Electronic Pacemaker Models of Parasystole

This study deals with a method of analysis of artificial pacemaker function which can be used to understand the electrocardiographic manifestations of some spontaneous rhythms. The modes of operation of 11 normally-functioning QRS-inhibited (VVI) pacemakers resembled those of spontaneous automatic nonprotected (nonparasystolic) rhythms. The function of 11 continuous asynchronous (fixed rate or VOO) pacemakers was similar to that of continuous-parasystolic rhythms. In 12 patients with malfunctioning QRS-inhibited (VVI) pacemakers, an abnormally-prolonged pacemaker refractory period was equivalent to intermittent parasystole with phase 3 protection; and non-sensing during the terminal portions of the cycle was the iatrogenic counterpart of intermittent parasystole with phase 4 protection. Premature beats occurring within the periods of phase 3 and phase 4 protection were "encompassed" by ectopic intervals equalling the ectopic cycle length, or twice the ectopic cycle length. Therefore, they were manifested differently from the "decelerating" and "accelerating" phases of modulation since premature beats occurring during the letter phases may be encompassed by ectopic intervals which are longer and shorter, respectively, than the ectopic cycle length. Because in previous reports the search for these phenomena was based on premises established "a priori," future studies should be designed to analyze tracings of "group beating" where no previous conclusions have been reached.     

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.     

From Cardiac Nociception to the Brain: The Unstable Character of Angina Pectoris

Sympathetic Afferents and Cardiac Pain. We analyzed some particular aspects of the peripheral pathways likely to be involved in the mediation of cardiac pain. The functional characteristics and the reflex function of cardiac sympathetic afferent fibers are discussed in relation to the afferent code transmitting nociception. A modified version of the intensity theory based on the extreme excitation of a spatially restricted population of afferent sympathetic fibers is proposed as the most likely mechanism involved in the genesis of cardiac pain.     

Long‐Term Results of Transcatheter Atrial Fibrillation Ablation in Patients with Impaired Left Ventricular Systolic Function

AF Ablation and Impaired Left Ventricular Function. Introduction: Long‐term outcome of AF ablation in patients with impaired LVEF is unknown. The aim of this study is to evaluate sinus rhythm (SR) maintenance, clinical status, and echocardiographic parameters over a long‐term period following atrial fibrillation (AF) transcatheter ablation in patients with left ventricular ejection fraction (LVEF) <50%. Methods and Results: A total of 196 patients (87.2% males, age 60.5 ± 10.2 years) with LVEF <50% underwent radiofrequency transcatheter ablation for paroxysmal (22.4%) or persistent (77.6%) AF. Patients were followed up for 46.2 (16.4–63.5) months regarding AF recurrences, functional class, and echocardiographic parameters. All patients underwent pulmonary vein isolation, while 167 (85.2%) required additional atrial lesions. Eleven (5.6%) patients suffered procedural complications. During follow‐up, 58 (29.6%) patients required repeated ablations. At the follow‐up end, 15 (7.7%) patients died, while 74 (37.8%) documented at least one episode of AF, atrial flutter, or atrial ectopic tachycardia. Eighty‐three (47.2%) patients maintained antiarrhythmic drugs. During follow‐up, NYHA class improved by at least one class more frequently among patients maintaining SR compared to those experiencing relapses (70.6% vs 47.9%, P = 0.003). LVEF showed a broader relative increase in patients maintaining SR (32.7% vs 21.4%; P = 0.047) and mitral regurgitation grading significantly decreased (P <0.001) only within these patients. At multivariable analysis SR maintenance emerged as an independent predictor (odds ratio 4.26, 95% CI 1.69–10.74, P = 0.002) of long‐term clinical improvement (reduction in NYHA class ≥1 and relative increase in LVEF ≥10%). Conclusions: Although not substantially worse than in patients with preserved LVEF, AF ablation in patients with impaired LVEF is affected by high long‐term recurrence rate. Among these patients SR maintenance is associated with greater clinical improvement. (J Cardiovasc Electrophysiol, Vol. 24, pp. 24‐32, January 2013)