Myocardial bridging is related to endothelial dysfunction but not to plaque as assessed by intracoronary ultrasound.
BACKGROUND
Myocardial bridge (MB) is characterised by focal compression of a coronary artery in systole by an overlying band of myocardium. Chronic compression and relaxation of the MB may produce endothelial dysfunction by direct stress.


OBJECTIVE
To determine whether MB alters endothelial function, thus influencing the plaque formation.


METHODS
128 patients (mean (SD) age 54.7 (10.9) years, 56 men) with typical angiographic systolic milking effects and >30% reduction in diameter of the coronary artery during systole after intracoronary nitrate (glyceryl trinitrate, 200 mug) infusion were studied. 231 control patients (mean (SD) age 52.9 (12.1) years, 111 men) without overt coronary artery disease including MB were also studied. Endothelial function was estimated by incremental acetylcholine (Ach) infusion into the left coronary ostium. Intracoronary ultrasound assessments were obtained in 74/128 patients with MB and 81/231 controls.


RESULTS
The mean (SD) vasoconstrictive response to maximal Ach was more pronounced at the bridging segments than at matched segments in controls (-71.9 (14.9) vs -30.3 (22.6), p = 0.009). Coronary vasoconstriction (>50%) to Ach was seen more often in the MB group than in controls (114/128 (89.1%) vs 81/231 (35.1%), p = 0.007). No significant correlation was found between the severity of MB and vasoconstriction in response to Ach. A typical half-moon phenomenon was seen in 71/74 (95.9%) cases of the MB group, but not in controls (p<0.001). Plaques at the bridging segments were absent in 67/74 (90.5%) and mild in 7/74 (9.5%) cases, as compared with those of matched segments of the left anterior descending coronary artery in controls (plaque burden 5.91 (1.37)% vs 24.71 (24.21)%, p = 0.002).


CONCLUSIONS
Despite the prominent relationship between MB and endothelial dysfunction, bridging segments are spared from atherosclerotic plaque formation.
Kim
J W
JW
Guro Hospital, Cardiovascular Centre, Korea University, 97 Gurodong-Gil, Guro-gu, Seoul, Republic of Korea 152-703.
Seo
H S
HS
Na
J O
JO
Suh
S Y
SY
Choi
C U
CU
Kim
E J
EJ
Rha
S-W
SW
Park
C G
CG
Oh
D J
DJ
D017023:Coronary Angiography / Q000379:methods; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000503:physiopathology; D004730:Endothelium, Vascular / Q000000981:diagnostic imaging* / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D054084:Myocardial Bridging / Q000000981:diagnostic imaging* / Q000503:physiopathology; D016896:Treatment Outcome; D014463:Ultrasonography; D014661:Vasoconstriction