An uncommon cause of inappropriate ICD shock.

In cases of electromagnetic interference (EMI), if the source of the inappropriate EMI cannot be identified, then the sensitivity of the device could be decreased, or the cycle length of the VF detection trigger zone changed.

Potential-guided versus anatomic-guided approach for slow pathway ablation of the common type atrioventricular nodal reentry tachycardia: a randomized study.

OBJECTIVE: The present study aimed to compare the effectiveness and safety of the potential- and the anatomic-guided approach for slow pathway ablation in patients with recurrent episodes of symptomatic common type atrioventricular (AV) nodal reentrant tachycardia. METHODS: Two hundred and twenty-eight patients were randomly assigned to undergo either a potential- (n=114, 47% men, mean age 52.85 +/- 14.04 years) or an anatomic-guided approach (n=114, 50% men, mean age 52.45 +/- 14.46 years) for radiofrequency ablation of the slow pathway.The mean duration of the follow-up period was 26.7 +/- 7.9 and 24.8 +/- 7.6 months in the potential- and anatomic- guided approach, respectively (P > 0.05). RESULTS: The success rate for slow pathway ablation was 100% in both ablative methods.The mean duration of atrial electrograms at the successful ablation sites of the potential- and the anatomic-guided approaches was 69 +/- 14 msec and 57 +/- 10 msec, respectively (P = 0.001).There were no significant differences between the potential- and the anatomic-guided approach regarding the duration of the procedure (121.13 +/- 56.83 vs. 109.93 +/- 57.12 min, P = 0.139), the duration of fluoroscopic exposure (6.12 +/- 3.32 vs. 6.64 +/- 3.33 min, P = 0.239) or the mean number of radiofrequency applications delivered (3.96 +/- 2.77 vs. 4.33 +/- 2.73, P = 0.311). Residual dual AV nodal pathway following successful ablation was observed in 9.6% of patients who underwent the potential-guided approach and in 23.7% of patients who underwent the anatomic method (P = 0.004). During followup, arrhythmia recurrence was observed in four patients (1.8%), two in each group (P > 0.05). CONCLUSIONS: The efficacy and safety of the slow pathway ablation is very high using either the potential- or the anatomic-guided approach.

Predictors of atrial fibrillation recurrence in patients with long-lasting atrial fibrillation.

BACKGROUND: Limited data are available on the predictors of atrial fibrillation (AF) recurrence in patients with chronic AF. OBJECTIVES: To evaluate potential clinical, echocardiographic and electrophysiological predictors of AF recurrence, after internal cardioversion for long-lasting AF. METHODS: A total of 99 consecutive patients (63 men and 36 women, mean age 63.33+/-9.27 years) with long-standing AF (52.42+/-72.02 months) underwent internal cardioversion with a catheter that consisted of two defibrillating coils. Shocks were delivered according to a step-up protocol. Clinical follow-up and electrocardiographic recordings were performed on a monthly basis for a 12-month period or whenever patients experienced symptoms suggestive of recurrent AF. RESULTS: Ninety-three patients (93.94%) underwent a successful uncomplicated cardioversion, with a mean atrial defibrillation threshold of 10.69+/-6.76 J. Immediate reinitiation of AF was observed in 15 patients (15.78%) of whom a repeated cardioversion restored sinus rhythm in 13 cases. Early recurrence of AF (within one week) was observed in 12 of 93 patients (12.90%). At the end of the 12-month follow-up period, during which seven patients were lost, 42 of the 86 remaining patients (48.84%) were still in sinus rhythm. Multivariate regression analysis showed that left atrial diameter (OR 1.126, 95% CI 1.015 to 1.249; P=0.025) and mitral A wave velocity (OR 0.972, 95% CI 0.945 to 0.999; P=0.044) were significant and independent predictors of AF recurrence, whereas age, left ventricular ejection fraction and AF cycle length were not predictive of arrhythmia recurrence. CONCLUSION: The present study showed that the left atrial diameter and mitral A wave velocity are the only variables associated with AF recurrence after successful cardioversion.

Ablation of atrial fibrillation in patients with heart failure: reversal of atrial and ventricular remodelling.

INTRODUCTION: The management of patients with heart failure and atrial fibrillation (AF) is a medical challenge, especially in the case of patients in whom sinus rhythm or rate control cannot be achieved with optimal pharmaceutical treatment. METHODS: Thirteen consecutive patients (11 men and 2 women, 35-70 years old, median age 55 +/- 23 years) with heart failure (NYHA I-IV, median ejection fraction 35 +/- 5%, range 25-40%) and symptomatic persistent (10 patients, 76.9%) or permanent (3 patients, 23.1%) AF, underwent circumferential ablation using a system of electroanatomic mapping with contact. Circumferential ablation, encircling the pulmonary veins in pairs, and linear ablation between the left and right superior pulmonary vein and along the mitral isthmus were performed. Follow up included 24-hour Holter monitoring and transthoracic echocardiogram at 1, 3, 6, 9 and 12 months. RESULTS: Eight patients (62%) remained in sinus rhythm at the end of the follow up and had achieved a statistically significant improvement in ejection fraction (from 37.5 8.75% to 60.0 +/- 3.75%, p = 0.011), reduction of left ventricular end-diastolic diameter (from 63.0 +/- 3.25 mm to 56.5 +/- 1.75 mm, p = 0.011) and reduction of left atrial diameter (from 49.0 +/- 5.5 mm to 44.5 +/- 4.25 mm, p = 0.011). In contrast, patients with relapse of AF had none of the above changes (p > 0.05). Prognostic indexes of AF recurrence appeared to be the failure to improve ejection fraction (p = 0.003), non-reversal of left ventricular (p = 0.002) and left atrial (p = 0.006) remodelling, a shorter energy application time (p = 0.030) and the presence of coronary artery disease (p = 0.035). None of the patients suffered any complication from the procedure. CONCLUSION: AF ablation in selected patients with heart failure and low ejection fraction is a relatively effective method of maintaining sinus rhythm, improving left ventricular systolic function and reversing atrial and ventricular remodelling.

Effect of atrial pressure increase on sinus node automaticity.

There is evidence suggesting that atrial electrophysiological properties may be changed by an acute increase in atrial pressure. The aim of the present study was to investigate the effect of alteration, in atrial pressure on sinus node recovery time. Twelve patients (8 men and 4 women, mean age 61.3 +/- 14.1 years) were included in this study. None of the patients had organic heart disease. Sinus node recovery time (SNRT) was measured following atrial pacing and atrioventricular (AV) pacing at sequential cycle lengths of 600, 545, 500, 461, 428, and 400 ms with two different AV intervals (150, 0 ms). Peak and minimal atrial pressure increased significantly from 8.5 +/- 2.8 to 20.1 +/- 2.9 mmHg (11.56 +/- 3.8 to 27.3 +/- 3.9 cmH2O) ( P=0.001) and from 2.06 +/- 1.69 to 5.33 +/- 2.9 mmHg (2.8 +/- 2.29 to 7.2 +/- 3.9 cmH2O), respectively (P=0.002) during AV interval modification. Sinus node recovery time did not change despite the increase in atrial pressure. Autonomic blockade had no effect on SNRT. This study demonstrates that atrial pressure increase does not significantly affect sinus node automaticity expressed by SNRT.

Facilitating internal cardioversion of chronic atrial fibrillation with ibutilide--predictors of atrial defibrillation-threshold decrease.

BACKGROUND: Internal atrial cardioversion has been successfully used in the treatment of atrial fibrillation. The object of this study was to depict the effect of ibutilide on sinus rhythm restoration and internal atrial defibrillation threshold in patients with chronic atrial fibrillation. MATERIAL/METHODS: Twenty-four patients (14 men and 10 women, mean age 63.16+/-8.55 years) with chronic atrial fibrillation were cardioverted using a single-lead system. The distal coil of the defibrillator catheter was placed in the coronary sinus and the proximal coil at the junction of the superior vena cava and the high right atrium. Synchronized biphasic shocks were applied using a step-up protocol from 1 to 30 joules until sinus rhythm was restored. In all patients with successful cardioversion, atrial fibrillation was reinduced and second cardioversion was attempted after intravenous administration of 1 mg ibutilide. RESULTS: Successful internal cardioversion was achieved in 22 (91.6%) and 23 (95.83%) patients before and after ibutilide administration, respectively. The amount of energy given was reduced from 13.89+/-11.44 to 8.28+/-9.64 joules (p=0.0001). Variables associated with the reduction of the defibrillation threshold after ibutilide administration were: duration of the last episode of atrial fibrillation (p=0.008), time since the first episode of atrial fibrillation (p=0.002), body mass index (p=0.01), ejection fraction (p=0.025), male gender (p=0.001), and diameter of the left atrium (p=0.028). CONCLUSIONS: Internal atrial defibrillation after ibutilide administration is a safe and effective method for sinus rhythm restoration, with concurrent significant reduction of the atrial defibrillation threshold.