Effect of preoperative antibiotic prophylaxis on surgical site infections complicating cardiac surgery.

OBJECTIVE: To evaluate the effect of an optimized policy for antibiotic prophylaxis on surgical site infection (SSI) rates in cardiac surgery. DESIGN: Prospective cohort study. SETTING: Tertiary medical center in Israel. METHODS: SSIs were recorded during a 10-year study period and ascertained through routine surveillance using the National Healthcare Safety Network (NHSN) methodology. Multivariable analyses were conducted to determine which significant covariates, including the administration of preoperative prophylaxis, affected these outcomes. RESULTS: A total of 2,637 of 3,170 evaluated patients were included, and the overall SSI rate was 8.4%. A greater than 50% reduction in SSI rates was observed in the last 4 years of the study. Overall and site-specific infection rates were similar for patients receiving cefazolin or vancomycin. SSIs developed in 206 (8.1%) of the 2,536 patients who received preoperative prophylaxis (within 2 hours of the first incision) compared with 14 (13.9%) of 101 patients who received antibiotic prophylaxis at a different time (P = .04; odds ratio [OR], 1.8; 95% confidence interval [CI], 1.0-3.3). After accounting for covariates, preoperative hospital stay (5 days or more), an NHSN risk category (2 or 3), age (60 years or more), surgeon's role, and the period of measurement were significantly associated with SSIs. Emergency surgery, age, surgeon's role, and nonpreoperative prophylaxis were found to be independent predictors of superficial SSI. CONCLUSIONS: We observed a progressive and significant decrease in SSI rates after the implementation of an infection control program that included an optimized policy of preoperative prophylaxis in cardiac surgery.

Cerebral microemboli during hip fracture fixation: a prospective study.

BACKGROUND: Recent studies have shown that cerebral fat microembolism takes place during surgery for hip or knee replacement. In this study, we examined the occurrence of cerebral microembolism, solid or gas, during a standard procedure of hip fracture fixation. METHODS: This was a prospective study of patients who underwent urgent surgery with a dynamic hip screw for hip fracture fixation. During surgery, patients were monitored with transcranial Doppler for detection of microemboli from right and left middle cerebral arteries. RESULTS: Twenty-two patients were included in the study; their median age was 82 yr (range, 51-97 yr). In nine (41%) patients, high intensity transient signals were recorded, indicating microemboli passage in the middle cerebral arteries. All nine patients had signals of both solid and gas emboli. One of these nine patients had a postoperative cerebrovascular accident. CONCLUSIONS: The incidence of cerebral microemboli during urgent surgery for hip fracture fixation is considerable. This phenomenon is not confined to hip or knee replacement surgery. The clinical implications of this finding require further investigation.

Surgical site infection rates following cardiac surgery: the impact of a 6-year infection control program.

BACKGROUND: To evaluate the impact of an infection control program on surgical site infections (SSIs) complicating cardiac operations. METHODS: Prospective cohort study of patients undergoing cardiac operations. Interventions included prospective surveillance, povidone-iodine scrub showers, depilation before surgery, administration of preoperative antibiotic prophylaxis in the operating room, and postdischarge follow-up. Logistic regression models were fitted to assess infection rates over time, adjusting for factors known to affect SSI rates. RESULTS: The overall SSI rate for 2051 procedures was 10.4%. Rates of superficial and deep incisional SSIs remained unchanged over the study period. The rates of all organ/space infections, mediastinitis, and SSIs because of methicillin-resistant Staphylococcus aureus during the first 2 years were 3.25%, 2.22%, and 1.48%, respectively, and they decreased to 1.17%, 0.73%, and 0.73%, respectively, by the end of 2002 (P = .01, P = .01, and P = .09, respectively). The adjusted odds ratios for these 3 types of infection at the end of 2002 compared with December 31, 1998, were 0.19 (95% confidence interval [95% CI]: 0.07-0.48), 0.20 (95% CI: 0.06-0.66), and 0.28 (95% CI: 0.08-0.97), respectively. CONCLUSION: We observed significant reductions in organ/space infection rates, particularly mediastinitis. These differences remained significant when adjusted for potential confounding variables.

Intermittent coronary sinus occlusion complicating coronary sinus cannulation during coronary artery bypass operation.

Coronary sinus (CS) thrombosis is a rare event, usually complicating invasive procedures that cause trauma to the CS. Based on anecdotal case reports, this pathology is frequently associated with serious complications and is commonly fatal. We describe a case of intermittent CS thrombosis resulting from CS cannulation during coronary artery bypass grafting operation. This complication was further complicated by myocardial infarction, left ventricular free wall rupture, and pseudoaneurysm formation. The characteristic echocardiographic findings and a review of the literature on this rare complication are presented.

Free fatty acids repress the GLUT4 gene expression in cardiac muscle via novel response elements.

Hyperlipidemia (HL) impairs cardiac glucose homeostasis, but the molecular mechanisms involved are yet unclear. We examined HL-regulated GLUT4 and peroxisome proliferator-activated receptor (PPAR) gamma gene expression in human cardiac muscle. Compared with control patients, GLUT4 protein levels were 30% lower in human cardiac muscle biopsies from patients with HL and/or type 2 diabetes mellitus, whereas GLUT4 mRNA levels were unchanged. PPARgamma mRNA levels were 30-50% lower in patients with HL and/or diabetes mellitus type 2 than in controls. Reporter studies in H9C2 cardiomyotubes showed that HL in vitro, induced by high levels of arachidonic (AA) stearic, linoleic, and oleic acids (24 h, 200 mum) repressed transcription from the GLUT4 promoter; AA also repressed transcription from the PPARgamma1 and PPARgamma2 promoters. Co-expression of PPARgamma2 repressed GLUT4 promoter activity, and the addition of AA further enhanced this effect. 5'-Deletion analysis revealed three GLUT4 promoter regions that accounted for AA-mediated effects: two repression-mediating sequences at -443/-423 bp and -222/-197 bp, the deletion of either or both of which led to a partial derepression of promoter activity, and a third derepression-mediating sequence at -612/-587 bp that was required for sustaining this derepression effect. Electromobility shift assay further shows that AA enhanced binding to two of the three regions of cardiac nuclear protein(s), the nature of which is still unknown. We propose that HL, exhibited as a high free fatty acid level, modulates GLUT4 gene expression in cardiac muscle via a complex mechanism that includes: (a) binding of AA mediator proteins to three newly identified response elements on the GLUT4 promoter gene and (b) repression of GLUT4 and the PPARgamma genes by AA.

Can regurgitant flow damage the left atrial endothelium in patients with prosthetic mechanical heart valves?

BACKGROUND AND AIM OF THE STUDY: Previous in-vitro studies of mechanical heart valves (MHVs) in the closed position demonstrated the formation of regurgitant flows, with bubbles and jets forming vortices during each systole. The study aim was to determine whether the regurgitant flow observed in patients with MHVs can damage the left atrial endothelium, due to shear stresses exerted on the endothelial layers. This objective has been accomplished by appropriate in-vitro simulation experiments. METHODS: In these experiments, leakage flow through several commercial MHVs was investigated. The geometry of the set-up closely resembled that of the left atrial anatomy. Water was forced through the slit of a closed MHV and directed toward the hemispherical cup coated with fluorescent paint. The flow field between the valve and the cup was photographed using high-speed videography, from which local velocities were measured, using digital particle imaging velocimetry. Qualitative damage to the surface of the cup was assessed from the amount of fluorescent paint removed from the cup. RESULTS: The experimental results and calculations indicated that flows through the gaps of the closed valves were sufficient to generate strong vortices, with velocities near the atrial wall in the range of 0.5 to 4.0 m/s, depending on the valve. This led to high shear stresses on the left atrial wall, which far exceeded physiologically acceptable levels. CONCLUSION: The calculated shear stresses exceeded by orders of magnitude the maximum physiologically tolerated stresses. This suggests that shear stresses associated with regurgitant jets in MHVs may damage the endothelial cells, leading to the activation of the inflammatory reaction, enhanced procoagulation, platelet activation and aggregation, and mechanical cell denudation.

Impact of body mass index on the outcome of patients with multivessel disease randomized to either coronary artery bypass grafting or stenting in the ARTS trial: The obesity paradox II?

The effect of body mass index (BMI) on outcomes after coronary artery revascularization remains controversial. We studied 1,203 patients who had multivessel coronary artery disease and underwent stenting (n = 599) or coronary artery bypass grafting (CABG; n = 604) in the Arterial Revascularization Therapies Study. Patients were assigned to 1 of 3 groups according to BMI: <25, 25 to 30, and >30 kg/m(2). At 3-year follow-up, the incidence of death, cerebrovascular events, or myocardial infarction was similar for these BMI categories regardless of the revascularization technique used. Rates of repeat revascularization procedures were significantly higher among patients who had been randomized to stenting but were similar across BMI groups. For patients who had been randomized to undergo CABG, there was a significant decrease in repeat revascularization procedures in obese patients (p = 0.03). Among patients who underwent stenting, BMI had no effect on the 3-year combined end point of rate of major adverse cardiac or cerebrovascular events. Among patients who underwent CABG, major adverse cardiac or cerebrovascular event rates were significantly lower for patients who were obese (11%) or overweight (16%) compared with patients who had a normal BMI (24%; p = 0.008). Thus, in a large cohort of patients who had multivessel coronary artery disease and underwent surgical or percutaneous revascularization, BMI had no effect on 3-year outcome of those who underwent stenting. Conversely, among patients who underwent CABG, those who were overweight or obese had a significantly better outcome than did those who had a normal BMI with regard to survival without major adverse cardiac or cerebrovascular events, mainly due to lower rates of repeat revascularization procedures.

Pseudoaneurysm of the mitral-aortic intervalvular fibrosa following aortic valve replacement - diagnosis and dynamic evaluation with multidetector CT and transesophageal echocardiography.

Sixteen-slice multidetector CT findings of a pulsatile pseudoaneurysm of the mitral-aortic intervalvular fibrosa, in a woman following aortic valve replacement, are presented. Multidetector CT depicted the pseudoaneurysm and enabled dynamic evaluation of its lumen through the cardiac cycle, documenting expansion during systole and almost complete collapse during diastole. This case illustrates the capabilities of multidetector cardiac CT in the evaluation of aortic valve pathology.

Mitral mechanical heart valves: in vitro studies of their closure, vortex and microbubble formation with possible medical implications.

OBJECTIVE: The goal of the present work was to create the closest possible in vitro fluid dynamic environment in which prosthetic mitral valves in the patients' hearts function, in order to demonstrate whether microbubbles are generated, and if yes, under what conditions and at which stage of the cardiac cycle. Microbubbles were observed in the blood of patients with mitral mechanical heart valves (MHV) by means of echocardiography. The phenomenon, often referred to as high-intensity transient signals (HITS), appears as bright, intense, high-velocity and persistent echoes detected by Doppler echocardiography at the instant of valve closure. The question is no longer whether microbubbles are being formed in patients with MHV. as an inherent aspect of their design, but rather how they evolve and when. The answer to this question was the objective of the present paper. METHODS: Hemodynamic conditions in which microbubbles were observed in patients with mitral MHV were simulated in our laboratory. We were able to describe the bubble formation process, as one consisting of nucleation and microbubble growth. While mild growth of nuclei is governed by diffusion, extensive growth of microbubbles is controlled by pressure drop during deceleration of the leaflets on the housing on the atrial side of the mitral MHV. RESULTS: The present study has shown that bubbles form in a fluid at the instant of closure of mechanical valves. The formation of vortices after valve closure, although clinically not yet observed, was also demonstrated in the present in vitro studies. We believe that impact of such vortices on the endothelial layer of the left atrial wall may have clinical significance. These two phenomena were not observed in bioprosthetic valves. CONCLUSIONS: As demonstrated, there exist two distinct phenomena characteristic of mechanical heart valves, which take place during valve closure, namely, that of vortex formation and that of microbubble growth. Both phenomena may have far reaching clinical implications.

Minimal dissection and continuous retrograde cardioplegia for aortic valve replacement in patients with a patent left internal mammary artery bypass graft.

BACKGROUND AND AIM OF THE STUDY: Aortic valve replacement (AVR) in patients with previous coronary artery bypass grafting (CABG) and a patent pedicled internal mammary artery (IMA) is often complicated by a need to dissect and clamp the IMA to achieve optimal myocardial protection. Eliminating this need may simplify and facilitate surgery; hence, a new surgical technique for use in these patients is described. METHODS: Five patients with previous CABG and functioning IMA who required AVR between January 1998 and October 2002 were studied. In all patients, the IMA was neither dissected nor clamped. Myocardial protection comprised an initial bolus of antegrade cardioplegia, followed by continuous retrograde infusion of tepid non-diluted oxygenated blood, supplemented with cardioplegic drugs to maintain cardiac arrest. The systemic and myocardial temperature was 30-32 degrees C. RESULTS: All patients underwent surgery as planned, and there was no operative mortality or myocardial infarction. One patient sustained a minor stroke. None of the IMA was injured. CONCLUSION: In patients requiring AVR, it is both possible and reasonable to leave the IMA undissected and unclamped. Limited experience suggests that this new technique provides adequate myocardial protection, while keeping surgery both simple and safe.

Comparison of bypass surgery and stenting for the treatment of multivessel disease: results from the ARTS trial in Israel.

BACKGROUND: The Arterial Revascularization Therapies Study was a multicenter, randomized trial designed to compare percutaneous coronary intervention with stenting versus coronary artery bypass graft surgery in 1,205 patients with multivessel coronary artery disease. The most appropriate type of treatment for these patients is still a matter of considerable debate. OBJECTIVES: To evaluate the clinical characteristics of patients enrolled in the ARTS trial in Israel in comparison to those worldwide, and to assess the 1 year outcome in these patients. METHODS: Between April 1997 and June 1998, a total of 1,205 patients with multivessel coronary artery disease, who were considered to be equally treatable with both modalities, were randomized to either stenting (n = 600) or CABG (n = 605) at 67 centers around the world. In Israel, 53 patients at four participating medical centers were randomized to either PCI with stents (n = 27) or CABG (n = 26). RESULTS: Clinical and angiographic characteristics were similar in the two groups, except for a significantly higher incidence of diabetic patients in Israel who were randomized to CABG, compared to those worldwide (35% vs. 16%, P = 0.01). Also, there were more patients with unstable angina in Israel (63 vs. 37%, P = 0.006). At 1 year follow-up, overall mortality and cerebrovascular accident rates were similar between the two groups and equivalent to results obtained around the world. There was a significantly higher incidence of myocardial infarction rates in patients randomized to stenting in Israel compared to patients worldwide (7.4 vs. 5.3%, P = 0.01) or to patients randomized to CABG in Israel (7.4 vs. 0%, P = 0.006). Similar to the overall ARTS results, there was a higher incidence of repeat revascularization procedures in patients assigned to the PCI with stenting arm (22.2 vs. 3.8%, P = 0.004) compared to those randomized to CABG, respectively. CONCLUSIONS: The results of this analysis of the Israeli ARTS population indicate that coronary stenting and bypass surgery yield similar findings with regard to mortality and stroke and are comparable to those obtained in the whole study group. Likewise, coronary stenting was associated with an increased incidence of repeat revascularization procedures as compared to CABG. However, patients in Israel randomized to stenting had a higher rate of myocardial infarction as compared to the overall results and to patients who underwent CABG in Israel. The present analysis provides important data for the safety and efficacy of either stenting or bypass surgery in treating patients with multivessel disease in Israel.

Bubble formation on St. Jude Medical mechanical heart valves: an in-vitro study.

BACKGROUND AND AIM OF THE STUDY: Bubble formation in blood, which has been observed during valve closure in patients with mechanical heart valves (MHVs), raises concern because of cognitive changes and potential activation of blood elements associated with thromboembolic phenomena. Bubble formation in the vicinity of MHVs has been described previously; the present in-vitro study was undertaken to quantitate bubbles leaving the heart and entering the systemic circulation, and to gain a closer perspective of this phenomenon and its potential clinical implications. METHODS: Experiments were performed in a left heart pulsed flow simulator with 29 mm mitral and 23 mm aortic St. Jude Medical MHVs; mitral and aortic bioprosthetic valves were used as controls. De-aerated water was pumped through the left heart pulsed flow simulator at a fixed rate of 70 beats/min and at different cardiac outputs. Bubble numbers and sizes were monitored photographically at the simulator exit. RESULTS: Numbers of bubbles per frame generated in MHVs in the mitral position ranged from 8 to 14 at cardiac outputs of 3 to 6.5 1/min; this corresponded to gas volumetric flow rates of 330 to 830 mm3/min. The number of bubbles per frame for the aortic MHV was 3 to 7, reflecting the less severe flow conditions and milder valve closure impact. The diameter of bubbles generated by the mitral valve was almost uniform (0.45 mm), while bubble diameters in the aortic valve ranged from 0.36 to 0.69 mm. CONCLUSION: Bubble formation was found to be an inherent flaw of the present generation of MHVs, and this problem should be addressed in future valve designs.

Successful invasive management and surgical repair of subacute ventricular rupture complicating myocardial infarction.

We describe a patient following acute myocardial infarction with a protracted clinical course presenting transient episodes of hypotension, who eventually developed cardiac tamponade. Echocardiography demonstrated pericardial effusion and emergency pericardiocentesis revealed blood. The patient's condition was stabilized and she underwent emergency thoracotomy with successful repair of left ventricular rupture. We discuss the literature and suggest an approach for management of patients with suspected ventricular rupture after myocardial infarction.