Prolongation of the QT interval in heart failure occurs at low but not at high heart rates

Abnormal left ventricular structure and function as in, for example, left ventricular hypertrophy or chronic heart failure, is associated with sudden cardiac death and, when the ejection fraction is depressed, with prolongation of the QT interval. The dependence on heart rate of QT interval prolongation in these conditions, and the relationship of any abnormalities either to deranged autonomic nervous system function or to an adverse prognosis, has not been well studied. We therefore investigated (1) the dependence on heart rate of the QT interval, and (2) the relationship between both QT interval and the QT/heart rate slope and markers of adverse prognosis in these two conditions. The QT interval was measured at rest and during exercise in 34 subjects with heart failure, 16 subjects with left ventricular hypertrophy and 16 age-matched controls with normal left ventricular structure and function. QTc (corrected QT) intervals at rest were significantly longer in heart failure patients (471+/-10 ms) than in controls (421+/-6 ms) or in subjects with hypertrophy (420+/-6 ms) (P<0.05). At peak exercise, despite the attainment of similar heart rates, the QT intervals no longer differed from each other, being 281+/-7 ms for controls, 296+/-11 ms in hypertrophy and 303+/-10 ms in heart failure (no significant difference). The QT/heart rate slope was significantly increased in heart failure [2.3+/-0.1 ms.(beats/min)(-1)] compared with controls [1.55+/-0.06 ms.(beats/min)(-1)] and hypertrophy [1. 66+/-0.1 ms.(beats/min)(-1)] (P<0.001). In left ventricular hypertrophy, despite animal data suggesting that QT interval prolongation should occur, no abnormalities were found in QT intervals at rest or during exercise. The QT/heart rate slope did not relate to any markers for an adverse prognosis, except that of prolongation of QT interval. Long QT intervals were associated principally with impairment of left ventricular systolic function. Our data emphasize the dynamic nature of the QT interval abnormalities found in heart failure.

"What should I say?": qualitative findings on dilemmas in palliative care nursing

The nursing literature suggests that talking and listening to patients about issues associated with death and dying, is both important and difficult, and may be improved with training. This discussion presents the results of recent nursing research to confirm, and elaborate on, this theme. In this research participants touched on many central issues in communicating with patients that included articulating a sense of discomfort and inadequacy about the whole process, detailing the innumerable blocks to open communication [e.g., interference, denial, unrealistic optimism, resistance, collusion and anger] and sharing their sense of success and failure. The insights of nurses who participated in this research testify to the ongoing need to prioritize the development of nursing skills and support in this challenging but important area.

Social and behavioural factors associated with HIV seroconversion in homosexual men attending a central London STD clinic: a feasibility study

An unmatched retrospective case control study was conducted to test the feasibility of investigating social and behavioural factors which may have contributed to recent HIV seroconversion in a group of homosexual men. Participants, recruited from a London sexually transmitted disease (STD) clinic, were sexually active and had had a negative HIV test with a subsequent test (positive (cases) or negative (controls)) within three to 15 months. Twenty cases and 22 controls were recruited between February and October 1995. There was no difference between cases and controls in: the number of regular or casual sexual partners, the proportion who were unaware of their regular partners' serostatus (cases 60%, controls 59%), or the proportion who had known HIV-positive regular partners (cases 20%, controls 23%). A significant difference in sexual behaviour was found only when the HIV status of partners, if known, was taken into account: cases were more likely than controls to have had unprotected receptive anal intercourse with a partner not known to be HIV-negative (OR = 5.5, CI = 1.15-29.50). Fifty per cent of the cases and 27% of the controls acquired acute STDs between the two HIV tests. All participants achieved high self-efficacy scores, but the controls believed their peers placed a greater value on safer sex. Cases cited emotional issues and the use of drugs and alcohol as contributing to their seroconversion, whereas controls cited a commitment to safer sex and the avoidance of high-risk situations as contributing to their remaining HIV-negative. The results illustrate the importance of acknowledging the concept of 'negotiated safety' in studies of sexual behaviour; seroconversion was only associated with unprotected sex with a partner not known to be HIV-negative. Despite high self-efficacy scores, indicating the skills to negotiate safer sex, high levels of unsafe anal intercourse were reported. Differences between cases and controls included the importance of safer sex, periods of emotional vulnerability, influence of peers and the appropriate use of condoms. There is a need for these results to be confirmed in a larger and more powerful study.

Investigating the relaxation rate, following diazo-2 photolysis, of a skinned trabecular preparation from guinea-pig hypertrophied left ventricle

Cardiac hypertrophy in the guinea-pig is not accompanied by a large shift in the expression of the predominant isoform of myosin in the left ventricle; however, in this species, thin filament proteins do change. We examined the relaxation, following laser flash photolysis of the photolabile caged Ca2+ chelator diazo-2, of a skinned trabecular preparation from the left ventricle of guinea-pigs that had undergone abdominal aortic banding. Sham-operated animals were used as controls; no guinea-pigs showed any signs of heart failure. We report that mild cardiac hypertrophy does not affect the relaxation rate of Triton-skinned trabeculae from the guinea-pig. However, there was a 35% reduction in the maximum force generated by trabeculae from the left ventricle of the abdominal aortic-banded animals. Additionally, alterations in key troponin subunits occur in the left ventricle of guinea-pigs with mild hypertrophy. We conclude that the thin filament protein changes do not influence trabecular relaxation rates, even though they probably affect maximal force generation. The cellular membrane systems of the intact guinea-pig heart, which were not a factor in this present study, appear to have an important role in the altered cardiac relaxation rates seen in hypertrophy.

Molecular and functional distributions of chloride conductances in rabbit ventricle

The regulation of cardiac electrical activity is critically dependent on the distribution of ion channels in the heart. For most ion channels, however, the patterns of distribution and what regulates these patterns are not well characterized. The most likely candidates for the genes that encode the cAMP- and swelling-activated chloride conductances in the heart are an alternatively spliced variant of CFTR and ClC-3, respectively. In this study we have 1) measured the density of CFTR and ClC-3 mRNA levels across the left ventricular free wall (LVFW) of the rabbit heart using in situ hybridization and 2) measured the corresponding current density of cAMP- and swelling-activated chloride channels in myocytes isolated from subepicardial, midmyocardial, and subendocardial regions of the LVFW. There was a highly significant gradient in the whole cell slope conductance of cAMP-activated chloride currents; normalized slope conductance at 0 mV was 15.7 +/- 1.8 pS/pF (n = 9) in subepicardial myocytes, 7.8 +/- 1.5 pS/pF (n = 11) in midmyocardial myocytes, and 4.9 +/- 1.1 pS/pF (n = 9) in subendocardial myocytes. The level of CFTR mRNA was closely correlated with the density of cAMP-activated chloride conductances in different regions of the heart, with the level of CFTR mRNA being three times higher in the subepicardium than in the subendocardium. The whole cell slope conductance of swelling-activated chloride channel activity, measured 3-5 min after the commencement of cell swelling, was higher in myocytes isolated from the subepicardium than in myocytes isolated from the midmyocardium or subendocardium. In contrast, there was a uniform expression of ClC-3 mRNA across the LVFW of the rabbit heart. These results suggest that the control of gene expression is an important contributor in regulating the distribution of cAMP-activated chloride channels in the rabbit heart but that it may be less important for the swelling-activated chloride channels.

A social science perspective on screening for Chlamydia trachomatis

A recent report from the chief medical officer's expert advisory group on Chlamydia trachomatis has recommended the setting up of two pilot projects to assess the feasibility of introducing a national chlamydia screening programme. In addition to screening all symptomatic individuals and all attenders at genitourinary medicine clinics, the report recommends opportunistic screening of sexually active young women and women at high risk of infection, who are attending either general practice or family planning clinics. The success of any new screening programme depends on a wide variety of factors, not least the acceptability of such screening to its target population. In recent years, social scientists have made significant contributions to the understanding of the psychological factors which facilitate or inhibit uptake of screening services. The aim of this report is to discuss briefly the contribution social scientists could make to the chlamydia screening programme in the United Kingdom. In particular, the possible effects of screening for a stigmatized condition such as a sexually transmitted infection are explored.

Normal regional distribution of membrane current density in rat left ventricle is altered in catecholamine-induced hypertrophy

OBJECTIVE

To test the hypothesis that changes in the normal regional distribution of potassium and calcium currents contribute to the different regional changes in action potential duration in isoprenaline-induced hypertrophy in rats.

METHODS

Hypertrophy was elicited in rats by seven daily injections of isoprenaline. Left ventricular myocytes were isolated from basal sub-endocardial, basal mid-myocardial and apical sub-epicardial tissue. Membrane currents were measured using the whole-cell patch-clamp technique at 35 +/- 1 degrees C.

RESULTS

Cell membrane capacitance was similar in all three groups and was increased by 17% in hypertrophy (P < 0.001, t-test). Changes in the calcium-independent transient outward current (Ito1) density in hypertrophy were different in the three regions (P < 0.05, ANOVA). Ito1 was reduced in sub-epicardial (control, 23.4 +/- 2.0 pA pF-1; hypertrophy, 15.8 +/- 1.5 pA pF-1, P < 0.01 ANOVA) and in mid-myocardial myocytes (control, 24.0 +/- 2.8 pA pF-1; hypertrophy, 13.8 +/- 1.3 pA pF-1, P < 0.01 ANOVA) and was not significantly altered in sub-endocardial myocytes (control, 8.5 +/- 0.7 pA pF-1; hypertrophy, 7.4 +/- 1.8 pA pF-1). Steady-state background current density was reduced in hypertrophy (P < 0.05, ANOVA). The regional difference in steady-state background current in control hearts (P < 0.05, ANOVA) was altered in hypertrophy. Calcium current (ICa) density was similar in the three regions studied in both control and hypertrophied hearts. ICa was reduced in hypertrophy (P < 0.05, ANOVA).

CONCLUSION

The normal regional differences in Ito1 are reduced, in steady-state background current are altered and in ICa are unchanged in catecholamine-induced hypertrophy in the rat left ventricle. These data may in part explain the reduction in the normal regional differences in APD observed in hypertrophy.

Exploring empathy as a variable in the evaluation of professional development programs for palliative care nurses

Research indicates that empathy, a quality regarded as fundamentally important to nursing practice, is a teachable skill. Because empathic nurse-patient relationships are particularly important in the care of the terminally ill, this has direct relevance to the professional development of palliative care nurses. This article discusses the place of empathy as a criterion variable in the evaluation of a professional development program for palliative care nurses introduced at the Centre for Mental Health Nursing Research at Queensland University of Technology, Brisbane, Australia. A modified version of the Staff-Patient Interaction Response Scale (SPIRS) was used as a pre- and postintervention measure to assess the expressed empathy of the participating nurses. The modifications to SPIR and its coding system to make it suitable for palliative care nursing, and the mechanisms for improving and evaluating the reliability of this instrument will be discussed. The full description of this particular modification of SPIRS for palliative care research is provided as an example of how this instrument could be used in projects for which nurses undertake the difficult task of providing compassionate care to the terminally ill.

Peer visitor support for family caregivers of seniors with stroke

The objectives of this nationally funded intervention study were to: (1) implement a home visiting support program for family caregivers of seniors with a recent stroke using experienced peers; (2) monitor, describe, and evaluate the support intervention process; and (3) measure the impact of the peer support intervention on caregivers' perceptions of their social support, burden, stress, and competence and the use of health-care services by stroke survivors. This paper focuses on the first two objectives. Twenty family caregivers were visited initially by a health professional (nurse, occupational therapist) for assessment, and thereafter twice weekly for 12 weeks by a peer (experienced family caregiver). Transcripts of audiotaped post-intervention and delayed post-intervention (3 and 6 months) interviews with participants and the diaries/logs of professionals and peers were subjected to content analysis. Peer visitors offered emotional, informational, and affirmational support to family caregivers. Family caregivers reported that the intervention met their support needs, lessened some of their caregiving demands, and enhanced their confidence and ability to cope.

Regional differences in the delayed rectifier current (IKr and IKs) contribute to the differences in action potential duration in basal left ventricular myocytes in guinea-pig

OBJECTIVE

To compare the properties of single myocytes isolated from different layers of the basal region of the left ventricle and to test the hypothesis that differences in the delayed rectifier current (IK) contribute to regional differences in action potential duration.

METHODS

Myocytes were isolated from basal sub-endocardial, mid-myocardial and sub-epicardial layers of the guinea-pig left ventricle. Membrane voltage and current were measured using the switch-clamp technique.

RESULTS

Mean action potential duration measured at 90% repolarisation (APD90) was longer in sub-endocardial myocytes than in mid-myocardial and sub-epicardial myocytes [APD90 ms at 0.2 Hz: sub-endocardial 292 +/- 12 (n = 40), mid-myocardial 243 +/- 8 (n = 42) and sub-epicardial 227 +/- 9 (n = 36), P < 0.001, analysis of variance (ANOVA)]. The APD-rate relationship (stimulation frequencies 2, 1, 0.2 and 0.017 Hz) was steeper in sub-endocardial than in mid-myocardial or sub-epicardial myocytes (P < 0.001, ANOVA). The density of IK was greater in mid-myocardial (4.05 +/- 0.09 pA pF-1) and sub-epicardial (3.90 +/- 0.41 pA pF-1) than in sub-endocardial myocytes (2.74 +/- 0.27 pA pF-1, P < 0.01 ANOVA). The rapidly-activating (IKr) and slowly-activating (IKs) components of IK were significantly smaller in sub-endocardial than in mid-myocardial or sub-epicardial myocytes. D,L-Sotalol-induced prolongation of APD90 was similar in the three regions studied.

CONCLUSIONS

There are significant transmural gradients in the electrophysiological properties of myocytes isolated from the base of the left ventricular free wall in guinea-pig. Sub-endocardial myocytes had a longer APD90 attributable in part to a significantly smaller IK density. We have been unable to identify M cells in the guinea-pig left ventricular free wall.

Regional differences in action potential characteristics and membrane currents of guinea-pig left ventricular myocytes

Regional differences in action potential characteristics and membrane currents were investigated in subendocardial, midmyocardial and subepicardial myocytes isolated from the left ventricular free wall of guinea-pig hearts. Action potential duration (APD) was dependent on the region of origin of the myocytes (P < 0.01, ANOVA). Mean action potential duration at 90 % repolarization (APD90) was 237 +/- 8 ms in subendocardial (n = 30 myocytes), 251 +/- 7 ms in midmyocardial (n = 30) and 204 +/- 7 ms in subepicardial myocytes (n = 36). L-type calcium current (ICa) density and background potassium current (IK1) density were similar in the three regions studied. Delayed rectifier current (IK) was measured as deactivating tail current, elicited on repolarization back to -45 mV after 2 s step depolarizations to test potentials ranging from -10 to +80 mV. Mean IK density (after a step to +80 mV) was larger in subepicardial myocytes (1.59 +/- 0.16 pA pF-1, n = 16) than in either subendocardial (1.16 +/- 0.12 pA pF-1, n = 17) or midmyocardial (1. 13 +/- 0.11 pA pF-1, n = 21) myocytes (P < 0.05, ANOVA). The La3+-insensitive current (IKs) elicited on repolarization back to -45 mV after a 250 ms step depolarization to +60 mV was similar in the three regions studied. The La3+-sensitive tail current, (IKr) was greater in subepicardial (0.50 +/- 0.04 pA pF-1, n = 11) than in subendocardial (0.25 +/- 0.05 pA pF-1, n = 9) or in midmyocardial myocytes (0.38 +/- 0.05 pA pF-1, n = 11, P < 0.05, ANOVA). The contribution of a Na+ background current to regional differences in APD was assessed by application of 0.1 microM tetrodotoxin (TTX). TTX-induced shortening of APD90 was greater in subendocardial myocytes (35.7 +/- 7.1 %, n = 11) than in midmyocardial (15.7 +/- 3. 8 %, n = 10) and subepicardial (20.2 +/- 4.3 %, n = 11) myocytes (P < 0.05, ANOVA). Regional differences in action potential characteristics between subendocardial, midmyocardial, and subepicardial myocytes isolated from guinea-pig left ventricle are attributable, at least in part, to differences in IK and Na+-dependent currents.

Mediating conflict and control: practice challenges for nurses working in palliative care

A work-based professional development program was offered to a group of registered nurses working in palliative care. The goal of the program was to improve skills in psychosocial care (Yates et al., 1996). Participants were encouraged to reflect critically on their practice experience within a group setting. The focus of the group discussion and reflection were shared practice incidents. Each participant was given the opportunity to identify and describe an incident from their professional practice that presented a challenging issue within palliative nursing. This paper explores the themes of conflict and control, evident within the collection of fifteen practice incidents and discusses the nurses' role as mediator. The concepts of patient advocacy and professional autonomy are challenged through the nurses' experience of providing care within a hierarchical and bureaucratic health service. The outcome of reflection for the organization is most effective when shared experience and collective action (rather than individual practice) are the focus.

The sexual health of travelers

Sex and travel do not infrequently coincide as pleasurable occupations. This articles explores the possible risks of unsafe sexual activity in a travel-related context, gives guidelines on how to decrease risks for both partners, and outlines how to manage the exposed or infected traveler on his or her return home. Both sexually transmitted infections and contraception are covered.

Influenza vaccinations of Washington state Medicare beneficiaries seen by physiatrists in the outpatient setting in 1994

OBJECTIVE

To compare influenza vaccination billing rates for patients seen by physiatrists with those of four other specialties: neurology, rheumatology, family practice, and internal medicine.

DESIGN

Retrospective cohort analysis using Medicare billing data.

PATIENTS

234,164 Medicare outpatients seen in Washington state between September 1 and December 31, 1994.

RESULTS

Based on Medicare's billing data, only 6 of 99 physiatrists ordered vaccinations, and they immunized only 159 (6%) of the patients seen. An additional 1,109 (42%) patients seen by physiatrists were vaccinated by other physicians. Physiatric patients were less likely to have been vaccinated than those seen by internists, family practitioners, or rheumatologists (p < .002), but equally likely as those seen by neurologists (p = .07). A significantly smaller percentage of physiatrists ordered vaccinations than all other specialties (p < .04). Utilizing pre-existing survey data, the misclassification rate (those immunized but not billed) was estimated at 22% of our original cohort. Thus, approximately 800 patients, one third of those seeing physiatrists, may not have been immunized. We estimated the increase in hospitalization costs to be $117 per nonvaccinated patient (total >$90,000).

CONCLUSIONS

Missed opportunities for vaccination by physiatrists appear to be more frequent than in other specialties and have potentially large health and economic costs.

Long-term follow-up of a randomized trial on adjuvant chemotherapy and hormonal therapy in locally advanced breast cancer

PURPOSE

To study the effects on survival, disease-free survival, and locoregional control of adjuvant hormonal and chemotherapy in patients with locally advanced breast cancer after a minimal follow-up period of 14 years.

METHODS AND MATERIALS

A total of 118 patients were randomized between radiotherapy alone (arm I); radiotherapy, 12 courses of cyclophosphamide, methotrexate, and 5-fluorouracil (CMF), and tamoxifen (arm II); adriamycine, vincristine (AV) alternated with CMF, then radiotherapy, followed by four cycles of chemotherapy (AV/CMF); and tamoxifen during the entire treatment period (arm III).

RESULTS

No improvement in survival, disease-free survival, or locoregional control was observed. After 6 years of follow-up, the overall survival curves grew apart, resulting in differences in 10-year survival rates: 15% (confidence interval-3%, 33%) between arms III and I.

CONCLUSION

Owing to the relatively small numbers of patients involved, the relative value of the three treatment modalities cannot be established completely.

Effect of atenolol or metoprolol on waking hour dynamics of the QT interval in myocardial infarction

In subjects with a recent acute myocardial infarction, the hour immediately following awakening is associated with an abrupt exaggeration of heart rate-dependent changes and variability of the QT interval. Beta blockers were observed to blunt these waking hour changes.

Insights from a nursing research program on social support

This paper highlights the conceptual and practical implications of a nursing research program that focuses on social support. The diverse dimensions of the construct of social support; its relationship to stress and coping; and its impact on health, health behaviour, and use of health services are explicated in the conceptual framework underpinning the program. These associations will be elucidated by citing examples from eight assessment studies and four intervention studies. The research program yielded new insights and reinforced reported findings of other social-support research.

Reliabilities of human judgements: measurements from photographic CT scan images

Studies of brain lesions are generally dependent on human judgement for identification and possibly for measurement, but estimates of reliability are frequently neglected. The present study involves three investigation based on X-ray CT scans into reliabilities of human judgements: (1) the areas of brain lesions identified over two occasions by a single judge, (2) brain areas based on the projection of scans by a second judge over two occasions, and (3) brain areas computed from brain outlines by two independent judges. Errors decreased geometrically over procedures in the order listed, reflecting the decreasing complexity of judgement involved. Nevertheless, all three reliabilities proved satisfactory, showing that these procedures may be applied consistently over occasions and between raters. This was reassuring since computerization is currently practicable only in (2) and (3), where errors were least. Although not always performed, reliability checks are important, as indicated by the outlier, Case 10. Where there is a large discrepancy, seeking the reason(s), with a view to standardizing the criteria of judgement, is preferable to automatic averaging, both as a safeguard in individual cases and also to estimate error of measurement in group studies. To assist decision in any particular instance as to whether averaging is an acceptable solution, a statistical rule of thumb is proposed for testing the significance of the difference between two judgements.