Gorlin Formula Calculator

The Gorlin formula estimates the effective opening area of a heart valve from blood flow and the pressure difference across that valve. Clinicians most often use it during cardiac catheterization to quantify mitral stenosis, although related forms can be used for other valves. The result is an anatomical estimate in square centimeters, not a diagnosis by itself. Echocardiography, symptoms, rhythm, loading conditions, and the quality of the invasive measurements all remain important when interpreting the number. This calculator uses cardiac output in liters per minute, heart rate in beats per minute, systolic ejection period in seconds, and mean transmitral pressure gradient in millimeters of mercury. It converts cardiac output to milliliters per minute and divides flow by heart rate, filling time, the Gorlin constant of 44.3, and the square root of the mean gradient. The displayed indexed area divides valve area by body surface area. Indexing can add context when body size differs substantially from an average adult, but guideline decisions generally consider the absolute valve area together with the full clinical picture. To reproduce the source page examples, this calculator labels areas of at least 2.0 cm² normal, 1.5 through 1.99 cm² mild stenosis, 1.0 through 1.49 cm² moderate stenosis, and below 1.0 cm² severe stenosis. Classification boundaries vary by source and must not replace specialist assessment. A value close to a boundary should never be treated as categorically different without considering measurement uncertainty. The Gorlin estimate is sensitive to flow. Low cardiac output, tachycardia, irregular rhythm, an inaccurately measured diastolic filling period, or simultaneous pressure recordings that are not properly aligned can materially change the result. Significant mitral regurgitation can also make forward cardiac output an imperfect representation of total transmitral flow. Average several representative beats when rhythm varies and use measurements acquired under the same physiological conditions. Use this tool as a transparent arithmetic aid for trained clinical interpretation. Confirm units before calculating and review implausible values at their source. Decisions about surveillance, medical treatment, intervention, or surgery require a qualified cardiology team with access to the patient’s examination, imaging, catheterization tracings, symptoms, and preferences.