Band-limited morphometric analysis of the intracardiac signal: implications for antitachycardia devices

Inappropriate electrical therapy and power efficiency play a major role in algorithm implementation for antitachycardia devices (ATD) that capture, store, and analyze the patient electrogram as an adjunct to rate determination. Morphologically based algorithms have been demonstrated to improve specificity, thereby decreasing occurrences of inappropriate electrical therapy. However, morphologically based algorithms are power demanding. Optimization of power efficiency can be achieved by eliminating unnecessary algorithmic computation, but must not compromise the effectiveness of algorithms, which perform direct analysis on raw signals. Significant reductions can be achieved by reduced sampling rates, which allow for increased overall ATD efficiency via concomitant decreases in computation and data storage. This investigation determined the upper and lower bounds for filter cut-off frequency beyond which detection precision by an established morphometric method for arrhythmia classification, correlation waveform analysis (CWA), was unfavorable. Four measurement statistics were used. In ten patients with inducible VT and VF, all bipolar intraventricular electrograms were classified correctly with a minimum passband of 10-50 Hz using any of the four measurement statistics. There was > or = 80% correct classification using all four measurement statistics with passbands having low frequency cutoffs < or = 15 Hz and high frequency cutoffs > or = 50 Hz. Correct classification of > or = 90% of unipolar electrograms during NSR, VT, and VF occurred using all four measurement statistics with a passband of 1-50 Hz. There was > or = 80% correct classification with passbands 1, 10, 15, or 20-500 Hz and 10-50 Hz. The classification of NSR, VT, and VF was most accurate on an intrapatient basis. Accuracy decreased using an interpatient rhythm classification. Optimum filter settings of 1-50 Hz and 10-50 Hz were determined for unipolar and bipolar electrograms, respectively. Sampling data at 120 Hz was found to be sufficient. Bipolar electrode configuration statistically outperformed unipolar data. In conclusion, morphometric analysis of bipolar and unipolar intraventricular electrograms appears to be achievable using band limited data and reduced sampling rates.

Augmented two-channel arrhythmia detection: an efficient diagnostic method for implantable devices

ICDs are highly effective in preventing sudden cardiac death. However, inappropriate device shocks caused by false-positive diagnoses are estimated to happen in 20% of all patients. The need for implantable electrical devices to detect with precision arrhythmias requiring therapy has spawned a variety of proposals for better means of tachycardia identification. To address this problem, the augmented two-channel arrhythmia detection (A2CAD) algorithm, a real-time scheme utilizing timing and morphology from both the atrial and ventricular channels, is introduced. The algorithm uses rate detection as a first stage and augments this with morphological signal analysis in rhythms that confound the rate only diagnoses. The software executes in real-time (online), and has been tested on 60 passages of two-channel intracardiac signals. The following arrhythmias constituted the test set: 10 AF and/or atrial flutter; 15 SVT; 16 VT; 10 ventricular flutter or VF; 5 sinus tachycardia; and 4 cases of AF concurrent with VF. Results from 60 patient cases indicate 57 (95%) of 60 success rate for A2CAD, validating its potential for implementation in future implantable devices.

Molecular cloning, expression and chromosomal localization of a human gene encoding a 33 kDa putative metallopeptidase (PRSM1)

The zincins are a superfamily of structurally-related Zn(2+)-binding metallopeptidases which play a major role in a wide range of biological processes including pattern formation, growth factor activation and extracellular matrix synthesis and degradation. In this paper we report the identification and complete primary structure of a novel 33 kDa protein which contains the zinc-binding HEXXH motif found in the zincin superfamily. We have named this novel protein PRSM1 (PRoteaSe, Metallo, number 1). The gene was identified by the immunoscreening of a human placental cDNA library using polyclonal antibodies raised to the 70 kDa human matrix metalloendopeptidase, type III procollagen N-proteinase [Halila, R. and Peltonen, L. (1986) Purification of human procollagen type III N-proteinase from placenta and preparation of antiserum. Biochem. J. 239, 47-52]. The protein is found in placenta and cultured osteosarcoma cells. PRSM1 could share sequence homology with the type III procollagen N-proteinase. The prsm1 gene is represented once in the human genome and is localized on chromosome 16 (q24.3).

Ground-based detectability of terrestrial and Jovian extrasolar planets: observations of CM Draconis at Lick Observatory

The detection of terrestrial-sized extrasolar planets from the ground has been thought to be virtually impossible due to atmospheric scintillation limits. However, we show that this is not the case especially selected (but nevertheless main sequence) stars, namely small eclipsing binaries. For the smallest of these systems, CM Draconis, several months to a few years of photometric observations with 1-m-class telescopes will be sufficient to detect the transits of any short-period planets of sizes > or = 1.5 Earth radii (RE), using cross-correlation analysis with moderately good photometry. Somewhat larger telescopes will be needed to extend this detectability to terrestrial planets in larger eclipsing binary systems. (We arbitrarily define "terrestrial planets" herein as those whose disc areas are closer to that of Earth's than Neptune's i.e., less than about 2.78 RE.) As a "spin-off" of such observations, we will also be able to detect the presence of Jovian-mass planets without transits using the timing of the eclipse minima. Eclipse minima will drift in time as the binary system is offset by a sufficiently massive planet (i.e., one Jupiter mass) about the binary/giant-planet barycenter, causing a periodic variation in the light travel time to the observer. We present here an outline of present observations taking place at the University of California Lick Observatory using the Crossley 0.9-m telescope in collaboration with other observatories (in South Korea, Crete, France, Canary Islands, and New York) to detect or constrain the existence of terrestrial planets around main sequence eclipsing binary star systems, starting with CM Draconis. We demonstrate the applicability of photometric data to the general detection of gas giant planets via eclipse minima timings in many other small-mass eclipsing binary systems as well.

Antibiotic treatment based on seminal cultures from asymptomatic male partners in in-vitro fertilization is unnecessary and may be detrimental

We questioned the policy of routine microbiological culture of semen prior to in-vitro fertilization (IVF) with a view to prescribing antibiotics to reduce the risk of introducing seminal infection into the embryo culture system. An initial retrospective study examined serum microbiology reports of 449 couples undergoing IVF or gamete intra-Fallopian transfer (GIFT). In semen samples taking >/=1 days to reach the microbiology laboratory compared with same-day delivery there was increased frequency of significant culture of enterococci (27 versus 15%, P < 0.01). In samples taking >/=2 days there was increased frequency of significant culture of Gram-negative bacilli (31 versus 12%, P < 0.01) and of overall culture of other potentially pathogenic organisms (26 versus 14%, P < 0.01). We questioned diagnostic accuracy and relevance. Therefore, in a prospective study, semen and high vaginal swabs obtained on the day of oocyte collection were cultured from 100 couples having IVF or GIFT, of whom 52 male partners had been treated with antibiotics following positive pre-IVF semen culture. The presence of bacteria in semen samples used only for IVF (n = 90) did not reduce fertilization rates nor lead to infection of the embryo culture system. However, there was an increased incidence of significant culture of vaginal Gram-negative bacilli in patients with treated partners compared with untreated partners [15/52 (29%) versus 5/48 (10%), P < 0.05]. Thus antibiotic therapy in the male partner may increase the likelihood of inoculation of antibiotic-resistant pathogenic bacteria from the vagina into the embryo culture system during vaginal oocyte collection. In asymptomatic patients, microbiological screening of semen samples prior to IVF treatment and subsequent treatment with antibiotic therapy in those with positive cultures appears to be unnecessary and may be detrimental to IVF outcome.

Endovascular grafting of abdominal aortic aneurysms. A preliminary study

OBJECTIVE

The authors report the experience of a single investigational center involving two Phase I and a Phase II clinical trials approved by the Food and Drug Administration (FDA) for the transfemoral implantation of woven Dacron grafts for abdominal aortic aneurysms.

SUMMARY BACKGROUND DATA

In 1993, EndoVascular Technologies, Inc. ([EVT]; Menlo Park, CA), began an FDA-approved clinical trial of repair of abdominal aortic aneurysms by transfemoral placement of a tube endograft. Subsequently, a bifurcated endograft trial was started. This the first single institution report using the EVT endograft for both tube and bifurcated aortic replacement.

METHODS

Seventeen patients were enrolled in two Phase I and one Phase II clinical trials. The Phase I tube graft trial and the Phase I bifurcated graft trial were nonrandomized studies. The Phase II tube graft trial consisted of a randomized prospective control trial of open endoaneurysmorrhaphy versus transfemoral placement of an endograft.

RESULTS

Seventeen patients were enrolled in the trial. The graft was placed successfully in all but one patient. Five patients randomized to open procedure and one declined to participate. Eleven patients with endografts are available for follow-up. One graft has been explanted for attachment system migration. One patient is a late failure because of persistent filling of the aneurysm sac.

CONCLUSION

Transfemoral placement of an endovascular graft is a viable and effective treatment of abdominal aortic aneurysms in the short term. Use of a bifurcated endograft will open the procedure to more patients. The ideal attachment system and graft material await long-term implantation follow-up.

Infant survival after cesarean section for trauma

HYPOTHESIS

Emergency cesarean sections in trauma patients are not justified and should be abandoned.

SETTING AND DESIGN

A multi-institutional, retrospective cohort study was conducted of level 1 trauma centers.

METHODS

Trauma admissions from nine level 1 trauma centers from January 1986 through December 1994 were reviewed. Pregnant women who underwent emergency cesarean sections were identified. Demographic and clinical data were obtained on all patients undergoing a cesarean section. Fetal distress was defined by bradycardia, deceleration, or lack of fetal heart tones (FHTs). Maternal distress was defined by shock (systolic blood pressure < 90) or acute decompensation. Statistical analyses were performed.

RESULTS

Of the 114,952 consecutive trauma admissions, more than 441 pregnant women required 32 emergency cesarean sections. All were performed for fetal distress, maternal distress, or both. Overall, 15 (45%) of the fetuses and 23 (72%) of the mothers survived. Of 33 fetuses delivered, 13 had no FHTs and none survived. Twenty infants (potential survivors) had FHTs and an estimated gestational age (EGA) of greater than or equal to 26 weeks, and 75% survived. Infant survival was independent of maternal distress or maternal Injury Severity Score. The five infant deaths in the group of potential survivors resulted from delayed recognition of fetal distress, and 60% of these deaths were in mothers with mild to moderate injuries (Injury Severity Score < 16).

CONCLUSIONS

In pregnant trauma patients, infant viability is defined by the presence of FHTs, estimated gestational age greater than or equal to 26 weeks. In viable infants, survival after emergency cesarean section is acceptable (75%). Infant survival is independent of maternal distress or Injury Severity Score. Sixty percent of infant deaths resulted from delay in recognition of fetal distress and cesarean section. These were potentially preventable. Given the definition of fetal viability, our initial hypothesis is invalid.

A matched filter method for ground-based sub-noise detection of terrestrial extrasolar planets in eclipsing binaries: application to CM Draconis

The photometric detection of extrasolar planets by transits in eclipsing binary systems can be significantly improved by cross-correlating the observational light curves with synthetic models of possible planetary transit features, essentially a matched filter approach. We demonstrate the utility and application of this transit detection algorithm for ground-based detections of terrestrial-sized (Earth-to-Neptune radii) extrasolar planets in the dwarf M-star eclipsing binary system CM Draconis. Preliminary photometric observational data of this system demonstrate that the observational noise is well characterized as white and Gaussian at the observational time steps required for precision photometric measurements. Depending on planet formation scenarios, terrestrial-sized planets may form quite close to this low-luminosity system. We demonstrate, for example, that planets as small as 1.4 Earth radii with periods on the order of a few months in the CM Draconis system could be detected at the 99.9% confidence level in less than a year using 1-m class telescopes from the ground. This result contradicts commonly held assumptions limiting present ground-based efforts to, at best, detections of gas giant planets after several years of observation. This method can be readily extended to a number of other larger star systems with the utilization of larger telescopes and longer observing times. Its extension to spacecraft observations should also allow the determination of the presence of terrestrial-sized planets in nearly 100 other known eclipsing binary systems.

A:V = 1:1 cardiac arrhythmia detection by VA interval analysis

Dual-chamber-sensing implantable-cardioverter defibrillators are soon expected to replace ventricular sensing devices. The addition of an atrial sensing lead will dramatically improve the specificity of arrhythmia detection. Even when using combined ventricular and atrial rate criteria, ambiguity in the case of atrial tachycardia with: anterograde conduction versus ventricular tachycardia with: retrograde conduction still remains. The introduction of dual-chamber sensing in antitachycardia devices allows for additional features, such as the measurement of atrioventricular (AV) and ventriculoatrial (VA) intervals. This study investigated relationships between AV and VA intervals to address problems arising in tachycardias with confounding 1:1 relationships. Thirty-one passages of 1:1 anterograde conduction from nine patients during atrial pacing at cycle lengths of 600-300 ms and 24 passages of 1:1 retrograde conduction from eight patients during ventricular pacing at cycle lengths of 600-300 ms were analyzed. Moving averages of three successive VA interval measurements were used to develop a criterion to be implemented into an algorithm to reduce ambiguity. Five randomly selected ventricular pacing passages were used as a training set. Upper and lower VA interval boundaries (234 ms and 132 ms) determined from the training set were used to classify 1:1 retrograde activation. To account for premature beats and outliers, the boundary criterion required 9 of 12 of the most recent moving averages to fall within the upper and lower limits. Of the 19 analyzed passages of ventricular pacing, 18 (95%) were correctly classified using the VA interval as an added feature. Of the 31 atrial pacing passages, 24 (77%) were correctly classified. Using only atrial or ventricular rates, all 1:1 tachycardias in this patient sample would be classified as ventricular tachycardia, resulting in false shocks. Specificity of diagnosis in ambiguous 1:1 tachycardias can be increased using VA interval measurements at the cost of minimum loss in sensitivity for ventricular tachycardia detection. This algorithm imposes little in additional computation for dual-chamber-sensing implantable-cardioverter defibrillators and greatly reduces the possibility of false shocks in 1:1 supraventricular tachycardias.

Ovarian hyperstimulation syndrome may be more likely if multiple pregnancy occurs following assisted conception

Whereas modern assisted conception with such techniques as in vitro fertilisation now helps many subfertile couples to fulfill their ambition to have a child, it has not been without a price. The increased incidence of multiple pregnancies, with their attendant maternal and perinatal sequelae following assisted conception is well known, but perinatologists may be far less familiar with the Ovarian Hyperstimulation Syndrome (OHSS) which is the other major complication when controlled ovarian hyperstimulation is used during assisted conception treatment. Mild forms of OHSS are common and require no more than symptomatic treatment. Severe forms of OHSS are uncommon occurring in 0.6% to 14% of IVF cycles, but are nonetheless very important to identify as they may lead to thrombo-embolic disease, cardiorespiratory dysfunction, renal failure and even death [6]. This review considers whether OHSS may be related to multiple pregnancy by reviewing the available literature and local experience.

Endocervical mucus pH is inversely related to serum androgen levels and waist to hip ratio

OBJECTIVE

To determine whether an inter-relationship exists between endocervical mucus pH, serum androgen levels, and waist to hip (W:H) ratio.

SETTING

Donor insemination clinic, University of Sheffield, Jessop Hospital, Sheffield, United Kingdom.

PATIENTS

One hundred patients receiving donor insemination.

INTERVENTIONS

Waist, hip, height, and weight measurements were recorded for 100 patients receiving donor insemination. At the onset of the LH surge when patients attended for their first insemination, a sample of endocervical mucus and blood was taken. The Insler score of the mucus was recorded and the pH was measured with multirange pH paper. Of the 100 patients studied, 10 cases had an endocervical mucus pH < 6 despite Insler scores of > 10. Serum T, DHEAS, and androstenedione levels were measured in the 10 patients with pH < 6 and in 26 patients selected at random from the 90 patients with pH > or = 6.

RESULTS

The W:H ratio was significantly higher in the patients with pH < 6 than pH > or = 6. No significant difference was seen in body mass index between the latter groups. All serum androgen levels were significantly higher in the patients with pH < 6 than pH > or = 7.

CONCLUSION

A potential link (serum androgen levels) between a powerful predictive factor of fertility (W:H ratio) and a potential mechanism of subfertility (low endocervical mucus pH) has been demonstrated. This observation warrants further detailed evaluation particularly as it has been shown that a low endocervical mucus pH may be corrected by simple inexpensive treatment.

Pediatric low energy lithotripsy with the Lithostar

Between November 1988 and July 1993, 238 renal stones and 208 ureteral stones were treated in 446 pediatric patients using 26 mobile and 2 fixed base Siemens Lithostar lithotriptors. The stones were treated by a group of 245 urologists using the modified Puigvert technique and the standard shock tube. The success rate for renal stones (asymptomatic fragments less than 4 mm.) was 76.6%, stone-free rate was 67.9%, retreatment rate was 14.1% and ancillary procedures were performed in 36.3%. The stone-free rate for ureteral stones was 91.1%, retreatment rate was 3.5% and ancillary procedures were performed in 17.7%. Anesthesia was required in 31% of the renal and 21% of the ureteral procedures. Sepsis in a 6-year-old child after treatment of a ureteral stone was the only major complication. Low energy lithotripsy with the Lithostar in our series of pediatric patients was safe and effective.

A comparative study of the percutaneous versus intraoral technique for mental nerve block

OBJECTIVE

Mental nerve block is frequently used to aid repair of facial lacerations; both percutaneous and intraoral approaches to blocking this nerve are used, but have never been compared. The authors compared the two techniques for pain of administration and effectiveness of anesthesia.

METHODS

A prospective, randomized, single-blind, crossover study was conducted using ten healthy volunteers aged 22 to 33 years. Patients having prior experience with mental nerve blocks, lidocaine allergy, active oral/facial infection, or previous facial fractures were excluded. Bilateral mental nerve blocks were done using intraoral technique on one side and percutaneous technique on the other. Both techniques were used by the same investigator and were carried out with 27-gauge needles and 2.5 mL of 2% buffered lidocaine at room temperature injected over 20 seconds. The oral mucosa was topically anesthetized with viscous lidocaine for 1 minute prior to intraoral injection. The orders of the blocks and sides of the face anesthetized were randomized. Subjective and objective pain (visual-analog scale), efficacy (anesthesia of lower lip), time to onset, and duration of anesthesia were evaluated.

RESULTS

The intraoral technique was subjectively less painful than the percutaneous approach in nine of ten subjects (p = 0.02). Scores on the visual-analog pain scale were significantly lower for the intraoral technique (p = 0.03). Intraoral injection produced lower-lip anesthesia in 10/10 subjects versus 7/10 for percutaneous (p = 0.25). Times to onset (approximately 1-2 minutes) and durations of anesthesia (approximately one hour) were similar for the two techniques.

CONCLUSION

The intraoral approach to the mental nerve block with adjunctive topical anesthesia was subjectively and objectively less painful than the percutaneous approach without adjunctive anesthesia. While the intraoral approach had a greater efficacy of lower-lip anesthesia and a longer duration of action, these differences were not statistically significant.

Discrimination of ventricular tachycardia from sinus tachycardia by antitachycardia devices: value of median filtering

Rate and rate variation algorithms used by implantable devices designed for management of life-threatening arrhythmias have major limitations in separating physiologic sinus tachycardia (ST) from pathologic ventricular tachycardia (VT) requiring therapy. These algorithms presently utilize criteria such as simple heart rate, stability of rate, or derivative of rate (sudden onset) which assumes a gradual onset for ST and an abrupt onset for VT. An alternative method employing median filtering was designed, tested, and compared to a previously published sudden onset rate algorithm using the same data set for analysis of performance. In 50 patients, the onset of ST during exercise and onset of VT were analysed. To accommodate occasional outlying intervals which might affect rate derived by averaging, a five-cycle median filter was used to smooth heart rate. Results from using a 'fixed-interval' or a 'percent' change in the median gave better discrimination of ST and VT than previously published 'fixed-interval' or 'percent' change algorithms. The superiority of median filtering performance was validated by statistical measures.

Comparison of intraoral and percutaneous approaches for infraorbital nerve block

OBJECTIVE

The infraorbital nerve block is frequently used during repair of facial lacerations; both percutaneous and intraoral approaches are used. The authors compared the two techniques for pain of administration and anesthetic effectiveness.

METHODS

A prospective, randomized, single-blind, crossover study was conducted using 12 healthy volunteers, aged 25-41 years. No patient had prior experience with infraorbital nerve anesthesia, lidocaine allergy, active oral/facial infection, or previous facial fractures. Bilateral infraorbital nerve blocks were done using the intraoral technique on one side and the percutaneous technique on the other. Both techniques were used by the same investigator and were carried out with 27-gauge needles and 2.5 mL of 2% buffered lidocaine at room temperature injected over 20 seconds. The oral mucosa was topically anesthetized with viscous lidocaine for 1 minute prior to intraoral injection. The orders of the blocks and sides of the face anesthetized were randomized. Pain of injection, anesthetic efficacy (anesthesia of upper lip), time to anesthetic onset, and duration of anesthesia were evaluated.

RESULTS

By visual-analog pain scale scores, there was less pain by the intraoral approach, although this difference did not achieve significance (p = 0.08). Overall, nine of the 12 subjects considered the intraoral technique less painful than the percutaneous approach (p = 0.14). The intraoral approach produced upper-lip anesthesia in 12 of 12 subjects, versus nine of 12 for the percutaneous technique (p = 0.25). The duration of anesthesia was longer with the intraoral approach (1.6 +/- 0.8 hours versus 0.9 +/- 0.4 hours) than with the percutaneous approach (p = 0.04). The two techniques were similar in times to anesthetic onset.

CONCLUSION

The intraoral approach to the infraorbital nerve block after adjunctive topical anesthesia appeared at least as effective in producing upper-lip anesthesia as the percutaneous approach without adjunctive topical anesthesia. Although the volunteers subjectively preferred the intraoral approach and visual-analog pain scores were lower for this approach, these differences did not achieve statistical significance. The intraoral approach was associated with a longer duration of upper-lip anesthesia.

Identification of subcellular targets and sensitive tests of ethanol-induced damage in isolated rat gastric mucosal cells

BACKGROUND/AIMS

The mechanisms of chemically induced injury are poorly understood. The purpose of this study was to develop a rapid method for isolation of gastric mucosal cells (GMCs) and sensitive tests for investigating cell damage and protection.

METHODS

GMCs were prepared from rat glandular stomach with pronase and ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) and kept in albumin-containing, albumin-free, or Hank's solutions. Initial cell viability and responsiveness were tested with trypan blue exclusion, and stimulation or inhibition of pepsinogen secretion were tested with carbachol, 16,16-dimethyl prostaglandin E2, or carbachol plus atropine. Plasma membrane damage was assessed by trypan blue exclusion, lactate dehydrogenase or cell protein leakage, mitochondrial integrity by succinic dehydrogenase activity, and nuclear lesions by ethidium bromide DNA fluorescence.

RESULTS

Incubation of GMC with ethanol resulted in 50% lethal dose for ethanol values of 12.3%, 7.4%, and 10.9% by trypan blue exclusion; 10.1%, 9.4%, and 9.1% by lactate dehydrogenase leakage; 12.8%, 10.0%, and 10.4% by succinic dehydrogenase; and 14.1%, 13.0%, and 11.5% by ethidium bromide DNA by binding using albumin-containing, albumin-free, and Hank's solutions, respectively.

CONCLUSIONS

Rat GMC with high and long viability can be isolated by low concentrations of pronase and EGTA. The adapted biochemical and microscopic methods are suitable for parallel examination of chemical injury of plasma membrane, mitochondria, and nuclei. Albumin increased ethanol 50% effective concentration to GMC. A combination of biochemical and morphological methods with ethanol-induced injury to GMC is proposed for direct cytoprotection investigations.