Pacemaker failure in elective DC cardioversion of atrial tachycardia

A 74-year-old woman with a VVI-rate-responsive pacemaker (Pacesetter 2033K; unipolar pacing electrode) was admitted for cardioversion of atrial tachycardia. Antiarrhythmic medication included flecainide 100 mg x 2. Electrical defibrillation was followed by transient, but severe nodal bradycardia and pacemaker malfunction characterized by loss of ventricular capture and sensing. The incident probably represents an example of pacemaker failure due to an acute increase in the stimulation threshold, most likely caused by current-induced tissue damage at the electrode-endomyocardial interface. Flecainide might have contributed to the increase in stimulation threshold. The clinician should be prepared for the possible consequences of pacemaker failure after external defibrillation.     

Exclusion of atrial thrombus by transesophageal echocardiography does not preclude embolism after cardioversion of atrial fibrillation. A multicenter study

BACKGROUND: Transesophageal echocardiography (TEE) has been used recently to detect atrial thrombi before cardioversion of atrial arrhythmias. It has been assumed that embolic events after cardioversion result from embolism of preexisting atrial thrombi that are accurately detected by TEE. This study examined the clinical and echocardiographic findings in patients with embolism after cardioversion of atrial fibrillation despite exclusion of atrial thrombi by TEE. METHODS AND RESULTS: Clinical and echocardiographic data in 17 patients with embolic events after TEE-guided electrical (n = 16) or pharmacological (n = 1) cardioversion were analyzed. All 17 patients had nonvalvular atrial fibrillation, including four patients with lone atrial fibrillation. TEE before cardioversion showed left atrial spontaneous echo contrast in five patients and did not show atrial thrombus in any patient. Cardioversion resulted in return to sinus rhythm without immediate complication in all patients. Thirteen patients had cerebral embolic events and four patients had peripheral embolism occurring 2 hours to 7 days after cardioversion. None of the patients were therapeutically anticoagulated at the time of embolism. New or increased left atrial spontaneous echo contrast was detected in four of the five patients undergoing repeat TEE after cardioversion including one patient with a new left atrial appendage thrombus. CONCLUSIONS: Embolism may occur after cardioversion of atrial fibrillation in inadequately anticoagulated patients despite apparent exclusion of preexisting atrial thrombus by TEE. These findings suggest de novo atrial thrombosis after cardioversion or imperfect sensitivity of TEE for atrial thrombi and suggest that screening by TEE does not obviate the requirement for anticoagulant therapy at the time of and after cardioversion. A randomized clinical trial is needed to compare conventional anticoagulant management with a TEE-guided strategy including anticoagulation after cardioversion.     

Radiofrequency and cryoablation of atrial fibrillation in patients undergoing valvular operations

BACKGROUND: Previous studies have shown that the maze operation can restore sinus rhythm and atrial transport function in patients with chronic atrial fibrillation. The purpose of this study was to test the feasibility of the application of radiofrequency and cryoablation as an alternative to the classic maze operation. METHODS: Twelve patients undergoing mitral valve procedures were included in this study. Radiofrequency and cryoablation were applied to create lesions in both atria to simulate the classic maze operation. RESULTS: There were two surgical deaths. At the mean follow-up of 10.25 months for the remaining 10 patients; 6 were in sinus rhythm, 2 in atrial rhythm, 1 in paroxysmal atrial tachycardia, and 1 in atrial fibrillation. Doppler echocardiography at 6-month follow-up showed emergence of biatrial transport function in 3 patients and right atrial contractility in 8. At 12-month follow-up of 5 patients, Doppler echocardiography showed biatrial transport function in 3 and right atrial contractility in 4. CONCLUSIONS: Our modified maze procedure during valvular operation is effective for achieving an acceptable success rate to restore sinus rhythm and atrial transport function in patients with chronic atrial fibrillation.     

Favorable effects of flecainide in transvenous internal cardioversion of atrial fibrillation

OBJECTIVES: The aim of the study was to evaluate the effects of intravenous (IV) flecainide on defibrillation energy requirements in patients treated with low-energy internal atrial cardioversion. BACKGROUND: Internal cardioversion of atrial fibrillation is becoming a more widely accepted therapy for acute episode termination and for implantable atrial defibrillators. METHODS: Twenty-four patients with atrial fibrillation (19 persistent, 5 paroxysmal) underwent elective transvenous cardioversion according to a step-up protocol. After successful conversion in a drug-free state, atrial fibrillation was induced by atrial pacing; IV flecainide (2 mg/kg) was administered and a second threshold was determined. In patients in whom cardioversion in a drug-free state failed notwithstanding a 400- to 550-V shock, a threshold determination was attempted after flecainide. RESULTS: Chronic persistent atrial fibrillation was converted in 13/19 (68%) patients at baseline and in 16/19 (84%) patients after flecainide. Paroxysmal atrial fibrillation was successfully cardioverted in all the patients. A favorable effect of flecainide was observed either in chronic persistent atrial fibrillation (13 patients) or in paroxysmal atrial fibrillation (5 patients) with significant reductions in energy requirements for effective defibrillation (persistent atrial fibrillation: 4.42+/-1.37 to 3.50+/-1.51 J, p < 0.005; paroxysmal atrial fibrillation: 1.68+/-0.29 to 0.84+/-0.26 J, p < 0.01). In 14 patients not requiring sedation, the favorable effects of flecainide on defibrillation threshold resulted in a significant reduction in the scores of shock-induced discomfort (3.71+/-0.83 vs. 4.29+/-0.61, p < 0.005). No ventricular proarrhythmia was observed for any shock. CONCLUSIONS: Intravenous flecainide reduces atrial defibrillation threshold in patients treated with low-energy internal atrial cardioversion. This reduction in threshold results in lower shock-induced discomfort. Additionally, flecainide may increase the procedure success rate in patients with chronic persistent atrial fibrillation.     

Efficacy of serial electrical cardioversion therapy in patients with chronic atrial fibrillation after valve replacement and implications for surgery to cure atrial fibrillation

In April 1993, a 51-year-old woman had a fever, and an infiltrative shadow was seen in the left upper lobe on a chest X-ray film. Repeated sputum cultures were positive for Mycobacterium avium complex. She underwent antituberculosis therapy consisting of pyrazinamide, ofloxacin, and streptomycin. Her symptom disappeared and the abnormal shadow resolved. In January 1994, she was admitted to the hospital because of bloody sputum and abnormal chest X-ray findings consisting of a left hilar mass and atelectasis of the left upper lobe. Bronchoscopy revealed multiple polypoid lesions without necrosis in the left upper-lobe bronchus. Histological examination showed that the tumor consisted of an aggregation of lymphocytes and plasma cells, and was positive for Ziehl-Neelsen stain. The acid-fast bacillus was identified as Mycobacterium avium by the DNA probe method. Anti-tuberculosis treatment was given: rifampicin, isoniazid, sparfloxacin, and clarithromycin. Three months later, the atelectasis and the polypoid mass in the left upper-lobe bronchus had disappeared. We believe that the polypoid lesions in the left upper-lobe bronchus were due to infection by Mycobacterium avium. The patient was HIV-negative and immunocompetent. Such endobronchial lesions caused by Mycobacterium avium are rare in HIV-negative hosts.     

Internal right atrial cardioversion of chronic atrial fibrillation: effects of low-energy biphasic shocks

This study evaluates the efficacy and safety of internal right atrial cardioversion of atrial fibrillation using a defibrillation right atrial catheter and 2 thoracic patches with low-energy biphasic shocks.     

Clinical and echocardiographic features influencing recovery of atrial function after cardioversion of atrial fibrillation

Atrial mechanical dysfunction after cardioversion for atrial fibrillation has been widely evaluated in recent years. Nevertheless, the influence of many clinical and echocardiographic parameters is not yet understood. The aim of the present study was to evaluate the influence of clinical and echocardiographic parameters on the return of effective atrial contraction. A total of 109 patients were evaluated: 41 patients had spontaneous recovery of sinus rhythm and 68 patients were randomly treated using either direct-current (DC) shock or intravenous procainamide. Elective cardioversion was accomplished pharmacologically in 23 patients (67%) and with DC shock in 29 patients (85%). Patients underwent a complete echocardiographic examination 1 hour after the restoration of sinus rhythm and after 1 and 7 days and 1 month. The following parameters were evaluated: patient age, cardiac disease, duration and etiology of atrial fibrillation, mode of cardioversion, left ventricular diameters and function, and left atrial diameter and function assessed as atrial ejection force. The relation between these variables and atrial ejection force was tested. Atrial ejection force was greater immediately and 24 hours after cardioversion in patients who had spontaneous recovery of sinus rhythm and in patients treated with drugs than in patients treated with DC shock. The mode of cardioversion was significantly associated with the recovery of atrial mechanical function by day 1 in univariate and multivariate analyses (odds ratio 0.14; 95% confidence interval 0.02 to 1.2). The other variable associated with the recovery of function was normal left atrial size (odds ratio 0.16; 95% confidence interval 0.12 to 1.6). In conclusion, atrial ejection force is a noninvasive parameter that can be easily measured and can provide accurate information about the recovery of left atrial mechanical function. The recovery of atrial function was influenced by the mode of cardioversion and the size of the left atrium.     

Alteration of peripheral vasodilatory reserve capacity after cardioversion of atrial fibrillation

In atrial fibrillation, exercise capacity is often reduced. This is usually ascribed to a decreased cardiac output as compared with sinus rhythm. Very few studies, however, have focused on changes in the peripheral blood flow during atrial fibrillation as a potential mechanism for exercise limitation. The aim of the present study was to determine the effect of conversion of atrial fibrillation to sinus rhythm on peripheral blood flow. Calf blood flow, using an electrocardiogram-triggered venous occlusion plethysmograph, and peak oxygen consumption (peak VO2), using treadmill exercise testing, were studied in 28 patients with chronic atrial fibrillation eligible for electrical cardioversion. Measurements were performed before cardioversion, and repeated 1 day and 1 month thereafter. Calf blood flow at rest, maximal calf blood flow, and minimal calf vascular resistance during the hyperaemic response immediately following 700 J of calf exercise were determined plethysmographically. One day and 1 month after cardioversion, 23 and 14 patients were still in sinus rhythm, respectively. In patients who still had sinus rhythm after 1 month, maximal calf blood flow increased from 33.7 +/- 12 to 40.0 +/- 13 ml. 100 ml-1.min-1 (P < 0.01) and minimal calf vascular resistance fell from 3.2 +/- 0.9 to 2.7 +/- 0.7 mmHg. ml-1. 100 ml-1. min-1 (P < 0.01); peak VO2 increased from 21.3 +/- 4 to 24.2 +/- 5 ml. min-1. kg-1 (P < 0.001). Calf blood flow at rest did not improve. In contrast, no significant changes in maximal calf blood flow, minimal calf vascular resistance and peak VO2 occurred in patients who had atrial fibrillation 1 month after cardioversion. A significant correlation was found between changes in maximal calf blood flow and peak VO2 1 month after cardioversion (r = 0.53, P < 0.01). One day after cardioversion, no changes in calf blood flow or peak VO2 were found, either in patients with sinus rhythm or atrial fibrillation. In conclusion, transition from chronic atrial fibrillation to sinus rhythm is associated with a (delayed) improvement in maximal calf blood flow, minimal calf vascular resistance, and peak VO2. Our findings suggest that increase in vasodilatory reserve capacity may contribute to the improvement of exercise capacity after cardioversion of atrial fibrillation.     

Electrophysiological properties in patients undergoing atrial compartment operation for chronic atrial fibrillation with mitral valve disease

AIMS: Surgical treatment for atrial fibrillation is now feasible in selective cases. The aim of this study was to assess the electrophysiological properties of patients undergoing atrial compartment operation for chronic atrial fibrillation. METHODS AND RESULTS: Electrophysiological studies were performed in 20 mitral valve patients with atrial fibrillation who had been maintained in sinus rhythm for more than 1 year after atrial compartment operation. Intra-cardiac recording and programmed electrical stimulation were performed in various atrial compartments. The parameters studied included sinus node function, atrial conduction and refractoriness, atrioventricular conduction function and inducible arrhythmias if any. Intra-cardiac recordings showed that the rhythm was of sinus origin in all cases, with the earliest atrial activity located in the high right atrium. The mean sinus cycle length was 750 +/- 110 ms, AH time 106 +/- 29 ms, and HV time 53 +/- 7 ms. The sinus node function was normal in 18 patients (90%), and only two patients had prolonged sinus node recovery and sino-atrial conduction. The right atrial appendage compartment was driven by the sinus node in all patients. However, the conduction time from the high right atrium to the right atrial appendage compartment was markedly prolonged in 12 of 15 patients (80%) undergoing the three-compartment operation in which an incision was placed between the high right atrium and right atrial appendage compartments. On the other hand, the electrical activities in the left atrial compartment were much more varied. In 13 of 20 patients (65%), the left atrial compartment was driven by the sinus node; 11 of the 13 patients had a normal or mildly prolonged conduction time (ranged 75 to 146 ms), whereas two patients had a marked delay in conduction (200 ms and 266 ms, respectively). In the remaining seven patients, the left atrial compartments were dissociated from the rest of the heart; five of them had a quiescent left atrium, one a fluttering left atrial rhythm, and one a slow left atrial rhythm. The effective refractory period was longer in the left atrial compartment (242 +/- 47 ms) as compared to that of the high right atrium (224 +/- 26 ms, P < 0.01) and right atrial appendage compartments (219 +/- 25 ms, P < 0.01). Programmed electrical stimulation could not induce atrial fibrillation in any patient, whereas two patients had inducible atrial flutter and three repetitive atrial responses. CONCLUSIONS: (1) Atrial compartment operation does not impair sinus node function in most cases. (2) Elimination of atrial fibrillation while maintaining the electrical connection between different atrial compartments is feasible.     

Electrophysiological characteristics of the human atria after cardioversion of persistent atrial fibrillation

BACKGROUND: In animal models, induced atrial fibrillation shortens the atrial effective refractory period (ERP) and reverses its physiological adaptation to rate. It is not clear whether this process, known as "electrical remodeling," occurs in humans. METHODS AND RESULTS: We determined the ERPs, at 5 pacing cycle lengths (300 to 700 ms) and in 5 right atrial sites, after internal cardioversion of chronic atrial fibrillation in 25 patients (14 in pharmacological washout and 11 on amiodarone). The ERPs were 195.5+/-18.8 ms in the washout and 206.3+/-17.9 ms in the amiodarone patients (P<0.0001). ERPs were closely correlated with the stimulation rates (r=0.95 in the washout and r=0.94 in the amiodarone group), and slope values indicating a normal (>/=0.07) or nearly normal (0.05 to 0.06) adaptation of ERP to rate were found in 77% of the 84 paced sites. The mean ERP was shorter in the lateral wall (198.1+/-17.9 ms) than in the atrial roof (203.3+/-21.5 ms) and in the septum (210.5+/-20.0 ms) (P<0.03). After 4 weeks of sinus rhythm, the mean ERP, determined again in 8 patients (4 in wash-out and 4 on amiodarone), was significantly increased compared with the basal study (221. 4+/-21.4 versus 197.8+/-18.3 ms, P<0.0001). CONCLUSIONS: After cardioversion of chronic atrial fibrillation, (1) atrial ERP adaptation to rate was normal or nearly normal in the majority of the cases, (2) a significant dispersion of refractoriness between different right atrial sites was present, and (3) ERPs were significantly increased after 4 weeks of sinus rhythm in both washout and amiodarone patients.     

Cardiac troponin T does not increase after electrical cardioversion for atrial fibrillation or atrial flutter

BACKGROUND: Leishmaniasis is an important protozoan disease. In the Americas it is produced by several species of the genus Leishmania, transmitted by sand flies of the genus Lutzomyia. Disease spectrum ranges from cutaneous ulceration to more serious involvement of oronasal mucosa that may progress to destruction of central structures of the face and to the life-threatening visceral forms. Leishmania Viannia braziliensis is the most widespread species in Brazil and is often associated with mucosal involvement. Cutaneous lesions are commonly localised in uncovered areas of the body. Genital lesions are rare. MATERIALS AND METHODS: A patient with an ulcerated lesion of the glans penis, followed subsequently by mucosal lesions of the nasal cavity and palate, is presented. Diagnostic procedures were: leishmanin skin test (Montenegro's test) and biopsy of the ulcer border processed for histopathological examination and culture in NNN medium. RESULTS: Leishmanin skin test was positive. Histopathology showed a granulomatous infiltrate containing some parasites. Culture was positive for Leishmania sp., and was later identified by zymodeme analysis and monoclonal antibodies as L.(V.) braziliensis. The patient was treated with pentavalent antimony at the dose of 10 (mg/kg)/day for 30 days and the lesions healed. COMMENTS AND CONCLUSIONS: In men, especially over 50 years of age, ulceration of the glans penis is highly suggestive of carcinoma. Precise differential diagnosis is imperative. A lesion, such as the one reported, may cause diagnostic difficulties when it presents in countries different from the source, where the condition is very uncommon. This is increasingly frequent in the current era of widespread air travel.     

Activation of the hemostatic mechanism after pharmacological cardioversion of acute nonvalvular atrial fibrillation

BACKGROUND: Given that the restoration of sinus rhythm after chronic atrial fibrillation is associated with embolic events, anticoagulation is prescribed before and after pharmacological and electrical cardioversion. However, the need for anticoagulation in patients with acute atrial fibrillation (lasting <48 hours) who undergo cardioversion is less clear. In addition, it is not known whether cardioversion to sinus rhythm determines a hypercoagulable state in these patients. METHODS AND RESULTS: In 21 patients with acute nonvalvular atrial fibrillation, plasma median concentrations of thrombin-antithrombin complex, a marker of thrombin generation, significantly increased from 2.8 ng/mL (interquartile range, 2.1 to 4.0 ng/mL) on hospital admission to 3.5 ng/mL (interquartile range, 2.9 to 6.0 ng/mL) after cardioversion to sinus rhythm obtained by means of infusion of antiarrhythmic drugs and decreased to 2.5 ng/mL (interquartile range, 2.0 to 3.5 ng/mL) at the 1-month follow-up visit (P=.04). Similarly, the levels of fibrinopeptide A, a marker of thrombin activity, increased from 1.1 nmol/L (interquartile range, 0.7 to 1.5 nmol/L) at baseline to 1.8 nmol/L (interquartile range, 1.1 to 3.0 nmol/L) after cardioversion and returned to 0.8 nmol/L (interquartile range, 0.6 to 1.1 nmol/L) at the 1-month follow-up visit (P=.02). CONCLUSIONS: A significant increase in plasma levels of the markers of thrombin generation and activity was observed in patients with acute atrial fibrillation early after pharmacological cardioversion to sinus rhythm. This is the first biochemical evidence that cardioversion of recent-onset atrial fibrillation determines a hypercoagulable state.     

Internal cardioversion of atrial fibrillation: marked reduction in defibrillation threshold with dual current pathways

BACKGROUND: The ultimate acceptance of a fully automatic atrial defibrillator will depend on the reduction of pain to acceptable levels, requiring a marked decrease in defibrillation thresholds. The purpose of this study was to determine whether atrial defibrillation thresholds can be reduced by sequential shocks delivered through two current pathways. METHODS AND RESULTS: Sustained atrial fibrillation was induced with rapid atrial pacing in 12 adult sheep. Defibrillation electrodes were positioned in the right atrial appendage (RAap), distal coronary sinus (DCS), proximal coronary sinus (CSos), main/left pulmonary artery junction (PA), and right ventricular apex (RV). Single-capacitor biphasic waveforms (3/1 ms) were delivered through combinations of these electrodes. Probability-of-success curves were determined for single shocks with a single current pathway and sequential shocks with either single- or dual current pathways. The ED50 for delivered energy for the dual current pathway RAap to DCS then CSos to PA was 0.36+/-0.13 J, which was significantly lower than the ED50 of the standard single current pathway RAap to DCS (1.31+/-0.3 J) and was significantly lower than all other configurations tested. CONCLUSIONS: Internal atrial defibrillation thresholds can be markedly reduced with two sequential biphasic shocks delivered over two current pathways compared with the standard single shock delivered over a single current pathway or with sequential shocks delivered over a single current pathway.     

Transesophageal echocardiographic predictors for maintenance of sinus rhythm after electrical cardioversion of atrial fibrillation

The aim of this study was to assess the value of transesophageal echocardiography (TEE) in patients with atrial fibrillation in predicting restoration and maintenance of sinus rhythm after electrical cardioversion. TEE was performed in 62 patients with atrial fibrillation before their first elective cardioversion. Clinical variables evaluated were: age, gender, duration, and etiology of atrial fibrillation. TEE variables included: left atrial (LA) length, width, and size, LA annulus size, as well as presence of LA spontaneous contrast, thrombus and mitral regurgitation, LA appendage size and flow, and left ventricular function. Based on initial outcome of cardioversion, patients were grouped into patients who remained in atrial fibrillation and in whom sinus rhythm was restored. The latter group of patients was followed for 1 year, and grouped into patients who reverted to atrial fibrillation and in whom sinus rhythm was maintained. Successful cardioversion was achieved in 50 of 62 patients (81%). None of the clinical or TEE variables were related to initial outcome. At 1-year follow-up, 29 of 50 patients (58%) who underwent successful cardioversion continued to have sinus rhythm. The following variables were related to maintenance of sinus rhythm: duration of atrial fibrillation (6.7 +/- 7.3 vs 2.0 +/- 2.4 months; p < 0.005); LA length (6.2 +/- 0.7 vs. 5.5 +/- 1.0 cm; p < 0.008); width (5.1 +/- 0.5 vs. 4.5 +/- 0.7 cm; p < 0.002); size (26.4 +/- 5.0 vs 19.8 +/- 6.5 cm2; p < 0.0005); annulus size (4.0 +/- 0.2 vs 3.7 +/- 0.3 cm; p < 0.0005); presence of LA spontaneous contrast (13 [62%] vs 4 [14%]; p < 0.002), and LA appendage flow (19 +/- 8 vs 36 +/- 15 cm/s; p < 0.0005). In multivariate logistic regression analysis, LA annulus size, but especially LA appendage flow, were significantly associated with maintenance of sinus rhythm. Thus, in TEE-guided electrical cardioversion of atrial fibrillation, variables often used to assess thromboembolic risk may also be used to predict 1-year outcome of cardioversion.     

Value of transesophageal echocardiography in the therapeutic management of non-valvular atrial fibrillation

Transoesophageal echocardiography (TOE) has transformed the management of atrial fibrillation. It has become the reference method for assessing thromboembolic risk and therefore the indication for anticoagulant therapy in non-valvular atrial fibrillation. The predictive factors of embolism are the presence of intraatrial spontaneous contrast echo or thrombosis, dilatation of the left atrial appendage (> 6 cm2) and reduced outflow velocities of the left atrial appendage (< 0.25 m/sec). The value of TOE before electrical cardioversion is under assessment. The predictive value of TOE in the success of cardioversion and maintenance of sinus rhythm at one year is subject of controversy. The projective ACUTE study (Assessment of Cardioversion Using Transoesophageal Echocardiography) should determine whether cardioversion guided by the results of TOE reduces the embolic risk and shortens the duration of anticoagulation before cardioversion.