[Exercise testing in patients with the sick sinus syndrome].
Heart rate response to exercise was compared in three groups of subjects; 22 patients (mean age 63.7 years) with sick sinus syndrome and no other significant heart disease (Group I); 10 subjects of the same age with stable, asymptomatic sinus bradycardia at rest (Group II); 29 age-matched controls (Group III). All subjects underwent maximal, symptom-limited exercise testing and the maximal heart rate (HR max), the ratio between HR max and the theoretical maximal heart rate (HR%), exercise capacity (EC) and the ratio between heart rate % and exercise capacity (HR%/EC) % of the three groups were compared. Maximal heart rate, heart rate % and (HR%/EC) % in Group I patients were significantly lower than in Group III subjects (119.1 +/- 24.0 vs 139.0 +/- 18.2; 76.0 +/- 13.9 vs 87.9 +/- 10.8 and 83.0 +/- 19.3 vs 97.5 +/- 15.1 respectively); (HR%/EC) % was significantly lower in Group I patients compared to Group II subjects (83.0 +/- 19.3 vs 101.5 +/- 28.6). Heart rate response was the same in Group I and Group II patients and exercise capacity did not differ in the three groups. Maximal heart rate, heart rate % and (HR%/EC) % were similar in Group II and Group III subjects. The association of (HR%/EC) % less than or equal to 85% with either HR max less than or equal to 110/min or HR% less than or equal to 70% at the end of maximal exercise testing may be suggestive of sick sinus syndrome. The reduced heart rate response during exercise may be helpful in assessing sick sinus syndrome in patients with no other signs of heart disease.