Dipyridamole thallium-201 scintigraphy for improved detection of left anterior descending coronary artery stenosis in patients with left bundle branch block.

In patients with left bundle branch block (LBBB) undergoing thallium-201 exercise scintigraphy septal perfusion defects are frequently observed irrespective of the presence or absence of coronary artery disease. Consequently, in these patients the specificity for detecting stenoses in the left anterior descending coronary artery (LAD) by thallium-201 scintigraphy is relatively low. It has been hypothesized that pharmacological vasodilation would result in higher specificity than conventional exercise thallium-201 scintigraphy because of a more uniform exploitation of coronary flow reserve. Twenty-five consecutive patients with LBBB underwent dipyridamole thallium-201 imaging and coronary arteriography within 3 months. The prevalence of coronary artery disease was estimated at 48 +/- 19%. Sensitivity for detection of LAD lesions was 100% and specificity was 88%. The positive predictive accuracy and the negative predictive accuracy were 80% and 100% respectively. The 'false positive' septal defects were of the non-reversible type. The appearance of septal perfusion defects was not dependent on changes in heart rate during dipyridamole infusion. This study indicates the value of dipyridamole thallium-201 imaging for non-invasive detection of LAD stenosis in patients with LBBB.

Hepatobiliary scanning with 99mTc-pyridoxylidene glutamate. A retrospective study investigating the criteria for differentiation between intrahepatic and extrahepatic obstruction.

In 70 99mTc-pyridoxylidene glutamate (PG) studies with verified diagnoses, the following scan patterns were found. (1) Normal: within 30 min of PG injection the scan reveals the liver, hepatic ducts, common bile duct, gallbladder and flow to the intestine; after 2 h the liver had a higher concentration of activity than the hepatic ducts or the common bile duct. (2) Complete extrahepatic obstruction: no hepatic excretion to the intestine is observed 18-24 h after PG injection, nor is activity observed in the hepatic ducts, common bile duct and gallbladder. (3) Incomplete extrahepatic obstruction: intestinal activity is observed within 18-24 h of PG injection; after 2 h the concentration of activity in the hepatic ducts or the common bile duct exceeds that in the liver (regardless whether activity is or is not demonstrated in the gallbladder). (4) No extrahepatic obstruction: serum bilirubin normal or increased; intestinal activity is observed within 18-24 h after PG injection, and activity is demonstrable during this period somewhere in the hepatic ducts, the common bile duct or the gallbladder; after 2 h the concentration of biliary activity should not exceed that in the liver. (5) If excretion to the intestine is observed within 18-24 h of PG injection without demonstrable activity in the hepatic ducts, common bile duct or gallbladder, then it is impossible to differentiate between (3) and (4).

Some factors affecting a commercial kit for radioimmunoassay of digoxin using tritiated digoxin.

Some factors affecting results of digoxin determinations using one commercially available radioimmunoassay kit are described and discussed. Serum of pregnant women, cord blood, amniotic fluid and serum of patients taking spironolactone may show erroneously high digoxin activity due to lack of specificity of the antiserum. Cross-reaction with digitoxin was found to vary substantially with antibody-lot. Haemaccel (5 g/1) in the sample leads to too low results. When ethanol (100 g/1) is present results are too high. The need for testing the specifity of every new lot of antiserum before use is stressed.