Chapter 11
Ambulatory Electrocardiography: Extending the ECG to allow assessment of cardiac electrical
events while the patient is ambulating during normal daily activities
Ambulatory electrocardiographic monitoring is typically used when a patient demonstrates
symptoms that are thought to be caused by transient arrhythmias or other transient cardiac
abnormalities.
symptoms may include: chest pain, syncope (fainting) or near syncope, dizziness, and irregular
heartbeats (palpitations)
These devices can also be used to detect asymptomatic cardiac arrhythmias such as atrial
brillation that may increase the risk of embolus formation & cause stroke.
several categories of ambulatory electrocardiographic recorders:
Continuous recorders:
-are typically used for 24 to 48 hours to investigate the relationship of symptoms and
electrocardiographic events that are likely to occur within that time frame.
Intermittent recorders:
-are used for longer periods (weeks to months) to provide brief intermittent recordings for
detection of events that occur infrequently
-these recordings are usually initiated by the patient when experiencing symptoms.
implantable loop recorder:
-is implanted just under the skin in the chest to monitor the heart’s electrical activity continuously
for as long as 2 to 3 years.
-The device can be programmed to initiate a recording when the heart rate falls below, or rises
above, a predetermined level, or it can be activated manually by the patient when a symptom
such as dizziness occurs.
fi
, Chapter 14
function of the circulation is to serve the needs of the body tissues:
-to transport nutrients to the tissues,
-to transport waste products away,
-transport hormones from one part of the body to another
arteries:
-transport blood under high pressure to the tissues.
-have strong vascular walls,
-blood ows at a high velocity in the arteries
arterioles:
-last small branches of the arterial system
-they act as control conduit (channels) through which blood is released into the capillaries.
-have strong muscular walls that can close the arterioles completely or, by relaxing, can dilate the
vessels
capillaries:
-exchange uid, nutrients, electrolytes, hormones, and other substances between the blood and
interstitial uid.
-walls are thin and have numerous minute capillary pores permeable to water and other small
molecular substances.
venules:
-collect blood from the capillaries and gradually coalesce (merge) into larger veins
veins:
-function as conduits for transport of blood from the venules back to the heart
-serve as a major reservoir of extra blood.
-Because the pressure in the venous system is low, the venous walls are thin.
-they are muscular enough to contract or expand
Because the same volume of blood ow (F) must pass through each segment of the circulation
each minute, the velocity of blood ow (v) is inversely proportional to the vascular cross-sectional
area (A): v = F/A
fl flfl fl fl
Ambulatory Electrocardiography: Extending the ECG to allow assessment of cardiac electrical
events while the patient is ambulating during normal daily activities
Ambulatory electrocardiographic monitoring is typically used when a patient demonstrates
symptoms that are thought to be caused by transient arrhythmias or other transient cardiac
abnormalities.
symptoms may include: chest pain, syncope (fainting) or near syncope, dizziness, and irregular
heartbeats (palpitations)
These devices can also be used to detect asymptomatic cardiac arrhythmias such as atrial
brillation that may increase the risk of embolus formation & cause stroke.
several categories of ambulatory electrocardiographic recorders:
Continuous recorders:
-are typically used for 24 to 48 hours to investigate the relationship of symptoms and
electrocardiographic events that are likely to occur within that time frame.
Intermittent recorders:
-are used for longer periods (weeks to months) to provide brief intermittent recordings for
detection of events that occur infrequently
-these recordings are usually initiated by the patient when experiencing symptoms.
implantable loop recorder:
-is implanted just under the skin in the chest to monitor the heart’s electrical activity continuously
for as long as 2 to 3 years.
-The device can be programmed to initiate a recording when the heart rate falls below, or rises
above, a predetermined level, or it can be activated manually by the patient when a symptom
such as dizziness occurs.
fi
, Chapter 14
function of the circulation is to serve the needs of the body tissues:
-to transport nutrients to the tissues,
-to transport waste products away,
-transport hormones from one part of the body to another
arteries:
-transport blood under high pressure to the tissues.
-have strong vascular walls,
-blood ows at a high velocity in the arteries
arterioles:
-last small branches of the arterial system
-they act as control conduit (channels) through which blood is released into the capillaries.
-have strong muscular walls that can close the arterioles completely or, by relaxing, can dilate the
vessels
capillaries:
-exchange uid, nutrients, electrolytes, hormones, and other substances between the blood and
interstitial uid.
-walls are thin and have numerous minute capillary pores permeable to water and other small
molecular substances.
venules:
-collect blood from the capillaries and gradually coalesce (merge) into larger veins
veins:
-function as conduits for transport of blood from the venules back to the heart
-serve as a major reservoir of extra blood.
-Because the pressure in the venous system is low, the venous walls are thin.
-they are muscular enough to contract or expand
Because the same volume of blood ow (F) must pass through each segment of the circulation
each minute, the velocity of blood ow (v) is inversely proportional to the vascular cross-sectional
area (A): v = F/A
fl flfl fl fl
