Why does the venous pressure increase if CO decreases (as in heart failure)?

Venous pressure. Complicated to explain but to oversimplify, the venous pressure increases when the fluid volume in the venous beds increases and can't be pumped out adequately by the right side of the heart. There are many processes in play and when heart failure is present, fluid is retained and right heart pressure may increase causing venous pressure to increase.

Related Questions

How is it that right atrial pressure rises in severe heart failure?

RAP. In severe CHF with right ventricular failure the rv pressure rises forcing the pressure up in the right atrium to achieve rv filling in diastole. Read more...

Is blood pressure usually low in someone with heart failure?

Only severe one. BP can be high or low in chf. In very advanced CHF it is common for BP to stay on lower side. Read more...
No. In CHF pts:systolic blood pressure - the top number of the blood pressure reading - lower than 100 mmhg had a mortality rate of 50 percent, significantly higher than the 32-percent rate observed in a comparison group of patients who had pressures between 130 and 139 mmhg. Low diastolic blood pressure - the lower number of a blood pressure reading - was also linked to increased mortality. Read more...

Would one papvr with no other abnormalities in the heart lead to right heart failure? My rv enlarged but normal function and, pressure. Lv normal too.

It is possible. You have elevated pulmonary vascular resistance. Though your RV function is normal it is enlarged. You may want to find out why you pulmonary vascular resistance is elevated. Do you have have a condition that is increasing your pulmonary blood flow? Are you having silent pulmonary embolism that is decreasing the size of your pulmonary vascular bed? Both conditions can raise your pulmonary vascular. Read more...