Factors influencing efficacy of exogenous surfactant in acute lung injury

Exogenous surfactant is currently being tested as a therapeutic modality for patients with acute respiratory distress syndrome (ARDS). Animal studies have shown that several factors may influence the efficacy of this treatment modality. These factors include the surfactant delivery method used (instillation vs. aerosolization), the timing of surfactant treatment over the course of injury, the specific surfactant preparation used, and the dose of surfactant administered. Each of these factors alone and together may influence the interaction of the exogenous surfactant with the host's alveolar environment. This, in turn, may dictate how a specific patient responds to a particular surfactant treatment strategy. It is suggested that patients at an early stage of lung injury will benefit from aerosolized exogenous surfactant whereas large quantities of an instilled exogenous surfactant may be necessary at later stages of injury. Future studies will clarify how a specific surfactant treatment strategy should be chosen for an individual patient with ARDS.

Lung parenchyma and type II cell morphometrics: effect of surfactant treatment on preterm ventilated lamb lungs

The effect of exogenous surfactant treatment on lung and type II cell structure of ventilated lambs of 137-138 days gestational age was studied. Thirty-four lambs were delivered and randomized to control or 100 mg/kg of natural sheep surfactant treatment groups. Lungs from one group of lambs not treated with surfactant were fixed before ventilation, and the other animals were ventilated to maintain normal blood gas values for 3, 24, or 48 h. Morphometric assessment of the inflation-fixed lung parenchyma of ventilated lungs was compared with the architectural appearance of alveoli and alveolar ducts in the unventilated lungs. Mechanical ventilation resulted in distension of alveolar ducts accompanied by the shallowing and loss of well-defined alveoli and areas of atelectasis at 3 h. These abnormalities increased in severity after 24 and 48 h of ventilation. Surfactant treatment before ventilation significantly reduced the extent and degree of dilatation and concomitant atelectasis. The fraction of normal parenchyma was 38 +/- 7% in untreated lambs vs. 64 +/- 6% in treated lambs after 24 h of ventilation. After 48 h of ventilation, significant differences between control (39 +/- 6%) and surfactant-treated (55 +/- 6%) lambs were still evident. Alveolar type II cells contained approximately 15% lamellar bodies by volume. Neither surfactant treatment nor time of ventilation altered the volume density of lamellar bodies or other organelles, except for a decrease in glycogen from 8% in nonventilated lungs to 2.5% in lungs ventilated for 24 h. These findings indicate that a surfactant treatment at birth results in the maintenance of more normal parenchyma with less atelectasis during prolonged ventilation of the immature lung.(ABSTRACT TRUNCATED AT 250 WORDS)

Exogenous surfactant therapy in thirty-eight hour lung graft preservation for transplantation

Previous work in our laboratory has documented alterations in surfactant composition and function after prolonged lung graft storage and transplantation in dogs (Am Rev Respir Dis 1993;148:208-15). To determine whether exogenous surfactant therapy was beneficial, we pretreated 13 canine double lung blocks with prostacyclin, flushed them with 4 degrees C modified Euro-Collins solution, and stored them at 4 degrees C for 37 to 38 hours. After left lung transplantation and immediately before reperfusion, eight dogs were administered 50 mg of bovine lung lipid extract surfactant per kilogram (50 mg/ml) directly into the left main bronchus and five served as nontreated control animals. Blood gases, peak inspired pressures, and individual pulmonary artery blood flows were measured every 30 minutes during 6 hours of reperfusion. The native right and transplanted left lungs were then lavaged and surfactant large and small aggregates and protein yields were analyzed. All nontreated animals had physiologic evidence of severe ischemia-reperfusion lung injury during reperfusion. Three of eight dogs treated with bovine lung lipid extract surfactant had near normal lung function at 6 hours of reperfusion, as reflected by maintenance of an oxygen tension/inspired oxygen fraction ratio of more than 400 mm Hg and a normal carbon dioxide tension. Five of eight dogs did not respond to surfactant therapy and had decreases in gas exchange identical to those of the control animals. Blood flow through the left pulmonary artery was maintained in the three animals that responded to exogenous surfactant, whereas flow significantly decreased to the left lung in all other animals, reflecting the patterns of gas exchange. In addition, the ratio of poorly functioning small surfactant aggregates to the well-functioning large aggregates isolated from lung lavage after 6 hours of reperfusion was decreased in surfactant-treated animals, especially in those exhibiting a beneficial physiologic response to surfactant therapy. We conclude that therapy with bovine lung lipid extract surfactant can result in excellent preservation of lung grafts after prolonged storage and transplantation, but that the results are not consistent. Further investigations are required to determine the factors responsible for the differential response to surfactant therapy.

Altered alveolar surfactant is an early marker of acute lung injury in septic adult sheep

The purpose of this study was to characterize changes in the endogenous surfactant system in adult sheep rendered septic via cecal ligation and perforation (CLP). Forty-eight hours after CLP, septic animals had significant increases in mean pulmonary artery pressure (PAP) (p < 0.01), cardiac index (CI) (p < 0.01), and arterial lactate (p < 0.05) values compared with their respective baseline values, while the same measurements in a sham-operated control group did not change significantly. The changes in the septic group were associated with significantly lower PaO2 (p < 0.05) and alveolar to arterial (A-a) oxygen gradient values (p < 0.01) at 48 h compared with baseline measurements. No changes in oxygenation occurred within the sham-operated group. Surfactant phospholipid (PL) composition and surface activity measurements of isolated alveolar surfactant aggregate forms were similar for the two groups at 48 h. However, the ratio of poorly functioning small aggregate forms (SA) to superior functioning large aggregates (LA) was significantly increased in the septic versus the sham-operated animals (p < 0.01). This was associated with significantly decreased surfactant protein A (SP-A), B (SP-B), and C (SP-C) levels in septic versus sham-operated animals (p < 0.05). We conclude that sepsis-associated lung injury resulted in altered alveolar surfactant aggregate forms. These changes, together with altered surfactant protein levels, may represent a very sensitive marker of acute lung injury in high-risk patients. Furthermore, these findings suggest that exogenous surfactant given at an early stage of lung injury may mitigate progressive lung dysfunction.

Clinical and morphologic expression of hypertrophic cardiomyopathy in patients > or = 65 years of age

Hypertrophic cardiomyopathy (HC) is most often identified in patients in the second through fifth decades of life, but has been increasingly recognized in older patients. The present report characterizes morphologic and clinical features of HC in 134 consecutively studied patients aged > or = 65 years referred to a tertiary center. Echocardiographic or clinical evaluation, or both, was performed in 134 patients aged 65 to 85 years (mean 72) at most recent evaluation. Selected findings were compared with those in 64 youthful patients with HC aged 15 to 35 years (mean 25). Most elderly patients (120 of 134, 90%) developed marked symptoms that usually became evident after age 55 years; 94 of 120 experienced sustained improvement with medical treatment or operation. Elderly patients had relatively mild left ventricular (LV) wall thickening (20 +/- 3 mm), generally confined to the septum. In most (i.e., 68%), septal hypertrophy was uniformly distributed with parallel right and left borders and associated with elliptical LV cavity shape; however, in 32%, an inhomogeneously hypertrophied septum bulged into the left ventricle, disrupting normal cavity shape. Dynamic subaortic obstruction was present under basal or provocable conditions in a particularly small LV outflow tract in 103 of 134 patients (77%), and was usually produced by relatively restricted excursion of the anteriorly displaced mitral leaflets and posterior septal motion. HC is characterized by age-related differences in both clinical and morphologic expression. Elderly patients with HC characteristically demonstrate onset of cardiac symptoms late in life, as well as distinctive LV morphology and dynamics of outflow obstruction.

Surface-area cycling of different surfactant preparations: SP-A and SP-B are essential for large-aggregate integrity

Surface-area cycling is an in vitro procedure for the conversion of large into small surfactant aggregates. In this procedure a tube containing a surfactant suspension is rotated end-over-end at 37 degrees C so that the surface area of the suspension changes twice each cycle. We have utilized this method to study the mechanisms involved in aggregate conversion. Several different surfactant preparations were analysed: (1) bovine natural surfactant, a sucrose-gradient-purified material containing surfactant phospholipid and surfactant-associated proteins (SP-) SP-A, SP-B and SP-C; (2) bovine lipid-extract surfactant, which contains the surfactant phospholipids and SP-B and SP-C; (3) mixtures of dipalmitoyl phosphatidylcholine and phosphatidylglycerol (7:3, w/w) reconstituted with one or more surfactant proteins. Aggregate conversion was measured by phosphorus analysis of a 40,000 g supernatant (small aggregate) and pellet (large aggregates) before and after surface-area cycling. Surface-area cycling of lipid extract surfactant or lipids plus SP-B or SP-C resulted in rapid aggregate conversion. Lipids alone were not converted. Only a small percentage of purified natural surfactant was converted into small aggregates. Addition of SP-A to lipid extract surfactant could inhibit aggregate conversion of this material, but this was only observed when an additional 1% (w/w) of SP-B was added to the lipid extract. It is concluded that SP-A is important for large-aggregate integrity. It appears that SP-A acts in conjunction with SP-B. The presence of SP-B and/or SP-C is required for aggregate conversion; it is proposed that this reflects the necessity for lipid adsorption in aggregate conversion.

Corticosteroids and fetal intervention interact to alter lung maturation in preterm lambs

The relationship between cortisol infusion and time of fetal catheterization on postnatal lung function of prematurely delivered lambs was investigated with the hypothesis that the intervention of catheterization would alter fetal responsiveness to the maturational effects of corticosteroids. Fetal catheterization was performed on d 117 or on d 122 of gestation. Cortisol or saline control infusions were begun on d 126, with delivery 60 h later on d 128. The animals were ventilated for 1.25 h after delivery, and compliance, the ventilation efficiency index, labeled albumin leak into and out of the lungs, alveolar and lung saturated phosphatidylcholine and surfactant protein A were measured to evaluate lung performance and biochemical indicators of maturation. Cortisol improved compliance and ventilation efficiency and decreased labeled albumin recovery without changing alveolar saturated phosphatidylcholine or surfactant protein A in the animals catheterized at 122 d relative to 122-d saline-infused animals. However, the animals catheterized at 117 d and infused with saline were as mature as assessed by compliance and ventilation efficiency as the 122-d cortisol-treated animals. The 117-d cortisol-infused animals had significantly augmented lung function relative to either 117-d saline-infused or 122-d cortisol-treated lambs and were the only group that had increased alveolar surfactant protein A and lung saturated phosphatidylcholine pool sizes. This study demonstrates that the response of the fetal lung to a maturational agent such as cortisol is dependent on the history of previous fetal interventions.

Aerosolized versus instilled exogenous surfactant in a nonuniform pattern of lung injury

Previous studies have shown that the underlying patterns of lung injury influence subsequent responses to aerosolized exogenous surfactant. The purpose of this study was to compare aerosolized versus tracheally instilled surfactant in a nonuniform lung injury. Adult sheep underwent whole lung lavage with subsequent HCl instillation into the right middle lobe (RML) and lingula (LING) to create a nonuniform injury. Animals were treated with either nebulized surfactant (Neb.Surf.), tracheally instilled surfactant (Inst.Surf.), or nebulized saline (Neb. Saline). PaO2, alveolar-arterial O2 gradient (PAO2-PaO2), PaCO2, and peak inspiratory pressure (PIP) values all significantly improved during 180 min of continuous aerosolization for Neb.Surf. animals compared with pretreatment values (p < 0.01) and with the other two treatment groups (p < 0.01). Although PaO2 and (PAO2-PaO2) values improved for the Inst.Surf. group by 180 min after treatment (p < 0.05), PaCO2 and PIP values were significantly increased 30 min after surfactant instillation (p < 0.05). Neb. Saline animals had no significant changes in physiologic parameters over 180 min. Approximately 8% of the total aerosolized surfactant deposited in lung tissue was recovered from the more severely damaged RML and LING, compared with approximately 50% of the total instilled surfactant recovered from these lobes. This resulted in significantly greater percentages of the total aerosolized surfactant deposited in each of the remaining lobes compared with the percent deposition of instilled surfactant (p < 0.05). Both the underlying pattern of lung injury and the exogenous surfactant delivery technique may influence clinical responses to surfactant therapy in patients with the adult respiratory distress syndrome (ARDS).

Degradation of surfactant-associated protein B (SP-B) during in vitro conversion of large to small surfactant aggregates

Pulmonary surfactant obtained from lung lavages can be separated by differential centrifugation into two distinct subfractions known as large surfactant aggregates and small surfactant aggregates. The large-aggregate fraction is the precursor of the small-aggregate fraction. The ratio of the small non-surface-active to large surface-active surfactant aggregates increases after birth and in several types of lung injury. We have utilized an in vitro system, surface area cycling, to study the conversion of large into small aggregates. Small aggregates generated by surface area cycling were separated from large aggregates by centrifugation at 40,000 g for 15 min rather than by the normal sucrose gradient centrifugation. This new separation method was validated by morphological studies. Surface-tension-reducing activity of total surfactant extracts, as measured with a pulsating-bubble surfactometer, was impaired after surface area cycling. This impairment was related to the generation of small aggregates. Immunoblot analysis of large and small aggregates separated by sucrose gradient centrifugation revealed the presence of detectable amounts of surfactant-associated protein B (SP-B) in large aggregates but not in small aggregates. SP-A was detectable in both large and small aggregates. PAGE of cycled and non-cycled surfactant showed a reduction in SP-B after surface area cycling. We conclude that SP-B is degraded during the formation of small aggregates in vitro and that a change in surface area appears to be necessary for exposing SP-B to protease activity.

Physiologic responses and distribution of aerosolized surfactant (Survanta) in a nonuniform pattern of lung injury

The underlying pattern of lung injury in patients with the adult respiratory distress syndrome (ARDS) may be nonuniform. The purpose of this study was to document whether a nonuniform pattern of lung injury influences treatment responses to aerosolized exogenous surfactant. Adult sheep underwent either total lung lavage (Tot Lav) or partial lung lavage (Par Lav) with saline, and they were subsequently mechanically ventilated for 90 min. Previous studies confirmed that this procedure induces acute lung injury. Partial lavage animals had their right upper lobe (RUL) protected from lavage by balloon obstruction of the RUL bronchus, and the occlusion was removed prior to the ventilatory period. Animals in both groups were then treated with either nebulized surfactant (Neb Surf) or nebulized saline (Neb Saline) for a further 180 min. PaO2, PaCO2, and peak inspiratory pressure significantly improved for the Tot Lav-Neb Surf animals compared with pretreatment values (p < 0.01). There were no significant changes for the other three groups (Tot Lav-Neb Saline, Par Lav-Neb Surf, Par Lav-Neb Saline). Lobar distribution of aerosolized [3H]surfactant in lung tissue revealed that Par Lav-Neb Surf animals had approximately 50% of the total surfactant recovered from the RUL compared with approximately 20% recovery from the RUL in the Tot Lav-Neb Surf group. The preferential deposition of exogenous surfactant in the RUL of the Par Lav-Neb Surf group resulted in significantly less surfactant deposited in other injured regions of the lung (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Lung function and surfactant distribution in saline-lavaged sheep given instilled vs. nebulized surfactant

Adult sheep (35 +/- 3 kg) underwent saline lung lavage and 1.5 h of mechanical ventilation to induce acute lung injury. Animals received 100 mg lipid/kg body wt of tracheally instilled surfactant (Inst Surf) or either nebulized surfactant (Neb Surf) or nebulized saline (Neb Saline) and were killed 3 h later. Inst Surf and Neb Surf groups had significant improvements in oxygenation (P < 0.01) and peak inspiratory pressures (PIP) (P < 0.05) compared with pretreatment values. Improvements in oxygenation and PIP for Inst Surf animals were significantly greater than for Neb Surf animals (P < 0.05). Volumes of maximal pressure of quasi-static pressure-volume curves measured at the time the animals were killed were significantly greater for Inst Surf and Neb Surf animals than for animals given Neb Saline (P < 0.05). Alveolar recovery of exogenous surfactant was 100 times greater for Inst Surf animals (1,732 +/- 70 mg) than for Neb Surf animals (15.3 +/- 2.9 mg) at the time they were killed. Although there were no differences in exogenous surfactant distribution patterns at the lobar level between the two surfactant-treated groups, distribution histograms calculated for 10-g lung pieces revealed the Neb Surf animals had significantly more pieces within 25% of the mean value of 1.0 (42.7 +/- 6.9%) than did Inst Surf animals (20.8 +/- 5.5%) (P < 0.01). Exogenous surfactant therapy improved lung function with significantly different quantities of surfactant deposited in lung tissue for the two delivery methods evaluated.

Discordance in degree of right and left ventricular dilation in patients with dilated cardiomyopathy: recognition and clinical implications

OBJECTIVES

The purpose of the present study was to assess the influence of variations in the relative degree of dilation of left and right ventricular chambers on the clinical outcome of patients with dilated cardiomyopathy.

BACKGROUND

Dilated cardiomyopathy, a primary myocardial disease characterized by ventricular dilation and systolic dysfunction, is generally associated with a poor prognosis. However, considerable variability has been observed in the clinical course and the morphologic and hemodynamic features in individual patients.

METHODS

We evaluated 67 consecutive patients with dilated cardiomyopathy and without evidence of ischemic or primary valvular heart disease. On the basis of diastolic ventricular chamber area measurements obtained by echocardiography, patients were classified into two groups: 38 patients with a relatively equal degree of left and right ventricular dilation (LV congruent to RV) and 29 patients with predominant and disproportionate dilation of the left ventricle (LV > RV).

RESULTS

The 67 patients ranged in age from 19 to 81 years (mean 56); 49 (73%) were male. The two subsets of patients with dilated cardiomyopathy did not differ with regard to age, left ventricular diastolic dimension, wall thickness and mass or ejection fraction. However, patients in the LV congruent to RV group showed more severe mitral and tricuspid regurgitation by Doppler echocardiography than did those in the LV > RV group (p = 0.01 for mitral and 0.004 for tricuspid regurgitation). Over the follow-up period of 2 to 60 months (mean 28), there were 19 deaths. Survival in the LV > RV group was significantly better than in the LV congruent to RV group (p = 0.03).

CONCLUSIONS

Patients with dilated cardiomyopathy represent a heterogeneous group with regard to both clinical outcome and the relative degree of left and right ventricular chamber dilation. Patients in the LV > RV subset appear to have better overall survival and less severe mitral and tricuspid regurgitation than do patients in the LV congruent to RV subset. Longitudinal studies are needed to determine whether these morphologic subsets in fact represent a continuum within the disease spectrum of dilated cardiomyopathy.

Surfactant and the adult respiratory distress syndrome

ARDS includes a complex series of events leading to alveolar damage, high permeability pulmonary edema, and respiratory failure. The endogenous pulmonary surfactant system is crucial to maintaining normal lung function, and only recently has it been appreciated that alterations in the surfactant system significantly contributed to the pathophysiology of the lung injury of patients with ARDS. Through a combination of analyzing BAL samples from patients with ARDS and extensive animal studies, there have been significant insights into the variety of surfactant abnormalities that can occur in injured lungs. These include altered surfactant composition and pool sizes, abnormal surfactant metabolism, and inactivation of alveolar surfactant by serum proteins present within the airspace. Positive effects of exogenous surfactant administration on acute lung injury have been reported. There is now a prospective, randomized clinical trial evaluating the efficacy of aerosolized exogenous surfactant in patients with ARDS. This trial has demonstrated improvements in gas exchange and a trend toward decreased mortality in response to the surfactant. Despite these encouraging results, there are multiple factors requiring further investigation in the development of optimal surfactant treatment strategies for patients with ARDS. Such factors include the development of optimal surfactant delivery techniques, determining the ideal time for surfactant administration during the course of injury, and the development of optimal exogenous surfactant preparations that will be used to treat these patients. With further clinical trials and continued research efforts, exogenous surfactant administration should play a useful role in the future therapeutic approach to patients with ARDS.

Usefulness of Doppler echocardiographic assessment of diastolic filling in distinguishing "athlete's heart" from hypertrophic cardiomyopathy

OBJECTIVE

In some athletes with a substantial increase in left ventricular wall thickness, it may be difficult to distinguish with certainty physiological hypertrophy due to athletic training from hypertrophic cardiomyopathy. The purpose of the present investigation was to determine whether assessment of left ventricular filling could differentiate between these two conditions.

DESIGN

Doppler echocardiography was used to obtain transmitral flow velocity waveforms from which indices of left ventricular diastolic filling were measured. Normal values were from 35 previously studied control subjects.

SETTING

Athletes were selected mostly from the Institute of Sports Science (Rome, Italy), and patients with hypertrophic cardiomyopathy were studied at the National Institutes of Health (Bethesda, Maryland).

PARTICIPANTS

The athlete group comprised 16 young competitive athletes with an increase in left ventricular wall thickness (range 13-16 mm; mean 14). For comparison, 12 symptom free patients with non-obstructive hypertrophic cardiomyopathy were selected because their ages and degree of hypertrophy were similar to those of the athletes.

RESULTS

In the athlete group, values for deceleration of flow velocity in early diastole, peak early and late diastolic flow velocities, and their ratio were not significantly different from those obtained in untrained normal subjects; furthermore, Doppler diastolic indices were normal in each of the 16 athletes. Conversely, in patients with hypertrophic cardiomyopathy, mean values for Doppler diastolic indices were significantly different from both normal subjects and athletics (p = 0.01 to 0.003), and one or more indices were abnormal in 10 (83%) of the 12 patients.

CONCLUSIONS

Doppler echocardiographic indices of left ventricular filling may aid in distinguishing between pronounced physiological hypertrophy due to athletic training and pathological hypertrophy associated with hypertrophic cardiomyopathy.

Platelet-activating factor antagonists decrease lung protein leak in preterm ventilated rabbits

OBJECTIVE

The preterm ventilated lung is characterized by an increased protein leak from the pulmonary vascular spaces into the air spaces, which interferes with lung function and plays a role in neonatal respiratory distress syndrome. To investigate the role of platelet-activating factor in this process, platelet-activating factor antagonists were given to preterm ventilated rabbits.

STUDY DESIGN

New Zealand White rabbits were delivered on day 28 of 31 days' gestation. Each rabbit pup received saline solution or one of two platelet-activating factor antagonists and were ventilated for 30 minutes with measurement of compliance, surfactant pool size, and protein leak into and out of the lung. Statistical analysis was performed with analysis of variance followed by Student-Newman-Keuls correction for multiple comparisons.

RESULTS

There were no differences in lung compliance, surfactant pool size, or protein leak out of the air spaces among any of the groups. Treatment with the platelet-activating factor antagonists decreased the protein leak into the air spaces by greater than 50% and into the lung as a whole by 40% (p less than 0.01).

CONCLUSION

Platelet-activating factor plays a role in the protein leak seen in the preterm lung, which contributes to neonatal respiratory distress syndrome.

Surfactant protein A metabolism in preterm ventilated lambs

Surfactant protein A (SP-A) metabolism was studied in vivo in 33 preterm ventilated lambs at 138 +/- 1 days gestational age by measuring recoveries of exogenously administered surfactant containing both radiolabeled SP-A and labeled saturated phosphatidylcholine (Sat PC) given via the trachea at birth. Endogenously secreted SP-A was also labeled with [35S]methionine and followed over 24 h. The exogenously labeled SP-A left the alveolar pool more rapidly than did Sat PC over the first 5 h of life (P less than 0.05), and both exogenously labeled SP-A and Sat PC were detected within lamellar bodies by 2 h, indicating uptake from the airspaces. The quantity of SP-A in alveolar washes increased about twofold from birth to 5 h of age, whereas alveolar Sat PC pools were constant over 24 h. The SP-A endogenously labeled with [35S]methionine was recovered at highest specific activities in the alveolar washes at 10 and 45 min after birth with no labeled SP-A detectable in lamellar body fractions until 2 h. The curve for endogenous SP-A labeling of lamellar bodies was similar to that for exogenous labeling, indicating that SP-A was initially secreted by a pathway independent of lamellar bodies with subsequent SP-A labeling of lamellar bodies. The kinetics of SP-A metabolism were very different than for Sat PC in preterm lambs.

Lung albumin recovery in surfactant-treated preterm ventilated lambs

Preterm ventilated animals and infants with respiratory distress syndrome (RDS) develop proteinaceous alveolar edema. To study the effect of postnatal age on intravascular radiolabeled albumin accumulation into lungs, preterm lambs at 132 days gestational age were ventilated after treatment with sheep surfactant or cow surfactant extract for periods as long as 24 h. Lambs not treated with surfactant were studied for only 5 h because of severe respiratory failure. All lambs were given radiolabeled albumin by intravascular injection 1 h before they were killed, and the net recovery of the labeled albumin was measured in the lung tissue and air space as quantified by alveolar lavage. Net 1-h radiolabeled albumin recoveries in the lungs decreased from 5 to 6% soon after birth to 0.9% at 24 h in the surfactant-treated groups (p less than 0.01). At 3 h there was less labeled albumin recovery by alveolar lavages in lambs treated with sheep surfactant than in control lambs and lambs treated with cow surfactant extract (p less than 0.05). Protein in alveolar washes from lambs treated with cow surfactant extract exceeded that in lambs treated with sheep surfactant at 3 h (p less than 0.05), but protein recoveries had decreased to similar values by 24 h, indicating a net clearance of air-space protein. These studies demonstrate a sixfold decrease in net albumin accumulation from birth to 24 h of age despite continued ventilation and oxygen exposure of the premature lamb lungs.

Considerations for racial differences in the athlete's heart

Exercise training is associated with changes in left ventricular morphology commonly referred to as the athlete's heart. The magnitude of these changes appears to be due in part to the type, intensity, and duration of training. Certain athletes develop more marked alterations in left ventricular morphology, however. This raises the consideration of whether the cardiac response to athletic training may also be influenced by genetic or racial factors.

Metabolism of exogenously administered surfactant in the acutely injured lungs of adult rabbits

Acute lung injury was induced in adult rabbits with a subcutaneous injection of N-nitro-so-N-methylurethane (NNNMU). Clearance of saturated phosphatidylcholine (Sat.PC) from a treatment dose of exogenous surfactant (100 mg/kg) in the injured lungs of these rabbits was similar to normal, control rabbits when measured 24 h after treatment. However, total Sat.PC pool sizes in both the alveolar wash and total lung at this time point were significantly lower for the injured lungs than for the control lungs (p less than 0.05), implying altered endogenous surfactant metabolism in response to surfactant treatment in the injured animals. Although both injured and control animals had comparable ratios of small to large surfactant aggregates, as measured by differential centrifugation of alveolar wash 5 min after treatment, by 24 h this ratio had increased 5-fold in the control animals and remained unchanged in the injured animals. This indicated diminished conversion of large surfactant aggregates to the smaller forms in lung injury. In vivo functional studies of these aggregates were performed by intratracheal injection into surfactant-deficient preterm rabbits. Large aggregates from normal adult rabbits given surfactant had superior functional properties than did the surfactant used for treatment alone, which in turn was better than large aggregates isolated from NNNMU-injured rabbits treated with surfactant. This indicates that the alveolar environment influenced the function of the exogenously administered surfactant differently in normal and injured rabbits.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypertrophic cardiomyopathy characterized by marked hypertrophy of the posterior left ventricular free wall: significance and clinical implications

This report describes a subgroup of 17 patients with hypertrophic cardiomyopathy and an unusual and distinctive pattern of left ventricular hypertrophy characterized on echocardiography by marked thickening of the posterior left ventricular free wall and virtually normal or only modestly increased ventricular septal thickness. This distribution of hypertrophy often created a distinctive pattern of "inverted" asymmetry of the posterior wall relative to the septum. The thickness of the posterior wall was 20 to 42 mm (mean 25), while that of the basal ventricular septum was only 12 to 24 mm (mean 17). The left ventricular outflow tract was narrowed because of anterior displacement of the mitral valve within the small left ventricular cavity. Systolic anterior motion of the mitral valve was present in 16 of the 17 patients. The patients ranged in age from 13 to 54 years (mean 31) at most recent evaluation; most (11 of 17, 65%) were severely symptomatic and had experienced important symptoms early in life (before age 40). The condition of only 4 of these 11 patients improved with medical therapy over an average follow-up period of 9 years; however, 6 of the 7 patients who had unsuccessful medical treatment and underwent operation with mitral valve replacement (5 patients) or ventricular septal myotomy-myectomy (1 patient) experienced symptomatic benefit from surgery. The subgroup of patients described in this report underscores the morphologic and clinical diversity that exists within the overall disease spectrum of hypertrophic cardiomyopathy. Characteristically, the patients were young, severely symptomatic and demonstrated evidence of outflow obstruction and an "inverted" asymmetric pattern of posterior free wall left ventricular hypertrophy. (ABSTRACT TRUNCATED AT 250 WORDS)

Left ventricular diastolic filling abnormalities identified by Doppler echocardiography in asymptomatic patients with sickle cell anemia

To determine whether left ventricular diastolic abnormalities are an early feature of sickle cell anemia, indexes of diastolic filling were obtained with pulsed Doppler echocardiography in 30 consecutive patients with this disease (mean age 29 years; range 19 to 39) who had not experienced symptoms of heart failure and had normal left ventricular systolic function. Data were compared with those in 30 normal control subjects of similar ages. Seventeen (57%) of the 30 patients with sickle cell anemia had evidence of abnormal left ventricular diastolic filling. Six of these 17 patients had a Doppler pattern consistent with "restrictive" filling, characterized by reduced early diastolic deceleration time (less than 110 ms) or an increased rate of decline of early flow velocity (EF slope greater than 7.4 m/s2), or both, as well as decreased late diastolic velocity-time integral (2.6 +/- 0.7 vs. 3.4 +/- 0.8 cm in normal subjects; p less than 0.05). Another 11 patients showed a Doppler waveform consistent with impaired relaxation, characterized by prolonged deceleration time (greater than 166 ms) or reduced EF slope (less than 3.8 m/s2), as well as increased late diastolic velocity-time integral (4.0 +/- 0.5 vs. 3.4 +/- 0.8 cm in normal subjects; p = 0.03). This Doppler echocardiographic analysis demonstrates that left ventricular diastolic filling patterns are altered in patients with sickle cell anemia and that these diastolic abnormalities may be present in the absence of symptoms of heart failure. These abnormal patterns suggest an intrinsic myocardial abnormality in patients with sickle anemia and may prove to be early markers of cardiac disease.

Aerosolized surfactant treatment of preterm lambs

To evaluate the potential for aerosolized surfactant treatments of surfactant deficiency, twin lamb fetuses were delivered at 130-132 days gestational age and received nebulized natural surfactant (Neb NS), nebulized Survanta (Neb Surv), tracheally instilled natural surfactant (Inst NS), or nebulized saline (Neb Saline). Neb NS and Neb Surv groups had significant increases in ventilatory efficiency index and dynamic compliance values (P less than 0.05). Both groups also had pressure-volume curves that were comparable to the Inst NS group. The Neb Saline control group had deterioration of the ventilation efficiency index and dynamic compliance values over time as well as pressure-volume curves that demonstrated smaller lung volumes compared with all three surfactant-treated groups (P less than 0.01). Delivery of aerosolized surfactant to the lung was only approximately 2 mg lipid/kg for the nebulized groups, a dose one-twentieth of that previously noted to be effective in instillation protocols. Distribution histograms of the aerosolized surfactant-treated groups differed from the instilled animals as there was more deposition in the right upper lobes and tracheae in the nebulized groups compared with the instilled group (P less than 0.05). Pulmonary blood flow was not altered by aerosolized surfactant treatment. Administration of aerosolized surfactant to preterm lambs improved lung function at a very low surfactant dose.

Altered surfactant function and metabolism in rabbits with acute lung injury

Lung injury was induced in rabbits with N-nitroso-N-methylurethane (NNNMU), and saturated phosphatidylcholine (Sat PC) pool sizes and phospholipid compositions were measured in alveolar wash subfractions isolated by differential centrifugation (large and small surfactant aggregates). Surfactant metabolism also was studied using intravascular and intratracheal radiolabels. Protein permeability, gas exchange, and compliance were significantly abnormal as lung injury progressed. At peak injury, there was a decrease in the large aggregate Sat PC pool size in alveolar wash accompanied by increased uptake of Sat PC from the air space and increased specific activity of both intravascular and intratracheal radiolabels in lamellar bodies. This was followed by a marked rise in the small aggregate pool size in the alveolar wash and increased secretion of Sat PC into the air spaces. Phospholipid compositions, total phospholipid-to-protein ratios, and in vivo functional studies using a preterm ventilated rabbit model were abnormal for both large and small aggregate surfactant fractions from the lung-injured rabbits. These studies characterize quantitative, qualitative, and functional changes of alveolar wash surfactant subfractions in NNNMU-injured lungs.

Diversity of patterns of hypertrophy in patients with systemic hypertension and marked left ventricular wall thickening

In selected patients with systemic hypertension it may be difficult to ascertain whether left ventricular (LV) hypertrophy is a secondary end-organ consequence of long-term elevations in blood pressure or, alternatively, a manifestation of a coexistent primary hypertrophic cardiomyopathy. To address this issue and better characterize LV hypertrophy in systemic hypertension, 2-dimensional echocardiography was used to define the patterns of LV hypertrophy in 102 patients with sustained systemic hypertension and marked degrees of wall thickening. Patients ranged in age from 31 to 88 years (mean 61) and were predominantly female (58%); all were black. By selection, each patient had a maximal LV wall thickness of greater than 15 mm (range 16 to 29). Distribution of hypertrophy was judged to be symmetric (i.e., concentric) in most patients (67 of 102, 66%). However, a substantial proportion (35 patients, 34%) demonstrated nonuniform, asymmetric patterns of hypertrophy in which at least 1 segment of the LV wall was at least 1.5 times the thickness of any other. In these 35 patients, the distribution of hypertrophy was similar to that characteristic of the morphologic spectrum of hypertrophic cardiomyopathy, with thickening of portions of both the ventricular septum and free wall in 16 patients, anterior and posterior ventricular septum alone in 11 patients and segmental involvement of only the anterior ventricular septum in 8. Patients with asymmetric patterns of wall thickening did not differ from the patients with symmetric hypertrophy with regard to age, sex or clinical findings. Asymmetric LV hypertrophy appears to represent an important feature of the morphologic spectrum of severe hypertensive heart disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Preparticipation echocardiographic screening for cardiovascular disease in a large, predominantly black population of collegiate athletes

Sudden death in young competitive athletes is most commonly due to underlying cardiovascular disease. Echocardiography has the potential to identify structural cardiovascular abnormalities, such as hypertrophic cardiomyopathy (HC), that have been incriminated in such events. In this study, echocardiography (2-dimensional and M-mode) was used as a primary screening test to assess 265 Howard University collegiate athletes for cardiovascular disease; 262 (99%) were black. Most athletes (234, 88%) had no definitive echocardiographic evidence of HC or other major cardiovascular diseases, but 30 (11%) had mitral valve prolapse, and 1 other athlete had a small atrial septal defect. In addition, 4 athletes were identified as having mild systemic hypertension. Most athletes (236 of 265) showed normal left ventricular wall thickness of less than or equal to 12 mm, but an important minority (29, 11%) had maximal ventricular septal thicknesses of greater than or equal to 13 mm that could not always be distinguished (by morphology alone) from mild anatomic expressions of nonobstructive HC. Based on this experience, preparticipation athletic screening using echocardiography as the primary test does not appear to be justified on a cost-effective basis. In addition, the substantial minority of subjects with increased wall thickness made clinical interpretation of the echocardiographic findings difficult in individual athletes.

Elderly patients with hypertrophic cardiomyopathy: a subset with distinctive left ventricular morphology and progressive clinical course late in life

This report describes a subgroup of 52 elderly patients with obstructive hypertrophic cardiomyopathy in whom certain clinical and morphologic features differed importantly from those of many other patients with this disease. Ages ranged from 60 to 84 years (mean 69) and 45 [87%] were women. Echocardiographic examination showed a relatively small heart, having only modest ventricular septal hypertrophy associated with marked distortion of left ventricular outflow tract morphology. By virtue of selection, left ventricular outflow tract size at end-diastole was substantially reduced, and anterior displacement of the mitral valve within the left ventricular cavity was particularly marked. Sizable deposits of calcium in the region of the mitral anulus, posterior to the mitral valve, appeared to contribute to the outflow tract narrowing. Systolic anterior motion of the mitral valve was severe (with apposition of the mitral valve and ventricular septum) in 32 patients and more moderate in 20. The mechanism by which systolic contact between the mitral valve and septum occurred in most patients appeared to differ from that observed more typically in many other patients with hypertrophic cardiomyopathy; in most elderly study patients, anterior excursion of the mitral valve leaflets was relatively restricted, and systolic apposition between the mitral valve and septum resulted from a combination of anterior motion of the mitral valve and posterior excursion of the septum. The vast majority (50 of 52) of the patients remained asymptomatic (or only mildly symptomatic) for most of their lives and often did not develop severe and intractable symptoms until the 6th or 7th decade (ages 56 to 81 years; mean 66). Of the 49 patients with at least 1 year follow-up study, only 12 had improvement with pharmacologic therapy; however, 14 of the 18 patients who underwent ventricular septal myotomy-myectomy or mitral valve replacement obtained symptomatic benefit from operation. In conclusion, obstructive hypertrophic cardiomyopathy in many elderly (and predominantly female) patients may assume a distinctive morphologic appearance and a progressive clinical course. This subgroup of patients appears to constitute an important segment of the disease spectrum of hypertrophic cardiomyopathy of cardiac disease in the elderly that previously has not been precisely defined nor fully appreciated.

Anomalous coronary artery originating from the left anterior descending artery and ending in a blind aneurysm

To the authors' knowledge this is the first report of an anomalous coronary artery originating from the left anterior descending artery and ending in a blind aneurysm.

Hypophosphatemia and respiratory failure: prolonged abnormal energy metabolism demonstrated by nuclear magnetic resonance spectroscopy

Hypophosphatemia has been shown to cause acute respiratory failure. The mechanism is believed to be due to decreased high-energy substrate availability at the cellular level leading to respiratory muscle dysfunction. However, direct measurement of these substrates has not been previously studied. A patient with hypophosphatemic respiratory failure is described in whom phosphocreatine and pH were continuously monitored using nuclear magnetic resonance spectroscopy. This revealed a defect in muscle metabolism that required several weeks to recover despite prompt correction of the serum phosphate level.

Tricuspid stenosis in prosthetic valve endocarditis. Diagnosis by Doppler echocardiography

Valvular stenosis is an uncommon finding in bacterial endocarditis involving native cardiac valves. Prosthetic valve endocarditis, however, is more commonly associated with obstruction. Bioprosthetic cardiac valves may be particularly prone to this complication. A case of bioprosthetic tricuspid valve endocarditis with stenosis diagnosed by Doppler echocardiography and confirmed by operative findings is presented.

Effects of transluminal coronary angioplasty on left ventricular systolic and diastolic function at rest and during exercise

The left ventricular global and regional systolic function, ventricular volumes, and peak diastolic filling rate (PDFR) were studied in 30 patients with coronary artery disease, before and 2 to 5 days after transluminal coronary angioplasty (PTCA), utilizing equilibrium radionuclide angiography at rest and during exercise. At rest, the global ejection fraction (EF) was unchanged before (60 +/- 9%) and after PTCA (62 +/- 10%). During exercise, global EF increased from 59 +/- 11% pre PTCA to 67 +/- 10 post PTCA (p less than 0.001). Twenty-two patients had abnormal EF response to exercise pre PTCA, versus seven post PTCA (p less than 0.001). Improvements in exercise regional EF paralleled the changes in global EF. End-systolic volume was unchanged at rest but decreased significantly with exercise post PTCA (60 +/- 36 ml pre vs 49 +/- 32 ml post PTCA, p less than 0.01). At rest, the PDFR was unchanged post PTCA (2.4 +/- 0.9 end-diastolic volume (EDV)/sec pre vs 2.5 +/- 0.8 EDV/sec post). During exercise, PDFR increased from 2.1 +/- 0.7 EDV/sec pre PTCA to 2.5 +/- 0.7 EDV/sec post PTCA (p less than 0.02). In conclusion, in patients with coronary artery disease, successful PTCA improves global and regional systolic function during exercise. Diastolic function is improved during exercise, a fact not previously demonstrated.

Pulsed Doppler echocardiographic determination of stroke volume and cardiac output: clinical validation of two new methods using the apical window

Two methods of measuring stroke volume and cardiac output with pulsed Doppler two-dimensional echocardiography were developed and validated against the thermodilution technique in 39 patients, 33 of which were in an intensive care unit. With the use of the apical four-chamber view, a mitral inflow method combined the velocity of left ventricular inflow at the mitral anulus with the cross-sectional area of the anulus calculated from its diameter at middiastole (area = pi r2). From the apical five-chamber view a left ventricular outflow method combined the velocity of left ventricular outflow with the cross-sectional area of the aortic anulus calculated from its diameter during early systole (parasternal long-axis view). Measurements with the mitral inflow and left ventricular outflow methods were obtained in 35 of 39 (90%) and 39 of 39 (100%) patients, respectively. Validation of the mitral method excluded patients with mitral regurgitation (n = 11) and validation of the left ventricular outflow method excluded those with aortic regurgitation (n = 4). Good correlations were observed between thermodilution and Doppler measurements of stroke volume and cardiac output for both the mitral anulus method (R = .96 and .87, respectively) and the left ventricular outflow method (R = .95 and .91, respectively). The results of the two methods correlated well with each other in patients without regurgitant valve lesions. A greater interobserver variability was observed with the mitral anulus method, which was related solely to greater variability in measuring the annular diameter.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of API 20E strips for identification of coagulase-negative staphylococci from the urinary tract

A previous study indicated that the API 230E system can identify coagulase-negative Staphylococcus species. A study was devised to evaluate the use of the API 20E system for this purpose. Because of the current interest in Staphylococcus saprophyticus the relationship of the API 20E results to novobiocin susceptibility was also examined. One hundred forty-nine isolates of coagulase-negative staphylococci from urine cultures were tested with the API 20E system. The identification of 49 isolates was confirmed by Kloos and Schleifer method. We found that the routine API 20E system did not provide more information than novobiocin susceptibility studies alone, and that there was good but not absolute correlation between novobiocin resistance and identification of S. saprophyticus.

Urinary tract infection due to coagulase-negative staphylococcus

One hundred and fifty-six urine specimens with a pure culture of coagulase-negative Staphylococcus were studied. One hundred and eighteen charts were reviewed for clinical evidence of urinary tract infections. Twenty-four cases of urinary tract infection were found. The younger females in the study tended to have infection due to novobiocin resistant Staphylococcus in contrast to males and older females.

Blood cultures in bacteremia

Blood cultures in a 700-bed hospital were examined for clinical relevance. During a six-month period 5,154 blood samples were drawn from 1,091 patients. Of the 124 patients with positive blood cultures, 7% had polymicrobic isolates. A review of hospital records for a three-year period revealed 162 charts with adequate documentation for evaluation of bacteremia. An additional 11 charts were found with inappropriately negative blood cultures. Fifteen percent of these patients were found to have polymicrobic isolates. The importance of establishing guidelines and criteria concerning acceptable blood culture practices is detailed.

Endocarditis due to Propionibacterium acnes

A case of Propionibacterium acnes endocarditis documented by blood culture and culture of the valve is presented. A brief review of the literature is summarized.

Operative experience with infective endocarditis and intracerebral mycotic aneurysm

The surgical management of eight patients with infective endocarditis and intracerebral mycotic aneurysm is presented. Three patients had craniotomy before valve replacement and four patients had valve replacement before craniotomy. There were no deaths related to the valve replacement or craniotomy. Two of the eight patients died in the hospital of continuing sepsis resulting from undrained foci of infection. It is concluded that the drug-addicted patient with a mycotic aneurysm and hemodynamic decompensation from endocarditis can be successfully treated by staging the operations according to the more severe problem.

Isolation and evaluation of clostridia from clinical sources

During a two-year period, 133 isolates of clostridia from clinical courses were obtained. These isolates are reviewed as to clinical significance and antimicrobial susceptibility. Adequate charts were available on 63 patients, nine (14%) of whom had their clinical source significantly altered by the presence of clostridia. Clostridia of little or no clinical significance were isolated from blood cultures from six patients. The occurrence of clostridial infections is unpredictable, and adequate clinical information is necessary to determine the need for identification of clostridial isolates.

Overnight refrigeration of urine specimens for culture

Some authorities state that urine may be refrigerated overnight and still be satisfactory for quantitative bacteriologic evaluation. The papers cited appear to us to be inadequate. Four hundred and fourteen urine cultures were evaluated comparing colony count before and after overnight refrigeration. Overnight refrigeration appears to be a satisfactory means of urine preservation for culture.

Microscopy of stained urine smears to determine the need for quantitative culture

Consecutive specimens (2,564) of urine were cultured quantitatively, and Gram-stained smears were prepared from centrifugates as well as from the uncentrifuged specimens. About half of the specimens harbored organisms, and the quantity seen in smears of the centrifugates correlated reasonably well with the numbers of viable organisms cultured from the specimens. For example, smears of 900 centrifugates had one or more organisms per oil immersion field; 712 of their respective specimens proved to have colony counts of 10(5) or greater, and 120 had 10(4) to less than 10(5). For 188 specimens, however, the smears falsely predicted greater than or equal to 10(5) colony-forming units (many of these fell into the group that had 10(4) to less than 10(5)) but failed to predict clinically significant concentration of 10(5) or greater in only 31. Predictive values are presented also for lesser quantities of organisms seen in such smears. With rare exception, smears of centrifugates were superior to those of whole specimens as predictors of the concentration of viable organisms. Evaluation of smears proved not to be biased by the operator; values did not deviate significantly depending upon whether one or several microbiologists performed the evaluations.

Pitting of agar surface by Pseudomonas stutzeri

A strain of Pseudomonas stutzeri which exhibited pitting of agar surfaces is described.