How to recognise reduced pulmonary blood flow clinically in the bed side ?
Posted Oct 21 2010 10:39am
During clinical examination of cyanotic congenital heart disease(CHD) , the major task is to differentiate conditions with reduced or increased pulmonary blood flow .
When a child with CHD is presented in clinical examinations , students are often asked to arrive at the diagnosis from history , physical examination before going in for ECG, X ray or echocardiography.
History, surprisingly can suggest the correct diagnosis in many (Most ?)
Reduced pulmonary blood flow is often associated with
Cyanosis appearing with /or worsening with exertion*
Hypoxic spells.(Almost always occur in reduced pulmonary blood flow )
History of squatting( Majority in reduced pulmonary flow)
Relief of dyspnea by assuming squatting position convey important hemodynamic information. It implies there is significant reduction in pulmonary blood flow in standing posture , that gets corrected in the squat position.For squatting to improve pulmonary blood flow there must be a communication between right and left heart .This is most often due to a large VSD, rarely an ASD .
*Note : Cyanosis is not specific for reduced pulmonary blood flow. In fact , simple reduction in pulmonary blood flow per se , cannot result in significant cyanosis .There need to be admixture /or right to left to shunt to produce cyanosis .Cyanosis in pure admixutre states like TGV, Single ventricle , Common AV canal , Common atrium TAPVC, are less Dependant on the reduction of pulmonary flow. In these situations RVOT obstruction if present will aggravate the baseline cyanosis.
Apart from direct evidence for reduced pulmonary blood flow , lack of evidence for increased pulmonary flow could often mean , we are actually dealing with reduced pulmonary blood flow.
The following are the clinical clues to suspect reduced pulmonary blood flow.
A quiet precardium*
A inconspicuous pulmonary component of S 2
Generally if S 2 is well split and both components are well heard it is highly likely the pulmonary blood flow is not reduced.
Lack of pulmonary arterial pulsations
Absence of mid diastolic flow murmurs in AV valves
Presence of continuous murmur in a patient with cyanotic CHD almost always mean reduced pulmonary flow and the lungs are perfused by alternate arterial collaterals (MAPCA)
* A silent heart is the hall mark of Tetrology of Fallot which constitutes 80% of all CHD with reduced pulmonary blood flow.