Critical appraisal (I): Fundamentals, tools, and application to scientific articles on outcomes and harmful effects Javier González de Dios; María Salomé Albi Rodríguez; Álvaro Gimeno Díaz de Atauri; Laura Cabrera Morente; Elena Pérez González; Carlos Ochoa Sangrador;

Prognostic role of novel variables in sudden cardiac death risk associated to hypertrophic cardiomyopathy María López Blázquez; María Ángeles Espinosa Castro; Reyes Álvarez García-Rovés; Miriam Centeno Jiménez; Ana Isabel Fernández Ávila; Francisco Javier Bermejo Thomas; Constancio Medrano López;

Clinical characteristics and mortality risk factors in patients aged less than 18 years with COVID-19 in Mexico and Mexico City Rosa María Wong-Chew; Daniel Ernesto Noyola; Antonio Rafael Villa;