Which of the following is indicative of severe mitral stenosis?

Severe mitral stenosis leads to increased pulmonary venous pressure due to the obstruction of blood flow from the left atrium to the left ventricle during diastole. When the mitral valve is narrowed, blood can back up in the left atrium, and as the condition progresses, this can lead to elevated pressures in the pulmonary veins. The increased pressure in the pulmonary circulation can result in symptoms such as pulmonary congestion, dyspnea, and potentially pulmonary edema as the body's compensatory mechanisms fail to manage the increased fluid load.

In the context of mitral stenosis, left ventricular pressure does not increase. The left ventricle may actually experience a decrease in pressure because it is filling less efficiently due to the obstruction at the mitral valve. The left atrium also works harder to overcome the resistance, leading to its enlargement. While systemic blood pressure can be affected in various ways with mitral stenosis, it is the pulmonary venous pressure that is a direct and critical measure indicating severe involvement of the mitral valve pathology.