Chronic atrial and intestinal dysrhythmia

Chronic atrial and intestinal dysrhythmia (CAID) is a disorder affecting the heart and the digestive system. CAID disrupts the normal rhythm of the heartbeat; affected individuals have a heart rhythm abnormality called sick sinus syndrome. The disorder also impairs the rhythmic muscle contractions that propel food through the intestines (peristalsis), causing a digestive condition called intestinal pseudo-obstruction. The heart and digestive issues develop at the same time, usually by age 20.

Sick sinus syndrome (also known as sinus node dysfunction) is an abnormality of the sinoatrial (SA) node, which is an area of specialized cells in the heart that functions as a natural pacemaker. The SA node generates electrical impulses that start each heartbeat. These signals travel from the SA node to the rest of the heart, signaling the heart (cardiac) muscle to contract and pump blood. In people with sick sinus syndrome, the SA node does not function normally, which usually causes the heartbeat to be too slow (bradycardia), although occasionally the heartbeat is too fast (tachycardia) or rapidly switches from being too fast to being too slow (tachycardia-bradycardia syndrome). Symptoms related to abnormal heartbeats can include dizziness, light-headedness, fainting (syncope), a sensation of fluttering or pounding in the chest (palpitations), and confusion or memory problems. During exercise, many affected individuals experience chest pain, difficulty breathing, or excessive tiredness (fatigue).

In intestinal pseudo-obstruction, impairment of peristalsis leads to a buildup of partially digested food in the intestines, abdominal swelling (distention) and pain, nausea, vomiting, and constipation or diarrhea. Affected individuals experience loss of appetite and impaired ability to absorb nutrients, which may lead to malnutrition. These symptoms resemble those caused by an intestinal blockage (obstruction) such as a tumor, but in intestinal pseudo-obstruction no such blockage is found.