1Herzzentrum Leipzig - Universität Leipzig Klinik für Innere Medizin/Kardiologie Leipzig, Deutschland
Background
The occurrence of graft occlusion following coronary artery bypass graft (CABG) surgery has been linked to the presence of native coronary artery competitive flow. Despite the fact that coronary angiography is insensitive to assess the physiologic significance of a coronary stenosis, it is used in daily practice to guide revascularization therapy. Data regarding the use of pressure-derived fractional flow reserve (FFR) to assess the hemodynamic significance of coronary stenoses prior to CABG are inconclusive. In addition, the penetration of FFR in clinical routine is limited for different reasons.
Recently, different systems have been developed to predict fractional flow reserve (FFR) based on coronary angiographic images, eliminating pressure wires or hyperemic agents. Preliminary data demonstrated a high concordance between off-site measured angiography-derived FFR and pressure wire–based FFR. However, the use of this technique prior to CABG is not well studied.
Objectives
To assess a correlation between pre-CABG angiography-derived FFR and graft occlusion.
Methods
Retrospective study of consecutive patients undergoing CABG in whom a follow-up angiogram had been performed. Angiography-based FFR was calculated with a dedicated software (vFFR, CAAS 8.2 Workstation, Pie Medical Imaging, Maastricht, The Netherlands), analyzing each major native coronary vessel before CABG. Post-CABG angiograms had to be conducted no sooner than 6 weeks post-surgery to exclude graft-failures due to technical factors and thrombosis. Statistical analysis was done using SPSS version 27.0 (IBM, Armonk, NY, USA).
Results
Between 2005 and 2014, 204 patients underwent pre-CABG angiography, followed by a post-CABG angiogram after a minimum of 6 weeks post-surgery. A total of 125 patients were excluded due to inadequate angiogram quality for vFFR assessment (outdated imaging system, improper vessel angles, vessel overlap or insufficient contrast). Consequently, 79 patients were deemed suitable for pre-CABG angiography-based vFFR analysis, including 132 grafted vessels (93 arterial and 39 venous grafts). The median age of the patients was 68 years [58 - 72] and median time between CABG and follow-up angiography was 3.85 years [1.33 - 8.80]. Vessels analyzed using vFFR were left anterior descending (LAD) (n= 60, 45.5%), left circumflex artery (LCX) (n=39, 29.5%), ramus intermedius (RIM) (n=8, 6.1%) and right coronary artery (RCA) (n=25, 18.9%). The mean pre-CABG vFFR in all grafted vessels was 0.59 (± 0.15).
A comparison between the occluded and the non-occluded grafts is shown in Table 1.
|
|
occluded grafts (n=18) |
non-occluded grafts (n=114) |
p-value |
|
Age |
60.5 [53.75 - 70] |
69 [57 - 72] |
0.162 |
|
Male gender |
15 (83.3%) |
94 (82.4%) |
0.927 |
|
Grafted vessel |
|
|
0.124 |
|
LAD |
5 (27.8%) |
55 (48.3%) |
|
|
LCX |
9 (50%) |
30 (26.3%) |
|
|
RIM |
0 |
8 (7%) |
|
|
RCA |
4 (22.2%) |
21 (18.4%) |
|
|
Graft type |
|
|
0.350 |
|
Arterial |
11 (61.1%) |
82 (71.9%) |
|
|
Venous |
7 (38.9%) |
32 (28.1%) |
|
|
Median follow-up time (years) |
4.9 [1.6 – 10.2] |
3.8 [1.3 – 8.8] |
0.351 |
|
Mean pre-CABG vFFR |
0.75 (±0.11) |
0.57 (±0.14) |
<0.001 |
To predict graft occlusion, a vFFR cutoff value of 0.7450 with an area under the curve (AUC) of 0.847 (95% C.I. 0.752–0.942) had a specificity of 0.722 and a sensitivity of 0.902. The ROC-analysis is shown in figure 1.
Conclusions
vFFR can be used as a noninvasive tool to predict graft patency in patients undergoing CABG with acceptable sensitivity and specificity. Further research is needed to correlate it with clinical impact.