This is a 2x2 cross over pilot study using low level transcutaneous vagus nerve stimulation (LLTS) to reverse diastolic dysfunction in patients with diastolic dysfunction. All patients will receive 2 separate, 1-hour sequences, at least 1 day apart, of active and sham LLTS, but the sequence will be randomized. Patients will be randomly assigned (1:1) to active/sham or sham/active LLTS. LLTS will be performed using a transcutaneous electrical nerve stimulation (TENS) device with electrodes attached to the tragus of the ear, which is innervated by auricular branch of the vagus nerve. Echocardiography will be performed after 30 minutes of LLTS or sham stimulation to assess diastolic function. Five-minute ECGs will be obtained for HRV analysis every 15 minutes of stimulation (total of 4 recordings).

Inclusion Criteria:

1. Male and female patients older than 18 year old
2. Evidence of diastolic dysfunction on echocardiogram within 24 months of study enrollment

Exclusion Criteria:

1. Left ventricular dysfunction (Left ventricular ejection fraction <40%)
2. Significant valvular disorder (i.e., prosthetic valve or hemodynamically relevant valvular diseases)
3. Recent (<6 months) stroke or myocardial infarction
4. Severe heart failure (NYHA class III or IV)
5. Recurrent vaso-vagal syncopal episodes
6. Unilateral or bilateral vagotomy
7. Pregnancy or breast feeding
8. Sick sinus syndrome (without a pacemaker), 2nd or 3rd degree AV block, bifascicular block or prolonged (PR>300ms) 1st degree AV block

through study completion (1 week)