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(2017)ThesisAbstract Aims: Assessment of the differences in diagnostic performance and radiation dose between Adaptive Statistical Iterative Reconstruction (ASIR) and High Definition (HD) CT coronary angiography (CTCA) compared with Filtered Back Projection (FBP) and Standard Definition (SD) CTCA using invasive coronary angiography as a reference standard. Methods: Data from 2069 consecutive patients undergoing CTCA was collected over a period of 2 years. A total of 30 patients were separately enrolled if they had a significant stenosis and underwent invasive coronary angiogram within 3 months. All 30 patients were scanned in high definition and then had 5 reconstructions performed using SD0%ASIR, SD50%ASIR, SD70%ASIR, HD50%ASIR and HD70% ASIR. Results: Median and total (including CACS) angiographic radiation dose for 2069 patients was 2.1 mSv and 2.7 mSv respectively. Determinants of radiation dose on multivariate regression analysis were scan voltage, tube current, padding, scan length and heart rate. The mean difference in adjusted angiographic radiation dose using ANCOVA between the ASIR cohort (n=624, mean 2.2 mSv) and FBP (n=572, mean 2.29 mSv) was 0.09 mSv (P 0.0008). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and Area under the curve (AUC) values using Receiver Operator Characteristic (ROC) curves on an intention to diagnose analysis were highest for the reconstruction HD with 70% ASIR at 94%, 89%, 75%, 98% and 0.93 for a >50% obstructive stenosis threshold on a per artery basis; and 88%, 88%, 64%, 97% and 0.91 for a >70% stenosis on a per artery basis; 100%, 67%, 96%, 100% and 0.83 for a >50% stenosis on a per patient basis; and 95%, 67%, 87%, 86% and 0.81 for a >70% stenosis on a per patient basis. The greatest benefit for HD with 70% ASIR was in patient subgroups of CACS>200, BMI>25 and stented arteries with AUC values of 0.93, 0.89 and 0.83 respectively. Conclusions: ASIR resulted in a lower adjusted angiographic radiation dose than FBP although the reduction of 4.2% was less than that observed in other studies due to the tube current reduction with ASIR scans being smaller in our study. HD with 70% ASIR reconstruction demonstrated the most robust diagnostic performance with higher specificity, PPV and AUC values than all other reconstructions due to a lower false positive rate. These benefits were the most pronounced in patients with a CACS>200, BMI>25 and stented arteries.
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(2015)ThesisAbstract 350 words maximum: (PLEASE TYPE) Background Indications for cardiac implantable electronic devices (CIED’s) continue to expand. Increases in the number of devices implanted have resulted in an increased incidence of complications. These complications sometime require extraction of CIED leads for definitive treatment. I explore the indications, complications, microbiology and success rates involved with lead extraction in a high volume centre over a 20 year period. I also report long term follow up of these patients including mortality, recurrent device infection and need for repeat procedures Methods and Results Retrospective analysis was reported of all consecutive patients undergoing lead extraction between 1992 and 2012. 1006 leads were extracted from 510 patients. The clinical success rate was 98.2% and complete procedural success rate was 92.2%. There was one intra-procedural death. Infection was the only identified predictor of increased complication (χ² for difference between groups 20, P < 0.0001). The mean follow up was 5.5+/-4.9 years (range 0.2 – 18 years). Cumulative mortality was 10.0% at 1 year and 33.0% at 10 years. Factors associated with increased long term mortality included cardiac device infection (CDI) (33% vs 17% for non-CDI; χ² 13.8, P = 0.0003), procedural complications (43% vs 27% for no complications; χ² 4.2, P = 0.04), age (75.0 +/- 10.9 years in patients who died vs 62.7 +/- 17.2 years, P < 0.0001) and impaired renal function (Creatinine 142.5 +/- 106.4 umol/L in patients who died vs 106.3 +/- 90.7 umol/L, P = 0.001). There was comparable mortality in those patients who did not have a replacement device after transvenous lead extraction (TLE) compared with a replacement (27 % vs 24 %, P = 0.72). The rate of CDI after TLE was 3.9 % (mean 11.6 months post extraction, range 0.3 to 84 months) and is higher in patients with retained lead fragments (13.5% vs 3.0% % with complete removal; χ² 10.7 P = 0.001). Conclusion Pacing and ICD leads can be safely extracted with mechanical techniques. Long term mortality following TLE is high particularly in those with systemic infection, procedural complications, advanced age and renal impairment. Device therapy can be safely withdrawn in some patients. Finally; retained fragments are a risk factor for CDI post extraction.
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(2021)ThesisBackground: Cervical spine degenerative conditions effect up to two-thirds of the population and are the most common cause of acquired disability in patients over the age of 50. These disorders commonly present with axial pain, myelopathy, radiculopathy or a combination of these symptoms. Surgical intervention is generally indicated in with failure of conservative management or with evidence of cord compression or myelopathy. Anterior cervical discectomy and fusion (ACDF) is an effective option. It is not well established what factors contribute to dysphagia and recurrent laryngeal nerve palsy complications following ACDF surgery. Objective: 1. To determine the rates of dysphagia and recurrent laryngeal nerve complications following ACDF reported in the literature and potential associated factors. 2. To determine rates of dysphagia and recurrent laryngeal nerve injuries in a large Australian series of ACDF by a single surgeon. Methods: For the systematic reviews, electronic searches were performed using electronic databases. Relevant studies reporting the rate of dysphagia or recurrent laryngeal nerve injury as an endpoint for patients undergoing ACDF for degenerative disease, myelopathy, cervical canal stenosis or ossification of the posterior longitudinal ligament were identified according to prior inclusion and exclusion criteria. Statistical analysis was performed using odds ratio (OR) as the effective size. I2 was used to explore heterogeneity. For the retrospective chart review, consecutive patients undergoing ACDF from 2015 to 2019 for cervical radiculopathy and/or myelopathy were included. Univariate logistic regression analysis was performed to identify risk factors of RLN palsy, swallowing problems and adjacent-level ossification disease (ALOD). Results and conclusions: We found that based on pooled analysis that there was a higher rate of dysphagia for multiple-level ACDF (6.6%) compared with single-level ACDF (4%). The pooled incidence of recurrent laryngeal nerve palsy from the literature was 1.2%, with no difference between multiple- and single-level ACDF. These rates were similar to analysis of our retrospective series, with 1.8% patients having recurrent laryngeal nerve palsy and 4.0% with clinical dysphagia. We confirm based on our series that multi-level operation was associated with higher rate of RLN palsy, but this was not affected by other factors including age, gender, and the use of plate, internal fixation or number of screws.
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(2022)ThesisBackground: Anterior lumbar interbody fusion (ALIF) remains one of the mainstay surgical approaches in treating painful degenerative disc disease with or without segmental instability in the lower spine. The risk factors and complication profile for ALIF differs significantly from other established fusion techniques. Objectives: The goal of the first part of this thesis is to establish the factors associated with long-term clinical outcome (Chapter 2) and short-term perioperative outcomes (Chapter 3) following ALIF. Chapter 4 focuses on the long-term radiographic evidence for biomaterial alternatives for ALIF implants, namely titanium (Ti)-coated PEEK integrated cages. Methods and Results: From a prospective cohort analysis of 147 patients undergoing ALIF, elderly age (≥64 years old) was associated with an increased rate of subsidence but does not affect clinical outcomes. Obesity was not associated with postoperative complications or follow-up patient-reported outcomes. Failed fusion was significantly higher for smokers, and they were significantly more likely than non-smokers to experience postoperative complications such as pseudoarthrosis. To assess risk factors for perioperative complications and readmissions after ALIF, the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database was analysed. ALIF was associated with prolonged length of stay and higher rate of return to operating theatre compared to posterior lumbar fusion. Obesity and alcohol intake increased the risk of 30-day readmissions. Discharge to non-home destination following ALIF was independently associated with wound complications and venous thromboembolism. Finally, a prospective follow-up study was performed to determine the long-term radiographic outcome following ALIF using Ti-coated PEEK cages with allograft and INFUSE. Effective fusion was achieved at up to 24-month follow-up for various indications including degenerative spine/disc disease, low grade lumbar isthmic spondylolisthesis, spondylotic radiculopathy and discogenic low back pain. Conclusions: Collectively, this thesis highlights the importance of personalising the care of an ALIF surgery patient, through identification and optimization of individual risk factors for short-term and long-term outcomes, as well as through choice of implant biomaterial and design.
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