Biomedical subjects

C Brookes

Publications and source records attributed to C Brookes.

9 recordsLinked to original sources

PubMed1999

Acute right ventricular dilatation in response to ischemia significantly impairs left ventricular systolic performance.

BACKGROUND: Right ventricular (RV) dilatation that occurs as a consequence of RV infarction is thought to produce hemodynamic instability by reducing left ventricular (LV) preload and compliance. We hypothesized that these geometric changes may also adversely affect LV systolic performance. METHODS AND RESULTS: Twelve 40-kg pigs were studied. Integrated conductance catheters and micromanometers were placed in both the LV and RV to allow simultaneous recordings of pressure and volume and derivation of indices of contractile function. RV ischemia was induced by balloon occlusion of the proximal right coronary artery (RCA) under 3 conditions: 1) with the pericardium intact, 2) with the pericardium intact and inotropic support, and 3) with the pericardium wide open. With an intact pericardium, RCA occlusion produced a decrease in LV end-diastolic volume associated with a marked decline in the contractile function. With the pericardium open, the same ischemic insult resulted in both LV and RV dilatation, which produced a significantly smaller negative effect on cardiac output (P=0.03), LV systolic pressure (P=0.02), LV preload-recruitable stroke work (P<0. 01), and LV end-systolic pressure-volume relations (P<0.01). Similarly, administration of dobutamine during RCA occlusion decreased the ventricular volume changes and produced a relative improvement in LV contractile performance. CONCLUSIONS: The hemodynamic compromise seen in association with acute RV dilatation within an intact pericardium is partly attributable to impaired LV systolic performance and cannot be wholly ascribed to changes in LV preload or compliance.

Animals↗

PubMed1997

Resting right ventricular function in patients with coronary artery disease: pressure volume analysis using conductance catheters.

Right ventricular pressure volume cycles from patients with coronary artery disease were created in order to assess their characteristics and the effects of peak ventricular pressure and right and left artery coronary disease. Thirty-three patients undergoing diagnostic catheterisation for ischaemic heart disease underwent right ventricular catheterisation with a micromanometer and a conductance catheter. Simultaneous pressure and volume signals were recorded and analysed as functions of time, and of each other, forming pressure volume cycles. A total of 19/33 (58%) patients had an abnormal pressure volume loop with a clear end systolic shoulder, and an isovolumic relaxation phase. The mean peak ventricular pressure for all patients was raised (35.2 S.D. 11.8 mmHg), but there was no correlation between indices of shape and peak systolic pressure. Values of dP/dtmax were also raised, but there was no significant difference in this or any other index between patients with left or right coronary artery disease. Thus, in patients with coronary artery disease, the right ventricular pressure volume loop is frequently abnormal in a pattern that is recognised as a feature of an increased ventricular afterload.

Angina Pectoris↗

PubMed1997

Clinical application of the conductance catheter technique in the adult human right ventricle.

This study examines the use of conductance catheters to assess human right ventricular volume. Ten patients undergoing diagnostic cardiac catheterisation underwent right heart catheterisation with a conductance catheter and micromanometer, and a thermodilution catheter before and after fluid loading. Parallel wall conductance (Vc), and the multiplication factor relating conductance and thermodilution derived stroke volumes (å) were derived at each steady state. Pressure-volume cycles were analyzed at steady state and during fluid loading. Fluid loading resulted in a significant increase in cardiac output, and change in maximum and minimum cycle volume. There was no significant change in å (mean 0.40 S.D. 0.20) or Vc (mean 126.4 S.D. 59.6 ml) at higher cardiac outputs or ventricular volumes. Right ventricular pressure-volume cycles were formed demonstrating characteristic lack of clear isovolumic contraction and relaxation phases, and low cycle efficiencies (mean 0.62 S.D. 0.16). Serial cycles recorded during volume loading defined an end systolic pressure-volume relation more reliably than a stroke work end diastolic volume relation. Thus, a conductance derived volume signal can be obtained in the human right ventricle which can be interpreted as a continuous and instantaneous index of right ventricular volume, allowing the construction of real time pressure-volume cycles.

Adult↗

PubMed1997

Right ventricular dysfunction during coronary artery occlusion: pressure-volume analysis using conductance catheters during coronary angioplasty.

OBJECTIVE: To study the effects of coronary artery occlusion on the pressure-volume relations of the right ventricle. DESIGN: Right ventricular pressure-volume cycles were studied using conductance catheters and micromanometers in 19 subjects undergoing coronary angioplasty in a tertiary referral cardiac centre. RESULTS: Catheter occlusions of either the left anterior descending coronary artery or the right coronary artery were associated with a decline in stroke work (mean change (SD): left-13.3 (15.8)%, p = 0.008; right -13.5(16.5)%, p = 0.04). Two patterns of change were evident: an upward shift usually associated with occlusion in the left coronary artery, and a rightward shift in the right coronary artery. In the former there was an increase in maximum ventricular volume (mean change: 3.0(2.7)%, p = 0.004) and in minimum ventricular volume (mean change: 2.3(2.7)%, p = 0.01) and a fall in peak pressure (mean change: -4.8 (5.1)%, p = 0.04). In the latter there was an increase in peak pressure (mean change 9.9(16.3)%, p = 0.04) and an increase in minimum ventricular volume (mean change 3.7(5.0)%, p = 0.02) leading to a fall in stroke volume (mean change -13.3(15.8)%, p = 0.008). CONCLUSIONS: Occlusion of the left anterior descending coronary artery or the right coronary artery is associated with a decline in right ventricular work. However, different patterns of change in indices of preload and afterload lead to different effects on overall right ventricular pump function.

Angioplasty, Balloon, Coronary↗

PubMed1996

Scapholunate instability--a spectrum of pathology.

Five cases of scapholunate instability are reported. The condition is commonly misdiagnosed in accident and emergency departments. The importance of a complete clinical assessment of the suspected scaphoid injury and the need to measure the scapholunate distance and the scapholunate angle on the radiographs is stressed.

Adult↗

PubMed1995

'Sticky' neutrophils, pathergic arthritis, and response to heparin in pyoderma gangrenosum complicating ulcerative colitis.

Pyoderma gangrenosum is strongly associated with inflammatory bowel disease and exhibits pathergy, occurring at sites of previous minor trauma. A patient is presented with a 21 year history of extensive ulcerative colitis, who developed pyoderma gangrenosum and arthralgia while receiving high dose corticosteroids for active ulcerative colitis. The arthralgia exhibited pathergy affecting particularly the left temporomandibular joint, which was stressed by an asymmetric bite, and the left elbow, which had been fractured many years previously. This prompted the hypothesis that neutrophils in this condition may be marginated, as a result of increased stickiness of either the neutrophil or the vascular endothelium. The introduction of heparin therapy was associated with rapid resolution of the arthralgia, pyoderma gangrenosum, and ulcerative colitis.

Adult↗

PubMed1990

Routine hospital admission in twin pregnancy between 26 and 30 weeks' gestation.

Of 141 women with twin pregnancies, 72 were randomly assigned to outpatient care and 69 to hospital admission between 26 and 30 weeks' gestation. There were no differences between the groups in the frequencies of major maternal complications in pregnancy and labour but more of those admitted to hospital than of the outpatient group had to be admitted after 30 weeks. There were no differences between the groups in the mean birthweights of the twins by birth order, or in their mean gestation at birth whether analysed by intention to treat or by the treatment given. 22 infants were delivered before 32 weeks' gestation in the inpatient group compared with 10 in the outpatient group. With the exception of small-for-dates infants, any trend towards greater morbidity or mortality was seen in the inpatient group. The policy of routine hospital admission of women with twin pregnancies from 26 weeks' gestation is not beneficial to mother or babies and should be abandoned.

Adult↗

PubMed1986

A reevaluation of the ferning test to detect ruptured membranes.

The ferning test for the detection of amniotic fluid, when first described, was reported to have no false positive results. Despite this and after initial enthusiasm it has never achieved widespread use. The test is easy to perform but interpretation requires care, and it is necessary to identify potentially confusing crystallization patterns to avoid false positive results. A reevaluation of the test is presented and a hitherto unrecognized false positive reaction due to an antiseptic solution is reported.

Amniotic Fluid↗

PubMed1984

Aflatoxin B1: effect on the synthesis and degradation of mitochondrial proteins in hepatocyte monolayers.

The effect of aflatoxin B1 (AFB1), a hepatocarcinogen, on mitochondrial and general protein synthesis and degradation has been studied. AFB1 (0.003, 0.03, 0.25 micrograms ml-1) inhibited total protein synthesis over a 5 h period by 30, 64 and 82%, respectively, measured by incorporation of [3H]leucine. After 24 h in the presence of AFB1 inhibition was 23, 77 and 100%, respectively. AFB1 inhibited total hepatocyte protein degradation in a concentration independent manner by approximately 50% i.e., from 1.4% h-1 to 0.7% h-1. The immediate effect of AFB1 on mitoribosomal and total mitochondrial protein synthesis and mitochondrial degradation has been assessed by two methods. Mitoribosomal synthesis of proteins was inhibited over a 5 h period by AFB1 in a concentration independent manner by approximately 43%. Total mitochondrial protein synthesis showed a 23 and 45% inhibition by AFB1 (0.003 and 0.03 micrograms AFB1 ml-1) over a 4 h period and 25 and 72% inhibition, respectively, after 24 h in culture. The rate of mitochondrial protein degradation was not altered. AFB1 inhibits dibutyryl cyclic AMP-induced tyrosine amino transferase (TAT) activity in hepatocytes by 57% at 0.003 micrograms ml-1 and 100% at 0.03 micrograms ml-1 over a 24 h period. Dibutyryl cyclic AMP increases the rate of degradation of proteins in hepatocyte monolayers from 1.4% h-1 to 2.7% h-1 and was inhibited at both concentrations of AFB1 used. AFB1 causes a rapid inhibition of total hepatocyte protein synthesis, synthesis of proteins in hepatocyte mitochondria and the synthesis of imported mitochondrial proteins. General hepatocyte and dibutyryl cyclic AMP-induced protein degradation are significantly inhibited by AFB1 whereas the degradation of mitochondrial proteins is unaffected.

Aflatoxin B1↗