The effect of systemic hypertension on exercise tomographic thallium-201 imaging in the absence of electrocardiographic left ventricular hypertrophy

This study was designed to assess the effect of systemic hypertension on exercise thallium-201 imaging. The study group consisted of 38 patients with systemic hypertension who were compared with 68 normotensive patients. All patients had a low pretest likelihood of coronary artery disease to minimize the influence of selection bias. Patients with electrocardiographic evidence of left ventricular hypertrophy were excluded. Single-photon emission computed tomographic thallium-201 images were obtained immediately after exercise and 4 hours after exercise. Thallium tomographic images were assessed qualitatively by 14 short-axis segments and were grouped into three coronary distributions. Regional and global quantitative analysis was also performed by using a reference study group at low risk for coronary artery disease. The hypertensive group demonstrated higher resting systolic blood pressure (137 ± 26 mm Hg vs 120 ± 14 mm Hg in the normotensive group, p = 0.0002) immediately before exercise. There was no significant difference between hypertensive and normotensive groups in peak exercise systolic blood pressure (181 ± 31 mm Hg vs 172 ± mm Hg, p = NS). The normotensive group achieved a significantly higher peak exercise heart rate (162 ± 18 vs 146 ± 20 beats/min in the hypertensive group, p = 0.0001) and higher estimated oxygen uptake (11.0 ± 3.4 vs 9.1 ± 2.7 metabolic equivalents [METS] in the hypertensive group, p = 0.003). However, rate-pressure products for both groups were nearly identical. Qualitative thallium-201 analysis revealed no significant difference in the total number of abnormal thallium-201 segments (normotensive 9%, hypertensive 6%, p = NS), the number of patients with at least one poststress abnormal segment (34% normotensive, 26% hypertensive, p = NS), or in the presence of an abnormal coronary distribution (18% normotensive, 21% hypertensive, p = NS). Quantitative thallium-201 analysis also showed no significant difference between these groups for the amount of abnormally perfused left ventricle, either overall (median 1 % of the left ventricle in the hypertensive group vs 2% in the normotensive group, p = NS) or within individual coronary territories (p = NS for any of the three coronary distributions). In the absence of electrocardiographic evidence of left ventricular hypertrophy, systemic hypertension does not cause an increase in false positive exercise thallium-201 tests.