Keywords: 12-lead electrocardiogram, cardiomyopathy and heart failure, myocardial infarction. AbstractPrognostic markers derived from standard ECG have always been seductive.Increased dispersion of durations of the P wave, of the QRS complex, or of the QT interval has been associated with the risk of atrial fibrillation, ventricular arrhythmias, sudden cardiac death, as well as with a general negative prognosis in various settings.However, these markers have intrinsic and methodological issues that question their utility. This paper presents data supporting the utility of QRS dispersion in clinical practice. Our investigation shows that QRS dispersion is a simple electrocardiographic marker with potential value in the assessment of patients in a variety of clinical settings: ischemic heart disease, heart failure, and cardiomyopathies.More studies are needed to validate QRS clinical utility for predicting the risk for ventricular arrhythmias and sudden cardiac death, and for the evaluation of the response to cardiac resynchronization therapy.Acne conglobata is a rare, severe form of acne vulgaris characterized by the presence of comedones, papules, pustules, nodules and sometimes hematic or meliceric crusts, located on the face, trunk, neck, arms and buttocks.Ionuț Donoiu et al. 133

Background P‐wave dispersion (PWD) is believed to be caused by inhomogeneous atrial conduction. This statement, however, is based on limited little solid evidence. The aim of this study was to determine the relationship between atrial conduction and PWD by means of invasive electrophysiological studies. Methods Cross‐sectional study in 153 patients with accessory pathways and atrioventricular node reentry tachycardia (AVNRT) undergoing an electrophysiological study. Different atrial conduction times were measured and correlated with PWD. Results Only the interatrial (P‐DCS) and left intra‐atrial conduction times (ΔDCS‐PCS) showed a significant correlation with PWD, but this correlation was weak. Multivariate linear regression analysis determined that both P‐DCS (β = 0.242; P = .008) and ΔDCS‐PCS (β = 0.295; P < .001) are independent predictors of PWD. Performing the multivariate analysis for arrhythmic substrates, it is observed that only ΔDCS‐PCS continued to be an independent predictor of PWD. Analysis of the receiver operating characteristic curves showed that regardless of the types of arrhythmic substrates, PWD discriminates significantly, but moderately, to patients with P‐DCS and ΔDCS‐PCS ≥75 percentile. Conclusions Interatrial and intraleft atrial conduction times were directly and significantly correlated with PWD, but only weakly, and were independent predictors of PWD. In general, PWD correctly discriminates patients with high values in interatrial and intraleft atrial conduction times, but moderately. This is maintained in cases with accessory pathways; however, in patients with AVNRT it only does so for intraleft atrial conduction times. Interatrial and intraleft atrial conduction times weakly explains PWD.

INTRODUCTION Many clinical settings lack the necessary resources to complete angiographic studies, which are commonly used to predict complications and death following acute coronary syndrome. Corrected QT-interval dispersion can be useful for assessing risk of myocardial infarction recurrence.OBJECTIVE Evaluate the relationship between corrected QT-interval dispersion and recurrence of myocardial infarction in patients with STsegment elevation. METHODSWe conducted a prospective observational study of 522 patients with ST-segment elevation myocardial infarction admitted consecutively to the Camilo Cienfuegos General Provincial Hospital in Sancti Spiritus, Cuba, from January 2014 through June 2017. Of these, 476 were studied and 46 were excluded because they had other disorders. Demographic variables and classic cardiovascular risk factors were included. Blood pressure, heart rate, blood glucose, and corrected and uncorrected QT-interval duration and dispersion were measured. Patients were categorized according to the Killip-Kimball classifi cation. Association between dispersion of the corrected QT-interval and recurrence of infarction was analyzed using a binary logistic regression model, a regression tree and receiver operator characteristic curves. RESULTSPatients with recurrent infarction (56; 11.8%) had higher average initial blood glucose values than those who did not have recurrence; the opposite occurred for systolic and diastolic blood pressure and for left ventricular ejection fraction. Dispersion of the corrected QT-interval was a good predictor of infarction recurrence according to a multivariate analysis (OR = 3.09; 95% CI = 1.105-8.641; p = 0.032). Cardiac arrest is the variable that best predicts recurrence. No recurrence of infarction occurred in 97% of patients without cardiac arrest, left ventricular ejection fraction >45% and corrected QTinterval dispersion <80 ms. CONCLUSIONS Risk of infarction recurrence is low in patients without cardiac arrest, with left ventricular ejection fraction >45% and with dispersion of corrected QT-interval <80 ms. Patients with corrected QT-interval dispersion ≥80 ms have greater risk of recurrence of infarction, which suggests that this variable could be used for stratifi cation of risk following ST-segment elevation myocardial infarction.

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Aim: To characterize the Tpeak-Tend, the Tpeak-Tend dispersion and Tpeak-Tend/QT in children and its relationship with clinical variables. Methods: Cross-sectional study in 126 children between 9 and 12 years of the Camilo Cienfuegos School in Santa Clara, Cuba. Clinical and anthropometric variables were obtained to determine their relationship with electrocardiographic parameters: Tpeak-Tend V5, Tpeak-Tend dispersion and Tpeak-Tend/QT ratio V5. In addition, laboratory tests were conducted. Results: Age and systolic blood pressure are associated with an increased probability of having values ​​of Tpeak-Tend/QT V5 ≥75 percentile for both sexes (OR: 1.72, CI 95%: 1.02-2.91; p= 0.043), (OR: 1.08, CI 95%: 1.01-1.16; p= 0.017) respectively. The body mass index and systolic blood pressure are linearly and significantly correlated with the Tpeak-Tend/QT V5 (r= 0.224; p= 0.012) and (r= 0.220; p= 0.014) respectively. Conclusions: The age of the patients and the systolic blood pressure figures are factors that increase the probability of having values ​​of the Tpeak-Tend/QT V5 ≥75 percentile. There was a significant linear correlation between the Tpeak-Tend/QT V5 with the body mass index and the systolic blood pressure.