Kamal R. Khabbaz

Postoperative cardiac tamponade in the modern surgical era

BACKGROUND Pericardial effusions resulting in cardiac tamponade (CT) are uncommon after open heart surgery (OHS) and are associated with significant morbidity and mortality. Characteristics and outcomes of patients who develop postoperative CT are poorly defined. Our objective was to further analyze the population at risk for developing postoperative CT, identify potential perioperative and surgical risk factors, and evaluate the impact of CT on patient outcomes. METHODS A retrospective analysis of 4,561 consecutive patients undergoing OHS at our institution was performed. Patients with clinical suspicion of pericardial effusion following surgery were evaluated by transthoracic or transesophageal echocardiography, and clinical parameters were analyzed. RESULTS Forty-eight (1%) of the 4,561 patients were found to have echocardiographic evidence of a moderate or large pericardial effusion, of whom 36 (74%) had evidence of CT. The mean age of the patients with CT was 61 years. Coronary artery bypass grafting (CABG) had been performed in 24% of these patients, valve +/- CABG in 73%, and other OHS procedures in 3%. The incidence of CT following CABG alone was 0.2%, whereas it was 0.6% after valve +/- CABG. Females had a higher risk for developing CT, and this occurred earlier in the postoperative period when compared with men. Aspirin, heparin, or warfarin were given to 84% of patients within 3 days of surgery. Mean time to diagnosis of CT was 10 +/- 1 days after OHS. Prior to diagnosis of CT, the maximum international normalized ratio (INR) and partial thromboplastin time (PTT) were 2.7 +/- 0.3 and 68 +/- 5 seconds, respectively. Forty-nine percent of pericardial effusions were posterior and 46% were circumferential; one-third of the effusions were considered large by echocardiography. There was one in-hospital cardiovascular death. CONCLUSIONS CT after OHS is more common following valve surgery than CABG alone and may be related to the preoperative use of anticoagulants. Females appear to be at higher risk for developing early postoperative CT. When diagnosed and treated promptly, postoperative CT should not significantly increase mortality.

Clinical benefits of endoscopic vein harvesting in patients with risk factors for saphenectomy wound infections undergoing coronary artery bypass grafting

OBJECTIVE The influence of endoscopic harvesting techniques on the prevalence of leg-wound complications after coronary artery bypass grafting remains to be defined for patients at high risk for the development of wound infections. METHODS Among 1473 patients undergoing coronary artery bypass grafting who had the saphenous vein harvested by either a continuous incision or skip incisions leaving intact skin bridges, we determined the prevalence of wound infections to be 9.6%. The following variables were entered into logistic regression analysis to identify significant risk factors that might be predictive of wound infection: diabetes, peripheral vascular disease, obesity, renal failure, steroid use, age, sex, and type of closure. We then prospectively randomized 132 patients found to be at high risk of wound infection to either endoscopic vein harvesting or a continuous open incision. RESULTS Univariate analysis showed female sex (P =.04), diabetes (P <.001), and obesity (P <.001) to be predictors of wound infection. In a multivariate model diabetes (P =.02) and obesity (P =.001) were independent predictors. In patients at high risk, the prevalence of wound infection was 4.5% for the endoscopic group versus 20% for the open group (P =.01). Vein procurement time was greater in the endoscopic group (65 minutes vs 32 minutes, P <.001), as was the number of vein repairs required (2.5 vs 0.6, P <.001). CONCLUSION The use of endoscopic vein harvesting decreases the prevalence of postoperative leg-wound infections in high-risk patients with diabetes and obesity. Whether this translates into an economic benefit that justifies the additional cost of that technology requires further analysis.

Serologic Markers of Brain Injury and Cognitive Function After Cardiopulmonary Bypass

Objective:To examine the association between biochemical markers of brain injury (MBI) and the inflammatory response in relation to neurocognitive deficiency (NCD) after cardiopulmonary bypass (CPB). Summary Background Data:In cardiac surgery, NCD is a common but underdiagnosed complication with an unclear pathophysiology leading to significant morbidity. Despite extensive investigation, identification of a MBI for clinical use and clarifying the pathophysiology of NCD have not been achieved. Methods:Forty patients undergoing CABG and/or valve procedures using CPB were administered a validated neurocognitive battery preoperatively and postoperatively at day 4 and 3 months. S-100b, neuron specific enolase (NSE), and tau protein were assayed as MBIs preoperatively and postoperatively at 6 hours and day 4. C-reactive protein (CRP), interleukin (IL)-6, C3a, and total peroxide levels were also quantified from serum. Impact of cardiotomy suction and antifibrinolytics on markers of brain injury was assessed. Results:The incidence of early NCD was 40% (16 of 40). NSE and tau protein at the 6-hour time point were both significantly elevated in the presence of NCD (NCD group) compared with those without NCD (NORM group) (8.69 ± 0.82 vs. 5.98 ± 0.61; P = 0.018 and 68.8 vs. 29.2%; P = 0.015; respectively). S-100b increase was not different between the NCD and NORM groups. Cardiotomy suction significantly elevated S-100b levels, whereas NSE and tau were not significantly influenced. Aprotinin did not have an effect on NCD or levels of MBIs. Also, the NCD group had significantly elevated CRP and peroxide levels compared with the NORM group at postoperative day 4 while C3a was significantly elevated at 6 hours. Conclusion:NSE and tau are better associated with NCD and less influenced by cardiotomy suction compared with S-100β. Inflammatory and oxidative stress is associated with NCD post-CPB.

Simultaneous carotid endarterectomy and coronary bypass: Perioperative risk and long-term survival

PURPOSE The purpose of this article is to examine the outcome of simultaneous coronary bypass-carotid endarterectomy (CABG-CEA) and to compare it with the outcome of endarterectomy alone (CEA alone) in patients at high cardiac risk. METHODS A retrospective review of the records and follow-up data for 100 consecutive patients who had undergone CABG-CEA and were at high risk and 114 patients who had undergone CEA, had overt coronary artery disease (angina, previous infarct, or ischemic electrocardiographic abnormalities), but had not undergone CABG was carried out. RESULTS Our CABG-CEA group had a high incidence of symptomatic carotid disease (57%) and contralateral occlusion (28%) when compared with patients in other reports. Patients in the CABG-CEA group were older (67.9 +/- 8.3 years vs 63.6 +/- 15.7 years, p = 0.01) and more often smokers (81% vs 52.6%, p = 0.01) than patients in the CEA alone group. Perioperative mortality was 8% for the CEA-CABG group and for 1.8% for the CEA alone group (p = 0.035). Perioperative stroke morbidity was 9% for the CEA-CABG group and 2.6% for the CEA alone group (p = 0.05). Life table survival at 1,3, and 5 years was 90%, 82%, and 73% versus 96%, 84%, and 76% for the CABG-CEA and CEA alone groups, respectively (p = 0.30). CONCLUSIONS Selection criteria for CABG-CEA greatly influence perioperative risk. Despite the greater age and more advanced coronary artery disease in the CABG-CEA group, long-term outcome differences are accounted for entirely by differences in perioperative morbidity and mortality. Prospective trials of strategies such as staged CEA and CABG to reduce perioperative risk are needed.

Calcium-Activated Potassium Channels Contribute to Human Coronary Microvascular Dysfunction After Cardioplegic Arrest

Background— Cardioplegic arrest (CP) followed by reperfusion after cardiopulmonary bypass induces coronary microvascular dysfunction. We investigated the role of calcium-activated potassium (KCa) channels in this dysfunction in the human coronary microvasculature. Methods and Results— Human atrial tissue was harvested before CP from a nonischemic segment and after CP from an atrial segment exposed to hyperkalemic cold blood CP (mean CP time, 58 minutes) followed by 10-minute reperfusion. In vitro relaxation responses of precontracted arterioles (80 to 180 μm in diameter) in a pressurized no-flow state were examined in the presence of KCa channel activators/blockers and several other vasodilators. We also examined expression and localization of KCa channel gene products in the coronary microvasculature using reverse transcriptase–polymerase chain reaction, immunoblot, and immunofluorescence photomicroscopy. Post-CP reperfusion relaxation responses to the activator of intermediate and small conductance KCa channels (IKCa/SKCa), NS309 (10−5 M), and to the endothelium-dependent vasodilators, substance P (10−8 M) and adenosine 5′diphosphate (10−5 M), were significantly reduced compared with pre-CP responses (P<0.05, n=8/group). In contrast, relaxation responses to the activator of large conductance KCa channels (BKCa), NS1619 (10−5 M), and to the endothelium-independent vasodilator, sodium nitroprusside (10−4 M), were unchanged pre- and post-CP reperfusion (n=8/group). Endothelial denudation significantly diminished NS309-induced vasodilatation and abolished substance P- or adenosine 5′ diphosphate-induced relaxation (P<0.05), but had no effect on relaxation induced by either NS1619 or sodium nitroprusside. The total polypeptide levels of BKCa, IKCa, and SKCa and the expression of IKCa mRNA were not altered post-CP reperfusion. Conclusion— Cardioplegic arrest followed by reperfusion after cardiopulmonary bypass causes microvascular dysfunction associated with and likely in part due to impaired function of SKCa and IKCa channels in the coronary microcirculation. These results suggest novel mechanisms of endothelial and smooth muscle microvascular dysfunction after cardiac surgery.

Three-Dimensional Echocardiographic Assessment of Changes in Mitral Valve Geometry After Valve Repair

BACKGROUND Application of annuloplasty rings during mitral valve (MV) repair has been shown to significantly change the mitral annular geometry. Until recently, a comprehensive two-dimensional echocardiographic evaluation of annular geometric changes was difficult owing to its nonplanar orientation. In this study, an analysis of the three-dimensional intraoperative transesophageal echocardiographic evaluation of the MV annulus is presented before and immediately after repair. METHODS We performed three-dimensional geometric analysis on 75 patients undergoing MV repair during coronary artery bypass graft surgery for mitral regurgitation or myxomatous mitral valve disease. Geometric analysis of the MV was performed before and immediately after valve repair with full rings and annuloplasty bands. The acquired three-dimensional volumetric data were analyzed in the operating room. Specific measurements included annular diameter, leaflet lengths, the nonplanarity angle, and the circularity index. Before and after repair data were compared. RESULTS Complete echocardiographic assessment of the MV was feasible in 69 of 75 patients (92%) within 2 to 3 minutes of acquisition. Placement of full rings resulted in an increase in the nonplanarity angle or a less saddle shape of the native mitral annulus (137 +/- 14 versus 146 +/- 14; p = 0.002. By contrast, the nonplanarity angle did not change significantly after placement of partial rings. CONCLUSIONS Mitral annular nonplanarity can be assessed in the operating room. Application of full annuloplasty rings resulted in the mitral annulus becoming more planar. Partial annuloplasty bands did not significantly change the nonplanarity angle. Neither of the two types of rings restored the native annular planarity.

Predicting DNA methylation level across human tissues

Differences in methylation across tissues are critical to cell differentiation and are key to understanding the role of epigenetics in complex diseases. In this investigation, we found that locus-specific methylation differences between tissues are highly consistent across individuals. We developed a novel statistical model to predict locus-specific methylation in target tissue based on methylation in surrogate tissue. The method was evaluated in publicly available data and in two studies using the latest IlluminaBeadChips: a childhood asthma study with methylation measured in both peripheral blood leukocytes (PBL) and lymphoblastoid cell lines; and a study of postoperative atrial fibrillation with methylation in PBL, atrium and artery. We found that our method can greatly improve accuracy of cross-tissue prediction at CpG sites that are variable in the target tissue [R2 increases from 0.38 (original R2 between tissues) to 0.89 for PBL-to-artery prediction; from 0.39 to 0.95 for PBL-to-atrium; and from 0.81 to 0.98 for lymphoblastoid cell line-to-PBL based on cross-validation, and confirmed using cross-study prediction]. An extended model with multiple CpGs further improved performance. Our results suggest that large-scale epidemiology studies using easy-to-access surrogate tissues (e.g. blood) could be recalibrated to improve understanding of epigenetics in hard-to-access tissues (e.g. atrium) and might enable non-invasive disease screening using epigenetic profiles.

Three-Dimensional Printing of Mitral Valve Using Echocardiographic Data

Three-dimensional (3D) printing has steadily gained traction as a clinical tool. Current applications include developing patient-specific implants, prostheses, and realistic anatomic models for surgical education and planning [(1,2)][1]. In cardiac surgery, patient-specific 3D models of hearts with

Dynamic 3-Dimensional Echocardiographic Assessment of Mitral Annular Geometry in Patients With Functional Mitral Regurgitation

BACKGROUND Mitral valve (MV) annular dynamics have been well described in animal models of functional mitral regurgitation (FMR). Despite this, little if any data exist regarding the dynamic MV annular geometry in humans with FMR. In the current study we hypothesized that 3-dimensional (3D) echocardiography, in conjunction with commercially available software, could be used to quantify the dynamic changes in MV annular geometry associated with FMR. METHODS Intraoperative 3D transesophageal echocardiographic data obtained from 34 patients with FMR and 15 controls undergoing cardiac operations were dynamically analyzed for differences in mitral annular geometry with TomTec 4D MV Assessment 2.0 software (TomTec Imaging Systems GmbH, Munich, Germany). RESULTS In patients with FMR, the mean mitral annular area (14.6 cm(2) versus 9.6 cm(2)), circumference (14.1 cm versus 11.4 cm), anteroposterior (4.0 cm versus 3.0 cm) and anterolateral-posteromedial (4.3 cm versus 3.6 cm) diameters, tenting volume (6.2 mm(3) versus 3.5 mm(3)) and nonplanarity angle (NPA) (154 degrees ± 15 versus 136 degrees ± 11) were greater at all points during systole compared with controls (p < 0.01). Vertical mitral annular displacement (5.8 mm versus 8.3 mm) was reduced in FMR compared with controls (p < 0.01). CONCLUSIONS There are significant differences in dynamic mitral annular geometry between patients with FMR and those without. We were able to analyze these changes in a clinically feasible fashion. Ready availability of this information has the potential to aid comprehensive quantification of mitral annular function and possibly assist in both clinical decision making and annuloplasty ring selection.

Intraoperative metabolic monitoring of the heart: II. Online measurement of myocardial tissue pH.

Under conditions of ischemia, the hydrogen ion [H+] accumulates in the myocardial tissue in proportion to the magnitude of the ischemic insult. The accumulation of [H+] is the result of both increased anaerobic production of [H+] secondary to decreased substrate and decreased washout of [H+] secondary to decreased coronary perfusion. The Khuri tissue pH electrode/monitoring system has been developed and validated over the past two decades. Its scientific basis and correlates have been established, and it is the only system that has been approved for use in humans. Myocardial tissue pH has been monitored in the anterior and posterior walls of the left ventricle in more than 700 patients undergoing major cardiac surgery. An understanding of the relationship between pH and temperature and between the pH and [H+] in tissues is important for the proper interpretation of the myocardial pH data generated in the course of an operation. Intraoperative monitoring of myocardial pH is the only modality available to the cardiac surgeon for online assessment and improvement of the adequacy of myocardial protection. By defining myocardial protection in terms of protection from myocardial tissue acidosis, this technology provides a new tool with which the comparative efficacy of the various myocardial protection techniques can be assessed. It also provides an online tool for assessing the adequacy of coronary revascularization, and has the potential of improving procedures and outcomes for off-pump coronary artery bypass grafting.