Intravenous phentolamine abolishes coronary vasoconstriction in response to mild central hypovolemia

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Abstract

Animal studies indicate alpha-adrenergic coronary vasoconstriction helps maintain left ventricular function during physiological stress. Whether this process occurs in humans is unknown. In the current study, we used transthoracic Doppler echocardiography to test the effect of lower body negative pressure (LBNP) on coronary blood flow velocity (CBV, left anterior descending coronary artery) and myocardial function in eight young healthy subjects before and after systemic infusion of phentolamine, a nonselective alpha blocker. Heart rate (HR) and blood pressure (BP) were monitored on a beat-by-beat basis. Peak diastolic CBV and myocardial systolic and diastolic tissue velocities (Sm and Em), were quantified at baseline, and at-5 mmHg,-10 mmHg, and-15 mmHg LBNP. Coronary vascular resistance index (CVRI) was calculated as the quotient of diastolic BP and CBV. Phentolamine reduced baseline diastolic BP and increased HR but did not affect the reflex adjustments to LBNP. The reduction in CBV due to LBNP was blunted by phentolamine at-10 mmHg and-15 mmHg. Importantly, the increase in CVRI (i.e., coronary vasoconstriction) was abolished by phentolamine at-5 mmHg (0.21 ± 0.06 vs. 0.83 ± 0.13),-10 mmHg (0.24 ± 0.03 vs. 1.68 ± 0.31), and-15 mmHg (0.27 ± 0.10 vs. 2.34 ± 0.43). These data indicate that alpha-adrenergic coronary vasoconstriction is present during low levels of LBNP. With alpha blockade, more coronary flow is needed to maintain cardiac function. Our data suggest that alpha-adrenergic tone enhances coronary flow efficiency, presumably by redistributing flow from the epicardium to the endocardium.

Original languageEnglish (US)
Pages (from-to)216-221
Number of pages6
JournalJournal of applied physiology
Volume116
Issue number2
DOIs
StatePublished - Jan 15 2014

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Lower Body Negative Pressure
Hypovolemia
Phentolamine
Vasoconstriction
Blood Pressure
Adrenergic Agents
Heart Rate
Social Adjustment
Endocardium
Physiological Stress
Blood Flow Velocity
Doppler Echocardiography
Pericardium
Left Ventricular Function
Vascular Resistance
Reflex
Echocardiography
Coronary Vessels
Healthy Volunteers

All Science Journal Classification (ASJC) codes

  • Physiology
  • Physiology (medical)

Cite this

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title = "Intravenous phentolamine abolishes coronary vasoconstriction in response to mild central hypovolemia",
abstract = "Animal studies indicate alpha-adrenergic coronary vasoconstriction helps maintain left ventricular function during physiological stress. Whether this process occurs in humans is unknown. In the current study, we used transthoracic Doppler echocardiography to test the effect of lower body negative pressure (LBNP) on coronary blood flow velocity (CBV, left anterior descending coronary artery) and myocardial function in eight young healthy subjects before and after systemic infusion of phentolamine, a nonselective alpha blocker. Heart rate (HR) and blood pressure (BP) were monitored on a beat-by-beat basis. Peak diastolic CBV and myocardial systolic and diastolic tissue velocities (Sm and Em), were quantified at baseline, and at-5 mmHg,-10 mmHg, and-15 mmHg LBNP. Coronary vascular resistance index (CVRI) was calculated as the quotient of diastolic BP and CBV. Phentolamine reduced baseline diastolic BP and increased HR but did not affect the reflex adjustments to LBNP. The reduction in CBV due to LBNP was blunted by phentolamine at-10 mmHg and-15 mmHg. Importantly, the increase in CVRI (i.e., coronary vasoconstriction) was abolished by phentolamine at-5 mmHg (0.21 ± 0.06 vs. 0.83 ± 0.13),-10 mmHg (0.24 ± 0.03 vs. 1.68 ± 0.31), and-15 mmHg (0.27 ± 0.10 vs. 2.34 ± 0.43). These data indicate that alpha-adrenergic coronary vasoconstriction is present during low levels of LBNP. With alpha blockade, more coronary flow is needed to maintain cardiac function. Our data suggest that alpha-adrenergic tone enhances coronary flow efficiency, presumably by redistributing flow from the epicardium to the endocardium.",
author = "Zhaohui Gao and Muller, {Matthew D.} and Sinoway, {Lawrence I.} and Leuenberger, {Urs A.}",
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T1 - Intravenous phentolamine abolishes coronary vasoconstriction in response to mild central hypovolemia

AU - Gao, Zhaohui

AU - Muller, Matthew D.

AU - Sinoway, Lawrence I.

AU - Leuenberger, Urs A.

PY - 2014/1/15

Y1 - 2014/1/15

N2 - Animal studies indicate alpha-adrenergic coronary vasoconstriction helps maintain left ventricular function during physiological stress. Whether this process occurs in humans is unknown. In the current study, we used transthoracic Doppler echocardiography to test the effect of lower body negative pressure (LBNP) on coronary blood flow velocity (CBV, left anterior descending coronary artery) and myocardial function in eight young healthy subjects before and after systemic infusion of phentolamine, a nonselective alpha blocker. Heart rate (HR) and blood pressure (BP) were monitored on a beat-by-beat basis. Peak diastolic CBV and myocardial systolic and diastolic tissue velocities (Sm and Em), were quantified at baseline, and at-5 mmHg,-10 mmHg, and-15 mmHg LBNP. Coronary vascular resistance index (CVRI) was calculated as the quotient of diastolic BP and CBV. Phentolamine reduced baseline diastolic BP and increased HR but did not affect the reflex adjustments to LBNP. The reduction in CBV due to LBNP was blunted by phentolamine at-10 mmHg and-15 mmHg. Importantly, the increase in CVRI (i.e., coronary vasoconstriction) was abolished by phentolamine at-5 mmHg (0.21 ± 0.06 vs. 0.83 ± 0.13),-10 mmHg (0.24 ± 0.03 vs. 1.68 ± 0.31), and-15 mmHg (0.27 ± 0.10 vs. 2.34 ± 0.43). These data indicate that alpha-adrenergic coronary vasoconstriction is present during low levels of LBNP. With alpha blockade, more coronary flow is needed to maintain cardiac function. Our data suggest that alpha-adrenergic tone enhances coronary flow efficiency, presumably by redistributing flow from the epicardium to the endocardium.

AB - Animal studies indicate alpha-adrenergic coronary vasoconstriction helps maintain left ventricular function during physiological stress. Whether this process occurs in humans is unknown. In the current study, we used transthoracic Doppler echocardiography to test the effect of lower body negative pressure (LBNP) on coronary blood flow velocity (CBV, left anterior descending coronary artery) and myocardial function in eight young healthy subjects before and after systemic infusion of phentolamine, a nonselective alpha blocker. Heart rate (HR) and blood pressure (BP) were monitored on a beat-by-beat basis. Peak diastolic CBV and myocardial systolic and diastolic tissue velocities (Sm and Em), were quantified at baseline, and at-5 mmHg,-10 mmHg, and-15 mmHg LBNP. Coronary vascular resistance index (CVRI) was calculated as the quotient of diastolic BP and CBV. Phentolamine reduced baseline diastolic BP and increased HR but did not affect the reflex adjustments to LBNP. The reduction in CBV due to LBNP was blunted by phentolamine at-10 mmHg and-15 mmHg. Importantly, the increase in CVRI (i.e., coronary vasoconstriction) was abolished by phentolamine at-5 mmHg (0.21 ± 0.06 vs. 0.83 ± 0.13),-10 mmHg (0.24 ± 0.03 vs. 1.68 ± 0.31), and-15 mmHg (0.27 ± 0.10 vs. 2.34 ± 0.43). These data indicate that alpha-adrenergic coronary vasoconstriction is present during low levels of LBNP. With alpha blockade, more coronary flow is needed to maintain cardiac function. Our data suggest that alpha-adrenergic tone enhances coronary flow efficiency, presumably by redistributing flow from the epicardium to the endocardium.

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U2 - 10.1152/japplphysiol.01048.2013

DO - 10.1152/japplphysiol.01048.2013

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JO - Journal of Applied Physiology

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