Coronary microcirculatory vasoconstriction during ischemia in patients with unstable angina.
OBJECTIVE
To verify the behavior of coronary microvascular tone during spontaneous ischemia in patients with unstable angina (UA).


BACKGROUND
In UA, the pathogenetic role of vasoconstriction is classically confined at the stenotic coronary segment. However, microcirculatory vasoconstriction has been also suggested by previous experimental and clinical studies.


METHODS
The study included 10 patients with UA (recent worsening of anginal threshold and appearance of angina at rest) and single-vessel CAD. Blood flow velocity was monitored by a Doppler catheter in the diseased artery. Transstenotic pressure gradient was monitored by aortic and distal coronary pressure monitoring. Stenosis resistance was calculated as the ratio between pressure gradient and blood flow, microvascular resistance as the ratio between distal pressure and blood flow. Measurements were obtained at baseline, following intracoronary adenosine (2 mg) and during transient ischemia. Aortic and distal coronary pressures were also measured during balloon coronary occlusion.


RESULTS
Adenosine did not affect stenosis resistance, while it decreased (p < 0.05) microvascular resistance to 52 +/- 22% of baseline. Angina and ischemic ST segment shift were associated with transient angiographic coronary occlusion in 7 of 10 patients; however, in no case was ischemia associated with interruption of flow. Despite markedly different flow values, distal coronary pressure was similar during adenosine and during spontaneous ischemia (48 +/- 15 vs. 46 +/- 20 mm Hg, respectively, NS). During ischemia, a marked increase in the resistance of both coronary stenosis and coronary microcirculation was observed (to 1,233% +/- 1,298% and 671% +/- 652% of baseline, respectively, p < 0.05). Distal coronary pressure was markedly reduced during balloon coronary occlusion (14 +/- 7 mm Hg, p < 0.05 vs. both adenosine and ischemia), suggesting the absence of significant collateral circulation.


CONCLUSIONS
In patients with UA, transient myocardial ischemia is associated with vasoconstriction of both stenotic arterial segment and downstream microcirculation.
Marzilli
M
M
CNR Institute of Clinical Physiology, Pisa, Italy.
Sambuceti
G
G
Fedele
S
S
L'Abbate
A
A
D000241:Adenosine / Q000008:administration & dosage; D000789:Angina, Unstable / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001783:Blood Flow Velocity; D001794:Blood Pressure; D017023:Coronary Angiography; D003326:Coronary Circulation / Q000187:drug effects / Q000502:physiology*; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000187:drug effects / Q000503:physiopathology*; D004562:Electrocardiography; D006801:Humans; D007269:Injections, Intra-Arterial; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D012720:Severity of Illness Index; D018608:Ultrasonography, Doppler; D018084:Ultrasonography, Interventional; D014655:Vascular Resistance / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects; D014665:Vasodilator Agents / Q000008:administration & dosage
D014665:Vasodilator Agents; D000241:Adenosine