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Electrocardiogram
Published in Kayvan Najarian, Robert Splinter, Biomedical Signal and Image Processing, 2016
Kayvan Najarian, Robert Splinter
As can be seen in Figure 9.1, the heart has four chambers: two atria and two ventricles. The atria work in unison and so do the ventricles. The atrium is separated from the venous system by a valve so that flow is only possible in one direction. The superior vena cava and the inferior vena cava lead into the right atrium in combination with the coronary sinus, while the pulmonary veins supply the left atrium. When the atrium contracts, it pumps the retained blood into the ventricle that is separated by a valve as well. The valve only allows flow from the atrium to the ventricle and not in the opposite direction. This valve is called the atrioventricular valve. The atrioventricular valve between the right atrium and the right ventricle is also called the tricuspid valve because of the three-leaf structure. The left atrium and left ventricle have the bicuspid valve, or mitral valve, that separates the two chambers.
Cardiovascular system
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
Blood circulates through the normal heart from the coronary sinus, inferior vena cava and superior vena cava into the right atrium and through the tricuspid valve into the right ventricle. It then passes via the pulmonary valve into the pulmonary artery and on to the lungs. Blood returns to the heart via the right and left pulmonary veins into the left atrium and then through the mitral valve into the left ventricle, where it passes through the aortic valve into the aorta. The blood supply to the cardiac muscle (myocardium) is by the right and left coronary arteries that arise from the aortic sinuses just above the aortic valve (Figs 9.2a–c).
Troubleshooting the difficult left ventricular lead placement in cardiac resynchronization therapy: current status and future perspectives
Published in Expert Review of Medical Devices, 2022
Jens Brock Johansen, Jens Cosedis Nielsen, Jens Kristensen, Niels CF Sandgaard
Cardiac implantable electronic devices (CIEDs) are an established treatment for patients with a variety of cardiac arrhythmias. CIED includes cardiac resynchronization therapy (CRT), also known as biventricular pacing. CRT is an important therapeutic advancement in patients with heart failure, bundle branch block, and reduced ejection fraction [1]. The essence of CRT is biventricular pacing, which aims to resynchronize contraction of the ventricles by endocardial pacing of the right ventricle (RV) and epicardial pacing of the left ventricle (LV) using a pacing lead placed in a side branch of the coronary sinus (CS) [2]. CRT improves cardiac performance, reduces heart failure symptoms, and furthermore reduces mortality [3,4]. In the recent “ESC Guidelines on cardiac pacing and cardiac resynchronization therapy,” CRT is now established as a class I (A) indication in the left bundle branch block (LBBB) with a QRS duration > 150 ms in patients with sinus rhythm and a class II (A) indication in heart failure patients with a significant portion of RV pacing [5]. Despite this evidence, several studies reported that some patients experience a clinical deterioration after CRT implantation [6,7]. Even though guideline criteria for CRT have been met, no clinical improvement can be measured after CRT in up to 30–40% of the patients who are considered the so-called nonresponders [5,6,8].
Uses and potential for cardiac magnetic resonance imaging in patients with cardiac resynchronisation pacemakers
Published in Expert Review of Medical Devices, 2019
Cardiac resynchronization therapy (CRT) pacemakers are a routine adjunct to the treatment of patients with reduced ejection fraction heart failure and an associated conduction issue such as left bundle branch block (LBBB) [1]. Dyssynchrony is over-represented in the heart failure population (approximately 25%) and increases the 1-year mortality risk by 70% [3]. CRT devices cause pre-excitation within the left and right ventricles through leads placed at the right atrium, right ventricle and coronary sinus (left ventricle). This helps co-ordinate contraction precisely resulting in improved stroke volume and myocardial efficiency [4]. Following implantation, patients generally have increased exercise capacity with fewer symptoms, improved hemodynamics and reduced mortality [1,5,6]. CRT devices can also have a defibrillator fitted (CRT-D) conferring additional survival in selected populations such as patients with diabetes or an ischaemic etiology [7].
Amplatzer patent foramen ovale occluder: safety and efficacy
Published in Expert Review of Medical Devices, 2019
Raouf Madhkour, Andreas Wahl, Fabien Praz, Bernhard Meier
The choice of the device size should be made according to the thickness of the septum secundum (SS, cranial part of interatrial septum) as well as the presence and extent of an atrial septal aneurysm (ASA). The length of the PFO tunnel is of little importance. The SS is best seen by transesophageal echocardiography (TEE) using a short axis view cutting the aortic root. The long axis bicaval view (a misnomer as it shows the superior vena cava to the right and the coronary sinus to the left but not the inferior vena cava) can also be used. The 25 mm Amplatzer PFO Occluder fits PFOs without thick SS or ASA. In the presence of one or both of these features (about 10–20%), a larger device (preferably the 35 mm Amplatzer PFO Occluder, or a 30 mm Amplatzer Cribriform Occluder with twin 30 mm disks, initially designed for cribriform atrial septal defects) is recommended [14]. The presence of a long tunnel, a small exit hole, or an ASA remote from the PFO may obviate the need for a larger occluder.