2.3 Echocardiographic evaluation
The echocardiographic evaluation was performed by a single operator
(LL). A commercially available system (Vivid 7, GE Vingmed ultrasound
AS) was used for all patients. Standard parasternal and apical views
were usedand acquired images were stored digitally in high analysis
still images and in cine loops (in a format of three consecutive beats
for analysis). A single observer blinded of the patients’ identity (not
the same person who performed the echocardiographic examination)
performed offline analysis using EchoPac (version 113 - GE Vingmed
ultrasound AS). On the day of the examination, echocardiographic
assessment was performed in a two-staged approach. Initially, a basic
echocardiogram was performed. All classic LV function related systolic
and diastolic indices were obtained, according to the European Society
of Cardiology and European Association of Cardiovascular Imaging
guidelines [22]. Left atrial volume
and LV mass were both indexed to patients’ body surface area.
In order to obtain 2DSTE data, both parasternal and apical views (at
frame rates 60-90Hz) were acquired. Thus, adequate spatial and temporal
resolution and accurate frame to frame tracking (for three consecutive
cardiac cycles) was ensured. The endocardial LV borders were manually
traced (region of interest). When tracking was poor in more than two
consecutive myocardial regions, the acquired data were declined. The
timings of aortic and mitral valve opening and closure were manually
defined by the use of pulsed-wave Doppler. No patient was excluded based
on poor 2DSTE-related echocardiographic data. 2DSTE analysis included
assessment of GLS and strain rate as also global radial and
circumferential strain and strain rate. LV twist was calculated as the
difference between apical and basal LV rotation as it was assessed from
equivalent short-axis views. Studies with >2 consecutive
segments (out of a total amount of 17) not adequately tracked were
deemed as inappropriate for the measurement of LV twist and rotation.
Untwist rate was measured as the peak negative time derivative of twist
during diastole. The time interval from R wave peak to the maximal
untwist was then calculated.
Following the baseline echocardiographic evaluation, infusion of
dipyridamole for 6 minutes (0.84mg/kg) was performed. CFR was calculated
as the ratio between hyperemic and basal coronary flow at the LAD area.
Just before the end of dipyridamole infusion a new echocardiographic
assessment (focused mainly on LV systolic and diastolic function
indices) was performed. At the end of the dipyridamole infusion,
125-250mg of aminophylline was administered to the patient, to
counteract any dipyridamole negative effect. The dose was dependent on
the patient’s status after dipyridamole infusion. Beverages containing
methylxanthines such as coffee, tea, chocolate and coke were prohibited
for at least 24 hours before the study. Patients with CFR
values<2 were referred for another ischemia stress test and/or
coronary angiographyto exclude potential significant epicardial stenosis
in the LAD area. None of the enrolled patients with CFR
values<2 had confirmed significant CAD. Intra-observer
variability for all indices of interest included in this study has been
previously reported [23].