Assessment of the cardiovascular and gastrointestinal autonomic complications of diabetes

Table 1 Toronto classification of diabetic sensory neuropathy[5]

Definition of minimal criteria for diabetic sensorimotor polyneuropathy	Clinical features
Possible	Reduced sensation, positive neuropathic sensory symptoms (burning pain in the distal lower extremities), symmetrical reduction in distal sensation and/unequivocally decreased or absent ankle reflexes
Probable	A combination of two or more of the following: Neuropathic symptoms, decreased distal sensation, or unequivocally decreased or absent ankle reflexes
Confirmed	Decreased nerve conduction on objective testing with signs and symptoms as above
Subclinical	Decreased nerve conduction on objective testing in the absence of signs or symptoms

Table 2 Time domain analysis variables and their physiological relevance

Variable (units)	Description	Physiological relevance
SDNN (ms)	Standard deviation of the normal RR (NN) interval reflecting all of the cyclic components responsible for variability in the period of recording	An overall estimate of HRV, but does not indicate the contribution of any particular influence
SDANN (ms)	Standard deviation of the averages of NN intervals calculated over a short period of time, usually less than five minutes	Reflects the influence of circadian rhythms on autonomic function
pNN50 (%)	The proportion of NN intervals having a difference of > 50 ms	Reflects predominant vagal influence on variability
Triangular index (ms)	The integration of the density distribution of all the NN intervals as a function of the maximum density	Overall estimate of HRV similar to SDNN
RMSSD (m/s)	The square root of the means squared differences in successive NN intervals	Estimate of the short-term components of HRV

SDNN: Standard deviation of normal-to-normal; NN: Normal-to-normal; HRV: Heart rate variability.

Table 3 A comparison of the various contemporaneous techniques for the measurement of gastrointestinal motility[43]

Technique	Area of the GI tract evaluated	Length of stay required in clinic/office	Acceptability to the patient	Radiation exposure	Physiological conditions of measurement	Standardization of test	Measurement of propagating contractions	Availability/expense of test	Ease of interpretation of the result
Gastric emptying scintigraphy	Stomach	c.5 h	High	Yes	Yes	No	No	Widely/moderately expensive	Moderate
Whole gut scintigraphy	Pan-GI	c.8 h	High	Yes	Yes	Yes	No	Very limited/very expensive	Difficult
Radio - opaque marker study	Stomach colon	30 min to	High	Yes	Yes	No	No	Widely/inexpensive	Easy
13C octanoic acid breath test	Stomach	c.4 h	High	No	Yes	Yes	No	Very limited/inexpensive	Relatively easy
Wireless motility capsule	Pan-GI	c.30 min	High	None	Yes	Yes	No	Limited/currently moderately expensive	Relatively easy

GI: Gastrointestinal.