ECG criteria
- Resting ECG without exercise — usually normal: normal QRS, normal or high-normal QTc
- During an exercise stress test (bicycle ergometry/treadmill) or emotional stress, as heart rate increases—often starting around 100–130 bpm—isolated ventricular ectopy appears; there is no rigid heart rate threshold, and the progression is individual
- With further increases in heart rate, ectopy typically becomes more complex: paired extrasystoles, followed by nonsustained runs of bidirectional or polymorphic ventricular tachycardia — though this is a likely rather than mandatory progression
- A classic, though not mandatory, sign is bidirectional ventricular tachycardia: a regular alternation of QRS complex polarity and axis from beat to beat, usually by approximately 180°; evaluated across all leads of the 12-lead ECG
- The complexity and likelihood of ventricular ectopy generally increase with greater adrenergic stimulation, but the relationship is nonlinear and individual (depending on genotype, age, and therapy)
- The QT interval and T-wave morphology on the resting ECG remain normal — this distinguishes CPVT from long QT syndrome
- Atrial ectopy and supraventricular arrhythmias may occur during the same exercise (due to the same calcium homeostasis defect in the atria)
- The episode may resolve upon cessation of exercise, but it can persist, recur, or degenerate into ventricular fibrillation
What it looks like on ECG
The resting ECG is typically normal: normal sinus rhythm, normal QRS duration, and QTc is generally not prolonged. Sinus bradycardia, nonspecific ST-T changes, and rare ventricular ectopy at rest may occur. A normal ECG does not rule out CPVT nor does it exclude structural heart disease, which is assessed by imaging methods (echocardiography, MRI). This fundamentally distinguishes CPVT from most other arrhythmogenic channelopathies and cardiomyopathies, where the resting ECG already suggests the diagnosis.
The key finding is an exercise stress test (bicycle ergometry, treadmill according to a standard protocol) or, in specialized settings, catecholamine infusion. As the heart rate increases during exercise, ventricular ectopy typically—though not necessarily following a rigid pattern—appears: initially premature ventricular complexes (frequently already at a heart rate around 100–130 bpm, although the threshold is individual), followed by paired extrasystoles and non-sustained runs of polymorphic or bidirectional ventricular tachycardia with further heart rate increases. There are no fixed heart rate threshold values that serve as diagnostic criteria; the sequence and rate of arrhythmia progression vary from patient to patient.
Bidirectional VT is manifested by a consistent alternation of the polarity and electrical axis of the QRS complex from beat to beat, usually by approximately 180°. It is assessed across all available leads of the 12-lead ECG; the inferior leads (II, III, aVF) often demonstrate this alternation clearly, but are not mandatory for diagnosis. Polymorphic VT presents with chaotically varying QRS morphology and amplitude without orderly alternation. Both variants can degenerate into ventricular fibrillation. Cessation of exercise frequently reduces ventricular ectopy, but this does not guarantee the rapid termination of VT—it may persist or recur, and ongoing sustained VT requires emergency treatment according to tachyarrhythmia algorithms. Beta-blockers in this context are the cornerstone of prophylactic therapy rather than a universal agent for the acute termination of already established VT.
Mechanism
CPVT is caused by mutations in genes that regulate calcium release from the cardiomyocyte sarcoplasmic reticulum. The RYR2 gene (ryanodine receptor type 2, autosomal dominant inheritance) is most frequently affected, followed less commonly by CASQ2 (calsequestrin, autosomal recessive inheritance), as well as TRDN (triadin), CALM1/CALM2/CALM3 (calmodulin), and a number of rarer genes. Mutations in intracellular calcium regulation proteins, including RYR2 gain-of-function variants and defects in CASQ2, TRDN, and other proteins, disrupt the control of calcium release from the sarcoplasmic reticulum and promote the occurrence of delayed afterdepolarizations (DADs). Upon an increase in sympathetic tone and catecholamine levels, the pathological diastolic calcium leak from the reticulum is enhanced, and excess intracellular calcium generates DADs and triggered activity. If such depolarization reaches the threshold, a premature ventricular complex occurs. Triggered activity driven by DADs and specific features of the ventricular activation sequence can lead to bidirectional or polymorphic VT; the exact mechanism of bidirectional VT is complex and cannot be reduced to a single focus. At rest, abnormal calcium leakage is usually insufficient to cause noticeable DADs and arrhythmia; during catecholaminergic stimulation, it increases and becomes arrhythmogenic—therefore, the probability and complexity of ventricular ectopy rise with increased adrenergic stress, although this relationship is nonlinear and is not determined by the prolongation of refractoriness or repolarization, unlike in long QT syndrome.
Causes
- RYR2 mutation (most common form, autosomal dominant inheritance pattern)
- CASQ2 mutation (autosomal recessive form)
- Rarer variants: TRDN (triadin) mutations, CALM1/CALM2/CALM3 (calmodulin), other calcium homeostasis genes
- Family history of unexplained syncope, seizures, or sudden death at a young age during physical exertion or strong emotions
- Triggering factors for the specific episode: physical exertion, fright, anger, sometimes swimming
Differential diagnosis
- Long QT syndrome (exercise-induced form, LQT1) — is also triggered by exertion; characterized by polymorphic VT of the torsades de pointes type in the setting of QT prolongation, but in some carriers the resting QTc may be normal, and triggers depend on the genotype (LQT1 is frequently triggered by exertion and swimming)
- Torsades de pointes — visually resembles polymorphic VT and occurs in the setting of a prolonged QT interval; in acquired long QT syndrome, it is more often pause-dependent, whereas in congenital LQTS, triggers may include exertion, swimming, emotions, a sudden noise, or sleep—depending on the genotype
- Idiopathic polymorphic VT/VF — considered after a comprehensive exclusion of structural heart disease, channelopathies, and other causes; a negative genetic test does not rule out CPVT by itself, and the diagnosis may remain clinical
- Brugada syndrome — polymorphic VT/VF more frequently occurs at rest or during sleep, and the resting ECG may show a Brugada pattern in V1–V2
- Arrhythmogenic right ventricular cardiomyopathy — regional or global RV (less frequently LV) alterations on echocardiography or MRI, T-wave inversion in V1–V3, and other specific ECG signs; ventricular tachycardia usually exhibits a left bundle branch block morphology with a corresponding axis. Epsilon wave is a rare and nonspecific sign, with low sensitivity and is not required for diagnosis
- Benign RV outflow tract PVCs during exercise — typically monomorphic morphology, usually does not progress to polymorphic VT; however, complex or polymorphic ectopy requires the exclusion of CPVT, structural heart disease, and other causes
Clinical significance and management
CPVT is one of the main causes of unexplained syncope and sudden cardiac death in children and young adults without structural heart disease, especially during sports or high emotion. Diagnosis is established clinically by the characteristic phenotype (syncope during exertion/emotion) and exercise stress test results (reproduction of ventricular ectopy/VT as heart rate increases) after ruling out structural heart disease on echocardiography; genetic testing (RYR2, CASQ2, etc.) helps confirm the etiology, refine risk stratification, and screen relatives, though a negative result does not rule out CPVT. The exercise stress test is the preferred provocation method; pharmacological provocation with catecholamines (epinephrine) is considered only in specialized centers when the exercise test is impossible or uninformative, given the limited sensitivity, specificity, and risks of the procedure.
Management guidelines: restriction of intense physical activity and competitive sports; baseline therapy with non-selective beta-blockers (often nadolol) at the maximum tolerated dose; if control is inadequate, addition of flecainide. Implantable cardioverter-defibrillator (ICD) implantation is generally indicated for survivors of cardiac arrest and selected patients with refractory life-threatening arrhythmias; it is important to remember that pain/emotional stress from ICD shocks can trigger an electrical storm, so an ICD does not replace medical therapy. Left cardiac sympathetic denervation may be considered for persistent life-threatening events despite optimal therapy or when therapy is not feasible. Such decisions are made individually in an expert center. If a pathogenic or likely pathogenic variant is identified in the proband, targeted cascade genetic testing of first-degree relatives is performed. Variant carriers and relatives with unknown/indeterminant status undergo clinical evaluation and follow-up with ECG and exercise testing appropriate for their age; definitively variant-negative relatives generally do not require such follow-up in the absence of other indications.
Common interpretation errors
- Ruling out CPVT solely on the basis of a normal resting ECG — the diagnosis requires an exercise stress test or provocation
- Confusing bidirectional VT in CPVT with digoxin toxicity — similar morphology, different clinical context (medication intake, age)
- Missing the diagnosis by interpreting polymorphic ectopy on an exercise test as a «normal response to exercise» without assessing the increasing complexity of the arrhythmia
- Measuring QTc during tachycardia and mistakenly concluding there is a prolonged QT, which misleads toward long QT syndrome
- Ruling out CPVT in the presence of a negative genetic test — a negative result does not exclude the disease, and the diagnosis can be clinical
- Underestimating a family history of sudden death during exertion as a key diagnostic sign
1. Which triggering factor is most characteristic of CPVT episodes?
CPVT is a catecholamine-dependent arrhythmia triggered by an increase in sympathetic tone during exertion or stress.
2. What resting ECG is typical for a patient with CPVT outside of provocation?
Unlike other channelopathies, in CPVT the QT interval and resting ECG morphology remain normal, and the substrate manifests only during exertion.
3. Which gene is most frequently mutated in the autosomal dominant form of CPVT?
Mutations in RYR2 (ryanodine receptor type 2) are the most common cause of autosomal dominant CPVT.
Frequently asked questions
How to distinguish CPVT from long QT syndrome?
In CPVT, the QT interval on the resting ECG is normal, and the arrhythmia occurs precisely during exertion or stress, increasing in complexity as the heart rate rises. In long QT syndrome, the QTc interval is often prolonged even at rest, although it may be normal in some carriers; the arrhythmia (torsades de pointes) can be triggered by exertion, pauses, or medications depending on the genotype.
Is CPVT dangerous?
Yes, without treatment CPVT is associated with a high risk of syncope and sudden cardiac death, especially in children and young adults during sports or strong emotions. With adequate beta-blocker therapy and activity restriction, the prognosis improves significantly.
Why is the resting ECG normal in CPVT?
At rest, abnormal calcium release from the sarcoplasmic reticulum is usually insufficient to cause noticeable delayed afterdepolarizations and arrhythmias. With catecholaminergic stimulation, this process is enhanced and becomes arrhythmogenic, which is why the clinical phenotype typically manifests during exertion or catecholaminergic stimulation rather than on a standard resting ECG.
Which study confirms the diagnosis of CPVT?
The basis of diagnosis is the clinical phenotype and the reproduction of characteristic ventricular ectopy, polymorphic, or bidirectional VT during an exercise stress test, against the background of a normal resting ECG and normal heart structure. Genetic testing (most commonly RYR2 or CASQ2) helps confirm the etiology and screen relatives, but a negative result does not rule out a diagnosis of CPVT.
Can I play sports with CPVT?
Competitive and intense sports are generally contraindicated due to the risk of triggering a life-threatening arrhythmia. The decision regarding the permissible level of physical activity is made individually by a cardiologist/arrhythmologist during therapy.
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Related terms
More in the «Channelopathies and Cardiomyopathies» section
Sources
- Surawicz B., Knilans T. Chou's Electrocardiography in Clinical Practice
- Hampton J. The ECG in Practice
- ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death
Educational material for medical students and physicians. Does not replace clinical guidelines and physical examination; the ECG must always be interpreted in conjunction with the clinical picture.