A B S T R A C T Although ST segment deflections have been widely utilized as a means of assessing the degree of underlying ischemic injury, the relationship of QRS complex alterations to the ischemic process is poorly understood. In this study we made a beat-to-beat analysis of the QRS complex in terms of ventricular activation time (CT) and R wave voltage (V) in the acutely ischemic porcine myocardium and analyzed the relationship of these responses to changes in the area of ischemic involvement, altered myocardial energy demands, and plasma [K+]o levels.With the onset of ischemia the QRS complex underwent a specific and reproducible biphasic sequence with an initial decrease in CT and V indicating a transient increase in the conduction velocity of the ischemic tissue. Subsequently both CT and V returned briefly to control and then increased dramatically, now indicating a marked decrease in conduction velocity. The time when CT first began to increase (Tc) was shortened by enlarging the area of ischemia or after an inotropic intervention and was lengthened by decreasing the area of ischemia or with administration of propranolol. Moreover Tc was found to be inversely proportional to plasma [K+]o in the range 3.4-8.8 mM, above which the initial decrease in CT and V was no longer present.We conclude that this biphasic sequence of QRS alterations in early myocardial ischemia is attributable to a progressive leakage of potassium out of the ischemic cells which in turn alters both the time-course and transmural pathway of the activation process through the ischemic tissue. These changes are related to both inotropic state and the area of ischemic involvement. INTRODUCTIONAlthough ST segment deflections have been widely utilized as a means of assessing the degree of underlying ischemic injury (1, 2) the relationship of QRS complex alterations to the ischemic process is poorly understood. The casual observations of changes in R wave amplitude noticed by some ST segment investigators after coronary artery occlusion in the dog (3-5) as well as the more specific studies of , Scher (9), and Durrer and van der Tweel (10) in the dog and goat suggest that ischemic QRS complex alterations may bear characteristic temporal and/or spatial relationships to the underlying ischemic process.In the present study we have characterized the temporal sequence of QRS complex alterations during early myocardial ischemia in the intact porcine heart, their modification by changes in the area of ischemic involvement, and altered myocardial energy demands, as well as the important role of potassium in their genesis.

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The solid angle theorem was used to analyze the relationships between TQ and ST segment deflections recorded from precordial and epicardial locations and the time course, size, shape, and transmural location of the ischemic process in the ventricular myocardium. Mathematical predictions were compared with experimental data from the intact heart. Precordial electrograms obtained in anesthetized close-chest pigs were compared with epicardial electrograms recorded directly from the heart's surface. Various areas of ischemia were produced by occluding large and small coronary artery branches, and the resultant changes in ischemic shape were delineated with Thioflavin S injections and postmortem ultraviolet photography. Formally derived equations and cumulative experimental data were in close agreement, suggesting that in the ischemic ventricle (1) TQ depression always accompanies ST elevation, (2) TQ and ST segment changes in magnitude and polarity are complex functions of ischemic size, shape, and transmural location; (3) precordial electrocardiogram (ECG) ST segment elevation is directly related to ischemic size; and (4) epicardial ECG ST segment elevation is inversely related to ischemic size. It is thus concluded that precordial and epicardial ECG TQ and ST segment deflections are complex functions of ischemic geometry and that their accurate interpretation with respect to ischemic size and shape and in the presence of pharmacological interventions is often difficult and may be misleading.

BackgroundIntrauterine Contraceptive Device (IUCD) is a highly effective and reversible modern contraceptive, which is still significantly underutilized in Ethiopia. The aim of this study was to identify factors affecting the use of IUCDs among women of reproductive age group in Addis Ababa. OPEN ACCESSCitation: Dereje N, Engida B, Holland RP (2020) Factors associated with intrauterine contraceptive device use among women of reproductive age group in Addis Ababa, Ethiopia: A case control study. PLoS ONE 15(2): e0229071. https://doi.org/ 10.The findings of the study reinforce the need of husbands/partners involvement in the interventions to enhance utilization of IUCD. Moreover, due attention should also be provided for delivering IUCD-related messages in the public mass-media.Factors associated with intrauterine contraceptive device use PLOS ONE | https://doi.