Introduction

Myotonic dystrophy (also known as dystrophia myotonica or DM) is a kind of muscular system related disorder, where weakness and other disability is also observed. It affects the multiple organ systems in the patients, and gets passed on to the next generation too. Many of the complications are assessed by having a detailed family history.

DM causes many disorders, like issues related to the heart’s electrical signals, infertility, cataract, diabetes etc. This is mainly classified into two types: Myotonic dystrophy type I (DM1) and Myotonic dystrophy type II DM2. DM1 is more common than DM2.

In DM1, muscles that are away from the center of the body get affected, and it is found in all age groups. The patient faces many issues, like problems while speaking, brain-related issues which do not allow the patient to communicate in a normal way. 

DM2 is a disorder related to the muscles near to the center of the body, and relates to the adult patients with a mean age of 48. This includes the hips and shoulders muscles. Patients, suffering with DM2, complain of the pain as one of the major issues.¹

Various kinds of heart-related complications are found in the patients suffering from  DM. A few of the alterations found in the DM patients are thickening in between the spaces of the heart cells, fat accumulation, increased workload on the heart cells, and a typical inflammation in the heart walls that shows the change in the rhythm on Electrocardiogram (ECG).²

Around 33% of the deaths are due to heart-related issues in DM patients, and a few of them due to heart failure. When the pumping of the heart becomes non-functional issues occur like blood flow decreases and the vessels that supply blood to the lungs get clogged.³

It shows almost no direct involvement of the heart in the beginning, only a few of the symptoms are observed.

Heart related complications in myotonic dystrophy

There is a remarkable number of heart related issues seen among the patients suffering from myotonic dystrophy, and the most common types of heart-related issues are compromised impulse conduction, fast heartbeat, weakening of the heart muscles, and the other one is the hardening of the heart muscles; and both of these conditions do not allow the heart to maintain the pumping of the blood.

When impulse conduction becomes faulty

Suffering with this complication, the patient’s heart cannot transmit the electrical impulse, generated by the pacemaker of the heart, the end-site. Impulse transmission is crucial for the heart muscles to contract and then relax, allowing the heart to pump the blood.

At the initial stages of DM, minute variation in the ECG is observed, and as the DM advances, intensified issues like breath shortening, dizziness, sudden unconsciousness, and even sudden death are seen. This development to the severe stages is slow, however, in a far lesser number of cases fast progression is observed, which is not easy to anticipate.

ECG is found with certain kinds of responses which indicate that the tissues of the heart are not normal, and there may be the existence of irregular heartbeat issues associated with the lower chambers of the heart, which is responsible for pumping the blood to the lungs (right chamber) and other body parts (left chamber).

When heart beats at high pace

It is medically called tachyarrhythmia. In this condition the patient’s heart beats at a pace more than 180 beats per minute. 

When upper chambers get involved

There are mainly two kinds of tachyarrhythmias found; one (known as atrial fibrillation) is related to the clot formation in the passage of the blood and the other one is related to the short circuit in the upper chamber of the heart. Both of these conditions are fully capable of causing death or permanent disability in the patient.

When lower chambers face the threat

Other types of heartbeat issues are related to the lower chambers (also known as ventricles) of the heart. There is no variation seen beat-to-beat, which gives ECG a completely normal nature. (this type is medically called monomorphic ventricular tachyarrhythmia).

On the other hand, the heart’s lower chamber is also involved in that fast heartbeat is characterized by variations in the rhythm (observed in the form of graphical representation on ECG, and medically known as polymorphic ventricular tachyarrhythmia). Even with a few seconds of existence, it is dangerous enough to stop the heart’s functionality. (i.e., cardiac arrest).

Heart muscles and blood supply are not well

When muscles of the heart do not contract and relax to maintain the pumping activity of the blood, that condition is called cardiac failure. Complete cardiac failure is not easily found, but mild effects can be detected.

Symptoms related to heart failure are not so commonly observed, because the patient found it a not-so-easy task due to cognitive impairment, and decreased activity, among the patients, also contributes to making it even worse.

Quite a few times, DM patients report having a feeling of heavy weight on the chest which is accompanied by chest pain, and this happens due to the complications associated with the small-sized blood vessels, carrying oxygen filled blood to the heart.

There are incidences when patients are found with the malfunctioning of the heart valves. The basic function of the heart valves is to maintain the flow of the blood in one direction, and its malfunction allows the blood to flow backward.^2,3,4

Diagnosis

• ECG is an important tool to diagnose the defects in patients who do not show any symptoms
• Genetic Parameters are important to diagnose DM
• The Presence of a typical enzyme level is assessed, like creatine kinase
• Liver functionality is observed carefully
• To evaluate nerve function, there are certain kinds of electrodiagnostic tests, which are useful in the DM diagnosis²

Management of the issues

The primary goal of DM management is to prevent sudden death, and there are two types of device-based therapies to prevent death among DM patients. 

The first is by maintaining the signal mechanism of the heart, it is performed by connecting the heart muscles with the insulated leads. This procedure is also known as pacing of the heart or cardiac pacing. These wires help to maintain the electrical supply to the heart muscles, which is not completely active naturally.

The second one is, the plantation of a special device in the chest. This device is called ICD (implantable cardioverter-defibrillator) and is powered by a battery. This device detects the irregular rhythm and then restores to normalize the heart functionality.

Medicines are given to the patients to stop degeneration of the heart muscles or to improve the degenerated muscles. Other kinds of medicines which are prescribed to DM patients facing heart issues are antiarrhythmics, which tackle irregular heartbeat.

An important fact is there are many cases where blockage, due to any clot, in the blood vessels is found. However due to the risk of heavy bleeding, anticoagulants for long periods are not easy to prescribe.

DM patients are suggested to be kept under surveillance as dangerous outcomes can appear without any prior signal. So, any kind of symptoms like abnormal heartbeat and pre-unconsciousness type of condition need immediate testing to confirm the exact level of severity.

As most of the heart complications in DM patients get intensified with age, a child heart specialist is always a good option to consult with, to manage the congenital issues or issues at an early age, before they get worse. Otherwise, the heart specialists treating adults is the only option to tackle the fully grown complications.³

Summary

Myotonic dystrophy, also called dystrophia myotonica or DM, is a muscle-related disorder that causes weakness and in many cases even disability. Multiple organs are affected by this and it is transmitted to the next generation.

Heart, diabetes and eyes related issues are caused by DM. It is classified into two types, based on the positions of the muscles it affects, like DM1 those muscles get attacked which are away from the center of the body, while in DM2, muscles which are near to the center of the body face the issues.

A few changes are found to occur in the structure of the heart due to cluster formation in the spaces between the cells or might be due to fat deposition in the walls of the heart. These affect the heart functionality and rhythm pattern gets changed on electrocardiogram (ECG). Complications grow as the age progresses.

Around two-third of the deaths are because of all the complications associated with DM patients and heart related covered rest of the death proportion. Main reasons are conductivity problems, heartbeat-related complications, and muscle deterioration. These can lead to heart failure and sudden death can happen as well.

ECG, enzyme activity, and a few electrical testing methods are used to diagnose it. Liver functionality is one of the methods used in DM’s diagnosis.

Due to the serious sudden effects patients are kept under surveillance, and medicines to control the heartbeat and to stop deterioration of the muscles are given. There are a few devices used to control the heartbeat and maintain the electrical signal.