Centrifugal Gradients of Rate and Organization in Human Atrial Fibrillation

Introduction: Animal studies show that atrial fibrillation (AF) may emanate from sites of high rate and regularity, with fibrillatory conduction to adjacent areas. We used simultaneous mapping to find evidence for potential drivers in human AF defined as sites with higher rate and regularity than surrounding tissue.
Materials and Methods: In 24 patients (age 61 ± 10 years; 12 persistent), we recorded AF simultaneously from 32 left atrial bipolar basket electrodes in addition to pulmonary veins (PV), coronary sinus, and right atrial electrodes. We measured AF cycle length (CL) by Fourier transform and electrogram regularity at each electrode, referenced to patient-specific atrial anatomy.
Results: We analyzed 10,298 electrode-periods. Evidence for potential AF drivers was found in 11 patients (five persistent). In persistent AF, these sites lay at the coronary sinus and left atrial roof but not PVs, while in paroxysmal AF six of nine sites lay at PVs (P < 0.05). During ablation, a subset of patients experienced AF CL prolongation or termination with a focal lesion; in each case this lesion mapped to potential driver sites on blinded analysis. Conversely, sequential mapping failed to reveal these sites, possibly due to fluctuations in dominant frequency at driver locations in the context of migratory AF.
Conclusions: Simultaneous multisite recordings in human AF reveal evidence for drivers that lie near PVs in paroxysmal but not persistent AF, and were sites where ablation slowed or terminated AF in a subset of patients. The future work should determine if real-time ablation of AF-maintaining regions defined in this fashion eliminates AF.     

Construction and psychometric evaluation of the Swedish language Person-centred Climate Questionnaire – staff version

Aim  The aim of the study was to construct and evaluate psychometric properties of the Swedish language Person-centred Climate Questionnaire – staff version.
Background  Person-centred care is often quoted but ill defined, and the literature warrants the development of valid and reliable measurement tools.
Methods  During 2006, a questionnaire was constructed and distributed to a sample of Swedish hospital staff ( n  = 600). Questionnaire data was subjected to item analysis and reduction. Psychometrical properties of the questionnaire were evaluated.
Results  The 14-item Person-centred Climate Questionnaire showed satisfactory psychometric properties. Measures of validity were good, internal consistency was high, Cronbach's alpha was satisfactory for the total scale (0.88) and test–retest reliability was adequate.
Conclusion  The results indicate that the staff Person-centred Climate Questionnaire is a valid and reliable tool for assessing staff perceptions of the person centredness of hospital environments.
Implications for nursing management  This instrument makes it possible to study the degree of person-centredness in relation to different organizational systems, environments, staff groups and managerial styles. In addition, staff variables such as turnover rates, health outcomes and efficacy can be related to staff perceived person centredness of the organization.     

Implantable Cardioverter Defibrillator Therapy for Primary Prevention of Sudden Cardiac Death after Myocardial Infarction:

Study Objective: To estimate the proportion of patients eligible for implantable cardioverter defibrillator (ICD) therapy for the primary prevention of sudden cardiac death after a myocardial infarction (MI), according to the current guidelines.
Methods: Eligibility was assessed retrospectively at 6 weeks in 513 post-MI survivors (age 66 ± 13 years, left ventricular ejection fraction 48.2 ± 17%) on the basis of an electrocardiogram and an echocardiogram.
Results: LVEF was ≤ 40% in 37% and ≤ 35% in 30%, and QRS duration was <120 ms in 89% and ≥120 ms in 11% of patients. The proportion of post-MI patients meeting the criteria set by guidelines were 37% for 2006 American College of Cardiology/American Heart Association/European Society of Cardiology (ACC/AHA/ESC) 26.5% for 2008 ACC/AHA/Canadian Heart Rhythm Society 16.3% for 2005 US Centers for Medicare and Medicaid Services (CMS), and 5.8% for the 2006 United Kingdom (UK) National Institute of Clinical Excellence (NICE). According to 2005 CMS and 2006 UK-NICE guidelines, Holter monitoring was required in 7% and 18%, respectively. For the United States (700,000 MI in 2006), the 2006 ACC/AHA/ESC guidelines equate to 216,783 ICD implantations/year. For UK (60,499 MI in 2006), the 2006 NICE guidelines equate to 2,941 ICD implantations, 10,488 Holter studies, and 1,065 VT induction tests/year.
Conclusions: Current ICD therapy guidelines for primary prevention of SCD post-MI demand a substantial increase in service provision worldwide.     

Do Permanent Pacemakers Need an Insulative Coating? Results of a Prospective Randomized Double-Blind Study

During conventional manufacturing of implanted pulse generators (IPGs), an insulative coating is often applied to prevent local muscle stimulation and myopotential sensing in unipolar pacing. This can limit the orientation of the IPG into its pocket, be a potential source of muscle stimulation via coating scratches, and result in an increase in IPG production costs. We hypothesized that advances in the design and construction of current IPCs and leads obviates the need for an insulative coating of the IPG. Using a double-blind prospective randomized design, 39 patients were implanted with either coated or uncoated otherwise identical IPGs (19 dual, 20 single chamber). All testing was done in unipolar and bipolar mode in both channels. A strength-duration curve for muscle stimulation was constructed for all patients with muscle stimulation. Myopotential sensing was established during isometric exercise. At 6-month follow-up when tested in unipolar mode, 3 of 15 (20%) patients with coated IPCs and 3 of 20 (15%) with uncoated IPCs had muscle stimulation at 5.0 V/ 1.5 ms or lower (P = NS). No patients in either population had muscle stimulation at their normally programmed output. Myopotential sensing occurred in all patients in unipolar mode at a mean of 2.29 ± 1.3 mV and 2.73 ± 1.14 mV for coated versus uncoated, respectively (P = NS). The statistical power of these negative observations was 80%. An insulative coating for pacemakers does not appear to alter sensing performance or cause a significant difference in the occurrence or characteristics of muscle stimulation.     

Hemodynamic Effects and Clinical Determinants of Defibrillation Threshold for Transvenous Atrial Defibrillation Using Biatrial Biphasic Shocks in Patients with Chronic Atrial Fibrillation

We assessed the relationship between the hemodynamic changes and shock intensity in transvenous atrial defibrillation for chronic AF. The correlation between the clinical profile and atrial DFT and the factors predicting maintenance of SR after successful defibrillation were also investigated. Atrial defibrillation using entirely transvenoas leads has been investigated as an alternative means of managing patients with AF. However, the hemodynamic consequence of this technique and the clinical factors predicting defibrillation efficacy have not been evaluated. Thirty-seven patients with chronic AF (4 weeks to 60 months) underwent transvenoas atrial defibrillation. Defibrillation was performed by delivering R wave synchronized, biphasic (3/3 ms) shocks with step-up voltages (20–400 V) between defibrillation catheters in the anterolateral right atrium and the distal coronary sinus. Clinical profile of the patients, the DFT, arterial blood pressure, and RH interval during defibrillation and the 6-month recurrence rate were determined. SR was restored in 33 (89%) of 37 patients and the DFT was 3.7 ± 1.4 J (317 ± 58 V). Transvenous atrial defibrillation resulted in a mild reduction in blood pressure (6 ± 10 mmHg), but substantial prolongation of longest postshock RR intervals (507 ± 546 ms), which were significantly related to the shock intensity (r = 0.5, P < 0.001). There was no ventricular proarrhythmia. The patients'age, body weight, duration of AF, left atrial diameter, and ejection fraction were not related to the success of defibrillation, not the 6-month maintenance rate of SR (39%). However, the patients'age was related to DFT. Apart from transient reduction in blood pressure and shock related pauses that may require backup pacing, transvenous biatrial defibrillation was a highly effective and well-tolerated technique. The absence of clinical determinant for successful defibrillation suggests that restoring SR by transvenous atrial defibrillation could be attempted in most patients with chronic AF.     

The Effect of Biphasic Waveform Tilt in Transvenous Atrial Defibrillation

Atrial defibrillation can be accomplished using low energy shocks and transvenous catheters. The biphasic waveform tilt required to achieve optimal atrial defibrillation thresholds (ADFTs) is, however, not known. The effect of single capacitor biphasic waveform tilt modification on ADFT was assessed in 20 patients. Following AF induction the defibrillation pulses were delivered between the catheters positioned in the coronary sinus and the right atrium.
The single capacitor biphasic waveform shocks, delivered over the same pathways, consisted of 65% tilt (65/65 biphasic waveform) to produce an overall tilt of 88%, or 50% tilt (50/50 biphasic waveform) to produce an overall tilt of 75%. Although 65/65 biphasic waveform delivers more energy, the shorter duration 50/50 biphasic waveform reduced stored energy ADFT 21%, from 1.34 ± 0.82 J with 65/65 biphasic to 2.06 ± 0.81 J. These differences were not statistically significant. Nine patients had lower ADFT with 50/50 biphasic waveform while five patients had lower ADFT with 65/65 biphasic waveform. Equivalent reduction in ADFT was seen in the remaining six patients. The ADFT was 0.83 ± 0.65 J when both tilts were considered. In conclusion, biphasic waveform tilt modification may affect the ADFT in an individual patient. The optimal biphasic waveform for ADFT is not known.     

The Retrogastric Transventricular Approach for Drainage of the "Supragastric" Pancreatic Pseudocyst

The majority of pancreatic pseudocysts develop in a retrogastric situation and are amenable to transgastric cystogastrostomy through the anterior gastric wall. We have encountered two pseudocysts in an unusual situation, in which adherence of the anterior gastric wall to the anterior parietal peritoneum precluded this approach. A retrogastric exposure through the lesser sac allowed for the creation of a cystogastrostomy through the superior aspects of the anterior and posterior gastric walls, adjacent to the lesser curvature of the stomach. This type of drainage is successful despite the theoretical failure to satisfy the dictum of dependent drainage.     

T Lymphocyte Subsets in Parenteral and Non-parenteral Heroin Abusers in Britain

Parenteral drug abusers comprise the second largest group of patients with the acquired immune deficiency syndrome (AIDS). To determine whether heroin abusers in Britain had immunologic abnormalities similar to those seen in AIDS, we determined T lymphocyte subsets in 14 parenteral heroin abusers and 10 non-parenteral heroin abusers. No significant differences were found in T4/T8 ratios or in the absolute numbers of T3, T4, or T8-positive cells. These results suggest that neither narcotic drugs nor repeated exposure to unsterile injectable substances are responsible for low T4/T8 ratios in parenteral drug abusers with AIDS.