This young man was having a panic attack, and his symptoms resolved without treatment. His heart is not enlarged and his lungs show normal vascular distribution and no sign of CHF.

The measurements used to assess for enlargement of the heart are called the 'cardio-thoracic ratio'. In this calculation, the maximum diameter of the thorax (from the inner ribs at the widest point) is compared to the maximum diameter of the heart (from the widest point on the right, indicated by the arrow, to the widest point on the left, also indicated by an arrow, measured in the horizontal plane. However, this measurement is hard to visually estimate quickly, so there is an easier way. If you draw a horizontal line segment from the widest point of the right heart to the midline, and another segment from the widest point of the left heart to the inner left ribs, these shorter segments are easy to visually compare. In a normal heart, the right-to-midline segment should be equal to or shorter than the left-to-rib segment, as in this case.