Atropine in Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT)

Pretreatment With Atropine to Reduce Exercise-triggered Ventricular Ectopy in Patients With Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT)

To test the hypothesis that increasing the sinus node rate with atropine treatment prior to exercise will reduce exercise-triggered ventricular ectopy compared to baseline in patients with CPVT.

This is a prospective cross-over trial that will enroll eligible patients with CPVT and perform a baseline treadmill exercise tolerance test (ETT) followed by a repeat treadmill ETT with I.V. atropine administered immediately prior to exercise. Atropine is a parasympathetic blocker and results in sinus tachycardia, which is expected to reduce the diastolic interval thereby reducing delayed after depolarizations and ventricular ectopy compared to baseline. Both ETTs will be performed on the same day with two hours of rest scheduled between ETTs. The primary analysis will be a paired comparison of the number of ventricular ectopic beats recorded during exercise (and recovery) at baseline and following pre-treatment with atropine. Secondary endpoints will include the presence of ventricular ectopy (yes/no), complex ventricular ectopy (couplets or greater, yes/no), and the number of runs of complex ventricular ectopy.

Inclusion Criteria:

• Age >/= 6 years
• Able to provide written informed consent
• Clinical diagnosis of CPVT
• Able to exercise on a treadmill
• Successful completion of a minimum of 2 exercise stress tests without adverse events

Exclusion Criteria:

• Contraindication to treadmill stress testing according to Vanderbilt University Medical Center's clinical protocols (unstable angina, decompensated congestive heart failure, severe hypertension (≥ 170/90 mmHg), acute myocardial infarction (<4 days), moderate to severe aortic stenosis, acute pulmonary embolism, severe pulmonary hypertension, outflow tract obstruction, hypertrophic cardiomyopathy, left main coronary stenosis, left bundle branch block)
• Females who are pregnant
• In the judgement of the investigator, any clinically significant ongoing medical or surgical condition that might jeopardize the subject's safety or interfere with the conduct of the study