Non-Invasive Cardiovascular Imaging in the Assessment of Coronary Microvascular and Myocardial Dysfunction

Christian Hamilton-Craig (2011). Non-Invasive Cardiovascular Imaging in the Assessment of Coronary Microvascular and Myocardial Dysfunction PhD Thesis, School of Medicine, The University of Queensland.

Attached Files (Some files may be inaccessible until you login with your UQ eSpace credentials)
Name Description MIMEType Size Downloads
s41556201_phd_final.pdf phd thesis final application/pdf 4.90MB 16
Author Christian Hamilton-Craig
Thesis Title Non-Invasive Cardiovascular Imaging in the Assessment of Coronary Microvascular and Myocardial Dysfunction
School, Centre or Institute School of Medicine
Institution The University of Queensland
Publication date 2011-08
Thesis type PhD Thesis
Supervisor Malcolm West
Richard Slaughter
Total pages 261
Total colour pages 20
Total black and white pages 241
Language eng
Subjects 110201 Cardiology (incl. Cardiovascular Diseases)
110320 Radiology and Organ Imaging
Abstract/Summary Cardiovascular imaging for the non-invasive diagnosis of myocardial disease is undergoing rapid change, with development of new technologies and applications. There is little comparative data about the use of these techniques in various cardiovascular conditions. This thesis explores the use of new techniques in non-invasive cardiac imaging (echocardiography, cardiac CT, and cardiovascular magnetic resonance) in the assessment of myocardial and microvascular disease, with a focus on clinically relevant studies. Contrast echocardiography in Australian clinical practice: Data were prospectively collected for all microsphere contrast echocardiography cases (n = 161) performed at the Prince Charles Hospital, Brisbane, between August 2007–June 2008. There was statistically significant improvement in endocardial definition scores after contrast administration (p = .0001), and reduction in inter-observer variability of wall motion assessment. These results reflect previously published data and indicate that contrast echocardiography is feasible in Australian clinical practice. Contrast transesophogeal echocardiography (TEE) compared to contrast-enhanced cardiac MRI (CMR) for the diagnosis of patent foramen ovale (PFO): Twenty-five patients (50 ± 13 years, 16 males) with cryptogenic ischemic stroke underwent contrast-enhanced TEE and contrast CMR for detection of possible PFO. When compared to TEE, CMR had a sensitivity of 50%, specificity 100%, negative predictive value 31%, positive predictive value 100%. These data suggest that TEE remains the cornerstone imaging diagnostic test to detect and characterise PFO in patients with ischemic cryptogenic stroke, and is superior current CMR sequences. Reversible microvascular dysfunction in the Tako-tsubo cardiomyopathy (TTC) demonstrated by myocardial contrast echocardiography: Fifteen Tako-tsubo patients (all women, 68 ± 14 years) underwent myocardial contrast echocardiography at baseline, during adenosine infusion (140 μg/kg/min) and at 1 month, and were compared with a group of anterior ST-elevation myocardial infarction (STEMI) patients with similar clinical characteristics (61 ± 11 years). In TTC subjects, as opposed to STEMI subjects, perfusion defects in the acute phase were transiently reduced by adenosine. At 1 month, markers of microvascular dysfunction significantly decreased in TTC subjects compared with baseline (P < .001 vs. baseline for all parameters). There were no changes in STEMI subjects at 1 month. These data strongly suggest that in TTC, acute and reversible coronary microvascular vasoconstriction represents a common pathophysiological mechanism. CMR in the evaluation of Tako-tsubo cardiomyopathy: Data were retrospectively reviewed from 27 consecutive patients with confirmed Mayo Clinic criteria for TTC (clinical, ECG, angiographic and left ventriculographic findings) presenting to our institution over a 2-year period. In this single-centre series, myocardial late gadolinium enhancement (LGE) was present in 41%, and occurred in a diffuse pattern through areas of myocardial stunning, 82% of which were >5SD above the signal in normal myocardium and was associated with worse myocardial injury. This likely represents diffuse myocyte damage. Absence of LGE should not, therefore, be used as a diagnostic criterion for TTC. Coronary microvascular function assessed by quantitative blush evaluator (QuBE); comparison with early cardiovascular magnetic resonance in patients with STEMI: Quantitative blush evaluator (QuBE) was compared with the gold standard CMR for the evaluation of microvascular obstruction (MVO) and its severity in patients with STEMI. Fifty-two STEMI subjects (60.1 ± 10.1 years, 35% male) treated with successful primary-percutaneous intervention were enrolled.There was a high correlation between QuBE and quantitative CMR indices of MVO severity. These data suggest that QuBE evaluation of myocardial blush after STEMI accurately risk-stratifies patients, provides useful prognostic information, and better informs decisions, such as the selection of patients requiring further imaging. Are endothelial progenitor cells (EPC) mobilised by myocardial ischemia or myocardial necrosis? EPC are bone marrow-derived elements with reparative properties known to be mobilised in the context of acute coronary syndromes. Fifteen STEMI patients (60.2 ± 7.8 years, 93% male) underwent EPC quantification by flow cytometry and evaluation of myocardial salvage by CMR. EPC were defined as CD34+/CD45-/KDR+ cells. EPC levels were positively correlated with the extent of area-at-risk (rho: 0.72, p: 0.002). These data suggest that EPC are mobilised in STEMI patients in proportion to the total myocardial ischemic insult, as represented by the area-at-risk on T2-weighted CMR, in a possible attempt to overcome ongoing microvascular dysfunction. Comparison of semi-quantitative and quantitative measures of infarct size and MVO by CMR: Visual scoring of infarct size and MVO was compared to quantitative computed volumetric assessment using dedicated software. 1344 myocardial segments were analysed in 84 patients who underwent CMR with LGE. The semi-quantitative visual scores accurately predicted infarct size and degree of MVO (r = .96) when compared to volumetric quantitative methods, with similar reproducibility. CMR and cardiac computed tomography (CCTA) in the assessment of heart failure: The hypothesis was tested that performing both CCTA and CMR in patients with new onset HF would non-invasively provide optimal anatomical and functional assessment. 426 coronary segmentsfrom 28 prospectively enrolled patients (38–77 years, 43% female) were analysed, and the diagnostic accuracy of CCTA, CMR and a combined strategy was compared to standard-of-care. CCTA with CMR provided an accurate, non-invasive assessment of the presence and degree of coronary disease, as well as the severity and aetiology of myocardial dysfunction. Myocardial viability by dual-energy delayed enhanced CCTA: A proof-of-concept study was designed to test the hypothesis that dual-energy delayed enhanced CCTA would visualise myocardial scar in a similar manner, and with similar resolution, to CMR. This documents the first use of a dual-energy delayed enhancement technique, which may provide a feasible alternative for myocardial viability assessment in patients with contraindications CMR. Further research will define the accuracy and reproducibility of this technique. Conclusion: Multi-modality cardiac imaging has changed the clinical practice of cardiology, with many choices available to the clinician and researcher. The studies in this thesis form a coherent theme for the exploration of novel cardiac imaging modalities, with a focus on myocardial and coronary microvascular dysfunction, allowing significant insights into how to choose the best test for the right reasons . These data have direct bearing on clinical decision-making.
Keyword cardiac imaging
Cardiovascular magnetic resonance
microvascular dysfunction
Additional Notes 14, 44, 45, 77, 78, 88, 91, 93, 115, 131,149, 156-7, 165, 189, 211-214, 218

Citation counts: Google Scholar Search Google Scholar
Created: Tue, 19 Jun 2012, 19:03:53 EST by Dr Christian Hamilton-craig on behalf of Library - Information Access Service