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Cardio Diabetes Medicine 2017 109

Microneurography: This technique is based on re- Intraoperative and perioperative cardiovascular in-
cording electrical activity emitted by peroneal, tibial, stability: Observations in diabetic patients under-
or radial muscle sympathetic nerves and identifica- going general anaesthesia reported that individuals
tion of sympathetic bursts. Bursts have a characteris- with DCAN required vasopressor support more of-
tic shape consisting of a gradual rise and fall that is ten than those without CAN. Individuals with DCAN
usually constrained by the cardiac cycle and at least may experience a greater decline in heart rate and
twice the amplitude of random fluctuations. Recent- blood pressure during induction of anaesthesia and
ly available fully automated sympathetic neurogram more severe intraoperative hypothermia resulting in
techniques provide a rapid and objective method that decreased drug metabolism and impaired wound
is minimally affected by signal quality and preserves healing .
1
beat-by-beat sympathetic neurograms.
Stroke: A recent study in 1,458 patients with type 2
diabetes reported that presence of DCAN, assessed
Clinical Implications by standard HRV testing, was one of the strongest
Mortality risk: DCAN is associated with a high risk predictors of ischemic stroke in this cohort together
of cardiac arrhythmias and with sudden death. Lon- with age and hypertension. Earlier reports showed
gitudinal studies of subjects with DCAN have shown similar associations .
1
5-year mortality rates 16–50% in type 1 and type 2 DM,
with a high proportion attributed to sudden cardiac Therapeutic Approaches
death . In the EURODIAB Prospective Cohort Study Glycaemic control: The DCCT demonstrated that in-
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of 2,787 type 1 DM patients, DCAN was the strongest tensive insulin therapy for type 1 DM reduced the inci-
predictor for mortality during a 7-year follow-up, ex- dence of DCAN by 53% compared with conventional
ceeding the effect of traditional cardiovascular risk therapy. The Epidemiology of Diabetes Interventions
factors. The mechanisms proposed to account for and Complications (EDIC) study, the prospective ob-
this increased mortality are: difficulty in recogniz- servational study of the DCCT cohort, has shown
ing angina (atypical manifestations such as nausea, persistent beneficial effects of past glucose control
shortness of breath and tiredness are common), as- on microvascular complications despite the loss of
ymptomatic ischemia or MI, dysfunction of the cor- glycaemic separation . In type 2 DM, the effects of
24
onary flow autoregulation, increased heart rate, LV glycaemic control are less conclusive. The VA Coop-
systolic and diastolic dysfunction, increased risk of erative Study demonstrated no difference in the prev-
arrhythmias (prolonged QT interval), decreased noc- alence of autonomic neuropathy in type 2 DM after 2
turnal protection against MI, changes in BP circadian years of tight glycaemic control compared with those
cycle, increased cardiac mass, increased risk of mi- without tight control. On the other hand, the Steno-2
croalbuminuria and, lastly, apnea . The death in bed Trial reported that a targeted, intensive intervention
1,2
syndrome, in which the triad CAN + sympathetic-ad- involving glucose control and multiple cardiovascular
renergic discharge + nocturnal hypoglycemia plays a risk factors reduced the prevalence of DCAN among
key role, is also well-known .
1,2
patients with type 2 DM and microalbuminuria.
Silent myocardial ischemia and diabetic cardiomy-
opathy: In a meta-analysis of 12 published studies, Other therapies: Data regarding the impact of lifestyle
Vinik et al1. reported a consistent association be- interventions in preventing progression of DCAN
tween DCAN and the presence of silent myocardial are emerging. Strictly supervised endurance training
ischemia, measured by exercise stress testing, with combined with dietary changes was associated with
point estimates for the prevalence rate ratios from weight loss and improved HRV in patients with min-
0.85 to 15.53. In the Detection of Ischemia in Asymp- imal abnormalities. In the Diabetes Prevention Pro-
tomatic Diabetics (DIAD) study of 1,123 patients with gram, indexes of DCAN improved most in the life-
type 2 diabetes, DCAN was a strong predictor of si- style modification arm compared with the metformin
lent ischemia and subsequent cardiovascular events. or placebo arm. ACE inhibitors, angiotensin receptor
The presence of DCAN was also linked to the de- blockers, or aldose reductase inhibitors appear prom-
1
velopment of diabetic cardiomyopathy in type 1DM ising but are yet to be validated .
because in these patients ventricular dysfunction of- Orthostatic hypotension: The treatment of orthostat-
ten precedes or occurs in the absence of significant ic hypotension is challenging. Nonpharmacological
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coronary artery disease or hypertension . Further treatments include avoidance of sudden changes in
studies are needed to clarify the complex interac- body posture to the head-up position; avoiding med-
tions between CAN, silent myocardial ischemia, and ications that aggravate hypotension, such as tricyclic
cardiomyopathy in diabetes.

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