Circadian analysis of myocardial infarction incidence in an Argentine and Uruguayan population

BACKGROUND: The occurrence of variations in the spectrum of cardiovascular disease between different regions of the world and ethnic groups have been the subject of great interest. This study report the 24-h variation of myocardial infarction (MI) occurrence in patients recruited from CCU located in Argentina and Uruguay. METHODS: A cohort of 1063 patients admitted to the CCU within 24 h of the onset of symptoms of an acute MI was examined. MI incidence along the day was computed in 1 h-intervals. RESULTS: A minimal MI incidence between 03:00 and 07:00 h and the occurrence of a first maximum between 08:00 and 12:00 h and a second maximum between 15:00 and 22:00 h were verified. The best fit curve was a 24 h cosinor (acrophase ~ 19:00 h, accounting for 63 % of variance) together with a symmetrical gaussian bell (maximum at ~ 10:00 h, accounting for 37 % of variance). A similar picture was observed for MI frequencies among different excluding subgroups (older or younger than 70 years; with or without previous symptoms; diabetics or non diabetics; Q wave- or non-Q wave-type MI; anterior or inferior MI location). Proportion between cosinor and gaussian probabilities was maintained among most subgroups except for older patients who had more MI at the afternoon and patients with previous symptoms who were equally distributed among the morning and afternoon maxima. CONCLUSION: The results support the existence of two maxima (at morning and afternoon hours) in MI incidence in the Argentine and Uruguayan population

Variability of breathing pattern during inspiratory elastic load

La ventilación pulmonar en humanos tiene una variabilidad respiración a respiración no lineal, compleja y caótica. El objetivo del trabajo fue: caracterizar la variabilidad del patrón respiratorio en perros (n: 8) anestesiados respirando bajo carga elástica umbral (CEU) inspiratoria (7 a 50 cm H2O). Con el flujo, presión traqueal y esofágica, se analizaron: tiempo inspiratorio (Ti), ritmo [tiempo espiratorio (Te); tiempo total (Ttot), y Ti/Ttot] e impulso central (Vt/Ti), variables relacionadas [volumen corriente (Vt) y ventilación pulmonar (Ve)]. Se determinaron: variabilidad grosera (varianzas), oscilaciones de baja frecuencia (análisis espectral) y memoria a corto plazo (análisis de autocorrelación). La CEU produjo disminución de la varianza de medias en Te, Ttot, Vt y Vt/Ti (p < 0.05). La media de las varianzas del Ti/Ttot aumentó (p < 0.005) y disminuyó para el Vt y el Vt/Ti (p < 0.05). En general, el porcentaje de oscilaciones de baja frecuencia (OB%) disminuyó (p < 0.02). Durante CEU alta, las variables de ritmo no cambiaron el porcentaje de registros con autocorrelación (AU%), pero el Vt y variables relacionadas disminuyeron los AU% (p < 0.005). Hubo correlación positiva (r: 0.955, p < 0.001) entre OB% y AU% en Vt y variables relacionadas, pero las variables de ritmo no mostraron correlación. En conclusión: La CEU indujo un patrón respiratorio más monótono. La memoria a corto plazo disminuyó en la fase inspiratoria y aumentó en la espiratoria. Estos cambios ocurrieron bajo anestesia, sugiriendo que ciertas estructuras suprapontinas pueden no ser imprescindibles para la generación de estos cambios.In humans, lung ventilation exhibits breath-to-breath variability and dynamics that are nonlinear, complex and chaotic. Our objective was to characterize the breathing pattern variational activity in anesthetized dogs (n: 8) breathing through threshold inspiratory elastic load (7 to 50 cm H2O). Starting from flow signal and tracheal and esophageal pressures, we analyzed inspiratory time (Ti), timing (expiratory time, Te; total time, Ttot; and Ti/Ttot) and central drive (Vt/Ti) and variables related to it (tidal volume, Vt and pulmonary ventilation, Ve). We measured gross variability (variances), low frequency oscillations (spectral analysis), and short term memory (autocorrelation analysis). Loading decreased variance of the mean values of Te, Ttot, Vt and Vt/Ti (p < 0.05); the mean of variances for Ti/Ttot increased (p < 0.005) while it decreased for Vt and Vt/Ti (p < 0.05). In general, percent of data recordings with low frequency oscillations (OB%) decreased (p < 0.02). During heavy load, timing parameters percent of data recordings with autocorrelations (AU%) did not change, but Vt and its related parameters decreased their AU% (p < 0.005). There was a positive correlation (r: 0.955, p < 0.001) between the existence of low frequency oscillations and autocorrelations for Vt and its related parameters, while timing variables did not show such a correlation. In conclusion, threshold elastic load induced a monotonous respiratory pattern. The short term memory decreased during inspiratory stage while increased during expiratory stage. These changes occurred during anesthesia suggesting that certain suprapontine structures may not be obligatory to induce them.Fil: D'Negri, Carlos E.. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; ArgentinaFil: Pessolano, Fernando A.. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; ArgentinaFil: de Vito, Eduardo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentin