Heart walls

Purely electrical models of the heart are only a start. Combined electromechanical finite-element models of the heart take into account the close relationship that exists between the electrical and mechanical properties of individual heart cells. The mechanical operation of the heart is also influenced by the fluid-structure interactions between the blood and the blood vessels, heart walls, and valves. All of these interactions would need to be included in a complete description of heart contraction. 

Myocardium The middle and thickest layer of cardiac muscle in the heart wall. 

Ideally biomarkers of activity should be identified at various times over the course of the study to support the pharmacodynamic activity (e.g., normalization of insulin, improvement in beta cell function as measured by C-peptide level, or control of glucose following transplantation of P pancreatic islet cells) improvement of motor coordination in mice with spinal cord damage following transplant of neurons or repair of heart function (e.g., functional measures such as LV ejection fraction, pressure volume loops, ventricular pressure and heart wall thickness). Such markers may also be useful in subsequent clinical... 

Hypokinetic heart wall motion abnormalities and early signs of chronic cardiomyopathy have been identified as a significant toxic effect of mitoxantrone in patients who received cumulative doses of 32-174 mg (31). Electrocardiographic T wave inversion and cardiac complications have been described from intensive therapy with mitoxantrone 40 mg/m over 5 days and cyclophosphamide 1550 mg/m for 4 days, given before bone marrow transplantation for metastatic breast cancer. All the patients had had previous exposure to doxorubicin in cumulative doses that did not exceed 442 mg/m (19). 

There are three distinct types of muscle tissue in vertebrates striated, smooth, and cardiac. Striated, or skeletal, muscle is attached, at least at one end, to the skeleton via tendons. This muscle type is often referred to as the voluntary muscle, as it can be consciously controlled. Smooth muscle is usually arranged in sheets or layers in tubular systems, such as arteries and veins (see Blood Vessels), the gastrointestinal and respiratory tracts, and the genitourinary tracts. The activities of the smooth muscles are not under conscious control rather they are coordinated by the autonomic (involuntary) nervous system. The cardiac muscle comprises the bulk of the heart wall proper and small amounts are found in the superior vena cava and pulmonary vein. The cardiac muscle is not under conscious control it has an automaticity center which responds to the autonomic nervous system when needed (see section Impulse Conduction). In the heart, cardiac muscle cells are joined in a network of fibers and are connected by gap junctions, which facilitate the conduction of electrical impulses through the cardiac muscle network. In addition to the typical cardiac myocytes, there are other cardiac muscle cells that are specialized to initiate, attenuate, or accelerate the electrical impulses for coordinated contraction of the cardiac network. 

The surface electrocardiography (ECG) in both acute and chronic phase of ischaemic heart disease (IHD) may give crucial information about the coronary artery involved and which is the area of myocardium that is at risk or already infarcted. This information jointly with the ECG-clinical correlation is very important for prognosis and risk stratification, as will be demonstrated in this book. Therefore, we will give in the following pages an overview of the anatomy of the heart, especially the heart walls and coronary tree, and emphasise the best techniques currently used for its study. 

The heart walls and their segmentation cardiac magnetic resonance (Figures 1.4-1.14)... 

In order to clarify the terminology of the heart walls, a committee appointed by ISHNE (International Society Holter Non-invasive Electrocardiography) has made the following recommendations (Bayes de Luna et al, 2006c) ... 

The perfusion of the heart walls and specific conduction system... 

LV is cone shaped, and, as a consequence, the four heart walls present well-defined borders at the base of the heart. However, these borders become less clear as the walls approach the apex, such that it is difficult to be sure if the infarction limited to apical area involves one or other walls. Furthermore, CMR shows that the inferobasal segment of inferior wall often does not bend upwards (Figure 1.13) thus, very fre quently all the inferior walls present the same horizontal or near-horizontal inclination. 

Axel L and Dougherty L 1989 Heart wall motion—improved method of spatial modulation of magnetization for MR imaging Radiology 72 349-50... 

Fig 1 19 Noncoated defibrillation electrodes (a) in this type of lead, coils are loose, and the extraction procedure can be more difficult. Histological cross-section of an implanted cardioverter-defibrillator (ICD) lead at the level of the bare shock coils in the heart (b). Fibrous tissue ingrowth in interstices between coils arrows), which fixes the ICD lead to the heart wall (from [13], and courtesy of St. Jude Medical)... 

I cm from the heart wall. An outer sheath is used as a workstation and for counterpressure and countertraction. The lead is then removed from the heart wall using countertraction. 

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