Ablation of Inappropriate Sinus Tachycardia

Ablation of Inappropriate Sinus Tachycardia Syndrome by Targeting Cardiac Neural Input

Hypothesis- Radiofrequency ablation, targeting the sympathetic input of the sinus node identified by 20Hz stimulation at the junction of the superior vena cava and the right atrium, will effectively reduce sinus rate acutely and will reduce palpitations due to inappropriate sinus tachycardia without the need for pacemaker implantation due to sinus node dysfunction post ablation.

Inappropriate sinus tachycardia syndrome describes a condition in which a patient's heart rate is intermittently (or persistently) higher than expected for the physiological circumstances, with ECG appearance indistinguishable from normal sinus rhythm, after the exclusion of medical conditions causing sinus tachycardia.

Hypothesis- Radiofrequency ablation, targeting the sympathetic input of the sinus node identified by 20Hz stimulation at the junction of the superior vena cava and the right atrium, will effectively reduce sinus rate acutely and will reduce palpitations due to inappropriate sinus tachycardia without the need for pacemaker implantation due to sinus node dysfunction post ablation.

Inclusion Criteria:

1. Patients between the ages of 18 and 80 years old, who are scheduled for an ablation procedure for suspected inappropriate sinus tachycardia, with symptomatic palpitations during periods where documented electrogram recordings suggest sinus tachycardia (holter, event recorder, or 12 lead ECG).
2. Sinus rate greater than 100 bpm with minimal physiologic challenge, or mean sinus rate during 24 hour holter more than 95bpm, or daytime resting heart rate more than 95bpm.
3. Symptoms (or sinus rate) not explained by an alternative medical or electrophysiological diagnosis.
4. Symptoms refractory to treatment with beta-blocker medication, or beta-blockers contra-indicated or not tolerated

Exclusion Criteria:

1. Children under 18 years of age (due to greater risk from exposure to X rays).
2. Any medical condition significantly increasing the risk of extending the ablation procedure or of X ray exposure, including pregnancy.
3. Significant orthostatic hypotension (due to need for rapid chronotropic response to fall in blood pressure)
4. An alternative cause for sinus tachycardia identified (e.g. hyperthyroidism or pheochromocytoma).
5. Inability or unwillingness to provide informed consent.