I met Belinda Anderson at the SAR conference in Ann Arbor.  We both are interested in HRV as a potential biomarker for Acupuncture’s effectiveness and she authored this incredible paper.  I only had access to its abstract before, but here is a link to the article:

HRVarticle[1] Belinda Anderson

It is comprehensive, thoughtful and looks at HRV as having the potential to capture the effects of Acupuncture as a systems approach.