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seagull
i'm pretty sure your a prof and not a student.
+30
nor16
nevertheless, we are greatful for explanation!
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niboonsh
I remember seeing a question describe parasternal lift in the context of pulm htn. still got this wrong tho fml
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anotherstudent
Did my question have a typo? It says O2 saturation in the right ventricle is 70, which is equal to the Right atrium and vena cava. It says the O2 saturation in the left ventricle is 82%, which is a decrease from the LA (95) but not equal to the RV, which is why I thought there wasn't a VSD, I assumed there was a weird shunt from the LV to some other part. Will O2 saturation not always equalize?
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pseudomonalisa
This is a right to left VSD due to the pulmonic stenosis present in Tetralogy of Fallot. O2 sat will be low (70) in the right ventricle, and from there it'll enter the left ventricle and mix with freshly oxygenated blood coming from the left atrium (95). Because of the mixing, the O2 sat of blood in the left ventricle will be somewhere in the middle of 70 and 95 (82 in this case). You're correct, though, that most other VSDs are left to right and you'd see greater O2 sat in the right ventricle in that case (not sure if it equalizes with the left ventricle though).
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furkan7
I does not need to equalizes.Moreover, in left to right shunt,left ventricle's O2 saturation is close to 100%
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an1
If the LV blood is going into the RV, why didn't it's O2 sat increase? neither did the pulmonary artery's. I agree it's TOF, but the sats really don't make sense for a VSD...
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peqmd
Not necessarily. Squatting just helps to increase preload => this will expand the left cardiac chambers and reduce R->L shift. It's a general principle to R->L shunt heart defects not specific to one disease
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ineedhelpwitmed
squatting increases afterload... @peqmd increasing the SVR will cause more blood to go through to pulm artery
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fagaga23
ok, got it. The "boot-shaped" heart is actually due to RV enlargement
"The toe of the boot is formed by the upward-pointing cardiac apex, which makes an acute angle with the diaphragm. The upturned cardiac apex is ascribed to right ventricular hypertrophy and occurs in 65% of patients with TOF"
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submitted by โlsmarshall(465)
"Parasternal heave (lift) occurs during right ventricular hypertrophy (i.e. enlargement) or very rarely severe left atrial enlargement." RV hypertrophy can be seen so easily because the RV is at the anterior surface of the chest.
In this patient blood from LA to LV decreases in saturation, so it is going somehwere. From the O2 sat. we can deduce there is probably a VSD (increased RV pressure would cause RVH and parasternal heave). Furthermor, the vignette is likely describing tetralogy of fallot (caused by anterosuperior displacement of the infundibular septum). In Tet spells, RV outflow is too obstructed and patient gets cyanosis and R>L shunting Squats increase SVR, decreasing R>L shunting, putting more blood through pulmonary circuit and relieving cyanosis.