Quantcast Size and Time Intervals of EKG Waves. - Cardiac Impairment

Share on Google+Share on FacebookShare on LinkedInShare on TwitterShare on DiggShare on Stumble Upon
Custom Search
 
  
 
d. Size and Time Intervals of EKG Waves. The size of the deflection waves
and particular time intervals are important when you are reading an electrocardiogram.
For example, the duration of a normal "P" wave is between 0.06 and 0.1 seconds, the
time it takes for depolarization current to pass through the atrial musculature. An
increased width of "P" wave may indicate left atrial abnormality or right atrial
hypertrophy (enlargement). The deflection of a normal "P" wave is small due to the thin
walled structure of the atria. A "P" wave is usually no more than 3 mm high. A taller "P"
wave may indicate that atrial enlargement has occurred due to hypertension, coronary
pulmonade, or congenital heart disease.
(1)  P-R interval. Measured from the beginning of the P wave to the
beginning of the R wave, this wave pattern represents the conduction time from the
beginning of atrial excitation to the beginning of ventricular excitation. This is the time it
takes for an electrical impulse to travel through the atria and atrioventricular node to the
remaining conducting tissues. A medical condition that disrupts this electrical impulse
will display itself as a P-R interval that is longer than 0.2 seconds, due to the increased
time it takes to travel the conducting tissues. The normal P-R interval is between 0.12
and 0.20 seconds.
(2)  Q wave. The Q wave is defined as the first down (negative) deflection
following the P wave but coming before the R wave.
(3)  QRS complex. This complex is made up of three waves: the Q, the R,
and the S waves. The QRS complex represents ventricular depolarization. A normal
QRS measurement is less than 0.12 seconds. The QRS complex is larger than the P
wave on an EKG because ventricular depolarization involves a greater muscle mass
than atrial depolarization.
(4)
R wave. The R wave is the first upward (positive) deflection that follows
the wave.
(5)  S-T segment. Beginning at the end of the S wave ending at the
beginning of the T wave, this wave represents the time between the end of the spread
of the heart's electrical impulse through the ventricles and repolarization of the
ventricles. When a patient has acute myocardial infarction, the S-T segment is
elevated. When the heart muscle does not receive enough oxygen, the S-T segment is
depressed.
(6)  T wave. Representing repolarization of the ventricular cells, the T wave
is flat when the heart muscle does not receive enough oxygen; for example, in
atherosclerotic heart disease. When the body's potassium level is increased, the T
wave may be elevated. This wave occurs after the QRS complex.
NOTE:
Refer to figure 2-6 to see these waves.
MD0571
2-9



Medical News
New Dominican law OKs abortion if life at risk
The Dominican Republic on Friday approved a law that for...
medicalxpress.com
Liberia holds Senate vote amid Ebola fears
Health workers manned polling stations across Liberia on Saturday as...
medicalxpress.com
FDA OKs Cubist antibiotic for serious infections
The Food and Drug Administration has approved a new medicine...
medicalxpress.com
Concerns raised about variable performance of some UK personal use breathalyzers
The ability of some breathalyzers widely sold to the UK...
medicalxpress.com
A winter break for Scope
Happy Holidays from all of us at Scope! We’re taking...
scopeblog.stanford.edu
Doc Groups Pan Meaningful Use Penalties
(MedPage Today) -- The program's "pass-fail" system is rigid and...
medpagetoday.com
Stanford dietitian explains how – not just what – you eat matters
Recent posts, including this one from last week and this...
scopeblog.stanford.edu
FDA approves AbbVie combo hepatitis C treatment
Patients with chronic hepatitis C have a new option for...
medicalxpress.com
Lost memories might be able to be restored, new study indicates
New UCLA research indicates that lost memories can be restored....
medicalxpress.com
AstraZeneca cancer drug, companion test approved
U.S. regulators on Friday granted accelerated approval to the first...
medicalxpress.com
Flu season, early again, hitting hard in South and Midwest
Health officials say the flu is now hitting hard in...
medicalxpress.com
Brazil to study legalization of medical marijuana
The Brazilian government says it will study the possibility of...
medicalxpress.com
Early exposure to antidepressants affects adult anxiety and serotonin transmission
About 15 percent of women in the United States suffer...
medicalxpress.com
Few Women Have Coverage for Egg Freezing
(MedPage Today) -- Such coverage is rare even for women...
medpagetoday.com
Long-Term Benzo Use Rampant in Older Patients
(MedPage Today) -- Cautions against the practice go unheeded by...
medpagetoday.com
This Week: Yes to SG Nominee, No to SGR Fix
(MedPage Today) -- Murthy confirmed, Congress let physicians stew, and...
medpagetoday.com
FDA OKs '3D' Combo for Hepatitis C
(MedPage Today) -- Drugs highly effective in clinical trials....
medpagetoday.com
MedPAC Wants Overhaul of Primary Care Bonus
(MedPage Today) -- Also seeks curbs on hospital admissions for...
medpagetoday.com
Olaparib Wins FDA Approval for Ovarian Cancer
(MedPage Today) -- But could be yanked if confirmatory trials...
medpagetoday.com
How to make it through holiday dinners without putting on the pounds
A lot of people are worrying about overeating over the...
scopeblog.stanford.edu
 


Privacy Statement - Copyright Information. - Contact Us

comments powered by Disqus

Integrated Publishing, Inc.
9438 US Hwy 19N #311 Port Richey, FL 34668

Phone For Parts Inquiries: (727) 755-3260
Google +