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MBME 6 (CK)


A 4 week old newborn is brought to physician b/c increasing difficulty feeding, poor weight gain, and excessive perspiration since birth. She was born at term after an uncomplicated pregnancy and delivery and weighed 7 lb 11oz, initial examination showed no abnormalities. Family history is noncontributory. She currently weighs 8 lb. Temp 98.6, pulse 160, RR 80 and labored. Grade 2/6 holosystolic murmur over the lower left sternal border. Lungs clear. Chest x-ray shows Cardiomegaly with increased pulmonary vascular markings. An ECG shows right ventricular hypertrophy. Which of the following is most likely explanation for absence murmur on initial examination?

A. High pulmonary vascular resistance
B. High systemic vascular resistence
C. Low pulmonary vascular resistance
D. Low systemic vascular resistance
E. Patent ductus arteriosus

CCC

This pt most likely got " VSD " :


-In order for a murmur to be present Blood has to flow across the defect from Higher Pressure Chamber to Lower Pressure Chamber.

-If the Pressure b/w two chambers is equal or nearly equal then there will be NO Flow across the defect ------ Hence NO Murmur.


-At Birth "Pulmonary Vascular Resistance is High" due to the

"Hypertrophy of Pulmonary Arterioles" during Fetal life keeping the pulmonary arterial pressure higher than normal that produce RV Hypertrophy.

*and cz of this High Pulmonary Vascular Resistance which transmit high pressure back to RV, result in "NO Shunting Across VSD"------ and this is the reason NO Murmur is detected on initial examination.


-Following birth "Involution Of Pulmonary Vasculature" start and Pulmonary Vascular Resistance start to decline as the arteriolar muscular hypertrophy regress----- and Resistance Falls to it's lowest point by the 6th wk of life

-and it is then (in a few wks after birth) when there is more shunting of blood across VSD producing a Holosystolic Murmur.

-This is the reason VSD detected in a few wks after the birth frequently on the first pediatrician's visit.


An infant with a large VSD will fail to thrive and become sweaty and tachypnoeic (breathe faster) with feeds.

SORRY I read the last sentence Ttoo fast i thought is asking why the patient has murmur.

THANK YOU

so bb is the answer,right?

"A" is correct. thanks