J. C. W. Crawley

Exercise-Induced S-T segment elevation in variant angina

Five patients with known ischemic heart disease had an unusual pattern of S-T segment depression during treadmill exercise testing followed by S-T segment elevation and chest pain in the postexercise period. Thallium-201 scintigraphy revealed reversible exercise-induced myocardial ischemia, in areas supplied by severely narrowed coronary arteries as documented by coronary arteriography. Ambulatory electrocardiographic recording for S-T segment shift using a frequency-modulated system showed S-T segment depressions and elevations at rest in the same leads that showed similar shifts during exercise tests. Three of the five patients had a myocardial infarction within 8 weeks of diagnosis, and two died. This syndrome may be associated with severe coronary artery disease and may have a very poor prognosis.

SPECT using Bremsstrahlung to quantify 90Y uptake in Baker's cysts: Its application in radiation synovectomy of the knee

The use of SPECT with Bremsstrahlung radiation has been investigated in studies on patients undergoing 90Y therapy for persistent synovitis of the knee. In particular, its value in the estimation of 90Y uptake into Bakers cysts was assessed and, to this end, realistic ‘knee phantoms’ were employed in order to calibrate for cysts of different size. Problems associated with the measurement of the extensive Bremsstrahlung spectrum and the estimation of cyst volume have been discussed. It is shown that, although the apparent volume of a cyst is markedly dependent on the chosen count rate threshold, volumes greater than about 30 ml can be estimated with reasonable accuracy using a threshold of 50%. The uptake of 90Y in cysts, measured on 3 occasions within the first 2 days in 10 patients, showed wide variation (0%–40%) between patients and was poorly related to the size of cysts on arthrograms and to the clinical response to therapy. In these studies, the ability to analyse SPECT slices provided a distinct advantage over planar imaging for discriminating between 90Y uptake in cysts and adjacent sites. Retention of 90Y in the total knee was also widely variable, with losses of 2%–38% observed 2 days after injection which, in general, were not fully accounted for by uptake in liver or lymph nodes. The changing distribution of 90Y colloid in the knee during the first two days, as observed in some patients, might explain part of the discrepancy.

Acute and chronic effects of sustained action buccal nitroglycerin in severe congestive heart failure

Vasodilators, such as nitroglycerin, have been widely used in the treatment of acute and chronic heart failure for therapeutic manipulation of the venous and arterial circulations to improve left ventricular function. We have tested the efficacy of a new formulation for sustained release buccal delivery of nitroglycerin (biological life 5-6 hr) in 21 patients with severe congestive heart failure due to ischaemic cardiomyopathy using maximal treadmill exercise testing and radionuclide angiography. A single-blind placebo-controlled acute and an open chronic phase (4 weeks) of treatment were employed. The mean dose was 23.4 mg daily, and clinical assessment suggested significant improvement in 15 patients. The mean ejection fraction (placebo) of 14.1% +/- 1.6 SEM increased to 19.1% +/- 1.7 (acute) and to 21.6% +/- 1.7 (chronic treatment) (P less than 0.001; n = 16). The mean exercise time increased from 3.02 +/- 0.4 min (basal) to 5.95 +/- 0.6 min (chronic) (P less than 0.001). Segmental wall motion abnormality was shown to improve after treatment for 4 weeks. There were no major side effects. Nine patients were reassessed after 24 weeks on the same regimen; exercise time and left ventricular ejection fraction were similar to the 4-week period, thus demonstrating a sustained improvement in cardiac function and functional capacity. A worthwhile functional and objective haemodynamic improvement was demonstrated in these patients with severe chronic congestive heart failure. This mode of treatment may have useful therapeutic value in the management of patients with a wide range of ischaemic heart failure.

Improved diagnostic accuracy of planar imaging with technetium 99m-labeled tetrofosmin compared with thallium-201 for the detection of coronary artery disease

BackgroundReceiver operating characteristic (ROC) curve analysis provides detailed information about the performance of a diagnostic test.Methods and ResultsAs part of a multicenter phase III trial, 160 patients with known or suspected coronary artery disease underwent planar stress-rest99mTc-labeled tetrofosmin and stress-redistribution201Tl imaging within 14 days of each other, to compare the diagnostic accuracy of these imaging modalities by ROC curve analysis. Coronary arteriography was used as the reference standard and greater than 70% stenosis was considered significant. ROC curve analysis showed improved detection of coronary artery disease with99mTc-labeled tetrofosmin compared with201Tl, with ROC curve areas of 0.765 versus 0.644, respectively (p=0.02).99mTc-labeled tetrofosmin also better identified single-vessel disease in those without previous myocardial infarction (ROC curve areas of 0.684 vs 0.510 for99mTc-labeled tetrofosmin and201Tl, respectively;p=0.04) and enhanced the detection of multivessel disease in those with previous myocardial infarction (ROC curve areas of 0.764 vs 0.638, respectively;p=0.02).ConclusionsDetailed assessment of diagnostic performance by ROC curve analysis shows that, for planar imaging,99mTc-labeled tetrofosmin enhances the detection of coronary artery disease compared with201Tl.

Animal and human studies of a new 99mTc labelled phosphine-isocyanide complex with possible applications to radionuclide ventriculography

A new 99mTc-phosphine-isocyanide complex with the general structure [99mTc (DEPE)2 (CNR)2]+ has been synthesised and tested in animals and one human. In three animal species (rat, rabbit, dog), the complex is an efficient myocardial imaging agent, while in humans it remains in the blood pool. The complex is 100% protein bound in animals and humans, but whereas in humans it is attached to a 51.5 kdalton protein (probably prealbumin), in rabbits it appears to be bound to a larger macromolecule (M.W.> 100 kdalton). The efficiency of the complex for blood pool labelling was tested in a human volunteer and compared with the standard in vivo red cell labelling technique with stannous pyrophosphate. A satisfactory radionuclide angiogram could be performed with less than 370 MBq of the complex. The count rate for the complex (cps/MBq) was 15% higher than that obtained with the labelled red cells and the absence of splenic activity was notable. In humans this complex appears to be an efficient blood pool labelling agent which might be useful for radionuclide ventriculography.

Improvement in left ventricular function after chronic treatment with methyldopa in hypertensive patients with left ventricular hypertrophy

SummaryA study was carried out in 18 hypertensive patients, 10 with left ventricular hypertrophy, to investigate the effect of long-term treatment with methyldopa (750 mg to 3 g daily for 6 months) on left ventricular function. Patients with coronary artery disease were excluded. Sustained isometric hand grip and cold pressor tests were used to increase afterload, and changes in left ventricular function were monitored with radionuclide angiography. The results showed that, in addition to producing significant reductions in systolic and diastolic blood pressure, the reduction in the left ventricular ejection fraction which occurred during the provocative tests in patients with left ventricular hypertrophy was either controlled or attenuated after methyldopa treatment.

A new method of imaging the right ventricle using peripheral vein infusion of xenon 127

We report the development of a new method for obtaining right ventriculograms using the peripheral intravenous infusion of a new tracer, 127Xe dissolved in saline. This tracer has a half life of 36 days, emits 172 keV and 203 keV photons, and is completely cleared by the lungs during pulmonary transit. The right ventricle can therefore be imaged free from interfering activity in the systemic circulation. The technique was used in 11 normal subjects and the results compared with those obtained using first pass and gated equilibrium blood pool angiography with 99mTc. Excellent images of the right ventricle were obtained and the tricuspid and pulmonary valve planes could be easily identified. This imaging technique has significant advantages over existing methods for the noninvasive assessment of right ventricular function.

New developments in the field of acute myocardial infarction imaging

We read with interest the article by Bell et al (1988) regarding the development of newer and more effective myocardial infarction imaging agents. 99Tcm pyrophosphate and its analogues have severe limitations for the imaging of acute myocardial infarction (Turi et al, 1985) because of low specificity, dependence on blood flow for its uptake by necrotic myocardium and poor image quality. We wish to draw your attention to the development of a promising new agent for the imaging of acute myocardial infarction: radiolabelled mono-clonal antimyosin antibodies. Experimental work (Khaw et al, 1982) has shown that antimyosin antibodies bind specifically to myocardial cells with acute irreversible damage to the cell membrane. Initial studies using the experimental animal model of acute myocardial infarction (Khaw et al, 1979) have shown that 125I-labelled antimyosin antibodies localize specifically at the site of myocardial infarction in high concentrations and there is a close correlation between the site of radi...