<span name="style_bold">Justification: </span>Palpitations are a frequent complaint during medical consultation. In a group of patients with inappropriate sinus tachycardia, we retrospectively, assessed the prevalence of cardiac contractile and thyroid dysfunction <span name="style_bold">Materials and methods: </span>We selected from all 24 hour Holter studies performed during 2006 at the Cardiology Service of the México Hospital (Costa Rica) those of patients with inappropriate sinus tachycardia, defined as mean heart rate equal o greater than 80 beats per minute (bpm) or multiple episodes of sinus tachycardia without physiologic explanation. We analyzed demographic data, echocardiographic presence or absence of systolic cardiac dysfunction and thyroid function by means of TSH and total T3-4. We excluded from the analysis those patients with known cardiac disease. <span name="style_bold">Results: </span>We selected 105 Holter registries from 380 studies, 27,6% or 81 were women, and 24 men. Mean age was 38,97 years old (range 9-81). The mean heart rate was 86,23 bpm (108-71), mean maximal heart rate 143,19 (189-111) and mean minimal heart rate 55,7 (89-22) bpm. In 49 patients an ejection fraction was available; a normal mean value of 0,6 (0,7-0,45) was reported. In 29 patients thyroid function tests were obtained and the mean value of free-T4 y TSH were between normal limits (1,48 ng/dL and 1,7 mUI/L respectively). <span name="style_bold">Conclusion: </span>The majority of patients consulting for palpitations and in whom a Holter analysis results in inappropriate sinus tachycardia, have no cardiac contractility nor thyroid dysfunction. Therefore, in this group of patients it is not justified to evaluate these parameters routinely.The majority of patients consulting for palpitations and in whom a Holter analysis results in inappropriate sinus tachycardia, have no cardiac contractility nor thyroid dysfunction. Therefore, in this group of patients it is not justified to evaluate these parameters routinely.

inadequate sinus tachycardia; ejection fraction; thyroid function