Biomedical subjects

C F Pieper

Publications and source records attributed to C F Pieper.

At least 19 recordsLinked to original sources

PubMed1996

Risk factors for nosocomial pneumonia: comparing adult critical-care populations.

The purpose of the study was to examine risk factors for nosocomial pneumonia in the surgical and medical/respiratory intensive care unit (ICU) populations. In a public teaching hospital, all cases of nosocomial pneumonia in the surgical and medical/respiratory ICUs (n = 20, respectively) were identified by prospective surveillance during a 5-yr period from 1987-1991. Each group of ICU cases was compared with 40 ICU control patients who did not acquire pneumonia, and analyzed for 25 potential risk factors. Surgical ICU patients were found to have consistently higher rates of nosocomial pneumonia than medical ICU patients (RR = 2.2). The strongest predictor for nosocomial pneumonia in both the surgical and medical/respiratory ICU groups was found to be prolonged mechanical ventilation (> 1 d) resulting in a 12-fold increase in risk over nonventilated patients. APACHE III score was found to be predictive of nosocomial pneumonia in the surgical ICU population, but not in the medical/respiratory ICU population. We conclude that certain groups deserve special attention for infection control intervention. Surgical ICU patients with high APACHE scores and receiving prolonged mechanical ventilation may be at the greatest risk of acquiring nosocomial pneumonia of all hospitalized patients.

APACHE↗

PubMed1995

Racial differences in the occurrence of herpes zoster.

The purpose of this study was to determine if there are racial differences in the occurrence of herpes zoster (shingles). The study population was the Duke Established Populations for Epidemiologic Studies of the Elderly, a probability sample of community-dwelling persons > 64 years old in North Carolina. Interviewers administered a comprehensive health survey to the participants that included questions about lifetime occurrence of shingles. Of the 3206 subjects, 316 (9.9%) had had zoster: 81 (4.5%) of 1754 blacks and 235 (16.1%) of 1452 whites had had shingles (P < .0001). After controlling for age, cancer, and demographic factors, blacks remained one-fourth as likely as whites (adjusted odds ratio 0.25, 95% confidence interval 0.18-0.35; P = .0001) to have experienced zoster. In summary, blacks had a significantly lower risk of developing herpes zoster than whites, a new finding in herpes zoster epidemiology.

Age Factors↗

PubMed1995

Functional and mobility impairments associated with Paget's disease of bone.

OBJECTIVE: To determine if patients with Paget's disease of bone involving the tibia, femur, and/or acetabular portion of the ilium had more impairments in function and mobility than age- and sex-matched control subjects. PATIENTS AND METHODS: A case control study with Paget's disease patients selected from a center for bone disease at a tertiary medical center; control subjects were volunteers from the Duke University Aging Center subject registry. Demographic characteristics, physical examination and serum alkaline phosphatase levels were obtained. Radiographs of the pelvis and lower extremities were evaluated by a radiologist. All participants completed a Functional Status Questionnaire (FSQ). Mobility measures included mobility skills protocol, 10-foot walk time, 360-degree turn left (number of steps), and 6-minute walk distance. RESULTS: The 12 Paget's disease patients were no different in age (70.7 +/- 6.2 years) than the 12 control subjects (69.5 +/- 6.2 years). Serum alkaline phosphatase levels were elevated in Paget's patients (539 +/- 530 IU/L), and normal in control subjects (85 +/- 17 IU/L). In addition to Paget's disease, radiographs showed joint space loss in joints proximate to the diseased bone. On the FSQ scales Paget's disease patients had significantly lower scores in basic activities of daily living (P < .05), instrumental activities of daily living (P < .001), and social activity than control subjects (P < .05). There was no difference between the groups on scales measuring mental health and quality of social interaction. On mobility measurements, Paget's disease patients showed significant impairments when compared with control subjects: mobility skills protocol score (22.5 +/- 2.5 vs 25.6 +/- 0.7, P < .001); 10-foot walk (3.96 +/- 1.3 vs 2.55 +/- 0.5 seconds, P < .001); 360 degree turn left (8.0 +/- 1.0 vs 5.9 +/- 0.6 steps, P < .001); and 6-minute walk (342.0 +/- 108.5 vs 519.4 +/- 100 meters, P < .001). CONCLUSION: When compared with control subjects, patients who have Paget's disease of bone involving the tibia, femur, or acetabular portion of the ilium have clinically and statistically significant functional and mobility impairments compared to age- and gender-matched controls.

Activities of Daily Living↗

PubMed1995

Improved spatial resolution for cardiac mapping using current source density-based electrode arrays.

The time of the minimum slope (i.e., the fastest negative deflection) in monopolar (MP) electrograms from normal hearts compares closely with time of phase 0 of the action potential in cells underlying the electrode, but poor rejection of far-field activity may limit the utility of MP electrode technology in dense arrays used for the study of ventricular tachycardia and fibrillation. The purpose of this study is to evaluate more myopic discrete bipolar (BP) and nondirectional, two-dimensional current source density (CSD) based arrays for rejection of far-field potentials and precision of activation time determination. Simultaneous recordings of the CSD, MP, and multiple BP electrograms were performed on normal dog epicardium. The time of the minimum slope in MP electrograms was compared to activation times in CSD and BP derivations using: (1) peak; (2) steepest slope; (3) zero crossing of the steepest sloping segment in either direction; and (4) waveform morphology. In vivo, CSD amplitude was reduced significantly more than MP and BP amplitudes by insertion of inert media between the heart and the electrodes. The time of the steepest slope in CSD electrograms designated activation times closest to the time of the minimum slope in MP electrograms (0.9 +/- 1.3 msec). We conclude that CSD provides a nondirectional electrode system that accurately defines the time of local activation and possesses better spatial specificity than MP electrode systems and BP electrode systems having the same interelectrode distances.

Animals↗

PubMed1994

Multivariable analysis of DNA ploidy, p53, and HER-2/neu as prognostic factors in endometrial cancer.

BACKGROUND: Several molecular-genetic alterations in endometrial cancers, including aneuploidy and aberrant expression of p53 and HER-2/neu, have been associated with poor prognosis. To determine the importance of molecular-genetic factors relative to more traditional surgical-pathologic prognostic factors, a multivariable analysis was performed. METHODS: Immunohistochemical staining for p53, HER-2/neu, estrogen receptor, progesterone receptor, and epidermal growth factor receptor was performed on frozen sections from 100 primary endometrial cancers. DNA ploidy was determined using computerized image analysis of Feulgen-stained touch preparations. In addition, information regarding surgical-pathologic features of the cancers was obtained. Univariable analysis was performed followed by multivariable analysis using Cox's proportional hazards model to identify variables predictive of poor prognosis. RESULTS: With univariable analysis, race, histologic type, stage, grade, myometrial invasion, estrogen receptor, progesterone receptor, ploidy, p53 and HER-2/neu were predictive of the presence of persistent or recurrent disease. In the multivariable analysis, only International Federation of Gynecology and Obstetrics stage (P = 0.005), grade (P = 0.005), myometrial invasion (P = 0.024), and ploidy (P = 0.028) were significant. CONCLUSIONS: Among molecular-genetic prognostic factors, DNA ploidy was the most strongly predictive of persistent or recurrent disease.

Aged↗

PubMed1994

Nutrition and function: is there a relationship between body mass index and the functional capabilities of community-dwelling elderly?

OBJECTIVE: To determine if there is a relationship between body mass index and the ability to perform the usual activities of living in a sample of community-dwelling elderly. DESIGN: Secondary data analysis of The National Health and Nutrition Examination Survey-I Epidemiologic Follow-up Study (1982-1984). Follow-up home interview of a population-based sample originally interviewed between 1971 and 1975 in the National Health and Nutrition Examination Survey-I (NHANES-I). PARTICIPANTS: Survivors of the original NHANES-I cohort who were 65 years of age or older and who were living at home at the time of the second interview (n = 3061). Excluded were those who could not be found, refused participation, or were institutionalized (n = 220), and those without complete height and weight data (n = 194). MAIN OUTCOME MEASURE: Functional status as measured by a 26-item battery. RESULTS: Bivariate analysis revealed a greater risk for functional impairment for subjects with a low body mass index or a high body mass index. The greater the extreme of body mass index (either higher or lower), the greater the risk for functional impairment. Logistic regression analysis indicated that both high and low body mass index continued to be significantly related to functional status when 22 other potential confounders were included in the model. CONCLUSION: The body mass index is related to the functional capabilities of community-dwelling elderly. The inclusion of this simple measurement in the comprehensive assessment of community-dwelling elderly is supported.

Activities of Daily Living↗

PubMed1994

Spectral analysis of activation time sequences.

Adequate spatial resolution of local activation is fundamental for the correct depiction of myocardial activation during ablative treatment of ventricular tachycardia. The widest allowable distances between recording sites that provide an accurate description of the field potential distribution is dictated by the Nyquist sampling theorem. Activation times are derived from the field potentials. However, because of noise intrinsic in activation detection algorithms, closer recording sites may be required than those theoretically computed. The purpose of this study is to examine the spatial frequency spectrum of epicardial activation time sequences computed by common activation detection algorithms, determine which algorithm is least noisy, and derive the recording site density necessary to avoid distortion of the epicardial activation map. Using 40 to 80 electrode linear arrays, monopolar and bipolar electrograms from the epicardium were recorded vertically (base to apex) and horizontally in 11 dogs. Activation times for bipolar electrograms were estimated using Peak, Fastest Zero Crossing, and Morphological algorithms. Activation times for monopolar electrograms were set equal to the time of the fastest negative deflection. Activation time sequences were analyzed using conventional Fourier techniques. Anomalous activation times from serially adjacent bipolar electrograms, which constitute algorithm noise, were studied. Horizontal and vertical interelectrode distances are 3.2 mm and 2.4 mm, respectively. Of the bipolar algorithms, the Morphological algorithm produced the fewest anomalous activation times. Mapping systems having more than 256 channels are required for accurate representation of epicardial activation in a typical 20-kg dog. The endocardial electrode spacing is unknown, but is expected to be at least as dense. Large global mapping systems or regionally dense arrays may offer advantages during catheter ablations for ventricular tachycardia and for studies into the mechanisms of ventricular tachycardia by accurately defining the cardiac activation pattern.

Algorithms↗

PubMed1994

Sociodemographic correlates of health beliefs among black and white community dwelling elderly individuals.

This study examined the hypothesis that sociodemographic characteristics such as age, education, race, and gender would be predictive of Multidimensional Health Locus of Control Subscale scores in a population-based sample of 342 community dwelling elderly individuals. Bivariate analysis revealed associations between black race, lower socioeconomic status, and lower education on the Chance and Powerful Others Subscales. While the multivariate analysis revealed no predictors for the Internal Subscale, a higher socioeconomic status, white race, and a higher level of education continued to predict low scores on the Chance Subscale when controlling for all other variables. Scores on the Powerful Others Subscale appeared to be a function of socioeconomic status and gender. Of note, the higher the education level for both men and women, the lower the scores on the Chance and Powerful Others Subscales. This sex by education interaction term reached statistical significance for the Chance Subscale. The results demonstrate the measurable influence of sociodemographic variables on the health beliefs of community dwelling elderly individuals.

Black or African American↗

PubMed1993

Association of osteoporotic vertebral compression fractures with impaired functional status.

PURPOSE: To determine if vertebral compression fractures in elderly women were associated with impairments in physical, functional, and psychosocial performance. SUBJECTS AND METHODS: Ten white women with confirmed vertebral compression fractures were age- and race-matched with 10 control subjects without fractures in a case-control design. All subjects invited to participate in this study were patients of the Geriatrics Division of the Department of Medicine at Duke University Medical Center. All study participants lived either in the community or in the independent-living sections of local retirement communities in and around Durham, NC. Subjects with fractures (mean age = 81.9 years, SD = 5.9 years) had two or more vertebral compression fractures in their medical records, whereas control subjects (mean age = 79.6 years, SD = 6.5 years) had no history of vertebral fractures. Spinal radiographs of all women confirmed group assignment. Physical, functional, and psychosocial performances were evaluated. Physical performance was assessed by measurements of maximal trunk extension torque and thoracic and lumbar spinal motion in the sagittal plane, functional reach, mobility skills, 10-ft timed walk, and 6-minute walk test. Thoracic and lumbar spinal configurations were also determined. Functional performance was assessed using the Functional Status Index. Psychosocial performance was assessed with the following scales: Hopkins Symptom Checklist 90 Revised, Rosenberg Self-Esteem Scale, West Haven-Yale Pain Inventory, Beck Depression Inventory, and single-item health-belief questions. RESULTS: Control subjects were not significantly different from patients with fractures in age, weight, number of current illnesses, number of prescribed medications, number of pain medications, ratings of lumbar spine degenerative disc disease, or lumbar spine facet joint arthritis. Activity levels and exercise participation were similar in both groups. Control subjects had no vertebral fractures, whereas fracture subjects had 4.2 +/- 2.6 fractures (range: 2 to 10). Thoracic kyphosis was increased and lumbar lordosis was reduced in fracture subjects. Fracture subjects had reduced maximal trunk extension torque, thoracic and lumbar spine sagittal plane motion, functional reach, mobility skills, and 6-minute walk test. The Functional Status Index showed reduced levels of functional performance in fracture subjects compared with controls with increased levels of assistance, pain with activity, and difficulty in activities. Psychosocial performance was limited in fracture subjects with increased psychiatric symptoms, increased pain, and greater perception of problems caused by health. CONCLUSION: Vertebral compression fractures are associated with significant performance impairments in physical, functional, and psychosocial domains in older women.

Activities of Daily Living↗

PubMed1993

Measured versus estimated creatinine clearance in a high-functioning elderly sample: MacArthur Foundation Study of Successful Aging.

OBJECTIVE: To assess the validity of several equations for estimating creatinine clearance in a large sample of high-functioning, community-dwelling elderly. DESIGN: Serum and 12-hour urine samples were collected and assayed for creatinine using the Jaffe total chromagen method. Fifteen clearance-estimating equations were evaluated for bias, accuracy, correlation with measured clearance values, and frequency of erroneous placement into renal function categories. Stepwise regression modeling and reliability testing were performed on a split sample to construct and assess a novel creatinine-clearance-estimating equation. SETTING: New Haven, Connecticut, East Boston, Massachusetts, and a five-county region in and around Durham, North Carolina. PARTICIPANTS: A subsample of community-dwelling men and women (age range 70-79 years) from the Established Populations for Epidemiological Studies of the Elderly was screened for physical and cognitive functioning and placed into high-, medium-, and low-functioning groups (n = 1354). High-functioning respondents who provided blood and complete urine samples (n = 762) were included in the present study. RESULTS: In general, estimated creatinine clearance was more closely correlated to measured values in males than in females. Most equations underestimated creatinine clearance, with average bias ranging from -33.1 mL/min to +19.6 mL/min. Predictive accuracy ranged from 18.2 mL/min to 38.0 mL/min. Equations were variable in their erroneous placement of individuals into renal function categories. Regression modeling yielded an equation which contained novel components but failed to provide better estimates of creatinine clearance than those already available. CONCLUSIONS: The equations evaluated here provide unacceptable predictions of creatinine clearance in normally aging individuals. We advocate the use of serum drug concentration measurements when available and encourage investigation into timed urine collections of short duration as alternatives to clearance-estimating equations in the elderly.

Activities of Daily Living↗

PubMed1993

Simultaneously collected monopolar and discrete bipolar electrograms: comparison of activation time detection algorithms.

Designation of the time of local activation is fundamental to electrophysiological mapping. In normal myocardium, the minimum slope in extracellular monopolar (MP) electrograms has been linked through simultaneous intracellular and extracellular recordings to phase 0 of the action potential. However, no similar correlation has been demonstrated for a parameter from bipolar (BP) electrograms, now commonly used during electrophysiological studies and intraoperative mapping. The purpose of this work is to compare the activation time, determined according to several common algorithms applied to BP electrograms, with the time of the minimum slope in MP electrograms. Simultaneous normal epicardial MP and BP electrograms were acquired from subjects undergoing surgery for Wolf-Parkinson-White Syndrome and from dogs. The activation time in BP electrograms was defined by four algorithms: (1) peak (P); (2) greatest absolute slope (S); (3) zero crossing of the segment containing the greatest slope (FZC); and (4) morphological (M). Each was compared to the time of the minimum slope in the simultaneously recorded MP response. The incidence of outliers was tabulated. The distribution of activation times computed using each BP algorithm was statistically different from the distribution of activation times derived from MP electrograms. M performed best (absolute difference: 2.6 +/- 2.9 msec; cor coef: 0.9925 in man). The M, P, FZC, and S algorithms produced 3.2%, 3.5%, 4.7% and 4.7% outliers, respectively. The overall performance of a morphologically based algorithm is superior to simplistic BP algorithms based only on slope or peak.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗

PubMed1993

The epicardial field potential in dog: implications for recording site density during epicardial mapping.

Investigations into mechanisms and successful surgical therapy of ventricular tachycardia (VT) depend upon accurate endocardial/epicardial mapping. Deduction of local activation is based upon parameters derived from the field potential (FP) (monopolar recording) or its first spatial derivative (bipolar recording). Adequate electrode spacing is an assumption fundamental to the mapping process, but the electrode spacing required for accurate representation of the FP is unknown. The purpose of this work is to derive the electrode spacing necessary to accurately describe the FP on the epicardium. In 11 dogs, electrograms from vertical (V) (base to apex) bands having 40 electrodes and horizontal (H) bands having 40 to 80 electrodes were sampled at 1 kHz. The spatial bandwidths (BW) were computed according to two criteria: (1) the frequency yielding 2% mean squared error (MSE) computed at the time of the greatest integrated magnitudes of the Fourier transform; and (2) the highest frequency bounding 95% power computed at each msec throughout the beat. Implied electrode spacings were defined according to the sampling theorem. The 5th percentiles of the implied electrode spacing distributions were used to define the widest interelectrode distance required to prevent spatial aliasing. H-5th percentile and V-5th percentile were, respectively: 2% MSE (3.5 mm, 2.3 mm); 95% power (3.6 mm, 2.3 mm). Thus, a typical 20-kg dog requires more than 250 recording sites for accurate epicardial mapping. Extrapolating to man, these results suggest inadequate electrode density may partially be responsible for incomplete and ambiguous reentry patterns often observed during intraoperative mapping.

Animals↗

PubMed1992

The impact of anticipation of job loss on psychological distress and worksite blood pressure.

The impact of occupational stressful life events on psychological distress and blood pressure was examined among employees of a major New York City brokerage firm undergoing massive layoffs. One hundred thirty-nine employees of the firm, who had participated in a blood pressure screening in 1986, were rescreened during the period of layoffs within their company in 1989. About two-thirds of the 139 employees reported being "somewhat" or "very" anxious or upset in 1989 during the period of layoffs, and psychological distress was significantly elevated among those employees reporting possible or definite layoff or job change and/or difficulty in obtaining a comparable job. However, we found no increase in overall blood pressure level, and no effect of anticipation of job loss on 1989 blood pressure when controlling for 1986 blood pressure level, age, body mass index, work hours, and other demographic variables. On the other hand, employment in a department sold to another employer on the day of screening, as well as employment in a clerical job title, were both associated with significant increases in diastolic blood pressure of about 5 mm Hg.

Anxiety↗

PubMed1992

Observations on the epicardial activation of the normal human heart.

Serial hand mapping techniques in man have identified 3 to 5 sites of epicardial breaktrough (EBT). However, transmural epicardial excitation from the widely distributed His/Purkinje system suggests a more complicated pattern may exist. Multielectrode arrays used with large mapping systems during surgery often present complicated and sometimes inconsistent activation patterns. The purpose of this work is to reconcile epicardial activation in the normal human heart with anatomical and endocardial/intramural physiological recordings using multichannel computer mapping requiring only a single beat, and rigorously defined and applied activation time detection algorithms. Eighteen subjects undergoing surgery for Wolff-Parkinson-White syndrome were recorded with a 119 site sock array during nonpreexcited sinus rhythm. None had evidence of coronary artery disease and all exhibited a normal 12-lead ECG except during periods of preexcitation or tachycardia. Each was recorded bipolarly and four also were recorded monopolarly. Recordings revealed 8.0 +/- 1.6 EBTs (range 5 to 12). Closely spaced, multiple EBTs often were observed and usually confirmed using different activation time detection algorithms. The earliest EBT always occurred over the anterior right ventricle at 14.3 +/- 6.5 msec (range -1 to 29 msec) after QRS onset. Subsequent EBTs could occur at any ventricular site with variable latencies. In contrast to previous reports describing epicardial spread of activation from a few foci, a mosaic of epicardial activation emerges. These data are consistent with endocardially initiated transmural activation of the epicardium suggested by the anatomy of the His/Purkinje system and intramural recordings.

Algorithms↗

PubMed1992

The effect of legal drinking age on fatal injuries of adolescents and young adults.

This study examined the effect of legal drinking age (LDA) on fatal injuries in persons aged 15 to 24 years in the United States between 1979 and 1984. Effects on pre-LDA teens, adolescents targeted by LDA, initiation at LDA, and post-LDA drinking experience were assessed. A higher LDA was also associated with reduced death rates for motor vehicle drivers, pedestrians, unintentional injuries excluding motor vehicle injuries, and suicide. An initiation effect on homicides was identified. Reductions in injury deaths related to drinking experience were not found. In general, a higher LDA reduced deaths among adolescents and young adults for various categories of violent death.

Accidents, Traffic↗

PubMed1991

Bandwidth-induced errors in parameters used for automated activation time determination during computerized intraoperative cardiac mapping: theoretical limits.

Two parameters commonly used when determining the time of local activation during computerized intraoperative cardiac mapping are the time of the peak in bipolar electrograms (BP) and the time of the largest negative slope (LNS) in monopolar electrograms (MP). The dependence of these parameters upon bandwidth was studied. A database of fast MP and BP was compiled from intraoperative recordings collected from epicardial sock arrays in man. Based on 95%, 99% and 99.9% of total signal power, the bandwidths of each response were determined. After removing specified frequencies using the Fourier transform, errors in determining these parameters were computed and characterized with respect to mean square error (MSE), percent power bandwidth and frequency content. The Fourier transform was used to abruptly filter out undesired upper frequencies. Filtering BP at 200 Hz produced a 1-ms shift in the peak in 17.0% of the electrograms, 0.4% of the peaks shifted by 2 ms and none shifted by more than 2 ms. Comparable shifts in the LNS occurred when filtering MP at 400 Hz. Retention of 95% of the power in a BP rarely (0.9%) changed the time of its peak by more than 1 ms. For MP, retention of 99.9% of the power was required for similar performance (3.6%). Thus, although BP have greater signal power in the higher frequencies than MP, a greater bandwidth is required when recording monopolarly in order to preserve the small amount of power necessary to define the time of the LNS with accuracy comparable to determination of the peak in BP.

Analog-Digital Conversion↗

PubMed1991

Influence of time of sampling onset on parameters used for activation time determination in computerized intraoperative mapping.

The purpose of this work is to determine the sensitivity of the estimated time of peaks and maximum slopes, commonly used in activation time computations, to the instant at which sampling is initiated. Based on complex and quickly changing waveforms, 471 monopolar (MP) and bipolar (BP) epicardial responses in man were selected. These were decimated from 10 kHz to simulate sampling at frequencies ranging from 200 Hz to 2,000 Hz. The peak and maximum absolute slope for BP and the minimum slope for MP were computed repeatedly starting at successive 100 microseconds intervals extending throughout the sampling period and compared with these parameters computed from the waveform sampled at 10 kHz. Slopes were estimated using each of four different algorithms. The average greatest shift (AGS) due to variations in sampling onset ranged from 11.2 +/- 3.5 (200 Hz) to 0.3 +/- 0.2 msec (2,000 Hz). For bipolar algorithms, the peak performed better than the slope algorithms (AGS: 5.9 +/- 3.3 to 0.3 +/- 1.0 msec). For MP algorithms, 2 point linear, and 3 and 5 point Lagrange slope estimates performed similarly (AGS: 5.6 +/- 3.3 to 0.3 +/- 0.2 msec); a 5 point least square fit algorithm performed poorly. Sampling MP and BP electrograms below 500 and 400, respectively, often caused maximum shifts greater than 4 msec. Thus, the resolution of the peak and estimated slope is not limited to the sampling period, variations in initiation of sampling can cause significant outliers especially at low sampling rates, and MP electrograms should be sampled faster than BP electrograms for comparable accuracy.

Electrocardiography↗

PubMed1991

Design and implementation of a new computerized system for intraoperative cardiac mapping.

A rapid, portable, yet inexpensive and expandable computer-based system utilizing current technology has been developed from experience in the operating room. An efficient operating system well suited for surgery is defined. New technology recording arrays fabricated from multielectrode flexible Kapton strips were developed and found to be easy to use and highly reliable. Novel arrays are created easily for research or special clinical applications. The system displays all incoming data in real time and transfers 16-s epochs to disk on command. After the user defines a beat for analysis, the computer determines the activation time for each channel, rejects unsatisfactory channels, and displays the results for review and modification before plotting the isochronal map on the monitor. The average time to recall data and produce a map is 16 s; if manual review of 120 channels is included, mapping time is less than 4 min. Clinical data recorded during surgery are discussed. The speed and operational ease demonstrated in the operating room make this computer/electrode system valuable both for surgery and for elucidating basic mechanisms of arrhythmias.

Algorithms↗