The Pre-brief
An 11 y/o boy suddenly collapses at a sporting event. His coach and fellow players witnessed a seizure-like activity immediately after collapsing. CPR was started immediately after the coaching staff could not find a pulse and EMS arrived to find the patient in cardiac arrest. Paramedics continued chest compressions, gave epinephrine via an intraosseous route, and delivered one shock. After that a return of spontaneous circulation (ROSC) occurred. The first prehospital EKG showed Polymorphic Ventricular Tachycardia (PVT) that responded to defibrillation. En route to the hospital, the patient began to move all of his extremities and responded to painful stimuli.
Hospital Course:
The patient was intubated upon arrival in the ED and sedated with propofol. The initial workup was unremarkable. Later in the pediatric intensive care unit (PICU), he developed pulmonary edema, but he continued to improve neurologically. He was eventually extubated and transferred out of the PICU. A cardiac MRI was unremarkable. The patient was given a diagnosis of Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT).
What is CPVT?
From the name, CPVT is a malignant arrhythmogenic disorder characterized by the following:
- An anatomically and structurally normal heart. This eliminates the possibility of Hypertrophic Cardiomyopathy (HOCM), Takutsubo Cardiomyopathy, or Arrhythmogenic Right Ventricular Dysplasia (ARVD).
- A normal baseline EKG (if obtained while at rest) will exclude conditions like short or long QT syndromes, Brugada or WPW.
- Polymorphic VT induced by physical or emotional stress.
CPVT is a difficult diagnosis to make during a routine clinic visit and can be easily misdiagnosed as vasovagal syncope or a seizure disorder. If not timely diagnosed and treated, CPVT has a mortality rate of up to 35%.
Children between the ages of 7 and 9 years are mostly affected, but CPVT can also present in children up to 12 y/o. It is uncommon in children less than 2 years of age.
Pathophysiology
CPVT is caused by mutations in the cardiac ryanodine receptor gene (RyR2) and calsequestrin isoform 2 gene (CASQ2). These two mutations are commonly seen in familial forms of CPVT. Under catecholaminergic stimulation, either mutation can result in excess calcium load during diastole resulting in delayed after-depolarization and subsequent dysrhythmias. Thirty percent of cases have a family history of exercise-induced syncope, seizure, or sudden death; therefore, obtaining a family history in these patients is extremely important.
Presentation:
The most common presentation of patients with CPVT is syncope with exertion. Some patients experience loss of consciousness after emotional stress or stimulant consumption. Many patients are misdiagnosed as having vasovagal syncope or epilepsy.
During physical or emotional stress, as the heart rate increases, one can see ventricular ectopy in the form of premature ventricular contractions (PVCs), which are isolated at first. PVCs then evolve into bigeminy followed by runs of non-sustained ventricular tachycardia. Eventually, VT becomes sustained VT and PVT before terminating into ventricular fibrillation.
Treatment:
-Lifestyle modifications include avoiding competitive sports and stimulants. Some patients can tolerate low-intensity exercises and are strongly encouraged to continue to do so.
-The first-line medical treatment is the use of a beta-blocker with Nadolol being the agent of choice. It is taken orally with a daily dose ranging between 40-320 mg.
-Other medications for those who cannot tolerate or failed a beta-blocker regimen include Verapamil and Flecainide.
-Implantable Cardioverter Defibrillator (ICD) is used for those who failed medications, or present with aborted cardiac arrest. A beta-blocker is added to avoid electrical storm caused by an adrenergic surge from the shocks
-Left Cardiac Sympathetic Denervation is a surgical approach to treat CPVT.
Management in the acute setting of PVT:
-The most important step is to recognize the possibility of CPVT in a young child of the right age (family or personal history of syncope and a seizure-like event)
-Epinephrine as part of ACLS can be counterproductive given the catecholaminergic surge. CPVT is a difficult diagnosis to make in general, especially in the prehospital setting. Paramedics should follow ACLS/PALS algorithms and focus on getting a thorough family history that can help the staff in the Emergency Department consider the possibility of CPVT in their differential diagnoses.
-When CPVT is suspected, intravenous beta-blockers are considered the first choice, similar to treatment of VT storm. I personally like Esmolol in these patients given its fast-on and fast-off action. Other beta-blockers can be used here as well.
-It is reasonable to give magnesium, especially in the setting of prolonged QTc interval.
The Debrief
- CPVT is an arrhythmogenic condition that is often misdiagnosed and undertreated.
- Think of CPVT in a child who suddenly collapses during physical activity or exercise.
- First-line treatment is a beta-blocker.
- Patients are instructed to avoid physical or emotional triggers.
