Search

OBJECTIVES Transcatheter aortic valve implantation improves survival in patients with severe aortic stenosis who are ineligible for surgical valve replacement; however, not all patients benefit from the procedure. We endeavoured to identify these patients using intraoperative echocardiography and hypothesized that intraoperative left ventricular function in response to the acute afterload reduction during the procedure was related to long-term outcomes. METHODS We prospectively included 64 patients who were scheduled for transcatheter aortic valve implantation and divided them into responders and non-responders based on their left ventricular intraoperative responses to the acute afterload reduction after valve deployment. Responders were defined by increases of ≥20% in left ventricular longitudinal peak systolic velocities determined by tissue Doppler echocardiography. All patients were assessed for the following outcomes at 12 months: cardiac mortality, adverse cardiac events, quality of life, New York Heart Association class, N-terminal pro-brain natriuretic peptide (NT-proBNP) and echocardiography. RESULTS Thirty-five patients (55%) were classified as responders and 29 patients (45%) as non-responders. Compared with responders, non-responders had higher risks of death (28 vs 9%, respectively, P = 0.04) and cardiac events (66 vs 26%, respectively, P < 0.01) during the 12-month follow-up. Significant long-term improvements in quality of life, NT-proBNP and left ventricular function were observed only in the responders. Preoperative risk stratification, intraoperative handling, aortic gradient and valve area were similar between groups. CONCLUSIONS Intraoperative assessment of left ventricular function by tissue Doppler echocardiography predicted long-term outcomes after transcatheter aortic valve implantation. Our results suggest that a preoperative test of myocardial contractile reserve might improve risk stratification and patient selection prior to the procedure.

OBJECTIVES Left ventricular function is expected to improve after transcatheter aortic valve implantation due to the acute reduction in afterload, but does not occur in all patients. We hypothesized that the immediate intraoperative response in systolic left ventricular longitudinal motion during the procedure could be a predictor of short-term outcome. METHODS Sixty-four patients treated with transcatheter aortic valve implantation for severe aortic stenosis were included. Transoesophageal 4- and 2-chamber echocardiograms were obtained immediately prior to and ∼15 min after valve implantation. Patients were defined as responders if their average left ventricular longitudinal peak systolic velocity increased by ≥20% from the preimplantation value and was related to the 3-month outcome. RESULTS Thirty-five patients were classified as responders, with an increase in the intraoperative longitudinal peak systolic velocity from an average of 2.2 ± 0.8 to 3.1 ± 1.1 cm/s (P < 0.001); the velocity was unchanged in the remaining 29 patients, who averaged 2.4 ± 1.1 cm/s. There were significantly fewer adverse cardiac events in the responder group at the 3-month follow-up (20 vs 45%, P = 0.03) and the New York Heart Association class was significantly better in the responders compared with non-responders. Responders had a significant reduction in N-terminal probrain natriuretic peptide levels [243 (113-361) vs 163 (64-273), P = 0.004] at the 3-month follow-up, whereas non-responders did not [469 (130-858) vs 289 (157-921), P = 0.48]. CONCLUSIONS An immediate improvement in the longitudinal peak systolic velocity during the transcatheter aortic valve implantation procedure predicted a better short-term outcome and may be useful in identifying patients who are at risk of a less favourable outcome after transcatheter aortic valve implantation.

The sec6/8 (exocyst) complex is implicated in targeting of vesicles for regulated exocytosis in various cell types and is believed to play a role in synaptogenesis and brain development. We show that the subunits sec6 and sec8 are present at significant levels in neurons of adult rat brain, and that immunoreactivity for the two subunits has a differential subcellular distribution. We show that in developing as well as mature neurons sec6 is concentrated at the inside of the presynaptic plasma membrane, while sec8 immunoreactivity shows a diffuse cytoplasmic distribution. Among established, strongly synaptophysin-positive neuronal boutons, sec6 displays highly differential concentrations, indicating a role for the complex independent of the ongoing synaptic-vesicle release activity. Sec6 is transported along neurites on secretogranin II-positive vesicles, while sec6-negative/secretogranin II-positive vesicles stay in the cell body. In PC12 cells, sec6-positive vesicles accumulate at the plasma membrane at sites of cell–cell contact. Neuronal induction of the PC12 cells with nerve growth factor shows that sec8 is not freely soluble, but may probably interact with cytoskeletal elements. The complex may facilitate the targeting of membrane material to presynaptic sites and may possibly shuttle vesicles from the cytoskeletal transport machinery to presynaptic membrane sites. Thus, we suggest that the exocyst complex serves to modulate exocytotic activity, by targeting membrane material to its presynaptic destination.

Objective Transcatheter aortic valve implantation in patients turned down for surgical aortic valve replacement is a high-risk procedure. Severe aortic stenosis is associated with impaired left ventricular longitudinal motion, and myocardial peak systolic velocity is a measure of left ventricular function in these patients. The present study aimed to quantify the acute changes in left ventricular function during the procedure by using myocardial tissue Doppler imaging and transthoracic cardiac output measurements. Design Prospective observational study. Setting Tertiary care university hospital. Participants 40 patients with severe aortic stenosis scheduled for transcatheter aortic valve implantation. Interventions Transesophageal 4-chamber and 2-chamber echocardiograms were performed immediately before and ~15 minutes after valve implantation. Longitudinal myocardial peak systolic velocity was obtained by tissue Doppler imaging from 8 basal segments and averaged. Cardiac output was measured by the lithium dilution method, and systemic vascular resistance index and stroke volume were calculated. Measurements and Main Results Longitudinal myocardial peak systolic velocity improved immediately after valve implantation, from –2.3±0.8 to –3.0±1.1 cm/sec (p

Phosphate activated glutaminase is a key enzyme in glutamate synthesis. Here we have employed a quantitative and high-resolution immunogold procedure to analyse the cellular and subcellular expression of this enzyme in the cerebellar cortex. Three main issues were addressed. First, is phosphate activated glutaminase exclusively or predominantly a mitochondrial enzyme, as biochemical data suggest? Second, to what extent is the mitochondrial content of glutaminase dependent on cell type and transmitter identity? Third, can individual neurons maintain a subcellular segregation of mitochondria with different glutaminase content? An attempt was also made to disclose the intramitochondrial localization of glutaminase, and to correlate the content of this enzyme with that of glutamate and glutamine in the same mitochondria (by use of triple labelling). Antisera to the N- and C-termini of glutaminase revealed strong labelling of the putatively glutamatergic mossy fibre terminals. The vast majority of gold particles (approximately 96%) was associated with the mitochondria. Equally high labelling intensities were found in mitochondria of perikarya and dendrites in the pontine nuclei, a major source of mossy fibres. The level of glutaminase immunoreactivity in parallel and climbing fibres (which like the mossy fibres are thought to use glutamate as transmitter) was only about 20% of that in mossy fibres, and similar to that in non-glutamatergic neurons (Purkinje and Golgi cells). Glial cell mitochondria were devoid of specific glutaminase labelling and revealed a much lower glutamate:glutamine ratio than did the mitochondria of mossy fibres. As to the submitochondrial localization of glutaminase, immunogold particles were often found to be aligned with the cristae, suggesting an association of the enzyme with the inner mitochondrial membrane. However, the existence of a glutaminase pool in the mitochondrial matrix could not be excluded. The outer mitochondrial membrane was unlabelled. The present study provides quantitative evidence for a substantial heterogeneity in the mitochondrial content of glutaminase. This heterogeneity applies not only to neurons with different transmitter signatures, but also to different categories of glutamatergic pathways. In terms of the routes involved, the synthesis of transmitter glutamate may be less uniform than previously expected.

Myocardial dysfunction may occur during weaning from cardiopulmonary bypass (CPB). Epicardial accelerometers have been shown to be useful in continuous monitoring of myocardial ischaemia during beating-heart surgery. We aimed to investigate whether an accelerometer can detect myocardial dysfunction during weaning from CPB.In 23 patients undergoing isolated aortic valve replacement (AVR), a three-axis accelerometer was attached to the left ventricle and 3D velocity was calculated from the signals. Peak early systolic velocity (Vsys) and velocity at aortic valve closure (Vavc) were measured. Measurements were undertaken during normothermia with 50% bypass flow and atrial pacing (90 beats/min) before aortic cross-clamping and after cross-clamp removal. Myocardial dysfunction was defined as VsysVavc, and patients were classified as having normal function or dysfunction. Left ventricular (LV) stroke work via pulmonary artery catheter and systolic velocity by echocardiography were compared between groups and used as reference methods.The accelerometer identified a substantial proportion of patients with myocardial dysfunction during weaning from CPB, 56% of patients compared with 11% before aortic cross-clamping. Patients classified with normal myocardial function during weaning significantly improved their LV stroke work and systolic velocity by echocardiography in response to AVR, whereas those classified with dysfunction did not. Accelerometer classification of normal function predicted an increase in echocardiographic systolic velocity [r = 0.63, regression coefficient 1.98, 95% CI (0.57, 3.40) (P0.01)].The accelerometer detected myocardial dysfunction during weaning from CPB in accordance with measures obtained by echocardiography and pulmonary artery catheter.NCT01926067. https://clinicaltrials.gov/.

High resolution immunogold cytochemistry was used to investigate the subcellular distribution of protein kinase C gamma and delta in Purkinje cells of the rat cerebellum. Postembedding incubation with an antibody raised to a peptide sequence near the C-terminus of protein kinase C gamma resulted in strong labelling along the dendrosomatic plasma membrane. A quantitative analysis indicated that this labelling reflected the existence of two pools of protein kinase C gamma; one membrane associated pool and one cytoplasmic pool located within 50 nm of the plasma membrane. The labelling along the plasma membrane showed a pronounced and abrupt increase when moving from the cell body into the axon initial segment. Gold particles signalling protein kinase C gamma were also enriched in putative Purkinje axon terminals in the dentate nucleus. The only organelle showing a consistent immunolabelling for protein kinase C gamma was the Golgi apparatus where the gold particles were restricted to the trans face. Protein kinase C gamma immunoreactivity also occurred in the Purkinje cell spines, with an enrichment in or near the postsynaptic density. Antibodies to protein kinase C delta produced a very different labelling pattern in the Purkinje cells. Most of the gold particles were associated with rough endoplasmic reticulum, particularly with those cisternae that were located close to the nucleus or in the nuclear indentations. No significant protein kinase C delta immunolabelling was detected at the plasma membrane or in Purkinje cell spines. The present data point to a highly specific compartmentation of the two major protein kinase C isozymes in Purkinje cells and suggest that these isozymes act on different substrates and hence have different regulatory functions within these neurons.