Marcus Karlsson

Influence of energy drinks and alcohol on post-exercise heart rate recovery and heart rate variability

Background:  Media have anecdotally reported that drinking energy drinks in combination with alcohol and exercise could cause sudden cardiac death. This study investigated changes in the electrocardiogram (ECG) and heart rate variability after intake of an energy drink, taken in combination with alcohol and exercise.

Abnormal heart rate variability and subtle atrial arrhythmia in patients with familial amyloidotic polyneuropathy.

Background: Cardiac autonomic dysfunction is a common complication of familial amyloidotic polyneuropathy (FAP), but cardiac arrhythmia and conduction disturbances are also common. We analyzed heart rate variability (HRV) in FAP patients using power spectrum analysis and Poincaré plot analysis.

Adaptive spatio-temporal filtering of disturbed ECGs: a multi-channel approach to heartbeat detection in smart clothing

Intermittent disturbances are common in ECG signals recorded with smart clothing: this is mainly because of displacement of the electrodes over the skin. We evaluated a novel adaptive method for spatio-temporal filtering for heartbeat detection in noisy multi-channel ECGs including short signal interruptions in single channels. Using multi-channel database recordings (12-channel ECGs from 10 healthy subjects), the results showed that multi-channel spatio-temporal filtering outperformed regular independent component analysis. We also recorded seven channels of ECG using a T-shirt with textile electrodes. Ten healthy subjects performed different sequences during a 10-min recording: resting, standing, flexing breast muscles, walking and pushups. Using adaptive multi-channel filtering, the sensitivity and precision was above 97% in nine subjects. Adaptive multi-channel spatio-temporal filtering can be used to detect heartbeats in ECGs with high noise levels. One application is heartbeat detection in noisy ECG recordings obtained by integrated textile electrodes in smart clothing.

Sound and vibration effects on infants' heart rate and heart rate variability during neonatal transport

Aim:  To measure the effect of sound and whole‐body vibration on infants’ heart rate and heart rate variability during ground and air ambulance transport.

Dysregulation of subcutaneous adipose tissue blood flow in overweight postmenopausal women

Objective: A putative link between abdominal obesity and metabolic-vascular complications after menopause may be due to a decreased adipose tissue blood flow (ATBF). The present work aimed to analyze possible changes in ATBF with being overweight and menopausal and its putative link to endothelial dysfunction and autonomic nervous system balance. Methods: Forty-three healthy women were classified into four groups according to weight and menopause status. The ATBF was measured by xenon washout while fasting and after oral glucose intake. The nitric oxide synthase inhibitor asymmetric dimethylarginine was used as a marker of endothelial function and heart rate variability-estimated autonomic nervous system activity. Results: Fasting ATBF was decreased in both overweight groups (P = 0.044 and P = 0.048) versus normal-weight premenopausal women. Normal-weight and overweight postmenopausal women exhibited lower maximum ATBF compared with normal-weight premenopausal women (P = 0.015 and P = 0.001, respectively), and overweight postmenopausal women exhibited lower maximum ATBF compared with normal-weight postmenopausal women (P = 0.003). A negative correlation was found between fasting ATBF and asymmetric dimethylarginine (P = 0.015), whereas maximum ATBF was negatively associated with sympathetic-parasympathetic nervous system balance (ratio of the power of the low frequency to the power of the high frequency; P = 0.002). Conclusions: Loss of ATBF flexibility in overweight postmenopausal women may contribute to the metabolic dysfunction seen in this group of women.

Automatic filtering of outliers in RR intervals before analysis of heart rate variability in Holter recordings: a comparison with carefully edited data

BackgroundUndetected arrhythmic beats seriously affect the power spectrum of the heart rate variability (HRV). Therefore, the series of RR intervals are normally carefully edited before HRV is analysed, but this is a time consuming procedure when 24-hours recordings are analysed. Alternatively, different methods can be used for automatic removal of arrhythmic beats and artefacts. This study compared common frequency domain indices of HRV when determined from manually edited and automatically filtered RR intervals.Methods and ResultsTwenty-four hours Holter recordings were available from 140 healthy subjects of age 1-75 years. An experienced technician carefully edited all recordings. Automatic filtering was performed using a recursive procedure where RR intervals were removed if they differed from the mean of the surrounding RR intervals with more than a predetermined limit (ranging from 10% to 50%). The filtering algorithm was evaluated by replacing 1% of the beats with synthesised ectopic beats. Power spectral analysis was performed before and after filtering of both the original edited data and the noisy data set. The results from the analysis using the noisy data were used to define an age-based filtering threshold. The age-based filtration was evaluated with completely unedited data, generated by removing all annotations from the series of RR intervals, and then comparing the resulting HRV indices with those obtained using edited data. The results showed equivalent results after age-based filtration of both the edited and unedited data sets, where the differences in HRV indices obtained by different preprocessing methods were small compared to the mean values within each age group.ConclusionsThe study showed that it might not be necessary to perform the time-consuming careful editing of all detected heartbeats before HRV is analysed in Holter recordings.In most subjects, it is sufficient to perform the regular editing needed for valid arrhythmia analyses, and then remove undetected ectopic beats and artefacts by age-based filtration of the series of RR intervals, particularly in subjects older than 30 years.

Blood pressure overshoot after tilt reversal in patients with familial amyloidotic polyneuropathy

The pathophysiology of the hemodynamic responses to postural stress in familial amyloidotic polyneuropathy (FAP) remains to be elucidated. The aim of the study was to evaluate hemodynamic responses after tilt reversal in FAP. Systolic blood pressure (BP) and heart rate variability (HRV) were analyzed in the baseline, 70° upright position, and after tilt reversal in 15 FAP patients and 14 healthy controls. Beat-to-beat BP was recorded with a Finapres device. Maximum systolic BP after tilt reversal was increased with 22±13 mm Hg in FAP patients as compared with baseline (BP overshoot), whereas controls showed a significantly lower BP overshoot (8±6 mm Hg, P<0.001). In all states, total spectral power and the power of the low and high frequency components were all significantly lower than those of the controls (P<0.01). In a linear regression analysis adjusted for age, we found a significant inverse relation between BP overshoot and HRV (total spectral power, power of the low-frequency and high-frequency components) in all three states (standardized β between −0.74 to −0.53, P<0.01). Five FAP patients presented a trial arrhythmia precluding HRV analysis: four of those presented BP overshoots ⩾12 mm Hg. BP overshoot may be a marker to assess the progression of cardiac autonomic dysfunction, especially as heart arrhythmia in many FAP patients prevent HRV analysis. In addition, assessment of the post-tilt BP reaction points to possible treatment modalities for orthostatic hypotension at least in the early stages of the disease.

Handheld ECG in analysis of arrhythmia and heart rate variability in children with Fontan circulation

BACKGROUND Our aim was to evaluate the intermittent use of a handheld ECG system for detecting silent arrhythmias and cardiac autonomic dysfunction in children with univentricular hearts. METHODS Twenty-seven patients performed intermittent ECG recordings with handheld devices during a 14-day period. A manual arrhythmia analysis was performed. We analyzed heart rate variability (HRV) using scatter plots of all interbeat intervals (Poincaré plots) from the total observation period. Reference values of HRV indices were determined from Holter-ECGs in 41 healthy children. RESULTS One asymptomatic patient had frequent ventricular extra systoles. Another patient had episodes with supraventricular tachycardia (with concomitant palpitations). Seven patients showed reduced HRV. CONCLUSIONS Asymptomatic arrhythmia was detected in one patient. The proposed method for pooling of intermittent recordings from handheld or similar devices may be used for detection of arrhythmias as well as for cardiac autonomic dysfunction.

Hemodynamic responses after tilt reversal in FAP

The aim of the study was to evaluate hemodynamic responses after tilt reversal in familial amyloid polyneuropathy (FAP). Systolic blood pressure (BP) and heart rate variability (HRV) were analyzed ...

A Test-Bed for Text-to-Speech-Based Pedestrian Navigation Systems

This paper presents an Android system to support eyes-free, hands-free navigation through a city. The system operates in two distinct modes: manual and automatic. In manual, a human operator sends text messages which are realized via TTS into the subject’s earpiece. The operator sees the subject’s GPS position on a map, hears the subject’s speech, and sees a 1 fps movie taken from the subject’s phone, worn as a necklace. In automatic mode, a programmed controller attempts to achieve the same guidance task as the human operator.