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Intramyocardial blood volume, perfusion and transit time in response to embolization of different sized microvessels
Stefan Möhlenkamp1, Patricia E Beighley, Eric A Pfeifer
1Department of Physiology and Biophysics, Alfred 2-409, Mayo Clinic and Foundation, Rochester, MN 55905, USA.
Insights
The size of microemboli significantly impacts coronary microcirculation, affecting blood volume and flow. Larger emboli cause more severe injury, while microvascular reserve mechanisms help preserve flow and transit time.
Area of Science:
- Cardiovascular Physiology
- Microcirculation Research
- Pathology
Background:
- Coronary microcirculation plays a vital role in maintaining myocardial perfusion.
- Microemboli can disrupt normal microvascular function and lead to myocardial injury.
- Understanding the impact of different microemboli sizes is crucial for diagnosing and treating cardiovascular conditions.
Purpose of the Study:
- To investigate the effects of different-sized microspheres on coronary microvascular blood volume (Bv), perfusion (F), and transit time (TT).
- To analyze the patterns of microvascular injury induced by varying microemboli.
- To assess the role of microvascular functional reserve during microembolization.
Main Methods:
- Quantified Bv, F, and TT in pigs at baseline and after injections of 10- or 100-microm microspheres.
- Performed measurements at rest and during adenosine-induced vasodilation.
- Examined microvascular injury through gross-pathologic and histologic analysis.
Main Results:
- 10-microm microspheres initially increased Bv and F, but progressively decreased with further injections.
- 100-microm microspheres consistently reduced Bv and F, regardless of quantity.
- Adenosine infusion during microsphere injection decreased peak Bv and F but did not alter TTs.
- Histologically, 100-microm microspheres caused patchy plugging, while 10-microm microspheres induced hemorrhagic injury.
Conclusions:
- Microemboli size and initial perfusion status dictate changes in intramyocardial Bv, F, and injury patterns.
- Microvascular functional reserve mechanisms are critical for preserving flow and transit time.
- These findings highlight the differential impact of microemboli size on coronary microvascular dynamics and myocardial integrity.
Objective:
To study the role of the coronary microcirculation in response to different-sized microemboli, we measured changes in intramyocardial microvascular blood volume (Bv), perfusion (F) and transit time (TT) and also microvascular patterns of injury.
Methods:
Bv, F and TT were quantitated in 24 pigs at baseline and again 2 min after repeat injections of 10- or 100-microm microspheres at rest or during intracoronary adenosine infusion. The association of Bv and TT was assessed in the microsphere pigs and in nine control pigs. Microvascular injury was studied on gross-pathologic and histologic samples.
Results:
At rest, initial injection of 10-microm microspheres led to increases in Bv and F, but progressively decreased with additional injections. In contrast, even small numbers of 100-microm microspheres always led to decreases in Bv and F. Injection of microspheres during adenosine-induced vasodilation always resulted in decreases in peak Bv and F irrespective of their diameters, but microvascular TTs remained unaltered. In control pigs, however, TTs were inversely related to adenosine-induced changes in Bv. Histologically, 100-microm microspheres resulted in patchy distribution of microcirculatory plugging, while 10-microm microspheres induced contiguous hemorrhagic myocardial injury.
Conclusion:
Microsphere-induced changes in intramyocardial Bv and F and the associated pattern of myocardial injury are related to the size of embolized microvessels and the initial perfusion state. Microvascular functional volume reserve mechanisms appear to play a key role accompanying flow- and TT-preservation.