David Hampton

Publications

• 1.08

  Impact points

  Improving sensing and detection performance in subcutaneous monitors.

  Peter van Dam, Chris van Groeningen, Richard P M Houben, David R Hampton

  Journal of electrocardiology. 09/2009;

  Implantable loop recorders (ILRs) are used for continuous assessment of patients at risk for syncope and arrhythmia. Device accuracy depends on appropriate sensing of the patient's electrocardiogram (ECG) signal. However, current methods for sensing cardiac electrical activity rely on simple thr... [more] Implantable loop recorders (ILRs) are used for continuous assessment of patients at risk for syncope and arrhythmia. Device accuracy depends on appropriate sensing of the patient's electrocardiogram (ECG) signal. However, current methods for sensing cardiac electrical activity rely on simple threshold detectors that are computationally efficient but nonspecific. We test the hypothesis that better ILR implant positions will increase detection accuracy. Ten healthy subjects were studied as they assumed 12 different postures. Body surface potential map (BSM) recordings were used to estimate bipolar R-wave amplitudes for 64 potential implant sites at 360 orientations per site. Optimal sites were identified as the combination of position and orientation that consistently gave the largest signal and the lowest variability during posture changes. Results showed that posture impacts the R-wave amplitude in both BSM and derived bipolar ECGs in healthy subjects. Specific postures are associated with significant drops in R-wave signal amplitude that could cause loss of signal detection in ILRs, especially in positions likely to displace the diaphragm. R-wave changes occurred abruptly as posture was changed. Optimal implant locations cluster near the center of the chest, aligned with the cardiac axis, consistent with the steeper isoelectric gradients known to be associated with these positions.
• 1.08

  Impact points

  Overcoming barriers to developing seamless ST-segment elevation myocardial infarction care systems in the United States: recommendations from a comprehensive Prehospital 12-lead Electrocardiogram Working Group.

  Daniel M Frendl, Sebastian T Palmeri, J Robert Clapp, David Hampton, Maria Sejersten, Dwayne Young, Barbara Drew, Robert Farrell, Jan Innes, James Russell, G Ian Rowlandson, Yanina Purim-Shem-Tov, B Kevin Underhill, Sophia Zhou, Galen S Wagner

  Journal of electrocardiology. 06/2009;

  BACKGROUND: Reducing time to reperfusion treatment for patients with ST-segment elevation myocardial infarction (STEMI) improves patient outcomes. Few medical systems consistently meet current benchmarks regarding timely access to treatment. Studies have widely demonstrated that prehospital 12-lead ... [more] BACKGROUND: Reducing time to reperfusion treatment for patients with ST-segment elevation myocardial infarction (STEMI) improves patient outcomes. Few medical systems consistently meet current benchmarks regarding timely access to treatment. Studies have widely demonstrated that prehospital 12-lead electrocardiography can facilitate early catheterization laboratory activation and is the most effective means of decreasing patients' time to treatment. METHODS: We gathered experts to examine the barriers to implementation of prehospital 12-lead electrocardiographic monitoring and transmission to in-hospital cardiologists in creating seamless STEMI care systems (STEMI-CS) and propose multidisciplinary approaches to overcoming these barriers. RESULTS AND CONCLUSIONS: Physicians, hospital systems, and emergency medical services often lack coordination of care delivery and receive fragmented funding and oversight. Clinical and regulatory guidelines do not emphasize local solutions to achieving clinical benchmarks, do not target incentives at all components of the STEMI-CS, and underemphasize risk-based approaches to protecting patient health. Integration of the multiple complex components involved in STEMI-CS is essential to improving care delivery.
• 3.58

  Impact points

  Effect on treatment delay of prehospital teletransmission of 12-lead electrocardiogram to a cardiologist for immediate triage and direct referral of patients with ST-segment elevation acute myocardial infarction to primary percutaneous coronary intervention.

  Maria Sejersten, Martin Sillesen, Peter R Hansen, Søren Loumann Nielsen, Henrik Nielsen, Sven Trautner, David Hampton, Galen S Wagner, Peter Clemmensen

  The American journal of cardiology. 04/2008; 101(7):941-6.

  Prehospital electrocardiogram (ECG) transmission to hospitals was shown to reduce time to treatment in patients with acute myocardial infarction. However, new technologies allow transmission directly to a mobile unit so an attending physician can respond irrespective of presence within or outside th... [more] Prehospital electrocardiogram (ECG) transmission to hospitals was shown to reduce time to treatment in patients with acute myocardial infarction. However, new technologies allow transmission directly to a mobile unit so an attending physician can respond irrespective of presence within or outside the hospital. The primary study purpose was to determine whether delays could be decreased in an urban area by transmitting a prehospital 12-lead ECG directly to the attending cardiologist's mobile telephone for rapid triage and transport to a primary percutaneous coronary intervention (PCI) center, bypassing local hospitals and emergency departments. A secondary purpose was to describe whether transport would be safe despite longer transport times. During a 2-year period, patients with acute nontraumatic chest pain had their prehospital ECG transmitted directly to a cardiologist's mobile telephone. Time to treatment was compared with historic controls. After ECG evaluation, 168 patients (30%) were referred directly for PCI, and 146 of these (87%) underwent emergent catheterization. In referred patients, median time from 911 call to PCI was significantly shorter than in the control group (74 vs 127 minutes; p <0.001). Accordingly, door-to-PCI time was 63 minutes shorter for referred patients versus controls (34 vs 97 minutes; p <0.001). During transport, 7 patients (4%) experienced ventricular fibrillation; 3 patients (2%), ventricular tachycardia; and 1 patient (0.5%), pulseless electrical activity, including 2 deaths (1%) caused by treatment-resistant arrhythmia. In conclusion, transmission of a prehospital 12-lead ECG directly to the attending cardiologist's mobile telephone decreased door-to-PCI time by >1 hour when patients were transported directly to PCI centers, bypassing local hospitals. Ambulance transport seems safe despite longer transport times.
• 1.08

  Impact points

  Diversion of ST-elevation myocardial infarction patients for primary angioplasty based on wireless prehospital 12-lead electrocardiographic transmission directly to the cardiologist's handheld computer: a progress report.

  Peter Clemmensen, Maria Sejersten, Martin Sillesen, David Hampton, Galen S Wagner, Søren Loumann Nielsen

  Journal of electrocardiology. 11/2005; 38(4 Suppl):194-8.

  BACKGROUND: Time to reperfusion is critical for outcome in patients with ST-elevation myocardial infarction (STEMI). In our region, patients are routinely treated by primary percutaneous coronary intervention (pPCI), but rerouting patients from the primary receiving hospital to a catheterization cen... [more] BACKGROUND: Time to reperfusion is critical for outcome in patients with ST-elevation myocardial infarction (STEMI). In our region, patients are routinely treated by primary percutaneous coronary intervention (pPCI), but rerouting patients from the primary receiving hospital to a catheterization center can cause unacceptable delays that may exceed 1 hour in the emergency department. Wireless transmission of prehospital electrocardiograms (ECGs) to receiving stations in hospitals has been shown to reduce time from symptom onset to reperfusion. However, transmission directly to a cardiologist's handheld digital device has not been investigated. AIM: To report preliminary data from a larger ongoing trial evaluating prehospital 12-lead ECG transmission to a cardiologist's handheld device in patients with symptoms suggesting an acute coronary syndrome. METHOD: Patients suffering acute, nontraumatic chest pain have their prehospital ECG transmitted by wireless technology directly to a cardiologist's handheld device at an invasive hospital, allowing diversion of STEMI cases to rapid pPCI. Transmission failures are documented. Times for symptom onset, 911 alert, ECG recording, hospital arrival, and pPCI are obtained. All time intervals are summarized as median values and are compared with historic controls from the Danish multicenter study, DANAMI-2. RESULTS: During the first 15 months of the trial, prehospital ECGs were transmitted for 408 chest pain patients with an overall success rate of 93%. Cardiologist receiving the ECGs recommended that 113 patients (28%) be diverted for pPCI. Mean time from symptom onset to 911 alert was 2 hours 16 minutes (range, 1 minute to 23 hours 15 minutes), and the ambulance response interval was 5 minutes (range, 1-25 minutes). The ambulance on-scene time had increased by 7 minutes compared with historic controls (P<.05). Time from ECG recording to hospital arrival was 25 minutes. The total prehospital time was 2 hours 57 minutes. The hospital treatment time was substantially reduced among diverted patients. Hospital arrival to procedure start was 40 minutes, compared with 94 minutes in the DANAMI-2 historic control group (P<.01). CONCLUSION: These preliminary data suggest that transmission of prehospital 12-lead ECGs directly to the attending cardiologist using handheld devices is a technologically sound concept without major safety concerns and markedly reducing time to reperfusion in patients with STEMI.
• 3.08

  Impact points

  Capnogram shape in obstructive lung disease.

  Baruch Krauss, Aaron Deykin, Alexander Lam, Joan J Ryoo, David R Hampton, Paul W Schmitt, Jay L Falk

  Anesthesia and analgesia. 04/2005; 100(3):884-8, table of contents.

  Small, preliminary studies have suggested that capnograms of obstructive lung disease (OD) exhibit a characteristic shape and that this shape may be correlated to changes in forced expiratory volume in 1 s (FEV(1)). We evaluated the association between capnograms and spirometry from subjects with OD... [more] Small, preliminary studies have suggested that capnograms of obstructive lung disease (OD) exhibit a characteristic shape and that this shape may be correlated to changes in forced expiratory volume in 1 s (FEV(1)). We evaluated the association between capnograms and spirometry from subjects with OD with normal and restrictive lung disease (RD) subjects. The study was conducted in a prospective, nonrandomized manner using a convenience sample of 262 subjects presenting to a pulmonary function laboratory. Capnograms were recorded before pulmonary function testing. Subjects with OD had capnograms that were significantly different from normal and RD subjects. These differences were progressive, increasing with disease severity. The average take-off angle of the ascending phase for severe OD was 7.2 degrees less (95% confidence interval [CI]: 4.0, 10.4) than for normals. The average alveolar plateau elevation angle was 0.8 degrees more (95% CI: 0.14, 1.4) for moderate OD than for normals, whereas the average elevation angle was 3.6 degrees more (95% CI: 2.9, 4.3) for severe OD than for normals. Differences between OD capnograms and normal and RD capnograms, correlating to changes in FEV(1), were sufficiently large enough to suggest that the capnogram could be used to discriminate between OD and normal.
• 1.08

  Impact points

  Modification of ACC/ESC criteria for acute myocardial infarction.

  Peter W Macfarlane, David Browne, Brian Devine, Elaine Clark, Evan Miller, Jodat Seyal, David Hampton

  Journal of electrocardiology. 02/2004; 37 Suppl:98-103.

  The American College of Cardiology (ACC) and European Society of Cardiology (ESC) recently proposed criteria for acute ST elevation myocardial infarction (STEMI). These criteria were based on STj >0.1 mV in limbs leads and V4-V6, or STj >0.2 mV in V1 to V3 with criteria being met in two contig... [more] The American College of Cardiology (ACC) and European Society of Cardiology (ESC) recently proposed criteria for acute ST elevation myocardial infarction (STEMI). These criteria were based on STj >0.1 mV in limbs leads and V4-V6, or STj >0.2 mV in V1 to V3 with criteria being met in two contiguous leads. The criteria were neither age nor sex dependent and the aim of the present study was to evaluate whether or not improved STEMI criteria that were age and gender dependent could be developed. A training set of 789 ECGs from patients presenting with chest pain due to cardiac and other causes was available for study. Revised criteria for STEMI were developed using these data as well as ECGs from a normal adult population of 859 males and 637 females. A test set of ECGs was available in the form of 1220 ECGs recorded from a separate hospital from patients presenting with chest pain. 248 patients had an acute myocardial infarction on the basis of conventional clinical criteria while 972 did not. There was an improvement in sensitivity using the new criteria compared to the old criteria from 41.5% to 46.7% while specificity improved from 96.0% to 98.5%. Specificity in normals improved from 92.6% to 99.8%. The conclusion drawn is that while the ACC/ESC criteria are simple to apply, they are not particularly specific and can be improved by being supplemented by other ECG measures and optimized for age and sex.
• 1.52

  Impact points

  The use of brain natriuretic peptide as a screening test for left ventricular systolic dysfunction- cost-effectiveness in relation to open access echocardiography.

  Victor Sim, David Hampton, Ceri Phillips, Su-Neng Lo, Sanjeev Vasishta, John Davies, Micheal Penney

  Family practice. 11/2003; 20(5):570-4.

  BACKGROUND: Heart failure due to left ventricular systolic dysfunction (LVSD) has a high prevalence in the adult population but is difficult to diagnose accurately on clinical grounds in the community. Early diagnosis is important as effective treatments are available to reduce morbidity and mortali... [more] BACKGROUND: Heart failure due to left ventricular systolic dysfunction (LVSD) has a high prevalence in the adult population but is difficult to diagnose accurately on clinical grounds in the community. Early diagnosis is important as effective treatments are available to reduce morbidity and mortality. Echocardiography is widely used to assess heart failure; however, this technology is relatively expensive and of limited availability. A potential diagnostic aid in primary care is the measurement of plasma brain natriuretic peptide (BNP). OBJECTIVE: This study was performed to assess the value of BNP measurement as a selective pre-screen for breathless patients referred for open access echocardiography. METHODS: BNP was measured by radioimmunoassay with prior extraction in 83 breathless subjects (age range 37-87 years, mean 72). Standard echocardiography was performed and left ventricular systolic function was assessed. RESULTS: The prevalence of LVSD was 31% in this group. At cut-off values chosen to give negative predictive values for LVSD of >98% (BNP = 19 pg/ml), the sensitivity, specificity and positive predictive value for BNP were 100, 49.1 and 46.9%. Using this BNP threshold as a pre-screen for echocardiography would make a net saving of pound 964.20 without compromising the diagnostic accuracy. CONCLUSION: BNP measurement appears to have a significant cost-effective benefit for the selection of patients for echocardiography.
• 4.23

  Impact points

  Specificity and sensitivity of automated external defibrillator rhythm analysis in infants and children.

  Elizabeth Atkinson, Bridget Mikysa, Jeffrey A Conway, Morgan Parker, Karla Christian, Jayant Deshpande, Timothy Kevin Knilans, Jacqueline Smith, Carolyn Walker, Ronald E Stickney, David R Hampton, Mary Fran Hazinski

  Annals of emergency medicine. 09/2003; 42(2):185-96.

  STUDY OBJECTIVES: The rhythm detection algorithms of automated external defibrillators have been derived from adult rhythms, and their ability to discriminate between shockable and nonshockable rhythms in children is largely unknown. This study evaluates the performance of 1 automated external defib... [more] STUDY OBJECTIVES: The rhythm detection algorithms of automated external defibrillators have been derived from adult rhythms, and their ability to discriminate between shockable and nonshockable rhythms in children is largely unknown. This study evaluates the performance of 1 automated external defibrillator algorithm in infants and children and evaluates algorithm performance with anterior-posterior versus sternal-apex lead placement. METHODS: We enrolled pediatric patients in a critical care unit, an electrophysiology laboratory, and a cardiac operating room. A monitor-defibrillator recorded ECGs by means of standard defibrillation-monitor pads. Selected 15-second rhythm samples were played into a LIFEPAK 500 automated external defibrillator, and the automated external defibrillator "shock/no shock" decision was documented. To determine sensitivity and specificity, the automated external defibrillator decision was compared with the "shockable" versus "nonshockable" rhythm classification provided by 3 expert clinicians who were blinded to the automated external defibrillator decision. RESULTS: We recorded 1,561 rhythm samples from 203 pediatric patients (median age 11 months; range, day of birth to 7 years). The automated external defibrillator recommended a shock for 72 of 73 rhythm samples classified as coarse ventricular fibrillation by expert review (sensitivity 99%; 95% confidence interval [CI] 93% to 100%); and correctly reached a "no shock advised" decision for 1,465 of 1,472 rhythm samples classified as nonshockable by experts (specificity 99.5%). Specificity was 99.1% (95% CI 97.8% to 99.8%) with the sternal-apex lead and 99.4% (95% CI 98.1% to 99.9%) with the anterior-posterior lead. CONCLUSION: This automated external defibrillator algorithm has high specificity and sensitivity when used in infants and children with either sternal-apex or anterior-posterior lead placement.
• 2.10

  Impact points

  The unreliability of subjective probe estimates of cyclofusional vergence performance.

  A E Kertesz, D R Hampton

  Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv für klinische und experimentelle Ophthalmologie. 02/1983; 220(2):100-1.

• Fusional vergence response to local peripheral stimulation.

  D R Hampton, A E Kertesz

  Journal of the Optical Society of America. 02/1983; 73(1):7-10.

  Horizontal, convergent disparities were introduced between dichoptic stimuli confined to small regions of the peripheral retina. Stimuli were presented at 32 locations: radial positions varied in 5-deg increments up to 20 deg, while angular position varied in 45-deg steps. The stimulus size and disp... [more] Horizontal, convergent disparities were introduced between dichoptic stimuli confined to small regions of the peripheral retina. Stimuli were presented at 32 locations: radial positions varied in 5-deg increments up to 20 deg, while angular position varied in 45-deg steps. The stimulus size and disparity were scaled in accordance with the cortical magnification factor. Eye movements were objectively measured, and the relative contributions of the motor and nonmotor components to the fusional response were evaluated as a function of stimulus eccentricity and angular position. Vergence responses elicited by peripheral disparities had longer latencies and durations and were more asymmetric than the movements elicited by foveal disparities. The composition of the fusional response changed with the position of the stimulus. The largest percentage of motor compensation was observed for stimuli located either near the line of sight or directly above it. The variations in the size of the motor response with increasing eccentricity could not be explained by the cortical magnification factor.
• 1.46

  Impact points

  The extent of Panum's area and the human cortical magnification factor.

  D R Hampton, A E Kertesz

  Perception. 02/1983; 12(2):161-5.

  The horizontal extent of Panum's fusional area was measured by means of a single-vertical-line stimulus placed at thirty-two locations throughout the peripheral visual field. These results were transformed by using known values of the human cortical magnification factor (CMF), and the hypothesis... [more] The horizontal extent of Panum's fusional area was measured by means of a single-vertical-line stimulus placed at thirty-two locations throughout the peripheral visual field. These results were transformed by using known values of the human cortical magnification factor (CMF), and the hypothesis that variations in the magnitude of Panum's area may be accounted for by variations in the CMF was tested. It was found that the increase in Panum's area with increasing stimulus eccentricity correlates well with the CMF, but that variations in the extent of Panum's area as a function of angular position around the line of sight do not correspond well with the CMF.
• 2.29

  Impact points

  The unreliability of nonius line estimates of vertical fusional vergence performance.

  A E Kertesz, D R Hampton, H W Sabrin

  Vision research. 02/1983; 23(3):295-7.

• Human response to cyclofusional stimuli containing depth cues.

  D R Hampton, A E Kertesz

  American journal of optometry and physiological optics. 02/1982; 59(1):21-7.

  The cyclofusional response to stimuli containing depth cues was studied. Eye positions were monitored by an objective, binocular, eye movement measuring technique while a psychophysical method was used to measure the stereoscopic responses. We found that the overall response contains both stereoscop... [more] The cyclofusional response to stimuli containing depth cues was studied. Eye positions were monitored by an objective, binocular, eye movement measuring technique while a psychophysical method was used to measure the stereoscopic responses. We found that the overall response contains both stereoscopic and cyclofusional components and that the cyclofusional response includes a large nonmotor, or sensory, contribution. The composition of the response was unaffected by changes in stimulus size. Increased stimulus complexity elicited larger cyclotorsional eye movements and diminished the amount of perceived inclination which was observed in the fused percept.
• 3.43

  Impact points

  Fusional response to extrafoveal stimulation.

  A E Kertesz, D R Hampton

  Investigative ophthalmology & visual science. 11/1981; 21(4):600-5.

  Horizontal and vertical fusional responses to extrafoveal stimulation were examined. An objective binocular eye movement measuring technique was utilized to position an artificial, stabilized scotoma over the central 10 degrees diameter area of one eye. The responses contained both a motor and nonmo... [more] Horizontal and vertical fusional responses to extrafoveal stimulation were examined. An objective binocular eye movement measuring technique was utilized to position an artificial, stabilized scotoma over the central 10 degrees diameter area of one eye. The responses contained both a motor and nonmotor, or sensory, component. The monocular eye movements were asymmetrical.