Myotonic Dystrophy is a type of Muscular Dystrophy. The heart is a kind of muscle so you would think it would be affected. The heart is affected but not in the way that you think. The heart muscle cell is not affected what causes the problems in myotonic dystrophy is the electrical conduction of the heart. The heart has an electric circuit like your car. Think of the problems like the circuit is not sending the proper signals to the engine to fire the cylinders at the right time. Sometimes the signals are too slow. Sometimes they are too fast. Sometimes they dont signal at all. Click the link below for a  brochure on this topic People that have either myotonic dystrophy or the congenital form are at a high risk of developing life threatening heart problems. There is a correlation between the number of repeats for the diseases and the severity of the cardiac problems. Eleven percent (11%) of patients in a recent study died suddenly from what is believed to be cardiac problems. Another 28% had cardiac problems of one type or another.    Heart Problems in Myotonic Dystrophy

Although coronary heart disease is not increased in DM patients, there is a greater than average occurrence of disturbed conduction issues among DM1 and DM2. The cardiac conduction defects are usually characterized by palpitations, fainting or near fainting spells can occur and should never be ignored. These can be fatal. These
arrhythmia’s can occur in an otherwise healthy heart. An arrhythmia is a disturbed conduction of the heartbeat. Cardiac arrhythmia’s and sudden death are a major cause of mortality in Myotonic Dystrophy patients, even in young patients with limited muscle problems. Acute arrhythmic disorders should be treated by a cardiac specialist who has
experience with DM patients. Patients must always let their attending physician know that
they have Myotonic Dystrophy. In many cases the physician may not be familiar with DM so the patient should be prepared to present materials to the physician.

Dr. William Groh in Indianapolis, IN USA is the recognized expert in the cardiac care of patients with myotonic dystrophy. Cardiac disease in MMD1, Groh says, is nearly always conduction disturbance, resulting from the gradual replacement of the heart’s conductive tissue with scar tissue, a process known as cardiac fibrosis. It’s the conduction of electrical signals that move through the heart that first disturbed in patients with myotonic dystrophy,

Conduction disturbance can lead to abnormal heart rhythms called arrhythmias. Arrhythmias that are too slow sometimes require a pacemaker that delivers regularly timed electrical impulses to bring the heart rate up to normal.

When the heart rhythm is too fast, an implantable defibrillator can deliver an electrical shock to restore a normal heart rhythm. These are called ICD’s

the underlying problem  with the heart in myotonic dystrophy s fibrosis and abnormalities in the heart that seem to specifically and primarily affect the conduction system, the specialized tissue that allows for electricity to flow through the heart. It leads to a higher risk of arrhythmias, and a small percentage of patients develop cardiomyopathy.”

The most serious arrhythmias are those that cause the lower chambers of the heart — the ventricles — to stop beating or to beat too slowly to sustain life; or to beat in a fast, uncoordinated and ineffective way. Both these fast and slow ventricular arrhythmias can lead to sudden death, and people with MMD1 unfortunately are at increased risk for that.

Here is a great video from the Library at the Myotonic Dystrophy Foundation. This video talks about the heart and the electrical issues in the heart with Myotonic Dystrophy

Pacemakers and Defibrillators: Pacemakers are generally used to manage a heartbeat that is too slow or irregular, caused by disorders that disrupt the heart’s normal electrical conduction system. This condition known as bradicardia can cause inadequate blood flow through the body creating symptoms such as fatigue, dizziness, and fainting.

*This information was copied from the evidence based clinical guidelines developed by the Collaborative Project Byall Scottish Clinical Genetics Services.