Minimally invasive aortic valve replacement with sutureless and rapid deployment valves: a report from an international registry (Sutureless and Rapid Deployment International Registry)†

OBJECTIVES

The impact of sutureless and rapid deployment (SURD) valves on the clinical outcomes of patients undergoing minimally invasive aortic valve replacement (MI-AVR) has still to be defined. The aim of this study was to assess clinical characteristics and in-hospital results of patients receiving SURD-AVR through less invasive approaches in the large population of the Sutureless and Rapid Deployment International Registry (SURD-IR).

METHODS

Of the 1935 patients who received primary isolated SURD-AVR between 2009 and 2018, a total of 1418 (73.3%) underwent MI interventions and were included in this analysis. SURD-AVR was performed using upper ministernotomy in 56.4% (n = 800) of cases and anterior right thoracotomy in 43.6% (n = 618). Perceval S was implanted in 1011 (71.3%) patients and Edwards Intuity or Intuity Elite in 407 (28.7%) patients.

RESULTS

Overall in-hospital mortality and stroke rates were 1.7% and 2%, respectively. A definitive pacemaker implantation was reported in 9% of cases and significantly decreased over the observational period, from 20.6% to 5.6% (P = 0.002). The Perceval valve was associated with shorter operative times and was more frequently implanted in patients receiving anterior right thoracotomy incision. The Intuity valve was preferred in younger patients and revealed superior postoperative haemodynamic results.

CONCLUSIONS

SURD-AVR was largely performed through less invasive approaches and can be considered as a primary indication in MI surgery. In the SURD-IR cohort, MI SURD-AVR using both Perceval and Intuity valves appeared a safe and reproducible procedure associated with promising early results.

Operative outcome of patients at low, intermediate, high and 'very high' surgical risk undergoing isolated aortic valve replacement with sutureless and rapid deployment prostheses: results of the SURD-IR registry

OBJECTIVES

The ideal strategy for the treatment of severe aortic valve stenosis in patients of varying risk categories has become a debated topic in the last years: should the transcatheter or surgical approach be adopted? The aim of this study was to evaluate the outcomes of low-, intermediate-, high- and very high-risk patients undergoing sutureless, rapid deployment aortic valve replacement.

METHODS

From 2007 to 2017, data on a total of 3651 patients were collected from the Sutureless and Rapid Deployment Aortic Valve Replacement International Registry (SURD-IR). Of these, 2057 patients who underwent primary isolated aortic valve replacement were considered for this analysis and classified as being at low (EuroSCORE <5; n = 500), intermediate (EuroSCORE 5-10; n = 901), high (EuroSCORE 11-20; n = 500) and very high (EuroSCORE >20; n = 156) preoperative risk.

RESULTS

Overall, a less invasive approach was used in 74.1% of patients and represented the most frequent (>50%) approach in all risk categories. The Perceval prosthesis was used more frequently than other devices, especially in patients at high and very high risk. Hospital mortality was 1.6%, 0.8%, 1.9% and 2.7% in low-, intermediate-, high- and very high-risk patients, respectively, with no significant differences among subgroups. Similarly, postoperative complication rates were similar across the different risk categories.

CONCLUSIONS

Surgical aortic valve replacement using sutureless, rapid deployment biological valve prostheses is associated with excellent results and represents a safe and effective treatment option for patients with severe aortic valve stenosis. This seems to be particularly true in patients with a higher risk profile.

Cardiac Surgery in Patients With Liver Cirrhosis (CASTER) Study: Early and Long-Term Outcomes

BACKGROUND

Patients with liver cirrhosis (LC) undergoing cardiac surgery (CS) face perioperative high mortality and morbidity, but extensive studies on this topic are lacking.

METHODS

All adult patients with LC undergoing a CS procedure between 2000 and 2017 at 10 Italian Institutions were included in this retrospective cohort study. LC was classified according to preoperative Child-Turcotte-Pugh (CTP) score and Model for End-Stage Liver Disease (MELD) score. Early-term and medium-term outcomes analysis was performed in the overall population and according to CTP classes.

RESULTS

The study population included 144 patients (mean age 66 ± 9 years, 69% male). Ninety-eight, 20, and 26 patients were in CTP class A, in early CTP class B (MELD score <12), or advanced CTP class B (MELD score >12), respectively. The main LC etiologies were viral (43%) and alcoholic (36%). Liver-related clinical presentation (ascites, esophageal varices, and encephalopathy) and laboratory values (estimated glomerular filtration rate, serum albumin, and bilirubin, platelet count) significantly worsened across the CTP classes (P = .001). Coronary artery bypass grafting or valve surgery (87% bioprosthesis) were performed in 36% and 50%, respectively. Postoperative complications (especially acute kidney injury, liver complication, and length of stay) significantly worsened in advanced CTP class B (P = .001). Notably, observed mortality was 3-fold or 4-fold higher than the EuroSCORE (European System for Cardiac Operative Risk Evaluation) II-predicted mortality, in the overall population, and in the subgroups. At Kaplan-Meier analysis, 1-year and 5-year cumulative survival in the overall population was 82% ± 3% and 77% ± 4%, respectively. The 5-year survival in CTP class A, early CTP class B, and advanced CTP class B was 72% ± 5%, 68% ± 11%, and 61% ± 10%, respectively (P = .238).

CONCLUSIONS

CS outcomes in patients with LC are significantly affected in relation to the extent of preoperative liver dysfunction, but in early CTP classes, medium-term survival is acceptable. Further analysis are needed to better estimate the preoperative risk stratification of these patients.

The Neochord Procedure After Failed Surgical Mitral Valve Repair

Surgical mitral valve reintervention is associated with significant morbidity and mortality, and repeat repair is not always feasible. We examine the clinical outcomes of the NeoChord procedure after failed conventional mitral valve repair. A total of 312 patients were treated with the NeoChord repair procedure between January 2014 and December 2018 at 5 European centers. Clinical and echocardiographic data were reviewed to identify patients who had a prior surgical mitral valve repair procedure. The primary endpoint (Patient Success) was a composite of placement of at least 2 neochordae and end-procedure mitral valve regurgitation (MR) ≤ mild, freedom from death, stroke, structural or functional procedure failure (MR > moderate), procedure or device-related unplanned procedures, cardiac-related rehospitalization, or worsening NYHA functional class at 1 and 2-year FU. Fifteen (15) patients were identified who required reoperation for failed surgical mitral valve repair. Mean time-to-reoperation was 2.7 years (2.2-6.1). Median intensive care unit stay was 24 hours and median hospitalization time was 7 days (6-8). No in-hospital deaths were observed. At discharge, mitral regurgitation was ≤ mild in 13 patients (86.7%). Patient success and freedom from more than mild MR were 92.3 ± 7.4% and 83.9 ± 10.4% at 1 and 2-year follow-up respectively. One high-risk patient presented with severe recurrent MR and died during surgical reintervention due to an acute aortic dissection. Selected patients can be successfully treated with the NeoChord procedure after failed surgical mitral valve repair. These results support a wider adoption of the NeoChord procedure as a first-line minimally invasive, alternative therapy to treat failed mitral valve repair.

Sutureless and rapid deployment implantation in bicuspid aortic valve: results from the sutureless and rapid-deployment aortic valve replacement international registry

Background

Benefits of sutureless and rapid deployment (SURD) bioprostheses in bicuspid aortic valves (BAV) are controversial. The aim of this study is to report the outcomes of patients undergoing aortic valve replacement (AVR) for BAV from the Sutureless and Rapid-Deployment Aortic Valve Replacement International Registry (SURD-IR).

Methods

Of the 4,636 patients who received primary isolated SURD-AVR between 2007 and 2018, 191 (4.1%) BAV patients underwent AVR with SURD valve.

Results

Overall 30-day mortality was 1.6%. The Intuity valve was implanted in 53.9% of cases, whereas the Perceval was implanted in 46.1%. Rate of stroke for isolated AVR was 4.2%. No case of endocarditis, thromboembolism, myocardial infarction, valve dislocation or structural valve deterioration was reported in the early phase. Rate of pacemaker implantation and moderate-severe aortic regurgitation (AR) were 7.9% and 3.7%, respectively.

Conclusions

BAV is not considered a contraindication for the implantation of SURD valves. However, detailed information of aortic root geometry as well as the knowledge of some technical considerations are mandatory for a good outcome.

Current trends of sutureless and rapid deployment valves: an 11-year experience from the Sutureless and Rapid Deployment International Registry

OBJECTIVES

Current evidence on sutureless and rapid deployment aortic valve replacement (SURD-AVR) is limited and does not allow for the assessment of the clinical impact and the evolution of procedural and clinical outcomes of this new valve technology. The Sutureless and Rapid Deployment International Registry (SURD-IR) represents a unique opportunity to evaluate the current trends and outcomes of SURD-AVR interventions.

METHODS

Data from 3682 patients enrolled between 2007 and 2018 were analysed. Patients were divided according to the date of surgery into 6 equal groups and by the type of intervention: isolated SURD-AVR (n = 2472) and combined SURD-AVR (n = 1086).

RESULTS

Across the 11-year study period, significant changes occurred in patient characteristics including a decrease in age and in estimated surgical risk. Less invasive approaches for isolated SURD-AVR increased considerably from 49.4% to 85.5%. The overall in-hospital mortality rate was 1.6% and 3.9% in isolated and combined procedures, respectively, with no change over time. The rate of perioperative stroke decreased significantly (from 4% to 0.5%), as did the rates of postoperative pacemaker implantation (from 12.8% to 5.9%) and aortic regurgitation (from 17.8% to 2.7%).

CONCLUSIONS

The present study provides a comprehensive analysis of the current trends and results of SURD-AVR interventions. The most notable changes over time were the increasing implantation of SURD valves in a younger population, with more frequent utilization of less invasive techniques. SURD-AVR demonstrated remarkable improvements in clinical outcomes with a significant reduction in the rates of stroke, pacemaker implantation and postoperative aortic regurgitation.

Full sternotomy and minimal access approaches for surgical aortic valve replacement: a multicentre propensity-matched study

OBJECTIVES

Surgical aortic valve replacement (AVR) can be performed via a full sternotomy or a minimal access approach (mini-AVR). Despite long-term experience with the procedure, mini-AVR is not routinely adopted. Our goal was to compare contemporary outcomes of mini-AVR and conventional AVR in a large multi-institutional national cohort.

METHODS

A total of 5801 patients from 10 different centres who had a mini-AVR (2851) or AVR (2950) from 2011 to 2017 were evaluated retrospectively. Standard aortic prostheses were used in all cases. The use of the minimally invasive approach has increased over the years. The primary outcome is the incidence of 30-day deaths following mini-AVR and AVR. Secondary outcomes are the occurrence of major complications following both procedures. Propensity-matched comparisons were performed based on the multivariable logistic regression model.

RESULTS

In the overall population patients who had AVR had an increased surgical risk based on the EuroSCORE, and the 30-day mortality rate was higher (1.5% and 2.3% in mini-AVR and AVR, respectively; P = 0.048). Propensity scores identified 2257 patients per group with similar baseline profiles. In the matched groups, patients who had mini-AVR, despite longer cardiopulmonary bypass (81 ± 32 vs 76 ± 28 min; P = 0.004) and cross-clamp (64 ± 24 vs 59 ± 21 min; P ≤ 0.001) times, had lower 30-day mortality rates (1.2% vs 2.0%; P = 0.036), reduced low cardiac output (0.8% vs 1.4%; P = 0.046) and reduced postoperative length of stay (9 ± 8 vs 10 ± 7 days; P = 0.004). Blood transfusions (36.4% vs 30.8%; P ≤ 0.001) and atrial fibrillation (26.0% vs 21.5%, P ≤ 0.001) were higher in patients who had the mini-AVR.

CONCLUSIONS

In a large multi-institutional recent cohort, minimal access approach aortic valve replacement is associated with reduced 30-day mortality rates and shorter postoperative lengths of stay compared to standard sternotomy. A prospective randomized trial is needed to overcome the possible biases of a retrospective study.

P752 Mitral regurgitation in patients with severe aortic stenosis: role of valvular calcification in the persistence of mitral regurgitation after aortic valve replacement

Introduction

mitral regurgitation is often associated with severe aortic stenosis but the indications for its correction at the time of aortic valve surgery are still unclear. Despite the indication for mitral valve repair or replacement in the case of severe secondary mitral regurgitation, many patients are left untreated. This is due to the common belief that secondary mitral regurgitation mostly improves after the aortic valve is treated.

Purpose

the aim of the study is to investigate the prevalence and distribution of mitral calcifications, their role in the development of mitral regurgitation and in its reduction after aortic valve replacement.

Methods

we reviewed all patient’s records who underwent aortic valve replacement for aortic stenosis at our institution from 12/2014 to 12/2016. Pre and post-operative echocardiograms were reviewed by experienced echocardiographer. Patients were then divided into 4 categories (functional, mild, moderate and severe calcification) on the basis of the presence, distribuition and severity of calcification on the mitral apparatus.

Results

at the end 651 patients were collected and analyzed. Mean age was 74yo. 334 (51,4%) of them were males. Most patients (63,1%) had only mild mitral regurgitation but 147 (22,6%) of them had moderate or severe mitral regurgitation. The presences of moderate or severe calcification of the mitral apparatus resulted to be a risk factor for the presence of mitral regurgitation associated with aortic stenosis as shown in Table 1. After surgical aortic valve replacement less than 21% of the patients showed a reduction of the degree of mitral regurgitation. We found no statistical difference between groups about mitral regurgitation changes after aortic valve replacement.

Conclusions

Mitral regurgitation is a common finding in patients with severe aortic stenosis and it’s prevalence is higher in patients with mitral calcifications. Few patients, however showed a reduction in the degree of mitral regurgitation after surgical aortic valve replacement with no difference related to the severity of annular or leaflets calcifications.

TABLE 1 Logistic regression for the presence of mitral regurgitation Mitral Regurgitation Change after Aortic Valve Replacement CALCIFICATION DEGREE OR C.I. 95% p Reduced p Unchanged p Increased p Functional 53(21%) 176(71%) 18(7%) Mild 1.244571 0.81 - 1.93 0.32 28(20%) 0.86 105(76%) 0.43 6(4%) 0.34 Moderate 1.637297 1.05 - 2.56 0.03* 25(17%) 0.41 109(76%) 0.34 9(6%) 0.86 Severe 2.369245 1.46 - 3.85 &lt;0.01* 29(25%) 0.48 78(68%) 0.67 7(6%) 0.86 OR= Odds Ratio; C.I.=Confidence Interval; Functional= no calcification; Mild, Moderate and Severe= degree of mitral annular and leaflets calcifications.

Minimally Invasive Redo Aortic Valve Replacement: Results From a Multicentric Registry (SURD-IR)

BACKGROUND

Reoperation for aortic valve replacement can be challenging and is usually associated with an increased risk for complications and mortality. The study aim was to report the results of a multicenter cohort of patients who underwent minimally invasive reoperative aortic valve replacement with a sutureless or rapid-deployment prosthesis.

METHODS

From 2007 to 2018 data from 3651 patients were retrospectively collected from the Sutureless and Rapid-Deployment Aortic Valve Replacement International Registry. Of them, 63 patients who had previously undergone cardiac surgery represented the study population. In-hospital clinical and echocardiographic outcomes were recorded.

RESULTS

Mean age of the selected 63 patients was 75.3 ± 7.8 years and logistic EuroSCORE 10.1. Surgery was performed by ministernotomy in 43 patients (68.3%) and by anterior right thoracotomy in 20 (31.7%); 31 patients (49.2%) received the Perceval valve (Livanova PLC, London, UK) and 32 (50.8%) the Intuity valve (Edwards Lifesciences, Irvine, CA). Mean cross-clamp time was 57.8 ± 23.2 minutes and cardiopulmonary bypass time 95.0 ± 34.3 minutes. Neither conversion to full sternotomy nor in-hospital deaths occurred. Postoperative events were ischemic cerebral events in 3 patients (4.8%), need for pacemaker implantation in 2 (3.6%), bleeding requiring reoperation in 5 (8.9%), and dialysis in 1 (1.6%). Median intensive care unit stay was 1 day, and median length of hospital stay was 10 days. On echocardiographic evaluation 1 patient showed a significant postoperative aortic regurgitation.

CONCLUSIONS

Minimally invasive reoperative aortic valve replacement with a sutureless or rapid-deployment prosthesis is a safe and feasible treatment strategy, resulting in fast recovery and improved postoperative outcome with no mortality and an acceptable complication rate.

A Challenging Case of MitraClip on a Tricuspid Valve With a Redundant Eustachian Valve: Surfing Into the Right Atrium

Transcatheter tricuspid valve intervention is gaining importance due to the development of percutaneous techniques addressing tricuspid regurgitation. The presence of a redundant eustachian valve can increase procedural complexity by restricting the manipulation of transcatheter devices. We present a case of torrential tricuspid regurgitation and a redundant eustachian valve hampering the manipulation of the delivery system. We were able to reach the tricuspid valve by looping 2 standard guidewires into the atrium. We performed a tricuspid-plasty by implanting 2 MitraClips with a satisfactory final result. This technique can be applied when the eustachian valve impairs navigation in the right atrium.

Aortic valve endocarditis complicated by proximal false aneurysm

Background

Aortic valve endocarditis remains a life-threatening condition, especially in cases of periannular complications. Aorto-ventricular discontinuity associated with proximal false aneurysm represents a severe picture caused by extensive tissue disruption and is usually associated with prosthetic valve infection. Complex surgical repair is required in these cases and continues to be associated with high mortality and morbidity rates.

Methods

We retrieved information for 32 patients undergoing operation for infective aortic valve/prosthetic valve endocarditis complicated by pseudoaneurysm arising from aorto-ventricular discontinuity. Patients were relatively young, mostly male and most of them had a prior cardiac operation. Aortic root replacement with valve graft conduit was performed in all cases; it was associated with other procedures in seven patients: CABG (n=2), MV surgery (n=3), MV surgery + CABG (n=1) and pulmonary valve replacement (n=1). We reported and analysed patient outcomes at early and mid-term follow-up.

Results

Pre-discharge mortality was 22% (n=7). The postoperative course was complicated in 24 (75%) cases. Eighteen patients (56%) sustained low cardiac output resulting in multiple organ failure syndrome and death in five cases. One patient (3%) experienced a major neurologic deficit with a permanent cerebral stroke. Acute kidney injury complicated the course in 12 cases (37%), continuous renal replacement therapy was necessary in four patients (12%). Overall survival and freedom from endocarditis and reoperation at 5-year was 59% and 89%, respectively.

Conclusions

Patients with complicated aortic valve endocarditis presented generally in a poor preoperative state. Surgical treatment poses a non-negligible risk of postoperative mortality and morbidity but provides an acceptable survival rate and a satisfactory recovery at mid-term.

Minimally invasive surgical versus transcatheter aortic valve replacement: A multicenter study

Objectives

Treatment of aortic valve stenosis is evolving, indications for transcatheter approach (TAVI) have increased but also surgical valve replacement has changed with the use of minimally invasive approaches. Comparisons between TAVI and surgery have rarely been done with minimally invasive techniques (mini-SAVR) in the surgical arm. Aim of the present study is to compare mini-SAVR and TAVI in a multicenter recent cohort.

Methods

Evaluated were 2904 patients undergone mini-SAVR (2407) or TAVI (497) in 10 different centers in the period 2011–2016. The Heart Team approved treatment for complex cases. The primary outcome is the incidence of 30-day mortality following mini-SAVR and TAVI. Secondary outcomes are the occurrence of major complications following both procedures. Propensity matched comparisons was performed based on multivariable logistic regression model.

Results

In the overall population TAVI patients had increased surgical risk (median EuroSCORE II 3.3% vs. 1.7%, p ≤ 0.001) and 30-day mortality was higher (1.5% and 2.8% in mini-SAVR and TAVI respectively, p = 0.048). Propensity score identified 386 patients per group with similar baseline profile (median EuroSCORE II ~3.0%). There was no difference in 30-day mortality (3.4% in mini-SAVR and 2.3% in TAVI; p = 0.396) and stroke, surgical patients had more blood transfusion, kidney dysfunction and required longer ICU and hospital length of stay while TAVI patients had more permanent pace maker insertion.

Conclusions

Mini-SAVR and TAVI are both safe and effective to treat aortic stenosis in elderly patients with comorbidities. A joint evaluation by the heart-team is essential to direct patients to the proper approach.

•

A comparison between TAVI and minimally invasive techniques has rarely been done

•

In a propensity-matched comparison from 10 different hospitals, TAVI and mini-SAVR provided optimal short-term outcome.

•

30-day mortality was 3.4% in mini-SAVR and 2.3% in TAVI (p = 0.396)

•

Mini-SAVR and TAVI are both safe and effective to treat aortic stenosis in elderly patients with comorbidities.

Monoclonal Antibody-Based Enzyme-Linked Immunosorbent Assays (ELISA) for the Measurement of Vitamin K-Dependent Protein S: The Effect of Antibody Immunoreactivity on Plasma Protein S Antigen Determinations

Two monoclonal antibodies (Mabs) specifically directed to human protein S (PS) - named 5E9E9 and 3B10.25 - were produced and their properties compared to those of 2 previously characterized anti-PS-Mabs (HPS-2 and S10). 3B10.25, similar to S10, was directed to the calcium-free conformation of PS and had virtually identical affinity for free and C4b-binding protein (C4b-BP)-bound PS; 5E9E9 similar to HPS-2, had no calcium-dependency and was selectively directed to free PS. All Mabs were equally reactive to freshly purified and thrombin-cleaved PS. To evaluate the influence of C4b-BP bound PS on PS antigen determinations, ELISA systems employing the four Mabs individually as capture antibody (Ab) and peroxidase-conjugated polyclonal anti-PS IgG as detecting Ab were developed and compared to immunoelectrophoresis (EIA) and to an ELISA employing polyclonal anti-PS IgG as capture and detecting Ab, in the determination of PS in purified systems and in plasma. With all the ELISAs there was parallelism of dilution cuiyes obtained with normal plasma and purified PS; however, supplementation of plasma with purified C4b-BP resulted in loss of parallelism when employing the Mabs directed to free PS as capture Ab. Influence of high C4b-BP on PS antigen determinations was confirmed in a series of plasma samples from patients with C4b-BP levels ranging from 70% to over 200%. Compared to the values obtained with the S10- or 3B10.25 - based ELISAs - which were similar despite a 10-fold difference in sample dilution -plasma PS was underestimated by the ELISAs employing 5E9E9 or HPS-2 while it was overestimated by EIA. In addition, plasma PS and C4b-BP levels were significantly correlated only when it was measured by EIA or the ELISAs employing S10, 3B10.25 or polyclonal IgG. These results highlight the potential influence of high C4b-BP on plasma PS antigen determination. Accurate measurement of PS by ELISA requires selection of antibodies with identical affinity for all plasma PS forms.

Immunological Reactivity of Serum Ferritin in Patients with Malignancy

Serum ferritin has been suggested as a tumor marker in the diagnosis of certain malignancies and for following the activity or dissemination of the malignant process. Since neoplastic tissues generally contain more acidic isoferritins than their normal tissue counterparts, it has also been suggested that the specific assay of such isoferritins in serum may be of particular value in the diagnosis of malignancy. In this work, we have evaluated ferritin concentration in the serum of normal subjects and patients with acute nonlymphocytic leukemia, Hodgkin's disease, breast cancer and lung cancer by simultaneously using three different immunoassays: an immunoradiometric assay based on polyclonal antibodies against human liver (basic, L-subunit rich) ferritin, a radioimmunoassay based on polyclonad antibodies against HeLa cell (acidic, H-subunit rich) ferritin, and an immunoradiometric assay based on the monoclonal antibody 2A4 raised against human heart (acidic, H-subunit rich) ferritin. Most of the patients studied had increased values for liver-type ferritin in the absence of increased iron stores. Binding of serum ferritin to concanavalin A did not prove to be useful in distinguishing a tumor-specific basic isoferritin. The HeLa ferritin assay was found to be less specific than the heart ferritin assay in the detection of acidic isoferritins, and did not provide any advantage over the liver assay in detecting the increased levels of serum ferritin associated with malignant disease. Heart-type ferritin was found in one-fifth of normal sera and 64% of sera from patients with malignancy. Values were very low compared with those for basic ferritin, ranging from less than 0.1 to 17% of total serum ferritin (geometric mean value 1.3%) in patients with malignancy. These findings indicate that at present there is little application for serum ferritin immunoassays based on antibodies to HeLa cell or heart ferritin in the diagnosis or monitoring of malignant disease. This seems to be due to the presence in human serum of biding factors which are responsible for the rapid clearance of acidic isoferritins from the circulation. The serum concentration of basic ferritin, however, can be useful in the diagnosis and management of some malignancies, and it is possible that studies on cell isoferritins can be important in biologic monitoring of neoplastic disorders. It should also be noted that the increased levels of serum ferritin found in patients with malignancy can exert adverse effects on the host immune response and perhaps an inhibitory effect on hematopoiesis.