Ventricular Nonmixing as a Source of Error in the Estimation of Ventricular Volume by the Indicator-Dilution Technic

Abstract

1. In the anesthetized dog, end-diastolic, end-systolic and stroke volumes for the left ventricle have been calculated according to the method of Holt from dilution curves recorded at the aortic root. For heart rates of less than 120 beats per minute, the catheterdensitometer systems used gave 90 to 95 per cent of the true concentration in the aortic root at the end of diastole. 2. Average volumes of 2.96, 1.63 and 1.33 ml./Kg. of body weight were calculated for each of these parameters. The interindividual and intraindividual variations about these means amounted to ± 30 to 50 per cent. 3. In approximately 15 per cent of the dilution curves the concentration of dye in the aortic root during early systole (phase of maximal ejection) showed a transient, markedly low value compared with that of the end of diastole. This can be explained only on the basis of the preferential ejection from the heart in early systole of the undyed, newly entering blood from the left atrium, which had mixed poorly with the residual volume of the ventricle. Qualitative inspection of cineangiograms confirmed this impression and demonstrated that a residuum of contrast medium failed to mix with the incoming blood from the left atrium. 4. In addition, there is evidence for the possibility of overestiination of stroke volumes from dilution curves recorded immediately proximal to the injection chamber. 5. Incomplete mixing of the left artial blood with the residual volume of the ventricle precludes accurate quantitation of the changes of volume in the ventricle by the simple formulas proposed by previous authors. This phenomenon may serve to explain the considerable variability that is found in the present study and in the literature.

Mixing in the right ventricle and pulmonary artery in man: evaluation of ventricular volume measurements from indicator washout curves

“…However, according to the findings of Freis and Heath (23), Swan and Beck (13), and Rhode, Kines, and Holt (25), as well as the present study, mixing is also not homogeneous above the semilunar valves. The significant underestimation of flow observed in the three curves sampled in the pulmonary artery after apex injection may indicate that blood with a high concentration of indicator coming from the apical region, ejected in late systole, does not mix completely with the blood ejected in the first part of systole and remains just above the valve until the next ejection.…”

“…These changes in concentration, which occur in a very short time, must be relatively large not to be completely obscured by the catheter-sampling technique. This phenomenon was first noted by Swan and Beck (13) in 16% of the washout curves recorded by sampling at a very high speed above the aortic valve, after ventricular injection, in dogs. These authors suggested that the "dips" were due to a very low concentration of indicator in the blood ejected at the beginning of systole.…”

“…Although the existence of homogeneous ventricular mixing is a prerequisite condition for the valid application of this technique, only a few descriptions of ventricular mixing have been reported. While the available information indicates that mixing does not appear to be homogeneous (12)(13)(14)(15), the significance of this observation with respect to estimations of ventricular volume has not been characterized adequately. Volume may still be estimated with validity in the absence of perfect mixing if the inhomogeneities are randomly distributed (16); if systematic regional differences in mixing do occur in the ventricle, however, estimates of volume will be systematically in error.…”

Myocardial Function and Lipid Metabolism in the Chronic Alcoholic Animal

“…While an absolute test of accuracy in vivo is not available, three studies comparing the indicator dilution technique with independent methods have shown good agreement (20)(21)(22). The study by Swan, Ganz, Wallace, and Tanura (21) represents a revision of a previous conclusion that the indicator dilution technique differed substantially from angiographic data (23).…”

The effects of posture and isoproterenol on the velocity of left ventricular contraction in man

“…LVEDV and LVESV were calculated from the ratio of ESV to EDV (obtained from thermodilution curves) and from the stroke volume (23,25,32). Although the validity of the indicator dilution method of determining left ventricular volume has been questioned (33,34) (14) have also concluded that indicator dilution provides reliable measurements of end-diastolic volume in the normal left ventricle, especially for purposes of assessing changes induced by various interventions.…”