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- Ramzy Guirguis, Ihab, 1963-
(författare)
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Insights into the effect of myocardial revascularisation on electrical and mechanical cardiac function
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Acute coronary syndrome is known for its effect on cardiac function and can lead to impaired segmental and even global myocardial function. Evidence exists that myocardial revascularisation whether pharmacological, interventional or surgical results in improvement of systolic and diastolic left ventricular (LV) function, particularly that of the long axis which represents the sub-endocardial function, known as the most sensitive layer to ischaemia. Objective: We sought to gain more insight into the early effect of pharmacological and interventional myocardial revascularisation on various aspects of cardiac function including endocrine, electrical, segmental, twist, right ventricular (RV) and left atrial (LA) function. In particular, we aimed to assess the response of ventricular electromechanical function to thrombolysis and its relationship with peptides levels. We also investigated the behaviour of RV function in the setting of LV inferior myocardial infarction (IMI) during the acute insult and early recovery. In addition, we aimed to assess in detail LA electrical and mechanical function in such patients. Finally, we studied the early effect of surgical revascularisation on the LV mechanics using the recent novel of speckle tracking echocardiography technology to assess rotation, twist and torsion and the strain deformation parameters as a tool of identifying global ventricular function. Methods: We used conventionally Doppler echocardiographic transthoracic techniques including M-mode, 2-Dimentional, myocardial tissue Doppler, and speckle tracking techniques. Commercially available SPSS as a software was used for statistical analysis. Results: 1-The elevated peptide levels at 7 days post-myocardial infarction correlated with the reduced mechanical activity of the adjacent non-infarcted segment thus making natriuretic peptides related to failure of compensatory hyperdynamic activity of the non-infarcted area rather than the injured myocardial segments. 2-RV segmental and global functions were impaired in acute IMI, and recovered in 87% of patients following thrombolysis. In the absence of clear evidence for RV infarction the disturbances in the remaining 13% may represent stunned myocardium with its known delayed recovery. 3-LA electromechanical function was impaired in acute inferior STEMI and improved after thrombolysis. The partial functional recovery suggests either reversible ischaemic pathology or a response to a non-compliant LV segment. The residual LA electromechanical and pump dysfunction suggest intrinsic pathology, likely to be ischaemic in origin. 4-LV function was maintained in a group of patients with multivessel coronary artery disease who underwent coronary artery bypass graft (CABG) surgery. Surgical myocardial revascularisation did not result in any early detectable change in the three functional components of the myocardium, including twist and torsion, as opposite to conventional percutaneous coronary intervention (PCI). Conclusion: The studied different materials in this thesis provide significant knowledge on various aspects of acute ischaemic cardiac pathology and early effect of revascularisation. The use of non-invasive imaging, particularly echocardiography with its different modalities, in studying such patients should offer immediate thorough bed-side assessment and assist in offering optimum management.
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| 2. |
- Marlevi, David
(författare)
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Non-invasive imaging for improved cardiovascular diagnostics : Shear wave elastography, relative pressure estimation, and tomographic reconstruction
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Throughout the last century, medical imaging has come to revolutionise the way we diagnose disease, and is today an indispensable part of virtually any clinical practice. In cardiovascular care imaging is extensively utilised, and the development of novel techniques promises refined diagnostic abilities: ultrasound elastography allows for constitutive tissue assessment, 4D flow magnetic resonance imaging (MRI) enables full-field flow mapping, and micro-Computed Tomography (CT) permits high-resolution imaging at pre-clinical level. However, following the complex nature of cardiovascular disease, refined methods are still very much needed to accurately utilise these techniques and to effectively isolate disease developments.The aim of this thesis has been to develop such methods for refined cardiovascular image diagnostics. In total eight studies conducted over three separate focus areas have been included: four on vascular shear wave elastography (SWE), three on non-invasive cardiovascular relative pressure estimations, and one on tomographic reconstruction for pre-clinical imaging.In Study I-IV, the accuracy and feasibility of vascular SWE was evaluated, with particular focus on refined carotid plaque characterisation. With confined arterial or plaque tissue restricting acoustic wave propagation, analysis of group and phase velocity was performed with SWE output validated against reference mechanical testing and imaging. The results indicate that geometrical confinement has a significant impact on SWE accuracy, however that a combined group and phase velocity approach can be utilised to identify vulnerable carotid plaque lesions in-vivo.In Study V-VII, a non-invasive method for the interrogation of relative pressure from imaged cardiovascular flow was developed. Using the concept of virtual work-energy, the method was applied to accurately assess relative pressures throughout complex, turbulence-inducing, branching vasculatures. The method was also applied on a dilated cardiomyopathy cohort, indicating arterial hemodynamic changes in cardiac disease.Lastly, in Study VIII a method for multigrid image reconstruction of tomographic data was developed, utilising domain splitting and operator masking to accurately reconstruct high-resolution regions-of-interests at a fraction of the computational cost of conventional full-resolution methods.Together, the eight studies have incorporated a range of different imaging modalities, developed methods for both constitutive and hemodynamic cardiovascular assessment, and utilised refined pre-clinical imaging, all with the same purpose: to refine current state cardiovascular imaging and to improve our ability to non-invasively assess cardiovascular disease. With promising results reached, the studies lay the foundation for continued clinical investigations, advancing the presented methods and maturing their usage for an improved future cardiovascular care.
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| 3. |
- Henein, Mark, 1960-
(författare)
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Left atrial function in health and disease
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Objectives of this thesis are:1) To study possible atrial interaction in patients with right and left ventricular outflow tract obstruction due to significant pulmonary (PS) and aortic valve stenosis (AS), respectively.2) To assess left atrial (LA) intrinsic myocardial function and its relationship to indirect measures of left ventricular (LV) filling pressures in patients with paroxysmal atrial fibrillation (PAF).3) To test the hypothesis that the LA function is affected in patients with pulmonary arterial hypertension (PAH).4) To test the hypothesis that raised LA pressure as shown by pulmonary capillary wedge pressure (PCWP) correlates with severity of LA intrinsic systolic function.We conducted 4 studies to achieve the objective sabove.Study IMethods:We studied 41 PS patients (age 36±10 year) and 41 AS patients (age 35 ± 12 year) and compared them with 27 controls (age 30 ± 7 year). RV and LV filling were recorded by conventional PW Doppler. Biventricular segmental function was studied using the PW tissue Doppler imaging (TDI) and M mode techniques.Results:The 2 patient groups had similar degree of ventricular outflow tract obstruction. In the pressureoverloaded ventricle, global systolic function was preserved but long axis function was impaired.Patients had higher peak late filling (Awave)and TDI late diastolic (a’) velocities recorded in the disease free ventricles despite having similar peak early filling velocities (E wave), E wave deceleration time and E/e’ ratios were not different from controls (p>0.05 for all). The accentuation of atrial activity (A wave) was moderately correlated with the degree of contra lateral ventricular outflow tract obstruction (p<0.001 for both).Conclusion:In the pressure overloaded ventricle long axis function is more sensitive than global function in revealing myocardial dysfunction. The increased contra lateral atrial systolic activity suggests an evidence for atrial interaction in the form of ‘Cross Talk’.Study IIMethods:Twentyfive PAF patients (age 68±7 year, 10 males) with Doppler signs of raised filling pressures were studied using speckle tracking echocardiography and compared with 21 controls. LA segmental longitudinal strain (S), strain rate (SR) and myocardial velocities during atrial systole were measured as were LA longitudinal and transverse diameters. Markers of LV filling pressures were E/A andE/e’.Results:LA longitudinal diameter was larger in patients (5.5±0.6 vs. 4.8±0.6cm,p<0.01) and global LAS and SR were reduced (p<0.05 for both) and correlated with E/A (r=0.52 and r=0.43, p<0.05 for both). LA segmental S and SR were uniformly reduced compared with controls (p<0.05 for all) and also correlated with E/A (p<0.05 for all). LA myocardial velocities (TDI) were highest at the annular level and lowest at the rear in both patients and controls (p<0.01 for all), with the absolute values at each level not different between groups. Myocardial velocities negatively correlated with E/A at the annular level only in patients (septal: r=0.52; lateral: r=0.62, p<0.01 for both).Conclusion:In PAF patients, LA systolic function is suppressed and is directly related to the raised filling pressures. While intrinsic global and segmental function can reproducibly be studied by S and SR, myocardial velocities reflect only regional motion. These findings provide a sound explanation to the known beneficial effect of vasodilators in PAF patients.Study IIIMethods:We studied LA size and reservoir function in 35 patients (age 63 ± 15 years, 16 male) with idiopathic PAH using speckle tracking echocardiography who also underwent right heart catheterization simultaneously to assess pulmonary artery systolic pressure, and compared them with 27 age and gender normal controls.Results:In PAH patients, LA longitudinal diameter was not different from controls but transverse diameter was reduced (3.0 ± 0.6 vs. 3.7 ± 0.5cm, p<0.001). LA lateral wall strain rate (SR) during LV systole (atrial reservoir function was reduced at annular (p<0.001) and mid cavity (p<0.01) levels as were septal segments (p<0.03, for both) compared to controls. Opposite to controls, the two LA walls responded differently to right heart pressures. Lateral SR inversely correlated with pulmonary artery systolic pressure (PASP) (annular: r=0.45, p<0.005 and midcavity: r=0.43, p<0.01), but not with right atrial pressure (RAP). In contrast, septal SR inversely correlated with RAP (annular: r=0.39, p=0.02 and midcavity: r=0.38, p=0.03) but not with PASP.Conclusion:In patients with PAH, LA reservoir function is significantly impaired showing reduced myocardial strain rate properties. In addition,segmental function differs in their response to raised right heart pressures with the septal wall related to right atrial pressure and lateral wall related to the PASP. These findings suggest an evidence for atrial interaction in PAH, which is likely to have significant impact on LV performance.Study IVMethods:We studied 46 patients, mean age 61 ± 13 years, 17 males, of various etiologies with exertional breathlessness who underwent right heart catheterization and simultaneous transthoracic Doppler echocardiography using spectral, tissue Doppler and speckle tracking echocardiography techniques for assessing LA structure and function.Results:PCWP correlated with direct measurements of LA structure and function: LA volume (r= 0.43, p<0.01), LA global systolic strain rate (r=0.79, p<0.001) and to a lesser extent with LA systolic filling fraction (r=0.52, p<0.001). PCWP also correlated with indirect measures of LA pressure: LV E/A (r=0.66, p<0.001), E wave deceleration time (r=0.54, p<0.001), lateral E/e’ (r=0.49, p<0.001) and LV isovolumic relaxation time (r=0.36, p<0.01). LA strain rate was 78% sensitive and 84% specific in identifying patients with PCWP>15 mmHg, having accurately predicted PCWP in 63% of the cases.Conclusion:PCWP correlates with LA intrinsic systolic function and to a much lesser degree with indirect Doppler measures of raised LV filling pressures. These findings should have significant clinical implications in identifying breathless patients with raised LA pressure.
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