Echocardiographic examination
All echocardiographic examinations were performed with an ultrasound
platform equipped with a matrix-array transducer (X5-1, Philips Epiq 7,
Philips Healthcare, Andover, MA, USA). Chamber quantification and other
measurements were done according to the relevant international
guidelines. For coronary flow measurements, distal part of the left
anterior descending artery (LAD) was visualized using high ultrasound
beam frequency (5-7 MHz). The color Doppler gain was optimized using
conventional techniques and the Nyquist limit was set to 0.16-0.50 m/s.
After visualization of the distal part of the LAD, pulse-wave Doppler
cursor was placed to measure coronary flow velocity and measurements
were done before and after dipyridamole infusion (0.84 mg/kg for 6
minutes). Patients were monitored during the procedure and heart rate
and blood pressure data were recorded at baseline, during infusion and
after the procedure. Coronary flow velocity reserve was calculated as
the ratio of the hyperemic peak flow velocity to the resting peak flow
velocity. We have previously reported interobserver and intraobserver
variability values for our laboratory (15,16).
All echocardiographic examinations, including CFVR measurements were
performed immediately after the stabilization of the patient. For
patients that needed intubation or intensive unit care due to any cause,
echocardiographic examinations were delayed until the patient was
transferred to the ward.