Kenneth MacArthur

Acute-phase responses to cardiopulmonary bypass in children weighing less than 10 kilograms

BACKGROUND Cardiopulmonary bypass induces a systemic inflammatory response. This study investigated, in a pediatric population, cytokine-induced responses and their potential modification by intraoperative steroid administration. METHODS Markers of the acute-phase response were measured perioperatively in 24 children weighing less than 10 kg undergoing cardiac operations. Those having operations with cardiopulmonary bypass were randomized to receive either no steroid (group I, n = 8) or 10 mg/kg methylprednisolone in the pump prime (group II, n = 10); patients undergoing nonbypass procedures were controls (group III, n = 6). RESULTS In all groups, plasma interleukin-6 level was elevated (p < 0.01) above baseline throughout the post-operative period, peaking earlier in group I. Levels of C-reactive protein peaked at 48 hours, and postoperative core temperature was raised in all groups. Levels of interleukin-6 from 2 to 6 hours and C-reactive protein at 24 hours postoperatively were greater (p < 0.05) in group I than in group II. Maximum interleukin-6 level, C-reactive protein level, and temperature were all significantly greater in group I than in group III. Maximum interleukin-6 level correlated with maximum C-reactive protein level in group I only (rs = 0.76; p < 0.05) and showed no association with temperature. Duration of bypass did not correlate with levels of interleukin-6. CONCLUSIONS This study demonstrated a marked acute-phase response to operation; the greater response to procedures with cardiopulmonary bypass was abrogated by intraoperative steroid administration. The importance of interleukin-6 as an inducer of acute phase proteins after bypass is supported by its association with C-reactive protein levels, but other factors must be important in the induction of pyrexia.

Surgical repair of double aortic arch: 16-year experience.

Double aortic arch (DAA) is a complete form of vascular ring causing tracheoesophageal compression. We analyzed long-term results of a series of DAAs, over a period of 16 years. Between 1987 and 2003, 29 children underwent surgery for airway and/or esophageal compression secondary to a DAA. Dominant symptoms were stridor, dysphagia, choking episodes, and life-threatening apneic spells (n = 7). Diagnosis was established by barium studies, bronchoscopy, echocardiogram, angiogram, computed tomography (CT), and magnetic resonance imaging (MRI). Seven patients had concurrent cardiac anomalies. Two children had an associated tracheoesophageal fistula. Surgery was accomplished by left thoracotomy (n = 25), right thoracotomy (n = 2) or median sternotomy (n = 2). The operative mortality was zero. There was one late death due to respiratory failure. Four (13.8%) patients had a surgical complication (chylothorax, 3 cases; acute renal failure, 1 case). Follow-up (mean 7.1 years; range 6 months to 16 years) was complete in all patients, and showed complete improvement in 22 patients and partial improvement in 6 patients. Early surgical repair of DAA is associated with low mortality, and results in marked symptomatic relief in most patients. Patients with tracheomalacia or associated asthma, constitute a high-risk group and may manifest persistent symptoms and require adjunctive procedures.

Pre-operative sildenafil and pulmonary endothelial-related complications following cardiopulmonary bypass : a randomised trial in children undergoing cardiac surgery*

In a randomised trial, we compared the effects of oral sildenafil (0.5 mg.kg−1) and placebo, administered the day before cardiac surgery, in 24 children. In sildenafil vs placebo patients, pre‐cardiopulmonary bypass median (IQR [range]) cyclic‐guanosine‐monophosphate was not significantly different (29.9 (2.1–208.1 [0.5–391.5]) vs 5.2 (0.3–54.6 [0–628.9]) pmol.ml−1, respectively). Post‐cardiopulmonary bypass, nitrate/nitrite levels were also not significantly different (0.7 (0–8.0 [0–142.8]) vs 0 (0–2.7 [0–52.7]) μM, respectively). Postoperatively, mean (SD) pulmonary vascular resistance (2.64 (2.28) vs 1.90 (1.12) WU.m−2, respectively and oxygenation index (5.29 (4.60) vs 3.38 (2.54), respectively) remained unchanged, whilst oxygen delivery (57.18 (21.24) vs 74.13 (35.46) ml.min−1.m−2, respectively) and bi‐ventricular systolic function (left ventricle 3.78 (0.94) vs 4.55 (1.08) cm.s−1, respectively; p = 0.002; right ventricle 6.93 (1.47) vs 8.09 (2.25) cm.s−1, respectively; p < 0.001) were significantly reduced in the sildenafil group. In this trial, pre‐operative sildenafil did not affect postoperative pulmonary vascular resistance. There was, however, a negative impact on ventricular function and oxygenation.

Tissue Doppler imaging following paediatric cardiac surgery: early patterns of change and relationship to outcome

In this study, tissue Doppler imaging (TDI) was used to assess changes in ventricular function following repair of congenital heart defects. The relationship between TDI indices, myocardial injury and clinical outcome was explored. Forty-five children were studied; 35 with cardiac lesions and 10 controls. TDI was performed preoperatively, on admission to paediatric intensive care unit (PICU) and day 1. Regional myocardial Doppler signals were acquired from the right ventricle (RV), left ventricle (LV) and septum. TDI indices included: peak systolic velocities, isovolumetric velocities (IVV) and isovolumetric acceleration (IVA). Preoperatively, bi-ventricular TDI velocities in the study group were reduced compared with normal controls. Postoperatively, RV velocities were significantly reduced and this persisted to day-1 (PreOp vs. PICU and day-1: 7.7+/-2.2 vs. 3.4+/-1.0, P<0.0001 and 3.55+/-1.29, P<0.0001). LV velocities initially declined but recovered towards baseline by day-1 (PreOp vs. PICU: 5.31+/-1.50 vs. 3.51+/-1.23, P<0.0001). Isovolumetric parameters in all regions were reduced throughout the postoperative period. Troponin-I release correlated with longer X-clamp times (r=0.82, P<0.0001) and reduced RV velocities (r=0.42, P=0.028). Reduced pre- and postoperative LV velocities correlated with longer ventilation (PreOp: r=0.54, P=0.002; PostOp: r=0.42, P=0.026). This study identified reduced postoperative RV velocities correlated with myocardial injury while reduced LV TDI correlated with longer postoperative ventilation.

Sinus venosus defect: Single-patch repair with caval enlargement

We present a single pericardial patch repair of the sinus venosus defect with anomalously connected pulmonary veins, incorporating enlargement of the superior vena cava. In our small series to date this procedure has been carried out without morbidity or mortality. Noninvasive follow-up by echocardiography and electrocardiography, over the short term, has not detected any stenosis of the venous pathways or sinus node dysfunction.

Synergistic interaction between right ventricular mechanical dyssynchrony and pulmonary regurgitation determines early outcome following tetralogy of Fallot repair

OBJECTIVE The ability of the right ventricle to tolerate acute pulmonary regurgitation (PR) following tetralogy of Fallot (TOF) repair is variable and the mechanisms that underlie this are not completely understood. We hypothesise that dyssynchronous wall mechanics affects the RV tolerance to postoperative PR with adverse effect on early surgical outcome. METHODS Twenty-four TOFs (mean age 19.5+/-15.5 months) undergoing elective repair were prospectively recruited. Ventricular wall mechanics was studied by tissue Doppler echocardiography following induction (preop) and postoperative day one (POD1) and compared with a control group (10 VSD/AVSD). Segmental dyssynchrony, defined as out-of-phase peak myocardial contraction, was determined at the base, mid, apical segments of the septum, RV and LV free walls and scored by the total number of affected segments. PR was graded from absent to severe and RV dimension was quantified by end-diastolic area index (RVEDAI). Cardiac index (CI) was measured by pulse contour cardiac output analysis. Outcome measures were CI, mixed venous oxygen saturation (SvO2), lactate, and duration of ventilation and critical care stay. RESULTS Preoperatively, biventricular free-wall motion was synchronous in both groups. Following surgery, TOF developed RV-septal dyssynchrony (>2 segments in 11 (46%) vs none in control, p=0.01), while the LV free wall remained normal in both groups. RV-septal dyssynchrony correlated with the ventilation time (rho=0.69, p=0.003), critical care stay (rho=0.58, p=0.02) in the presence of PR (n=16), but not with other outcome measures. The relationships between dyssynchrony and early outcome were not seen when PR was absent. In the presence of PR, median RVEDAI was greater with higher dyssynchrony score (>3 segments; p=0.009). The degree of PR did not affect critical care/ventilation time or RVEDAI. The presence of transannular patch (p=0.007) or at least moderate PR (p=0.01) was associated with a more severe dyssynchrony. CONCLUSIONS Dyssynchronous RV-septal wall mechanics occurs early after Fallot repair. The magnitude of dyssynchrony appears to interact synergistically with pulmonary regurgitation to influence RV dimension and early outcome.

Impact of stentless aortic valves on left ventricular function and hypertrophy: current best available evidence.

Abstract  Past four decades have seen a gradual evolution in aortic valve replacement surgery. The ideal valve substitute should combine central flow, low transvalvular gradient, low thrombogenicity, durability, easy availability, resistance to infection, freedom from anticoagulation, and easy implantability. Although there are several types of valves available to replace the diseased aortic valve—autograft, allograft, xenograft, mechanical, and bioprosthetic valves—none is ideal. On one end of the spectrum is the pulmonary autograft, which comes closest to achieving these goals, but creates a double valve procedure for single valve disease, while on the other end are the mechanical valves and stented tissue valves, which allow easy “off the shelf” availability as well as easy implantability but are limited by the potential drawback of causing intrinsic obstruction to some extent because of the space occupied by the stent and sewing ring. Stentless xenograft aortic valves have been developed as a compromise between these ends of the valve spectrum. Stentless aortic valves have been reported to provide more physiologic hemodynamic behavior and cause more timely and thorough regression of ventricular hypertrophy. This review article attempts to evaluate current best available evidence from randomized controlled trials to assess the impact of stentless aortic valves on left ventricular function and hypertrophy.

Does a balloon atrial septostomy performed before arterial switch surgery increase adverse neurological outcomes

This best evidence topic in congenital cardiac surgery was written according to a structured protocol. The question addressed was whether the use of balloon atrial septostomy (BAS) before the arterial switch surgery for transposition of the great arteries (TGA) improved the final outcome. Altogether more than 251 papers were found using the reported search, of which 12 represented the best evidence to answer the clinical question. The search was further limited to recent articles since the results have improved compared with previous years, due to newer equipment and techniques. This narrowed the search to five papers that have focused on this issue since 2006 when a study of 29 term neonates identified BAS as major risk factor for focal brain injury and reinvigorated the debate of adverse neurological outcome especially in the context of the fact that total correction by the arterial switch procedure is routine in neonates now. Subsequently, a prospective study of 64 newborn infants followed by another study of 26 neonates with TGA, have shown no association between BAS and brain injury. Similarly, in a study of more than 2000 cases of dTGA, no association has been found between BAS and increased risk of clinical stroke either in the neonatal period or in follow-up hospitalizations. On the other hand, another nationwide data analysis of 8681 patients with TGA, has shown increased risk of stroke in patients undergoing BAS but it could only show association and not establish causation of the complication. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated.

Myocardial expression of heat shock protein 70i protects early postoperative right ventricular function in cyanotic tetralogy of Fallot

BACKGROUND Right ventricular dysfunction occurs after tetralogy of Fallot repair and may relate to greater myocardial vulnerability to ischemia-reperfusion injury in cyanotic patients. The inducible form of heat shock protein 70 (HSP-70i), a molecular chaperone, is upregulated in response to cellular stress and limits myocardial injury against ischemia-reperfusion. We evaluated the myocardial expression of HSP-70i and its relation to right ventricular function and clinical outcome in patients with tetralogy of Fallot undergoing corrective surgery. METHODS Twenty patients with tetralogy of Fallot were studied: 10 cyanotic (group Cy) and 10 noncyanotic (group noCy). Western blot was used to quantify HSP-70i from resected right ventricular outflow tract myocardium at baseline and subsequent ischemic time. Biventricular function was quantified by tissue Doppler echocardiography and compared with that of 15 age-matched healthy children. Postoperative systemic perfusion was assessed by mixed venous oxygen saturation, oxygen extraction ratio, and lactate. RESULTS Group Cy had thicker septum (median 0.85 vs 0.66 cm; P = .01) and longer crossclamp time (median 100.0 vs 67.5 minutes; P = .004). There were no difference in HSP-70i between groups at baseline (4.12 vs 3.44 relative optical density; P = .45) or subsequent ischemic time. Preoperative biventricular systolic function was reduced in patients with tetralogy compared with controls with further postoperative right ventricular impairment. Group Cy had higher troponin-I levels (median 16.5 vs 11.1 ng/mL; P = .04) and inotrope scores (14.0 vs 6.5; P = .05) but no differences in ventricular function, mixed venous oxygen saturation, oxygen extraction ratio, and lactate between groups. In group Cy, baseline HSP-70i correlated with better postoperative right ventricular function (rho = 0.80; P = .009), mixed venous oxygen saturation (rho = 0.68; P = .04), and oxygen extraction ratio (rho = -0.71; P = .03). These relationships were absent in group noCy. CONCLUSIONS The association of HSP-70i expression with improved right ventricular function and systemic perfusion suggests an important cardioprotective effect of HSP-70i in cyanotic tetralogy of Fallot.

Cystatin C: influence of perfusion and myocardial injury on early (<24 h) renal function after pediatric cardiac surgery

Background:  Cardiopulmonary bypass (CPB)‐associated renal dysfunction following cardiac surgery is well recognized. In patients with renal disease, cystatin C has emerged as a new biomarker which in contrast to creatinine (Cr) is sensitive to minor changes in glomerular filtration rate (GFR).