Control banding workshop, 4-5 November 2002, London.
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Hazardous Substances↗
Biomedical subjects
P J Oldershaw
Publications and source records attributed to P J Oldershaw.
Microvascular obstruction and missed infarction.
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Aged↗
Stent implantation reduces restenosis in patients with suboptimal results following coronary angioplasty.
BACKGROUND: Primary intracoronary stenting reduces the rate of restenosis when compared with balloon angioplasty (PTCA) in selected patients. The strategy of PTCA followed by provisional stent placement for suboptimal PTCA results may be preferable to universal stenting but has not yet been tested in a randomized trial. METHODS: An attempt was made to obtain an optimal result with PTCA alone in 143 patients. Stenting was required in 50 patients (35%) for significant coronary dissection or PTCA failure. In the remaining 93 patients, the angiographic result was assessed immediately using on-line quantitative coronary angiography and classified as either optimal (<15% residual stenosis) or suboptimal (>/=15% residual stenosis). Sixteen patients (11%) had an optimal result from PTCA. The remaining 77 (54%) patients had a suboptimal result and were immediately randomized either to no further treatment or to the placement of a stent. The primary end-point was the rate of restenosis (>50% stenosis), assessed by quantitative coronary angiography, at 6 months. RESULTS: Angiographic follow-up was completed in 132 patients. Restenosis occurred in 53 (36,69)% of patients with a suboptimal result randomized to PTCA alone compared with 24 (12,41)% of patients randomized to stent (P=0.023). There was no significant difference in minimal luminal diameter at follow-up between the randomized groups. The rate of restenosis was 14 (2,43)% in patients with an optimal PTCA result and 14 (5,28)% in those that required stenting. CONCLUSIONS: Optimal angiographic results following conventional PTCA are rare and the restenosis rate following suboptimal results is high. The strategy of stenting suboptimal results is associated with a significant reduction in the rate of stenosis.
Angioplasty, Balloon, Coronary↗
The importance of differentiating ReoPro (c7E3 abciximab) induced thrombocytopenia from heparin-induced thrombocytopenia.
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Abciximab↗
Myocardial contractility is not constant during spontaneous atrial fibrillation in patients.
BACKGROUND: The variation in stroke volume and pulse pressure characteristic of atrial fibrillation is usually ascribed to time-dependent ventricular filling, implying a single positive relationship between end-systolic pressure and volume, which defines a single state of myocardial contractility. We tested the hypothesis that contractility also varies. METHODS AND RESULTS: We measured the left ventricular pressure and volume continuously with a conductance catheter with catheter-tip micromanometer introduced retrogradely into the left ventricle. The end-systolic pressure-volume relationship was determined in 6 patients in atrial fibrillation undergoing cardiac catheterization for diagnostic purposes and 4 control patients in sinus rhythm undergoing coronary artery bypass graft surgery. The normal positive relationship between end-systolic pressure and volume was found in the control patients, but no such positive relationship was found in any patient in atrial fibrillation. In the latter, the slopes of the linear regressions were either not significantly different from zero or significantly negative (r values <0.08), both results indicating a change in contractility from beat to beat. Significantly negative relationships were found between end-systolic volume and preceding R-R interval (-0.82<r<-0.24), indicating the presence of mechanical restitution. Significantly positive relationships were found between end-systolic volume and the R-R interval before the preceding R-R interval (0.35<r<0.74), indicating the presence of postextrasystolic potentiation. CONCLUSIONS: Myocardial contractility is constantly changing from beat to beat in atrial fibrillation because of the influence of the force-interval relationships.
Aged↗
Validation of a new intraoperative technique to evaluate load-independent indices of right ventricular performance in patients undergoing cardiac operations.
BACKGROUND: Assessment of right ventricular performance in the perioperative period is difficult because there is no generally accepted method of measuring right ventricular volume. We set out to determine whether conductance technology could provide a valuable technique for the investigation of intraoperative right ventricular function. METHODS AND RESULTS: Three validating studies were performed in 25 patients undergoing routine coronary revascularization. Study 1: The influence of conductance catheter position in the right ventricle was examined in 10 patients. Insertion of the conductance catheter through the outflow tract was associated with a larger gain constant and a smaller parallel conductance compared with insertion through the tricuspid valve. Study 2: The reproducibility of contractility measurements with the use of a conductance catheter was examined in 7 additional patients. Removal and reinsertion of the conductance catheter was not associated with any significant difference in right ventricular volume or contractile function. Study 3: Right ventricular performance before and after cardiopulmonary bypass was compared in 8 additional patients. There was a fall in the slope of the right ventricular preload recruitable stroke work from 15.6 (3.8) to 11.0 (5.1) mm Hg (P=.01) and an increase in the slope of the end-diastolic pressure-volume relations from 0.05 (0.02) to 0.11 (0.05) mm Hg/mL (P=.001). CONCLUSIONS: The conductance technique can be used to study perioperative changes in right ventricular performance. Insertion of the conductance catheter through the outflow tract provides stable and reproducible data. There is significant impairment of right ventricular contractility in the early postoperative period.
Cardiac Catheterization↗
Left ventricular parallel conductance during cardiac cycle in children with congenital heart disease.
This study examines the accuracy of the conductance catheter technique and, in particular, parallel conductance [expressed as offset volume (Vc)] changes during the cardiac cycle in the human left ventricle. Two groups of patients were assessed: group 1, with an open atrial septal defect, and group 2, with an interventricular communication. In a subgroup, pre- and postoperative data were compared to assess the possible impact of shunting or anatomic considerations on our measurements. Vc is normally obtained by a saline-dilution technique previously described by Baan et al. [Vc(Baan); J. Baan, E. T. Van der velde, H. G. Debruin, G. J. Smeenk, J. Koops, A. D. Van Dijk, D. Temmerman, P. J. Senden, and B. Buis. Circulation 70: 812-823, 1984]. This does not take into account potential changes during the cardiac cycle. Four cardiac cycles were taken from the hypertonic saline washin and were divided into six equal isochrones between the maximum and minimum first derivatives of left ventricular pressure (dP/dtmax and dP/dtmin, respectively). The apparent ventricular volume was regressed against stroke volume for the corresponding cardiac cycle. The volume at the gamma-intercept corresponds to the Vc at each time interval [Vc(t)]. In group 1, there was a variation in Vc(t) during systole, but the temporal changes were quite small, on the order of 4.28% (SD = 5.18%) of total corrected end-diastolic volume (mean maximal variation of 2.60 ml). Furthermore, the value of Vc obtained at dP/dtmax was not significantly different from that obtained at dP/dtmin. For group 2 as a whole, mean Vc(Baan) did not change significantly with ventricular septal defect closure (preoperative, 8.85 +/- 11.1 ml; postoperative, 9.82 +/- 11.84 ml). Group 2 children also exhibited a systolic cyclical variation in Vc(t) similar to group 1. Finally, Vc(t) as a percentage of end-diastolic volume was no different when group 1 and group 2 were compared. We conclude that in the left ventricle, even in the presence of a left-to-right shunt, there is a small but insignificant difference in parallel conductance during ventricular ejection. The magnitude of this cyclical change does not preclude ventricular volume measurement in congenital heart disease by the conductance catheter technique.
Child↗
Plasma brain natriuretic peptide concentrations in patients with chronic mitral regurgitation.
BACKGROUND AND AIMS OF THE STUDY: Patients with chronic mitral regurgitation (MR) are often referred for surgery only after irreversible left ventricular (LV) dysfunction has developed. Our aim was to determine whether plasma brain natriuretic peptide (BNP) concentrations could serve as a marker for early LV dysfunction in this condition. METHODS: Twenty-two patients with isolated chronic MR and echocardiographic evidence of at least moderate regurgitation were studied. RESULTS: Plasma BNP concentrations were significantly higher in patients than in normal volunteers (20.85 +/- 16.9 versus 3.37 +/- 0.9 pmol/l; p = 0.007). Concentrations increased with increasing severity of symptoms and were highest in those in NYHA class IV, but did not correlate with LV dimensions, fractional shortening or left atrial size. Of note, two asymptomatic patients with high BNP concentrations were referred for surgery within the 12-month follow up period due to symptom progression. CONCLUSIONS: Plasma BNP concentrations are elevated in most patients with isolated chronic MR, including those who are asymptomatic with normal LV dimensions. The significance of these findings is uncertain, but they suggest that changes in ventricular physiology occur early in the disease process and before they can be detected echocardiographically. Longitudinal studies are required to determine if patients with high BNP levels have an adverse prognosis and if this can be altered by earlier surgical intervention.
Adult↗
Does parallel conductance vary during systole in the human right ventricle?
OBJECTIVES: Right ventricular (RV) contractile performance remains poorly characterised, particularly in humans. Conductance catheter techniques have the potential to overcome the geometric difficulties in RV volume measurement that have hindered systematic studies of RV pressure volume relations. The present study examines changes in parallel conductance (Vc) that may occur during the cardiac cycle in the human right ventricle. METHODS: Using signals obtained from custom-built conductance catheters, six isochronal systolic values of Vc (Vc(t)) were measured during hypertonic saline wash-in. Studies were performed in nine patients undergoing right heart catheterisation. Their ages ranged from 7 to 39 years (median = 16) and their weights ranged from 20.3 to 84.7 kg (median = 50.0 kg). Measurements of mean Vc and isochronal Vc(t) and its variability during systole were assessed. Mean Vc was measured using the Baan technique (Vc(Baan)), Vc(t) was measured from six systolic isochrones obtained during the same period of hypertonic saline wash-in. RESULTS: The temporal changes in Vc(t) were small (mean 5.8%, median = 4.4%, range = 0.6-17.9%) of total corrected end-diastolic volume (mean maximal variation of 7.7 ml). The value of Vc(t) obtained at dp/dtmax (mean = 99.1 ml; median = 104.75 ml; range 20.15-196.7 ml) was not significantly different to that obtained at dp/dtmin (mean = 100.0 ml; median = 110.87 ml; range = 20.0-204.2 ml) (P > 0.05), but both were higher than the single Vc measurement (Vc(Baan)) obtained using the standard approach (P = 0.02). The correlation between Vc(Baan) and Vc(t) for group data; (Vc(Baan) = 89.69 ml, s.d. = 43.73 ml; Vc(t) = 98.16 ml, s.d. = 50.16 ml) produces a regression slope of 0.99 for all studies (P = 0.02). CONCLUSION: We conclude that parallel conductance does vary during systole in the human right ventricle of adults and older children after repair of congenital abnormalities but there is no significant difference in Vc(t) at dp/dtmin and dp/dtmax. However, there was a significant difference when the isochronal Vc(t) measurement is compared with the standard single value technique (Vc(Baan)) obtained using the hypertonic saline wash-in method. The excellent correlation between Vc(t) and Vc(Baan) suggests that the correction of Vc for the phase of the cardiac cycle is unnecessary for most purposes when studying the human right ventricle.
Adolescent↗
The determination of volume of right ventricular casts using a conductance catheter.
Conductance catheters were used to assess the volume of right ventricular models made from post-mortem casts. Models were made from silastic rubber and filled with saline. The correlation between volume assessed by conductance catheter and real volume was investigated as saline was withdrawn from, and injected into, five models. The mean regression between real and conductance-derived volume was 1.05 (SE 0.04 mean R2 0.94 SE 0.02) with Y-intercept -0.25 ml SE 1.72. Parallel wall conductance was assessed through the tricuspid orifice sealed with human tricuspid tissue, or left open, and found to be negligible. There was no difference between volumes measured by a catheter through either the pulmonary or tricuspid orifice. We conclude that conductance catheters are suitable for the assessment of right ventricular volume, despite the complex geometry.
Adolescent↗
Muscular false tendons, aberrant left ventricular papillary musculature, and severe electrocardiographic repolarisation abnormalities: a new syndrome.
Three patients (age 18-39 years; two men) with normal exercise capacity, normal left ventricular function, large muscular false tendons within the left ventricle, and anomalously placed papillary muscles associated with giant T wave inversion on the electrocardiogram are described. The absence of adverse cardiovascular events at long-term follow up (mean 13 years) indicates that this is a benign unrecognised syndrome.
Adult↗
Guillain-Barré syndrome following cardiopulmonary bypass.
Two cases of Guillain-Barré syndrome occurring after otherwise uneventful cardiac surgery using cardiopulmonary bypass are presented. Although Guillain-Barré syndrome has been reported after surgical procedures, it has never been reported after cardiopulmonary bypass. Recent literature supports an immune mediated process for Guillain-Barré. Cardiopulmonary bypass may act as the trigger for this immune mediated response.
Blood Transfusion↗
An overview of survival studies in patients with heart failure.
Heart failure is associated with poor prognosis, but recent large-scale investigations have generated valuable and practical information to help improve clinical management and patient survival. This review presents an overview of the findings of recent heart failure survival studies and how these may affect therapeutic strategy for patients with this condition.
Double-Blind Method↗
Development of pragmatic exposure-control concentrations based on packaging regulation risk phrases.
This paper relates United Kingdom and other national Occupational Exposure Limits (OELs) for volatile organic substances to the Risk Phrases (RPs) which they are assigned under EEC Classification, Packaging and Labelling Directives. The OELs for organic volatiles assigned RP 20 ('harmful by inhalation'), RP 23 ('toxic by inhalation') and RP 26 ('very toxic by inhalation') fitted better to the cumulative log-normal distribution than to the cumulative normal distribution and the means for RPs 23 and 26 were not significantly different. The means for RP 20 and RP 23/26 were 100 mg m-3 (or 25 ppm) and 5 mg m-3 (or 1 ppm), respectively. In the absence of any relevant, specific information, it is suggested that these values may be useful as guidelines for pragmatic exposure-control concentrations (PECCs) for the control of exposure by inhalation in workplaces handling substances labelled with these RPs.
Environmental Exposure↗
Analysis of left ventricular wall movement before and after reimplantation of anomalous left coronary artery in infancy.
Five infants who underwent direct reimplantation or redirection of an anomalous left coronary artery from the pulmonary artery to the aorta were studied. There were no deaths from the procedure. Anastomoses were patent at a mean follow up of 33 months. Left ventricular angiograms before and after operation were digitised frame by frame. Analysis of wall motion showed considerable generalised hypokinesia with no change in cavity shape before operation. After reimplantation there was a significant improvement of global ventricular function as assessed by ejection fraction and end diastolic shape index. There was also a tendency for the shape index change to increase; this was compatible with better global systolic function. Three of the four patients who were restudied showed normal isometric and contour wall motion plots. One child, the oldest at the time of operation, still showed asynchronous onset of contraction and isovolumic relaxation. The procedure offers a low risk of mortality and a high rate of patency of the anastomosis. Improvement of ventricular function can be remarkable and its extent cannot be assessed simply by ejection fraction measurements.
Anastomosis, Surgical↗
Prosthetic valve endocarditis.
Prosthetic valve endocarditis occurs in 2-4% of patients with prosthetic valves and carries a mortality of around 50%. A low index of suspicion should enable early diagnosis. The empirical use of antibiotics in patients with a prosthetic valve who develop an unexplained fever is inappropriate. Careful liaison between cardiologist, microbiologist and cardiac surgeon is essential for optimal management.
Diagnosis, Differential↗
The clinical features, management and outcome of persistence of the arterial duct presenting in adult life.
We have reviewed the 25 patients who, between 1973 and 1988, presented to the Brompton Hospital in adulthood with persistence of the arterial duct (ductus arteriosus). As pulmonary arteriolar resistance is the main determinant of management and prognosis in this condition, the patients were divided into groups with either normal or mild elevation of resistance (less than 10 units/m2: 19 patients) or with severe elevation (greater than 10 units/m2: 6 patients). Patients with normal pressures or mild elevation tended to be older (mean age 45 years). Many (70%) were asymptomatic, but dyspnoea with signs of left heart failure was the commonest presenting complaint. Surgical closure of the duct was performed in 16 with good result in all. Survival for the entire group, however, was long. There was a symptomatic indication for surgery (due to hyperdynamic circulation) in 5. In those with severely elevated pulmonary arteriolar resistance, the mean age of presentation was 31 years and the survival short. The commonest presenting symptom was dyspnoea. Surgical closure of the duct was attempted in two patients but with a poor outcome in both. All patients with an elevated resistance had developed this complication by the third decade of life. Significant elevation was not a feature of older patients, suggesting that, in this age group, the risk of elevation is slight. Surgery, nonetheless, may be indicated for relief of symptoms due to a large systemic to pulmonary shunt.
Adult↗