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
What is the difference between a sinus pause and a sinoatrial block?
A sinus pause does not reflect a multiple of the P-P interval and can last any amount of time. A Sinoatrial block with represent a multiple of the previous P-P interval.
What is the difference between a PJC and a Junctional escape beat?
A PJC fires prematurely where as the Junctional Escape Beat fires when the SA node fails to fire.
What is the rate for Vtach?
100-200bpm
What is brugadas sign in V-tach
The interval form the beginning of the R wave to the bottom of the S wave must be more than 0.10s.
(Possibly helpful in determining V-tach vs SVT with abberancy)
What is the duration of the QRS complex in v-tach?
Must be >0.16s
what is Josephsons sign in V-tach?
A small notching near the low point of the S-wave.
Are the complexes in precordial lead positive or negative in V-tach?
Always Negative.
What is the rate of ventricular flutter? (a very fast V-tach)
200-300 bpm
Still technically a V-tach.
What is a first degree heart block?
Consistently long PR interval
What is a second degree type I heart block?
Gradually lengthening PR interval followed by a dropped beat.
What is a second degree type 2 heart block?
Grouped beats with 1 dropped beat between groups. P wave with no following QRS.
(Consistent PR interval)
What are the 3 layers of the heart?
Endocardium (Inner lining)
Myocardium (Muscle)
Epicardium (Outerlayer)
What percentage of blood moves from atria to ventricles passively?
70% enters ventricles passively. 30% is pumped during atrial contraction.
What are the valves between the atria and ventricles called, and what attaches to the preventing reguritation?
Right valves are tricuspid
Left are Mitral
They are attaches to chordae tendinae and anchored to papillary muscles on the ventricle walls.
What is the name of the sac surround the heart?
What fluid does it contain?
Pericardial sac
Serous fluid
How many pulmonary veins are there?
4
What is starlings law?
The greater the stretch the greater the force of contraction.
What is the difference between cardiac muscle tissue and normal skeletal muscle tisse?
Intercalated disc between cells allowing faster impulse transmission. As well as automaticity.
What are the 3 layers of an artery?
Intima (Smooth inner lining of endothelial cells)
Media (The thick middle layer of muscle and elastic fibers)
Adventitia (The outer layer of fibrous, collagenous tissue)
What are the 3 factors in regulation of blood flow?
Local response- Partial pressure of oxygen leading to precapillary sphincters to open.
Humoral response- Catecholamines I.e Norepinephrine. leads to vasoconstriction.
Nervous response- Sympathetic nervous system.
What is pulsus paradoxus?
A drop in blood pressure during INSPIRATION due to increased venous return causing the right side of the heart to fill more leading to reduced space in the left side of the heart.
What is BECKs triad?
Hypotension, muffle heart sounds, JVD
What is automaticity?
The intrinsic ability to spontaneously depolarize
What 2 types of cell make up the myocardium?
Nodal (non contracting) and contractile
What is the term for all muscle cells contracting as one?
Functional syncytium
What is the resting membrane potential for nodal cells compared to contractile cells?
Nodal -60mv
Contractile 85-90mv
What is the threshold potential for NODAL cells?
-40mv
What is the threshold potential for CONTRACTILE cardiac cells?
-70mv
What are the phases of cardiac contractility?
0 - DEPOLARIZATIONsodium ions rush in causing depolarization up to +10mv
1 - SLIGHT REPOLARIZATION potassium channels open causing slight repolarization towards 0mv
2 - PLATEAU PHASE Calcium channels are open causing influx of positive ions, and potassium channels are open causing efflex of positive ions.
3 - REPOLARIZATION calcium channels close, Potassium channels remain open causing
4 - back are resting membrane potential
What are the HR based on large box calculations?
300, 150, 100, 75, 60, 50, 43, 37, 33, 30
