Improved Patient Outcomes by Normalizing Sympathovagal Balance: Midodrine and Parasympathetic and Sympathetic Monitoring
Abstract
Nicholas L DePace, Aaron I Vinik, Cesar R Acosta, Jeysel M Pinales, Michael Yayac, Joseph Colombo
A function of the Parasympathetic and Sympathetic (P&S) nervous systems is to maintain proper tissue perfusion, including of the heart and brain upon head-up postural change standing. Orthostatic dysfunction (OD) is associated with pooling of blood in the lower extremities, insufficient vascular support of the heart, and poor brain perfusion. Abnormal P&S responses to standing help to guide therapy for the individual patient. Midodrine is often the primary recommendation to correct P&S dysfunction upon standing. P&S Monitoring (Physio PS, Inc, Atlanta, GA) differentiates OD-subtypes in 2727 cardiology patients, serially tested. P&S Monitoring non-invasively, independently, and simultaneously measures P&S activity, including the normal P-decrease followed by an S-increase with head-up postural change (standing). S-Withdrawal (SW) and P-Excess (PE) are two types of autonomic dysfunction that are associated with OD. SW differentiates OD from Syncope (an S- excess with stand, e.g. Vasovagal Syncope). PE often masks SW by inflating the S-response to stand. OD based solely on BP and HR responses to provocation remains difficult to differentiate, especially early in its development and difficult to track upon follow-up. The latter is important to ensure relief of not only the abnormal BP response to stand (e.g. Orthostatic Hypotension) or HR (e.g. Postural Orthostatic Tachycardia Syndrome) but the SW or PE as well. SW underlies the majority of Dysautonomia patients with lightheadedness (whether masked or not, 82.0%, p=0.0061). Midodrine relieves SW and ultimately Lightheadedness and associated symptoms within 9 months (75.4%, p=0.0323). P&S Monitoring provides more information, enabling earlier and more specific diagnosis and therapy for improved patient outcomes. P&S dysfunction upon standing may be most well relieved by very low doses of oral vasoactive medications such as Midodrine (Proamatine), Mestinon (Pyridostigmine), or Northera (Droxidopa). In this study we focus on Midodrine.