US STOCKS-Wall St drops as earnings season begins on dour note
* Alcoa marks biggest percentage fall since 2011
* St. Jude falls after warning on battery flaw in heart device
* Apple at 10-month high after Samsung scraps Galaxy Note 7
* Indexes down: Dow 0.9 pct, S&P 1 pct, Nasdaq 1.27 pct (Updates to early afternoon)
By Yashaswini Swamynathan
Oct 11 (Reuters) - U.S. stocks tumbled on Tuesday, with the S&P 500 and the Nasdaq on track for their worst day in one month, after Alcoa kicked off the earnings season on a dour note.
Alcoa's shares fell nearly 11 percent, their worst day in five years after the aluminum producer reported quarterly revenue and profit that fell short of the market's expectation.
All major S&P 500 indexes were lower, with healthcare dropping to its lowest level since the post-Brexit selloff in late June.
Markets are likely to be more volatile as the earnings season turns the spotlight on valuations, while a tight race for the White House and a potential U.S. interest rate hike by the year-end add to the jitters. Continuación...