Determinants of Efficacy of Atrial Pacing in Preventing Atrial Fibrillation Recurrences

Atrial Pacing in Atrial Fibrillation. Introduction: Several studies have shown that single or dual site atrial pacing is effective in reducing he frequency of recurrent atrial fibrillation (AF) in selected patients. However, it is still unclear what the best predictors are of long-term efficacy of atrial pacing. Methods and Results: Forty-seven patients with paroxysmal AF requiring demand pacing underwent electrophysiologic study and dual chamber pacemaker implant. After 4 months of follow-up, patients were divided into two groups according to the presence (group 1) or absence (group 2) of symptomatic AF recurrences. Atrial pacing markedly reduced AF recurrences in all patients. Twenty-four patients were free of arrhythmia. The basal state conduction times (CT_s) and the incremental conduction times (ICT_s), during programmed electric stimulation between the high right atrium (HRA) and the coronary sinus ostium (CS_os) but not between the HRA and the His-bundle region, were significantly longer in group 1. There was no statistical difference in the effective refractory period (ERP) recorded at the HRA, the low right atrium (LRA), and the CS_s between the two groups, whereas the differences between the greatest and least recorded ERPs measured from the HRA, LRA, and CS_os (δERP) were significantly greater in group 1 patients. Two parameters were selected by discriminant multivariate analysis, namely δCT_os (ICT-CT between HRA and CS_os and δERP. The first bad a greater relative importance in predicting AF recurrence (r²= 0.33 and r²= O.1, respectively). Conclusion: Single site atrial pacing is effective in reducing AF recurrences, with decreasing efficacy in patients with greater right atrial conduction delay and wider refractoriness dispersion.     

Treatment Strategies for Long and Calcified Lesions

This study discusses the treatment strategies used to approach long lesions, lesions in small vessels, and calcified lesions. Traditional treatment strategies for these lesion subtypes have yielded high acute complication rates and poor long-term outcome. A prospective analysis of 160 lesions was performed using intravascular ultrasound (IVUS) guided PTCA for the treatment of long lesions and lesions in small vessels, while a retrospective analysis of 106 calcified lesions was performed that were treated with the combination of rotablation and stenting. Acute and short-term results of TVUS guided PTCA with spot stenting show a 30-day major adverse cardiac event rate (MACE) of 5% with a high procedural success rate (96%), while the long-term outcome resulted in an agiographic restenosis rate of 17.4% and a target lesion revascularization rate of 13%. The combination of rotablation and stenting also rendered results in calcified lesions of a 93% angiographic success rate and a long-term outcome of restenosis of 22.5%. Optimal coronary stenting after rotational atherectomy in calcified lesions can be performed with a high success rate, an acceptable rate of procedural complications, and a low rate of stent thrombosis. This approach was associated with a low incidence of angiographic restenosis compared with results obtained with other interventional approaches. IVUS guided PTCA with spot stenting allows safe treatment of long lesions and lesions in small vessels. Short-term and long-term outcomes including 6-month MACE and angiographic restenosis appear to be better than results achieved in historical controls that utilize balloon angioplasty alone or stents in a manner where the lesion is covered from the proximal normal segment to the distal normal segment.     

Uncommon complication of endoscopic ureterolithotripsy: The stone granuloma

Endoscopic management of urolithiasis is one of the commonest urological procedures today. It is usually safe and effective but one of the possible complications is ureteral obstruction. Stone fragmentation after ballistic lithotripsy and ureteral wall perforation could explain the mechanism responsible for this occurrence. We report a case of stone granuloma, occurring after a ballistic ureterolithotripsy.     

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 at rial fibrillation (AF) and to identify the factors affecting the at rial defihrillation threshold (ADT). Forty-nine patients with persistent (lasting ≥ 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 fight 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 IV) 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.     

Ventricular Parasystole: A Chronobiologic Study

Previous works have reported circadian rhythms for several cardiovascular parameters. A chronobiologic rhythm is characterized by: mesor (a rhythm-determined average), amplitude (half difference between the highest and lowest values), and acrophase (timing of high point in degrees and/or in hours) along with 95% confidence limits. We performed 24-hour ECG Holler monitoring in seven patients (mean age, 50.6 years) with ventricular parasystole (VP) in order to determine whether the chronotropic activity of parasystolic foci has a circadian rhythm similar to that of the sinus node. For each Holter recording parasystolic rates (PRs) and heart rates (HRs) were calculated every hour. Furthermore, a mean hourly PR and a mean hourly HR were calculated from the hourly PRs and HRs of the patients. The statistic chronobiologic analysis was done by single and mean cosinor methods. Correlation between mean hourly PR and HR was evaluated by Pearson's V coefficient. A statistically significant rhythm (P < 0.05) was found for the single and mean rhythms both of HR and PR. In our patients, HR had acrophase at 1.27 P.M., mesor at 73.28 beats/min, and amplitude at 9.53 beats/min, whereas PR had acrophase at 1.42 P.M., mesor al 38.31 beats/min, and amplitude at 3.64 beats/ min. Chronobiological data and the high direct correlation between mean hourly HRs and mean hourly PRs (r = 0.96, P < 0.001) indicate a similar circadian variability of the chronotropic activity of sinus nodes and parasystolic foci. Although several hypotheses can be made, responsiveness of parasystolic foci to circadian variations of the autonomic nervous system tone (sympathetic and/or vagal) and/or circulating substances (particularly catecholamines) seems the more probable one for explaining our findings.     

CELL CYCLE AND ORGANELLE ENZYME CHANGES IN THE REGENERATING LIVER OF THE ALCOHOLIC RAT

Chronic ethanol effect on regenerating post-partial hepatectomyrat liver was studied from 0 to 80 hr to evaluate sequentialchanges. The rate of restoration in liver mass was comparablebetween controls (C) and ethanol (E) treated rats. Cell cyclechanges included a decrease in magnitude and duration of theearly peak in DNA synthesis (24 hr). However, the second peak(40 hr) was increased in magnitude so that the net change wasnegligible. Histone synthesis increased markedly, whereas thymidinekinase activity was moderately increased. The net effect wasan accelerated accumulation of DNA (0.18 mg of DNA/g liver/hrvs 0.29 mg of DNA/g liver/hr; C vs E). The M phase of the cellcycle was initially delayed by ethanol, but once initiated,it exhibited greater numbers of mitoses reaching significanceat 72 hr. It is concluded that although ethanol induces multiplechanges, the overall process of restoring liver mass and cellnumber (DNA synthesis) is not impaired.