Cardiac Channelopathies
Cardiac channelopathies are a group of heterogeneous disorders that affect the ion channels of the heart. These disorders cause cardiac arrhythmias in otherwise healthy and typically young individuals and can lead to syncope, cardiac arrest and sudden death. The ion channels mediate the flow of potassium, sodium and calcium across the myocytes. Inherited channelopathies can be due to mutations in  sodium, potassium, or calcium ion channel genes and are characterized by prolonged ventricular repolarization and risk for polymorphic ventricular tachycardia-and/or ventricular fibrillation.

Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT)
The clinical presentation of CPVT is similar to that of LQT1 and is characterized by an exercise induced ventricular arrhythmia and/or syncope occurring during physical activity or acute emotional stress.  Unlike LQTS, the resting ECG will most often appear normal, showing no signs of the syndrome.  Instead, CPVT is suspected when ventricular tachycardia, rather than the torsades de pointes (TdP) commonly associated with LQTS, is induced but then ‘fades’ during an exercise stress test.  Unfortunately, the ECG and exercise stress test findings are not always sufficiently sensitive or specific to diagnose CPVT.  CPVT1 is inherited in an autosomal dominant pattern and shows incomplete penetrance. Identifying affected family members can be difficult, but is imperative.

Approximately 50-55% of individuals affected with CPVT harbor a mutation in the RYR2 gene which encodes the pore-forming subunit of the cardiac calcium release channel. RYR2 is the basis of the FAMILION CPVT Test.  Mutations in the RYR2 channel are annotated as Type 1 CPVT (CPVT1)

The majority of cardiac events in CPVT occur during childhood, adolescence and young adulthood.  CPVT should be regarded as highly lethal.  If left untreated, 30% of CPVT patients will develop symptoms by age 10, 80% by age 40 with an overall mortality rate of 30 – 50%.

Adapted from: Napolitano C, et al. Diagnosis and treatment of catecholaminergic polymorphic ventricular tachycardia. Heart Rhythm. 2007;4:675-678.

The efficacy of β-blockers in CPVT is lower than that of LQT1.  Nearly 50% of patients taking a β-blocker will continue to experience cardiac arrhythmias and may require an implantable cardioverter defibrillator (ICD).  A two year study by Priori et al. indicated that among CPVT patients with an ICD, 50% of them received an appropriate shock.

1-877-2-PGXHEALTH (877-274-9432)