Adrenergic stimulation is well known for having an important role in the induction of ventricular arrhythmias in different arrhythmogenic cardiomyopathies. Isoproterenol, or isoprenaline, a non-selective β-adrenergic agonist, is commonly used in the provocative test to induce catecholamine-sensitive ventricular arrhythmias. The test can serve as an additional diagnostic tool for the early identification of patients at risk of malignant arrhythmias, particularly in patients with suspected arrhythmogenic heart disease of the left ventricle, although the prognostic significance of this test is not yet fully clarified.
The isoproterenol test is performed after the interruption of β-blockers, calcium channel blockers and other antiarrhythmic agents for ≥ 5 half-lives. The test is carried out in the electrophysiology room, in the presence of suitable personnel and equipment for cardiopulmonary resuscitation. The test is generally practiced in the context of an electrophysiological study. A continuous infusion of isoproterenol is carried out according to the dosages and infusion rate established on the basis of the weight and pathology of the patient under examination (see attached diagrams). The 12-lead ECG tracing is recorded continuously from the start of the infusion ≤ 10 minutes after the cessation of the infusion.
The test is considered positive if a monomorphic or polymorphic VT is sustained during the test or within 10 minutes from the end of the infusion. The infusion is immediately stopped if the test has been positive and, in the case of VT, an electrical cardioversion is performed or a β-blocker is injected intravenously.
The isoproterenol test is practiced to assess the inducibility of potentially serious and fatal arrhythmias. The risk of the isoproterenol test is, however, very controlled, given that the test is performed in the presence of suitable personnel and cardiopulmonary resuscitation equipment in case of the immediate treatment of any evoked arrhythmia. The risk is commensurate with the need to know the risk of developing serious arrhythmias in the individual patient.
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