Marcus P. Haw

Hepatic changes in the failing Fontan circulation

Background: The failing Fontan circulation is associated with hepatic impairment. The nature of this liver injury is poorly defined. Objective: To establish the gross and histological liver changes of patients with Fontan circulation relative to clinical, biochemical and haemodynamic findings. Methods: Patients were retrospectively assessed for extracardiac Fontan conversion between September 2003 and June 2005, according to an established clinical protocol. Twelve patients, mean age 24.6 (range 15.8–43.4) years were identified. The mean duration since the initial Fontan procedure was 14.1 (range 6.9–26.4) years. Results: Zonal enhancement of the liver (4/12) on CT was more common in patients with lower hepatic vein pressures (p = 0.007), and in those with absent cardiac cirrhosis on histological examination (p = 0.033). Gastro-oesophageal varices (4/12) were more common in patients with higher hepatic vein pressure (21 (6.3) vs 12.2 (2.2) mm Hg, p = 0.013) and associated with more advanced cirrhosis (p = 0.037). The extent of cirrhosis (7/12) was positively correlated with the hepatic vein pressure (r = 0.83, p = 0.003). A significant positive correlation was found between the Fontan duration and the degree of hepatic fibrosis (r = 0.75, p = 0.013), as well as presence of broad scars (r = 0.71, p = 0.021). Protein-losing enteropathy (5/12) occurred more frequently in patients with longer Fontan duration (11.7 (3.2) vs 17.9 (6.1) years, p = 0.038). Conclusions: Liver injury, which can be extensive in this patient group, is related to Fontan duration and hepatic vein pressures. CT scan assists non-invasive assessment. Cardiac cirrhosis with the risk of developing gastro-oesophageal varices and regenerative liver nodules, a precursor to hepatocellular carcinoma, is common in this patient group.

The Gap-Junctional Protein Connexin40 Is Elevated in Patients Susceptible to Postoperative Atrial Fibrillation

Background —Atrial fibrillation (AF), a cardiac arrhythmia arising from atrial re-entrant circuits, is a common complication after cardiac surgery, but the proarrhythmic substrate underlying the development of postoperative AF remains unclear. This study investigated the hypothesis that altered expression of connexins, the component proteins of gap junctions, is a determinant of a predisposition to AF. Methods and Results —The expression of the 3 atrial connexins–connexins 43, 40, and 45 —was analyzed at the mRNA and protein levels by Northern and Western blotting techniques and immunoconfocal microscopy in right atrial appendages from patients with ischemic heart disease who were undergoing coronary artery bypass surgery. Twenty percent of the patients subsequently developed AF, which allowed retrospective division of the samples into 2 groups, non-AF and AF. Connexin43 and connexin45 transcript and protein levels did not differ between the groups. However, connexin40 transcript and protein were expressed at significantly higher levels in the AF group. Connexin40 protein was markedly heterogeneous in distribution. Conclusions —Atrial myocardium susceptible to AF is distinguished from its nonsusceptible counterpart by elevated connexin40 expression. The heterogeneity of connexin distribution could give rise to different resistive properties and conduction velocities in spatially adjacent regions of tissue, which become enhanced and, hence, proarrhythmic the higher the overall level of connexin40.

A prospective randomized study to evaluate the renoprotective action of beating heart coronary surgery in low risk patients.

OBJECTIVES Cardiopulmonary bypass (CPB) is widely regarded as an important contributor to renal failure, a well recognized complication following coronary artery surgery (coronary artery bypass grafting (CABG)). Anecdotally off-pump coronary surgery (OPCAB) is considered renoprotective. We examine the extent of renal glomerular and tubular injury in low-risk patients undergoing either OPCAB or on-pump coronary artery bypass (ONCAB). METHODS Forty low-risk patients with normal preoperative cardiac and renal functions awaiting elective CABG were prospectively randomized into those undergoing OPCAB (n=20) and ONCAB (n=20). Glomerular and tubular injury were measured respectively by urinary excretion of microalbumin and retinol binding protein (RBP) indexed to creatinine (Cr). Daily measurements were taken from admission to postoperative day 5. Fluid balance, serum Cr and blood urea were also monitored. RESULTS No mortality or renal complication were observed. Both groups had similar demographic makeup, Parsonnet score, functional status and extent of coronary revascularization (2.1+/-1.0 vs. 2.5+/-0.7 grafts; P=0.08). Serum Cr and blood urea remained normal in both groups throughout the study. A significant and similar rise in urinary RBP:Cr occurred in both groups peaking on day 1 (3183+/-2534 vs. 4035+/-4079; P=0.43) before reapproximating baseline levels. These trends were also observed with urinary microalbumin:Cr (5.05+/-2.66 vs. 6.77+/-5.76; P=0.22). Group B patients had a significantly more negative fluid balance on postoperative day 2 (-183+/-1118 vs. 637+/-847 ml; P=0.03). CONCLUSIONS Although renal complication or serum markers of kidney dysfunction were absent, sensitive indicators revealed significant and similar injury to renal tubules and glomeruli following either OPCAB or ONCAB. These results suggest that avoidance of CPB does not offer additional renoprotection to patients at low risk of perioperative renal insult during CABG.

Novel application of vacuum assisted closure technique to the treatment of sternotomy wound infection

Infection of the sternotomy wound is a potentially devastating and sometimes lethal complication following cardiac surgery. Established treatment may involve a combination of debridement, packing, delayed closure, plastic reconstruction, re-wiring and irrigation dependent on the severity of infection. Vacuum assisted closure, originally adopted for the treatment of non-healing wounds, has recently gained popularity among various surgical specialities in managing complex wound infection. Here we describe this novel technique of managing postoperative sternal wound infection.

Hepatic fibrosis and cirrhosis in the Fontan circulation: a detailed morphological study

Aims: To describe the histological features of the liver in patients with a Fontan circulation. Methods: Specimens from liver biopsies carried out as part of preoperative assessment prior to extracardiac cavopulmonary conversion of an older style Fontan were examined and scored semi-quantitatively for pertinent histological features. To support the use of the scoring, biopsy specimens were also ranked by eye for severity to allow correlation with assigned scores. Results: Liver biopsy specimens from 18 patients with a Fontan circulation were assessed. All specimens showed sinusoidal fibrosis. In 17 cases there was at least fibrous spur formation, with 14 showing bridging fibrosis and 2 showing frank cirrhosis. In 17 cases at least some of the dense or sinusoidal fibrosis was orcein positive, although a larger proportion of the dense fibrous bands were orcein positive compared with the sinusoidal component. All specimens showed marked sinusoidal dilatation, and 14 showed bile ductular proliferation; 1 showed minimal iron deposition, and 1 showed mild lobular lymphocytic inflammation. There was no cholestasis or evidence of hepatocellular damage. Similar appearances were observed in 2 patients with severe tricuspid regurgitation. Discussion: The histological features of the liver in patients with a Fontan circulation are similar to those described in cardiac sclerosis. Sinusoidal dilatation and sinusoidal fibrosis are marked in the Fontan series. The presence of a significant amount of orcein negative sinusoidal fibrosis suggests there may be a remediable component, although the dense fibrous bands are predominantly orcein positive, suggesting chronicity and permanence. No inflammation or hepatocellular damage is evident, suggesting that fibrosis may be mediated by a non-inflammatory mechanism.

Pediatric tracheal homograft reconstruction: A novel approach to complex tracheal stenoses in children

PURPOSE Tracheal stenosis can be a life-threatening problem in children. Long-segment tracheal stenosis and recurrent tracheal stenosis are especially problematic. Tracheal homograft reconstruction represents a novel therapeutic modality for these patients. METHODS Cadaveric trachea is harvested, fixed in formalin, washed in thimerosal (Methiolate), and stored in acetone. The stenosed tracheal segment is opened to widely patent segments proximally and distally. The anterior cartilage is excised and the posterior trachealis muscle or tracheal wall remains. A temporary silicone rubber intraluminal stent is placed and absorbable sutures secure the homograft. Regular postoperative bronchoscopic treatment clears granulation tissue. The stent is removed endoscopically after epithelialization over the homograft. Twenty-four children with severe tracheal stenosis (age 5 months to 18 years, mean +/- standard error of the mean = 8.18 +/- 1.21 years) underwent tracheal homograft reconstruction. All but one had had previous unsuccessful reconstructive attempts. Ten lesions were congenital, nine were posttraumatic, and five were due to prolonged intubation. RESULTS Follow-up ranged from 5 months to 10 years (3.79 +/- 0.70 years). Twenty patients survive (20/24 = 83%), 16 without any airway problems. Four patients are still undergoing treatment. One patient requiring emergency extracorporeal membrane oxygenator support before the operation died 10 days after tracheal homograft reconstruction. Another patient with severe preoperative mediastinal sepsis died 3.5 months after tracheal homograft reconstruction. Two patients with functional airways died late of unrelated problems. CONCLUSIONS Tracheal homograft reconstruction demonstrates encouraging short-term to medium-term results for children with severe recurrent tracheal stenosis. Postoperative bronchoscopic and histologic studies provide evidence of epithelialization and support the expectation of good long-term results.

Electrophysiological Mapping and Ablation of Intra-Atrial Reentry Tachycardia After Fontan Surgery With the Use of a Noncontact Mapping System

BACKGROUND Atrial tachyarrhythmias are a complication of Fontan surgery. Conventional electrophysiological mapping and ablation techniques are limited by the complex anatomic and surgical substrate and a high arrhythmia recurrence rate. This study investigates the use of noncontact mapping to identify arrhythmia circuits and guide ablation in Fontan patients. METHODS AND RESULTS Eleven arrhythmias were recorded in 6 patients. Noncontact mapping improved recognition of the anatomic and surgical substrate and identified exit sites from zones of slow conduction in all clinical arrhythmias. Radiofrequency linear lesions were targeted across these critical zones in 5 patients. One patient underwent surgical cryotherapy. Although immediate success was achieved in 3 of 5 patients with radiofrequency ablation, 2 patients had a recurrence after a mean of 6.4 months of follow-up. The patient who underwent cryoablation remains free of arrhythmias. CONCLUSIONS Noncontact mapping can identify arrhythmia circuits in the Fontan atrium and guide placement of ablation lesions. Arrhythmia recurrence is high, possibly because of inadequate lesion creation rather than inaccurate mapping and lesion targeting.

Aortic valve replacement in children: are mechanical prostheses a good option?

OBJECTIVE The choice of the most appropriate substitute in children with irreparable aortic valve lesions remains controversial. The aim of this study was to assess early and late outcomes following aortic valve replacement (AVR) with mechanical prostheses in children. PATIENTS Fifty-six patients (42 male, 14 female, mean age 11.2, range 1-16 years) undergoing AVR with mechanical prostheses between October 1972 and January 1999 were evaluated. Thirty-six patients (64.2%) underwent previous cardiac surgery. Disease aetiology was congenital in 47 patients (congenital aortic stenosis in 33, and other congenital abnormalities in 14) (83.9%), infective in four (7. 1%), rheumatic in two (3.4%), and three (5.3%) had connective tissue disorders. Haemodynamic indication for AVR was aortic regurgitation (AR) in 24 (42.8%), aortic stenosis (AS) in 22 (39.2%) and mixed disease in ten (17.8%). Twenty-eight patients (50.0%) were in New York Heart Association (NYHA) class III-IV before surgery. Concomitant procedures were performed in 31 patients (55.3%), including aortic root enlargement in 28 (50%). The mean size of implanted valves was 22.4 mm (range 17-27 mm). All patients received long-term anticoagulation treatment with sodium warfarin, aiming to maintain an international normalized ratio (INR) between 2.5-3.0. The mean follow-up was 7.3 years (range 0-26, total 405 patient-years). RESULTS Operative mortality was 5.3% (three patients). Three patients developed complete heart block requiring pacing, two of them permanently. Late events included valve thrombosis (one), transient stroke (one), paravalvular leak of a mitral prosthesis (one), aneurysm of sinus of Valsalva (one) and pannus ingrowth (one). There was no major haemorrhagic event. Five patients required re-operation (8.9%), but none due to outgrowth of the valve. Regarding actuarial freedom from thrombo-embolism, any valve-related event and re-operation at 20 years was 93, 86.6 and 86. 4%. There were three late deaths. Actuarial survival, including operative mortality, at 10 and 20 years was 91 and 84.9%. The actuarial survival for the group of the patients with congenital AS (n=33) at 10 and 20 years was 93.5%, whereas for the children with other congenital heart problems (n=14) this was 85.7 and 64.3% (P=0. 09). At the latest clinical evaluation, 44 children were in NYHA class I and six were in class II. The mean gradient across the aortic prosthetic valve on echocardiography was 17.9 mmHg (range 0-47 mmHg). CONCLUSIONS Mechanical AVR, with enlargement of the aortic root if necessary, remains an excellent treatment option in children. It is associated with acceptable operative mortality, low incidence of late events and re-operation, and provides good long-term survival. It clearly represents a good alternative to available biological substitutes, including the pulmonary autograft (Ross procedure).

Cardiac surgery in the elderly.

OBJECTIVE There has been a gradual increase in the number of elderly patients referred for cardiac surgery. These patients present a difficult challenge, they are usually symptomatic yet at high risk for intervention. The aim of this study is to review our experience with cardiac surgery in patients aged 80 years or older. PATIENTS AND METHODS Between January 1981 and October 1997, 242 patients; 135 female, 107 male, mean age 82.8 years (range 80-95) underwent surgery on cardiopulmonary bypass in our unit. Surgery was performed on 14 as an emergency and 136 on an urgent (patient restricted to a hospital bed due to symptoms) basis. Pre-operatively 182 (75.2%) were in NYHA functional class 3 or 4. RESULTS Early mortality was 14 (5.7%). A mitral valve procedure and emergency surgery were significantly associated (P < 0.05) with an increased risk of operative mortality. Median ITU and in-hospital stay was 1 day (range 0-33) and 10 (range 6-49) days, respectively. Ninety-three percent of patients were living independently at home 2 months post-operatively. Survival (+/-SEM) is 98% complete (totals 557 patient years) and including early mortality at 1 and 5 years was 85.5+/-2.4% (n = 154), and 67.7+/-4.3% (n = 33). Survival for patients undergoing isolated aortic valve replacement (AVR) and coronary artery bypass grafting (CABG) at 5 years was 64.8+/-7.8% and 79.7+/-7.4%, respectively. Survival was significantly worse in patients undergoing a mitral procedure. Using Coxs proportional hazards model only type of operation (mitral surgery) was significantly associated with worse survival. CONCLUSION Cardiac surgery can be performed in a selected elderly population with a low operative mortality. Post-operatively elderly patients attain an excellent quality of life and survival. Emergency and mitral surgery in this group of patients is less rewarding.

Tracheal reconstruction in children using cadaveric homograft trachea.

OBJECTIVE We report the use of cadaveric human tracheal homograft in the treatment of severe long segment congenital tracheal stenosis in children. METHODS Five children (aged 5 months-8 years) with severe life-threatening airway obstruction due to long segment congenital tracheal stenosis had failed conventional management. All were ventilator dependent or rapidly deteriorating at the time of surgery, two were on extracorporeal membrane oxygenation, and no alternative therapy was available. The stenosed trachea was removed and the posterior trachealis muscle left in situ when possible. Surgical technique involved the use of cardiopulmonary bypass in four of five cases. Stored cadaveric tracheal homograft tissue was shaped and inserted over a silastic intra-luminal stent which was kept in place for up to 3 months. Regular bronchoscopy was necessary postoperatively to clear granulation tissue, which resolved on removal of the stent. RESULTS Four patients are all now without stents, intubation or tracheostomy. Three are without airway problems 16, 14, and 9 months after surgery and one attends for occasional dilatation of a distal tracheal stenosis, but is now at home despite other severe multiple congenital problems. One patient presented with complete disruption of the trachea and mediastinal sepsis and was supported on extracorporeal membrane oxygenation prior to surgery; this patient eventually died of airway failure and sepsis. CONCLUSIONS The application of cadaveric human tracheal homograft to congenital tracheal stenosis is novel. Its use in five children who would otherwise have died has provided an extra therapy in an extremely difficult group of patients.