[Myocardial perfusion study in patients who do not reach submaximal frequency on ergometry]

The aim of the study was to evaluate the sensitivity and specificity of TI-201 myocardial perfusion SPECT for the diagnosis of ischaemic cardiopathy in a group of patients with chronotropic insufficiency.

The examinations of 750 patients who had attended for the diagnosis of ischaemic cardiopathy during 2005-2006 were selected. 28 % (n = 209) did not reach submaximal frequency. Data on the diagnosis was collected in 112 by telephone interview. Ergometry and SPECT were carried out following the usual techniques.

Patients who reached submaximal frequency and patients with chronotropic insufficiency did not show differences in age and exercise time. The proportion of patients on beta-blocker treatment, with clinically positive ergometries and pathological SPECT was higher in the patient group which had not reached 85 % of their maximum frequency. The data obtained in the patient group which did not reach submaximal frequency and followed-up by telephone interview showed a SPECT sensitivity of 84 % and specificity of 96 %. The sensitivity of the ergometry was 25 % and its specificity was 96 %.

Ergometry with myocardial perfusion SPECT has adequate sensitivity and specificity for the diagnosis of ischaemic cardiopathy, even in patients with chronotropic incompetence. The proportion of pathological examinations is higher in those patients in whom tachycardia could not be sufficiently induced, which seems to indicate that the inability to reach submaximal frequency is related with a higher probability of having ischaemic cardiopathy.