Systolic and diastolic time intervals in the critically ill patient

Mattar, João; Shoemaker, W. C.; Diament, Décio; Lomar, André Villela; Lopes, AC; Freitas, Etiane de Oliveira; Stella, Francisco P.; Factore, LA

doi:10.1097/00003246-199111000-00014

Cited by 36 publications

(21 citation statements)

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“…Furthermore, the ICG can simultaneously provide other variables such as the left ventricular ejection time and the pre-ejection period. These variables have also been used as good indices for assessing the contractility of the heart (Máttar et al 1991). Further studies would be, therefore, required for the accurate and wide application of the ICG.…”

Section: Accuracy Of the Measurement Of Sv And Qmentioning

confidence: 99%

Validity of the Adaptive Filter for Accurate Measurement of Cardiac Output in Impedance Cardiography

Ono

Yasuda

et al. 2004

Tohoku J. Exp. Med.

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The purpose of this study was to assess the validity of an adaptive filter, the scaled Fourier linear combiner (SFLC), in the impedance cardiography (ICG). Eight healthy males underwent constant-load bicycle exercise at different intensities from unloaded to near maximal intensity. The stroke volume (SV) and cardiac output (Q 4 ) measured by ICG at each condition were compared with those by the CO 2 rebreathing method. We found that the noises were greatly reduced in the impedance waveform and that the inflection points, so-called the B-and X-points, were clearly detected even during strenuous exercise using the SFLC. Although a high correlation was observed between Q 4 s measured by the two methods, the mean values of Q 4 s in each method differed significantly and the regression line also differed significantly from the identity line. Likewise, a significant correlation was observed between SVs obtained by the two methods, but a significant difference in the group mean values and a trend of the regression line were observed. These findings suggest that the use of SFLC in ICG improves the performance in eliminating the noises and in detecting the inflection points in the waveform, thereby contributing to the accurate and beat-to-beat measurements of SV and Q 4 especially during exercise. impedance cardiography; adaptive filter; cardiac output; stroke volume; CO 2 rebreathing

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Section: Accuracy Of the Measurement Of Sv And Qmentioning

confidence: 99%

Validity of the Adaptive Filter for Accurate Measurement of Cardiac Output in Impedance Cardiography

Ono

Yasuda

et al. 2004

Tohoku J. Exp. Med.

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“…A number of studies using different apparatuses including ICG, carotid pulse tracing or echo ultrasound, reported an inverse relationship between HR and STI mainly between HR and LVET ( Van der Hoeven et al 1977;Vanfraechem 1979;Miyamoto et al 1983;Máttar et al 1991). However, those relationships were measured only for several degrees of exercise intensity.…”

Section: Relationships Hr Versus Tsi Pep and Lvetmentioning

confidence: 99%

“…These include body posture (Miyamoto et al 1983;Smith et al 1989), physical training (Vanhees et al 1984;Krzemiński et al 1989), aging and cardiovascular diseases (Van der Hoeven et al 1977;Máttar et al 1991;Thomas and Crowther 1993). For example, Miyamoto et al (1983) reported that the regression line between HR and LVET shifted downward, but the regression line between HR and PEP was shifted upward by the postural change from supine to upright.…”

Section: Relationships Hr Versus Tsi Pep and Lvetmentioning

confidence: 99%

“…Previously, these parameters had been mainly determined by using the electrocardiogram (ECG), phonocardiogram (PCG) and carotid pulse tracing; however, carotid pulse tracing was often thought to be difficult due to movement artefacts, especially during exercise (Pigott and Spodick 1971;Wolfe et al 1978). The impedance cardiograph (ICG) that was firstly proposed by Kubicek et al (1966Kubicek et al ( , 1970 for the measurement of stroke volume (SV) and cardiac output (Q 4 ), had been also used for the measurement of LVET, PEP and other parameters relating to the cardiac cycle (Lababidi et al 1970;Máttar et al 1991). However, controversy remains on how to determine these parameters from the ICG.…”

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confidence: 99%

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Beat-to-Beat Evaluation of Systolic Time Intervals during Bicycle Exercise Using Impedance Cardiography

Ono

Miyamura

Yasuda

et al. 2004

Tohoku J. Exp. Med.

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In order to elucidate the beat-to-beat changes of the systolic time intervals (STI) during exercise, we proposed new techniques relating to an adaptive filter and detection algorithms for B-and X-points in the impedance cardiograph (ICG). Six male subjects underwent a ramp bicycle exercise up to maximum intensity during which an ECG, ICG and phonocardiogram (PCG) were continuously measured. Following the application of an adaptive filter, the scaled Fourier linear combiner (SFLC), to the first derivative (dZ/dt) of the base impedance (∆Z) and PCG waveforms, the B-and X-points were automatically determined. For the B-point detection we used three criteria: the zero-crossing point (B zero ), the 15% response point (B 15% ) of the negative peak of the dZ/dt (dZ/dt min ) and a new algorithm (B new ). The X-point was separately determined by using the ICG and PCG waveforms. It was found that the shape of the dZ/dt waveform directly affected the determination of the Band X-points. The B-points determined using B zero and B 15% criteria were sometimes unstable caused by the location of a notch preceding the dZ/dt min compared to the B new . The time difference between the X-points measured by the ICG and PCG was mostly within ± 20 milliseconds but statistically significant. Although a wide variation was seen in R-R intervals, the STI were more stable. The relationships between HR and STI from rest to maximal exercise showed a gentle curvilinear relationship. It is suggested that the STI can be obtained precisely on a beat-to-beat basis by using the adaptive filter and detection algorithms for the inflection points of the ICG even during maximum exercise. left ventricular ejection time; pre-ejection period; total systolic interval; impedance cardiography; ramp exercise

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“…4,5 It is simple to ascertain both the systolic and diastolic time intervals by ICG and use these measures to make clinical determinations of pathophysiologic mechanisms. 11,12 The PEP is the isovolumic contraction interval beginning with the initiation of the QRS complex at point Q and ending with the start of mechanical systole as marked by the initial deflection of the systolic waveform. The left ventricular ejection time (LVET) begins at the end of the PEP and ends at the closure of the aortic valve when ejection ends as determined by the dZ/dt waveform.…”

Section: 10mentioning

confidence: 99%

Bench to Bedside: Electrophysiologic and Clinical Principles of Noninvasive Hemodynamic Monitoring Using Impedance Cardiography

Summers

Shoemaker

Peacock

et al. 2003

Academic Emergency Medicine

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114

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The evaluation of the hemodynamic state of the severely ill patient is a common problem in emergency medicine. While conventional vital signs offer some insight into delineating the circulatory pathophysiology, it is often impossible to determine the true clinical state from an analysis of blood pressure and heart rate alone. Cardiac output measurements by thermodilution have been the criterion standard for the evaluation of hemodynamics. However, this technology is invasive, expensive, time-consuming, and impractical for most emergency department environments. Impedance cardiography (ICG) is a noninvasive method of obtaining continuous measurements of hemodynamic data such as cardiac output that requires little technical expertise. ICG technology was first developed by NASA in the 1960s and is based on the idea that the human thorax is electrically a nonhomogeneous, bulk conductor. Variation in the impedance to flow of a high-frequency, low-magnitude alternating current across the thorax results in the generation of a measured waveform from which stroke volume can be calculated by a modification of the pulse contour method. To adequately judge the possible role of this technology in the practice of emergency medicine, it is important to have a sufficient understanding of the basic scientific principles involved as well as the clinical validity and limitations of the technique.

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Systolic and diastolic time intervals in the critically ill patient

Cited by 36 publications

References 0 publications

Validity of the Adaptive Filter for Accurate Measurement of Cardiac Output in Impedance Cardiography

Validity of the Adaptive Filter for Accurate Measurement of Cardiac Output in Impedance Cardiography

Beat-to-Beat Evaluation of Systolic Time Intervals during Bicycle Exercise Using Impedance Cardiography

Bench to Bedside: Electrophysiologic and Clinical Principles of Noninvasive Hemodynamic Monitoring Using Impedance Cardiography

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