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Vasomotor tone affects diastolic coronary flow and flow impediment by cardiac contraction similarly
P Bouma1, P Sipkema, N Westerhof
1Laboratory for Physiology, Free University, Amsterdam, The Netherlands.
Insights
Cardiac contraction impacts coronary blood flow. Vasodilation increases diastolic flow but does not alter how ventricular pressure and contractility affect coronary flow dynamics.
Area of Science:
- Cardiovascular Physiology
- Coronary Circulation
- Hemodynamics
Background:
- Cardiac contraction significantly influences coronary arterial flow.
- Understanding this relationship is crucial for diagnosing and treating cardiac conditions.
Purpose of the Study:
- To investigate the effect of cardiac contraction on coronary arterial flow.
- To compare these effects under conditions of normal vasomotor tone versus maximal vasodilation.
Main Methods:
- Isolated blood-perfused rat heart model with a left ventricular balloon.
- Ventricular pressure and contractility were manipulated.
- Coronary flow reduction due to contraction was analyzed using multiple regression.
Main Results:
- Vasodilation, induced by adenosine, increased diastolic coronary blood flow significantly (4.06-fold).
- The relationship between coronary flow reduction and developed ventricular pressure (devPLV) and elastance (devELV) was quantified.
- No significant difference was observed in the increases in diastolic flow, SP, or SE between control and vasodilation states.
Conclusions:
- Maximal vasodilation increases diastolic coronary blood flow.
- Vasodilation does not alter the relative contributions of ventricular pressure and contractility to coronary flow dynamics.
Abstract:
We studied the effect of cardiac contraction on coronary arterial flow with vasomotor tone (control) and during maximal vasodilation with adenosine in the isolated blood-perfused rat heart at constant perfusion pressure (105 mmHg) with a left ventricular balloon (n = 6). Ventricular pressure was changed by volume changes and contractility via postextrasystolic potentiation. Contractility was expressed as the slope of the end-systolic pressure-volume ratio, elastance. Constant vasomotor tone was judged from stable diastolic flow. Coronary flow reduction (diastolic minus systolic flow, delta CBF, ml.min-1.g-1) due to contraction was related to developed ventricular pressure (devPLV) and developed elastance (devELV, systolic minus diastolic elastance) by multiple regression: delta CBF = SP.devPLV+SE.devELV+I, where SP and SE represent changes in coronary blood flow due to changes in devPLV and devELV, respectively, and I is intercept. In control, delta CBF = (0.016 +/- 0.008).devPLV + (0.0022 +/- 0.0009).devELV + (0.29 +/- 0.77); during vasodilation, delta CBF = (0.046 +/- 0.011).devPLV + (0.009 +/- 0.0053).devELV + (2.50 +/- 2.56). Diastolic flow increased by a factor of 4.06 +/- 1.57 (SD) during vasodilation. The increases in diastolic flow, SP, and SE were not different. We conclude that vasodilation has similar effects on diastolic flow and flow amplitude without affecting the relative contributions of ventricular pressure and contractility.