The successful clinical applicability of rotary left ventricular assist devices (LVADs) has led to research interest in devising a total artificial heart (TAH) using two rotary blood pumps (RBPs). The major challenge when using two separately controlled LVADs for TAH support is the difficulty in maintaining the balance between pulmonary and systemic blood flows. In this study, a starling-like controller (SLC) hybridized with an adaptive mechanism was developed for a dual rotary LVAD TAH. The incorporation of the adaptive mechanism was intended not only to minimize the risk of pulmonary congestion and atrial suction but also to match cardiac demand. A comparative assessment was performed between the proposed adaptive starling-like controller (A-SLC) and a conventional SLC as well as a constant speed controller. The performance of all controllers was evaluated by subjecting them to three simulated scenarios [rest, exercise, head up tilt (HUT)] using a mock circulation loop. The overall results showed that A-SLC was superior in matching pump flow to cardiac demand without causing hemodynamic instabilities. In contrast, improper flow regulation by the SLC resulted in pulmonary congestion during exercise. From resting supine to HUT, overpumping of the RBPs at fixed speed (FS) caused atrial suction, whereas implementation of SLC resulted in insufficient flow. The comparative study signified the potential of the proposed A-SLC for future TAH implementation particularly among outpatients, who are susceptible to variety of clinical scenarios.
For patient's receiving mechanical circulatory support, malfunction of the left ventricular assist device (LVADs) as well as mal-positioning of the cannula imposes serious threats to their life. It is therefore important to characterize the flow pattern and pressure distribution within the ventricle in the presence of an LVAD. In this paper, we present a 2D axisymmetric fluid structure interaction model of the passive left ventricle (LV) incorporating an LVAD cannula to simulate the effect of the LVAD cannula placement on the vortex dynamics. Results showed that larger recirculation area was formed at the cannula tip with increasing cannula insertion depth, and this is believed to reduce the risk of thrombus formation. Furthermore, we also simulated suction events (collapse of the LV) by closing the inlet. Vortex patterns were significantly altered under this condition, and the greatest LV wall displacement was observed at the part of the myocardium closest to the cannula tip.
We report a case of transient complete heart block with Stokes-Adams attack due to acute rheumatic fever. The patient was a 12-year old boy whose illness satisfied the criteria of acute rheumatic fever. A temporary transvenous cardiac pacer was necessary to tide him over the complete heart block. The rarity of this complication of acute rheumatic fever is highlighted.
The problems of pediatric cardiology in Asia can be summarized as follows. In the countries like India, Indonesia, Malaysia, Pakistan and some other countries especially with government support like Thailand, the priority is primary health care. Except in Japan, cardiac care for children is not well supported financially. Training in pediatric cardiology is not readily available. Consequently small numbers of pediatric cardiologists, pediatric cardiac surgeons and active centres are available even in Japan. It is importannt to reduce the incidence of rheumatic fever and rheumatic heart disease by prevention of streptococcal infections and to increase the standard of living and environment. Transportation and referral system diagnosis, and treatment and follow-up is a special problem in neonatal care in relation to heart disease. Concentration of physicians, medical schools and cardiac centers in urban areas, old customs and poor understanding of people about the treatability and preventability of heart diseases in children complicate the improvement in the management of children with heart diseases.
Chronic Heart Failure (CHF) is a debilitating illness commonly encountered in primary care. Its prevalence in developing countries is rising as a result of an ageing population, and an escalating epidemic of hypertension, type 2 diabetes and coronary heart disease. CHF can be specifically diagnosed as Heart Failure with Reduced Systolic Function (HF-RSF) or Heart Failure with Preserved Systolic Function (HF-PSF). This paper illustrates a common presentation of HF-PSF in primary care; and critically appraises the evidence in support of its diagnosis, prognosis and management. Regardless of the specific diagnosis, long term management of CHF is intricate as it involves a complex interplay between medical, psychosocial, and behavioural factors. Hence, there is a pressing need for a multidisciplinary team management of CHF in primary care, and this usually takes place within the broader context of an integrated chronic disease management programme. Primary care physicians are ideally suited to lead multidisciplinary teams to ensure better co-ordination, continuity and quality of care is delivered for patients with chronic conditions across time and settings. Given the rising epidemic of cardiovascular risk factors in the Malaysian population, preventive strategies at the primary care level are likely to offer the greatest promise for reducing the growing burden of CHF.
Infarct extension involves necrosis of healthy myocardium in the border zone (BZ), progressively enlarging the infarct zone (IZ) and recruiting the remote zone (RZ) into the BZ, eventually leading to heart failure. The mechanisms underlying infarct extension remain unclear, but myocyte stretching has been suggested as the most likely cause. Using human patient-specific left-ventricular (LV) numerical simulations established from cardiac magnetic resonance imaging (MRI) of myocardial infarction (MI) patients, the correlation between infarct extension and regional mechanics abnormality was investigated by analysing the fibre stress-strain loops (FSSLs). FSSL abnormality was characterised using the directional regional external work (DREW) index, which measures FSSL area and loop direction. Sensitivity studies were also performed to investigate the effect of infarct stiffness on regional myocardial mechanics and potential for infarct extension. We found that infarct extension was correlated to severely abnormal FSSL in the form of counter-clockwise loop at the RZ close to the infarct, as indicated by negative DREW values. In regions demonstrating negative DREW values, we observed substantial fibre stretching in the isovolumic relaxation (IVR) phase accompanied by a reduced rate of systolic shortening. Such stretching in IVR phase in part of the RZ was due to its inability to withstand the high LV pressure that was still present and possibly caused by regional myocardial stiffness inhomogeneity. Further analysis revealed that the occurrence of severely abnormal FSSL due to IVR fibre stretching near the RZ-BZ boundary was due to a large amount of surrounding infarcted tissue, or an excessively stiff IZ.