In an original manuscript in this issue of Cardiovascular Revascularization Medicine , Linda Lee et al. [ ] describe an innovative method of assessing the right forearm arterial circulation by performing forearm digital subtraction angiography (DSA) via the 5F access sheath prior to diagnostic catheterization and coronary intervention.
The authors arrive at the conclusion that the minimal, proximal, middle, and distal artery radial diameters (as measured by single plain DSA) were substantially smaller in females than in males. The manuscript is confirming formerly published and indisputable common knowledge that all females’ arteries, including the radial artery, are smaller in diameter than their counterparts in males ( Table 1 ). The novelty of this study is the methodology to assess the vessel diameters (single plain DSA). There are, however, a few questions related to this technique:
- a)
Is this the fastest and least expensive method to obtain the information regarding the radial and brachial anatomy and dimension?
This methodology is highly applicable since it can be done within seconds and no additional equipment or training is required. Data analysis is, however, time-consuming but can be potentially simplified with computer-based measurement algorithms. It is considerably faster than performing ultrasound imaging, which can potentially be expedited by extremely skillful experts (one report reported that ultrasound data acquisition requires 6.4 ± 1.8 minutes for both hands 2 ).
- b)
Are these measurements, accurate and reproducible?
The forearm DSA is 2-dimensional and hence generates single-view vessel diameters and not the vessel cross-sectional area. Eccentric lesions can be missed. Vessel-overlap or tortuosity may further result in suboptimal vessel diameter assessment. Ultrasound, computed tomography angiography, and magnetic resonance angiography, or even 3-dimensional rotational angiography, provide a 3-dimensional image of the vessel and hence tend to reflect more accurately the vessel dimensions.
The radial artery may respond with spasm to initial wire or sheath advancement and with incremental vasodilatation after vasodilator injection. Hence the measurement time should allow the “vasodilator cocktail” used to exert its full vasodilatory effects on the vessel.
- c)
Is this method safe?
The authors did not encounter any safety issues, but clearly there is potential for inducing pain and arterial spasm or injury with contrast administration through the end-hole radial sheath. The contrast load is truly minimal and hence contrast-induced nephropathy is not a concern.
- d)
Are the data obtained from radial DSA useful? Do they have any procedural implications? Will the knowledge used for such procedures change the procedure plan and consequently improve patients’ experience and outcomes while reducing access failure, complications, procedure, and fluoroscopy time?
Forearm pre-procedural DSA can potentially alarm us regarding certain issues (suboptimal vessel diameter, vessel stenosis, radial loops) that can have implications for patient discomfort, procedural time complications and success. Similar strategies have been used effectively employing pre-procedural ultrasound [ , ].
Moreover, DSA can allow us to prepare with specialty wires and sheaths to mitigate some of these forearm problems or, alternatively, seek different arterial access.
However, there are many other operational issues that can’t be predicted from the forearm DSA: mostly, more proximal stenosis, calcifications, tortuosity, friction points, or challenging unique congenital or acquired anatomy are not delineated.
While the right forearm DSA can potentially provide us with right ulnar measurements and anatomy, it does not provide us with the anatomy of the contralateral wrist arterial bed (left ulnar, radial and brachial arteries) and hence as opposed to pre-procedural ultrasound, DSA does not enable us to make even selection of best wrist access.
Moreover, when a 5F sheath is placed in the right radial artery, most operators will shy away from accessing the ipsilateral ulnar. However, at least the SWITCH trial suggested [ ] that performing the procedure via ipsilateral ulnar artery (n=36) after the radial artery has been accessed and was found to be unsuitable for intervention is a safe strategy without ischemic implications.
- e)
Can we refine this method and selectively apply radial DSA to certain populations?
- 1)
Targeting selective populations: The study identified females as a population with lower radial artery diameters, and this was confirmed by others. Other populations with possible suboptimal radial access are subjects with diabetes mellitus, peripheral arterial occlusive disease, the elderly, and subjects with previous large-bore sheaths. It is probably of most value to perform forearm DSA on these subjects to enhance procedure efficacy and safety.
- 2)
Specifically-designed microcatheters:
After accessing the radial artery with 0.018” wire, instead of inserting a 5F sheath for the DSA, the DSA ( Fig. 1 ) can be performed with dilator of the 5F Merit Mini-access kit (MAK-401, Merit Medical, South Jordan, Utah, USA) ( Fig. 2 ). The quality of the DSA and the dye load can be minimized by arterial tourniquet applied to the right wrist prior to the DSA injection. If upon injection one decides to access the ipsilateral ulnar artery, the dilator can be removed from the radial artery and brief manual pressure will seal the puncture site almost immediately. An even better and safer injection can be executed via longer micro-dilators with side holes.
- 1)
