Heartflow Holding Inc. is aiming to bring its noninvasive, artificial intelligence (AI)-based test for coronary heart disease to more doctors and patients via a merger with Longview Acquisition Corp. II. The deal, valued at an enterprise value of about $2.4 billion, is the latest in a steady stream of med techs queueing up to go public via a “blank check” special purpose acquisition company (SPAC) this year.