Editing Cardiac catheterization (section)

===Valve assessment===
[[Echocardiography]] is a non-invasive method to evaluate the heart valves. However, sometimes the valve pressure gradients need to be measured directly because echo is equivocal for the severity of valve disease. Invasive assessment of the valve can be done with catheterization by placing a catheter across the valve and measuring the pressures simultaneously on each side of the valve to obtain the pressure gradient.<ref>Grossman & Baim's cardiac catheterization, angiography, and intervention. Moscucci, Mauro, (Eighth edition). Philadelphia. p. 272. {{ISBN|9781451127409}}. OCLC 829739969.</ref> In conjunction with a right heart catheterization, the valve area can be estimated. For example, in [[aortic valve area calculation]] the Gorlin equation can be used to calculate the area if the cardiac output, pressure gradient, systolic period, and heart rate are known.{{citation needed|date=March 2021}}