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 language | English (US) |
|---|---|
| Pages (from-to) | 216-221 |
| Number of pages | 6 |
| Journal | Journal of applied physiology |
| Volume | 116 |
| Issue number | 2 |
| DOIs | |
| State | Published - Jan 15 2014 |
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All Science Journal Classification (ASJC) codes
- Physiology
- Physiology (medical)
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Intravenous phentolamine abolishes coronary vasoconstriction in response to mild central hypovolemia. / Gao, Zhaohui; Muller, Matthew D.; Sinoway, Lawrence I.; Leuenberger, Urs A.
In: Journal of applied physiology, Vol. 116, No. 2, 15.01.2014, p. 216-221.Research output: Contribution to journal › Article
TY - JOUR
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.
UR - http://www.scopus.com/inward/record.url?scp=84892939102&partnerID=8YFLogxK
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U2 - 10.1152/japplphysiol.01048.2013
DO - 10.1152/japplphysiol.01048.2013
M3 - Article
C2 - 24311747
AN - SCOPUS:84892939102
VL - 116
SP - 216
EP - 221
JO - Journal of Applied Physiology
JF - Journal of Applied Physiology
SN - 8750-7587
IS - 2
ER -