Bicuspid Aortic Valve With Borderline Root Growth: Does the Marfan Evidence for Medical Therapy Apply?
His aortic root is still below the surgical threshold, but its growth rate over two years is faster than expected — and the medical therapy that might slow it further has much of its evidence built in a different condition.
C.V., a 41-year-old man who works as a software engineer, has known about his bicuspid aortic valve for over a decade, ever since a murmur picked up during a routine physical led to an echocardiogram he still remembers being surprised by — he'd never had a symptom, and has none now. He has kept every follow-up imaging appointment since, treating it the way he treats a recurring calendar reminder at work: not urgent, but not something to skip either.
That discipline is what makes the trend on his last two scans notable. His aortic root measured 4.3 cm two years ago and 4.6 cm on this visit — still below the roughly 5.0 to 5.5 cm range where surgical repair becomes the clear standard, but the number that matters is the annualized one, and 0.3 cm across two years works out to 0.15 cm a year. That sits above the 0.05 to 0.1 cm a year most bicuspid aortas manage, and well short of the 0.3 cm in a single year that the current guidelines define as rapid growth for a bicuspid valve specifically. It lands in an awkward middle: not fast enough to be an intervention trigger on its own, not slow enough to file away, and small enough that serial-measurement variability could account for a share of it. He has no family history of aortic dissection, no other connective-tissue features, and no symptoms referable to his valve or his aorta. The question in front of his cardiology team isn't whether to operate — nobody is proposing that at 4.6 cm — but whether his growth rate justifies starting medical therapy aimed at slowing it further, extrapolating from evidence built almost entirely in a different population. Beta-blocker and ARB therapy to slow aortic growth has real trial support in Marfan syndrome specifically; whether that benefit transfers to bicuspid-valve-associated aortopathy, a related but mechanistically distinct condition, is genuinely less settled.
In clinic, reviewing two years of imaging
A 0.3 cm increase over two years — 0.15 cm a year, and I'll concede at the outset that this is half the rate the guidelines call rapid for a bicuspid valve — is still a trend that deserves a response, not just a note for the next scan. The Marfan evidence for beta-blockers and losartan slowing aortic growth is real and reasonably strong, and while I'll grant the trial evidence specifically in bicuspid-valve aortopathy is thinner, the underlying mechanism — wall stress reduction — isn't obviously population-specific. I'd rather start therapy now, while he's asymptomatic and normotensive, than wait for stronger BAV-specific evidence that may be years away.
If his root had been stable at 4.3 to 4.4 cm over the same two years, or if this were a single 0.3 cm jump inside one year, which would put him over the guideline threshold outright, I wouldn't be having this argument at all — surveillance alone is entirely appropriate for a slow or non-progressive bicuspid aortopathy at this size. The case for treating here rests specifically on the growth rate, not the diagnosis alone.
I want to be careful about extrapolating Marfan-specific trial evidence onto a mechanistically different condition just because both involve aortic dilation. Marfan's aortopathy is driven by a defined fibrillin-1 abnormality with a well-characterized effect on TGF-beta signaling that ARBs specifically target; bicuspid aortopathy's underlying mechanism is more heterogeneous and less clearly matched to that same pathway. He's also normotensive with no symptoms — starting a medication with real side-effect burden for a benefit that hasn't been clearly demonstrated in his actual condition is a real cost to weigh against an uncertain gain.
I'm not dismissing the growth-rate concern — it's genuinely worth acting on. My disagreement is narrower: I'd rather shorten his surveillance interval and confirm this growth rate is real and sustained before committing him to indefinite medication with a weaker evidence base than the one we're borrowing it from.
Both of these positions are defensible, and I think the actual resolution is in how we sequence them rather than picking one outright. A repeat surveillance scan in six months, rather than the usual annual interval, tells us within a reasonable timeframe whether 4.3-to-4.6 was a real accelerating trend or closer to measurement noise — and it should be done on the same modality, at the same level, measured the same way, since a good part of an apparent 0.3 cm change can come from comparing a root diameter obtained one way against one obtained another. If the growth rate is confirmed on that shorter interval, starting losartan — better tolerated than a beta-blocker and mechanistically plausible even outside Marfan — becomes a much better-justified decision than starting it today on two data points alone.
Agreed: surveillance interval shortened to six months rather than annual, home blood pressure monitoring started, and no medication started today.
Losartan starts at that point, on stronger evidence specific to his own trend rather than borrowed entirely from Marfan data.
Surveillance returns to a standard annual interval, and medical therapy is not started.
The decision either way will rest on his own confirmed trend, not on applying evidence from a different condition to two data points.