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Dynamics of flow velocities in endocardial and epicardial coronary arterioles

Eiji Toyota1, Yasuo Ogasawara, Osamu Hiramatsu

  • 1Dept. of Cardiology, Kawasaki Medical School, 577 Matsushima, Kurashiki, Okayama 701-0192, Japan. etoyota@med.kawasaki-m.ac.jp

American Journal of Physiology. Heart and Circulatory Physiology
|November 20, 2004
PubMed

Insights

The heart

Area of Science:

  • Cardiovascular Physiology
  • Myocardial Blood Flow Dynamics

Background:

  • The subendocardium, a critical region of the left ventricle, exhibits heightened vulnerability to hypoperfusion and ischemia.
  • Existing theories for this susceptibility involve transmural variations in hemodynamics, metabolism, and wall stress, but mechanisms remain unclear.

Purpose of the Study:

  • To investigate the mechanisms behind subendocardial vulnerability by dynamically measuring endocardial and epicardial blood flow velocities.
  • To correlate hemodynamic and wall stress differences with observed flow patterns in coronary arterioles.

Main Methods:

  • Utilized a high-speed, charge-coupled device (CCD) intravital videomicroscope with a rod-probe lens for in vivo measurements.
  • Measured blood flow velocities in subendocardial and subepicardial coronary arterioles of beating canine hearts.

Main Results:

  • Subendocardial arterioles displayed significant systolic flow-velocity reversal (systolic slosh ratio: 84%, retrograde velocity > -40 mm/s).
  • Subepicardial arterioles showed predominantly forward systolic flow (systolic slosh ratio: 25%, max velocity ≈ -20 mm/s).
  • These differences in flow patterns were statistically significant (P < 0.0005 and P < 0.05, respectively).

Conclusions:

  • Retrograde systolic flow in the subendocardium may be 'wasteful,' requiring diastolic refilling and reducing net perfusion time.
  • This systolic retrograde flow is hypothesized to contribute to the subendocardium's susceptibility to ischemic injury.

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