{'fraction_non_alphanumeric': 0.0241260462826194, 'fraction_numerical': 0.006154603643525357, 'mean_word_length': 5.137462235649547, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Microvolt T‐Wave Alternans in Type 2 Diabetic Patients with Poor Glycemic Control

To the Editor: Molon et al.1 in a recent Journal study set to evaluate the prevalence of positive microvolt T-wave alternans (MTWA) in type 2 diabetic patients with poor glycemic control, and no apparent cardiovascular pathology. The authors detected a statistically higher prevalence of positive MTWA in type 2 diabetic patients in comparison with healthy controls; also among diabetic patients, the ones with abnormal MTWA had higher hemoglobin A1c (HbA1c) values, and slightly lower heart rate variability, assessed by the root mean square of successive heart rate RR intervals. In a multivariate logistic regression analysis, HbA1c predicted an abnormal MTWA, independent of a host of carefully selected relevant confounders. The authors provided a reasonable discussion of the plausible mechanisms linking an elevated HbA1c and an abnormal MTWA, the limitations of attributing mechanistically the latter to the former, the nature of their study (cross-sectional), and what needs to be done in the future to elucidate the matter further. Molon et al. have a marvelous opportunity to explore a causal relationship of HbA1c and MTWA by restudying their diabetic patients with an elevated HbA1c after appropriate tighter control of their glycemic status, consequent reduction of the HbA1c, and its influence on the MTWA. Also, the same applies to their diabetic patients with an index normal (or low abnormal) HbA1c, subsequent rise of this glycemic index, and its impact on the MTWA. The diabetic patients in this report did not have higher blood pressure than the control patients. However, patients with type 2 diabetes often reveal left ventricular hypertrophy (LVH) and/or diastolic dysfunction (DD) at echocardiographic evaluation, even in the absence of hypertension. This study did not provide data on the prevalence of LVH or DD in the evaluated cohort. Patients with LVH and/or DD are characterized by electrocardiogram (ECG) repolarization changes (inverted or flat T-waves in the lateral leads, and tall T-waves in the right precordial leads); one wonders as to the influence of such ECG alterations on the value of MTWA (on which positivity or negativity was conferred in this study), had all the diabetic cohort patients, or the ones with an elevated HbA1c, had such changes in excess of what was observed in the patients of the control cohort. The authors could provide some insight about the relevance of the T-wave amplitude on the value of the MTWA (a recently expressed speculation),2 by providing data on the T-wave amplitude in all, or in the key ECG leads, in the control patients, and the diabetic patients with and without elevated HbA1c. Such dependence of the MTWA value on the T-wave amplitude could possibly show in a multivariate analysis that HbA1c is not an independent predictor of the magnitude of MTWA, although HbA1c could also retain its predictive value. The MTWA’s dependence on T-wave amplitude may imply that the magnitude of the MTWA may not necessarily be an expression of the degree of the propensity for ventricular arrhythmias or sudden death. Finally, and although all studies employing the spectral method of analysis use the cutpoint of = 1.9 ≥ μV for MTWA positivity, it should be kept in mind that this cutpoint was based on studies of patients with cardiac pathology, spontaneous or programmed electrophysiology studyinduced ventricular arrhythmias, aborted sudden death, or ischemic and nonischemic cardiomyopathy. One wonders whether a more appropriate approach herein would have been to evaluate, using receiver-operator-characteristic curves statistics, what is the cutpoint of MTWA that separates more effectively control patients from type 2 diabetic patients, and diabetic patients with high HbA1c from those with normal HbA1c. Such efforts may readdress the “issue of = 1.9 ≥ μV cutpoint,” which is automatically being implemented, but probably inappropriately particularly for studies like the one under consideration.