Active Compression Cardioversion for Refractory Atrial Fibrillation

Two methods are commonly employed in performing external transthoracic cardioversion. “Hands-on” cardioversion utilizes external paddles placed over the cardiac apex and right pectoral region, whereas “hands-off” cardioversion uses large skin patches (anterior near the left sternal border and posterior between the 2 scapulae). The difference between these 2 methods include both location of the defibrillator electrodes and presence or absence of contact pressure. The utility of additional pressure over the electrodes during shock delivery has been previously described by Kerber and colleagues.[1Kerber RE Kouba C Martins J Kelly K Low R Hoyt R Ferguson D Bailey L Bennett P Charbonnier F Advance prediction of transthoracic impedance in human defibrillation and cardioversion: importance of impedance in determining the success of low-energy shocks.Circulation. 1984; 70: 303-308Crossref PubMed Scopus (116) Google Scholar, 2Kerber RE Grayzel J Hoyt R Marcus M Kennedy J Transthoracic resistance in human defibrillation: influence of body weight, chest size, serial shocks, paddle size and paddle contact pressure.Circulation. 1981; 63: 676-682Crossref PubMed Scopus (207) Google Scholar] In dogs, Cohen and colleagues[3Cohen TJ Noubani H Goldner BG Tucker KJ Quan W Trazzer AS Stern G Active compression-decompression defibrillation provides effective defibrillation during cardiopulmonary resuscitation.Am Heart J. 1995; 130: 186-187Abstract Full Text PDF PubMed Scopus (7) Google Scholar] demonstrated a lowering of defibrillation threshold by applying pressure and actively compressing over an anterior skin patch during the defibrillation procedure. In addition, a reduction in transthoracic impedance was observed with this method. This study examines the utility of active compression cardioversion for treatment of atrial fibrillation, which was refractory to high energy cardioversion in humans.Results are expressed as mean ± SD. Twenty-two patients (17 men and 5 women) with a mean age of 68 ± 13 years (range 48 to 90) and a mean body surface area of 2.08 ± 0.4 m2 (range 1.35 to 3.18 m2) were referred for elective cardioversion of atrial fibrillation between February 1996 and December 1996 and enrolled in this study. A pair of external skin patches were used in an anterior-posterior configuration using a standard defibrillator (HP43100A, Hewlett-Packard Corporation, Palo Alto, California; Lifepak, Physio-Control Corporation, Redmond, Washington; or Zoll D1400, Zoll Medical, Burlington, Massachusetts) in which synchronized energy was delivered utilizing damped sinusoidal direct-current shocks (Lown Waveform).[4Cohen TJ Defibrillation.in: Rakel RE Saunders Manual of Medical Practice. WB Saunders, Philadelphia1996: 238-240Google Scholar] Patients were routinely anesthetized with propofol (1 to 2.5 mg/kg or approximately 20 to 40 mg/10 seconds in order to induce anesthesia) and were monitored using standard equipment which included pulse oximetry, external blood pressure monitor, and an electrocardiogram. An initial energy of 200 J was used in 14 patients, whereas 300 J was applied in 3 patients, 150 J in 1 patient, and 360 J in 4 patients due to differences in body size. Patients who failed the first shock received subsequent 360-J shocks up to 3 repetitions (step-up method). Infrequently, skin patches were repositioned slightly after failed attempts in order to improve contact and field geometry. Patients who failed all the standard cardioversions with ≥2 high-energy shocks (and ≥1 being 360 J) underwent active compression cardioversion at the same setting. During active compression cardioversion, manual pressure was applied over the anterior skin patch using an insulator (disconnected defibrillator paddle applied over external skin patch) with approximately 20 to 40 pounds of pressure, while the 360-J shock was delivered through a standard defibrillator. Patients found to be in atrial flutter at the time of cardioversion were excluded from the study. For patients who successfully converted, the energy required for cardioversion (cardioversion energy) was defined by the first successful cardioversion.Seventeen of 22 patients (77%) were successfully cardioverted via the standard approach with a cardioversion energy of 271 ± 79 J. Five patients failed standard cardioversion (energy >360 J) and underwent active compression cardioversion, and 4 of 5 patients (80%) converted to sinus rhythm via a single 360-J active compression shock. One patient who was morbidly obese (460 pounds with a body surface area of 3.18 m2) failed standard active compression cardioversion, and also failed a modified active compression cardioversion method using sequential shocks (2 defibrillators), but eventually converted on antiarrhythmic therapy. Transthoracic impedance was recorded in only 1 patient who received active compression cardioversion using a HP43100A defibrillator (Physiol Control and Zoll defibrillators do not have an impendance measurement feature). In this patient the transthoracic impedance decreased from 77 to 64 ohms with pressure resulting in a successful cardioversion. An analysis of patient characteristics (including age, body surface area, left atrial size, presence of chronic obstructive pulmonary disease, coronary artery disease, hypertension, and presence of arrhythmic drugs) showed no significant difference between patients who had successful versus failed standard cardioversion of atrial fibrillation. The overall cardioversion success rate in our series was 96% (21 of 22 patients) using active compression cardioversion along with the standard method as compared with 77% (17 of 22 patients) using the standard method alone.Previous investigators have demonstrated the limitations of standard external cardioversion. Therefore, alternative methods including transesophageal and intracardiac (internal) cardioversion have been more recently pursued.[4Cohen TJ Defibrillation.in: Rakel RE Saunders Manual of Medical Practice. WB Saunders, Philadelphia1996: 238-240Google Scholar] Each of these invasive methods, however, require additional catheters or probes, and to date none of these devices have been approved by the Food and Drug Administration (FDA). The active compression cardioversion technique is simple and can easily be applied in-hospital using a standard FDA-approved defibrillator with a disconnected defibrillator paddle in order to apply pressure to potentially decrease transthoracic impedance.[1Kerber RE Kouba C Martins J Kelly K Low R Hoyt R Ferguson D Bailey L Bennett P Charbonnier F Advance prediction of transthoracic impedance in human defibrillation and cardioversion: importance of impedance in determining the success of low-energy shocks.Circulation. 1984; 70: 303-308Crossref PubMed Scopus (116) Google Scholar, 2Kerber RE Grayzel J Hoyt R Marcus M Kennedy J Transthoracic resistance in human defibrillation: influence of body weight, chest size, serial shocks, paddle size and paddle contact pressure.Circulation. 1981; 63: 676-682Crossref PubMed Scopus (207) Google Scholar] This may achieve an increase in current flow through the atrial myocardium and thereby result in a successful cardioversion in those who have failed the standard approach. Further trials are necessary to define more precisely the utility and optimal method of active compression cardioversion (including electrode location, ideal pressure, necessity of impedance monitoring, and biphasic defibrillation waveform once it is commercially available) and to determine whether this method will significantly impact the overall conversion rate during external cardioversion of atrial fibrillation.In conclusion, the application of manual pressure over standard external skin patches during cardioversion of atrial fibrillation provides a simple noninvasive method for the treatment of failed standard “hands-off” external cardioversion. This active compression cardioversion technique may reduce transthoracic impedance resulting in an improvement in the overall cardioversion success rate when compared with the standard method. Two methods are commonly employed in performing external transthoracic cardioversion. “Hands-on” cardioversion utilizes external paddles placed over the cardiac apex and right pectoral region, whereas “hands-off” cardioversion uses large skin patches (anterior near the left sternal border and posterior between the 2 scapulae). The difference between these 2 methods include both location of the defibrillator electrodes and presence or absence of contact pressure. The utility of additional pressure over the electrodes during shock delivery has been previously described by Kerber and colleagues.[1Kerber RE Kouba C Martins J Kelly K Low R Hoyt R Ferguson D Bailey L Bennett P Charbonnier F Advance prediction of transthoracic impedance in human defibrillation and cardioversion: importance of impedance in determining the success of low-energy shocks.Circulation. 1984; 70: 303-308Crossref PubMed Scopus (116) Google Scholar, 2Kerber RE Grayzel J Hoyt R Marcus M Kennedy J Transthoracic resistance in human defibrillation: influence of body weight, chest size, serial shocks, paddle size and paddle contact pressure.Circulation. 1981; 63: 676-682Crossref PubMed Scopus (207) Google Scholar] In dogs, Cohen and colleagues[3Cohen TJ Noubani H Goldner BG Tucker KJ Quan W Trazzer AS Stern G Active compression-decompression defibrillation provides effective defibrillation during cardiopulmonary resuscitation.Am Heart J. 1995; 130: 186-187Abstract Full Text PDF PubMed Scopus (7) Google Scholar] demonstrated a lowering of defibrillation threshold by applying pressure and actively compressing over an anterior skin patch during the defibrillation procedure. In addition, a reduction in transthoracic impedance was observed with this method. This study examines the utility of active compression cardioversion for treatment of atrial fibrillation, which was refractory to high energy cardioversion in humans. Results are expressed as mean ± SD. Twenty-two patients (17 men and 5 women) with a mean age of 68 ± 13 years (range 48 to 90) and a mean body surface area of 2.08 ± 0.4 m2 (range 1.35 to 3.18 m2) were referred for elective cardioversion of atrial fibrillation between February 1996 and December 1996 and enrolled in this study. A pair of external skin patches were used in an anterior-posterior configuration using a standard defibrillator (HP43100A, Hewlett-Packard Corporation, Palo Alto, California; Lifepak, Physio-Control Corporation, Redmond, Washington; or Zoll D1400, Zoll Medical, Burlington, Massachusetts) in which synchronized energy was delivered utilizing damped sinusoidal direct-current shocks (Lown Waveform).[4Cohen TJ Defibrillation.in: Rakel RE Saunders Manual of Medical Practice. WB Saunders, Philadelphia1996: 238-240Google Scholar] Patients were routinely anesthetized with propofol (1 to 2.5 mg/kg or approximately 20 to 40 mg/10 seconds in order to induce anesthesia) and were monitored using standard equipment which included pulse oximetry, external blood pressure monitor, and an electrocardiogram. An initial energy of 200 J was used in 14 patients, whereas 300 J was applied in 3 patients, 150 J in 1 patient, and 360 J in 4 patients due to differences in body size. Patients who failed the first shock received subsequent 360-J shocks up to 3 repetitions (step-up method). Infrequently, skin patches were repositioned slightly after failed attempts in order to improve contact and field geometry. Patients who failed all the standard cardioversions with ≥2 high-energy shocks (and ≥1 being 360 J) underwent active compression cardioversion at the same setting. During active compression cardioversion, manual pressure was applied over the anterior skin patch using an insulator (disconnected defibrillator paddle applied over external skin patch) with approximately 20 to 40 pounds of pressure, while the 360-J shock was delivered through a standard defibrillator. Patients found to be in atrial flutter at the time of cardioversion were excluded from the study. For patients who successfully converted, the energy required for cardioversion (cardioversion energy) was defined by the first successful cardioversion. Seventeen of 22 patients (77%) were successfully cardioverted via the standard approach with a cardioversion energy of 271 ± 79 J. Five patients failed standard cardioversion (energy >360 J) and underwent active compression cardioversion, and 4 of 5 patients (80%) converted to sinus rhythm via a single 360-J active compression shock. One patient who was morbidly obese (460 pounds with a body surface area of 3.18 m2) failed standard active compression cardioversion, and also failed a modified active compression cardioversion method using sequential shocks (2 defibrillators), but eventually converted on antiarrhythmic therapy. Transthoracic impedance was recorded in only 1 patient who received active compression cardioversion using a HP43100A defibrillator (Physiol Control and Zoll defibrillators do not have an impendance measurement feature). In this patient the transthoracic impedance decreased from 77 to 64 ohms with pressure resulting in a successful cardioversion. An analysis of patient characteristics (including age, body surface area, left atrial size, presence of chronic obstructive pulmonary disease, coronary artery disease, hypertension, and presence of arrhythmic drugs) showed no significant difference between patients who had successful versus failed standard cardioversion of atrial fibrillation. The overall cardioversion success rate in our series was 96% (21 of 22 patients) using active compression cardioversion along with the standard method as compared with 77% (17 of 22 patients) using the standard method alone. Previous investigators have demonstrated the limitations of standard external cardioversion. Therefore, alternative methods including transesophageal and intracardiac (internal) cardioversion have been more recently pursued.[4Cohen TJ Defibrillation.in: Rakel RE Saunders Manual of Medical Practice. WB Saunders, Philadelphia1996: 238-240Google Scholar] Each of these invasive methods, however, require additional catheters or probes, and to date none of these devices have been approved by the Food and Drug Administration (FDA). The active compression cardioversion technique is simple and can easily be applied in-hospital using a standard FDA-approved defibrillator with a disconnected defibrillator paddle in order to apply pressure to potentially decrease transthoracic impedance.[1Kerber RE Kouba C Martins J Kelly K Low R Hoyt R Ferguson D Bailey L Bennett P Charbonnier F Advance prediction of transthoracic impedance in human defibrillation and cardioversion: importance of impedance in determining the success of low-energy shocks.Circulation. 1984; 70: 303-308Crossref PubMed Scopus (116) Google Scholar, 2Kerber RE Grayzel J Hoyt R Marcus M Kennedy J Transthoracic resistance in human defibrillation: influence of body weight, chest size, serial shocks, paddle size and paddle contact pressure.Circulation. 1981; 63: 676-682Crossref PubMed Scopus (207) Google Scholar] This may achieve an increase in current flow through the atrial myocardium and thereby result in a successful cardioversion in those who have failed the standard approach. Further trials are necessary to define more precisely the utility and optimal method of active compression cardioversion (including electrode location, ideal pressure, necessity of impedance monitoring, and biphasic defibrillation waveform once it is commercially available) and to determine whether this method will significantly impact the overall conversion rate during external cardioversion of atrial fibrillation. In conclusion, the application of manual pressure over standard external skin patches during cardioversion of atrial fibrillation provides a simple noninvasive method for the treatment of failed standard “hands-off” external cardioversion. This active compression cardioversion technique may reduce transthoracic impedance resulting in an improvement in the overall cardioversion success rate when compared with the standard method.