[Effect of caffeine on myocardial blood flow during pharmacological vasodilation]. / Effekt von Koffein auf den myokardialen Blutfluss unter pharmakologischer Vasodilatation.

Pharmacologic stress with adenosine is frequently used for noninvasive detection of coronary artery disease. Dietary intake of caffeinated food, beverages or medications might alter adenosine-induced hyperemic blood flow, thereby compromising the diagnostic sensitivity of adenosine stress testing. In this case we report on a male patient with CAD. Myocardial blood flow at rest and during adenosine-induced hyperemia 2 hours after consumption of decaffeinated coffee and again without caffeine intake were quantified by ammonia PET. After caffeine intake there was a clearly diminished increase of myocardial blood flow during adenosine. The average coronary flow reserve in the myocardium was 1.3 after caffeine. In the baseline study without caffeine the coronary flow reserve has been improved to 2.3. Caffeine intake alters the coronary vasodilatory capacity. These findings emphasize the importance of carefully screening patients for intake of caffeinated food prior to adenosine stress testing.

[Myocardial perfusion under H.E.L.P. -apheresis. Objectification by PET]. / Myokardiale Perfusion unter H.E.L.P.-Apherese. Objektivierung durch PET.

Due to endothelial dysfunction (ED), coronary vasodilation capacity is reduced in patients with hypercholesterolemia. Cholesterol lowering may largely restore endothelial function. Currently, it is supposed that the onset of this therapeutic effect takes weeks or even months. However, by means of LDL apheresis, a significant LDL reduction may be achieved within hours. Dynamic quantitative positron emission tomography (PET) performed before and after LDL apheresis showed that mean global myocardial perfusion can be measured at rest and after pharmacological vasodilation with dipyridamole using N13 ammonia as tracer.A total of 35 patients (11 women and 24 men) with documented coronary heart disease and hypercholesterolemia underwent PET immediately prior to LDL apheresis and 18-20 hours thereafter. In addition to the decrease in LDL cholesterol (from 175+/-50 to 77+/-25 mg/dl) and fibrinogen (from 287+/-75 to 155+/-52 mg/dl), a significant improvement of myocardial blood flow under dipyridamole (177+/-59 vs 217+/-82 ml/min 100 g, p<0.0001), of coronary flow reserve (2.10+/-0.82 vs 2.62+/-1.02, p<0.0001) and of minimal coronary resistance (0.56+/-0.20 vs 0.44+/-0.17 mmHg 100 g min/ml, p<0.0001) were achieved. Plasma viscosity decreased only by 7.8%. Within 20 hours after single LDL apheresis a 20% improvement of coronary vasodilation capacity was noninvasively demonstrated and quantified.

Deactivation of thalamocortical activity is responsible for suppression of parkinsonian tremor by thalamic stimulation: a 99mTc-ECD SPECT study.

Four patients with Parkinson's disease (PD) achieved excellent improvement of their unilateral tremor by chronic deep brain stimulation (DBS) of the contralateral ventral intermediate (Vim) nucleus of the thalamus. Repeated measurements of cerebral blood flow were obtained 14 days apart off and on stimulation using 99mTc-ECD SPECT. Subjects were scanned at rest and the data were compared with those of normal healthy volunteers. During stimulation, there were highly significant deactivations in the motor area and supplementary motor area on the electrode side and in the prefrontal area and the anterior cingulum bilaterally. No cerebellar deactivation was detected. We conclude that the mechanism responsible for suppression of parkinsonian tremor by thalamic stimulation is deactivation of thalamocortical activity.

Intratumoral arteriovenous shunting in malignant gliomas.

OBJECTIVE: Intratumoral arteriovenous shunting in glioblastomas has been suspected but neither proven nor quantified. METHODS: Using a previously described technique of selective intra-arterial intratumoral injection of 99mTc-labeled microparticles (macroaggregated albumin), we measured the amount of radioactivity, by cerebral and pulmonary scintigraphy, in seven patients with malignant gliomas (six with glioblastomas and one with an anaplastic oligodendroglioma). The pulmonary shunt index was calculated as a percentage from the pulmonary/pulmonary plus cerebral radioactivity ratio. RESULTS: The results revealed a mean pulmonary shunt index of 67% (range, 47-89%), indicating that most of the microparticles injected into the tumor via the arterial route bypassed the tumor and reached the lungs. The measured arteriovenous shunting was greater when the injection was performed in an artery exclusively perfusing the tumor. CONCLUSION: Important intratumoral arteriovenous shunting exists in glioblastomas. The potential consequences of this finding for intra-arterial treatment strategies are discussed.