Cardiovascular Flashcards
What are the three shunts in fetal circulation?
1) Ductus venosus Umbilical vein (oxygenated) --> IVC
2) Foramen ovale
RA (oxygenated) –> LA
3) Ductus arteriosus Pulmonary artery (deoxygenated from SVC) --> Aorta (after the great vessels)
Where does fetal erythropoiesis occur?
“Young Liver Synthesizes Blood”
Yolk sac (3-10 wk)
Liver (6 wk-birth)
Spleen (15-30 wk)
Bone marrow (22 wk+)
What is used to keep a PDA open?
To close it?
PGE keeeeeps it open
Indomethacin closes it
What does the umbilical vein become?
Ligamentum teres hepatis
within falciform ligament
What do the umbilical arteries become?
Medial umbilical ligaments
What does the ductus arteriosus become?
Ligamentum arteriosum
What does the ductus venosus become?
Ligamentum venosum
What does the foramen ovale become?
Fossa ovale
What does the urachus become?
Median umbilical ligament
Urachus is part of the allantoic duct (portion between bladder & umbilicus)
What does the notochord become?
Nucleus pulposus of intervertebral disc
What does it mean to be right heart dominant vs. left?
Right dominant (85%) - the posterior descending artery arises from the RCA
Left dominant (8%) - the PD arises from the Left circumflex
Codominant (7%)
What heart chamber composes the back of the heart?
What can be seen with pathology?
The LA is the most posterior chamber. Enlargement can cause dysphagia (esophageal compression) or hoarseness (recurrent laryngeal)
Myocardial infarction:
What leads will show alterations?
What artery is infarcted?
Left lateral wall
Leads I, AVL, V5, V6
LCX or LCA infarction
Myocardial infarction:
What leads will show alterations?
What artery is infarcted?
Anterior
Leads: V2-V4
LAD
Myocardial infarction:
What leads will show alterations?
What artery is infarcted?
Septal
Leads: V1,V2
LAD
Myocardial infarction:
What leads will show alterations?
What artery is infarcted?
Inferior
Leads: II,III,AVF
PDA or RCA
What are the equations for Cardiac Output?
CO = Stroke Volume * HR
CO =
O2 consumption rate)/(arterial O2 content - venous O2 content
What are the equations for mean arterial pressure?
MAP = (2/3)Diastolic + (1/3)Systolic
MAP = CO x TPR
What factors increase myocardial O2 consumption?
^Afterload
^Contractility
^HR
^Heart size (wall tension)
How does blood pH affect potassium levels?
Potassium moves the opposite direction of protons across cell membranes in order to maintain charge.Thus:
Acidosis –> hyperkalemia
Alkalosis –> hypokalemia
What effect does insulin have on potassium?
INsulin causes K+ shift INto cells.
This is why DKA pts are hyperkalemic at first but may become hypokalemic with treatment. (Also because acidosis –> hyperkalemia).
How does acidosis decrease contractility?
H+ shifts into cardiac cells, so K+ shifts out –> hyperpolarization of the membrane
How are preload and afterload affected by dilating drugs?
vEnodilators decrease prEload
vAsodilators decrease Afterload
What can decrease contractility?
Beta blockade CHF Acidosis Hypoxia/Hypercapnia Non-dihydropyridine CCB's
What is the equation for ejection fraction?
What is a normal ejection fraction?
EF = (EDV - ESV)/EDV
Normal is >55%
What portion of the vasculature accounts for most of the resistance to flow?
Arterioles
What is the total resistance of vessels in series?
In parallel?
Series:
Total = R1 + R2 + R3. . .
Parallel:
1/Total = 1/R1 + 1/R2 + 1/R3. . .
What factors determine resistance?
Viscosity & vessel length increase resistance
Radius decreases resistance
What are the waves on a jugular venous pulse tracing?
a = RA contraction c = RV contraction (valve bulges backward) v = RA filling against closed tricuspid
What causes the dicrotic notch seen on aortic pressure tracings?
Transient backward flow back into the LV, which causes closure of the valve. The elastic recoil of the aorta can then exert its effects, causing an increase in pressure.
When is an S3 heard?
Normal in children & pregnancy
Otherwise indicates ^filling pressures and/or a dilated LV.
What causes wide splitting of S2?
Wide splitting: varies with respiration but is always wider than expected.
Caused by pulmonic stenosis or RBBB
What causes fixed splitting of the S2 heart sound?
ASD is the only etiology
Left to right shunt causes splitting all of the time
What causes paradoxical splitting?
Inspiration: They close together
Expiration: P2 closes before A2
Aortic stenosis & LBBB
Where is a HOCM murmur heard best?
Systolic murmur at the left sternal border (3rd intercostal space)
Where are aortic & pulmonic regurgitation heard best?
Diastolic murmurs at the left sternal border (3rd intercostal space)
What can be heard with an ASD?
Where?
Pulmonary flow murmur & diastolic rumble heard best at pulmonic area.
What effect does inspiration have on murmurs?
Expiration?
Inspiration –> ^intensity of right heart sounds
Expiration –> ^intensity of left heart sounds
What effect does the hand grip technique have on murmurs?
^systemic vascular resistance
Louder: AR, MR, VSD, MVP
Softer: AS, HOCM
What effect does valsalva have on murmurs?
Decreases venous return
Louder: MVP, HOCM
Softer: Most murmurs
What effect does rapid squatting have on murmurs?
Increases venous return
Softer: MVP, HOCM
What is heard with mitral/tricuspid regurgitation?
Mitral - Holosystolic blowing murmur loudest at apex & radiates to axilla.
Tricuspid - Holosystolic blowing murmur loudest at tricuspid area & radiates to RSB.
How does aortic stenosis sound?
What else is seen?
Systolic ejection click followed by crescendo-decrescendo murmur. Heard best at the aortic area & radiates to carotids.
“Pulsus parvus et tardus” = weak pulses w/ a delayed peak
What causes aortic stenosis?
What are the symptoms?
Causes:
Bicuspid aortic valve
Calcific aortic stenosis
Symptoms:
Syncope
Angina
Dyspnea on exertion
How does a VSD sound?
What effect does size of the VSD have on the sound?
Holosystolic, harsh murmur loudest at tricuspid area.
How does mitral valve prolapse sound?
Midsystolic click then crescendo murmur. Heard bast at the apex.
Enhanced by decreased venous return (standing, valsalva).
What can cause mitral valve prolapse?
Often associated with young adult women. Caused by:
Myxomatous degeneration
Rheumatic fever
Chordae rupture
It ^susceptibility to infective endocarditis.
What does aortic regurgitation sound like?
What else can be seen?
Immediate blowing diastolic decrescendo murmur. Heard best at LSB.
Wide “water hammer” pulse pressures & head bobbing can also be seen.
What can cause aortic regurgitation?
Aortic root dilation (syphilis or idiopathic)
Bicuspid aortic valve
Endocarditis
Rheumatic fever (mitral always involved)
How does mitral stenosis sound?
Diastolic opening snap, followed by rumbling late diastolic murmur.
99% are due to rheumatic fever
What does a PDA sound like?
What causes it?
Continuous “machinery” murmur heard best at infraclavicular area.
Caused by congenital rubella or prematurity.
What is the best prognostic indicator of mitral stenosis?
Aortic stenosis?
Time to opening snap (MS) or ejection click (AS)
Mitral: Early opening snap –> more severe
Aorta: Early ejection click –> less severe
What channels are responsible for the slow diastolic depolarization seen in the SA & AV node?
If (funny) channels –> Na+ flows into the cell slowly
What are the resting membrane potentials of cardiac pacemaker cells?
Myocytes?
Pacemaker cells = -70 mV
Myocytes & His-Purkinje = -90 mV