Localization of the origin of arrhythmias for ablation: from Electrocardiography to advanced endocardial mapping systems

Radiofrequency catheter ablation techniques have had a dramatic impact on the treatment of a variety of cardiac arrhythmias. However, catheter ablation of complex arrhythmias, such as intra-atrial reentry, ventricular tachycardias, and atrial fibrillation, continues to pose a major challenge. This stems from limitations of fluoroscopy and conventional catheter-based mapping techniques that limit the accurate anatomic localization of complex arrhythmogenic substrates. In this article, ECG features of complex arrhythmias are reviewed, which may facilitate the planning of an ablation procedure. The physical principles of the newly available catheter-based endocardial mapping techniques and their clinical applicability for treatment of complex arrhythmias are discussed. The role of intracardiac echocardiography to facilitate mapping and ablation is reviewed.

Catheter ablation of ventricular tachycardia in patients with structural heart disease

Radiofrequency catheter ablation has revolutionized therapy of most forms of supraventricular tachycardia and ventricular tachycardia in the absence of structural heart disease by providing arrhythmia cure in almost 90% of patients. However, this treatment has not been nearly as successful in patients with ventricular tachycardia in the setting of structural heart disease, because of a number of factors. Some of these limitations are technical (imprecise mapping tools, multiple regions requiring ablation) although others are patient-related (hemodynamic instability during arrhythmia, progression of disease process). Because of these and other factors, the majority of patients in this group are treated with implantable defibrillators. Ablative therapy has an adjunctive role in their management, mainly to decrease the frequency of device therapy (particularly shocks). This review will discuss mapping and ablation techniques as well as patient selection and evaluation for this procedure.

Pulsed electron avalanche knife (PEAK) for intraocular surgery

PURPOSE

To develop a better and more economical instrument for precise, tractionless, "cold" cutting during intraocular surgery. The use of highly localized electric fields rather than laser light as the means of tissue dissection was investigated.

METHODS

A high electric field at the tip of a fine wire can, like lasers, initiate plasma formation. Micrometer-length plasma streamers are generated when an insulated 25 micron (microm) wire, exposed to physiological medium at one end, is subjected to nanosecond electrical pulses between 1 and 8 kV in magnitude. The explosive evaporation of water in the vicinity of these streamers cuts soft tissue without heat deposition into surrounding material (cold cutting). Streamers of plasma and the dynamics of water evaporation were imaged using an inverted microscope and fast flash photography. Cutting effectiveness was evaluated on both polyacrylamide gels, on different tissues from excised bovine eyes, and in vivo on rabbit retina. Standard histology techniques were used to examine the tissue.

RESULTS

Electric pulses with energies between 150 and 670 microJ produced plasma streamers in saline between 10 and 200 microm in length. Application of electric discharges to dense (10%) polyacrylamide gels resulted in fracturing of the gel without ejection of bulk material. In both dense and softer (6%) gels, layer by layer shaving was possible with pulse energy rather than number of pulses as the determinant of ultimate cutting depth. The instrument made precise partial or full-thickness cuts of retina, iris, lens, and lens capsule without any evidence of thermal damage. Because different tissues require distinct energies for dissection, tissue-selective cutting on complex structures can be performed if the appropriate pulse energies are used; for example, retina can be dissected without damage to the major retinal vessels.

CONCLUSIONS

This instrument, called the Pulsed Electron Avalanche Knife (PEAK), can quickly and precisely cut intraocular tissues without traction. The small delivery probe and modest cost make it promising for many ophthalmic applications, including retinal, cataract, and glaucoma surgery. In addition, the instrument may be useful in nonophthalmic procedures such as intravascular surgery and neurosurgery.

The amblyopia treatment study visual acuity testing protocol

OBJECTIVE

To evaluate the reliability of a new visual acuity testing protocol for children using isolated surrounded HOTV optotypes.

METHODS

After initial pilot testing and modification, the protocol was evaluated using the Baylor-Video Acuity Tester (BVAT) to present isolated surrounded HOTV optotypes. At 6 sites, the protocol was evaluated for testability in 178 children aged 2 to 7 years and for reliability in a subset of 88 children. Twenty-eight percent of the 178 children were classified as having amblyopia.

RESULTS

Using the modified protocol, testability ranged from 24% in 2-year-olds to 96% in 5- to 7-year-olds. Test-retest reliability was high (r = 0.82), with 93% of retest scores within 0.1 logMAR unit of the initial test score. The 95% confidence interval for an acuity score was calculated to be the score +/-0.125 logMAR unit. For a change between 2 acuity scores, the 95% confidence interval was the difference +/-0.18 logMAR unit.

CONCLUSIONS

The visual acuity protocol had a high level of testability in 3- to 7-year-olds and excellent test-retest reliability. The protocol has been incorporated into the multicenter Amblyopia Treatment Study and has wide potential application for standardizing visual acuity testing in children.

A statistical approach to an outbreak of endophthalmitis following cataract surgery at a hospital in the West of Scotland

The number of cases of endophthalmitis following cataract surgery caused considerable concern in a West of Scotland hospital throughout 1998 and early 1999. A multi-disciplinary team including infection control nurses, doctors, public health officials,epidemiologists and statisticians was set up to investigate the situation. This paper examines the statistical issues surrounding the investigation. A method based on the Poisson distribution showed that the number of cases was significantly higher than expected. Fisher's Exact Test and Logistic Regression were then applied to the data from two related case control studies. These analyses showed that a higher risk of endophthalmitis was associated with being female, having a vitrectomy or having a previous history of respiratory disease. Finally, a method was devised to enable staff to recognize more quickly when the number of cases of endophthalmitis was becoming higher than expected. The method should find application in other clinical situations where the probability of rare events is known.

Biofilm formation by gram-negative bacteria on central venous catheter connectors: effect of conditioning films in a laboratory model

Human blood components have been shown to enhance biofilm formation by gram-positive bacteria. We investigated the effect of human blood on biofilm formation on the inner lumen of needleless central venous catheter connectors by several gram-negative bacteria, specifically Enterobacter cloacae, Pseudomonas aeruginosa, and Pantoea agglomerans. Results suggest that a conditioning film of blood components promotes biofilm formation by these organisms in an in vitro system.

Vancomycin resistance among strains of Staphylococcus epidermidis: effects on adherence to silicone

Nosocomial device-related infections with Gram-positive cocci and their resistance to vancomycin are of increasing occurrence. We examined clinical isolates of relatively avirulent coagulase-negative staphylococci for their resistance to vancomycin and for their capabilities to adhere in vitro to medical grade silicone. Vancomycin resistance was found in 9 of 20 isolates, but there was no correlation between adherence capacity to silicone in the absence of vancomycin and vancomycin resistance for a given strain. Vancomycin in the medium, adsorbed to the surface of medical grade silicone or adsorbed on nongrowing cells, reduced adherence of representative Staphylococcus epidermidis to medical grade silicone.

Preventing experimental vertical transmission of scrapie by embryo transfer

This study investigated whether the transmission of naturally occurring scrapie in sheep can be prevented using embryo transfer. Embryos were collected from 38 donor ewes in a Suffolk sheep flock with a high incidence of naturally occurring scrapie, treated with a sanitary procedure (embryo washing) recommended by the International Embryo Transfer Society and then transferred to 58 scrapie-free recipient ewes. Ninety-four offspring were produced. None of the offspring or the recipient ewes developed scrapie. Furthermore, offspring derived from embryos collected from donor ewes bred to the immunohistochemically positive ram did not develop scrapie. We conclude that scrapie was not transmitted to offspring via the embryo nor was the infective agent transmitted to recipient ewes during embryo transfer procedures.

Electrospray ionization mass spectrometry of tribenzyltin substituted-phenoxyacetate compounds

Hydrolysis products of organotin compounds RC(6)H(4)OCH(2)COOSn(CH(2)ph)(3) (R = o-NO(2), 1; m-NO(2), 2; p-NO(2), 3; o-CH(3), 4; o-OCH(3), 5; o-Cl, 6; o-Br, 7) and RC(6)H(3)OCH(2)COOSn(CH(2)ph)(3) (R = o,o-2CH(3), 8, o-OCH(3), p-CHO, 9; o,p-2Cl, 10), produced in aqueous acetonitrile solution, have been investigated by electrospray mass spectrometry (MS) and MS(n) techniques. The complexes [Y(2)SnXR'](-), [Y(3)SnXR'](-), [Y(3)SnX(2)R'](-), [Y(2)SnX(3)R'](-), and fragment ions of [Y(3)SnR'](-), plus abundant RC(6)H(4)(or RC(6)H(3))OCH(2)COO(-) and RC(6)H(4)(or RC(6)H(3))O(-) ions are observed in negative mode, whereas the protonated molecular ion [M + H](+), complexes [Y(2)SnXR'](+), [Y(3)SnXR'](+), [Y(2)SnX(2)R'](+), [Y(3)SnX(2)R'](+), [Y(2)SnX(3)R'](+), [Y(3)SnX(3)R'](+), as well as [YSnXR'](+), [M - CH(2)ph](+), XSn(+), (phCH(2))(3)Sn(+), phCH(2)Sn(+) (Y = &bond;CH(2)ph, X = &bond;OOCCH(2)OC(6)H(4)R(or C(6)H(3)R)) are detected in the positive mode. Water adduct ions are seen in both modes. The assignments are facilitated by agreement between observed and calculated isotopic patterns and tandem mass spectrometry studies.

Knowing and not knowing. Some thoughts about insight

This paper examines the concept of insight from the point of view that insight is about knowing. As a process it is how one comes to know, and as a construct it is what becomes known. Utilizing detailed clinical material from the analysis of a young girl, the paper approaches this issue by asking. How did Amy go about knowing? The multifaceted analytic relationship, the dimensions of change, and the analyst's technique are highlighted.

Mechanisms underlying the reentrant circuit of atrioventricular nodal reentrant tachycardia in isolated canine atrioventricular nodal preparation using optical mapping

The reentrant pathways underlying different types of atrioventricular (AV) nodal reentrant tachycardia have not yet been elucidated. This study was performed to optically map Koch's triangle and surrounding atrial tissue in an isolated canine AV nodal preparation. Multiple preferential AV nodal input pathways were observed in all preparations (n=22) with continuous (73%, n=16) and discontinuous (27%, n=6) AV nodal function curves (AVNFCs). AV nodal echo beats (EBs) were induced in 54% (12/22) of preparations. The reentrant circuit of the slow/fast EB (36%, n=8) started as a block in fast pathway (FP) and a delay in slow pathway (SP) conduction to the compact AV node, then exited from the AV node to the FP, and rapidly returned to the SP through the atrial tissue located at the base of Koch's triangle. The reentrant circuit of the fast/slow EB (9%, n=2) was in an opposite direction. In the slow/slow EB (9%, n=2), anterograde conduction was over the intermediate pathway (IP) and retrograde conduction was over the SP. Unidirectional conduction block occurred at the junction between the AV node and its input pathways. Conduction over the IP smoothed the transition from the FP to the SP, resulting in a continuous AVNFC. A "jump" in AH interval resulted from shifting of anterograde conduction from the FP to the SP (n=4) or abrupt conduction delay within the AV node through the FP (n=2). These findings indicate that (1) multiple AV nodal anterograde pathways exist in all normal hearts; (2) atrial tissue is involved in reentrant circuits; (3) unidirectional block occurs at the interface between the AV node and its input pathways; and (4) the IP can mask the existence of FP and SP, producing continuous AVNFCs.

Prospective comparison of the startle test (recoil) and non-stress test

OBJECTIVE

Our purpose was to compare fetal heart rate reaction to external physical stimulation with the non-stress test (NST).

METHODS

This was a prospective study evaluating documentation of fetal heart accelerations by two methods. The standard NST was performed prior to the ultrasound evaluation. The NST results were not available to the ultrasonographer. M-mode ultrasound was used to establish a stable fetal heart rate. The ultrasound transducer was used to stimulate fetal movement by indentations of the uterus over the fetal small parts. A second fetal heart rate was determined within 15 s after stimulation.

RESULTS

A total of 122 patients had 159 studies performed. The fetal heart rate range due to fetal startle (recoil) was -22 to 14 (median of 3) in the 45 fetuses with non-reactive NSTs and 1 to 38 (median of 15) in the 114 fetuses with a reactive NST (p <0.001). A receiver operating curve comparing the fetal response to the startle and the NST revealed an area under the curve of 0.972, consistent with high specificity and sensitivity.

CONCLUSION

The fetal heart rate response to external stimulation correlates with the formal NST.

Gambling as an addictive disorder among athletes: clinical issues in sports medicine

This article examines the role of gambling as an addictive disorder experienced by athletes, both college and professional. Gambling may often be seen as a comorbid factor with other addictions and with depression among athletes. The focus on addictions among athletes has gained considerable attention among sports medicine clinicians. Diagnostic indicators, risk and protective factors, and a stage model of addiction among athletes are addressed. An algorithm and pathway of care for athletes with an addictive disorder is offered as are recommendations that sports physicians, sports medicine specialists, coaches and counsellors need to address athletes who have an addictive disorder.

Resistance of cattle to scrapie by the oral route

Early epidemiological information indicated that bovine spongiform encephalopathy (BSE) originated from scrapie in sheep. The question arose if scrapie in North America would induce a BSE-like disease in cattle. Six years ago, we reported that brain tissue from sheep with scrapie caused a neurologic disease when injected directly into the brains of cattle, but the disease induced was different from BSE as it occurs in the United Kingdom and Europe. Here, we report that cattle fed raw brain or meat and bone meal and tallow prepared from sheep with scrapie remained normal for 8 years after exposure. This work indicates that cattle are highly resistant to North American scrapie by the oral route.

serpent, a GATA-like transcription factor gene, induces fat-cell development in Drosophila melanogaster

The GATA-like transcription factor gene serpent is necessary for embryonic fat-cell differentiation in Drosophila (Sam, S., Leise, W. and Hoshizaki, D. K. (1996) Mech. Dev. 60, 197–205) and has been proposed to function in a cell-fate choice between fat cell and somatic gonadal precursors (Moore, L. A., Broihier, H. T., Van Doren, M. and Lehmann, R. (1998) Development 125, 837–44; Riechmann, V., Irion, U., Wilson, R., Grosskortenhaus, R. and Leptin, M. (1997) Development 124, 2915–22). Here, we report that deregulated expression of serpent in the mesoderm induces the formation of ectopic fat cells and prevents the migration and coalescence of the somatic gonadal precursors. The ectopic fat cells do not arise from hyperproliferation of the primary fat-cell clusters but they do associate with the endogenous fat cells to form a fat body that is expanded in both the dorsal/ventral and anterior/posterior axes. Misexpression of serpent also affects the differentiation of muscle cells. Few body-wall muscle precursors are specified and there is a loss of most body-wall muscle fibers. The precursors of the visceral mesoderm are also absent and concomitantly the visceral muscle is absent. We suggest that the ectopic fat cells might originate from cells that have the potential, but do not normally, differentiate into fat cells or from cells that have acquired a fat-cell fate. In light of our results, we discuss the role of serpent in fat-cell specification and in cell fate choices.

Comparison of preschool vision screening methods in a population with a high prevalence of astigmatism

PURPOSE

To compare the effectiveness of four methods of screening 3- to 5-year-old children for astigmatism high enough to require spectacle correction.

METHODS

Lea Symbols Visual Acuity Screening (LSVAS), MTI Photoscreening (MTIPS), Nidek KM-500 Keratometry Screening (KERS), and Retinomax K-Plus Noncycloplegic Autorefraction Screening (NCARS) were attempted on 379 preschool children who are members of a Native American tribe having a high prevalence of astigmatism that is primarily corneal in origin. The need for spectacle correction was determined by cycloplegic refraction. Receiver Operating Characteristic (ROC) curves were fit, confidence intervals were determined, and area under the curves was compared.

RESULTS

Astigmatism > or = 1.00 D was present in the right eye of 47.5% and in the left eye of 48.0% of children. Spectacles were prescribed for children < 48 months of age who had cylinder > or = 2.00 D and children > or = 48 months who had cylinder > or = 1.50 D, with the result that 33% of subjects required spectacles. Area under the ROC curve was 0.98 for NCARS, 0.92 for KERS, 0.78 for MTIPS, and 0.70 for LSVAS, and each of these values differed significantly from the other three (all P < 0.007). Testability was significantly higher for NCARS (99.5%) and KERS (99.7%) than for MTIPS (93.5%) and LSVAS (92.0%).

CONCLUSIONS

In a population that included many children with astigmatism, objective, fully automated screening methods (NCARS and KERS) were superior to both visual acuity screening and photoscreening with subjective interpretation in identifying children who had astigmatism requiring spectacle correction.

Central clinical research issues in electrophysiology: report of the NASPE Committee

This article contains the results of an attempt by appointed members of the North American Society of Pacing and Electrophysiology to define the research frontier in electrophysiology and suggest areas of study as an aid in setting the research agenda.

Is knowledge about signs and symptoms of preterm labor related to low birth weight?

The intent of this study was to explore the relationship of patient knowledge about the signs and symptoms of preterm labor and low birth weight. To this end, 538 women were interviewed in the postpartum period. Five aspects of preterm labor knowledge (abdominal tightness, vaginal discharge, cramping, diarrhea, and bleeding) were sought, along with standard demographic information. Data were analyzed as dichotomous variables and compared using odds ratios. Logistic regression was chosen to calculate adjusted odds ratios, including only those factors found to be associated with low birth weight. Patient knowledge of each varied from 46 to 87% for the five items. Only one third knew all five areas. Knowledge of the importance of abdominal tightness, vaginal discharge, and cramping were associated with a reduction in low birth weight, as was knowledge of all five aspects. However, regression analysis failed to support a significant association with any of the five areas alone or when considered as a group. The low sensitivity of the relationship between patient knowledge and low birth weight and the lack of correlation after regression suggest that programs focusing on enhanced patient education may have limited benefits.

Diagnosis of preclinical and subclinical scrapie in a naturally infected sheep flock utilizing currently available postmortem diagnostic techniques

Scrapie is a naturally occurring transmissible encephalopathy of sheep and goats. Currently available methods for diagnosis are the presence of characteristic histopathologic changes and detection of an abnormal form of prion protein (PrPres) in the brains of affected animals. This study documents preclinical and subclinical scrapie in a flock of 16 sheep utilizing histopathology, immunohistochemistry (IHC), western blot, and electron microscopy (for scrapie-associated fibrils) for confirmation of the disease. Prior to necropsy, none of the sheep showed signs of clinical scrapie. Based on the results of histopathology and positive PrPres tests, 3 ewes were found to have subclinical scrapie. An additional ewe, which did not have histopathologic changes in the brain but was positive by IHC and western blot,was considered a preclinical case of scrapie. None of the sheep had amyloid in the brain stem.

Effects of an external nasal dilator on the work of breathing during exercise

PURPOSE

The effect of an external nasal dilator on the work of breathing (WOB) was measured during exercise in 14 untrained college students (age, 23 +/- 2.7 yr).

METHODS

Two maximal, incremental ergometer tests were performed to exhaustion. Subjects wore a placebo or an active nasal dilator strip, in random order, during each test. An esophageal balloon was placed through each of the subject's mouth into the esophagus for measurement of inspiratory elastic work (INEW), inspiratory resistive work (INRW), and expiratory resistive work (EXRW). Subjects breathed through a Hans Rudolph(R) face mask that covered both the mouth and nose during both tests. Measured variables included oxygen uptake (VO2), ventilation (VE), tidal volume (VT), frequency of breathing (f), INEW, INRW, and EXRW (work expressed in joules). An alpha level was set at P < 0.05.

RESULTS

No significant differences were found in INEW, INRW, and EXRW between conditions at 70% of VO2max (mean +/- SD; Placebo: INEW, 25.6 +/- 17.8 J.min-1; INRW, 22.4 +/- 15.8 J.min-1; EXRW, 16.7 +/- 12.3 J.min-1; Active: INEW, 24.7 +/- 12.9 J.min-1; INRW, 19.7 +/- 11.9 J.min-1; EXRW, 15.2 +/- 8.6 J.min-1; P > 0.05). No difference was found in INEW, INRW, and EXRW at maximal exercise between conditions (mean +/- SD; Placebo: INEW, 50.2 +/- 29.9 J.min-1; INRW, 67.3 +/- 42.3 J.min-1; EXRW, 102.3 +/- 78.4 J.min-1; Active: INEW, 45.7 +/- 19.6 J.min-1; INRW, 62.6 +/- 36.7 J.min-1; EXRW, 86.3 +/- 50.9 J.min-1; P > 0.05). There were no differences in VO2, VE, VT, or f between conditions.

CONCLUSION

Wearing an external nasal dilator does not significantly reduce the work of breathing during exercise.

Objective quantification of plaque using digital image analysis

Dental plaque is the precursor to many oral diseases (e.g. gingivitis, periodontitis, caries) and thus its removal and control are an important aspect of oral hygiene. Many of the oral care products available today remove or inhibit the growth of dental plaque. Historically, the antiplaque efficacy of products was measured in blinded clinical trials where the amount of plaque on teeth is assessed via subjective visual grading with predefined scales such as the Turesky index. The ability of the examiner to consistently apply the index over time and the sensitivity of the scales often leads to large, expensive clinical trials. The present invention is an automatic measurement of plaque coverage on the facial surfaces of teeth using a digital image analysis technique. Dental plaque disclosed with fluorescein is digitally imaged under long-wave ultraviolet light. Ultraviolet illumination of fluorescein-disclosed plaque produces an image where the pixels of the image can be categorically classified based on color into one of five classes: teeth; plaque; gingiva; plaque on gingiva, or lip retractors. The amount of plaque on teeth can be determined by summation of the number of plaque pixels. The percent coverage is calculated from the number of plaque pixels and teeth pixels in the image. The digital image analysis of plaque allows facial plaque levels to be precisely measured (RSD = 3.77%). In application, the digital image analysis of plaque is capable of measuring highly significant plaque growth inhibition of a stannous fluoride dentifrice with as few as 10 subjects in a cross-over design.

Role of clinical microbiology laboratories in the management and control of infectious diseases and the delivery of health care

Modern medicine has led to dramatic changes in infectious diseases practice. Vaccination and antibiotic therapy have benefited millions of persons. However, constrained resources now threaten our ability to adequately manage threats of infectious diseases by placing clinical microbiology services and expertise distant from the patient and their infectious diseases physician. Continuing in such a direction threatens quality of laboratory results, timeliness of diagnosis, appropriateness of treatment, effective communication, reduction of health care-associated infections, advances in infectious diseases practice, and training of future practitioners. Microbiology laboratories are the first lines of defense for detection of new antibiotic resistance, outbreaks of foodborne infection, and a possible bioterrorism event. Maintaining high-quality clinical microbiology laboratories on the site of the institution that they serve is the current best approach for managing today's problems of emerging infectious diseases and antimicrobial agent resistance by providing good patient care outcomes that actually save money.

Inhibition of the Na(+)/H(+) exchanger delays the development of rapid pacing-induced atrial contractile dysfunction

BACKGROUND

Atrial mechanical stunning due to atrial fibrillation may persist after restoration of sinus rhythm. Although the mechanism of rapid rate-related contractile dysfunction remains unknown, ischemia, pH changes, and calcium overload have been postulated as potential mechanisms. We hypothesized that blockade of the Na(+)/H(+) exchanger (NHE) would alter atrial contractile dysfunction from rapid rates.

METHODS AND RESULTS

Twenty-three anesthetized dogs were studied and subjected to 5 hours of rapid right atrial pacing. Ten received an inhibitor of the NHE, 10 received saline, and 3 received nifedipine. All animals underwent placement of 2 sonomicrometers on the left atrium, transesophageal echocardiography, and invasive hemodynamic monitoring. All measurements were made in sinus rhythm. Except for baseline and postdrug measurements, reduction in left atrial fractional shortening was significantly less at all time points in the NHEI group than in the control and nifedipine groups (P:=0.05). The percent change from baseline of left atrial function at all time intervals as assessed by left atrial appendage contraction velocity (LAACV) was significantly less in the NHEI group than in the control (P:=0.05) group. LAACV was significantly preserved at all time intervals (except 300 minutes) in the NHEI group compared with the nifedipine group (P:=0.05). The only significant difference in hemodynamics among the groups was between the control and the nifedipine groups at 30 minutes after drug (P:=0.05).

CONCLUSIONS

Treatment with HOE642 significantly blunts the decline in left atrial mechanical function from rapid atrial rates compared with both control and nifedipine-treated groups.