You might be surprised by three of the hottest healthcare stocks on the market right now. They're not big biotechs. They're not household names.

Edwards Lifesciences (NYSE:EW), Zimmer Biomet Holdings (NYSE:ZBH), and Zoetis (NYSE:ZTS) recently hit all-time highs. What's driving these healthcare stocks -- and are they smart picks to buy right now?

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1. Edwards Lifesciences

Edwards Lifesciences ranks as one of the 10 biggest medical device stocks on the market. The company develops transcatheter aortic valve replacement (TAVR), surgical structural heart, critical care, and transcatheter mitral and tricuspid therapies. And Edwards is getting even bigger: Its stock has jumped more than 40% so far this year.

TAVR is the main driver of Edwards' success this year. The company launched its new Sapien 3 Ultra heart valve in Europe. Edwards Lifesciences CEO Michael Mussallem said in the company's second-quarter conference call that he expects Sapien 3 Ultra will generate the majority of its TAVR sales in Europe by the end of 2019.

Edwards also recently won Food and Drug Administration (FDA) approval for Sapien 3 Ultra in the U.S. The company's U.S. TAVR procedures are already growing by mid-teen percentages. That number could be boosted by Edwards' new device.

2. Zimmer Biomet

Zimmer Biomet is enjoying one of its best years ever so far in 2019 with shares up over 30% year to date. The company develops and markets a variety of products used in orthopedic reconstruction, sports medicine, trauma treatment, dental implants, and more.

The stock received a big boost from Zimmer Biomet's better-than-expected second-quarter results. The company also put to rest speculation that it might pull back from its full-year guidance after former CFO Dan Florin announced that he was stepping down. Zimmer Biomet CEO Bryan Hanson cleared up any concerns during the company's Q2 conference call.

Instead of lowering its guidance, the company expressed increasing optimism. Zimmer Biomet previously projected that it would achieve constant-currency revenue in line with its weighted-average market growth rate beginning in 2020. But the company's turnaround has gone so well that it thinks the goal will be achieved beginning next quarter. This higher level of confidence in Zimmer Biomet's future has investors coming off the sidelines.

3. Zoetis

Like Edwards Lifesciences, Zoetis stock has soared more than 40% so far in 2019. The company ranks as the leader in the animal health industry, marketing products worldwide for livestock and companion animals.

A major key to Zoetis' success this year has been to consistently beat Wall Street earnings expectations. In the second quarter, for example, the company topped analysts' earnings estimates by nearly 10%. Zoetis' companion animals segment performed especially well in Q2, with year-over-year operational sales growth of 22%.

But Zoetis' track record hasn't only been impressive this year. Since the company was spun off from Pfizer in 2013, it has delivered steady financial results. Zoetis CEO Juan Ramon Alaix said in the company's Q2 conference call that this solid performance stemmed from Zoetis consistently growing its revenue faster than the market while it grew its adjusted net income faster than revenue -- year in and year out.

Are they buys?

Despite Zimmer Biomet's improvement demonstrated this year, I'm not enthusiastic about the stock. It's encouraging that the company's turnaround appears to be on track, but my view is that Zimmer Biomet doesn't offer enough sizzle for growth-oriented investors and its dividend yield is too low to be attractive to investors who prefer buying dividend stocks.

Zoetis is delivering stronger growth than Zimmer Biomet. I think that the animal health company's future looks bright as the middle classes expand in developing nations, driving higher demand for meat products and increasing pet ownership. However, my main concern with Zoetis as an investing alternative is that its valuation already reflects tremendous expectations for growth. 

I'm tempted to echo the sentiments for Zoetis when it comes to Edwards Lifesciences. But I'm really bullish about the prospects for the company's Sapien 3 Ultra heart valve. Although Edwards Lifesciences stock is valued at a premium, I think it's worth consideration for long-term growth investors.