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Biomedical subjects

S Armstrong

Publications and source records attributed to S Armstrong.

At least 73 records · Page 4Linked to original sources
PubMed1997

Long-term results of surgery for active infective endocarditis.

OBJECTIVE: This paper was undertaken to determine the long-term outcome of active infective endocarditis treated with antibiotic and radical excision of infected tissues by surgery. METHODS: From October 1978 to August 1994, 122 consecutive patients were operated on during the acute phase of infective endocarditis. There were 85 men and 37 women whose mean age was 50 years, ranging from 20 to 79. Surgery was needed because of one or more of the following complications: cardiogenic/septic shock in 19 patients, congestive heart failure in 68, persistent sepsis in 64, peripheral embolization in 20, and cerebral embolization in 10. The offending microorganism was identified in 110 patients, staphylococci were the most common ones. Seventy-six patients had native valve endocarditis and 46 had prosthetic valve endocarditis. Simple valve replacement or repair was performed in 60 patients and radical resection of the valve and surrounding tissues with reconstruction of the heart with either fresh autologous pericardium or glutaraldehyde-fixed bovine pericardium was performed in 62 with paravalvular abscess. Pulmonary autograft and aortic homograft were used in only three patients, the remaining patients had either bioprostheses or mechanical heart valves if valve repair was not feasible. RESULTS: There were nine deaths, for an operative mortality of 7.4%. Logistic regression analysis identified preoperative shock and renal failure as predictors of operative mortality. Operative survivors were followed up from 4 to 173 months, mean of 56.4. The actuarial survival at 10 years was 61 +/- 6%. Logistic regression analysis identified preoperative New York Heart Association functional class IV and perioperative renal failure as predictors of late mortality. Eight patients developed recurrent endocarditis 10-102 months postoperatively. The freedom from recurrent endocarditis at 10 years was 79 +/- 9%. All patients who developed this late complication had paravalvular abscess at the time of original operation. CONCLUSIONS: These data suggest that surgery for active infective endocarditis yield a high probability of eradicating the infection with relatively low operative mortality and good long-term results.

Abscess↗
PubMed1997

The impact of Filgrastim schedule variation on hematopoietic recovery post-chemotherapy.

BACKGROUND: A phase 2 trial was done to study effects of varying treatment schedule of Filgrastim (r-metHuG-CSF) on hematologic recovery following chemotherapy. PATIENTS AND METHODS: Forty-six patients with extensive small-cell carcinoma of the lung were randomized to receive one of three Filgrastim schedules following cyclophosphamide, doxorubicin, and etoposide (CAE) chemotherapy for up to six cycles of treatment. Chemotherapy was delivered on days 1-3 of each 21-day cycle with Filgrastim initiated at 5 micrograms/kg/day subcutaneously (SC) beginning on day 4, day 6, or day 8 and continuing until post-nadir neutrophil recovery. RESULTS: During the first cycle of chemotherapy, the duration of neutropenia was similar for all three schedules; however, the pattern of absolute neutrophil count (ANC) recovery differed. In subsequent cycles of treatment, an improvement in the severity of neutropenia occurred in patients on the day-4 and day-6 schedules compared with the first cycle of chemotherapy. By contrast, patients on the day-8 schedule continued to experience neutropenia similar to that seen in cycle one. Patients on the day-8 schedule also experienced a greater magnitude of grade IV thrombocytopenia in later cycles of treatment. CONCLUSION: Timing of Filgrastim administration post-chemotherapy has profound effects on hematologic recovery. Delay of Filgrastim until day 8 was associated with suboptimal hematologic recovery compared with administration of Filgrastim on day 4 or day 6. Initiation of Filgrastim on day 4 or day 6 showed a similar pattern of hematologic recovery. Beginning Filgrastim on day 6 is associated with a decrease in the total dose of Filgrastim administered.

Adult↗
PubMed1997

Compression hosiery.

Compression hosiery is used in the prevention of ulceration in vulnerable individuals. Compliance is achieved by good assessment, measurement, fitting and education.

Anthropometry↗
PubMed1996

Analysis of lymphocytes from uranium mineworkers in Namibia for chromosomal damage using fluorescence in situ hybridization (FISH).

Workers in the open pit uranium mine in Namibia appear to suffer from health problems including malignant diseases at a much higher prevalence when compared with the general population. The objective of the present study was to determine whether long-term exposure to low-dose uranium increases the risk of biological radiation damage which could lead to malignant diseases. In order to investigate this risk, we measured the relative frequency of chromosome alterations using Fluorescence in situ hybridization (FISH). A representative cohort of 11 non-smoking miners, were compared to a control group of 9 individuals with no occupational history in mining. We determined a significant increase in chromosome aberrations in the circulating lymphocytes of miners versus the non-smoking controls (p = 0.0000096). Therefore, we concluded that these uranium exposed miners are at an increased risk to acquire genetic damage, which may be associated with an increased risk for malignant transformation.

Adult↗
PubMed1996

Long-term results of operation for paravalvular abscess.

BACKGROUND: Operation for infective endocarditis with paravalvular abscess is reportedly associated with high mortality and morbidity rates. In an attempt to improve surgical outcome, an approach of radical resection of the abscess and inflamed tissues and reconstruction of the heart with either fresh or glutaraldehyde-fixed bovine pericardium was adopted by two surgeons at our institution. METHODS: From 1979 to 1995, 70 consecutive patients with active infective endocarditis and paravalvular abscess underwent operation. Their mean age was 49 years (range, 16 to 75 years), and 50 patients (71%) were men. Thirty-four patients had native and 36 had prosthetic valve endocarditis (8 had had composite replacement of the aortic valve and ascending aorta). Most patients (78%) were in New York Heart Association functional class IV. The principal indication for operation was cardiogenic or septic shock in 11 patients, or one or more of the following: persistent sepsis despite adequate antibiotic therapy in 36, congestive heart failure in 31, and recurrent emboli in 16. Staphylococci were responsible for the infection in 37 patients (53%). The abscess was in the mitral annulus in 11 patients, in the aortic root in 44, and in the aortic root and at least one other annulus in 15. After wide resection of the abscess, we reconstructed the heart and annuli with autologous or bovine pericardium. Mechanical heart valves were implanted in 36 patients, bioprostheses in 30, and aortic homografts in 2; valve repair was possible in 2. Sixteen patients required composite replacement of the ascending aorta and aortic valve. RESULTS: There were 9 operative deaths (13%). Infections caused by staphylococci and infections in multiple annuli were associated with increased operative mortality rates. Only 1 patient had persistent infection and required reoperation. The mean follow-up was 56 +/- 40 months. There were 12 late deaths, mostly cardiac. The actuarial survival including operative deaths was 64% +/- 8% at 8 years. In 8 patients, recurrent infective endocarditis developed 10 to 102 months after operation. The freedom from recurrent endocarditis was 76% +/- 10% at 8 years. CONCLUSIONS: This experience indicates that radical resection of the abscess and reconstruction of the heart with pericardium yield an excellent chance of eradicating the infection in patients with infective endocarditis and paravalvular abscess. The type of valve implanted may not be as important as radical resection of the abscess. These patients appear to have a greater than average risk of recurrent endocarditis.

Abscess↗
PubMed1996

Geometric mismatch of the aortic and pulmonary roots causes aortic insufficiency after the Ross procedure.

BACKGROUND: Geometric mismatch between the two semilunar valves can cause aortic insufficiency after the Ross procedure. Thus, whenever the aortic root is larger than the pulmonary root, surgical reduction of the aortic anulus or of the sinotubular junction (or both) to match the diameters of the pulmonary root is necessary to prevent late malfunction of the pulmonary autograft. METHODS: The Ross procedure was performed in 81 patients during the past 5 years. The diameters of the aortic and pulmonary roots were measured in 77 patients. Reduction of the aortic anulus and of the sinotubular junction was necessary in 27 patients, reduction of the aortic anulus alone in 12, and reduction of the sinotubular junction alone in 10. The pulmonary autograft was implanted in the subcoronary position in the aortic root in two patients, as a complete root replacement in 58, and as an inclusion root in 21. RESULTS: There was one operative death, caused by myocardial infarction. Aortic insufficiency developed in one patient who did not have measurement and reduction of the aortic anulus, and aortic root replacement was necessary 2 weeks later. Patients have been followed up from 2 to 64 months (mean 15 months). Two patients have required late reoperations: one because of pulmonary artery stenosis and the other because of a false aneurysm between the autograft and the mitral valve. The most recent Doppler echocardiographic study shows that 90% of the patients have only trace or no aortic insufficiency, and 10% have mild aortic insufficiency. CONCLUSION: This experience suggests that adjustment of the diameter of the aortic anulus or of the sinotubular junction of the aorta may be important to prevent aortic insufficiency after the Ross procedure.

Adolescent↗
PubMed1996

Spanning organizational boundaries to improve care and service: inpatient and outpatient chronic peritoneal dialysis.

The University of Michigan Health Systems (UMHS), an academic, tertiary care health system, provides chronic peritoneal dialysis (PD) along an inpatient-outpatient continuum that gives patients access to an integrated system of settings, services, and care levels. An evaluation of key indicators was conducted to determine the quality of PD services as chronic dialysis clients were admitted to one UMHS inpatient unit. The challenge of matching the chronic PD patient's needs with the appropriate level of care along the health care continuum was addressed. This information presents an effective way to use quality data to improve PD care practices and patient outcomes.

Continuity of Patient Care↗
PubMed1996

Replacement of chordae tendineae with Gore-Tex sutures: a ten-year experience.

BACKGROUND AND AIMS OF THE STUDY: Expanded polytetrafluoroethylene sutures have been used for the replacement of chordae tendineae of the mitral valve since 1985 at The Toronto Hospital. This study examines the long term results of mitral valve repair with chordal replacement with this material. MATERIALS AND METHODS: From July 1985 to December 1993, 134 consecutive patients with mitral regurgitation due to degenerative disease of the mitral valve underwent mitral valve repair with replacement of elongated or ruptured chordae tendineae with one to six (mean of 2.8) Gore-Tex sutures. The patients' mean age was 61 years, range 22-86. In addition to mitral valve repair, 14 patients underwent aortic valve surgery, three underwent replacement of the ascending aorta, six underwent tricuspid valve repair, nine underwent the maze procedure for atrial fibrillation, and 13 underwent coronary artery bypass. The patients were followed for between 20 and 116 months, mean 51 months. No patient has been lost to follow up. RESULTS: There were one operative and eight late deaths. The actuarial survival at eight years was 88% +/- 6%. Four patients required reoperation, one for persistent hemolysis and three for recurrent mitral regurgitation. The Gore-Tex chordae were not responsible for the reoperation in any patient. The freedom from reoperation at eight years was 96% +/- 2%. CONCLUSIONS: Expanded polytetrafluoroethylene sutures are excellent for chordal replacement during mitral valve repair and do not fail during the first decade following surgery. This material has allowed us to increase the probability of successful mitral valve repair in patients with degenerative disease of the mitral valve and prolapse of both leaflets.

Adult↗
PubMed1995

The Hancock II bioprosthesis at ten years.

The Hancock II bioprosthesis was used for heart valve replacement in 843 patients from 1982 to 1993. Aortic valve replacement (AVR) was performed in 536 patients, mitral valve replacement (MVR) in 250, and aortic and mitral valve replacement (DVR) in 57. The mean age was 64 +/- 12 years. Before operation, 80% of the patients were in New York Heart Association functional class III or IV; approximately one-third of the patients had coronary artery disease, and 60 patients had ascending aorta aneurysm. There were 47 operative deaths (AVR, 4%; MVR, 7%; DVR, 10%) and 147 late deaths. Follow-up was complete in 98.6% of the patients and extended from 3 to 140 months (mean, 59 months). At the last follow-up, 84% of the patients were in New York Heart Association class I or II. The actuarial survival at 10 years was 63% +/- 4% for AVR, 55% +/- 5% for MVR, and 53% +/- 9% for DVR. At the end of 10 years, the freedom from thromboembolic complications was 80% +/- 4% for AVR, 88% +/- 3% for MVR, and 86% +/- 5% for DVR; the freedom from endocarditis was 95% +/- 2% for AVR, 96% +/- 1% for MVR, and 87% +/- 5% for DVR; the freedom from primary tissue failure was 92% +/- 3% for AVR, 81% +/- 6% for MVR, and 65% +/- 16% for DVR; and the freedom from reoperation was 89% +/- 2% for AVR, 81% +/- 6% for MVR, and 61% +/- 15% for DVR. The durability of this bioprosthetic valve was affected by the patient's age and by the position where it was implanted. The clinical results of the Hancock II bioprosthesis at 10 years are comparable to those of other current porcine and pericardial valves.

Actuarial Analysis↗
PubMed1995

Reconstruction of the mitral anulus. A ten-year experience.

Reconstruction of the mitral anulus was done in 93 patients because of extensive calcification in 24, infective endocarditis with annular abscess in 27, damaged anulus as a result of previous valve replacement in 36, and rupture of the posterior wall of the left ventricle after mitral valve replacement in 6. The reconstruction was done with fresh autologous pericardium in 30 patients, glutaraldehyde-fixed bovine pericardium in 56, and Dacron graft in 7. An appropriately tailored patch was sutured to the endocardium of the left ventricle or to fibrous skeleton of the heart, or to both. Sixty patients had had previous operation; most patients were in New York Heart Association functional class IV and 15 were in shock. The mitral valve was repaired in 10 patients and replaced in 83. Other procedures were aortic valve replacement in 40, tricuspid valve repair in 25, coronary artery bypass in 12, and replacement of the ascending aorta in 2. Eight patients died in the perioperative period. Postoperative complications were common. Patients were followed up from 12 to 96 months, with a mean of 30 months. There have been 18 late deaths, mostly cardiac. The actuarial survival at 5 years was 68% +/- 6%. A total of 8 patients have required reoperation: 4 because of endocarditis, 2 because of bioprosthetic valve failure, and 2 because of patch dehiscence. The freedom from reoperation was 80% +/- 8% at 5 years. The freedom from patch dehiscence was 95% +/- 4% at 5 years. Reconstruction of the mitral anulus has been an extremely useful operative technique for patients with complex mitral valve disease.

Adolescent↗
PubMed1995

Prospective and retrospective reports of mood states before relapse to substance use.

In a prospective design, it was predicted that the role of negative mood in precipitating relapses and crises among alcohol-dependent participants would be greater when assessed with retrospective mood ratings than when assessed by prospective mood ratings because of participants' attributional biases. This hypothesis was not supported. Support was found, however, for a relationship between negative bias and the amount of negative mood assessed at the time the retrospective report was given. As has been previously found, the most frequent precipitant of relapses and crises in this study was negative emotional states. Female participants were more likely to report interpersonal and less likely to report intrapersonal determinants than male participants. Minor relapses were more likely to be precipitated by social pressure and less likely to be related to negative emotions than major relapses.

Adolescent↗
PubMed1995

In vitro ischaemic preconditioning of isolated rabbit cardiomyocytes: effects of selective adenosine receptor blockade and calphostin C.

OBJECTIVE: The aim was to determine if in vitro ischaemic preincubation can precondition cardiomyocytes and if the responses to adenosine receptor antagonists are similar to those previously determined during "metabolic" preconditioning with glucose deprivation or adenosine agonists. METHODS: Isolated rabbit cardiomyocytes were preconditioned with 10 min of ischaemic preincubation, followed by a 30 min postincubation before the final sustained ischaemic period. The protein kinase C inhibitor calphostin C or the adenosine receptor antagonists 8-sulphophenyltheophylline (SPT), BW 1433U, and 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) were added either during the preincubation or into the final ischaemic pellet. Adenosine deaminase (10 U.ml-1) was added during ischaemic preincubation. Rates of contracture and extent of injury were determined by sequential sampling and assessment of trypan blue permeability following 85 mOsM swelling. RESULTS: Myocytes were preconditioned by a 10 min in vitro ischaemic preincubation. Preincubation with 100 microM SPT or with adenosine deaminase, or addition of 200 nM calphostin C into the final ischaemic pellet did not alter rates of rigor contracture but nearly abolished protection. A significant degree of protection was maintained following ischaemic preincubation with the highly selective adenosine A1 receptor blocker DPCPX (10 microM), while the A1/A3 antagonist BW 1433U (1 microM) severely limited protection. SPT and BW 1433U added only into the final ischaemic pellet of preconditioned cells significantly blocked protection, while protection was maintained in the presence of DPCPX. CONCLUSIONS: Ischaemic preconditioning of cardiomyocytes is blocked by adenosine receptor antagonists known to bind to A3 receptors but not by DPCPX which has high affinity for A1 receptors, but little affinity for A3 receptors. Maintenance of protection during the final ischaemic phase has a similar receptor specificity. Blockade of protein kinase C activity abolishes protection. Ischaemic and metabolic preconditioning in vitro appear to occur through similar pathways.

Animals↗
PubMed1995

Hyaluronic acid (hyaluronan) in experimental osteoarthritis.

We studied the effects of intraarticular (ia) administration of hyaluronic acid (HA) (Mw approximately 9 x 10(5)) (Artz) on cartilage integrity and release into synovial fluid (SF) of keratan sulfate peptides (KS-pep) in an ovine model of early osteoarthritis (OA) induced by meniscectomy. Five consecutive weekly injections of HA (2 ml, 10 mg/ml) or saline (2 ml) were initiated 16 weeks after meniscectomy, and animals were sacrificed 5 weeks after the last injection. SF was sampled 8, 16, 23, and 26 weeks postoperation. In the saline injected animals KS-pep levels increased progressively in SF, relative to nonoperated controls (p < 0.05). KS-pep levels in SF of the HA treated group also increased, but were not statistically different from controls. Using a modified Mankin histological scoring system, cartilage at necropsy of HA injected joints showed less damage than similar regions of saline treated animals. A new mechanism for the protective effects of HA on cartilage is proposed.

Animals↗
PubMed1995

Left ventricular function after mitral valve surgery.

This study examined the effects of various operative procedures on the mitral valve of patients with mitral regurgitation due to degenerative disease of the mitral valve. A randomized clinical trial on the type of annuloplasty ring used at surgery revealed that early postoperative left ventricular systolic function was better in patients who had a flexible ring than in patients who had a rigid ring. Two years after surgery there were no differences between these groups and most patients were found to have fairly normal left ventricular function. The long term results of mitral valve repair in 184 patients revealed a 10-year actuarial survival of 86% +/- 6%. A randomized trial on the effect of preservation of chordae tendineae during mitral valve replacement revealed that the beneficial effect of this procedure on left ventricular function is a lasting one; five years after surgery patients who had mitral valve replacement with preservation of the chordae tendineae have better exercise capacity, and better left ventricular systolic function and performance. The long term results of mitral valve replacement in 154 patients revealed a 10-year actuarial survival of 69% +/- 5%. Logistic regression analysis indicated that age greater than 65 years and complete excision of the native mitral valve were predictors of late mortality. Of those patients, 70 had had chordal preservation during surgery and 84 did not. These two subgroups were remarkably similar preoperatively, but the 10-year actuarial survival was 80% +/- 6% for patients who had chordal preservation and 63% +/- 6% for those who did not. The mitral valve should be repaired whenever possible; if replacement is necessary it should be performed with preservation of the chordae tendineae.

Actuarial Analysis↗