Displaying all 3 publications

  1. Chan BT, Yeoh HK, Liew YM, Aziz YFA, Sridhar GS, Hamilton-Craig C, et al.
    Med Biol Eng Comput, 2017 Oct;55(10):1883-1893.
    PMID: 28321684 DOI: 10.1007/s11517-017-1639-5
    This study aims to investigate the measurement of left ventricular flow propagation velocity, V p, using phase contrast magnetic resonance imaging and to assess the discrepancies resulting from inflow jet direction and individual left ventricular size. Three V p measuring techniques, namely non-adaptive (NA), adaptive positions (AP) and adaptive vectors (AV) method, were suggested and compared. We performed the comparison on nine healthy volunteers and nine post-infarct patients at four measurement positions, respectively, at one-third, one-half, two-thirds and the conventional 4 cm distances from the mitral valve leaflet into the left ventricle. We found that the V p measurement was affected by both the inflow jet direction and measurement positions. Both NA and AP methods overestimated V p, especially in dilated left ventricles, while the AV method showed the strongest correlation with the isovolumic relaxation myocardial strain rate (r = 0.53, p 
    Matched MeSH terms: Diastole/physiology
  2. Leong CN, Dokos S, Andriyana A, Liew YM, Chan BT, Abdul Aziz YF, et al.
    Int J Numer Method Biomed Eng, 2020 01;36(1):e3291.
    PMID: 31799767 DOI: 10.1002/cnm.3291
    Myocardial infarct extension, a process involving the enlargement of infarct and border zone, leads to progressive degeneration of left ventricular (LV) function and eventually gives rise to heart failure. Despite carrying a high risk, the causation of infarct extension is still a subject of much speculation. In this study, patient-specific LV models were developed to investigate the correlation between infarct extension and impaired regional mechanics. Subsequently, sensitivity analysis was performed to examine the causal factors responsible for the impaired regional mechanics observed in regions surrounding the infarct and border zone. From our simulations, fibre strain, fibre stress and fibre stress-strain loop (FSSL) were the key biomechanical variables affected in these regions. Among these variables, only FSSL was correlated with infarct extension, as reflected in its work density dissipation (WDD) index value, with high WDD indices recorded at regions with infarct extension. Impaired FSSL is caused by inadequate contraction force generation during the isovolumic contraction and ejection phases. Our further analysis revealed that the inadequacy in contraction force generation is not necessarily due to impaired myocardial intrinsic contractility, but at least in part, due to inadequate muscle fibre stretch at end-diastole, which depresses the ability of myocardium to generate adequate contraction force in the subsequent systole (according to the Frank-Starling law). Moreover, an excessively stiff infarct may cause its neighbouring myocardium to be understretched at end-diastole, subsequently depressing the systolic contractile force of the neighbouring myocardium, which was found to be correlated with infarct extension.
    Matched MeSH terms: Diastole/physiology*
  3. Raman P, Suliman NB, Zahari M, Kook M, Ramli N
    Eye (Lond), 2018 07;32(7):1183-1189.
    PMID: 29491486 DOI: 10.1038/s41433-018-0057-8
    OBJECTIVE: To assess the relationship between baseline intraocular pressure (IOP), blood pressure (BP) and ocular perfusion pressure (OPP), and the 5-year visual field progression in normal-tension glaucoma (NTG) patients.

    DESIGN: Prospective, longitudinal study.

    METHODS: Sixty-five NTG patients who were followed up for 5 years are included in this study. All the enrolled patients underwent baseline 24-h IOP and BP monitoring via 2-hourly measurements in their habitual position and were followed up for over 5 years with reliable VF tests. Modified Anderson criteria were used to assess VF progression. Univariable and multivariable analyses using Cox's proportional hazards model were used to identify the systemic and clinical risk factors that predict progression. Kaplan-Meier survival analyses were used to compare the time elapsed to confirmed VF progression in the presence or absence of each potential risk factor.

    RESULTS: At 5-year follow-up, 35.4% of the enrolled patients demonstrated visual field progression. There were statistically significant differences in the mean diastolic blood pressure (p  43.7 mmHg (log rank = 0.018).

    CONCLUSION: Diastolic parameters of BP and OPP were significantly lower in the NTG patients who progressed after 5 years. Low nocturnal DOPP is an independent predictor of glaucomatous visual field progression in NTG patients.

    Matched MeSH terms: Diastole/physiology*
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