Integrative Cardiovascular Laboratories

Pressure Myograph

 

 

 

 

 

 

This technique is used to examine intrinsic properties of isolated resistance vessels (arterioles and small arteries).

1. The blood vessel is isolated using a stereo microscope, microscissors and microforcepses.
2. The vessel is mounted on two glass cannulas in a microvessel chamber and secured with a ligature.
3. The proximal cannula is connected to a pressure reservoir or a pressure servo controler.
4. The distal cannula is closed with a stopcock ("blind sac" preparation, no luminal flow).
5. The chamber is superfused with heated and oxygenated buffer solution.
6. The chamber is mounted on a stage of a microscope (inverted or regular depending on the chamber type) connected to a video camera.
7. The signal from the video camera is leading to the video card of a personal computer equipped with a video dimensioning software.
8. The vessel is visualized on the computer monitor and internal diameter is measured by adjusting the guides superimposed by the software.
9. The software also captures images (1frame/sec), which are stored as digital files for documentation.

 

 

 

 

 

 

 

 

Advantages:

1. Void of neural and circulating influences
2. Constant transmural pressure, no luminal flow - minimizes changes in shear forces
3. Direct visualization of the blood vessel
4. Allows precise control of transmural pressure - myogenic responses can be studied
5. Endothelium can be removed (e.g. air perfusion) to examine endothelium-independent responses

Limitations:

1. Vascular segment is isolated from the surrounding tissue
2. Drugs cannot be applied from the luminal side without inflicting flow
3. Adventitial side drug application prevents larger molecules (e.g. peptides) from reaching the endothelium - endothelium-dependent effects of bradykinin, substance P, angiotensin II cannot be studied
4. Smaller arterioles can are increasingly challenging to preparate