Underdeveloped left ventricle impairs systemic circulation

Steps:

• The lower left chamber is the left ventricle, responsible for pumping oxygenated blood from the lungs to the body.
• A smaller left ventricle reduces the volume of blood it can eject per beat.
• This blood exits the ventricle through the aorta to supply the systemic arteries.
• Thus, aortic blood flow decreases due to diminished left ventricular output.

Why A is correct:

• The aorta is the primary vessel receiving blood from the left ventricle; reduced ventricular size directly lowers flow per the cardiac output equation (CO = HR × SV), where stroke volume (SV) is impaired.

Why the others are wrong:

• B. Pulmonary artery carries deoxygenated blood from the right ventricle to the lungs, unaffected by left-side defects.
• C. Pulmonary vein returns oxygenated blood to the left atrium, upstream of the ventricle and unchanged.
• D. Vena cava delivers deoxygenated blood to the right atrium, part of right-side input not impacted.

Final answer: A