Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT)
Submitted by Dr. Andrew Krahn.
Updated December 2006
Catecholaminergic: Adrenaline or exercise related
Polymorphic: More than one appearance (the beats have multiple shapes on the ECG) Ventricular: from the lower/pumping chamber of the heart
Tachycardia: rapid heart beat
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is thankfully a rare disorder that causes palpitations, blackouts and sudden death, usually related to exertion or stress. In some situations, there is a family history of other affected members, including tragic sudden death.
Vignette: A fourteen year old female presented with two episodes of loss of consciousness during moderate exercise. She recalled being vaguely aware of a sense of skipping in her chest before losing consciousness. Her friends noticed that she looked pale for a few seconds, and slumped to the ground. She awakened within a few seconds, and felt perfectly well within a few minutes. Her mother and aunt had similar episodes while playing baseball as adolescents, and had given up public singing and baseball as a result. Her great uncle died suddenly at age 22 while playing hockey. Subsequent testing showed normal structure of her heart, and a normal resting ECG without QT prolongation.
Exercise testing resulted in multiple premature ventricular beats (Doctors call them PVCs) coming from several different places of the heart accompanied by a sense of palpitations. When beats became frequent, the patient experienced lightheadedness. Similar findings were noted when her aunt and mother were assessed. Beta blockers were prescribed (medication that inhibits the adrenaline input into the heart), with elimination of PVCs during exercise. She remained free of blackouts for 3 years since her initial testing, when an extended family member had sudden death during exercise. The family requested an implantable defibrillator (ICD), which was implanted after a lengthy discussion with her doctors about the risks and benefits of the device. She is now flourishing in University.
CPVT - The Skinny
The above case illustrates how many patients with CPVT present, and that most patients can have an excellent outcome if the disease is recognized and treated. The disease tends to first present after puberty in early adolescence with palpitations or blackouts. Given the trend of modern smaller families, there may not be any evidence that other family members are affected. Recent evidence has demonstrated mutations on chromosome 1 in the gene that codes for the ryanodine receptor are responsible for CPVT. These are DNA “typos” that lead to misfiring when making the protein that makes up this receptor inside the heart muscle cell. The heart muscle then has trouble appropriately handling calcium inside the cell, which upsets the balance of electrical charges and leads to the abnormal heart beats when the cell is stimulated by adrenaline. This process is not affected by calcium in the blood or diet, and does not affect the QT interval.
Genetic testing: Genetic testing has the potential to help both individuals and families determine if the disease is present, and assist with treatment decisions. At present, this type of testing is not available in Canada except in specific research settings. Simply checking for the gene is not possible in this condition, like most other genetic causes of arrhythmia. Most new patients will have a new genetic abnormality if it can be detected (called a private mutation), so the process is expensive and time consuming since a gene sequencer has to read every letter of the DNA in the region of the gene to look for the typo. Because this is a relatively new genetic discovery in such a rare disease, little is know about the meaning of specific mut...