Starting Aortic Root Prophylaxis in Marfan Syndrome: Losartan or Atenolol First
A single patient whose aortic root has just crossed the threshold his own care team set years ago for starting prophylactic therapy, with two drugs shown to work about equally well and a whole adult life ahead of him to actually take one of them.
T.K., a 24-year-old man, works as a paralegal at a mid-sized law firm, a job he took right out of college and has held steadily since. He was diagnosed with Marfan syndrome at sixteen, after a pediatrician noted his tall stature and unusually long fingers during a routine physical and connected it to his mother's own confirmed diagnosis — a family history that meant his own diagnosis, once suspected, was quickly confirmed rather than a prolonged diagnostic search.
His aortic root has been tracked by annual echocardiogram ever since, and this year's measurement, 4.3cm, crosses the size threshold his pediatric cardiologist had set years ago as the trigger for starting prophylactic therapy — a threshold reached now for the first time, not something that's been hovering near the line for years. He has no history of aortic dissection, no significant mitral valve prolapse, and no lens dislocation. He is, in every other respect, a healthy 24-year-old, which is part of what makes the decision in front of the team feel consequential: whatever he starts today, he is likely to be taking for decades.
Atenolol's protective effect comes from reducing the mechanical stress on the aortic wall through lowered heart rate and contractility, the original and longest-studied approach to slowing Marfan-related root growth. That comparison comes from a trial of 608 patients aged six months to twenty-five years, mean age near eleven — he sits at the top of its range, not in its center. Losartan works through an entirely different mechanism, blocking angiotensin II receptors in a way thought to reduce excess TGF-beta signaling — the pathway Marfan's underlying fibrillin-1 mutation is believed to dysregulate — which was the specific rationale that generated real enthusiasm that losartan might outperform atenolol rather than just match it.
Two drugs, comparable data, a multi-decade decision
I'd start atenolol first. It has the longer track record in Marfan — not just growth-rate data, but a small randomized trial from the 1990s reporting fewer clinical endpoints, which is much of why beta-blockade became the default. Losartan's growth-rate data from the largest dedicated trial is genuinely comparable, I'm not disputing that. But I'd rather start from the drug the field has the most accumulated experience with, thin as the hard outcomes evidence is for either of them.
I'd start with losartan instead, precisely because the efficacy is comparable and the tolerability isn't. That trial wasn't designed to settle tolerability and didn't report an advantage either way, so I'm arguing from the drug classes rather than from its results — fatigue and exercise intolerance are real, common complaints with beta-blockade, and for a 24-year-old who's otherwise healthy and active, that's not a minor side note. If two drugs reduce root growth about equally well, I'd rather start with the one he's more likely to actually keep taking without resenting it.
I'm not arguing atenolol's outcomes evidence doesn't matter — I'm arguing that evidence doesn't help him if tolerability problems mean adherence quietly erodes over the years that evidence is supposed to cover.
The adherence point is the one I'd weight most heavily, precisely because of the time horizon here. A tolerability difference that looks modest across a several-year trial can compound very differently across several decades of daily use, and this is a drug he'll be taking essentially for the rest of his life. I'd start with losartan, hold atenolol in reserve as an add-on if growth isn't adequately controlled, and revisit this as many times as his imaging gives us reason to.
Started on losartan today. Annual echocardiographic surveillance continues, with atenolol addition or combination therapy planned if his root growth rate isn't adequately slowed by next year's imaging.
It continues as monotherapy, with atenolol held in reserve rather than added preemptively.
Atenolol is added on top rather than substituted, moving toward the combination approach.
The cardiologist's preference for atenolol's longer track record was never actually refuted — the team simply judged that, for a 24-year-old facing decades of daily therapy, a comparable-efficacy drug he's more likely to tolerate was worth trying first, with the more established option always available if it doesn't hold up.