Effects of chronic insulin treatment on blood pressure in rats.

There is an evident epidemiological association between plasma insulin levels and blood pressure. The mechanism that relates insulin to blood pressure and the role of insulin in the pathogenesis of arterial hypertension have not been clearly defined. The present study was designed to examine the effects of chronic hyperinsulinism on blood pressure and to determine different related morphological variables. WistarKyoto rats were subcutaneously injected with insulin (25 UI/Kg of weight) daily during the eight weeks of the experiment. Data were collected on systolic and diastolic arterial pressures and heart rate by plethysmography and direct recording (in the last week), and on morphological variables. A statistically significant elevation of systolic arterial pressure was produced after the sixth week of hyperinsulinaemia. At the end of the treatment, the systolic arterial pressure was 173.7 +/- 26.1 in the hyperinsulinaemic rats versus 153.09 +/- 21.7 in the control group. The values obtained by direct recording and by plethysmography did not differ. These results indicate that chronic hyperinsulinism produces a significant elevation in systolic blood pressure levels in the rats studied.

False-positive Tc-99m sestamibi SPECT in a patient with left bundle branch block.

A 37-year-old man with atypical chest pain and complete left bundle branch block showed a marked exercise induced septal defect on Tc-99m sestamibi stress testing. A repeat examination at rest the next day revealed complete reversal of the previous septal defect. Coronary angiography two days later showed a normal coronary artery system. Left bundle branch block has been associated with false-positive results of exercise (and more recently, dipyridamole) TI-201 examinations for septal ischemia. The case presented here may be the first reported example of a false positive Tc-99m sestamibi examination for septal ischemia in the presence of left bundle block.

Pheochromocytoma: diagnosis by scintigraphy using iodine 131 metaiodobenzylguanidine.

We summarize our experience using iodine 131 metaiodobenzylguanidine (131I MIBG) imaging in 24 patients with suspected pheochromocytoma and compare 131I MIBG imaging with other imaging modalities such as computerized tomography and magnetic resonance imaging. Our results confirm the high sensitivity and excellent specificity reported from other centers experienced in 131I MIBG imaging. This radiopharmaceutical permits noninvasive, safe, accurate detection of pheochromocytomas of all types. Iodine 131 MIBG scintigraphy is especially efficacious in the detection of extra-adrenal, recurrent, and metastatic tumors. We review precautions in the screening of patients for 131I MIBG examination, imaging techniques, and drugs that interfere with tumor uptake of 131I MIBG. Though 131I MIBG imaging has some limitations, it deserves strong consideration whenever the diagnosis of pheochromocytoma is suspected.

Pectoralis muscle uptake of thallium-201 after arm exercise ergometry. Possible confusion with lung thallium-201 activity.

Pectoralis muscle uptake of thallium-201 was noted in 8 (73%) out of 11 patients after exercise arm ergometry. Uptake varied from mild to marked and potentially could be confused with pulmonary Tl-201 activity with a resulting false-positive diagnosis of exercise-induced left ventricular dysfunction. The three patients exhibiting negative or trace Tl-201 uptake had suboptimal exercise efforts. The characteristics of pectoralis muscle Tl-201 uptake are illustrated, and differentiation from true lung Tl-201 activity is discussed.