1,721,017 research outputs found
Far-field oversensing of atrial signals: an unusual cause for very short V-V intervals and inappropriate implantable cardioverter defibrillator therapy
No full textInappropriate implantable cardioverter-defibrillator therapy during exercise: What is the mechanism?
No full textObstructive sleep apnea and coronary artery disease
No full textIn the recent years intensive research has revealed numerous negative consequences of obstructive steep apnea (OSA) for the cardiovascular system. The pathophysiological interaction between OSA and coronary artery disease is complex and comprises neural, humoral, mechanical and haemodynamic components. One of the most important effects of OSA is an increase of sympathetic nerve traffic, which persists during the day and is thought to play a key role in the association of OSA and elevated systemic blood pressure. Nowadays, OSA is accepted as an independent risk factor for arterial hypertension. Several investigations support an association of OSA with ischemic ST-segment changes, ventricular arrhythmias, and sudden cardiac death. In line with this, a growing body of evidence strongly supports OSA having prognostic implications for cardiovascular morbidity and mortality. Continuous positive airway pressure (CPAP) has been shown to have several beneficial effects on the cardiovascular system. Uncontrolled studies indicate that it reduces cardiovascular risk in patients with severe OSA and increased risk or manifest coronary artery disease. However, ongoing studies still have to confirm this. (C) 2007 Elsevier Ltd. All rights reserved
Unusual cause for an increase of the sensing integrity counter in a patient with inappropriate implantable cardioverter-defibrittator therapy
No full textWe describe the case of a patient who presented with multiple implantable cardioverter-defibrillator (ICD) shock discharges 12 months after device implantation. Upon device interrogation, intermittent oversensing of electrical noise and potential ICD lead failure were suggested by a significant increase in the sensing integrity counter (SIC), a cumulative count of very short ventricular sensed intervals. Analysis of stored episodes, however, revealed that inappropriate ICD therapy had been caused by intermittent T-wave oversensing (TWO), and that the increase of the SIC resulted from the coincidence of TWO and premature ventricular complexes (PVCs). T-wave oversensing resolved and the SIC did not increase any more during follow-up after adjustment of ventricular sensitivity. The coincidence of TWO and PVCs should therefore be considered as an uncommon cause for short ventricular sensed intervals in ICD patients presenting with a suspect increase in the SIC
Restoration of blunted force-frequency-relationship by cardiac resynchronization in patients with severe chronic heart failure
No full textRemote Magnetic Catheter Navigation for Cavotricuspid Isthmus Ablation in Patients With Common-Type Atrial Flutter
No full textBackground-Conventional catheter ablation of cavotricuspid isthmus (CTI)-dependent atrial flutter is a widely applied standard therapy. Remote magnetic catheter navigation (RMN) may provide benefits for different ablation procedures, but its efficacy for CTI ablation has not been evaluated in a randomized, controlled trial. Methods and Results-Ninety patients undergoing de novo ablation of atrial flutter were randomly assigned to conventional manual (n = 45) or RMN-guided (n = 45) CTI ablation with an 8-mm-tip catheter. Complete bidirectional isthmus block was achieved in 84% (RMN) and 91% (conventional catheter ablation) of the cases (P = 0.52). RMN was associated with shorter fluoroscopy time (median, 10.6 minutes; interquartile range [IQR], 7.6 to 19.9, versus 15.0 minutes; IQR, 11.5 to 23.1; P = 0.043) but longer total radiofrequency application (17.1 minutes; IQR, 8.6 to 25, versus 7.5 minutes; IQR, 3.6 to 10.9; P 20 minutes) or unsuccessful ablation. Conclusions-RMN-guided CTI ablation is associated with reduced radiation exposure but prolonged ablation and procedure times as compared with conventional catheter navigation. Our findings suggest that ablation lesions produced with an RMN-guided 8-mm catheter are less effective irrespective of CTI anatomy
Subthreshold test pulses versus low energy shock delivery to estimate high energy lead impedance in implanted cardioverter defibrillator patients
No full textThe high energy lead impedance is valuable for detecting lead failure in ICDs, but until recently shock delivery was necessary for high energy impedance measurement. This study compared the use of subthreshold test pulses and low energy test shocks to estimate the high energy impedance. Immediately after implantation of Ventak Prizm ICDs in 29 patients, the lead impedance was measured with five subthreshold (0.4 muJ) test pulses, 5 low energy (1.1 J) shocks, and two to three high energy (16 +/- 4.5 J) shocks. The mean impedances measured using high energy shocks, low energy shocks, and subthreshold pulses were 42.0 +/- 7.3 Omega, 46.5 +/- 8.1 Omega, and 42.4 +/- 7.1 Omega, respectively. The impedances measured using high and low energy shocks differed significantly (P < 0.0001), while those obtained by high energy shocks and low energy pulses did not (P = 0.63). According to-the Pearson correlation coefficient, the impedance measurements with subthreshold pulses and low energy shocks were both closely correlated (P < 0.0001) with impedance values determined with high energy shocks. However, while the impedance values tended to be higher when measured with low energy shocks, the concordance correlation coefficient (c) was higher for subthreshold test pulse versus high energy shock (c = 0.92) than for low versus high energy shock (c = 0.73). Furthermore, the intraindividual variability of impedance measurements was lower with subthreshold pulse measurements than with low energy shocks. Compared with low energy shocks, impedance measurement with subthreshold pulses has higher reproducibility and a higher correlation with the impedance obtained by high energy shock delivery. Safe and painless high energy impedance estimation with subthreshold pulses might, therefore, help to detect ICD lead failure during routine follow-up
Thromboembolism in Atrial Fibrillation
No full textThromboembolism is a severe complication in atrial fibrillation. This overview presents thromboembolic disease as a single entity, ranging from stroke through mesenteric ischemia to acute limb ischemia. The PubMed, Embase, and Cochrane databases were systematically searched for the terms "atrial fibrillation" and "thromboembolism" in reports published from January 1986 to September 2009. The information of 10 evidence-based practice guideline documents and 61 further sources was systematically extracted. In atrial fibrillation, the average annual stroke risk is increased by 2.3% (lethality 30%). The annual incidence of acute mesenteric ischemia is 0.14% (lethality 70%), and that of acute limb ischemia is 0.4% (lethality 16%). In total, approximately 80% of embolism-related deaths are from stroke and 20% from other systemic thromboembolism. The ischemic symptoms generally have an acute onset but may mimic other diseases, particularly in mesenteric ischemia. Early diagnosis and treatment can limit or even prevent tissue infarction. Guideline-recommended therapy with aspirin or warfarin reduces the thromboembolic risk. Suitable patients may optimize their warfarin therapy by self-monitoring of the international normalized ratio (INR). New oral and parenteral anticoagulants with more stable pharmacokinetics are being developed. In conclusion, atrial fibrillation predisposes to thromboembolism. If ischemic stroke or systemic thromboembolism occurs, early diagnosis and treatment can improve outcomes. The thromboembolic risks are reduced by guideline-adherent antithrombotic therapy with warfarin or aspirin. Future directions may include self-monitoring of the international normalized ratio and novel anticoagulants. (C) 2010 Elsevier Inc. All rights reserved. (Am J Cardiol 2010;105:502-510
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