Enlarged heart competes with lungs for chest space

By Will Boggs, MD

NEW YORK (Reuters Health) - The heart enlargement that develops in people suffering from chronic heart failure takes up extra space in the chest cavity, thereby reducing the capacity of the lungs, according to a new report. This contributes to the problem of breathlessness for heart failure patients.

As Dr. Bruce D. Johnson told Reuters Health, "Some of the loss in lung function is due to the increasing heart size within the thoracic cavity. This also likely contributes to the rapid shallow breathing pattern in heart failure patients at rest and during exercise and likely increases the work and cost of breathing."

Johnson, from the Mayo Clinic in Rochester, Minnesota, and colleagues examined the relationship between volumes of the thorax, heart and lungs -- measured on X-rays -- in 44 heart failure patients and in 44 "control" subjects without cardiovascular disease.

While there was no significant difference in the total volume of the thorax between patients and controls, the investigators report in the medical journal Chest, the volume of the heart was significantly higher and lung volume was lower among heart failure patients.

The differences were accentuated in severe heart failure. "As the disease of heart failure progresses, the heart continues to enlarge and compete for intra-thoracic space at the expense of other organs like the lungs," Johnson said.

This competition, he added, may be enhanced in patients with conditions like obesity and obstructive lung disease, which also influence how much space is available in the chest cavity.

"The problem is that as heart failure worsens, the heart may enlarge, blood backs up due to the failing left ventricle, fluid accumulates in the lungs and it is a combination of factors that cause a deterioration in lung volumes and flow rates," Johnson explained.

"Currently, aggressive medical management of heart failure patients to prevent the remodeling and enlarging of the heart is the best treatment," he advised.

SOURCE: Chest, July 2006.