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Jan-Erik Karlsson

Publications and source records attributed to Jan-Erik Karlsson.

7 recordsLinked to original sources
PubMed2006

Feature extraction for systolic heart murmur classification.

Heart murmurs are often the first signs of pathological changes of the heart valves, and they are usually found during auscultation in the primary health care. Distinguishing a pathological murmur from a physiological murmur is however difficult, why an "intelligent stethoscope" with decision support abilities would be of great value. Phonocardiographic signals were acquired from 36 patients with aortic valve stenosis, mitral insufficiency or physiological murmurs, and the data were analyzed with the aim to find a suitable feature subset for automatic classification of heart murmurs. Techniques such as Shannon energy, wavelets, fractal dimensions and recurrence quantification analysis were used to extract 207 features. 157 of these features have not previously been used in heart murmur classification. A multi-domain subset consisting of 14, both old and new, features was derived using Pudil's sequential floating forward selection (SFFS) method. This subset was compared with several single domain feature sets. Using neural network classification, the selected multi-domain subset gave the best results; 86% correct classifications compared to 68% for the first runner-up. In conclusion, the derived feature set was superior to the comparative sets, and seems rather robust to noisy data.

Aged↗
PubMed2005

Denial in patients with a first-time myocardial infarction: relations to pre-hospital delay and attendance to a cardiac rehabilitation programme.

BACKGROUND: Survival of a myocardial infarction and subsequent prognosis are highly dependent on the time between onset of symptoms and medical intervention. DESIGN: This cross-sectional study examines whether patients who used the psychological defence mechanism of denial when faced with symptoms of a first-time myocardial infarction tended to also show a prolonged delay in going to the hospital and to be less willing to participate in a cardiac rehabilitation programme. METHODS: One hundred and seven patients, 78 men and 29 women, were enrolled in this study. The sample was divided into two groups depending on whether the patients sought medical help within 4 h after they began experiencing myocardial infarction symptoms (non-delayers) or whether they waited longer (delayers). Denial was measured with the Hackett and Cassem semi-structured interview 3-5 days after the patients entered the hospital. Data on participation (attenders) or not (non-attenders) in the rehabilitation programme was also obtained. RESULTS: Forty-nine patients exhibited a prolonged delay and 76 patients did not attend the rehabilitation programme. Both prolonged delay and a lesser readiness to attend the rehabilitation programme that was offered were related to a greater use of denial. In addition, the great majority of the patients categorized as being high deniers were found to also be both delayers and non-attenders. CONCLUSIONS: The results suggest denial to increase the health risks of persons potentially prone to myocardial infarction. If our knowledge about this psychological defence mechanism is increased, we might be able to reach more patients in alternative and individually based cardiac rehabilitation programmes.

Adult↗
PubMed2004

Vascular and nerve damage in workers exposed to vibrating tools. The importance of objective measurements of exposure time.

The aim of the present study was to compare the development of vibration white fingers (VWF) in workers in relation to different ways of exposure estimation, and their relationship to the standard ISO 5349, annex A. Nineteen vibration exposed (grinding machines) male workers completed a questionnaire followed by a structured interview including questions regarding their estimated hand-held vibration exposure. Neurophysiological tests such as fractionated nerve conduction velocity in hands and arms, vibrotactile perception thresholds and temperature thresholds were determined. The subjective estimation of the mean daily exposure-time to vibrating tools was 192 min (range 18-480 min) among the workers. The estimated mean exposure time calculated from the consumption of grinding wheels was 42 min (range 18-60 min), approximately a four-fold overestimation (Wilcoxon's signed ranks test, p<0.001). Thus, objective measurements of the exposure time, related to the standard ISO 5349, which in this case were based on the consumption of grinding wheels, will in most cases give a better basis for adequate risk assessment than self-exposure assessment.

Acceleration↗
PubMed2004

Pulsed tissue Doppler imaging for the detection of myocardial ischaemia, a comparison with myocardial perfusion SPECT.

In order to compare the diagnostic ability of pulsed tissue Doppler and myocardial perfusion Single Photon Emission Computed Tomography (SPECT) in patients with a history of unstable coronary artery disease, CAD, 26 patients, 22 men and four women, age 47-76 years, were investigated in a prospective study, 5-10 day after an episode of unstable angina. Tissue Doppler and two-dimensional echocardiography were performed during dobutamine stress testing and myocardial scintigraphy after bicycle exercise and at rest. Patients with a normal SPECT had higher peak systolic velocity during dobutamine infusion, 18.9 +/- 4.1 cm s(-1), than patients with ischaemia, 12.2 +/- 3.8 cm s(-1) (P<0.001) or scar, 8.8 +/- 3.0 cm s(-1) (P<0.01). In a territorial analysis the difference in peak systolic velocity between areas with a normal and abnormal SPECT was less apparent. Failure to achieve >/=13 cm s(-1) in mean-peak systolic velocity was the most accurate criterion for detection of significant CAD on SPECT. We conclude that pulsed tissue Doppler can be used for objective quantification of left ventricular wall motion during dobutamine stress testing and for identification of patients with CAD on SPECT but not for identification of regional ischaemia.

Aged↗
PubMed2003

Nurse-led heart failure clinics improve survival and self-care behaviour in patients with heart failure: results from a prospective, randomised trial.

AIM: The aim of this trial was to prospectively evaluate the effect of follow-up at a nurse-led heart failure clinic on mortality, morbidity and self-care behaviour for patients hospitalised due to heart failure for 12 months after discharge. METHODS: A total of 106 patients were randomly assigned to either follow-up at a nurse-led heart failure clinic or to usual care. The nurse-led heart failure clinic was staffed by specially educated and experienced cardiac nurses, delegated the responsibility for making protocol-led changes in medications. The first follow-up visit was 2-3 weeks after discharge. During the visit the nurse evaluated the heart failure status and the treatment, gave education about heart failure and social support to the patient and his family. RESULTS: There were fewer patients with events (death or admission) after 12 months in the intervention group compared to the control group (29 vs 40, p=0.03) and fewer deaths after 12 months (7 vs 20, p=0.005). The intervention group had fewer admissions (33 vs 56, p=0.047) and days in hospital (350 vs 592, p=0.045) during the first 3 months. After 12 months the intervention was associated with a 55% decrease in admissions/patient/month (0.18 vs 0.40, p=0.06) and fewer days in hospital/patient/month (1.4 vs 3.9, p=0.02). The intervention group had significantly higher self-care scores at 3 and 12 months compared to the control group (p=0.02 and p=0.01). CONCLUSIONS: Follow up after hospitalisation at a nurse-led heart failure clinic can improve survival and self-care behaviour in patients with heart failure as well as reduce the number of events, readmissions and days in hospital.

Aged↗
PubMed2002

Monoclonal antibodies selective for low molecular weight neurofilaments.

Neurofilaments are necessary for the maintenance of axonal caliber and structural organization of nerve cells. The low molecular weight form of neurofilament, the neurofilament light protein, which serves as the core of the filament, was used as immunogen for generation of hybridomas with selective reactivity with this form of the filament. Six hybridomas, out of approximately 100 tested clones, were highly discriminatory. All involved epitopes were localized to the rod region of the antigen, as determined by alpha-chymotrypsin digestion of the purified filament and enzymatic peptide mapping. Synthetic peptides (20 mers) covering the entire rod region did not react with the antibodies. A phage display peptide library was used to identify four consensus sequences for the antibodies. The results indicate that all epitopes were of conformational type. Pair-wise BIAcore data furthermore indicated that the epitopes were independent. The access to such specific reagents is a prerequisite for further elucidation of the biology of the low molecular weight form of neurofilaments proteins.

Animals↗