventricular filling during atrial fibrillation. Because both an immediate reduction of heart rate and a delayed recovery of atrial booster pump function played an important part in the improvement of cardiac function the long-term effects of cardioversion should be assessed at least a month after cardioversion.

Time-course of recovery of atrial contraction after cardioversion of chronic atrial fibrillation

We aimed to study the time-course of recovery of atrial contraction after cardioversion of chronic atrial fibrillation (duration of more than 3 months) to sinus rhythm. Using M-mode, two-dimensional and pulsed Doppler echocardiography, we determined left atrial (LA) and ventricular (LV) dimensions, peak velocities, and velocity-time integrals of early and atrial filling velocity-time profiles in both LV and right ventricular (RV) inflows (peak E and peak A, Ea and Aa). Results of the LA and LV functions in seven elderly patients (an initial study group) were as follows. The extent of the LA dimensional reduction resulting from atrial contraction was significantly increased up to 5-8 weeks compared with values 0-1 day after cardioversion [from 1.3 +/- 0.8 (mean +/- SD) mm to 3.9 +/- 1.1, P < 0.01]. In conjunction with the progressive increase in peak A, the ratio of peak E to peak A (peak E/A) was significantly decreased and reached a plateau at 5-8 weeks (from 1.93 +/- 0.59 to 0.67 +/- 0.11, P < 0.01). LV fractional shortening was increased significantly 5-8 weeks after cardioversion (from 0.20 +/- 0.06 to 0.29 +/- 0.05, P < 0.01). Since a large part of the improvement in LA contraction was expected to occur in an early stage after cardioversion, we studied eight additional patients more frequently in the early stage (an additional study group). Furthermore, we studied the time course of LA and right atrial (RA) contractions.(ABSTRACT TRUNCATED AT 250 WORDS)

Delayed restoration of atrial function after conversion of atrial flutter by pacing or electrical cardioversion

It is often suggested but never proven that atrial function is not affected during atrial flutter, nor after its conversion to normal sinus rhythm. To evaluate this hypothesis, a prospective study was performed in 22 patients (age range 20 to 88 years) with atrial flutter. Diastolic transmitral flow was analyzed with echo-Doppler before and after conversion. After randomization, conversion was attempted with overdrive pacing or up to two 50 J shocks. If the initial method was unsuccessful, a 200 J shock was administered. All patients were converted to sinus rhythm with this protocol. Shortly after conversion (at 1 and 6 hours), atrial contribution to ventricular filling was absent in 4 of 22 patients. In the remaining 18 patients, atrial contribution to ventricular filling was small. Atrial contribution to transmitral flow improved from 20 to 27% within 24 hours (p < 0.01) and increased further to 38% at 6 weeks (p < 0.005). Peak velocity of late diastolic filling increased from 0.28 m/s after 1 hour to 0.39 m/s after 24 hours (p < 0.0001) and improved even further during later follow-up. In 1 patient, an effective atrial systole was not observed until the 14th day. Cardiac output did not change significantly during the study period. No differences were observed between the conversion modalities. In conclusion, atrial dysfunction is present immediately after conversion of atrial flutter to normal sinus rhythm. This dysfunction occurs also after overdrive pacing and can last > 1 week. The findings suggest that stasis in the atria can remain temporarily present after successful conversion of atrial flutter to sinus rhythm.

Role of prophylactic anticoagulation for direct current cardioversion in patients with atrial fibrillation or atrial flutter

The need for prophylactic anticoagulation to prevent embolism before direct current cardioversion is performed for atrial fibrillation or atrial flutter is controversial. To examine this issue further, a retrospective review was undertaken to assess the incidence of embolic complications after cardioversion. The review involved 454 elective direct current cardioversions performed for atrial fibrillation or atrial flutter over a 7 year period. The incidence rate of embolic complications was 1.32% (six patients); the complications ranged from minor visual disturbances to a fatal cerebrovascular event. All six patients had atrial fibrillation, and none had been on anticoagulant therapy (p = 0.026). The duration of atrial fibrillation was less than 1 week in five of the six patients who had embolic complications. Baseline characteristics of patients with a postcardioversion embolic event are compared with those of patients who did not have an embolic event. There was no difference in the prevalence of hypertension, diabetes mellitus or prior stroke between the two groups, and there was no difference in the number of patients who were postoperative or had poor left ventricular function. Left atrial size was similar between the two groups. No patient in the embolic group had valvular disease. No patient with atrial flutter had an embolic event regardless of anticoagulant status; therefore, anticoagulation is not recommended for patients with atrial flutter undergoing cardioversion. Prophylactic anticoagulation is pivotal in patients undergoing elective direct current cardioversion for atrial fibrillation, even those with atrial fibrillation of less than 1 week's duration.