Electrocardiographic patterns of autonomic dysfunction in the diagnosis of autonomic neuropathy in patients with type 2 diabetes mellitus

Type 2 diabetes mellitus poses a serious threat to the health of people worldwide. Despite active detection and stringent measures to control and treat diabetes, the condition leads to a variety of complications, including autonomic neuropathy, resulting in autonomic cardiac denervation associated with an increased risk of painless myocardial ischemia and sudden cardiac death. However, digital verification by finding electrocardiographic (ECG) patterns of autonomic dysfunction is possible.

The available literature on ECG patterns of myocardial electrical instability, which reflect autonomous myocardial dysfunction, was summarized. A literature review of scientific papers on ECG diagnosis of autonomic myocardial dysfunction in patients with type 2 diabetes mellitus over the past 5 years was performed using PubMed and eLIBRARY data.

Among different ECG patterns that reflect autonomic dysfunction, the most common is the investigation of heart rhythm variability, which is based on the mathematical analysis of respiration rate intervals. The simplest variables are used to obtain a series of statistical indicators such as SDANN, RMSSD, NN50, and pNN50. A new and understudied ECG pattern of autonomic dysfunction is heart rate turbulence (HRT), which is a short-term rhythm change that develops in response to a ventricular extrasystole. The extrasystole is followed by a short episode of sinus tachycardia lasting several cardiac cycles, which is followed by a longer episode of bradycardia. These heart rate fluctuations are based on baroreflex compensation of intracardiac hemodynamic changes. Two parameters are estimated to characterize the HRT: turbulence onset and turbulence slope. A specific marker of autonomic dysfunction is the rate of cardiac rhythm recovery after controlled exercise. A recovery rate of <12 beats per first minute was associated with an increased risk of all-cause mortality, whereas a reduction in recovery rate of <40 beats per 2 min was found to be a strong independent risk factor for all-cause mortality.

An imbalance in the tone of sympathetic and parasympathetic systems underlies all the described indicators. Therefore, a risk-stratifying significance of autonomic dysfunction markers in a wide range of pathologies, including peptic ulcer disease, gallstone disease, hypertension, chronic heart failure, chronic obstructive pulmonary disease, bronchial asthma, thyreopathies, and anemias apart from type 2 diabetes mellitus, exists. This explains the high sensitivity of tests, while having a low positive predictive value and specificity. The ease of performing tests dictates the need for further study of the features of autonomic dysfunction markers in patients with type 2 diabetes mellitus, since these markers are associated with a high risk of painless myocardial ischemia and sudden cardiac death.

Currently, several ECG patterns (heart rate variability, HRT, and heart rate recovery rate) reflect autonomous myocardial dysfunction. The patterns enable early detection of autonomous neuropathy in patients with type 2 diabetes mellitus, which will allow timely diagnosis and adequate therapy. However, further study is required due to their low specificity to identify the peculiarities in specific nosological forms.