European Journal of Echocardiography 2006 7(4):293-297; doi:10.1016/j.euje.2005.06.010
Copyright © 2005, The European Society of Cardiology
What is a "normal" right ventricle?
Sylva Kovalova*,
Josef Necas and
Jaroslav Vespalec
Centre of Cardiovascular Surgery and Transplantation, Pekarska 53, 656 91 Brno, Czech Republic
Received 5 April 2005; received in revised form 6 June 2005; accepted after revision 15 June 2005.
* Corresponding author. Tel.: +420 5431 82530; fax: +420 5432 11218. sylva.kovalova{at}cktch.cz
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Abstract
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Aims The aim of this project was to define normal values of
right ventricular (RV) volumes and ejection fraction (EF) in
healthy population using 2D echocardiography.
Methods and results The "patient" group comprised 91 healthy volunteers aged 17–62 years. RV volumetry was based on ellipsoidal shell model method. Left ventricular (LV) volumes were assessed by Teichholz formula. All volumes were indexed per m2 of BSA and the rate distribution of measured and calculated values were evaluated. The normal range of individual parameters was expressed as mean value±2 standard deviations (
). A pair test was used to compare corresponding results of the RV and LV measurements. The regression analysis was used to test the relationship between LV and RV volumes and age. Indexed enddiastolic and endsystolic RV volumes were 79.1±29.9ml and 32.6±19.7ml, respectively, EF being 50±9.7% in men and 58±13.6% in women. No correlation with patient's age was observed.
Conclusion Enddiastolic and endsystolic volumes of RV were significantly higher than those of LV. EF of RV was lower as compare to LV. Right ventricular EF in men was lower than that in women. There was no correlation between EF and patient's age.
Keywords: Right ventricular volumetry; Right ventricular ejection fraction; 2D Echocardiography; Ellipsoidal shell model; Normal values
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1 Introduction
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In daily echocardiographical practice there is a need for exact
quantification of right ventricular (RV) volumes (tricuspid
and pulmonary regurgitation, interatrial shunts) as well as
exact assessment of right ventricular ejection fraction (EF)
(pulmonary hypertension, ischemic heart disease, cardiomyopathies).
There are two major challenges: firstly, selection of the appropriate
method and secondly, the interpretation of the results.
At present several methods enable non-invasive quantification of RV volumes and EF (MRI,1–3 radionuclides4,5 and echocardiography6,7). There is a little experience in RV volumetry generally. Though MRI is considered the gold standard in RV volumetry,1–3 the selection of preferred method is influenced also by its availability, cost, patient's comfort and repeatability during follow-up, therefore echocardiography might be preferred. Our experience as well as recent literature indicate that echocardiography is a relatively easy and reliable also in this respect.6,7
Concerning the interpretation of volumes and EF of the RV, there is still lack of generally accepted "normal" values and there is also a wide range variability of hitherto published data.1,4,5,8,9 The aim of our study was to answer the question – what are the "normal" values of volumes and EF of the right ventricle as assessed by 2D echocardiography.
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2 Material and methods
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Right ventricular volumetry was accomplished using "ellipsoidal
shell model" with corresponding formula
V=2/3
Pd. Area
P was
measured in our modification of apical four-chamber view and
distance
d in parasternal short axis. All measurements were
performed in both systole and diastole. The difference of enddiastolic
(EDV) and endsystolic volume (ESV) yielded stroke volume (SV).
SV expressed as percentage of EDV represents RV EF. Exact specification
of projections and validation of the model and method used was
carried out on a group of 82 patients as published before.
7
All measurements were performed on SONOS 5500 (Agilent Technologies, Inc., Andover, Massachussetts) using S3 probe in harmonic imaging mode.
The patient group consisted of 91 healthy normotensive volunteers. Forty-six were men and 45 women with an average age of 39 years (range 17–62). All of them had a normal echocardiogram. Their respective RV volumes and EF were calculated as mentioned above. Left ventricular volumes were calculated using commercial software and Teichholz equation. All volumes were indexed per m2 of BSA.
We analysed the distribution rate of all measured and calculated values as well as average values and median. "Normal range" was defined as mean value±2. Corresponding values of the right and left ventricles were compared using a pair test. Statistical difference between right and left ventricular EF was tested by Student t-test. The correlation between the age and EF of respective RV and LV was tested by regression analysis.
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3 Results
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The distribution rate of values measured and calculated (indexed
EDV, ESV, SV and EF) of the RV and LV approximately matches
normal Gaussian distribution (
Figs. 1–4
). The indexed
values of RV and LV volumes and EF are presented in
Table 1.
The indexed EDV (EDVI) and ESV (ESVI) of the RV were significantly
greater than those of the LV (pair
t-test,
=0.1%). There was
no significant difference between indexed SV (SVI) of the RV
and LV. This supports the validity of the RV volumetric method
used. EF of the RV is significantly lower than that of the LV
(pair
t-test,
=0.1%).
When comparing male and female patients, EDVI and ESVI of the RV in males exceed significantly those in females, which in turn explains the significantly lower RV EF in males as compare to females (Fig. 5). In contrast LV EF in both males and females did not show any significant difference (Table 2). RV and LV EF of the persons in our study were not dependent on the age (Fig. 6).
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4 Discussion
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Evaluation of the RV function based on quantitative volumetry
is superior to semiquantitative methods, however it requires
solid methodology: exact projections and accuracy in measurements.
Distribution of values of indexed ventricular volumes and EF
in our study approached Gaussian curve, which is typical for
biological measurements. Minor deviations from ideal shape can
be explained by a relatively small number of persons in study
and inherent inaccuracy of measurements.
"Normal values" of RV1,4,5,8–10 and LV1,4,5,11–16 volumes and ejection fraction appear rarely in the literature. They usually are not the main aim of the studies, but only represent some smaller control groups evaluated by different methods. Therefore, the results are very inconsistent and vary widely. The "normal ranges" of averaged RV volumes and EF by different authors are shown in Table 3. Our results are within these ranges. Similar to our results, all studies comparing RV and LV volumetry by whichever method, found higher estimates for RV systolic and diastolic volumes than those of the LV.1,4,5
Systolic function of the ventricles is usually given as their
EF. The estimation of EF in LV is a standard part of a routine
echocardiographic examination. In our study group the lowest
value of LV EF was 50%. Taking into account the accepted standard
for normal values expressed as average value±2 standard
deviations, the LV EF in our study was 61.2±8.9%. The
male subgroup did not significantly differ from the female one
(
Table 2). These results correspond with the accepted normal
range of LV EF, the lower range being 50–55%.
There is a distinct difference in normal values of RV EF compared with the LV. The lowest value in our study group was 40%, the average value±2 being 53.9±14.2. There was also a significant difference in RV EF between male and female subgroups (Table 2). To assume as the lower range of RV EF we suggest 40% for males and 45% for females. No explanation for this difference is known. In our study the average age of males was lower than that of females, but not significantly. Therefore, we also tested the relation of ventricular EF to the age. We did not observe any correlation of EF with patient's age for either ventricle, although some authors declare slight tendency of decline of EF with age,17 others do not.18
Afterload is another potential factor influencing RV EF. Some authors showed decrease in RV EF under chronically increased afterload.19 We do not suspect increased pulmonary arterial pressure in healthy subjects of our study. Pulmonary arterial pressure rises during physical exertion. In our male subgroup over a half of the subjects used to exercise regularly at least twice a week, but none engaged in professional or endurance sports. In contrast to men, women were more sedentary and only a few of them exercised regularly. One may suggest that the RV (similarly to the LV) may react to the exercise by physiological dilatation and a lower resting EF, which in fact represents functional reserve in a trained person. Exact explanation of the above relationship is beyond this study and would require another specifically aimed analysis.
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5 Study limitation
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The main limitation is a relatively small study group. Increasing
the data set would further refine the range of normal values
of RV volumes and EF.
Only indirect validation of the ellipsoidal shell model using SV determination by thermodilution has been accomplished.
Our "normal" values might be valid only for the described method.
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6 Conclusions
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Enddiastolic and endsystolic RV volumes are greater than those
of the LV, while RV EF is lower than that of LV.
In our study the mean value of RV EF in males was lower than in females.
Normal mean value of RV EF is 53.9%. The lower range in males is 40% and in females 45%.
No relationship between RV EF and age in healthy individuals was found.
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References
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Abstract
1 Introduction
