Israel Medical Association Journal

Background: Heart rate variability is a sensitive marker of cardiac sympathetic activity.

Objectives: To determine whether long-term hyperthyroidism induced by thyroxine suppressive therapy affects HRV[1].

Methods: Nineteen patients treated with suppressive doses of thyroxin for thyroid cancer and 19 age-matched controls were enrolled. Thyroid function tests and 1 minute HRV were performed on all subjects and the results were compared between the groups. The 1 minute HRV was analyzed during deep breathing and defined as the difference in beats/minute between the shortest and the longest heart rate interval measured by eletrocardiographic recording during six cycles of deep breathing.

Results:  One minute HRV during deep breathing was significantly lower among thyroxine-treated patients compared to healthy controls (25.6 ± 10.5 vs. 34.3 ± 12.6 beats/min, P < 0.05). There were no significant differences in mean, maximal and minimal heart rate between the groups

Conclusions: Thyroxine therapy administered for epithelial thyroid cancer resulted in subclinical hyperthyroidism and significantly decreased HRV due to autonomic dysfunction rather than basic elevated heart rate.

Background: Syncope is a common clinical problem that often remains undiagnosed despite extensive and expensive diagnostic evaluation.

Objectives: To assess the diagnostic evaluation, costs and prognosis of patients hospitalized for syncope in a tertiary referral center according to discharge diagnosis.

Methods: We retrospectively reviewed the medical records of patients with a diagnosis of syncope discharged from a tertiary referral center in 1999. In addition, mortality data were obtained retrospectively a year after discharge for each patient.

Results: The study group comprised 376 patients. Discharge etiologies were as follows: vasovagal 26.6%, cardiac 17.3%, neurological 4.3%, metabolic 0.5%, unexplained 47.3%, and other 4%. A total of 345 patients were admitted to the internal medicine department, 28 to the intensive cardiac care unit, and 3 to the neurology department. Cardiac and neurological tests were performed more often than other tests, with a higher yield in patients with cardiac and neurological etiologies respectively. The mean evaluation cost was 11,210 ± 8133 shekels, and was higher in the ICCU[1] than in internal medicine wards (19,210 ± 11,855 vs. 10,443 ± 7314 shekels, respectively; P = 0.0015). Mean in-hospital stay was 4.9 ± 4.2 days, which was longer in the ICCU than in medicine wards (7.2 ± 5.6 vs. 4.6 ± 3.5 days, respectively; P = 0.024). Short-term mortality rates (30 days after discharge) and long-term mortality rates (1 year after discharge) were 1.9% and 8.8% respectively, and differed according to discharge etiology. LTM[2] rates were significantly higher in patients discharged with cardiac, neurological and unknown etiologies (not for vasovagal), compared with the general population of Israel (1 year mortality rate for the age-adjusted [65 years] general population = 2.2%). The LTM rate was higher in patients discharged with a cardiac etiology than in those with a non-cardiac etiology (15.4% vs. 7.4%, P = 0.04). Higher short and long-term mortality rates were associated with higher evaluation costs.

Conclusions: Hospitalization in a tertiary referral center for syncope is associated with increased mortality for most etiologies (except vasovagal), cardiac more than non-cardiac. Despite high costs of inpatient evaluation, associated with more diagnostic tests, longer in-hospital stay and higher mortality rates, nearly half of the patients were discharged undiagnosed. Outpatient evaluation should be considered when medically possible.