P2257Self-care abilities and depression symptoms linked to brain injury in heart failure

Methods

Two high-resolution T1-weighted data were collected from each 42 HF subjects (age, 55.65±7.61; 30 male; LVEF 27.74±9.40%; NYHA class II/III) using a 3.0-Tesla MRI scanner. Depression, anxiety, sleep quality, daytime sleepiness, cognition, and self-care issues were examined with Beck Depression Inventory (BDI), Beck Anxiety Inventory (BAI), Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), Montreal Cognitive Assessment (MoCA), and Self-Care of Heart Failure Inventory (SCHFI) respectively. Both T1-weighted scans were realigned, averaged, and segmented into gray matter (GM), white matter, and cerebrospinal fluid tissue type. GM maps were normalized (unmodulated) to a common space and smoothed to obtain GM density maps. The smoothed GM density maps were used to examine the association of brain damage with disease symptoms (SPM 12; partial correlation; covariates, age and gender; p<0.005). Region of interest analyses were performed in prefrontal cortices, insular lobe and hippocampus to evaluate the correlation using partial correlation (SPSS, covariates, age and gender, p<0.05).

Results

The average scores for BAI 9.55±9.90, BDI 8.69±7.05, ESS 7.00±3.72, MoCA 24.64±3.48, PSQI 6.62±3.90, maintenance 73.12±13.78, management 70.28±13.98, and confidence 73.77±15.96 were calculated. Significant negative correlations was observed between GM density values and BAI (prefrontal cortices, r=−0.532, p<0.001), BDI (prefrontal cortices, r=−0.60, p<0.001; insula, r=−0.528, p<0.001, hippocampus, r=−0.432, p<0.005), ESS (prefrontal cortices, r=−0.419, p=0.007; insula, r=−0.443, p=0.004), and PSQI (prefrontal cortices, r=−0.517, p=0.001) scores, and positive correlation between GM density values, MoCA (prefrontal cortices, r=0.462, p=0.003) and SCHFI scores (maintenance: prefrontal cortices, r=0.422, p=0.007; insula, r=0.412, p=0.009, hippocampus, r=0.455, p=0.004; management: prefrontal cortices, r=0.728, p=0.001; insula, r=0.707, p=0.001, hippocampus, r=0.775, p<0.001) (Figure 1).

Figure 1

Conclusions

HF subjects show more wide-spread and significant correlations between regional GM density values and BDI as well as SCHFI management scores compared to the other disease symptom measures. The findings suggest that damage in mood, autonomic, and cognitive functions sites better correlate with BDI and SCHFI over other measures.

Acknowledgement/Funding

NIH/NINR 1R01 NR014669

Selectively diminished corpus callosum fibers in congenital central hypoventilation syndrome

Congenital central hypoventilation syndrome (CCHS), a condition associated with mutations in the PHOX2B gene, is characterized by loss of breathing drive during sleep, insensitivity to CO2 and O2, and multiple somatomotor, autonomic, neuropsychological, and ophthalmologic deficits, including impaired intrinsic and extrinsic eye muscle control. Brain structural studies show injury in peri-callosal regions and the corpus callosum (CC), which has the potential to affect functions disturbed in the syndrome; however, the extent of CC injury in CCHS is unclear. Diffusion tensor imaging (DTI)-based fiber tractography procedures display fiber directional information and allow quantification of fiber integrity. We performed DTI in 13 CCHS children (age, 18.2±4.7 years; eight male) and 31 control (17.4±4.9 years; 18 male) subjects using a 3.0-Tesla magnetic resonance imaging scanner; CC fibers were assessed globally and regionally with tractography procedures, and fiber counts and densities compared between groups using analysis-of-covariance (covariates; age and sex). Global CC evaluation showed reduced fiber counts and densities in CCHS over control subjects (CCHS vs. controls; fiber-counts, 4490±854 vs. 5232±777, P<0.001; fiber-density, 10.0±1.5 vs. 10.8±0.9 fibers/mm2, P<0.020), and regional examination revealed that these changes are localized to callosal axons projecting to prefrontal (217±47 vs. 248±32, P<0.005), premotor (201±51 vs. 241±47, P<0.012), parietal (179±64 vs. 238±54, P<0.002), and occipital regions (363±46 vs. 431±82, P<0.004). Corpus callosum fibers in CCHS are compromised in motor, cognitive, speech, and ophthalmologic regulatory areas. The mechanisms of fiber injury are unclear, but may result from hypoxia or perfusion deficits accompanying the syndrome, or from consequences of PHOX2B action.

Central autonomic regulation in congenital central hypoventilation syndrome

Congenital central hypoventilation syndrome (CCHS) patients show significant autonomic dysfunction in addition to the well-described loss of breathing drive during sleep. Some characteristics, for example, syncope, may stem from delayed sympathetic outflow to the vasculature; other symptoms, including profuse sweating, may derive from overall enhanced sympathetic output. The dysregulation suggests significant alterations to autonomic regulatory brain areas. Murine models of the genetic mutations present in the human CCHS condition indicate brainstem autonomic nuclei are targeted; however, the broad range of symptoms suggests more widespread alterations. We used functional magnetic resonance imaging (fMRI) to assess neural response patterns to the Valsalva maneuver, an autonomic challenge eliciting a sequence of sympathetic and parasympathetic actions, in nine CCHS and 25 control subjects. CCHS patients showed diminished and time-lagged heart rate responses to the Valsalva maneuver, and muted fMRI signal responses across multiple brain areas. During the positive pressure phase of the Valsalva maneuver, CCHS responses were muted, but were less so in recovery phases. In rostral structures, including the amygdala and hippocampus, the normal declining patterns were replaced by increasing trends or more modest declines. Earlier onset responses appeared in the hypothalamus, midbrain, raphé pallidus, and left rostral ventrolateral medulla. Phase-lagged responses appeared in cerebellar pyramis and anterior cingulate cortex. The time-distorted and muted central responses to autonomic challenges likely underlie the exaggerated sympathetic action and autonomic dyscontrol in CCHS, impairing cerebral autoregulation, possibly exacerbating neural injury, and enhancing the potential for cardiac arrhythmia.

Reduced caudate nuclei volumes in patients with congenital central hypoventilation syndrome

Congenital central hypoventilation syndrome (CCHS) children show cognitive and affective deficits, in addition to state-specific loss of respiratory drive. The caudate nuclei serve motor, cognitive, and affective roles, and show structural deficits in CCHS patients, based on gross voxel-based analytic procedures. However, the magnitude and regional sites of caudate injury in CCHS are unclear. We assessed global caudate nuclei volumes with manual volumetric procedures, and regional volume differences with three-dimensional surface morphometry in 14 CCHS (mean age+/-SD: 15.1+/-2.3 years; 8 male) and 31 control children (15.1+/-2.4 years; 17 male) using brain magnetic resonance imaging (MRI). Two high-resolution T1-weighted image series were collected using a 3.0 Tesla MRI scanner; images were averaged and reoriented (rigid-body transformation) to common space. Both left and right caudate nuclei were outlined in the reoriented images, and global volumes calculated; surface models were derived from manually-outlined caudate structures. Global caudate nuclei volume differences between groups were evaluated using a multivariate analysis of covariance (covariates: age, gender, and total intracranial volume). Both left and right caudate nuclei volumes were significantly reduced in CCHS over control subjects (left, 4293.45+/-549.05 vs. 4626.87+/-593.41 mm(3), P<0.006; right, 4376.29+/-565.42 vs. 4747.81+/-578.13 mm(3), P<0.004). Regional deficits in CCHS caudate volume appeared bilaterally, in the rostral head, ventrolateral mid, and caudal body. Damaged caudate nuclei may contribute to CCHS neuropsychological and motor deficits; hypoxic processes, or maldevelopment in the condition may underlie the injury.

Hypoxia reveals posterior thalamic, cerebellar, midbrain, and limbic deficits in congenital central hypoventilation syndrome

Congenital central hypoventilation syndrome (CCHS) patients show deficient respiratory and cardiac responses to hypoxia and hypercapnia, despite apparently intact arousal responses to hypercapnia and adequate respiratory motor mechanisms, thus providing a model to evaluate functioning of particular brain mechanisms underlying breathing. We used functional magnetic resonance imaging to assess blood oxygen level-dependent signals, corrected for global signal changes, and evaluated them with cluster and volume-of-interest procedures, during a baseline and 2-min hypoxic (15% O(2), 85% N(2)) challenge in 14 CCHS and 14 age- and gender-matched control subjects. Hypoxia elicited significant (P < 0.05) differences in magnitude and timing of responses between groups in cerebellar cortex and deep nuclei, posterior thalamic structures, limbic areas (including the insula, amygdala, ventral anterior thalamus, and right hippocampus), dorsal and ventral midbrain, caudate, claustrum, and putamen. Deficient responses to hypoxia included no, or late, changes in CCHS patients with declining signals in control subjects, a falling signal in CCHS patients with no change in controls, or absent early transient responses in CCHS. Hypoxia resulted in signal declines but no group differences in hypothalamic and dorsal medullary areas, the latter being a target for PHOX2B, mutations of which occur in the syndrome. The findings extend previously identified posterior thalamic, midbrain, and cerebellar roles for normal mediation of hypoxia found in animal fetal and adult preparations and suggest significant participation of limbic structures in responding to hypoxic challenges, which likely include cardiovascular and air-hunger components. Failing structures in CCHS include areas additional to those associated with PHOX2B expression and chemoreceptor sites.

Hypercapnic exposure in congenital central hypoventilation syndrome reveals CNS respiratory control mechanisms

Congenital central hypoventilation syndrome (CCHS) patients show impaired ventilatory responses and loss of breathlessness to hypercapnia, yet arouse from sleep to high CO2, suggesting intact chemoreceptor afferents. The syndrome provides a means to differentiate brain areas controlling aspects of breathing. We used functional magnetic resonance imaging to determine brain structures responding to inspired 5% CO2-95% O2 in 14 CCHS patients and 14 controls. Global signal changes induced by the challenge were removed on a voxel-by-voxel basis. A priori-defined volume-of-interest time trends (assessed with repeated measures ANOVA) and cluster analysis based on modeling each subject to a step function (individual model parameter estimates evaluated with t-test, corrected for multiple comparisons) revealed three large response clusters to hypercapnia distinguishing the two groups, extending from the 1) posterior thalamus through the medial midbrain to the dorsolateral pons, 2) right caudate nucleus, ventrolaterally through the putamen and ventral insula to the mid-hippocampus, and 3) deep cerebellar nuclei to the dorsolateral cerebellar cortex bilaterally. Smaller clusters and defined areas of group signal differences in the midline dorsal medulla, amygdala bilaterally, right dorsal-posterior temporal cortex, and left anterior insula also emerged. In most sites, early transient or sustained responses developed in controls, with little, or inverse change in CCHS subjects. Limbic and medullary structures regulating responses to hypercapnia differed from those previously shown to mediate loaded breathing ventilatory response processing. The findings show the significant roles of cerebellar and basal ganglia sites in responding to hypercapnia and the thalamic and midbrain participation in breathing control.

fMRI signal changes in response to forced expiratory loading in congenital central hypoventilation syndrome

Congenital central hypoventilation syndrome (CCHS) patients show impaired ventilatory responses to CO2 and hypoxia and reduced drive to breathe during sleep but retain appropriate breathing patterns in response to volition or increased exercise. Breath-by-breath influences on heart rate are also deficient. Using functional magnetic resonance imaging techniques, we examined responses over the brain to voluntary forced expiratory loading, a task that CCHS patients can perform but that results in impaired rapid heart rate variation patterns normally associated with the loading challenge. Increased signals emerged in control ( n = 14) over CCHS ( n = 13; ventilator dependent during sleep but not waking) subjects in the cingulate and right parietal cortex, cerebellar cortex and fastigial nucleus, and basal ganglia, whereas anterior cerebellar cortical sites and deep nuclei, dorsal midbrain, and dorsal pons showed increased signals in the patient group. The dorsal and ventral medulla showed delayed responses in CCHS patients. Primary motor and sensory areas bordering the central sulcus showed comparable responses in both groups. The delayed responses in medullary sensory and output regions and the aberrant reactions in cerebellar and pontine sensorimotor coordination areas suggest that rapid cardiorespiratory integration deficits in CCHS may stem from defects in these sites. Additional autonomic and perceptual motor deficits may derive from cingulate and parietal cortex aberrations.

Functional magnetic resonance imaging responses to expiratory loading in obstructive sleep apnea

Obstructive sleep apnea (OSA) is characterized by diminished upper airway muscle phasic and tonic activation during sleep, but enhanced activity during waking. We evaluated neural mechanisms underlying these patterns with functional magnetic resonance imaging procedures during baseline and expiratory loading conditions in nine medication-free OSA and 16 control subjects. Both groups developed similar expiratory loading pressures, but appropriate autonomic responses did not emerge in OSA cases. Reduced neural signals emerged in OSA cases within the frontal cortex, anterior cingulate, cerebellar dentate nucleus, dorsal pons, anterior insula and lentiform nuclei. Signal increases in OSA over control subjects developed in the dorsal midbrain, hippocampus, quadrangular cerebellar lobule, ventral midbrain and ventral pons. Fastigial nuclei and the amygdala showed substantially increased variability in OSA subjects. No group differences were found in the thalamus. OSA patients show aberrant responses in multiple brain areas and inappropriate cardiovascular responses to expiratory loading, perhaps as a consequence of previously-demonstrated limbic, cerebellar and motor area gray matter loss.

The relationship between obesity and mortality in patients with heart failure

OBJECTIVES

The study aimed to evaluate the role of obesity in the prognosis of patients with heart failure (HF).

BACKGROUND

Previous reports link obesity to the development of HF. However, the impact of obesity in patients with established HF has not been studied.

METHODS

We analyzed 1,203 patients with advanced HF followed in a comprehensive HF management program. The patients were subclassified into categories of body mass index (BMI) defined as: underweight BMI <20.7 (n = 164), recommended BMI 20.7 to 27.7 (n = 692), overweight BMI 27.8 to 31 (n = 168) and obese BMI >31 (n = 179). This sample size allows the detection of small effects (0.02), with a power of 0.80 and an alpha level of 0.05 for comparing one-year survival between BMI groups.

RESULTS

The four BMI groups had similar profiles in terms of ejection fraction (mean 0.22), sodium, creatinine and smoking. The obese and overweight groups had significantly higher rates of hypertension and diabetes, as well as higher levels of cholesterol, triglycerides and low density lipoprotein cholesterol. The four BMI groups had similar survival rates. Ejection fraction, HF etiology and angiotensin-converting enzyme inhibitor use predicted survival on univariate analysis (p < 0.01), although BMI did not. On multivariate analysis, cardiopulmonary exercise tests, pulmonary capillary wedge pressure and serum sodium were strong predictors of survival (p < 0.05). Higher BMI was not a risk factor for increased mortality, but was associated with a trend toward improved survival.

CONCLUSIONS

In a large cohort of patients with advanced HF of multiple etiologies, obesity is not associated with increased mortality and may confer a more favorable prognosis. Further studies need to delineate whether weight loss promotion in medically optimized patients with HF is a worthwhile therapeutic goal.

Predictors of isotonic exercise in patients with heart failure

PURPOSE

Study aims were to determine the predictors of isotonic resistance exercise performance in patients with advanced heart failure and to compare the preexercise values of patients who experienced a negative physiologic response to resistance exercise with those who had minimal or no response.

METHODS

A correlational design was used. After pharmacologic left ventricular unloading therapy using a pulmonary artery catheter, 34 patients with advanced heart failure performed graduated isotonic weight-lifting exercises. Measurements were made of hemodynamics and rating of perceived exertion after each test.

RESULTS

The following variables, measured at baseline, were significantly correlated with the amount of weight patients were able to lift: rating of perceived exertion (RPE; r = -0.42, P = 0.014); diastolic blood pressure (DBP; r = 0.49, P = 0.03); systolic blood pressure (SBP; r = 0.40, P = 0.017); pulmonary capillary wedge pressure (PCWP; r = 0.39, P = 0.026); and right atrial pressure (RAP; r = 0.35, P = 0.041). Multiple regression analysis, using a stepwise procedure, showed that 47% of the variance in exercise performance was explained by DBP, RPE, and PCWP. There were no significant differences in baseline hemodynamics, ejection fraction, or age between the group of patients who had a negative hemodynamic response at peak exercise and the group of patients who had minimal or no response.

CONCLUSIONS

Resting PCWP, DBP, and RPE can provide important information to help clinicians predict isotonic resistance exercise performance in patients with advanced heart failure. However, those patients who have a negative response to this type of exercise cannot be distinguished at baseline by clinical characteristics or age.

Freedom from congestion predicts good survival despite previous class IV symptoms of heart failure

BACKGROUND

This study determined whether evidence of congestion after 4 to 6 weeks of heart failure management predicted outcome for patients hospitalized with chronic New York Heart Association class IV symptoms. Class IV symptoms predict high mortality rates, but outcome is not known for patients who improve to establish freedom from congestion. Revised estimates at 1 month could facilitate decisions regarding transplantation and other high-risk interventions.

METHODS

At 4 to 6 weeks after hospital discharge, 146 patients were evaluated for congestion by 5 criteria (orthopnea, jugular venous distention, edema, weight gain, and new increase in baseline diuretics). Heart failure management included inpatient therapy tailored to relieve congestion, followed by adjustments to maintain fluid balance during the next 4 weeks.

RESULTS

Freedom from congestion was demonstrated at 4 to 6 weeks in 80 (54%) patients, who had 87% subsequent 2-year survival compared with 67% in 40 patients with 1 or 2 criteria of congestion and 41% in 26 patients with 3 to 5 criteria. The Cox proportional hazards model identified left ventricular dimension, pulmonary wedge pressure on therapy, and freedom from congestion as independent predictors of survival. Persistence of orthopnea itself predicted 38% 2-year survival (without urgent transplantation) versus 77% in 113 without orthopnea. Serum sodium was lower and blood urea nitrogen and heart rate higher when orthopnea persisted.

CONCLUSIONS

The ability to maintain freedom from congestion identifies a population with good survival despite previous class IV symptoms. At 4 to 6 weeks, patients with persistent congestion may be considered for high-risk intervention.

The hemodynamic effects of isotonic exercise using hand-held weights in patients with heart failure

BACKGROUND

Controversy surrounds the use of resistance exercise in patients with heart failure because of concerns that increases in rate-pressure product and systemic vascular resistance might lead to increased afterload and decreased cardiac output.

METHODS

Following pharmacologic left ventricular unloading therapy using a pulmonary artery catheter, 34 patients with advanced heart failure performed isotonic weightlifting exercise at 50%, 65%, and 80% of the calculated one repetition maximum. Measurements were made of hemodynamics, ST segment, rate-pressure product, serum norepinephrine, rating of perceived exertion, and dysrhythmias following each exercise set.

RESULTS

Repeated analysis of variance showed significant increases in systolic blood pressure (p = 0.0005), diastolic blood pressure (p = 0.01), rate-pressure product (p = 0.005); serum norepinephrine (p = 0.004), and rating of perceived exertion (p = 0.0005). However, systemic vascular resistance and cardiac output did not change significantly (p>0.05). Pulmonary capillary wedge pressures, the incidence of dysrhythmias, and ST segments did not significantly differ from baseline. No patients experienced angina or dyspnea during the study.

CONCLUSIONS

Isotonic exercise using hand-held weights was well tolerated hemodynamically and clinically, and no patients experienced adverse outcomes during exercise.

Visualization of sleep influences on cerebellar and brainstem cardiac and respiratory control mechanisms

Cerebellar and vestibular structures exert substantial influences on breathing and cardiovascular activity, particularly under conditions of extreme challenges. Influences from these structures, as well as from the ventral medullary surface, are greatly modified during sleep states. Vestibular lesions abolish the pronounced phasic autonomic variation found in the rapid eye movement sleep state, and spontaneous ventral medullary surface activity, as assessed by optical procedures, is greatly diminished in that state. Neural responses from the ventral medullary surface to hypotensive challenges are enhanced and appear "undampened" during the rapid eye movement sleep state. Functional magnetic resonance imaging reveals activation to blood pressure challenges in widespread brain areas of humans, and especially in cerebellar sites, such as the fastigial nucleus. A subset of victims of sudden infant death syndrome, a sleep-related disorder, appear to succumb from cardiovascular failure of a shock-like nature, and often show neurotransmitter receptor deficiencies in the ventral medullary surface, caudal midline raphe hypotensive regions, and the inferior olive, a major afferent relay to the cerebellum. Afferent and efferent vestibular/cerebellar structures, or sites within the cerebellum may mediate failure mechanisms in sudden infant death syndrome and a number of other sleep-disordered breathing and cardiovascular syndromes.

Comparison of Internet versus lecture instructional methods for teaching nursing research

Although many higher education programs are using the Internet to teach classes, there are few published reports on the effectiveness of this method on test scores or student satisfaction. The purpose of this study was to compare test and student satisfaction scores of graduate nursing students who take a nursing research course via the Internet with those of students who take the same course via traditional lecture instruction. In addition, student technical support use and Internet student lecture attendance also were examined. A total of 97 students (Internet, 44; lectures, 53) participated. There were no significant differences in test scores and overall course student satisfaction (P > .05). However, the Internet students reported significantly higher (P = .04) stimulation of learning compared with the traditional lecture students. Technical support use by the Internet students was high initially and was related to software problems. Of interest were the large proportion of Internet students (73 percent) who attended at least 3 of the 10 lectures. Use of the Internet to teach graduate-level nursing research can provide comparable learning and student satisfaction to traditional lecture instructional methods.

Improved survival in patients with nonischemic advanced heart failure and syncope treated with an implantable cardioverter-defibrillator

The purpose of this study was to assess whether in patients with syncope and heart failure due to nonischemic cardiomyopathy, treatment with an implantable cardioverter-defibrillator (ICD) compared with conventional medical therapy is associated with a reduction in sudden death and total mortality. Patients with advanced heart failure who have syncope have been shown to be at high risk for sudden death. Further risk stratification has been difficult in patients with nonischemic cardiomyopathy in whom inducibility on electrophysiologic study is not predictive of future risk. Of 639 consecutive patients with nonischemic cardiomyopathy referred for heart transplantation, 147 patients with history of syncope and no prior history of sustained ventricular tachycardia or cardiac arrest were identified. Outcomes were compared for the 25 patients managed with an ICD and 122 patients managed with conventional medical therapy. There were no differences in the baseline variables in the 2 groups of patients, including age, ejection fraction, and medical treatments for heart failure, but patients receiving an ICD were more likely to have had nonsustained ventricular tachycardia (56% vs. 15%, p = 0.001). During a mean follow-up of 22 months, there were 31 deaths, 18 sudden, in patients treated with conventional therapy, whereas there were 2 deaths, none sudden, in patients treated with an ICD. An appropriate shock occurred in 40% of the ICD patients. Actuarial survival at 2 years was 84.9% with ICD therapy and 66.9% with conventional therapy (p = 0.04). Thus, in patients with nonischemic cardiomyopathy and syncope, therapy with an ICD is associated with a reduction in sudden death and an improvement in overall survival.

Acquisition of electrophysiologic signals during magnetic resonance imaging

We describe a low cost system for acquiring electrophysiological signals during magnetic resonance imaging. The system consists of high common-mode-rejection and low noise operational amplifiers, coupled by fiber optic cables to a receiver located at the periphery of the magnetic field. The system minimizes noise introduction which would contaminate image signals.

Skin test anergy in advanced heart failure secondary to either ischemic or idiopathic dilated cardiomyopathy

Skin tests to recall antigens are performed as indicators of clinical outcomes in heart failure (HF). A diminution in the response to recall antigens, termed "anergy," is regarded as an indication of poorer clinical prognosis, although little analysis has been done to support that conclusion. Patients with advanced HF (n=222) in New York Heart Association classes III and IV, with complete datasets for all of the variables, were studied. The sample was 77% men, mean age 52+/-12 years, and left ventricular ejection fraction, 21+/-7. Patients with ischemic (n=113) and idiopathic (n=109) disease were analyzed separately. The relation of anergy to 1-year mortality and selected hemodynamic factors, blood chemistries, medications, and nutritional status markers was analyzed. Anergy was present in 45% (47% idiopathic and 42% ischemic) of patients. Anergy was related to 1-year mortality (univariate p=0.038) in patients with ischemic, but not idiopathic, HF. Anergic patients with ischemic HF had shorter survival times (p=0.035). Lower cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), and triglycerides were predictors (p <0.001) of mortality in idiopathic HF. In ischemic HF, lower cholesterol, LDL, and triglycerides were univariate predictors (p <0.001, p=0.004, and p=0.005, respectively) of skin test anergy, but not mortality. Thus, there were distinct differences in clinical correlates of skin test anergy in patients with idiopathic and ischemic HF. This study supports evaluation of anergy to skin tests as one of the markers of mortality in patients with ischemic HF.

Impact of a comprehensive heart failure management program on hospital readmission and functional status of patients with advanced heart failure

OBJECTIVES

To assess the impact of a comprehensive heart failure management program, functional status, hospital readmission rate and estimated hospital costs were determined and compared for the 6 months before and the 6 months after referral.

BACKGROUND

The course of advanced heart failure is characterized by progressive clinical deterioration reflected in frequent hospital admissions, which comprise the major financial cost.

METHODS

Over a 3-year period, 214 patients were accepted for heart transplantation and discharged after evaluation, which included adjustments in medical therapy and intensive patient education. Patients were in New York Heart Association functional class III or IV (94 and 120 patients, respectively), with a mean left ventricular ejection fraction of 0.21, peak oxygen consumption of 11 ml/kg per min and a total of 429 hospital admissions in the previous 6 months (average 2.0 per patient). Changes in the medical regimen included a 98% increase in angiotensin-converting enzyme inhibitor dose and a flexible diuretic regimen after 4.2-liter net diuresis, with counseling also regarding diet and progressive exercise.

RESULTS

During the 6 months after referral, there were only 63 hospital readmissions (85% reduction), with 0.29/patient (p < 0.0001). Functional status improved as assessed by functional class (p < 0.0001) and peak oxygen consumption (15.2 vs. 11.0 ml/kg per min, p < 0.001). The same results were seen after excluding the 35 patients without full 6-month follow-up (9 deaths, 14 urgent transplant procedures during hospital readmission, 12 elective transplant procedures from home); 34 hospital admissions occurred after referral, compared with 344 before referral. Even when adding in the initial hospital admission after referral for these 179 patients, there was a 35% decrease in total hospital admissions in the 6-month period. The estimated savings in hospital readmission costs after subtracting the initial hospital costs for management was $9,800 per patient.

CONCLUSIONS

Comprehensive heart failure management led to improved functional status and an 85% decrease in the hospital admission rate for transplant candidates discharged after evaluation. The potential to reduce both symptoms and costs suggests that referral to a heart failure program may be appropriate not only for potential heart transplantation, but also for medical management of persistent functional class III and IV heart failure.

Six-minute walk test and heart rate variability: lack of association in advanced stages of heart failure

BACKGROUND: The 6-minute walk and heart rate variability have been used to assess mortality risk in patients with heart failure, but their relationship to each other and their usefulness for predicting mortality at 1 year are unknown. OBJECTIVE: To assess the relationships between the 6-minute walk test, heart rate variability, and 1-year mortality. METHOD: A sample of 113 patients in advanced stages of heart failure (New York Heart Association Functional Class III-IV, left ventricular ejection &lt; 0.25) were studied. All 6-minute walks took place in an enclosed, level, measured corridor and were supervised by the same nurse. Heart rate variability was measured by using (1) a standard-deviation method and (2) Poincare plots. Data on RR intervals obtained by using 24-hour Holter monitoring were analyzed. Survival was determined at 1 year after the Holter recording. RESULTS: The results showed no significant associations between the results of the 6-minute walk and the two measures of heart rate variability. The results of the walk were related to 1-year mortality but not to the risk of sudden death. Both measures of heart rate variability had significant associations with 1-year mortality and with sudden death. However, only heart rate variability measured by using Poincare plots was a predictor of total mortality and risk of sudden death, independent of left ventricular ejection fraction, serum levels of sodium, results of the 6-minute walk test, and the standard-deviation measure of heart rate variability. CONCLUSIONS: Results of the 6-minute walk have poor association with mortality and the two measures of heart rate variability in patients with advanced-stage heart failure and a low ejection fraction. Further studies are needed to determine the optimal clinical usefulness of the 6-minute walk and heart rate variability in patients with advanced-stage heart failure.

Six-minute walk test and heart rate variability: lack of association in advanced stages of heart failure

BACKGROUND

The 6-minute walk and heart rate variability have been used to assess mortality risk in patients with heart failure, but their relationship to each other and their usefulness for predicting mortality at 1 year are unknown.

OBJECTIVE

To assess the relationships between the 6-minute walk test, heart rate variability, and 1-year mortality.

METHOD

A sample of 113 patients in advanced stages of heart failure (New York Heart Association Functional Class III-IV, left ventricular ejection < 0.25) were studied. All 6-minute walks took place in an enclosed, level, measured corridor and were supervised by the same nurse. Heart rate variability was measured by using (1) a standard-deviation method and (2) Poincaré plots. Data on RR intervals obtained by using 24-hour Holter monitoring were analyzed. Survival was determined at 1 year after the Holter recording.

RESULTS

The results showed no significant associations between the results of the 6-minute walk and the two measures of heart rate variability. The results of the walk were related to 1-year mortality but not to the risk of sudden death. Both measures of heart rate variability had significant associations with 1-year mortality and with sudden death. However, only heart rate variability measured by using Poincaré plots was a predictor of total mortality and risk of sudden death, independent of left ventricular ejection fraction, serum levels of sodium, results of the 6-minute walk test, and the standard-deviation measure of heart rate variability.

CONCLUSIONS

Results of the 6-minute walk have poor association with mortality and the two measures of heart rate variability in patients with advanced-stage heart failure and a low ejection fraction. Further studies are needed to determine the optimal clinical usefulness of the 6-minute walk and heart rate variability in patients with advanced-stage heart failure.

Predictors of natural killer cell-mediated cytotoxicity deficiency in advanced heart failure secondary to either ischemic or idiopathic dilated cardiomyopathy

The effect of psychologic variables (situational emotional state and psychiatric diagnosis) and physiologic variables (plasma norepinephrine, decreased cardiac exercise capacity, and elevated pulmonary capillary wedge pressure) on natural killer cell activity was evaluated in 19 patients with advanced heart failure of ischemic or idiopathic origin. Only peak exercise capacity was independently predictive of natural killer cell deficiency.

Voluntary control of vascular tone by using skin-temperature biofeedback-relaxation in patients with advanced heart failure

BACKGROUND

Advanced heart failure is characterized by activation of the sympathetic nervous system and intense vasoconstriction. Biofeedback-relaxation techniques have been used successfully to treat conditions with similar pathophysiological features.

OBJECTIVES

The purpose of this study was to determine if conscious control of skin temperature via a biofeedback-relaxation technique could produce vasodilation and alter central hemodynamic status and circulating levels of catecholamines in patients with heart failure.

METHODS

Forty patients with advanced heart failure were randomly assigned to either an intervention or a control group. The study was done in a special cardiac step-down unit accepting patients for hemodynamic monitoring. The patients in the intervention group had one session of skin-temperature biofeedback augmented by imagery of hand warmth and modified progressive muscle relaxation. Skin temperature, systemic vascular resistance, cardiac output, plasma levels of norepinephrine and epinephrine, oxygen consumption, respiratory rate, and pulmonary wedge pressure were measured before and after the biofeedback session. Control patients had the same measurements made but were not given instruction in biofeedback-relaxation techniques.

RESULTS

Patients in the biofeedback-relaxation and control groups had comparable clinical profiles at baseline. Patients undergoing biofeedback-relaxation showed the following changes: (1) increase in skin temperature of 3.1 +/- 2.8 degrees F (1.7 +/- 1.5 degrees C) in the finger and 1.5 +/- 5.2 degrees F (0.4 +/- 1.2 degrees C) in the foot, (2) increase in cardiac output of 0.30 +/- 0.33 L/min, (3) decrease in systemic vascular resistance of 152 +/- 225 dyne.sec.cm-5, and (4) decrease in respiratory rate of 4.5 +/- 3.2 breaths per minute. The biofeedback group exhibited no changes in catecholamine levels or oxygen consumption. No changes in any of these parameters were seen in the control group.

DISCUSSION

Despite the presence of marked vasoconstriction in patients with advanced heart failure, a single session of biofeedback-relaxation can increase finger temperature and cardiac output and decrease systemic vascular resistance and respiratory rate, apparently without effect on systemic levels of catecholamines or oxygen consumption.

Improving survival for patients with atrial fibrillation and advanced heart failure

OBJECTIVES

We attempted to determine whether changes in heart failure therapy since 1989 have altered the prognostic significance of atrial fibrillation.

BACKGROUND

Atrial fibrillation occurs in 15% to 30% of patients with heart failure. Despite the recognized potential for adverse effects, the impact of atrial fibrillation on prognosis is controversial.

METHODS

Two-year survival for 750 consecutive patients discharged from a single hospital after evaluation for heart transplantation from 1985 to 1989 (Group I, n = 359) and from 1990 to April 1993 (Group II, n = 391) was analyzed in relation to atrial fibrillation. In Group I, class I antiarrhythmic drugs and hydralazine vasodilator therapy were routinely allowed. In Group II, amiodarone and angiotensin-converting enzyme inhibitors were first-line antiarrhythmic and vasodilating drugs.

RESULTS

A history of atrial fibrillation was present in 20% of patients in Group I and 24% of those in Group II. Patients with atrial fibrillation in the two groups had similar clinical and hemodynamic profiles. Among patients with atrial fibrillation, those in Group II had a markedly better 2-year survival (0.66 vs. 0.39, p = 0.001) and sudden death-free survival (0.84 vs. 0.70, p = 0.01) than those in Group I. In each time period, survival was worse for patients with than without atrial fibrillation in Group I (0.39 vs. 0.55, p = 0.002) but not in Group II (0.66 vs. 0.75, p = 0.09).

CONCLUSIONS

The prognosis of patients with advanced heart failure and atrial fibrillation is improving. These findings support the practice of avoiding class I antiarrhythmic drugs in this group and may reflect recent beneficial changes in heart failure therapy.

Comparison of four methods of assessing heart rate variability in patients with heart failure

BACKGROUND

Heart rate variability reflects autonomic tone and is used to assess progression and prognosis in a variety of illnesses. However, multiple heart rate variability methods exist and are not necessarily equivalent.

OBJECTIVES

To compare four methods of heart rate variability in heart failure patients and healthy subjects.

METHODS

Twenty-four-hour Holter recordings were obtained in 50 heart failure patients and 50 age- and gender-matched control patients. From these recordings, heart rate variability was assessed by histograms, standard deviation, Poincaré plots, and spectral analysis.

RESULTS

For R-R interval histograms, standard deviation, and Poincaré plots, diminished heart rate variability was identified in 65% to 100% of heart failure patients versus 0% to 8% of controls. Agreement among these tests ranged from 69% to 96%. Spectral values varied greatly over the recording period, even in the same subject, possibly because of variations in activity. Only 16% of heart failure patients had spectral values that were identified as abnormal. Agreement between spectral analysis and the other methods ranged between 58% and 67%.

CONCLUSIONS

Heart rate variability assessed over a 24-hour period with different techniques yields similar but not identical results. Heart rate variability assessed from spectral analysis of short periods of data varied markedly in a 24-hour period and should not be compared with measures obtained from 24-hour methods. Standardization of subject activity and recording time is necessary for comparison of spectral analysis of brief periods. Further research is required to determine if differences among methods assessing 24-hour heart rate variability yield complementary information.

Comparison of four methods of assessing heart rate variability in patients with heart failure

BACKGROUND: Heart rate variability reflects autonomic tone and is used to assess progression and prognosis in a variety of illnesses. However, multiple heart rate variability methods exist and are not necessarily equivalent. OBJECTIVES: To compare four methods of heart rate variability in heart failure patients and healthy subjects. METHODS: Twenty-four-hour Holter recordings were obtained in 50 heart failure patients and 50 age- and gender-matched control patients. From these recordings, heart rate variability was assessed by histograms, standard deviation, Poincare plots, and spectral analysis. RESULTS: For R-R interval histograms, standard deviation, and Poincare plots, diminished heart rate variability was identified in 65% to 100% of heart failure patients versus 0% to 8% of controls. Agreement among these tests ranged from 69% to 96%. Spectral values varied greatly over the recording period, even in the same subject, possibly because of variations in activity. Only 16% of heart failure patients had spectral values that were identified as abnormal. Agreement between spectral analysis and the other methods ranged between 58% and 67%. CONCLUSIONS: Heart rate variability assessed over a 24-hour period with different techniques yields similar but not identical results. Heart rate variability assessed from spectral analysis of short periods of data varied markedly in a 24-hour period and should not be compared with measures obtained from 24-hour methods. Standardization of subject activity and recording time is necessary for comparison of spectral analysis of brief periods. Further research is required to determine if differences among methods assessing 24-hour heart rate variability yield complementary information.

Improving survival for patients with advanced heart failure: a study of 737 consecutive patients

OBJECTIVES

This study sought to determine whether survival and risk of sudden death have improved for patients with advanced heart failure referred for consideration for heart transplantation as advances in medical therapy were systematically implemented over an 8-year period.

BACKGROUND

Recent survival trials in patients with mild to moderate heart failure and patients after a myocardial infarction have shown that angiotensin-converting enzyme inhibitors are beneficial, type I antiarrhythmic drugs can be detrimental, and amiodarone may be beneficial in some groups. The impact of advances in therapy may be enhanced or blunted when applied to severe heart failure.

METHODS

One-year mortality and sudden death were determined in relation to time, baseline variables and therapeutics for 737 consecutive patients referred for heart transplantation and discharged home on medical therapy from 1986 to 1988, 1989 to 1990 and 1991 to 1993. Medical care was directed by a single team of physicians with policies established by consensus. From 1986 to 1990, the hydralazine/isosorbide dinitrate combination or angiotensin-converting enzyme inhibitors were the initial vasodilators, and class I antiarrhythmic drugs were allowed. After 1990, captopril was the initial vasodilator, given to 86% of patients compared with 46% of patients before 1989. After mid-1989, class I agents were routinely withdrawn, and amiodarone was used for frequent ventricular ectopic beats or atrial fibrillation (53% of patients after 1990 vs. 10% before 1989).

RESULTS

The total 1-year mortality rate decreased from 33% before 1989 to 16% after 1990 (p = 0.0001), and sudden death decreased from 20% to 8% (p = 0.0006). Adjusted for clinical and hemodynamic variables in multivariate proportional hazards models, total mortality and sudden death were lower after 1990.

CONCLUSIONS

The large reduction in mortality, particularly in sudden death, from advanced heart failure since 1990 may reflect an enhanced impact of therapeutic advances shown in large randomized trials when they are incorporated into a comprehensive approach in this population. This improved survival supports the growing practice of maintaining potential heart transplant candidates on optimal medical therapy until clinical decompensation mandates transplantation.

Timing of sudden death in patients with heart failure

OBJECTIVES

The purpose of this study was to determine the timing of sudden death in patients with advanced heart failure.

BACKGROUND

The frequency of sudden cardiac death and myocardial infarction is greatest in the morning hours, suggesting that physiologic processes associated with morning activities may trigger these events. In patients with advanced heart failure, a variety of mechanisms may cause sudden death, and the frequency of their occurrence may differ from that in other patient groups, perhaps altering the timing of sudden death in heart failure.

METHODS

Deaths among 566 consecutive patients followed up after treatment for advanced heart failure were prospectively categorized as sudden death, death due to heart failure or noncardiac death. For 72 sudden deaths the time of death was determined from witnesses to the event and from death certificates.

RESULTS

Sudden death occurred 2.5 times more frequently between 6:01 AM and 12 noon than in the three other 6-h intervals, with 46% of deaths occurring during this period (p < 0.005). The morning peak occurred both in patients with coronary artery disease and in those with nonischemic causes of heart failure.

CONCLUSIONS

Despite a variety of potential mechanisms of sudden death and underlying causes of heart disease in patients with heart failure, the 24-h distribution of sudden death in these patients is similar to that observed in other patient groups. Morning surges in sympathetic nervous system activity may promote a variety of sudden death mechanisms, including ischemic and nonischemic arrhythmias.

Complex heart rate variability and serum norepinephrine levels in patients with advanced heart failure

OBJECTIVES

This study was designed to examine the relation of the Poincaré plot heart rate variability pattern to sympathetic nervous system activity as assessed by serum norepinephrine.

BACKGROUND

Poincaré plots demonstrate a complexity of beat to beat behavior not readily detected by other heart rate variability measures. Previous studies have described two abnormal Poincaré patterns in patients with heart failure: a torpedo pattern with reduced beat to beat variability and a complex pattern with clustering of points.

METHODS

To assess the relation of these plots to sympathetic activity, plasma norepinephrine at rest and a standard deviation measure of heart rate variability were analyzed in 21 patients with heart failure (mean left ventricular ejection fraction [+/- SD] 0.22 +/- 0.05).

RESULTS

Eleven subjects had a torpedo-shaped and 10 subjects had a complex Poincaré plot pattern. These two groups did not differ significantly in age, functional class, disease etiology, left ventricular ejection fraction, heart rate, ventricular ectopic activity or in a standard deviation measure of heart rate variability. However, patients with a complex Poincaré plot pattern had higher norepinephrine levels (722 +/- 373 pg/ml) than patients with torpedo-shaped plots (309 +/- 134 pg/ml) (p = 0.003). Patients with a complex pattern also had more severe hemodynamic decompensation, as evidenced by their higher levels of pulmonary capillary wedge and mean pulmonary artery pressures and lower values for cardiac index than those of patients with a torpedo-shaped plot.

CONCLUSIONS

Complex Poincaré plots are associated with marked sympathetic activation and may provide additional prognostic information and insight into autonomic alterations and sudden cardiac death in patients with heart failure.

Recurrent ventricular tachycardia

Recurrent ventricular tachycardia presents nurses with multiple challenges in terms of the knowledge of arrhythmia etiology, treatment, identification of potential problems, and physiologic and psychologic interventions before, during, and after an electrophysiology study. To assist in the understanding of arrhythmia etiology, the predominant electrophysiologic mechanisms for recurrent ventricular tachycardia are discussed. Also discussed are the procedures that can occur during an electrophysiology study and treatment options. Implications for nurses are discussed and include such factors as potential adverse physiologic and psychologic incidents that may be manifested in the pre- or postelectrophysiology study period.

Sudden cardiac death in patients with heart failure

Sudden cardiac death accounts for up to one half of the heart failure deaths each year. Thus, an understanding of the possible mechanisms, markers, and treatments of sudden cardiac death is an important component in the care of this patient population. This article discusses recent hypotheses as well as both preventative and interruptive therapies for sudden cardiac death in heart failure.

Effects of ventricular ectopy on sinus R-R intervals in patients with advanced heart failure

OBJECTIVE

To determine the effect of ventricular ectopy on subsequent sinus R-R intervals.

DESIGN

Comparative, repeated-measures design.

SETTING

University medical center.

SUBJECTS

Ten consecutive sinus R-R intervals and their standard deviations before and after ventricular ectopy from 24-hour ambulatory electrocardiogram recordings were obtained from 25 patients with heart failure (left ventricular ejection fraction 0.18 +/- 0.08; New York Heart Association Functional Class III-IV) and three healthy subjects.

RESULTS

The effects of 7564 single ventricular ectopic beats, 272 ventricular couplets, and 49 episodes of ventricular tachycardia in the patients with heart failure and 1369 single ventricular ectopic beats in the three healthy subjects were evaluated. Repeated-measures ANOVA indicated no significant differences in sinus R-R intervals immediately before or after ventricular ectopy. Standard deviation of sinus R-R intervals before and after ventricular ectopy did not differ significantly.

CONCLUSIONS

Ventricular ectopy does not significantly alter subsequent sinus R-R intervals and is unlikely to affect measurement of heart rate variability, particularly by techniques that use standard deviation methods.

Significance of aborted cardiac arrest and sustained ventricular tachycardia in patients referred for treatment therapy of advanced heart failure

Cardiac arrest in patients with heart failure may be the result of remediable factors such as pulmonary edema, drug toxicity, or electrolyte abnormalities, or it may be due to primary arrhythmias. The relation of prior aborted cardiac arrest or sustained ventricular tachycardia to subsequent prognosis was assessed in 458 consecutive patients referred for management of advanced heart failure (left ventricular ejection fraction 0.2 +/- 0.07). All patients received tailored vasodilator and diuretic therapy and were then followed as outpatients. Patients were divided into four groups: 388 patients (85%) with no prior cardiac arrest or sustained ventricular tachycardia, 31 patients (7%) with a primary arrhythmia cardiac arrest, 22 patients (5%) with a secondary cardiac arrest, and 17 patients (4%) with sustained ventricular tachycardia without cardiac arrest. Patients with cardiac arrest resulting from a primary arrhythmia were usually treated with antiarrhythmic drugs (25 patients), and five patients received an implantable defibrillator. After hospital discharge actuarial 1-year sudden death risk (17%) and total mortality (24%) rates for the group with primary arrhythmia were similar to corresponding values in patients with no history of cardiac arrest or sustained ventricular tachycardia (17% and 30%, respectively). In patients with a secondary cardiac arrest as a result of exacerbation of heart failure (11 patients), torsade de pointes (10 patients), or hypokalemia (one patient), therapy focused on removal of aggravating factors. Actuarial 1-year sudden death (39%) and total mortality (54%) rates for the group with secondary arrest were higher than for patients without a history of cardiac arrest (p = 0.003 and 0.005, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Heart rate variability in congenital central hypoventilation syndrome

Heart rate variability was assessed in 12 patients with congenital central hypoventilation syndrome (CCHS) and in age- and sex-matched controls using SD of time intervals between R waves (R-R intervals), R-R interval histograms, spectral analysis, and Poincaré plots of sequential R-R intervals over a 24-h period using ambulatory monitoring. Mean heart rates in patients with CCHS were 103.3 +/- 17.7 SD and in controls were 98.8 +/- 21.6 SD (p greater than 0.5, NS). SD analysis of R-R intervals showed similar results in both groups (CCHS 102.2 +/- 36.0 ms versus controls 126.1 +/- 43.3 ms; p greater than 0.1, NS). Spectral analysis revealed that, for similar epochs sampled during quiet sleep and wakefulness, the ratios of low-frequency band to high-frequency band spectral power were increased for 11 of 12 patients with CCHS during sleep, whereas a decrease in these ratios was consistently observed in all controls during comparable sleep states (chi 2 = 20.31; p less than 0.000007). During wakefulness, the ratios of low-frequency band to high-frequency band spectral power were similar in both patients with CCHS and controls. Poincaré plots displayed significantly reduced beat-to-beat changes at slower heart rates in the CCHS patients (chi 2 = 24.0; p less than 0.000001). The scatter of points in CCHS Poincaré plots was easily distinguished from controls. All CCHS patients showed disturbed variability with one or more measures. The changes in moment-to-moment heart rate variability suggest that, in addition to a loss of ventilatory control, CCHS patients exhibit a dysfunction in autonomic nervous system control of the heart.

Patterns of beat-to-beat heart rate variability in advanced heart failure

Diminished heart rate variability is associated with high sympathetic tone and an increased mortality rate in heart failure cases. We constructed Poincaré plots of each sinus R-R interval plotted against the subsequent R-R interval from 24-hour Holter recordings of 24 healthy subjects (control group) and 24 patients with heart failure. Every subject in the control group had a comet-shaped Poincaré plot resulting from an increase in beat-to-beat dispersion as heart rate slowed. No patient with heart failure had this comet-shaped pattern. Instead, three distinctive patterns were identified: (1) a torpedo-shaped pattern resulting from low R-R interval dispersion over the entire range of heart rates, (2) a fanshaped pattern resulting from restriction of overall R-R interval ranges with enhanced dispersion, and (3) complex patterns with clusters of points characteristic of stepwise changes in R-R intervals. Poincaré pattern could not be predicted from standard deviations of R-R intervals. This first use of Poincaré plots in heart rate variability analysis reveals a complexity not readily perceived from standard deviation information. Further study is warranted to determine if this method will allow refined assessment of cardiac-autonomic integrity in heart failure, which could help identify patients at highest risk for sudden death.

Clinical management of the patient with an acute myocardial infarction

The clinical care of patients with myocardial infarction has evolved to embrace not only palliative measures but also strategies to decrease pre-hospital delay and direct interventional measures to promote myocardial salvage. Thrombolysis has emerged as a therapy that significantly improves mortality and morbidity, particularly if administered early in the infarction process. Major thrombolytic agents and their administration schedules, adverse reactions, and adjunctive therapies are reviewed.

Optimal late potential criteria for reducing false positive signal-averaged electrocardiograms

The purposes of this study were to determine for signal-averaged electrocardiograms in normal subjects: (1) the incidence of false positives for various filter frequencies and late potential criteria and (2) reproducibility over time. In 46 normal volunteers, the QRS vector magnitude was bidirectionally high-pass filtered at 25, 40, and 100 Hz. As high-pass filter frequency increased, QRS duration decreased from 98 +/- 9 to 92 +/- 9 msec (p less than 0.0001), terminal QRS root mean square voltage decreased from 60 +/- 41 to 14 +/- 9 microV (p less than 0.0001), and terminal QRS low amplitude signal duration increased from 27 +/- 7 to 41 +/- 14 msec (p less than 0.0001). For individual parameters, the incidence of false positive tests ranged from 2% to 41%, whereas there were no false positive tests for the combination of abnormal QRS duration plus either root mean square voltage or low amplitude signal duration. Measurements were repeated after 6.4 +/- 0.3 months in 26 subjects and were highly reproducible at all filter settings. The potentially high incidence of false positive tests with some criteria has important implications for the use of signal-averaged electrocardiography as a screening test in patient populations with various arrhythmia risks.

Late potentials are unaltered by ventricular filling pressure reduction in heart failure

Exacerbation of heart failure may increase susceptibility to arrhythmias. Therefore tests to assess the risk of arrhythmia, performed after hemodynamic improvement, may be of limited value. To determine whether hemodynamic improvement alters ventricular late potentials detected by signal-averaged ECG, we studied 27 consecutive patients with dilated heart failure (left ventricular ejection fraction 0.20 +/- 0.06, 15 with coronary artery disease) before and 3 +/- 2 days after tailored vasodilator and diuretic therapy reduced ventricular filling pressures. QRS duration, terminal QRS amplitude (root mean square [RMS]), and low-amplitude (less than 40 microV) signal (LAS) duration were determined by an automated algorithm from the vector magnitude of the QRS high-pass filtered at 25 Hz and at 40 Hz. Despite marked decreases in pulmonary capillary wedge (27 +/- 7 to 16 +/- 5 mm Hg, p less than 0.001) and right atrial (13 +/- 7 to 7 +/- 4 mm Hg, p less than 0.001) pressures and a 20% increase in cardiac output, there was not a significant change in QRS duration, RMS, or LAS. Before and after therapy late potentials, defined as abnormal QRS duration RMS, or LAS, were present in 14 (52%) patients with filtering at 25 Hz and in 22 (81%) patients with filtering at 40 Hz. The signal-averaged ECG after hemodynamic improvement predicted the results during exacerbation of heart failure in all patients. Thus in patients with advanced heart failure the signal-averaged ECG obtained after hemodynamic improvement reflects the findings during exacerbation of heart failure.

Comparison of thermodilution and transthoracic electrical bioimpedance cardiac outputs

Current methods of measuring cardiac output require the invasive insertion of a thermodilution catheter with its concomitant risks and complications. We examined the noninvasive method of transthoracic electrical bioimpedance (TEB) in comparison with thermodilution cardiac outputs in a sample of 44 critically ill patients with poor left ventricular function (left ventricular ejection fraction less than 30%) and with either ischemic or idiopathic dilated cardiomyopathy. Dyspnea, mitral regurgitation, tricuspid regurgitation, and difference between real and ideal weight had the most marked effects on the correlation between the two methods, with lesser influence by left ventricular ejection fraction, height, weight, hemoglobin, hematocrit, and aortic regurgitation. TEB and thermodilution cardiac outputs were correlated, at r = 0.51 (p less than 0.00009), but the low reliability and low percentage of TEB readings within 0.5 L/min of thermodilution cardiac outputs (31%) renders TEB inadequate for clinical measurement of cardiac outputs in this patient population.

Comparison of frequency of late potentials in idiopathic dilated cardiomyopathy and ischemic cardiomyopathy with advanced congestive heart failure and their usefulness in predicting sudden death

Signal-averaged electrocardiograms were obtained in 62 consecutive patients with advanced congestive heart failure (CHF) undergoing evaluation for possible heart transplantation to determine if late potentials: (1) provide unique information compared to assessment of ventricular ectopic activity on ambulatory electrocardiogram, and (2) identify a subgroup of CHF patients with higher sudden death risk. Patients with a history of cardiac arrest or sustained ventricular tachycardia were excluded. CHF was due to old myocardial infarction in 40 patients and idiopathic dilated cardiomyopathy in 22 patients. Late potentials were present in 16 of 40 (40%) patients with old infarction but in only 3 of 22 (14%) patients with nonischemic CHF (p = 0.03). Twenty-four-hour ambulatory electrocardiograms were obtained in 34 patients (55%). Total ventricular ectopic activity and repetitive forms of ectopy were similar in patients with and without late potentials. Nine patients died suddenly, 9 had nonsudden death, 15 underwent heart transplantation and 29 were alive and well after a mean follow-up of 218 +/- 154 days. At 1 year, the actuarial risk of death was 37% and of sudden death was 20%. Sudden death risk was 12% in patients with late potentials versus 21% in those without (p = 0.73). Thus, the incidence of the arrhythmia substrate producing late potentials depends on the CHF etiology. The signal-averaged electrocardiogram and ambulatory electrocardiogram provide independent information for possible risk assessment in CHF. However, late potentials are poor predictors of sudden death risk when CHF is advanced, possibly due to the heterogeneity of causes of sudden death--ventricular tachycardia being only 1 of many possible mechanisms.

Noninvasive identification of patients at risk for ventricular tachycardia with the signal-averaged electrocardiogram

The signal-averaged electrocardiogram (SAE) is a noninvasive means of detecting cardiac late potentials. Late potentials in patients with coronary artery disease indicate a high risk for the development of ventricular tachycardia. Although the usefulness of the SAE for directing therapy has not yet been clearly established, the test appears to be useful in the stratification of arrhythmia risk in select groups of high-risk patients. As critical care nurses frequently care for these patients, they need to be familiar with tools such as the SAE that may be used in high-risk patient assessment. This article describes the physiologic basis underlying the use of the SAE, the SAE technique, implications for nursing practice, and clinical applications of the SAE.