Caristo Diagnostics built a heart test for the patients a heart scan sends home. That was the product decision. Everything the company has done since follows from it.
On July 29 the FDA granted De Novo authorization to CaRi-Heart, software that reads coronary inflammation off a routine CT angiogram. The scan is one the cardiologist already ordered. CaRi-Heart measures the fat around the coronary arteries, scores the inflammation there, and returns an estimate of the patient's risk of dying from cardiovascular disease over the next ten years. Caristo, an Oxford spinout, plans to start selling it in the United States this quarter.
The market was the negative result
Coronary CT angiography is good at finding blockages. A patient turns up with chest pain, gets scanned, the radiologist finds no obstructive disease, and the patient goes home reassured.
Caristo's validation data has something to say about that group. In a UK study of more than 40,000 patients scanned at eight hospitals, published in The Lancet and followed for a median of 2.7 years, the patients with no obstructive coronary artery disease accounted for two-thirds of the major adverse cardiac events and two-thirds of the cardiac deaths.
There are two products sitting in that finding. One is a better blockage reader, and that shelf is crowded. HeartFlow cleared an updated plaque analysis platform last September, and Caristo's own CaRi-Plaque, cleared in 2025, handles plaque and stenosis. The other product is a test for the people the blockage reader clears. Nothing on the market did that, which is why there was no predicate to point at and why the file went in as a De Novo.
The billing codes were live in January
The American Medical Association gave CaRi-Heart two Category III CPT codes, 0992T and 0993T, effective January 1, 2026. The authorization came through on July 29. The billing path was in place close to seven months before the product could legally be sold here.
Category III codes are tracking codes. No payer is obligated to pay against them, and plenty of them expire without ever converting to Category I. What they do is give the claim somewhere to go. An imaging center running the test next month has a number to put on the form, and the volume that number collects is the evidence any future Category I application will stand on.
I push clients toward that sequence and it is reliably the least popular thing I say in the room. Engineering wants to finish the device. The regulatory consultant wants the submission in. Pulling the CFO and a coding specialist into a product meeting feels early to everyone except the person who has watched a cleared product sit on a shelf because nobody could work out how a hospital would bill for it.
What the De Novo bought
Founders hear De Novo and think slow lane. It is more work. It is also a signal, and the signal is decent news: the FDA routes you there when it considers your device moderate risk and inside the boundaries it is prepared to accept. A high-risk device is already in a PMA.
At Galen we got that signal in a pre-submission response and took the hint. At the very end of the process the FDA asked us what the new regulation should say, because there was nothing in the CFR describing what we had built. We wrote a paragraph we liked and sent it over as a PDF. They asked for it in Word. A day or two later the clearance arrived, and the regulation describing our device was word for word what we had sent them.
Caristo holds that position now for measuring coronary inflammation on CT. Anyone who wants to sell into that category has to be substantially equivalent to Caristo. That is worth having. It is worth a good deal more when there are codes to bill against and a launch already scheduled behind it.
The authorization is the last thing that happened at Caristo, not the first. Someone decided the market was the patients whose scan comes back clean, and the study population, the claim, and the billing codes all followed from that one sentence. That call belongs to whoever owns the product. If a regulatory consultant is making it at your company, the wrong person is holding the pen.
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Dave Saunders is the founder of Base Reality Group and a Fractional CPO for product companies. He was a founder and operator at Galen Robotics, where the surgical-robotics platform earned FDA De Novo authorization in 2023, and he managed a 35-patent portfolio licensed from Johns Hopkins. He wrote Founders Who Finish and publishes The Build. More about Dave →