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How to Perform and Interpret Provocative Testing for the Diagnosis of Brugada Syndrome, Long-QT Syndrome, and Catecholaminergic Polymorphic Ventricular Tachycardia

Sudden cardiac death (SCD) is predominantly related to coronary artery disease and its sequelae, cardiomyopathy, and congenital or valvular heart disease. No structural abnormalities are detectable in 5–8% of SCDs.1 Identified ion channelopathies such as Brugada syndrome, long-QT syndrome (LQTS), and catecholaminergic polymorphic ventricular tachycardia (CPVT) contribute to this incidence. The diagnosis requires a high level of suspicion because of a resting ECG that is often borderline, intermittently normal, or frankly normal. Genetic testing does not provide a simple solution to this issue, as it is often neither sensitive nor specific even when the phenotype points to a specific entity and may yield results that are difficult to interpret (ie, variants of unknown significance). Pharmacological and/or exercise testing by manipulation/stressing the cardiac action potential can accentuate the desired abnormality or provoke a characteristic arrhythmia response. A systematic approach to clinical testing that includes drug provocation results in unmasking of the cause of apparently unexplained aborted SCD in >50% of patients and is very helpful in directing genetic testing of the index case and family to diagnose genetically mediated arrhythmia syndromes.2 This review will seek to highlight the clinical utility of provocative testing and describe how to perform and interpret provocative testing for the diagnosis of Brugada syndrome, LQTS, and CPVT.

### Performing Provocative Testing

Pharmacological challenge should be performed in an area that has comprehensive monitoring and resuscitation equipment (including an external cardioverter-defibrillator). Testing should be performed with continuous monitoring of the patient by adequately trained/experienced personnel in an area equipped with advance resuscitation equipment (including external defibrillator) and personnel trained in advance resuscitation and an expert physician promptly available. Given the potential risk for hemodynamically compromising ventricular arrhythmias during exercise stress testing (particularly when exercise stress testing for CPVT), we advise the presence of physically capable personnel to prevent the patient …