Final Answer:
Left to Right Shunts (Acyanotic):
If the SYSTEMIC vascular resistance (SVR) is greater than the PULMONARY vascular resistance (PVR), then the blood is FORCED back into the PULMONARY circulation. There is INCREASED pulmonary blood flow which leads to ACYANOTIC defects, including Atrial and Ventricular SEPTAL Defects (ASD, VSD), Patent DUCTUS ARTERIOSUS (PDA), and Atrioventricular Canal Defect (AVCD).
Right to Left Shunts (Cyanotic):
If the PULMONARY vascular resistance (PVR) is greater than the SYSTEMIC vascular resistance (SVR), then the blood is SHUNTED from the right to the left heart. There is DECREASED PULMONARY blood flow which leads to CYANOSIS. Defects include Tricuspid ATRESIA and Tetralogy of Fallot (TOF) with Ventral Septal Defect, Pulmonary Stenosis, Overriding Aorta, and Right Ventricular Hypertrophy.
Step-by-step explanation:
Left-to-right shunts are determined by the relationship between systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR). If SVR is greater than PVR, blood is forced back into the pulmonary circulation, resulting in increased pulmonary blood flow. This condition leads to defects like atrial and ventricular septal defects (ASD, VSD), patent ductus arteriosus (PDA), and atrioventricular canal defect (AVCD). These defects allow blood to flow from the left side of the heart to the right, causing pulmonary overcirculation.
On the other hand, right-to-left shunts occur when PVR is greater than SVR. This leads to decreased pulmonary blood flow and cyanosis, as blood is shunted from the right heart to the left heart without passing through the lungs for oxygenation. Defects associated with right-to-left shunts include tricuspid atresia and Tetralogy of Fallot (TOF). TOF is characterized by a ventral septal defect, pulmonary stenosis, overriding aorta, and right ventricular hypertrophy. The imbalance in resistance forces deoxygenated blood to bypass the pulmonary circulation, resulting in cyanosis and a characteristic set of cardiac anomalies.
Understanding these shunt conditions is crucial for diagnosing and managing congenital heart defects, guiding appropriate interventions to optimize cardiac function and patient outcomes.