Editing Lecture 12 Heart Defects

*continued here from [[Lecture 11 Fetal Physiology]] on 01/31/11 at 11:25AM.

==Congenital and Acquired Heart Anatomical Abnormalities==

===Objectives===
*The diagnosis of most heart abnormalities begins with the stethoscope and a knowledge of the heart cycle.  For each of the abnormalities studied, when would a murmur be heard during the heart cycle and over which valve, if a valve is involved? 
*In the six abnormalities studied, which would have enlarged end diastolic volumes?  In each situation, why is the EDV enlarged?
*In the six abnormalities studied, which would have reduced end diastolic volumes?  In each situation, why is the EDV reduced?

===Statistics===
*9 of every 1000 live births has a heart defect that requires intervention.
*1.7 of every 1000 children develops type 1 diabetes
*So cardiac abnormalities are far, far more common than T1DM.


*We do a ton of cardiac procedures (procedure, cost, death rate):
**Not cheap
**Coronary Artery Bypass Graft, $85,653, 2.1% 
**Angioplasty Procedure, $44,110, 0.8% 
**Diagnostic Catheterization, $25,322, 0.9% 
**Pacemaker, $43,101, 0.9% 
**Implantable Defibrillator, $99,845, 0.8% 
**Valves/Septal Defect, $119,918, 5.1% 
**Cardiac catheterizations
***Much less expensive than surgeries
***1.3 million!
***Mostly for coronary artery disease
***Many of these are done in children to detect problems.


*We do a ton of open heart surgeries, too: 
**Valve replacements: 106,000 
**Bypass (cardiac revascularization): 469,000
**Heart transplant: 2,192
**Septal Defects: 124,000 
**Total open-heart procedures: 699,000 

===Atrial septal defect===
*'''Atrial septal defect''' is the '''second most common congenital heart defect'''.
*Often there is a physical hole between the atrial other than the foramen ovale.
*Can sometimes be repaired with a patch.
*Once fixed, pt is able to grow bigger and strong and to exercise much more strenuously.
*Atrial septal defects allow movement of blood from the left atrium to the right atrium because blood pressure is higher in the left atrium.
*S&S:
**There isn't usually hypoxia at rest
***Because blood is passing left to right
***However, the systemic loop will have less capacity to exercise, etc.
**The heart is limited to normal or moderate exercise because it is getting less blood than it needs for extreme exercise.
**Causes increased pulmonary blood pressure because of high right ventricular output (because right atrium is extra full because left atrium donated some extra).
***Increased bp in the pulmonary circuit can generate hypertrophy of the arterial vascular muscle.
***Because oxygenated blood is getting pushed to the lungs, they contract slightly causing increased pulmonary resistance.
**Pulmonary hypertension (see two points above)
**Right ventricular chamber may enlarge (in response to higher preload)
**Right ventricular muscular hypertrophy
**Heart sounds may be generated:
***Diastolic murmur as blood is pushed form left atrium to right atrium,
****This is a soft sound or may not be audible at all.
***3rd or 4th heart sound because of right ventricle's stretched state,
***Louder pulmonary valve sound because of higher pulmonary pressure,
***Splitting of second heart sounds because the right ventricle takes longer to pump against an increased afterload.
**Right ventricular failure, eventually.

===II.  Ventricular Septal Defect===
*The ventricular septum is complicated
**It is solid muscle
**It is weaved together like a basket
**If not weaved just correctly, there can be opening form one ventrical to the next.
**There is also a dense connective tissue at the top of each ventricle that if not well connected can allow passage of blood.
*These defects can be really big causing a large load on the ventricle.
*Ventricular septal defect is '''the most common congenital cardiac defect'''.
*This is a hole between the two ventricles.
*Small defects tend to close spontaneously in chidlren.
*75% of cases require surgery before the age of 5.
*Causes all the same problems as atrial defect.
*In addition, if the hole is large enough, there will be increased work required by the left ventricle.
*S&S:
**Ventricular systole murmur volume is indirectly proportional to the area of the hole.
**Left ventricle is overstretched and fails.
**Risk of endocarditis is increased because of shear flow over edges of shunt.
***This can generate clots on the septum that get washed into the coronary arteries, the brain, the gut, the respiratory tract, etc.

===III.  Semilunar valve stenosis===
*With semilunar valve stenosis there is a problem with ventricular ejection because the aortic or pulmonary valves are stiffened.
*Recall that work is the stroke volume multiplied by the pressure (W = SV * P).
*When the valve is stiff, it increases the work the ventricles must do to eject the blood.
*S&S:
**Ventricular hypertrophy to maintain cardiac output in light of increased work demand
**EDV is increased by the ejection fraction is below normal.
**Venous pressure (and therefore atrial pressure) are elevated because of ventricular pressure overload.  (That is, venous pressure goes up because the ventricle must reach a higher systolic pressure to get blood through the stenosed valve.)
**Systolic murmur is audible because the blood turbulantly rushes around the stenosed valve.

===IV. Semilunar valve insufficiency===
*In this situation the valve is causing pressures in the ventricle to be abnormally high.
*This increase in pressure causes "over-distension".
**"distention: the act of expanding by pressure from within" per [http://wordnetweb.princeton.edu/perl/webwn wordnet]
*In this pathology, during systole, blood flows out of the ventricle, through the valve but then some returns to the ventricle during diastole.
*Recall that work is the stroke volume multiplied by the pressure (W = SV * P)
*Before we could replace valves, we sometimes knicked stenosed valves with a knife to make them an insufficient valve for which the heart can better compensate.
*S&S:
**The ventricular chamber will expand and the ventricle will hypertrophy but not to the extent seen in stenosis.
**EDV will increase and the ejection fraction will be increased, however, the effective stroke volume that actually stays in the aorta may be below normal.
**Arterial and venous pressures will rise because ventricular volume overload 
**A diastolic murmur will be heard as the blood moves backward through the valve during diastole.
***Like a flag in the wind; constant throughout diastole.


*stopped here on 01/31/11 at 12PM.


===V. Atrioventricular stenosis===
*In this pathology, blood has difficulty entering the ventricle from the atrium.
*Recall that work is stroke volume times pressure (W = SV * Pressure)
*With AV stenosis the ventricle does not fill properly so the EDV is low.
*S&S:
**The ventricle may become smaller than normal.
***This results because of a low SV and the ventricle being under worked.
**EDV is decreased by ejection fraction is increased.
**Atrial and venous pressure are elevated because of AV valve resistance.
**Diastolic murmur is heard as blood must be forced through the AV valves.
**3rd and 4th heart sounds may also be heard

===VI. Atrioventricular insufficiency===
*AV insufficiency allows blood to flow backward form the ventricle to the atrium
*The ventricle ends up being overworked because it has to generate more pressure over a larger volume in order to generate the correct output in spite of the fact that some of its effort is spent on pushing blood back into the atrium.
*S&S:
**Ventricular chamber enlarged and hypertrophied
**EDV is elevated, ejection fraction is elevated, however, the effective stroke volume is decreased
**Arterial and venous pressure are increased because of back flow from the ventricular systole
**Systolic murmur can be heard as blood moves into the atrial during ventricular systole (3/4th sound)

===Clinical case===
*45 yo f
*bicuspid aortic vavle
 
*A. Aortic regurgitation
**
*B. Aortic stenosis
**
*C. Mitral regurgitation
**
*D. Mitral stenosis
**
*E. Mitral valve prolapse
**

===Clinical case===
*87 yo f
 
*A. loss of papillary muscle function in the right ventricle.
**
*B. loss of papillary muscle function in the left ventricle.
**
*C. a clot obstruction of the aortic valve.
**
*D. a clot obstruction of the mitral valve.
**
*E. a transmural breakdown of the left ventricular wall infarct.
**