Ask the Clinical Instructor: A Q&A column for those new to the Cath Lab
- 11 Nov 08
- Posted on: 11/5/08
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It should be noted that IVUS and pressure wire procedures require that the patient receive anticoagulants prior to the beginning of the procedure. Since a catheter or a wire is being placed in the coronary artery, these medications must be given to prevent life-threatening clotting on the devices. At our facility, we try to utilize bivalirudin (Angiomax, The Medicines Company, Parsippany, NJ) as much as possible, because of the short half-life of the medication. If the procedure results in a negative finding, then the sheath can be removed within 2 hours.
A FFR of 1.0 is normal, but coronary arteries generally show a FFR > 0.94. As a general rule, FFR findings and their recommended course of treatment can be seen in Table 1.1
FFR can also be used to determine an appropriate course of treatment for a patient. A recent case at our facility demonstrates the importance that FFR can have in the determination of treatment. The patient presented with continuing chest pain on exertion. The RCA is totally occluded (probably chronic) and a large posterior descending artery (PDA)/posterolateral artery (PLA) system is noticed on angiography of the left arteries. The collaterals to the PL/PD appear to come from the LAD and circumflex. The chronic total occlusion (CTO) appears moderate in length once the collateral and main vessels are visualized, with a calcific channel outlined (Figures 5-7).
The LAD shows “lumpidy-bumps,” but nothing more than a 70-80% (remember, it is subjective) lesion. There are smaller lesions throughout the artery. The circumflex has a lesion that could be repaired with angioplasty.
The discussion that took place in this case was whether or not to fix the circumflex and bring the patient back later in an attempt to open the CTO in the RCA. Further review of the LAD angiograms aroused suspicion about the lesions present. If the lesions were not significant, the angioplasty would proceed; however, if the lesions were significant, the patient would be sent to surgery for at least a three-artery bypass.
Since IVUS would clearly show a calcium burden, which was somewhat visible on the angiograms, the PressureWire (Radi Medical Systems, Wilmington, MA) is utilized to determine the physiological status of the artery. It is also possible that the IVUS catheter may not completely reach the lesions or be able to pass through the tortuosity in the LAD.
Even upon placement of the wire, before adenosine administration, a gradient was present across the lesion (Figure 8).
After the administration of adenosine, the gradient increases to a maximum of 0.63. The decision was made to send the patient to surgery, since the LAD had physiologically significant disease as demonstrated by FFR (Figures 9 and 10).
It is best to simply remember that IVUS looks at structure, and FFR looks at physiology. While sometimes structure is all you need to know in order to intervene on a lesion, sometimes it is not enough. We want to make sure that before we place a foreign body in the patient (stent) that the patient really needs it. Sometimes knowing the physiologic status of the vessel is important to make the appropriate decision for the patient. Most importantly, the physician now has documentation to show the basis for their decision, instead of relying on angiography alone.
If you have any questions about this article, or you or your lab have a question about a particular topic, please send an email to email@example.com.
Next month, a question concerning vasovagal response will be addressed.
1. Baim DS, ed. Grossman’s Cardiac Catheterization, Angiography, and Intervention. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006.
2. Brigouri C, Anzuini A, Airoldi F, et al. Intravascular ultrasound criteria for the assessment of the functional significance of intermediate coronary artery stenosis and comparison with fractional flow reserve. Am J Cardiol 2001;878:136-141.
3. Jasti V, Ivan E, Yalamanchili V, et al. Correlations between fractional flow reserve and intravascular ultrasound in patients with ambiguous left main coronary artery stenosis.
4. Libby P, Bonow RO, Mann DL, Zipes DP. Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine. 8th Edition. Philadelphia: Elsevier Science; 2007.