Left Ventricular Mass Index Calculator

Background.

The left ventricle thickens when it works against a heavy load for years. Long-standing high blood pressure, a narrowed aortic valve and inherited cardiomyopathies all add muscle to its walls, and a heart that has grown heavier carries more risk of heart failure, arrhythmia and stroke than its blood pressure alone would suggest. Left ventricular mass puts a number on that growth, and dividing it by body surface area lets a large adult and a small one be compared on the same scale.

Most echocardiography reports still estimate the mass from three straight-line measurements taken at end-diastole: the thickness of the septum, the internal diameter of the cavity and the thickness of the posterior wall. Picture the ventricle as an ellipsoid shell about twice as long as it is wide, whose volume comes close to the cube of its diameter. Cube the outer diameter, subtract the cube of the cavity, and what remains is the volume of muscle. Multiply by the density of heart muscle, apply the correction from the method's autopsy validation, and you have grams: about 182 g for a heart with 1 cm walls around a 5 cm cavity.

The cubing is both the method's strength and its weakness. It is quick and reproducible from a standard view, but every millimetre counts three times over: on an average-sized heart, a septum read 1 mm too thick adds about 12 g. The shape assumption also breaks down in ventricles distorted by an old infarct, an aneurysm or thickening confined to one segment, where 3D echocardiography or cardiac MRI gives a truer figure.

The calculator reports the mass and the index only. It does not label the result normal or hypertrophied; compare it with the sex-specific reference ranges your laboratory uses, and leave interpretation to the clinician who has the whole study in front of them.

What is left ventricular mass index calculator?

Left ventricular mass is the weight of the muscle in the left ventricle's walls, in grams, estimated here from end-diastolic echocardiographic dimensions. The mass index divides it by body surface area to give grams per square metre, so the value can be judged against the size of the person it belongs to. It describes how much muscle there is, not how well that muscle contracts, and it is the standard echocardiographic measure for detecting and following left ventricular hypertrophy.

Mass and wall thickness are related but not interchangeable. Walls can be thick around a small cavity while the total mass stays within range, a pattern called concentric remodelling, and a dilated ventricle with walls of ordinary thickness can carry a high mass. That is why the guideline reads the mass index alongside relative wall thickness rather than relying on either number alone.

Indexing has its own blind spot. Body surface area rises with body fat as well as lean mass, but fat does not demand more heart muscle, so dividing by a large surface area can make a heavy heart in a person with obesity look ordinary. Indexing to height raised to the power 2.7 avoids that, which is why some laboratories report it as well.

How to use this calculator.

1. 01Take the septal thickness, internal diameter and posterior wall thickness from the same end-diastolic frame in the parasternal long-axis view, measured perpendicular to the long axis of the ventricle at about the level of the mitral leaflet tips. A cut that runs obliquely across the ventricle lengthens all three numbers at once.
2. 02Enter all three in centimetres; reports in millimetres divide by 10, so a 9 mm septum is 0.9 cm. Keep chordae, trabeculations and pericardium out of the wall measurements, because anything included is cubed into the result.
3. 03Enter body surface area in square metres, worked out from height and weight with the formula your laboratory uses; it is not calculated here. The Mosteller formula, √(height in cm × weight in kg ÷ 3600), gives 1.84 m² for someone 175 cm tall weighing 70 kg.
4. 04Read the mass in grams and the index in g/m², and set the index against the sex-specific reference range your echo laboratory reports. When comparing studies over time, use the body surface area from each visit: a 175 cm adult going from 70 to 80 kg moves from 1.84 to 1.97 m², and the same 181.976 g heart then indexes about 6.5% lower.

The formula.

LVM = 0.8 × 1.04 × [(IVSd + LVIDd + PWTd)³ − LVIDd³] + 0.6, and LVMI = LVM ÷ BSA. The sum IVSd + LVIDd + PWTd is the outer diameter of the ventricle at end-diastole. Cubing it approximates the volume enclosed by the outside of the muscle; subtracting LVIDd³ removes the blood-filled cavity and leaves the volume of myocardium, in millilitres when the dimensions are in centimetres. Multiplying by 1.04, the specific gravity of heart muscle in grams per millilitre, converts volume to mass. The factor 0.8 and the added 0.6 g correct the raw cube estimate to match hearts weighed at autopsy, and the ASE/EACVI 2015 recommendations keep them.

The cube itself comes from the shape assumption. A prolate ellipsoid whose long axis is twice its short-axis diameter D has a volume of (π/6) × D × D × 2D = (π/3)D³, and π/3 is about 1.047, close enough to 1 that the volume is taken as simply D³. Applied once to the outer diameter and once to the cavity, the difference is the shell of muscle. Together the constants mean each millilitre of that shell counts for 0.8 × 1.04 = 0.832 g. The 0.6 g offset barely registers on a heart of 180 g; the 0.8 factor, by contrast, trims the raw estimate by a fifth.

Because the wall thicknesses sit inside a cubed term, small errors in them grow. Differentiating the formula gives a rule of thumb: each extra millimetre on either wall adds roughly 0.25 g times the square of the outer diameter in centimetres, about 12 g for a 7 cm ventricle, while each extra millimetre of cavity adds about 0.25 g times the difference between the squares of the outer and inner diameters, about 6 g in the same heart. In the worked example, 1 mm more septum raises the mass by 6.8% and 1 mm more cavity by 3.3%. Errors that stretch every dimension together compound: a measuring line tilted 15° from perpendicular reads each dimension about 3.5% long, and the example heart's mass then comes out near 201.9 g instead of 181.976 g, almost 11% too high. The correction factors were fitted to end-diastolic measurements, so dimensions from any other frame of the cardiac cycle fall outside what the formula was calibrated for.

A worked example.

Frequently asked questions.

References& sources.

1. [1]ASE/EACVI, Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults, 2015.
2. [2]Lang et al., Journal of the American Society of Echocardiography 28(1), 2015.
3. [3]BIPM, The International System of Units (SI Brochure), 9th ed., version 3.01, coherent derived units and quantity equations.
4. [4]NIST Special Publication 811, Guide for the Use of the International System of Units, 2008 edition.
5. [5]ASE, Cardiac Chamber Quantification in Adults guideline page.