Myocardial uptake and washout kinetics of T1-201 with the VEX (vasodilator plus exercise) test: contribution of stress mode components and coronary stenosis severity.

OBJECTIVE: To assess the vasodilator plus exercise (VEX) test as an adjunct to myocardial perfusion imaging with respect to the accuracy of kinetics of thallium-201 (Tl-201) and other indicators of ischemia. SETTING: A nuclear medicine laboratory in which patients referred for myocardial scintigraphy are triaged to undergo the stress component with symptom-limited bicycle exercise, dipyridamole or VEX as appropriate. DESIGN: Cases having correlating scintigraphy and angiography (n = 425) were selected retrospectively. Immediate poststress and redistribution images were quantified using a circumferential profile analysis with interpolative background subtraction. For each of nine sectors on the left anterior oblique image, multivariate analyses were performed, comparing the relative uptake and net washout of Tl-201 to the exercise workload attained, use of dipyridamole, time to redistribution, gender, and the angiographic presence and severity of stenoses at five key sites. Washout values standardized according to gender, exercise level and time to redistribution, were compared with relative uptake profiles and ST depression using receiver operating curves. RESULTS: For each sector, a significant contribution to Tl-201 washout was made by the exercise level (P < 0.001) and by at least one site of stenosis (P < 0.0001), but not by use of dipyridamole (P > 0.5); female gender was associated with increased washout (P < 0.01) except for the three lateral sectors. For each stress modality, standardized washout performed better than ST depression but not as well as relative uptake profiles in detecting coronary artery disease. CONCLUSIONS: For combined pharmacological-exercise stress, quantitative uptake profiles may assist in confirming subjective scan interpretation; washout profiles, even when standardized for gender and stress level, are suboptimal for confirming defect reversibility.

The usefulness of stress tests performed in the nuclear medicine department: mathematical methods to assess efficacy at various angiographic endpoints.

Stress myocardial perfusion scintigraphy (SMPS) may be used to amplify or supplant information available from stress electrocardiography (ECG) in directing the clinical management of patients, including the need for coronary angiography. The apparent usefulness of SMPS may depend on referral bias, the stress mode employed and the criterion for disease. We compared markers of ischaemia on quantitative planar SMPS with 201 Tl in 503 referred patients; stress was tailored to the individual patient to include exercise (n = 154), dipyridamole (n = 118) or a combination of the two (n = 231). Four angiographic criteria of increasing severity (A-D) were targeted. The fraction of the population receiving diagnostic benefit was calculated for reversible defects (RD) or lung uptake (LU) in comparison to concurrent ST depression; abnormal baseline tracings and fixed 201Tl defects were regarded as indeterminate. Decision tree induction, a computer-learning algorithm and logistic regression were also used to assess the contribution of 13 scintigraphic and other input variables. In comparison to ST depression, RD showed incremental value in 167 (33%) patients with criterion A, decreasing to 5% with criterion D; LU showed its greatest benefit (21%) with criterion D. Both scintigraphic markers were more useful with dipyrida-mole-based tests than with exercise alone. Decision trees induced at each criterion for disease showed the predominant contribution of scintigraphic results in comparison to clinical and ECG data. In conclusion, in a referred population with a frequent requirement for pharmacological stress, the clinical utility of scintigraphy can be determined by comparison of markers of ischaemia; the results will depend, however on the angiographic criterion for disease.

Cardiac sequelae of acute stroke.

The possibility that acute stroke produces an increase in sympathetic tone with resultant cardiac abnormalities was examined in 100 stroke patients admitted to a stroke ICU and in 50 controls found to have diagnoses other than stroke or TIA after admission to the Unit. Continuous 24 hour Holter ECG tapings were performed and serum cardiac enzymes and plasma norepinephrine concentrations were measured within 48 hours after admission. Significantly, (p less than .001) more serious arrhythmias were observed during 24 hour Holter ECG monitoring in stroke patients compared with controls and the difference remained (p less than .01) after matching for age and co-existing heart disease. Arrhythmias were more common in older stroke (p less than .001) and older control (p = .05) patients and with infarction of the cerebral hemispheres (p less than .05) as compared to brainstem lesions. Arrhythmia occurrence was independent of the presence of co-existing heart disease and the level of sympathetic activity. However, the 15 stroke patients with abnormally high CK values (mean 34.3 units) had a higher (p less than .02) mean plasma norepinephrine concentration (650.4 pg/ml) than stroke patients with normal CK (427.7 pg/ml). Acute stroke may cause cardiac arrhythmias and myocardial cell damage, the latter through stroke induced increases in sympathetic tone.

Unnecessary diuretic therapy in the elderly.

The possible beneficial or adverse effects of long-term diuretic use in the elderly were evaluated in 60 males (mean age 80.0 years) and 17 females (mean age 84.3 years). All subjects were found to have no obvious need for diuretics when initially assessed and were not receiving concurrent digoxin therapy. Residents were randomly allocated to placebo or active groups with stratification for prior hypertension or congestive heart failure (CHF) and they were followed for one year in a double-blind design. Mean BP, heart rate and weight at one year were similar to baseline values in both groups. Six active and two placebo subjects developed CHF and two other placebo subjects had a return of BP to hypertensive levels. Serum creatinine, cholesterol, potassium and BUN were significantly improved at one year in the placebo group. Chronic diuretic use did not alter appreciably the occurrence of CHF or hypertension in this elderly population and may not be necessary.