Block 1 - Anatomy - The Heart; Intro to EKGs Flashcards
What is indicated by the arrow in this image?
Pericardial effusion
(medium gray fluid surrounding line of heart wall)
What is the purpose of the pericardium?
To prevent friction;
to secure the heart in place
To what is the pericardium susceptible?
Infection, metastases, effusion
What nerves supply the fibrous and parietal pericardia?
The phrenic nerves
What nerves innervate the visceral pericardium?
The sympathetic trunks and vagus nerves
What does this CXR indicate?
What other signs or symptoms might be present?
Pericardial effusion, possible cardiac tamponade;
Beck’s triad (JVD, hypotension, muffled heart sounds)
Describe the location of the IVC, lower esophagus, and descending aorta in relation to the heart.
IVC (on the right);
esophagus (medial);
descending aorta (lateral)
Why is the abdominal aorta predisposed to abdominal aneurysms?
Lack of vasovasorum that is present in the upper aorta
What are the ABCs of the branching aortic arch?
Aorta, Brachiocephalic, Common carotid (left), Subclavian (left)
To what types of vascular issues is the aorta susceptible?
Atherosclerosis, inflammation, shear stress, and aneurysm formation
What are some clinical sequelae of long-term hypertension?
Cardiac hypertrophy, heart failure
What are some of the signs and symptoms of heart failure?
(ignore left-right distinctions)
Shortness of breath and crackles in lung sounds (pulmonary edema);
pitting edema, JVD, hepatosplenomegaly
What are some deadly potential side effects of chronic hypertension?
AMI, stroke, renal failure
For which cardiac sounds is the diaphragm of the stethoscope ideal?
The pulmonic and aortic regions
For which cardiac sounds is the bell of the stethoscope ideal?
The mitral region
For which cardiac region is the bell or diaphragm of the stethoscope acceptable?
The tricuspid region
What is the most commonly replaced heart valve?
What is the second most commonly replaced?
Aortic;
mitral
What do you suspect after reviewing this X-ray?
Possible aortic dissection
(here is the emergency CT confirmation)
How can an aortic dissection or tear be treated?
With a dacron graft
Proximal aortic dissection should be considered in the differential in what scenarios?
Chest pain that moves to the back;
chest pain in the setting of a wide mediastinum on CXR;
or chest pain associated with an elevated BP
Who is most at risk for aortic dissection?
Older, hypertensive patients;
smokers;
or those with an underlying predisposition (e.g. Marfan’s syndrome)
What are the principal coronary arteries?
Right coronary a. –> Acute marginal a. + posterior descending a.
Left main coronary a. –> left anterior descending a. + circumflex a. + left marginal a.
What vein follows along the circumflex artery and then empties into the coronary sinus?
The great cardiac vein
What vein follows along the inferior portion of the circumflex and ends in the coronary sinus?
The posterior vein of the left ventricle
What vein runs along the posterior descending artery before emptying into the coronary sinus?
The middle cardiac vein
When do the coronary arteries fill?
During diastole
What space separates the atria from the ventricles?
What vessel lines this groove?
The coronary sulcus;
the coronary sinus
How long is the period from occlusion of the coronary arteries to cell death?
4 - 6 hours
Define myocardial infarction.
Myocyte death due to loss of perfusion to cardiac tissue. This is due either to loss of flow from vascular occlusion or from increased (but unmet) demand.
What cardiac procedure can restore an occluded coronary artery?
Angioplasty
What structure in what part of the brain controls cardiac innervation?
The cardiovascular center;
the medulla oblongata
What types of nerve fibers does the cardiovascular center (medulla oblongata) emit?
Sympathetic and parasympathetic
What nerve carries parasympathetic activity for the cardiovascular control center (medulla oblongata)?
What is the parasympathetic effect on the heart?
The vagus nerve;
decreases HR and force of contraction
What parts of the heart are innervated by the vagus nerve?
The SA node, AV node, and the atrial myocardium
What parts of the heart are innervated by sympathetic fibers?
What effect do they have?
The SA node, AV node, and the atrial and ventricular myocardium;
increased HR and force of contraction
Where do they autonomic nerves converge before innervating the heart?
The cardiac plexuses around the aorta and trachea
What dermatomal distribution is activated in ‘referred pain’ during acute coronary syndromes?
Which level is just the medial arm?
T1 - T5
(can be as distant as the angle of the jaw all the way to the xiphoid process and everything lateral and to the left of these two points);
T1
Which coronary artery supplies the SA and AV nodes?
The right coronary artery
Which coronary artery supplies the anterior 2/3 of the interventricular septum?
The left anterior descending artery
Which coronary artery supplies the left atrium?
The circumflex
What may be some potential side effects in heart contraction as a result of infarction of the right coronary artery?
Patients whose RCA is occluded may develop bradycardia or a block in the AV node due to impaired blood supply to conduction tissue
What may be some potential side effects in heart activity as a result of infarction of the left main coronary artery?
Patients who block the LCA may suffer loss of function of the interventricular septum and have poor contractility. They may also develop a bundle branch block.
Why are posterior coronary wall infarcts rare?
The dual blood supply from the right coronary arteries and circumflex arteries
A patient has angina and normal epicardial arteries. What other diagnoses should be included in the differential?
Aortic stenosis, hypertension
(left ventricular hypertrophy and increased oxygen demand)
Why might there be chest pain in cases of aortic stenosis and chronic hypertension?
Increased oxygen demand due to left ventricular hypertrophy
Why might aggressive reduction of blood pressure be counterproductive in a case of acute coronary syndrome?
The coronary insufficiency may be exacerbated
What equation relates cardiac output and stroke volume?
CO = SV x HR
What is a potential negative effect of tachycardia?
Decreased cardiac perfusion and ventricular filling during diastole
From what part of the aorta do the coronary arteries arise?
The aortic sinuses
Why do different heart tissues (atrial, ventricular, sinoatrial) have differing action potential shapes?
Differences in conductance channels and the way ions cross their differing membranes
What are the four phases of ventricular or atrial action potentials?
0 - depolarization;
1 - initial repolarization
2 - plateau
3 - repolarization
4 - diastolic potential
What event is responsible for phase 0 of ventricular or atrial action potentials?
What principal ion is involved?
Depolarization
(Na+ influx)
What event is responsible for phase 1 of ventricular or atrial action potentials?
What principal ion is involved?
Initial repolarization
(K+ efflux)
What event is responsible for phase 2 of ventricular or atrial action potentials?
What principal ion is involved?
Plateau
(Ca+ influx)
What event is responsible for phase 3 of ventricular or atrial action potentials?
What principal ion is involved?
Repolarization
(K+ efflux)
What event is responsible for phase 4 of ventricular or atrial action potentials?
What principal ion is involved?
Diastolic (resting) potential
(Na+-K+ ATPase and K+ leak channels)
What is the diastolic (resting) potential of cardiac myocytes?
What is the diastolic (resting) potential of most neurons?
- 85 mV;
- 70 mV
What features of cardiac muscle allows for synchronized, uniform depolarization down a length of tissue?
The SA - AV - Purkinje conduction system;
gap junctions between cardiac myocytes
What three cardiac tissues are responsible for these three action potentials?
A - Ventricles
B - Atria
C - SA node
What type of cationic channel allows for the specialized conductance seen in the SA node?
If (‘funny’) channels
The slope of which segment of which of these action potentials determines heart rate?
Phase 4 of the SA node potential
(basically, the length of the diastolic period in this autorhythmic tissue;
the length of the depolarization and repolarization should be fairly constant;
so, the length of this ‘latent’ period is what matters most)
What is indicated by a steep slope of phase 4 of the SA node action potential?
Rapid heart rate (short diastole)
What is indicated by a shallow slope of phase 4 of the SA node action potential?
Slow heart rate (long diastole)
Which phases are present in the ventricular and atrial action potentials but NOT in the sinoatrial action potentials?
Phases 1 and 2
What about the SA node action potential would indicate a rapid heart rate?
A steep slope of phase 4
What about the SA node action potential would indicate a slow heart rate?
A shallow slope of phase 4
What does it mean that the EKG uses a bipolar system?
There must be at two nodes (electrodes) in a sequence;
one electrode must be positive, one electrode must be negative
EKG terminology:
define segment,
define interval.
Segment - A straight line connecting two waves;
interval - at least one wave + the associated segment
What cardiac structure is often damaged during traumatic accidents (e.g. motorcycle or car crashes)?
The ligamentum arteriosum
Describe the conduction system of the atria.
SA –> internodal pathways (+ Bachmann’s Bundle) –> AV node
What conduction system extends from the right atrium to the left atrium?
Bachmann’s Bundle
How long is the conduction delay in the AV node?
What is the purpose of this delay?
The absence of what ionic channel creates this delay?
1/10 of a second;
to allow complete atrial emptying and ventricular filling;
Na+ (ONLY Ca++ and K+ are involved)
How large is the average heart?
The size of the patient’s fist (about 250 g)
Describe the conduction system from the AV node to the ventricles.
AV node –> Bundle of His –> Left and right bundle branches –> Purkinje fibers
What feature of the heart allows for equal inflow and outflow (typically)?
The Frank-Starling mechanism;
the more blood that enters the heart, the more the heart is stretched, the stronger the contraction
What might exaggerated (very tall) QRS peaks indicate about the heart?
Hypertrophy
Define cardiac output.
Define stroke volume.
Liters pumped out per minute;
volume ejected per heartbeat
What valve can be impaired by left ventricular hypertrophy?
The mitral valve
(leading to dysfunction and associated murmurs)
What is the Frank-Starling law of the heart?
The output of the heart is directly proportional to its input.
(strength of ventricular contraction is proportion to EDV)
Where are crackles usually heard best?
What do they indicate?
The lower lung fields;
heart failure
How does norepinephrine increase heart rate and contractility?
What ion is involved?
Increased calcium release from the sarcoplasmic reticulum
(calcium-induced calcium release)
Is opening and closing of the heart valves an active or passive process?
Entirely passive
(entirely pressures-based)
Is it normal to hear S3 and S4 heart sounds in an adult?
No;
they indicate grave pathophysiological conditions
Is it normal to hear S3 and S4 heart sounds in a child?
S3 - yes, sometimes;
S4 - no
Will a patient receiving a cardiac valve replacement need to be started on immunosuppressants?
No;
the replacement valves are usually coated in non-reactive substances
The great cardiac vein runs alongside which coronary artery?
The circumflex
The posterior vein of the left ventricle follows along which artery?
The descending portion of the circumflex artery
The middle cardiac vein follows along which artery?
The small cardiac vein follows along which artery?
The posterior descending a.;
the right coronary a.
What is another name for the posterior descending artery?
The posterior interventricular artery
Assuming a right-dominant heart, what portion of the heart is supplied by the circumflex artery?
What portion of the heart is supplied by the posterior descending artery?
What part of the heart is supplied by the conus artery?
The lateral left ventricle;
the posterior interventricular area;
the anterior right ventricle
Approximately what percentage of patients have a right-dominant heart?
90%
Approximately what percentage of patients have a left-dominant heart?
10%
Do myocardial damage and pericardial damage present in the same way?
No;
pericardial pain follows a phrenic nerve distribution;
myocardial pain follows a T1 - T5 distribution
The visceral afferents carrying myocardial pain signals to the CNS follow along what other nerves back to the spinal cord?
The sympathetic nerves
(although the sympathetic nerves are NOT afferent; they are strictly efferent - these nerves simply follow the same physical pathway)
Is the vagus nerve solely composed of parasympathetic fibers?
No;
there are also visceral afferent fibers within it
Name the branch of the right coronary artery (in a right-dominant heart) supplying the following cardiac tissues:
A - posterior 1/3 of the interventricular septum
B - upper right ventricle
C - the SA node
D - lower right ventricle
A - posterior descending a.
B - a. of the conus
C - sinoatrial nodal branch of the RCA
D - acute marginal a. of RCA
Which heart valve is closely associated with the movement of the interventricular septum?
Describe the mechanism.
The tricuspid;
the moderator band (septomarginal trabeculum) extends from the septum to the anterior papillary muscle
What is the name of the band of conductive tissue extending along the border of the right atrium from the SA node to the AV node?
The crista terminalis
What is the name of the band of conductive tissue extending along the right interventricular septum to the anterior papillary muscle?
The moderator band (septomarginal trabeculae)
