Gaze and attention: Mechanisms underlying the therapeutic effect of optokinetic stimulation in spatial neglect

Left smooth pursuit eye movement training in response to large-field visual motion (optokinetic stimulation) has become a promising rehabilitation method in left spatial inattention or neglect. The mechanisms underlying the therapeutic effect, however, remain unknown. During optokinetic stimulation, there is an error in visual localisation ahead of the line of sight. This could indicate a change in the brain's estimate of one's own direction of gaze. We hypothesized that optokinetic stimulation changes the brain's estimate of gaze. Because this estimate is critical for coding the locus of attention in the visual space relative to the body and across sensory modalities, its change might underlie the change in spatial attention. Here, we report that in healthy participants optokinetic stimulation causes not only a directional bias in the proprioceptive signal from the extraocular muscles, but also a corresponding shift of the locus of attention. Both changes outlasted the period of stimulation. This result forms a step in investigating a causal link between the adaptation in the sensorimotor gaze signals and the recovery in spatial neglect.

No short-term treatment effect of prism adaptation for spatial neglect: An inclusive meta-analysis

Despite 25 years of research on the topic, there is still no consensus on whether prism adaptation is an effective therapy for visuospatial neglect. We have addressed this question through a meta-analysis of the most well-controlled studies on the topic. Our main meta-analytic model included studies with a placebo/sham/treatment-as-usual control group from which data from right hemisphere stroke patients and left-sided neglect could be aggregated. The short-term treatment effects on the two commonly used standard tests for neglect, the conventional Behavioural Inattention Test (BIT-C) and cancellation test scores were combined into one random effect model justified by the fact that 89% of the BIT-C score is determined by cancellation tasks. With this approach, we were able to obtain a larger and more homogeneous dataset than previous meta-analyses: sixteen studies including 430 patients. No evidence for beneficial effects of prism adaptation was found. The secondary meta-analysis including data from the Catherine Bergego Scale, a functional measure of activities of daily living, also found no evidence for the therapeutic effects of prism adaptation, although half as many studies were available for this analysis. The results were consistent after the removal of influential outliers, after studies with high risk-of-bias were excluded, and when an alternative measure of effect size was considered. These results do not support the routine use of prism adaptation as a therapy for spatial neglect.

Proprioceptive contribution to oculomotor control in humans

Stretch receptors in the extraocular muscles (EOMs) inform the central nervous system about the rotation of one's own eyes in the orbits. Whereas fine control of the skeletal muscles hinges critically on proprioceptive feedback, the role of proprioception in oculomotor control remains unclear. Human behavioural studies provide evidence for EOM proprioception in oculomotor control, however, behavioural and electrophysiological studies in the macaque do not. Unlike macaques, humans possess numerous muscle spindles in their EOMs. To find out whether the human oculomotor nuclei respond to proprioceptive feedback we used functional magnetic resonance imaging (fMRI). With their eyes closed, participants placed their right index finger on the eyelid at the outer corner of the right eye. When prompted by a sound, they pushed the eyeball gently and briefly towards the nose. Control conditions separated out motor and tactile task components. The stretch of the right lateral rectus muscle was associated with activation of the left oculomotor nucleus and subthreshold activation of the left abducens nucleus. Because these nuclei control the horizontal movements of the left eye, we hypothesized that proprioceptive stimulation of the right EOM triggered left eye movement. To test this, we followed up with an eye-tracking experiment in complete darkness using the same behavioural task as in the fMRI study. The left eye moved actively in the direction of the passive displacement of the right eye, albeit with a smaller amplitude. Eye tracking corroborated neuroimaging findings to suggest a proprioceptive contribution to ocular alignment.

On line bisection: Validity and reliability of online measures of pseudoneglect

This study assessed pseudoneglect using line bisection and perceptual landmark tasks in two matched online sessions. Line bisection bias was characterized by the traditional measure of Directional Bisection Error (DBE), and by Endpoint Weightings Bias (EWB), derived from an "endpoint weightings" analysis, made possible by the independent manipulation of left and right endpoints. EWB is proposed to index the relative attentional allocation to the two ends of the line. The expected leftward bias (pseudoneglect) was found, with larger effect sizes for EWB (d = -0.34 in both sessions) than for DBE (-0.22 in Session 1 and -0.14 in Session 2). Although EWB was slightly less reliable than DBE, it was more sensitive to pseudoneglect, and the endpoint weightings method has further advantages, including the option of an additional measure of non-lateralized attention. A substantial proportion of participants had difficulty following the instructions for the landmark task, which highlights the need for clear instructions and performance checks for this task. This study shows that line bisection can be used to measure pseudoneglect online, and provides grounds to suggest that the task should routinely include the independent manipulation of left and right endpoints, so that an endpoint weightings analysis can be performed.

Peripheral reaching in Alzheimer's disease and mild cognitive impairment

Recent evidence has implicated areas within the posterior parietal cortex (PPC) as among the first to show pathophysiological changes in Alzheimer's disease (AD). Focal brain damage to the PPC can cause optic ataxia, a specific deficit in reaching to peripheral targets. The present study describes a novel investigation of peripheral reaching ability in AD and mild cognitive impairment (MCI), to assess whether this deficit is common among these patient groups. Individuals with a diagnosis of mild-to-moderate AD, or MCI, and healthy older adult controls were required to reach to targets presented in central vision or in peripheral vision using two reaching tasks; one in the lateral plane and another presented in radial depth. Pre-registered case–control comparisons identified 1/10 MCI and 3/17 AD patients with significant peripheral reaching deficits at the individual level, but group-level comparisons did not find significantly higher peripheral reaching error in either AD or MCI by comparison to controls. Exploratory analyses showed significantly increased reach duration in both AD and MCI groups relative to controls, accounted for by an extended Deceleration Time of the reach movement. These findings suggest that peripheral reaching deficits like those observed in optic ataxia are not a common feature of AD. However, we show that cognitive decline is associated with a generalised slowing of movement which may indicate a visuomotor deficit in reach planning or online guidance.

Attention attracts action in healthy participants: An insight into optic ataxia?

Patients with optic ataxia following lesions to superior parts of the posterior parietal cortex make large errors when reaching to targets in the peripheral visual field. These errors are characterised by a contraction, or attraction, towards the point of fixation. These patients also have a reduced ability to allocate visual attention away from the point of fixation, but it is unclear whether the core symptom of misreaching is related to these attentional problems. In neurologically-intact adults, we tested the effect of an attention-demanding dual-task performed at fixation upon visually-guided reaching to peripheral targets. The dual task was associated with delayed movement initiation, and a shortened deceleration phase of movement suggesting a reduced ability to benefit from online control. It also induced a small but consistent shift of reaching endpoints towards the side of fixation. Our experimental restriction of visual attention thus impaired both the programming and control of reaching, and induced a spatial pattern of errors that was qualitatively reminiscent of optic ataxia, albeit much less severe. These findings are consistent with a close functional link between attention and action in the healthy brain, and suggest that attentional disturbances could be a core component of optic ataxia following parietal lesions.

Assessment of visually guided reaching in prodromal Alzheimer's disease: a cross-sectional study protocol

INTRODUCTION

Recent evidence has implicated the precuneus of the medial parietal lobe as one of the first brain areas to show pathological changes in Alzheimer's disease (AD). Damage to the precuneus through focal brain injury is associated with impaired visually guided reaching, particularly for objects in peripheral vision. This raises the hypothesis that peripheral misreaching may be detectable in patients with prodromal AD. The aim of this study is to assess the frequency and severity of peripheral misreaching in patients with mild cognitive impairment (MCI) and AD.

METHODS AND ANALYSIS

Patients presenting with amnestic MCI, mild-to-moderate AD and healthy older-adult controls will be tested (target N=24 per group). Peripheral misreaching will be assessed using two set-ups: a tablet-based task of lateral reaching and motion-tracked radial reaching (in depth). There are two versions of each task, one where participants can look directly at targets (free reaching), another wheren they must maintain central fixation (peripheral reaching). All tasks will be conducted first on their dominant, and then their non-dominant side. For each combination of task and side, a Peripheral Misreaching Index (PMI) will be calculated as the increase in absolute reaching error between free and peripheral reaching. Each patient will be classified as showing peripheral misreaching if their PMI is significantly abnormal, by comparison to control performance, on either side of space. We will then test whether the frequency of peripheral misreaching exceeds the chance level in each patient group and compare the overall severity of misreaching between groups.

ETHICS AND DISSEMINATION

Ethical approval was provided by the National Health Service (NHS) East of England, Cambridge Central Research Ethics Committee (REC 19/EE/0170). The results of this study will be published in a peer-reviewed journal and presented at academic conferences.

Estimation of Elastic Recovery, Work of Decompression and Young's Modulus Using a Rotary Tablet Press

Capping and lamination occur when the bonds within a tablet cannot withstand the elastic recovery during decompression. To estimate tablet recovery, it is necessary to subtract the machine recovery from the total recovery during decompression. A direct relationship between the force and machine deformation is applied in a novel fashion to calculate in-die tablet recovery on a Manesty Betapress and to estimate the Young's modulus, E, of various solids from the recovery data. The E values of about twenty-five pharmaceutical solids were found to be in reasonable agreement with literature values. This procedure allows in-process analysis of tablet recovery and gives E without the use of specialized equipment.

Current outcome of heart transplantation: a 10-year single centre perspective and review

BACKGROUND

Heart transplantation (HTx), the gold standard therapy for advanced heart failure, is limited by donor availability; alternative therapies are now becoming available.

AIM

We examined the outcome of HTx with current immunosuppressive and adjunctive therapy.

DESIGN AND METHODS

We analysed the outcome of 399 consecutive patients who underwent transplantation at our centre (1995-2007). Prior to HTx 23% (98) required inotropic support, 8.5% (34) an intra-aortic balloon pump and 11% (43) a ventricular assist device.

RESULTS

Actuarial patient survival was 86% at 30 days, 79% at 1 year and 62% at 10 years. Survival was similar regardless of the heart failure severity, P=0.22. The cumulative incidence of allograft vasculopathy, Costanzo grade≥2, was 7% at 5 years and 23% by 10 years with an 11% cumulative probability of requiring a percutaneous coronary intervention by 10 years. Allograft function was preserved with a mean±SD left ventricular ejection fraction of 73±7% at 1 year and 74±8% at 10 years. The cumulative incidence of malignancy by 10 years was 27% (skin malignancy 13% and post transplant lymphoproliferative diseases 10%). The cumulative incidence of developing chronic kidney disease (CKD) with an estimated glomerular filtration rate≤45 ml/min/1.73 m2 was 42% at 1 year, 62% at 5 years and 72% at 10 years and of requiring long-term renal replacement therapy was 10.6% at 10 years.

CONCLUSION

HTx provided good medium-term survival for patients with advanced heart failure, independent of its severity. The incidence of allograft vasculopathy was lower than reported previously but malignancy and CKD remain cause for concern.

Heat shock protein 27 is associated with freedom from graft vasculopathy after human cardiac transplantation

Experimental studies have suggested that protective genes protect allografts from cardiac allograft vasculopathy (CAV), the major complication after cardiac transplantation. Here we have sought to confirm this hypothesis using long-term heart transplant recipients. Twenty-two patients that were 9 years or older after transplant were investigated; 11 of these were without angiographic evidence of CAV; 11 had developed early CAV at 1 to 3 years after transplant. To identify proteins that may act as protectors from CAV, a global proteomic approach was used comparing cardiac biopsies from 12 patients taken within the first 2 weeks after transplant and those taken after 9 years from the same patient. Proteins were separated by 2-D gel-electrophoresis, detected by silver staining, and analyzed using Progenesis software. A particular protein spot was found in 4/6 biopsies from patients without CAV, but absent from 5/6 biopsies from those with CAV (P=0.24); however, quantitative analysis of spot intensity showed a significant difference (0.061+/-0.05 versus 0.003+/-0.01, P=0.04). This spot was identified by mass spectrometry and a combination of techniques as a diphosphorylated form of HSP27. Immunohistochemistry of further biopsies not only validated that HSP27 was more abundantly expressed on biopsies without CAV but also showed it to be localized to blood vessels. In contrast, vessels from patients with CAV did not express HSP27 (P=0.028x10(-4)). Immunohistochemistry of 12 further early biopsies and nontransplanted heart showed HSP27 to be present in normal blood vessels. These findings suggest that expression of a specific diphosphorylated form of HSP27 is associated with healthy blood vessels; it appears to be lost from vessels of patients with graft vasculopathy.

Efficacy and safety of fluvastatin therapy for hypercholesterolemia after heart transplantation

BACKGROUND

Hypercholesterolemia is frequent after heart transplantation. Statins can reduce cholesterol levels but their use in heart transplant patients is complicated by pharmacokinetic interactions with cyclosporin and the risk of serious adverse effects including rhabdomyolysis. Fluvastatin has been used safely to treat hypercholesterolemia in renal transplant patients but there are few data relating to its use after heart transplantation. Therefore, we conducted a randomised blinded placebo controlled trial.

METHODS AND RESULTS

Seventy-nine patients, 3 months to 12 years after heart transplantation with a low density lipoprotein (LDL) cholesterol between 3.5 and 8.0 mmol/l were randomly assigned, in a 2:1 ratio, to receive either fluvastatin 40 mg od (n=52) or matching placebo (n=27). Changes in total cholesterol (TC) in the fluvastatin and placebo groups were -17.0% and +4.5%, respectively, (p<0.001); the corresponding changes in LDL were -20.5% and +4.8% (P<0.001) and in triglycerides -14.5% and +7.1% (p=0.012) at the end of the 1-year study period. Withdrawals were more frequent in the fluvastatin group (23% vs. 11% p=0.24). Two deaths occurred during the study (the rate expected from International Society of Heart Lung Transplantation registry) and appeared to be unrelated to the study medication. There were no episodes of rhabdomyolysis or other serious drug-related side effects.

CONCLUSIONS

Fluvastatin (40 mg/day) was both an effective and a safe treatment for hypercholesterolemia in patients who had undergone heart transplantation more than 3 months previously.

Determinants of outcome after heterotopic heart transplantation

BACKGROUND

Donor availability is currently the major factor limiting the use of heart transplantation as a treatment for severe heart failure. Heterotopic heart transplantation may address this issue by allowing the use of smaller donor organs, which otherwise may not be used.

METHODS

We analyzed the outcome of 42 consecutive, adult heterotopic transplantations performed between 1993 and 1999 at our center and compared them with the 303 consecutive orthotopic transplants performed in adult patients during the same period.

METHODS

Univariate analysis showed a relative risk for death of 1.8 at 1 year after transplantation for the heterotopic group compared with the orthotopic transplantation group (p = 0.04). Multiple regression analysis using a proportional hazards model showed that donor-recipient size-mismatch, i.e., donor body surface area < or =75% of recipient body surface area (p = 0.0001), donor age (p = 0.0001), and use of a female donor (p = 0.04) were significant risk factors but heterotopic transplantation per se was not. A Kaplan-Meier survival analysis of heterotopic vs orthotopic transplantation showed that 30-day survival was 76% vs 87%. By 1 year, this was 59% vs 74%. At 3 years, the comparison was 56% vs 69%. Repeating this analysis after sub-dividing the heterotopic group into those size-matched vs size-mismatched, the 1-year survival was 81% vs 45%, respectively (p = 0.02).

CONCLUSIONS

Heterotopic transplantation using a size-matched graft resulted in similar survival to that seen after orthotopic transplantation during the same period. Heterotopic transplantation with an undersized graft resulted in significantly decreased survival.

Circulating C-type natriuretic peptide is increased in orthotopic cardiac transplant recipients and associated with cardiac allograft vasculopathy

C-type natriuretic peptide (CNP) is a potent, endothelial-derived relaxant and growth-inhibitory factor. Accelerated vascular disease is an important cause of morbidity in cardiac transplant recipients, and endothelial dysfunction is now well recognized in patients with cardiovascular disease. CNP has not previously been investigated following cardiac transplantation. We therefore studied plasma levels of immunoreactive CNP in patients early and late after heart transplantation, compared with levels in healthy subjects. We measured CNP in extracted human plasma using an antibody against human CNP-(1-22). CNP levels were significantly elevated in 13 cardiac recipients 2 weeks post-transplant [2.64+/-0.26 pmol/l (mean+/-S.E.M.)] compared with those in the normal healthy subjects (0.62+/-0.04 pmol/l; n=20, P<0.001). Plasma levels of CNP were also significantly elevated in a second group of established cardiac transplant recipients (1.15+/-0.07 pmol/l; n=46) studied 1-13 years post-transplant when compared with the healthy subjects (P<0.001). In the group studied later after transplantation, CNP levels were significantly associated with systolic blood pressure (P<0.05) and were higher in patients with angiographic post-transplant coronary artery disease (P=0.032). In conclusion, these findings clearly demonstrate that CNP is elevated soon after cardiac transplantation and remains raised in patients even several years post-transplant. CNP may be important as a circulating or local hormone involved in vascular contractile function and in the pathophysiology of cardiac allograft vasculopathy following heart transplantation.

Long-term results after aortic valve replacement in patients with congestive heart failure. Homografts vs prosthetic valves

OBJECTIVES

The aim of this study was to assess the influence of valve substitute (homograft vs prosthetic valve) on the long-term survival and late valve-related complication rates following aortic valve replacement in patients with aortic valve disease and congestive heart failure.

BACKGROUND

The effect of choice of valve substitute on outcome after aortic valve replacement in patients with pre-operative heart failure is unknown. The superior haemodynamic profile of homografts may be of particular benefit.

METHODS

We retrospectively analysed pre-operative, operative and follow-up data on 518 adults in functional classes III and IV, who, over the 25 years 1969-1993, had their initial aortic valve replacement at Harefield hospital. Follow-up conducted during 1996 to April 1997 and totalling 4439 patient-years was 96.1% complete. Using multivariate analysis, independent risk factors for different complications and mortality were defined.

RESULTS

Overall 5-, 10- and 20-year survival was 80+/-2%, 62+/-2% and 30+/-3%, respectively, with no significant difference between valve types. However, homografts (n=381) independently reduced the rate of serious complications and cardiac death, whereas mechanical valves were an independent adverse risk factor for late mortality. The rates of anticoagulant-related bleeding and thromboembolism were increased by mechanical valves, whereas primary tissue failure was the main complication of homografts.

CONCLUSIONS

Long-term outcome of homograft aortic valve replacement in patients with congestive heart failure is acceptable, with a reduced rate of serious complications and cardiac death. Further improvements would be expected if the rate of primary tissue failure could be reduced.

Using three-dimensional ultrasound to detect craniosynostosis in a fetus with Pfeiffer syndrome

A case of fetal Pfeiffer's syndrome is presented, showing the contribution of three dimensional (3D) sonography in the diagnosis of craniosynostosis--a major feature of this syndrome.

Stabilisation of medically refractory ventricular arrhythmia by intra-aortic balloon counterpulsation

OBJECTIVE

To review the efficacy of intra-aortic balloon counterpulsation (IABCP) in medically refractory ventricular arrhythmia.

DESIGN

Retrospective analysis of the outcome of patients with ventricular arrhythmia treated with IABCP after transfer between 1992 and 1997.

SETTING

Tertiary cardiac referral centre.

PATIENTS

21 patients (mean age 58 years) who underwent IABCP for control of ventricular arrhythmia. All had significant left ventricular impairment (mean ejection fraction 28.6%); 18 had coronary artery disease.

RESULTS

Before IABCP, 10 patients had incessant monomorphic ventricular tachycardia and 11 had paroxysmal ventricular tachycardia and/or ventricular fibrillation (VT/VF). IABCP resulted in suppression of ventricular arrhythmia in 18 patients, of whom 13 were weaned from IABCP. After stabilisation of ventricular arrhythmia, 10 patients were maintained on medical treatment alone and one underwent endocardial resection. IABCP was maintained until cardiac transplantation in five patients. One patient had a fatal arrest before discharge and one died from progressive heart failure. IABCP failed to control ventricular arrhythmia in three patients and was subsequently discontinued. A cardiac assist device was employed in one of these until cardiac transplantation; the other two were eventually stabilised on medical treatment. Nineteen patients were discharged from hospital. Overall survival was 95% at mean follow up of 25.7 months.

CONCLUSIONS

IABCP can be an effective means of controlling refractory ventricular arrhythmia, allowing time for the institution of more definitive treatment.

Fah1p, a Saccharomyces cerevisiae cytochrome b5 fusion protein, and its Arabidopsis thaliana homolog that lacks the cytochrome b5 domain both function in the alpha-hydroxylation of sphingolipid-associated very long chain fatty acids

A search of the Saccharomyces cerevisiae genome data base for cytochrome b5-like sequences identified a 1.152-kilobase pair open reading frame, located on chromosome XIII at locus YMR272C (FAH1). That gene encodes a putative 384-amino acid protein with an amino-terminal cytochrome b5 domain. The b5 core domain shows a 52% identity and 70% similarity to that of the yeast microsomal cytochrome b5 and a 35% identity and 54% similarity to the b5 core domain of OLE1, the S. cerevisiae Delta-9 fatty acid desaturase. Expression of the S. cerevisiae FAH1 cytochrome b5 domain in Escherichia coli produces a soluble protein that exhibits the typical oxidized versus reduced differential absorbance spectra of cytochrome b5. Sequence analysis of Fah1p reveals other similarities to Ole1p. Both proteins are predicted to have two hydrophobic domains, each capable of spanning the membrane twice, and both have the HX(2-3)(XH)H motifs that are characteristic of membrane-bound fatty acid desaturases. These similarities to Ole1p suggested that Fah1p played a role in the biosynthesis or modification of fatty acids. Disruption of the FAH1 gene in S. cerevisiae did not give any visible phenotype, and there was no observable difference in content or distribution of the most abundant long chain saturated and unsaturated 14-18-carbon fatty acid species. Northern blot analysis, however, showed that this gene is expressed at much lower levels ( approximately 150-fold) than the OLE1 gene, suggesting that it might act on a smaller subset of fatty acids. Analysis of sphingolipid-derived very long chain fatty acids revealed an approximately 40-fold reduction of alpha-HO 26:0 and a complementary increase in 26:0 in the gene-disrupted fah1Delta strain. GAL1 expression of the S. cerevisiae FAH1 genes in the fah1Delta strain restores alpha-HO 26:0 fatty acids to wild type levels. Also identified are a number of homologs to this gene in other species. Expression of an Arabidopsis thaliana FAH1 gene, which does not contain the cytochrome b5 domain, in the fah1Delta strain produced an approximately 25-fold increase in alpha-HO 26:0 and reduced the levels of its 26-carbon precursor, suggesting that it functions in very long chain fatty acid hydroxylation using an alternate electron transfer mechanism.

A novel cytochrome b5-like domain is linked to the carboxyl terminus of the Saccharomyces cerevisiae delta-9 fatty acid desaturase

Cytochrome b5 is an amphipathic mobile membrane protein that is predominantly located at the endoplasmic reticulum surface. It is an essential component of a number of membrane-bound redox systems. In animal and fungal cells cytochrome b5 is thought to be an electron donor for sterol modifying enzymes and fatty acid desaturases. Disruption of the Saccharomyces cytochrome b5 gene, however, yielded cells that had no nutritional requirement for either sterols or unsaturated fatty acids. Expression of sterol and fatty acid-modifying genes was increased in the cytochrome b5-disrupted cells, however, suggesting that cytochrome b5 may play some nonessential role in these functions. Unsaturated fatty acids in yeast are formed by Ole1p, an oxygen-dependent delta-9 fatty acid desaturase that is an intrinsic endoplasmic reticulum membrane protein. Although the yeast delta-9 fatty acid desaturase does not appear to require cytochrome b5, introduction of the rat liver stearoyl-CoA desaturase gene into an ole1-disrupted, cytochrome b5-disrupted yeast strain revealed that this enzyme specifically requires cytochrome b5 to function. Comparison of the coding sequences of the yeast and rat desaturase genes showed that the yeast protein contains a 113-amino acid carboxyl-terminal extension not found in the rat enzyme. That extension has regions of strong homology to cytochrome b5, particularly in the heme binding and electron transfer motifs. Truncation or disruption of the desaturase cytochrome b5-like domain in cells that contain the wild type diffusible b5 produced unsaturated fatty acid auxotrophy, suggesting that the cytochrome b5-like domain of Ole1p plays an essential role in the desaturase reaction.

Late endothelial function of free and pedicled internal mammary artery grafts

The internal mammary artery has greater long-term patency than the saphenous vein when used for coronary bypass grafting. Therefore, bilateral use of the internal mammary artery for grafting with the right internal mammary artery used as a "free" graft may result in improved graft survival. The study objectives were to compare the endothelial-dependent and -independent vasodilatory response in free and pedicled internal mammary artery grafts in patients who had previously undergone coronary surgery. Free (group 1, n = 8) and pedicled (group 2, n = 7) internal mammary artery grafts were studied by comparing the response to selective infusion of the endothelial-dependent vasodilator substance P (1.4 up to 22.4 pmol/min in doubling dose increments) followed by isosorbide dinitrate (2 mg over 2 minutes), in patients undergoing coronary angiography, 1 month to 6 years after coronary surgery. Maximal dilatory response to substance P was 8.7% +/- 1.8% in pedicled grafts compared with 8.8% +/- 2.3% in free grafts (p = not significant), with the dose response for both groups being similar. Infusion of isosorbide dinitrate produced only minimal further dilatation in both groups. No significant difference was found in endothelium-dependent and -independent vasodilatory response between free and pedicled internal mammary artery grafts, suggesting that the use of the free right internal mammary artery and other arterial grafts may enhance graft survival.

Direct relationship between ischaemic burden and myocardial release of products of lipid peroxidation in patients undergoing percutaneous transluminal coronary angioplasty

BACKGROUND

Recent studies have shown that free radical activity is increased in humans during percutaneous transluminal coronary angioplasty. These studies, however, have failed to localize the site of free radical activity or to demonstrate a relationship between ischaemic burden and free radical production.

METHODS

The relationship between ischaemic burden and subsequent lipid peroxidation was studied during 16 inflations in eight patients undergoing angioplasty to anterior descending artery lesions. Two inflations 15 min apart were studied in each patient, one using a conventional (occlusive) balloon and one using the ACS Rx 'perfusion' balloon. The severity of the ischaemic insult associated with each inflation was assessed by contrast ventriculography, change in left ventricular end-diastolic pressure and myocardial lactate release 30 s after balloon deflation. Plasma levels of lipid peroxidation products were assessed by analysis of thiobarbituric-acid-reactive substances.

RESULTS

A direct relationship was observed between the ischaemic burden and the myocardial release of lipid peroxidation products over the first 4 min after balloon deflation (F = 5.6; P < 0.006). In each patient, one of the inflations was associated with a greater degree of ischaemia. Left ventricular ejection fraction was lower (P < 0.001) and left ventricular end-diastolic pressure was higher (P < 0.002) during the 'ischaemic' inflations. Myocardial release of lipid peroxidation products was significantly higher after the 'ischaemic' balloon inflation (F = 7.65; P < 0.009).

CONCLUSION

Brief periods of human myocardial ischaemia result in myocardial release of lipid peroxidation products in direct proportion to the severity of the preceding ischaemic insult.

A new method of estimating volume during powder compaction and the work of compaction on a rotary tablet press from measurements of applied vertical force

The volume per unit mass of a powder bed, V', during compaction on a rotary tablet press has been expressed as a function of pressure, P using a modification of Kawakita's equation: V = (V'o-V')P'/(P+P') + V', where V'o, V' and P' constitute a set of unique values for a given powder or powder mix under specified tableting conditions. The volume, V, is determined from the machine deformation constant which is the relationship between applied vertical force and the deformation of the tablet press and the punches. An iterative method is described which allows the determination of V'o, V' and P' from the slope and intercept of V vs 1/(P+P') where all values are evaluated at peak pressure. By substituting these values into the equation, the volume of a given powder bed during compaction up to peak pressure can be accurately predicted from the pressure vs time curve. This method of estimating volume and hence punch displacement, is much simpler than an earlier analytical method which was derived from direct measurements of punch displacement under running conditions. Since volume is an explicit function of pressure, the work of compaction is also a function of pressure. Estimates of the work of compaction are in good agreement with values calculated using our previous method. Values of V'o, V' and P' are reported for 35 pharmaceutical materials and could be incorporated into a database library of drugs and tableting excipients. This database could then be used for the quality control of incoming raw materials (batch to batch assessment) and for the comparison of materials from alternative sources.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary endothelial function in cardiac transplant recipients with accelerated coronary disease

BACKGROUND

Previous studies with the endothelium-dependent vasodilator substance P have shown a preserved vasodilator response in cardiac transplant recipients with angiographically normal coronary arteries. Although endothelial dysfunction is known to occur in cardiac transplant recipients with accelerated coronary disease, the degree to which the endothelium is affected is not known precisely. The aim of the present study was to examine endothelial function in accelerated coronary disease following cardiac transplantation.

METHODS

Thirteen cardiac transplant recipients with epicardial coronary disease underwent substance P infusion. The response to incremental doses of substance P was measured in smooth segments of affected coronary arteries. Substance P was infused over 2 min with a starting dose of 1.4 pmol/min and a maximum of 22.4 pmol/min, reached by doubling the dose in steps, followed by an infusion of 2 mg isosorbide dinitrate over 2 min.

RESULTS

Substance P caused less vasodilation at lower concentrations, with a significantly higher dose required to achieve half maximal dilation compared with cardiac transplant recipients with no coronary disease. The mean maximal dilatation achieved with substance P was 22.98 +/- 4.62% compared to 21.95 +/- 4.9% with isosorbide dinitrate; the latter value was not significantly different from the maximal dilation achieved in cardiac transplant recipients without coronary disease.

CONCLUSIONS

In cardiac transplant recipients with accelerated coronary disease the functional vasodilatory ability of the coronary endothelium is impaired in segments of apparently unaffected epicardial arteries, which may lead to an increase in the resting vasoconstrictor tone and have important functional and therapeutic implications.

Relationship between myocardial collagen and echo amplitude in non-fibrotic hearts

The aim of the study was to investigate the relationship between myocardial collagen and regional echo amplitude in humans with non-fibrotic myocardium. The ratio of myocardial collagen to total myocardial protein was determined as the hydroxyproline/leucine ratio in endomyocardial biopsies obtained from the right ventricular side of the interventricular septum in orthotopically transplanted hearts. Regional echo amplitude was measured in the interventricular septum. Patients were studied prospectively. Twenty-five patients (five female, 20 male) who had undergone orthotopic cardiac transplantation were studied 355 to 2939 days (1009 +/- 718, mean +/- SD) post-transplantation at the time of annual cardiac catheterization and endomyocardial biopsy. Patient ages varied from 22 to 62 years (46 +/- 11). Donor ages were 14 to 47 years (25 +/- 8) and the ischaemic time, 90 to 245 min (151 +/- 42). Cardiac transplantation was performed for end-stage cardiac failure in all patients. The aetiology of cardiac failure was valvular heart disease in three, dilated cardiomyopathy in eight and ischaemic heart disease in the remainder. Echo amplitude studies were performed within 24 h of endomyocardial biopsy. All but one patient were on an immunosuppressive regime consisting of cyclosporine A and azathioprine with additional steroids in three. The remaining patient, who was the longest surviving patient in the study group, had never been treated with cyclosporine. This patient was maintained on steroids and azathioprine alone. No patient had clinical or histological evidence for acute cardiac rejection and all were clinically well. Five patients had angiographic evidence of coronary artery disease. All subject studies were performed at Harefield Hospital.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary angioplasty in cardiac transplant recipients

Accelerated coronary artery disease following cardiac transplantation remains an important obstacle to long-term survival and the correct management strategy remains unclear. This observational, prospective study was designed to examine the feasibility of using percutaneous transluminal coronary angioplasty (PTCA) in the treatment of post-transplant coronary disease. Thirteen consecutive patients were selected from the total population of 276 transplant recipients who underwent routine coronary angiography between 1987 and 1990. Selection of patients was on angiographic criteria alone and PTCA was performed to all accessible stenoses with more than 80% luminal narrowing. PTCA was performed using standard angioplasty equipment and procedure as considered appropriate for the individual lesion. A successful PTCA was defined as more than 30% reduction in luminal narrowing and a residual narrowing of less than 50%. Restenosis was defined as a loss of 50% or more of the gain achieved at the time of successful PTCA or more than a 30% increase in narrowing at the site of stenosis. A total of 31 lesions were dilated in this group and a successful result was achieved in 29 of these (93%) and in 12 of the 13 patients. The one patient with failed PTCA underwent later successful coronary artery bypass grafting to complete revascularization. Four of the 13 patients have had two angioplasty procedures, two for restenosis and two for disease progression in other sites. One patient died 15 months after the initial PTCA and the remaining 12 were asymptomatic with good exercise tolerance and ventricular function at a mean of 19 months (range 1-39 months) following first PTCA.(ABSTRACT TRUNCATED AT 250 WORDS)

Doppler examination of superior vena caval flow for the detection of acute cardiac rejection

BACKGROUND

Doppler echocardiographic studies have previously documented abnormalities of mitral flow during acute rejection similar to those seen in patients with "restrictive" physiology. As central venous flow is known to be abnormal in such patients, it was proposed that examination of superior vena caval flow with Doppler echocardiography might be useful for the detection of acute cardiac rejection.

METHODS AND RESULTS

Thirty orthotopic cardiac transplant patients, 15 of whom had acute cardiac rejection diagnosed by endomyocardial biopsy, were studied within 36 hours of biopsy. Superior vena caval Doppler flow velocities as well as mitral and tricuspid flow velocities were recorded using a Hewlett-Packard Sonos 500/1000 echocardiograph system. Examinations were performed blinded to the biopsy result. Mitral and tricuspid peak early flow velocities in the nonrejector group were similar to those seen in normal subjects (mitral, 70 +/- 5 cm/sec; tricuspid midexpiratory apnea, 50 +/- 11 cm/sec). Superior vena caval flow was abnormal with 13 of 15 patients demonstrating a biphasic pattern of forward flow with dominant diastolic flow. In the 15 patients with acute cardiac rejection, both mitral and tricuspid flow velocities developed a "restrictive"-type pattern with increased peak early flow velocities (mitral, 89 +/- 24 cm/sec; tricuspid midexpiratory apnea, 63 +/- 19 cm/sec; p < or = 0.05 versus nonrejectors) and decreased mitral early flow-velocity deceleration times (rejectors, 97 +/- 26 msec; nonrejectors, 144 +/- 41 msec; p < or = 0.05). The pattern of superior vena caval flow became markedly abnormal with a virtually complete loss of forward systolic flow (rejectors, 4.4 +/- 6.6 cm/sec; nonrejectors, 26.1 +/- 8.8 cm/sec at midexpiratory apnea; p < or = 0.0001). In 10 of 15 patients, systolic forward flow was absent. If acute rejection was defined as forward systolic flow < or = 17 cm/sec, then sensitivity was 100%, specificity was 80%, and predictive accuracy was 90%.

CONCLUSIONS

During acute cardiac rejection, forward systolic superior vena caval flow is markedly diminished compared with nonrejectors. This is accompanied by other Doppler echocardiographic features consistent with the development of "restrictive" physiology. It is postulated that the loss of forward systolic flow in the superior vena cava is due to diminished long-axis shortening of the right ventricle associated with acute cardiac rejection.

Paradoxical early lengthening and subsequent linear shortening of the QT interval in response to exercise

The QT responses to exercise during ventricular pacing were evaluated in 12 patients in whom permanent pacemakers were implanted for complete heart block. The initial response of the QT to exercise was a paradoxical lengthening during the first minute of exercise (mean 4.8 ms P < 0.01). Thereafter, the QT was found to shorten in a linear fashion in response to increasing exercise, both in terms of exercise duration (r = 0.787; P < 0.001) and atrial rate (r = 0.712; P < 0.001). The total QT shortening with exercise was small (20 ms for a mean increase in atrial rate of 60 beats.min-1) and displayed substantial inter-individual variability (9-31 ms). These results explain some of the limitations of the QT pacemaker, and provide insights in to the dynamics of the QT response, which may help tailor the programming of these systems to the individual patient.

Early and long term results of re-operation for coronary artery disease

OBJECTIVE

To define the incidence, possible causes, operative procedure, and early and medium term results of patients undergoing reoperation for coronary artery disease.

DESIGN

A retrospective analysis of patients undergoing reoperation in one hospital during a 10 year period.

SETTING

A regional cardiothoracic centre.

PATIENTS

115 patients had reoperation for recurrent angina, 1-17 years (mean (SD) 7.4 (3.9)) after primary revascularisation.

MAIN OUTCOME MEASURES

They received 279 grafts (2.4 grafts per patient); 58% of the grafts were anasatomosed to previously grafted vessels. The internal mammary artery was used in 87% of patients who required grafts to the left anterior descending coronary artery.

RESULTS

Reoperation accounted for 8.3% of the total number of patients who underwent coronary bypass grafting. Graft failure alone or in combination with other factors was judged to be the cause of recurrence of symptoms in 87%. 42% of patients had two or more coronary risk factors. The early mortality was 5.2% and the actuarial survival at five and 10 years was 90.4% and 88.4% respectively. 85% of the survivors had initial complete relief of angina and 14% had partial improvement. Freedom from recurrent symptoms at five and 10 years was 66.6% and 34.6% respectively.

CONCLUSIONS

Vein graft failure either alone or in combination with progression of native coronary disease is the main cause for symptomatic deterioration after bypass grafting. Reoperation can be performed with slightly increased risk and can give good early and medium term results.

Heterotopic heart transplantation and recipient heart operation in ischemic heart disease

The role of heterotopic heart transplantation in coronary heart disease has not been defined. Between 1983 and 1988, 28 patients with end-stage ischemic heart disease were managed by heterotopic heart transplantation and adjunctive operation on the recipient heart: coronary artery bypass grafts and aneurysmectomy, 20; coronary artery bypass grafts, 5; and aneurysmectomy, 3. Indications were feasibility of operative procedures to the recipient heart and small donor size (61% of the donors were less than 15 years). The 1-year and 5-year actuarial survival was 79% and 63%. Of the 22 patients who survived to 2-year follow-up, all of whom had been severely limited (New York Heart Association grade III/IV) preoperatively, 20 were in grades I or II at 2-year follow-up (p less than 0.001). In 14 of 22 patients (64%), the recipient heart augmented the donor cardiac output substantially, and in 4 the recipient heart supported the patient when the donor heart failed to eject. In conclusion, this series demonstrates the efficacy of heterotopic transplantation combined with operation to the recipient heart in the management of patients with end-stage ischemic heart disease.

Changes in myocardial echo amplitude during reversible ischaemia in humans

OBJECTIVE

This study investigated the changes in regional myocardial ultrasonic backscatter, measured as myocardial echo amplitude, that occur during reversible myocardial ischaemia in humans.

DESIGN

Left anterior descending coronary angioplasty was used to produce reversible myocardial ischaemia in human subjects. Regional myocardial echo amplitude was studied in the interventricular septum and left ventricular posterior free wall before, during, and after coronary occlusion with the angioplasty balloon. Wall motion analysis of the left ventricle was performed from simultaneous cross sectional echocardiographic imaging. Patients were studied prospectively.

PATIENTS

Six patients (mean age 56 (SD 11), range 46 to 69 years) with single vessel, left anterior descending coronary artery stenoses, were investigated during elective coronary angioplasty. A total of 11 balloon inflations were studied.

SETTING

All patient studies were performed at Harefield Hospital. Echo amplitude analysis was performed at the Royal Brompton Hospital.

INTERVENTIONS

Angioplasty was performed by the usual procedure at Harefield Hospital for elective coronary angioplasty. All routine medication including beta blockers and calcium antagonists were continued. Inflation pressures were up to 12 atm (1212 kPa) and mean inflation time ranged from 30 to 120 (86 (31)) s. In four studies the first inflation was examined, in three the second, in two the third, and in one each the fourth and fifth inflations. Echo amplitude and cross sectional echo-cardiographic studies were recorded with a 3.5 MHz Advanced Technology Laboratories (ATL) (720A/8736 series) mechanical sector scanner and an ATL Mark III (860-1 series) echocardiograph system with 45 dB logarithmic grey scale compression.

MAIN OUTCOME MEASURES

Regional echo amplitude was examined in four regions of the left ventricle--namely, the basal and mid-septum, and basal and mid-posterior wall. Consecutive end diastolic and end systolic frames were analysed and cyclic variation was determined as the difference between the level of echo amplitude at end diastole and at end systole. Measurements were made before balloon inflation, at peak inflation, and after balloon deflation. Regional wall motion and systolic wall thickening were analysed qualitatively.

RESULTS

Before balloon inflation, cyclic variation in echo amplitude was noted in all regions (basal septum, 2.4 (SD 1.1) dB; mid-septum, 2.5 (1.1) dB; basal posterior wall, 3.3 (2.1) dB; mid-posterior wall, 3.9 (1.6) dB). During balloon inflation there was a significant fall in cyclic variation to 0.4 (0.9) dB (p < 0.0002) in the mid-septum. This was predominantly owing to an increase in end systolic echo amplitude from 5.4 (2.0) dB to 9.3 (1.9) dB (p < or = 0.01). This was associated with the development of severe hypokinesis or akinesis in the mid-septum. No significant changes in echo amplitude occurred in the three other regions examined. Changes were completely reversed after balloon deflation.

CONCLUSIONS

These results suggest a causal relation between occlusion of the supplying coronary artery and blunting of myocardial echo amplitude cyclic variation. It is suggested that balloon occlusion produced myocardial ischaemia. The resultant impairment of myocardial contraction then caused a blunting of cyclic variation in echo amplitude. The results of this study provide further data about the ability of quantitative studies of ultrasonic backscatter to identify alterations in the myocardium during injury.

Optimized Hemodynamics by Implantation of a Dual Chamber Pacemaker After Heterotopic Cardiac Transplantation

A patient who underwent prior heterotopic cardiac transplantation had persistent complaints of dyspnea, palpitations, and fatigue in spite of normal pump function of the donor heart. Repeated Holter monitoring excluded paroxysmal arrhythmias. It was thought that synchronization of both heart rates might alleviate his symptoms. The intrinsic heart rate of the donor heart was 90 beats/min, the recipient heart was 60 beats/min with acceleration up to 130 beats/min on exercise. A DDD pacemaker was implanted, the atrial lead was positioned in the right ventricule of the donor heart and the ventricular lead in the atrium of the recipient heart. Search for an optimal AV interval was evaluated by echo-Doppler and intraarterial pressure recordings. By increasing the AV interval from 125 to 300 msec, the maximum aortic flow velocity of the recipient heart increased from 1.0 to 1.2 m/sec. Left ventricular end-diastolic diameter remained unchanged, left ventricular end-systolic diameter decreased from 52 to 48 mm. Wall motion of the recipient left ventricle improved. At an AV interval of 125 msec there was alternate systolic contraction of both hearts, resulting in arterial pressure waves at a rate of 180/min. This did not relieve his symptoms and he complained further of headaches. At an AV interval of 300 msec contraction of the recipient heart just preceded that of the donor heart, resulting in arterial pressure waves at a rate of 90/min, normalization of the wave form, relief of symptoms, and improvement of exercise tolerance.

Peak offset times as an indication of stress relaxation during tableting on a rotary tablet press

During powder compaction on a Manesty Betapress, peak pressures, Pmax, are reached before the punches are vertically aligned with the centres of the upper and lower compression roll support pins. The interval between the time taken to reach this alignment and the time to reach Pmax is defined as the peak offset time, t(off). The duration of t(off) depends on the ability of the compacted powder to relieve stress and is an indication of the predominant mechanisms of particle deformation during consolidation. Thus, at a given Pmax, short t(off) values are characteristic of materials that consolidate mainly by brittle fracture while longer values indicate an increase in plastic flow. On the Betapress, the decrease in stress during t(off) occurs under conditions approaching constant strain and t(off) therefore, is an indirect measure of stress relaxation. Stress relaxation, and hence t(off), decreases with increase in Pmax due to the reduction in the porosity of the compact and consequent restriction of plastic flow into the void spaces. In addition to Pmax, the effects of variables such as punch head geometry, press speed and formulation on t(off) are reported.

Oral treatment with enoximone in patients referred for cardiac transplantation

A prospective, uncontrolled, open ended study was performed to assess the effect of treatment with oral enoximone therapy in patients with end stage cardiac failure unresponsive to conventional treatment. The primary objective of treatment, hospital discharge, was achieved in 27 of 35 patients studied. Baseline haemodynamics were obtained in 21 patients. The mean cardiac index of patients who improved by one or more grades (New York Heart Association) was 2.1 litres/min while, in those who had less improvement, the mean cardiac index was 1.5 l/min (P less than 0.01). The average duration of treatment was 13 weeks, treatment being discontinued in 25 patients within twelve weeks. The main reasons for discontinuation were side effects (n = 11), and progressive cardiac failure (n = 7). The prognosis of patients in whom therapy was discontinued was very poor, only 5 of 28 being discharged from hospital without cardiac transplantation. Sudden death was uncommon (1/13), and Holter monitoring in 17 showed no aggravation of ventricular arrhythmias. Oral treatment with enoximone is a useful adjunct in the treatment of end stage cardiac failure.

Substance P for evaluation of coronary endothelial function after cardiac transplantation

The endothelium-dependent vasodilator substance P dilates normal and diseased coronary vessels in humans in vivo and produces a maximal response similar to that seen with intracoronary isosorbide dinitrate. Twelve cardiac transplant recipients underwent intracoronary infusion of substance P after routine annual investigations. All patients were well, with no evidence of rejection and with angiographically normal coronary arteries. Substance P was infused at 2 ml/min for 2 min into the coronary artery, starting at a dose of 1.4 pmol/min and increasing by doubling increments, and followed by isosorbide dinitrate (1 mg/min) infused over 2 min. Coronary artery diameter was measured in 23 vessel segments from 12 transplant recipients. The following doses were infused: saline solution (1 ml/min), substance P (0.7 [three patients], 1.4, 2.8, 5.6, 11.2, 22.4 pmol/min) and isosorbide dinitrate (1 mg/min). The mean percent increase in diameter (+/- SEM) in response to increasing doses of substance P was as follows: 0, 6.5 +/- 2.9%, 10.9 +/- 2.9%, 12.1 +/- 2.9%, 16.5 +/- 2.6%, 19.2 +/- 3.1% and 25.8 +/- 2.2%, respectively. Half maximal dilation was produced with 1.4 to 2.8 pmol/min of substance P; the maximal response (mean percent diameter change) was 22 +/- 2.5%. This was not significantly different from that achieved with isosorbide dinitrate. It is concluded that coronary endothelial function as assessed by response to substance P is preserved in cardiac transplant recipients with angiographically normal coronary arteries. Substance P may be a suitable agent for testing endothelial function in these patients.

Detection of free radicals and cholesterol hydroperoxides in blood taken from the coronary sinus of man during percutaneous transluminal coronary angioplasty

Patients undergoing percutaneous transluminal coronary angioplasty (PTCA) were investigated for the production of free radicals and cholesterol hydroperoxides during reperfusion. Fifteen patients were studied. Ischaemia during balloon inflation was assessed by serial coronary sinus lactate analysis (mean maximal increase in anterior descending artery dilation was 130%), and by the demonstration of reperfusion hyperaemia (mean increase of coronary sinus oxygen saturation 74%). Free radicals were detected by electron spin resonance (ESR) spin trapping using the spin trap PBN (N-t-Butyl-alpha-phenylnitrone). Radical adducts were detected in up to 50% of samples taken during reperfusion after anterior descending lesion angioplasty. No radicals were detected in control samples or during the ischaemic phase. Radical detection was positively correlated with the change in coronary sinus lactate (p less than 0.025). Coronary sinus cholesterol hydroperoxide analysis did not show a significant increase over control during reperfusion, due in part to unexpectedly high pre angioplasty levels. This study provides clear evidence for the production of a burst of free radicals and evidence for lipid peroxidation in the minutes following myocardial reperfusion during angioplasty. A relationship between the severity of the ischaemic insult and the detection of radical adducts has also been found.

Comparison of calculated and experimentally determined punch displacement on a rotary tablet press using both Manesty and IPT punches

An indirect method of calculating punch displacement on a rotary tablet press from measurements of the change in punch force with the turret position was in good agreement with direct measurements of punch displacement made using a linear variable displacement transducer (LVDT)-slip ring system. The direct measurements were made during the compaction of three direct compression agents using Manesty punches. However, the agreement between calculated and experimentally determined punch displacements was unsatisfactory when IPT punches were used. The IPT punches have a much flatter punch head profile than the Manesty punches. Due to this difference, the analytic equation does not accurately describe the dynamics of the press under normal operating conditions. Terms in the analytic equation, determined originally under static conditions, were re-evaluated under dynamic conditions for both sets of tooling using the LVDT-slip ring system. Excellent agreement for both IPT and Manesty punches was found between punch displacement calculated using the revised analytic equation and direct experimental measurements. Punch displacements determined from punch head profile and machine geometry only, without taking machine deformations into account, were shown to differ widely from the calculated and experimental values.

Cardiac involvement by lymphoma: diagnostic difficulties

A patient presenting with recurrent tamponade was subsequently shown to have non-Hodgkin's lymphoma. Catheterization demonstrated obstruction of the tricuspid valve by tumour and shunting through a patent foramen ovale. The difficulties in making an ante-mortem diagnosis of cardiac lymphoma are discussed.