Sketchy Path: Left-To-Right Shunts

Question 1

The mixed venous blood should be about ___% oxygenated.

Answer 1

75

(This is represented by the comics that were 75% off but are now 80%; this increase is what you would see if there were a LTR defect.)

Question 2

What causes Eisenmenger’s syndrome to develop?

Answer 2

Pulmonary arterial hypertension leads to increased right-sided pressure and reversal of the LTR flow.

(Think of Dr. Eisenmenger’s red cat’s cradle to remember PAH.)

Question 3

Small VSDs cause what kind of murmur?

Answer 3

A loud, harsh, holosystolic murmur heard best at the lower-left sternal border (like the harsh punch to the SMALL guy leading to him spraying systolic split on the bigger guy)

Question 4

When do VSD murmurs typically become evident?

Answer 4

Around 4 to 10 days of life (not at birth)

Question 5

What two types of presentations occur in VSDs?

Answer 5

• Pink babies with small VSDs (like the pink baby behind the small nerd)
• Blue babies with large VSDs (like the baby in the blue blanket on the other side)

Question 6

Most ASDs occur from ______________.

Answer 6

defects in the septum secundum (like the kid holding open the second set of doors)

Question 7

What causes PFO?

Answer 7

Failure of fusion between the septum primum and septum secundum (like the “Fusion Failed” sign on the doors)

Question 8

Emboli through an ASD or PFO is called _____________.

Answer 8

cryptogenic stroke

This is represented by Astro Girl shooting darts through the doors held open by the kid.

Question 9

Unlike VSDs, ASDs almost never __________.

Answer 9

close spontaneously

Question 10

What can cause brief RTL flow across an ASD?

Answer 10

Sneezing, straining, or any process that rapidly increases venous return (like the kid straining to hold open the doors)

Question 11

ASDs caused what kind of murmur?

Answer 11

• Systolic crescendo murmur with split S2 (like the systolic spray gun of the Astro Girl cosplayer and the SiSters held apart by the angry mom)
• Diastolic murmur caused by excessive tricuspid flow (like the rumbling monster in the diastolic diamond cave on the cover of Astro Girl)

Question 12

What kind of murmur is heard in PFOs?

Answer 12

None

To diagnose PFO, you need to do an agitated saline study and have the patient strain to increase RTL flow.

(Think of the bubbles floating through the almost closed door.)

Question 13

During gestation, _______ keep the ductus arteriosus open.

Answer 13

E2 (like the kid hitting the duct open with the pro-slugger bat)

Question 14

What murmur is typical of PDAs?

Answer 14

Continuous machine-like murmur (like the kid dressed in a Transformers costume)

Question 15

What physical exam sign is typical of PDAs?

Answer 15

• Widened pulse pressure
• Deoxygenation worse in the lower extremities (like the transformer’s blue pants) because the PDA is distal to the left subclavian

Question 16

Coarctation of the aorta leads to narrowing near the ____________.

Answer 16

ligamentum arteriosum (like the dip in the pipe near the DUCT caused by the Turner girl)

Question 17

Like PDA, coarctation presents with _______________.

Answer 17

cyanosis worse in the lower extremities (like the Turner girl’s pink top and blue leggings)

Question 18

Other than differential cyanosis, coarctation of the aorta can cause _______________.

Answer 18

• Aortic dissection (cracking pipe where guy is trying to get the Turner girl)
• Cerebral hemorrhage (red paint on his hat)
• Limb claudication (black paint on his legs)
• Delayed femoral pulses (delayed afternoon events in the schedule)

Question 19

Which artery does the internal thoracic artery branch off?

Answer 19

The subclavian (which is why those with coarctation get anterior intercostal notching)

Question 20

The turbulent blood flow from a structural defect can cause ____________, long-term.

Answer 20

infective endocarditis (like the “fear that will INFECT YOUR HEART” sign)

Note: this does not occur in ASD, though, because the pressure differential is not great enough. (Think of AStro girl zapping the fear monster.)