We determined the LVEF, the LV end-systolic pressure (Pes)-end-systolic volume (Ves) relationship slope (ie, end-systolic elastance [Ees]), the LV stroke work (SW)-end-diastolic volume (Ved) relationship slope (ie, the preload recruitable SW [PRSW]), the ratio of Pes to stroke volume (SV) [ie, effective arterial elastance [Ea]), ventriculaorterial coupling (as the Ees/Ea ratio), and the maximal rate of rise of LV pressure (dP/dtmax)-Ved relationship from the variably loaded beats produced by transient caval occlusion during both DDD and AAI pacing modes. In addition, we estimated diastolic performance indexes as the minimum (maximal negative) rate of rise of LV pressure (dP/dtmin) and the time constant of isovolumic relaxation (t).
Finally, we measured myocardial oxygen consumption (MVo2) indirectly using the pressure-work index (PWI), which is well correlated with the directly measured MVo2. To calculate the PWI, we used the following equation that has been proposed by Rooke and Feigl:
PWI = [4.08 X 10 – 4 X (SAP X HR)] + [3.25 X 10 – 4 X
(0.8 X SAP + 0.2 X DAP)] X [HR X (SV/BW)] + 1.43
where SAP is systolic arterial BP, DAP is diastolic arterial BP, HR is heart rate, and BW is body weight.
A 0.014-inch, 15-MHz Doppler guidewire (FloWire; Cardio-metrics; Mountain View, CA) was used to measure coronary flow velocity in the proximal left anterior descending artery and the proximal dominant coronary artery, and the quantitative flow was calculated as the product of the vessel cross-sectional area and half of the time-averaged peak coronary flow velocity. canadian family pharmacy
All measurements were made at least 5 min after the infusion of the contrast medium to the coronary vessels.
Coronary flow reserve (CFR) was defined as the ratio of coronary blood flow at maximal hyperemia (ie, after intracoronary administration of 18 |j,g adenosine) to that at baseline.