Contribution of vasomotion to vascular resistance: a comparison of arteries from virgin and pregnant rats

Intrinsic oscillatory activity, or vasomotion, within the microcirculation has many potential functions, including modulation of vascular resistance. Alterations in oscillatory activity during pregnancy may contribute to the marked reduction in vascular resistance. The purpose of this study was 1) to mathematically model the oscillatory changes in vessel diameter and determine the effect on vascular resistance and 2) to characterize the vasomotion in resistance arteries of pregnant and nonpregnant (virgin) rats. Mesenteric arteries were isolated from Sprague-Dawley rats and studied in a pressurized arteriograph. Mathematical modeling demonstrated that the resistance in a vessel with vasomotion was greater than that in a static vessel with the same mean radius. During constriction with the alpha1-adrenergic agonist phenylephrine, the amplitude of oscillation was less in the arteries from pregnant rats. We conclude that vasomotor activity may provide a mechanism to regulate vascular resistance and blood flow independent of static changes in arterial diameter. During pregnancy the decrease in vasomotor activity in resistance arteries may contribute to the reduction in peripheral vascular resistance.

Ventriculo-arterial discordance: switching the morphologically left ventricle into the systemic circulation after 3 months of age

OBJECTIVE

To retrospectively examine a 4 year policy of restoring the morphologically left ventricle to the systemic circuit in patients presenting after 3 months of age with ventriculo-arterial discordance with or without associated atrio-ventricular discordance. This policy was stimulated by the known tendency of the morphologically right ventricle to develop dysfunction sooner or later when left in the systemic circuit. Such a policy dictates a more complex surgical approach and, at this point, it remains controversial whether or not the increased surgical complexity is warranted.

METHODS

From July 1, 1993 to March 31, 1997, a total of 29 patients were entered into a protocol for placement of the morphologically left ventricle into the systemic circuit. Three groups of patients were identified. Group I; congenitally corrected transposition in 14 patients -- were treated with either a Senning plus arterial switch operation or Senning plus Rastelli procedure. Group II; failed atrial switch procedure in 12 patients of which nine proceeded to arterial switch operation with Senning or Mustard takedown and atrial reseptation. Group III; D-transposition of the great vessels presenting more than 1 year after birth in three patients who underwent arterial switch operation alone. A deconditioned morphologically left ventricle required reconditioning by means of preparatory pulmonary artery banding in 17 of 29 patients. In the patients requiring pulmonary artery banding, an average of 2.1 pulmonary artery bandings was required to prepare the morphologically left ventricle for a systemic pressure workload.

RESULTS

In those patients with a deconditioned morphologically left ventricle requiring preparatory pulmonary artery banding, the mean ratio between the left ventricular and right ventricular systolic pressure increased from 0.48 to 0.95. The left ventricular mass increased from 46.6 to 81.8 g/m2 in five patients subjected to serial MRI measurement. Three patients failed the preparatory pulmonary artery banding and did not proceed to anatomical correction. Two subsequently died at a later time. In the patients proceeding to complete anatomical correction: group I -- there were no early or late deaths. Two patients required pacemaker implantation post-operatively. Group II -- there were two in-hospital deaths, one early due to intrapulmonary hemorrhage and one late, secondary to postoperative left ventricular failure with a stormy post-operative course requiring successful ECMO placement and weaning. These patients were 18 and 25 years old, respectively. One patient proceeded to cardiac transplantation 3 months after surgery due to ongoing morphologically left and right ventricular dysfunction. Group III -- all patients continue to do well.

CONCLUSIONS

Late anatomic correction of ventriculo-arterial discordance with or without atrio-ventricular discordance can be performed at a relatively low risk. Reconditioning of the morphologically left ventricle can be achieved by sequential pulmonary banding but is not without risk. Failure to achieve adequate reconditioning of the morphologically left ventricle by pulmonary artery banding in the older patient probably increases the risk of non-survival and may be offset by timely transplantation. Longer follow-up and an assessment of the functional status of these patients is required to assess whether or not this complex surgical approach is indeed warranted.

Vascular rejection post heart transplantation is associated with positive flow cytometric cross-matching

OBJECTIVE

Use of flow cytometry cross-matching for measurement of donor-specific alloreactivity and monitoring anti-donor antibodies is well established. This study was performed to determine (1) its accuracy as a marker of vascular rejection, (2) its correlation with post-transplant outcome and (3) its ability to monitor highly sensitized patients requiring antibody removal with plasma exchange.

METHODS

Serial serum samples from 99 heart transplant recipients were examined for the presence of anti-donor antibodies of the IgG class that were reactive with T and/or B cryopreserved donor lymphocytes. A sub-group of 20 HLA sensitized patients required plasma exchange to remove the anti-HLA antibodies and were monitored with flow cytometry cross-matching to assess the degree of antibody removal.

RESULTS

Positive T-cell reactions were observed in 26 patients and positive B-cell reactions in 54. Twenty patients had vascular rejection. A significantly larger number of patients with a positive flow cytometry cross-match had vascular rejection (42% versus 12% for T-cell reactions, and 32% versus 7% for B-cell reactions; P = 0.002 each). Of the patients who had vascular rejection, 11 had a positive T-cell reaction (flow cytometry cross-match sensitivity of 55%), and 17 had a positive B-cell reaction (sensitivity of 85%). Of the 79 patients who did not develop vascular rejection, 64 had a negative T-cell reaction (specificity of 81%), and 42 had a negative B-cell reaction (specificity of 53%). The actuarial 2-year survival estimates were significantly higher in patients with negative T-cell reactions (90% versus 75%; P = 0.04), and B-cell reactions (95% versus 78%; P = 0.02). In the highly sensitized subgroup (n = 20) the effectiveness of plasma exchange to decrease anti-HLA antibody reactivity was a strong predictor of outcome. For patients in whom plasma exchange (PE) reduced anti-donor reactivity, 1-year survival was 87% compared to 25% in those whom PE did not reduce the level of antibody binding as assessed with flow cytometry cross-matching (P < 0.0001).

CONCLUSIONS

Flow cytometry cross-matching provides a valuable marker for the detection of vascular rejection after cardiac transplantation. Quantitative measurements may allow evaluation of the efficacy of treatment modalities employed in the management of vascular rejection in an attempt to improve outcome.

Risk factors for death after heart transplantation: does a single-center experience correlate with multicenter registries?

BACKGROUND

Risk factors for death after heart transplantation (Tx) are frequently documented from multicenter registries. Although this information is helpful, it reflects a whole range of experiences and results, and may not translate to a particular center. This study was performed to (1) evaluate pre-Tx factors affecting mortality in a single-center experience, and (2) compare these factors with risk factors obtained from multicenter registry reports.

METHODS

Review of our transplant database between January 1984 and December 1995 identified 405 adults who received a primary heart Tx. Multiple factors were analyzed, including demographics, Tx era, cytomegalovirus status, United Network for Organ Sharing status of recipient, presence of pulmonary hypertension, previous cardiac operations, mechanical ventilation or circulatory support, ischemia time, number of rejection episodes, and preoperative flow cytometry crossmatching.

RESULTS

One- and 5-year survival rates were 87.8% and 73.4%, respectively (Kaplan-Meier). Contrary to multicenter registry reports, our data indicate that reoperative procedures, left ventricular assist device support, increasing donor and recipient age, and ischemia time up to 4.2 hours are not risk factors for death after Tx. Likewise, mode of donor death is not a risk factor affecting outcome. Significant risk factors for mortality identified by multivariate analysis included early transplant era (1984 to 1989; p = 0.002), female donor (p = 0.042), cytomegalovirus-seropositive donor (p = 0.048), high pulmonary vascular resistance (p = 0.018), and intraaortic balloon pump support (p = 0.03). It also identified a positive B-cell flow cytometry crossmatch (p = 0.015) to be a risk factor with univariate analysis.

CONCLUSIONS

Our data identify a group of recipients, reportedly at high risk in multicenter registries, who are not at increased risk of death after Tx. This information supports the growing experience with older donors and recipients and with bridged transplants, and has allowed us to expand our donor pool. These prognostic factors at evaluation allow more liberal selection of patients and donors for transplantation.

Optimizing mitral valve exposure with conventional left atriotomy

The standard surgical approach to the mitral valve is accomplished through a longitudinal incision in the left atrium, posterior and parallel to the interatrial groove. Many other surgical approaches have evolved. This report describes a technique of optimizing mitral valve exposure via the standard approach. These modifications are simple, do not lengthen the procedure, and usually obviate the need for more complex maneuvers.

Partial left ventriculectomy and mitral valve repair for end-stage congestive heart failure

OBJECTIVE

Partial left ventriculectomy (PLV), pioneered by Batista, has been proposed as an alternative treatment strategy in patients with refractory congestive heart failure. In order to analyze the midterm outcome of PLV and mitral valve (MV) repair and stratify patients according to risk, we prospectively studied 57 consecutive patients who underwent this procedure at the Cleveland Clinic Foundation (CCF).

METHODS

Patients had a mean age of 53 years and were predominantly males (74%). In 95% the etiology of heart failure was idiopathic dilated cardiomyopathy. All patients had a left ventricular end diastolic diameter of >7cm and were in New York Heart Association (NYHA) functional classes III and IV. A total of 54 patients (95%) were awaiting heart transplantation. Preoperatively, requirements included inotropes in 23 (40%), intraaortic balloon pump counterpulsation in 3 (5.3%), and left ventricular assist device placement (LVAD) in 1 (1.8%). Concomitant procedures included MV repair (55 patients), MV replacement (2), tricuspid valve repair (34 patients), coronary artery bypass graft (CABG) (5), and aortic valve repair or replacement (1 patient each).

RESULTS

Measurements preoperatively and at 3 months demonstrated improvement in left ventricular ejection fraction (14.4 +/- 7.7-23.2 +/- 10.7%, P < 0.001), left ventricular end diastolic volume (254 +/- 85-179 +/- 73 ml, P < 0.001) and left ventricular end diastolic diameter (8.4 +/- 1.1-6.3 +/- 0.9 cm, P < 0.001). Peak oxygen consumption (MVO2) increased from 10.6 +/- 3.9 to 15.3 +/- 4.5 ml/kg per min (P < 0.001). Cardiac index did not change (2.2 l/min per m2), although 40% had been on inotropes preoperatively and none were on inotropes at 3 months. NYHA functional class improved from 3.6 +/- 0.5 preoperatively to 2.2 +/- 0.9 at 3 months (P < 0.001). LVAD support was required as rescue therapy in 11 patients (17%). Actuarial freedom from procedure failure, defined as death or relisting for transplant, was 58% at 1 year. Hospital mortality was 3.5% (n = 2). On follow-up, there were 7 late deaths (including 3 sudden deaths) giving an actuarial survival of 82% at 1 year. Multivariate risk factor analysis revealed that age less than 40 years was associated with failure (P = 0.02).

CONCLUSIONS

Although PLV with MV repair is now a surgical option in the treatment of end-stage congestive heart failure, caution is advised as early failures are unpredictable and mechanical support may be required as rescue therapy. Better risk stratification and patient selection may improve outcome. Further study is required to determine the procedure's exact role in the treatment of congestive heart failure.

Factors influencing HLA sensitization in implantable LVAD recipients

BACKGROUND

Patients bridged to transplantation (TX) with the implantable left ventricular assist device (LVAD) may be at increased risk for the development of panel-reactive antibodies (PRA) during support.

METHODS

To investigate that, we evaluated 60 patients who received the HeartMate LVAD at our institution, of whom 53 had PRA results available for analysis. T lymphocyte PRA levels were examined before LVAD, at the peak PRA level during LVAD support (PEAK), and just before TX. A PRA level more than 10% was considered indicative of sensitization against HLA antigens.

RESULTS

The only factor that had a significant effect on PRA levels before LVAD was patient's sex (1.3% for men versus 7.4% for women; p = 0.005). During LVAD support, peak PRA levels increased significantly and the sex-associated differences were no longer evident (33.3% men, 34.3% women; not significant). At the time of TX, PRAs decreased to 10.9% (men) and 7.0% (women) (not significant). We examined the influence of blood products received before TX on PRA levels. Patients who received less than the median number of total units (<median) had lower peak PRA values (22.3% versus 49.2%; p = 0.01) and TX PRA values (3.5% versus 22.1%; p = 0.02) than those receiving more than the median (>median). When examined by the type of blood product, only the number of platelet transfusions significantly increased the peak PRA (<median: 24% versus >median: 46.9%; p = 0.03). Patients who received blood that was leukocyte-depleted tended to have lower TX PRA levels (2.9%) compared with those who did not (13.9%, p = 0.18). Forty-two patients were successfully bridged to TX, with three early and two late deaths after TX. Whereas 39 patients received transplants without intervention, 3 were treated by plasmapheresis with a 77% reduction in their HLA antibody levels at TX as measured by flow cytometry.

CONCLUSIONS

Patients with the implantable LVAD are at significant risk for the development of anti-HLA antibodies during support. Although this sensitization is often transient, intervention using plasmapheresis may be useful for some patients.

Video-assisted thoracic surgery (VATS) for spontaneous pneumothorax

Video-assisted thoracic surgery (VATS) involves using a thoracoscope with a camera chip attached to a video monitor which allows certain thoracic procedures to be performed with limited incisions. Using VATS, 170 procedures have been performed on 158 patients including 42 procedures on 39 patients with spontaneous pneumothorax. There were 24 males and 15 females with age ranging from 17 to 84 yr (mean 36.7). Indication for operation included recurrent pneumothorax in 20 (51 per cent), persistent pneumothorax in 16 (41 per cent) and bilateral pneumothorax in 3 (8 per cent). The main therapeutic strategies were apical pleurectomy, in all (42) and blebectomy/bullectomy in 38 (90 per cent). There was one hospital death (hospital mortality 2.5 per cent) in an elderly patient who developed multi organ failure post bullectomy and persistent air leak. One patient (2.5 per cent) required conversion to formal thoracotomy. Mean post-operative chest tube duration was 2.7 days and mean post-operative hospital stay was 5.1 days. There has been no recurrence of pneumothorax in this series during short term follow up (mean 18 months). Our experience indicates an expanding role for video-assisted thoracic surgery in the management of patients with spontaneous pneumothorax.

Tricuspid valve repair with the Cosgrove-Edwards Annuloplasty System

The technique of tricuspid valve repair with the Cosgrove-Edwards Annuloplasty System is described. This system provides a measured plication of the tricuspid valve annulus with a technique that is easily reproducible and permits physiologic motion of the tricuspid annulus.

Pregnancy prevention among urban adolescents younger than 15: results of the 'In Your Face' program

Data from a pregnancy prevention program operating through school-based clinics in four New York City junior high schools suggest that an intensive risk-identification and case-management approach may be effective among very young adolescents. Among students given a referral to a family planning clinic for contraception, the proportion who visited the clinic and obtained a method rose from 11% in the year before the program began to 76% in the program's third year. Pregnancy rates among teenagers younger than 15 decreased by 34% over four years in the program schools. In the fourth year of the program, the pregnancy rate in one school that was unable to continue the program was almost three times the average rate for the other three schools (16.5 pregnancies per 1,000 female students vs. 5.8 per 1,000).

8-epi PGF2 alpha generation during coronary reperfusion. A potential quantitative marker of oxidant stress in vivo

BACKGROUND

Myocardial reperfusion is believed to be associated with free radical injury. However, indexes of oxidative stress in vivo have been limited by their poor specificity and sensitivity. Isoprostanes are stable products of arachidonic acid formed in a nonenzymatic, free radical-catalyzed manner. We have developed a sensitive and specific assay for one of these compounds, 8-epi prostaglandin (PG) F2 alpha.

METHODS AND RESULTS

To address its utility as an index of oxidative stress during coronary reperfusion, we measured urinary levels by gas chromatography/mass spectrometry in a canine model of coronary thrombolysis, in patients with acute myocardial infarction treated with thrombolytic therapy, and in patients after elective coronary artery bypass surgery. Urinary 8-epi PGF2 alpha was unchanged after circumflex artery occlusion in a canine model of coronary thrombolysis (n = 13; 437.2 +/- 56.4 versus 432.7 +/- 55.2 pmol/mmol creatinine) but increased significantly (P < .05) immediately after reperfusion (553.8 +/- 64.7 pmol/mmol). Urinary levels were increased (P < .001) in patients (n = 12) with acute myocardial infarction given lytic therapy (265.8 +/- 40.8 pmol/mmol) compared with age-matched control subjects (n = 20; 91.5 +/- 11.8 pmol/mmol) and patients with stable coronary disease (n = 20; 95.7 +/- 6.3 pmol/mmol). Preoperative levels rose from 113.2 +/- 11.8 to 248.2 +/- 86.3 pmol/mmol at 30 minutes into revascularization to 332.2 +/- 82.6 pmol/mmol by 15 minutes after global myocardial reperfusion (P < .05) and dropped to 181.2 +/- 50.4 pmol/mmol at 30 minutes and 120.2 +/- 9.9 pmol/mmol at 24 hours after bypass surgery (n = 5). Corresponding changes in spin adduct formation, found with electron paramagnetic resonance, were noted in 2 patients.

CONCLUSIONS

These data support the hypothesis that free radical generation occurs during myocardial reperfusion. Measurement of isoprostane production may serve as a noninvasive index of oxidative stress.

Surgical relief of tracheobronchial obstruction in infants and children

OBJECTIVE

Congenital tracheobronchial obstruction (TBO) presents a complex problem both in terms of diverse aetiology, presence of associated anomalies and the operative strategy to be adopted. We report a single centre experience in managing this difficult problem.

METHODS

Twenty-four infants and children with TBO referred to our unit over a 12-year period are reviewed. Aetiology of TBO included vascular rings (n = 9), anomalous innominate artery (n = 6), congenital tracheal stenosis (n = 5), segmental bronchial stenosis (n = 2) and pulmonary artery compression of the main bronchi (n = 2). Seven patients had concurrent cardiac anomalies. Stridor was the commonest presenting symptom (67%). Mean delay from onset of symptoms to referral was 19 months. One patient died preoperatively due to acute airway obstruction. Mean age at operation was 33.1 +/- 42 months (range 4 days-156 months) and 11 children were under 1 year at the time of surgery. In cases of TBO secondary to vascular rings, division of the ring resulted in relief of symptoms in seven cases, with two requiring further surgery for resultant tracheomalacia. Four of the five patients having tracheal resection were operated on with the use of cardiopulmonary bypass; three of these patients had concurrent correction of cardiac lesions, with two survivors. Tracheobronchial anastomoses were carried out using continuous polydioxanone (PDS). Patients with anomalous innominate arteries required aortopexy in five and innominate artery suspension in one, while those with pulmonary artery compression of the main bronchi had correction of their intracardiac defects (n = 2).

RESULTS

Hospital mortality was 8.7% and there has been one late death due to Eisenmenger syndrome secondary to pulmonary regurgitation, atrial septal defect (ASD) and patent ductus arteriosus (PDA). On follow-up (mean 40 +/- 31 months), 19 patients are alive and symptom free. There have been no anastomotic strictures following tracheobronchial resection. The single most important predictor of mortality was the presence of associated cardiac anomalies.

CONCLUSIONS

TBO can be managed effectively by a single operation in both infants and children without a detrimental effect on tracheal growth. We advocate consideration of concurrent repair of the tracheal and cardiac lesions. Cardiopulmonary bypass (CPB) allows this concurrent correction of cardiac lesions and also facilitates tracheal resection.

Video-assisted control of haemorrhage post coronary artery bypass surgery

Excessive bleeding post coronary artery bypass surgery (CABG) remains a major source of morbidity and mortality. Approaching this bleeding with a resternotomy, while necessary in the vast majority of cases, is associated with an increased incidence of infections and sternal wound complications. A thoracoscopic approach in select patients with a pleural based collection is described.

The diverse potential of thoracoscopic assisted surgery

Thoracoscopy has been a part of thoracic surgical practice for many years. The introduction of the camera chip and newer instrumentation has awakened a new interest in this technique and led to the development of video-assisted thoracic surgery (VATS). One hundred and seventy consecutive procedures performed on 158 patients are reviewed. Video-assisted techniques have proven useful in a broad spectrum of thoracic surgical procedures both diagnostic (n = 90) and therapeutic (n = 80). Hospital mortality was 1.3%. Conversion to formal thoracotomy was required in 2.5%, and re-exploration for bleeding in 0.6%. The technique was safe and the incidence of complications acceptable. VATS was particularly helpful in diagnosing "indeterminate" pulmonary nodules (sensitivity of 95%), interstitial lung disease (histological diagnosis in all), anterior mediastinal masses and post transplant pneumonitis. VATS may now be the surgical treatment of choice in those with spontaneous pneumothorax, and it also proved useful in a variety of benign disorders. Its role in the management of empyaema is limited with a 57% conversion rate. While pulmonary resections are feasible, its role in the therapeutic management of malignancy is questioned. Further studies are required to define the precise role of VATS in thoracic surgery.

Emergency sleeve lobectomy after blunt chest trauma in a child

The clinical features and successful management of a patient with right main bronchus disruption after blunt chest trauma are described. The presentation was one of bilateral tension pneumothoraces. A high index of suspicion, coupled with appropriate airway management at presentation, was vital for the successful treatment of this patient. Surgical resection using a sleeve lobectomy, an operation rarely used in trauma patients, was highly effective in this patient, and the technique is described in this report.

The development, reliability, and validity of a risk factor screening survey for urban minority junior high school students

PURPOSE

To develop and evaluate a risk factor screening survey as a mechanism to identify inner-city junior high school students who may benefit from medical or mental health services available in school-based clinics.

METHODS

A 36-item health risk factor screening survey was developed and administered to 3,787 predominantly Hispanic students from four schools in an economically disadvantaged, medically underserved New York City school district. Students who indicated that they were experiencing one of five major risk factors (suicidality, sexual activity, parental or guardian substance use, personal substance use, or having run away) were scheduled to visit the clinic for services, and to have their survey responses validated by clinic interview.

RESULTS

The development of the screening tool resulted in a short, easy to read and understand survey instrument that was feasible to administer within a classroom setting. The reliability of the instrument was excellent, and the results of the validity study indicated that it was successful in identifying students who did not need clinic services. The screening tool produced mixed results in identifying those truly in need through single item identification (e.g., produced a moderate number of "false positives"), although combining items on the screening tool produced much higher positive predictive values.

CONCLUSIONS

This screening tool can be used to effectively focus limited clinical resources on those in need. Outreach surveys of this type should be considered as a valuable component of a school-based clinic service delivery strategy.

Characteristics of users and nonusers of health clinics in inner-city junior high schools

PURPOSE

To compare the demographic, behavioral, psychosocial, and academic characteristics of users versus nonusers of inner-city junior high school-based health clinics.

METHODS

Students who used (n = 1344) and did not use (n = 2394) the health clinics based in four junior high schools in an economically disadvantaged, medically underserved New York City school district were compared on their responses to a health risk survey administered at the end of the 1991/92 academic year.

RESULTS

Compared to students who did not use the clinics, students who used the clinics were more likely to have had unprotected sexual intercourse, to have had suicide intentions or attempts, to be suspended from school for fighting, to be exposed to violence and the illicit drug culture, to hold beliefs favoring involvement in sexual intercourse and suicidality, and to have failed subjects in school.

CONCLUSIONS

Users of these junior high school-based health clinics are engaging in behaviors and hold beliefs that place them at risk for serious adverse health outcomes. School-based clinics have the potential to provide early intervention for these high risk adolescents.

Carrying and using weapons: A survey of minority junior high school students in New York City

To explore weapon carrying among young, inner-city adolescents, a survey was administered in fall 1993 to 2005 predominately Hispanic students (mean age = 12.8 years) in three New York City junior high schools. The survey revealed that 21% of students reported personally carrying a weapon; guns and knives were the weapons most commonly carried. Most of those who carried guns reported that they bought them. Forty-two percent indicated that they had a family member or close friend who had been shot. Boys and older students were more likely to report carrying weapons. Preventive efforts may need to begin before or on entry into junior high school rather than high school.