Drug Therapy For IST

Drug therapy for IST is reasonably effective in many patients, but achieving optimal results often requires trial-and-error attempts with several drugs, singly or in combination.

Beta blockers block the effect of adrenaline on the sinus node, and since patients with IST have an exaggerated response to adrenaline, using beta blockers is logical. They are reasonably effective in many patients with IST.

Calcium blockers can slow the action of the sinus node, but have been only marginally effective in for IST.

Non-drug therapy For IST

Increase salt intake. This must be done with the approval of the physician, because it goes against society's and the medical profession's prejudice against sodium. But salt increases the blood volume, and to the extent that a reduced blood volume contributes to symptoms, increasing the salt intake might help alleviate symptoms.

Sinus node ablation. Cardiologists, especially electrophysiologists, have largely been swayed by the data suggesting that IST is primarily a disorder of the sinus node (as opposed to a more generalized disorder of the autonomic nervous system.) Subscribing to this point of view, as we have noted, has limited their horizons in administering drug therapy. It has also created a certain amount of enthusiasm for using radiofrequency ablation (a technique in which part of the cardiac electrical system is cauterized through a catheter) to modify the function of, or even destroy the function of, the sinus node.

Sinus node ablation has so far achieved only limited success. While IST has been reported as being successfully treated in up to 80% of patients immediately after sinus node ablation, the IST recurs within a few months in the large majority of these patients.

Waiting. One reasonable non-pharmacologic approach to managing IST is to do nothing. While the natural history of this disorder has not been formally documented, it seems likely that IST tends to improve over time in most patients. "Doing nothing" may not be an option in patients who are severely symptomatic, but many patients with IST can tolerate their symptoms once they are assured that they do not have a life-threatening cardiac disorder, once they are told that the problem is likely to improve on its own eventually, and once they are enlightened as to the treatment options.

Sources:

Krahn, AD, Yee, R, Klein, GJ, Morillo, C. Inappropriate sinus tachycardia: Evaluation and therapy. J Cardiovasc Electrophysiol 1995; 6:1124.

Schulze, V, Steiner, S, Hennersdorf, M, Strauer, BE. Ivabradine as an alternative therapeutic trial in the therapy of inappropriate sinus tachycardia: a case report. Cardiology 2008; 110:206.