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T-Wave Amplitude Variability in Chagas Disease. Introduction: Measurement of beat-to-beat T-wave amplitude variability (TWV) has been described as a promising new technique for the stratification of arrhythmic risk in postmyocardial infarction and dilated cardiomyopathy patients. Chagas disease (ChD) can lead to a potentially lethal cardiopathy that can present with ventricular arrhythmias, heart blocks, heart failure, and sudden death. The aim of the study was to evaluate the prognostic value of TWV in ChD patients in addition to traditional prognostic predictors. Methods and Results: The study enrolled 113 ambulatory ChD patients (62 men; age: 42 ± 9 years) in sinus rhythm and without other systemic diseases, evaluated by a standard clinical protocol. We computed TWV in 10-minute ECG recordings obtained in controlled resting conditions. TWV was defined as the median values among 8 consecutive 50-ms T-wave segments and dichotomized as either ≤ or > 30 μV2. The association of TWV and death was evaluated by Cox proportional-hazards analysis, considering other established predictors. During mean follow-up time of 106 ± 28 months, 14 patients died. A value of median TWV > 30 μV2 predicts increased risk of death in a multivariate analysis (HR = 5.76, 95% CI 1.31–25.23, P = 0.014), in addition to depressed left ventricular function, presence of nonsustained ventricular tachycardia and QRS duration >133 ms. Conclusion: Repolarization variability, evaluated by TWV, is independently related to the risk of death in ChD. This noninvasive methodology could facilitate the identification of patients who may benefit from more aggressive therapeutic strategies. (J Cardiovasc Electrophysiol, Vol. 22, pp. 799-805, July 2011)

The struggle among social classes or castes is well known in humans. Here, we show that caste inequality similarly affects societies of ants, bees and wasps, where castes are morphologically distinct and workers have greatly reduced reproductive potential compared with queens. In social insects, an individual normally has no control over its own fate, whether queen or worker, as this is socially determined during rearing. Here, for the first time, we quantify a strategy for overcoming social control. In the stingless bee Schwarziana quadripunctata, some individuals reared in worker cells avoid a worker fate by developing into fully functional dwarf queens. \ud \ud