West Nile virus infection of Thoroughbred horses in South Africa (2000-2001)

REASONS FOR PERFORMING STUDY

West Nile virus (WNV) infection is endemic in southern Africa. With the recent emergence of WNV infection of horses in Europe and the USA the present study was performed to estimate the risk of seroconversion to WNV in a cohort of 488 young Thoroughbred (TB) horses.

OBJECTIVES

To estimate the risk of seroconversion to WNV among a cohort of South African TB yearlings sold at the 2001 National Yearling Sales (NYS) and to determine whether the risk varied geographically. Two horses were also infected with a recent South African isolate of WNV to evaluate its virulence in horses.

METHODS

Serum samples were collected from the cohort of 488 TB yearlings at the 2001 NYS. Serum samples that were collected from the same horses at the time that they were identified were sourced from our serum bank. Sera from 243 of the dams that were collected at the time that the foals were identified were also sourced from our serum bank. These sera were subjected to serum neutralisation (SN) tests for antibody to WNV.

RESULTS

Approximately 11% of yearlings seroconverted to WNV on paired serum samples collected from each animal approximately 12 months apart. Studfarms with WNV-seropositive yearlings were widely distributed throughout South Africa and SN tests on sera from their dams indicated that exposure to WNV was even more prevalent (75%) in this population. Neurological disease was not described in any of the horses included in this study and 2 horses inoculated with a recent lineage 2 South African isolate of WNV showed no clinical signs of disease after infection and virus was not detected in their blood.

CONCLUSIONS

Infection of horses with WNV is common in South Africa, but infection is not associated with neurological disease.

POTENTIAL RELEVANCE

In contrast to recent reports from Europe, North Africa, Asia and North America, the results of our field and experimental studies indicated that exposure of horses to the endemic southern African strains of WNV was not associated with neurological disease.

Deficiency of TNFalpha converting enzyme (TACE/ADAM17) causes a lean, hypermetabolic phenotype in mice

Energy homeostasis involves central nervous system integration of afferent inputs that coordinately regulate food intake and energy expenditure. Here, we report that adult homozygous TNFalpha converting enzyme (TACE)-deficient mice exhibit one of the most dramatic examples of hypermetabolism yet reported in a rodent system. Because this effect is not matched by increased food intake, mice lacking TACE exhibit a lean phenotype. In the hypothalamus of these mice, neurons in the arcuate nucleus exhibit intact responses to reduced fat mass and low circulating leptin levels, suggesting that defects in other components of the energy homeostasis system explain the phenotype of Tace(DeltaZn/DeltaZn) mice. Elevated levels of uncoupling protein-1 in brown adipose tissue from Tace(DeltaZn/DeltaZn) mice when compared with weight-matched controls suggest that deficient TACE activity is linked to increased sympathetic outflow. These findings collectively identify a novel and potentially important role for TACE in energy homeostasis.

[Craniosynostosis: is prenatal diagnosis possible?]

The authors report a case which demonstrates how an interdisciplinary collaboration between the obstetrician and pediatrician may be activated in the event of a suspected fetal malformation, in this case craniosynostosis, although it is important to recognise the diagnostic limitations of ultrasonography regarding this type of pathology.

Fractal analysis: a new method for evaluating fetal heart rate variability

In this report we describe how the technique of "deterministic chaos" can be successfully applied to the study of fetal cardiotocography (CTG). The CTG tracings were analysed, after identification as "normal" or "pathological" by experts and by a computerised system, to evaluate the correlation dimension (D2), and the graphic analysis of the attractors which visualize the phase-space of the system that generated the signal (of the state of the underlying hypothetical system). Thanks to this analysis of the traces, it is possible to detect the existence of chaos in the system that generates a certain signal in this case the fetal heart rate. Normal CTG traces at term (37-41 wks) show a fractal dimension (D2) index ranging from 4.22 to 5.22; highly pathological CTG tracings show a D2 ranging from 2.0 to 3.09. Moreover, we introduced recurrence plots in the study of CTG, as tool for non stationary signals, working in real time. To our knowledge this is one of the first attempts to apply fractal analysis and recurrence plots in the evaluation of fetal heart rate in pregnancy, using very small data sets.

Surgical management of left ventricular free wall rupture after acute myocardial infarction

Left ventricular rupture after acute myocardial infarction occurs more often than suspected and diagnosis is rarely made before death. Left ventricular rupture has been reported to contribute to the overall in-hospital mortality after acute myocardial infarction in up to 24% of cases and to be present in 40% of patients dying within the first week after infarction. Only prompt diagnosis and aggressive surgical treatment can be lifesaving under these circumstances. Between February 1991 and August 1993 five patients underwent emergency operation for left ventricular rupture after acute myocardial infarction using exclusively transoesophageal echocardiography as a diagnostic tool. All patients had evidence of cardiac tamponade and electrocardiography showed signs of anterolateral acute myocardial infarction in one, inferolateral acute myocardial infarction in three and lateral acute myocardial infarction in one. In two cases the infarcted area was debrided and an interrupted pledgetted 2/0 polypropylene suture was placed from inside of the ventricle outward to the epicardial surface and then through the pericardial patch. In the other three cases an original technique was used: an autologous glutaraldehyde-stiffened pericardial patch was sealed over the infarcted area using fibrin glue and fixed with running suture on the surrounding healthy myocardium. One patient died in the operating room because of low cardiac output syndrome which was possibly the result of an excessively extended area of infarction. Left ventricular rupture is a catastrophic complication of acute myocardial infarction and prompt diagnosis with transoesophageal echocardiography followed by emergency operation can be lifesaving.(ABSTRACT TRUNCATED AT 250 WORDS)

[Reparative surgery of the mitral valve in bacterial endocarditis]

INTRODUCTION

Short and long-term results of valve repair for pure mitral insufficiency resulting from native valve endocarditis are reported in 28 consecutive patients with a mean age of 55 years (range 18-74).

METHODS

Six patients had acute endocarditis, with positive blood cultures in three of them. The mean time between onset of endocarditis symptoms and operation was 23 days in patients with acute endocarditis and 4.6 years in patients with healed endocarditis. Preoperatively, 87% of the patients were in NYHA class III. Indications for operation were heart failure (24 patients) and uncontrolled sepsis (4 patients). Mitral valvuloplasty was combined with other procedures in 4 patients. There was previous underlying valve pathology in 75%.

RESULTS

Mitral repair was performed according to the techniques proposed by Carpentier; in 2 cases we used an original technique consisting of a double-orifice repair. Only one patient died in the hospital (operative mortality: 3.5%). By actuarial methods 96% of the patients were alive 6 years postoperatively. During the follow-up period there was no recurrence of endocarditis and no reoperation for valvular insufficiency. Ninety-three per cent of the patients were in NYHA class I or II.

CONCLUSIONS

We conclude that mitral valve repair for insufficiency resulting from bacterial endocarditis is possible in acute and healed disease, has a low operative mortality and has resulted in patients free of recurrent infection. Mitral valve repair is an attractive alternate to valve replacement in bacterial endocarditis.

Impact of autologous blood predonation on a comprehensive blood conservation program

Preoperative autologous donation has been shown to be a highly effective measure in reducing homologous blood use in cardiac operations. The aim of our study was to verify the effectiveness of this procedure and to see whether it is compatible with a comprehensive blood conservation program. Three hundred forty-eight patients (group 1) donated an average of 657 +/- 199 mL of blood before open heart operation, whereas 344 patients (group 2) without autologous predonation were used as a control. The two groups were compared with regard to homologous blood use and the possibility of applying other blood conservation measures. Homologous transfusion rate in group 1 was 12.6%, whereas in group 2 it was 46% (p < 0.001). Patients with three units of predonated autologous blood had a transfusion rate of 0.8% (p < 0.001 compared with group 2). In group 1, acute normovolemic hemodilution was accomplished in a lower number of patients and with a lower average withdrawal (338 +/- 102 versus 403 +/- 145 mL; p < 0.001). Other blood conservation measures such as the return of mediastinal drainage and use of residual blood of extracorporeal circulation were applied with similar results in both groups. In our experience, preoperative autologous donation was compatible with the application of other blood conservation measures, but acute normovolemic hemodilution was achieved in a lower number of patients. Preoperative autologous donation proved to be a highly effective method for reducing banked blood use and therefore homologous blood exposure during and after cardiac operations.

Improved results with mitral valve repair using new surgical techniques

From January 1987 to July 1994, 299 consecutive patients ranging from 4 to 80 years of age underwent mitral repair for pure valve insufficiency due to degenerative disease (59%), rheumatic disease (23%), endocarditis (12%) or ischemic heart disease (6%). During the initial period, a variety of reparative methods were used following the principles originally described by Carpentier. More recently, in our institution other surgical techniques have been introduced: specifically, prolapse of the anterior leaflet was corrected either by replacing the chordae with polytetrafluoroethylene (PTFE) sutures or simply by anchoring the prolapsing free edge to the facing edge of the posterior leaflet ("edge-to-edge" technique). Chordal transposition has also been used occasionally to correct the prolapse of the anterior leaflet. The hospital mortality rate was 1.3%. According to actuarial methods, the overall survival rate was 94% at 7 years, and freedom from reoperation was 86%. Significant incremental risk factors for reoperation were: no use of prosthetic ring, correction of the prolapse of the anterior leaflet by triangular resection or chordal shortening and ischemic etiology of the mitral insufficiency (freedom from reoperation at 7 years was 61%, 56% and 51%, respectively). In the late postoperative period (mean follow-up 3.6 years), 95% of the patients were in NYHA class I or II; four patients had thromboembolic episodes, two hemorrhagic complications and two endocarditis. No patient in whom the prolapse of the anterior leaflet was corrected by the recently introduced technique has required reoperation. The anterior mitral leaflet prolapse was therefore neutralized as an incremental risk factor for reoperation and this has contributed to the improved overall results of mitral valve repair.

Oxidative stress during reperfusion of human hearts: potential sources of oxygen free radicals

OBJECTIVE

The aim was to examine the role of neutrophil activation in the genesis of oxidative stress during the early phases of reperfusion after ischaemia in patients subjected to aortocoronary bypass grafting.

METHODS

Ten selected patients were studied. All had normal ejection fraction and normal left ventricular end diastolic pressures before operation. Each patient required at least three grafts, so that the duration of aortic crossclamping exceeded 30 min, the minimum ischaemic period required to detect oxidative stress upon reperfusion. Oxidative stress was assessed by measuring the formation and release of oxidised glutathione (GSSG) in the coronary sinus 1 min before and 3 min after the start of the cardiopulmonary bypass, and then 1, 5, 10, and 20 min after removal of the aortic clamp, and again 5 and 10 min after the end of the cardiopulmonary bypass. The arterial-coronary sinus difference for neutrophils, elastase-alpha 1 protease complex (elastase), and creatine phosphokinase was also monitored at the same intervals.

RESULTS

Before clamping GSSG was undetectable in arterial and coronary sinus blood. There was no significant arterial-coronary sinus difference for neutrophils or elastase [53(SEM 66) cell.ml-1 and 1.10(2.49) micrograms.litre-1, respectively[. Five minutes after re-establishment of coronary blood flow, there was both a release of GSSG into the coronary sinus [arterial-coronary sinus difference: 11(2.6) nmol.dl-1] and an accumulation of neutrophils in the heart [arterial-coronary sinus difference: 262(33), P < 0.01 cell.ml-1], whereas no elastase release from the heart was measured [arterial-coronary sinus difference 7.6(4.46) microgram.litre-1, NS]. The arterial levels of elastase increased progressively during the operation from 48(5) microgram.litre-1 (preclamping) to 405(62) microgram.litre-1, P < 0.01 (end of the cardiopulmonary bypass).

CONCLUSIONS

These data indicate that, in man, neutrophils do accumulate in the myocardium during early reperfusion. However, they are not activated when oxidative stress occurs. It is unlikely that the neutrophil localisation in the heart has pathological significance in the production of oxygen free radicals during early reperfusion. Free radical accumulation in the coronary vessels may contribute to disorders of coronary flow associated with reperfusion.

Recovery of myocardial function. The ultimate target of coronary revascularization

Recovery of myocardial contraction represents an important target of coronary revascularization and the preoperative recognition of viable akinetic (hibernating) myocardium is a crucial point of the preoperative investigation of patients with chronically depressed left ventricular function. In 14 patients dobutamine infusion during echocardiography was utilized to evoke the contractile reserve retained by viable akinetic segments. Redistribution of thallium(TI)-201 after the rest injection was also used to assess the viability of akinetic areas. The wall motion response to dobutamine infusion predicted immediate postoperative improvement in 85 of 93 segments (sensitivity 91.3%) and identified 25 of the 32 segments which did not exhibit early postoperative improvement (specificity 78.1%). Rest redistribution of TI-201 demonstrated high sensitivity (93.0%) but low specificity (43.7%) for predicting the early recovery of regional wall motion. When late recovery was also considered, the specificity of this method increased to 64.0%. Rest distribution of TI-201 identifies viability which is not necessarily associated with the early recovery of function postoperatively. When the echo-dobutamine test is positive, on the other hand, the recovery of function usually occurs immediately after revascularization and the operative risk is expected to be low even in the presence of severely compromised left ventricular function.

[Reconstructive surgery of pure mitral insufficiency. Operative results and follow-up in 128 patients]

Short and long-term results of valve repair for pure mitral insufficiency are reported in 128 consecutive patients with a mean age of 49 years (range 4-75). The etiology of the mitral valve dysfunction was degenerative in 54% of the cases, rheumatic in 30%, ischemic in 9.5%, endocarditic in 6.5%. Preoperatively, 91% of the patients were in NYHA class II or III. The anatomic lesions and the mechanism of mitral regurgitation were identified preoperatively by transthoracic and/or transesophageal echocardiography. Cardiac catheterization was performed only in patients with multiple valvular dysfunction and/or with evidence of concomitant coronary artery disease. Mitral repair was performed according to the techniques proposed by Carpentier. Only one patient died in the hospital (operative mortality: 0.8%). By actuarial methods, 96% of the patients were alive 4 years postoperatively, and 84% were reoperation free. Freedom from reoperation was significantly higher in patients who received a prosthetic ring than in those who had other types of anuloplasty (96% vs 67%; p < 0.05). During the follow-up period no patient had thromboembolic episodes. Ninety-seven per cent of the 112 patients who survived the operation and were not reoperated were in NYHA class I or II. These results confirm the validity of reconstructive surgery in pure mitral insufficiency. The use of a prosthetic ring gives stability to the repair and improves long-term results.

Oxygen free radicals and myocardial damage: protective role of thiol-containing agents

It has been suggested that the sudden presence of oxygen during reperfusion after a period of ischemia may be toxic for the myocardial cell. The oxygen molecule is capable of producing reactions in the cell, forming highly reactive free radicals, and inducing lipid peroxidation of membranes, altering their integrity and increasing their fluidity and permeability. The ischemic and reperfused cardiac cell is the prime candidate for this reaction sequence and may explain the molecular mechanism underlying the pathologic events related to membrane dysfunction and calcium homeostasis. However, the myocardium has a series of defense mechanisms including the enzymes superoxide dismutase (SOD), catalase, and glutathione peroxidase plus other endogenous antioxidants such as vitamin E, ascorbic acid, and cysteine to protect the cell against the cytotoxic oxygen metabolites. The prerequisite for oxygen free radical involvement in ischemia and reperfusion damage is that ischemia alters the defense mechanisms against oxygen toxicity. It is known that ischemia may impair mitochondrial SOD and, with reperfusion, oxidative stress may occur as shown by tissue accumulation and release of oxidized glutathione. This tripeptide molecule in the cofactor of glutathione peroxidase, the enzyme that removes hydrogen and lipid peroxides. Its formation and subsequent release is a reliable index of oxidative damage. In our study, we investigated the effects of N-acetylcysteine on oxidative damage in the isolated rabbit heart. N-acetylcysteine increases, in a dose-dependent manner (from 10(-7) to 10(-5) M), the myocardial glutathione content and provides an important degree of protection against ischemia and reperfusion. Oxidative stress does not occur, mitochondrial function is maintained, enzyme release is reduced, and contractile recovery is increased. Similarly, we administered N-acetylcysteine in the pulmonary artery of coronary artery disease patients undergoing coronary bypass grafting (150 mg/kg in 1 hour followed by 150 mg/kg in 4 hours). The degree of oxidative stress on reperfusion was reduced and recovery of cardiac function improved. In this article, we review the cardioprotective role of thiol-containing agents.

Optimal exposure of the mitral valve through an extended vertical transeptal approach

The mitral valve was approached through a vertical transeptal incision extended into the roof of the left atrium in 111 patients. Good exposure was invariably provided even in unfavorable situations such as a small left atrium combined with right ventricular hypertrophy or a previously implanted aortic prosthesis. The only hospital death in the entire series was not related to this approach to the mitral valve. Due to breakage of the suture in the roof of the left atrium and to incomplete reconstruction of the atrial septum resulting in a large left-to-right shunt, 2 patients required reinstitution of cardiopulmonary bypass. Both had a smooth postoperative course. Other intra- or postoperative complications related to the incision did not occur. Duration of cardiopulmonary bypass and aortic occlusion was not significantly different from that of patients operated upon through the conventional left atrial approach in the year preceding the experience embraced by this study. Only 3 of 52 patients who were preoperatively in sinus rhythm were discharged in atrial fibrillation. Enhanced atrial vulnerability was demonstrated preoperatively in all 3. These data support a wide application of the extended vertical transeptal approach in mitral valve surgery.

Time course of human atrial natriuretic factor release during cardiopulmonary bypass in mitral valve and coronary artery diseased patients

We determined the time-course of the release of atrial natriuretic factor (ANF) during cardiopulmonary bypass (CPB) in six patients undergoing coronary artery bypass (CAD) and eight patients undergoing valve replacement for mitral stenosis (MS). Before CPB, the arterial ANF was significantly higher in MS patients than in CAD patients (243 +/- 38 and 29 +/- 5.8 pg/ml respectively, P less than 0.01). With the onset of CPB, the acute pressure unloading of the atria induced a significant, rapid decrease of ANF only in MS patients (-64% of pre-CPB value at 5 min) and no major changes in CAD patients. Clamping of the aorta induced a further progressive reduction of ANF release to almost zero in both groups. Readmission of coronary flow to the empty atria with declamping resulted in an increase in the plasma level of ANF in both groups to reach the concentration present in MS patients before CPB. After CPB, the ANF levels decreased in CAD patients while remaining elevated in MS patients. These data suggest that ANF release from human atria depends on atrial filling pressure and other unknown factors.

Hepato-atrial anastomosis as emergency treatment for traumatic rupture of suprahepatic inferior vena cava and hepatic veins

The case of a 21-year-old patient operated on as an emergency for traumatic rupture of the suprahepatic inferior vena cava (IVC) and hepatic vein (HVs) is presented. Since anatomic reconstruction of the ruptured vessels was considered unfeasible, a direct anastomosis was instituted between the right atrium and the liver capsule around the disrupted IVC and HVs, using extracorporeal circulation, deep hypothermia and circulatory arrest. Hemorrhage was easily controlled and the patient survived. As far as we know, this operation, originally developed for the treatment of the Budd-Chiari syndrome, has never been used before as a life saving procedure under the circumstances described.

Occurrence of oxidative stress during reperfusion of the human heart

We have investigated the relation between occurrence of myocardial oxidative stress and functional recovery during postischemic reperfusion in 20 selected patients subjected to aortocoronary bypass grafting. Patients were selected for having normal percent ejection fraction and left ventricular end-diastolic pressure before the operation. Occurrence of oxidative stress was assessed by measuring the formation and release of oxidized glutathione (GSSG) in the coronary sinus immediately before aortic cross-clamp, 1, 5, 10, and 20 minutes after removal of aortic cross-clamp, and 10 and 20 minutes after the end of cardiopulmonary bypass. Reduced glutathione (GSH), lactate, and creatine phosphokinase release were also monitored with the same timing. Standard hemodynamic measurements were recorded by means of a triple-lumen thermodilution pulmonary artery catheter before sternotomy, 15 minutes after the end of cardiopulmonary bypass, and during the 24 hours after termination of cardiopulmonary bypass. Reperfusion in patients after a short period of ischemia (less than 30 minutes; group 1) resulted in a small and transient release in the coronary sinus of GSSG and GSH and in a progressive improvement of hemodynamic parameters reaching a stable state 4 hours after the operation. In patients with a period of ischemia longer than 30 minutes (group 2), reperfusion induced a marked and sustained release of lactate, GSH, and GSSG; the arteriocoronary sinus difference for GSSG was still negative after the end of cardiopulmonary bypass. The arteriocoronary sinus difference for creatine phosphokinase also remained negative for as long as 20 minutes after cardiopulmonary bypass, and the rate of functional recovery was significantly delayed, reaching the values of group 1 only 12 hours after the operation. In these patients there was a positive correlation (r = 0.88, p less than 0.01) between the duration of ischemia and the myocardial arteriovenous difference for GSSG. In addition, there was a negative correlation between the arteriocoronary sinus difference for GSSG and cardiac index measured 2, 4, and 6 hours after the operation. These data suggest for the first time that, depending on the severity of the ischemic period, oxidative stress occurs during reperfusion of patients with coronary artery disease who are subjected to heart surgery and that it may be linked with a delay in postoperative recovery of cardiac function.

[Intermittent opening and flow of a mitral valve prosthesis caused by acute and chronic thrombosis]

The case report concerns a female with intermittent opening and flow of Bjork mitral prosthesis demonstrated by echo-doppler. Dyspnoea and rapidly worsening heart failure were also present. Anatomic confirmation during cardiac surgery showed a fresh thrombus over old one. Principal instrumental criteria of prosthesis thrombosis are finally reported.

Arterial cannulation and myocardial protection in severe diffuse aortic calcification

A patient with diffuse and severe aortic calcification is described. The patient had a double vessel coronary disease and it was impossible to cannulate the ascending aorta or the femoral arteries for the cardiopulmonary bypass. Arterial cannulation was performed in the innominate artery and both mammary arteries were used during a short period of ventricular fibrillation.

Myocardial revascularization after failure of percutaneous transluminal coronary angioplasty

From 1980 to 1983, 299 procedures for percutaneous transluminal coronary angioplasty were performed in 265 patients. The procedure failed in 88 patients, 72 of whom underwent myocardial revascularization within 1 week following the angioplasty attempt. Operation on an emergency basis was required in 35 patients because of a major complication during or after coronary artery dilatation, whereas the remaining 37 patients underwent elective operation following failure without complication. Coronary occlusion occurred in 23 patients, coronary dissection without occlusion in four, perforation of the coronary artery in one patient, and no visible angiographic changes accounted for the severe myocardial ischemia in the remaining 7 patients. Signs of acute myocardial infarction were present preoperatively in 13 of the 35 patients (37.1%) who underwent emergent operation. Among the factors analyzed, only the absence of collateral circulation and the extent of coronary disease were directly related to the development of complications with percutaneous transluminal coronary angioplasty. There were no early or late deaths in this series. Postoperative complications occurred in seven patients (20%) of the group undergoing emergency operation and in none of the group having elective operation. New postoperative myocardial infarction developed in three patients (8.6%). In six of the 13 patients with preoperative evidence of necrosis, the electrocardiogram returned to normal without other signs of acute infarction after the operation, whereas myocardial infarction was complete in the remaining seven patients. Thus, patients who have complications from percutaneous transluminal coronary angioplasty should undergo immediate operation; for those in whom the procedure fails without complication, surgical treatment can be postponed and performed electively later on if indicated by the clinical incapacity of the patient.