Radial catheterization should not be considered a niche technique isolated to the arterial tree. The forearm is also the source of a rich supply of veins that can offer conduits for right heart catheterization. The first human right heart catheterizations were done through arm veins, but advances in modern technology have made this approach once again relevant for the modern catheterization laboratory, where right heart catheterization continues to be utilized concurrent to arterial catheterization in about 7% of cases. Presently, balloon-tipped right heart catheters can be obtained down to 4 Fr in size for pressure measurements and oxygen saturations, or 5 Fr if the addition of thermodilution cardiac output is needed.
Compared to learning transradial arterial techniques, the approach through the venous system to the right heart is simple. The most important step is having venous access. This access can be anywhere on the forearm, but in reality is limited by the lack of commercially available right heart catheters longer than 110 cm. Often, the antecubital region is used as the default site of venous access as this is proximal enough to reach the pulmonary wedge position regardless of patient height. While modern right heart catheters are soft and flexible in order to pass up either the lateral cephalic vein or medial basilic veins, procedures such as endomyocardial biopsies using stiffer equipment are probably best suited to pass up the straighter basilic system. In such cases, venous access should be focused on the medial/ulnar side of the arm that tends to drain up the basilic system.