Comparison of vasoactive response of left and right internal thoracic arteries to isosorbide-dinitrate and nitroglycerin: an in vitro study.
OBJECTIVE
The internal thoracic artery (ITA) is the most important graft in coronary artery bypass grafting. Its distal region is, however, prone to vasospasm. We studied the effects of nitroglycerin (NTG) and isosorbide-dinitrate (DSDN) on distal segments of left versus right ITA.


METHODS
Rings of distal segments (6 to 9 mm proximal to bifurcation) of the human left and right ITA were studied. After baseline contraction of the rings, achieved using 60 mmol/L of KCl, they were exposed to increasing doses of ISDN and NTG (10 to 100 microg/ml), and dose-response curves were recorded.


RESULTS
The contractile response of left ITA rings to KCl were significantly lower than those of right ITA rings (1.87 +/- 0.25 g versus 3.5 +/- 0.61 g, p < 0.005). Both nitrates inhibited the contractile response in a concentration-dependent manner, with relaxing effects of ISDN higher than those of NTG (p < 0.01) in both left and right ITA rings.


CONCLUSIONS
The distal segment of the left ITA is less prone to vasospasm than that of the right. ISDN has a considerably higher relaxant effect on this segment than NTG. We therefore recommend favoring high doses of ISDN over NTG as an antispastic measure.
Paz
Y
Y
Department of Thoracic and Cardiovascular Surgery, The Tel Aviv Sourasky Medical Center, Tel Aviv University, Israel.
Frolkis
I
I
Kramer
A
A
Pevni
D
D
Shapira
I
I
Lev-Ran
O
O
Mohr
R
R
D001026:Coronary Artery Bypass / Q000379:methods; D004305:Dose-Response Relationship, Drug; D006801:Humans; D066298:In Vitro Techniques; D007548:Isosorbide Dinitrate / Q000008:administration & dosage / Q000494:pharmacology*; D008323:Mammary Arteries / Q000187:drug effects* / Q000502:physiology; D005996:Nitroglycerin / Q000008:administration & dosage / Q000494:pharmacology*; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000494:pharmacology*
D014665:Vasodilator Agents; D005996:Nitroglycerin; D007548:Isosorbide Dinitrate