Acute changes in forearm venous volume and tone using radionuclide plethysmography

Area of Science:

• Cardiovascular physiology
• Nuclear medicine imaging

Background:

• Assessing acute changes in human forearm veins is crucial for understanding vascular dynamics.
• Blood pool scintigraphy offers a potential method for evaluating regional forearm vascular volume and pressure-volume relationships.

Purpose of the Study:

• To validate blood pool scintigraphy as a method for studying acute changes in human forearm veins.
• To compare the effects of nifedipine and nitroglycerin on forearm venous capacity and pressure-volume relationships.

Main Methods:

• Simultaneous data collection using radionuclide (blood pool scintigraphy) and mercury-in-rubber strain-gauge techniques in 16 patients.
• Measurement of forearm vascular volume and pressure-volume (P-V) curves before and after administration of sublingual nifedipine (NIF) or nitroglycerin (GTN).

Main Results:

• Blood pool scintigraphy demonstrated high reproducibility, comparable to the strain-gauge method (Syx 3.1% vs. 3.2%).
• Measurements of acute forearm venous volume changes correlated well between the two techniques (r = 0.86).
• Nitroglycerin significantly increased forearm vascular volume and shifted the venous P-V curve rightward (venodilation), while nifedipine showed no significant changes.

Conclusions:

• Blood pool scintigraphy is a validated and reproducible method for assessing acute changes in human forearm venous volume and pressure-volume relationships.
• Nitroglycerin induces venodilation and increases venous unstressed volume, whereas nifedipine does not significantly alter forearm venous capacity or compliance.