CARDIAC AUTONOMIC NEUROPATHY IN DIABETES

CARDIAC AUTONOMIC NEUROPATHY IN DIABETES

            Caradiac autonomic neuropathy assesses autonomic nervous system that innervates circulatory system (cardiovascular reflex). Caradiac autonomic neuropathy induces severe postural hypotension and silent MI and lead to sudden cardiac death.

• Sudden syncope
• Light headedness
• Transient visual loss
• Pallor
• Extreme weakness
• Diaphorism
• Post prandial hypotension
• Reduced exercise tolerance
• Ischemic pattern on ECG

            Neuropathy of sympathetic afferent nerve fibers responsible for painless infarction on exercise diabetic patient less able to increase heart rate, blood pressure and cardiac output.

Heart Rate

            Parasympathetic fibres affected early i.e. damage tests are

1. Heart Rate response to deep breathing: continuing ECG taken in deep inspiration and expiration (6 breath/min) max and minimum RR calculated,  converted to beats/min normal 15 beats/min. <10 is abnormal.
2. Immediate heart rate response to standing
3. Valsalva ratio

Blood Pressure

            Cardiac sympathetic damage

1. BP response to sudden standing (portural hypotension) normal fall in blood pressure <10mmHg, <30 abnormal, 11-29 bordernline.
2. BP response to sustain handgrip max diastolic blood pressure, resting DBP normal >16 mmHg, if <10mm Hg abnormal and 11-15 borderline.
3. BP response to cold pressure test rinse in ice cold water normal DBP increases >8mm Hg

Worsen CAN

            ACE, a blockers, methyl dopa, clonidine, phenothiazine, barbiturate, tricyclic and antidepresents.

CAN Management

            Strict glycemic control, a lipoic acid (antioxidant), aldose reduction inhibitor and L-carnitine.

CONCLUSION:

            CAN decisive tests;

1. Valsalva ratio <1.1
2. Portural hypotension >30mm Hg fall (SBP)
3. Failure of DBP to rise in sustained handgrip <10mmHg
4. Failure of DBP to rise on cold pressure <8mm rise

REFERENCE:

            RSSDI Text Book of Diabetes Mellitus