Cyanotic congenital heart defects Flashcards
(37 cards)
In TGA, what defects must be present to maintain circulation?
ASD, VSD, PDA, Foramen ovale
What are the clinical features of transposition?
- Cyanosis from birth
- CHF signs
- Effortless tachypnoea
- Single and loud S2
- No murmur in intact septum
* 6. Hypoxia with acidosis- not responding to hyperoxitest.
What are the ECG findings in TGA?
Normal or RVH (upright T in V1 may be only abnormality after day 3)
BVH if VSD, PSA or Pulmonary vascular disease present
CXR findings in TGA?
Cardiomegaly with increased pulmonary vascularity
Egg shaped cardiac silhouette
Management of TGA?
PGE1 infusion
Atrial balloon septoplasty (Rashkind)
Corrective surgery within weeks of birth
Steps in managing a cyanotic neonate
- CXR (may reveal pulmonary cause)
- ECG
- ABG in room air (a high pCO2 suggests lung or CNS problems, a low pH seen in sepsis, shock or severe hypoxaemia)
- Hyperoxitest
- UA line: Differential between pre and post ductal suggests shunt
- PGE1
What are the duct dependant systemic circulations?
Coarctation of aorta
Hypoplastic left heart
Critical AS
Interrupted aortic arch
What are the duct dependant pulmonary circulations?
TGA Pulmonary atresia with/without VSD Critical PS TOF Tricuspid atresia TAPVD with obstruction Ebstein's anomaly
What abnormalities are present in TOF?
- RVOTO
- VSD (large enough to equalize pressures in both ventricles)
- RVH (secondary to RVOTO)
- Overriding aorta (varies)
In TOF, what is the most common type of RVOTO?
Infundibular stenosis- 45%
Rarely at PV level-10%
Combo- 30%
What are the associations of TOF?
Downs
22q microdeletion syndrome (DiGeorge)
CHARGE
VACTERL
Examination findings in TOF?
Varying degrees of cyanosis, tachypnoea and clubbing
RV tap along left sternal edge, systolic thrill ULSE
Ejection click in the aorta
Single S2 (P2 too soft to hear)
Loud Ejection systolic murmur and mid-ULSE (PS). More severe obstruction, softer and shorter the murmur.
*Acyanotic form- VSD and infundibular murmur along LSE.
ECG findings in TOF?
RAD in cyanotic TOF, normal axis in acyanotic
RVH
CXR findings in cyanotic TOF?
Normal heart size or smaller than normal
Decreased lung vascular markings
Boot shaped heart
What is the natural history of TOF?
- Worsening cyanosis
- Polycythaemia secondary to cyanosis (relative iron deficiency states)
- Hypoxic spells
- Growth retardation
- Brain abscesses and CVAs rarely occur
- SBE occasional
- Aortic regurg
- Coagulopathy is late complication of chronic cyanosis
What are the characteristics of a tet spell?
Hyperpnoea, irritability, prolonged crying, increasing cyanosis, decreased intensity of murmur.
Peak incidence 2-4 months
Usually in morning after crying, feeding or poos.
Severe spells- limpness, convulsions, CVA and death
What are the broad categories for the causes of cyanosis?
- Inadequate alveolar ventilation
- Desaturated blood bypassing effective alveolar units
- Increased deoxygenation in the capillaries
- Methaemoglobinaemia
How to differentiate cardiac vs pulmonary cyanosis?
Hyperoxitest- Inhaling 100% O2 in the presence of a shunt will increase the concentration of oxygen in the blood but the corresponding saturation of the Hb-O2 dissociation curve is not proportionally increased.
How does oxygen in plasma differ from Hb?
Hb is sigmoid, plasma is linear.
How does fetal Hb differ from adults? and when is it reached
Greater affinity for O2, favouring the extraction of O2 from the maternal circulation, but slow to release into the tissues.
3 months
What increases Hb’s affinity for oxygen?
- Alkalosis
- Hypothermia
- Decreased 2.3.DPG
- Decreased ATP
What are the consequences and complications of cyanosis?
- Polycythaemia- bone marrow stimulated through Epo . Viscous blood exacerbates CHF
- Clubbing
- CNS- CVA and brain abscesses. Central venous thromboses.
- Bleeding disorders- Thrombocytopaenia, prolonged PTT
- Hypoxic spells and squatting
- Scoliosis
- Hyperuricaemia and gout
What is the acidosis in cyanotic heart disease caused by? and the consequences
Low arterial oxygenation causes anaerobic glycolysis
Both detrimental to myocardial function, together with volume overload leads to CHF
Stimulate the carotid and cerebral chemoreceptors to increase RR
How are persistent truncus arteriosis and single ventricle similar?
- Almost complete mixing of systemic and pulmonary blood
- Identical pressures in the ventricles
- Level of oxygen saturation in the systemic circulation is proportional to PBF.