Channelopathies

In this section, we will go over several channelopathies and arrhythmic syndromes that are important to recognize as they increase a patient's risk of sudden cardiac death. This section is closely linked to the Polymorphic Ventricular Tachycardia section. 

This will include the following topics:

• Brugada syndrome: a classic arrhythmic syndrome associated with dysfunction of sodium channels that classically presents with sudden cardiac arrest during febrile illnesses and during sleep. We will discuss the pathophysiology of Brugada syndrome and how this problem can cause ventricular arrhythmias via phase 2 reentry and other mechanisms, and demonstrate an ECG of VF in Brugada syndrome. We will discuss the difference between the Type 1 and Type 2 ECG patterns, and how to use provocative testing to elucidate the diagnosis. We will also describe Brugada phenocopies, which are disorders that can present with characteristic ECG features of Brugada syndrome in the absence of any true genetic channel abnormality.

• Long QT syndrome: a syndrome of QT prolongation related to several different genetic mutations and channel dysfunctions that leads to an increased risk of torsades de pointes, a deadly ventricular arrhythmia. We will discuss the difference phenotypic subtypes of long QT syndrome (such as Type 1, Type 2, and Type 3) and discuss how this leads to generation of torsades de pointes. We will also cover acquired abnormalities that may mimic long QT syndrome.

• J wave syndromes: a set of syndromes that are related to the development of malignant ventricular arrhythmias via various mechanisms such as phase 2 reentry, related to malignant "J waves".  We will describe how to identify this and separate it from other causes of J waves, such as benign early repolarization or hypothermia.

• Catecholaminergic polymorphic ventricular tachycardia syndrome (CPVT): an inherited dysfunction of intracellular calcium regulation that characteristically leads to syncope or cardiac arrest during episodes of high catecholamines, such as exercise or strong emotion. We present the typical arrhythmias associated with this condition, such as bidirectional and polymorphic VT, and the pathophysiology behind these arrhythmias.

• Short QT syndrome: an inherited group of channelopathies that cause faster repolarization, resulting in long QT, but also increase the risk of various arrhythmias, such as atrial fibrillation and ventricular tachyarrhythmias. We will discuss the pathophysiology behind these conditions, how to diagnose these with ECGs, and the differential diagnosis of acquired causes of short QT (such as digitalis or hypercalcemia).

• Familial ST-elevation syndrome: also known as Bundgaard syndrome, this is a recently identified arrhythmic syndrome characterized by unexplained ST elevation and an increased risk of ventricular arrhythmias and sudden cardiac death.