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Cardiovascular Disease
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
This occurs when intermittently the P wave is not followed by a QRS complex. The block to conduction occurs in the AV node and can be of two types: Mobitz type 1 (Wenckebach; Figure 7.21b): the PR interval increases with each beat until an atrial impulse is not conducted and then the PR interval returns to normal. This is usually physiological and due to high vagal tone.Mobitz type 2 (second-degree AV block; Figure 7.21c): the PR interval does not change, but the QRS complex fails to follow the P wave because of a regularly or intermittently occurring block, which is usually below the AV node in the bundle branches or bundle of His. If there are two P waves to one QRS complex, it is a 2 : 1 block; if there are three P waves to one QRS complex, it is a 3 : 1 block. The degree of block can vary. A pacemaker is usually indicated.
Deaths Following Cardiac Surgery and Invasive Interventions
Published in Mary N. Sheppard, Practical Cardiovascular Pathology, 2022
Complications from pacemaker implantation can be divided into immediate, intermediate and late-term complications. The rates of complications range from <1% to 6%. Immediate complications include pneumothorax, pericarditis, haemothorax, cardiac perforation, air embolism and lead dislodgement. Intermediate complications include haematomas around the pacer and infection with erosion through the skin, venous thrombosis or stenosis, pain or discomfort at the pocket site and mechanical disruption of the tricuspid valve with tricuspid regurgitation. Late complications include lead fracture or insulation breaks due to mechanical stresses, increases in pacing threshold or impedances due to tissue ingrowth, and device infections, often with systemic bloodstream infection. Treatment of the late-term complications of device implantation is often complicated, requiring lead extraction, which can be technically challenging and carries a risk of central venous or cardiac perforation, haemothorax and death. As already stated, old leads will often be left in situ.
The Aortic Valve
Published in Theo Kofidis, Minimally Invasive Cardiac Surgery, 2021
Theodor Fischlein, Giuseppe Santarpino
For the second prosthetic model for Intuity (8300A), the scientific publications are fewer than those present on Perceval. After the publication of the main trial (TRANSFORM), there was a high incidence of pacemaker implants for which subsequent studies on the mechanisms underlying this risk have been published. In summary, to date this prosthesis is not recommended for patients “with risk factors” to implant a pacemaker [23,28]. On the contrary, Perceval prostheses that initially showed high pacemaker rates, after appropriate suggestions and modifications of the implantation techniques, brought the incidence of this risk to the same values that can be recorded in patients with “conventional” prosthesis implants [29].
The use of digital health in heart rhythm care
Published in Expert Review of Cardiovascular Therapy, 2023
Donald P. Tchapmi, Chris Agyingi, Antoine Egbe, Gregory M. Marcus, Jean Jacques Noubiap
Pacemakers are one type of CIED along with implantable defibrillators (ICD) and devices providing cardiac resynchronization therapy (CRT). Pacemakers are pulse generators that can be temporary or permanent. They are mostly used in patients with symptomatic bradycardia or high-grade atrioventricular block [24]. ICDs are used to prevent sudden cardiac death from ventricular arrhythmia, while CRT is used in heart failure management accompanied by a conduction disorder [25]. ICDs can prevent sudden cardiac death, while CRT can improve cardiac function and quality of life, and reverse left ventricular remodeling in patients with heart failure. These devices monitor cardiac electrical activity and some have remote monitoring capabilities. Providers can have remote access via a secure portal to information stored in the device. Studies have shown that the use of remote monitoring plus clinic visits leads to reduced arrhythmia burden, time to detection and treatment of arrhythmias, and number of clinic visits compared to clinic visits alone. Patients also have a better experience and benefit from a feeling of safety with remote monitoring [26].
Brugada syndrome
Published in Acta Cardiologica, 2021
Haarika Korlipara, Giridhar Korlipara, Srinivas Pentyala
There are two types of cardiac cells that assist with conduction in the heart: pacemaker and non-pacemaker cells. Pacemaker cells drive the rate and rhythm of the heart and include the sinoatrial (SA) and atrioventricular (AV) nodes. They undergo spontaneous depolarisation and therefore have no true resting membrane potential, and once they reach a threshold voltage of about −40 mV, they trigger an action potential with rapid and complete depolarisation followed by repolarization [4]. Non-pacemaker cardiac cells include the cardiomyocytes in the atria and ventricles as well as the Purkinje conduction system within the ventricles. Contrasting to pacemaker cells, they have true resting potentials (between −90 and −80 mV) and undergo rapid depolarisation followed by a prolonged phase of depolarisation, known as the plateau phase [4]. Specifically, rapid inward movement of
How Is Temporal Processing Affected in Children with Attention-deficit/hyperactivity Disorder?
Published in Developmental Neuropsychology, 2020
Isabel Suarez, Carlos De Los Reyes Aragón, Elisa Diaz, Tania Iglesias, Ernesto Barcelo, Jorge Ivan Velez, Laurence Casini
This functional model proposes that time judgments come from a pacemaker- accumulator internal clock and involve memory and comparison stages. In this model, subjects estimate time intervals using an internal clock consisting of three components: a clock stage with a pacemaker and an accumulator, a memory stage, and a decision-comparison stage. Intervals are determined by the amount of pulses that are emitted at a regular rate by the pacemaker and stored in the accumulator. A switch controls the transfer of pulses from the pacemaker to the accumulator, such that when the switch closes, pulses pass into the accumulator. Thus, the more pulses accumulate, the longer the subjective estimation of the given duration is. Next, depending on the context or the requirements of the task, the pulses stored in the accumulator can be transferred to the working memory and then to the long-term memory, called the reference memory. Finally, in the decision-making stage, the amount of pulses stored in the working-memory is compared to the amount stored in the reference memory to produce a temporal judgment.