Sinoatrial nodeThe sinoatrial node (also known as the sinuatrial node, SA node or sinus node) is an oval shaped region of special cardiac muscle in the upper back wall of the right atrium made up of cells known as pacemaker cells. The sinus node is approximately 15 mm long, 3 mm wide, and 1 mm thick, located directly below and to the side of the superior vena cava. These cells can produce an electrical impulse known as a cardiac action potential that travels through the electrical conduction system of the heart, causing it to contract.
Catecholaminergic polymorphic ventricular tachycardiaCatecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited genetic disorder that predisposes those affected to potentially life-threatening abnormal heart rhythms or arrhythmias. The arrhythmias seen in CPVT typically occur during exercise or at times of emotional stress, and classically take the form of bidirectional ventricular tachycardia or ventricular fibrillation. Those affected may be asymptomatic, but they may also experience blackouts or even sudden cardiac death.
Gallop rhythmA gallop rhythm refers to a (usually abnormal) rhythm of the heart on auscultation. It includes three or four sounds, thus resembling the sounds of a gallop. The normal heart rhythm contains two audible heart sounds called S1 and S2 that give the well-known "lub-dub" rhythm; they are caused by the closing of valves in the heart. The first heart sound (S1) is closure of the valve at the end of ventricular filling (the tricuspid and mitral valves); the second heart sound (S2), is closure of the aortic and/or the pulmonary valves as the ventricles relax.
Inappropriate sinus tachycardiaInappropriate sinus tachycardia (IST) is a type of cardiac arrhythmia. Inappropriate sinus tachycardia is caused by electrical signals in the body speeding up the heart, rather than a physical deformity of the heart. This may be caused by a disturbance and/or failure of the autonomic nervous system. Research into the mechanism and etiology (cause) of inappropriate sinus tachycardia is ongoing. While sinus tachycardia is very common and is the most common type of tachycardia, it is rare to be diagnosed with Inappropriate Sinus Tachycardia as an independent symptom that is not part of a larger condition.
Paroxysmal supraventricular tachycardiaParoxysmal supraventricular tachycardia (PSVT) is a type of supraventricular tachycardia, named for its intermittent episodes of abrupt onset and termination. Often people have no symptoms. Otherwise symptoms may include palpitations, feeling lightheaded, sweating, shortness of breath, and chest pain. The cause is not known. Risk factors include alcohol, caffeine, nicotine, psychological stress, and Wolff-Parkinson-White syndrome, which often is inherited. The underlying mechanism typically involves an accessory pathway that results in re-entry.
Vietnamese phonologyThe phonology of Vietnamese features 19 consonant phonemes, with 5 additional consonant phonemes used in Vietnamese's Southern dialect, and 4 exclusive to the Northern dialect. Vietnamese also has 14 vowel nuclei, and 6 tones that are integral to the interpretation of the language. Older interpretations of Vietnamese tones differentiated between "sharp" and "heavy" entering and departing tones. This article is a technical description of the sound system of the Vietnamese language, including phonetics and phonology.
