Echocardiographic studies were done using the Sonoscape SSI-8000 Machine in the LUTH Cardiovascular Laboratory with a 3.5 MHz transducer probe. The subjects were laid in the left decubitus position. The researcher then performed 2 Dimensional (2D), 2D directed M-mode and Doppler transthoracic echocardiography in parasternal, apical and subcostal views on all 219 subjects.
2D-directed M-mode measurements were done in accordance with the
recommendations of the American Society of Echocardiography.74 The M-mode readings taken at aortic valve level from the parasternal long axis view (PLAX) were: left atrial diameter (LAD), aortic root diameter (AO), and right ventricular outflow tract (RVOT) diameter. M-mode readings taken at mitral valve tip level were: left ventricular end systolic and diastolic diameter (LVDS, LVDD), right ventricular end diastolic diameter (RVDD), left ventricular wall thickness consisting of interventricular septal thickness
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(IVS) and posterior wall thickness (PWT) at end diastole, E point septal separation (EPSS) and RV wall thickness. LV mass was determined by the formula below.74,75
LV mass = 0.8 x {1.04[(LVDD + PWTd + IVSd)3 - (LVDD)3]} + 0.6 g
The LV mass was indexed to body surface area to obtain the LV mass index (LVMI) Left ventricular end diastolic (EDV) and systolic (ESV) volumes were determined by the teicholz equation76 as follows:
EDV = 7 x LVDD3 2.4 + LVDD ESV = 7 x LVDS3
2.4 + LVDS
LV ejection fraction (LVEF) was then derived as follows:
LVEF = EDV – ESV / EDV x 100
RV Tricuspid Annular Plane Systolic Excursion (TAPSE) was acquired at an apical 4 chamber view, placing an M mode cursor through the lateral edge of the tricuspid annulus and then measuring the amount of longitudinal motion of the annulus at peak systole. Efforts were made to ensure that the M-mode cursor was parallel to the tricuspid annular plane, and measurements were taken at the end of expiration. TAPSE < 1.6cm will be taken as RV systolic dysfunction.14
2D Echocardiographic features investigated include: shape of the RV, RV basal diameter and wall thickness, left and right atrial size, interventricular septal wall motion abnormalities, and valve morphology.
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D-sign abnormality of the IVS was assessed in the parasternal short axis view using the eccentricity index14 calculated as follows:
Eccentricity Index = LV Anteroposterior dimension LV Septolateral dimension
A ratio > 1 suggests RV overload.14
Measurement of short axis LV dimensions are illustrated below in Fig 1:
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Figure 1: Determination of the eccentricity index in PSAX view. D1-LV septolateral dimension, D2-LV anteroposterior dimension.77
Doppler echocardiography was performed to determine the following:
- Pulmonary artery systolic pressure (PASP)
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- Mean Pulmonary artery pressure (mPAP) - LV diastolic function
- Severity of mitral regurgitation
PASP was determined by the TR jet method following the American Society of
Echocardiography guidelines for the assessment of the right heart.14 The peak TR jet velocity was measured by colour Doppler guided continous wave Doppler in the apical 4-chamber view, parasternal right ventricular inflow view and parasternal short axis view at aortic valve level. The highest velocity obtained from any of these views was selected. The RAP was estimated from the size and collapsibilty of inferior vena cava (IVC). The long axis of the IVC was visualized in the subcostal view. IVC diameter was measured by 2D-guided M-mode measurement just distal to the junction of the hepatic veins which lie approximately 0.5-3.0cm to the ostium of the right atrium.14 Two IVC measurements were obtained. IVCmax at end expiration and IVCmin after the subjects were asked to sniff. The following estimated RAP values were assigned based on ASE recommendations14 :
IVC diameter percentage collapse with sniff RAP
≤2.1cm >50% 3mmHg
≤2.1cm <50% 8mmHg
>2.1cm >50% 8mmHg
>2.1cm <50% 15mmHg
The PASP was then calculated using the formula below:
PASP = 4(VTR) 2 + RAP
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A cut off value of PASP > 36mmHg suggesting PH was employed in this study based on 2009 ESC12 and 2010 ASE14 recommendations. These were the prevailing guidelines during the planning and execution of this study.
mPAP was derived from the acceleration time of the RVOT pulsed wave Doppler profile using the formula:
mPAP = 79 – 0.45 [ RVOT AcT]14,55
cut off value of mPAP ≥ 25mmHG suggesting PH was employed based on ASE recommendations.14
The study population was separated to PH and non-PH sub-groups at using both the PASP and mPAP criteria in order to compare their clinical and echocardiographic characteristics.
LV diastolic function was asssessed according to the guidelines of the 2009 American Society of Echocardiography (ASE) recommendations for the evaluation of Left ventricular diastolic dysfunction48. Left ventricular diastolic function was assessed using Transmitral Doppler velocites, Left atrial volume, and tissue Doppler of the septal and lateral mitral annulus. All Doppler measures were taken at the end of expiration, using the average of measurements obtained during three consecutive cardiac cycles.
Transmitral pulse wave Doppler velocity measurements were obtained with a 2mm sample volume placed at the tips of the mitral valve leaflets to assess peak E (early diastolic), A (late diastolic) velocities and E wave deceleration time (DT). The isovolumic relaxation time was measured from an apical 5 chamber view with the sample volume placed midway between the aortic and mitral valves.
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Pulse wave tissue Doppler imaging was performed in the apical 4 chamber view to acquire septal and lateral mitral annular velocities. The sample volume of 2-3mm was positioned within the basal ventricular wall less than 1cm to the septal and lateral insertion sites of the mitral leaflets and adjusted as necessary to cover the longitudinal excursion of the mitral annulus in both systole and diastole. The velocity scale was adjusted to 20cm/sec above and below the baseline.
The gain and filter settings were minimized to exclude high velocity low amplitude signals due to blood flow.48 This was done automatically by the preset tissue Doppler mode of the machine.
Measurements taken were septal annular early diastolic velocity (septal e’), lateral annular early diastolic velocity (lateral e’), and E/e’ ratio (i.e ratio of the transmitral E and tissue Doppler e’
velocities). The average of the septal e’ and lateral e’ velocities was employed in calculating the E/e’ ratio.48
Left atrial volume (LAV) was calculated by the area-length method65,74 as follows:
Left atrial volume (ml) = 0.85 x (LA area in AP4CH* view) x (LA area in AP2CH** view) LA long axis length***
* Apical 4 chamber
**Apical 2 chamber
***This was measured in both AP4CH and AP2CH views; the shorter length was used.74
The LAV was indexed to body surface area to obtain the left atrial volume index (LAVI)
Diastolic dysfunction was graded according to ASE recommendations48 as shown in table 2.
Table 2 : Grading of Diastolic dysfunction Parameter Normal
function
Grade I diastolic dysfunction
Grade II diastolic dysfunction
Grade III diastolic dysfunction
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LAVI ≤34ml/m2 >34ml/m2 >34ml/m2 >34ml/m2
E/A ratio >0.8 <0.8 0.8-1.5 >2.0
DT 160-200ms >200ms 160-200ms <160ms
Septal e’ ≥8cm/s <8cm/s <8cm/s <8cm/s
Lateral e’ ≥10cm/s <10cm/s <10cm/s <10cm/s
E/e’ ratio ≤ 8 ≤ 8 9-12 ≥13
Mitral regurgitation severity was assessed as follows :
Mitral regurgitant volume (MRvol) using the formula:
MRvol = MV Stroke volume (SVmitral) - LV outflow tract stroke volume (SVLVOT) 78
55 SVmitral was derived by the formula79 below:
SVmitral = CSA mitral annulus x VTI transmital PW Doppler profile ( CSA – cross sectional area, VTI – Velocity Time Integral)
The CSA of the mitral annulus was derived from the diameter of the mitral annulus in the AP4CH view.79
SVLVOT was derived by the formula79 below:
SVLVOT = CSA LVOT x VTI LVOT PW Doppler profile
The CSA of the LVOT was derived from the diameter of the LVOT in the parasternal long axis view.79
MR severity was graded according to the ASE guidelines78 as follows:
Parameter Mild Moderate Severe
Regurgitant volume (ml) <30 30 – 60 >60