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Biomedical subjects

D Richens

Publications and source records attributed to D Richens.

At least 19 recordsLinked to original sources
PubMed2003

Rupture of the aorta following road traffic accidents in the United Kingdom 1992-1999. The results of the co-operative crash injury study.

OBJECTIVE: The true incidence and survivability of blunt traumatic aortic rupture following road traffic accidents in the UK is unclear. The objective of this study was to determine the extent of blunt traumatic aortic rupture in the UK after road traffic accidents and the conditions under which it occurs. METHODS: Data for the study was obtained from the Co-operative Crash Injury Study database. Road traffic accidents that happened between 1992 and 1999 and included in the Co-operative Crash Injury Study database were retrospectively investigated. RESULTS: A total of 8285 vehicles carrying 14,435 occupants were involved in 7067 accidents. There were 132 cases of blunt traumatic aortic rupture, of which the scene survival was 9% and the overall mortality was 98%. Twenty-one percent of all fatalities had blunt traumatic aortic rupture (130/613). Twenty-nine percent were due to frontal impacts and 44% were due to side impacts. Twelve percent of the blunt traumatic aortic rupture cases in frontal vehicle impacts were wearing seat belts and had airbag protection and 19% had no restraint mechanism. The Equivalent Test Speed of the accident vehicles, (where equivalent test speed provides an estimate of the vehicle impact severity and not an estimate of the vehicle speed at the time of the accident), ranged from 30 to 110 km/h in frontal impacts and from 15 to 82 km/h in side impacts. CONCLUSION: Blunt traumatic aortic rupture carries a high mortality and occurred in 21% of car occupant deaths in this sample of road traffic accidents. Impact scenarios varied but were most common from the side. The use of an airbag or seat belt does not eliminate risk. The injury can occur at low severity impacts particularly in side impact.

Accidents, Traffic↗
PubMed2002

The mechanism of injury in blunt traumatic rupture of the aorta.

Rupture of the aorta accounts for a significant proportion of fatalities following blunt trauma. A great deal of consensus exists describing the circumstances under which acute traumatic aortic dissection occurs as well as its investigation and management. However, there remains some controversy surrounding the pathogenic aetiology underlying this injury. Univariate and multivariate models of blunt traumatic aortic rupture (BTAR) are discussed. To account for the consistency in the nature of BTAR, despite a range of trauma scenarios, the concepts of dynamic multivariate models and a final common pathway are introduced. Clinical management is described elsewhere. Greater understanding of the mechanism of BTAR could lead to a range of safety systems aimed at a reduction in its incidence and severity.

Aorta, Thoracic↗
PubMed2002

Minimal access mitral valve replacement.

Minimally invasive mitral valve surgery has recently been advocated as an alternative to the conventional median sternotomy approach. It has several documented advantages and requires a close relationship betweeen the surgeons, anaesthetist and perfusionist for a successful outcome. This article demonstrates our surgical technique for replacement of the mitral valve. The various aspects of the specialised equipment used are also described.

Anesthesia, General↗
PubMed1997

An experimental study of intra aortic balloon pumping within the intact human aorta.

OBJECTIVE: Intra-aortic balloon pumping is a therapeutic technique which carries a significant morbidity related to the interaction between the balloon catheter and the aorta. The aim of this study was to visualise directly the dynamic action of the balloon catheter within the cadaveric human aorta in an artificial circulation. METHODS: An artificial circulation was constructed using of PVC tubing, a filter and a roller pump. A series of five intact cadaveric human aortas were then individually studied by placing each in series within the circuit. A balloon catheter was advanced via the left common iliac artery into the descending aorta under direct angioscopic vision. Balloon pumping was then commenced. The circuit was perfused with normal saline at a flow rate of 3 l/min. Pump actions of 1:1 and 1:2 were simulated. Each aorta at the end of the experiment was subjected to histological examination. RESULTS: The balloon only appeared to make direct contact with the wall of the aorta during deflation when it was swept to one side by the circulating fluid. During maximal inflation the only points of contact were the tip of the catheter and the entry site. Side branches of the aorta were not occluded by the balloon. There was considerable atheromatous debris visualised within the lumen of the aorta. Atheromatous plaques were seen to fissure and disrupt by a pressure wave action and not by direct contact with the balloon. CONCLUSION: The balloon catheter moves relative to the wall of the aorta during inflation and deflation. Contact between the balloon and the aorta only occurs during deflation. Side branches of the aorta are not occluded by the catheter. Plaque disruption and embolus formation appear to result from pressure wave action rather than direct contact with the balloon. This may have implications for future balloon design. Further investigation of this poorly understood interaction between the balloon and the aortic wall is required.

Adult↗
PubMed1997

Vascular remodelling in intramyocardial resistance vessels in hypertensive human cardiac transplant recipients.

OBJECTIVE: Cardiac transplant recipients often develop hypertension as a side effect of immunosuppressive treatment. The aim of this study was to use the serial endomyocardial biopsies taken to monitor rejection to study the early and sequential arterial changes in human myocardial resistance arteries as hypertension develops. METHODS: At least 14 biopsies were studied from each of 23 patients, divided into a normotensive group (12 patients with a diastolic pressure never greater than 90 mm Hg) and a hypertensive group (11 patients with more than 10% of diastolic pressure measurements above 100 mm Hg). Morphometric analysis of between 30 and 50 arteries and arterioles in two widely separated histological levels from each biopsy was undertaken using an Optomax image analyser. RESULTS: There was a correlation between blood pressure, particularly diastolic pressure, and rate of medial thickening of intramyocardial coronary resistance arteries and arterioles (P = 0.0025). There was also a correlation between serum cyclosporin A concentrations and mean artery wall thickness (P = 0.003). CONCLUSIONS: Hypertension and cyclosporin A treatment are associated with significant wall thickening of intramyocardial resistance vessels in cardiac allograft recipients. These changes may be functionally and clinically important.

Arterioles↗
PubMed1996

Infective endocarditis of the tricuspid valve in an orthotopic heart transplant recipient.

A 43-year-old orthotopic heart transplant recipient had coagulase-negative staphylococcus endocarditis 26 weeks after the operation. A diagnosis of endocarditis was confirmed and followed up by serial transoesophageal echocardiography. Treatment with intravenous gentamycin and vancomycin cured her endocarditis, and a 2.5 cm vegetation regressed significantly. She has been well since and, at 14 months after transplantation, was back to her normal activities. Although repeated blood culture yielded only intermittent light growths of coagulase-negative staphylococci, there were several positive samples. In a setting of infective features, light growths of coagulase-negative staphylococcus should be taken seriously if repeatedly positive in heart transplant recipients or other immunocompromised patients. Transesophageal echocardiography offers significant advantages over the transthoracic modality in suspected endocarditis.

Adult↗
PubMed1995

Arterial lesions associated with medial disorganization and fibrosis in endomyocardial biopsies from human cardiac allografts.

We describe distinctive arterial lesions in endomyocardial biopsies from patients with human cardiac allografts. The lesions affected principally the media of small arteries and consisted of misorientation of smooth muscle cells and fibrosis. This remodelling was most prevalent in the subadventitial zone, but sometimes extended to involve the full thickness of the media. In the most extreme cases medial smooth muscle cells ran parallel to the long axis of the vessel and were segregated into small bundles and single cells separated by collagen which merged with the adventitial fibrosis. The intima was always normal. Abnormal arteries were present in 16% of 603 consecutive biopsies from 44 patients, and 39% of lesions occurred in 16% of patients. No lesions were found in endomyocardial biopsies from 25 non-transplanted patients, nor in mucosal biopsies from both transplanted and non-transplanted patients, confirming that the appearances were not due to biopsy artefact. There was early arterial remodelling in biopsies within two weeks of transplantation and none of the stages resembled vascular rejection. Fifty per cent of biopsies from some patients contained arterial lesions, suggesting that in susceptible patients they are common.

Adult↗
PubMed1995

Ventilatory and gas exchange abnormalities on exercise in chronic heart failure.

The mechanism of breathlessness on exertion in patients with chronic heart failure are still not fully understood. We therefore investigated the effects of ventilatory and gas exchange abnormalities on exercise capacity in chronic heart failure. Exercise testing was performed in 30 patients with exertional breathlessness due to chronic heart failure and in 30 controls, using continuous transcutaneous blood gas monitoring. Maximal symptom-limited oxygen consumption as (V'O2) as a percentage predicted was reduced in patients (45 +/- 10%; mean +/- SD) compared to controls (87 +/- 7). The ventilatory response (minute ventilation/carbon dioxide production (V'E/V'CO2)) was significantly increased in patients compared to controls (39.9 +/- 7.7 and 25.9 +/- 3.6, respectively). The dead space to tidal volume ratio (VD/VT) was raised in patients compared to controls at rest (0.45 +/- 0.04 vs 0.35 +/- 0.02, respectively) and this persisted on exertion (0.40 +/- 0.05 in patients and 0.20 +/- 0.05 in controls). At maximal symptom-limited exercise, V'E/V'CO2 was inversely related to the % predicted V'O2 in patients, but not in controls (r = -0.62 and r = -0.24, respectively). In patients, V'E/V'CO2 was significantly correlated with VD/VT at maximum exercise (r = 0.82). Patients with chronic heart failure have a significant degree of "wasted ventilation" on exertion, which is associated with increased ventilatory response. The increased ventilatory response on exertion appears to contribute to exercise limitation in these patients.

Adult↗
PubMed1994

Heart transplantation: initial results in Scotland.

Between 1st Jan 1992 and 1st Sept 1993 164 patients were referred as candidates for heart transplantation in Scotland. 79 were accepted for transplantation and 39 of these received orthotopic heart transplants. 30 day mortality was zero. Mean time on intensive care post operatively was 46.35 hrs and mean time to hospital discharge was 17.03 days. Cumulative actuarial survival (survival at 18 months post operatively) was 87%. There were three deaths, two from infection at six and 19 weeks and one from neoplasia at 37 weeks. Mean time to rejection was 38.54 days. Linear rejection rates at 0-3, 3-6, 6-9, 9-12, 12-15 and 15-18 months were 1.86, 0.94, 0.6, 0.04, 0 and 0 events per 100 pt-days respectively. Linear infection rates at 0-3, 3-6, 6-9, 9-12, 12-15 and 15-18 months were 1.81, 0.17, 0.1, 0, 0.05 and 0.18 events per 100 pt-days respectively. The heart transplant programme in Scotland has been successful in terms of operative mortality and short to medium term survival.

Female↗
PubMed1992

Early results of direct repair of aortic interruption by the lateral approach.

Eleven consecutive patients were operated on for interruption of the aortic arch by direct aortoplasty through a lateral approach. Median age was 5 days and median weight, 3.52 kg. All received prostaglandin E. Four of the 11 required preoperative ventilatory and inotropic support. Diagnosis was by echocardiography with one confirmed by angiography. There were five type B and six type A interruptions. Aortic continuity was achieved through a left thoracotomy. The aorta and great vessels were mobilized, and after clamps were placed above and below the interruption, ductal tissue was excised and direct anastomosis performed. There was one death from sepsis. One patient died of pulmonary hypertension early after the second operation for correction of other anomalies, and 1 died of hypoplastic lungs after 6 months of ventilation. In 10 of the 11 patients there was no postoperative gradient. Palliative staged approach for correction of this malformation is advocated. The need for bypass and profound hypothermia is removed. This approach restores aortic continuity without sacrifice of the major vessels, use of ductal tissue, or use of prosthetic grafts that will necessitate reoperation.

Aorta, Thoracic↗
PubMed1990

Dissection of the left main coronary artery: diagnosis by angioscopy.

A 58-year-old woman with mitral valve disease was investigated with cardiac catheterization. At catheterization, a suspected dissection of the left main coronary artery occurred. This diagnosis was confirmed at urgent operation by intraoperative angioscopy. The patient underwent mitral valve replacement and coronary artery bypass grafting and made a good postoperative recovery. Coronary angioscopy at operation provides a useful means of diagnosing pathology in the left main coronary artery.

Cineradiography↗