Not a physician.

It's kinda in the center but because the left ventricle is BIG makes it looks like it's off the left. Also, the left ventricle beats the hardest, it gives the feeling that the heart is on the left.

I heard that it is to make room for the stomach, which is off to the other side.

Also, rib cage has spine and sternum that limit the available space directly in the middle.

And for those wanting to know more, the reason the left ventricle is bigger and beats harder is because of the path blood takes through your body. It gets pumped out of your left ventricle to supply all the cells in your body with oxygen and nutrients, then it returns to the heart and gets pumped out of your right ventricle to the lungs where it resupplies its oxygen and gets rid of carbon dioxide, then returns back to the heart to get pumped out of the left ventricle again. So the right side has a much shorter route it has to send the blood through and therefore doesn't need to be as big.

We're getting into things not relevant to the original question now, but a fun fact is that while many people think what defines an artery and a vein is whether it carries oxygenated or de-oxygenated blood, this is actually not true. The left ventricle does pump blood through arteries to the rest of your body and then that blood returns back to the heart through veins, but the right ventricle pumps de-oxygenated blood through the pulmonary artery to the lungs, and then the oxygenated blood returns to the heart through the pulmonary vein. So it's actually the direction of the flow relative to the heart that defines veins and arteries, not the oxygenated state of the blood it carries.

This is not true. It's quite close to the center but the reason it's off to one side is due to how the heart develops. The heart starts out as a set of two straight tubes which fuse together. The heart is actually beating in this state as a straight tube. The heart's final shape is due to a twisting of this tube. You can visualize this with a string. Grab it with each hand about an inch apart. Then gently twist it as you bring your hands a little closer together. You'll see that the string will bulge out to the side. Normally the heart will bulge out to the left which is why the left lung has one less lobe than the right.

Normally, both the left and right ventricles point to the left, about +60° down from horizontal. But it's relatively common to see anything from -30 to +100° from a horizontal line to the left. This is called the heart's axis and it can be determined by ECG. It is true that in something like high blood pressure for example, the left ventricle enlarges so much that this axis will change to <-30° and similarly with high pulmonary pressure causing right ventricle enlargement to shift the axis >+100°. There are also situations, e.g. dextrocardia where the heart is switched to the right and situs inversus where all the internal organs are on the opposite side. But normally the heart is on the left and points down and to the left.

This is not true. The stomach is also mostly on the left side, with the liver mostly on the right.

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