News:Abnormal pressure gradient distal to the implanted bare metal stent is associated with the occurrence of in-stent restenosis

February 12, 2008 By Vijayalakshmi Kunadian MBBS MD MRCP [mailto:vkunadian@perfuse.org]

Significant developments have been made in the field of percutaneous coronary intervention in terms of reducing the occurrence of restenosis within coronary arteries with the use of bare metal stents and recently with the use of drug eluting stents compared to balloon angioplasty alone. In addition to assessing the significance of coronary artery lesions and the outcomes of interventions on coronary angiography, functional assessment of coronary artery lesions using physiological techniques such as fractional flow reserve (FFR) measurements have played an important role in the management of patients with coronary artery disease.

Despite these advances, in the current era interventionists continue to observe in-stent restenosis among patients who receive bare metal and drug eluting stents (DES). In a recent publication in Circulation, Jensen and colleagues from Denmark have used the simple technique of fractional flow reserve and distal pressure gradients to identify patients who are at risk of developing in-stent restenosis (ISR) following bare metal stent implantation.

This study consisted of 98 patients with de novo single vessel coronary artery disease. PressureWire (Radi Medical Systems, Uppsala Sweden) was used to measure pressure gradients [Pd/Pa (hyperemic pressure within the coronary artery measured using the PressureWire)/(mean aortic pressure measured using the guide catheter)] at (1) the distal most part of the coronary artery [FFR], (2) just distal to the stent, (3) just proximal to the stent and (4) at the ostium of the coronary artery. Residual pressure drop was defined as the difference in Pd/Pa at points 1 and 2. They divided the patients into two groups. Group I consisted of patients with hyperemic Pd/Pa at point 1 minus hyperemic Pd/Pa at point 2 <0 (abnormal residual Pd/Pa). Group II consisted of patients with hyperemic Pd/Pa at point 1 equals hyperemic Pd/Pa at point 2.

The investigators demonstrated that the FFR was significantly reduced among patients in group I compared to those in group II (0.88±0.21 versus 0.97±0.05, p<0.001). The reference diameter of the coronary arteries were significantly lower among patients in group I compared to group II (reference diameter 2.9±0.6 vs. 3.3±0.5, p<0.001). ISR was identified in 44% of patients in group I compared to only 8.1% among those in group II (p<0.001) at 9 months. The reference diameter of the coronary arteries, residual abnormal Pd/Pa and stent length were significantly associated with an increased rate of ISR.

This study demonstrates that pressure gradients measured using PressureWire can be used to identify those patients who are at risk of developing in-stent restenosis. It is known that the use of DES significantly reduces the incidence of ISR. The current study is limited by the fact that it cannot be used to identify patients who would benefit from DES as the measurements are calculated post bare metal stent implantation. However, this could help identify patients who are at risk of ISR and maintain these patients on optimal medical therapy. The investigators speculate that the drop in pressure gradient distal to the stent could be due to the presence of diffuse disease in these arteries rather than due to poor stent expansion or residual focal stenosis although this was not confirmed in the current study using intravascular ultrasound studies.