Cardiomyopathy or thickening of the heart muscle can be secondary to many things. The most common is high blood pressure. Just as the muscle in your arms begins to get bigger as you exercise it, the same thing happens to the heart. Excessive blood pressure lead to enlargement of the heart muscle as well. Other things that can cause cardiomyopathy is chronic obstructive pulmonary disease and ephysema. These diseases are most commonly seen in smokers. As it becomes more difficult for the heart to circulate blood to the lungs, the heart muscle begins to increase in size. It is not healthy to have swelling in the heart muscle as it is strongly suggestive of underlying cardiopulmonary disease. In the worst case scenarios cardiomyopathy can result in sudden death. Please make sure you follow your doctors instructions carefully and take your medications regularly to ensure that you remain healthy.
As I said earlier, if you are a long time smoker this can lead to increase in the size of the heart because your heart would have to work harder to pump blood to the lungs. The lungs would not be as efficient in performing the exchange of oxygen for carbon dioxide and as such there would be blood pooling in the lungs. This can ofen lead to accumulation of fluid. Therefore this would place greater pressure on the heart to work harder. Just by the mere fact that your heart is working harder would make the heart muscle hypertrophy (enlarge) for the same reason that a bodybuilders biceps enlarge when he works out by lifting weights in the gym.
Another source of fluid in or rather around the heart is something call a pericardial effusion. This is essentially fluid in the sac that surrounds the heart. This can happen because of infection, hypothyroidism, kidney failure, and medications such as hydralazine, isonizid and dilantin.