Anna Gąsiorowska

Suppression of heart rate variability after supramaximal exertion.

Wingate test is short anaerobic exercise, performed with maximal power, whereas aerobic exercise at 85% maximal heart rate (HRmax) may be performed for long period. Sustained HR elevations and changes in autonomic activity indices have been observed after latter kind of exercise. Several studies reported reduction in mean interval between consecutive R peaks in ECG (RRI) 1 h after Wingate test; however, underlying changes in autonomic activity remain elusive. In eight young males, RRI and heart rate variability (HRV) were measured daily over two 5‐day trials. Subjects exercised on third day of each trial, measurements were taken 1 h after (i) two consecutive 30‐s bouts of Wingate tests or (ii) after a 30‐min exercise at 85% HRmax, with subjects in supine rest and breathing either spontaneously or at controlled rates of 6 and 15 breaths / min. RRI was significantly shorter after Wingate and submaximal exercise, reduction of high‐ and low‐frequency components of HRV attained reliability only after Wingate tests. This pattern remained preserved for three modes of breathing: spontaneous, 6 and 15 breaths /min. After 24 and 48 h, no exercise effects were traceable. We hypothesize that (i) anaerobic exertion is followed by sustained inhibition of vagal activity, (ii) parasympathetic system plays dominant role in mediating suppression of high‐ and low‐HRV frequency components during postexercise recovery, (iii) degree of alteration of autonomic activity caused by anaerobic and strenuous aerobic exercise may be similar and (iv) normalization of vagal activity precedes normalization of sympathetic cardiac nerves activity during final stage of postexercise recovery.

Determination and Prediction of One Repetition Maximum (1RM): Safety Considerations

Determination and Prediction of One Repetition Maximum (1RM): Safety Considerations Strength training is recommended for slowing age-dependent deterioration of muscular strength and for rehabilitating patients with muscle weakening illnesses. Reliable assessment of muscle strength is important for proper design of strength training regimes for prevention, rehabilitation, and sport. One repetition maximum (1RM) is an established measure of muscular strength and is defined as the value of resistance against which a given movement can be performed only once. Proper assessment of 1RM is time consuming, and may lead to muscle soreness as well as temporary deterioration of the function of the tested muscles. Attempts at indirect 1RM determination based on the maximum number of repetitions performed have predicted 1RM with a variable degree of accuracy. Cardiovascular safety has been neglected in 1RM determination, although arterial blood pressure increases considerably when exercising against maximal or near maximal resistance. From the perspective of cardiovascular safety, favorable 1RM measurement methods should avoid performance of repetitions until failure; movement against high resistance and muscle fatigue both increase blood pressure. Although such techniques are likely less accurate than the current methods, their prediction accuracy be sufficient for therapeutic strength training.

Impedance cardiography: Recent advancements

The aim of this paper is the presentation of recent advancements in impedance cardiography regarding methodical approach, applied equipment and clinical or research implementations. The review is limited to the papers which were published over last 17 months (dated 2011 and 2012) in well recognised scientific journals.

Effects of a brief Valsalva manoeuvre on hemodynamic response to strength exercises

Strength training is a recommended measure against loss of strength and muscle mass because of age‐ or illness‐induced inactivity. Strength exercises may impose heavy cardiovascular load by increasing heart rate and blood pressure. To increase strength efficiently, a heavy load has to be applied; this, however, leads to a spontaneous Valsalva manoeuvre, which additionally raises blood pressure. Avoidance of this manoeuvre is recommended. If the additional rise in arterial blood pressure caused by Valsalva manoeuvre is smaller than intrathoracic or intracranial pressures during this manoeuvre, Valsalva manoeuvre may actually protect arteries located in the thorax and in the brain by diminishing transmural pressure acting across these vessels. Effect of controlled breathing or brief Valsalva manoeuvre on arterial pressure at rest and during knee extension against 15‐repetition maximum resistance was evaluated. In 12 healthy young men blood pressure was measured continuously and non‐invasively, knee angle, speed of respiratory air or mouth pressure (MP) were continuously registered. Each combination of respiratory and exercise manoeuvres was repeated six times, for every of last three repetitions peak and trough systolic and diastolic pressure were determined. Strength exercises elevated peak pressures more than trough pressures, systolic more than diastolic. Valsalva manoeuvre increased only peak systolic and peak diastolic pressure. This increase was in average lesser than MP, thus rendering an argument in favour of protective role of brief Valsalva manoeuvre because of decline in transmural pressure acting on thoracic and possibly cerebral arteries. However, there was strong individual variability, and in few instances, arterial pressure increased because of brief Valsalva manoeuvre more than MP; thus in some subjects, the manoeuvre might enhance transmural pressure acting on thorax arteries.

Early hemodynamic response to the tilt test in patients with syncope.

Introduction Our aim was to evaluate the differences in the early hemodynamic response to the tilt test (HUTT) in patients with and without syncope using impedance cardiography (ICG). Material and methods One hundred twenty-six patients (72 female/48 male; 37 ±17 years) were divided into a group with syncope (HUTT(+), n = 45 patients) and a group without syncope (HUTT(–), n = 81 patients). ECG and ICG signals were continuously recorded during the whole examination, allowing the calculation of heart rate (HR), stroke volume (SV), and cardiac output (CO) for every beat. The hemodynamic parameters (averaged over 1 min) were analyzed at the following points of the HUTT: the last minute of resting, the period immediately after the tilt (0 min), 1 min and 5 min after the maneuver. The absolute changes of HR, SV and CO were calculated for 0, 1, and 5 min after the maneuver in relation to the values at rest (ΔHR, ΔSV, ΔCO). Also, the percentage changes were calculated (HRi, SVi, COi). Results There were no differences between the groups in absolute and percentage changes of hemodynamic parameters immediately after and 1 min after tilting. Significant differences between the HUTT(+) and HUTT(–) groups were observed in the 5th min of tilting: for ΔSV (–27.2 ±21.2 ml vs. –9.7 ±27.2 ml; p = 0.03), ΔCO (–1.78 ±1.62 l/min vs. –0.34 ±2.48 l/min; p = 0.032), COi (–30 ±28% vs. –0.2 ±58%; p = 0.034). Conclusions In the 5th min the decrease of hemodynamic parameters (ΔSV, ΔCO, COi) was significantly more pronounced in HUTT(+) patients in comparison to the HUTT(–) group.

Signal quality evaluation in Ambulatory Impedance Cardiography

A fundamental question regarding ambulatory impedance cardiography monitoring is evaluation of the rate of artefacts during impedance holter recordings. It is also important to know what is the average length of recordings, which are too noisy for automatic analysis. Another problem is the question of how representative are the mean values from periods of different length for evaluating trends. With the aim to evaluate these uncertainties 12 male patients with atrial fibrillation (aged 36-78 years) and 6 healthy males (24-68 years) as a control underwent examination (using ReoMonitor) lasting for 12 hours starting from about 18:00. The ratio of artefact free cycles to the total number of cycles was calculated for the same hour of recording (during daytime activity) when the averaging period varied from 5 to 60 minutes. Also the rates of artefact-free recordings were calculated for each 30- minute period during the daytime (18.00-23.00) and over the night period (23:00-04:00). The percentage of cycles recognised as normal according to the criteria of automatic determination of cardiac parameters from impedance cardiography signals varied from 20% during the daytime up to 90% during the night hours, when 5-minute period are analysed.

Influence of aerobic training on neurohormonal and hemodynamic responses to head-up tilt test and on autonomic nervous activity at rest and after exercise in patients after bypass surgery

BACKGROUND Little is known about the influence of aerobic training on the neurohormonal and hemodynamic responses to head-up tilt (HUT) and on autonomic balance at rest and after exercise in optimally treated, low risk post-coronary artery bypass grafting (CABG) patients. METHODS One hundred male patients, mean age 56 ± 6 years, 3 months after CABG, were randomized to either 6-week training on cycloergometer, 3 times a week, at 70-80% of max tolerated heart rate (HR) (training group, n = 50) or to a control group (n = 50). At baseline and at the end of the study, all patients underwent: (1) cardiopulmonary exercise test with HR recovery (HRR) assessment; (2) 60% HUT during which HR, blood pressure (BP), stroke volume (SV by impedance cardiography) were monitored and blood samples were taken for determination of plasma catecholamines and ANP levels, and plasma renin activity; (3) assessment of HR variability (HRV) in the time and frequency domains at rest. RESULTS During the final tests, HUT-induced changes in HR, BP, SV, cardiac output, total peripheral resistance, and noradrenaline were significantly lower in training group than in controls. In addition, after training faster post-exercise HRR, increased SDNN and a tendency towards an increase in the high frequency HRV power spectrum were found. CONCLUSIONS Aerobic training improved neurohormonal and hemodynamic responses to head-up tilt test and favorably modified sympatho-vagal balance in low risk post-CABG patients.

Relationships Between Systolic Time Intervals and Heart Rate During Initial Response to Orthostatic Manoeuvre in Men of Different Age

Relationships Between Systolic Time Intervals and Heart Rate During Initial Response to Orthostatic Manoeuvre in Men of Different Age An analysis of transient changes in physiological parameters in response to the standardized tests could be used to evaluate the efficiency of the regulatory processes. Relationships between systolic time intervals and heart rate following the action of standing up from the supine position were investigated in 41 healthy men, aged 20 to 59 years, classified into three groups: (22 to 26 yrs, n=14), (33 to 49, yrs, n=13) and (51 to 59 yrs, n=14). The protocol consisted of the following sequence: laying down (20 minutes) - standing up (8 minutes). Ejection time, pre-ejection period, electromechanical systole, heart rate and the length of R-R intervals were continuously calculated using automatized impedance cardiography and electrocardiogram. The ratio of ejection time to pre-ejection period in young men was significantly higher in comparison with the other groups. The ratio of ejection time to the length of R-R interval increased with age in supine position and after standing up when R-R interval was maximal. It was suggested that changes of ejection time to pre-ejection period during the orthostatic manoeuvre are rather the result of balance between heart rate and hemodynamic factors, than solely related to heart rate.

Empirical Mode Decomposition in Analysis of Hemodynamic Response to Static Handgrip

The empirical mode decomposition (EMD) of biological signals is used to detect reaction to physiological stimuli and to identify global trends in slowly changing variables. We applied EMD to analyze hemodynamic reaction to handgrip in 9 healthy males (aged 21.3 ± 0.3 years) and 10 male patients following coronary artery bypass grafting (aged 55 ± 6 years). Subjects squeezed a dynamometer with 30% of individually determined maximal force for 3 min. The aim of the study was to check whether the application of EMD to the signals could bring any objective quantitative or qualitative measures allowing one to distinguish physiological states of healthy subjects and patients. Hemodynamic data were collected using a battery-powered, ambulatory impedance cardiography device (ReoMonitor) incorporating a single ECG channel. Heart rate (HR), R-R interval (RR), stroke volume (SV), cardiac output (CO), left ventricular ejection time (ET), pre-ejection period (PEP), maximum amplitude of the dz/dt signal (Amp), and basic chest impedance (Z0) were calculated automatically using the software earlier developed for ReoMonitor. The dedicated computer program allows to calculate and display the dynamics of basic and derivative parameters, describing the impact of systolic time intervals on RR intervals, or the relationship between them (e.g. PEP/ET). The EMD procedure was applied to identify the components of each basic hemodynamic parameter and all their derivatives. We observed the most pronounced effect of handgrip in second and third intrinsic mode functions (IMF), which particularly manifested in parameters describing the ratio of systolic time intervals to the length of RR.

The Quality of Automatic Artifact Identification in Ambulatory Impedance Cardiography Monitoring

In Ambulatory Impedance Cardiography (AICG), a large number of motion artifacts might occur in recordings collected during exercises. The adequate identification of the artifacts is the most important task for automatic analysis of the AICG signals. The aim of this study was to manually assess the efficiency of the classification algorithm described in our earlier papers. We intended to identify which point detected on ECG and impedance cardiography (ICG) curves is more likely to provide false indications. It was found that in most cases the artifacts were created by false recognition of the point of closing of the aortic valve (97%, range 91-100%). Modifications of the appropriate part of the algorithm were suggested.