Cardiology 2 Flashcards
What creates a bouncing pulse?
aortic regurgitation, anaemia, sepsis cause large stroke volume typically causing a bouncing pulse with a high amplitude and wide pulse pressure
what may cause a slow rising pulse?
aortic stenosis
what is the JVP determined by?
determined by right atrial pressure
what does tricuspid regurgitation do to the JVP wave form?
giant V waves
Where does the right atrium receive blood from?
the superior and inferior vena cavae
where does the left atrium receive blood from?
the four pulmonary veins
what are the atrium and ventricles separated by?
the annulus fibrosus - this forms a skeleton for the AV valves and electrically insulates the atria from the ventricles
what is the cardiac silhouette formed by on CXR
the left is formed by the aortic arch, pulmonary trunk, the left atrial appendage and the LBV
The right the silhouette is formed by the RA and the superior and inferior venae cave and the lower right border is formed by the RV
where to the left and right coronary arteries arise from?
the left and right sinuses of the aortic root distal to the aortic valve
What does the left coronary artery divide into ?
left anterior descending (which runs in the inter ventricular groove
left circumflex artery which runs posteriorly in the atrioventricular groove
Which part of the heart does the LAD supply?
supply to the anterior part of the septum and the anterior, lateral and apical walls of the LV.
What part of the heart does the circumflex supply?
the posterior and inferior segments of the LV
where does the RCA run and what does it supply?
runs in the right atrioventricular groove
gives branches that supply the RA, RV and inferoposterior aspects of the LV
Where does the posterior descending artery run and what does it supply?
it runs in the posterior interventricular groove and supplies the inferior part of the of the interventricular septum
This vessel is a branch of the RCA in 90% of people
in the remainder of people it is supplied by the circumflex
which coronary artery supplies the SA and AV node?
the RCA supplies the SA node in 60% of individuals and the AV node in 90% of individuals.
Proximal occlusion of the RCA can result in sinus bradycardia and AV nodal block
Where is the SA node located?
it is situated at the junction of the superior vena cava and the right atrium
Function of SA node?
specialised arterial cells that depolarise at a rate influenced by the autonomic nervous system and by circulating catecholamines.
During normal sinus rhythm, this depolarisation waves propagates through the atria via sheets of atrial myocytes.
How is depolarisation conduction from atrial to ventricles?
through the AV node
the annulus fibrosus forms a conduction barrier between the atria and the ventricles, preventing transmission of conduction except through the AV node.
where is the AV node located and what is its function ?
The AV node is a midline structure extending from the right side of the inter arterial septum , penetrating the annulus fibrosus anteriorly. It conducts relatively slowly, producing necessary time delay between atrial and ventricular contraction.
what is the His-purkinje system composed of ?
the bundle of His extending from the AV node in the inter ventricular septum, the right and left bundle branches passing along the ventricular septum and into the respective ventricles
The anterior and posterior fascicles of the left bundle branch
The smaller Purkinje fibrest that ramify through the ventricular myocardium
The tissues of the His-Purkinje system conduct very rapidly and allow near-simultaneous depolarisation of the entire ventricular myocardium
Nerve supply of the heart
The heart is innervated by both sympathetic and parasympathetic fibres.
Adrenergic nerves from the cervical sympathetic chain supply muscle fibres in the atria and ventricle and the eletrical conducting system
Parasympathetic pre-ganglionic fibres and sensory fibres reach the heart through the vagus nerve.
Cholinergic nerves supply the AV and SA nodes via muscarnic (M2) receptors
What does activation of beta 1 adrenoreceptors in the heart result in ?
Activation of beta 1 adreoceptors in the heart results in positive inotropic and chronotropic effects
what is inotropic?
Increase cardiac contractility, which improves cardiac output and helps maintain blood pressure and perfusion to the body. Inotropes work by acting on the cardiomyocytes, or heart muscle cells. Positive inotropes increase the force of the heartbeat, while negative inotropes decrease it
What is chronotrope?
Change the heart rate and rhythm by affecting the heart’s electrical conduction system and the nerves that influence it. Positive chronotropes increase heart rate, while negative chronotropes decrease it. Chronotropes are used to treat conditions such as hypertension, angina, and arrhythmias
what does activation of beta 2 adrenoceptors result in?
activation of beta 2 adrenoceptors in vascular smooth muscle causes vasodilation
what causes base heart rate and what causes it to increase
Under resting conditions, vagal inhibitory activity ptr-dominates and the heart rate is slow
Adrenergic stimulation, associated with exercise, emotional stress, fever and so one, causes the heart rate to increase.
what can happen in disease states to the nerve supple to the heart?
In disease states the nurse supply to the heart may be affected. for example in heart failure the sympathetic system may be up-regulated and DM the nerves themselves may become damaged by autonomic neuropathy so that there is little variation in heart rate.
Myocardial contraction?
Each myocyte branches and integrates with adjacent cells
An intercalated disc permits electrical conduction via gap junctions and mechanical conduction via the fascia adhering, to adjacent cells
The cross links between actin and myosin molecules contain ATPase, which breaks down ATP to provide energy for the contraction
During the plateau phase of the action potential, calcium ions enter the cell and are mobilised from the sarcoplasmic reticulum. They bing to the troponin and thereby precipitate contraction by shortening the sarcomere through through the intedigitation of the actin an myosin molecules
what regulates the cardiac muscle contraction
the force of cardiac muscle contraction, or the inotropic state, is regulated b the influx of calcium ions through slow calcium channels
what is ANP?
atrial natueritic peptide
secreted by atrial myocytes in response to stretch
vasodilator - reduces BP
Acts as a diuretic - promoted renal excretion of water and sodium
What is BNP
produced by ventricular cardiomyocytes in response to stretch
what does Neprilysin do?
breaks down ANP and BNP and other proteins - in doing so acts a vasoconstrictor
what is Poiseuille’s law?
resistance Is inversely proportional to the fourth power of the radius .
what leads to vasoconstriction and vasodilation?
Neurogenic constirction operates by alpha adreoceptors on vascular smooth muscle
Dilation via muscaranic and beta 2 adrenoceptors
Systemically and locally released vasoactive substances influence tone; vasoconstrictors include noradrenaline, angiotensin II and endothelin 1
Adenosine, bradykinin, prostaglandins and nitric oxide are vasodilators
what is the role of the endothelium ?
Plays a vital role vascular homeostasis
It synthesis and releases many vasoconstrictive mediators that cause vasodilation, including nitric oxide, prostacyclin, endothelium derived hyper polarising factor
and vasoconstriction including endothelin-1 and angiotensin II.
It has a major influence on the key regulatory steps in the recruitment of inflammatory cells and on the formation and dissolution of thrombus
Once activated the endothelium expresses surface receptors such as E-selectin, intercellular adhesion molecule type 1 and platelet-endothelial cell adhesion molecule type 1 (PECAM-1) which mediate rolling, adhesion and migration of inflammatory leucocytes into the subintima.
The endothelium stores vWF which promotes thrombus formation by linking lately adhesion to denuded surfaces
what may damage to the endothelium lead to ?
Damage to the endothelium may disturpt the balance of regulation of vascular tone and BP and lead to vascular dysfunction, tissue ischaemia and hypertension
What happens when an intravascular thrombus forms?
once intravascular thrombus forms, tissue plasminogen activator is rapidly released from a dynamic storage pool within the endothelium to induce fibrinolysis and thrombus dissolution
what happens to JVP during inspiration and expiration?
JVP falls on inspiration
Rised on expiration
what happens to BP and HR during inspiration and expiration?
Inspiration BP falls and HR increases
Expiration BP rises and HR slows
what is pulses paradoxus?
exaggerated fall in BP during inspiration
seen in severe airway obstruction (asthma/COPD)
Also characteristic of cardiac tamponade
what does the P wave represent on ECG?
atrial depolarisation
What is the normal PR interval ?
0.12-0.2 seconds
it reflects the duration of AV nodal conduction
What is the QRS complex?
ventricular myocardial depolarisation
what is the t wave?
ventricular repolarisation
what is considered a wide QRS?
> 0.12 seconds
what is a normal QT interval
male < 0.44 seconds
Female < 0.46 seconds
what causes prolonged QTC ?
congenital long QT syndrome
low potassium
low magnesium
low calcium
some drugs
Indications of exercise ECG
to confirm diagnosis of Angina
To evaluate stable angina
to assess prognosis following MI
To assess outcome after coronary revascularisation
To diagnose and evaluate the treatment of exercise induced arrhythmias
What are the high risk finding on exercise ECG?
low threshold for ischaemia
fall in BP on exercise
Widespread, marked or prolonged ischaemia on ECG
Exercise induced arrhythmia
when is stress testing contraindicated?
ACS
decompensated heart failure
severe HTN
what calculation is used to estimate the pressure gradient across a valve?
Bernoulli equation
=4x(peak velocity (m/sec))2
What is TOE useful for?
useful for imaging structures like the left atrial appendage, pulmonary veins, thoracic aorta and intertribal septum which may be poorly visualised on TTE
what is a stress echo?
used in patients with suspected CAD who are unsuitable for exercise stress testing - such as mobility problems or pre-existing bundle branch block
Give a high dose of an inotrope such as dobutamine
myocardial segments with poor perfusion will become ischaemic and contact poorly under stress manifesting a wall motion abnormality on the scan
Low dose dobutamine can induce contraction in hibernating myocardium such patients may benefit from bypass surgery or PCI
when is CTCA useful?
in the initial assessment of patients with chest pain and a low or intermediate likelihood of disease, it has a high negative predictive value in excluding coronary artery disease
What is CMR useful for?
useful for imaging the aorta, suspected dissection and can define anatomy of the heart and great vessels in patients with congenital heart disease
Useful for detecting infiltrative conditions affecting the heart and good to evaluate the RV which is difficult by echo
physiological data can be obtained Erin the signal returned from moving blood to allow quantification of blood flow across regurgitant or stenotic valves
It is also possible to asses regional wall motion in patients with suspected coronary disease or cardiomyopathy
Myocardial perfusion and viability can be assessed
Delayed enhancement can be used to identify myocardial scarring and fibrosis
What is left heart catheterisation used for?
it involves assessing there arterial circulation, usually through the radial artery to allow catheterisation of the aorta, LV and coronary arteries.
Used for coronary angio to give info about extent and severity of coronary stenosis, thrombus and calcification
Left ventriculography can be performed during the procedure to determine the size and function of the LV and to demonstrate MR.
what is right heart catheterisation used for?
to assess the right heart and pulmonary artery pressures
to detect intracardiac shunts by measuring oxygen saturation in different chambers
