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PubMed2006

Cardiac monitoring and treatment for children and adolescents with neuromuscular disorders.

Dilated cardiomyopathy, hypertrophic cardiomyopathy, and cardiac rhythm disturbances are important features of certain neuromuscular disorders in children, adolescents, and young adults. This article summarizes the cardiac features seen in patients with Duchenne muscular dystrophy, Becker muscular dystrophy, myotonic dystrophy, Friedreich's ataxia, and Emery-Dreifuss muscular dystrophy. The optimal management of these cardiac features remains contentious, but increasingly these patients are referred for routine cardiological assessment in the absence of symptoms. This article examines the value of routine screening and drug interventions for cardiac complications in asymptomatic and symptomatic individuals with neuromuscular disorders. We recommend a pragmatic approach, actively looking for cardiac conditions which will benefit from early intervention, but avoiding routine screening for asymptomatic conditions in which there is no evidence of benefit from early intervention.

Adolescent↗
PubMed2000

[Treatment of choice and long-term prognosis for ventricular arrhythmias].

Treatment of choice and long-term prognosis of the patients with ventricular arrhythmias are described in terms of prevention of sudden cardiac death and/or recurrence of life-threatening arrhythmias(ventricular tachycardia and ventricular fibrillation). 1) As to the long-term prognosis of ventricular tachyarrhythmias, presence of organic heart disease and degree of cardiac dysfunction are major determining factors. 2) The prognosis of patients with ventricular arrhythmias depends on how sudden cardiac death and life-threatening arrhythmias can be prevented. Among various methods, the electrophysiological test and its guided-therapy for antiarrhythmic drugs are now believed to be the most effective method for the prediction and prevention of the life-threatening events. We propose that the signal averaged electrocardiography is the best screening method as non-invasive approach for the selection of patients undergoing the electrophysiological test. 3) There are still certain limitations as to the prediction of sudden cardiac death and/or prevention of recurrent life-threatening arrhythmias by antiarrhythmic drug treatments in the certain numbers of patients depending on their basal cardiac disease and functional impairment. At present, catheter ablation procedure and implantable cardioverter defibrillator are the choice of the treatment in these cases. 4) In addition to conventional antiarrhythmic drugs, the treatment for the basal cardiac condition is mandatory for the long-term prognosis in the patients with ventricular arrhythmias.

Catheter Ablation↗
PubMed2003

A new terminology for describing left and right ventricular conduction abnormalities.

The words we use to describe a medical condition should match our knowledge of it. Unfortunately, at times, the words we used long ago persist after new knowledge of the subject has become apparent; so it is with left and right ventricular conduction system abnormalities. The words left or right bundle-branch block no longer reflect our knowledge of the condition. Accordingly, this essay describes a new terminology that more accurately describes the numerous abnormalities that compose left and right ventricular conduction system block as well as their numerous subsets. A brief account of the cardiac conditions associated with the conduction defects is also presented.

Bundle-Branch Block↗
PubMed1992

Sodium- and calcium-dependent steps in the mechanism of neonatal rat cardiac myocyte killing by ionophores. I. The sodium-carrying ionophore, monensin.

Toxicosis by monensin, a Na(+)-selective ionophore, induces skeletal and cardiac muscle necrosis. Cultured neonatal rat cardiac myocytes were killed by monensin (greater than 0.2 micrograms/ml) beginning at 30 min and completing by 60-90 min. Other cultured cell types presumably lacking excitable membranes were not killed by monensin under these conditions. Cardiac myocytes were also killed by nigericin and nonactin (monovalent cation-carrying ionophores with low ion selectivity), but not by valinomycin, which has a high selectivity for K+. Monensin-induced killing was associated with formation of blebs in cell membranes and subsequent swelling of the cells during the early phases of killing, whereas surface membranes of cells permeabilized to trypan blue dye contained discrete small holes visible by scanning electron microscopy. Monensin-induced killing occurred at extracellular Na+ concentrations greater than or equal to 10 mM, but not when Li+, K+, Cs+, Rb+, or choline ions replaced Na+ at concentrations up to 0.15 M. Killing was prevented at extracellular pH values less than or equal to 6.4 and was enhanced by ouabain, an inhibitor of Na+/K(+)-ATPase-mediated Na+ transport. Several characteristics of monensin-induced cardiac myocyte killing were similar to those observed during killing induced by the Ca(2+)-carrying ionophore, A23187 plus Ca2+, including a requirement for extracellular Ca2+ concentrations greater than 0.5 mM, inhibition by Mn2+ and Ni2+, and an associated stimulation of arachidonic acid release. The cell killing characteristics are consistent with a monensin-induced Na+ influx which admits toxic levels of extracellular Ca2+ to the cytoplasm of cells with excitable membranes, possibly via Na+/Ca2+ antiporter protein(s).

Animals↗
PubMed1998

Truncus arteriosus: ten-year experience with homograft repair in neonates and infants.

BACKGROUND: Early complete repair of truncus arteriosus with homograft reconstruction of the right ventricular outflow tract was performed and long-term results were evaluated. METHODS: Review of 46 consecutive patients with truncus arteriosus who underwent primary correction between June 1987 and May 1997 was performed. Ages ranged from 21 days to 7.2 years (median, 62 days) and weights from 1.8 to 21.5 kg (median, 3.4 kg). Ten patients were operated on before 1 month of age, 20 between 1 and 3 months, 13 between 3 months and 1 year, and 3 at an older age. Associated cardiac conditions were encountered frequently, the most common being coronary artery anomalies (n = 16), truncal valve incompetence (n = 12), and interrupted aortic arch (n = 5). The right ventricular outflow tract was reconstructed with an aortic (n = 28) or a pulmonary homograft (n = 18). RESULTS: There were two hospital deaths (4.3%). Both patients had severe truncal valve regurgitation and interrupted aortic arch together with other unfavorable conditions. Survival in uncomplicated truncus arteriosus was 100%. Follow-up was from 3 months to 10 years (mean, 36 months). There was one late death 4 months after the initial repair, presumably because of cardiac reason. Actuarial survival was 93% at 4 months and beyond. Actuarial freedom of reoperation in the 27 hospital survivors with aortic homografts was 43% at 75 months; it was 73% at 62 months in the 17 patients surviving with pulmonary homografts. CONCLUSIONS: Neonatal or early infancy complete repair is the treatment with the best potential for survival. The homograft remains our conduit of choice to establish continuity between the right ventricle and the pulmonary artery. Management of severe truncal valve incompetence remains a surgical challenge.

Actuarial Analysis↗
PubMed2001

Screening of ischemic heart disease with cavernous artery blood flow in erectile dysfunctional patients.

Erection is a hemodynamic event and accordingly, erectile dysfunction (ED) is closely related with ischemic heart disease. We should confirm that the cardiac condition of the ED patient is safe enough to perform sexual intercourse prior to beginning treatment for ED. Asymptomatic ischemic heart disease cannot be diagnosed only in an interview, but it's difficult to perform cardiac exercise tests on all patients complaining of ED. Therefore, screening methods to evaluate patients who should undergo exercise tests are needed. Sixty patients with erectile dysfunction participated in this study. Physical examinations, interviews, and color Doppler examinations were conducted. Chest X-rays and electrocardiograms of all patients in the resting position were obtained, as were electrocardiograms following exercise. Echocardiograms, treadmill test results, thallium exercise scintigrams, and coronary angiograms were obtained as required for diagnosis. Two patients were excluded because they had obvious arteriogenic ED due to perineal injury. Fifty-eight patients underwent Doppler evaluations of their cavernous arteries and heart exercise tests. Fourteen patients (24.1%) were diagnosed with ischemic heart disease. Although six of them had already been diagnosed with ischemic heart disease, eight were newly diagnosed by the exercise tests. Cardiovascular risk factors such as advanced age, hyperlipidemia, diabetes mellitus, hypertension, smoking, and obesity were not sufficient predictive factors. The mean peak systolic velocity of the patients without ischemic heart disease was 34.6 cm/s vs 22.0 cm/s in those with ischemic heart disease. Only 3.7% of patients whose peak systolic velocity in the cavernous artery was equal to or exceeded 35 cm/s had ischemic heart disease. On the other hand, 41.9% of patients with peak systolic velocity of less than 35 cm/s had ischemic heart disease. The sensitivity of peak systolic velocity against ischemic heart disease was 92.9%, and specificity was 59.1%. In ED patients, incidences of complications involving symptomatic or asymptomatic ischemic heart disease were found to be high. The peak systolic velocity in the cavernous artery is thought to be a useful predictive factor of ischemic heart disease in ED patients. When a patient reveals a peak systolic velocity of less than 35 cm/s, he should undergo heart exercise tests prior to treatment of ED.

Adult↗
PubMed1980

[Experience with computed transmission tomography of the heart in vivo].

Cardiac computed tomography in its present form provides useful information about the heart for clinical use in patients with heart disease and for investigative work in such patients and living animals. Its great reconstructive power and unmatched density resolution are particularly advantageous in the study of ischemic heart disease. Because of its non-invasive character cardiac computed tomography has the potential of becoming an effective screening tool for large numbers of patients with suspected or known coronary heart disease. Other cardiac conditions such as valve disease and congenital lesions can also be examined with high diagnostic yield. However presently available scanners suffer from low repetion rate, long scan times and the fact that only one transverse cardiac level at a time can be obtained. The development which must be accomplished in order to eliminate these weaknesses is technically feasible. The availability of a dynamic cardiac scanner would greatly benefit the treatment of patients with heart disease and facilitate the inquiry into the pathophysiology of such diseases.

Angina Pectoris↗
PubMed1989

Circulatory Support 1988. Weaning and bridging.

After a patient has been supported with a circulatory assist device, the expected outcomes are weaning, bridging, or discontinuation of support. An early insertion of the device will avoid deterioration of the heart and other organs to an irreversible condition. Cardiac assistance for a minimum of 24 hours is recommended with a mild dose of anticoagulant. It is necessary to monitor the hemodynamic functions during circulatory support and weaning. Most of the mechanical devices are quite reliable, and complications during ventricular assist are easily managed. The patient should be in the same condition as in ordinary elective transplant candidate before transplantation. Patients with an artificial heart or ventricular assist device should not be on the priority emergency list for cardiac transplantation. Patients suffering from cardiogenic shock can be stabilized with a ventricular assist device to allow the heart to recover or be provided with other treatment. A circulatory support device can also be used as a bridge for patients awaiting a cardiac transplant.

Assisted Circulation↗
PubMed2005

Effect of skin surface cooling on central venous pressure during orthostatic challenge.

Orthostatic stress leads to a reduction in central venous pressure (CVP), which is an index of cardiac preload. Skin surface cooling has been shown to improve orthostatic tolerance, although the mechanism resulting in this outcome is unclear. One possible mechanism may be that skin surface cooling attenuates the drop in CVP during an orthostatic challenge, thereby preserving cardiac filling. To test this hypothesis, CVP, arterial blood pressure, heart rate, and skin blood flow, as well as skin and sublingual temperatures, were recorded in nine healthy subjects during lower body negative pressure (LBNP) in both normothermic and skin surface cooling conditions. Cardiac output was also measured via acetylene rebreathing. Progressive LBNP was applied at -10, -15, -20, and -40 mmHg at 5 min/stage. Before LBNP, skin surface cooling lowered mean skin temperature, increased CVP, and increased mean arterial blood pressure (all P < 0.001) but did not change mean heart rate (P = 0.38). Compared with normothermic conditions, arterial blood pressure remained elevated throughout progressive LBNP. Although progressive LBNP decreased CVP under both thermal conditions, during cooling CVP at each stage of LBNP was significantly greater relative to normothermia. Moreover, at higher levels of LBNP with skin cooling, stroke volume was significantly greater relative to normothermic conditions. These data indicate that skin surface cooling induced an upward shift in CVP throughout LBNP, which may be a key factor for preserving preload, stroke volume, and blood pressure and improving orthostatic tolerance.

Adaptation, Physiological↗
PubMed2004

Cardiac myocyte-specific HIF-1alpha deletion alters vascularization, energy availability, calcium flux, and contractility in the normoxic heart.

At a resting pulse rate the heart consumes almost twice-as much oxygen per gram tissue as the brain and more than 43 times more than resting skeletal muscle (1). Unlike skeletal muscle, cardiac muscle cannot sustain anaerobic metabolism. Balancing oxygen demand with availability is crucial to cardiac function and survival, and regulated gene expression is a critical element of maintaining this balance. We investigated the role of the hypoxia-inducible transcription factor HIF-1alpha in maintaining this balance under normoxic conditions. Cardiac myocyte-specific HIF-1alpha gene deletion in the hearts of genetically engineered mice caused reductions in contractility, vascularization, high-energy phosphate content, and lactate production. This was accompanied by altered calcium flux and altered expression of genes involved in calcium handling, angiogenesis, and glucose metabolism. These findings support a central role for HIF-1alpha in coordinating energy availability and utilization in the heart and have implications for disease states in which cardiac oxygen delivery is impaired. Heart muscle requires a constant supply of oxygen. When oxygen supply does not match myocardial demand cardiac contractile dysfunction occurs, and prolongation of this mismatch leads to apoptosis and necrosis. Coordination of oxygen supply and myocardial demand involves immediate adaptations, such as coronary vasodilatation, and longer-term adaptations that include altered patterns of gene expression (2-4). How the expression of multiple genes is coordinated with oxygen availability in the heart and the impact of oxygen-dependent gene expression on cardiac function are insufficiently understood. Further elucidating these relationships may help clarify the molecular pathology of various cardiovascular disease states, including ischemic cardiomyopathy and myocardial hibernation (5, 6).

Animals↗
PubMedDate not supplied

Management of cerebral embolism of cardiac origin.

The cardiac conditions most commonly associated with cerebral embolism are rheumatic heart disease (RHD), atherosclerotic heart disease (myocardial infarction and atrial arrhythmias) and other kinds of nonvalvular atrial fibillation (AF). The natural history of cerebral embolism from these cardiac sources is reviewed. Virtually all rheumatic hearts producing emboli have mitral stenosis, but not all of them are in AF. Of patients with RHD, 10--20% will experience a systemic embolus, and approximately half will have a recurrence, usually early. Of patients with a myocardial infarction, 5--12% will have a clinically apparent systemic embolus, and one-third to one-half have a recurrence, usually early. As many as 10--20% of patients with nonrheumatic AF have a systemic embolus. Anticoagulation reduces systemic embolism to 10--20% of the natural incidence in RHD, and it reduces embolic recurrences to 10--20% of the natural recurrence rate. Anticoagulation diminishes the incidence of emboli in myocardial infarction to 25% of the natural incidence. It is not known what effect anticoagulation has on the incidence of embolism in nonrheumatic AF. The data regarding the effect of valvulotomy and prosthetic valve placement in RHD are briefly reviewed. Recommendations are made for the use and timing of anticoagulation based on the available data.

Anticoagulants↗
PubMed2003

Reductions in systemic and skeletal muscle blood flow and oxygen delivery limit maximal aerobic capacity in humans.

BACKGROUND: A classic, unresolved physiological question is whether central cardiorespiratory and/or local skeletal muscle circulatory factors limit maximal aerobic capacity (VO2max) in humans. Severe heat stress drastically reduces VO2max, but the mechanisms have never been studied. METHODS AND RESULTS: To determine the main contributing factor that limits VO2max with and without heat stress, we measured hemodynamics in 8 healthy males performing intense upright cycling exercise until exhaustion starting with either high or normal skin and core temperatures (+10 degrees C and +1 degrees C). Heat stress reduced VO2max, 2-legged VO2, and time to fatigue by 0.4+/-0.1 L/min (8%), 0.5+/-0.2 L/min (11%), and 2.2+/-0.4 minutes (28%), respectively (all P<0.05), despite heart rate and core temperature reaching similar peak values. However, before exhaustion in both heat stress and normal conditions, cardiac output, leg blood flow, mean arterial pressure, and systemic and leg O2 delivery declined significantly (all 5% to 11%, P<0.05), yet arterial O2 content and leg vascular conductance remained unchanged. Despite increasing leg O2 extraction, leg VO2 declined 5% to 6% before exhaustion in both heat stress and normal conditions, accompanied by enhanced muscle lactate accumulation and ATP and creatine phosphate hydrolysis. CONCLUSIONS: These results demonstrate that in trained humans, severe heat stress reduces VO2max by accelerating the declines in cardiac output and mean arterial pressure that lead to decrements in exercising muscle blood flow, O2 delivery, and O2 uptake. Furthermore, the impaired systemic and skeletal muscle aerobic capacity that precedes fatigue with or without heat stress is largely related to the failure of the heart to maintain cardiac output and O2 delivery to locomotive muscle.

Adenosine Triphosphate↗
PubMed1986

Sympathectomy in the treatment of angina and arrhythmias.

Sympathectomy has been used as treatment for several different cardiac conditions. These include classic angina pectoris, Prinzmetal's angina, paroxysmal atrial tachycardia, ventricular tachycardia, and long QT syndrome. To understand the rationale of such treatment, the innervation of the human heart is reviewed with discussion of the cardiac plexus and coronary innervation. Results in published studies are summarized and discussed.

Angina Pectoris↗
PubMed2005

Comparative effectiveness of total population versus disease-specific neural network models in predicting medical costs.

The objective of this research was to compare the accuracy of two types of neural networks in identifying individuals at risk for high medical costs for three chronic conditions. Two neural network models-a population model and three disease-specific models-were compared regarding effectiveness predicting high costs. Subjects included 33,908 health plan members with diabetes, 19,264 with asthma, and 2,605 with cardiac conditions. For model development/ testing, only members with 24 months of continuous enrollment were included. Models were developed to predict probability of high costs in 2000 (top 15% of distribution) based on 1999 claims factors. After validation, models were applied to 2000 claims factors to predict probability of high 2001 costs. Each member received two scores-population model score applied to cohort and disease model score. Receiver Operating Characteristic (ROC) curves compared sensitivity, specificity, and total performance of population model and three disease models. Diabetes-specific model accuracy, C = 0.786 (95%CI = 0.779-0.794), was greater than that of population model applied to diabetic cohort, C = 0.767 (0.759-0.775). Asthma-specific model accuracy, C = 0.835 (0.825-0.844), was no different from that of population model applied to asthma cohort, C = 0.844 (0.835-0.853). Cardiac-specific model accuracy, C = 0.651 (0.620-0.683), was lower than that of population model applied to cardiac cohort, C = 0.726 (0.697-0.756). The population model predictive power, compared to the disease model predictive power, varied by disease; in general, the larger the cohort, the greater the advantage in predictive power of the disease model compared to the population model. Given these findings, disease management program staff should test multiple approaches before implementing predictive models.

Age Factors↗
PubMedDate not supplied

Enhanced external counterpulsation--a therapeutic option for patients with chronic cardiovascular problems.

EECP is a non-invasive outpatient treatment for cardiovascular disease refractory to medical and/or surgical therapy. It has been cleared by the Food and Drug Administration for the treatment of a variety of cardiac conditions including congestive heart failure and chronic stable angina. A course of therapy consists of 35 one-hour treatments given once or twice daily. Augmented diastolic pressure and retrograde flow improve myocardial perfusion, while systolic unloading reduces cardiac workload and oxygen requirements. As a result of this treatment, most patients experience increased time to onset of ischemia, increased exercise tolerance, a reduction in the number and severity of anginal episodes, and improved quality of life. Evidence has been presented that this effect lasts well beyond the immediate post-treatment period with some patients symptom-free for several years. Because patients principally seek medical care to live longer or feel better, heart programs need to offer their patients the latest medical advances which have the potential of improving patient survival and health status (symptoms, functioning, and quality of life). Heart programs face a challenging economic future. Increased competition makes it necessary to implement strategies for market differentiation. Those programs most attuned to what their patients define as critical to quality would be most likely to succeed. Over the past decade, there have been a growing number of patients with chronic angina who have exhausted the standard revascularization armamentarium. Because coronary artery bypass grafts occlude and restenosis occurs at angioplasty sites, many patients no longer have suitable coronary anatomy for additional procedures. Also, as the population ages, the proportion of patients with diffuse coronary disease, congestive heart failure, significant co-morbid illness, and poor functional status increases. The incapacitating effects of angina on patients' abilities to work, maintain regular social interactions, and participate in the usual activities of daily living are well described. In spite of the ongoing successes of catheter-based revascularization techniques, the population of patients with intractable angina continues to grow; and ironically, advancements in medical therapy have resulted in an increasing number of patients who are living with severe left ventricular dysfunction and congestive heart failure. Recent studies have estimated that approximately 5-15% of patients undergoing coronary angiography may be considered to have advanced coronary artery disease. Considering that 1,713,000 cardiac catheterizations were performed in 1996 in the United States, approximately 100,000-250,000 patients per year may be eligible for newer treatments for coronary artery disease. More recent statistics in the AHA Heart and Stroke Update report that in 2001, nearly one million patients had coronary artery bypass graft surgery or percutaneous coronary intervention, (Figure 1). Of these, 125,650 patients experienced persistent angina.

Activities of Daily Living↗
PubMed2003

The association between emotional upset and cardiac arrhythmia during daily life.

Ventricular arrhythmia exhibits considerable within-subject variability that cannot be attributed to clinical status alone. This investigation examined the extent to which cardiac arrhythmia was associated with psychological and physical factors assessed during the hour preceding arrhythmic or nonarrhythmic activity. Approximately twice hourly, 46 patients randomly completed a diary assessing mood and physical symptoms during 24-hr electrocardiographic monitoring. Greater negative emotion was associated with increased arrhythmia. Additionally, greater negative emotion was significantly associated with increased arrhythmia among participants in a low left ventricular ejection fraction group (LVEF). However, this relationship between negative emotion and arrhythmia was not observed among higher LVEF participants. These findings contribute to a larger body of evidence suggesting that negative moods may exacerbate cardiac conditions.

Adult↗
PubMed1988

Altitude, training and human performance.

The effect of altitude on human performance is complex. Numerous variables are known to change from sea-level measures. Maximum aerobic power is depressed as ascent occurs and this impairs the ability to work maximally. While changes in haematological variables would theoretically counterbalance the loss in aerobic power, they have not been shown to do so. The environmental stress of cold may have positive effects on aerobic capacity at altitude, but this has been little investigated in humans. Pulmonary ventilation increases with altitude and the measure of hypoxic ventilatory response holds some promise of predicting humans who may benefit from altitude conditioning. Cardiac function is well maintained while lung function is not. The preferred fuel for exercise at altitude seems to be fat, while carbohydrate metabolism is dramatically changed. Much is not known of high altitude anorexia and muscle mass loss. Conditioning at altitude is known to benefit performance at altitude. The evidence for a sea-level benefit from altitude training as yet remains elusive. While selected individuals may benefit, the reasons why have not been determined.

Altitude↗
PubMed2004

Measurement of continuity of care in cardiac patients: reliability and validity of an in-person questionnaire.

BACKGROUND: Breaks in continuity of care occur during the care of patients with cardiac conditions, such as congestive heart failure (CHF) and atrial fibrillation (AF), during their hospitalization, the discharge process or follow-up care. Recently, to measure continuity of care for such patients, a comprehensive questionnaire was developed to reflect the cardiac patient's perspective on multifaceted aspects of continuity of care. OBJECTIVE: To examine the psychometric properties of an in-person interview questionnaire for the measurement of continuity of care in patients recently hospitalized with CHF or AF. METHODS: The Heart Continuity of Care Questionnaire (HCCQ) was administered to 350 cardiac patients (176 with CHF and 174 with AF) at least six months after discharge from hospitals in two urban centres. The questionnaire was assessed by item and principal components analysis. Factors derived from principal components analysis were assessed for internal consistency and construct validity against variables of comorbidity, health status and symptom severity. RESULTS: A principal components analysis produced three subscales. These subscales were internally consistent, and demonstrated construct validity through expected correlations with other variables and theoretical constructs. CONCLUSION: The present study supports the reliability and validity of the HCCQ for measuring continuity of care. The HCCQ subscales correspond to the theoretical components of continuity of care that have been proposed, namely relational, informational and management continuity. The HCCQ subscales may be of value for identifying problems in continuity of care and for evaluating interventions aimed at improving continuity of care for cardiac patients after hospital discharge.

Adult↗