Saddle-shape annuloplasty increases mitral leaflet coaptation after repair for flail posterior leaflet

BACKGROUND

The primary goal of surgical mitral repair is the reestablishment of normal leaflet coaptation. Surgical techniques that maintain or restore leaflet geometry promote leaflet coaptation. Recent 3-dimensional (3D) echocardiographic studies have shown that saddle-shaped annuloplasty has a salutary influence on leaflet geometry. Therefore we hypothesized that saddle-shaped annuloplasty would improve leaflet coaptation in cases of repair for flail posterior leaflet segments.

METHODS

Sixteen patients with flail posterior segment and severe mitral regurgitation had valve repair using standard techniques. Eight patients received saddle-shaped annuloplasty and 8 patients received flat annuloplasty. Real-time 3D transesophageal echocardiography was performed before and after repair. Images were analyzed using custom software to calculate mitral annular area (MAA), septolateral dimension (SLD), intercommissural width (CW), total leaflet area (TLA), and leaflet coaptation area (LCA).

RESULTS

Postrepair MAA (flat, 588.6±26.5 mm2; saddle, 628.0±35.3 mm2; p=0.12) and TLA (flat, 2198.5±151.6 mm2; saddle, 2303.9±183.8 mm2; p=0.67) were similar in both groups. Postrepair LCA was significantly greater in the saddle group than in the flat group (226.8±24.0 mm2 and 154.0±13.0 mm2, respectively; p=0.02).

CONCLUSIONS

Real-time 3D echocardiography and novel imaging software provide a powerful tool for analyzing mitral leaflet coaptation. When compared with flat annuloplasty, saddle-shaped annuloplasty improves LCA after mitral valve repair for severe mitral regurgitation secondary to flail posterior leaflet segment. Use of saddle-shaped annuloplasty devices may increase repair durability.

Transcatheter closure of patent ductus venosus with the Amplatzer vascular plug in twin brothers

We describe the transcatheter closure of a patent ductus venosus in twin brothers with an ill-defined systemic illness and respiratory failure using the Amplatzer vascular plug. To our knowledge, this is the first description of the use of the Amplatzer vascular plug for ductus venosus closure.

Influence of Enterococcus faecalis proteases and the collagen-binding protein, Ace, on adhesion to dentin

Enterococcus faecalis is a pathogen that persists in medicated root canals. Here, we tested the hypothesis that the E. faecalis proteases, serine protease and gelatinase, and the collagen-binding protein (Ace) contribute to adhesion to the root canal. Scanning electron microscopy was used to examine dentin binding by four E. faecalis strains: OG1RF, the wild type, and three mutant derivatives of OG1RF, TX5128, TX5243 and TX5256 deficient in serine protease and gelatinase, serine protease, and Ace, respectively. For each strain, 20 root halves were exposed to 3 x 10(9) to 5 x 10(9) cells/ml for 6 h, and 50 fields per root half were examined for adherent bacteria. Statistical analysis revealed that adherence of OG1RF was significantly greater than the mutant strains (P < 0.001), while significant differences were not detected between the protease mutants. The data indicate that serine protease and Ace aid E. faecalis binding to dentin, while the role of gelatinase is uncertain.

Prevention of the ingress of a known virulent bacterium into the root canal system by intracanal medications

Contamination of the root canal system by persistent, enteric bacteria via leakage through interim restorations has been well documented. This in vitro study evaluated the ability of interappointment medications to prevent contamination of the root canal system by Enterococcus faecalis. Coronally unsealed, medicated tooth roots fixed in a closed system were contaminated daily with a standardized, aerobic, broth culture of E. faecalis. Four medications were evaluated (n = 15): group A, calcium hydroxide/methylcellulose paste; group B, camphorated parachlorophenol/calcium hydroxide paste; group C, 1% chlorhexidine/methylcellulose gel; and group D, calcium hydroxide points. The mean number of days to contamination as indicated by turbidity in the closed system was the following: group A, 37; group B, 46; group C, 16; group D, 5; and a positive control (no medication), 3. A one-way analysis of variance with a Scheffe post hoc test (p = 0.05) detected significant differences in effectiveness with A and B superior to C and D, and C superior to D.

Failure properties of suture anchors in the glenoid and the effects of cortical thickness

The ultimate pullout strength and fatigue properties of a screw-design suture anchor implanted in the anterior glenoid rim were investigated and compared with results from a nonscrew-design suture anchor. Twenty-two cadaveric glenoids were harvested and one to two anchors were implanted in the superior and inferior quadrants. Fifty-seven Statak 3.5 anchors (Zimmer, Warsaw, IN) were tested and compared with results obtained in a previous study on 50 Mitek GII anchors (Mitek Products, Inc, Westwood, MA). The specimens were mounted on an Instron fatigue testing machine (Instron Corp, Canton, MA) and cycled between preselected minimum and maximum loads until pullout. The Mitek GII maintained a higher pullout strength than the Statak 3.5 after cyclic loading. Cortical thickness at the implantation sites was measured, and found to decrease monotonically from superior to inferior positions. The ultimate pullout strength, and subsequently the fatigue life, of both types of suture anchors depended directly on cortical thickness. The significantly lower performance of both anchors when placed inferiorly emphasizes the importance of correct anchor selection, number, and placement in this region. All anchors settled during the first 10 to 100 cycles, resulting in partial exposure of the implant. Intraoperative cycling of the anchors before suture tying may be necessary to achieve complete settling and prevent subsequent loss of coaptation between capsule and glenoid. The study shows that for the anchors to last 1,000 cycles or more, less than 50% of the theoretical ultimate pullout strength should be applied cyclically. With aggressive early rehabilitation exercises, this significant decrease in fixation strength could shift reconstruction failure from suture breakage or soft tissue tearing to anchor pullout.

Fatigue properties of suture anchors in anterior shoulder reconstructions: Mitek GII

Suture anchors have simplified anterior capsule labral reconstruction. During rehabilitation the shoulder goes through many repetitions of range of motion exercises. These exercises will repetitively submaximally load the anchor and in theory should reduce the pullout strength of the suture anchor. No published reports exist on the fatigue strengths and properties of one of the most commonly used anchors: Mitek GII suture anchors. Fifty trials of cyclic submaximal load were done on 22 cadaveric glenoids with an average age of 66.8 years (range, 40 to 90 years). At two to three different sites on the same specimen, the anchors were inserted according to manufacturer's specifications. The anchors were tested to failure on a Instron 1331 servohydraulic mechanical testing system at 2 Hertz sinusoidal loading pattern using steel sutures and a predetermined load. There were 22 (44%) tests performed in the superior quadrant and 28 (56%) tests in the inferior quadrant. All anchors pulled out, and no wires broke. There were statistically significant differences between the superior and inferior portion of the glenoid with regard to number of cycles to failure at a given maximum load. The anchors underwent an average of 6,220 cycles before pullout at an average load of 162 N (SD = 73 N). In the superior quadrant, the average ultimate pullout strength was 237 N (SD = 42 N), whereas in the inferior quadrant the average ultimate pullout strength was 126 N (SD = 36 N). Hence, the ultimate pullout strength of the Mitek GII anchor was significantly higher (P < .002) in the superior quadrant than in the inferior quadrant. Using a least squares regression analysis, it was possible to predict the fatigue life of the superiorly and inferiorly placed suture anchors over a wide range of cycles. The R-squared values for trendlines showed good reliability (superior R2 = 0.55; inferior R2 = 0.28). The fatigue life curves for the two different quadrants were normalized using the ultimate pullout strength. This new, universal curve predicts the fatigue life of the Mitek GII anchor as a percentage of the ultimate pullout strength for any selected location. For a clinically relevant number of cycles, no more than approximately 40% to 50% of the ultimate pullout strength of the suture anchor can be cyclically applied to the anchor to guarantee a life for the duration of rehabilitation. For the entire system, the inferiorly placed anchors dictate the amount of cyclically applied load the system can experience without failing, and rehabilitation should be adjusted accordingly.

White cell reduction in platelet concentrates and packed red cells by filtration: a multicenter clinical trial. The Trap Study Group

BACKGROUND

Most previous studies on white cell (WBC) reduction by filtration have been small-scale studies conducted under tightly controlled laboratory conditions. Their results would be the ideal, rather than what might be expected during routine operation.

STUDY DESIGN AND METHODS

To obtain information on routine filtration of blood components, data have been collected from a large-scale, ongoing, multicenter clinical trial designed to determine the effectiveness of WBC reduction in or ultraviolet B radiation of platelet concentrates before transfusion in preventing platelet alloimmunization and platelet transfusion refractoriness. The WBC content of blood components both before and after filtration was determined by automated cell counters and a manual propidium iodide-staining method, respectively. Platelet and red cell losses during filtration were measured.

RESULTS

The average platelet losses after filtration were 24 +/- 15 percent and 20 +/- 9 percent for apheresis platelets and pooled platelets, respectively. The frequencies at which filtered platelet concentrates contained high levels of residual WBCs (> 5 x 10(6)) were 7 percent and 5 percent for apheresis platelets and pooled platelets, respectively. Further analysis of the platelet filtration data showed that greater numbers of total initial WBCs in the pooled platelets were associated with increased percentages of filtration failure (> 5 x 10(6) residual WBCs). For packed red cells, the average losses during filtration were 23 +/- 4 percent and 15 +/- 3 percent for CPDA-1 units and Adsol units, respectively. The frequencies at which filtered red cells contained > 5 x 10(6) residual WBCs were 2.7 percent for one type of filter and 0.3 percent for another type of filter.

CONCLUSION

There were significant losses of platelets during filtration, which could add to the costs of WBC reduction and lead to possible increases in donor exposures. Filtration failures still occurred, despite careful observation of the standard filtration procedures. The number of total WBCs in pooled platelets before filtration has been identified as an important factor in determining the success of WBC reduction.

Isolation and partial characterization of the Campylobacter rectus cytotoxin

Previously, we reported the antigranulocytic activity of Campylobacter rectus media supernatants containing lipopolysaccharide (LPS) and a 104 kDa protein. Here, we monitored the release of protein and LPS through the growth cycle of C. rectus ATCC 33238 and identified the 104 kDa protein as the cytotoxin. LPS in media supernatants was quantitated by a KDO assay; the 104 kDa protein was detected on immunoblots with specific antibody (A104) and quantitated by amino acid analysis of membrane immobilized protein bands. C. rectus cell product release was independent of cell lysis. Over 24 h, the 104 kDa protein was released linearly while LPS was released in two plateaus; both increased in C. rectus culture supernatants 3 h after inoculation achieving maximum concentrations at 21 h of 3.1 micrograms/ml and 14.6 micrograms/ml, respectively. In 2 h, trypan blue viability assays, 37-47 micrograms of 12, 18 and 24 h supernatant protein killed 33-43% of HL-60 cells. Supernatant toxicity was heat sensitive and inhibited by A104. Sequencing the 16 N-terminal amino acids of the cytotoxin distinguished it from described C. rectus proteins. Similarities between epitopes and amino acid compositions of the Actinobacillus actinomycetemcomitans leukotoxin and C. rectus cytotoxin were observed. These data indicate that C. rectus secretes a 104 kDa cytotoxin.

Atypical structure of the 23S ribosomal RNA molecule in certain oral bacteria

Ribosomal RNA (rRNA) isolated from Wolinella recta and seven related bacteria was examined by agarose gel electrophoresis. The 23S rRNA molecule could not be detected in W. recta, Wolinella curva, Bacteroides gracilis, or Bacteroides ureolyticus. In place of the 23S molecule, there were three smaller molecules of approximately 1700, 650, and 600 bases designated 23S alpha, 23S beta, and 23S delta, respectively. An intact 23S rRNA molecule could be isolated from Wolinella succinogenes, Campylobacter concisus, and Campylobacter sputorum. The cleavage sites of the W. recta 23S rRNA molecule were located by direct RNA sequence analysis and were found to be in similar locations, nucleotides 546 and 1180, as cleavage sites described in other prokaryotes. The presence or absence of the 23S rRNA molecule may be a useful marker for these micro-organisms.

Classification of deaths after myocardial infarction as arrhythmic or nonarrhythmic (the Cardiac Arrhythmia Pilot Study)

The Cardiac Arrhythmia Pilot Study (CAPS) was a randomized, double-blind trial of antiarrhythmic drugs (encainide, flecainide, moricizine, imipramine and placebo) in 502 patients with at least 10 ventricular premature complexes/hour, 6 to 60 days after acute myocardial infarction. CAPS tested the feasibility of performing a larger study to determine if suppression of ventricular ectopic activity after acute myocardial infarction could improve survival. Patients in CAPS were followed for 1 year. All death or cardiac arrest events were evaluated by at least 2 investigators using a classification scheme that characterized the underlying mechanism as cardiac arrhythmic, cardiac nonarrhythmic or noncardiac. Forty-five patients (9%) died or had cardiac arrest during the 1-year follow-up, 29 (64%) within 1 hour from the onset of symptoms and 16 greater than 1 hour from the onset of symptoms. Twenty-three deaths (51%) were classified as arrhythmic, 19 (42%) as nonarrhythmic and 3 (7%) as noncardiac. Acute myocardial ischemia or infarction was associated with the death/cardiac arrest event in 16 patients (36%), 8 in the arrhythmic death group. Discrepancies in classification among reviewers were particularly common in patients with long-standing symptoms of congestive heart failure, in whom it was frequently difficult to identify the precise moment of the onset of symptoms in the death/cardiac arrest event. Using only the temporal relation of symptoms to categorize deaths or cardiac arrests, the mechanism of 12 (27%) of the 45 patients was in disagreement with the classification based on the Events Committee review. Classification of death as sudden or nonsudden is not equivalent to the classification of death as arrhythmic or nonarrhythmic.

Comparison of daily and seasonal exposures of young monkeys to ozone

Oxidant air pollution tends to occur in both seasonal and daily cycles of polluted and clean air. To compare the effects of these 2 cycles, we exposed 2 groups of 7-month-old male monkeys to 0.25 ppm (0.49 mg/m3) of ozone (UV photometric standard) 8 h/day either daily or, in the seasonal model, days of alternate months during a total exposure period of 18 months. This is a longer ozone exposure period than any previously reported. A control group breathed only filtered air. Young monkeys were studied as their lungs are similar to those of man and their lungs, like those of man, grow over a period of several years. Monkeys from the seasonal exposure model, but not those exposed daily, had significantly increased total lung collagen content, chest wall compliance, and inspiratory capacity. All monkeys exposed to ozone had respiratory bronchiolitis with significant increases in related morphometric parameters. The only significant difference between seasonal and daily groups was in the volume fraction of macrophages. Even though the seasonally exposed monkeys were exposed to the same concentration of ozone for only half as many days, they had larger biochemical and physiological alterations and equivalent morphometric changes as those exposed daily. Lung growth was not completely normal in either exposed group. Long-term effects of oxidant air pollutants which have a seasonal occurrence may be more dependent upon the sequence of polluted and clean air than on the total number of days of pollution. Estimations of the risks of human exposure to seasonal air pollutants from effects observed in animals exposed daily may underestimate long-term pulmonary damage.

Motor units and histochemistry in rat lateral gastrocnemius and soleus muscles: evidence for dissociation of physiological and histochemical properties after reinnervation

A reexamination of the question of specificity of reinnervation of fast and slow muscle was undertaken using the original "self" nerve supply to the fast lateral gastrocnemius (LG) and slow soleus muscles in the rat hindlimb. This paradigm takes advantage of the unusual situation of a common nerve branch, which supplies both a fast and slow muscle, and of the opportunity to keep the reinnervating nerve in its normal position. In addition it provides a test of the effects of cross-reinnervation among muscles of the same functional group. The properties of soleus and LG muscles and of individual muscle units were characterized in normal rats and in rats 4-14 mo after cutting the lateral gastrocnemius-soleus (LGS) nerve and suture of the proximal stump to the dorsal surface of the LG muscle. Individual muscle units were functionally isolated by stimulation of single motor axons to LG or soleus muscle contained in teased filaments in the L4 and L5 ventral roots. Motor units were classified as fast contracting fatiguable (FF), fast contracting fatigue resistant (FR), and slow (S) on the basis of criteria described in the cat by Burke et al. and applied to rat muscle units by Gillespie et al. Muscle fibers were classified as fast glycolytic (FG), fast oxidative glycolytic (FOG), and slow oxidative (SO) on the basis of histochemical staining for myosin ATPase, nicotinamide-adenine dinucleotide diaphorase (NADH-D), and alpha-glycerophosphate (alpha-GPD). Reinnervated muscles developed less force and weighed less in accordance with having fewer than normal motor units and having lost denervated muscle fibers. Normal LG contained a small proportion of S-type motor units (9%), whereas the majority (80%) of control soleus units were S type. After reinnervation, each muscle contained similar proportions of fast and slow motor units with S-type units constituting 30% of units in both muscles. When compared with the normal motor-unit sample, there was no significant change in average twitch and tetanic force in reinnervated muscles for each type of motor unit. However, the range within each type was greater, and there was considerable overlap between types. Twitch contraction time was inversely correlated with force in normal and reinnervated muscles as shown previously in self- and cross-reinnervated LGS in the cat. Changes in proportions of motor units in reinnervated LG were accompanied by corresponding changes in histochemical muscle types. This contrasted with reinnervated soleus in which the proportion of muscle fiber types was not significantly changed from normal despite significant change in motor-unit proportions.(ABSTRACT TRUNCATED AT 400 WORDS)

Institutional differences in therapeutic decision making in the Coronary Artery Surgery Study (CASS)

This article examines institutional differences in therapeutic decision making in the Coronary Artery Surgery Study (CASS). The initial decision to use medical therapy or coronary artery bypass surgery for coronary artery disease is studied. Data from the CASS registry and a survey of CASS principal investigators were used to examine the effects of institutional characteristics, individual physician characteristics, and decision making responsibility on the recommended therapy, the actual therapy, and the ratio of the observed to expected number of surgeries. The results indicated that the experience and involvement of the surgeon in the decision making process were related to actual and recommended rates of surgery. The percentage of urgent transfers from other hospitals and the percentage of surgical referrals to outside hospitals were related to the ratio of the observed to expected numbers of surgery, an adjusted rate of surgery. A major conclusion of this study is that despite the effects of certain institutional constructs, scientific criteria in the form of clinical and angiographic data are the most important determinants of whether a patient receives coronary artery bypass surgery.

Reinnervation of the lateral gastrocnemius and soleus muscles in the rat by their common nerve

To determine whether there is any specificity of regenerating nerves for their original muscles, the common lateral gastrocnemius soleus nerve (l.g.s.) innervating the fast-twitch lateral gastrocnemius (l.g.) and slow-twitch soleus muscles was sectioned in the hind limb of twenty adult rats. The proximal nerve stump was sutured to the dorsal surface of the l.g. muscle and 4-14 months later, the contractile properties of the reinnervated l.g. and soleus muscles and their single motor units were studied by dissection and stimulation of the ventral root filaments. Contractile properties of normal contralateral muscles were examined for comparison and motor units were isolated in l.g. and soleus muscles for study in a group of untreated animals. Measurement of time and rate parameters of maximal twitch and tetanic contractions showed that the rate of development of force increased significantly in reinnervated soleus muscles and approached the speed of l.g. muscles but rate of relaxation did not change appreciably. In reinnervated l.g. muscles, contraction speed was similar to normal l.g. muscles but relaxation rate declined toward the rates of relaxation in control soleus muscles. After reinnervation by the common l.g.s. nerve, the proportion of slow motor units in l.g. increased from 10 to 31% and decreased in soleus from 80 to 31%. The relative proportions of fast and slow motor units in each muscle were the same as the proportions of fast and slow units in the normal l.g. and soleus muscles combined. It was concluded that fast and slow muscles do not show any preference for their former nerves and that the change in the force profile of the reinnervated muscles is indicative of the relative proportions of fast and slow motor units: fast units dominate the contraction phase and slow units the relaxation phase of twitch and tetanic contractions of the muscle.

Long-term fate of bypass grafts: the Coronary Artery Surgery Study (CASS) and Montreal Heart Institute experiences

Both the Veterans Administration Cooperative Study and the European Coronary Surgery Study have provided only brief accounts of graft patency rates in their surgically treated patients. In the Veterans Administration Cooperative Study, at an average of 1 year after operation, 69% of the grafts were patent among 208 patients; 88% of patients had at least one patent graft, and 58% had all grafts patent. In the European Coronary Surgery Study, angiographic examination of the grafts was performed within 9 months of operation in 84 patients, and showed a patency rate of 90%; in 223 patients, the examination was performed at between 9 and 18 months, and showed a 77% patency rate. In the Coronary Artery Surgery Study (CASS), graft patency rates were evaluated within 60 days of operation in 129 patients, a median of 18 months after operation in 121 patients, and a median of 5 years after operation in 197 patients. Cumulative vein graft patency (per distal anastomosis) was 90% early, 82% at 18 months, and 82% at 5 years. At least one graft anastomosis was patent early in 97% of patients, at 18 months in 96% of patients, and at 5 years in 97% of patients; all graft anastomoses were patent early in 81% of patients, at 18 months in 70% of patients, and at 5 years in 67% of patients. The incidence of vein graft stenosis of 50% or more was 10% at 18 months and 8% at 5 years after operation. The excellent results reported in CASS were associated with marked improvement in quality of life and excellent survival 5 years after operation in surgically treated patients, as previously reported.(ABSTRACT TRUNCATED AT 250 WORDS)

A test of the National Death Index using the Coronary Artery Surgery Study (CASS)

The National Death Index (NDI) is a central, computerized index of death record information compiled from records submitted by the Vital Statistics Office of each state to the National Center for Health Statistics. A selection of 1180 cases, including 370 decedents, from the Coronary Artery Surgery Study was sent to the NDI to test the reliability of the index in identifying decedents. Five possible matching rules are considered: an NDI match with soundex included, an NDI match without soundex matches, an NDI match on social security number, an NDI match on personal data (first name, last name, sex, race, and month, day, and year of birth), and an NDI match on social security number or personal data. In determining death, the greatest positive predictive value was given by a match on social security number, while the greatest negative predictive value was given by an NDI match with soundex included. Further comparisons of sensitivity and specificity, and figures that relate predictive values to the population mortality rate, are given to assist potential users in determining an optimal matching rule.

A randomized trial of coronary artery bypass surgery. Survival of patients with a low ejection fraction

The Coronary Artery Surgery Study (CASS) was designed to compare medical and surgical treatment of selected patients with chronic, stable coronary artery disease. This report concerns a subset of patients with reduced ventricular function. Of 780 patients randomly assigned to medical or surgical treatment, 160 had ejection fractions above 0.34 but below 0.50 at base line and have been followed for an average of seven years. Eighty-two patients were assigned to medical therapy, and 78 to surgery; the two groups were comparable at base line with regard to prognostically important variables. At seven years, 84 per cent of patients in the surgical group were alive, as compared with 70 per cent of the medical group (P = 0.01). Nearly half the patients with impaired ventricular function had triple-vessel disease at entry; at seven years, observed survival in this group was 88 and 65 per cent for those assigned to surgical and medical treatment, respectively (P = 0.009). Survival of patients with single-vessel or double-vessel disease was similar in the two treatment groups. We conclude that patients with triple-vessel disease and ejection fractions higher than 0.34 but lower than 0.50 appear to have improved seven-year survival with elective bypass surgery.

Survival following coronary artery bypass grafting in patients with severe angina pectoris (CASS). An observational study

This observational study evaluates the effects of the severity of angina pectoris and the treatment method upon the survival of 4,209 patients in the Coronary Artery Surgery Study registry. In this nonrandomized study, these patients met the criteria used in the Coronary Artery Surgery Study randomized trial, except for the degree of angina pectoris and the method of selection of treatment. The 5 year survival rate was greater than or equal to 93% in patients with Class I and II angina pectoris and normal left ventricular function, regardless of the number of involved vessels or treatment received. Late survival of surgically treated patients with Class III and IV angina pectoris and normal left ventricular function was similar, regardless of the number of vessels involved (greater than or equal to 92% at 5 years). Nonoperatively treated patients with Class III and IV angina pectoris and normal left ventricular function had poorer 5 year survival rates, lowest (74%) in patients with three vessel disease (p less than 0.0001). This difference was also observed in patients with abnormal left ventricular function, three vessel disease, and Class III and IV angina pectoris; the 5 year survival rates were 82% for the operative group and 52% for the nonoperative group (p less than 0.0001). These data confirm the importance of clinical as well as anatomic factors in determining the prognosis of patients with ischemic heart disease and indicate that coronary artery bypass grafting can improve late survival in patients with triple vessel disease and severe angina pectoris.

The relationship between axon diameter, myelin thickness and conduction velocity during atrophy of mammalian peripheral nerves

The atrophy of cutaneous (sural) and muscle (medial gastrocnemius) nerves proximal to a ligation were studied in cats for periods up to 9 months, using light and electron microscopy, conduction velocity measurements and computer simulations. As atrophy proceeds, nerve fibres become increasingly non-circular. Cross-sectional areas of axons and fibres (axon + myelin) were measured. The diameters of equivalent circles (having the same axon and fibre cross-sectional area) were then calculated. A linear relation was found between axon diameter and fibre diameter, but the slope decreased as atrophy continued. This indicates that the axon cross-sectional area decreases relatively more than the total fibre area. Reduction in conduction velocity correlates more closely with reduction in axon diameter than fibre (axon + myelin) diameter. The ratio of the inner (axon) perimeter to the outer (myelin) perimeter remains constant at or near the optimal value of 0.6 for conduction in all groups of fibres at all periods of atrophy. Furthermore, the thickness of the myelin remains constant for a given perimeter over the entire period of atrophy studied. This suggests that the number of turns of myelin and the length of each turn remain unchanged during peripheral nerve atrophy. A simple geometric model explains how this can occur without gaps developing between the axon and myelin or between the turns of myelin. The Frankenhaeuser-Huxley equations for conduction in myelinated nerve fibres predict changes in conduction velocity similar to those observed, if the axons atrophy without changes in myelin. The advantages of this mode of atrophy are discussed.

The clinical spectrum of coronary artery disease and its surgical and medical management, 1974-1979. The Coronary Artery Surgery study

Data from the National Heart, Lung, and Blood Institute's Coronary Artery Surgery Study (CASS) are used to describe the types of persons who undergo coronary angiography for possible coronary artery bypass surgery, the reasons patients receive coronary bypass surgery, and operative mortality results, as well as changing trends in the therapy assigned. The review is designed to provide background material for those assessing coronary artery bypass technology.

C2: a data base management system developed for the Coronary Artery Surgery Study (CASS) and other clinical studies

For the Coronary Artery Surgery Study (CASS), large variable amounts of data on different form-types are collected on many different patients. In this paper, we describe C2, a "state-of-the-art" command-oriented data base system developed in response to the needs of maintaining a large complex data base and performing subsequent analyses on a large number of studies. C2 provides a friendly, interactive interface with the researcher as well as a powerful method for data extraction, data transformation, and the merging of files from the CASS data base.

Determinants of coronary surgery in a consecutive patient series from geographically dispersed medical centers. The coronary artery surgery study

The Coronary Artery Surgery Study registry enrolled 24,959 patients from 1974 through 1979. Of these patients, 12,556 had anginal chest pain symptoms and significant angiographic coronary disease (greater than or equal to 70% lesion in a major vessel or greater than or equal to 50% in the left main coronary artery) and were considered coronary bypass surgery candidates. Stepwise linear discriminant-function analysis of clinical and angiographic determinants of therapeutic assignment revealed that myocardial jeopardy (a composite score of the relationship of proximal lesions to retained wall motion in anterior and inferior segments) was the most important determinant. Site-to-site variability, another important predictor of therapeutic assignment, was assessed after adjusting for differing patient populations and was found to be significant (p less than 0.001). Other significant predictors were angina severity, the number of operable vessels, change in activity level, unstable angina and the presence of a left main lesion. Temporal changes (between 1974 and 1979) in the use of beta-blocking drugs and in therapeutic assignment of patients with left main lesions and one-vessel disease suggested altered decision-making in response to the reporting of major coronary surgery trials. We conclude that the dominant factors in therapeutic assignment for patients with completed arteriographic evaluations reflect considerations of jeopardized myocardium and continuing diversity of opinion about the importance of therapeutic and prophylactic indications for coronary surgery.

Percutaneous transluminal coronary angioplasty: report from the Registry of the National Heart, Lung, and Blood Institute

Data have been collected from 34 centers in the United States and Europe performing percutaneous transluminal coronary angioplasty since September 1977. The procedure was carried out in 631 patients, with an average age of 51 years (range 23 to 76), of whom 80 percent had single vessel coronary disease, 17 percent had double or triple vessel disease and 3 percent had stenosis of the left main coronary artery. Coronary angioplasty was successful (greater than 20 percent decrease of coronary stenosis) in 59 percent of the stenosed arteries. The mean degree of stenosis was reduced from 83 to 31 percent. Emergency coronary bypass operation was required in 40 patients (6 percent). Myocardial infarction occurred in 29 patients (4 percent). In-hospital death occurred in six patients (1 percent), three with single vessel and three with multivessel disease. Ninety-one patients have been followed up for at least 1 year after coronary angioplasty. Of the 65 patients with an initially successful angioplasty, 83 percent were in improved condition compared with their status before angioplasty. Thus, the initial satisfactory results obtained in a few centers have now been confirmed in many centers using transluminal coronary angioplasty.