Sudden arrhythmic death syndrome (SADS)

Sudden arrhythmic death syndrome (SADS) is an umbrella term used to describe unexplained deaths in younger people whose official cause of death is listed as undetermined. In these cases, the patient’s death is typically thought to result from some sort of undiagnosed heart condition that causes an arrhythmia, or an abnormal heart rhythm. The onset of an arrhythmia causes the patient’s heart to beat erratically and leads to a potentially fatal heart attack. One of several forms of sudden death syndrome (SDS), SADS predominantly occurs among young and middle-aged adults who have genetic arrhythmia syndromes such as long QT syndrome, catecholaminergic polymorphic ventricular tachycardia (CPVT), and Brugada syndrome. Since the victims of SADS are typically unaware that they have a genetic heart condition, these deaths often cannot be prevented. That said, further deaths may be prevented if the family members of someone who has died as a result of SADS get tested for genetic arrhythmia syndromes.

Background

Otherwise unexplained deaths that are attributed to SADS are usually caused by some sort of genetic arrhythmia syndrome. Arrhythmias are abnormal heart rhythms that can cause various cardiac problems ranging from harmless fluttering to fatal heart attacks. Such abnormal rhythms occur when the electrical impulses responsible for controlling a person’s heartbeat stop working properly and cause the heart to beat too quickly, too slowly, or irregularly.

The heart is composed of four distinct chambers: a pair of upper chambers called the atria and a pair of lower chambers called the ventricles. The heart’s rhythm is controlled by the sinus node, a natural pacemaker found in the right atrium. The sinus node produces the electrical impulses that cause the heart to beat by stimulating the atria muscles to contract and push blood into the ventricles. After that, the electrical impulses produced by the sinus node travel to a cluster of cells known as the atrioventricular (AV) node. The AV node subsequently slows the impulses before sending them on to the ventricles. The brief delay that occurs as this happens give the ventricles time to fill up with the blood being pumped from the atria. When the electrical impulses rerouted from the AV node finally reach their destination, the ventricles contract and pump the blood they are holding out to the lungs and the rest of the body. Under normal circumstances, this whole process plays out at a rapid pace that results in the heart beating at approximately sixty to one hundred beats per minute when a person is at rest.

The two main types of arrhythmias are tachycardia and bradycardia. While tachycardia refers to an abnormally fast heartbeat, bradycardia is to an abnormally slow heartbeat. Tachycardia, which is typically the more dangerous form of arrhythmia, can occur in either the atria or ventricles. The several types of tachycardia affect the heart differently, with some causing little more than rapid heartbeats or palpitations and others often leading to more serious and even potentially fatal consequences. While arrhythmias frequently arise as a result of issues like heart disease or stress, others may be tied to genetically inherited syndromes.

Overview

Sudden arrhythmic death syndrome (SADS) refers to a group of genetic heart conditions that can lead to sudden death in otherwise healthy young people. Although these conditions can be treated before they become fatal, they often go undiagnosed until it is too late to prevent death. Fortunately, several key warning signs might suggest a person has a potentially dangerous SADS condition. Most importantly, a family history of sudden, unexpected death before the age of forty is a strong indicator of a genetic SADS condition. In addition, symptoms like fainting or seizure during exercise or excitement or chest pain or shortness of breath during these times may also be signs of a SADS condition.

In 2017, the American Heart Association reported that approximately 210,000 Americans die suddenly and unexpectedly because of sudden cardiac arrest every year. When no other cause can be definitively established, the deaths of younger patients from sudden cardiac arrest are typically attributed to SADS. When SADS is officially declared to be the cause of a person’s death, members of the deceased’s family are often urged to get screened for SADS conditions to help prevent further premature deaths.

SADS deaths occur when a person has an underlying and likely undiagnosed heart condition that causes a dangerous arrhythmia. When triggered, a severe arrhythmia causes the heart to beat erratically to the point that the person no longer has a pulse and a heart attack occurs. The arrhythmias associated with SADS conditions all involve issues with the electrical impulses that control how the heart beats. Some of the most well-known SADS conditions include Brugada syndrome, long QT syndrome, catecholaminergic polymorphic ventricular tachycardia (CPVT), and Wolff Parkinson White syndrome. Brugada syndrome causes a disruption in the flow of sodium or potassium ions into the heart’s cells. This interferes with the electrical impulses that regulate the heartbeat and leads to rapid and life-threatening arrhythmias. Brugada syndrome is most common among young men from Southeast Asian ethnic backgrounds. Long QT syndrome is a condition in which arrhythmias are caused by a delay in the heart’s electrical system called prolonged repolarization. This delay results from abnormalities of the microscopic pores found in the heart’s ion channels. CPVT is a SADS condition related to proteins within heart cells that regulate the release of calcium ions. In those who have CPVT, these proteins function abnormally and lead to an increase of calcium inside heart cells that can ultimately cause arrhythmias. Wolff Parkinson White syndrome is a condition in which the presence of an extra conduction pathway leads to an electrical abnormality that causes arrhythmias.

Prevention of premature death from SADS condition is primarily contingent on establishing a diagnosis before it is too late. Once a diagnosis has been made, patients with a known SADS condition may need to take steps to avoid serious consequences. These steps might include avoiding medications that trigger symptoms, treating fevers quickly, using caution when exercising, following a heart-healthy diet, and regularly visiting a family doctor or cardiologist. Some patients may also benefit from the insertion of an implantable cardioverter-defibrillator (ICD). ICDs monitor heart rhythm and deliver a small shock to restore normal function when an arrhythmia occurs.

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