Why Is Heartflow (HTFL) Stock Up? Guidance Went From 24% To 42%

TL;DR

• Heartflow traded at $38.10, up 22.86%, at 5:43am ET Friday, against Thursday's $31.01 close, per stockanalysis.com. Investing.com had $38.44, up 23.96%, at 5:56am, off the same close. Both are premarket prints on thin volume, not a session.
• Q2 revenue was $64.1 million, up 48%, against roughly $56.6 million expected. Non-GAAP loss per share came in at $0.07 against the $0.19 the Street had.
• The raise is worth more than the beat. Full-year guidance went to $246-250 million from $228-232 million, an $18 million lift at the midpoint on a quarter that beat by about $7.5 million.
• Five months ago this company guided 2026 to 24-26% growth. It now guides 40-42%. 2025 grew 40%. The slowdown management forecast in March has been taken back in full.
• Non-GAAP gross margin hit 83.3%, up from 75.5%. Operating expenses still ran 111% of revenue, so the growth is real and the profits are not here yet.

The Board

The same company, five months apart, describing two different years.

Why Is Heartflow Stock Up?

Heartflow beat its second quarter and then raised full-year revenue guidance by $18 million, more than twice the size of the beat. That is the whole move. The numbers came out after Thursday's close, Investing.com had the stock up 16.1% at about $36 in extended trade, and it has kept going overnight.

Heartflow sells AI analysis of coronary CT scans. Its original product, FFRCT, works out whether a narrowed artery is actually restricting blood flow, which is the question that otherwise sends a patient to an invasive catheter lab. Its newer one, Plaque Analysis, quantifies what the plaque is made of. The company listed on the Nasdaq at $19.00 a share in August 2025, raising $364.2 million gross.

The Raise Is Bigger Than The Beat

Work the arithmetic and the guide does something the headline does not show.

Consensus wanted about $56.6 million of revenue. Heartflow reported $64.1 million. Call that a $7.5 million beat. If management had simply let that flow through to the year and changed nothing else, the full-year midpoint would have gone from $230 million to about $237.5 million.

Instead it went to $248 million. So roughly $10.5 million of the raise refers to quarters that have not happened yet.

24%, Then 32%, Then 42%

Here is the sequence, all of it against a 2025 base of $176.0 million:

• March 18, with the 2025 results: $218-222 million, described as 24-26% growth. Against $176.0 million that is +23.9% to +26.1%. It checks.
• May 14, with Q1: $228-232 million, 29-32%. That is +29.5% to +31.8%. It checks.
• August 13, with Q2: $246-250 million, 40-42%. That is +39.8% to +42.0%. It checks.

2025 itself grew 40%, to $176.0 million from roughly $126 million. So the March guide told the market that Heartflow's growth rate was about to be cut nearly in half, and the August guide says it will not decelerate by a single point. Five months, same management, same year.

I read that as a company that set a beatable number in March and has spent two quarters walking it back up. That is a normal thing for a first-full-year public company to do, and it is not a criticism, but it does change what the third raise would be worth. The guide has been lifted twice already, and it no longer has room to be modest twice more.

What The Back Half Actually Assumes

This is where I would push back on the enthusiasm.

First half revenue was $116.7 million: $52.6 million in Q1, $64.1 million in Q2. Subtract that from the new guide and the implied second half is $129.3 million to $133.3 million, which is 10.8% to 14.2% above the first half.

Now compare that with what just happened. Q2 was 21.9% above Q1 on its own. The guide therefore has the back half growing sequentially at roughly half the pace the business just managed in a single quarter.

Two readings. Either the FFRCT and Plaque ramp genuinely flattens from here, or this is the third conservative number in five months and it gets raised again in November. I lean toward the second, because the pattern is right there in the guidance history, but I would hold that view loosely: a 48% quarter is a hard comparison to lap, and the international line grew 12% against the US line's 51%. International is only $4.5 million of the $64.1 million, so it barely moves the total, and it is also the part of the business that is not working yet.

The margin guide carries the same shape. Q2 delivered 83.3% non-GAAP gross margin, and the full year is guided to about 82%. Given 82.0% in the first half, the guide implies the second half comes in flat rather than building on Q2.

The Cost Line Is Not Fixed Yet

The margin story is genuine. Non-GAAP gross margin went from 75.5% to 83.3%, 7.8 points in a year, on volume leverage over what is essentially a software business running on scanned images.

What it has not yet paid for is the rest of the company. Operating expenses were $71.1 million against $53.2 million of gross profit, which is where the $17.9 million GAAP operating loss comes from, and 111% of revenue. Strip out stock compensation and the other non-GAAP adjustments and the operating loss is $7.9 million, with adjusted EBITDA at negative $6.7 million. Net loss was $15.7 million, or $0.18 a share.

Against $246.8 million of cash and investments at June 30, none of that is a solvency question. At the current non-GAAP burn the balance sheet lasts years, and interest income on the cash pile is itself covering a couple of million a quarter of the gap. The question is not survival, it is how much revenue this thing needs before the operating line crosses zero on a GAAP basis, and the release does not answer it.

What The Price Assumes

At $38.44, on 86.24 million shares, Heartflow is worth about $3.32 billion. Against the midpoint of the guide it just raised, that is 13.4 times 2026 revenue for a business that does not yet make money on any measure.

That multiple is defensible for 40% growth at an 83% gross margin, and it is also the entire bull case in one number, so there is no cushion in it. The premarket sits within about 7% of the $41.22 52-week high and at roughly double the $19.00 IPO price a year ago. Anyone buying here is paying for the November raise before it exists.

My view: the business is better than the March guide implied and the stock is no longer cheap enough to be an easy call. If the third raise lands in November, this holds. If the back half comes in at the guide instead of above it, 13.4 times revenue is where the argument starts.

One gap I could not close: the release quotes higher US FFRCT and Plaque case volumes but the version I could reach does not break out Plaque Analysis revenue for the quarter. At Q1 the company put the 2026 Plaque outlook at $19-21 million. I could not source an updated figure, so I am leaving it out of the arithmetic above rather than estimating it.

For other guidance-raise movers this week, see Eton Pharmaceuticals, and for how recent listings have fared, SunScout's post-IPO break. Friday's macro slate is in the retail sales timetable, and next week's reporters are in the earnings calendar.

The One-Line Read

In March, Heartflow guided 2026 growth down to 24%. It now guides 42%, the same pace as last year. The stock is near its high on a guide whose back half still looks deliberately light.