(Circulation. 1996;93:1160-1169.)
© 1996 American Heart Association, Inc.
Articles |
Relation of Mean Right Atrial Pressure to Echocardiographic and Doppler Parameters of Right Atrial and Right Ventricular Function
Presented in part at the 44th Annual Scientific Session of the American College of Cardiology, New Orleans, La, March 20, 1995.
From the Section of Cardiology, Department of Medicine, Baylor College of Medicine and The Methodist Hospital, Echocardiography Laboratory, Houston, Tex.
Correspondence to William A. Zoghbi, MD, Director of Echocardiography Research, Baylor College of Medicine and The Methodist Hospital, 6550 Fannin, SM 677, Houston, TX 77030.
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Abstract |
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 Top Abstract IntroductionMethods Results Discussion References |
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Background A paucity of data exists as to the relation of mean right atrial pressure (RAP) to Doppler parameters of right atrial and ventricular filling. Furthermore, whether echocardiographic parameters of right atrial and right ventricular function and inferior vena cava improve the relation of Doppler filling dynamics with RAP has not been explored.
Methods and Results Doppler and echocardiographic studies were performed simultaneously with measurements of mean RAP in consecutive patients who either had a central venous catheter in the Intensive Care Unit or underwent catheterization of the right side of the heart. The initial population consisted of 35 patients with a mean age (±SD) of 60±15 years; 34% were on mechanical ventilation. Mean RAP averaged 9±5.7 mm Hg (range, 2 to 28 mm Hg). Among tricuspid inflow parameters, the strongest relation with RAP was observed with the ratio of early to late velocity (r=.66). For hepatic venous flow, systolic filling wave indexes had the best relation with atrial pressure, the highest being for systolic filling fraction (r=-.86). Weaker relations were noted with the use of right atrial volumes, right ventricular function, and inferior vena caval diameters. The addition of any of these variables did not improve the relation of systolic filling fraction with RAP. The regression equation (RAP=21.6-24 systolic filling fraction) was tested prospectively in the estimation of atrial pressure in 50 patients. The correlation coefficient was .89 in the prospective group and .88 in the total group of 85 patients. The mean difference between predicted and actual pressures in the whole population was -0.2±2.6 mm Hg. The sensitivity and specificity for mean RAP>8 mm Hg were 86% and 92%, respectively.
Conclusions Among echocardiographic and Doppler parameters of right atrial and right ventricular function, hepatic venous flow dynamics relate best to mean atrial pressure and can be used clinically to estimate mean RAP.
Key Words: diastole • echocardiography • ventricles • pressure • atrium
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Introduction |
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TopAbstractIntroductionMethods Results Discussion References |
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The determination of right and left ventricular filling pressures is important clinically for the diagnosis and management of various hemodynamic conditions.1 2 3 4 Furthermore, assessment of right atrial pressure (RAP) is needed in the echocardiography laboratory for the estimation of systolic right ventricular and pulmonary artery pressures.5 6 7 8 Although clinical evaluation of jugular venous pulsations is usually used to estimate RAP, it may be difficult in certain individuals because of obesity or a short neck, and such an examination may not always be possible in a busy echocardiography laboratory.6 7
The relation of Doppler and echocardiographic parameters of left-side cardiac structure and function to left ventricular filling pressure has been investigated in several studies.9 10 11 Mitral and pulmonary venous flow dynamics and left atrial size have been shown to relate to and allow estimation of left atrial pressure.9 10 11 In contrast, a few studies in selected patients have evaluated the right-side hemodynamic correlates of right atrial and right ventricular filling dynamics.12 13 14 Tricuspid and hepatic vein flow dynamics have been described in patients with restrictive cardiomyopathy13 and have been used to help differentiate constrictive pericarditis from restrictive cardiomyopathy.14 15 On the other hand, studies on the changes in the diameter of the inferior vena cava in response to negative intrathoracic pressure have demonstrated a significant relation of this index to RAP.16 17 18 19 Such an approach, however, requires the patient's cooperation and has been limited in mechanically ventilated individuals.18 A comprehensive evaluation of the relation of echocardiographic and Doppler parameters of right ventricular function, right atrial function, and inferior vena cava to mean RAP in patients with a variety of clinical conditions has not previously been performed. Because several of these parameters can be obtained from routine cardiac ultrasound examination, it is important to evaluate which of these parameters has the best relation to RAP and whether a combination of these indexes improves the clinical estimation of right ventricular filling pressure. Accordingly, this study was undertaken to assess the relation of Doppler parameters of hepatic vein and tricuspid inflow, right ventricular, right atrial function, and inferior vena cava to mean RAP in consecutive patients undergoing measurement of RAP. The relation among these parameters was defined. The best relation with mean RAP was tested prospectively in the estimation of mean RAP.
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Methods |
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TopAbstractIntroductionMethods Results Discussion References |
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All consecutive patients undergoing catheterization of the right side of the heart or who had in-dwelling central venous catheters in the Intensive Care Units at The Methodist Hospital (Houston, Tex) during a cumulative 3-month period were eligible for this study. The investigation protocol was approved by the Institutional Review boards of The Methodist Hospital and Baylor College of Medicine. All patients gave informed consent before participation in the study. Simultaneous recordings of transthoracic echocardiographic studies and mean RAP were performed in all patients (see below). Exclusion criteria included inadequate recordings of pressure or Doppler tracings, tricuspid stenosis, severe tricuspid regurgitation assessed by color-flow Doppler,20 the presence of a prosthetic tricuspid valve, and nonsinus rhythms (atrial flutter or fibrillation, paced rhythm, or complete heart block). The echocardiographic and hemodynamic protocols and inclusion and exclusion criteria were identical in the initial and prospective populations.
Echocardiographic and Doppler
Studies
The echocardiographic studies were performed by
use of a Hewlett Packard ultrasound system (Sonos 1000) equipped with
2.5- and 3.5-MHz transducers with the patient in the supine position.
Standard echocardiographic imaging was performed from
the parasternal, apical, and subcostal windows for the evaluation of
right and left ventricular function and assessment of the
size of the right atrium and inferior vena cava.
Color-flow Doppler was used to screen for the presence of
valvular regurgitation. A pulsed Doppler
recording of tricuspid inflow was obtained from the low
parasternal and apical windows, with the sample volume placed at the
tip of the tricuspid valve. Ten to 15 cardiac cycles from each window
were recorded at a sweep speed of 100 mm/s. A recording of
hepatic vein flow velocity was obtained from the subcostal window, with
the sample volume placed 1 to 2 cm in the hepatic veins, close to their
entrance into the inferior vena cava. Similarly, 10 to 15
cardiac cycles were recorded.
Echocardiographic Measurements
Right ventricular function was quantified by use of
a modified Simpson's rule21 from the four-chamber
view in technically adequate studies and was visually assessed in all
cases through changes in right ventricular
dimensions.22 Maximal right atrial volume preceding
tricuspid valve opening and minimal right atrial volume after atrial
contraction were measured from the apical four-chamber view. Right
atrial volumes and emptying fractions were calculated with modified
Simpson's rule. From the two-dimensional subcostal views, maximal
inferior vena caval diameter and minimal diameter after a
sniff test were measured, from which a collapse index in percent was
obtained.17 In patients on mechanical ventilation, the
approach used to determine maximal and minimal inferior
vena caval diameters was similar to that of Jue et
al.18
Doppler Measurements
Tricuspid
inflow measurements were performed from the window
providing the highest overall velocities, implying the least angulation
with flow. The following parameters were measured (Fig 1
)
as previously described in detail23 : peak
early inflow velocity, peak late velocity, and their ratio; atrial
filling fraction; deceleration time; and acceleration time.
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From the
hepatic vein flow velocity, the following
parameters were measured (Fig 1
): peak velocity and
time-velocity integral of the systolic,
diastolic, and atrial reversal waves. Ratios of
systolic to diastolic peak velocity and
time-velocity integral also were derived. Systolic filling
fraction was calculated as the time-velocity integral of the
systolic wave divided by the sum of time-velocity integrals
of the systolic and diastolic waves. Velocity
reversal occasionally observed at the end of the systolic wave
was not included in the systolic wave or in the calculation of
systolic filling fraction. Systolic filling fraction
was also derived from peak velocities as peak systolic wave
velocity divided by the sum of peak systolic and
diastolic velocities. Duration of the atrial reversal wave
was measured from beginning to end of the atrial reversal wave (Fig
1).
All measurements represent an average of five to seven consecutive cardiac cycles. We have previously shown that tricuspid inflow parameters derived with this approach are almost identical to those obtained during end-expiratory apnea.23 Similar results were observed with hepatic vein flow parameters in our laboratory, with the mean percent difference between averaged values and those at end-expiratory apnea being 4±3% for peak systolic velocity, 6±5% for peak diastolic velocity, and 4.5±6% for peak velocity of atrial reversal. Quantification of Doppler and echocardiographic variables was performed by a single observer without knowledge of clinical or hemodynamic data.
Hemodynamic Recordings and
Measurements
Pressure calibration was performed before and immediately
after
pressure measurements. All readings were referenced to midaxillary line
with the patient in the supine position. Determination of mean RAP was
performed with Medex reusable transducers. All patients with central
venous catheters (7.9F or 9F) in the Intensive Care Units had chest
radiograms identifying the position of the catheter in the superior
vena cava close to its junction with the right atrium or in the high
right atrium. For patients in the catheterization
laboratory, the proximal port of the Swan-Ganz catheter was used for
measurements. All pressure recordings were obtained
simultaneously with the Doppler tracings and
echocardiographic imaging. Pressure measurements were
determined at end expiration, and an average of three to five cycles
was obtained.
Reproducibility
Interobserver and intraobserver
reproducibilities of Doppler
parameters and predicted mean RAP were performed in 10
studies chosen at random. Measurements were obtained from the same
recordings (but not necessarily the same beats) by a second
observer and later by the first observer. Variability was expressed as
the difference between observations and the mean percent error, derived
as the absolute difference between the two sets of observations divided
by mean of the observations.
Statistical Analysis
Results are expressed as mean±SD.
An unpaired t test
was used to compare variables between groups of patients. To
compare qualitative ventricular function assessment and
mean RAP, the 
2 test was used. Correlations
between echocardiographic and Doppler
parameters of systolic and diastolic
function and mean RAP, age, and heart rate were performed with linear
regression analysis. Stepwise multiple linear regression was
subsequently performed. The best derived equation from the initial
study group was then used to predict RAP in the prospective population.
Statistical significance was set at P
.05.
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Results |
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TopAbstractIntroductionMethods Results Discussion References |
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Initial Population
Of the 45 patients screened, 10 were excluded: 5 because of nonsinus rhythms, 3 for severe tricuspid regurgitation, and 2 because of inadequate recording of hepatic venous flow. The initial population therefore consisted of 35 patients, 19 women and 16 men with a mean age of 60±15 years. Fourteen patients had studies in the cardiac catheterization laboratory. Table 1
shows the
clinical diagnoses of the initial group.
Left ventricular ejection fraction averaged 48±15%
(range, 18% to 67%). Twelve patients (34%) were on mechanical
ventilation. Overall right ventricular function was
depressed in 10 patients (28%) and normal in 25. Right
ventricular ejection fraction ranged between 25% and 80%
(mean, 49±15%). Right atrial maximal volume averaged 43±21.5
cm3 (range, 21 to 142 cm3); minimal volume,
24±19 cm3 (range, 8 to 118 cm3); and atrial
emptying fraction, 46.5±13.6% (range, 17 to 68%). Maximal diameter
of the inferior vena cava averaged 1.4±0.52 cm (range, 0.7
to 2.6 cm), with a minimal diameter after the inspiratory effort of
0.83±0.6 cm (range, 0 to 2.2 cm) and a percent collapse of
47±22%
(range, 8% to 100%). Diameter of the hepatic vein at the site of
Doppler interrogation averaged 0.9±0.36 cm (range, 0.5 to 2 cm).
Table 2 details the results of the
hemodynamic and Doppler measurements.
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Relation of Echocardiographic Measurements to
Mean RAP
Table 3 lists the echocardiographic
parameters in patients with normal mean RAP (8 mm Hg) and
elevated pressure. Right atrial emptying fraction was significantly
lower in patients with elevated mean RAP, as was the percent
inferior vena caval collapse. Although absolute
measurements of minimal and maximal right atrial volumes and vena caval
diameters were larger in patients with elevated RAP, this difference
reached statistical significance with inferior vena caval
measurements. Right ventricular function tended to be lower
in patients with elevated RAP but was not significantly different.
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Weak
relations were observed between right atrial volumes and mean RAP
(r=.49 and r=-.45 for minimum volume and
emptying fraction, respectively; both P<.01). The best
correlations of inferior vena caval measurements with mean
RAP were observed with percent collapse (r=-.63,
P<.0001; Fig 2) and minimum diameter
(r=.5, P<.01). In the subgroup of patients with
mechanical ventilation, no significant correlation was observed
(r=.4, P=.23 for maximal diameter;
r=.25, P=.45 for minimal diameter;
r=.24, P=.48 for collapse index of the
inferior vena cava; Fig 2). In the group without mechanical
ventilation, correlations of inferior vena caval
measurements were stronger, the best being for the collapse index
(collapse index: r=-.76, P<.001, mean
RAP=19-0.21xcaval collapse index; SEE=4.2 mm Hg;
r=.4; P=.05 for maximal diameter;
r=.66 for minimal diameter; Fig 2).
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Relation Between Doppler Parameters and Mean
RAP
Table 4 compares Doppler parameters
in patients with normal and elevated mean RAP. Among tricuspid inflow
variables, the ratio of early to late velocity was the most
significant difference between the two groups, followed by atrial
filling fraction. The other parameters had directional
changes but did not reach statistical significance. For hepatic vein
flow parameters, results with the maximal systolic,
diastolic, and atrial reversal velocities were almost
identical to those observed with time-velocity integral
measurements. Of the hepatic vein flow parameters, the
systolic filling wave (peak velocity or time-velocity
integral) and parameters that incorporated this measurement
were significantly different in patients with normal versus elevated
RAP (Table 4). A tendency for longer duration of the atrial
reversal
wave was seen in the group with elevated mean RAP.
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Correlations between
mean RAP and Doppler parameters of
tricuspid and hepatic vein flow velocities are shown in Table
5. Among tricuspid inflow parameters, the
most significant relation with mean RAP was observed with the ratio of
early to late velocity (r=.66; Fig 3). Weak
relations were observed with early and late velocities and atrial
filling fraction, whereas no significant relation was seen with
acceleration or deceleration time. On the other hand, stronger
relations were seen between Doppler parameters of
hepatic vein flow and RAP, particularly with parameters
that included the systolic filling wave alone or in combination
with diastolic filling wave (r range, -.76
to -.86; Table 5). The highest correlation was between
mean RAP
and systolic filling fraction (r=-.85 for
velocities and r=-.86 for time-velocity integrals;
Fig 4). Excluding patients with heart rates >90 beats
per minute (n=7) resulted in a correlation coefficient between
systolic filling fraction and mean RAP of .92. The duration of
atrial reversal wave related significantly to RAP
(r=.63).
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Significant interrelations were observed among tricuspid Doppler parameters and those of hepatic vein flows. A significant correlation was noted between tricuspid early velocity and hepatic vein diastolic velocity (r=.47, P=.03) and between the ratio of early to late velocity and systolic filling fraction (r=-.61, P=.002).
Relation of Doppler Variables to Right
Ventricular Systolic Function
In the group with depressed right
ventricular
systolic function (n=10), deceleration time was shorter
compared with the group with normal function (154±82 versus
257±82
milliseconds, P<.01). A trend for a higher early
velocity and ratio of early to late velocity along with shorter
acceleration time in patients with depressed right
ventricular function was also seen. For hepatic flow
variables, the only significant difference was observed with
systolic filling fraction (0.34±0.28 and 0.59±0.14 in
depressed and normal function, respectively; P<.05). The
group with depressed right ventricular systolic
function tended to have lower peak systolic velocity, higher
peak diastolic and atrial reversal velocities, and a longer
duration of atrial reversal wave. A statistically significant but weak
relation was noted between right ventricular ejection
fraction and systolic filling fraction (r=.38,
P<.01).
Relation of Doppler Variables to Right Atrial Volumes and
Inferior Vena Caval Dimensions
The most significant relation observed
between right atrial
function and tricuspid inflow dynamics was that of right atrial
emptying fraction to tricuspid ratio of early to late velocity
(r=-.66, P=.003). Trends for a higher
ratio
of early to late velocity with larger atrial maximal and minimal
volumes were noted but did not reach statistical significance. Other
tricuspid inflow parameters did not relate significantly to
atrial volumes or emptying fraction.
For hepatic venous flow, significant inverse correlations were observed between systolic filling fraction and right atrial maximal volume (r=-.45) and minimal volume (r=-.51), and a direct correlation was noted with right atrial emptying fraction (r=.57). A significant relation (r=-.48) was observed between atrial emptying fraction and the difference in duration of the atrial reversal wave and tricuspid A wave. Other hepatic vein flow variables related poorly to right atrial volumes and function. A significant correlation was noted between inferior vena caval collapse index and systolic filling fraction (r=.64, P=.01).
Relation of Doppler Variables to Pulmonary Artery
Pressure, Age, and Heart Rate
A trend was noted in patients with
higher pulmonary artery
systolic pressure to have a higher ratio of early to late
velocity, shorter deceleration time, and lower hepatic vein
systolic filling fraction. However, none reached statistical
significance. No significant relation was observed between age or heart
rate and Doppler parameters of tricuspid or hepatic
vein flows.
Prediction of Mean RAP in a Prospective Population
Table
6 shows the sensitivity and specificity of
the best Doppler and two-dimensional variables for
separating normal from elevated (>8 mm Hg) mean RAP in the initial
population. The best separation was seen with systolic filling
fraction. With stepwise multiple linear regression analysis,
the relation of systolic filling fraction to mean RAP was not
improved by the addition of tricuspid or hepatic vein Doppler
parameters or echocardiographic
measurements of right ventricular and atrial function or
inferior vena cava. The best model in the prediction of RAP
was Mean RAP=21.6-24xSFF, where RAP is in millimeters of
mercury and SFF is systolic filling fraction, derived as
hepatic vein systolic time-velocity integral divided
by the sum of systolic and diastolic
time-velocity integrals. This equation was also similar to that
derived with maximal velocity measurements.
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The above relation was
tested prospectively in a separate patient
population for the estimation of mean RAP. Of 58 patients screened, 8
were excluded. Reasons for exclusion were severe tricuspid
regurgitation in 2 patients, inability to record
hepatic venous flow in 3, and nonsinus rhythm in 3. The prospective
population therefore consisted of 50 patients, 30 men and 20 women with
a mean age of 60±17 years (range, 17 to 85 years); 4 patients were
younger than 40 years of age. Left ventricular ejection
fraction averaged 51±16.6% (range, 16% to 75%). Ten patients had
depressed right ventricular systolic function.
Fifty percent were on mechanical ventilation. Tables 2 and
7 give the hemodynamic data and clinical
diagnoses, respectively, of this group. Mean RAP ranged between 1 and
22 mm Hg (mean, 9.16±5.33 mm Hg), and systolic filling
fraction ranged between 0% and 0.85% (mean, 0.55±0.2%). Predicted
RAP with the regression equation correlated well with observed RAP
(r=.89) with a regression equation close to the identity
line (Fig 5).
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In the whole group of 85 patients, 20 had
depressed right
ventricular systolic function. Of 49 patients with
normal RAP, 6 had depressed right ventricular function. Of
36 patients with elevated RAP, 22 had normal right
ventricular systolic function. Fig 5 shows the
correlation between Doppler-predicted and observed mean RAP in
the total population. The relation was similar in patients on
mechanical ventilation (r=.91) and in ambulatory patients in
the catheterization laboratory (r=.85). The
difference between predicted and observed pressure averaged
-0.31±2.41 mm Hg in the prospective group (range, -6 to 6
mm Hg) and -0.2±2.6 mm Hg in the 85 patients (Fig
6). Sensitivity and specificity for a mean RAP of >10
mm Hg were 82% and 96%, respectively, for the 85 patients; with 8 mm
Hg as the cutoff, sensitivity and specificity were 86% and 92%,
respectively.
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Reproducibility
Table 8 shows intraobserver
and interobserver
reproducibilities of Doppler parameters of hepatic vein
flow and derived mean RAP with the regression equation. Intraobserver
and interobserver derivations of mean RAP were highly correlated
(r=.93 and .95, respectively). Reproducibility of
tricuspid inflow variables has been previously reported from our
laboratory.23
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Discussion |
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TopAbstractIntroductionMethods Results Discussion References |
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This study demonstrates that among various echocardiographic and Doppler variables of the right side of the heart, Doppler parameters of hepatic vein flow, particularly those including the systolic filling wave, had the strongest relation to mean RAP. The interrelation among echocardiographic and Doppler parameters was evaluated. The strong relation observed between systolic filling fraction and mean RAP was maintained in a prospective patient population with a variety of cardiac and noncardiac clinical conditions.
Relation of Tricuspid Inflow Variables to RAP
Tricuspid
diastolic inflow reflects the effect of
filling pressure, right ventricular relaxation, and net AV
compliance. Similar to mitral inflow, the pattern of tricuspid inflow
in normal individuals has been shown to depend on age among other
factors, with the older age group having a reduced early
diastolic filling.23 24 In the present
study, the confounding effects of filling pressures and right
ventricular disease have altered the above relation with
age, with a tendency for only a lower ratio of early to late velocity
in older individuals. The effect of disease states on the relation of
mitral inflow dynamics with age also was demonstrated previously in our
laboratory.25 The dependence of tricuspid filling dynamics
on loading conditions was described previously.26 A higher
mean RAP results in a greater initial transvalvular
gradient and therefore in a higher early velocity and ratio of early to
late velocity. Deceleration time is likely to be affected predominantly
by net AV compliance and tricuspid valve area rather than actual
pressures,27 accounting for the weak relation observed
between this parameter and mean RAP. Overall, the
multifactorial determinants of tricuspid inflow variables most
likely precluded a stronger relation of tricuspid inflow dynamics with
mean RAP.
Relation of Hepatic Venous Flow to RAP
The phases of hepatic
venous flow in normal individuals were
described recently.28 Determinants of the systolic
forward flow include atrial relaxation, descent of the tricuspid
annular plane toward the ventricular apex, and RAP. The
higher the RAP, the lower the pressure gradient between the hepatic
veins and the right atrium and thus the lower the forward
systolic flow. This observation was described previously in
patients with restrictive heart disease and elevated filling
pressures.12 13 In the present study, systolic
forward flow parameters, particularly systolic
filling fraction, derived with either time-velocity integrals or
maximal velocities, had the best relation to mean RAP and allowed a
good estimation of atrial pressure in patients with a variety of
underlying clinical conditions. Although right ventricular
function was also a determinant of systolic filling fraction,
this relation was much weaker and failed to contribute significantly in
the multivariate model. Similarly, other
echocardiographic and Doppler
parameters that related significantly to mean RAP failed to
add to the already strong relation of systolic filling fraction
with mean RAP.
The relations described here for atrial filling dynamics are similar overall to those described previously for the left side of the heart. The high correlations of hepatic vein systolic filling fraction observed in this study are similar to those observed between pulmonary venous systolic filling fraction and left atrial pressure by use of transesophageal echocardiography (r=.88).9 The weak but significant relation found between the duration of atrial reversal wave and RAP also was reported previously.29 However, the lack of a significant relation between velocity of atrial reversal wave and mean atrial pressure in the present study has not been consistently demonstrated for the left atrium.9 11 29 The lack of correlation between diastolic and atrial reversal velocities and mean RAP may reflect that each relates best to atrial v and a pressure waves, respectively, rather than mean atrial pressure.12
With respiratory variability present in any right-side Doppler velocity recording, measurements were performed as an average of several consecutive beats, which yields results similar to those obtained during end-expiratory apnea.23 This allowed assessment of RAP in patients with dyspnea or on mechanical ventilation in whom the relation of systolic filling fraction with RAP proved to be similar to those without assisted ventilation. Exclusions related mostly to nonsinus rhythms and occasional technical difficulties in patients in the Intensive Care Unit. Unlike recordings of pulmonary vein flow,30 Doppler assessment of hepatic vein flow with the transthoracic approach is simpler and feasible in the majority of patients even in Intensive Care Units, as shown in this study, thus allowing assessment of RAP in most patients. Furthermore, transesophageal echocardiography was shown to offer no advantage over the transthoracic approach in obtaining the above measurements.31
Relation Between Tricuspid and Hepatic Venous Flow
The higher
the early velocity across the tricuspid valve, the
smaller the blood volume in the right atrium and hence the greater the
forward flow from the hepatic veins in diastole. Such a
relation was described previously for left-side inflow
patterns.29 The difference in duration of hepatic venous
atrial reversal and tricuspid A wave was related only weakly to mean
RAP (r=.27). A similar weak relation was described
previously for this variable derived from left-side Doppler
measurements and pulmonary capillary wedge pressure. This index
has been shown in the left ventricle to relate well with the left
ventricular A wave and end-diastolic
pressure.11 In this study, measurements of right
ventricular diastolic pressures were not
available to assess this relation.
Systolic Right Ventricular Function and
RAP
Patients with depressed right ventricular function
were observed to have a shorter tricuspid deceleration time,
predominant diastolic flow in the hepatic veins, and a
tendency for higher early velocity and ratio of early to late velocity.
A significant overlap in these Doppler variables, however, was
observed among patients with normal and abnormal right
ventricular systolic function, which stems from the
several determinants of ventricular filling
dynamics.2 32 Right ventricular
systolic function was a poor discriminator of mean RAP, which
can be explained predominantly by the wide range of loading conditions
in the present population. Right ventricular
systolic function related weakly to hepatic vein
systolic filling fraction in the present study, a finding
consistent with previous observations by Basnight et
al,33 who demonstrated no relation between
systolic pulmonary venous flow and left
ventricular ejection fraction. Similarly, in a study by
Keren et al,34 10 of 28 patients with dilated
cardiomyopathy had preserved systolic and
diastolic pulmonary veins flows despite
significantly reduced mitral annular descent. In addition, the presence
of reduced systolic venous flow in patients with restrictive
cardiomyopathy, elevated atrial pressure, and
preserved ventricular systolic
function13 35 further support that ventricular
systolic function, through descent of the cardiac base, is a
minor determinant of atrial filling dynamics compared with atrial
pressure. However, in patients with pericardial disease such as
constrictive pericarditis or cardiac tamponade, assessment of mean
atrial pressure with systolic filling fraction is limited
because the systolic venous wave usually is preserved despite
elevated filling pressures.35 36 In these cases,
usually
suspected with echocardiographic findings of a plethora
of the inferior vena cava, exaggerated respiratory
variability in ventricular inflow dynamics, septal bounce,
or pericardial effusion, determination of atrial pressure with the
proposed Doppler method should not be performed.
Right Atrial Function and RAP
Measurements of right atrial
volumes and function related
significantly to RAP. With the relation of atrial pressure to volume,
larger atrial volumes at end systole and end diastole and
lower emptying fractions were found to be associated with higher mean
RAP. However, because atrial compliance and function are also
significant modifiers of this relation, the weak yet significant
relations observed between atrial volumes and mean RAP may be accounted
for on this basis. The presence of a larger atrial volume at the onset
of ventricular systole (minimal atrial volume) is likely to
reduce forward systolic flow from the hepatic veins. A larger
atrial volume at the end of ventricular systole (maximal
atrial volume) is also likely to cause similar findings, hence the
negative correlations observed between right atrial volumes and hepatic
vein systolic filling fraction. The addition of atrial volumes
and function in the multivariate model did not improve
the already strong relation of systolic filling fraction to
mean RAP.
Inferior Vena Cava and RAP
Measurement of inferior vena caval
diameter and its
change during an inspiratory effort, commonly a sniff test, is used
frequently in the echocardiography laboratory to
estimate RAP.17 Its use is limited, however, in tachypneic
patients and those on mechanical ventilation.18 Another
limitation is the difficulty of standardizing the inspiratory effort.
Previous studies have demonstrated a good relation between the collapse
index of the inferior vena cava and RAP in patients without
assisted ventilation.17 In patients with mechanical
ventilation, however, inferior vena caval collapse has been
shown to relate poorly to mean RAP (r=.13), whereas maximal
caval diameter showed only a weak relation in these patients
(r=.58).18 Our findings are similar to those
previously reported. Because the present population included
patients with and without assisted ventilation, overall weaker
relations with the caval collapse index were demonstrated for the whole
population. When patients were separated into those with and without
mechanical ventilation, the relations observed were nearly identical to
those previously reported.16 17 Even in patients
without
assisted ventilation, the relation of caval collapse index with mean
RAP was weaker than that for systolic filling fraction,
with a larger spread and standard error of estimate. Similar to other
echocardiographic indexes, the addition of
parameters derived from the inferior vena cava
did not improve the relation of hepatic vein systolic filling
fraction to mean RAP.
Clinical Implications
Estimation of RAP is helpful in the
overall management of patients
with hemodynamic disorders and in the derivation of
pulmonary artery pressure with Doppler
echocardiography. Among all parameters
tested, hepatic vein systolic filling fraction,
inferior vena caval collapse index, and the ratio of early
to late velocity of tricuspid inflow have provided useful yet simple
indexes for the assessment of mean RAP. Determination of
systolic filling fraction provided a reasonable estimate of
mean RAP, with a 95% CI of ±5 mm Hg, smaller than that observed with
the other parameters tested, and is in general the
preferred method for estimating mean RAP. Doppler
recordings of tricuspid inflow and
echocardiographic imaging of the vena cava during an
inspiratory effort, however, are also important in the overall
evaluation of right-side hemodynamics and, in
addition to hepatic venous flow, are already acquired routinely in
several laboratories. Assessment of these parameters
corroborates findings of atrial filling dynamics and is important when
derivation of mean RAP cannot be performed with systolic
filling fraction. The latter was feasible in 82% of the total patients
screened (n=103), the majority of whom were in an intensive care
setting, and therefore would be applicable to an even higher percentage
of the general population.
It is noteworthy to mention the characteristics of patients in whom the observed relations in this study may not be applicable. These include patients with nonsinus rhythm or pericardial diseases in whom parameters derived from the inferior vena cava would be more accurate for estimation of RAP. Application of the current Doppler relations also should be reserved for middle-aged and older individuals (age group of present study) because of the effect of age on filling dynamics. Patients with severe tricuspid regurgitation, who usually have reversal of the systolic hepatic vein flow, also were not included in the present study and await evaluation. On the other hand, in patients on mechanical ventilation, inferior vena caval collapse index should not be used, and estimation of mean RAP with systolic filling fraction is the preferred method.
Limitations
The effect of respiration on right-side inflow
has been
well described.23 Although simultaneous
recording of respiration was not performed in this study, we
have shown previously that averaging consecutive cardiac cycles yields
almost identical results to those during end-expiration apnea. This
allows evaluation and application of the current findings in the
general population, including dyspneic patients and those on mechanical
ventilation, without the need for special devices for recording
of simultaneous respiration.
In the present study, we measured mean RAP and did not quantify phasic RAP. This was performed because pressure was measured with clinically available fluid-filled catheters rather than high-fidelity micromanometers. The fluid-filled catheters used may have had some damping effect on the phasic pressure waveforms. The use of mean RAP is much less affected by damping,37 is used clinically in hemodynamic management, and has been advocated in previous studies for the assessment of pulmonary artery pressure.6 Furthermore, in the estimation of pulmonary artery pressures, the use of peak atrial v wave may result in overestimation of pulmonary pressure.6 7
Right ventricular isovolumic relaxation time was not measured and may have helped improve the relation of tricuspid inflow dynamics in the evaluation of RAP in a manner analogous to left-side pressures.10 11 30 In contrast to the left ventricle, however, measurement of right ventricular isovolumic relaxation time requires phonocardiography for optimum accuracy, which adds to the complexity of the evaluation and renders it less clinically applicable.
Conclusions
Among
echocardiographic parameters of
right-side cardiac structure and function and Doppler
variables of right atrial and ventricular filling
dynamics, parameters that included hepatic systolic
wave had the strongest relation to mean RAP. The use of hepatic vein
systolic filling fraction provided a good prediction of mean
RAP in a population with a variety of underlying clinical
conditions. Thus, Doppler
echocardiography provides an assessment of
RAP that can be used clinically in the overall
hemodynamic evaluation of right atrial and
ventricular function.
|
Acknowledgments |
|---|
Computational assistance was provided by the CLINFO Project, funded by grant RR-00350 from the Division of Research Resources, NIH, Bethesda, Md. We wish to thank Eula Landry for her assistance in the preparation of this manuscript.
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Footnotes |
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Guest editor for this article was Bernadine Healy, MD, Cleveland (Ohio) Clinic Foundation.
Received May 22, 1995; revision received October 4, 1995; accepted October 15, 1995.
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References |
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