Pericardial mesothelioma, the rarest form of the disease, develops in the mesothelial cells of the membrane surrounding the heart known as the pericardium. The pericardium is made up of two layers that offer protection and support to the heart. The outer layer (the parietal layer) lines the entire chest cavity while the inner layer (the visceral layer) lines the heart.

Pericardial mesothelioma is caused by exposure to asbestos; however, scientists are still unsure of how asbestos fibers become lodged in the pericardium. One theory suggests that the fibers are broken down into smaller pieces in the lungs and are absorbed into the bloodstream. The fibers then flow through the heart, become stuck in the pericardium, and cause inflammation that can lead to cancerous growths.

The majority of pericardial symptoms are caused by fluid build up and thickening of pericardial layers. Some common symptoms of this asbestos-induced disease include:

• Heart palpitations or an irregular heartbeat
• Heart murmurs
• Chest pain
• Difficulty breathing
• Coughing
• Fever or night sweats
• Fatigue