Introduction
Jervell and Lange-Nielsen Syndrome (JLNS) is a type of long QT syndrome that results in the delayed repolarization of cardiac myocytes, which is observed as an increase in the QT interval on an electrocardiogram (ECG), as well as congenital bilateral sensorineural deafness1, 5-8. This is due to homozygous or compound heterozygous mutations in either the KCNQ1 gene or the KCNE1 gene that result in the complete loss of function of the slowly activating delayed rectifier potassium channels (Iks) in cardiac muscle tissue and in the inner ear.1, 5-8 The structure and function of this channel will be considered with respect to the effects of mutations in KCNQ1 and KCNE1, the resulting pathophysiology and treatment of this disorder.
Structure and Function of the Iks Channel
The Iks channel is a voltage-gated channel that is responsible for the repolarization of cardiac myocytes as well as the maintenance of the endocochlear potential via K+ efflux1. This channel is encoded by two genes: KCNQ1 and KCNE11. The KCNQ1 gene encodes the α subunit of this channel, four of which combine to form a tetramer1. Each α subunit spans the membrane six times (Figure 1) - the first four segments allow the detection of voltage changes and the last two segments create a pore through which K+ can pass2. The β subunit encoded by the KCNE1 gene displays a single transmembrane portion and confers the characteristic properties of the Iks channel by associating with the pore portion of the tetramer2. To determine the stoichiometry of α subunits to β subunits, Nakajo and colleagues (2) injected RNA pertaining to KCNQ1 and KCNE1 into Xenopus laevis oocytes and examined the level of expression of each of these genes by fluorescently tagging the re...
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When a muscle contracts and relaxes without receiving signals from nerves it is known as myogenic. In the human body, the cardiac muscle is myogenic as this configuration of contractions controls the heartbeat. Within the wall of the right atrium is the sino-atrial node (SAN), which is where the process of the heartbeat begins. It directs consistent waves of electrical activity to the atrial walls, instigating the right and the left atria to contract at the same time. During this stage, the non conducting collagen tissue within the heart prevents the waves of electrical activity from being passed directly from the atria to the ventricles because if this were to happen, it would cause a backflow. Due to this barrier, The waves of electrical energy are directed from the SAN to the atrioventricular node (AVN) which is responsible for transferring the energy to the purkyne fibres in the right and left ventricle walls. Following this, there is a pause before the wave is passed on in order to assure the atria has emptied. After this delay, the walls of the right and left ventricles contract
“Ebstein’s anomaly is a rare cardiac anomaly that occurs in approximately one in 20,000 live births and accounts for less than 1% of all congenital heart disease (Ebstein’s anomaly in adults)”. The goal of this paper is to examine Ebstein’s Anomaly - to understand what it is, how it affects the heart, possible presenting symptoms, and other possible complications associated with this anomaly. Diagnosis of this anomaly is key in treating patients, thus echocardiographic as well as other test modalities are vital in assessing what the treatment options are available, as well as discerning what the prognosis may be. Advancing test modalities have helped distinguish Ebstein’s Anomaly with other differential diagnoses. Developments with testing modalities coupled with comprehensive calculations, formulas, and measurements have facilitated correctly diagnosing, and therefore properly treating cardiac patients.
Millions of people suffer from heart valve disease every year (“US Markets for Heart Valves”, 2007). Out of all of the heart valve diseases, “mitral regurgitation is the second most common valvular heart disease” (Baumgartner et al., 2006). This is due to the fact that the mitral valve experiences the most pressure and blood flow compared to the other valves in the heart (“US Markets for Heart Valves”, 2007). The disease occurs when blood leaks back into the left auricle from the left ventricle, which is caused by the mitral valve not closing properly (Lantada et al., 2009). The majority of the time, the mitral valve does not function correctly due to a structural abnormality (Buckner et al., 2010). These abnormalities can occur in either the papillary chords or the papillary muscles (Lantada et al., 2009). The frequency of the mitral valve abnormalities, especially in the elderly population, led to extensive research to find a solution (“US Markets for Heart Valves”, 2007).
Zhang, Y. B., Harwood, J., Williams, A., Ylänne-McEwen, V., Wadleigh, P. M., & Thimm, C.
...Hallert, C., C. Grant, S. Grehn, C. Grannot, S. Hultent, G. Midhagens M. Strom, H. Svensson,
Anatomy of the heart consists of the Atria, which is a collection of blood and not much pump force, Auricle which is attached to the atria to increase potential volume filling, Ventricles have thought myocardium and do the majority of pumping blood, Exterior is the coronary sulcus and the anterior and posterior sulci, the apex is inferior and only the larger left side, and then the base is the superior flattened top of the heart. As we know the heart does conduct electricity, the resting threshold of the heart is -90mV and has a fast and slow channel. Fast channels are transitory whereas slow channels are long lasting which allows for prolonged depolarization. The heart has different rates of depolarizations, it has a central node (SA) which “is the heart 's natural pacemaker”(Medicine Net) which has a BPM of
Hypertrophic cardiomyopathy is an inherited disease that affects the cardiac muscle of the heart, causing the walls of the heart to thicken and become stiff. [1] On a cellular level, the sarcomere increase in size. As a result, the cardiac muscles become abnormally thick, making it difficult for the cells to contract and the heart to pump. A genetic mutation causes the myocytes to form chaotic intersecting bundles. A pathognomonic abnormality called myocardial fiber disarray. [2,12] How the hypertrophy is distributed throughout the heart is varied. Though, in most cases, the left ventricle is always affected. [3] The heart muscle can thicken in four different patterns. The most common being asymmetrical septal hypertrophy without obstruction. Here the intraventricular septum becomes thick, but the mitral valve is not affected. Asymmetrical septal hypertrophy with obstruction causes the mitral valve to touch the septal wall during contraction. (Left ventricle outflow tract obstruction.) The obstruction of the mitral valve allows for blood to slowly flow from the left ventricle back into the left atrium (Mitral regurgitation). Symmetrical hypertrophy is the thickening of the entire left ven...
Tackett, J. L., Lahey, B. B., van Hulle, C., Waldman, I., Krueger, R. F., & Rathouz, P. J. (2013).
Segal, E. A., Cimino, A. N., Gerdes, K. E., Harmon, J. K., & Wagaman, M. (2013). A
Zosuls, K. M., Ruble, D. N., Tamis-LeMonda, C. S., Shrout, P. E., Bornstein, M. H., & Greulich,
The heart is a pump with four chambers made of their own special muscle called cardiac muscle. Its interwoven muscle fibers enable the heart to contract or squeeze together automatically (Colombo 7). It’s about the same size of a fist and weighs some where around two hundred fifty to three hundred fifty grams (Marieb 432). The size of the heart depends on a person’s height and size. The heart wall is enclosed in three layers: superficial epicardium, middle epicardium, and deep epicardium. It is then enclosed in a double-walled sac called the Pericardium. The terms Systole and Diastole refer respectively and literally to the contraction and relaxation periods of heart activity (Marieb 432). While the doctor is taking a patient’s blood pressure, he listens for the contractions and relaxations of the heart. He also listens for them to make sure that they are going in a single rhythm, to make sure that there are no arrhythmias or complications. The heart muscle does not depend on the nervous system. If the nervous s...
Cardiofaciocutaneous syndrome is a very rare and serious genetic disorder that generally affects the heart, facial features, and skin of an individual. It is caused by a desultory gene mutation, which takes place in one of four genes. Those genes are known as BRAF, MEK1, MEK2, and KRAS. From research, it is also suspected there is a possibility that other genes are associated with the rare condition. This disorder holds multiple alternative names, a long history, obvious symptoms, extensive amounts of interesting data, and is lucky enough to be supported by numerous organizations that will stop at nothing to help.
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