Author + information
- Received August 31, 1982
- Revision received December 7, 1982
- Accepted December 10, 1982
- Published online May 1, 1983.
- Henry Gewirtz, MD*,
- David O. Williams, MD, FACC and
- Albert S. Most, MD, FACC
- ↵*Address for reprints: Henry Gewirtz, MD, Cardiology Section, Rhode Island Hospital, 593 Eddy Street, Providence, Rhode Island 02902.
Experimental coronary artery stenoses produced by external constrictors that reduce vessel diameter by 50% under basal conditions have been shown to reduce myocardial hyperemic flow reserve. Because such lesions may exhibit dynamic increases in severity during coronary vasodilation, the results of these studies are not necessarily applicable to human patients with fixed, proximal coronary stenoses of similar baseline severity. Accordingly, the present study was conducted in 16 closed chest conscious pigs in order to assess the effects of a fixed, rigid 50% stenosis on maximal myocardial hyperemic flow and transmural distribution of blood flow. Eight pigs (Group I, stenosis) were instrumented with a 50% stenosis and eight were not (Group II, control). After obtaining control measurements of hemodynamics and regional myocardial blood flow (microsphere technique), adenosine was infused at doses of 100, 200 and 400 μg min-1(x 10 minutes at each dose) directly into the left anterior descending coronary bed distal to the stenosis (Group I) or at a similar level in animals without a stenosis. Hemodynamics and blood flow measurements were made at the 10th minute of each infusion level of adenosine.
The results (mean ± 1 standard deviation) of the study were as follows. Under basal conditions, transmural, endocardial and epicardial flows (ml min-1g-1) in Group I pigs (1.48 ± 0.40, 1.51 ± 0.45 and 1.30 ± 0.35, respectively) did not differ significantly from respective flows in Group II pigs (1.56 ± 0.26, 1.57 ± 0.27 and 1.43 ± 0.30). Likewise baseline endocardial to epicardial flow ratios were comparable between the two groups (Group I = 1.16 ± 0.22 versus Group II =1.11 ± 0.09, p = NS). Transmural, endocardial and epicardial blood flow in Group I pigs increased to the same extent as respective flows in Group II pigs at each dose of adenosine tested. Maximal transmural, endocardial and epicardial flows in Group I pigs increased, respectively, to levels 3.56 ± 1.56, 3.56 ± 2.03 and 3.26 ± 1.16 above baseline values. Similar responses occurred in Group II (3.38 ± 1.02, 3.21 ± 0.91 and 3.25 ± 1.44, respectively). The endocardial/epicardial flow ratio in Group I at maximal vasodilation (1.20 ± 0.34) did not differ significantly from that in Group II (1.19 ± 0.34). Thus, the data demonstrate that in contrast to 50% stenoses formed with external coronary constrictors, fixed proximal 50% stenoses do not reduce maximal myocardial hyperemic flow reserve.
- Received August 31, 1982.
- Revision received December 7, 1982.
- Accepted December 10, 1982.
- American College of Cardiology Foundation