Alterations in myocardial thallium-201 distribution in patients with chronic systemic hypertension undergoing single-photon emission computed tomography

To characterize thallium-201 distribution in singlephoton emission computed tomography (SPECT) cardiac images and polar bullseye maps, 100 patients with chronic systemic hypertension due to end-stage renal disease were studied and the results compared with those in 35 normotensive control subjects. Thallium-201 SPECT was performed after exercise in all control subjects and 70 hypertensive patients, and after intravenous dipyridamole in 30 patients. A frequent finding in hypertensive patients was a fixed decrease in the normal lateral-to-septal count density ratio in immediate thallium-201 SPECT images (1.02 ± 0.10 vs 1.17 ± 0.08 in control subjects, p < 0.00001) and in 3-hour delayed images (1.02 ± 0.11 vs 1.11 ± 0.08 in control subjects, p < 0.00001). No significant difference in count density ratio was present in patients undergoing treadmill versus diypridamole intervention. In 35 patients the count density ratio was >2.0 standard deviations below the normal mean, creating the false impression of a fixed lateral defect (i.e., myocardial infarction). In 12 patients, myocardial wall thickness was measured at end-diastole by 2-dimensional echocardiography. Wall thickness was increased (>11 mm) in all patients. The mean lateral-to-septal wall thickness ratio was 1.08 ± 1.11; in no patient was the ratio < 0.76 to indicate selective septal hypertrophy. The lateral-to-septal wall thickness and lateral-to-septal thallium-201 count density ratios correlated poorly (r = 0.43). It is concluded that in hypertensive patients with diffuse myocardial hypertrophy there is a decrease in thallium-201 count density ratio in SPECT images, frequently creating apparent lateral wall fixed defects and mimicking myocardial infarction.