Cardioversion in atrial fibrillation: indications, thromboembolic prophylaxis, and role of transesophageal echocardiography

Atrial fibrillation: the newest frontier in arrhythmia management

At least 2.3 million people in the United States have atrial fibrillation. Since the risk for developing atrial fibrillation increases with age, the number of people with atrial fibrillation is expected to rise sharply. Atrial fibrillation is a complex condition that adversely influences mortality, morbidity, quality of life, and use of health care resources. Knowledge generated from extensive research has led to innovative management strategies. As the number of individuals with atrial fibrillation increases and treatment options expand, nurses in a variety of settings will be challenged to respond to the multifaceted needs of this population. This review discusses the significance of atrial fibrillation and summarizes research findings influencing current management strategies. Pharmacologic therapies are reviewed and new technologies for atrial fibrillation treatment are introduced. Nursing assessment and treatment of patients' response to atrial fibrillation are discussed. Recommendations for patient education are offered. A plan describing specific nursing diagnoses, outcomes, interventions, and activities for care of patients with atrial fibrillation is presented.

Safety of electrical cardioversion in patients with atrial fibrillation

OBJECTIVES

To determine the incidence of thromboembolic complications after electively performed electrical cardioversion in patients with atrial fibrillation and to assess the clinical variables associated with an increased risk of thromboembolism after cardioversion.

PATIENTS AND METHODS

This is a retrospective analysis of 834 successful electrical cardioversions performed in 717 patients from 1990 through 1994. Outcome measures included embolic complications at 1-month follow-up after cardioversion and logistic regression models to measure the associations among clinical, anticoagulation, and thromboembolic events and to identify independent predictors of these events.

RESULTS

The rate of embolic events after cardioversion was low (0.9%; 95% confidence interval, 0.4%-1.8%). Patients with a therapeutic international normalized ratio had no embolic events. Adequate anticoagulation was independently associated with reduced risk of thromboembolism. Hypertension and diabetes mellitus were independently associated with increased risk of embolization.

CONCLUSION

Adequate anticoagulation reduced the risk of embolization after cardioversion. Diabetes mellitus and hypertension are independently associated with increased risk of embolization early after cardioversion.

Thromboembolic complications after electrical cardioversion in patients with atrial flutter

PURPOSE

To determine the incidence of thromboembolic complications after cardioversion in patients with atrial flutter.

SUBJECTS AND METHODS

We reviewed 615 electrical cardioversions performed electively in 493 patients with atrial flutter. Embolic complications were evaluated during the 30 days after cardioversion. Follow-up data were obtained by follow-up visits and by contacting the treating physician.

RESULTS

Anticoagulants had been administered in 415 cardioversions (67%). Cardioversion was successful in 570 procedures (93%). Three embolic events (in 3 patients) occurred in the 30 days after 550 successful cardioversions with completed follow-up (0.6% of successful procedures; 95% confidence interval, 0.1% to 1.6%). Two of the 3 patients had not been anticoagulated, whereas the third patient had subtherapeutic oral anticoagulation. No embolic event occurred in procedures performed with adequate anticoagulation. The incidence of embolism in patients regardless of subtherapeutic anticoagulation was 1% (3 of 303 successful cardioversions).

CONCLUSIONS

We observed a low (0.6%) incidence of postcardioversion thromboembolic complications in patients with atrial flutter. Embolic events did not occur in patients with adequate anticoagulation.

Safety of electrical cardioversion in patients with previous embolic events

OBJECTIVE

To assess thromboembolic complications in cardioversions in patients with atrial fibrillation or flutter and a previous embolic event.

PATIENTS AND METHODS

The study population consisted of 104 patients with previous embolic events who underwent 128 electrical cardioversions for termination of atrial fibrillation or flutter. The primary outcome measure was successful cardioversion.

RESULTS

Anticoagulants were administered in 118 procedures (92%). Cardioversion was successful in 108 (84%) of the 128 procedures. Only 1 embolic event occurred within 30 days after cardioversion (incidence, 0.9% of successful procedures; 95 % confidence interval, 0.02%-5.3%). The single embolic event was a transient neurologic deficit occurring 22 days after cardioversion in a patient with previous atrial fibrillation. This patient had a sub-therapeutic level of anticoagulation. Transesophageal echocardiography revealed no spontaneous echo contrast or thrombi before the procedure. No thromboembolism was noted in patients who had therapeutic anticoagulation or in those with failed cardioversion.

CONCLUSION

Patients with previous embolism are not at additional risk of thromboembolic complications after cardioversion if anticoagulation is adequate.

Role of transesophageal echocardiography-guided cardioversion of patients with atrial fibrillation

Electrical cardioversion of patients with atrial fibrillation (AF) is frequently performed to relieve symptoms and improve cardiac performance. Patients undergoing cardioversion are treated conventionally with therapeutic anticoagulation for three weeks before and four weeks after cardioversion to decrease the risk of thromboembolism. A transesophageal echocardiography (TEE)-guided strategy has been proposed as an alternative that may lower stroke and bleeding events. Patients without atrial cavity thrombus or atrial appendage thrombus by TEE are cardioverted on achievement of therapeutic anticoagulation, whereas cardioversion is delayed in higher risk patients with thrombus. The aim of this review is to discuss the issues and controversies associated with the management of patients with AF undergoing cardioversion. We provide an overview of the TEE-guided and conventional anticoagulation strategies in light of the recently completed Assessment of Cardioversion Using Transesophageal Echocardiography (ACUTE) clinical trial. The two management strategies comparably lower the patient's embolic risk when the guidelines are properly followed. The TEE-guided strategy with shorter term anticoagulation may lower the incidence of bleeding complications and safely expedite early cardioversion. The inherent advantages and disadvantages of both strategies are presented. The TEE-guided approach with short-term anticoagulation is considered to be a safe and clinically effective alternative to the conventional approach, and it is advocated in patients in whom earlier cardioversion would be clinically beneficial.

Atrial fibrillation: is there a role for low-molecular-weight heparin?

Atrial fibrillation (AF) is the most common form of tachyarrhythmia and carries a significant risk of serious thromboembolic complications. Anticoagulation is used for long-term thromboprophylaxis and for short-term management in a number of clinical situations, among which is the medical or electrical cardioversion of AF to sinus rhythm. Current guidelines recommend prompt cardioversion with heparin cover for AF of <48 h duration, and several weeks of warfarin therapy prior to cardioversion when the duration of disease is longer. Recent animal and human studies, however, have shown that swifter cardioversion is likely to be more successful in achieving sinus rhythm and in reducing the risk of recurrence of AF. Other observations have demonstrated that thrombi can develop within a few hours of the development of AF. These considerations suggest that cardioversion should be carried out as early as possible in all cases, and that the most sensitive means of detecting atrial thrombi, currently transesophageal echocardiography (TEE), should be used to screen all patients prior to cardioversion. Within this context, there is growing interest in the use of low-molecular-weight heparin (LMWH) as an anticoagulant therapy in AF. Compared with unfractionated heparin, LMWH therapy does not involve prolonged intravenous administration, hospitalization, or laboratory monitoring; LMWH therefore has the potential to greatly simplify anticoagulation therapy for AF, especially pericardioversion. Recent studies have demonstrated that LMWH can be used safely and effectively in place of unfractionated heparin for acute treatment at the onset of AF and during early cardioversion. For example, in patients with AF, a strategy of immediate administration of dalteparin (100 IU/kg s.c. twice daily) continued for 11 days, combined with early TEE and immediate cardioversion in patients with no thrombus, resulted in sinus rhythm in 74% of patients after a median of 7 days. Low-molecular-weight heparin therapy may also find a role perioperatively and in selected patients, notably those with warfarin intolerance, as a replacement for warfarin following cardioversion. Controlled clinical studies are still required, however, to establish a firm, evidence-based foundation for the use of LMWHs in AF.