Cardiology Flashcards
What is the electrical pathway of the heart? (6 things)
Sinoatrial node
Internodal pathways
Atrioventricular node
Bundle of his
Bundle branches
Purkinje fibers
What is the intrinsic rate of the sinoatrial node?
60-100 bpm
What is the intrinsic rate of the AV node?
45-50 bpm
What is the intrinsic rate of the bundle branches?
40-45 bpm
What coronary artery does the SA node receive its blood supply from?
Right coronary artery (59% of the time)
Left circumflex (38% of the time)
Mixed (3% of the time)
What is the role of the AV node?
To slow impulse travel from atria to ventricle allowing the atria to fully contract before the ventricle is stimulated.
What region of the heart does the left bundle branch innervate?
The left ventricle and left side of the interventricular septum
What does the right bundle branch innervate?
The right ventricle and right interventricular septum
What are the 3 main POSITIVELY charged ions in the body?
Calcium, Potassium, Sodium
What is the main NEGATIVELY charged ion in the body?
Chloride
What is the resting membrane potential of a cardiac myocyte?
-90mv
What limb leads make a lead 1 view?
Which is positive and which is negative?
Right arm (Negative), and left arm (Positive)
What limb leads make a lead 2 view?
Which is positive and which is negative?
Right arm (Negative), and left leg (Positive)
What limb leads make a lead 3 view?
Which on is positive, and which on is negative?
Left arm (Negative), and left leg (Positive)
What do the smallest boxes on and ECG represent?
1 mm vertically, 0.04s horizontally
What is the normal duration for the PR interval?
0.12s - 0.20s
What is the normal duration for QRS?
0.06s - 0.11s (Maybe 0.12)
When is a Q wave considered pathological?
When it is greater than 0.03s wide, or greater than 1/3 the height of the R wave. Considered in the setting of suspected cardiac ischemia.
What leads may show ST elevation up to 1mm in normal circumstances?
Leads I, II, III
What are the intervals for calculating HR on an ECG?
(Large box calculation method)
300, 150, 100, 75, 60, 50