Postcardioversion atrial electrophysiologic changes induced by oral verapamil in patients with persistent atrial fibrillation.

OBJECTIVES: The aim of our study was to verify the effect of oral administration of verapamil on atrial electrophysiologic characteristics after cardioversion of persistent atrial fibrillation (AF) in humans. BACKGROUND: Discordant findings have been reported regarding the efficacy of verapamil in preventing the electrical remodeling induced by AF. METHODS: We determined the effective refractory periods (ERPs) at five pacing cycle lengths (300 to 700 ms) and in five right atrial sites after internal cardioversion of persistent AF (mean duration 238.1+/-305.9 days) in 19 patients. Nine patients received oral verapamil (240 mg/day) starting four weeks before the electrophysiologic study, whereas the other 10 patients were in pharmacologic washout. RESULTS: The mean ERPs were 202.0+/-22.7 ms in the washout group and 189.3+/-18.5 ms in the verapamil group (p < 0.0001). The degree of adaptation of refractoriness to rate was similar in the two groups (mean slope value in the washout group and verapamil group: 0.07+/-0.03 and 0.08+/-0.05, respectively), showing a normal or nearly normal adaptation to rate in the majority of the paced sites in both groups. The mean ERP was slightly longer in the septum than in the lateral wall and in the roof, both in the washout and verapamil groups. CONCLUSIONS: In patients with persistent AF, long-term administration of verapamil before internal cardioversion resulted in 1) shortening of atrial ERPs; 2) no change in refractoriness dispersion within the right atrium; and 3) no change in atrial ERP adaptation to rate.

Single shock endocavitary low energy intracardiac cardioversion of chronic atrial fibrillation.

BACKGROUND: Discomfort related to low-energy internal cardioversion (LEIC) represents a real problem in patients (pts) with atrial fibrillation (AF). The aim of our study was to verify if a single shock could restore sinus rhythm (SR) with a lower discomfort for the pt. METHODS: Thirty pts with chronic AF were randomized to receive a single 350 V shock (15 pts) or multiple shocks of increasing energy (15 pts). Three leads were positioned, respectively, in the coronary sinus and in the lateral right wall for shock delivery, and in the right ventricular apex for R wave synchronization. Truncated, biphasic shocks were used. In the first group a single 350 V shock was directly delivered and a second 400 V shock was given only if SR has not been restored. In the second group, beginning at 50 volts the voltage was increased in steps of 50 volts until SR restoration. No patient was sedated. After each shock the pts were asked to rate their discomfort on a scale of 1 to 5 (1 = not perceived, 5 = severe discomfort). RESULTS: SR was restored in all the subjects. In group 1 SR was obtained in 12/15 (80%) pts with the first 350 V (8.1 +/- 0.8 joules) shock, while the remaining 3 patients required the second 400 V (10.2 +/- 0.3 joules) shock. In group 2 the mean atrial defibrillation threshold was 346.7 +/- 1029.7 volts (8.0 +/- 101.5 joules). Then discomfort score was 2.5 +/- 0.6 in group 1 and 3.3 +/- 10.6 in group 2 (p < 0.01). CONCLUSIONS: A single shock of 350 V restores SR in the majority of pts with chronic AF; by use this new approach, LEIC is tolerated better than the multiple shocks step-up protocol.

Spatial extension of local pacing capture in the lateral free wall of the right atrium during clinical chronic atrial fibrillation.

OBJECTIVES: The aims of our study were to define the spatial extension of local atrial pacing capture (LAPC) in the right lateral atrial wall and to verify the effects of antiarrhythmic drugs on capture extension. BACKGROUND: Recently, LAPC during spontaneous chronic atrial fibrillation (AF) has been demonstrated directly in humans, but no systematic attempt has been made to evaluate its spatial extension. METHODS: The study was conducted in 14 consecutive patients with chronic AF, nine of whom were taking antiarrhythmic drugs. A Franz catheter for pacing and monophasic action potential recording was positioned in the lateral right atrial wall. An octopolar recording lead was positioned about 10 mm apart. The presence of atrial capture and its extension (number of captured bipolar pairs) were evaluated during decremental pacing. RESULTS: Forty-eight atrial capture attempts were made. LAPC was achieved in all the performed attempts. The AF types immediately before capture were type 1 in 35 (73%) and type 2 in 13 (27%) episodes. In 32 episodes, the capture was lost within 15 seconds and in the remaining 16 pacing was stopped after 15 seconds of stable capture. In 26 episodes, capture extended radially up to 4 cm from the pacing site, in 18 up to 3 cm, in 3 up 1 cm and in 1 up 1 cm. The mean extension in patients being treated with antiarrhythmic drugs was significantly greater than what was seen in untreated patients (3.8 +/- 0.4 vs 2.9 +/- 0.7 cm, p < 0.00001). Capture loss was less frequently observed when all four of the bipolar recording sites had been captured (13/25, 52% vs 19/23, 82%, respectively, p = 0.05). CONCLUSIONS: LAPC in the lateral right atrial wall extends over a radius of 30-40 mm in the majority of capture episodes and is greater in patients treated with antiarrhythmic drugs. Our results suggest that, at least theoretically, simultaneous multisite pacing could be used to terminate AF. Moreover, a reduction in the atrial defibrillation threshold could be expected performing low-energy internal cardioversion during LPC.

[The efficacy of high- and low-energy intracavitary cardioversion in chronic atrial fibrillation refractory to transthoracic cardioversion]. / Efficacia della cardioversione endocavitaria ad alta e bassa energia nella fibrillazione atriale cronica refrattaria alla cardioversione transtoracica.

BACKGROUND: The purpose of our study was to evaluate the efficacy and safety of intracavitary cardioversion (IC) with either high (HEIC) or low (LEIC) energy in patients with chronic atrial fibrillation (AF) refractory to external cardioversion. METHODS: Forty patients underwent IC with either high (30 pts) or low energy (10 pts); HEIC was performed by delivering one or more shocks between one electrode of the lead positioned in the right atrium and a back plate. The following energy values were used in sequence: 100, 200, 300 joules. In LEIC shocks were delivered between two custom-made decapolar leads (one in the coronary sinus and another one in the right lateral atrial wall) beginning from 50 Volts and increasing the voltage by steps of 50 Volts. Another catheter in the right ventricular apex was used for ventricular synchronization. RESULTS: Sinus rhythm was restored in 24/30 (80%) patients undergoing HEIC and in 10/10 (100%) patients undergoing LEIC. No serious or permanent complications occurred. CONCLUSIONS: HEIC and LEIC are effective in patients with AF refractory to external cardioversion. Both the procedures seem to be safe.

Intra-atrial defibrillation of human atrial fibrillation.

Low-energy intra-atrial defibrillation is a new therapeutic option for restoring sinus rhythm in patients with atrial fibrillation (AF). The success rate is quite high when right atrium-coronary sinus or right atrium-pulmonary artery electrode configurations are used, although the former is associated with a slightly lower defibrillation threshold. Several issues regarding the safety and tolerability of the procedure remain unresolved. Our experience and that of others indicate that low-energy intra-atrial cardioversion is safe even during exercise, provided the shock is well synchronized with the QRS and the preshock RR interval is > 500 msec. Reported defibrillation thresholds in patients with persistent AF range from 4 to 8 J, and shocks of this type inevitably are associated with some degree of discomfort. Measures aimed at lowering the defibrillation threshold (e.g., use of biphasic waveforms, antiarrhythmic pretreatment, and use of a single effective shock, as opposed to the multiple shocks delivered in research settings) can be expected to increase patient tolerance and extend the indications for low-energy intra-atrial cardioversion. The procedure currently is indicated for patients with persistent AF who are resistant to external defibrillation unable or unwilling to undergo general anesthesia. The procedure could be expanded to patients affected by obesity in whom the efficacy of external cardioversion is lower.

Low energy intracardiac cardioversion of persistent atrial fibrillation.

The aims of the study were to verify the efficacy and safety of low energy internal cardioversion (LEIC) in patients with persistent atrial fibrillation (AF) and to identify the factors affecting the atrial defibrillation threshold (ADT). Forty-nine patients with persistent (lasting > or = 10 days) AF underwent LEIC. In each patient, two 6 Fr custom-made catheters with large active surface areas were positioned in the coronary sinus (cathode) and the lateral right wall (anode), respectively, for shock delivery, and a tetrapolar lead was placed in the right ventricular apex for R wave synchronization. Truncated, biphasic (3 ms + 3 ms), exponential shocks were used, beginning at 50 V and increasing in steps of 50 V until sinus rhythm had been restored. Mild sedation (diazepam 5 mg i.v.) was administered to 12 patients. Sinus rhythm was restored in all the subjects with mean voltage and energy levels of 352.0 +/- 80.3 V and 8.2 +/- 3.4 J, respectively. The ADT in patients pretreated with amiodarone (6.4 +/- 1.8 J) was lower than that of patients who had not received any antiarrhythmic drugs (9.2 +/- 3.7) (P = 0.04). No ventricular arrhythmias were induced by any of the atrial shocks, and no other complications were observed. During a mean follow-up of 162.9 +/- 58.7 days, AF recurred in 21 (43%) patients; 71% of these occurred in the first week after cardioversion. LEIC is effective in restoring sinus rhythm in patients with persistent AF. The technique seems to be safe and does not require general anesthesia or, in most cases, sedation. Patients pretreated with amiodarone have lower ADTs.

Prognostic value of left ventricular mass in uncomplicated acute myocardial infarction and one-vessel coronary artery disease.

This study assesses the relative prognostic value of increased left ventricular (LV) mass compared with residual ischemic myocardium and angiographic characteristics of the diseased vessel in 76 patients with uncomplicated acute myocardial infarction associated with 1-vessel coronary artery disease (CAD). All patients underwent symptom-limited treadmill exercise testing, resting and dipyridamole echocardiography and coronary angiography before discharge, and were followed-up for 32 +/- 6 months. LV measurements were obtained in diastole according to the Penn convention. Measurements of LV mass were divided by body surface area to obtain LV mass index. A cut-off value of 135 g/m2 body surface area for men and 112 g/m2 for women was prospectively selected. The individual effects of clinical, stress testing and angiographic variables were evaluated by using the Cox regression model. Echocardiographic LV mass index was increased in 43 patients and normal in 33. There was no intergroup difference with respect to baseline clinical and angiographic variables, ejection fraction and prevalence of stress-induced ischemia. During follow-up there were 23 cardiac events in the 43 patients with increased LV mass index and only 5 in the 33 with normal LV mass index (p < 0.001). No patient died or had nonfatal reinfarction among patients with normal LV mass. Cox survival analysis identified an increased LV mass index as the only independent predictor of cardiac events (chi-square = 7.9; p < 0.005; RR = 5.4). Thus, these data suggest that LV mass is an important independent risk factor in patients with uncomplicated acute myocardial infarction associated with 1-vessel CAD.