cardiovascular autonomic neuropathy (CAN)
Last edited 09/2018
Cardiac autonomic neuropathy (CAN) is the impairment of cardiovascular autonomic control in the setting of diabetes after exclusion of other causes.
- there have been recommended five simple tests, the cardiac autonomic reflex
tests, to establish the diagnosis (1):
- 1) heart rate variability (HRV) with deep breathing
- 2) HRV lying to standing
- 3) the Valsalva manoeuvre;
- 4) postural fall in blood pressure; and
- 5) blood pressure response to sustained handgrip
- a single abnormal test may indicate early CAN, and three positive tests
are recommended for a definitive diagnosis (1,2)
- prevalence data are highly dependent on the diagnostic criteria, type of
tests and normative data sets used, age, and gender
- rates are reported as high as 35% in type 1 DM and 44% in type 2 DM,
with a prevalence rate of up to 60% in longstanding diabetics (3)
- rates are reported as high as 35% in type 1 DM and 44% in type 2 DM,
with a prevalence rate of up to 60% in longstanding diabetics (3)
- association with increased mortality risk
- older studies have shown 5-year mortality rates as high as 16-50 % in T1DM and T2DM, with a high proportion attributed to sudden cardiac death (4,5)
- more recently published meta-analysis included 2,900 subjects with diabetes
reported a pooled relative risk of mortality of 3.45 (95 % CI, 2.66-4.47)
in patients with CAN (6)
- progression of CAN usually begins with parasympathetic denervation, followed
by sympathetic tone enhancement and eventually sympathetic denervation
- resting tachycardia is often the presenting sign (ranging from 100
to 130 bpm)
- as CAN progresses in severity then there is a decrease in heart rate
- baroreflex sensitivity
- in subclinical CAN will initially have abnormalities in HRV - this is then followed by changes in baroreflex sensitivity (1)
- in advanced CAN, orthostasis will result secondary to sympathetic denervation along with impaired baroreflex sensitivity and decreased noradrenaline response to change in posture
- resting tachycardia is often the presenting sign (ranging from 100
to 130 bpm)
Management:
- seek expert advice
- weight loss in obese diabeticss and aerobic exercise for patients with both type 1 and type 2 DM has been shown to improve HRV and cardiac autonomic functionality (1,2)
- early and comprehensive glycaemic control is believed to help prevent diabetic complications and potentially reverse CAN symptoms (1,2)
- pharmaceutical management of HRV is controversial - there is no definitive
treatment - agents considered include beta blockers, digoxin, verapamil
and ACE inhibitors
- treatment of orthostatic hypotension is required in general only when patients are symptomatic
Reference:
- Ewing DJ et al. The value of cardiovascular autonomic function tests: 10 years experience in diabetes. Diabetes Care 1985; 8 (5):491-498.
- Dimitropoulos G, Tahrani AA, Stevens MJ. Cardiac autonomic neuropathy in patients with diabetes mellitus. World J Diabetes 2014; 5 (1):17-39.
- Pop-Busui R. What do we know and we do not know about cardiovascular autonomic neuropathy in diabetes? J Cardiovasc Transl Res 2012; 5: 463-468.
- Navarro X, Kennedy WR, Sutherland DE. Autonomic neuropathy and survival in diabetes mellitus: effects of pancreas transplantation. Diabetologia. 1991; 34(Suppl 1):S108-S112.
- Ewing DJ, Campbell IW, Clarke BF. Assessment of cardiovascular effects in diabetic autonomic neuropathy and prognostic implications. Annals of Internal Medicine. 1980; 92:308-311.
- Maser RE, Mitchell BD, Vinik AI, Freeman R. The association between cardiovascular autonomic neuropathy and mortality in individuals with diabetes: a meta-analysis. Diabetes Care. 2003; 26:1895-1901