Internal Right Atria1 Cardioversion of Chronic Atria! Fibrillation: Effects of Low-Energy Biphasic Shocks

Jacques Mansourati, MD, Vakrie Valls-Bertault, Jean-Marie Larlet, MD,

Benoit Maheu, MD, Marc Hero, cind Jean-Jacques Blanc, MD

A trial fibrillation (AF) is associated with the loss of organized atria1 contractions, a risk factor for

thromboembolic events and hemodynamic deteriora- tion. Therefore, the restoration of sinus rhythm, when feasible, is I of the major therapeutic options in pa- tients with AF. For this purpose, antiarrhythmic drugs or external direct current (DC) shocks are attempted. Transthoracic electrical cardioversion has been shown to be effective in <80% of cases,‘,’ leaving >20% of patients in AF. Internal cardioversion, which was in- troduced in the 197Os, has initially been disappoint- ing.“-5 However, in 1987, Levy et al” introduced int- racavitary high-energy shocks (200 to 300 J) with a high success rate, a result that was subsequently con- firmed in patients who could not be converted by external DC shocks,’ even when associated with phar- macologic methods.8 Moreover, internal shocks were reported to have some side effects due to the high- energy level delivered. ‘9 Efforts have recently been made to lower this level. Different procedures have been proposed. The procedure most frequently re- ported has been the right atrial-left atria1 (via the coronary sinus or left pulmonary artery) DC shock. The success rate remains high with an energy level of generally <5 J.iO-‘X The main limitation for this irit- racavitary technique is the need for coronary sinus lead placement. This prompted us to study the efficacy of internal cardioversion with a “moderate” energy level, but with a simpler procedure.

. . . Patients were recruited among those referred for

transthoracic AF cardioversion. The study group con- sisted of 21 patients (19 men; mean age 61.4 ? 2.2 years) with long-lasting AF (mean duration 2.5 months, range 15 days to 6 months; in 2 patients the precise onset of AF was unknown). Six patients had been already converted to sinus rhythm by DC shock but AF recurred. The 1.5 remaining patients could not be converted to sinus rhythm by 3 transthoracic an- teroposterior shocks, although the procedure recom- mended by Ewyi4 was followed and 21 shock was delivered with an energy of 300 J. Internal cardiover- sion was usually attempted 2 to 8 days after failure of external cardioversion. After informed consent was obtained, and using the same anticoagulation regimen as for external DC shock, internal cardioversion was attempted. Amiodarone was given in 18 cases for > 1

From the Department oi Cardiology, University Hospital of Brest UI-~ Medtronic-frolce, best, Fra:xe 6;. Mawxkti’s address is: Dcparr- rnent of Cardicloav Hbital de Ia Cavule Blalcbe. CHU Brest. Bouieva:d Ta~guy”%ge~lt: 29609 Brest Cedex, FFance. ManJscr:pt received Mar& 30, 1998; revised manuscript rccelved arx ac- cepted june 24, 199%

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month before defibrillation (3 patients did not receive any antiarrhythmic drugs).

A large-surface (general surface: 125 mm21 active surface: 355 mm’) electrode catheter (Transvene 6937 Medtronic Inc., Minneapolis, Minnesota) was percu- taneously introduced in the right femoral vein and fluoroscopically positioned in the middle of the right atria1 cavity as far as possible from the atrioventricular node with the tip (inactive) in the superior vena cava. A second quadripolar electrode introduced in the same femoral vein was positioned in the right ventricular apex to synchronize the internal shock with the QRS and to allow backup pacing.” Two commercially available patches (R2 PADS, Cardiotronics Systems, Inc., Draper, Utah) were attached to the anterior and posterior parts of the chest wall. After positioning both electrodes, patients were anesthetized (Diprivan [propofol], Zencca Pharma, Cergy, France) and shocks were delivered (model 5358A Medtronic Inc.) between the intra-atria1 electrode (cathode) and both thoracic patches (anode). The applied energy levels were 2, 4, 6, and 8 J successsively at l-minute inter- vals between attempts, and in cases where these low levels failed, the energy was increased to 15, 20, 25, and 34 J (maximum biphasic energy level delivered by the external defibrillator). No further intracavitary shocks were attempted in those patients who did not return to sinus rhythm with 34 J. Patients were mon- itored during the entire procedure and for 24 hours afterward. An echocardiogram was performed within 2 hours of the end of the procedure. Patients were discharged 24 to 48 hours after the procedure with a prescription for antiarrhythmic drugs and oral antico- agulation for a minimum of 3 weeks. Follow-up data were completed from outpatient files or by telephone calls to each patient’s general practitioner or cardiol- ogist.

History and echocardiographic examination re- vealed that 4 patients had lone AF (19%). Structural heart disease was diagnosed in 17 patients (81%): idiopathic-dilated cardiomyopathy in 5 patients (240/o), ischemic cardiomyopathy in 3 patients (14%), obstructive hypertrophic cardiomyopathy in 2 patients (lo%), valvular disease in I patient (5%), and isolated atria1 dilation (> 18 cm’) on echocardiogram in 6 patients (28%). Obesity (body mass index >25) was observed in 9 patients and was identified as a possible cause of external DC cardioversion failure. Thyroid function tests were normal in all patients.

Internal cardioversion restored sinus rhythm in 16 of the 21 patients included in the study group (76.2%). The mean energy level delivered in patients who re- covered sinus rhythm was 24.3 -C 2.1 J. Shocks with an energy level 510 J were consistently ineffective.

0002-9 149/98/$19.00 1285 PII SOOO2-9149(98)00619-S

Attempts with 15 J were successful in 5 cases, 20 J in 3 cases, 25 J in 2 cases, and 34 J in 6 cases: AF recurred immediately in 1 patient, within 6 hours in a second patient, and within 36 to 48 hours in another patient. Finally, 13 patients were discharged in. sinus rhythm. Although the number of patients who failed to recover sinus rhythm is low, no clear criteria allowed differentiation between the “success” and the “failure” groups.

No serious side effect was observed during (par- oxysmal atrioventricular block, sustained bradycardia or proarrhythmic effect) or after the procedure (ven- tricular stunning, significant pericardial effusion). Af- ter a mean follow-up period of 12 months, 9 patients of the 13 discharged in sinus rhythm (69%) remained in sinus rhythm.

. . . Transthoracic electrical cardioversion remains a

conventional treatment of AF, and with pharmaco- logic cardioversion, it is the only treatment proven effective in restoring sinus rhythm. Although it sel- dom causes side effects, its limitations are now clear: requirement of general anesthesia and limited success rate (80 %).*T~ This latter limitation justified the intro- duction of endocavitary shock procedures, initially with high-energy levels and more recently with much lower energies. Although general anesthesia was sys- tematically administered in our series, it did not al- ways seem necessary for energy levels ~20 J.‘” Sinus rhythm was restored in >70% of patients iyho were not cardioverted by pharmacologic means and/or transthoracic DC shocks. Although this success rate is slightly lower, it is not significantly different from that observed in studies using the same procedure.15 The reason for this success rate is the large surface of the electrode and the use of 2 patches, allowing the cur- rent to pass through a large amount of the atria1 myocardium. Another important result from the present study is the absence of the serious side effects that occur in high-energy intracavitary cardiover- si0n.l.” This safety factor is certainly the result of reduced energy levels from an average of 200 J in previous studies 1,7-y to <34 J in the present study. If results in a larger number of patients concur with those reported in this study, it would seem to be unnecessary, from a patient safety standpoint, to in- troduce a right ventricular electrode for backup pacing or to further decrease the level of intracavitary energy. However, as the relation between energy and pain remains debatable, it seems possible that an energy requirement of < 10 J might avoid the need for general anesthesia. This is already feasible, but this procedure requires the use of intracoronary sinus electrodes, a time-consuming and complex method compared with

the one used in the present study. Technical refine- ments (probably catheter positioning) may allow the delivery of low-energy levels using our protocol.‘” The concept of intracavitary cardioversion is based on the hypothesis that restoration of sinus rhythm pro- vides a better patient outcome than “controlled” AF. Although this hypothesis seems valid, it has not been confirmed by hard data and-requires further study.

In conclusion, this study shows that low or mod- erate energy internal cardioversion is safe and ef- fective in restating sinus rhythm in patients with AF. Further teclmical improvements should sim- plify the procedure and lower the energy delivered without altering the success rate to avoid or at least limit the need for anesthesia.

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F. Low-energy cardioversion of spontaneous atria1 fibrillation. Immediate and long-term results. Circularion 1997;96:253-259. 13. Alt E. Schmitt C, Ammcr R; Plewan A, Evans F, Pasquantino J, Ideker T, Lehmann G, Putter K, SchGmig A. Effect of electrode position on outcome of low-energy intracardiac cardiovcrsion of atria1 fibrillation. Am J Cmdiol 1997; 79:621-625. 14. Ewy GA. Optimal technique for electrical cardioversion of atria1 fibrillation. Circulation 1992;86:1645-1647. 15. Neri R, Palermo P, Cesario AS, Baragli D, Amici E, Gambelli G. Internal cardioversion of chronic atria1 fibrillation in patients. PACE 1997;20:2237-2242. 16. Cooper RAS, Smith WM, Ideker RE. Internal cardioversion of atrial fibril- lation. Marked reduction in defibrillation threshold with dual current pathways. Circulation 1997;96:2693- 2700.

1286 THE AMERICAN JOC;RNAL OF CARDIOLOGYe VOL. 82 NOVEMBER 15, 1998