, Rohit Arora3, 4, Nicholas L. DePace5 and Aaron I. Vinik6
(1)
Autonomic Laboratory Department of Cardiology, Drexel University College of Medicine, Philadelphia, PA, USA
(2)
ANSAR Medical Technologies, Inc., Philadelphia, PA, USA
(3)
Department of Medicine, Captain James A. Lovell Federal Health Care Center, North Chicago, IL, USA
(4)
Department of Cardiology, The Chicago Medical School, North Chicago, IL, USA
(5)
Department of Cardiology, Hahnemann Hospital Drexel University College of Medicine, Philadelphia, PA, USA
(6)
Department of Medicine, Eastern Virginia Medical School Strelitz Diabetes Research Center, Norfolk, VA, USA
Sample Normals: Trends Plots
The following plots (Figs. 10.1 and 10.2) demonstrate normal P&S monitoring responses. Depicted are the trend plots from MPGRs. The plots present activity level in terms of P&S activity measures (bpm2, blue and red, respectively) on the ordinate and time on the abscissa. The vertical broken lines delineate the six phases of the test, from “A” initial (resting) baseline to “F” standing (see Table 10.1). The first plot in the series (Fig. 10.1, top graph) is from a 7-year-old child. Notice the higher level of resting autonomic activity and general parasympathetic activity throughout the test. This is associated with development and parasympathetically mediated increased metabolism supporting the pediatrics’ growth and development rate. This elevated parasympathetic activity continues into the adolescent years (Fig. 10.1, second graph from the top) and seems to resolve during the “transition” years around age 21 (Fig. 10.1, bottom two graphs), about the time when growth and development stops. At that time, the subject’s ANS settles into the more adult-like level of activity (see Fig. 10.2). For example, the two graphs labeled “Transition Years” (see Fig. 10.1, bottom two graphs) are plots from 19 to 21 years old. As it turns out, the upper graph is from the 21 years old and looks more like the pediatric, whereas the trend plot from the 19 years old looks more like an adult’s. Everyone ages at a different rate.
Fig. 10.1
Sample normals, ages 7 through 21
Fig. 10.2
Sample normals, ages 34 through 93
Table 10.1
(Table 6.1, repeated for convenience) The durations, in minutes, of each phase of the Autonomic Assessment
Event | Duration | |
|---|---|---|
A | Rest (initial baseline) | 5:00 |
B | Deep breathing | 1:00 |
C | Baseline | 1:00 |
D | Valsalva | 1:35 |
E | Baseline | 2:00 |
F | Head-up postural change (stand) | 5:00 |
The next series of plots (Fig. 10.2) are from normal adult subjects and from normal geriatric subjects (e.g., no diabetes, hypertension, heart, renal, or pulmonary disease). It is obvious that the 93-year-old subject (Fig. 10.2, bottom graph) has severely depleted P&S function. However, when compared against age-matched normals, the results are normal, and this patient does not have symptoms of diabetes, hypertension, or heart or pulmonary disease. This helps to confirm the fact that all will experience advanced autonomic dysfunction and CAN. It is a fact of life.
Sample Normals: Response Plots
The P&S values presented in the baseline, DB, Valsalva, and stand response plots are the averages of the respective segments of the trend plot, over the time frame of that section of the trend plot (see Table 10.1).
Resting, Initial, Baseline
The baseline response plot (Fig. 10.3) presents resting sympathetic activity on the abscissa and resting parasympathetic activity on the ordinate. The gray area indicates normal P&S responses. The diagonal broken line indicates perfect balance (SB = 1.0). The area between the two solid diagonal lines, including the gray area and the broken diagonal line, indicates normal SB (notice normal balance is possible regardless of the absolute P&S values). The normal resting P&S ranges (RFa and LFa, respectively) for adults are from 1.0 to 10.0 bpm2. The borderline range is from 0.5 to 1.0 bpm2. For pediatrics the corresponding normal ranges for both RFa and LFa are from 2.0 to 15.0 bpm2. The normal range for SB (LFa/RFa, unitless) is 0.4 < SB < 3.0. This may be refined further based on recommendations within the clinical literature. As discussed above, the geriatric cardiology literature recommends low-normal SB (0.4 < SB < 1.0). For younger adults high-normal SB (1.0 < SB < 3.0) is associated with lower rates of morbidity, including depression.
Fig. 10.3
The resting (baseline) response plot template
Deep Breathing and Valsalva Challenges
The normal ranges for the DB and Valsalva challenge responses are age adjusted (see Fig. 10.4) [1]. The abscissa for both plots is age. The ordinate for the DB response plot is parasympathetic activity (RFa, bpm2). The ordinate for the Valsalva response plot is sympathetic activity (LFa, bpm2). If the value plotted on these graphs is preceded by “x,” this indicates that the response was also baseline adjusted. The gray areas of these two graphs are based on published clinical data that assume normal resting baseline results.
