Cardiology Flashcards
The circumflex artery is a branch of the:
Left coronary artery
The tricuspid valve is:
located between the right atrium and right ventricle
The thick, muscular middle layer of the heart wall necessary for contraction is the?
myocardium
The cavity between the parietal and visceral pericardium contains pericardial fluid, approx?
30-50ml
Myocytes are jointed together into a continuous mass of ned-to-end gap junctions called
intercalated discs
T/F: the myocardial walls of each ventricle are much thicker than the atria
True
T/F: the coronary arteries originate from the aorta and the suppliers of arterial blood to the heart
True
Cardiac output
the amount of blood pumped by the left ventricle in 1 min
Stroke volume is dependent on preload, after load, and _________
myocardial contractility
A classic sign of decreased cardiac output is:
- change in mental status
- dyspnea
- hypotension
Parasympathetic control of the heart is provided by the:
vagus nerve
The ventricles are innervated mainly by the:
somatic nerve fibers
The primary chief mediator of the sympathetic division of the autonomic nervous system is
norepinephrine
Chronotropy refers to
heart rate
Acetylcholine affects the heart by:
decreasing the heart rate
T/F: contractile cells generate an initial spark that sends current through your pacemaker cells
False
T/F: the nervous system can increase and decrease heart rate contractility and generate electrical impulses
False
Resting membrane potential in contractile cells is always recorded from the inside of the cell as:
-70mV to -90mV
In a normal heart, the primary pacemaker is the
SA node
The inherent beats/min of the AV node is:
40-60
T/F: The SA node is located in the left atrium, posterior to the tricuspid valve
False
The AV node is also known as the
gatekeeper
Depolarization takes place when
sodium ions rush into the cell
The AV junction is formed by the AV node and the:
Bundle of His
Atrial kick is MOST accurately defined as
15-30% of ventricular filling caused by atrial contraction
The mechanism of ectopic impulses are:
enhanced automaticity AND re-entry
Re-entry occurs when an impulse is:
delayed or blocked
T/F: a specific polarity is designated to each electrode regardless of selection
False
T/F: precordial chest leads view electrical activity in the heart on a transverse/horizontal plane
True
T/F: lead aVF is a “distant recording electrode” and does NOT view any wall of the heart
True
Each small square represents __ mV
0.1
the vertical axis of the graph paper corresponds with
voltage
A biphasic waveform represents an electrical impulse that moves
perpendicular to the positive electrode
An ECG machine is properly calibrated when an electrical signs is produced measuring __ mV
1
ECG paper normally records at a constant speed of
25mm/sec
The most common cause of acute coronary syndromes is what
rupture of atherosclerotic plaque
T/F: s&s of angina may be atypical in diabetics, the elderly and women
True
S&S of stable angina may occur after
- exertion
- emotional distress
- eating
- environmental stressors (ex. heat)
T/F: pts will ALWAYS experience chest pain during myocardial infarctions
False
What are common signs of an MI?
- confusion
- denial
- ashen skin
T/F: distinguishing between unstable angina and AMI can be accomplished during initial presentation
False
With regards to 15 lead placement, V4R is placed:
5th intercostal space at right midclavicular line
The 1st change in the evolving pattern of STEMI is
development of the T wave
A Q wave is pathological when it is:
more than 1/3rd the height of the R wave in the lead
Reciprocal changes in inferior leads are
Leads I and AVL
15 lead ECG placement consists of which new leads:
V4R, V8 and V9
Acute coronary syndromes refer to all of the following
- ST segment elevation MI
- Non ST segment elevation
- unstable angina
The left coronary artery divides into which two branches:
- circumflex
- LAD artery
Mean vector lies between
0 and +90
Two lead method of axis deviation involves which leads:
I and aVF
Criteria for identification of a right or left BBB includes a QRS equal or greater than 0.12s and
A QRS produced by supraventricular activity
T/F: V2 is the single best lead to use when differentiating between right and left BBB
False
T/F: with regards to a RBBB, the last 0.04secs of the QRS is deflected upright
True
Increase in thickness of a chamber due to pressure overload:
hypertrophy
Right atrial enlargement produces
abnormally tall and peaked initial part of P wave
T/F: left ventricular hypertrophy is a STEMI imitator
True
T/F: with regards to pericarditis, symptoms are made better by lying flat and worse by sitting up
False
T/F: in pericarditis, concave ST elevation is noted in almost every lead (except aVR and V1)
True
Hyperkalemia is abnormally high level of what serum in the blood
Potassium
T/F: tall and tented T waves are present in mild cases of hyperkalemia
True
T/F: hyperkalemia is a STEMI imitator
True
VF and aystole occur in hyperkalemia patients with a blood serum of:
10-12 mEq/L
A 15 lead ECG should be performed on
- any inferior MI
- tall R waves and ST depression in V1-V3
Tunica intima is what layer of the coronary artery
innermost
Monomorphic ventricular tachycardia is best described as:
3 or more unifocal PVCs in a row at a rate >100
ST segment is best described as:
- early repolarization of the ventricles
PR interval is considered prolonged if it is more than how many seconds in duration
0.20s
Multifocal atrial tachycardia is best described as
irregularly irregular
Common characteristics of SVT include
- p waves are non-discernable
- regular
- > 100 bpm
Atrial flutter is most commonly caused by
a rapid re-entry circuit
Location of MI - V1 and V2 elevated
- affected myocardial area: septal
- occluded artery: proximal LAD
Location of MI - V3 and V4 elevated
- affected myocardial area: anterior
- occluded artery: LAD
Location of MI - V5 and V6 elevated
affected myocardial area: lateral (apical)
occluded artery: distal LAD, circumflex or right coronary artery
Location of MI - I and aVL elevated
affected myocardial area: lateral
occluded artery: circumflex artery
Location of MI - II, aVF, and III elevated
affected myocardial area: inferior
occluded artery: 90% RCA, 10% LCx
Location of MI - V7, V8 and V9 elevated
affected myocardial area: posterolateral (posterior)
occluded artery - RCA or LCx
When does the left coronary artery become occluded:
lateral, septal and anterior MI
STEMI ECG Changes - 1st change
Development of T wave (hyperacute phase)
- increases in height, more symmetrical and pointed
- may occur within first few mins of infarction
STEMI ECG Changes - 2nd change
ST elevation (early acute phase)
- primary indication of myocardial injury in progress
- may occur within the first few hours of infarction
STEMI ECG Changes - 3rd change
T wave inversion (later acute phase)
- T wave inversion suggests presence of ischemia
STEMI ECG Changes - 4th change
Development of Q wave (fully evolved phase)
- 1st evidence that tissue death has occurred
STEMI ECG Changes - final change
The Q wave remains (healed phase)
- in time, the T wave regains its normal contour and ST segment returns to isoelectric line BUT Q waves remain as evidence an infarct occurred
What is automaticity?
ability of cardiac pacemaker cells to generate or initiate their own electrical impulse
What is excitability?
irritability: the ability of cardiac cells to respond to an electrical stimulus
What is conductivity?
ability of cardiac cells to transmit an electrical stimulus to other cardiac cells
What is contractility?
ability of cardiac cells to shorten, causing cardiac muscle contraction in response to electrical stimulus
What is polarization?
phase of readiness
-the muscle is relaxed and the cardiac cells are ready to receive and impulse
What is depolarization?
phase of contraction
- the cells have transmitted an electrical impulse, usually causing the cardiac muscle to contract
What is repolarization
recovery phase
- the muscle has contracted and the cells are returning to a ready state
Cardiac Action Potential - Phase 0
Rapid depolarization phase
- cell membrane has reached “threshold potential”
- sodium channels permit rapid entry of Na into cells making inside more positive than outside of the cell
Cardiac Action Potential - Phase 1
Early repolarization phase
- flow of sodium into cell stops
- potassium channels open which results in a decrease in the number of positively charged ions in the cell and drop in membrane potential
Cardiac Action Potential - Phase 2
Plateau phase - prolonged repolarization phase
- calcium channels open
- at the same time, potassium continues to leave the cell
Cardiac Action Potential - Phase 3
Rapid repolarization phase
- calcium channels close
- while potassium continues to exit the cell
Cardiac Action Potential - Phase 4
Resting membrane potential
- there is still excess of Na inside and K outside, which causes the sodium-potassium pump to activate
- the Na travels back out and K travels back in
- membrane returns to its resting membrane potential
- phase 0 begins all over again
Beginning with the right atrium, describe the normal flow of blood through the heart, lungs and to the systemic circulation
- through the inferior and superior vena cava into the right atrium, through the tricuspid valve into the right ventricle, through the pulmonary valve, through to the right and left pulmonary arteries, to the lungs to become oxygenated
- down through the right and left pulmonary veins into the left atrium through the bicuspid valve into the left ventricles, where it is pumped through the aortic valve into the aortic arch and to the rest of the body
What are the phases of Systole
4 phases
- phase 1 - isovolumetric contraction (ventricles squeezing but not pumping)
- phase 2 - ventricular ejection (pumping vigorously)
- phase 3 - protodiastole (pumping less)
- phase 4 - isovolumetric relaxation (relaxing, valves closing to end systole)
Discuss the phases of diastole
3 phases
- phase 1 - rapid refilling (atria dumping blood into ventricles)
- phase 2 - diastasis (slowing blood flow)
- phase 3 - atrial kick (atria contracting to squeeze remainder of blood into ventricles)
“All-or- nothing” principle
- the action potential along the cell membrane acts as a stimulus to the adjacent regions of the cell membrane
- this causes excitability and once started, it spreads and continues on to the next cell and so forth
Define absolute refractory period
the cardiac muscle cannot respond to any stimulation
Define relative refractory period
the cardiac muscle is more difficult than normal to excite, yet it can still be stimulated
Intrinsic rate of the SA node:
60-100
Intrinsic rate of the purkinje fibres:
20-40
Right coronary arteries:
Right coronary artery
- posterior descending artery
- right marginal artery
Left coronary arteries:
Left coronary artery
- circumflex artery
- left anterior descending artery
What is the single best lead to use for differentiating between a right and left BBB?
Lead V1
1st degree AV block
PR interval is prolonged (>0.20secs), prolonged and constant
2nd degree Type I AV block
PR interval lengthens with each cycle
- gradually longer PR interval until a QRS complex is dropped
