Functional characteristics of human macro-reentry: a study of "pre-excited" circuits by extrastimulus method

The effect of improved conduction in areas of delay was tested during macro-reentry within the His-Purkinje system, in an attempt to separate the role of conduction delay from that of prematurity of the extrastimulus as the key determinant of reentry. Using the right ventricular extrastimulus technique (S1S2 method), both the critical His-Purkinje system delays and the zone of S1S2 intervals causing His-Purkinje system reentry were determined. Then, using a previously described technique of atrioventricular (AV) sequential pacing during the basic drive, the potential site of His-Purkinje system conduction delay was (anterogradely) excited earlier (pre-excitation), as compared with the control S1S2 method. This produced a decrease in retrograde His-Purkinje system delay (S2H2), as compared with the same S1S2 interval during the control method. Changing the degree of pre-excitation at each S1S2 interval allowed for determination of the critical (or shortest) S2H2 delay necessary for His-Purkinje system reentry at each coupling interval. Of importance was the observation that the critical delay was not specific for each case but varied with the prematurity of S2. For example, the critical S2H2 delay required for reentry was actually less at shorter S1S2 intervals as compared with longer S1S2 intervals (from 206 +/- 25 to 187 +/- 20 ms, p less than 0.01). These data suggest that manifestation of reentry is a complex interplay between degree of prematurity and conduction delay. The so-called critical conduction delay can be readily modified by altering the site of block, which in turn may be dependent on prematurity of the extrastimulus.     

Immunoenzymatic visualization of tetrodotoxin (TTX) in Cephalothrix species (Nemertea: Anopla: Palaeonemertea: Cephalotrichidae) and Planocera reticulata (Platyhelminthes: Turbellaria: Polycladida: Planoceridae).

Tetrodotoxin (TTX) was localized as brown color in different tissues of an undescribed species of the nemertean genus Cephalothrix (phylum Nemertea) and a turbellarian Planocera reticulata (phylum Platyhelminthes) on light microscopy by means of a monoclonal anti-TTX antibody. In the Cephalothrix sp., TTX was recognized in the vesicles apically arranged in the bacillary cells in the epidermis, basal lamina, the granular cells in the proboscis epithelium, rhynchocoel epithelium, and the vesicles in the basal portion of the intestinal wall near the blood vessels and rhynchocoel. The excretory system and the ovum also showed positive reaction of TTX antigen-antibody. On the other hand, the hermaphrodite flatworm P. reticulata exhibited TTX antigen-antibody complex only in their ovum. To our knowledge, this is the first experimental effort on micro-distribution of TTX in invertebrates.     

Multiparameter calibration of a natural history model of cervical cancer

The objective of this study was to develop a comprehensive natural history model of human papillomavirus (HPV) and cervical cancer using a two-step approach to model calibration. In the first step, the authors utilized primary epidemiologic data from a longitudinal study of women in Brazil and identified a plausible range for each input parameter that produced model output within the 95% confidence intervals of the data. In the second step, they performed a simultaneous search over all input parameters to identify parameter sets that produced output consistent with data from multiple sources. A goodness-of-fit score was computed for 555,000 unique parameter sets using a likelihood-based approach, and a sample of good-fitting parameter sets was used in the model to illustrate the advantage of the calibration approach by projecting a range of benefits associated with cervical cancer prevention policies. The calibrated model had reasonable fit to the data in terms of duration and prevalence of HPV infection for high-risk types, prevalence of precancerous lesions, and incidence of cancer. The authors found that leveraging primary data from longitudinal studies provides unique opportunities for model parameterization of the unobservable nature of HPV infection and its role in the development of cervical cancer.     

Cost differences between academic and nonacademic hospitals: a case study of surgical procedures

Decreased public funding, a competitive healthcare market, and higher patient care costs have been blamed for the present financial challenges that confront academic health centers. The authors examined the costs associated with graduate medical education, particularly, indirect medical education expenses in the operating room. The results indicate that it is more costly for teaching hospitals to provide surgical care to patients in the operating room. The academic health center's indirect graduate medical expenses only covered a portion of the increased costs. If the missions of academic health centers are perceived as a public good, policy makers must design a system that more appropriately compensates academic health centers for the additional costs associated with surgical procedures in graduate medical education.     

Effectiveness of chemotherapy counselling on self-esteem and psychological affects among cancer patients in Malaysia: Randomized controlled trial

Objectives

The aim of this study was to implement and evaluate the outcomes of chemotherapy counselling based on the “Managing Patients on Chemotherapy” module on self-esteem and psychological affect (anxiety, depression) of cancer patients by pharmacists in ten selected government hospitals in Peninsular Malaysia.

Modulation of conduction and refractoriness in atrioventricular junctional reentrant circuit. Effect on reentry initiated by atrial extrastimulus.

The importance of activation sequence of an atrioventricular junctional reentrant (AVJRe) circuit, before delivery of an extrastimulus, has received little attention in studies concerned with clinical tachycardias. In this study a change in activation sequence was accomplished using bidirectional activation (V-A sequential pacing) during the basic drive (V1A1-V1A1). It was noted that, compared with an atrial extrastimulus (A2) after an atrial drive (A1-A1), earlier activation (by V1 impulse of the V1A1-V1A1 drive) consistently improved conduction, or decreased refractoriness, or both, in the anterograde as well as the retrograde pathway of the AVJRe circuit. In all patients, five with AV nodal reentry and six with Wolff-Parkinson-White syndrome, reentrant tachycardia could be prevented during V-A sequential pacing. In four of eleven patients, reentry was prevented despite achieving the so-called critical atrioventricular nodal delays that had previously caused reentry during control study. This finding suggested that conduction delay necessary for reentry was related to the site of block, which in turn was affected by V-A sequential pacing. We concluded that changing the activation sequence during basic drive modulates conduction and refractoriness in AVJRe circuits, and allows the study of a wide range of electrophysical factors that prevent or permit reentry.     

Does lowering pulmonary arterial pressure eliminate severe functional tricuspid regurgitation? Insights from pulmonary thromboendarterectomy

OBJECTIVES: Because pulmonary thromboendarterectomy (PTE) can result in an immediate reduction in pulmonary artery (PA) pressure, we sought to evaluate the effect of PTE on severe tricuspid regurgitation (TR) without tricuspid annuloplasty. BACKGROUND: Few data exist regarding the frequency and magnitude of functional TR improvement after reduction in PA pressure. METHODS: We identified 27 patients with severe TR, defined by a regurgitant index (RI) >33%, who underwent PTE. The RI, tricuspid annular diameter (TAD), apical displacement of leaflet coaptation, and estimated PA systolic pressure were determined on pre- and post-PTE echocardiograms. Patients were stratified based on resolution (RI < or =33%) or persistence (RI >33%) of severe TR. RESULTS: Comparing pre- and post-PTE echocardiography results, severe TR resolved in 19 of 27 (70%) patients. This group had a more effective PA systolic pressure reduction after PTE (49 +/- 20 mm Hg vs. 32 +/- 16 mm Hg by echocardiography, p = 0.075, and 37 +/- 16 mm Hg vs. 16 +/- 13 mm Hg by catheter measurement, p = 0.004). No difference was observed in TAD, apical displacement of the tricuspid valve, or other features compared with the group with persistent severe TR. There was a trend toward longer hospital stays in the group with persistent severe TR (19 +/- 15 days vs. 14 +/- 9 days; p = 0.55). CONCLUSIONS: After significant PA pressure reduction by PTE, severe functional TR with a dilated annulus may improve without annuloplasty despite dilated tricuspid annulus diameters.