Effects of heart rate on phasic Y-graft blood flow and flow reserve in patients with complete arterial myocardial revascularizaton: an intravascular Doppler catheter study.
OBJECTIVE
It is not well established whether the blood flow of arterial composite Y-grafts can efficiently respond to the flow demand of the coronary system early postoperatively. The aim of this study was to evaluate if soon after the operation, arterial composite Y-grafts can increase blood flow in response to an increase in myocardial oxygen consumption (MVO2).


METHODS
Twenty-seven patients who received complete arterial myocardial revascularization using the left internal thoracic artery (LITA) and the radial artery (RA) as composite Y-graft gave their consent to a pre-discharge coronary angiography and intravascular flow velocity measurements using a Doppler guide wire. Flow measurements were performed in the LITA main stem, the distal LITA and the RA, both at rest and during atrial pacing at the 85% of the patient age-predicted maximum. The heart rate-systolic blood pressure product was considered as an indirect index of MVO2. Hyperemic flow was determined after injection of adenosine. The flow reserve (FR) was defined as the ratio of blood flow during maximal hyperemia (Qmax) to baseline flow (Qbasal).


RESULTS
Atrial pacing increased MVO2 significantly (P<0.000). None of the patients developed ischemic S-T segment modifications or complained of chest pain. Q(basal) increased significantly in the LITA main stem (P=0.001), distal LITA (P=0.041) and RA (P=0.004) while Qmax did not change significantly. As a consequence, the FR decreased in the LITA main stem (P=0.002), distal LITA (P<0.000) and RA (P<0.000) but was not completely exhausted.


CONCLUSIONS
Soon after the operation, arterial composite Y-grafts can significantly increase blood flow in response to conditions of increased MVO2, keeping normal the myocardial O2 supply-to-demand ratio.
Lemma
Massimo
M
Division of Cardiovascular Surgery, L. Sacco Hospital, Via G.B. Grassi 74, 20157 Milan, Italy. massimo.lemma@fastwebnet.it
Mangini
Andrea
A
Gelpi
Guido
G
Innorta
Andrea
A
Danna
Paolo
P
Lavarra
Francesco
F
Piccaluga
Emanuela
E
Antona
Carlo
C
D000368:Aged; D001783:Blood Flow Velocity; D006328:Cardiac Catheterization; D002304:Cardiac Pacing, Artificial; D003326:Coronary Circulation; D003327:Coronary Disease / Q000378:metabolism / Q000503:physiopathology* / Q000601:surgery*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008297:Male; D008323:Mammary Arteries / Q000601:surgery; D008875:Middle Aged; D009204:Myocardial Revascularization; D009206:Myocardium / Q000378:metabolism; D010101:Oxygen Consumption; D018579:Patient Selection; D017534:Radial Artery / Q000601:surgery; D018084:Ultrasonography, Interventional