Results
Fifty-six patients were included in the original study at our center.
Thirty vs 26 patients for the on- respective off-pump groups. All
patients were alive 30 days postoperatively. One patient in each group
needed early reoperation for bleeding. Two patients developed sternal
wound infections, 2/56 (3.6%) and three patients had leg wound
infections, 3/56 (5.3%). One patient in the on-pump group needed repeat
revascularization with percutaneous coronary intervention (PCI) and one
patient in the off-pump group underwent redo surgery due to new coronary
lesions and mitral regurgitation. Five patients in the on-pump group and
two patients in the off-pump group had died, 7/56 (12.5%). Five out of
seven patients died from non-cardiac causes.
The five-year follow-up included 49 patients with 25 vs 24 patients in
the on- and off-pump groups respectively. All patients underwent a
clinical evaluation according to protocol. Five patients were excluded
from CTA due to renal failure and two patients in each group refused to
participate in this sub-study. Forty patients underwent CTA with 139
distal anastomoses analyzed, see figure 1. Patient characteristics at
five years are reported, see table 1. Similar mean age, gender
distribution and most risk factors between the groups. All patients were
on anti-platelet therapy. Some numerical differences between the two
groups, for example more patients in NYHA class I in the on-pump group.
No patient reported pain from the SV harvesting site and only one
patient reported numbness. Small coronary targets, ≤ 1mm in diameter,
were more frequent in the right coronary territory, 10/41 (24.7%). Six
patients received a NT SVG to left anterior descending (LAD) artery due
to either borderline stenosis or surgical injury to the LITA. In four
patients the NT SVG was used to substitute the LITA in patients with
multiple co-morbidities. The mean grafting rate per patient was 3.8 and
3.1 distal anastomoses in the on- and off-pump groups respectively.
The overall five-year patency rate according to the number of distal
anastomoses was 123/139, (88.5%) of which 73/80 (91.3%) were in the
on-pump group and 50/59 (84.7%) in the off-pump group. The patency rate
was higher for the grafts used to the LAD territory than for those
grafts used to both the circumflex (Cx) and the right coronary
territories, independent of the surgical method used, see figure 2. The
total patency rate for LITA was 29/30 (96.7%) and for the NT SVGs
94/109 (86.2%). The patency rate of LITA was similar between the
groups, on-pump 16/16 (100%) and off-pump 13/14 (92.8%). The patency
rate for NT SVGs was also similar between both surgical procedures,
57/64 (89.1%) in the on-pump group and 37/45 (82.2%) in the off-pump
group. However, all NT SVGs that were used to bypass the LAD and the
diagonal (D) branches were patent, 20/20 grafts in the on-pump group
and12/12 grafts in the off-pump group. The lowest patency for the NT SVG
was to the right coronary territory, particularly in off-pump surgery,
16/20 (80.0%) and 10/16 (62.5%) for the on- and off-pump groups
respectively, see table 2.
Analyses of a possible superiority in patency for the two surgical
procedures stratified to the different target coronary arteries was
performed, see table 3. The difference in patency between on- and
off-pump was 6.5% (95% CI -7.1 - 20.1; p=0.35), i.e. superiority was
not found. For the target coronary arteries, statistically significant
differences were found for LAD/D vs Cx (difference 10.6, 95% CI 2.0 –
19.2; p=0.02), LAD/D vs posterior descending artery (PDA) (difference
26.2, 95% CI 10.4 – 41.9; p<0.001) and LAD/D vs Cx or PDA
(difference 17.9, 95% CI 9.2 – 26.6; p<0.001). The
difference in patency between Cx and PDA was not significant, 15.6 (95%
CI -2.2 – 33.4; p=0.09).
As superiority for either of the two surgical procedures was not found,
we analyzed a possible equivalence between graft patency in the on- and
off-pump groups, see figure 3. We tested an equivalence with a span of
at most ± 10 percentage units. As indicated in the figure, the upper
95% CI limit exceeds the limit of 10 % units (15.79) and the lower
95% CI limit is below zero, reaching the value of -2.78. In accordance
with Fleming 11 and Blackwelder 12this indicates an inconclusive result, thus neither superiority nor
equivalence can be statistically verified, and this is most likely due
to a lack of power.