Patients with severe pulmonary stenosis may present with which of the following signs?

Severe pulmonary stenosis is characterized by the narrowing of the outflow tract from the right ventricle to the pulmonary artery, which leads to increased pressure in the right ventricle during systole. This pressure gradient results in a characteristic systolic ejection murmur that is best heard at the left upper sternal border. The murmur is caused by the turbulent blood flow as it is forced through the narrowed outflow tract into the pulmonary artery.

The presence of this murmur is a classic sign of pulmonary stenosis, making it an essential component of the auscultatory findings in patients with this condition. The other choices do not align with the typical presentations associated with severe pulmonary stenosis. For instance, left axis deviation may not be directly linked to pulmonary stenosis, a diastolic murmur is more indicative of conditions involving regurgitation rather than stenosis, and palpitations are generally more related to arrhythmias or other cardiac conditions rather than the mechanical obstruction caused by pulmonary stenosis itself. Thus, the correct answer, indicating the presence of a systolic ejection murmur, accurately reflects the clinical presentation of patients with severe pulmonary stenosis.