Abstract
Background: Transthoracic echocardiography (TTE) in prone
position is challenging. Innovative use of transesophageal
echocardiography (TEE) probe to perform TTE for such patients was
described; but reproducibility and correlation of the TTE measurements
by this technique with those obtained by the standard supine TTE study
are still unknown.Methods: We enrolled 30 non-COVID-19 individuals, with a mean
(SD) age 35 (10.9) years and 11 females, to study the agreement between
the transthoracic measurements of the left ventricular (LV), left atrial
(LA) and aortic dimensions obtained in prone position using an external
TEE probe versus the standard supine position using the conventional TTE
probe. Results: There were no significant differences between
LV end-diastolic and end-systolic diameters, septal wall thickness,
posterior wall thickness and aortic root dimensions in the prone versus
the supine positions, while the mean ejection fraction (EF) (60.3% vs.
63.1%, P = 0.014) and mean LA dimensions (1.8 vs. 1.9 cm/m2, P
< 0.001) were significantly lower in the prone position. The
mean time of scans was significantly longer in the prone as compared to
the supine position (12.5 vs 4.5 minutes, P < 0.001). All
supine studies had good quality while in the prone position 4 studies
were of poor quality, and one was non-diagnostic.Conclusions: Assessment of cardiac dimensions and systolic
function in the prone position using transthoracic TEE probe was
feasible. LV and aortic dimensions agreed well with the standard TTE in
supine position, however, LA dimensions and EF were lower in the prone
position.Keywords: COVID-19, transthoracic echocardiography,
transesophageal, prone position, cardiac dimensions, systolic function.
Introduction
Preexisting cardiovascular diseases are linked to more severe COVID-19
infection. Additionally, cardiovascular complications can be a
significant contributor to the mortality associated with this disease.1,
2
It has been shown that prone ventilation can improve oxygenation in
patients with acute respiratory distress syndrome (ARDS) secondary to
COVID-19.3 Echocardiography used to assess their cardio-circulatory
status, may be very challenging in patients kept in the prone position
using conventional transthoracic echocardiography (TTE).
Transesophageal echocardiography (TEE) is a traditional solution that
can be performed in the prone position and was reported to be a safe
procedure in ARDS patients.4 However, TEE carries a heightened risk of
spread of the COVID-19, as it can promote the aerosolization of a large
amount of virus.5 Additionally, acute access to TEE study is a logistic
problem particularly that it requires highly trained professionals on
image acquisition and interpretation.
Ugalde et al.6 and Giustiniano et al.7 had previously described
techniques to obtain TTE using the conventional probe during prone
position ventilation, but those techniques were demanding and required
special positioning and preparations.
Lately, Marvaki A et al.8 described an innovative use of the TEE probe
to perform a transthoracic study on patients with COVID-19, who were
invasively ventilated in the prone position. This was feasible and of
acceptable diagnostic value. However, the reproducibility and
correlation of the echocardiographic measurements obtained by this novel
technique with those obtained by the standard transthoracic study are
still unknown.
The aim of this work was to compare the basic left ventricular (LV),
left atrial (LA) and aortic (Ao) dimensions obtained by TTE imaging in
the prone position using a TEE probe versus the standard supine position
using the conventional TTE probe in apparently healthy adults.
Patients and methods
Thirty apparently healthy non-COVID-19 patients, referred for routine
TTE at the outpatient clinic of cardiology department at Cairo
University hospital, were prospectively enrolled in July 2020. Each
participant was examined in the same sitting, both in the prone position
using a TEE probe and in the standard supine position using the
conventional TTE probe, by two independent operators. All scans were
performed with a Philips Affiniti 50C machine using the S4-2 TTE probe
and the X7-2t TEE probe (Philips Healthcare, Andover, MA).
The basic LV internal dimensions, wall thickness, and ejection fraction
(EF), in addition to left atrial (LA) and aortic root (AoR) dimensions
were obtained carefully in either position from electrocardiographically
(ECG) - gated two-dimensional (2D) images of parasternal long axis view
with great attention to be perpendicular to LV/LA long axis.
The standard supine position studies were done according to the American
Society of Echocardiography (ASE) and European Association of
Cardiovascular Imaging (EACVI) recommendations.9 Regarding the prone
study the same innovative technique recently described by Marvaki A et
al.8 was adopted. In this technique, the operator was
standing on the left side of the patient at the level of the head,
facing the patient’s right side. The probe was anchored to patient’s
chest wall against bed mattress. The tip of the probe lubricated by gel
was placed in the standard left parasternal position in the third or
fourth left intercostal space. The transducer was facing upwards and was
supported underneath by operator’s left hand. The probe shaft was held
with the right hand to allow rotation. Images of the long axis of the
heart were obtained at zero angle as in the conventional TTE parasternal
long-axis view (Figure 1), while images of the short axis view were
obtained by increasing the angle to 60 -120 degrees , usually at the
level of the mitral valve. By rotating the probe clockwise, the
mid-papillary level was obtained (Figure 2), while great vessels level
was obtained by anticlockwise rotation.
The scan time was measured, and the image quality was graded as poor,
fair, good or non-diagnostic. The quality of the images acquired by the
TEE probe in the prone position was compared to that of the images
obtained by TTE probe in the supine position.