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Effect of vasopressin on phasic coronary blood flow
Insights
Vasopressin significantly increases blood pressure and total peripheral resistance, leading to reduced coronary blood flow, particularly during diastole. This study reveals vasopressin
Area of Science:
- Cardiovascular Physiology
- Pharmacology
- Hemodynamics
Background:
- Vasopressin is known for its vasoconstrictive properties.
- Its specific effects on coronary circulation require detailed hemodynamic analysis.
Purpose of the Study:
- To investigate the impact of vasopressin on coronary blood flow and related hemodynamic parameters.
- To characterize the relationship between coronary perfusion pressure and blood flow during vasopressin infusion.
Main Methods:
- Hemodynamic measurements (aortic blood pressure, ventricular pressure, aortic and circumflex blood flow) in 12 open-chest dogs.
- Vasopressin infusion (25 mU/kg/min) and analysis of impedance spectrum.
- Vaginal nerve stimulation to induce long diastoles for pressure-flow relationship analysis.
- Acute changes in perfusion pressure induced by arteriovenous fistula.
Main Results:
- Vasopressin increased mean aortic blood pressure (+55% diastolic, +40% systolic) and total peripheral resistance (+200%).
- Coronary blood flow decreased significantly, with a more pronounced reduction in diastolic flow (-33%).
- Vasopressin increased critical closing pressure (Pf0) and decreased coronary conductance.
Conclusions:
- Vasopressin exerts significant vasoconstrictive effects on coronary circulation, primarily impacting diastolic flow.
- The drug alters coronary autoregulation by increasing critical closing pressure and reducing conductance.
- Vasopressin does not influence delayed active coronary vasodilation.
Abstract:
The effects of vasopressin on the coronary circulation have been studied with regard to its general hemodynamic effects. Aortic blood pressure (BP), left ventricular pressure (LVP), aortic blood flow (AoBF), and circumflex blood flow (CBF), were measured in 12 open-chest dogs, under control conditions and during vasopressin infusion (25 mU/kg/min). During vasopressin infusion, the mean aortic blood pressure (MBP) was increased from 104 +/- 23 mm Hg to 161 +/- 23 mm diastolic blood pressure (DBP) was more increased (+55%) than the systolic blood pressure (SBP) (+40%). AoBF was decreased from 2.169 +/- 0.408 l/min to 1.118 +/- 0.303 l/min; and the heart rate was decreased by 18%. The total combined left ventricular power did not change significantly. The increase in total peripheral resistance (TPR) (+200%) was the main change in impedance spectrum. The mean circumflex coronary blood flow (MCBF) was decreased from 48 +/- 8.6 ml/min to 33.4 +/- 9.7 ml/min. This decrease was more important in the diastolic circumflex blood flow (DCBF) (-33%) than in the systolic one (-0.8%). The diastolic pressure time index (DPTI) was more increased than the systolic pressure time index (SPTI). The DPTI/SPTI ratio was increased from 0.91 to 1.3. Long diastoles, induced by vagus nerve stimulation, have permitted to characterise the relationship between pressure and coronary blood flow during diastole. This relationship was linear under basal condition, and during vasopressin perfusion. This made it possible to determine the critical closing pressure (Pf0), and the coronary conductance (the slope of the regression curve). Vasopressin induced an increase in Pf0, from 33.7 +/- 95 to 77.4 +/- 16.07 mm Hg (p less than 0.001), and a decrease in coronary conductance, from 0.8 +/- 0.32 to 0.5 +/- 0.1 ml/min/mm Hg. The effect of an acute change in perfusion pressure on the coronary flow, under control conditions and during vasopressin infusion was studied by opening a large arteriovenous fistula. Unclamping of the fistula, under control conditions, allowed to realize an acute fall in DBP from 82.5 +/- 6.36 to 35.5 +/- 9.19 mm Hg, and in DCBF, from 58.5 +/- 9.2 to 20 +/- 9.8 ml/min. During vasopressin infusion, a similar fall in perfusion pressure lead to a zero diastolic circumflex blood flow, for a diastolic aortic blood pressure of 56 +/- 12 mm Hg. However, vasopressin did not affect the delayed active coronary vasodilatation.