This study examined the early phase transplant coronary artery disease (TxCAD), as measured by the quantitative coronary angiography (QCA) mean lumen diameter loss (MLDL). A comparison was made between the large primary versus the smaller branch vessels. The relationship of different non-immunological and immunological factors to the development of TxCAD was examined, and we correlated the QCA data to that obtained from intracoronary ultrasound (ICUS). 121 patients who were transplanted between September 1994 and June 1999 were studied and followed up for a period of one to five years. 103 patients were males (85%) and the mean age was 48.5 10 years. We found that TxCAD was predominantly a disease of the large vessels, as evidenced by greater MLDL in the first years after transplant. The MLDL increased with time in both the large and small vessels and the greatest loss occurred in the first year. The first year MLDL was a predictor of long-term MLDL. The relative changes in lumen diameter measured by QCA and ICUS were similar. A low early left ventricular echocardiographic ejection fraction was related to greater MLDL in the large vessels as was donor male sex. Domino and non-domino hearts did not differ in the long-term MLDL. Total ischaemic time, RATG induction of immunosuppression, baseline vessel tone, acute rejection, CMV infection, total number of HLA mismatches and the first year mean antivimentin antibodies level, were not related to MLDL, nor was the baseline right and left heart catheter haemodynamic data. In conclusion, TxCAD as measured by QCA-MLDL was predominantly a disease of the large epicardial vessels and was predicted by a low early echocardiographic ejection fraction. Both QCA and ICUS could be used to assess TxCAD and their measurements were well correlated.

In this thesis high intensity focused ultrasound (HIFU) is utilized for myocardial ablation(thermal mode) and for the erosion of atherosclerotic plaque modelling(mechanical mode). These two applications were investigated in-vitro and in-vivo models. MRI was utilized to monitor the effects (thermal or mechanical) created by HIFU. The first application was tested in freshly excised lamb heart tissue, and in rabbit in-vivo. The second application (plaque erosion) was tested in cylindrical chalks and Hydroxyapatite-polyalactide(HA-PLA) composite in-vitro. In the thermal mode the aim was to evaluate a flat rectangular (3x10 mm2) MRI compatible transducer operating at 5.3 MHz. The main task was to explore the feasibility of creating deep lesions at a maximum 15 mm depth in myocardial tissue. The size of thermal necrosis in heart tissue was estimated as a function of power and time using a simulation model. The system was then tested in an excised lamb heart. In this thesis, we were able to create lesions of 15mm deep with acoustic power of 6W for an exposure of approximately one minute. The contrast to noise ratio (CNR) between lesion and heart tissue was evaluated using Fast Spin Echo (FSE). The CNR value was approximately 22 using T1W FSE. Maximum CNR was achieved with repetition time (TR) between 300 and 800 ms. Using T2W FSE, the corresponding CNR was approximately 13 for the 14 in-vivo experiments, The average lesion depth in the in-vivo experiments was 11.93 mm with a standard deviation of 0.62 mm. The size of the lesion in the other two dimensions was close to 3x10 mm2 (size of the transducer element). A feasibility study, was also carried out, in order to investigate the effectiveness of a therapeutic protocol in removing atherosclerotic plaque using pulsed HIFU(mechanical mode-cavitation). ln order to achieve this, the effect of various parameters such as intensity, Pulse- Repetition-Frequency(PRF.), Duty-Factor(DF), presence of bubbles and focal depth were explored. Various in-vitro experiments were carried out, mainly on cylindrical chalks. The efficiency of pulsed-cavitational HIFU was also investigated further, in-vitro during experiments on HA-PLA composite. The study showed that the size of the generated holes on chalks as expected increases with increased parameters being investigated ( i.e. intensity, power factor and duty factor). Duty factor was proven to be a critical parameter. An optimum value of the duty factor is approximately 10%. Lowest values of DF mean lost of the cavitation effect. The effect of HIFU in removing plaque was also verified using MRI images. As mentioned above, the effect of bubbles was also investigated. It is obvious, that with the presence of bubble . cavitation was enhanced achieving better penetration results on the chalks.The size of the holes generated on the chalks by the planar transducer in a plane parallel to the transducer face is slightly less(8.5x3 mm2) than the transducer area (10x3 mm2). Positive results were obtained in carrying out experiments on HA-PLA composites using both, spherical and planar transducers. In conclusion this research provides evidence which suggests that HIFU can be used as an alternative technique for the treatment of heart arrthythmias and for the erosion of atherosclerotic plaque.

No description available.

No description available.

No description available.

No description available.

No description available.

Cardiopulmonary Bypass (CPB) isolates the heart from the circulatory system. As a result, Coronary Artery Bypass Graft (CABG) surgery has become a common treatment for coronary artery disease (CAD) relieving angina and improving health related quality of life (HRQOL) and mood. However, CABG has been associated with Central Nervous System (CNS) dysfunction and successful surgery can be marred by cognitive impairment and/or poor HRQOL/ mood.

Intermittent antegrade warm blood cardioplegia (lAWBC) is a relatively new technique of myocardial protection we have little data regarding the use of magnesium (Mg²⁺) with this type of mayocardial protection strategy. Magnesium is cardioprotective and has been routinely used to supplement cardioplegic solutions in our unit during coronary artery bypass graft (CABG) surgery. However there is no consensus about the optimal Mg²⁺ concentration that should be used. We hypothesised the adding Mg²⁺ to IAWBC can improve clinical outcome in patients undergoing CABG surgery.

The critical care environment is a complex arena in which clinical judgements of the ventilated patients pain state are made over the course of their surgical trajectory. The presence of the critical care nurse at the bedside is the key to informed judgement in this unpredictable and fragile situation. This study sought to capture the judgement process of thirty critical care nurses in the context of the ventilated patient in pain in the immediate phase after cardiac surgery i.e. six-hours. Evidence of the judgement process was sought using the Lens Model as a framework, utilising the cognitive side of the model. Moreover, in order to capture this phenomenon of interest, the researcher observed the pain behaviours of thirty ventilated patients in the immediate phase post cardiac surgery. Within-methods triangulation was employed as an approach for justifying and underpinning knowledge by acquiring additional knowledge, which was seen as pertinent to this naturalistic case study. The data collection approach included think-aloud by thirty critical care nurses and simultaneous researcher observation over a six-hour period in the natural habitat of the ventilated patient post cardiac surgery. The findings give tentative support for the hypothesis that critical care nurses use a pattern of cues to make a judgement of ventilated patients' pain state in the immediate phase post cardiac surgery. Conversely, there was tentative support for the hypothesis that ventilated patients convey a pattern of cues to the critical care nurse in the immediate phase post cardiac surgery. Moreover, tentative conclusions are afforded which are as follows: a judgement structure is employed by critical care nurses which is comprised of two stages. The initial stage involves a pattern of physiological, behavioural general, covert behaviour, physical, overt motor pain behaviour, mechanical, technical, paraclinical, knowledge and pain descriptor cues. These aforesaid cues are utilised and integrated into a small number of intermediate judgements which operate as second order cues. Consequently the second order cues are combined in order to make a final judgement of the ventilated patient's pain state in the immediate phase post cardiac surgery: '(s)he is in acute pain' or '(s)he is not in acute pain'. In addition, critically ill ventilated patients convey a pattern of pain cues to the critical care nurses which comprises of physiological, behavioural general, overt motor pain behaviour cues, patient ventilator dysynchrony cues and verbal subjective pain behaviour cues. The pattern of cues conveyed by the ventilated patient may be influenced by many factors in an unpredictable and delicate surgical trajectory and chief among these factors is haemodynamic instability. The critical care nurse must make sense of all of this to gain access to the pattern of cues.