Catecholaminergic polymorphic ventricular tachycardia

Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) is an inherited cardiac disorder characterized by an abnormal heart rhythm known as ventricular tachycardia, which arises in response to physical activity or acute emotional stress. It is considered a rare genetic condition that can lead to syncope (fainting), cardiac arrest, or even sudden cardiac death in young individuals with structurally normal hearts.

Pathophysiology

CPVT is primarily caused by mutations in genes that encode proteins responsible for calcium regulation within the cardiac myocyte. The most commonly implicated genes are the RYR2, which encodes the ryanodine receptor, and CASQ2, which encodes calsequestrin. These mutations lead to an abnormal calcium release from the sarcoplasmic reticulum, causing the heart muscle cells to contract inappropriately.

Symptoms and Diagnosis

Individuals with CPVT may experience symptoms such as dizziness, palpitations, syncope, or seizures, typically triggered by physical or emotional stress. In some cases, the first manifestation of the disorder can be sudden cardiac death. Diagnosis is based on the clinical history, family history, genetic testing, and the characteristic findings on exercise stress testing or Holter monitoring, where exercise or stress can provoke the characteristic bidirectional ventricular tachycardia or ventricular fibrillation.

Treatment and Management

Management strategies for CPVT aim to prevent the occurrence of arrhythmias and include:

• Beta-blockers: The first-line pharmacological treatment to prevent adrenergically mediated arrhythmias.
• Calcium channel blockers: May be used in combination with beta-blockers if the response is inadequate.
• Implantable Cardioverter Defibrillator (ICD): Recommended for high-risk patients or those who have experienced a cardiac arrest.
• Lifestyle modification: Includes avoidance of competitive sports and situations that can lead to emotional stress.

Prognosis

The prognosis for individuals with CPVT who are not treated is poor due to the risk of recurrent arrhythmias and sudden cardiac death. However, with appropriate diagnosis, genetic counseling, and treatment, many patients can lead a normal life.

Glossary of Terms

• Adrenergically mediated arrhythmias - Abnormal heart rhythms triggered by the body's adrenaline response.
• Bidirectional ventricular tachycardia - A type of tachycardia where the electrocardiogram (ECG) shows alternating QRS complex axes.
• Cardiac myocyte - The muscle cells in the heart responsible for contraction and conducting electrical impulses.
• Cardiac arrest - A sudden cessation of heart function.
• CASQ2 - A gene encoding the calsequestrin protein, involved in calcium regulation within the heart cells.
• Genetic counseling - The process of advising individuals and families affected by or at risk of genetic disorders.
• Holter monitoring - A continuous recording of the heart's electrical activity for 24 hours or longer.
• Implantable Cardioverter Defibrillator (ICD) - A device implanted in the chest that can detect and stop abnormal heart rhythms.
• Palpitations - A sensation of the heart racing or thumping.
• RYR2 - A gene that encodes the ryanodine receptor, which is involved in the release of calcium from the sarcoplasmic reticulum.
• Sarcoplasmic reticulum - The specialized type of smooth endoplasmic reticulum found in muscle cells, involved in the regulation of calcium ions.
• Syncope - A temporary loss of consciousness due to a fall in blood pressure.
• Ventricular fibrillation - A rapid and erratic heart rhythm originating from the heart's ventricles, which can lead to collapse and death if not treated immediately.