PREVALENCE OF CARDIOVASCULAR AUTONOMIC DYSFUNCTION ASSESSED BY SPECTRAL-ANALYSIS, VECTOR ANALYSIS, AND STANDARD-TESTS OF HEART-RATE VARIATION AND BLOOD-PRESSURE RESPONSES AT VARIOUS STAGES OF DIABETIC NEUROPATHY

To establish a test battery for the detection and characterization of cardiovascular autonomic neuropathy (CADN) and to evaluate its prevalence, a number of autonomic function tests based on spectral analysis, vector analysis, and standard tests of heart rate variation and blood pressure responses were performed in 261 diabetic patients aged 11-76 years with various stages of peripheral neuropathy. The percentages of abnormal results in the individual tests based on heart rate variation were 6-31 % in 115 patients without peripheral neuropathy, 16-45 % in 61 patients with subclinical neuropathy, 22-59 % in 73 patients with symptomatic peripheral neuropathy, and 67-100 % in 12 patients with the latter in conjunction with autonomic symptoms (p < 0.05). The most frequently abnormal indices, each representing a different physiological basis, were the coefficient of variation, low-frequency and mid-frequency power spectrum at rest, mean circular resultant, postural change in systolic blood pressure, and, in particular, the max/min 30:15 ratio and Valsalva ratio. CADN, defined as the presence of greater-than-or-equal-to 3 abnormalities among these seven parameters was detected in none of 120 control subjects, 13.0 % of the patients without peripheral neuropathy, 34.4 % of those with subclinical neuropathy, 49.3 % of those with symptomatic peripheral neuropathy, and in 100 % of the subjects with the latter and concomitant autonomic symptoms (p < 0.05). The overall prevalence of CADN in 103 patients completing all parameters was 46.6 %. The corresponding rate of CADN defined as greater-than-or-equal-to 2 abnormalities among the five tests included in an optimized version of the battery proposed by Ewing and Clarke 1 was 38.8 %. We conclude that: (1) the stage of peripheral neuropathy is a strong determinant of the prevalence of CADN, but the latter may also be detected selectively; (2) the max/min 30:15 and Valsalva ratios represent the most frequently abnormal standard tests; and (3) the combination of indices based on spectral, vector and conventional analysis of heart rate variation tends to be relatively more sensitive in detecting CADN when compared with a modified version of the most commonly used test battery.