The following are sample studies that attempt to answer the questions: “Why test?” “How to intervene?” “What are the expected outcomes?”

Why autonomic testing for a diabetic? Autonomic function testing is recommended for diabetics. True. “But,” you say, “they do not feel anything until neuropathy presents, then it is “too late.” You are absolutely correct … until now.

Autonomic dysfunction, while still asymptomatic, can now be detected long before neuropathy presents (see Fig. 31.1) [1, 2]. Early autonomic decline is asymptomatic. As seen in Fig. 31.1, the initial decline may steal over 80 % of a patients function before first presentation. The reduced rate of decline is associated with clinical intervention. However, this intervention is typically not associated with autonomic dysfunction! A typical first intervention is for GERD or some GI upset – not autonomic dysfunction. So, eventually, the diabetes again overtakes the patient and autonomic function falls below normal levels. Then diabetic autonomic neuropathy (DAN, once both P and S are below the neuropathy threshold) presents quickly followed by cardiac autonomic neuropathy (CAN, once parasympathetic activity is lower than sympathetic activity). This supports the rationale behind early and frequent autonomic function testing as recommended by the ADA [3] and ACCE [4]. For example, for a type 2 diabetic, autonomic function testing is recommended within two years of diagnosis. For it is known that at the time of diagnosis, the average patient diagnosed with type 2 diabetes has had diabetes for 5 years. Add two more years to that and the diseases has been damaging the patient for 7 years. Figure 31.1 suggests that in 7 years, nearly half of the patient’s normal autonomic function has been taken by the disease.

The case study presented in Fig. 31.2 is from an endocrinology practice and is of a 63-year-old, 6′1″, 225#, male, type 2 diabetic patient also diagnosed with hypertension and prescribed with Zocor. The patient is reported to have difficult-to-control blood glucose but volunteers no other symptoms. He associates his fatigue, exercise intolerance, pallor, loss of appetite, GI upset, sleep difficulties, frequent headache, and cognitive disturbance with his age. However, he reports that these symptoms only started happening since his last birthday. Prior to the first test, patient is highly noncompliant, denying that the diabetes is affecting him. He has been diagnosed with CAN by his physician.

The serial testing (Fig. 31.2) is shown from top to bottom. On the left are the trend plots showing P&S activity (blue and red, respectively) for the six phases of the clinical study: from left to right, the sections are rest, deep breathing, baseline, Valsalva challenge, and standing (see Chap. 5). The first trend plot confirms the poor control, and from the corresponding table, sympathetic withdrawal (SW, circle in the LFa column) upon standing is demonstrated, a sympathetic decrease from 0.87 at rest to 0.79 bpm² with standing. SW contributes to high BP and is associated with fatigue and exercise intolerance. Valsalva parasympathetic excess (PE, circle in RFa column) is also demonstrated, a parasympathetic increase from 0.38 to 1.11 bpm² with Valsalva. PE is associated with the remainder of his reported symptoms. Based on his first Autonomic Assessment (with P&S monitoring), he was diagnosed with DAN and continued high BP (resting BP = 179/80), and 6.25 mg carvedilol was introduced.

His second assessment was 3 months later. His symptoms were reported to have been reduced, with little change in his resting BP, and some signs of normalized responses to challenge. His SW is reversed, but his PE persists. This was determined to be a work in progress based primarily on the reduction in reported symptoms and reversal of SW. Therefore, no change in therapy was ordered. His third P&S assessment is presented at the bottom of Fig. 31.2. This appears to be as rather normal response plot for a 63-year-old. His SW remains reversed; his resting BP is reduced to 152/84. While his PE persists, there are no associated symptoms, including difficult-to-control BP or blood glucose. PE tends to take longer to correct. This continues to be a work in progress, as his SB (now 4.57) is still high. He was prescribed Avapro (an ARB) to further reduce his resting BP as well as his resting sympathetic activity to normalize his SB. He is scheduled for follow-up testing in 3 months. The current goal is to reduce his resting sympathetic activity to establish and maintain low-normal SB to minimize morbidity and mortality risk.

The next two patients presented (see Fig. 31.3) are also diagnosed with type 2 diabetes and show the difference between a highly compliant patient and a noncompliant patient. The patients are from a family practitioner. The former is a 54-year-old, 6′3″, 282 lb male at the time of the test and had been diagnosed with diabetes for more than 25 years (upper trend plot and data table in Fig. 31.3). The latter is a 41-year-old, 5′11″, 193 lb male at the time of the test and had been diagnosed with diabetes for only 5 years. Both are presenting for a regular checkup and are ordered to sit for their first Autonomic Assessment.

At rest, the 54-year-old (upper row of data) demonstrates low P&S activity indicating DAN, with elevated resting BP. DAN may be normal for his age. However, given his normal SB and normal autonomic responses to challenge, he seems well maintained. He demonstrates a 6/13 mmHg drop in BP upon standing. A drop in BP upon standing with normal autonomic responses suggests that the possible orthostasis does not have an autonomic component, consider a vascular study to further diagnose. This patient is not reporting any symptoms, including symptoms of orthostasis. He is considered by his physician to be well managed.

At rest, the 41-year-old demonstrates normal autonomic HR and BP responses, confirming the reports of normal from his physician based on the office physical, yet he is difficult to control. He demonstrates a low DB response indicating autonomic dysfunction. His P&S Valsalva responses are borderline high, indicating SE (a beta-adrenergic response) and PE. Upon standing, he demonstrates PE. Stand PE masks SW as well as contributes to the symptoms of PE [5]. The SW is associated with the 16/9 mmHg drop in BP upon standing.

By comparing these two patients at rest, the importance of “physiologic” age as measured through P&S monitoring is demonstrated versus “chronologic” age. The chronologically older patient (diagnosed with diabetes for over 25 years) demonstrates abnormal resting responses, yet he is well maintained and looks healthy and fit. The chronologically younger patient (diagnosed with diabetes for only 5 years) demonstrates normal resting response, yet he is poorly controlled and has numerous, significant problems. P&S monitoring during challenge “completes the picture” and provides evidence of underlying pathology.

Hypertension is a BP issue. Why monitor the ANS? There are many reasons.