Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Volcano (VOLC), a company that makes precision-guided medical devices to aid in diagnosing coronary and peripheral vascular diseases, fell as much as 20% after updating its third-quarter, full-year, and 2014 revenue guidance below the current Wall Street consensus.

So what: According to Volcano's press release, the company delivered just a 2.2% increase in sales for the third quarter to $95.8 million. Volcano's management notes that while its intravascular imaging and fractional flow reserve segments performed well, a negative foreign exchange impact of $5.4 million and weak PCI sales in the U.S. hurt its results. Wall Street had expected $97.1 million in sales this quarter. For the full year, Volcano pitted its forecast at $391 million to $395 million, which is also below the $398.7 million that analysts expected. Finally, as icing on the cake, Volcano projected revenue growth of 9% to 11% in fiscal 2014, which at the midpoint of its 2013 guidance would be $428 million to $436 million -- also below the $442 million the Street was looking for. On the heels of this update, JPMorgan Chase, Credit Suisse and Canaccord Genuity all downgraded Volcano.

Now what: I'm in both a forgiving and unforgiving mood given today's revenue update. On one hand, I can understand that Volcano has little control over its foreign exchange pressures, and I'm willing to absolve its third-quarter miss on that accord. However, weakness in product sales in the U.S. moving forward is a completely different story when the company is essentially hugging the profitability flat-line. This is a case where the products are certainly exciting, and I can see Obamacare potentially leading to more preventative treatments that incorporate Volcano's tools; but the promise hasn't translated into consistent profits. Until such time as that happens, I'd simply prefer to stick to the sidelines.