Myocardial blood flow assessment with 82rubidium-PET imaging in patients with left bundle branch block

OBJECTIVES: Perfusion abnormalities are frequently seen in Single Photon Emission Computed Tomography (SPECT) when a left bundle branch block is present. A few studies have shown decreased coronary flow reserve in the left anterior descending territory, regardless of the presence of coronary artery disease. OBJECTIVE: We sought to investigate rubidium-82 (82Rb) positron emission tomography imaging in the assessment of myocardial blood flow and coronary flow reserve in patients with left bundle branch block. METHODS: Thirty-eight patients with left bundle branch block (GI), median age 63.5 years, 22 (58%) female, 12 with coronary artery disease (≥70%; GI-A) and 26 with no evidence of significant coronary artery disease (GI-B), underwent rest-dipyridamole stress 82Rb-positron emission tomography with absolute quantitative flow measurements using Cedars-Sinai software (mL/min/g). The relative myocardial perfusion and left ventricular ejection fraction were assessed in 17 segments. These parameters were compared with those obtained from 30 patients with normal 82Rb-positron emission tomography studies and without left bundle branch block (GII). RESULTS: Stress myocardial blood flow and coronary flow reserve were significantly lower in GI than in GII (p<0.05). The comparison of coronary flow reserve between GI-A and GI-B showed that it was different from the global coronary flow reserve (p<0.05) and the stress flow was significantly lower in the anterior than in the septal wall for both groups. Perfusion abnormalities were more prevalent in GI-A (p=0.06) and the left ventricular ejection fraction was not different between GI-A and GI-B, whereas it was lower in GI than in GII (p<0.001). CONCLUSION: The data confirm that patients with left bundle branch block had decreased myocardial blood flow and coronary flow reserve and coronary flow reserve assessed by 82Rb-positron emission tomography imaging may be useful in identifying coronary artery disease in patients with left bundle branch block.

application of unconventional PET tracers in nuclear medicine

The production and application of PET tracers has been a unique step in the progress of nuclear medicine in last two decades. The most important PET tracers include F-18, C-l 1 and N-13 radioisotopes and many nuclear medicine centers throughout the globe are using them. However some new tracers are under their way to the mass administration, currently being in the clinical trials or preliminary studies. Gallium-66 and 68 tracers such as Ga-DOTANOC and Ga-DOTANIC are currently being used in many neuroendocrine tumor studies in human in Europe and North America, and global application of these tracers remain to the cheaper and easier providence of [68]Ge[68]Ga generators. Copper tracers such as[61,62,64]Cu-ATSM and [61,62,64]Cu-PTSM are the most important unconventional tracers used in hypoxia and perfusion studies respectively using PET technology. Copper tracers can easily be produced using a medium cyclotron with simple chemistry. Many other interesting PET radioisotopes such as Tc-94m [HL. 52 min], 1-124 [HL. 100h], Y-86 [HL. 14.7] and rubidium tracers are being studied in some research centers in the world. This review article would describe the properties, mechanisms, production routes and problems of unconventional PET tracers with a look to the future of some important drug candidates

Effect of sensitization on membrane ion fluxes & intracellular calcium in guineapigs.

BACKGROUND & OBJECTIVES: The biochemical mechanisms underlying the development of sensitization-induced airway hyperresponsiveness (AHR) in asthma are poorly defined. Alterations in the regulation of intracellular calcium may play an important role in its pathogenesis. We carried out this study to see the effect of sensitization with ovalbumin on membrane ion fluxes and intracellular calcium in a guinea pig model. METHODS: Airway reactivity to inhaled histamine was measured initially and after sensitization with ovalbumin in 28 guineapigs. Intracellular calcium [Ca(2+)]i was measured in tracheal smooth muscle cells and peripheral leukocytes using fluorescent dye FURA 2AM. Calcium and sodium ion influx across the cell membrane was measured in leukocytes. Ouabain-sensitive Rubidium ((86)Rb) influx was measured in tracheal smooth muscles cells. The activities of Na(+), K(+) ATPase and Ca(2+) ATPase were measured in tracheal smooth muscle cells. Lipid peroxides were measured in plasma. RESULTS: Airway responsiveness was significantly (P<0.001) increased after sensitization along with an increase in [Ca2+]i levels in leukocytes and tracheal smooth muscle cells, higher rates of (45)Ca and (22)Na influx in leukocytes and higher (86)Rb influx rates in tracheal smooth muscle cells, and increased levels of lipid peroxides in plasma. INTERPRETATION & CONCLUSION: In guineapig model of asthma sensitization to allergen increased the membrane permeability to calcium and sodium, and intracellular calcium levels. These alterations may play a role in the pathogenesis of airway hyper-responsiveness following sensitization.

86RB+ efflux as an index of calcium paradox

In the present study isolated rat hearts were perfused with calcium free media for 2,4,6,8, and 10 minutes followed by calcium repletion 86Rb+ efflux, protein leakage, percentage rise in resting tension and recovery of developed tension were evaluated. Mechanical activity was not lost completely when calcium was deprived for periods less than 6 minutes, however, readmission of calcium was accompanied by reduction of contractile recovery and 86Rb+ loss. Calcium depletion for a longer periods produced, on calcium readmission, loss of mechanical activity, 86Rb+ and protein loss. A dissociation between some of the indices of the calcium paradox is being shown in this study. The magnitude of contracture does not parallel 86Rb+ efflux and protein loss. In many experimental studies only one or tow indices are used, the assumption being made is that these are sufficient to define the extent of cell damage. This assumption may be dangerous as these indices are not necessarily parallel. Hypothermia and a low calcium concentration perfusion during, the calcium deprivation period, protected the heart against calcium paradox-induced damage and prevented 86Rb+ and protein loss. 86Rb+efflux is suggested here as an alternative index of calcium paradox as it is sensitive and reflects of cell damage