Flashcards in Chapter 3 Deck (198)
What can result from blockage of the RCA?
Inferior wall MI and/or disturbances in AV nodal conductions
Occlusion of what artery is called the widow maker?
Occlusion of the left main coronary artery
What can result from blockage of the circumflex artery?
lateral wall MI
in some patients, occlusion of the circumflex can also lead to a posterior wall MI
increased blood concentration of what electrolytes will decrease automaticity?
Decreased sodium, potassium and calcium
decreased concentrations of what electrolytes will increased automaticity?
K+ and Ca2+
What is the term that describes the ability of cardiac muscle cells to respond to an external stimulus, such as that from a chemical, mechanical or electrical source?
What is the term that describes the ability of a cardiac cell to receive and electrical impulse and conduct it to an adjoining cardiac cell?
(Via intercalated disks)
What's the term that describes the ability of myocardial cells to shorten, thereby causing cardiac muscle contraction, in response to electrical stimuli
The state when the inside of a cell is more negative than the outside of the cell
What causes depolarization
movement of sodium into the cell
Where does depolarization occur in the heart
depolarization proceeds from innermost later of the heart to the outermost layer (endocardium --> Epicardium)
What on the ECG represents ventricular repolarization?
ST segment and T wave
what occurs after the relative refractory period and allows a weaker-than-normal stimulus to cause cardiac cells to depolarize?
seen at the end of the T wave
- because the cell is more excitable than normal, dysrhythmias can develop during this period
What's the primary pacemaker and what's its intrinsic rate?
SA node, 60-100 bpm
What are the bpm of the different pacemakers?
SA node: 60 - 100 bpm
AV junction: 40 - 60 bpm
Purkinje fibers: 20 - 40 bpm
What heart surface is viewed from the three standard limb leads?
Lead I - lateral heart
Leads II and III - inferior heart
What heart surface is viewed from each of the augmented leads?
aVR - non
aVL - lateral
aVF - inferior
Where is lead V1 placed?
4th intercostal space on the R next to the sternum
Where is lead V2 placed?
4th intercostal space on the L next to the sternum
Where is lead V4 placed?
left midclavicular line in the 5th intercostal space
If time doesn't permit obtaining all of the R chest leads, which is the lead of choice?
What leads view the inferior surface of the heart?
II, III, aVF
What leads view the septal surface of the heart?
What leads view the anterior surface of the heart?
What leads view the lateral surface of the heart?
I, aVL, V5, V6
how much time does a 1mm box stand for?
how much time does a large box stand for?
0.2 seconds (contains 5 x 1 mm boxes)
how many mV does the height of one block correspond to?
0.1 mV for each 1 mm box
What signifies a pathological Q wave?
Abnormal Q waves are more than .04 s in duration or more than one-third the height of the following R wave in that lead