CONGENITAL HEART DEFECTS Flashcards
What does cyanosis mean?
blue-purple discolouration of skin and mucous membranes caused by an elevated blood conc. of deoxygenated Hb.
How does cyanosis occur in congenital heart disease?
cyanosis results from defects that allow poorly oxygenated blood from right side of heart to be shunted to the left side of the heart, bypassing the lungs
What causes acyanosis?
defects that result in left to right shunting
What is the result of large left to right shunts at atrial, septal or great vessel level?
Cause pulmonary artery volume and pressure to increase and can be associated with later development of pulmonary arteriolar hypertrophy and increased resistance to flow
Overtime the elevated pulmonary resistance may cause the shunt to reverse direction –> hypoxemia and cyanosis e.g. seen in Eisenmenger syndrome
Give examples of congential heart diseases which are acyanotic.
ASD, VSD, PDA
Obstructive lesions: aortic stenosis (hypoplasia), pulmonary stenosis (valve, outflow branch), coarctation of the aorta, mitral stenosis
give examples of cyanotic congenital HD
Tetralogy of Fallot
Transposition of great arteries
univentricular heart
Discuss Atrial septal defects (ASD).
ASD is a persistent opening in the interatrial septum after birth.
ASDs relatively common (1 in 1500 live births)
What is the most common site of an ASD?
region of the foramen ovale - known as ostium secundum ASD. Defect arises from inadequate formation of the septum secundum, excessive resorption of the septum primum or both
What is a less common site for an ASD?
in the inferior portion of the interatrial septum - adjacent to AV valves
called the ostium primum defect. abnormality results from failure of septum primum to fuse with endocardial cushions
What are the haemodynamic effects of an ASD?
increased pulmonary blood flow
RV volume overload
pulmonary hypertension is rare
eventual right heart failure
What is a sinus venosus defect?
a type of atrial septal abnormality.
an ‘unroofing’ defect with absence of normal tissue between right pulmonary vein(s) and RA but often atrial septum is actually intact.
Sinus venosus defects often large and result in flow from right pulmonary veins and LA into right atrium –> similar pathophysiology of ASD
What is PFO?
patent foramen ovale
found in around 20% of population
normally permanently seals by age of 6 months via fusion of atrial septa
PFP remains when fusion fails to occur
Why is a PFO usually clinically silent?
because the one way valve, though not sealed remains functionally closed as LA pressure is greater than RA pressure
PFO takes significance if RA pressure becomes elevated e.g. in states of pulmonary hypertension or right heart failure, resulting in right to left intracardiac shunting
In this case deoxygenated blood passes directly into arterial circulation
Why is the link between a PFO and a systemic embolism?
Patient suffering from a systemic embolism is likely to have a PFO
situation = paradoxical embolism
occurs when thrombus in systemic vein breaks loose, travels to RA, passes across PFO to LA (if right heart pressures are elevated, at least transiently e.g. a cough) –> systemic arterial circulation
Discuss the pathophysiology of an uncomplicated ASD.
oxygenated blood from LA shunted to RA.
results in volume overload and enlargement of RA and RV
if RV compliance decreases over time due to excess load, the left to right shunt may lessen
if severe pulmonary vascular disease develops e.g. Eisenmenger syndrome, the shunt may reverse –> cyanosis
What is a VSD?
Ventricular septal defect is an abnormal opening in the interventricular septum
Where are VSDs located - give the most common location and others?
Most often located in membranous (70%) and muscular (20%) portions of septum
rare VSDs occur just below aortic valve or adjacent to AV valves
Discuss the haemodynamic changes that accompany VSDs.
- Left to right shunt
- LV volume overload
- pulmonary venous congestion
- eventual pulmonary hypertension
shunting from LV –> RV causes increased pressure and volume in pulmonary artery –> pulmonary circulation, LA and LV experience volume overload
initially increased blood return to LV –> increased SV via Frank Starling mechanism
eventually increased volume overload –> chamber dilatation, systolic dysfunction, and HF
VSD leads to eventual pulmonary hypertension. What can this lead to?
augmented circulation through the pulmonary vasculature can cause pulmonary vascular disease as early as 2 years old.
As pulmonary vascular resistance increases –> intracardiac shunt may reverse its direction (Eisenmenger syndrome) –> cyanosis
What are atrioventricular septal defects?
defects that arise from faulty development of embryonic endocardial tissues
What is a PDA?
Patent ductus arteriosus
the ductus arteriosus is the vessel that connects the left pulmonary artery to the descending aorta during fetal life.
PDA results when ductus fails to close after birth –> persistent connection between the great vessels
What causes the ductus arteriosus to constrict after birth?
smooth muscle of the ductus arteriosus usually constricts due to sudden rise in blood oxygen tension and a reduction in level of circulating PGs. Over next few weeks intimal prolif. and fibrosis –> permanent closure
Discuss the pathophysiology of PDA.
As pulmonary resistance drops postnatally, the shunt reverse direction and blood flows from aorta into pulmonary circulation instead.
Due to Left to R shunt, the pulmonary circulation, LA and LV become volume overloaded
can lead to LV dilatation and left sided heart failure
Eisenmenger syndrome can develop causing reverse shunting
What is congenital aortic stenosis and how is it caused?
most often caused by abnormal structural development of the valve leaflets
most common abnormality is coarctation of the aorta
The aortic valve in congenital AS usual have a bicuspid leaflet structure instead of a tricuspid leaflet config, causing an eccentric stenotic opening through which blood is ejected
bicuspid valves often become progressively stenotic over many years as the leaflets progressively fibrose and calcify –> common cause of AS in adults
