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Fever, hyperventilation, diarrhea and severe infections can also cause tachycardia, primarily due to increase in metabolic demands. [citation needed] Upon exertion, sinus tachycardia can also be seen in some inborn errors of metabolism that result in metabolic myopathies, such as McArdle's disease (GSD-V).
Sinus tachycardia is a normal response to physical exercise or other stress, when the heart rate increases to meet the body's higher demand for energy and oxygen, but sinus tachycardia can also be caused by a health problem. [4] An elite athlete's heart recorded during a maximum effort workout maintaining over 180 bpm for 10 minutes.
Tachycardia may result in palpitation; however, tachycardia is not necessarily an arrhythmia. Increased heart rate is a normal response to physical exercise or emotional stress. This is mediated by the sympathetic nervous system on the sinus node and called sinus tachycardia.
All of these mechanisms make POTS patients' hearts work harder to cause the same response: increased heart rate after a few minutes of standing and not enough blood flow to the brain.
The Cushing reflex classically presents as an increase in systolic and pulse pressure, reduction of the heart rate (bradycardia), and irregular respiration. [4] It is caused by increased pressure inside the skull. [4] These symptoms can be indicative of insufficient blood flow to the brain as well as compression of arterioles. [4] [5]
Junctional ectopic tachycardia (JET) is a rare tachycardia caused by increased automaticity of the AV node itself initiating frequent heartbeats. On the ECG, junctional tachycardia often presents with abnormal morphology P-waves that may fall anywhere in relation to a regular, narrow QRS complex. It is often due to drug toxicity. [22]
Reentry can produce single ectopic beats, or it can trigger paroxysmal tachycardia. Triggered beats are considered to be due to after-depolarizations triggered by the preceding action potential. These are often seen in patients with ventricular arrhythmias due to digoxin toxicity and reperfusion therapy after myocardial infarction (MI).
Often sinus node dysfunction produces no symptoms, especially early in the disease course. Signs and symptoms usually appear in more advanced disease and more than 50% of patients will present with syncope or transient near-fainting spells as well as bradycardias that are accompanied by rapid heart rhythms, referred to as tachycardia-bradycardia syndrome [4] [5] Other presenting signs or ...