Reference EPFL-CONF-173780View record in Web of Science Record created on 2012-01-11, modified on 2017-12-10

It has been shown that repolarization alternans, a beat-to-beat alternation in action potential duration, enhances dispersion of repolarization above a critical heart rate and promotes susceptibility to ventricular arrhythmias. It is unknown whether repolarization alternans is measurable in the atria using standard pacemakers and whether it plays a role in promoting atrial fibrillation. In this work, atrial repolarization alternans amplitude and periodicity are studied in a sheep model of pacing-induced atrial fibrillation. Two pacemakers, each with one right atrial and ventricular lead, were implanted in 4 male sheep after ablation of the atrioventricular junction. The first one was used to deliver rapid pacing for measurements of right atrial repolarization alternans and the second one to record a unipolar electrogram. Atrial repolarization alternans appeared rate-dependent and its amplitude increased as a function of pacing rate. Repolarization alternans was intermittent but no periodicity was detected. An increase of repolarization alternans preceding episodes of non-sustained atrial fibrillation suggests that repolarization alternans is a promising parameter for assessment of atrial fibrillation susceptibility.

In pacing-induced models of atrial fibrillation (AF) that mimic atrial high-frequency foci, the increase in AF susceptibility over time is not paralleled by any increase in dispersion of repolarization (DOR). Measurements of effective refractory periods (ERP), however, were performed by using extrastimuli, which bears significant limitation because it cannot evaluate any dynamic increase in DOR that may arise at rapid rates. Repolarization alternans (Re-ALT), a beat-to-beat alternation in action potential duration, enhances DOR above a critical heart rate. It is unknown, however, whether Re-ALT plays a role in promoting AF. Method and results: two DDD pacemakers, each with right atrial (RA) and ventricular leads, were implanted in 4 male sheep (50-80 kg). The 1st pacemaker was used to deliver 1) electrophysiology protocols for measurements of RA ERP (S1S2) and of RA Re-ALT threshold (S1S1), and 2) intermittent RA burst pacing (for 5 sec followed by 2 sec of sinus rhythm) until sustained AF developed. The 2nd pacemaker was used to record a single broadband unipolar RA electrogram (EGM). The AV junction of the 3rd and 4th sheep has been ablated by RF in order to dissociate far-field ventricular activity from RA EGM. RA repolarization wave was detected following depolarization. Sustained AF was successfully induced after 1-14 weeks of intermittent RA burst pacing. RA ERP decreased progressively from 185±39 ms (pre-activation) to 125±15 ms and to 110±20 ms after 2 and 4 weeks of burst pacing respectively. Importantly, Re-Alt threshold (255±15 ms) did not change during the time course RA burst pacing, but the range of pacing CL during which RA Re-ALT was observed increased until sustained AF developed (45±5 ms before vs 105±25 after 2 weeks of RA pacing). Interestingly, despite aggressive atrial burst pacing protocol, significant changes in atrial histology were not observed. Conclusion: we report here for the first time in vivo measurements of atrial Re-Alt using standard pacemaker technology in a chronic sheep model of pacing-induced AF. Interestingly, Re-Alt threshold did not change during the time course of pacing-induced AF but the pacing CL range during which Re-Alt was observed increased proportionally to the decrease in RA ERP. These parameters were unrelated to significant atrial tissue alterations, but involved cellular alterations including at least important proteins involved in intracellular Ca cycling. Our findings suggest that atrial Re-Alt might be a mechanism by which DOR transiently increases, promoting wavebreaks and AF at rapid rates.

Drug therapy treatment of cardiac arrhythmias has been disappointing, while percutaneous catheter ablation, efficient and at low risk, has become the first line therapy of the majority of rhythm disturbances, in only two decades. The ultimate challenge, which is atrial fibrillation ablation, is on the way to be successfully solved. This is mainly due to: innovative ablational energy sources; 3D virtual electro-anatomical reconstructions of heart cavities, to map and understand complex arrhythmias' circuits; revolutionary magnetic navigation systems that permit the target positioning of the catheters in the most inaccessible places, even though the operator works at a command board placed away from the patient.

The investigation of unexplained syncope remains a challenging clinical problem. In the present study we sought to evaluate the diagnostic value of a standardized work-up focusing on non invasive tests in patients with unexplained syncope referred to a syncope clinic, and whether certain combinations of clinical parameters are characteristic of rhythmic and reflex causes of syncope.Methods and results317 consecutive patients underwent a standardized work-up including a 12-lead ECG, physical examination, detailed history with screening for syncope-related symptoms using a structured questionnaire followed by carotid sinus massage (CSM), and head-up tilt test. Invasive testings including an electrophysiological study and implantation of a loop recorder were only performed in those with structural heart disease or traumatic syncope. Our work-up identified an etiology in 81% of the patients. Importantly, three quarters of the causes were established non invasively combining head-up tilt test, CSM and hyperventilation testing. Invasive tests yielded an additional 7% of diagnoses. Logistic analysis identified age and number of significant prodromes as the only predictive factors of rhythmic syncope. The same two factors, in addition to the duration of the ECG P-wave, were also predictive of vasovagal and psychogenic syncope. These factors, optimally combined in predictive models, showed a high negative and a modest positive predictive value.ConclusionA standardized work-up focusing on non invasive tests allows to establish more than three quarters of syncope causes. Predictive models based on simple clinical parameters may help to distinguish between rhythmic and other causes of syncope.

Die medizinischen Titel der Preistrager entsprechen dem Stand zur Zeit der jeweiligen Preisverleihung. Die 21 mit einem * gekennzeichneten Preistrager haben in der Zwischenzeit den Titel eines Professors erhalten. Daraus kann man erkennen, dass der Wissenschaftliche Ausschuss der Schweizerischen Herzstiftung weit vorausschauend dem Potenzial und der Qualitat der Kandidaten entsprechend den Preis zugesprochen hat.

INTRODUCTION:The complete circuit of reentrant left atrial tachycardias (LATs) occurring after ablation for atrial fibrillation (AF) has not been well described. Identifying discrete isthmuses critical to these LATs may simplify their elimination by catheter ablation. METHODS AND RESULTS:Fifteen patients (all male, 56 +/- 8 years) with 15 reentrant LATs following AF ablation underwent activation and entrainment mapping. Eleven patients (11 LATs) had a single localized site with low amplitude (0.16 +/- 0.05 mV), fractionated long duration (131 +/- 23 msec) electrograms coinciding with an isoelectric interval of 106 +/- 24 msec between flutter waves on all 12 ECG leads. Three-dimensional mapping and entrainment revealed this site to be a narrow markedly slowly conducting isthmus adjacent to ablated left (n = 8) or right (n = 3) pulmonary vein (PV) ostia, and critical to nine small diameter (15 +/- 3 mm) and two large diameter (49 +/- 2 mm) circuits. One radiofrequency (RF) application on this isthmus eliminated LAT in all 11 patients. Four patients (four LATs) with large circuits around the mitral annulus and/or PV ostia lacked isoelectric ECG intervals and slow-conducting isthmuses and required multiple RF applications across anatomically wide, rapidly conducting isthmuses. CONCLUSION:Focally ablatable narrow isthmuses of slow conduction are critical for the majority of reentrant LAT occurring after ablation for AF. The role and presence of these isthmuses can be anticipated by observing significant isoelectric intervals between flutter waves on all 12-surface ECG leads. Their distinctive electrophysiological characteristics allow their identification and elimination by simple RF ablation.

Results: during FU, syncope recurred in 40 pts (32.2%).The frequency of syncopal episodes was significantly reduced during FU (from 2.884-4.49/year to 0.254-0.95/year,p<0.001).The probability of remaining syncope free after 58 months was 68% in general.According to mukivariate analysis female gender (RR 2.52, 95%CI 1.23-5.18,p=0.012), young age (<25year, RR 4.00, 95%CI 1.67-9.83,p=0.002) and syncope rate before TT (RR 1.05, 95%CI 1.006-1.099,p=0.025) were all independent predictors of time to first syncope recurrence.The TT resuk, the type of positive response and treatment or not were not statistically significant predictors of syncope recurrences.Conclusion: basic predictors of syncope recurrence in VVS patients are female gender, pts' young age and the rate of syncopal episodes.

syncope.HUT was performed according to the Italian protocol, including NTG provocation in 25 patients.During follow-up lasting 1-2 years in 6 patients syncope recurred (group I) and in 26 patients did not (group II).

Each year at least 300,000 people in the United States and 8000 to 10,000 people in Switzerland suffer from out-of-hospital cardiac arrest, mostly due to ventricular fibrillation. Early defibrillation provides definitive treatment for most of cardiac arrest victims. Semi-automatic external defibrillators are easy to handle devices allowing to deliver an early electric shock and can be successfully used by lay people following minimal training. Newer strategies of defibrillation designed to respond faster to out-of-hospital cardiac arrest, including public access defibrillation, as well as improvement of each link of the chain of survival appears as the best strategy for the management of out-of-hospital cardiac arrest.

Methods: For this purpose, were measured the N-terminal part proANP (1-98) plasma levels in 50 hypertensive patients with a history of paroxysmal atrial fibrillation (PAF) (group A) and in 30 hypertensive patients without previous history of PAF (group B). In 12 patients from group A, NT-proANP levels were measured during the paroxysm of AF. The patients were also assessed with ambulatory ECG and echocardiography. Results: There were no differences between the two groups, A and B, regarding the clinical data and demographic data. Patients on group A had increased both left ventricular mass index and left atrial dimension compared to group B (1154-27 vs 854-19 gr/m 2 and 3.774-0.3 vs 3.514-0.4 cm, respectively, p <0.05 for both cases), while the left ventricular ejection fraction did not differ (65% vs 67%). The NTpro ANP plasma levels were significantly higher in group A than group B (3623.874-3186 vs 1945.394-586.88 fmol/ml, p=0.0004). In addition, NT-pro ANP plasma levels were significantly higher during PAF (8155.9914-3904.72 fmol/ml, p=0.00204). By applying a multivariate model it was revealed that NT-pro ANP levels were significantly and independently associated with PAR Conclusion: NT-pro ANP levels could be a significant and reliable predictive index for the detection of patient prone to the development of PAF in essential hypertensive patients while in sinus rhythm. 758 High plasma levels of BNP or NT-pro-ANP for the detection of hypertensive patients vulnerable to atrial fibrillation?

Driving a motor car has become an essential part of modern life in all developed countries. People who live in remote areas, especially in rural communities, rely upon their vehicles for getting to work, as well as for many other daily activities, such as shopping and going to cultural and social events. Regardless the reason for it, being deprived of the right to drive may therefore represent a serious restriction of lifestyle, is always a major narcissistic wound and may impair social integration.

Keywords: LTS1 Reference LTS-CONF-2001-003View record in Web of Science Record created on 2006-06-14, modified on 2016-08-08