Bioimpedance cardiography measurements of cardiac output and other cardiovascular parameters

Hemodynamic effects of heart rate lowering in patients admitted for acute heart failure: the RedRate-HF Study (Reduction of heart Rate in Heart Failure)

BACKGROUND

In patients admitted for acute heart failure (HF) indication for drugs which reduce the heart rate (HR) is debated. The multicentre prospective study Reduction of heart Rate in Heart Failure (RedRate-HF) was designed to analyse the hemodynamic effects of an early reduction of HR in acute HF.

METHODS

Hemodynamic parameters were recorded by using the bioimpedance technique, which was shown to be accurate, highly reproducible and sensitive to intra-observer changes. Lowering HR was obtained by ivabradine 5 mg bd, given 48-72 h after admission on the top of optimized treatment. Patients were followed at 24, 48, 72 h after drug assumption and at hospital discharge.

RESULTS

Twenty patients of a mean age of 67 ± 15 years, BNP at entry 1348 ± 1198 pg/ml were enrolled. Despite a clinical stabilization, after 48-72 h from admission, HR was persistently >70 bpm. Ivabradine was well tolerated in all patients with a significant increase in RR interval from 747 ± 69 ms at baseline to 948 ± 121 ms at discharge, P < 0.0001. Change in HR was associated with a significant increase in stroke volume (baseline 73 ± 22 vs. 84 ± 19 ml at discharge, P = 0.03), and reduction in left cardiac work index (baseline 3.6 ± 1.2 vs. 3.1 ± 1.1 kg/m2 at discharge, P = 0.04). Other measures of heart work were also significantly affected while cardiac output remained unchanged.

CONCLUSION

The strategy of an early lowering of HR in patients admitted for acute HF on top of usual care is feasible and safe. The HR reduction causes a positive increase in stroke volume and may contribute to saving energy without affecting cardiac output.

FEATURES OF RHEOVASOGRAPHIC PARAMETERS OF THE TIBIA IN VOLLEYBALL PLAYERS OF A HIGH LEVEL OF SKILL OF THE YOUTH AGE

OBJECTIVE

Aim of the work was to determine the peculiarities of rheographic parameters of the tibia in volleyball players of the general group and individual somatotypes.

PATIENTS AND METHODS

Materials and Methods: A comprehensive examination of 108 highly skilled volleyball players and 130 practically healthy girls aged between 16 and 20 years who did not play sports was conducted. The rheovasographic parameters of the tibia were determined using tetrapolar reocardiography on a computer diagnostic complex with the assessment of amplitude, time, and indicators of the ratio of amplitude and time rheovasographic parameters. A somatotypological study was conducted based on a calculated modification of the Heath-Carter method (1990) with the division of volleyball players and non-athletes into 4 constitutional groups: mesomorphic, ectomorphic, ecto-mesomorphic, and intermediate type.

RESULTS

Results: Significant differences in the value of individual amplitude and most tibia rheovasographic parameters between volleyball players and girls of the control group were revealed. In athletes, the amplitudes of the systolic, diastolic and rapid blood filling, the duration of the rheographic wave, the time of the ascending and descending parts of the rheogram and slow blood filling were statistically significantly higher. Somatotypological features of peripheral hemodynamic indicators were determined in volleyball players; the greatest differences in the indicators of regional blood circulation on the tibia were recorded for representatives of the ectomorphic somatotype; between volleyball players and non-athletes with ecto-mesomorphic somatotype, there was no significant difference in the value of all tibia rheovasographic parameters.

CONCLUSION

Conclusion: Systematic training and competitions lead to prominent changes in rheovasographic indicators of the tibia in young female volleyball players, which are manifested by a better state of capillary and venous blood filling of the tibia muscles, but at the same time a reduced speed of regional blood flow due to a reduced tone of the vascular wall of small and medium arteries.

Comparative study of cardiac output measurement by regional impedance cardiography and thermodilution method in patients undergoing off pump coronary artery bypass graft surgery

Background:

An ideal CO monitor should be noninvasive, cost effective, reproducible, reliable during various physiological states. Limited literature is available regarding the noninvasive CO monitoring in open chest surgeries.

Aim:

The aim of this study was to compare the CO measurement by Regional Impedance Cardiography (RIC) and Thermodilution (TD) method in patients undergoing off pump coronary artery bypass graft surgery (OPCAB).

Settings and Design:

We conducted a prospective observational comparative study of CO measurement by the noninvasive RIC method using the NICaS Hemodynamic Navigator system and the gold standard TD method using pulmonary artery catheter in patients undergoing OPCAB. A total of 150 data pair from the two CO monitoring techniques were taken from 15 patients between 40-70 years at various predefined time intervals of the surgery.

Patients and Methods:

We have tried to find out the accuracy, precision and cost effectiveness of the newer RIC technique. Mean CO, bias and precision were compared for each pair i.e.TD-CO and RIC-CO as recommended by Bland and Altman. The Sensitivity and specificity of cutoff value to predict change in TD-CO was used to create a Receiver operating characteristic or ROC curve.

Results:

Mean TD-CO values were around 4.52 ± 1.09 L/min, while mean RIC- CO values were around 4.77± 1.84 L/min. The difference in CO change was found to be statistically not significant (p value 0.667). The bias was small (-0.25). The Bland Altman plot revealed a mean difference of -0.25 litres. The RIC method had a sensitivity of 55.56 % and specificity of 33.33 % in predicting 15% change in CO of TD method and the total diagnostic accuracy was 46.67%.

Conclusion:

A fair correlation was found between the two techniques. The RIC method may be considered as a promising noninvasive, potentially low cost alternative to the TD technique of hemodynamic measurement.

Signal processing techniques applied to impedance cardiography ICG signals - a review

Over the last decade, Computer-Aided Diagnosis (CAD) systems have been provided significant research focus by researchers. CAD systems have been developed in order to minimise visual errors, to compensate manual interpretation, and to help medical staff to take decisions swiftly. These systems have been considered as powerful tools for a reliable, automatic, and low-cost monitoring and diagnosis. CAD systems are based on analysis and classification of several physiological signals for detecting and assessing different diseases related to the corresponding organ. The implementation of these systems requires the application of several advanced signal processing techniques. Specifically, in cardiology, CAD systems have achieved promising results in providing an accurate and rapid detection of cardiovascular diseases (CVDs). Particularly, the number of works on signal processing field for impedance cardiography (ICG) signals starts to grow slowly in recent years. This paper presents a review study of signal processing techniques applied to the ICG signal for the denoising, the analysis, the classification and the characterisation purposes. This review is intended to provide researchers with a broad overview of the currently used signal processing techniques for ICG signal analysis, as well as to improve future research by applying other recent advanced methods.

The repeatability of estimated systolic time intervals in healthy subjects using seismocardiogram and electrocardiogram

OBJECTIVE

We investigated the repeatability of systolic time intervals (STIs) in healthy subjects using a combination of seismocardiogram (SCG) and electrocardiogram (ECG). STIs have been extensively used in the past to quantify heart performance, particularly the left ventricle. In this study, STIs included pre-ejection period (PEP), left ventricular ejection time (LVET), and their ratio.

APPROACH

We conducted the repeatability test of STI estimation through two experiments. The first involved three consecutive one-minute recordings separated by one-minute intervals, and the second involved two one-minute recordings separated by 24 h. Twenty healthy subjects participated in our study. We considered the coefficient of variation (CV) to quantify the repeatability. As there was no agreed upon values for optimal CV values, we compared our results with an alternative method using a combination of impedance cardiography (ICG) and ECG. Similar to our method, the alternative method was noninvasive and could be employed for personal heart monitoring. We also studied the repeatability after STIs were corrected for heart rate using two approaches. The first approach used a multiplicative factor per subject based on the heart rates in each recordings of that subject. The second approach employed sex-specific regression models for all subjects (Weissler's equations).

MAIN RESULTS

We found that the repeatability of our method (SCG and ECG) was in agreement with the alternative method (ICG and ECG) in both experiments. Moreover, the Weissler's equations approach for heart rate increased the repeatability.

SIGNIFICANCE

It can be concluded that estimation of PEP, LVET and their ratio through SCG and ECG signals was repeatable in healthy subjects.

[CHANGES IN RHEOGRAPHIC INDICATORS OF SHIN IN ATHLETES OF DIFFERENT KINDS OF SPORTS]

We determined the changes of time, amplitude and derivatives of these indicators of rheovasograms of shin in sportsmen of youth age and high level of skills engaged in volleyball, athletics and wrestling with sports experience at least 3 years. We determined significant differences in the value of time, amplitude and derivatives of these indicators ofrheovazograms of shin in males youth age, depending on the impact of intense exercise. The volleyball players compared to youth who do not exercise, reliably large values of the overall tone of the arteries (11,2%), arteries of large diameter (8,2%), arteries of medium and small diameters (13,5%), time ascending part of rheovazograms (2%) and a slow passage (5,9%) and less dycrotycs index (17%), duration ofrheographic wave (3,7%), time descending part of rheovazograms (10%). The persons of control group had higher values of baseline impedance than wrestlers (9,9%) and athletes (13,7%) and all amplitude indicators rheograms of the shin than athletes (average 12-15%) and wrestlers (22-23%). The size and volume of blood flow to the arteries of the extremities adapted to the metabolic needs of the relevant muscles. In volleyball players compared to the athletes, a lower duration of rheographic wave (10%), time of downlink part of the rheograms (12,7%), the base impedance (17,2%), amplitude of the systolic wave (17%) and rapid blood filling (21%), all indicators tone of arteries (12,2-16,9%) and greater value of time of rising part of rheograms (3,5%) and slow blood filling (5,9%). Wrestlers compared to the athletes have a lower duration of rheographic wave (6,1%), time of downlink part of the rheograms (6,1%), the amplitude of the systolic wave (9,3%), compared with volleyball players set lower values of average speed of fast blood filling (15,6%), tone of arteries with different diameters (15-16,5%), all amplitude indicators (20-28%), time slow blood filling (9,7%), ascending parts rheogram (10,3%). Thus, the level ofphysical activity and especially muscle activity has a significant effect on the performance of regional blood flow.

Process techniques for human thoracic electrical bio-impedance signal in remote healthcare systems

Analysis of thoracic electrical bio-impedance (TEB) facilitates heart stroke volume in sudden cardiac arrest. This Letter proposes several efficient and computationally simplified adaptive algorithms to display high-resolution TEB component. In a clinical environment, TEB signal encounters with various physiological and non-physiological phenomenon, which masks the tiny features that are important in identifying the intensity of the stroke. Moreover, computational complexity is an important parameter in a modern wearable healthcare monitoring tool. Hence, in this Letter, the authors propose a new signal conditioning technique for TEB enhancement in remote healthcare systems. For this, the authors have chosen higher order adaptive filter as a basic element in the process of TEB. To improve filtering capability, convergence speed, to reduce computational complexity of the signal conditioning technique, the authors apply data normalisation and clipping the data regressor. The proposed implementations are tested on real TEB signals. Finally, simulation results confirm that proposed regressor clipped normalised higher order filter is suitable for a practical healthcare system.

Therapeutic implications of implantable device-based monitoring of patients with heart failure

Heart failure is one of the most common medical problems faced by patients and clinicians. It has the potential for high morbidity and mortality, and its overall financial cost to society is enormous. Management of heart failure is often difficult and time consuming, and is sometimes frustrating. The usual signs and symptoms of heart failure may not be obvious early in an exacerbation, which has prompted the development of other methods to identify early and subtle clinical changes to initiate early intervention. Current implantable devices, such as defibrillators and pacemakers, can monitor changes in heart rate and heart rate variability, patient activity, arrhythmia frequency, and thoracic impedance, all of which may be markers of clinical decline. Newer implantable devices can also measure right ventricular pressures, oxygen saturation, and pulmonary artery pressures. Many of these technologies have been shown to be feasible and potentially helpful, but outcomes data showing reductions in morbidity and mortality are currently limited. Importantly, none of these newer technologies should be used in isolation; all must be used in combination with clinical findings to provide effective disease management.