A new Canadian study in the New England Journal of Medicine, published Wednesday, shows a direct link with a risk of a bulge in the body's main artery and a heart condition some people are born with.
This heart defect is called bicuspid aortic valve. It's the most common congenital heart defect, and it affects 1.3 per cent of the world's population.
"The silent killer is aneurysm [in patients with bicuspid aortic valve]," said Dr. Subodh Verma, a cardiac surgeon at St. Michael's Hospital in Toronto, and this study's lead author.
People with this condition have aortic valves with two flaps (essentially a hinge that opens and closes and ensures that oxygenated blood is pumped from the heart to the rest of the body) instead of the normal three.
Jeffrey Robinson, 54, of Scarborough, Ont., was diagnosed with a bicuspid aortic valve in 2008 when he was 48 through a stress test.
"I thought a stress test would be a good idea because I was approaching 50," said Robinson.
Doctors have known for many years that one-third of people with this heart defect may need surgery either on their aorta or to replace their defective aortic valve with an artificial one.
Verma said these findings are important because they show that patients with this heart defect have a higher risk of aortic aneurysm — a potentially fatal condition involving unstable widening of the aorta. This is one of two major complications of having a bicuspid aortic valve. The other life-threatening complication is tearing of the aorta (aortic dissection), which often leads to sudden death.
Matthew Chimko, 26, of Markham, Ont., found out that he had a bicuspid aortic valve when he was 25 years old. "It was quite a shock, it came out of the blue," he said. "I was considered an urgent case because I was so young."
Aortic aneurysm
Aortic aneurysm is a term for widening of the aorta to more than 1.5 times normal size.
Normally, the root (where the aorta attaches to the heart) is 25 milimetres.
When Robinson was diagnosed in 2008, his aortic root was 41 millimetres, and when he had his surgery on Feb. 26, 2013, it was 50 millimetres.
"Dr. Verma monitored me to measure the diameter of my aneurysm every six months to see how fast it was expanding," said Robinson.
The cutoff width for surgery is 50 millimetres.
"[This condition] is responsible for more morbidity and mortality than the effects of all other congenital heart defects combined," Verma said.
While aneurysms can happen for many reasons, they always cause an underlying weakness in the wall of the aorta. Sometimes these aneurysms are painful, which is a sign of impending rupture. If this happens, massive internal bleeding occurs and, without immediate treatment, shock and death can happen within minutes to hours.
Verma said it's important for patients with bicuspid aortic valves to be aware of two things:
- Their risk of having an aortic aneurysm.
- The possibility that the abnormal valve could stop working completely.
People who have an aortic aneurysm need to seek the advice of a cardiologist or cardiac surgeon to help them understand when they should have surgery and how extensive it will be.
"These operations are complex and at times require not only stopping the heart but also stopping circulation to the brain," said Verma. "It is paramount that the risk of complications from surgery be weighed against the risk of aneurysm rupture or dissection."
What is the risk?
Up to 50 per cent of people with bicuspid aortic valves will have larger aortas. This problem starts in childhood, and it gets worse over the person's lifetime. In children with bicuspid aortic valves, this stretching happens faster than it does in their peers with normal hearts.
Aortic aneurysms can happen because of genetic problems with the structure of the aorta, or as a result of changes in blood flow that put excessive stress on its wall.
According to this study, there are three patterns that cause these aneurysms to form. The authors suggest that two of them may not be genetic as previously thought.
"There's a subgroup [of patients] in which a genetic component exists, but in the majority this is not the case," said Verma.
Other factors that increase your risk of aortic aneurysm are:
- Initial aortic width (the larger this is, the bigger it's annual rate of expansion).
- Older age.
- Male sex.
- High systolic blood pressure (the top number, which is also the higher of the two numbers; it measures the pressure in the arteries when the heart muscle contracts).
- Co-exisiting heart defects like hardening of the aortic valve (aortic stenosis) and a malfunctioning or incompetent aortic valve that doesn't pump blood as efficiently as it normally would (aortic regurgitation).
- Aortic valve structure.
Should I be screened?
Bicuspid aortic valves are diagnosed with transesophageal echocardiography, a form of ultrasound that uses a probe to takes a 3D image of the heart.
First-degree relatives (e.g. siblings and children) of people with this heart condition should be checked to see if they have it. Annual echocardiography (a picture of the heart) is recommended for patients whose aortic width is more than 40 millimetres.
Robinson's siblings and children have been screened, and none of them have this heart condition.
Seventy per cent of patients with bicuspid aortic valves won't need surgery on their valve or their aorta, but still need to be monitored closely.
"The good news for patients is that [this defect] doesn't kill everyone," said Verma.
"I was fortunate in that I had time to prepare — there were almost five years between when it was first found and when they operated," said Robinson.
Robinson works in construction. He recovered well and returned to his job in August 2013. "I feel very lucky. I found out about something that easily could have killed me," he said.
What should I do?
According to Verma, there are four things people with bicuspid aortic valves need to consider:
- People with this heart condition shouldn't panic. "The vast majority may not require surgery," he said.
- This condition doesn't necessarily require completely giving up physical activity. Once an aneurysm develops, the authors suggest that people should avoid strenuous exercise, since this might increase blood pressure and cause the aneurysm to get bigger. "Severe exercise that increases intrathoracic pressure should be avoided, but people should continue to lead an active lifestyle," said Verma.
- Bicuspid aortic valves need to managed on an individual basis. "Absolute size may not be the only way," said Verma. "Family history and other risk factors also need to be considered."
- Currently there isn't one specific medication to manage this condition. "Lowering blood pressure appears to be the most important factor at this point in time," said Verma.
In the future, surgeons are hoping to develop a blood test or a biomarker that will help them identify this condition more easily.
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