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Chapter 22 Safety-Critical Systems And Engineering Design: Cardiac And Blood-Related Devices
Published in B H Brown, R H Smallwood, D C Barber, P V Lawford, D R Hose, Medical Physics and Biomedical Engineering, 2017
Any defects in conduction of the cardiac impulse can cause a change in the normal sinus rhythm and this is called an arrhythmia. Heart block occurs when the conduction system between atria and ventricles fails. This will not usually stop the heart because other pacemaking areas of the ventricles will take over or, if the blockage is not complete, some impulses may get through from the atria, but the heart rate will fall. This is called bradycardia (slow heart rate) and it may mean that the heart cannot supply the body’s demands and so dizziness or loss of consciousness may occur.
Electrocardiogram
Published in Kayvan Najarian, Robert Splinter, Biomedical Signal and Image Processing, 2016
Kayvan Najarian, Robert Splinter
The A-V node can suffer several types of damages that are also referred to the heart block. The main five gradations of heart block that can be distinguished are as follows: first- and second-degree block, bundle-branch block, right-bundle-branch block (RBBB), and left-bundle-branch block (LBBB).
Baroreflex control model for cardiovascular system subjected to postural changes under normal and orthostatic conditions
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
V. L. Resmi, R. G. Sriya, N. Selvaganesan
The integrated block diagram of cardiovascular system and baroreflex control is shown in Figure 1. The red and blue arrows in Figure 1 indicate the flow of oxygenated blood and deoxygenated blood, respectively. The upper block represents cardiopulmonary system which includes the blood flow between heart and lungs. The middle block represents cardiovascular system which consists of heart and systemic vasculature. The heart block is characterized by contractility (c), heart rate (H) and stroke volume (Vstr). The vasculature is characterized by arterial and venous pressures (Pa, Pv), compliances (Cv, Ca) and peripheral resistance (R). The lower block represents baroreflex control which consists of baroreceptors, medulla oblongata and sympathetic and parasympathetic control. The baroreceptor takes MAP as the input and produces firing rates (n) which are given as information to the medulla oblongata. This produces chemical tones (Ts, Tp) which controls the heart and vascular characteristics.
Can we reduce conduction disturbances following transcatheter aortic valve replacement?
Published in Expert Review of Medical Devices, 2020
Alberto Alperi Garcia, Guillem Muntané-Carol, Lucia Junquera, David del Val, Laurent Faroux, François Philippon, Josep Rodés-Cabau
Although the need for PPI is recognized as the most impactful complication among conduction disturbances following TAVR, new-onset LBBB is even more frequent and should also be taken into consideration. New-onset persistent LBBB has a negative impact on left ventricular function [38] and associates with a less favorable cardiac reverse remodeling after TAVR demonstrated by cardiac magnetic resonance evaluation [39]. It also confers a greater risk of complete heart block (CHB) or high degree atrioventricular block (HAVB) leading to PPI, and has also been associated with higher rates of heart failure hospitalization, cardiovascular mortality, and all-cause mortality in a recent metanalysis evaluating more than 7000 patients with new-onset post-TAVR LBBB [36]. The rate of new-onset LBBB with earlier and newer generation valves has been of 32% (ranging from 4% to 65%) [40] and 16.4% (ranging from 5.8% to 23%), respectively [41,42].
Heart failure and right ventricular pacing – how to avoid the need for cardiac resynchronization therapy
Published in Expert Review of Medical Devices, 2019
Maria F. Paton, Klaus K. Witte
The principle issue facing implanters and their patients is that despite the adverse effects of RV pacing, many patients will not develop LVSD or HF as a consequence of long-term RV pacing, while others will develop it rapidly and follow a fulminant course [5]. The benefit of more complex approaches is likely to be limited to a subgroup of patients that must be identified prior to the initial procedure. Despite considerable investment, the features predicting preventable future clinical deterioration due to incident pacing-related LV dysfunction remain elusive although the presence of pre-existing cardiovascular co-morbidities increases the risk .Even the simplest clinical feature, complete heart block recorded indication is unreliable since at long-term follow-up a large proportion will not require high amounts of RV pacing (Figure 3) [76].