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The
significance of coronary flow reserve in chest pain syndromes
Julia Radó
Tamás Forster
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The increase in coronary blood flow occuring
with augmented myocardial oxygen demands is regulated by changes
in the vascular resistance of the coronary arteries. The ability
to increase coronary blood flow in response to vasoactive mechanisms
is coronary flow reserve. |
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The major epicardial coronary arteries
contribute only about 5% to the total vascular resistance. The
intramyocadial coronary arterioles are responsible for the majority
of coronary resistance. |
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The coronary blood flow regulation is
controlled by endothelial, metabolic, myogenic and neurohumoral
mechanisms. |
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The term "microvascular angina pectoris"
was proposed by Cannon and Epstein in 1985 for the symptoms
"angina pectoris + positive ergometry test + epicardial
coronary arteries without stenosis." |
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Microvascular impairment - interactions of morphological and functional changes
Microvascular impairment is prominent in patients with angina
pectoris, manifested in systemic hypertension, in diabetic patients,
in cases of other metabolic and rheologic disorders as a result
of endothelial dysfunction, vascular remodelling, changes in
vascular reactivity and cardiac muscle hypertrophy.
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In the presence of normal epicardial
arteries and normal microvasculature, the CFR is normal. Severe
flow limiting epicardial stenosis or microvascular pathologic
state of the coronary arterioles result the diminution of the
CFR. |
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A normal coronary flow reserve is approximately
four to five. With methods measuring not absolute coronary blood
flow, but relative changes in perfusion or flow velocities the
values are lower. The CFR is influenced by age, heart rate,
preload, use of vasoactive pharmacological agents. |
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In a group of patients with systemic
hypertension and left ventricular hypertrophy (pts with valvular
disaese or known CHD and diabets mellitus were excluded) the
CFR was reduced. 6 months after effective antihypertensive therapy
with ACE-inhibitor or Ca-antagonist the repeated CFR increased
significantly, although it did not reach the normal vale.
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A group consisting 18 pts with diabetes
mellitus was examined (exclusion criteria were hypertension,
left ventricular hypertrophy, evidence of valvular or coronary
heart diseases) with the method of TEE using Dipyridamole. The
measurements confirmed significantly reduced CFR. |
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In 18 pts coronary angiography showed
no substantial alterations despite chest pains and positive
ergometry test. The perfusion was also determined through stress
myocardial scintigraphy SPECT examination. In 15 of 18 pts the
CFR had reduced distinctly (2,25), perfusion disorders in all
of these pts have been observed, especially inhomogeneity of
perfusion and reverse redistribution. |
2004
