Estimation of cardiac output and pulmonary vascular resistance by contrast echocardiography transit time measurement: a prospective pilot study
Cardiovascular Ultrasound
Estimation of cardiac output and pulmonary vascular resistance by contrast echocardiography transit time measurement: a prospective pilot study
Brian G Choi 0
Reza Sanai 0
Benjamin Yang 0
Heather A Young 1
Ramesh Mazhari 0
Jonathan S Reiner 0
Jannet F Lewis 0
0 The GW Heart & Vascular Institute, The George Washington University , Washington, DC , USA
1 Department of Epidemiology & Biostatistics, The George Washington University , Washington, DC , USA
Background: Studies with other imaging modalities have demonstrated a relationship between contrast transit and cardiac output (CO) and pulmonary vascular resistance (PVR). We tested the hypothesis that the transit time during contrast echocardiography could accurately estimate both CO and PVR compared to right heart catheterization (RHC). Methods: 27 patients scheduled for RHC had 2D-echocardiogram immediately prior to RHC. 3 ml of DEFINITY contrast followed by a 10 ml saline flush was injected, and a multi-cycle echo clip was acquired from the beginning of injection to opacification of the left ventricle. 2D-echo based calculations of CO and PVR along with the DEFINITY-based transit time calculations were subsequently correlated with the RHC-determined CO and PVR. Results: The transit time from full opacification of the right ventricle to full opacification of the left ventricle inversely correlated with CO (r = −0.61, p < 0.001). The transit time from peak opacification of the right ventricle to first appearance in the left ventricle moderately correlated with PVR (r = 0.46, p < 0.01). Previously described echocardiographic methods for the determination of CO (Huntsman method) and PVR (Abbas and Haddad methods) did not correlate with RHC-determined values (p = 0.20 for CO, p = 0.18 and p = 0.22 for PVR, respectively). The contrast transit time method demonstrated reliable intra- (p < 0.0001) and inter-observer correlation (p < 0.001). Conclusions: We describe a novel method for the quantification of CO and estimation of PVR using contrast echocardiography transit time. This technique adds to the methodologies used for noninvasive hemodynamic assessment, but requires further validation to determine overall applicability.
Contrast echocardiography; Hemodynamics; Cardiac output; Pulmonary vascular resistance
Background
Invasive hemodynamic assessment by right heart
catheterization (RHC) is a mainstay of evaluation of
patients with pulmonary hypertension and congestive heart
failure, [
1,2
] but this procedure subjects patients to risks
including venous access complications, arrhythmias and,
in rare circumstances, even death [3]. Non-invasive
hemodynamic assessment has become commonplace,
often supplanting invasive assessment. Several
echocardiographic methods have been developed using
echocardiography to estimate pulmonary vascular resistance
(PVR) and cardiac output (CO) [
4-8
]. However, accurate
assessment of right heart pressures and pulmonary
vascular resistance, compared to invasive measurements
has proven less reliable. One different approach was
utilized by Galanti et al. [
9
], who measured
transpulmonary transit times of intravenous Albunex in dogs as
an indicator of cardiac output. They noted an excellent
correlation between the pulmonary transit rate, as
measured by the time to first echocardiographic presence in
the left ventricle, with thermodilution cardiac output. This
technique, however, has not been validated in humans.
Ultrasonic contrast agents have been used to improve
image quality for echocardiography, [
10
] but a potential
role in assessment of PVR and CO has not yet been
defined. Investigators using other imaging modalities have
suggested using transit times to assess these measures
[
11-13
]. In this prospective pilot study, we tested the
hypothesis that transit time assessment during
contrastenhanced echocardiography could accurately estimate
both PVR and CO compared to the gold-standard of
RHC in patients without evidence of structural right
heart disease.
Methods
Patients
38 consecutive adult patients clinically referred for
rightheart catheterization were evaluated for potential
inclusion in the study. The exclusion criteria were known or
suspected right-to-left, bi-directional, or transient
rightto-left cardiac shunts or pulmonary arteriovenous
malformations (AVM), tamponade, previously documented
moderate to severe tricuspid or pulmonic insufficiency,
right ventricular hypokinesis, or prior adverse reaction
to Definity or hypersensitivity to perflutren. The study
was approved by George Washington University
institutional review board, and informed, written consent was
obtained from all patients. After consent, 5 patients were
found to not meet enrollment criteria: 4 did not have
right-heart catheterization (including 1 with suspected
tamponade), 1 had right ventricular systolic dysfunction.
6 patients were excluded from analysis secondary to
timing errors with contrast injection (i.e. (...truncated)