Aortic Stenosis

Recall: Which statement best describes the pathophysiology of aortic stenosis? Choose the most accurate description of how it affects blood flow and the left ventricle.

• Narrowing of the aortic valve obstructs outflow from the left ventricle, causing increased LV pressure and concentric hypertrophy

• Dilation of the aortic valve allows regurgitation into the left ventricle, leading to eccentric hypertrophy

• Stiffening of the mitral valve prevents LV filling, reducing end-diastolic volume without pressure changes

• Narrowing of the pulmonary valve increases right ventricular afterload, leading to RV hypertrophy

Strategic thinking: A 68-year-old with exertional chest pain, syncope episodes, and a harsh systolic ejection murmur radiating to the carotids is suspected of having aortic stenosis. Which diagnostic approach most directly confirms valve narrowing and gradient severity?

• Chest X-ray to assess cardiomegaly and pulmonary congestion

• Electrocardiogram to detect left ventricular hypertrophy patterns

• Echocardiography with Doppler to measure transvalvular gradients and valve area

• Cardiac biomarkers to evaluate myocardial injury

Recall: Which statement best describes the pathophysiology of an Atrial Septal Defect (ASD)?

• An opening between the left and right ventricles allows oxygenated blood to mix with deoxygenated blood

• A persistent opening in the atrial septum permits left-to-right shunting of oxygenated blood from the left atrium to the right atrium

• A narrowing of the aortic valve creates increased left ventricular outflow resistance

• A patent ductus arteriosus keeps fetal circulation pathways open between the aorta and pulmonary artery

Application: A 17-year-old presents with easy fatigability, dyspnea on exertion, and a fixed split S2 on auscultation. Based on these findings, which initial diagnostic test is most appropriate to confirm Atrial Septal Defect?

• Chest X-ray to assess lung fields and cardiac silhouette

• Electrocardiogram to detect ventricular arrhythmias

• Echocardiography to visualize interatrial septal defect and flow across it

• Cardiac enzymes to evaluate myocardial injury

Recall the fundamental pathophysiology of a ventricular septal defect (VSD). Which statement best describes the hemodynamic consequence in an unrepaired VSD?

• Right-to-left shunt from the right ventricle to the left ventricle causing cyanosis

• Left-to-right shunt from the left ventricle to the right ventricle increasing pulmonary blood flow

• Obstruction of outflow from both ventricles resulting in decreased systemic perfusion

• Complete separation of the ventricles preventing any mixing of blood

A 6‑month‑old infant presents with poor feeding, tachypnea, and a pansystolic murmur at the left lower sternal border. Which diagnostic test is most appropriate to confirm a ventricular septal defect and assess its size and location?

• Chest X‑ray to visualize cardiomegaly and pulmonary edema

• Electrocardiogram to detect conduction abnormalities

• Transthoracic echocardiography with Doppler to delineate the septal defect and shunt

• Pulse oximetry to measure peripheral oxygen saturation

Patent ductus arteriosus (PDA) is a condition where a fetal vascular connection remains open after birth. Which statement best describes the pathophysiology of PDA?

• Persistent connection between the pulmonary artery and the aorta causing left-to-right shunt

• Failure of the foramen ovale to close leading to right-to-left shunt

• Narrowing of the aortic isthmus obstructing systemic outflow

• Single common arterial trunk supplying both systemic and pulmonary circulations

A term infant presents with a continuous “machinery” murmur and bounding pulses. Which associated finding most strongly supports the diagnosis of PDA?

• Wide pulse pressure with signs of pulmonary overcirculation

• Cyanosis that improves with squatting

• Diminished femoral pulses compared with brachial pulses

• Fixed splitting of the second heart sound

A 6-month-old presents with cyanosis and a history of "tet spells" relieved by squatting. Based on TOF pathophysiology, which mechanism most directly explains why squatting improves symptoms?

• It increases systemic vascular resistance, reducing right-to-left shunt across the VSD

• It decreases venous return to the right heart, lowering RV pressure

• It increases pulmonary valve opening, enhancing forward flow to lungs

• It raises heart rate, improving cardiac output despite the shunt

Coarctation of the aorta most directly leads to which hemodynamic consequence due to narrowing of the aortic lumen?

• Uniform blood pressure in upper and lower extremities

• Decreased pressure proximal and increased pressure distal to the narrowing

• Increased pressure proximal with decreased perfusion distal to the narrowing

• Global reduction in systemic vascular resistance