Scaling submaximal exercise cardiac output and stroke volume: the HERITAGE Family Study.

This study investigated different methods of scaling submaximal cardiac output (Q) and stroke volume (SV) to best normalize for body size (body surface area [BSA], height [Ht], weight [Wt], and fat-free mass [FFM]). Q and SV were measured at both an absolute (50 W) and a relative power output (60 % of VO2max) in 337 men and 422 women, 17 to 65 years of age. Traditional ratio scaling was examined in addition to allometric scaling, where scaling exponents ( B) were determined for each body size variable (x) that best normalized the physiological outcome variables (y) for body size (y = ax(b)). With ratio scaling, regardless of the body size variable (x = BSA, Ht, Wt, FFM), there was no evidence of a linear relationship between x and y (y = Q or SV). A linear relationship is a necessary condition for appropriate normalization. Further, when ratio-scaled variables (e.g., Q/BSA) were correlated to the body size variable (e.g., BSA) by which they were scaled, significant (p

The chemoreflex in young boys and girls.

In order to determine the influence of the chemoreflex on the cardiovascular system of young children, 35 boys and 35 girls (all 7 - 9 years old) performed three minutes of 30 % maximal voluntary contraction (MVC) static handgrip (SHG) exercise followed by four minutes of blood flow occlusion in the previously exercised arm, and then six minutes of passive recovery. Heart rate (HR) and blood pressure (BP) were measured each minute. Twenty girls performed a second occlusion trial to determine reliability. Reliability coefficients for HR (R = 0.51 - 0.78), diastolic (R = 0.46 - 0.81) and systolic (R = 0.57 - 0.78) BP throughout the occlusion trial were moderately high. There was a similar increase in HR (19 +/- 8 vs. 16 +/- 10 %), diastolic (34 +/- 12 vs. 34 +/- 16 %) and systolic (18 +/- 9 vs. 15 +/- 7 %) BP in boys and girls, respectively, during three minutes 30 % MVC exercise. During the occlusion period, diastolic (43 +/- 31 vs. 47 +/- 26 %) and systolic (51 +/- 25 vs. 54 +/- 32 %) BP dropped similarly during minute one but remained elevated significantly above baseline in both boys and girls the entire four-minute period. During the recovery period, minute one SBP and DBP dropped similarly in boys (23 +/- 37, 20 +/- 37 %) and girls (20 +/- 38, 12 +/- 38 %), respectively. In boys and girls DBP remained significantly above baseline the entire recovery period. HR in boys and girls returned to baseline immediately following SHG exercise and remained there through recovery. In conclusion, as reported in adults, the drop in HR to baseline during post-exercise ischemia with a concomitant maintenance of BP significantly above baseline indicates that at least two separate mechanisms, with varying influence, are responsible for HR and BP control in young children. Further, the chemoreflex operates similarly in young boys and girls.

Less invasive Thoratec LVAD insertion: a surgical technique.

Left Ventricular Assist Device (LVAD) implantation is historically a complicated, invasive operation performed on critically ill patients and is often associated with bleeding and multiorgan morbidity. The purpose of this investigation was to devise an LVAD insertion technique, utilizing the concepts of less invasive cardiac surgery, that would be a less complicated operation, with low morbidity, and still meet all the goals of the standard procedure. We describe the technical details of a "less invasive" LVAD implantation.

Prescription and administration of around the clock analgesics in postoperative pediatric cardiovascular surgery patients.

Despite an increased awareness of postoperative pain management in infants and children, they are still often undermedicated. The importance of providing maximum comfort to children following cardiac surgery is accentuated with shortened hospital stays that require early ambulation to achieve early discharge. The purposes of this study were to evaluate the administration of prescribed around the clock (ATC) pain medication and documentation of pain assessment when administering pro re nata (prn) analgesics. A descriptive design was used to study 114 consecutive patients who underwent surgery for congenital heart disease. Administration of ordered ATC medications was best in the sternotomyl > 24 months of age group and poorest in the thoracotomyl < 24 months of age group. The use of the Wong-Baker FACES Pain Rating Scale in patients who were > 36 months of age (n = 71) was 38% for predose evaluation and only 15% for postdose evaluation. Findings suggest that the postoperative pain of infants and young children demands better attention. The administration of prescribed ATC medications is imperative in providing maximal postoperative pain relief in the pediatric cardiovascular surgery patient.

Reproducibility of cardiovascular, respiratory, and metabolic responses to submaximal exercise: the HERITAGE Family Study.

This study determined the reproducibility of cardiovascular, respiratory, and metabolic responses to submaximal cycle ergometer exercise at two power outputs (50 W and 60% VO2max) on each of two separate days in a sample of 390 subjects (198 men and 192 women) participating in the HERITAGE Family Study. The same protocol was conducted across 3 d in an intracenter quality control substudy which included an additional 55 subjects. Reproducibility estimates included technical error, coefficient of variation, and intraclass correlation for each of the selected variables for both subject populations. Further, since the data were collected across four clinical centers, intraclass correlations were also computed separately by clinical center. Most variables were highly reproducible, with coefficients of variation below 9% and intraclass correlations over 0.80. These results were consistent for both subject populations and across all four clinical centers. Reproducibility indicators were generally better at the higher power output. It is concluded that within-subject day-to-day variation and measurement unreliabilities are generally small compared with the between-subject variance in the response to submaximal exercise at each of the clinical centers of the HERITAGE Family Study.

Cardiovascular responses to exercise in children.

The cardiovascular system of children responds to exercise differently than does that of an adult, although the mechanisms behind the differences are unclear. During dynamic exercise, it has been reported that heart rate (HR) response to the initiation of exercise is both faster and slower in children than adults. Furthermore, HR recovery has been reported to be faster in children. During submaximal steady state exercise, HR and total peripheral resistance are higher, while stroke volume [SV (ml)] and cardiac output [Q (L/min)] are lower in children at a given rate of work. At maximal exercise intensities HR is higher while SV and Q are lower in children than adults. Differences in cardiovascular responses to dynamic exercise between young boys and girls have also been reported. The majority of studies report that HR is lower and SV is higher in boys than girls at a given rate of work, although data to the contrary have been reported. These differences seem to be related to larger hearts in the boys. Further, the majority of the studies report that Q is similar in young boys and girls at a given rate of work. Few studies have reported differences between boys and girls at maximal intensities of exercise, and the results of those studies are inconsistent. Less is known about cardiovascular responses of children to static exercise compared with adults. A number of studies have reported that HR response to handgrip exercise is greater in children than adults, while others have reported no difference in this response. Even fewer studies have compared boys and girls in their cardiovascular response to static exercise and the results of these studies are also inconsistent. During prolonged exercise both children and adults exhibit cardiovascular drift (gradual increase in HR and decrease in SV). The direction and degree to which these changes differ between children and adults is unclear, with both greater and lesser responses being reported in children. Few studies have investigated differences in cardiovascular response to prolonged exercise between boys and girls. Those that have, report no difference between young boys and girls.

Cardiovascular responses to treadmill and cycle ergometer exercise in children and adults.

This study was conducted to determine whether submaximal cardiovascular responses at a given rate of work are different in children and adults, and, if different, what mechanisms are involved and whether the differences are exercise-modality dependent. A total of 24 children, 7 to 9 yr old, and 24 adults, 18 to 26 yr old (12 males and 12 females in each group), participated in both submaximal and maximal exercise tests on both the treadmill and cycle ergometer. With the use of regression analysis, it was determined that cardiac output (Q) was significantly lower (P

Cardiovascular responses to submaximal exercise in 7- to 9-yr-old boys and girls.

The purpose of this study was to investigate whether differences exist between boys and girls in submaximal cardiovascular responses to exercise on both the treadmill and cycle ergometer. Twenty-four (12 boys and 12 girls) 7- to 9-yr-old children participated in two maximal (one treadmill and one cycle) and four submaximal tests (two treadmill and two cycle). There were no significant differences between the boys and girls in maximal oxygen consumption (L.min-1 or mL.kg-1.min-1) or physical characteristics except for a significantly larger left ventricular mass in the boys versus the girls (78.8 vs 66.0 g, respectively). Submaximal cardiovascular variables were measured at three different work rates on both exercise modalities. Oxygen consumption at the different work rates was not different between boys and girls on either exercise modality. The trend was for heart rate to be lower and stroke volume higher in boys versus girls, but this difference was only significant for heart rate at 4 miles.h-1 (142.9 vs 155.5 beats.min-1, respectively). It is concluded that in this sample of 7- to 9-yr-old boys and girls there are few significant differences in submaximal cardiovascular responses to exercise on either exercise modality.

Cardiovascular-radical outcome method is effective in complex congenital cardiac lesions.

BACKGROUND: The cardiovascular-radical outcome method is a proactive process of patient care that uses standard critical pathway methodology to reduce negative variation while encouraging positive variation to accelerate recovery. Its effectiveness in patients with complex congenital heart disease is explored. METHODS: Two hundred fourteen consecutive patients with congenital heart disease were cared for using the cardiovascular radical outcome method. Age ranged from 2 days to 19 years (median age, 3 years). Cardiovascular radical outcome method data were compared with the pathway plan data for each patient. RESULTS: Survival was 99% (211 patients) with an overall reduction in stay of 156 days (0.74 day/patient) (p < 0.0001). Only 10 patients (5%) exceeded the pathway plan; 201 (95%) reached the planned length of stay (critical pathway method), and 127 patients (60%) had a shorter length of stay than expected by the critical pathway method. One hundred forty-eight patients (70%), including 95 (64%) with more complex conditions, had a length of stay of 3 days and 18% achieved a 2-day length of stay, the maximal response. The process was most effective in the most complex groups, although preoperative comorbidities influenced outcomes. Outcome assessment demonstrated minimal morbidity and excellent family satisfaction. CONCLUSIONS: The radical outcome method is effective in reducing the length of stay of patients with complex congenital heart disease. The power is in the process rather than the plan, and the method provides optimal patient care and family satisfaction.

Radical outcome method. A new approach to critical pathways in congenital heart disease.

BACKGROUND: Treatment of congenital heart disease has entered a new era of healthcare delivery and cost containment. Critical pathway method (CPM) has been previously demonstrated by us to produce a significant reduction in average length of stay (ALOS) in hospital of -44%. A new approach, radical outcome method (ROM), has produced comparable results that appear to improve over time. The dynamic nature is examined. METHODS AND RESULTS: Two hundred consecutive patients with congenital heart disease were treated by a single surgeon at a single health maintenance organization (HMO) facility. ROM was used in all patients. This method uses seven critical moments at which shortening rather than confirmation of the ALOS is possible. This process is completed by the second post-operative day. Overall mortality was 1%. The 200 patients were divided into two consecutive groups of 100 patients to determine the effectiveness of ROM over time. Fifty sets were matched. ALOS hospital decreased by 29 days (mean, 0.6 d/set), P < .003. Thirty sets who underwent cardiopulmonary bypass had a 16% decrease (P < .03), and 20 sets in whom nonbypass procedures were performed had a decrease of 16% (P < .02). ALOS in hospital for the 50 sets decreased from 3.7 to 3.1 days (-16%, P < .003). Outcome data demonstrated no significant difference. CONCLUSIONS: ROM, a proactive approach to hospital stay, is a dynamic process that reduces ALOS in hospital. This is achieved by both reducing negative variation in the standard CPM and allowing for positive variation. Outcome data confirm that this approach can reduce ALOS in hospital while providing optimal patient care and family satisfaction, a standard for the new era of healthcare delivery.

Individual differences in working memory strategies for reading expository text.

This study investigated whether individual differences in working memory (WM) span are associated with different WM management strategies during the reading of expository text. In Experiment 1, probe questions were presented on line during reading to determine whether thematic information was maintained in WM throughout comprehension. The data indicated that readers across the range of WM span maintained thematic information in WM throughout the reading of a given passage. In Experiment 2, sentence reading times and accuracy for both topic and detail questions were measured in two conditions: when topic sentences were present and when topic sentences were absent. Subjects performed similarly across the range of WM span in the topic-present condition, but lower span subjects performed more poorly on detail questions in the topic-absent condition. In Experiment 3, the topic-present condition of the second experiment was replicated, except that subjects expected to receive questions about details only. Thematic processing and retention of topic and detail information all increased with span. Taken together, these results suggest that, for more difficult text processing tasks, high- and low-span subjects adopt different WM management strategies and these strategies influence what is learned from reading the text.

Intermediate results from the period of the Congenital Heart Surgeons Transposition Study: 1985 to 1989. Congenital Heart Surgeons Society Database.

BACKGROUND: The period of the Congenital Heart Surgeons Society (CHSS) study (1985 to 1989) provided a transition in the treatment of d-transposition of the great arteries. During this unusual time frame neonatal arterial switch (AS) and neonatal or late atrial baffle repair (Senning) were used in near equal proportion at one reporting institution. All the procedures were performed at this single institution, avoiding the variability intrinsic to a multicenter study. Intermediate follow-up of the results is presented. METHODS: During the period of the CHSS study, January 1985 to March 1989, 46 patients were enrolled in the CHSS study at one institution. Forty-four underwent either neonatal arterial (n = 14, 32%) or neonatal atrial (n = 19, 43%) or late atrial (n = 11, 25%) repair of d-transposition of the great arteries. Ages ranged from 4 to 80 days. Overall survival for the entire series was 91% (40/44). The survival of the AS group operate on in the neonatal period was 93% (13/14). The survival of the Senning group was 90% (27/30); late Sennings, 91% (10/11); and neonatal Sennings, 92% (12/13). Six neonatal Sennings were crossovers from the AS group with an 83% survival (5/6). RESULTS: Intermediate follow-up of 5.2 to 9.2 years revealed no late deaths. In the AS group there was no ventricular failure, no arrhythmias, and one reoperation for supravalvar pulmonic stenosis. In the Senning group, there was no ventricular failure, but significant complications developed in 10 patients: cardiac arrhythmias in 7, tachyarrhythmias requiring pharmacologic therapy in 4, and bradyarrhythmias in 3, 2 requiring permanent pacemaker insertion. Left ventricular outflow tract (subpulmonic) stenosis developed in 3 patients, 1 requiring a left ventricular to pulmonary artery conduit and permanent pacemaker. Systemic atrioventricular valve insufficiency has developed in 3 patients. CONCLUSIONS: Results at one reporting institution from the CHSS study during this period of transition from late atrial repair (Senning) to neonatal atrial or arterial repair show comparable early mortality in all groups. However, the intermediate results at a mean of 6.7 years reveal fewer arrhythmic and functional complications in the AS group. The possibility of neonatal repair combined with low early and intermediate morbidity and mortality confirm AS as the treatment of choice for d-transposition of the great arteries.

Comparison of maximal oxygen consumption with oral and nasal breathing.

The major cause of exercise-induced asthma (EIA) is thought to be the drying and cooling of the airways during the 'conditioning' of the inspired air. Nasal breathing increases the respiratory system's ability to warm and humidity the inspired air compared to oral breathing and reduces the drying and cooling effects of the increased ventilation during exercise. This will reduce the severity of EIA provoked by a given intensity and duration of exercise. The purpose of the study was to determine the exercise intensity (%VO2 max) at which healthy subjects, free from respiratory disease, could perform while breathing through the nose-only and to compare this with mouth-only and mouth plus nose breathing. Twenty subjects (11 males and 9 females) ranging from 18-55 years acted as subjects in this study. They were all non-smokers and non-asthmatic. At the time of the study, all subjects were involved in regular physical activity and were classified, by a physician, as free from nasal polyps or other nasal obstruction. The percentage decrease in maximal ventilation with nose-only breathing compare to mouth and mouth plus nose breathing was three times the percentage decrease in maximal oxygen consumption. The pattern of nose-only breathing at maximal work showed a small reduction in tidal volume and large reduction in breathing frequency. Nasal breathing resulted in a reduction in FEO2 and an increase in FECO2. While breathing through the nose-only, all subjects could attain a work intensity great enough to produce an aerobic training effect (based on heart rate and percentage of VO2 max).

Aortic implantation is possible in all cases of anomalous origin of the left coronary artery from the pulmonary artery.

BACKGROUND: Anomalous origin of the left coronary artery from the pulmonary artery (PA) optimally is treated by creation of a multiple coronary system. This study explores the use of aortic implantation employing alternative methods to achieve coronary transfer in all patients, regardless of the site of origin of the anomalous coronary artery, avoiding the problems of bypass grafts and tunnel procedures. METHODS: During the period 1986 to 1994, 11 patients aged 6 months to 8 years (mean age, 2.6 years) underwent repair. Coronary artery origin from the PA included left sinus in 3, posterior in 2, right sinus in 2, intramural aorta with its orifice at the bifurcation of the main and right PA in 1, high left main PA in 1, high at the bifurcation of main and right PA in 1, and anterior in 1. Findings included angina in 4, prior infarctions in 3, ischemia in 7, left ventricular dysfunction in 6, mitral regurgitation in 5, atrial septal defect in 2, and echocardiograms suggestive of endocardial fibrosis in 4. One patient had prior ligation with ventricular dysfunction and collateralization and recanalization. A single patient was asymptomatic. Repair was accomplished by direct transfer using the PA sinus of Valsalva as a button in only 6; tubular reconstruction was used in 4 when the distance was too great to avoid tension; 2 short tubes were constructed with PA wall in 2 of the 3 left sinus origins, whereas 2 long tubes of PA wall were used (1 high on the left side of the main PA and 1 with left anterior descending origin from the anterior sinus of Valsalva in a patient with malrotation [end neo-artery to side aortic reconstruction]); finally, in situ transfer and intraaortic reconstruction (unroofing and anastomosis) was performed in 1 intramural coronary artery. Division of the PA, mobilization of the distal PA, division of the ductus, and direct reanastomosis of the PA was performed in 3 tubular reconstructions, as well as all 6 direct coronary transfers. RESULTS: There were no operative or late deaths. Follow-up of 2 to 100 months (mean, 46 months) revealed no new angina or infarctions, improved function and decreased mitral regurgitation. Echocardiographic and angiographic studies demonstrated patency and prograde flow in the new coronary systems. CONCLUSIONS: Aortic implantation is the treatment of choice for anomalous origin of the left coronary artery. Methods such as direct transfer, tubular reconstruction, and in situ transfer make such implantation possible in all patients regardless of the site of coronary origin, distance from the aorta, or coronary artery configuration.

Role of the clinical nurse coordinator in successful implementation of critical pathways in pediatric cardiovascular surgery patients.

Critical pathways reduce variations in clinical management and achieve quality patient outcomes within a defined time while reducing the average length of stay (ALOS). The critical path is a day-by-day plan that specifies the use and timing of procedures in relation to the stage in the patient's recovery. Variations from that plan are identified and aggressively approached. This article outlines the clinical nurse coordinator's role in utilizing critical pathways for the congenital heart surgery patients. Successful implementation of the pathways using the clinical nurse coordinator's role is supported by analysis of ALOS in 286 patients.

Critical pathway methodology: effectiveness in congenital heart surgery.

Critical pathway methodology has been demonstrated to provide producible reduction in average length of stay (ALOS) in adults in certain diagnostic-related groups and operations such as coronary artery bypass grafting. The efficacy of this approach in congenital heart surgery was explored. Two hundred eighty-six consecutive patients from a health maintenance organization treated by a single surgeon since the institution of diagnostic-related group coding at that health maintenance organization constituted the study group. One hundred fourteen patients were treated at a university hospital without critical pathway methodology (group 1) and 172, subsequently at the health maintenance organization institution using the methodology (group 2). Operation/lesion, age, and diagnostic-related group matching was possible in 61 pairs. Examination of the ALOS Hospital (operative and postoperative days) for the entire cohort revealed a 43.8% reduction in ALOS Hospital (p < 0.0001) and a 39.0% reduction in ALOS Intensive Care Unit (p < 0.0001). There was also significant reduction in ALOS Hospital and ALOS Intensive Care Unit in the operation/lesion-matched subsets. Outcome measures including operative and late mortality, readmission, unscheduled emergency room and clinic visits, and health maintenance organization family assessment survey demonstrated no improvement in outcome with increased hospital stay. Thus, critical pathway methodology when used in patients undergoing a congenital heart operation produces a significant reduction in hospital stay and intensive care unit stay as well as quality patient care with uniformity of outcome.

Maximal vascular conductance in right ventricular myocardial circulation.

With acutely increasing right ventricular (RV) hypertension, failure eventually occurs because of RV ischemia. This study examines the effects of RV hypertension on the diastolic right coronary circulation. Conscious dogs instrumented to measure right coronary artery pressure and blood flow were studied after maximal coronary vasodilation with chromonar. Diastolic coronary pressure-flow relations, described by slope (conductance) and zero-flow, pressure axis intercept (Pf = 0), were generated before and during RV hypertension. Diastolic Pf = 0 increased from 11.8 +/- 6.5 to 17.1 +/- 7.1 (means +/- SD, P < 0.01) Torr, with no change in conductance. During RV hypertension, RV diastolic pressure increased. To examine possible mechanisms for the increase in Pf = 0, pressure-flow relations were generated before and after volume loading, without systolic hypertension. Diastolic Pf = 0 increased from 15.5 +/- 3.1 to 20.8 +/- 4.1 Torr, suggesting that changes in Pf = 0 with RV hypertension were mediated by increased filling pressures. Pressure flow relations were derived from mean right coronary flow and RV driving pressure before and during RV hypertension. Under these conditions, Pf = 0 is close to zero; the use of RV driving pressure provides a method for calculating maximal right coronary conductance.