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Dynamics of coronary occlusion in the pathogenesis of myocardial infarction
W P Santamore1, B W Yelton, J D Ogilby
1Philadelphia Heart Institute, Presbyterian Medical Center, Pennsylvania 19104.
Insights
Even minor coronary artery blockages can cause heart attacks. Dynamic changes in blood vessel size, like constriction and collapse, significantly increase this risk, highlighting the role of vasomotion in myocardial infarction.
Area of Science:
- Cardiovascular Physiology
- Biomedical Engineering
- Pathophysiology
Background:
- Coronary artery stenoses often reduce lumen size due to vasoconstriction, pressure changes, or collapse.
- The combined effects of vasoconstriction and plaque rupture with thrombus formation can lead to complete blood flow cessation, even with minimal obstruction.
Purpose of the Study:
- To investigate the hypothesis that dynamic changes in coronary artery stenosis significantly impact blood flow and occlusion.
- To compare the occlusion potential of rigid versus dynamic stenoses under simulated plaque rupture and thrombus formation.
Main Methods:
- Utilized a validated computational model of the coronary circulation.
- Applied standard hemodynamic equations to determine pressure drop and flow through stenotic segments.
- Simulated rigid stenoses and dynamic stenoses incorporating proximal vasoconstriction and distal collapse.
- Modeled plaque rupture as a decrease in lumen area without altering arterial wall properties.
Main Results:
- Rigid stenoses required significantly larger thrombus volumes for occlusion compared to dynamic stenoses.
- A 60% rigid stenosis needed a 40% plaque rupture for occlusion, whereas a 60% dynamic stenosis required only a 12% plaque rupture.
- Simulated vasoconstriction and passive collapse in dynamic stenoses demonstrated that small plaque ruptures could lead to vessel occlusion.
Conclusions:
- Mild coronary lesions, when combined with dynamic vasomotion, can precipitate myocardial infarction.
- Vasomotion plays a critical role in the pathogenesis of most myocardial infarcts, often exacerbating the effects of minimal stenotic lesions.
Abstract:
In most coronary artery stenoses in humans, lumen size decreases in response to acute vasoconstriction, reduced aortic pressure or passive collapse. Because the effects of vasoconstriction and plaque rupture with thrombus formation are additive, in some cases total cessation of flow may result from only minimal obstruction by thrombus. This hypothesis was investigated with use of a previously developed model of the coronary circulation in which the pressure drop across and flow through an arterial stenosis were determined by standard hemodynamic equations. The vessel wall was assumed to be composed of pliable and rigid sections, as is the case in most arterial stenoses in humans. The computer analysis was conducted for a rigid stenosis and for a dynamic stenosis in which proximal artery constriction and distal collapse were simulated. Plaque rupture with subsequent thrombus formation was simulated as a decrease in lumen area without effect on the arterial wall. Compared with a dynamic stenosis, a rigid stenosis required a significantly larger thrombus for vessel occlusion. Thrombus formation equal to the nonobstructed area of the lumen was required to occlude a rigid vessel; a 60% stenotic vessel required a 40% plaque rupture with thrombus formation for occlusion. However, for a dynamic stenosis, if vasoconstriction and passive collapse were simulated, small plaque ruptures led to vessel occlusion: a 60% stenotic vessel required only a 12% plaque rupture with thrombus formation for occlusion. This analysis indicates that even mild coronary lesions may be responsible for myocardial infarction, suggesting that vasomotion may be a very important element in the pathogenesis of most myocardial infarcts.