OB week 2

paired tubular structures fuse at 22 days caudal portion bends to form atrioventricular loop, develops a single common atrium, the space between the R/L atrium is called the ostium primum; is disappears when... septum primum develops along the cephalad portion of the atrium and toward the endocardial cushions before complete fusion, ostium secundum forms, opening within it is foramen ovale the great vessels arise from the common trunk - truncus arteriosus week 7: twisting forms aorticopulmonary septum days 19-30: long process with many pairs to form aorta and pulmonary arches

Embryology

Fetal Circulation

placenta is sole source of oxygen for fetus oxy blood in placenta --> umbilical vein --> ductus venosus/IVC/SVC --> rt atrium --> foramen ovale --> Lt atrium --> Lt ventricle --> aorta --> distal arteries --> umbilical artery --> placenta OR rt atrium --> rt ventricle -- >pulmonary artery --> ductus arteriosis --> descending aorta --> distal ateries --> umbilical artery -- > placenta

What are some of the things we are looking for or assessing when evaluating a 2D echo? what is a normal fetal heart rate? what are PAC's, PVC's? what are PAC's associated with? define tachycardia. name the 3 categories of SVTs what are SVTs associated with? define bradycardia? what is congenital heart block? what maternal disorder is it associated with? what is complete heart block? 40% of complete heart block fetuses have? how do we check for situs? what is levocardia? what is dextrocardia? what is dextroposition? what is mesocardia? which situs is associated with chest masses?

Answers situs, viability, 4CH, ventricular/atrial septae, LVOT, RVOT, 3VV, aortic arch, ductal arch 120-180 BPM; 100-120 at 5.5-6 wks; 170 by 9-10 wks; 130 by term abnormal atrial and ventricular contractions originating from locations other than the sinus node PAC's ass.c redundancy of foramen ovale membrane, caffeine, smoking, multiple pregnancies heart rate greater than 180 BPM supraventricular tachycardias (SVTs) more common than ventricular tachycardia a) paroxysmal supraventricular tach-: atrial rate 180-300, conduction rate 1:1b) atrial flutter: atrial rate 300-400 conduction rate 2:1-4:1...ass.c heart blockc) atrial fibrillation: atrial rate >400, irregular vent rate 120-160; ventricular tach. is rapid heart rate associated with >3 consecutive premature ventricular systoles structural cardiac lesions 10%; can lead to hydrops and death; prolonged FHR failure of transmission of impulses from atrium to ventricles; immature/absent  conduction system maternal collagen vascular disease (systemic lupus erythematosus complete disassociation between atrial and vent. rates (odd ratios). ass.c non-immune hydrops structural cardiac anomalies, prognosis is poor stomach and heart on Lt side ? normal position of heart on left side of chest apex is directed rightward, heart is primarily in right chest heart in normal axis, displaced to the right by external process (e.g. left-sided chest mass) heart is central with apex pointing anteriorly dextroposition