Assessing the Incidence of Aortic Complications in Patients with Bicuspid Aortic Valves

Assessing the Incidence of Aortic Complications in Patients with Bicuspid Aortic Valves

Amy Leigh Miller, Joseph Loscalzo

While bicuspid aortic valves are known to be associated with aortic dilation and dissection, the risk of dissection in this population has recently been called into question. Michelena and colleagues (2011) have published a study of the Olmstead County population to assess the incidence of aortic complications in patients with bicuspid aortic valve (AV) who come from a single defined geographical population and whose care is provided at a single center. All patients diagnosed with bicuspid AV by echocardiogram from 1980 to 1999 were included. Studies of patients whose echocardiograms had been read as indeterminate were re-reviewed by two clinicians and categorized as definite bicuspid AV, tricuspid AV, or uncertain AV morphology. Of 41,687 local residents who underwent echocardiograms during the study period, 1% had definite (n=416) or uncertain (n=63) AV morphology. In the latter group, 41 patients were subsequently demonstrated to have tricuspid valves, leaving only 22 with uncertain AV morphology. Follow-up was from review of medical records for patients who remained in the region, and by telephone interviews and mail surveys for those who moved away. Mean follow-up time was 16 years; 2% were lost to follow-up.

In 71% of cases, an abnormal auscultatory finding on examination prompted the echocardiogram. Patients with bicuspid AV were predominantly male (69%), and 96% were >18 years of age. Associated congenital heart defects were present in 13% of patients, and 7% had aortic coarctation. Aortic stenosis was present in 23% of patients and aortic regurgitation in 59% of patients. Acute aortic dissection occurred in 2 of 416 patients during follow-up; in one case, the bicuspid valve had previously been surgically replaced. Aortic dimensions on their last echocardiogram prior to dissection were 52 and 50 mm, both of which were increased from their baseline value. An additional 2 cases of aortic dissection in patients with bicuspid AV were identified in patients presenting with aortic dissection who were not known to have bicuspid AV. Excluding these latter 2 patients, relative to the previously reported incidence of aortic dissection in normal subjects in Olmstead County, bicuspid AV had a relative risk of 8.4 for aortic dissection. Aortic aneurysm was present at the time of bicuspid AV diagnosis in 32 patients (using a diagnostic criterion of 48 mm) and developed in an additional 49 patients a mean of 14 years after bicuspid AV diagnosis (relative risk, 86.2 compared with the general population of Olmstead County). Of 49 patients who underwent repair of their thoracic aorta, pathology was available for 25, of whom 52% had evidence of cystic medial degeneration. Mortality rates did not deviate from those of the general population for the duration of follow-up; however, 25% of patients required surgery on their aorta, 53% required valve replacement, and 26% developed aortic aneurysms over the course of follow-up.

The high percentage of patients undergoing aortic repair and/or valve replacement over the course of follow-up underscores that this is not a "natural history" study of bicuspid AV; it reflects complication rates in a population that is carefully followed and managed expectantly. Bicuspid AV clearly has significant associated morbidity, including a high relative risk of aortic dissection. Nonetheless, this study suggests that with appropriate management, this morbidity can be handled without excess mortality.
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[TD="class: contentBody"]Michelena HI et al. Incidence of aortic complications in patients with bicuspid aortic valves. JAMA 2011;306:1104.
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