** Shares of healthcare conglomerate Johnson & Johnson JNJ.N down 1.9% at $248.91 premarket

** Q2 sales at JNJ's medical technology unit came in at $8.93 billion, below analysts' average estimate of $8.97 billion - LSEG-compiled data

** Co says unit's sales hurt by a drop in demand for its Impella heart pumps, following a U.K. study that raised questions about the use of the pumps during high-risk coronary procedures

** Reports Q2 adj. profit of $2.90 per share vs analysts' average estimate of $2.85 per share

** Q2 revenue of $25.31 billion beats analysts' average expectation of $25.05 billion

** JNJ attributes revenue to strong growth from immunology drug Tremfya and cancer blockbuster Darzalex

** Up to last close, stock up 22.7% YTD