Charles J. Lutz

Matrix metalloproteinase inhibitor prevents acute lung injury after cardiopulmonary bypass.

BACKGROUND Acute lung injury (ALI) after cardiopulmonary bypass (CPB) results from sequential priming and activation of neutrophils. Activated neutrophils release neutral serine, elastase, and matrix metalloproteinases (MMPs) and oxygen radical species, which damage alveolar-capillary basement membranes and the extracellular matrix, resulting in an ALI clinically defined as adult respiratory distress syndrome (ARDS). We hypothesized that treatment with a potent MMP and elastase inhibitor, a chemically modified tetracycline (CMT-3), would prevent ALI in our sequential insult model of ALI after CPB. METHODS AND RESULTS Anesthetized Yorkshire pigs were randomized to 1 of 5 groups: control (n=3); CPB (n=5), femoral-femoral hypothermic bypass for 1 hour; LPS (n=7), sham bypass followed by infusion of low-dose Escherichia coli lipopolysaccharide (LPS; 1 microgram/kg); CPB+LPS (n=6), both insults; and CPB+LPS+CMT-3 (n=5), both insults plus intravenous CMT-3 dosed to obtain a 25-micromol/L blood concentration. CPB+LPS caused severe lung injury, as demonstrated by a significant fall in PaO(2) and an increase in intrapulmonary shunt compared with all groups (P<0.05). These changes were associated with significant pulmonary infiltration of neutrophils and an increase in elastase and MMP-9 activity. CONCLUSIONS All pathological changes typical of ALI after CPB were prevented by CMT-3. Prevention of lung dysfunction followed an attenuation of both elastase and MMP-2 activity. This study suggests that strategies to combat ARDS should target terminal neutrophil effectors.

Left versus right atrial difference in dominant frequency, K+ channel transcripts, and fibrosis in patients developing atrial fibrillation after cardiac surgery

BACKGROUND The development of atrial fibrillation (AF) after cardiac surgery is associated with adverse outcomes; however, the mechanism(s) that trigger and maintain AF in these patients are unknown. OBJECTIVE The purpose of this study was to test our hypothesis that postoperative AF is maintained by high-frequency sources in the left atrium (LA) resulting from ion channel and structural features that differ from the right atrium (RA). METHODS Forty-four patients with no previous history of AF who underwent cardiac surgery consented to LA and RA biopsies. Histologic sections evaluated fatty infiltration, fibrosis, and iron deposition; quantitative reverse transcription-polymerase chain reaction (RT-PCR) assessed ion channel expression. In a subset of 27 patients, LA and RA unipolar recording leads were also placed. In patients who developed AF, the dominant frequency (DF) for each lead was calculated using fast Fourier transform. RESULTS DFs during AF were LA 6.26 +/- 0.8 Hz, RA 4.56 +/- 0.7 Hz (P <.01). RT-PCR revealed LA-to-RA differences in mRNA abundance for Kir2.3 (1.8:1) and Kir3.4 (2.3:1). While LA fibrosis was greater in patients developing AF compared with those remaining in normal sinus rhythm (10.8% +/- 11% vs. 3.8% +/- 3.5%; P = .03), the amount of LA fibrosis inversely correlated with the LA DF. CONCLUSIONS This is the first demonstration of LA-to-RA frequency differences during postoperative AF, which are associated with LA-to-RA differences in mRNA levels for potassium channel proteins and LA fibrosis. These results strongly suggest that sources of AF after cardiac surgery are located in the LA and are stabilized by LA fibrosis.

Multiple sequential insults cause post-pump syndrome

BACKGROUND We hypothesize that post-pump syndrome (PPS) following cardiopulmonary bypass (CPB) can be caused by multiple minor insults and that the mechanism of PPS is a priming and subsequent activation of polymorphonuclear (PMN) leukocytes. In this study extensive pathophysiologic and morphometric assessment was undertaken in a porcine model of sequential insult PPS. METHODS Pigs were anesthetized, placed on a ventilator, instrumented for measurements of hemodynamic function, and separated into five groups: (1) Control (n = 4)--surgery only, (2) CPB (n = 4)--placed on femoral-femoral hypothermic (28 degrees C) bypass for 1 h, (3) LPS (n = 6)--underwent sham CPB followed by infusion of low dose endotoxin [E. coli lipopolysaccharide (LPS-1 microg/kg)], (4) Heparin + protamine + LPS (HP + LPS, n = 4)--were heparinized without CPB for 1 h, following which protamine and LPS were infused and (5) CPB + LPS (n = 8)--subjected to both CPB and LPS. RESULTS Only CPB + LPS resulted in acute respiratory distress typical of PPS as indicated by a significant decrease in PaO2 and increase in intrapulmonary shunt fraction (p<0.05). CPB + LPS significantly increased tissue density and the number of sequestered monocytes and PMNs (p<0.05) above all other groups. Alveolar macrophages (AM) increased equally in all groups receiving LPS. CONCLUSIONS CPB primes the inflammatory system causing pulmonary PMN sequestration without lung injury. Exposure to an otherwise benign dose of endotoxin results in activation of the sequestered PMNs causing PPS. This study confirms that PPS can be caused by multiple minor insults.

Atrial myxomas: Pathologic types, tumor location, and presenting symptoms

Abstract  Background: Atrial myxoma is the most common cardiac neoplasm. Although not widely reported, two anatomic types have been observed: solid and papillary. We examined whether differences in gross or microscopic appearance and location correlated with symptomatology, specifically congestive heart failure (CHF), neurologic symptoms, and embolic events. Methods: We performed a retrospective review of atrial myxomas removed from 1972 to 2002, recording the clinical presentation, diagnostic modality, tumor location, gross, and microscopic features for each patient. Twenty‐six patients (16 females and 10 males) had atrial myxomas excised. Two patients (one female and one male) were excluded due to unavailable pathologic slides. Results: In 24 patients there were 15 solid and 9 papillary tumors. CHF was more prevalent in solid myxomas, while neurologic symptoms and embolic events were more common in papillary tumors. Tumor location further correlated with presenting symptoms. Ninety‐two percent of patients presenting with CHF had tumors attached to the atrial septum. Extraseptal myxomas more frequently presented with neurologic (80% vs. 29%) and embolic features (50% vs. 25%). All patients exhibiting clefted tumor surface had a history of embolization. A higher percentage of solid myxomas (93%) showed hemorrhage within the tumor than with papillary (56%). Conclusions: CHF was more common with solid myxomas, and neurologic and embolization events were more common in the papillary type. Septal tumor location showed strong association with CHF, while extraseptal location correlated with neurologic events. We speculate that the various gross and microscopic patterns reflect secondary changes within these neoplasms over the course of their natural history.

Elevated Pre-Operative Serum Peptides for Collagen I and III Synthesis Result in Post-Surgical Atrial Fibrillation

OBJECTIVES This study sought to determine if serum markers for collagen I and III synthesis, the carboxyl terminal peptide from pro-collagen I (PICP) and the amino terminal peptide from pro-collagen III (PIIINP), correlate with left atrial (LA) fibrosis and post-operative atrial fibrillation (AF). BACKGROUND AF after cardiac surgery is associated with adverse outcomes. We recently demonstrated that LA fibrosis is associated with post-operative AF in patients with no previous history of AF. METHODS Fifty-four patients having cardiac surgery without a history of AF consented to left and right atrial biopsies and a pre-operative peripheral blood draw. Picrosirius red staining quantified the percentage of fibrosis, and reverse transcriptase polymerase chain reaction assessed atrial tissue messenger ribonucleic acid transcripts involved in the fibrosis pathway. PICP and PIIINP levels were measured using an enzyme immunosorbent assay. RESULTS Eighteen patients developed AF, whereas 36 remained in normal sinus rhythm. LA fibrosis was higher in patients who developed AF versus normal sinus rhythm (6.13 ± 2.9% vs. 2.03 ± 1.9%, p = 0.03). LA messenger ribonucleic acid transcripts for collagen I, III, transforming growth factor, and angiotensin were 1.5- to 2.0-fold higher in AF patients. Serum PICP and PIIINP levels were highest in AF versus normal sinus rhythm (PICP: 451.7 ± 200 ng/ml vs. 293.3 ± 114 ng/ml, p = 0.006; PIIINP: 379 ± 286 pg/ml vs. 191.6 ± 162 pg/ml, p = 0.01). Furthermore, there was a linear correlation between LA fibrosis and serum PICP levels (R(2) = 0.2; p = 0.01), and of the markers, only PICP was independently associated with AF. CONCLUSIONS This demonstrates that serum PICP and PIIINP levels correlate with the presence of LA fibrosis and may act as predictors for post-operative AF even in the absence of previous history of AF.

Exogenous surfactant and positive end-expiratory pressure in the treatment of endotoxin-induced lung injury

OBJECTIVE To evaluate the efficacy of treating endotoxin-induced lung injury with single dose exogenous surfactant and positive end-expiratory pressure (PEEP). DESIGN Prospective trial. SETTING Laboratory at a university medical center. SUBJECTS Nineteen certified healthy pigs, weighing 15 to 20 kg. INTERVENTIONS Pigs were anesthetized and surgically prepared for hemodynamic and lung function measurements. Animals were randomized into four groups: a) Control pigs (n = 4) received an intravenous infusion of saline without Escherichia colilipopolysaccharide (LPS); b) the LPS group (n = 5) received an intravenous infusion of saline containing LPS (100 microg/kg); c) the PEEP plus saline group (n = 5) received an intravenous infusion of saline containing LPS. Two hours after LPS infusion, saline was instilled into the lung as a control for surfactant instillation, and the animals were placed on 7.5 cm H2O of PEEP; d) the PEEP plus surfactant group (n = 5) received an intravenous infusion of saline containing LPS. Two hours following LPS infusion, surfactant (50 mg/kg) was instilled into the lung and the animals were placed on 7.5 cm H2O of PEEP. PEEP was applied first and surfactant or saline was instilled into the lung while maintaining positive pressure ventilation. All groups were studied for 6 hrs after the start of LPS injection. At necropsy, bronchoalveolar lavage was performed and the right middle lung lobe was fixed for histologic analysis. MEASUREMENTS AND MAIN RESULTS Compared with LPS without treatment, PEEP plus surfactant significantly increased PaO2 (PEEP plus surfactant = 156.6 +/- 18.6 [SEM] torr [20.8 +/- 2.5 kPa]; LPS = 79.2 +/- 21.9 torr [10.5 +/- 2.9 kPa]; p<.05), and decreased venous admixture (PEEP plus surfactant = 12.5 +/- 2.0%; LPS = 46.9 +/- 14.2%; p< .05) 5 hrs after LPS infusion. These changes were not significant 6 hrs after LPS infusion. PEEP plus surfactant did not alter ventilatory efficiency index (VEI = 3800/[peak airway pressure - PEEP] x respiratory rate x PacO2), or static compliance as compared with LPS without treatment at any time point. Cytologic analysis of bronchoalveolar lavage fluid showed that surfactant treatment significantly increased the percentage of alveolar neutrophils as compared with LPS without treatment (PEEP plus surfactant = 39.1 +/- 5.5%; LPS = 17.4 +/- 6.6%; p< .05). Histologic analysis showed that LPS caused edema accumulation around the airways and pulmonary vessels, and a significant increase in the number of sequestered leukocytes (LPS group = 3.4 +/- 0.2 cells/6400 micro2; control group = 1.3 +/- 0.1 cells/6400 micro2; p < .05). PEEP plus saline and PEEP plus surfactant significantly increased the total number of sequestered leukocytes in the pulmonary parenchyma (PEEP plus surfactant = 8.2 +/- 0.7 cells/6400 micro2; PEEP plus saline = 3.9 +/- 0.2 cells/6400 micro2; p <.05) compared with the control and LPS groups. CONCLUSIONS We conclude that PEEP plus surfactant treatment of endotoxin-induced lung injury transiently improves oxygenation, but is unable to maintain this salutary effect indefinitely. Thus, repeat bolus dosing of surfactant or bolus treatment followed by continuous aerosol delivery may be necessary for a continuous beneficial effect.

Endotoxin-stimulated alveolar macrophage recruitment of neutrophils and modulation with exogenous surfactant.

OBJECTIVE To determine whether endotoxin-stimulated alveolar macrophages would attract neutrophils and whether exogenous surfactant treatment would modulate this chemoattraction. DESIGN Alveolar macrophages were harvested from bronchoalveolar lavage fluid and neutrophils from the blood of anesthetized guinea pigs. SUBJECTS Hartley guinea pigs. INTERVENTIONS Alveolar macrophages were suspended in RPMI 1640 and stimulated with 1 microg/mL of lipopolysaccharide (LPS), the supernatant removed and the alveolar macrophages were incubated in either RPMI or RPMI with surfactant at two different doses (292 microg/mL or 875 microg/mL) for 16 hrs. MEASUREMENTS AND MAIN RESULTS The supernatant was extracted from the alveolar macrophages and placed in a chemotaxis plate and the migration of neutrophils was measured. Chemotaxis of all cell types to be tested was measured by a change of absorbance on a microplate reader set at 492 nm. Results were compared with alveolar macrophages not stimulated with LPS, RPMI alone, and N formyl-methionyl-leucyl-phenylalanine (FMLP). The supernatant of the stimulated alveolar macrophages increased neutrophil chemotaxis as compared with unstimulated alveolar macrophages, and RPMI (p < .05). Surfactant treatment with 292 microg/mL significantly decreased LPS-stimulated alveolar macrophages induced neutrophil chemotaxis. Treatment with 875 microg/mL of surfactant did not alter neutrophil chemotaxis. CONCLUSIONS Alveolar macrophages stimulation with LPS increased the chemotaxis of neutrophils. Treatment with surfactant at a concentration of 875 microg/mL did not alter neutrophil migration; however, treatment with 292 microg/mL significantly decreased neutrophil chemotaxis suggesting that at low concentrations, surfactant inhibits chemokine release and may reduce pulmonary neutrophil sequestration in vivo.

Pulmonary surfactant function following endotoxin: effects of exogenous surfactant treatment.

In a porcine model of endotoxin-induced adult respiratory distress syndrome (ARDS) we tested the hypothesis that the severity of lung injury would vary with the concentration of endotoxin and that reestablishment of normal surfactant function with exogenous surfactant would vary with the severity of lung injury. The therapeutic effects of exogenous surfactant treatment on pulmonary surfactant function have varied greatly in animal models of ARDS. This has created discrepancies in the literature that may be due in part to a difference in the severity of the pulmonary lesion. Yorkshire pigs were anesthetized, placed on a ventilator, and surgically prepared for hemodynamic and lung function measurements. Pigs received either 25 (25LPS) or 50 (50LPS) μg/kg of Escherichia coli lipopolysaccharide (LPS) followed by exogenous surfactant (SURF, 100 mg/kg) instillation, and were randomized into five groups: Control = sham LPS (n = 4); 25LPS (n = 6); 50LPS (n = 6); 25LPS + SURF (n = 5); and 50LPS + SURF (n = 6). Treatments were followed by histological and surfactant function evaluation. Histological evaluation showed the hallmarks of ARDS. Pulmonary surfactant function assessed by surface tension minimum (ymin) was significantly (p < .05) elevated in both the 25LPS (20.2 ± 2, dyne/cm) and 50LPS (19 ± 3, dyne/cm) groups as compared with the Control group (10 ± 1, dyne/cm). Exogenous surfactant reduced ymin in the 25LPS + SURF group (9 ± 2 dyne/cm, p < .05 vs. 25LPS) but not in the 50LPS + SURF group (20 ± 1 dyne/cm, p < .05 vs. Control and 25LPS + SURF). Surfactant treatment was more effective in reestablishing normal surfactant function in animals subjected to a low dose of endotoxin, compared with animals receiving a higher dose.

Is body mass index a risk factor for isolated off-pump coronary revascularization?

Abstract  Objective: The influence of body mass index (BMI) as a risk factor for isolated off‐pump coronary artery bypass (OPCAB) surgery is unknown. We postulated that BMI ≥ 30 kg/m2 would adversely affect outcomes following OPCAB at our institution.

Videomicroscopy provides accurate in vivo assessment of pulmonary microvascular reactivity in rabbits

When defining the mechanism of hypoxic pulmonary vasoconstriction (HPV), investigators have employed ex vivo preparations because of the belief that accurate, quantitative assessment of pulmonary microvessels could not be obtained in vivo. We hypothesize that accurate, quantitative assessment of pulmonary microvascular reactivity can be performed using a simple, in vivo preparation. Our aim was to provide this quantitative assessment in a defined animal model, and to confirm that the chosen preparation could discriminate changes in microvascular reactivity as influenced by endogenous mediators. New Zealand rabbits were instrumented for in vivo microscopy and direct measurement of subpleural arterioles. Rabbits were first randomized to either control (n = 7) or endotoxin (n = 5), infusion of Escherichia coli lipopolysaccharide (200 Fg/kg). All rabbits were then exposed to a repeated protocol of normoxia (21% O2) for 20 min and then hypoxia (15% O2) for 10 min over 2 h. The changes in arteriole diameter were measured at the end of each interval. Normal pulmonary arterioles repeatedly constrict 15+/-3.5% during hypoxia. Altering endogenous vasoactive mediators, as with infusion of endotoxin, caused a loss of hypoxia-induced vasoconstriction. The results of our study validate this experimental preparation for the reliable quantification of pulmonary microvascular reactivity and investigation of hypoxic pulmonary vasoconstriction under both normal and pathologic conditions.