Author + information
- Received August 1, 1988
- Revision received January 25, 1989
- Accepted February 8, 1989
- Published online August 1, 1989.
- Dennis E. Morgan, MD∗,
- Charles W. Tomlinson, MD, PHD, FACC∗,
- A. Karim Qayumi, MD, PHD,
- Philip M. Toleikis, MSc,
- Briege McConville and
- W.R. Eric Jamieson, MD, FACC
- ↵∗Address for reprints: Charles W. Tomlinson, MD, Division of Cardiology, McMaster University, Hamilton General Hospital. 237 Barton Street East, Hamilton, Ontario, Canada L8L 2X2.
Eight dogs were studied by simultaneous invasive hemodynamic and two-dimensional echocardiographic methods to determine whether left ventricular contractility is altered by 2 weeks of rapid atrial pacing. Additionally, this study evaluated the response of three ventricular contractility indexes to both the pacing intervention and acute load alteration. The indexes compared were ejection fraction, peak systolic pressure to end-systolic volume index ratio (SBP/ESVI) and end-systolic wall stress to end-systolic volume index ratio (ESWS/ESVI).
After 2 weeks of pacing at 265 ± 20 min−1 (mean ± SD), cardiac index and ejection fraction were reduced to 73 ± 38 ml/kg per min and 22 ± 6%, respectively, from 161 ± 22 and 46 ± 7 before pacing (both p < 0.001). Concomitantly, SBP/ESVI and ESWS/ESVI were reduced to 34 ± 10 mm Hg/ml per kg and 54 ± 19 g/cm2 per ml per kg, respectively, from 84 ± 29 and 121 ± 36 before pacing (both p < 0.005). There were high correlations for the changes in SBP/ESVI and ejection fraction (r = 0.94, p < 0.001) and ESWS/ESVI and ejection fraction (r = 0.89, p < 0.003). Acute afterload alteration with phenylephrine depressed ejection fraction but not SBP/ESVI or ESWS/ESVI.
Therefore, this study demonstrates 1) that left ventricular weeks of rapid atrial pacing, and 2) that SBP/ESVI and contractility is markedly depressed in the dog by 2 ESWS/ESVI are superior to ejection fraction as ventricular contractility indexes because these ratios accurately measure contractility changes but are influenced less by afterload conditions.
↵∗ Present address: Division of Cardiology, RG-22, University of Washington School of Medicine, 1959 NE Pacific Street, Seattle, Washington 98195.
☆ This work was supported by a grant from the British Columbia Heart Foundation, Vancouver.
- Received August 1, 1988.
- Revision received January 25, 1989.
- Accepted February 8, 1989.