Advanced Pathophysiology Congenital Heart Defects Flashcards
The word congenital** refers to
existing at birth
Congenital heart defects may develop from
chromosome abnormalities
single-gene abnormalities
conditions during pregnancy that affect the baby
combination of genetic and environmental problems
unknown causes
Of children with a heart defect, 30% have other
physical, developmental & cognitive disorders
Diagnosis of cardiac anomalies may be done
in utero, found on newborn physical, ECHO, EKG, Chest x-ray, cardiac cath, CMRI, CT, TEE, Holter recording
Preop eval for cardiac anomalies focuses on
heart murmur on preop evaluation
functional status, growth & development
reviews most recent echo/labs/tests
-children with a history of CHF, cyanosis, pHTN, and young age are at a potentially higher risk
There is _______ secondary to fluid filled lungs and a hypoxic environment.
high PVR
There is _______ secondary to large surface area of the low resistance utero-placental bed
low SVR
The most oxygenated blood from the _____ perfuses the _________ by shunting across the liver via the ductus venosus and shunting across the heart via the foramen ovale
umbilical vein; brain & heart
___________ precipitates the transition from fetal to adult circulation
clamping of the umbilical cord and inflation of the lungs
Lug inflation increases
PaO2
lowers PVR, increasing pulmonary blood flow and increased return to LA
increased LA pressure above RA pressure causes a functional closure of the PFO
The ductus arteriosus remains patent in utero due to
hypoxia, mild acidosis, and placental prostaglandins***
-removal of these factors at birth causes functional closure of DA
A PDA often occurs in
premature infants with lung disease
______ can be used to try & close a PDA
Indomethacin***** (an anti-prostaglandin)
Certain _______ can cause the newborn to revert to fetal circulation
physiologic stresses
The neonatal myocardium is characterized by general
immaturity & decreased number of myofibrils
-decreased contractility & decreased relaxation
The neonatal myocardium includes:
RV & LV are equal in size
- parasympathetic is well developed
- sympathetic innervation is poorly developed
- immature SR results in poor release & reuptake of intracellular calcium
Classifications of CHD classified as
L-R shunts- “pink lesions”
R-L shunts- “blue lesions”
obstructive
“mixed” or cyanotic****
Describe left to right shunts & provide examples.
connects arterial and venous circulation resulting in increased pulmonary blood flow “pink lesions”
E.g. PDA, ASD, VSD
Describe right to left shunts & provide examples
venous blood is ejected systemically; there is decreased pulmonary blood flow & patients are cyanotic “blue lesions”
- e.g. ASD or VSD with pulmonary HTN, TOF during Tet spell
Describe obstructive CHD & provide examples.
prevent ventricular flow from either side of the heart, decrease cardiac output
-e.g. coarctation of the aorta, aortic stenosis
Describe “mixed” or cyanotic CHD & provide examples.
mixing of venous & arterial blood
-e.g. hypoplastic left heart syndrome
Large left to right shunts result in pulmonary over circulation. ______ is increased as a large component of LV output bypasses the systemic circulation, enters the lungs and rapidly returns to the left side of the heart.
RV preload
Describe Eisenmenger’s syndrome.
when large VSDS are uncorrected, the resulting pulmonary hypertension can reverse the shunting of blood across the defect. The previously “left to right shunt becomes right to left
Mixing lesions occur when a
functional single ventricle ejects the mixed systemic and pulmonary venous return.
Patients with mixing lesions are often
cyanotic and are often dependent on the PDA at birth
An atrial septal defect is often
asymptomatic and discovered incidentally (murmur)
Large atrial septal defects that are left untreated can cause
right sided volume overload (usual Qp/Qs>2) with RA & RV dilation & increased pulmonary blood flow
Repair for an atrial septal defect can be
a closure device in cath lab or surgery
The most common congenital defect in children is
ventricular septal defect
A ventricular septal defect leads to
pulmonary over circulation due to left to right shunting in an isolated lesion
if defect is large pressure equalizes in both ventricles & pulmonary blood flow will be greater leading to symptoms of CHF & irreversible damage to pulmonary vascular bed
_______ syndrome may occur in ventricular septal defect and describes the shunt reversing direction when the PVR is high enough.
Eisenmenger’s
Describe restrictive VSD.
small size & limited pulmonary over circulation
Describe unrestrictive VSD.
large flow across the septum with balance between SVR & PVR
Isolated large VSDs are managed via
diuretics for the first few months of life
Indications for surgery for VSD include
poor feeding, reduced weight gain, & increases in incidence of respiratory infections
The _________ is at risk during VSD repair.
conduction system that runs along the ventricular septum
As PVR falls in the first months of life, the flow across the VSD can
increase greatly (as high as Qp/Qs >3)
The ductus arteriosus is a leftover fetal artery connection between the
aorta & the pulmonary artery
when this artery remains open after birth it is called a patent ductus arteriosus
Unrestricted PDA will have significant
L to R shunting
Significant______ into the pulmonary circulation lowers the systemic diastolic BP compromising distal perfusion (i.e. mesenteric/renal & coronary perfusion)
diastolic run off*****
Patent ductus arteriosus is commonly closed with
cardiac catheterization (coil or device)
Surgical closure for a patent ductus arteriosus is a
left thoracic approach and the ductus is closed by a suture tie or metal clip
Whenever there is an abnormal connection between the let and right sides of the heart, there must be vigilance in
de-airing all intravenous fluids
smaller the child, the more significant air can be
Even if the flow is predominantly left-to right, the direction can change at any time & if air enters the left side of the heart, it can
travel to the brain and cause ischemia
Complete atrio-ventricular canal is a
free communication between all four chambers of the heart
- it is located where the atrial septums join the ventricular septums. involves atrias, ventricles, tricuspid, & mitral valves. Results in the formation of a single large valve
The common AV valve is often
regurgitant
_______ make the greatest percentage of patients with CAVC
down syndrome children
CAVC requires _____ repair
surgical repair with septum patch & new valves
usually repaired <6 months before pulmonary vascular changes develop
Problems with CAVC repair nclude
residual septal defects, AV valve regurgitation, post-op pulmonary reactivity, & conduction system damage
Coarctation is a
narrowing in the aorta commonly occurring immediately distal to the origin of the left subclavian artery
The coarctation is most often located near the
ductus arteriosus; if narrowing is proximal to the ductus it is ‘pre-ductal’; if it is distal to the ductus it is ‘post-ductal’
Coarctation is frequently associated with
bicuspid aortic valve
Critical coarctations will present with
circulatory collapse, shock, & acidosis due to poor distal perfusion
-PGE1 is started to reopen the ductus and distal perfusion remains ductal dependent until surgery
Coarctation presents with
upper extremity hypertension, decreased lower extremity pulses, and LVH
The surgical approach for repair of coarctation is
left thoracotomy and subclavian flap angioplasty sacrifices the left subclavian artery
the left arm will then need to be perfused by collateralization
With surgical repair of coarctation, blood pressure must be measured in
the right arm
-the aortic cross clamp will be proximal to the left subclavian artery
_________ can be done in the cardiac cath lab for coarctation.
Balloon dilation
Pulmonary valve stenosis is a
narrowing that causes the RV to work harder to pump blood past the blockage
-usually it is part of other complex lesions
Symptoms of pulmonary valve stenosis
depend on the severity of obstruction
Pulmonary valve stenosis is often treated with
balloon dilation
Aortic valve stenosis is a
narrowing that causes the LV to work harder to move blood past the blockage
Severe aortic stenosis in utero may impair
LV development
_______is a treatment option for severe aortic stenosis.
balloon dilation
Valve replacement at young ages requires
may revisions over time
The ross procedure is performed on patients diagnosed with
aortic stenosis and is an alternative to prosthetic valve replacement
In the Ross procedure, the diseased
aortic root is resected the patient’s own pulmonary valve root is excised and implanted into the aortic position
- the coronary arteries are then re-implanted into the “neo aortic” root
- An RV to PA connection and valve is made with cadaveric tissue or a conduit
- the RV-PA connection may require revision over time but it provides better long term solution to the aortic valve
Advantages to the Ross procedure include
freedom from long-term anticoagulation
-the valve grows as the patient grows
Disadvantages to the Ross procedure include
single valve disease (aortic) is treated with 2 valve procedure
A Blalock-Taussing-Thomas shunt is an operation to
create a type of systemic to pulmonary shunt
The Classic BTS is when the
subclavian artery*** is divided and directly anastomosed to the ipsilateral pulmonary artery
The modified BTS is when a
synthetic shunt** between the subclavian artery & PA
With the classic BTS, it allows the
patient’s own subclavian artery to grow so no need for revision
- the pulses in the ipsilateral arm will be decreased or non-palpable
- prudent to expect a classic BTS in older adult survivors of CHDs
With the modified BTS, the ipsilateral arm
reflects true pressures & is available for a-line placement
- artificial material will not grow with the patient
- hypotension leads to sluggish flow and possibly thrombosis which can be critical*****
The four key features of the tetralogy of fallot are
- ventricular septal defect (VSD)
- right ventricular outflow tract obstruction (RVOT)
- overriding aorta (aorta lies directly over the VSD)
- Right ventricular hypertrophy
* ****
Repair for TOF is usually within
first 6 months of life
Neonates with hypercyanotic spells who are too small for definitive repair may be palliated with a
BTT shunt
In TOF, hypertrophy of the right ventricular myocardium is secondary to
pressure overload
The limitation of pulmonary blood flow & the magnitude of ventricular level right to left shunting account for the degree of ______ in TOF
cyanosis
On XR, TOF can be seen as a
Boot shaped heart due to RVH
The most common cyanotic cardiac lesion is
TOF
Hypercyanotic or “TET spells” are
acute dynamic increases in the pulmonary outflow tract obstruction (spasm) may result in an intensely cyanotic episode due to right to left shunting
-combination of RVOTO & VSD
Causes of TET spells include
crying, feeding, acidosis, catecholamines, & surgical stimulation
Treatment for TET spells includes,
increase SVR or relax the spasm
- child will squat to increase afterload
- this position increases the SVR, decreases the HR, and decreases the right to left shunt across the VSD
Anesthetic treatment for TET spells includes
100% fiO2, sedation, fluid, beta blocker, or alpha agonist to increase afterload and slow down the heart rate
Tetralogy of Fallot repair includes closure of
ventricular septal defect with a patch & relief of right ventricular outflow tract obstruction by removing some of the thickened muscle
TOF repair eliminates intracardiac shunting at the
ventricular level (cyanosis) and addresses the right ventricular outflow tract obstruction (may also include enlarging the left and right pulmonary arteries)
Anesthesia for TOF repair includes
avoid “Tet spell”
generous premedication
sufficient anesthesia & analgesia
avoid reductions in SVR
RV output is the limiting factor on overall CO
treat a Tet spell quickly with phenylephrine if necessary
Treatment of a Tet spell intraoperatively includes
exacerbated right to left shunting (Cyanosis)***
- 100% oxygen
- knees to chest
- fluid bolus
- hyperventilation
- sedation
- esmolol 0.5 mg/kg IV or propranolol 0.1-0.3 mg/kg bolus
- phenylephrine 1-10 mcg/kg IV
After repair of the TOF, the hypertrophied RV has
poor compliance which is worsened in the immediate post op period due to right ventriculotomy
-maintain adequate filling volume
A PFO or small ASD is created in TOF repair, that becomes a
“pop off valve” if right sided pressures increase
CO is maintained at the expense of modest systemic desaturation
After TOF repair, over time the tricuspid valve may become
incompetent leading to RV overload & ventricular ectopy
________ can be damaged in the TOF repair
The conduction system
RV decompensation may occur over time in the TOF repair due to
free pulmonary insufficiency in trans-annular patch repair
