Part 12 Flashcards
Depolarization changes a cardiac myocyte’s membrane potential to make it less ___, allowing for…
negative, …the mechanical contraction of the myocyte
Cardiac myocyte primary function
-contraction initiated with electrical depolarization (removal of negative resting potential) coordinated from myocyte to myocyte
The heart can conduct signals ___ to ___, or via the ____ system which is much faster
cell to cell, conduction system
AV delay allows for…
…contraction of the atria before the ventricle
P wave represents…
Atrial depolarization from the SA node for about .08-.1 sec
PR SEGMENT represents…
The time in which the impulse is traveling within the AV node where conduction velocity is greatly slowed
QRS complex represents…
Ventricular depolariztiation normally about .06-.1 seconds
ST segment represents…
The period of time from which the entire ventirlce has depolarized and corresponds to the plateau phase of the ventricular action potential before ventricular repolarization occurs
T wave represents…
ventricular repolarization which typically tkes longer than the wave of depolarization
12 lead EKG
Use of 10 electrodes placed in standard locations on the body in that each show a different perspective of the heart’s electrical activity
Electrode placement of a 12 lead ekg
- V1 right 4th intercostal space sternal border
- V2 left 4th intercostal space sternal border
- V3 between V2 and V4
- V4 at the left 5th intercostal space mid clavicular line
- V5 5th intercostal space anterior axillary line
- V6 5th intercostal space mid axillary line
- 1 on left arm
- 1 on right arm
- 1 on left leg
- 1 on right leg
A wave of ___ traveling ___ a positive electrode results in a ____ deflection of an EKG trace, while traveling ___ a positive electrode resuls in a ___ deflection.
depolarization (positive charge) toward, positive, away, negative
PEA
Pulseless electrical activity, occurs when the patient has normal electrical conduction but a lack of a pulse often seen in cardiac arrest where the heart either does not contract or there is insufficient cardiac output to supply the organs
Automaticity of the heart
Refers to ability of cardiac muscles to depolarize spontaneously without outside stimulation from nervous system at the SA node (normal pacemaker of heart), despite also receiving innervation from sympathetic and parasympathetic fibers
Conduction system pathway of the normal heart
- SA node in right atrium
- bachmann’s bundle goes to left atrium
- AV node receives the signal from the SA node and delays ventricular contraction
- AV goes thru bundle of His
- Bundle of His goes to bundle branches and then to purkinje fibers
- At the apex we see the signal then finally move to the ventricular myocardium where it contracts
PR Segment vs PR Interval
Segment is from the end of the P wave to the start of the QRS complex, interval is from the start of the P wave to the start of the QRS complex
A prolonged PR interval >___sec indicates ____
.2, first degree heart block (conduction defect in AV node)
A prolonged QRS complex >___sec indicates ___
.1 sec, bundle branch block
QT interval represents…
Timeline of both ventricular depolarization and repolarization, ranges from .2-.4 seconds depending on heart rate (have to measure corrected QT (QTc)
The right atrium and ventricle are ___ compared to the left
more anterior
Y axis of an EKG is measured in ___ but is almost always commonly described in ____
mv, mm
Tall P wave indicates….
…right atrial enlargement
Delta wave
A sign of early excitation of ventricles, indicative of re-entry such as global (wolff-parkinson-white syndrome causing tachycardia in children) characterized by a slurred upstroke of the QRS complex
U wave
Follows T wave, not always present, same direction of deflection of the T but much smaller amplitude (often not picked up), unknown what it represents
Hyperkalemia causes ___ on an ekg finding, what does hypokalmeia cause?.
Increased amplitude and peaking of T wave, flat or inverted T wave
1 square represents what values in mm, sec, and mv horizontal and vertically?
1mm or .04 sec horizontally, and 1mm or .1mv vertically
R wave gets progressively ___ from V1 to V4-5, loss of this can indicate what?
Bigger, loss of ventricular myocardial conduction (often MI)
ST segment elevation indicates…
ST segment depression indicates…
elevation indicates acute infarction and pericardidits, and depression in ischemia
T wave abnormalities
, may become inverted, peaked, or flattened due to ischemia, infarction, or medications
Chest pain (most of the time, sometimes other areas) upon exertion that is relieved upon rest, always assume….
….cardiac in nature until proven otherwise
Dependent edema definition
Gravity dependent, refers to edema that shifts in observation depending on how the patient is positioned (if bed ridden in flanks and back, if upright then feet) often seen in congestive heart failure
Classic angina pain presentation
Sharp pain that radiates to the shoulders and sometimes the jaw
Left sided heart failure results in blood pooling in the ___, right side results in blood pooling in the ___
lungs, extremities
Paroxysmal nocturnal dyspnea definitoin
A form of orthopnea where a patient awakes suddenly with feeling of suffocation and has to quickly sit upright for relief, a sign of cardiovascular condition
Orthopnea (cardiac history)
Dyspnea that occurs in the recumbent position caused by redistribution of blood from abdominal and lower body venous vasculature to chest increasing workload of heart, develops within minutes of laying flat, often a sign of cardiac disease
claudication (cardiac history)
Sharp pain caused by absence of blood flow often experienced in the extremities and during exercise, often a sign of cardiac disease
Coarctation of aorta
Aortic arch narrowing, often congenital condition that results in a smaller aorta past the 3 great vessels that therefore requires left ventricle to work much harder to pump blood to perfuse the lower extremity, often a sign of cardiac disease
Fatty streak development
Intracellular lipid accumulation in the early stage progression of atherosclerosis, often seen in ages 4-5 in about 50% of patients and indicative of slight increasing endothelial dysfunction (but does not manifest with any clinical symptoms and is clinically “silent”)
Stable plaque vs vulnurable plaque
Stable - a buildup of cholesterol that has fibrous scar tissue forming around it as well as migrating smooth muscle tissues that narrow the lumen of the artery (fibrous plaque)
Vulnurable - occurs in more advanced stages of atherosclerosis, where scar tissue has calcified over and if endothelium is damaged collagen is exposed causing platelets to aggregate and clot forming a thrombus at risk for embolism
Metabolic syndrome
A condition characterized by 3 of the following
- abdominal obesity (>40 inch males and 35 inch in females)
- HDL below 40mg/dL male and 50mg/dL female
- hypertension >130/85mmHg
- elevated fasting glucose to either pre-diabetic (>110mg/dL) or diabetic stage (>125mg/dL)
Apolipoprotein B100 serum lab study and healthy values
Measurement test of secondary marker for LDL measuring a substrate of LDL indicating risk of developing cardiovascular disease, with normal values below 100mg/dL
Ultra sensitive CRP and homocystine serum lab studies
Measurement test that detects non specific marker of inflammation that could be indicating increased inflammation of vessels and heart putting patient at risk for heart attack, but could also be due to any number of inflammatory conditions or infection
Statin therapy and pregnancy
Contraindicated!!! can be replaced with less effective bile acid sequestrant
Patients with triglycerides greater than ___mg/dL are at risk for developing ___ and therefore require ____ therapy if triglycerides exceed ___mg/dL
1000mg/dL, Spontanous pancreatitis, fibrate, 500
Hyperlipidemia secondary prevention guidelines
-begin statin therapy independent of baseline LDL levels, if patients do not acheive <70 mg/dL LDL (monitored every six weeks) then maximize statin therapy and consider adding a second agent (Ezetimibe)
How does the wave of electrical current generated in the heart spread to adjoining cells?
gap junctions allow ions to pass freely from cell to cell