Ambulatory 24-h ECG monitoring and cardiovascular autonomic assessment for the screening of silent myocardial ischemia in elderly type 2 diabetic hypertensive patients.

The aim of the study was to evaluate the usefulness of Holter monitoring for the detection of silent myocardial ischemia (SMI) in elderly type 2 diabetic patients with hypertension and the possible relationship between SMI and cardiovascular autonomic neuropathy (CAN). Two hundred and forty-three asymptomatic outpatients, aged 65-75 years, with type 2 diabetes and essential hypertension underwent 24-h ECG monitoring and 5 tests for the evaluation of both parasympathetic (heart rate variability, response to breath deeping, and Valsalva manoeuvre) and sympathetic (cold pressor test and orthostatic hypotension test) autonomic function. A total of 518 asymptomatic episodes of ST depression during Holter monitoring indicative of SMI were detected in 51 of the 243 studied patients (20.9 %). None of the patients with ST depression episodes exhibited a normal response to at least one of the evaluated autonomic function tests, whereas 22 of the 192 patients without ST changes (11.4 %) exhibited a normal response to all tests. Abnormality in both parasympathetic and sympathetic function test responses was found in 94.1 % of patients with ST depression episodes vs 26.1 % of those without ST changes (P < 0.001). Statistical evaluation of the relationship between the abnormal response to single autonomic function test and episodes of ST depression was highly significant for all the 5 tests (P < 0.001). These results indicate that: (a) Holter monitoring enables to detect ST segment changes indicative of SMI in 20.9 % of elderly diabetic patients with hypertension; (b) the presence of autonomic cardiac dysfunction in these patients suggests a role of diabetic neuropathy in the pathogenesis of SMI; and (c) findings of severe autonomic dysfunction in more than 25 % of patients without ST depression episodes suggest that these patients might be at risk of myocardial ischemia and should possibly be addressed to closer specialistic evaluation, since Holter monitoring might have not detected SMI in these patients due to its low sensitivity and relatively short duration of recordings.