Figure 5. Diagrams show the hemodynamics in a normal heart and in a heart with mitral valve stenosis. LV = left ventricle. 1, During atrial diastole in the normal heart, the left atrium (LA) fills with blood from the pulmonary veins. 2, During atrial systole in the normal heart, the mitral valve opens wide, and most of the atrial contents is discharged into the left ventricle (large arrow), with only a small amount refluxing into the pulmonary veins (small arrows). 3, During atrial diastole in the case of mitral valve stenosis with no venospasm, the venous size is normal. 4, During atrial systole with no venospasm, however, much of the atrial content refluxes back into the compliant veins (short arrows) because of the high resistance to outflow through the stenosed mitral valve (long arrow). 5, During atrial systole with protective venospasm, the veins contract, and only minimal venous reflux (short arrows) can occur. Most of the atrial content will be discharged into the left ventricle (long arrow); that is, venospasm protects left atrial function. (Reprinted and adapted, with permission, from reference 7.)