Prevalence, characteristics and natural course of inappropriate sinus tachycardia

To study the prevalence, characteristics and natural course of inappropriate sinus tachycardia (IST).

The prevalence and characteristics of IST were evaluated in a random sample of 604 middle-aged subjects. Seven of the subjects (1.16%) fulfilled the contemporary diagnostic criteria of IST. The systolic (147 ± 11 mmHg vs. 130 ± 13 mmHg, P < 0.001) and diastolic ambulatory blood pressures (92 ± 7 mmHg vs. 81 ± 8 mmHg, P < 0.001) were higher among the subjects with IST than among the controls. The other laboratory, echocardiographic and personality measurements, with the exception of the hostility score (10 ± 2 vs. 8 ± 3, P < 0.001), revealed no differences between the groups. The natural course and prognosis of the disorder was assessed among the subjects fulfilling the IST criteria and nine previously diagnosed IST patients. During a mean follow-up of 6.0 ± 2.4 years, none of the subjects developed any clinical or echocardiographic evidence of structural heart disease despite ongoing palpitations, and there was no significant reduction in the 24-h average HR (94 ± 2 bpm vs. 89 ± 8 bpm, P = 0.204).

The prevalence of IST in a middle-aged population was higher than previously assumed. Despite the chronic nature of the disorder, the prognosis of IST was benign. The causal relationship between IST and hypertension and/or hostile personality type remains speculative.