Effect of nitroglycerin on regional myocardial blood flow abnormality induced by atrial pacing; a clinical study in myocardial infarction

Naka, M.; Tsuji, K.; Arai, H.

Kokyu to Junkan. Respiration and Circulation 30(2): 173-181


ISSN/ISBN: 0452-3458
PMID: 6805060
Accession: 005256607

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Nitroglycerin (NTG) is effective to ischemic attacks. The mechanisms for this should be considered in 2 different aspects: a systemic vasodilatory effect resulting in reducing myocardial O2 consumption and an effect on regional myocardial blood flow (r-MBF). The influence of NTG on r-MBF during increased myocardial O2 demand in patients with coronary artery disease was evaluated. In 16 patients with anterior myocardial infarction, r-MBF values were measured, using 133Xe clearance method, at rest and during atrial pacing before and after sublingual administration of NTG, repeatedly. On the anterior surface of left ventricle in 60.degree.LAO ). After the sublingual administration of NTG, r-MBF decreased in each region. During atrial pacing following NTG administration, only in AS there was a significant increase in r-MBF (47 .+-. 17 to 64 .+-. 19, P < 0.05), and not in the other 2 regions (AL: 57 .+-. 16 to 66 .+-. 19, PL: 64 .+-. 20 to 73 .+-. 19, NS, respectively). Atrial pacing produced a significant increase in heart rates and a slight decrease in systolic blood pressures both before and after NTG. Double product (heart rate .times. systolic blood pressure), an indicator of myocardial O2 demand, showed a significant increase caused by atrial pacing before (9.6 .+-. 3.2 to 17.4 .+-. 3.8, (P < 0.01)) and after NTG (9.3 .+-. 2.9 to 14.6 .+-. 3.0, (P < 0.01)). A wide variation in r-MBF values was observed in the individual patients, and the correlation existed between r-MBF and double product in each region before and after NTG (r = 0.57 .apprx. 0.80). .DELTA.r-MBF .times. 103/.DELTA.double product, produced by atrial pacing, was much less in AS than in PL (1.59 .+-. 1.64, 3.14 .+-. 1.31, P < 0.05), and after NTG it became inversely greater in AS than the other (3.22 .+-. 1.92, 1.62 .+-. 1.73, P < 0.05). NTG selectively probably increased the r-MBF in infarcted regions accompanied with the increase of myocardial O2 demand, allowing the enhancement of coronary reserve for the viable myocardium. NTG may prevent the myocardium, which is perfused by stenotic vessels, from ischemia by improvement of blood flow distribution, in addition by reducing O2 demand.