Clinical Characteristics and Diagnosis

RVOT tachycardia appears to be more common in women with 2:1 female predominance [26]. Familial occurrence has not been reported. Symptoms develop typically between the ages of 20 and 50 years, but presentation in childhood and infancy has been observed. Patients may present with palpitations, atypical chest pain, or dizziness. About 10% develop syncope during VT [2,27-31].

The two predominant clinical phenotypes of this tachycardia are nonsustained, repetitive, mono-morphic VT (RMVT) and paroxysmal, sustained VT; both are characterized by sensitivity to adeno-sine. RMVT is more common. Typically, it occurs at rest, has a pattern of a nonsustained salvos, and can be incessant, with frequent premature ventricular beats. In contrast, paroxysmal idiopathic VT is usually exercise-induced or associated with stress, may be sustained and separated by long intervals of sinus rhythm with relatively infrequent premature ventricular beats. There is considerable overlap between these two phenotypes. RVOT monomorphic extrasystoles and sustained RVOT VT appear to be two extremes of the spectrum of the same arrhythmic disorder.

The diagnosis of idiopathic RVOT VT is made after exclusion of other pathologies. ARVC/D in subtle forms may not always be detected even following Task Force criteria [32].

The resting 12-lead electrocardiogram during sinus rhythm is usually normal in RVOT idiopathic VT. Approximately 10% of these patients have complete or incomplete RBBB. The signal-averaged-ECG (SAECG) is typically normal.

Exercise testing reproduces the patient's clinical arrhythmia in 25% to 50% of the cases [2, 27, 30]. Tachycardia can be initiated either during exercise or during recovery. RMVT is often suppressed during exercise but recurs after stopping exercise expressing

Fig. 12.2 • Idiopathic RVOT tachycardia. A The 12 lead ECG shows tachycardia with a left bundle branch block configuration and frontal plane axis directed inferiorly. Note that the QRS in negative in AVL. B ECGs of paroxysmal (repetitive) monomorphic RVOT VT

its dependence on a critical heart rate. Relation of the arrhythmia to exercise has not been shown to be of prognostic value [30].

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