Background: Cardiovascular autonomic neuropathy (CAN) is a complication of diabetes mellitus (DM) and has been regarded as a parameter associated with a poor outcome.
Aim: We investigated whether indices of cardiovascular autonomic function have prognostic value in the current era of pharmacological therapy recommended for DM patients with coexisting coronary artery disease (CAD), which consists of drugs that affect autonomic balance, i.e. angiotensin-converting enzyme inhibitors (ACEI), angiotensin receptor blockers (ARB), beta-blockers, and statins.
Methods: We studied 127 consecutive patients with type 2 DM and angiographically documented stable CAD (age: 64 years, women: 28%, treatment: ACEI/ARBs: 100%, statins: 98%, beta-blockers: 88%, insulin therapy: 46%). The assessment of autonomic balance within the cardiovascular system included heart rate variability (HRV) (time and spectral-domain analyses) and non-invasive evaluation of baroreflex sensitivity (sequence and controlled breathing methods). Primary end-points were cardiovascular mortality and urgent hospital admissions due to cardiovascular symptoms.
Results: During the mean follow-up of 502 +/- 161 days, 28 patients (22%) experienced a cardiovascular event: 7 died and 21 were admitted to hospital. We found the following predictors of an increased risk of the combined end point (cardiovascular death and hospitalisation): elevated level of N-terminal BNP (for log NT-proBNP - HR = 2.6, p = 0.004), severe CAD (3-vessel disease - HR = 2.4, p = 0.02), renal insufficiency (eGFR < 60 ml/min/1.73 m2 - HR = 2.7, p = 0.008), and female gender (HR = 3.2, p = 0.002). None of the indices of autonomic balance had prognostic value (p > 0.2 for all).
Conclusion: In the population of diabetic patients with stable CAD who receive optimal pharmacological therapy, indices of impaired autonomic function are no longer predictors of poor outcome.