Changes in myocardial blood volume a wide range of coronary driving pressures: Role of capillaries beyond the autoregulatory range

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Abstract

Objective: To determine whether, when the vasomotor capacity of the coronary arterioles is exhausted at rest, myocardial blood volume decreases in order to maintain a normal capillary hydrostatic pressure, even at the expense of myocardial axygen delivery. Methods: 18 dogs were studied. In group 1 (n = 9), coronary driving pressure (CDP) was reduced by 10-80 mm Hg below normal by a stenosis; in group 2 (n = 9), it was increased 20-80 mm Hg above baseline by increasing aortic pressure with phenylephrine. Myocardial contrast echocardiography (MCE) was undertaken to measure the myocardial blood volume fraction and myocardial blood flow (MBF). Results: In group 1 dogs, as CDP was reduced, both coronary blood flow (CBF) and MBF decreased. Myocardial blood volume fraction also decreased and myocardial vascular resistance increased, while coronary sinus PO2 decreased. In group 2 dogs, as CDP was increased, epicardial CBF increased but MBF remained unchanged because of a decrease in myocardial blood volume fraction. Myocardial vascular resistance decreased, however, implying the presence of coronary arteriovenous shunting, which was supported by a progressive increase in the coronary sinus PO 2. Conclusions: Wnen arteriolar tone is exhausted so that CBF becomes dependent on CDP, myocardial blood volume decreases in order ta maintain a constant capillary hydrostatic pressure, which takes precedence over myocardial oxygen delivery. These novel findings implicate capillaries in the regulation of CBF beyond the autoregulatory range.

Original languageEnglish (US)
Pages (from-to)1199-1205
Number of pages7
JournalHeart
Volume90
Issue number10
DOIs
StatePublished - Oct 2004
Externally publishedYes

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Blood Volume
Pressure
Hydrostatic Pressure
Coronary Sinus
Dogs
Vascular Resistance
Arterioles
Phenylephrine
Echocardiography
Arterial Pressure
Pathologic Constriction
Oxygen

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

Cite this

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title = "Changes in myocardial blood volume a wide range of coronary driving pressures: Role of capillaries beyond the autoregulatory range",
abstract = "Objective: To determine whether, when the vasomotor capacity of the coronary arterioles is exhausted at rest, myocardial blood volume decreases in order to maintain a normal capillary hydrostatic pressure, even at the expense of myocardial axygen delivery. Methods: 18 dogs were studied. In group 1 (n = 9), coronary driving pressure (CDP) was reduced by 10-80 mm Hg below normal by a stenosis; in group 2 (n = 9), it was increased 20-80 mm Hg above baseline by increasing aortic pressure with phenylephrine. Myocardial contrast echocardiography (MCE) was undertaken to measure the myocardial blood volume fraction and myocardial blood flow (MBF). Results: In group 1 dogs, as CDP was reduced, both coronary blood flow (CBF) and MBF decreased. Myocardial blood volume fraction also decreased and myocardial vascular resistance increased, while coronary sinus PO2 decreased. In group 2 dogs, as CDP was increased, epicardial CBF increased but MBF remained unchanged because of a decrease in myocardial blood volume fraction. Myocardial vascular resistance decreased, however, implying the presence of coronary arteriovenous shunting, which was supported by a progressive increase in the coronary sinus PO 2. Conclusions: Wnen arteriolar tone is exhausted so that CBF becomes dependent on CDP, myocardial blood volume decreases in order ta maintain a constant capillary hydrostatic pressure, which takes precedence over myocardial oxygen delivery. These novel findings implicate capillaries in the regulation of CBF beyond the autoregulatory range.",
author = "Le, {Dai-Trang (Elizabeth)} and Jayaweera, {A. R.} and Kevin Wei and Coggins, {M. P.} and Jonathan Lindner and Sanjiv Kaul",
year = "2004",
month = "10",
doi = "10.1136/hrt.2003.020875",
language = "English (US)",
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pages = "1199--1205",
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T1 - Changes in myocardial blood volume a wide range of coronary driving pressures

T2 - Role of capillaries beyond the autoregulatory range

AU - Le, Dai-Trang (Elizabeth)

AU - Jayaweera, A. R.

AU - Wei, Kevin

AU - Coggins, M. P.

AU - Lindner, Jonathan

AU - Kaul, Sanjiv

PY - 2004/10

Y1 - 2004/10

N2 - Objective: To determine whether, when the vasomotor capacity of the coronary arterioles is exhausted at rest, myocardial blood volume decreases in order to maintain a normal capillary hydrostatic pressure, even at the expense of myocardial axygen delivery. Methods: 18 dogs were studied. In group 1 (n = 9), coronary driving pressure (CDP) was reduced by 10-80 mm Hg below normal by a stenosis; in group 2 (n = 9), it was increased 20-80 mm Hg above baseline by increasing aortic pressure with phenylephrine. Myocardial contrast echocardiography (MCE) was undertaken to measure the myocardial blood volume fraction and myocardial blood flow (MBF). Results: In group 1 dogs, as CDP was reduced, both coronary blood flow (CBF) and MBF decreased. Myocardial blood volume fraction also decreased and myocardial vascular resistance increased, while coronary sinus PO2 decreased. In group 2 dogs, as CDP was increased, epicardial CBF increased but MBF remained unchanged because of a decrease in myocardial blood volume fraction. Myocardial vascular resistance decreased, however, implying the presence of coronary arteriovenous shunting, which was supported by a progressive increase in the coronary sinus PO 2. Conclusions: Wnen arteriolar tone is exhausted so that CBF becomes dependent on CDP, myocardial blood volume decreases in order ta maintain a constant capillary hydrostatic pressure, which takes precedence over myocardial oxygen delivery. These novel findings implicate capillaries in the regulation of CBF beyond the autoregulatory range.

AB - Objective: To determine whether, when the vasomotor capacity of the coronary arterioles is exhausted at rest, myocardial blood volume decreases in order to maintain a normal capillary hydrostatic pressure, even at the expense of myocardial axygen delivery. Methods: 18 dogs were studied. In group 1 (n = 9), coronary driving pressure (CDP) was reduced by 10-80 mm Hg below normal by a stenosis; in group 2 (n = 9), it was increased 20-80 mm Hg above baseline by increasing aortic pressure with phenylephrine. Myocardial contrast echocardiography (MCE) was undertaken to measure the myocardial blood volume fraction and myocardial blood flow (MBF). Results: In group 1 dogs, as CDP was reduced, both coronary blood flow (CBF) and MBF decreased. Myocardial blood volume fraction also decreased and myocardial vascular resistance increased, while coronary sinus PO2 decreased. In group 2 dogs, as CDP was increased, epicardial CBF increased but MBF remained unchanged because of a decrease in myocardial blood volume fraction. Myocardial vascular resistance decreased, however, implying the presence of coronary arteriovenous shunting, which was supported by a progressive increase in the coronary sinus PO 2. Conclusions: Wnen arteriolar tone is exhausted so that CBF becomes dependent on CDP, myocardial blood volume decreases in order ta maintain a constant capillary hydrostatic pressure, which takes precedence over myocardial oxygen delivery. These novel findings implicate capillaries in the regulation of CBF beyond the autoregulatory range.

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