Measurement of right ventricular volume by conductance catheter in closed-chest pigs

1995 ◽  
Vol 269 (3) ◽  
pp. H869-H876 ◽  
Author(s):  
T. M. Stamato ◽  
R. S. Szwarc ◽  
L. N. Benson
Keyword(s):  
Right Ventricular ◽  
Cardiac Cycle ◽  
Ventricular Volume ◽  
Gain Factor ◽  
Conductance Catheter ◽  
Closed Chest ◽  
Inferior Caval Vein ◽  
Pulmonary Flow ◽  
Volume Relation ◽  
Parallel Conductance

This study details the effects of changes in right ventricular (RV) volume on the conductance catheter gain factor both over a broad volume range and within the cardiac cycle. In seven closed-chest anesthetized pigs, a conductance catheter was introduced transvenously and positioned to span the RV long axis, including the outflow tract. Parallel conductance was determined using a saline dilution technique. Conductance volume gain factor (alpha) was computed using stroke volume obtained by thermodilution over a range of volumes obtained by volume loading or sustained partial occlusion of the inferior caval vein. The chest was then opened, an ultrasonic flow probe was placed around the pulmonary artery, and the conductance-derived RV volume was compared with the pulmonary flow integral over the course of ejection. When volume was varied over a broad range, an inverse relation between RV volume and alpha was observed (P < 0.001). This did not cause significant nonlinearity of the conductance-volume relation. The relation was also relatively linear during the course of ejection within the cardiac cycle. These results indicate that the conductance catheter may be employed, using the described technique, to assess RV volume under steady-state conditions.

Right ventricular volume measurement by conductance catheter

2003 ◽  
Vol 285 (4) ◽  
pp. H1774-H1785 ◽  
Author(s):  
Mark H. D. Danton ◽  
Gerald F. Greil ◽  
John G. Byrne ◽  
Michael Hsin ◽  
Lawrence Cohn ◽  
...  
Keyword(s):  
Right Ventricular ◽  
Cardiac Cycle ◽  
Complex Geometry ◽  
Ventricular Volume ◽  
Volume Measurement ◽  
Gain Factor ◽  
Conductance Catheter ◽  
Conductance Method ◽  
Parallel Conductance ◽  
Factor Α

Continuous ventricular volume measurement by the conductance method assumes a homogeneous electrical field dispersed throughout and contained within the ventricle. Because of dense trabeculation and complex geometry, right ventricular (RV) volume description by this method may be seriously compromised. This study sought to determine the accuracy and limitations of RV volume measurement by conductance, with magnetic resonance (MR) imaging (MRI) used as a reference, in the porcine RV. Anesthetized pigs ( n = 5, 45–55 kg) were placed in a 1.5-T magnet, and ECG-gated transverse MR images (5-mm slices) were acquired during the complete cardiac cycle. RV cavity volumes were subsequently determined by Simpson's technique. Animals were then instrumented with an RV conductance catheter and an ultrasonic pulmonary artery flow probe. Conductance catheter signals were recorded using single- and dual-field (SF and DF) excitation, and the saline-dilution technique was used to correct volumes for parallel conductance. The gain factor (α) was calculated as the ratio of conductance- to MRI-derived stroke volume (αSV). Variation of α during the cardiac cycle was computed by comparing RV conductance volumes with 1) MRI volumes at isochronal time points within the cardiac cycle [α( t)] and 2) the pulmonary flow integral during ejection. After calibration, the conductance-MRI volume relation was modeled linearly with good correlation [ r = 0.96 (SF) and r = 0.94 (DF)], close to the line of identity. Individual conductance-MRI plots displayed a slight curvilinear relation that was concave toward the MRI axis. Consistent with this finding, α( t) varied significantly during the cardiac cycle (0.49 and 0.39 by SF for end systole and end diastole, respectively, P = 0.011). DF excitation resulted in improved volume measurement [αSV = 0.41 (SF) and 0.96 (DF)], with less variation in α( t) (1.0 and 0.92 by DF for end systole and end diastole, respectively, P = 0.66). These results indicate that, with calibration, the conductance method can measure absolute RV volume under steady-state conditions. However, the curvilinearity and α( t) variation would indicate the potential for nonlinearity when RV volumes are varied over a wider range.

Left ventricular parallel conductance during cardiac cycle in children with congenital heart disease

1997 ◽  
Vol 273 (1) ◽  
pp. H295-H302 ◽  
Author(s):  
P. A. White ◽  
R. R. Chaturvedi ◽  
D. Shore ◽  
C. Lincoln ◽  
R. S. Szwarc ◽  
...  
Keyword(s):  
Septal Defect ◽  
Cardiac Cycle ◽  
Ventricular Volume ◽  
Left Ventricular ◽  
Conductance Catheter ◽  
End Diastolic Volume ◽  
Catheter Technique ◽  
Group 2 ◽  
Parallel Conductance ◽  
Group 1

This study examines the accuracy of the conductance catheter technique and, in particular, parallel conductance [expressed as offset volume (Vc)] changes during the cardiac cycle in the human left ventricle. Two groups of patients were assessed: group 1, with an open atrial septal defect, and group 2, with an interventricular communication. In a subgroup, pre- and postoperative data were compared to assess the possible impact of shunting or anatomic considerations on our measurements. Vc is normally obtained by a saline-dilution technique previously described by Baan et al. [Vc(Baan); J. Baan, E. T. Van der velde, H. G. Debruin, G. J. Smeenk, J. Koops, A. D. Van Dijk, D. Temmerman, P. J. Senden, and B. Buis. Circulation 70: 812-823, 1984]. This does not take into account potential changes during the cardiac cycle. Four cardiac cycles were taken from the hypertonic saline washin and were divided into six equal isochrones between the maximum and minimum first derivatives of left ventricular pressure (dP/dtmax and dP/dtmin, respectively). The apparent ventricular volume was regressed against stroke volume for the corresponding cardiac cycle. The volume at the gamma-intercept corresponds to the Vc at each time interval [Vc(t)]. In group 1, there was a variation in Vc(t) during systole, but the temporal changes were quite small, on the order of 4.28% (SD = 5.18%) of total corrected end-diastolic volume (mean maximal variation of 2.60 ml). Furthermore, the value of Vc obtained at dP/dtmax was not significantly different from that obtained at dP/dtmin. For group 2 as a whole, mean Vc(Baan) did not change significantly with ventricular septal defect closure (preoperative, 8.85 +/- 11.1 ml; postoperative, 9.82 +/- 11.84 ml). Group 2 children also exhibited a systolic cyclical variation in Vc(t) similar to group 1. Finally, Vc(t) as a percentage of end-diastolic volume was no different when group 1 and group 2 were compared. We conclude that in the left ventricle, even in the presence of a left-to-right shunt, there is a small but insignificant difference in parallel conductance during ventricular ejection. The magnitude of this cyclical change does not preclude ventricular volume measurement in congenital heart disease by the conductance catheter technique.

scholarly journals Dynamic correction for parallel conductance, GP, and gain factor, α, in invasive murine left ventricular volume measurements

2009 ◽  
Vol 107 (6) ◽  
pp. 1693-1703 ◽  
Author(s):  
John E. Porterfield ◽  
Anil T. G. Kottam ◽  
Karthik Raghavan ◽  
Daniel Escobedo ◽  
James T. Jenkins ◽  
...  
Keyword(s):  
Hypertonic Saline ◽  
Ventricular Volume ◽  
Left Ventricular ◽  
Time Varying ◽  
Dynamic Correction ◽  
Muscle Properties ◽  
Closed Chest ◽  
Catheter Technique ◽  
Parallel Conductance

The conductance catheter technique could be improved by determining instantaneous parallel conductance (GP), which is known to be time varying, and by including a time-varying calibration factor in Baan's equation [α( t)]. We have recently proposed solutions to the problems of both time-varying GP and time-varying α, which we term “admittance” and “Wei's equation,” respectively. We validate both our solutions in mice, compared with the currently accepted methods of hypertonic saline (HS) to determine GP and Baan's equation calibrated with both stroke volume (SV) and cuvette. We performed simultaneous echocardiography in closed-chest mice ( n = 8) as a reference for left ventricular (LV) volume and demonstrate that an off-center position for the miniaturized pressure-volume (PV) catheter in the LV generates end-systolic and diastolic volumes calculated by admittance with less error ( P < 0.03) (−2.49 ± 15.33 μl error) compared with those same parameters calculated by SV calibrated conductance (35.89 ± 73.22 μl error) and by cuvette calibrated conductance (−7.53 ± 16.23 μl ES and −29.10 ± 31.53 μl ED error). To utilize the admittance approach, myocardial permittivity (εm) and conductivity (σm) were calculated in additional mice ( n = 7), and those results are used in this calculation. In aortic banded mice ( n = 6), increased myocardial permittivity was measured (11,844 ± 2,700 control, 21,267 ± 8,005 banded, P < 0.05), demonstrating that muscle properties vary with disease state. Volume error calculated with respect to echo did not significantly change in aortic banded mice (6.74 ± 13.06 μl, P = not significant). Increased inotropy in response to intravenous dobutamine was detected with greater sensitivity with the admittance technique compared with traditional conductance [4.9 ± 1.4 to 12.5 ± 6.6 mmHg/μl Wei's equation ( P < 0.05), 3.3 ± 1.2 to 8.8 ± 5.1 mmHg/μl using Baan's equation ( P = not significant)]. New theory and method for instantaneous GP removal, as well as application of Wei's equation, are presented and validated in vivo in mice. We conclude that, for closed-chest mice, admittance (dynamic GP) and Wei's equation (dynamic α) provide more accurate volumes than traditional conductance, are more sensitive to inotropic changes, eliminate the need for hypertonic saline, and can be accurately extended to aortic banded mice.

Conductance catheter measurement of left ventricular volume: evidence for nonlinearity within cardiac cycle

1995 ◽  
Vol 268 (4) ◽  
pp. H1490-H1498 ◽  
Author(s):  
R. S. Szwarc ◽  
D. Laurent ◽  
P. R. Allegrini ◽  
H. A. Ball
Keyword(s):  
Stroke Volume ◽  
Cardiac Cycle ◽  
Time Derivative ◽  
Reference Method ◽  
Ventricular Volume ◽  
Left Ventricular ◽  
Conductance Catheter ◽  
Systolic Volume ◽  
End Diastolic Volume ◽  
End Systolic Volume

The conductance catheter gain factor, alpha, is usually determined by an independent measure of stroke volume and, as such, is assumed to be constant. However, nonlinearity of the conductance-volume relation has been proposed on theoretical grounds. The present study was designed to establish the extent of nonlinearity, or variability of alpha, within the cardiac cycle using magnetic resonance imaging (MRI) as the reference method. Pentobarbital-anesthetized minipigs (n = 10, 10–13 kg) were instrumented with left ventricular (LV) conductance and Millar catheters. Conductance catheter signals were recorded, and volumes were corrected for parallel conductance using a saline-dilution technique. Animals were then placed in a 4.7-T magnet, and first time derivative of LV pressure-gated transverse MRI images (5-mm slices) acquired during isovolumic contraction (end diastole) and relaxation (end systole). LV cavity volumes were then determined using a third-order polynomial model. The gain alpha was computed three ways: by dividing conductance stroke volume by MRI stroke volume (alpha SV), by dividing conductance end-diastolic volume by MRI end-diastolic volume (alpha ED), and by dividing conductance end-systolic volume by MRI end-systolic volume (alpha ES). alpha SV was 0.62 +/- 0.15, with alpha ED (0.71 +/- 0.17) significantly lower than alpha ES (0.81 +/- 0.21; P < 0.001). Using alpha SV to adjust conductance gain (i.e., assuming constant gain) resulted in a significantly larger end-diastolic volume (25.8 +/- 4.6 ml) and smaller ejection fraction (46.8 +/- 7.2%) than those obtained with MRI (23.0 +/- 4.1 ml and 53.1 +/- 7.3%, respectively; P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Does volume catheter parallel conductance vary during a cardiac cycle?

1990 ◽  
Vol 258 (6) ◽  
pp. H1933-H1942 ◽  
Author(s):  
E. B. Lankford ◽  
D. A. Kass ◽  
W. L. Maughan ◽  
A. A. Shoukas
Keyword(s):  
Left Ventricular Volume ◽  
Cardiac Cycle ◽  
Ventricular Volume ◽  
Volume Measurement ◽  
Blood Pool ◽  
Mean Value ◽  
Left Ventricular ◽  
The One ◽  
Parallel Conductance

Absolute left ventricular volume measurement by the conductance (volume) catheter requires subtraction of the conductance contribution from structures extrinsic to the cavity blood pool. Previously, this parallel conductance volume (Vp) has been assumed constant throughout the cardiac cycle, and the technique described for its estimation in situ yields a single value. We present a new method for parallel conductance determination that yields multiple estimates during systole, enabling an assessment of Vp variability [Vp(t)]. For isolated blood-perfused ejecting canine left ventricles with empty (vented) right ventricles, Vp(t) displayed virtually no variation throughout systole. For in situ hearts, despite the presence of other cardiac chambers, Vp(t) also displayed little variation, with no statistically significant deviation from its mean value throughout systole. Volume signal simulations found the new technique to be less sensitive to signal noise and thus more robust than the one previously published. The isolated and in situ heart data indicate that for the left ventricle, the parallel conductance is relatively constant throughout normal ejection.

Continuous monitoring of right ventricular volume changes using a conductance catheter in the rabbit

1992 ◽  
Vol 73 (5) ◽  
pp. 1770-1775 ◽  
Author(s):  
P. L. Solda ◽  
P. Pantaleo ◽  
S. Perlini ◽  
A. Calciati ◽  
G. Finardi ◽  
...  
Keyword(s):  
Stroke Volume ◽  
Right Ventricular ◽  
Small Animal ◽  
Ventricular Volume ◽  
Left Ventricular ◽  
Conductance Catheter ◽  
Volume Changes ◽  
Conductance Changes ◽  
Lv Volume

To assess the reliability of conductance (G) catheter for evaluating right ventricular (RV) volume changes, a miniature (3.5F) six-electrode catheter was developed and tested in 11 New Zealand rabbit hearts. In five animals the heart was excised; in six it was left in the thorax. RV conductance was recorded while the RV was filled with blood in 0.25-ml steps at different left ventricular (LV) volumes. Linear correlation of measured conductance vs. reference volumes was computed. RV conductance was highly correlated with reference volume [correlation coefficient (r) ranging from 0.991 to 0.999]. Slope of regression lines was not significantly affected by LV volume variations in 1-ml steps or by acute conductance changes of structures surrounding the heart, whereas the intercept was affected only by the 0- to 1-ml LV volume change. In four rabbits, RV conductance changes during a cardiac cycle [stroke volume- (SV) G] were compared in vivo with electromagnetic flow probe-derived estimates of SV (SVem) as stroke volume was varied by graded inferior vena caval occlusion. SV-G correlated well with SVem (r ranging from 0.92 to 0.96). This correlation persisted after the thorax was filled with saline; however, significant differences were found in individual slopes (P < 0.001). These results show that the conductance catheter has a potential to reliably monitor in vivo relative RV volume changes in small-animal hearts.

Simultaneous LV and RV volumes by conductance catheter: effects of lung insufflation on parallel conductance

1998 ◽  
Vol 275 (2) ◽  
pp. H653-H661 ◽  
Author(s):  
Richard S. Szwarc ◽  
Howard A. Ball
Keyword(s):  
Inferior Vena ◽  
Vena Cava ◽  
Ventricular Volume ◽  
Blood Pool ◽  
Spontaneous Respiration ◽  
Conductance Catheter ◽  
Catheter Technique ◽  
Volume Measurements ◽  
Baseline Values ◽  
Parallel Conductance

One aspect in the measurement of ventricular volume using the conductance catheter technique is the assessment of parallel electrical conductivity of structures extrinsic to the ventricular blood pool. Because it is sometimes necessary to make volume measurements during ventilation or spontaneous respiration, the extent to which parallel conductance may vary with lung insufflation was investigated. Anesthetized pigs (11–15 kg) were ventilated and instrumented with both left (LV) and right ventricular (RV) conductance and pressure-tip catheters and end-hole catheters for injection of hypertonic saline into the inferior vena cava and pulmonary artery. Data were recorded during ventilation with tidal volumes of 10 and 20 ml/kg, and the associated fluctuations to LV and RV end-diastolic (EDV) and stroke (SV) volumes were measured. With the use of a saline dilution technique, parallel conductance (Vc) was determined for each ventricle with the ventilator off and lungs insufflated to 0, 10, and 20 ml/kg. Whereas ventilation caused marked oscillations in LV and RV EDV and SV, these variations could not be attributed to Vc, which remained statistically unchanged from their baseline values of 34.1 ± 3.1 in the LV and 31.1 ± 4.4 in the RV. These results indicate that the fluctuations that occur in conductance catheter-derived LV and RV volume signals with ventilation are not caused by any significant changes to parallel conductance.

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