Anatomical relationship between mitral valve annulus and circumflex artery and its surgical implications

BACKGROUND

Performing surgical procedures around the mitral valve (MV) annulus can cause iatrogenic lesions on the circumflex artery (Cx). The risk of this iatrogenesis comes from the proximity between this vessel and the MV annulus.

OBJECTIVE

To evaluate the relation between the MV annulus and the Cx at different spots of its path and highlight the risks of its damage.

METHODS

Fifty cadaveric adult human hearts were studied. Each heart was categorized depending on coronary dominance, and Cx was classified in type 1 (Cx giving off only the left posterior ventricular artery) and type 2 (Cx reaching the crux cordis and giving off the posterior interventricular branch). Three reference spots were chosen: A- when Cx begins to run across the coronary sulcus; B- immediately before the left posterior ventricular artery emerges and C- in the midpoint of the two previous points; to measure the diameter of the Cx and the MV annulus. Values of P<0.05 were considered significant.

RESULTS

A total of 43 (86%) hearts were classified in type 1. These hearts showed that the diameter of the Cx in spot A is bigger than in the B and C spots (P=0.001). The 7 hearts (14%) classified in type 2 did not exhibit a difference in the diameter of the Cx in the A, B and C spots (NS). Also, the thickness of the fibrous annulus, in type 1 and type 2 hearts were not different between the three spots (NS).

CONCLUSION

The present study showed that the diameter of the Cx varies depending on the heart type. This knowledge might improve the success rate of cardiac surgeries and decrease the rates of iatrogenic Cx lesions.

Feeding and nonnutritive sucking habits and prevalence of open bite and crossbite in children/adolescents with Down syndrome

OBJECTIVE

To analyze the influence of breastfeeding, bottle feeding, and nonnutritive sucking habits on the prevalence of open bite and anterior/posterior crossbite in children with Down syndrome (DS).

MATERIALS AND METHODS

A cross-sectional study was carried out in 112 pairs of mothers/children with DS between 3 and 18 years of age at a maternal/children's hospital in Rio de Janeiro, Brazil. The children with DS were clinically examined for the presence of open bite as well as anterior and posterior crossbite. Information on breastfeeding, bottle feeding, and nonnutritive sucking habits was collected using a structured questionnaire. The control variables were age and mouth posture of children/adolescents and mother's schooling. Statistical analysis of the data was performed using the chi-square test and multiple logistic regression.

RESULTS

The prevalence of anterior open bite was 21%, anterior crossbite was 33%, and posterior crossbite was 31%. The use of bottle feeding for more than 24 months (prevalence ratio [PR] = 1.6) was associated with the occurrence of open bite. Having breastfed for less than 6 months (PR = 1.4) and pacifier sucking for more than 24 months (PR = 3.1) were associated with the prevalence of anterior crossbite. Finger sucking (PR = 2.9) and the use of bottle feeding for more than 24 months (PR = 2.6) were associated with posterior crossbite.

CONCLUSION

The prevalence of open bite and crossbite in children with DS was associated with the use of bottle feeding and pacifier sucking for more than 24 months, breastfeeding for less than 6 months, and finger sucking.

Actions and interactions of ethanol and imipramine on the rat sinus node

We studied the actions and interactions of ethanol and imipramine on the sinus node. Strips of the right rat atrium including the sinus node were superfused with Tyrode's solution at 37 degrees C while beating spontaneously. The preparations were exposed to imipramine or ethanol alone as well as to the two drugs in combination while recording membrane potentials with standard intracellular microelectrodes. The results obtained show that ethanol 0.8 and 2.4 g/l exerted a positive chronotropic action. On the other hand, imipramine 0.25 mg/l did not modify the sinus node rate. However, it reduced significantly the positive chronotropic action of ethanol. The sinus node rate decreased under the action of a higher concentration of imipramine (1 mg/l). When ethanol was tested in combination with this concentration of imipramine, the effect of the latter prevailed. In conclusion, a concentration of imipramine that did not affect the sinus node rate antagonized the positive chronotropic action of ethanol. In addition, the negative chronotropic action of a higher concentration of imipramine prevailed over the positive action of ethanol. The results obtained provide additional support to the notion that the use of ethanol and cardioactive drugs in combination may result in significant changes in the actions of either of the two, or both. This is of clinical relevance, since at least some of the individuals under treatment with cardioactive drugs will be alcoholics and/or social drinkers.

Cardiac beta-adrenergic mediated chrono- and inotropic effects of imipramine in vitro

Clinical and experimental studies show that tricyclic antidepressants in "therapeutic plasma concentrations" can increase heart rate, myocardial contractility and blood pressure. Our study was undertaken to analyze the role of beta-adrenergic stimulation in the chronotropic and inotropic effects of imipramine. Strips of rat right atrium including the sinus node, which were beating spontaneously, were used to study chronotropism. Strips of the left atrium, electrically stimulated to beat at 1 Hz, were used to study inotropism. The preparations were superfused in vitro with Tyrode's solution at 37 degrees C and exposed to imipramine while recording membrane potentials or force of contraction. Imipramine exerted dose-dependent biphasic actions. Imipramine 0.8 microM produced positive chronotropic and inotropic actions which were blocked by propranolol. Imipramine 1.6 microM depressed the sinus node automaticity, but it did not modify the force of contraction. Imipramine 3.2 microM depressed both the sinus node automaticity and the myocardial contractility. In conclusion, imipramine in "therapeutic plasma concentrations" produces beta-adrenergic mediated cardiac positive chronotropic and inotropic actions. The possible mechanisms of the depressant effects of imipramine itself on automaticity and contractility are still not clear. The results presented can explain stimulatory and depressant cardiac effects of therapeutic doses and overdoses of tricyclic antidepressants.