A prospective, multi-center, randomised controlled trial for evaluation of the effectiveness of the Blimp scoring balloon in lesions not crossable with a conventional balloon or microcatheter: the BLIMP study

BACKGROUND

Balloon uncrossable coronary lesions are lesions that cannot be crossed with a conventional balloon. Multiple balloons have been designed to overcome this problem. The Blimp balloon has a very low scoring profile (0.6 mm) with a very high rated burst pressure (30 atmospheres). We aimed to evaluate the efficacy of this balloon compared to customary low-profile balloons.

METHODS

We conducted a multicenter, prospective, randomised, controlled trial in which 126 patients with an uncrossable lesion were randomly (1:1 randomization) assigned to treatment first with the Blimp balloon or low-profile balloon. The primary endpoint was the success of crossing the lesion after initial failure with a microcatheter (group A) or with a conventional balloon (group B).

RESULTS

Overall, the first attempt of Blimp was successful in 29 out of 61 cases (48%) while the LP balloon immediately crossed in 30 out 67 cases (45%; p = 0.761). Using a low-profile balloon in the BLIMP group after failure of the Blimp balloon increased the success to 64% (39 out of 61 cases). Using the Blimp balloon in the low-profile first group after failure of the low-profile balloon increased the success to 60% (40 out of 67 cases). After the placement of a guide catheter extension, the overall successful lesion crossing in the BLIMP group was 80% (49 out of 61 cases) compared to 76% (51 out of 67 cases) in the LP Balloon group (p = 0.327).

CONCLUSIONS

The Blimp balloon catheter showed no superiority to customary low-profile balloons in uncrossable lesions. It can however be complementary in treating uncrossable lesions.

Sex differences in the impact of coronary artery disease on long-term survival after transcatheter aortic valve implantation

Background

It has been suggested that the complexity of coronary artery disease (CAD) is a determinant of worse outcomes after transcatheter aortic valve implantation (TAVI). However, no data is available showing this applies equally to both sexes.

Purpose

Males are usually overrepresented in studies regarding CAD and care should be used when translating these results to the female population. The purpose of this analysis was to compare sex specific clinical outcomes in patients undergoing TAVI with and without coexisting CAD.

Methods

All patients undergoing TAVI at a tertiary referral centre between 2008 and 2020 were included and outcomes up to five years after TAVI were prospectively recorded. Baseline and residual (after revascularization) SYNTAX-scores (SS) were retrospectively calculated to make groups of different CAD complexity.

Results

A total of 605 patients, of whome 284 (46.9%) female patients, underwent TAVI. Five years after TAVI, females and males had similar overall survival (62 vs 59%, p=0.320) and cardiovascular mortality (22% vs 20%, p=0.540), respectively. Females were older (82.7y vs 80.8y, p<0.001), had a higher left ventricular ejection fraction (53.7% vs 49.4%, p<0.001) and higher aortic valve mean gradient (45.7 vs 41.6 mmHg, p=0.002). EuroScore II was comparable between both groups (26.8 vs 27.5, p=0.330). Females had less obstructive CAD (49% vs 64%, p<0.001) and less complex CAD (mean SS: 8.3 vs 12.6, p<0.001), despite reporting similar rates of angina (10% vs 11%, p=0.492). While in males CAD complexity was not predictive of survival (fig 1A) or cardiovascular mortality (fig 2A), females showed worse survival (fig 1B) and cardiovascular mortality (fig 2B) with increasing CAD complexity. This difference seems not to be driven by a lower rate of revascularization since women with CAD received significantly more percutaneous coronary interventions (PCI) (41% vs 24%, p=0.001) and trended towards more complete revascularization (residual SS <8 70% in females vs 52% in males, p=0.054). Background medical therapy with aspirin (70% vs 72%, p=0.710), other antiplatelet agents (61% vs 57%, p=0.390) and statins (71% vs 81%, p=0.065) was not different between both groups. A possible explanation for the similar rates of angina despite less complex CAD in females might be a higher prevalence of underlying microvascular dysfunction, which is also known to be related with an increased rate of cardiovascular events.

Conclusion

We show that in females outcomes after TAVI are significantly influenced by co-existing CAD and its complexity, while in males this is less pronounced. We identified a subgroup of females with a SS >22 that are at particular high risk for fatal cardiovascular events after TAVI. Therefore, awareness for CAD and close follow-up in combination with guideline-directed treatment of complex CAD in females undergoing TAVI is crucial.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research Foundation Flanders

Beta-blocker target dosing and tolerability in a dedicated heart failure clinic in Johannesburg

BACKGROUND

Despite the significant clinical benefits of beta-blockers in heart failure with reduced ejection fraction (HFrEF), prescription for and adherence to these agents is reported to be poor. There are few data on the use and tolerance of beta-blocker therapy in patients with HFrEF in South Africa and it is unknown whether these patients would benefit from further heart rate-lowering therapy.

METHODS

Data from all patients with HFrEF attending the heart failure clinic of Charlotte Maxeke Johannesburg Academic Hospital from January 2000 to December 2014 were retrospectively collected. We first determined the rates of beta-blocker intolerance in this population and then categorised the patients according to their most recent dose of beta-blocker (low, moderate or target dose) in order to identify factors associated with beta-blocker intolerance. Lastly, we used the data to identify patients who would be suitable for further treatment with heart rate-lowering therapy.

RESULTS

Five hundred patients, with a median follow up of 58.7 months, were identified during the study period. Black South Africans constituted the majority (66.4%) and most patients had HFrEF due to hypertension (32.8%). At the last recorded clinic visit at the end of the study period, 489 patients (97.8%) were taking a beta-blocker with 59.8% prescribed a beta-blocker at target dose. Consistent with previous data, bradycardia was the commonest cause for failing to reach target beta-blocker dose. Only 61 (12%) patients were on no (n = 11) or low (n = 50) dose of beta-blocker at final clinic visit. As per current guidelines, only 10.6% (n = 53) of this cohort of patients would qualify for further treatment with heart rate-lowering therapy.

CONCLUSIONS

In a dedicated heart failure clinic in South Africa, beta-blockers were well-tolerated in the treatment of HFrEF. The potential role of specific heart rate-lowering therapy in patients treated adequately with heart failure medication and proper up-titration of beta-blockers is relatively small.

Nursing and midwifery revalidation

This article details the Nursing and Midwifery Council revalidation requirements essential for all registered nurses and midwives in the United Kingdom. Nursing revalidation is effective from April 2016 and is built on the pre-existing post-registration education and practice. Unlike the previous process, revalidation provides a more robust system which is clearly linked to the code and should assist towards the delivery of quality and safe effective care.

Four steps to interpreting arterial blood gases

This article examines acid-base balance and the interpretation of arterial blood gases (ABG). The article begins with a brief revision of related physiology, followed by a description of the primary disorders associated with acid-base imbalance. The normal ranges and the significance of abnormal ABG results are explored. The article concludes by providing an easy to follow four-step guide to ABG interpretation with practice examples presented in the CPD task section.

The principles and practice of interpreting cardiac rhythm strips: a seven-step model

This open learning zone article examines the cardiac cycle and the interpretation of cardiac rhythm strips. The article begins with a brief revision of related physiology followed by a description of normal sinus rhythm and the main cardiac rhythm abnormalities. The article concludes by providing easy to follow steps for use in the interpretation of cardiac rhythm strips with practice examples presented in the continuing professional development (CPD) task section.

HIP12 is a non-proapoptotic member of a gene family including HIP1, an interacting protein with huntingtin

Huntingtin-interacting protein I (HIP1) is a membrane-associated protein that interacts with huntingtin, the protein altered in Huntington disease. HIP1 shows homology to Sla2p, a protein essential for the assembly and function of the cytoskeleton and endocytosis in Saccharomyces cerevisiae. We have determined that the HIP1 gene comprises 32 exons spanning approximately 215 kb of genomic DNA and gives rise to two alternate splice forms termed HIP1-1 and HIP1-2. Additionally, we have identified a novel protein termed HIP12 with significant sequence and biochemical similarities to HIP1 and high sequence similarity to Sla2p. HIP12 differs from HIP1 in its pattern of expression both at the mRNA and protein level. However, HIP1 and HIP12 are both found within the brain and show a similar subcellular distribution pattern. In contrast to HIP1, which is toxic in cell culture, HIP12 does not confer toxicity in the same assay systems. Interestingly, HIP12 does not interact with huntingtin but can interact with HIP1. suggesting a potential interaction in vivo that may influence the function of each respective protein.

Higher brain blood flow at amygdala and lower frontal cortex blood flow in PTSD patients with comorbid cocaine and alcohol abuse compared with normals

Posttraumatic stress disorder (PTSD) patients with histories of cocaine and alcohol abuse (CA-PTSD) were compared with normal volunteers. Positron emission tomography (PET) scans with 15O-butanol were used to compare regional cerebral blood flow (rCBF) between the groups during rest and during an auditory continuous performance task (ACPT). CA-PTSD patients had significantly higher rCBF in right amygdala and left parahippocampal gyrus than normals during the ACPT. Normals had higher rCBF at frontal cortex during the resting scan and during the ACPT. The role of the amygdala in attention and fear conditioning suggests that increased amygdala rCBF may be related to clinical features of PTSD. Cocaine use may be associated with increased amygdala rCBF in PTSD patients. Amygdala and frontal cortex attention system components may be reciprocally related and their relative contributions to processing of neutral stimuli perturbed in CA-PTSD.

Subtype-specific enhancement of NMDA receptor currents by mutant huntingtin

Evidence suggests that NMDA receptor-mediated neurotoxicity plays a role in the selective neurodegeneration underlying Huntington's disease (HD). The gene mutation that causes HD encodes an expanded polyglutamine tract of >35 in huntingtin, a protein of unknown function. Both huntingtin and NMDA receptors interact with cytoskeletal proteins, and, for NMDA receptors, such interactions regulate surface expression and channel activity. To determine whether mutant huntingtin alters NMDA receptor expression or function, we coexpressed mutant or normal huntingtin, containing 138 or 15 glutamine repeats, respectively, with NMDA receptors in a cell line and then assessed receptor channel function by patch-clamp recording and surface expression by western blot analysis. It is interesting that receptors composed of NR1 and NR2B subunits exhibited significantly larger currents when coexpressed with mutant compared with normal huntingtin. Moreover, this effect was selective for NR1/NR2B, as NR1/NR2A showed similar currents when coexpressed with mutant versus normal huntingtin. However, ion channel properties and total surface expression of the NR1 subunit were unchanged in cells cotransfected with NR1/NR2B and mutant huntingtin. Our results suggest that mutant huntingtin may increase numbers of functional NR1/NR2B-type receptors at the cell surface. Because NR1/NR2B is the predominant NMDA receptor subtype expressed in medium spiny neostriatal neurons, our findings may help explain the selective vulnerability of these neurons in HD.

A YAC mouse model for Huntington's disease with full-length mutant huntingtin, cytoplasmic toxicity, and selective striatal neurodegeneration

We have produced yeast artificial chromosome (YAC) transgenic mice expressing normal (YAC18) and mutant (YAC46 and YAC72) huntingtin (htt) in a developmental and tissue-specific manner identical to that observed in Huntington's disease (HD). YAC46 and YAC72 mice show early electrophysiological abnormalities, indicating cytoplasmic dysfunction prior to observed nuclear inclusions or neurodegeneration. By 12 months of age, YAC72 mice have a selective degeneration of medium spiny neurons in the lateral striatum associated with the translocation of N-terminal htt fragments to the nucleus. Neurodegeneration can be present in the absence of macro- or microaggregates, clearly showing that aggregates are not essential to initiation of neuronal death. These mice demonstrate that initial neuronal cytoplasmic toxicity is followed by cleavage of htt, nuclear translocation of htt N-terminal fragments, and selective neurodegeneration.

Life without huntingtin: normal differentiation into functional neurons

Huntington disease (HD) is a neurodegenerative disorder associated with polyglutamine expansion in a recently identified protein, huntingtin. Huntingtin is widely expressed and plays a crucial role in development, because gene-targeted HD-/- mouse embryos die early in embryogenesis. To analyze the function of normal huntingtin, we have generated HD-/- embryonic stem (ES) cells and used an in vitro model of ES cell differentiation to analyze their ability to develop into neuronal cells. Expression analysis of wild-type ES cells revealed that huntingtin is expressed at all stages during ES cell differentiation with high expression in neurons. Expression levels increased with the maturation of differentiating neurons, demonstrating that expression of huntingtin is developmentally regulated in cell culture and resembles the pattern of expression observed in differentiating neurons in the mouse brain. It is interesting that HD-/- ES cells could differentiate into mature postmitotic neurons that expressed functional voltage- and neurotransmitter-gated ion channels. Moreover, both excitatory and inhibitory spontaneous postsynaptic currents were observed, indicating the establishment of functional synapses in the absence of huntingtin. These results demonstrate that huntingtin is not required for the generation of functional neurons with features characteristic of postmitotic neurons in the developing mouse brain.

The influence of huntingtin protein size on nuclear localization and cellular toxicity

Huntington disease is an autosomal dominant neurodegenerative disorder caused by the pathological expansion of a polyglutamine tract. In this study we directly assess the influence of protein size on the formation and subcellular localization of huntingtin aggregates. We have created numerous deletion constructs expressing successively smaller fragments of huntingtin and show that these smaller proteins containing 128 glutamines form both intranuclear and perinuclear aggregates. In contrast, larger NH2-terminal fragments of huntingtin proteins with 128 glutamines form exclusively perinuclear aggregates. These aggregates can form in the absence of endogenous huntingtin. Furthermore, expression of mutant huntingtin results in increased susceptibility to apoptotic stress that is greater with decreasing protein length and increasing polyglutamine size. As both intranuclear and perinuclear aggregates are clearly associated with increased cellular toxicity, this supports an important role for toxic polyglutamine-containing fragments forming aggregates and playing a key role in the pathogenesis of Huntington disease.

Caspase cleavage of gene products associated with triplet expansion disorders generates truncated fragments containing the polyglutamine tract

The neurodegenerative diseases Huntington disease, dentatorubropallidoluysian atrophy, spinocerebellar atrophy type 3, and spinal bulbar muscular atrophy are caused by expansion of a polyglutamine tract within their respective gene products. There is increasing evidence that generation of truncated proteins containing an expanded polyglutamine tract may be a key step in the pathogenesis of these disorders. We now report that, similar to huntingtin, atrophin-1, ataxin-3, and the androgen receptor are cleaved in apoptotic extracts. Furthermore, each of these proteins is cleaved by one or more purified caspases, cysteine proteases involved in apoptotic death. The CAG length does not modulate susceptibility to cleavage of any of the full-length proteins. Our results suggest that by generation of truncated polyglutamine-containing proteins, caspase cleavage may represent a common step in the pathogenesis of each of these neurodegenerative diseases.

Length of huntingtin and its polyglutamine tract influences localization and frequency of intracellular aggregates

It is unclear how polyglutamine expansion is associated with the pathogenesis of Huntington disease (HD). Here, we provide evidence that polyglutamine expansion leads to the formation of large intracellular aggregates in vitro and in vivo. In vitro these huntingtin-containing aggregates disrupt normal cellular architecture and increase in frequency with polyglutamine length. Huntingtin truncated at nucleotide 1955, close to the caspase-3 cleavage site, forms perinuclear aggregates more readily than full-length huntingtin and increases the susceptibility of cells to death following apoptotic stimuli. Further truncation of huntingtin to nucleotide 436 results in both intranuclear and perinuclear aggregates. For a given protein size, increasing polyglutamine length is associated with increased cellular toxicity. Asymptomatic transgenic mice expressing full-length huntingtin with 138 polyglutamines form exclusively perinuclear aggregates in neurons. These data support the hypothesis that proteolytic cleavage of mutant huntingtin leads to the development of aggregates which compromise cell viability, and that their localization is influenced by protein length.

HIP1, a human homologue of S. cerevisiae Sla2p, interacts with membrane-associated huntingtin in the brain

Huntington disease (HD) is associated with the expansion of a polyglutamine tract, greater than 35 repeats, in the HD gene product, huntingtin. Here we describe a novel huntingtin interacting protein, HIP1, which co-localizes with huntingtin and shares sequence homology and biochemical characteristics with Sla2p, a protein essential for function of the cytoskeleton in Saccharomyces cerevisiae. The huntingtin-HIP1 interaction is restricted to the brain and is inversely correlated to the polyglutamine length in huntingtin. This provides the first molecular link between huntingtin and the neuronal cytoskeleton and suggests that, in HD, loss of normal huntingtin-HIP1 interaction may contribute to a defect in membrane-cytoskeletal integrity in the brain.

Human huntingtin derived from YAC transgenes compensates for loss of murine huntingtin by rescue of the embryonic lethal phenotype

Huntington disease (HD) is caused by expansion of a CAG trinucleotide repeat in exon 1 of a novel gene. The HD protein (huntingtin) plays a critical role in early embryonic development since homozygous targeted disruption of the murine HD gene results in embryonic lethality by day 7.5. To rescue this phenotype by transgene based huntingtin expression it is therefore essential to express the protein early enough in development in the appropriate cells. Since YAC based transgenes are known to be regulated in an appropriate temporal and tissue-specific manner, we sought to rescue the embryonic lethality by breeding YAC transgenic mice expressing human huntingtin with mice heterozygous for the targeted disruption. We generated viable offspring homozygous for the disrupted murine HD gene but expressing human huntingtin derived from the YAC. This result clearly shows that YAC transgene based expression of huntingtin occurs prior to 7.5 days gestation. Additionally, we show that human huntingtin expression in YAC transgenic mice follows an identical tissue distribution and subcellular localisation pattern as that of the murine endogenous protein and that expression levels of 2-3 times endogenous can be achieved. This shows that human huntingtin under the influence of its native promoter, despite differences to the murine protein, is functional in a murine background and can compensate for loss of the murine protein. These results show that YAC transgenic approaches are a particularly promising route to producing an animal model for disorders associated with CAG expansion.

Setting up an Nd:YAG laser training course

We report our experience in developing a two-day training course for the Nd:YAG (Neodymium: Yttrium-Aluminium-Garnet) laser and describe the curriculum. This project arose from an attempt to modify an existing course on the CO2 laser for a newly-acquired Nd:YAG laser in such a way as to adequately demonstrate the properties of the latter and to highlight dissimilarities with the CO2 laser. The course, which is taught on a 1:1 student to instructor basis, uses both videotapes and a series of locally developed exercises to appraise the trainee of the potential of this tool. Both inanimate objects and live subjects (anaesthetized rats) are used in the exercises. Examples of the exercises developed and the principles they demonstrate are given, as well as specific problems that were overcome in order to produce a course that adequately covered the subject whilst containing costs at a reasonable level. The need for extensive hands-on use of the laser is emphasised.

Treatment of proximal aortic hypertension after thoracic aortic cross-clamping in dogs. Phlebotomy versus sodium nitroprusside/isoflurane

Thoracic aortic cross-clamping causes proximal aortic hypertension. Theoretically, the method used to treat hypertension can influence spinal cord perfusion pressure and neurologic outcome. Phlebotomy was compared to sodium nitroprusside/isoflurane in terms of ability to treat increased proximal mean aortic pressure (MAPp) after thoracic aortic cross-clamping in dogs. Dogs were assigned randomly to one of three groups depending on the method used to treat hypertension after cross clamping: 1) phlebotomy (n = 10); 2) sodium nitroprusside/isoflurane (n = 11); and 3) control (no treatment) (n = 8). In each dog, anesthesia was maintained with isoflurane in oxygen, 1.4% end-tidal. The thoracic aorta was occluded 2.5 cm distal to the left subclavian artery for 50 min and then was released. Hemodynamics, cerebrospinal fluid pressure (CSFP), and regional blood flows by the radioactive microsphere technique, were measured at 1) baseline; 2) 2 min after aortic cross-clamping; 3) after treatment of proximal aortic hypertension; 4) 5 min after aortic unclamping; and 5) 30 min after resuscitation. At 24 h, a neurologic assessment was performed. Thoracic aortic cross-clamping increased MAPp, decreased distal MAP (MAPd), and reduced lumbar spinal cord perfusion pressure (SCPPl), [SCPPl = MAPd - CSFP], in all three groups. Control of increased MAPp necessitated removal of 36 +/- 9 ml/kg of blood in the phlebotomy group. In the sodium nitroprusside/isoflurane group, sodium nitroprusside (16 micrograms.kg-1.min-1) was infused and end-tidal isoflurane concentration increased to 2.5 +/- 0.7%, restoring MAPp to baseline level.(ABSTRACT TRUNCATED AT 250 WORDS)