Implantable Atrial Defibrillators

Implantable Atrial Defibrillators. Due to the limited efficacy of antiarrhythmic drugs for atrial fibrillation, several nonpharmacologic therapeutic options have evolved. One of these is an implantable atrial defibrillator. Recent studies have shown that internal atrial defibrillation is feasible with relatively low energies. To date, the optimal electrode configuration involves large surface area catheters in the right atrium and coronary sinus. In humans, atrial defibrillation can generally be achieved with < 2 J using this electrode configuration and a biphasic shock waveform. For shocks < 5 J, there is no significant pathological damage to the atria or coronary sinus. Further investigation is needed to guarantee that atrial defibrillation shocks do not provoke ventricular arrhythmias. Preliminary data suggest that atrial defibrillation shocks synchronized to R waves that are not closely coupled are safe. In addition, the shocks are well tolerated if the shock energy is < 1.5 J. With additional studies to confirm the safety of implantable atrial defibrillators, further reduce shock energy, and improve patient tolerance, an implantable atrial defibrillator can become an acceptable therapy for patients with symptomatic, paroxysmal atrial fibrillation.     

The Development of Platelet Factor 3 Activity by Latex Particles--An Interaction with Plasma

Platelet factor 3 activity of polystyrene latex particles was found to beabsent when the particles were tested without prior incubation with plasma.Following such incubation, the particles developed considerable but suboptimal activity. An interaction between the particles and some plasmacomponent(s) during the incubation period which gives rise to a labile typeof activity has been postulated.

Submitted on July 10, 1963 Accepted on August 6, 1963     

Intra-ocular haemorrhage,a frequent complication of acute promyelocytic leukaemia

We have found a high incidence of ocular haemorrhage in patients with acute promyelocytic leukaemia (APL). We describe a series of seven consecutive cases of APL, five of which developed ocular haemorrhage. There were no consistent detectable abnormalities in coagulation predictive of ocular damage. Ocular haemorrhage occurred despite the use of aggressive blood product support and its incidence was not altered by the use of the anti fibrinolytic agent tranexamic acid or by the use of heparin. Complete spontaneous resolution of the ocular pathology occurred in three of the five cases of ocular haemorrhage and partial recovery occurred in one. The fifth patient required surgical intervention. The mechanisms underlying the coagulopathy associated with APL are poorly understood. We discuss the evidence in support of primary disseminated intravascular coagulation and primary fibrinolysis. A logical approach to the management of the bleeding complications in APL can only follow greater understanding of the underlying pathophysiology.     

Investigation into Causes of Abnormal Cerebral MRI Findings Following PVAC Duty‐Cycled,Phased RF Ablation of Atrial Fibrillation

Asymptomatic Cerebral Lesions with Phased RF. Introduction: Left atrial catheter ablation of the pulmonary veins (PVs) is an established option for patients with atrial fibrillation (AF). Asymptomatic cerebral emboli (ACE) detected by diffusion weighted MRI (DW‐MRI) following AF ablation has been reported at varying rates. This variability may be linked to procedural variables and demographic risk factors. Animal studies with the multielectrode pulmonary vein ablation catheter (PVAC) have identified potential sources of emboli, including air introduced during PVAC introduction, inadequate anticoagulation, and high current densities when the distal (E1) and proximal (E10) electrodes are in contact. We sought to evaluate the incidence, size, and number of DW‐MRI findings with procedural modifications that potentially reduce the embolic load. Methods: Thirty‐seven AF patients (59 ± 10 years, 73% male, all with paroxysmal AF, left atrial [LA] diameter 44 ± 7 mm, left ventricular ejection fraction 57 ± 7%) underwent MRI sequences preceding ablation, within 24 hours postablation, and at 4–6 weeks. During the procedure all patients were on uninterrupted phenprocoumon, an attempted activated clotting time (ACT) level >300 seconds, had the PVAC introduced under saline, and antral ablation was started with a 2:1 bipolar/unipolar mode. Files from the ablation unit (GENius v14.4) were retrospectively analyzed to determine the relationship between E1 and E10 in close proximity and DW‐MRI findings. Results: Post procedure, 10/37 patients (27%) were positive for new DWI cerebral lesions. Nine of 10 patients had a single lesion, and 1/10 patient had 2 lesions. Average lesion size was 3.1 ± 3.9 mm (2–14 mm). One of 10 (10%) had lesions at MRI follow‐up. No neurological symptoms were observed. Eighteen of 37 (49%) of procedures had evidence of E1/E10 interaction. In the subgroup of patients with and without E1 and E10 in close proximity, the DW‐MRI rate was 8/18 (44%) and 2/19 (11%), respectively (P = 0.029). Conclusions: The source of positive DW‐MRI findings in LA ablation involves several factors. Controlling anticoagulation and careful sheath management helps to reduce the number and size of DW‐MRI lesions. With the PVAC catheter, an ablation with the E1 and E10 in close proximity increases the risk of a DW‐MRI finding. In the future, electrodes E1 and E10 should be kept apart to help reduce the incidence of acute ACE. (J Cardiovasc Electrophysiol, Vol. 24, pp. 121‐128, February 2013)     

Acute Effects of Multisite Left Ventricular Pacing on Mechanical Dyssynchrony in Patients Receiving Cardiac Resynchronization Therapy

BackgroundA novel quadripolar left ventricular (LV) pacing lead has the ability to deliver multisite LV pacing (MSLV). We set out to characterize the safety and changes in acute mechanical dyssynchrony with MSLV in cardiac resynchronization therapy (CRT) patients.Methods and ResultsProspective multicenter study in 52 patients receiving CRT. An acute pacing protocol comprising 8 MSLV configurations covering a range of delays was compared with conventional CRT (baseline). Transthoracic tissue Doppler imaging (TDI) was used to measure the standard deviation of time to peak contraction of 12 LV segments (Ts-SD) and delayed longitudinal contraction. No ventricular arrhythmia occurred in any of the 52 patients. Complete TDI datasets were collected in 41 patients. Compared with baseline: 1) The mean Ts-SD was significantly lower for the optimal MSLV configuration (35.3 ± 36.4 vs 50.2 ± 29.1 ms; P < .001); 2) at least 1 MSLV configuration exhibited a significant dyssynchrony improvement in 63% of patients; and 3) the mean number of LV segments with delayed longitudinal contractions was significantly reduced with the optimal MSLV configuration (0.37 ± 7.99 vs 2.20 ± 0.19; P < .001).ConclusionsAcute MSLV was acutely safe, and a proportion of MSLV vectors resulted in a significant reduction in echocardiographic dyssynchrony compared with conventional CRT.     

Virological and Immunological Studies in Patients with Acute Viral Hepatitis

One hundred and seven patients with acute viral hepatitis (AVH) were studied prospectively regarding the viral aetiological agent HAV, HBV and NANB (by exclusion) using radioimmunoassay. Acute HAV infection occurred in 43 patients, and acute HBV infection in 34 patients, while HDS occurred in two patients only. Acute, presumably NANB, infection occurred in 28 patients. Ten out of 28 sera of patients with AHBV infection were positive for smooth muscle antibody by immunofluorescence. Important findings include: (1) presence of delta superinfection in the absence of HBsAg; (2) HBsAg as the only marker in two patients with AHBV infection; (3) concurrent presence of HBsAg and anti-HBsAg in three patients with AHBV infection.