Cardiology Flashcards
What is the pericardium?
Membrane that surrounds and protects the heart
What are the two parts (layers) of the pericardium?
Fibrous pericardium
Serous pericardium
What is the inner visceral layer of the serous pericardium also called?
Epicardium
Normally how much pericardial fluid is in the pericardial cavity?
15-50ml
What is the function of the pericardial fluid?
Reduces friction between the two layers of serous pericardium as the heart moves
What are the three layers of the heart wall?
Epicardium
Myocardium
Endocardium
What is the myocardium?
A thick, helical middle layer of the heart wall composed of cardiac muscle
What is the endocardium?
The thin internal layer of the heart wall made of endothelium and sub endothelial connective tissue, or a lining membrane that covers the valves
What is the auricle of the heart?
A wrinkled pouch like structure on the anterior surface of the atria
What is the purpose of the auricles of the heart?
Each one slightly increases the capacity of its atrium so it can hold a larger volume of blood
What are sulci and what do they contain?
They are grooves on the surface of the heart that contain coronary blood vessels and a variable amount of fat
What does each sulcus mark?
The external boundary between two chambers of the heart
What does the deep coronary sulcus mark?
It encircles the heart and marks the external boundary between the superior atria and inferior ventricles
What marks the external boundary of the ventricles on the heart?
Anteriorly - the anterior interventricular sulcus
Posteriorly - the posterior interventricular sulcus
From what 3 blood vessels does the right atrium receive blood?
Superior vena cava
Inferior vena cava
Coronary sinus
What is a prominent feature in the interatrial septum, and what is it a remnant of?
Fossa ovalis - remnant of foramen oval
Where is the sinoatrial node located?
Right atrium, where the SVC joins the atrial tissue mass
What causes activation of the pacemaker of the heart without external activation?
The SA node has an unstable resting potential and is repeatedly depolarising to the threshold spontaneously
What structures conduct the impulse generated by the SA node across the left and right atrium?
Internodal tracts and Bachmanns bundle
What are the three internal tracts that transmit impulses across the atria?
Anterior
Wenkebach
Thorel’s
The heart is supplied by autonomic fibres from where?
The cardiac plexus
Where is the deep cardiac plexus located?
On the anterior surface of the bifurcation of the trachea
Where does the superficial cardiac plexus lie?
On the arch of the aorta
Is the cardiac plexus sympathetic or para-sympathetic?
Both
What fibres make up the parasympathetic nervous supply of the heart?
Presynaptic fibres of the vagus nerve
Name three effects of sympathetic stimulation to the heart.
Increased heart rate
Increased impulse conduction
Increased force of contraction
Name three effects of parasympathetic stimulation to the heart.
Slowed heart rate
Reduced force of contraction
Constrict coronary arteries
What do postsynaptic parasympathetic fibres release and what does it bind to?
Acetylcholine - muscarinic receptors
When fluid is pumped through a closed system, what two factors determine its flow?
Pressure and resistance
According to Darcy’s Law, what is mean arterial blood pressure equal to?
Cardiac output multiplied by total peripheral resistance
MABP = CO x TPR
What is laminar flow?
Also known as streamline flow, occurs when a fluid flows in parallel layers, with no disruption between layers
What are the primary areas in the cardiovascular system responsible for resistance to blood flow?
Mainly arterioles
To a lesser extent, capillaries and venules too
Where is the steepest fall in blood pressure?
Arterioles
What is elastance?
Quality of recoiling or returning to an original form after removal of pressure.
Way to describe the elastic properties of a blood vessel
What is compliance? (in relation to vessels)
Ability of a vessel to distend and increase volume with increasing transmural pressure
Which part of the cardiovascular system has the highest compliance?
veins and venules
What percentage of total blood volume is normally in the veins and venules?
70%
What is the difference in compliance between arteries and veins?
Veins are about 20 times more compliant than arteries
In blood vessels, what is the transmural pressure equal to?
Pressure inside the vessel minus the interstitial pressure
What does the Law of Laplace state about vessels?
The total circumferential wall tension at equilibrium is counterbalanced by the total pressure in the lumen.
i.e. the tension in the wall of a blood vessel depends on the radius, thickness of the wall and the transmural pressure
What does the elastic recoil of the aorta do to the blood flow?
It converts what would be intermittent flow into a continuous, albeit pulsatile, flow through the arterial system
What are Windkessel vessels?
Aorta and large elastic vessels
What is pulse pressure?
The difference between systolic and diastolic pressure
What is the mean arterial blood pressure?
Pressure averaged over the whole cardiac cycle
In terms of percentage, how much time does the heart spend in diastole?
60%
What is the mean arterial blood pressure roughly equal to?
Diastolic pressure, plus one third of the pulse pressure
What are Korotkoff sounds?
Varying sounds heard with a stethoscope she measuring blood pressure
What measures mean arterial blood pressure and where are they located?
Arterial baroreceptors
Located in the wall of the aortic arch and in the carotid sinus
What is the carotid sinus?
An enlarged part of the internal carotid artery just after it rises from the common carotid artery
What do atrial stretch receptors measure?
Atrial blood volume
A rise in levels of which ion causes contraction of the heart muscle?
Calcium
What category of factors alter the contractility of cardiac muscle?
And name one.
Inotropic factors
Noradrenaline
What type of agents affect atrioventricular conduction?
Dromotropic agents
How do chronotropic agents affect heart rate?
By affecting nerves controlling the heart or changing the rhythm produced by the SA node
In a heart beat, what is the absolute refractory period?
A period immediately following the firing of a nerve fibre when it cannot be stimulated no matter how great a stimulus applied
What is the relative refractory period?
The period shortly after the firing of a nerve fibre when partial depolarisation has occurred and a greater than normal stimulus can stimulate a second response
What is first-degree (incomplete) heart block?
Abnormally slow conduction in the AV node, where delay is greater than normal
How does first-degree heart block appear on an ECG?
An extended PR interval
What happens to the impulses in second-degree heart block?
A fraction of the impulses from the atria are conducted to the ventricles
How is second-degree heart block Mobitz type II seen on an ECG?
Ventricular contraction is only initiated every second (2:1) or third (3:1) atrial contraction
What is seen on an ECG in Wenkebach block (second-degree heart block Mobitz I)?
The PR interval progressively lengthens until there is no transmission from atria to ventricles and a QRS complex is missed. The cycle then begins again
What happens in third-degree heart block?
Conduction between atria and ventricles is abolished
What can cause third-degree heart block?
Ischaemic damage to nodal tissue or the bundle of His
What does third-degree heart block: AVN escape look like on ECG?
Complete dissociation between P wave and QRS complex. Narrow QRS (<0.12s), about 40bpm
What does third-degree heart block: ventricular escape look like on ECG?
Complete dissociation between P wave and QRS complex. Wide QRS (>0.12s). Heart rate usually down to less than 20bpm
What does bundle branch block look like on ECG?
Wide QRS complex, usually with a bit of a M or W shape, showing that activation is delayed from one side to the other
What does the Frank-Starling law of the heart state?
That stroke volume of the heart increases in response to an increase in the volume of blood filling the heart, when all other factors remain constant
What is an important consequence of Starlings law of the heart, in regards to stroke volume?
That stroke volume between the left and right ventricles are matched
Which law is Darcy’s law analogous to?
Ohm’s law
Which vessels are capacitance vessels and why?
Veins, because they can serve as blood volume reservoirs
What binds to beta1-receptors?
The catecholamines - noradrenaline and adrenaline
What does activation of cardiac beta1-receptors result in?
Positive inotropic effect = increases contractility
Positive chronotropic effect = increases heart rate
What can cause aortic stenosis?
Calcified valves
Congenital bicuspid valve
Rheumatic fever
What is the typical history of aortic stenosis?
Syncope
Angina
Dyspnoea
What is the character of the pulse like in aortic stenosis?
Slow rising, narrow pulse pressure
What is the management for aortic stenosis?
Aortic valve replacement
Balloon Valvuloplasty
Medical flow up - for mild-moderate
What is a TAVI?
Transcutaneous Aortic Valve Implantation
What is infective endocarditis?
Infection of endocardium or vascular endothelium
What are some signs of infective endocarditis?
Sepsis
May have valve regurgitation
New heart murmur
Janeway lesions
