Abstract
The exact mechanism or mechanisms by which nitroglycerin exerts its beneficial effect on pacing-induced regional myocardial ischemia has not been elucidated previously. In open-chest, anesthetized canine preparation a fixed, flow limiting stenosis was applied to the left anterior descending (LAD) coronary artery and heart rate was increased by atrial pacing. Mass spectrometry was used to measure myocardial oxygen (PmO2) and carbon dioxide (PmCO2) tensions. Myocardial blood flow was measured by the radioactive microsphere technique. Application of the stenosis resulted in regional decreases in PmO2 and increases in PmCO2 of greater magnitude in the subendocardial than in the subepicardial layer. Atrial pacing resulted in a further decrease in PmO2 and in increase in PmCO2 as well as a reduction in subendocardial blood flow. Nitroglycerin (TNG) infusion reduced mean arterial pressure 20 mm Hg, resulting in a 14 mm Hg reduction in PmCO2 in the more ischemic subendocardial layer (P < 0.05). Myocardial blood flow decreased in all regions; however, the magnitude of this decrease was less in the ischemic region. Addition of aortic constriction abolished both the afterload and preload lowering effects of nitroglycerin but improved ischemic zone blood flow. These data demonstrate that nitroglycerin reduces the severity of pacing-induced regional myocardial ischemia primarily by reducing the determinants of myocardial oxygen demand. We found that when these effects are counteracted, improvement in myocardial oxygen supply becomes the dominant mechanism.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 569-576 |
| Number of pages | 8 |
| Journal | Circulation Research |
| Volume | 48 |
| Issue number | 4 |
| State | Published - 1981 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Physiology
- Cardiology and Cardiovascular Medicine
Cite this
Effects of nitroglycerin on regional myocardial ischemia induced by atrial pacing in dogs. / Gerry, J. L.; Schaff, Hartzell V; Kallman, C. H.; Flaherty, J. T.
In: Circulation Research, Vol. 48, No. 4, 1981, p. 569-576.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Effects of nitroglycerin on regional myocardial ischemia induced by atrial pacing in dogs
AU - Gerry, J. L.
AU - Schaff, Hartzell V
AU - Kallman, C. H.
AU - Flaherty, J. T.
PY - 1981
Y1 - 1981
N2 - The exact mechanism or mechanisms by which nitroglycerin exerts its beneficial effect on pacing-induced regional myocardial ischemia has not been elucidated previously. In open-chest, anesthetized canine preparation a fixed, flow limiting stenosis was applied to the left anterior descending (LAD) coronary artery and heart rate was increased by atrial pacing. Mass spectrometry was used to measure myocardial oxygen (PmO2) and carbon dioxide (PmCO2) tensions. Myocardial blood flow was measured by the radioactive microsphere technique. Application of the stenosis resulted in regional decreases in PmO2 and increases in PmCO2 of greater magnitude in the subendocardial than in the subepicardial layer. Atrial pacing resulted in a further decrease in PmO2 and in increase in PmCO2 as well as a reduction in subendocardial blood flow. Nitroglycerin (TNG) infusion reduced mean arterial pressure 20 mm Hg, resulting in a 14 mm Hg reduction in PmCO2 in the more ischemic subendocardial layer (P < 0.05). Myocardial blood flow decreased in all regions; however, the magnitude of this decrease was less in the ischemic region. Addition of aortic constriction abolished both the afterload and preload lowering effects of nitroglycerin but improved ischemic zone blood flow. These data demonstrate that nitroglycerin reduces the severity of pacing-induced regional myocardial ischemia primarily by reducing the determinants of myocardial oxygen demand. We found that when these effects are counteracted, improvement in myocardial oxygen supply becomes the dominant mechanism.
AB - The exact mechanism or mechanisms by which nitroglycerin exerts its beneficial effect on pacing-induced regional myocardial ischemia has not been elucidated previously. In open-chest, anesthetized canine preparation a fixed, flow limiting stenosis was applied to the left anterior descending (LAD) coronary artery and heart rate was increased by atrial pacing. Mass spectrometry was used to measure myocardial oxygen (PmO2) and carbon dioxide (PmCO2) tensions. Myocardial blood flow was measured by the radioactive microsphere technique. Application of the stenosis resulted in regional decreases in PmO2 and increases in PmCO2 of greater magnitude in the subendocardial than in the subepicardial layer. Atrial pacing resulted in a further decrease in PmO2 and in increase in PmCO2 as well as a reduction in subendocardial blood flow. Nitroglycerin (TNG) infusion reduced mean arterial pressure 20 mm Hg, resulting in a 14 mm Hg reduction in PmCO2 in the more ischemic subendocardial layer (P < 0.05). Myocardial blood flow decreased in all regions; however, the magnitude of this decrease was less in the ischemic region. Addition of aortic constriction abolished both the afterload and preload lowering effects of nitroglycerin but improved ischemic zone blood flow. These data demonstrate that nitroglycerin reduces the severity of pacing-induced regional myocardial ischemia primarily by reducing the determinants of myocardial oxygen demand. We found that when these effects are counteracted, improvement in myocardial oxygen supply becomes the dominant mechanism.
UR - http://www.scopus.com/inward/record.url?scp=0019415221&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0019415221&partnerID=8YFLogxK
M3 - Article
C2 - 6780231
AN - SCOPUS:0019415221
VL - 48
SP - 569
EP - 576
JO - Circulation Research
JF - Circulation Research
SN - 0009-7330
IS - 4
ER -