[Effect of magnesium on arrhythmia after valvular replacement].
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Adolescent↗
Biomedical subjects
C X Jia
Publications and source records attributed to C X Jia.
Validation study of a new transit time ultrasonic flow probe for continuous great vessel measurements.
Continuous measurement of cardiac output is important during experimental and clinical cardiac surgery as an indicator of ventricular function. Previous flow probes underestimated flow secondary to position and flow (S-series probes; Transonic Systems, Inc., Ithaca, NY), required frequent calibrations (electromagnetic), and were cumbersome to use. The new A-series probe (ASP) by Transonic Systems, Inc., uses a new X method of ultrasonic illumination insensitive to perturbations in flow. The ASPs were found to be accurate during in vitro studies, but have not been validated in vivo. Six anesthetized pigs were instrumented for right atrium to left atrium bypass, and ASPs were placed on the ascending aorta and pulmonary artery. Baseline measurements included aortic (Ao) and pulmonic flow (P), and thermodilution (Td) cardiac output. Animals then were placed on right heart bypass, and flow was randomly varied from 1 to 6 L/min, and Ao flow was recorded. In addition, ASPs were rotated and their direction reversed. After data collection, the occlusive roller pump (RP) was calibrated using a timed collection method. Calibrated RP flows were plotted versus ASP flows, and regression was applied. There was no difference between mean Ao, P, and Td cardiac outputs at baseline. In addition, changes in position and direction of the probe did not affect measurement of flow. The ASPs showed a highly linear correlation with RP ([r = 0.98, p < 0.01] ASP[L/min] = 0.98 RP-0.032). During laminar flow states, ASPs are accurate and insensitive to position on the great vessels.
Animals↗
Conductance artifacts in a novel in vitro model of ventriculothoracic electrical coupling.
The utility of open chest conductance (COND) ventriculography is limited by artifacts altering the relationship between COND and left ventricular (LV) volume. Pressure-COND loops often lean to the left during LV volume reduction by caval occlusion. Time varying alterations in the pericardial-LV contact area affect electrical coupling in the open chest during the cardiac cycle, producing COND artifacts. In this study, an open-mediastinum model was constructed. Components represented the LV, blood, pericardium, and thoracic contents. Varying ventriculothoracic coupling was simulated by changing the volume of pericardial saline (0, 30, 60 ml). Raw dual field COND was repeatedly (n = 20) compared with volumes of normal saline from 60 to 120 ml at 5 ml intervals. Groups were compared by linear regression and repeated measures ANOVA. Artifacts significantly (p < 0.01) altered parallel COND, indicated by the y-intercept, with the exception of 0 versus 30 ml. The slope constant also changed significantly, with the exception of 30 versus 60 ml. These results suggest that variable pericardial-LV contact can cause time varying artifacts in COND in the open chest. Therefore, posterior insulation may reduce artifacts in COND ventriculography and should be tested for this effect.
Analysis of Variance↗
Conductance-echocardiography correlation during changes in left ventricular volume.
Conductance (COND) measurements of left ventricular volume, satisfactory under steady state conditions, may be altered by extraneous factors during complex experiments or cardiac surgery. A reference technique is needed to detect changes in the COND-left ventricular volume relationship. This technique should indicate when recalibration of COND is needed. Accordingly, we assessed the relationship between left ventricular COND and the area of left ventricular short-axis cross section (SACS) by two-dimensional echocardiography during vena caval occlusion. Thirteen anesthetized pigs underwent a median sternotomy and insertion of a COND catheter. Two-dimensional echocardiography and COND were displayed and recorded simultaneously on a digital video monitor. Data were analyzed at end-diastole during the filling phase after vena caval occlusion, because the quality of two-dimensional echocardiography was better during recovery. Results demonstrated a linear relationship between left ventricular COND and SACS at end-diastole, with a positive slope. Correlation coefficients ranged from 0.88 to 1.0 and averaged 0.96 +/- 0.01 (SE). The overall mean relationship was (SACS) = 0.40 (COND) - 17. It is concluded that SACS by two-dimensional echocardiography can be employed to confirm COND measurements of left ventricular end-diastolic volume during laboratory experiments or cardiac surgery. Stability of the SACS-COND relationship indicates that COND calibration is valid. Changes in the SACS-COND relationship would require recalibration of COND. Data markedly deviating from a linear SACS-COND relation reflect experimental error and should be discarded.
Animals↗
Electrical isolation of the heart. Stabilizing parallel conductance for left ventricular volume measurement.
Modern indices of left ventricular function require accurate measurement of left ventricular volume (LVV). Although conductance catheter (COND) measurements of LVV have been found to be reproducible under steady state conditions in closed chest animals, after median sternotomy, measurements of LVV are subject to exaggerated variation in parallel conductance (alpha Vc) outside of the left ventricle. Current calibration methods for measuring alpha Vc include hypertonic saline injection and quantitative two dimensional echocardiography. Unfortunately, these methods are hampered by imprecision, since frequent changes in alpha Vc in the open chest make recalibration impractical. Accordingly, a latex wrap technique was developed to insulate the left ventricle from extracardiac sources of alpha Vc in the open chest. Anesthetized pigs (n = 5) underwent a median sternotomy with insertion of a 6 French COND-micromanometer combination catheter into the left ventricle. Three conditions were tested: 1) unaltered; 2) metallic retractor outside of the pericardium (metal); and 3) latex wrap between the metal and pericardium. Pressure/COND loops showed that the insulator improved the shape of the loops and decreased alpha Vc, as measured by an echo-area/COND relationship, whereas metal increased alpha Vc and produced artifacts in the loops. In conclusion, electrical isolation eliminates distortion of pressure/COND loops related to extracardiac sources of alpha Vc, therefore allowing for accurate COND measurements in the open chest.
Animals↗