Why would a Patent Foramen Ovale lead to pulmonary hypertension?
High-pressure blood from left side of heart pushes through FO into right side of heart, which pumps increased blood volume into pulmonary artery thorugh pulmonary circulation. The pressure in the pulmonary circulation would be very high due to a left-right shunting of blood.
How would a Patent Foramen Ovale result in cyanosis in an animal?
Initially, oxygenated blood would flow from high-pressure left side through FO into right side of heart.
This would increase the pressure in the pulmonary circulation, and resistance would increase in those vessels.
This increased peripheral resistance would cause right side of heart to pump harder, increasing pressure in the right side. The higher right-side pressure reverses the left-right shunt to right-left, forcing deoxygenated blood through the FO into the left side, to be pumped out into aorta. Not enough blood gets oxygenated & it all gets mixed before it reaches the systemic circulation, so animal doesn't get enought oxygen.
What is the portosystemic shunt?
It is usually caused by a remnant of the ductus venosus from the foetal circulation, that enables oxygenated blood from the placenta to mostly bypass the liver and go straight to the heart, to be pumped out to the system via the aorta.
In PSS, the foetal shunt doesn't close, and so deoxygenated, nutrient-filled UNFILTERED deoxygenated blood from the GIT that is supposed to enter the liver via the portal vein instead gets diverted directly into the heart.
What is a potentially fatal consequence of PSS?
- Blood ammonia levels rise
- Uncleared toxins lead to hepatic encephalopathy (impaired brain function; confusion, head pressing, coma)
What is a Persistent Aortic Arch?
Failure of the right 4th aortic arch to become part of the proximal right subclavian artery.
Leads to degeneration of the aortic arch and the left aortic arch.
What are the physological consequences of a persistent right aortic arch?
The persistent right aortic arch passes near the oesophagus and if it persists the oesophagus can end up encircled by the persistent arch, the ligamentum arteriosum and by the base of the heart. This inhibits growth of the oesophagus and thus the passage of food to the stomach.
What is Patent Ductus Arteriosus & what is the main physiological consequence?
The ductus arteriosus is a shunt in the developing fetus from the 6th aortic arch between the pulmonary and aortic trunks.
At birth, this shunt is meant to close to form the ligamentum arteriosus, however in some cases it persists giving rise to the condition 'Patent Ductus Arteriosus'.
This defect eventually causes hypertrophy of the right and left ventricles due to increased workload.
What is Congenital Diaphragmatic Hernia?
Development defect in which diaphragmatic ligaments fail to fuse or form with the body wall, allowing abdominal organs to migrate into the thoracic cavity.
Problems can occur with:
- left &/or right crura
- dorsolateral transverse septum
- failure to close pleuroperitoneal folds
- weakness or gap in oesophageal hiatus
- central tendon
What abdominal organ is herniated most frequently into the pericardial cavity in Congenital Diaphragmatic Hernia?
Followed by intestines, spleen, then stomach.
What defects make up the Tetralogy of Fallot?
. 1. Pulmonary Infundibular Stenosis - A narrowing of the right ventricular outflow tract (pulmonary artery)
2. Right Ventricular Hypertrophy - Right ventricle is more muscular than normal
3. Ventricular Septal Defect - A hole between the 2 ventricles
4. Overriding Aorta - When the aorta is situated directly above a ventricular septal defect instead of the left ventricle
This tetrology of defects together lead to hypoxia.