In the short run, P/E compression if the market doesn't think there is growth in the next year around 20-25%. Eventually the expansion into Japan and approval of further reimbursments for surgery other than Prostatectomy will increase earnings by 20-30% since the market in Japan should be 20-30% the size of the US. That alone will reduce the P/E into the ~20 range given the current stock price. A normal P/E surrogate is Growth plus 6. If you look over the long trends for ISRG this is a pretty good P/E indicator. Since the timing of the Japanese expansion is uncertain the domestic General surgery growth is what is currently supporting the ~33 P/E.
You won't find this growth P/E algorithm in any text books. I derived it from statistical best fit curves for dozens of medical companies growth vs P/E and used a 1st order best fit curve.
P/E(as a number) = Growth (percent times 100 as a number) + 6. This also seems to be applicable to other industries and companies as well. Try it out and see. When ISRG was growing as 80% year over year their P/E was ~85. Have fun.