[MRI compatible cardiac pacemakers and implantable cardioverter defibrillators]. / MR kompatibilní kardiostimulátory a implantabilní kardiovertery-defibrilátory.

Implanted cardiac pacemaker (PM) or implantable cardioverter defibrillator (ICD) has been so far considered a contra-indication to magnetic resonance imaging (MRI). In the last few years MRI conditional cardiac implantable electronic devices have been marketed enabling patients undergo MRI under specific conditions. We present current state of the art and provide overview of available MRI conditional devices. Magnetic resonance imaging in these patients should be performed only in cases where the requested information can not be obtained using alternative imaging technique.

Catheter ablation for paroxysmal atrial fibrillation: a randomized comparison between multielectrode catheter and point-by-point ablation.

INTRODUCTION: Catheter ablation for paroxysmal atrial fibrillation is widely used for patients with drug-refractory paroxysms of arrhythmia. Recently, novel technologies have been introduced to the market that aim to simplify and shorten the procedure. AIM: To compare the clinical outcome of pulmonary vein (PV) isolation using a multipolar circular ablation catheter (PVAC group), with point-by-point PV isolation using an irrigated-tip ablation catheter and the CARTO mapping system (CARTO group; CARTO, Biosense Webster, Diamond Bar, CA, USA). METHODS: Patients with documented PAF were randomized to undergo PV isolation using PVAC or CARTO. Atrial fibrillation (AF) recurrences were documented by serial 7-day Holter monitoring. RESULTS: One hundred and two patients (mean age 58 ± 11 years, 68 men) were included in the study. The patients had comparable baseline clinical characteristics, including left atrial dimensions and left ventricular ejection fraction, in both study arms (PVAC: n = 51 and CARTO: n = 51). Total procedural and fluoroscopic times were significantly shorter in the PVAC group (107 ± 31 minutes vs 208 ± 46 minutes, P < 0.0001 and 16 ± 5 minutes vs 28 ± 8 minutes, P < 0.0001, respectively). The AF recurrence was documented in 23% and 29% of patients in the PVAC and CARTO groups, respectively (P = 0.8), during the mean follow-up of 200 ± 13 days. No serious complications were noted in both study groups. CONCLUSIONS: Clinical success rates of PV isolation are similar when using multipolar circular PV ablation catheter and point-by-point ablation with a three-dimensional (3D) navigation system in patients with PAF, and results in shorter procedural and fluoroscopic times with a comparable safety profile.

Superoxide dismutase mimetic tempol inhibits hypoxic pulmonary vasoconstriction in rats independently of nitric oxide production.

Hypoxic pulmonary vasoconstriction (HPV), an important physiological mechanism, is regulated by changes in the production of and interactions among reactive oxygen species (ROS). There is controversy, however, over whether HPV is mediated by an increase or a decrease in ROS production. Also, the role of NO in HPV remains unclear. The aim of this study was to investigate whether the inhibition of HPV by the antioxidant tempol was dependent on the concentration of NO, and how its effect was influenced by increased basal pulmonary vascular tone. In isolated rat lungs, we measured vasoconstrictor responses to acute ventilatory hypoxia before and after administration of tempol during perfusion with or without L-NAME. We found that tempol abolished HPV independently of NO production. When we increased basal vascular tone by K(+)-induced depolarization, we also found that tempol completely inhibited HPV. Our results indicate that inhibition of HPV by the superoxide dismutase mimetic tempol does not depend on either NO production or a decrease in basal vascular tone.