The most common congenital valve abnormality is a bicuspid aortic valve, which is seen in 1-2% of the population. A well-known cardiologist taught me that the natural history of a bicuspid valve goes by the Rule of 3. Over a lifetime, one third of patients will get aortic deficiency, a third will get aortic stenosis and the rest will have no serious cardiac pathology. As you’ll recall, a normal aortic valve is trileaflet, so having two cusps leads to more wear and tear on this apparatus. In addition, there are associations between a bicuspid aortic valve and other congenital abnormalities. In a series, 22 of 74 patients (30%) had other anomalies. The most common association is with coarctation of the aorta. As many as 30-40% of patients with coarctation have a bicuspid aortic valve. Atrial septal defects are also common. More recently, patients who were found to have a bicuspid aortic valve had a higher prevalence of disease and enlargement of the aortic root and ascending aorta.
In an attempt to determine the effects of a bicuspid aortic valve, a recent study (Tzemos N et al. JAMA 2008;300:1317-25) followed a group of young adults over nine years. The group consisted of 642 adults with a mean age of 35. These patients where born with bicuspid aortic valves. They found that the 10-year mortality rate of the bicuspid aortic valve group wasn’t significantly different than the control population (4% vs 3%). But on the other hand, 161 of these trial patients expe-rienced one or more primary cardiac events. This suggests that these patients need to be followed up every 3 to 5 years for an echocardiogram with at least the first visit involving a cardiac MRI.
In people who present with symptoms of heart failure or valvular abnormalities in their 40-50s, a bicuspid aortic valve may be the culprit of their pathology. Initially, I would get either a CT or MR study to evaluate the proximal aorta. In addition, I’d follow these patients long term for development of valvular pathology. If their initial echo is totally normal, a repeat study is recommended in 3-5 years, depending on the size of the aorta and pathology of their valve. This will guide appropriate surgical intervention to repair or replace the aorta.
Bicuspid aortic valve is not a benign process for many. The data from Toronto suggests that at the age of 35 serious pathology has been detected in 25 % of patients. We need to interpret these findings as follows: patients who are being followed in a congenital heart disease clinic are there because of high disease burden and may not represent all patients with bicuspid aortic valve. But the finding that this condition causes significant pathology by the age of 35, however, should be a wake-up call that all individuals with bicuspid valves require long-term surveillance.
Gregory P. Curnew, MD, FRCPC is Associate Professor at McMaster University in Hamilton, ON, and Director of the Coronary Care Unit at Hamilton General Hospital.