Stealthy Sympara Medical quietly secured $5.5 million in funding from a handful of investors for the hypertension device it’s developing.

San Francisco-based Sympara disclosed the funding in a regulatory filing, after recording $4.3 million with the SEC in 2013.

Sympara is led by CEO and chief science officer Kevin Ehrenreich, who spent more than 5 years with Abbott (NYSE:ABT) including as an advisor for new business ventures in devices and imaging, before founding Sympara in 2011.

Longitude Capital lists Sympara as a portfolio company; Versant Ventures partner Ross Jaffe lists Sympara among the startup boards on which he sits, but Versant does not list Sympara in its own portfolio.

In a patent filing, Sympara describes its device as being positioned near a dermal bone to selectively activate baroreceptors or nerves to reduce blood pressure and alter the sympathetic nervous system.