Biomedical subjects
Publications and source records attributed to M F Sturridge.
Based on statistics from the UK, the incidence of myxoma is about 1:1,000,000/year. Three recent cases of recurrent myxoma are reported, one where excision was probably incomplete, one where tumour implantation may have occurred and one where a mesenchymal sarcoma was misinterpreted histologically. The relative importance of these three factors in recurrence of cardiac tumours after surgical excision is discussed.
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This study examines the clinical and surgical outcome of a group of 55 patients (mean age 33 years) with secundum atrial septal defect who underwent surgical repair of this defect between 1981 and 1990. A group of 25 of these patients underwent late echocardiographic follow-up. Fifty-two patients underwent repair by direct suturing and three by patch closure. Surgical mortality was nil. There was one late death of a 58 year old who died from cardiac failure 4 years after surgery. Late postoperative morbidity consisted of two patients; one, age 63 at the time of surgery, required mitral and tricuspid valve replacement 6 years later and one, age 77 at surgery, developed cardiac failure 3 years later. Atrial fibrillation persisted in the six patients who had the rhythm before surgery and developed postoperatively in two patients aged 54 and 58. Two patients aged 49 and 57 developed immediate postoperative sinus node dysfunction requiring permanent pacing. The mean age at surgery of those six patients who suffered cardiac morbidity was 60 years. The patients with preoperative angiographic evidence of mitral valve prolapse were significantly older (P < 0.001) and had higher mean pulmonary artery pressures (P < 0.001) than patients with normal valves. There was no significant relationship between shunt size and mitral valve prolapse. Echocardiographic follow-up showed persistent mitral valve prolapse in all nine patients who developed the condition preoperatively. Five patients developed mitral valve prolapse with mitral regurgitation postoperatively, one of whom needed subsequent mitral and tricuspid valve replacement. These five patient were on average older (mean age 54) but the group was too small to prove significance. The follow-up data illustrate the current low mortality and morbidity associated with surgical closure of atrial septal defects. Late postoperative echocardiography had revealed not only that mitral valve prolapse persists in those patients who developed the condition pre-operatively but that new cases of mitral valve prolapse with mitral regurgitation can occur after atrial septal defect closure.
A case of endocarditis caused by Propionibacterium acnes associated with an aortic root abscess is presented. This supports the current opinion that aortic root abscesses are not necessarily associated with microorganisms of high virulence.
Fifty cases of aortic valve endocarditis during a 6-year period between 1982 and 1988 were reviewed. Twenty-three (46%) had aortic root complications by way of aortic root abscess or mycotic aneurysm in the perivalvular area. Patients with root complications were grouped into the aortic root abscess (ARA) group and those without into a non root abscess (NARA) group. Prosthetic valve endocarditis dominated in the ARA group (12 and four cases of prosthetic valve infection in the ARA and NARA groups, respectively; P less than 0.01). Surgical mortality was significantly higher at 13.6% in the ARA group as opposed to 2.2% in the NARA group (P less than 0.05). Post-operative aortic regurgitation was present in 8 (57%) of 14 patients in the ARA group surviving surgery but in only two (8.7%) of 23 patients in the NARA group (P less than 0.03). We conclude that aortic root complications are a frequent occurrence in aortic valve endocarditis, lead to an increased operative mortality and is associated with a high incidence of post-operative aortic regurgitation.
In two patients presenting with myocardial infarction, one with a subendocardial infarction and the second patient with a classic Q wave infarction, pedunculated left ventricular thrombi were detected in the course of subsequent routine cardiac catheterization. Both patients underwent successful surgical thrombectomy.
We have reviewed experience with aminoglycosides in cardiac surgical prophylaxis from 1984 to 1989. In the first two years, prospectively randomized trials (517 patients) allowed comparison of tobramycin (three-day course) with a non-toxic antibiotic, teicoplanin. A significant excess rise in serum creatinine was present at the end of the first postoperative week in patients given tobramycin (165 vs 149 patients, 95% CI 3-17 microM. P less than 0.01, which was most marked in ten oliguric patients with trough serum levels over 2 mg/l (95% CI 7-52 microM). However, no patient needed haemodialysis and only one case of possible ototoxicity was identified. During the next three years, of 912 patients given two to three days gentamicin, 29 patients were shown to have potentially toxic serum levels and oliguria. Three individual cases are described, including one of ototoxicity and one of nephrotoxicity neeeding haemodialysis. The hazards of aminoglycoside toxicity are probably small compared with the failure of other antibiotics to cover staphylococci that may later cause wound infection or endocarditis. However, surgeons should probably be advised to check the aminoglycoside level in all patients on the first post-operative day.
Low energy level internal direct current shocks were used to defibrillate the hearts of 168 patients during procedures performed on cardiopulmonary bypass. In all cases, the core temperature was greater than 32 degrees C and care was taken to correct hypokalaemia and acid-base balance prior to defibrillation. In 78 patients (46%), defibrillation required 2 joules or less, and in 139 (82.7%) cases, defibrillation was effected with 4 joules or less. Only 4 patients required more than 10 joules to defibrillate the heart. This study shows that it is possible to defibrillate hearts during cardiopulmonary bypass with energy levels well below the 20-30 joule shocks commonly used.
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Wound infection after clean surgery prolongs hospital stay but the organism most commonly isolated from wound discharge, Staphylococcus epidermidis, is often dismissed as a contaminant or commensal. The wounds of 517 patients were assessed, after cardiac surgery, by a wound-scoring method ('ASEPSIS') and a close comparison was made of the appearance and clinical outcome of 89 wounds, from which bacteria were isolated. There was no significant difference in the scores of 49 wounds, where S. epidermidis was the sole isolate (9.5 per cent of all wounds, 95 per cent CI 6.9-12.0 per cent), and 13 wounds infected with Staphylococcus aureus (2.5 per cent, 95 per cent CI 1.2-3.9 per cent). Repeat cultures were obtained from 21 of the 49 wounds and, in 16 of these, the second isolate showed the same biochemical reactions and antibiotic resistance pattern as the first. Infection of sternal wounds is commoner with coagulase-negative staphylococci than with S. aureus and, clinically, is just as severe.
Despite antibiotic prophylaxis in cardiac surgery, gram-positive bacteria can be isolated in up to 10% of intraoperative blood cultures. During a prospective randomized trial, blood was collected from the oxygenator at the end of bypass in 58 patients given teicoplanin and in 60 others given flucloxacillin and tobramycin. Coagulase-negative staphylococci were cultured from 16 patients given teicoplanin but in only four cases after flucloxacillin and tobramycin (Fisher's exact test, P = 0.005). In contrast, Propionibacterium spp. or coryneforms were isolated from 22 patients given flucloxacillin and tobramycin and from only one patient in the teicoplanin group. There were no cases of prosthetic valve endocarditis. After 3 h exposure to 4 x MIC of teicoplanin there was only a 10-60 fold reduction in cfus of Staphylococcus epidermidis, which may partly explain the excess of these organisms.
In this study, the pharmacokinetics of teicoplanin have been studied in serum, fat and bone during and after cardiac surgery with two dose (400 and 200 mg) and three dose (400 mg each) regimens in a total of 49 patients. For comparison, 20 other patients, who had received a regimen of flucloxacillin (500 mg qds for five days) and tobramycin (1.5 mg/kg initially then 80 mg tds for three days), were similarly investigated. The lowest mean serum level of teicoplanin during operation was 6.9 mg/l in the two dose regimen and 9.7 mg/l with the three dose regimen. Mean serum levels of flucloxacillin and tobramycin fell to 7 and 1.4 mg/l respectively by the end of operation. At the end of bypass, fat washings contained a mean of 1.2 mg/l of teicoplanin and bone washings a mean of 6.3 mg/l. Mean tobramycin levels were 0.4 and 0.9 mg/l respectively and flucloxacillin less than 1 mg/l in washings from both tissues. The low levels of teicoplanin in fat may explain an excess of Gram-positive sternal infections in the accompanying clinical trial.
Teicoplanin, a new glycopeptide antibiotic, has a serum half-life of 47 h and excellent activity against Gram-positive bacteria, including methicillin resistant staphylococci, making it a potentially useful drug for cardiac surgical prophylaxis. In two prospective randomized studies, we have compared it with a broad spectrum regimen of an aminoglycoside and flucloxacillin. In the first trial, teicoplanin (400 mg on induction of anaesthesia and 200 mg 24 h later), was compared with tobramycin (80 mg tds for three days) and flucloxacillin (500 mg qds for 5 days) in 314 patients. Teicoplanin prophylaxis resulted in a significantly greater number of sternal wound infections (P less than 0.01), due to Gram-positive bacteria. Furthermore, Gram-negative bacteria were responsible for more respiratory and urinary infections after teicoplanin prophylaxis. In the second trial, comprising 203 patients, the teicoplanin dose regimen was changed to three doses of 400 mg but this did not improve the rates of infection.
Three hundred and twenty patients originally entered into a randomised study to assess the effect of aspirin and dipyridamole on the patency of coronary bypass grafts one year after operation were clinically reassessed a mean of 6.6 years (range 4.3-8.6) after operation. Patients were recruited between 1978 and 1982 after the present policy of total revascularisation had been adopted. During the follow up period there were 25 deaths of which 17 were due to cardiac causes (average annual cardiac mortality 0.8%). Of 280 patients available for contact, 250 (89.3%) attended an outpatient interview. Ninety four (37.6%) patients complained of recurrent angina but in only 23 (9.2%) was this severe. Two hundred and eleven (84.4%) of the 250 patients underwent exercise stress testing. There were 73 (34.6%) abnormal tests of which 52 were in the group of 94 patients with recurrent angina. Myocardial infarction occurred in nine of the 250 patients during the follow up period. Twenty six patients (10.4%) had reinvestigation for symptoms. This group had a graft occlusion rate of 52%. Half these patients have required reoperation and 20 of 22 occluded or severely stenosed grafts were replaced. In only two instances were vein grafts inserted into vessels with new disease. Half of the original group were given aspirin (330 mg three times a day) plus dipyridamole (75 mg three times a day). Of the 250 patients interviewed, 122 took aspirin and dipyridamole from the second postoperative day for a mean of 25 months, with warfarin for three months. The other 128 patients took placebo for a mean of 23 months together with warfarin for three months. This long term treatment with aspirin plus dipyridamole conferred no significant benefit for all clinical outcomes measured at a mean of 6.6 years.
Four patients with infective endocarditis were examined by digital subtraction angiography immediately before operation. In three a root abscess was suspected and the remaining patient was believed to have a false aneurysm at an infected aortic cannulation site. In all the cases digital subtraction angiography showed the structure in several projections and confirmed the presence of a cavity. Subsequent operation confirmed the site and nature of the lesions.
The body temperature is measured routinely and carefully charted in our own and presumably all units. Pyrexia is normal after bypass and is discounted on the basis of clinical experience in the first few days. If this pyrexia persists, a search for infection may be instigated and discharge from the hospital may be delayed. A clinical trial of antibiotic prophylaxis provided the opportunity to collect and collate 6-hourly temperature observations for 314 patients for 1 week after operation. The length of bypass and the presence of lower respiratory tract infection were positively correlated with the duration of postoperative fever. However, neither surgical sepsis nor urinary tract infection had any consistent effect on the duration or magnitude of postoperative fever in the first week.
A controlled trial of antibiotic prophylaxis in cardiac surgery compared a two-dose regimen of teicoplanin with a longer conventional course of flucloxacillin and tobramycin. In 12 patients the susceptibility of the bacterial skin flora of four different sites to each of the three antibiotics was determined and the results are reported here. Less than 1% of the Gram-positive colonies showed reduced sensitivity to teicoplanin (MIC greater than or equal to 4 mg l-1). Before operation, 99% inhibition of Gram-positive growth was achieved at 26 (54%) of 48 sites by 1 mg l-1 of flucloxacillin and 13 (27%) sites by 2 mg l-1 tobramycin. By the 7th day after operation there was a significant reduction in the number of sites showing similar sensitivity to flucloxacillin [16 (33%) sites, P less than 0.05]. The use of teicoplanin was not associated with the emergence of Gram-negative skin flora but tobramycin promoted acquisition of aminoglycoside-resistant strains.
Postoperative wound infection can greatly prolong hospital stay after cardiac surgery, so the identification of predisposing factors may help in prevention or early institution of treatment. Transfer of organisms from the leg to the sternum during coronary artery surgery has been proposed as a major additional cause of sepsis. The definition of wound infection is not standardised and therefore makes comparison between centres difficult. In a prospective study of 517 patients, a wound scoring method (ASEPSIS) has been used to register all abnormal wounds to maximise the chances of identifying factors predisposing to infection. Abnormal healing was noted in 99 (19%) sternal wounds and 29 (8%) leg wounds. Obesity was the principal risk factor (P less than 0.005). Diabetes, reoperation, length of preoperative hospital stay, age, sex, or previous cardiac surgery had little effect on wound healing. The range of bacteria isolated from chest wounds after coronary artery surgery was similar to that after valvular surgery, but the rate of isolation was significantly greater. With careful attention to technique, leg wound infection rarely presented a clinical problem and did not appear to be a source of bacteria infecting the chest wound.