Heterogeneous ozone effects on the DNA methylome of bronchial cells observed in a crossover study.

We used a randomized crossover experiment to estimate the effects of ozone (vs. clean air) exposure on genome-wide DNA methylation of target bronchial epithelial cells, using 17 volunteers, each randomly exposed on two separated occasions to clean air or 0.3-ppm ozone for two hours. Twenty-four hours after exposure, participants underwent bronchoscopy to collect epithelial cells whose DNA methylation was measured using the Illumina 450 K platform. We performed global and regional tests examining the ozone versus clean air effect on the DNA methylome and calculated Fisher-exact p-values for a series of univariate tests. We found little evidence of an overall effect of ozone on the DNA methylome but some suggestive changes in PLSCR1, HCAR1, and LINC00336 DNA methylation after ozone exposure relative to clean air. We observed some participant-to-participant heterogeneity in ozone responses.

Quantile causal mediation analysis allowing longitudinal data.

Mediation analysis has mostly been conducted with mean regression models. With this approach modeling means, formulae for direct and indirect effects are based on changes in means, which may not capture effects that occur in units at the tails of mediator and outcome distributions. Individuals with extreme values of medical endpoints are often more susceptible to disease and can be missed if one investigates mean changes only. We derive the controlled direct and indirect effects of an exposure along percentiles of the mediator and outcome using quantile regression models and a causal framework. The quantile regression models can accommodate an exposure-mediator interaction and random intercepts to allow for longitudinal mediator and outcome. Because DNA methylation acts as a complex "switch" to control gene expression and fibrinogen is a cardiovascular factor, individuals with extreme levels of these markers may be more susceptible to air pollution. We therefore apply this methodology to environmental data to estimate the effect of air pollution, as measured by particle number, on fibrinogen levels through a change in interferon-gamma (IFN-γ) methylation. We estimate the controlled direct effect of air pollution on the qth percentile of fibrinogen and its indirect effect through a change in the pth percentile of IFN-γ methylation. We found evidence of a direct effect of particle number on the upper tail of the fibrinogen distribution. We observed a suggestive indirect effect of particle number on the upper tail of the fibrinogen distribution through a change in the lower percentiles of the IFN-γ methylation distribution.

Prenatal and early life exposure to traffic pollution and cardiometabolic health in childhood.

BACKGROUND: Prenatal exposure to traffic pollution has been associated with faster infant weight gain, but implications for cardiometabolic health in later childhood are unknown. METHODS: Among 1418 children in Project Viva, a Boston-area pre-birth cohort, we assessed anthropometric and biochemical parameters of cardiometabolic health in early (median age 3.3 years) and mid- (median age 7.7 years) childhood. We used spatiotemporal models to estimate prenatal and early life residential PM2.5 and black carbon exposure as well as traffic density and roadway proximity. We performed linear regression analyses adjusted for sociodemographics. RESULTS: Children whose mothers lived close to a major roadway at the time of delivery had higher markers of adverse cardiometabolic risk in early and mid-childhood. For example, total fat mass was 2.1 kg (95%CI: 0.8, 3.5) higher in mid-childhood for children of mothers who lived <50 m vs. ≥200 m from a major roadway. Black carbon exposure and traffic density were generally not associated with cardiometabolic parameters, and PM2.5 exposure during the year prior was paradoxically associated with improved cardiometabolic profile. CONCLUSIONS: Infants whose mothers lived close to a major roadway at the time of delivery may be at later risk for adverse cardiometabolic health.

Ramucirumab combined with FOLFOX as front-line therapy for advanced esophageal, gastroesophageal junction, or gastric adenocarcinoma: a randomized, double-blind, multicenter Phase II trial.

BACKGROUND: We report the first randomized, Phase II trial of ramucirumab, an anti-vascular endothelial growth factor receptor-2 monoclonal antibody, as front-line therapy in patients with advanced adenocarcinoma of the esophagus or gastric/gastroesophageal junction (GEJ). PATIENTS AND METHODS: Patients from the USA with advanced esophageal, gastric, or GEJ adenocarcinoma randomly received (1:1) mFOLFOX6 plus ramucirumab (8 mg/kg) or mFOLFOX6 plus placebo every 2 weeks. The primary end point was progression-free survival (PFS) with 80% power to detect a hazard ratio (HR) of 0.71 (one-sided α = 0.15). Secondary end points included evaluation of response and overall survival (OS); an exploratory ramucirumab exposure-response analysis was undertaken. RESULTS: Of 168 randomized patients, 52% of tumors were located in the stomach/GEJ and 48% in the esophagus. The trial did not meet the primary end point of PFS [6.4 versus 6.7 months, HR 0.98 (95% confidence interval 0.69-1.37)] or the secondary end point of OS (11.7 versus 11.5 months) in the intent-to-treat (ITT) population. Objective response rates (45.2% versus 46.4%) were similar between arms. Most Grade ≥3 toxicities did not differ significantly between arms, yet premature discontinuation of FOLFOX and ramucirumab (for reasons other than progressive disease) was more common among ramucirumab- versus placebo-treated patients. In an exploratory analysis that censored for premature discontinuation, the HR for PFS favored the ramucirumab arm (HR 0.76), particularly in patients with gastric/GEJ cancer. An exploratory exposure-response analysis indicated that patients with higher ramucirumab exposure had longer OS. CONCLUSION: The addition of ramucirumab to front-line mFOLFOX6 did not improve PFS in the ITT population. CLINICALTRIALSGOV IDENTIFIER: NCT01246960.

Causal mediation analysis for longitudinal data with exogenous exposure.

Mediation analysis is a valuable approach to examine pathways in epidemiological research. Prospective cohort studies are often conducted to study biological mechanisms and often collect longitudinal measurements on each participant. Mediation formulae for longitudinal data have been developed. Here, we formalize the natural direct and indirect effects using a causal framework with potential outcomes that allows for an interaction between the exposure and the mediator. To allow different types of longitudinal measures of the mediator and outcome, we assume two generalized mixed-effects models for both the mediator and the outcome. The model for the mediator has subject-specific random intercepts and random exposure slopes for each cluster, and the outcome model has random intercepts and random slopes for the exposure, the mediator, and their interaction. We also expand our approach to settings with multiple mediators and derive the mediated effects, jointly through all mediators. Our method requires the absence of time-varying confounding with respect to the exposure and the mediator. This assumption is achieved in settings with exogenous exposure and mediator, especially when exposure and mediator are not affected by variables measured at earlier time points. We apply the methodology to data from the Normative Aging Study and estimate the direct and indirect effects, via DNA methylation, of air pollution, and temperature on intercellular adhesion molecule 1 (ICAM-1) protein levels. Our results suggest that air pollution and temperature have a direct effect on ICAM-1 protein levels (i.e. not through a change in ICAM-1 DNA methylation) and that temperature has an indirect effect via a change in ICAM-1 DNA methylation.

Phase I study of every 2- or 3-week dosing of ramucirumab, a human immunoglobulin G1 monoclonal antibody targeting the vascular endothelial growth factor receptor-2 in patients with advanced solid tumors.

BACKGROUND: Ramucirumab is a fully human immunoglobulin G1 monoclonal antibody receptor antagonist designed to block the ligand-binding site of vascular endothelial growth factor receptor-2 (VEGFR-2). An initial phase I study evaluated ramucirumab administered weekly in advanced cancer patients. This phase I study of ramucirumab [administered every 2 or 3 weeks (Q2W or Q3W)] examined safety, maximum tolerated dose, pharmacokinetics, immunogenicity, antitumor activity, and pharmacodynamics. PATIENTS AND METHODS: Patients with advanced solid malignancies were treated with escalating doses of ramucirumab i.v. over 1 h. Blood was sampled for pharmacokinetics studies throughout treatment; levels of circulating vascular endothelial growth factor-A (VEGF-A) and soluble VEGF receptors (R)-1 and -2 were assessed. RESULTS: Twenty-five patients were treated with ramucirumab: 13 with 6, 8, or 10 mg/kg Q2W, and 12 with 15 or 20 mg/kg Q3W. The median treatment duration was 12 weeks (range 2-81). No dose-limiting toxicities were observed. The most frequently reported adverse events (AEs) included proteinuria and hypertension (n = 6 each), and diarrhea, fatigue and headache (n = 4 each). Treatment-related grade 3/4 AEs were: two grade 3 hypertension (10 and 20 mg/kg), one each grade 3 vomiting, fatigue (20 mg/kg), atrial flutter (15 mg/kg), and one each grade 4 duodenal ulcer hemorrhage (6 mg/kg) and grade 4 pneumothorax (20 mg/kg). Pharmacokinetic analysis revealed low clearance and half-life of ∼110-160 h. Analysis of serum biomarkers indicated considerable patient-to-patient variability, but trends toward elevated VEGF-A and a transient decline in soluble VEGFR-2. Fifteen patients (60%) had best response of stable disease, with a median duration of 13 months (range 2-18 months) in tumor types including colorectal, renal, liver, and neuroendocrine cancers. CONCLUSION: Ramucirumab was well tolerated. Study results led to recommended phase II doses of 8 mg/kg Q2W and 10 mg/kg Q3W. Prolonged stable disease was observed, suggesting ramucirumab efficacy in various solid tumors. CLINICALTRIALSGOV: NCT00786383.

Safety, tolerability, and pharmacokinetics of single and multiple doses of intravenous cixutumumab (IMC-A12), an inhibitor of the insulin-like growth factor-I receptor, administered weekly or every 2 weeks in patients with advanced solid tumors.

BACKGROUND: Type 1 insulin-like growth factor receptor (IGF-IR) signaling is often dysregulated in cancer. Cixutumumab, a fully human IgG1 monoclonal antibody, blocks IGF-IR and inhibits downstream signaling. The current study determined the recommended dose, safety, and pharmacokinetic (PK) profile of weekly or every-2-week dosing of cixutumumab. PATIENTS AND METHODS: Two open-label, multicenter phase I studies evaluated weekly (3-15 mg/kg) or every-2-weeks (6-15 mg/kg) dosing of cixutumumab in patients with advanced solid tumors. Serial blood samples for PK were collected up to 168-336 h (day 8-15) following the first administration of cixutumumab. Efficacy was evaluated as best overall tumor response. RESULTS: A total of 24 and 16 patients were enrolled in the weekly and every-2-week dosing studies, respectively. Treatment-emergent adverse events (≥10%) included hyperglycemia, fatigue, anemia, nausea, and vomiting. Severe adverse events (AE) were infrequent; one serious AE (grade 3 electrocardiogram QT prolongation) was deemed possibly cixutumumab-related (10 mg/kg every-2-weeks). One death occurred due to disease progression (6 mg/kg weekly cohort). Maximum serum concentrations increased with dose. A maximum tolerated dose was not identified; pre-determined target serum minimum concentrations (60 µg/mL) were achieved with ≥6 mg/kg weekly and ≥10 mg/kg every-2-week dosing. Cixutumumab terminal elimination half-life is approximately a week (individual range, t1/2 = 4.58-9.33 days based upon 10 mg/kg every 2 weeks). Overall, stable disease was achieved in 25% of all patients. CONCLUSIONS: Cixutumumab was associated with favorable safety and PK profiles. A dosing regimen of 10 mg/kg every 2 weeks was recommended for subsequent disease-focused clinical trials.

Activation of progelatinase A (MMP-2) by neutrophil elastase, cathepsin G, and proteinase-3: a role for inflammatory cells in tumor invasion and angiogenesis.

Gelatinase A (MMP-2), a matrix metalloproteinase (MMP) involved in tumor invasion and angiogenesis, is secreted as an inactive zymogen (proMMP-2) and activated by proteolytic cleavage. Here we report that polymorphonuclear neutrophil (PMN)-derived elastase, cathepsin G, and proteinase-3 activate proMMP-2 through a mechanism that requires membrane-type 1 matrix metalloproteinase (MT1-MMP) expression. Immunoprecipitation of human PMN-conditioned medium with a mixture of antibodies to elastase, cathepsin G, and proteinase-3 abolished proMMP-2 activation, whereas individual antibodies were ineffective. Incubation of HT1080 cells with either purified PMN elastase or cathepsin G or proteinase-3 resulted in dose-and time-dependent proMMP-2 activation. Addition of PMN-conditioned medium to MT1-MMP expressing cells resulted in increased proMMP-2 activation and in vitro invasion of extracellular matrix (ECM), but had no effect with cells that express no MT1-MMP. MMP-2 activation by PMN-conditioned medium or purified elastase was blocked by the elastase inhibitor alpha(1)-antitrypsin but not by Batimastat, an MMP inhibitor, showing that elastase activation of MMP-2 is not mediated by MMP activities. The PMN-conditioned medium-induced increase in cell invasion was blocked by Batimastat as well as by alpha(1)-antitrypsin, showing that PMN serine proteinases trigger a proteinase cascade that entails proMMP-2 activation: this gelatinase is the downstream effector of the proinvasive activity of PMN proteinases. These findings indicate a novel role for PMN-mediated inflammation in a variety of tissue remodeling processes including tumor invasion and angiogenesis.

Topical hepatic hypothermia attenuates pulmonary injury after hepatic ischemia and reperfusion.

BACKGROUND: Prolonged periods of hepatic ischemia are associated with hepatocellular injury and distant organ dysfunction in experimental models. Neutrophils (PMN) and tumor necrosis factor (TNF)-alpha have been implicated, mostly because of their local deleterious effects on the hepatocyte after hepatic ischemia and reperfusion (I/R) injury. We hypothesize that topical hepatic hypothermia (THH) reduces ischemia and reperfusion-induced hepatic necrosis, PMN infiltration, TNF-alpha release, and consequent acute pulmonary injury. STUDY DESIGN: Sprague-Dawley rats (250 to 300g) were evenly divided into three groups: 90 minutes of normothermic (37 degrees C) partial hepatic ischemia (normothermic I/R), 90 minutes of hypothermic (25 degrees C) partial hepatic ischemia (hypothermic I/R), and sham laparotomy (without ischemia). There were six animals in each experimental group per time point unless otherwise specified. Hepatic necrosis and PMN infiltration were evaluated and scored on hematoxylin and eosin-stained liver specimens 12 hours after reperfusion. Serum TNF-alpha levels were determined by ELISA at 0 minutes, 15 minutes, 30 minutes, 1 hour, and 12 hours postreperfusion. Pulmonary PMN infiltration and vascular permeability were measured by myeloperoxidase activity and Evans blue dye extravasation, respectively, to quantitate pulmonary injury 12 hours after reperfusion. RESULTS: Normothermic I/R results in a significant increase in TNF-alpha at 15 and 30 minutes (p < 0.005), PMN infiltration (p < 0.001), and hepatic necrosis (p < 0.001), compared with sham. Institution of THH reduced peak serum TNF-alpha levels by 54% at 15 minutes (p < 0.005) and by 73% at 30 minutes (p < 0.001) postreperfusion compared with normothermic I/R. Similarly, hepatic PMN infiltration and necrosis at 12 hours were reduced by 60% (p < 0.05) and 47% (p < 0.05), respectively. Myeloperoxidase activity and Evans blue extravasation (measures of acute lung injury) were reduced by 42% and 39%, respectively, with institution of THH compared with animals undergoing normothermic I/R (p < 0.001). CONCLUSIONS: These results demonstrate that THH protects the liver from ischemia and reperfusion-induced necrosis and PMN infiltration. In addition, THH reduces the serum levels of TNF-alpha and associated pulmonary injury. These data suggest that the ischemic liver is a potential source of inflammatory mediators associated with hepatic ischemia and reperfusion-induced pulmonary injury.

Neutrophil-derived serine proteinases enhance membrane type-1 matrix metalloproteinase-dependent tumor cell invasion.

BACKGROUND: Matrix metalloproteinase-2 degrades a variety of basement membrane components and is essential for tumor invasion. We have previously reported that membrane type-1 matrix metalloproteinase (MT1-MMP) cooperates with neutrophil-derived serine proteinases (NDPs; elastase, cathepsin G, protease-3) to activate matrix metalloproteinase-2. We therefore hypothesized that NDPs enhance tumor-cell invasion. METHODS: Clones of human HT1080 fibrosarcoma cells transfected with MT1-MMP sense (HT-SE) or antisense CDNA (HT-AS) were used. These cells express either high (HT-SE) or extremely low levels (HT-AS) of MT1-MMP relative to nontransfected HT1080 cells (HT-WT). The cells were incubated in the presence or absence of purified NDP, with or without alpha 1-antitrypsin or the MMP inhibitor batimastat. Cell invasion was measured with the use of Boyden chambers with polycarbonate membranes coated with a reconstituted extracellular matrix. RESULTS: Under control conditions HT-WT and HT-SE cells were 4-fold more invasive than HT-AS cells. The addition of NDP increased HT-WT and HT-SE cell invasion 60% to 100% but had no effect on HT-AS cells. alpha 1-antitrypsin or batimastat did not decrease the baseline invasiveness of HT-WT and HT-SE cells; however, they abrogated the stimulatory effect of NDP. CONCLUSIONS: HT1080 cell invasion depends on MT1-MMP expression. MT1-MMP overexpression does not increase invasiveness by itself. NDPs increase invasion by MT1-MMP expressing cells by activating matrix metalloproteinase-2.

Activation of tumor cell matrix metalloproteinase-2 by neutrophil proteinases requires expression of membrane-type 1 matrix metalloproteinase.

BACKGROUND: Matrix metalloproteinase-2 (MMP-2), an enzyme involved in tumor invasion, is secreted as an inactive proenzyme and requires interaction with membrane-type 1 MMP (MT1-MMP) for activation. We have previously demonstrated that polymorphonuclear neutrophils (PMNs) release a soluble factor(s) that activates pro-MMP-2. Therefore, we tested the hypothesis that PMN-derived proteinases act in concert with MT1-MMP to activate pro-MMP-2. METHODS: Human HT-1080 cells transfected with MT1-MMP cDNA (HT-SE) or the corresponding antisense cDNA (HT-AS) or an empty vector (HT-V), which expressed differing levels of MT1-MMP, were incubated with serum-free, human PMN-conditioned medium with or without proteinase inhibitors. The culture supernatants were analyzed by gelatin zymography. RESULTS: Ht-1080 cells expressing basal (HT-V) or low levels (HT-AS) of MT1-MMP secreted MMP-2 in proenzyme from (72 kd). Ht-1080 cells with high levels of MT1-MMP (HT-SE) secreted pro MMP-2 and a 68 kd intermediate activation product. Addition of PMN-conditioned medium to either HT-SE or HT-V clones resulted in dose-dependent generation of active, 62 kd MMP-2. In contrast, when PMN-conditioned medium was added to HT-AS clones, no MMP-2 activation occurred. CONCLUSIONS: PMN-derived serine proteinases act in concert with MT1-MMP to activate proMMP-2. This finding indicates a potential role for inflammatory cells in promoting extracellular matrix breakdown during tumor invasion.

Soluble factor(s) released from neutrophils activates endothelial cell matrix metalloproteinase-2.

OBJECTIVE: Polymorphonuclear leukocyte (PMN) infiltration and microvascular injury are hallmarks of the tissue remodeling associated with multiple organ failure. These processes require the concerted action of various proteolytic enzymes, including serine and matrix metalloproteinases (MMPs). Matrix metalloproteinase-2 (MMP-2) plays an important role in the turnover of various ECM components, including type IV collagen, fibronectin, and gelatins. Like all MMPs, MMP-2 is secreted as an inactive zymogen (proMMP-2) and activated extracellularly by limited proteolytic cleavage. The physiologic mechanism(s) of proMMP-2 activation remains unclear. This study was designed to characterize the effect of PMNs on the activation of proMMP-2 produced by endothelial cells. METHODS: PMNs and human umbilical vein endothelial cells (HUVECs) were grown either separately or together for 2-16 h. To evaluate the role of cell-cell contact, cocultures were also established in which the two cell types were separated by a semipermeable polycarbonate membrane. Alternatively, PMN-conditioned medium was added to HUVEC cultures with or without various proteinase inhibitors (aprotinin, 1,10-phenanthroline, Batimastat, E-64, eglin c peptide, or pepstatin A). After incubation, the culture supernatants were analyzed by gelatin zymography to characterize the gelatinases. RESULTS: HUVECs produce MMP-2 in its inactive (72 kDa) form. PMNs produce high levels of MMP-9 (gelatinase B, 92 kDa) but no MMP-2. Coculture of PMNs with or addition of PMN-conditioned medium to HUVECs results in the production of active (62 kDa) MMP-2. ProMMP-2 activation by PMN-conditioned medium is not blocked by inhibitors of plasmin, cysteine-, acid-, or metalloproteinases. CONCLUSION: PMNs release a soluble factor that activates endothelial cell MMP-2 through a novel mechanism independent of cell-cell contact and not attributable to the activities of plasmin, cysteine-, acid-, or metalloproteinases. These findings may provide insight into the tissue remodeling that accompanies PMN-mediated microvascular injury.

Cardiopulmonary bypass primes polymorphonuclear leukocytes.

Polymorphonuclear leukocyte (PMN) superoxide (.O2-) production has been implicated in the pathogenesis of cardiopulmonary bypass (CPB)-related end organ injury. PMN "priming" has been described as an event which enhances the release of .O2- following a second, activating insult. We hypothesized that PMN priming occurs during CBP and is temporally related to the plasma level of complement (C3a), interleukin (IL)-6, and IL-8. PMNs were isolated from 10 CPB patients pre-bypass (preCPB), 5 min after protamine administration (PROT), and at 6 and 24 h post-CPB. PMN .O2- production was measured by a cytochrome c reduction assay in the presence or absence of either phorbol 12-myristate-13-acetate (PMA, 0.4 microgram/ml) or N-formyl-methionyl-leucyl-phenylalanine (FMLP, 1 microM) and also after priming with 2000 nM platelet-activating factor (PAF) followed by activation with either PMA or FMLP. Plasma levels of C3a, IL-6, and IL-8 were determined by enzyme-linked immunosorbent assay. PMA-activated PMN .O2- production was significantly elevated at 6 h post-CPB compared to pre-CPB levels (11.04 +/- 0.9 vs 7.62 +/- 0.57, P = 0.009), indicating that CPB is associated with in vivo PMN priming. When PMNs were primed in vitro with PAF and then activated with PMA or FMLP, .O2- release at 6 h post-CPB was also significantly greater than pre-CPB levels (16.04 +/- 0.74 vs 12.2 +/- 0.92, P = 0.038; and 17.33 +/- 1.38 vs 13.33 +/- 1.35, P < 0.05), indicating that CPB acts synergistically with PAF to prime PMNs. Levels of C3a rose significantly over pre-CPB levels at PROT (P = 0.001), and IL-6 and IL-8 rose over pre-CPB levels at 6 h post-CPB (P = 0.01 and P = 0.006, respectively). These findings demonstrate that CPB not only directly primes PMNs, but also potentiates priming of PMNs by PAF. This "primed" PMN state, which coincided with the increased plasma levels of inflammatory mediators, may suggest a mechanism of predisposition to organ dysfunction following CPB.

Thrombosis and malignancy: pathogenesis and prevention.

An increased incidence of thrombosis has been observed in cancer patients for over a century. The hypercoagulable state of malignancy results from multiple mechanisms including activation of the coagulation cascade and alterations of cellular blood components and endothelial cells by tumor cells. Studies have been done to determine the role of prophylactic anticoagulation therapy in cancer patients, and have shown to reduce safely the incidence of thrombosis in patients receiving treatment for metastatic breast cancer and in patients with implanted upper extremity venous catheters. Further studies are needed to determine the contribution of newly described genetic risk factors for thrombosis in order to stratify the risk for thrombosis in patients with cancer.

Single and multivessel port-access coronary artery bypass grafting with cardioplegic arrest: technique and reproducibility.

OBJECTIVES: Although minimally invasive coronary artery bypass grafting is now feasible, using this technique to perform anastomoses on the beating or fibrillating heart may yield poorer graft patency than the standard open techniques that use cardioplegic arrest. This study tested the feasibility and anastomotic reproducibility of minimally invasive coronary bypass using newly developed port-access coronary artery bypass technology (Heartport, Inc., Redwood City, Calif.), which allows endovascular cardiopulmonary bypass, cardiac venting, aortic occlusion, and cardioplegic arrest for internal thoracic artery-coronary artery anastomoses. METHODS: Nineteen dogs had thoracoscopic takedown of either single (n = 14) or bilateral (n = 5) internal thoracic arteries followed by minimally invasive coronary bypass with cardioplegic arrest, done by means of the port-access system. The anastomotic technique was modified after the fourth animal by switching from a microscope to a 2.5 cm oval port and performing a conventional anastomosis with operative loupes. The adequacy of delivery of cardioplegic solution, ventricular decompression, and anastomotic patency was assessed. RESULTS: The crossclamp and bypass times were 50 +/- 15 minutes and 87 +/- 28 minutes (mean +/- standard deviation), respectively. The mean myocardial temperature after cardioplegia was 17 degrees +/- 1 degree C and the aortic pressure (-3 +/- 9 mm Hg) and pulmonary artery pressure (4 +/- 1 mm Hg) were low throughout the procedure. All animals were weaned from bypass without inotropic agents. Angiograms and autopsies demonstrated successful thoracic artery takedown and anastomotic patency in 18 of 19 animals, with 100% anastomotic patency after the technique had been modified after the fourth animal. CONCLUSION: This study describes a reproducible technique for minimally invasive coronary bypass that allows myocardial protection, anastomotic precision, and predictable thoracic artery graft patency. Clinical trials are indicated.

Minimally invasive mitral valve replacement: port-access technique, feasibility, and myocardial functional preservation.

OBJECTIVE: This experiment examined the feasibility of minimally invasive port-access mitral valve replacement via a 2.5 cm incision. METHODS: The study evaluated valvular performance and myocardial functional recovery in six mongrel dogs after port-access mitral valve replacement with a St. Jude Medical prosthesis (St. Jude Medical, Inc., St. Paul, Minn.). Femoro-femoral cardiopulmonary bypass and a balloon catheter system for myocardial protection with cardioplegic arrest (Heartport, Inc., Redwood City, Calif.) were used. The mitral valve was replaced through a 2.5 cm port in the left side of the chest, and the animals were weaned from bypass. Cardiac function was measured before and at 30 and 60 minutes after bypass. Left ventricular pressure and electrical conductance volume were used to calculate changes in load-independent indexes of ventricular function. RESULTS: Each procedure was successfully completed. Recovery of left ventricular function was excellent at 30 and 60 minutes after bypass compared with the prebypass values for elastance (30 minutes = 4.04 +/- 0.97 and 60 minutes = 4.27 +/- 0.57 vs prebypass = 4.45 +/- 0.96; p = 0.51) and for preload recruitable stroke work (30 minutes = 76.23 +/- 4.80 and 60 minutes = 71.21 +/- 2.99 vs prebypass = 71.23 +/- 3.75; p = 0.45). Preload recruitable work area remained at 96% and 85% of baseline at 30 and 60 minutes (p = not significant). In addition, transesophageal echocardiography demonstrated normal prosthetic valve function, as well as normal regional and global ventricular wall motion. Autopsy revealed secure annular-sewing apposition and normal leaflet motion. CONCLUSIONS: These results suggest that minimally invasive mitral valve replacement using percutaneous cardiopulmonary bypass with cardioplegic arrest is technically reproducible, achieves normal valve placement, and results in complete cardiac functional recovery. Minimally invasive mitral valve replacement is now feasible, and clinical trials are indicated.