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PubMed1985

What is a "save"?: Outcome measures in clinical evaluations of automatic external defibrillators.

Automatic external defibrillators (AEDs) represent an important technologic innovation in the management of out-of-hospital cardiac arrest. We propose the following concept: AEDs are machines with the limited task of ventricular fibrillation (VF) identification, countershock delivery, and defibrillation. They cannot be expected to produce "saves" independently. This study tested this concept by using the same AED in two different emergency medical systems: outcomes dependent upon the device should be the same in both groups, whereas outcomes dependent upon patient and system factors should be different. Paramedics, with the AED as their initial monitor/defibrillator, treated 16 cardiac arrest patients in VF; EMTs (emergency medical technicians), with the same AED, treated 17 patients in VF. There were no significant differences in the outcomes proposed to be machine-dependent: sensitivity, defined as the percentage of VF rhythm segments shocked; specificity, defined as the percentage of non-VF rhythms not shocked; and defibrillation of segments of VF to non-VF rhythms. There were, however, differences in the outcomes dependent on patient and system factors (paramedic group presented first): percent converted to a perfusing rhythm (23% vs 69%; p less than 0.05); percent admitted to the hospital (19% vs 65%; p less than 0.025); and percent discharged from the hospital (6% vs 29%; p = N.S.). We conclude that AEDs should be compared and evaluated on device-dependent outcomes and not on the basis of producing "saves".

Aged↗
PubMed1991

Patients with a high defibrillation threshold: clinical characteristics, management, and outcome.

Of 125 patients prepared to receive implantable cardioverter-defibrillators (ICDs) with the patch-patch configuration of the difibrillating electrodes, 23 (18%) had high (greater than or equal to 25 joules) defibrillation thresholds (DFTs). These patients had lower left ventricular ejection fractions (27 +/- 12 vs 34 +/- 13; p less than 0.03) and a higher incidence of previous heart surgery (47% vs 19%; p less than 0.01) than patients with normal DFTs but did not differ in age, type of heart disease, incidence of concomitant heart surgery, or use of antiarrhythmic medication. Defibrillators were implanted in 18 of these 23 patients, 12 during the initial surgery and six after repeat DFT testing 2 weeks later. After 22 +/- 11 months of follow-up, four patients with ICDs died (two suddenly, and two of nonsudden cardiac causes). Two patients without ICDs died of nonsudden cardiac causes. Appropriate shocks were received by five patients (29%) including both who died suddenly later. A high DFT may be more common than previously stated. It is associated with poor ventricular function and previous heart surgery. Repeated DFT testing may be useful in some patients. A high DFT does not preclude successful ICD shocks, but other therapies may provide better results.

Aged↗
PubMed1992

Effects of acute and prolonged administration of propafenone on internal defibrillation in the pig.

Some antiarrhythmic sodium channel blocking drugs have been found to increase the energy necessary for internal defibrillation. Propafenone is a new drug that has been shown to be efficacious in the therapy of supraventricular and ventricular arrhythmias, and is of potential use in patients with defibrillators. The effects of short-term and prolonged propafenone administration on the internal defibrillation threshold (DFT) were determined in 43 pigs randomized to one of four groups: saline infusion (n = 10); propafenone infusion (n = 10); placebo administration for 8 days (n = 10); or propafenone administration for 8 days (n = 13). Two mesh electrodes were sutured on the right lateral and left lateral epicardial surface and current was delivered from the right electrode to the left electrode. Triplicate DFTs were obtained before and at 40 and 80 minutes after infusion of drug or placebo. In pigs receiving long-term administration, after baseline DFTs were obtained the electrodes were removed and the chest was closed. Following 8 days of drug or placebo administration, DFTs were redetermined. No changes were observed in the short- or long-term control groups. DFTs were lower after propafenone administration: either short-term infusion (20 +/- 6.2 joules at baseline; 15.6 +/- 5 joules at 40 minutes, p less than 0.05; 10.2 +/- 6 joules at 80 minutes, p less than 0.001) or long-term administration (17.8 +/- 2.6 joules at baseline versus 12 +/- 3.2 joules on drug, p less than 0.002). Decreased ventricular cycle lengths were found with acute administration of propafenone. Three pigs died during long-term administration of propafenone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Influence of magnesium ion on human ventricular defibrillation after aortocoronary bypass surgery.

The administration of magnesium ion (Mg++) has been reported to defibrillate the ventricles and to decrease the incidence of arrhythmias after cardiopulmonary bypass. In a prospective study of 76 randomly selected patients undergoing coronary artery bypass grafting, patients received either no Mg++, 0.25 mEq/kg of Mg++ during cardiopulmonary bypass with the aorta clamped, or 0.375 mEq/kg of Mg++ before cardiopulmonary bypass. Spontaneous resumption of a cardiac rhythm or spontaneous defibrillation during reperfusion was not significantly affected by Mg++ administration. However, the number of shocks to initial and to sustained defibrillation and the energy required for the last direct-current shock was greatest in patients who received Mg++ before bypass and in those whose plasma Mg++ was greater than 2.26 mg/dl. Thus, the administration of Mg++ may have adverse effects on the heart if intraoperative plasma Mg++ exceeds 2.26 mg/dl.

Cardiopulmonary Bypass↗
PubMed1986

Cardiac arrest treated with a new automatic external defibrillator by out-of-hospital first responders.

Two hundred sixty patients in cardiac arrest were treated with an automatic external defibrillator by first-responding firefighters before arrival of paramedics. On average, first responders arrived 5 minutes before paramedics. Of 118 patients with ventricular fibrillation, 91 (77%) were administered shocks, 21 (23%) of whom had return of pulse and blood pressure by the time paramedics arrived. Fifty-six (62%) were admitted to the hospital and 30 (33%) survived. The survival rate for all 118 victims discovered with ventricular fibrillation was 27%. The device correctly classified the initial and all subsequent rhythms in 92 patients with asystole, 46 with electromechanical dissociation, and 22 others with presumed respiratory arrest; it did not deliver any inappropriate shocks to patients or to the rescuers using the device. An automatic external defibrillator can be used by first responders as an adjunct to basic life support, and its use may improve survival by shortening the time to defibrillation.

Allied Health Personnel↗
PubMed1983

Automatic defibrillation in man: is it feasible?

Twenty-eight patients who survived multiple arrhythmic cardiac arrest refractory to medical therapy underwent implantation of the automatic defibrillator without additional antiarrhythmic surgery. Lateral thoracotomy was used for implantation in 14 patients and the subxiphoid technique was used in 14. There was no operative mortality and surgical complications were minimal. The longest follow-up was 29 months and the average was 14 months. The implanted device correctly identified and reverted 50 episodes of spontaneous malignant ventricular tachyarrhythmias in six hospitalized patients. After discharge, 20 episodes of automatic out-of-hospital resuscitations occurred in eight patients. Kaplan-Meier survival curves, based on the assumption that out-of-hospital defibrillations would otherwise have been lethal, indicated an expected 1 year mortality of 60 percent. Seven deaths were in fact observed in this period for an actual mortality rate of 30 percent. We conclude that automatic defibrillation is clearly feasible in man and appears to increase survival in selected high-risk patients.

Actuarial Analysis↗
PubMed1996

Effects of epinephrine and vasopressin on median fibrillation frequency and defibrillation success in a porcine model of cardiopulmonary resuscitation.

OBJECTIVE: This study was designed to assess whether median frequency of ventricular fibrillation (VF) correlates with myocardial blood flow and defibrillation success during cardiopulmonary resuscitation (CPR) after epinephrine or vasopressin administration. METHODS AND RESULTS: After 4 min of VF and 3 min of CPR, 14 pigs received 0.045 mg/kg epinephrine or 0.4 U/kg vasopressin. Using radio-labeled microspheres, median myocardial blood flow during CPR before, and 90 s and 5 min after drug administration (DA) was 15.5 (12.6, 23.1; 25th percentile, 75th percentile), 26.4 (18.5, 29.1), 16.9 (14.9, 19.1) mL min-1 100 g-1, respectively, in the epinephrine, and 16.9 (15.4, 18.9), 48.1 (36.9, 68.9) (P < 0.05 vs. before DA), 52.3 (38.5, 65.0) mL min-1 100 g-1, respectively, in the vasopressin group. Using spectral analysis of VF, median frequency of VF was 11.0 (10.7, 11.8), 11.3 (9.6, 13.1), 10.2, (8.8, 11.4) Hz, respectively, in the epinephrine, and 10.1 (10.0, 10.5), 11.7 (11.1, 14.2) (P < 0.05 vs. before DA), 13.2 (11.5, 13.9) Hz, respectively, in the vasopressin group at the same points in time. Median frequency correlates significantly with myocardial blood flow in the epinephrine (n = 21); rs = 0.772; P < 0.001) and in the vasopressin group (n = 21; rs = 0.905; P < 0.001). Median fibrillation frequency before the first defibrillation was 13.0 (12.2, 13.2) Hz in resuscitated (n = 8) and 9.2 (8.3, 10.2) Hz (n = 6) in non-resuscitated animals (P < 0.01). CONCLUSIONS: We conclude that median frequency of VF reflects myocardial blood flow and the chance of successful defibrillation during closed-chest CPR after vasopressor treatment in a porcine model of VF.

Adrenergic Agonists↗
PubMed1988

Effect of recainam on the energy required for ventricular defibrillation in dogs as assessed with implanted electrodes.

The effect of recainam (WY-42,362), a new class IC antiarrhythmic drug, on ventricular defibrillation was evaluated with the use of implanted superior vena cava and left ventricular patch electrodes in 17 normal dogs anesthetized with sodium pentobarbital. The energy required for a 50% probability of successful defibrillation (E50) was used as the index of ventricular defibrillation threshold. The dogs were classified into three groups: a saline group (n = 6), a low dose recainam group (n = 6) and a high dose recainam group (n = 5). The low dose infusion involved an intravenous loading dose of 3.75 mg/kg body weight over 20 min followed by a maintenance infusion of 0.0375 mg/kg per min. The high dose infusion was double those rates. The low dose recainam infusion produced a plasma recainam concentration of 3.1 +/- 0.3 micrograms/ml and significantly increased QRS duration by 11.3 +/- 3% during sinus rhythm. The high dose recainam infusion produced a plasma concentration of 7.7 +/- 0.9 microgram/ml and significantly increased QRS duration by 27 +/- 7% in sinus rhythm. Recainam did not change ventricular effective refractory period or sinus cycle length. The mean change in E50 between control and infusion periods was 1 +/- 5% in the saline group (8.5 +/- 1.4 versus 8.6 +/- 1.6 joules); 42 +/- 11% in the low dose recainam group (8.1 +/- 1.0 versus 11.3 +/- 1.3 joules) and 92 +/- 17% in the high dose recainam group (11.2 +/- 2.1 versus 20.5 +/- 2.5 joules).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Comparison of monophasic with single and dual capacitor biphasic waveforms for nonthoracotomy canine internal defibrillation.

Monophasic and single capacitor and dual capacitor biphasic truncated exponential shocks were tested in pentobarbital-anesthetized dogs with use of a nonthoracotomy internal defibrillation pathway consisting of a right ventricular catheter electrode and a subcutaneous chest wall patch electrode. Seven dogs weighing 20.2 +/- 0.5 kg were utilized. Monophasic pulses of 10 ms duration were compared with three biphasic pulses. All biphasic waveforms had an initial positive phase (P1) followed by a terminal negative phase (P2) and the total duration of P1 plus P2 was 10 ms. The dual capacitor biphasic waveform (P1 9 ms, P2 1 ms) had equal initial voltages of P1 and P2. Two simulated single capacitor biphasic waveforms were also tested, the first designed to minimize the magnitude of P2 (P1 9 ms, P2 1 ms with initial voltage of P2 equal to 0.3 of the initial voltage of P1) and the second to maximize P2 (P1 5 ms, P2 5 ms with initial voltage of P2 = 0.5 P1). Alternating current was used to induce ventricular fibrillation and four trials of eight initial voltages from 100 to 800 V were performed for each of the four waveforms. Stepwise logistic regression was utilized to construct curves relating probability of successful defibrillation and energy. In the logistic model, the dual capacitor biphasic and single capacitor biphasic waveforms that maximized P2 were associated with significantly (p less than 0.001) lower energy requirements for defibrillation than those of the monophasic waveform. The single capacitor biphasic waveform that minimized P2 was not significantly better than the monophasic waveform.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Long-term outcome with the automatic implantable cardioverter-defibrillator.

The automatic implantable cardioverter-defibrillator was implanted in 270 patients because of life-threatening arrhythmias over a 7 year period. There was a history of sustained ventricular tachycardia or fibrillation, or both, in 96% of these patients, 80% had one or more prior cardiac arrests and 78% had coronary artery disease as their underlying diagnosis. The average ejection fraction was 34%, and 96% of these patients had had an average of 3.4 antiarrhythmic drug failures per patient before defibrillator implantation. There were four perioperative deaths and eight patients had generator infection or generator erosion, or both, during the perioperative period or during long-term follow-up. Concomitant antiarrhythmic drug therapy was given to 69% of patients. Shocks from the device were given to 58% of patients. and 20% received "problematic" shocks. The device was removed from 16 patients during long-term follow-up for a variety of reasons. There were 7 sudden cardiac deaths and 30 nonsudden cardiac deaths, 18 of which were secondary to congestive heart failure. The actuarial incidence of sudden death, total cardiac death and total mortality from all causes was 1%, 7% and 8%, respectively, at 1 year, and 4%, 24% and 26% at 5 years. The automatic implantable cardioverter-defibrillator nearly eliminates sudden death over a long-term follow-up period in a high risk group of patients. It has an acceptable rate of complications or problems, or both, and most late deaths in these patients are nonsudden and of cardiovascular origin.

Death, Sudden↗
PubMed1989

Combined automatic implantable cardioverter-defibrillator and pacemaker systems: implantation techniques and follow-up.

The automatic implantable cardioverter-defibrillator (AICD) effectively prevents death due to ventricular tachycardia or ventricular fibrillation. Some patients who need an AICD also require cardiac pacing to treat symptomatic bradycardia, bradycardia after defibrillation, or to provide a rate floor to reduce the frequency of bradycardia-related ventricular arrhythmias. Some patients also can benefit from antitachycardia pacing. A mapping technique to implant a pacemaker and AICD sensing leads is presented. For patients with a pacemaker who later need an AICD, the left ventricle is mapped with use of the AICD rate-sensing electrodes to identify a site at which the minimal pacemaker stimulus and maximal ventricular electrogram amplitudes are recorded. An external cardioverter-defibrillator that has amplifiers similar to those in the AICD is used to monitor the rate-sensing electrogram. For patients with an implanted AICD, pacemaker implantation is undertaken by mapping the right ventricle with the pacemaker lead while the AICD is in standby mode; the AICD beep monitor is then used to determine a site where pacemaker stimulus detection by the AICD does not occur. Eight patients underwent implantation of a combined AICD-pacemaker system (four ventricular antitachycardia pacemakers, three ventricular demand pacemakers and one atrial demand pacemaker). Neither inhibition of AICD arrhythmia detection nor double counting occurred. Satisfactory AICD-pacemaker function was shown in all patients postoperatively, and no pacemaker malfunction was observed. Thus, with currently available technology, a combined AICD-pacemaker system can be implanted with satisfactory function of both devices and without adverse device-device interactions.

Aged↗
PubMed1992

Transthoracic defibrillation: effect of sternotomy on chest impedance.

The purpose of this study was to determine the effect of sternotomy on transthoracic impedance, a major determinant of current flow and defibrillation success. Transthoracic impedance was determined by using a validated test-pulse technique that does not require actual shocks. Seventeen patients undergoing median sternotomy were studied prospectively. Transthoracic impedance was determined before operation, 3 to 5 days after operation and (in eight patients) greater than or equal to 1 month after operation. When measured using paddle electrodes placed in the standard apex-right parasternal defibrillating position, transthoracic impedance declined after sternotomy in all patients, from 77 +/- 18 to 59 +/- 17 omega (p less than 0.01); smaller declines were demonstrated by using other electrode positions. Transthoracic impedance remained below the preoperative level in the eight patients who underwent a second set of measurements at least 1 month after operation. Six normal subjects not undergoing sternotomy underwent serial transthoracic impedance measurements at least 5 days apart; mean transthoracic impedance did not change. It is concluded that transthoracic impedance declines after sternotomy. At any operator-selected energy level a higher current flow will result after sternotomy; this may facilitate postoperative defibrillation.

Cardiography, Impedance↗
PubMed1996

Testing different biphasic waveforms and capacitances: effect on atrial defibrillation threshold and pain perception.

OBJECTIVES: The goal of this study was to compare the effect of different tilts and capacitances for biphasic shocks on atrial defibrillation efficacy and pain threshold. BACKGROUND: Although biphasic shocks have been shown to be superior to monophasic shocks, the effect of tilt and capacitance on atrial defibrillation success and pain perception has not been studied in patients. METHODS: Atrial defibrillation threshold (DFT) testing was performed using a right atrial appendage/coronary sinus lead configuration in 38 patients with a history of paroxysmal atrial fibrillation undergoing an invasive electrophysiologic study. Biphasic waveforms with 40%, 50%, 65%, 80%, 30%/50% and 40%/50% were tested randomly in 22 patients (Group 1). In 16 patients (Group 2), a 65% tilt waveform with 50- and 120-microF capacitance was tested. Before sedation, pain sensation was graded by 15 patients in Group 1 after delivery of a 0.5-J shock and by 10 patients in Group 2 after two 1.5-J shocks with 50- and 120-microF capacitance were delivered. RESULTS: The DFT energy for the 50% tilt waveform was significantly lower than the 65%, 80% and 30%/50% tilt waveforms. The 40%/50% tilt waveform provided slightly lower energy requirements than the 50% tilt waveform. Nine patients (60%) described the 0.5-J shock as very painful, and four (26.6%) complained of slight pain. The 50-microF capacitor lowered energy requirements compared with the 120-microF capacitor. Six patients (60%) perceived the 1.5-J 50-microF capacitor shock as more painful, whereas three (30%) perceived both shocks as equally painful. CONCLUSIONS: Biphasic waveforms with 50% tilt in both phases and a smaller tilt in the positive phase than that in the negative phase (40%/50%) provided a decrease in energy requirements at atrial DFT. In addition, stored energy was reduced by biphasic shocks with 50-microF capacitance compared with 120-microF capacitance. Despite the reduction in energy requirements, shocks < 1 J continued to be perceived as painful in the majority of patients.

Aged↗
PubMedDate not supplied

Early defibrillation program: problems encountered in a rural/suburban EMS system.

Many studies have shown improved survival of cardiac arrest patients by the use of early defibrillation (EMT-D) in the field. This prospective study was the first in Pennsylvania and was undertaken to determine if an EMT-D program would be successful in our suburban/rural setting. One hundred two EMTs were trained to use a semi-automatic defibrillator and data were collected over 16 months. There were 96 cardiac arrests, with only 33 patients (34%) presenting with initially treatable dysrhythmias--ventricular fibrillation (VF) or tachycardia (VT). Twenty-three patients (24%) were admitted to the hospital; survival to hospital discharge occurred in only 5 patients (5.2%). Survival to hospital admission was higher among VF/VT presenting rhythms (36%) than for those with other rhythms (17%, P = 0.07), but survival to discharge among VF/VT rhythms (9%) was not statistically different from other rhythms (3%, P = 0.45). Among VF/VT patients, survival to discharge was correlated with shorter call to first defibrillation intervals. Mean call to response interval was longer than in other reported studies (7.2 +/- 4.3 minutes). In addition, there was a high drop-out rate of EMT participants, no central/uniform early access system (that is, 911), and a lower rate of CPR than reported in other studies. It is concluded that introduction of an EMT-D program without careful analysis of systems response factors will not lead to the improved cardiac arrest survival percentages that have previously been reported.

Adult↗
PubMed2006

Home defibrillation: a feasibility study in myocardial infarction survivors at intermediate risk of sudden death.

BACKGROUND: Out-of-hospital cardiac arrest occurs at home in 65-80% of cases and is often witnessed. We designed a study to explore the feasibility of a home defibrillation program (a) evaluating the retention of cardiopulmonary resuscitation and automated external defibrillators (AED) use skills (BLSD) (b) assessing the impact on anxiety, depression, and quality of life and (c) recording the critical issues emerging from program implementation. METHODS: Thirty-three post-myocardial infarction patients and their 56 relatives received BLSD training and an AED. Assessment of BLSD skills, levels of anxiety, and depression and quality of life were scheduled every 3 months for 1 year or until a common stopping date. RESULTS: Overall BLSD score was 26 +/- 3 at baseline vs. 22 +/- 5 at 3 months (P < .0001), 21 +/- 6 at 6 months (P < .0001), 22 +/- 4 at 9 months (P < .0001) and 23 +/- 5 at 12 months (P = .001). Conversely, the BLSD component AED use" remained stable throughout the study. Quality of life, anxiety, and depression scores remained constant. Compliance to BLSD retraining sessions and AEDs checks decreased over time and was influenced by a concomitant clinical appointment. CONCLUSIONS: BLSD performance of families of post-myocardial infarction patients decreases over time, even though the ability to operate AEDs appears to be the least affected component. Compliance with retraining sessions and AED checks declines over time and is improved if they are combined with clinical appointments. The implementation of a home defibrillation program does not affect anxiety, depression, or the quality of life.

Aged↗
PubMed2004

Comparison of the effects of removal of chest hair with not doing so before external defibrillation on transthoracic impedance.

Chest hair contributes significantly to transthoracic impedance (TTI) during defibrillation. The magnitude of this effect has not been established using external paddles. We compared TTI in 40 men before elective cardiac surgery, and before and after shaving their chests. Chest hair causes a significant increase in TTI during external defibrillation, the magnitude of the effect being related to both the quantity of hair and force applied to the defibrillation paddles. When the chests of nonhirsute patients were shaved, a decrease in TTI occurred, which was probably related to the creation of low-impedance pathways through skin abrasions.

Adult↗
PubMed2005

Cost-effectiveness of training unselected laypersons in cardiopulmonary resuscitation and defibrillation.

PURPOSE: The cost-effectiveness of cardiopulmonary resuscitation (CPR) and defibrillation training for laypersons unselected for risk of encountering cases of cardiac arrest is not known. We compared the costs and health benefits of alternative resuscitation training strategies for adults without professional first-responder duties who are at average risk of encountering cases of out-of-hospital cardiac arrest. METHODS: We constructed a cost-effectiveness analytic model. Data on cardiac arrest epidemiology and the effectiveness of CPR/defibrillation training were obtained from the medical literature. Instructional costs were determined from a survey of training programs. Downstream cardiac arrest survivor quality-adjusted life expectancy and long-term health care costs were derived from prior studies. We compared three strategies for training unselected laypersons: CPR/defibrillation training alone, training combined with home defibrillator purchase, and no training. The main outcome measures were total instructional costs for trainees combined with health care costs for additional cardiac arrest survivors, and quality-adjusted survival for additional patients resuscitated by trainees. RESULTS: CPR/defibrillation training yielded 2.7 quality-adjusted hours of life at a cost of 62 US dollars per trainee (202,400 US dollars per quality-adjusted life-year [QALY] gained). Training laypersons in CPR/defibrillation with subsequent defibrillator purchase cost 2,489,700 US dollars per QALY. In contrast, CPR/defibrillation training cost less than 75,000 US dollars per QALY if trainees lived with persons older than 75 years or with persons who had cardiac disease, or if total training costs were less than 10 US dollars. CONCLUSION: Training unselected laypersons in CPR/defibrillation is costly compared with other public health initiatives. Conversely, training laypersons selected by occupation, low training costs, or having high-risk household companions is substantially more efficient.

Adult↗
PubMed2004

Reproducibility of internal atrial defibrillation threshold in paroxysmal and persistent atrial fibrillation.

BACKGROUND: Several pharmacological or technical factors may affect atrial defibrillation threshold (ADFT) for internal cardioversion (ICV) in the treatment of atrial fibrillation (AF). METHODS: We evaluated the reproducibility of ADFT in lone paroxysmal (electrically induced AF, 10 pts, 51+/-4 years) or persistent AF (15 pts, 64+/-7 years). The AF pattern (F-F interval) was characterised before each ICV attempt. A first step-up synchronised ICV test (ICV1, biphasic shock waveform 6 ms/6 ms) with increasing energy levels from 0.2 to 20 J was performed by a dual-lead defibrillation system (right atrium-coronary sinus configuration) connected to an external cardioverter defibrillator. After 30 min of stable sinus rhythm, a new sustained AF was induced (>20 min duration) and ICV protocol was repeated (ICV2). The AF cycle length was recorded for 30 s from the lateral wall of right atrium in basal condition and before each cardioversion attempt. RESULTS: The mean values of AF cycle length before a successful shock were similar in both AF populations (paroxysmal AF: pre-ICV1 175+/-21 ms vs pre-ICV2 181+/-20 ms (p=NS); persistent AF pre-ICV1 194+/-25 ms vs pre-ICV2 202+/-15 ms (p=NS)). No significant differences were observed between the two successful ICV tests concerning intensity, energy and impedance levels. The value of ADFT energy was reproducible in paroxysmal AF population (SD differences 1.2, coefficient of variability 9.6%). In persistent AF group only the impedance was reproducible (SD differences 2.6 Omega, coefficient of variability 4.5%), but not the energy requirements (SD differences 9.6, coefficient of variability 44.3%). CONCLUSIONS: ADFT is reproducible in paroxysmal AF patients, while a high coefficient of variability is present in persistent AF, possibly related to different patterns of re-entrant circuits in the reinduced AF. This observation is important in order to evaluate factors influencing ICV-ADFT correctly in AF patients.

Aged↗