Impact of a CE-Marked Medical Software Sensor on COVID-19 Pandemic Progression Prediction: a Register Study Using Machine Learning Methods

Background

To address the current COVID-19 and any future pandemic, we need robust, real-time, and population-scale collection and analysis of data. Rapid and comprehensive knowledge on the trends in reported symptoms in populations provides an earlier window into the progression of viral spread, and helps to predict the needs and timing of professional health care.

Objective

The objective of this study was to use a Conformité Européenne (CE)-marked medical online symptom checker service, Omaolo, and validate the data against the national demand for COVID-19–related care to predict the pandemic progression in Finland.

Methods

Our data comprised real-time Omaolo COVID-19 symptom checker responses (414,477 in total) and daily admission counts in nationwide inpatient and outpatient registers provided by the Finnish Institute for Health and Welfare from March 16 to June 15, 2020 (the first wave of the pandemic in Finland). The symptom checker responses provide self-triage information input to a medically qualified algorithm that produces a personalized probability of having COVID-19, and provides graded recommendations for further actions. We trained linear regression and extreme gradient boosting (XGBoost) models together with F-score and mutual information feature preselectors to predict the admissions once a week, 1 week in advance.

Results

Our models reached a mean absolute percentage error between 24.2% and 36.4% in predicting the national daily patient admissions. The best result was achieved by combining both Omaolo and historical patient admission counts. Our best predictor was linear regression with mutual information as the feature preselector.

Conclusions

Accurate short-term predictions of COVID-19 patient admissions can be made, and both symptom check questionnaires and daily admissions data contribute to the accuracy of the predictions. Thus, symptom checkers can be used to estimate the progression of the pandemic, which can be considered when predicting the health care burden in a future pandemic.

Left ventricular ejection fraction adds value over the GRACE score in prediction of 6-month mortality after ACS: the MADDEC study

Background

Reduced left ventricular ejection fraction (LVEF) is a risk marker for mortality after an acute coronary syndrome (ACS). Global Registry of Acute Coronary Events (GRACE) risk score, developed almost two decades ago, is the preferred scoring system for risk stratification in ACS. The aim of this study was to validate the GRACE score and evaluate whether LVEF has incremental predictive value over the GRACE in predicting 6-month mortality after ACS in a contemporary setting.

Methods

A retrospective analysis of all 1576 consecutive patients who were admitted to Tays Heart Hospital and underwent coronary angiography for a first episode of ACS (2015–2016). Clinical risk factors were extensively recorded. Adjusted Cox regression analysis was used to analyse the associations between LVEF and the GRACE score with 6-month all-cause mortality. The incremental predictive value was assessed by the change in C-statistic by Delong’s method for paired samples and by index of discrimination improvement (IDI).

Results

In univariable analysis, both LVEF and the GRACE were associated with 6-month mortality, and after applying both variables into the same model, the results remained significant (GRACE score: HR: 1.036, 95% CI 1.030 to 1.042; LVEF: HR: 0.965, 95% CI 0.948 to 0.982, both HRs corresponding to a one unit change in the exposure variable). The GRACE score demonstrated good discrimination for mortality (C-statistic: 0.833, 95% CI 0.795 to 0.871). Adding LVEF to the model with the GRACE score improved model performance significantly (C-statistic: 0.848, 95% CI 0.813 to 0.883, p=0.029 for the improvement and IDI 0.0171, 95% CI 0.0016 to 0.0327, p=0.031).

Conclusions

Adding LVEF to the GRACE score significantly improves risk prediction of 6-month mortality after ACS.

Extensive phenotype data and machine learning in prediction of mortality in acute coronary syndrome - the MADDEC study

Objective: Investigation of the clinical potential of extensive phenotype data and machine learning (ML) in the prediction of mortality in acute coronary syndrome (ACS). Methods: The value of ML and extensive clinical data was analyzed in a retrospective registry study of 9066 consecutive ACS patients (January 2007 to October 2017). Main outcome was six-month mortality. Prediction models were developed using two ML methods, logistic regression and extreme gradient boosting (xgboost). The models were fitted in training set of patients treated in 2007-2014 and 2017 (81%, n = 7344) and validated in a separate validation set of patients treated in 2015-2016 with full GRACE score data available for comparison of model accuracy (19%, n = 1722). Results: Overall, six-month mortality was 7.3% (n = 660). Several variables were found to be significantly associated with six-month mortality by both ML methods. The xgboost scored the best performance: AUC 0.890 (0.864-0.916). The AUC values for logistic regression and GRACE score were 0.867(0.837-0.897) and 0.822 (0.785-0.859), respectively. The AUC value of xgboost was better when compared to logistic regression (p = .012) and GRACE score (p < .00001). Conclusions: The use of extensive phenotype data and novel machine learning improves prediction of mortality in ACS over traditional GRACE score. KEY MESSAGES The collection of extensive cardiovascular phenotype data from electronic health records as well as from data recorded by physicians can be used highly effectively in prediction of mortality after acute coronary syndrome. Supervised machine learning methods such as logistic regression and extreme gradient boosting using extensive phenotype data significantly outperform conventional risk assessment by the current golden standard GRACE score. Integration of electronic health records and the use of supervised machine learning methods can be easily applied in a single centre level to model the risk of mortality.

Segmentation of facial bone surfaces by patch growing from cone beam CT volumes

OBJECTIVES

The motivation behind this work was to design an automatic algorithm capable of segmenting the exterior of the dental and facial bones including the mandible, teeth, maxilla and zygomatic bone with an open surface (a surface with a boundary) from CBCT images for the anatomy-based reconstruction of radiographs. Such an algorithm would provide speed, consistency and improved image quality for clinical workflows, for example, in planning of implants.

METHODS

We used CBCT images from two studies: first to develop (n = 19) and then to test (n = 30) a segmentation pipeline. The pipeline operates by parameterizing the topology and shape of the target, searching for potential points on the facial bone-soft tissue edge, reconstructing a triangular mesh by growing patches on from the edge points with good contrast and regularizing the result with a surface polynomial. This process is repeated for convergence.

RESULTS

The output of the algorithm was benchmarked against a hand-drawn reference and reached a 0.50 ± 1.0-mm average and 1.1-mm root mean squares error in Euclidean distance from the reference to our automatically segmented surface. These results were achieved with images affected by inhomogeneity, noise and metal artefacts that are typical for dental CBCT.

CONCLUSIONS

Previously, this level of accuracy and precision in dental CBCT has been reported in segmenting only the mandible, a much easier target. The segmentation results were consistent throughout the data set and the pipeline was found fast enough (<1-min average computation time) to be considered for clinical use.

Automatic segmentation for detecting uterine fibroid regions treated with MR-guided high intensity focused ultrasound (MR-HIFU)

PURPOSE

Up to 25% of women suffer from uterine fibroids (UF) that cause infertility, pain, and discomfort. MR-guided high intensity focused ultrasound (MR-HIFU) is an emerging technique for noninvasive, computer-guided thermal ablation of UFs. The volume of induced necrosis is a predictor of the success of the treatment. However, accurate volume assessment by hand can be time consuming, and quick tools produce biased results. Therefore, fast and reliable tools are required in order to estimate the technical treatment outcome during the therapy event so as to predict symptom relief.

METHODS

A novel technique has been developed for the segmentation and volume assessment of the treated region. Conventional algorithms typically require user interaction ora priori knowledge of the target. The developed algorithm exploits the treatment plan, the coordinates of the intended ablation, for fully automatic segmentation with no user input.

RESULTS

A good similarity to an expert-segmented manual reference was achieved (Dice similarity coefficient = 0.880 ± 0.074). The average automatic segmentation time was 1.6 ± 0.7 min per patient against an order of tens of minutes when done manually.

CONCLUSIONS

The results suggest that the segmentation algorithm developed, requiring no user-input, provides a feasible and practical approach for the automatic evaluation of the boundary and volume of the HIFU-treated region.

The PredictAD project: development of novel biomarkers and analysis software for early diagnosis of the Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia affecting 36 million people worldwide. As the demographic transition in the developed countries progresses towards older population, the worsening ratio of workers per retirees and the growing number of patients with age-related illnesses such as AD will challenge the current healthcare systems and national economies. For these reasons AD has been identified as a health priority, and various methods for diagnosis and many candidates for therapies are under intense research. Even though there is currently no cure for AD, its effects can be managed. Today the significance of early and precise diagnosis of AD is emphasized in order to minimize its irreversible effects on the nervous system. When new drugs and therapies enter the market it is also vital to effectively identify the right candidates to benefit from these. The main objective of the PredictAD project was to find and integrate efficient biomarkers from heterogeneous patient data to make early diagnosis and to monitor the progress of AD in a more efficient, reliable and objective manner. The project focused on discovering biomarkers from biomolecular data, electrophysiological measurements of the brain and structural, functional and molecular brain images. We also designed and built a statistical model and a framework for exploiting these biomarkers with other available patient history and background data. We were able to discover several potential novel biomarker candidates and implement the framework in software. The results are currently used in several research projects, licensed to commercial use and being tested for clinical use in several trials.

Hyperimmunoglobulinemia D and periodic fever syndrome in children. Review on therapy with biological drugs and case report

Hyperimmunoglobulinemia D syndrome (HIDS) is a rare, autosomal recessively inherited autoinflammatory disease caused by mutations in the mevalonate kinase gene. HIDS usually starts in infancy with recurrent fever episodes lasting 3-7 days and recurring every 4-6 weeks, with only partial symptom decrease in adulthood. Fever is typically accompanied by abdominal pain, vomiting, diarrhoea and cervical lymphadenopathy, and sometimes by skin and joint symptoms. Blood leukocytes and serum C-reactive protein are elevated during the episode, and in addition, high levels of interleukine-1 (IL-1), IL-6 and tumour necrosis factor (TNF) and respective soluble receptors have been measured. Instead, serum immunoglobulin D (IgD) is usually normal until 3 years of age. Currently, there is no established treatment for HIDS. Thus far, four children have been successfully treated with etanercep, TNF-alpha inhibitor, and three children with anakinra, IL-1 receptor antagonist.

CONCLUSION

This review summarizes currently available data on the use biological medicines for HIDS in children. A Finnish 1.5-year-old patient with disease onset at 6 months of age, treated successfully with anakinra, is presented.

Compliance and technical feasibility of long-term health monitoring with wearable and ambient technologies

We developed a system consisting of both wearable and ambient technologies designed to monitor personal wellbeing for several months during daily life. The variables monitored included bodyweight, blood pressure, heart-rate variability and air temperature. Two different user groups were studied: there were 17 working-age subjects participating in a vocational rehabilitation programme and 19 elderly people living in an assisted living facility. The working-age subjects collected data for a total of 1406 days; the average participation period was 83 days (range 43-99). The elderly subjects collected data for a total of 1593 days; the average participation period was 84 days (range 19-107). Usage, technical feasibility and usability of the system were also studied. Some technical and practical problems appeared which we had not expected such as thunder storm damage to equipment in homes and scheduling differences between staff and the subjects. The users gave positive feedback in almost all their responses in a questionnaire. The study suggests that the data-collection rate is likely be 70-90% for typical health monitoring data.

Methods of artificial enlargement of the training set for statistical shape models

Due to the small size of training sets, statistical shape models often over-constrain the deformation in medical image segmentation. Hence, artificial enlargement of the training set has been proposed as a solution for the problem to increase the flexibility of the models. In this paper, different methods were evaluated to artificially enlarge a training set. Furthermore, the objectives were to study the effects of the size of the training set, to estimate the optimal number of deformation modes, to study the effects of different error sources, and to compare different deformation methods. The study was performed for a cardiac shape model consisting of ventricles, atria, and epicardium, and built from magnetic resonance (MR) volume images of 25 subjects. Both shape modeling and image segmentation accuracies were studied. The objectives were reached by utilizing different training sets and datasets, and two deformation methods. The evaluation proved that artificial enlargement of the training set improves both the modeling and segmentation accuracy. All but one enlargement techniques gave statistically significantly (p < 0.05) better segmentation results than the standard method without enlargement. The two best enlargement techniques were the nonrigid movement technique and the technique that combines principal component analysis (PCA) and finite element model (FEM). The optimal number of deformation modes was found to be near 100 modes in our application. The active shape model segmentation gave better segmentation accuracy than the one based on the simulated annealing optimization of the model weights.

Long-term subjective and objective sleep analysis of total sleep time and sleep quality in real life settings

Sleep quality is one of the key elements of the human health status. By observing sleep patterns we can gain information about personal wellbeing. Consumer electronic sleep analysis solutions are now available for use in long-term conditions. In this study we compare different measures for total sleep time and sleep quality. We analyzed visually long- term sleep data collected with actigraphy, sleep logs and ambient sensors to gain more reliable results and compared these results to each single method's output. Correlations of visually analyzed total sleep time between actigraphy total sleep time (correlation coefficient (r) = 0.662, p <0.01) and sleep log total sleep time (r = 0.787, p <0.01) were high. Also comparison between subjective and objective sleep quality was analyzed and small, but significant correlation was found (r = 0.270, p < 0.01).

Estimating intensity of physical activity: a comparison of wearable accelerometer and gyro sensors and 3 sensor locations

Automatic estimation of physical activity using wearable sensors can be used for promotion of a healthier lifestyle. In this study, accelerometers and gyroscopes attached to ankle, wrist and hip were used to estimate intensity of physical activity. The estimates are compared to metabolic equivalent (MET) obtained from a portable cardiopulmonary exercise testing system. Data from common everyday tasks and exercise were collected with 11 subjects. The tasks include, e.g., ironing, vacuuming, walking, running and cycling on exercise bicycle (ergometer). The strongest linear correlation with metabolic equivalent was obtained with the tri-axial accelerometer attached to the ankle (r=0.86).

Automatic extraction of mandibular bone geometry for anatomy-based synthetization of radiographs

We present an automatic method for segmenting Cone-Beam Computerized Tomography (CBCT) volumes and synthetizing orthopantomographic, anatomically aligned views of the mandibular bone. The model-based segmentation method was developed having the characteristics of dental CBCT, severe metal artefacts, relatively high noise and high variability of the mandibular bone shape, in mind. First, we applied the segmentation method to delineate the bone. Second, we aligned a model resembling the geometry of orthopantomographic imaging according to the segmented surface. Third, we estimated the tooth orientations based on the local shape of the segmented surface. These results were used in determining the geometry of the synthetized radiograph. Segmentation was done with excellent results: with 14 samples we reached 0.57+/-0.16 mm mean distance from hand drawn reference. The estimation of tooth orientations was accurate with error of 0.65+/-8.0 degrees. An example of these results used in synthetizing panoramic radiographs is presented.

Docetaxel with epirubicin--investigations on cardiac safety

The aim was to evaluate clinical and subclinical cardiac toxicity of epirubicin-docetaxel (ET) combination. Breast cancer patients were given epirubicin (75 mg/m2 for 15 min), followed 1 h later by a 1-h infusion of docetaxel (75 mg/m2) q3w as first-line treatment. Cardiac function was monitored using a 24-h ambulatory electrocardiogram (ECG), left ventricular ejection fraction (LVEF), physical examination and chest radiography. The median LVEF did not decrease during the course of the treatment: median LVEF was 64% prior to treatment and 68% after cycle 8. The 24-h ECG did not reveal any significant changes in heart rate variability. The number of extrasystoles or cardiac arrhythmia did not increase with the ET treatment. No patient experienced congestive heart failure during treatment or the mean follow-up of 34 months. We conclude that first-line ET caused no major cardiac changes during 6 months of treatment (8 cycles) or during follow-up. Twenty-four-hour ECG, combined with echocardiography to measure LVEF, was a feasible method for the close monitoring of the cardiac effects during chemotherapy.

Docetaxel does not impair cardiac autonomic function in breast cancer patients previously treated with anthracyclines

The effects of docetaxel treatment on autonomic cardiac function was studied with 24-h ECG recordings in breast cancer patients pretreated with anthracyclines. Twenty-four women were evaluated before docetaxel treatment and after 3-4 courses of docetaxel 100 mg/m(2). The heart rate, cardiac extrasystoles and heart rate variability (HRV) in both the time and frequency domain were assessed from 24-h ECG recordings. The acute effects of docetaxel were calculated from 1-h recordings immediately prior to, during and after infusion. Long-term effects were evaluated from 24-h recordings performed before treatment and after 3-4 courses of docetaxel. There was no increase in the number of cardiac extrasystoles during docetaxel infusion. The number of ventricular extrasystoles decreased from 14 (23) to 7 (14) during and 5 (10) after the first infusion (p=0.02). The heart rate, HRV and extrasystoles were similar before and after 3-4 courses of docetaxel. The treatment did not abolish circadian variability of the heart rate. Docetaxel did not deteriorate autonomic cardiac function. In conclusion, our findings suggest that docetaxel does not have harmful cumulative effects on autonomic control of the heart and is therefore unlikely to be cardiotoxic.

Docetaxel and autonomic cardiovascular control in anthracycline treated breast cancer patients

BACKGROUND

Taxoids are new chemotherapeutic agents effective in the treatment of breast cancer. Paclitaxel treatment has been reported to cause some cardiac side effects and both paclitaxel and docetaxel to cause mild, mainly sensory, peripheral neuropathy. Autonomic function tests are sensitive measures of autonomic neuropathy and cardiac regulation. The purpose of this study was to find out whether docetaxel changes neural cardiovascular regulation in breast cancer patients previously treated with anthracyclines.

PATIENTS AND METHODS

Nine women treated for metastatic breast cancer with docetaxel were studied prior to the docetaxel treatment and after the third or fourth course. Autonomic cardiovascular function tests were performed and heart rate and blood pressure variability were assessed with power spectrum analysis.

RESULTS

Heart rate variability or the heart rate responses to the autonomic function tests did not change after docetaxel treatment. The blood pressure response to standing was enhanced and systolic blood pressure variability decreased after three to four cycles of docetaxel.

CONCLUSIONS

Docetaxel treatment did not deteriorate vagal cardiac control in breast cancer patients after exposure to epirubicin. The observed changes in blood pressure responses suggest that docetaxel changes sympathetic vascular control. However, these changes seem to be related to altered cardiovascular homeostasis rather than peripheral sympathetic neuropathy.

Increased amplitude modulation of continuous respiration precedes sudden infant death syndrome -detection by spectral estimation of respirogram

The immaturity of the control of the autonomic nervous system has been suggested as one of the key factors in the pathophysiology of sudden infant death syndrome (SIDS). Therefore, the attenuated control of respiration may also cause more slow oscillatory breathing among infants at risk of SIDS. In this study, patterns of respiratory activity (RAV) and heart rate variability (HRV) were examined in Medilog-records prospectively obtained from 22 tape recordings made on 16 babies subsequently suffering from SIDS and from 22 matched control babies. A total of 248 signal segments, 120 s in duration, representing the state of regular breathing were visually selected for further analysis. The digitised signal sets were detrended, Fast-Fourier-transformed and autospectra as well as cross-spectra for the HRV and HRV were computed. The RAV and HRV were examined at two spectral bands: (1) a low frequency (LF) band 0.03-0.17 Hz (1.8-10 cycles/min) and (2) a high frequency (HF) band 0.3-1.3 Hz (18-90 cycles/min). Different parameters of each band were tested in the spectral analysis of cardiorespiratory control. The LF/HF-ratio of the spectral peak area of the respiratory activity and the LF/HF-ratio of the spectral band area of the respiratory activity were greater in the SIDS group when compared to the controls. No significant intergroup differences were found in the parameters of HRV, or the cross-spectral parameters. Interestingly, the technique appeared helpful in displaying that the victims of SIDS had a significantly greater amount of slow oscillation in the continuous respiratory signal (1.05+/-1.89 vs. 0.41+/-0.57, P=0.02). In the victims of SIDS the respiratory control system seems to be less stable and cause more slow oscillatory breathing and this can be detected using spectral analysis of respiratory activity even during breathing that visually seems to be regular.

Paclitaxel changes sympathetic control of blood pressure

Paclitaxel has become part of standard therapy in the treatment of ovarian and breast cancer. Concern has been raised about the effects of paclitaxel on cardiovascular function. Therefore, this study of the effects of paclitaxel on autonomic cardiovascular control was initiated. Eighteen women treated for ovarian or breast cancer were examined with autonomic cardiovascular function tests, once before the treatment and once after the second course of paclitaxel. Heart rate and blood pressure variability and changes in heart rate and blood pressure responses to the tests were measured. Baroreflex sensitivity was calculated from the Valsalva manoeuvre non-invasively. Paclitaxel did not change heart rate variability at rest compared with the pretreatment level. However, medium frequency variability of blood pressure was smaller after treatment with paclitaxel. Paclitaxel treatment did not impair the heart rate and blood pressure responses to the autonomic function tests. The results do imply that paclitaxel alters sympathetic control of blood pressure. Nevertheless, paclitaxel does not appear to precipitate autonomic cardiac neuropathy.

Haemodynamic response to head-up tilt in elderly hypertensives and diabetics

To examine the haemodynamic mechanism associated with postural hypotension (PH) in elderly people, haemodynamic response to head-up tilt was studied in 14 elderly hypertensives and 13 elderly diabetics. Hypertensives and diabetics were divided into those with or without PH, defined as > or = 10 mmHg decline in mean blood pressure in response to head-up tilt. There was no significant change in cardiac output in hypertensives or diabetics with PH, whereas there was a significant increase during tilt in hypertensives without PH (p < 0.0001) and diabetics without PH (p = 0.0054). Hypertensives without PH showed a significant decrease in total peripheral resistance in response to head-up tilt (p = 0.0043). In hypertensives with PH and in both diabetic groups, there was no change in total peripheral resistance in response to head-up tilt. There was no difference in ejection fractions or heart rate responses between subjects with and without PH in either disease group. The difference in cardiac output change was not explained by myocardial changes observed at echocardiography nor by heart rate response nor by differences in total peripheral resistance. The results suggest that an increase in cardiac output in response to changing posture may be more important than vasoconstriction in protecting elderly subjects from PH.

The role of potassium in postural hypotension: electrolytes and neurohumoral factors in elderly hypertensive patients using diuretics

OBJECTIVE

To study the association between postural hypotension and (i) electrolyte levels and (ii) neurohumoral factors in elderly hypertensive patients using diuretics.

DESIGN

Cross-sectional study of patients and controls.

SETTING

The subjects were gathered from senior citizen clubs or they were referred to the study by general practitioners. The subjects were examined on a geriatric ward in Turku City Hospital.

SUBJECTS

Seven subjects with postural hypotension and 13 controls.

MEASUREMENTS

Plasma electrolyte levels and neurohumoral response to head-up tilt.

RESULTS

There were significantly more hypokalaemic subjects in the postural hypotension group (5/7) than in the control group (1/13) (P < 0.01). The plasma potassium level was negatively correlated to plasma aldosterone (r = -0.57; P < 0.01) and renin activity (r = -0.69; P < 0.001). Subjects with postural hypotension had higher levels of noradrenaline, both supine (P < 0.05) and during tilt (P < 0.05). There were no significant differences in supine or tilt levels of plasma adrenaline, vasopressin, atrial natriuretic peptide, aldosterone and renin activity between the groups.

CONCLUSION

The results suggest that potassium depletion is associated with postural hypotension in elderly hypertensive patients using diuretics. However, it is unclear whether there is a causative link between potassium depletion and postural hypotension or whether they are both caused by some other factor, e.g. volume contraction.

Spectral analysis of heart rate variability in evaluation of sympathetic function in elderly subjects

Plasma concentration of noradrenaline is often used as a measure of sympathetic nervous activity. Recently, the method of spectral analysis of heart rate variability has been introduced to detect autonomic dysfunction. To examine whether spectral analysis of heart rate variability is useful in evaluating sympathetic function, changes in the heart rate variability in the low-frequency spectral band were compared with the change of plasma noradrenaline in response to head-up tilt in elderly hypertensives (n = 13) and diabetics (n = 13). In hypertensive subjects, there was an increase in relative low-frequency power (p = 0.015) and an increase in plasma noradrenaline level (p = 0.040) in response to head-up tilt. Diabetics did not show corresponding changes. There was no change in absolute low-frequency power in either group. It is concluded that spectral analysis of heart rate variability can be useful in evaluating sympathetic function in elderly subjects.

Pre-excitation syndrome in Leber's hereditary optic neuropathy

Pre-excitation syndrome is common in families with Leber's hereditary optic neuropathy (LHON). 24 Finnish families with LHON were screened for the 11778 and the 3460 mitochondrial DNA mutations. 5 of 30 individuals with LHON and the 11778 mutation had the Wolff-Parkinson-White pre-excitation syndrome. None of 10 with the 3460 mutation or of 11 with "other" mutations had this syndrome. Overall, 5 of 51 LHON patients and 9 of 112 symptom-free maternal relatives had Wolff-Parkinson-White syndrome (9%). In paternal relatives, the frequency was 1.6%. Mitochondrial DNA causal for LHON may contribute to pre-excitation syndrome.

Association of breathing movements to the variability of heart rate and blood pressure in foetal lambs

Heart rate (HR) variability and arterial blood pressure (BP) variability were analysed as functions of foetal breathing movements (FBMs) by means of power spectral analysis in seven foetal lambs during the third trimester of gestation. No evidence of FBM-related changes, either in mean HR, mean systolic or diastolic arterial pressures, were found. Mean arterial pulse pressure, HR variability, and BP variability increased during FBMs. The increase in BP variability occurred at frequencies higher than 0.35 Hz, i.e. those of FBMs. The increase in HR variability occurred at 0.07-1.0 Hz, i.e. at every frequency band except the lowest one. Thus, the increase in HR variability was not frequency-specifically related to FBMs. During FBMs the periodic variability of HR at frequencies > 0.35 Hz was only 10% of total HR variability. We suggest that the FBM-related changes of BP variability may be mediated by direct peripheral, hydraulic mechanisms. HR changes involve autonomic control systems: the vagal component of baroreflex seems to be relatively insensitive, whereas the very slow vasomotor component of HR variability is dominant.

Effects of glycopyrrolate and atropine on heart rate variability

Analysis of heart rate variability, combined with physiological tests (deep breathing and tilt tests) was used to characterise the effects of atropine and glycopyrrolate on the parasympathetic nervous tone of the heart in healthy male volunteers. The low dose of atropine (120 micrograms) administered as a continuous infusion in 15 min was associated with parasympatomimetic effects estimated by the slowing of the heart rate and an increase of the mean and beat-to-beat heart rate variability. The bradycardia and increase of heart rate variability following infusion of glycopyrrolate (50 micrograms) was less marked and did not differ significantly from that of placebo. The higher doses of atropine (720 micrograms) and glycopyrrolate (300 micrograms) administered as a continuous infusion in 15 min produced an equal vagal cardiac blockade characterised by significant tachycardia and a decrease in overall and beat-to-beat heart rate variability. It is concluded that at low doses the parasympatomimetic action of glycopyrrolate is less marked than that of atropine; and at higher doses only small differences exist between these two muscarinic antagonists in their effects on cardiac vagal outflow, assessed by heart rate and heart rate variability.

Children in sauna: cardiovascular adjustment

Children's circulatory adjustment to a 10-minute heat stress in a climatic chamber was studied in 61 children and 20 adolescents and young adults. The thermal conditions corresponded to those of an ordinary Finnish sauna bath. In all subjects the rectal temperature and heart rate increased during the heat exposure (P less than .001). Systolic and diastolic blood pressures remained unchanged in sauna, but the systolic and especially the diastolic blood pressure decreased (P less than .001) in children less than 10 years of age immediately after the heat exposure; two vasovagal collapses developed. Cardiac output increased in all but the less than 5-year-old children (P less than .001). This was due to a significant decrease in stroke volume (32.9%) (P less than .001) in children less than 5 years old. Stroke volume declined slightly even in the older subjects. These changes indicate that the Finnish sauna bath puts great demands on a child's circulatory regulation. To avoid possible cardiovascular side effects, particularly small children should be supervised carefully during sauna bathing.

Effect of posture on spontaneous and thermally stimulated cardiovascular oscillations

STUDY OBJECTIVE

The aim of the study was to investigate the effect of posture on thermally stimulated cardiovascular oscillations.

DESIGN

The effect of increased gravitational stress (rising from sitting to standing position) on the thermally stimulated cardiovascular oscillations was measured in young male volunteers. Extensive cardiovascular function data were obtained using a cardiovascular investigation protocol.

SUBJECTS

The volunteers were five fit young men, aged 20-21 years. EXPERIMENTS AND MAIN RESULTS: Cardiovascular changes from sitting to standing indicated increased sympathetic and decreased parasympathetic influence on heart and skin blood vessels; mean heart rate increased, beat to beat heart rate variability diminished, high frequency periodic heart rate variability decreased, low frequency heart rate oscillations and ratio of low frequency to high frequency heart rate variability increased, mean skin blood flow and oscillations of skin blood flow decreased (all p less than 0.05). Thermal skin stimulation at 0.01-0.10 Hz frequency increased both sitting and standing 0.10 Hz periodic heart rate variability (p less than 0.05), and 0.10 Hz thermal stimulation entrained the heart rate oscillations in sitting and standing subjects (p less than 0.05). In contrast, skin blood flow oscillations in sitting subjects decreased, while in standing subjects it increased during 0.10 Hz thermal stimulation compared to the corresponding prestimulus values (p less than 0.04).

CONCLUSIONS

On the basis of previous physiological experiments, these results suggest coupling between thermoregulatory and 0.10 Hz reflex activities.

Plasma pharmacokinetics of Idarubicin and its 13-hydroxymetabolite after intravenous and oral administration under fasting and non-fasting conditions

The plasma pharmacokinetics of Idarubicin and its 13-hydroxy-metabolite have been studied in 10 patients with solid tumours after intravenous and oral administration under fasting and non-fasting conditions in a randomized cross-over design. The plasma concentration time curves of Idarubicin after intravenous administration could be described by the open two or three compartment models. No pharmacokinetic modelling of Idarubicin was possible after oral administration. After oral administration of Idarubicin, the amount of intact drug was higher under non-fasting conditions. The extensive and long-lasting appearance of Idarubicinol suggests that this cytotoxic metabolite is of major clinical importance in i.v. and oral therapy with Idarubicin. The pharmacokinetics of Idarubicinol was not affected by food intake.

Pharmacokinetics of 4' epi-adriamycin after morning and afternoon intravenous administration

The chronopharmacokinetics of 4' epi-adriamycin (Epi) have been studied in ten patients with gynecological malignancies. The drug (45 mg m-2) was administered as a short time (5.0 min) intravenous infusion at 7 a.m. and 7 p.m., in a randomized cross-over design. The pharmacokinetics of Epi were evaluated according to the statistical moment theory. Morning and afternoon dosing of Epi was not bioequivalent. The area under the plasma concentration-time curve (AUC), the maximum plasma concentration (Cmax), mean residence time (MRT) and the terminal half-life time (t1/2) could differ by more than 35% after morning and afternoon dosing. The inter-individual variation of AUC and Cp,max were larger after morning dosing than after afternoon dosing (P less than 0.04). The morning dose of Epi resulted in higher values of AUC in seven of the ten treated patients as compared to the afternoon dose. The terminal half-life times were shorter in eight of the patients after the morning dose.

A non-invasive method for testing neural circulatory control in man

Exaggerated cardiovascular responsiveness is common in young men and may cause non-specific symptoms and poor performance. Conventional autonomic function tests are not clinically useful. We have therefore designed a thermal entrainment method to evaluate sympathetic and parasympathetic cardiovascular function in subjects with dystonic symptoms and orthostatic intolerance. Oscillations of thermal gradient in the skin were produced by standardised periodic stimulation of the lower part of the arm with warm and cool water. Vasomotor activity of the skin induced oscillations of arterial blood pressure which were thought to be regulated by sympathetic and parasympathetic heart rate control and by oscillation of the sympathetically controlled peripheral vascular resistance. We tested the method in subjects with cardiovascular symptoms (n = 7) and controls (n = 7). At supine rest, the frequency response of the heart rate variability to the thermal stimulation at frequencies of 0.01, 0.02, 0.03 and 0.1 Hz was significantly different (p = 0.008) between symptomatic subjects and controls. The gain of the heart rate control was increased to 0.03 Hz [-1.3(SEM 0.5) dB v -3.8(0.8) dB, p = 0.068] and decreased at 0.1 Hz [-3.9(1.1) dB v -1.5(0.6) dB, p = 0.076] in the test group compared to the control group. At stimulus frequencies of less than 0.03 Hz the individual overall heart rate variability of the subjects with symptoms stayed below the mean control value, at 60(6) ms v 79(15) ms, p = 0.16. The cutaneous temperature oscillations at the site of stimulation, frequency response of the oscillations of the skin blood flow and respiration to the thermal stimulation, and mean heart rate were similar in the both groups. The results show that this thermal entrainment method quantifies the increased sympathetic and decreased parasympathetic cardiac control of subjects with dystonic symptoms.

Multivariate autoregressive modeling of autonomic cardiovascular control in neonatal lamb

The neonatal cardiovascular control system is a complicated interactive system which is under vigorous development at birth. From the measurement point of view the cardiovascular control is a closed-loop system. However, it can be examined on a beat-by-beat basis by analyzing circulatory-controlled variables with advanced signal analysis techniques. This paper proposes to use a multivariate autoregressive modeling technique in the analysis of several simultaneous physiological signals in order to examine interactions and inherent properties in the system. With the proposed multivariate autoregressive modeling technique, a signal is modeled as a linear combination of its own past and the past values of the other simultaneous signals plus a predictive error term of the model. The interactions in the system after the model identification are analyzed in frequency domain utilizing power spectrum estimates of the signals and signal contributions. The applicability of the proposed method was examined by a three-variable model between heart rate, blood pressure and respiration in the study of autonomic cardiovascular control in a chronic neonatal lamb model, in which the cardiovascular status was changed by using a beta-adrenergic autonomic nervous blockade. The study showed that the multivariate autoregressive modeling technique is a feasible technique in studying complicated interactions within the cardiovascular control system.

Interaction of heart rate and respiration in newborn babies

Variability of heart rate (HRV) and transthoracic electric impedance respirogram (TEZ) were examined by spectral analysis in three groups of neonates: healthy term babies (22), healthy preterm babies (21), and preterm babies with respiratory distress syndrome (RDS) (11). Heart rate, TEZ, PtcO2, and PtcCO2 were monitored during quiet sleep on the 1st, 3rd, and 5th day of postnatal life. Autospectra for trend-corrected segments of heart rate and TEZ as well as their cross-spectral density was in less than 0.2 Hz [low frequency (LF)] area (less than 12 cycles/min) in all the neonates. Intergroup comparisons of average band-integrated spectra revealed that the LF spectral density of HRV was greater in the term babies than in the preterm babies on day 3. In the babies with RDS, both LF and high-frequency (HF, greater than 0.2 Hz) were abnormally low throughout the study. In the term infants, the TEZ amplitude spectrum was flat on day 1. On later days, a peak corresponding to the average respiratory rate emerged. In the healthy preterm babies, there was a LF peak in TEZ autospectrum on all days. In the babies with RDS, the peak of ventilator frequency was initially present; finally, the respiratory activity accumulated in the LF area. In the cross-spectra of term babies, there was a LF peak on all days. On day 5, an additional HF peak appeared, representing respiratory sinus arrhythmia. In the healthy preterm babies, only a LF peak was present.(ABSTRACT TRUNCATED AT 250 WORDS)

Autonomic neuropathy and vibration exposure in forestry workers

The variation in heart rate (HRV) at rest and during deep breathing (6 cycles a minute) of 88 professional lumber jacks was studied using a computer technique. The traditional indexes of HRV (CV, CVS, MEAN) were calculated and the spectral components of the HRV were also computed. There was a significant difference (p less than 0.001) between the HRV indexes during the deep breathing test in those with the shortest (CV = 10.1 +/- 1.1) and those with the longest (CV V 6.2 +/- 0.4) exposures to vibration. The values of the HRV indexes decreased with age, but multiple regression analysis showed that the total exposure time to vibration had an independent negative association with the HRV. There were significant differences in all the frequency bands (frequency related power, FRP) of the heart rate between those with the longest and those with the shortest exposures. The HRV during a deep breathing test is associated with the activity of the parasympathetic nervous system and is decreased in autonomic neuropathies. Our results suggest that prolonged exposure to the vibration caused by a chain saw has a negative effect on the parasympathetic activity and thus causes autonomic dysfunction.

Effects of haemodialysis on heart rate variability in chronic renal failure

The influence of haemodialysis (HD) on the heart rate variability (HRV) was investigated in nine non-diabetic patients on maintenance haemodialysis. The R-R intervals were measured in recordings during spontaneous quiet breathing and during controlled deep breathing before and after a single HD session. The HRV was expressed as the standard deviation of the mean R-R interval in 3 min ECG recordings. Heart rate variability is the irregularity in the heart rate mainly caused by autonomic control mechanisms. The long-term HRV during quiet breathing was statistically significantly (p less than 0.05) higher after the HD than before. The HRV in the intermediate frequency range of 0.075-0.125 Hz was also significantly increased by the HD. This suggests that some metabolic agents interfering with the heart rate regulation are removed by the haemodialysis, and as a result a better function of the autonomic cardiac control is achieved in uraemic patients.

Rapid changes in rate-corrected and uncorrected systolic time intervals during cold pressor test

The changes in heart rate and systolic time intervals were studied in a group of 10 young healthy male volunteers during immersion of their hand in ice water for 1 min. The heart rate and systolic time intervals were measured from electro-, phono-, and impedance cardiograms in the standard way. When the cold immersion was done in the supine position the left ventricular ejection time (LVET) and the electromechanic systole (Q-S2Tc) shortened, and when corrected for the heart rate the Q-S2Tc lengthened in the beginning of the immersion. In the head-up position the Q-S2T shortened in the beginning of the immersion while the rate-corrected systolic time intervals remained unchanged. Most of the changes in the systolic time intervals disappeared before the last quarter of the cold immersion. It was observed that during the cold immersion the linear regression coefficients between the heart rate and the Q-S2T in the supine position as well as between the heart rate and the LVET, Q-S2T and the PEP in the head-up position were greater than the regression coefficients used in the rate correction.

Patterns of QT/QS2 ratio in vasomotorically labile young men

The QT/QS2 ratio in seven 21-year-old men with a history of vasomotor lability was measured when they were resting supine and during orthostatic, Valsalva and diving reflex tests. The vasolability was characterized by an abnormal sympathicotonic heart rate (HR) response to the orthostatic test and vacillating inferoapical T waves in the ECG. The results of the vasolabile subjects were compared to those of seven fit control subjects of the same age. In spite of equal HR's in both groups the vasolabile subjects' QT/Q2 ratio constantly exceeded 1.00 during the whole test protocol and it was higher than of the controls (P = 0.04). The reversed QT/QS2 relationship in the test subjects seemed to be due both to a prolongation of the QT time and a shortening of the QS2 time. This difference prevailed throughout although the reaction pattern to autonomic stimulations was equal in both groups. We considered an inadequate neural control of the heart, possibly with metabolic and haemodynamic interactions, responsible for the prolongation of the electrical systole in relation to the electromechanical systole in the heart of the vasomotorically labile subjects.

Relationship between systolic time intervals and heart rate during four circulatory stress tests

The linear regression equations between heart rate and systolic time intervals were calculated before and during a handgrip test, an orthostatic test, the Valsalva test and a cold pressor test. The subjects were 30 healthy men, average age 20 years. During the 1st min of orthostasis the regression line of the left ventricular ejection time (LVET) was significantly (P less than 0.05) steeper than at rest and that of the pre-ejection period (PEP) was significantly (P less than 0.01) less steep than at rest, and the regression between HR and the PEP/LVET ratio deviated significantly (P less than 0.001) from zero. During the Valsalva maneuver, the regression line of the LVET became significantly (P less than 0.001) steeper than at rest and the regression coefficient of the PEP changed from negative to positive, the difference being significant (P less than 0.001); the regression between HR and the PEP/LVET also deviated significantly (P less than 0.001) from zero. During the cold pressor test the regression line of the electromechanic systole (Q-S2 time) was significantly (P less than 0.01) less steep than at rest. It was concluded that the use of regression equations calculated for the systolic time intervals and heart rate at rest can lead to errors when applied to rate correction of systolic time intervals during an orthostatic, Valsalva, or a cold pressor test.

Heart rate variability, cardiac mechanics, and subjectively evaluated stress during simulator flight

The effects of a simulator flight task on the heart rate variation (HRV) and hemodynamic variables were studied in nine pilots with instrument flight ratings. An electrocardiogram (ECG), phonocardiogram (PCG), and impedance cardiogram (ICG) were recorded continuously during three successive flights. Indices of HRV, power spectra, and autocorrelograms were computed from the R-R interval signal. Stroke volume (SV), cardiac output (CO), and systolic time intervals (STI) were determined by means of the ECG, PCG, and ICG. A scaling method for a subjective evaluation of tiredness, effort, and success during the flight was used. The repeats of the flight task decreased the heart rate (HR), CO, and cardiac index (CI). The different phases of the flight altered the HR (mean 97 min-1, S.E.M. 4 min-1), total HRV (RMSM) (mean 33 ms, S.E.M. 5 ms), and the periodic HRV. Subjectively, the pilots felt only moderate stress. The subjectively evaluated tiredness was significantly associated with the STI. Moderate informative stress in the flight simulator affected the chronotropic parameters of the heart. The inotropic state of the heart was not affected by the different phases of the flight but possibly by the diminishing sympathetic drive with accommodation during the repeats.

Decreased heart rate variation in decerebration syndrome: quantitative clinical criterion of brain death?

Heart rate variation (HRV) was measured in 12 children with brain death. Computer analysis demonstrated an overall heart rate variation (RMSM) of 3.5 to 9.6 msec (mean, 6.0 msec). The respective figures for beat-to-beat variation (RMSSD) were 4 to 16 msec (mean, 7.7 msec). Normal infants (RMSM, 20 to 30 msec) and children (RMSM, 50 to 90 msec) and infants with respiratory distress syndrome (RMSM, 10 to 20 msec) have a clearly higher HRV than those with brain death. In all subjects a periodic component of the HRV with a cycle length of 5.9 +/- 0.26 seconds was discovered. In five patients an additional periodic component was found that corresponded exactly to the rate of artificial respiration. This study demonstrated the value of accurate digital techniques in the characterization of fixed heart rate in decerebration. This phenomenon could be considered one clinical criterion of brain death.