Page 17 - Delaware Medical Journal - September 2016
P. 17
SCIENTIFIC ARTICLE
measured VO2 CO and estimated VO2
CO calculations correlated poorly
(R=0.57; ICC=0.59). Direct continuously measured VO2 CO and thermodilution
CO calculations correlated poorly as well (R=0.51; ICC=0.60). Furthermore, when the CO from these different methods of VO2 measurement was utilized to calculate aortic valve areas, those areas derived from direct continuously measured and estimated VO2 values correlated poorly as well (Figure 1A, R=0.68; ICC=0.55). Similarly, the correlation between AVA based on direct continuous VO2 and
TD was poor (Figure 1B, R=0.66; ICC=0.60).
Using a constant assumed VO2 value led to a large discrepancy in repeated CO measurement during the case (R=0.62; ICC=0.57). Repeated TD CO was associated with less discrepancy (R=0.78; ICC=0.84). Although direct continuously measured VO2 changed at times during the course of a procedure, requiring a pause to await a relatively stable value (although measurements were only made when a steady state was achieved), the resulting repeated CO measurements were closely correlated (R=0.93; ICC=0.96).
In regards to AVA, although there was good correlation in AVA calculated from repeated assumed VO2 CO (Figure
2A, R=0.85; ICC=0.89) and TD CO (Figure 2B, R= 0.93; ICC=0.94), AVA based on direct continuous VO2 CO was very reproducible (Figure 2C, R=0.99;ICC>0.99).
DISCUSSION
CO calculated by direct continuous
from those based on estimated VO2 values and thermodilution, as does the
related calculation of AVA. The superb reproducibility of AVA, a value that should using this direct continuous VO2 technique suggests this is the superior CO technique. Although direct VO2 based CO was
felt to be the gold standard historically, cumbersome measurement techniques led to the adoption of the estimated VO2 determination.9 However, many CCL computer systems, including our widely used software program (Phillips Xper, Melbourne, Fla.) make an assumption
of a patient’s VO2 based on an equation developed by LaFarge and Miettinenin.5 This equation was developed with regression analysis using patients aged 3-40 years with congenital heart disease and an average age of 12 years.5 The authors themselves recommended against using this equation for patients older than 40 years of age.5 Unfortunately using
the assumed Fick calculation in patients older than 40 years of age, as were all our validity of the hemodynamic assessment.
TABLE 1: Baseline Characteristics of Consecutive Patients
CHARACTERISTICS:
N=30
Age (mean)
73 (52-88)
Males
68%
Coronary Artery Disease
64%
Hypertension
100%
Diabetes
32%
Cardiomyopathy
55%
Valvular Heart Disease
83%
Mild Tricuspid Regurgitation
65%
Moderate or Severe Tricuspid Regurgitation
10%
Mild Pulmonary Hypertension
62%
Moderate to Severe Pulmonary Hypertension
11%
Atrial Fibrillation
50%
Peripheral Arterial Disease
14%
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