Catecholaminergic polymorphic ventricular tachycardia exercise stress testing

Exercise Stress Testing is the primary diagnostic test and the most helpful clinical tool in diagnosing CPVT as it can reproducibly evoke the typical ventricular tachycardia during acute adrenergic activation (exercise). During exercise stress testing, sinus rhythm accelerates and beyond a heart rate of 120-130 beats per minute, isolated and often monomorphic ventricular premature beats (VPBs) typically occur first and then increase with heart rate to bigeminy. Subsequently, the VPBs become polymorphic or bidircetional, and as the exercise increase, they form bursts of non-sustained polymorphic ventricular tachycardia or bidirectional ventricular tachycardia (VT). With continuous activity, the arrhythmia persists and becomes more rapid, eventually assuming the appearance of polymorphic ventricular tachycardia (VT), which is very fast, fibrillation-like and leads to syncope. The arrhythmias disappear on stopping the exercise. Bidirectional ventricular tachycardia (VT) is the hallmark finding of catecholaminergic polymorphic ventricular tachycardia.

• CPVT is a diagnosis based on reproducing ventricular arrhythmias during exercise stress testing, syncope occurring during physical activity and acute emotion, and a history of exercise or emotion-related palpitations and dizziness with an absence of structural cardiac abnormalities.
• It has been observed that arrhythmias in CPVT often appear in a uniform and reproducible pattern that facilitates the recognition of affected patients.^[1]
• Exercise Stress Testing is the primary diagnostic test and the most helpful clinical tool in diagnosing CPVT.
• Exercise Stress Testing helps in the following:
  1. Diagnosing CPVT as it can reproducibly evoke the typical ventricular tachycardia during acute adrenergic activation;
  2. Defines limit for any allowed physical activity in the hospital setting;
  3. Useful in monitoring the response to beta-blocker therapy of affected individuals in reproducible conditions.
• Changes in the ECG recorder during exercise stress testing are as follows:
  • During exercise testing, sinus rhythm accelerates and beyond a heart rate of 120-130 beats per minute, isolated and often monomorphic ventricular premature beats (VPBs) typically occur first and then increase with heart rate to quadrigeminy, trigeminy, and bigeminy.
  • Subsequently, the VPBs become polymorphic, and as the exercise increase, they form bursts of non-sustained polymorphic ventricular tachycardia (VT).
  • If the activity is stopped, the arrhythmia disappears in the reverse order without clinical symptoms.
  • However, when the activity is continued, the arrhythmia persists and becomes more rapid, eventually assuming the appearance of polymorphic ventricular tachycardia (VT), which is very fast, fibrillation-like and leads to syncope.
  • In a subset of patients the ventricular arrhythmias already disappear with ongoing exercise.^[2]
  • Another type of polymorphic VT observed in CPVT patients is the bidirectional VT, which is a peculiar form of polymorphic VT characterized by right bundle-branch block pattern and 180° rotation of the QRS complex from beat to beat (alternating right and left QRS axis deviation).^[1]
  • The occurrence of a bidirectional ventricular tachycardia (VT), which is the hallmark sign of CPVT is highly specific but not present in all patients.
  • The bidirectional VT seen in CPVT are thought to originate from the His-Purkinje system from the alternating activation of the purkinje fibers of the two ventricles.^[3][4][5]

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