2008年3月27日 星期四

Laplace's law

Q: What is Laplace's law and how does it relate to cardiac hypertrophy?

A:
  • Laplace's law is as follows: T = (P × R)/M where T is the tension in the walls, P is the pressure difference across the walls, R is the radius of the vessel and M is the thickness of the wall.
  • In dilated cardiomyopathy, after prolonged increases in afterload (in the setting of hemodynamic stress such as hypertension), the heart becomes distended and the radius of the ventricle increases.
  • To create the same pressure during ejection of the blood, much larger wall tension has to be developed by cardiac muscle and the ventricular wall thickens.
  • The dilated hypertrophic heart requires more energy (and oxygen consumption) to pump the same amount of blood as compared to the heart of normal size.
  • Dilated cardiomyopathy causes increases in the risks of ischemia and arrhythmias.
Teaching topics from the New England Journal of Medicine - Vol. 358, No. 13, March 27, 2008

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