Clinical Considerations
- Tetralogy of Fallot is a congenital heart malformation involving multiple structural defects.
- Tetralogy means a set of four findings.
- Tetralogy of Fallot classically includes a ventricular septal defect, narrowing of the pulmonary outflow path, right ventricular hypertrophy, and an overriding or right-shifted aorta.
- Pulmonary outflow narrowing makes the right ventricle pump against extra resistance, which helps explain the right ventricular hypertrophy.
- Congenital malformation means an abnormal structure present at birth.
- Interventricular septum is the wall separating the right and left ventricles.
- Defective interventricular septum allows abnormal communication between ventricles.
- Right ventricular hypertrophy means enlargement of right ventricular muscle because it must pump against increased resistance.
- Pulmonary artery narrowing or pulmonary valve narrowing can overload the right ventricle in tetralogy of Fallot.
- In Tetralogy of Fallot, the aorta is usually described as overriding or shifted toward the right, so it receives blood from both ventricles through the septal defect.
- Dextroposed aorta means the aorta is shifted toward the right side.
- Early surgical repair is important in tetralogy of Fallot before pulmonary constriction worsens.
- Right heart is the functional side that serves pulmonary circulation.
- Pulmonary system is the circulation that sends blood to the lungs for gas exchange.
- Left heart is the functional side that serves systemic circulation.
- Systemic system is the circulation that sends blood to the body tissues.
- Right atrium receives venous blood returning from the body.
- Venous blood usually means blood returning from tissues with lower oxygen content.
- Right ventricle receives blood from the right atrium.
- Pulmonary trunk carries blood from the right ventricle toward the lungs.
- Pulmonary venous blood enters the left atrium after gas exchange in the lungs.
- Left ventricle pumps blood into the aorta.
- The aorta is the main artery that distributes blood into systemic circulation.
- Sympathetic innervation to the heart comes from upper thoracic spinal-cord levels.
- Parasympathetic innervation to the heart travels through the vagus nerves.
- Vagus nerves carry parasympathetic fibers to many thoracic and abdominal organs.
- Autonomic modulation changes heart rate and contraction strength but does not start the heartbeat.
- Atrial natriuretic peptide is a hormone made especially by atrial heart cells.
- B-type natriuretic peptide is another heart-produced hormone involved in blood-pressure regulation.
- Natriuretic means promoting sodium excretion by the kidneys.
- Renal sodium secretion and renal water secretion increase when natriuretic peptides act.
- Renin release is inhibited by natriuretic peptides.
- Blood pressure falls when sodium and water excretion increase and renin release decreases.
- Sympathetic stimulation accelerates heart rate and increases contraction force.
- Coronary vessels supply the heart muscle itself.
- Coronary vasodilation occurs with sympathetic innervation in this context.
- Parasympathetic stimulation slows heart rate and reduces contraction force.
- Coronary vasoconstriction occurs with parasympathetic innervation in this context.
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