Ken Ouriel is the PI for the new PIVOTAL study and Roger Greenhalgh was the PI for the UK Small Aneurysm Trial.
Ouriel made the case for a trial to see whether endovascular abdominal aortic aneurysm repair (EVAR) should be carried out on patients with aneurysms less than 5.5cms. He argued that the greatest risk factor for rupture is size and that there is considerable supporting data to show that aneurysm rupture is related to size. He mentioned the 5/10/20% rule
– 5 cm – 5% cumulative risk of rupture per year
– 6 cm – 10% cumulative risk of rupture per year
– 7 cm – 20% cumulative risk of rupture per year
Ouriel’s own data on 100 AAA ruptures showed that 5.1% of all ruptures occur below 5 cm and 1.9% of all ruptures occur below 4 cm. Aortic diameter is dependent on age and gender and standardization of AAA diameter to patient size (3rd vertebral body) was the best predictor of rupture.
He also quoted the UK Small Aneurysm Trial (SAT) which showed that mortality was lower in the early surgery group at eight years: “The survival curves crossed at three years and at eight years, mortality in the early surgery group was 7.2 percentage points lower than that in the surveillance group (P=0,03). Ouriel also pointed out that both the UK SAT and US ADAM trials documented the need for eventual repair in approximately 70% of patients initially managed with surveillance. In addition the disparity between surveillance and surgery was greatest in larger aneurysms (4 to 5.5cms) in UK SAT.
He summarized the logic behind EVAR for 4-5.5 cm aneurysms as follows: The open vs. observation trials (UK-SAT and ADAM) demonstrated similarity or superiority of surveillance compared to early repair. These findings were documented despite a perioperative mortality rate of 5.4% in UK-SAT and 2.1% in ADAM. Recent Cleveland Clinic data has mortality rates of 1.8 % for both EVAR and open repair. If a procedure could be performed with a lower perioperative mortality rate, that procedure might be able to “beat” surveillance in patients with smaller AAA.The recent Cleveland Clinic Study also shows that EVAR performs best in smaller AAA. “Endovascular aneurysm repair is associated with lower periprocedural mortality than open repair” Ouriel said. The longer-term results of endovascular repair appear most impressive in smaller AAA, with impressive durability and an extremely low risk of subsequent rupture. Using ‘transitive’ logic; if the UK and ADAM trials found open AAA repair similar or slightly better than observation, and if the mortality rate of endovascular AAA repair is better than open, endoAAA should be better than surveillance in patients with smaller (4 – 5.5 cm) AAA.”
Roger Greenhalgh defended UK SAT. He pointed out that the trial was about the timing of the operation. The key issue was to determine whether surgery had a chance of beating natural history and gain additional life years. Both the UK and US trials failed to show this.
He also pointed out that the significant P-value highlighted by Ouriel was when the study was out of protocol and significance in terms of lower mortality for early surgery was shown in this one year only.
Greenhalgh concluded that it is hard to see even with recent EVAR 30 day results how it can beat surveillance. “Surveillance is safe”, Greenhalgh concluded.