Dissection risks may not justify surgery for moderately dilated aortas
medwireNews: Calls to reduce the recommended threshold in aortic diameter for prophylactic surgery for aortic dissection may have been overstated, conclude the authors of a study published in the Journal of the American College of Cardiology.
The team found that, while the risk of aortic dissection or rupture does increase in correlation with aortic diameter, the absolute risk is still low in people with moderately dilated aortas.
The finding raises questions about the risk–benefit profile of prophylactic aortic repair in these patients – a procedure that carries a mortality rate of up to 30%.
“This risk sets a high bar for surgical results if the treatment is to be less dangerous than the disease”, write Thoralf Sundt III (Massachusetts General Hospital, Boston, USA) and colleagues.
The researchers looked at echocardiographic data on 4654 adults who attended a cardiology clinic with maximal aortic diameters of 40–55 mm. The patients had no history of connective tissue disorder, inflammatory aortic disease or history of ascending aortic surgery, but 586 (12.6%) had bicuspid aortic valves (BAVs).
During a median follow-up of 40.1 months, 13 patients experienced aortic dissection and one patient had an aortic rupture. This equates to a linearised incidence of aortic events of 0.1% per patient–year, the team reports. The estimated risk of aortic event within 5 years was 0.4%, 1.1% and 2.9% for baseline aortic diameters of 45, 50 and 55 mm, respectively.
The researchers found that the aortic event rate was significantly associated with baseline aortic diameter and with age. But the presence of BAV did not increase the risk of dissection independent of aortic diameter.
Sundt and colleagues say that this finding challenges a recent trend to lower the intervention threshold even further for patients with BAV. In a statement published this year, the American College of Cardiology/American Heart Association said that elective repair of the ascending aorta is reasonable in BAV patients with a diameter of 45–55 mm, and replacement is recommended at diameters of 55 mm or more.
However, BAV was a risk factor for aortic expansion, as was female gender.
Practice guidelines have set a recommended threshold for prophylactic surgery of 55 mm in nonsyndromic patients. But the researchers say that recent studies have reported acute aortic dissection in patients with smaller aortic diameters, including one which found this was the case for 59% of presenting patients.
“Accordingly, there has been enthusiasm for lowering the threshold for elective aortic repair”, they write.
However, they say that their findings indicate that more emphasis should be place on other factors to determine whether surgery is appropriate, such as flow dynamics and innate aortic wall properties.
Future research should look at the relationship between these parameters, as well as aortic size, on the risk of aortic dissection, they conclude.
By Kirsty Oswald
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