PALPITATIONS AND PASSING OUT (ARRHYTHMIAS): PROBLEMS WITH CONTROL BY THE NERVOUS SYSTEM

Inappropriate function of the autonomic nervous system may cause abnormally slow heartbeats or, more often, pauses’. The reflexes that automatically control the heartbeat temporarily seen to go haywire in some people. One of these reflexes seems to have its basis in evolution: in certain animals, such as walruses, the heartbeats are known slow down abruptly to an extraordinary degree when they dive into frigid waters. This decrease reduces the rate at which they usej up energy and oxygen so they can remain submerged longer.
Some people have pauses (and subsequent symptoms) because the part of the autonomic nervous system that promotes heart slowness suddenly does its job too well. Occasionally, this change can actually be provoked. For example, a tight necktie or collar may press on a region of the carotid artery in the neck tailed the carotid sinus. Nerves running through the neck at this point become activated by this pressure and may send a “slow down” message to the sinus node of the heart.  (Don’t confuse the carotid sinus and the sinus node—they are entirely different structures.) If you are too sensitive to the “slow down” signal, your heart may not just slow down a little (which would be normal), but it may actually stop for 5, 10 or even more seconds. The result is syncope. This type of syncope is called “carotid sinus hypersensitivity.”
Other factors may activate the “slowing” part of the autonomic nervous system, such as straining at a bowel movement, urinating, gagging, or applying pressure to the eyeballs.
Doctors check for evidence of autonomic nervous system malfunction in people who report syncope by pressing (or massaging) on the carotid sinus while watching an electrocardiogram monitor. The doctor checks beforehand to make sure there is no evidence of blockage in the carotid artery, because the massage may aggravate it and precipitate a stroke.
Sometimes pain, fear, exhaustion, or low blood pressure can provoke bradycardia as well as further lowering of the blood pressure. When this happens you may faint. “Simple fainting” (also referred to as vasovagal syncope) usually be distinguished from other more serious causes of loss of consciousness by the circumstances and by the associated symptoms. Typically, fainting is preceded by sweatiness, nausea, a prickly sensation in skin, pallor, and at least a few seconds of “graying out” before the actual blackout occurs. This response is different from carotid sinus hypersensitivity or other types of syncope in which the passing out is characteristically abrupt, with little or no warning.
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PALPITATIONS AND PASSING OUT (ARRHYTHMIAS): PROBLEMS WITH CONTROL BY THE NERVOUS SYSTEMInappropriate function of the autonomic nervous system may cause abnormally slow heartbeats or, more often, pauses’. The reflexes that automatically control the heartbeat temporarily seen to go haywire in some people. One of these reflexes seems to have its basis in evolution: in certain animals, such as walruses, the heartbeats are known slow down abruptly to an extraordinary degree when they dive into frigid waters. This decrease reduces the rate at which they usej up energy and oxygen so they can remain submerged longer.Some people have pauses (and subsequent symptoms) because the part of the autonomic nervous system that promotes heart slowness suddenly does its job too well. Occasionally, this change can actually be provoked. For example, a tight necktie or collar may press on a region of the carotid artery in the neck tailed the carotid sinus. Nerves running through the neck at this point become activated by this pressure and may send a “slow down” message to the sinus node of the heart.  (Don’t confuse the carotid sinus and the sinus node—they are entirely different structures.) If you are too sensitive to the “slow down” signal, your heart may not just slow down a little (which would be normal), but it may actually stop for 5, 10 or even more seconds. The result is syncope. This type of syncope is called “carotid sinus hypersensitivity.”Other factors may activate the “slowing” part of the autonomic nervous system, such as straining at a bowel movement, urinating, gagging, or applying pressure to the eyeballs.Doctors check for evidence of autonomic nervous system malfunction in people who report syncope by pressing (or massaging) on the carotid sinus while watching an electrocardiogram monitor. The doctor checks beforehand to make sure there is no evidence of blockage in the carotid artery, because the massage may aggravate it and precipitate a stroke.Sometimes pain, fear, exhaustion, or low blood pressure can provoke bradycardia as well as further lowering of the blood pressure. When this happens you may faint. “Simple fainting” (also referred to as vasovagal syncope) usually be distinguished from other more serious causes of loss of consciousness by the circumstances and by the associated symptoms. Typically, fainting is preceded by sweatiness, nausea, a prickly sensation in skin, pallor, and at least a few seconds of “graying out” before the actual blackout occurs. This response is different from carotid sinus hypersensitivity or other types of syncope in which the passing out is characteristically abrupt, with little or no warning.*179\252\8*

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