Management of Familial Sudden Cardiac Death Syndromes
People with a family history of sudden cardiac death (SCD) syndrome have a greater risk of dying from an acute heart abnormality. While patients who have coronary artery disease or have suffered a heart attack have a greater chance of succumbing to SCD, the same can happen to those with a genetic predisposition to certain SCD conditions – without any previous symptoms or warnings.
There are certain inherited conditions – with genes mapped to certain chromosomes – that can lead to SCD. The more common ones include:
- Hypertrophic Cardiomyopathy (HCM). One in 500 patients has this condition characterized by an overly large stiffness and thickness of the heart wall in the left ventricle. When the muscle tissue becomes overgrown in the heart wall between the ventricles or septal region, the condition becomes hypertrophic obstructive cardiomyopathy (HOCM). Young athletes who die suddenly while under tremendous competition are often found to have HCM or HOCM.
- Arrhythmogenic Right Ventricular Dysplasia (ARVD). ARVD is where the heart muscle in the right ventricle becomes filled with fat and scar tissue, resulting in an abnormal rapid heartbeat. A genetic condition, it can happen at any age, but is most common in people younger than 35.
- Brugada Syndrome. Also an inherited condition, Brugada syndrome is when the ventricles beat very quickly (ventricular fibrillation), thus preventing adequate blood flow to the body and brain. This results in fainting and, without immediate medical attention, even death. Not all who have this condition will have arrhythmias, so it can come on suddenly and without warming. It usually affects people in their 30s but can occur at any age.
- Short QT Syndrome (SQTS) and Long QT Syndrome (LQTS). As shown on an EKG, the Q-T interval represents the time for contraction of the heart ventricles, from electrical activation to inactivation. The shorter than normal time interval known as Short QT syndrome can cause both atrial fibrillation and the often fatal ventricular fibrillation. Long QT syndrome can also result in arrhythmias, including life-threatening ventricular tachycardia.
- Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT). Inherited in at least a third of all cases, this condition most commonly occurs in children and young adults. CPTV results in often rapid heartbeats, especially with exercise or during emotional periods, and can result in dizziness, fainting and even death.
Treatment and Management
Diagnosis and treatment of these familial SCD syndromes begins with identifying whether any family members have developed or died from these heart conditions. The cardiologists of Methodist DeBakey Cardiology Associates perform careful diagnosis and monitoring of symptoms with mostly non-invasive procedures, including EKG, echocardiogram and trans-esophagael echocardiogram (TEE), MRI, stress test and wearing a Holter monitor. Treatment options include medications and possibly more invasive measures such as heart catheterization, surgery and implantation of pacemakers and defibrillators.
Most people with HCM or MOCM don’t exhibit any symptoms until the conditions progress, eventually appearing as shortness of breath, palpitations, chest pain, dizziness and fatigue, and even fainting. Treatments include taking medication, dual chamber pacemakers, myectomy and alcohol septal ablation, and possibly an implantable defibrillator for patients who are at increased SCD risk.
Treatment and management of ARVD is focused on preventing SCD through the use of anti-arrhythmic medications and implantable defibrillators. Patients with a family history should be aggressively monitored, and relatives of those patients should also be screened by using non-invasive tests on a regular basis.
Since life-ending ventricular fibrillation can come with no warning, the key to treating Brugada syndrome is to prevent the fibrillation from occurring in the first place. This is done through the use of an implantable cardioverter-defibrillator (ICD) which continuously monitors the heart rhythm. When an arrhythmia is detected, the defibrillator shocks the heart back into a normal heart beat.
SQTS and LQTS are treated with medications to control and prevent the onset of atrial fibrillation and other arrhythmias, but life-threatening arrhythmias including ventricular fibrillation must be avoided by implanting a defibrillator. CPVT is also controlled using medications such as beta-blockers, but often in conjunction with defibrillators as well.