Atropine in Catecholaminergic Polymorphic Ventricular Tachycardia (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