We excluded 171 individuals for previous cardiovascular disease (acute myocardial infarction, heart failure, cardiac surgery, and stroke), 248 for use of beta-blocker medication, 381 for use of other medications that could interfere HRV measures (ACE inhibitor, calcium channel blockers, and antiarrhythmic drugs), 1 for presenting arrhythmia during ECG recording (atrial fibrillation or atrial flutter), and 1 for use of an external cardiac pacemaker. The gene discussed is ACE; the disease is atrial flutter.