Cardiology AI Flashcards
What are sinuses of Valsalva?
Dilations of the aortic root that lie immediately beyond the aortic valve.
What does the left subclavian artery supply?
The left thoracic limb and some vertebral arteries.
What do bronchial veins drain?
Systemic vessels that perfuse lung tissue and empty into the pulmonary veins.
What is the function of the interventricular septum?
To contribute a critical proportion of right ventricular systolic function.
What is the left ventricular free wall’s contribution to the cardiac mass?
It makes up the left and caudal aspects of the cardiac mass.
What do Thebesian veins empty into?
The cavities of both left and right ventricles.
What is the role of the right side of the heart?
To facilitate low pressure flow from systemic veins into the low-resistance pulmonary circulation.
What is the cranial vena cava responsible for draining?
Venous drainage from the head, neck, and thorax.
What does the caudal vena cava drain?
Venous drainage from the abdomen and caudal body.
What is the function of the azygous vein?
It drains the dorsal walls of the abdomen and thorax and forms a physiologic anastomosis between the caudal and cranial vena cava, bypassing the cranial abdomen.
What does the right atrium empty into?
The tricuspid valve orifice.
What is the right ventricle?
A low-pressure conduit between the systemic veins and the pulmonary artery.
What is the function of the tricuspid valve?
To act as a three-leaflet atrioventricular valve.
What is the location of the right ventricular free wall?
It makes up the cranial and right-lateral aspects of the cardiac mass.
What is the pulmonic valve?
A three-leaflet semilunar valve that is anatomically separate from the aortic, mitral and tricuspid valves.
What is the function of papillary muscles?
To project from the myocardium and tense the valve leaflets slightly before peak systole.
What are chordae tendinae?
Structures that attach the tricuspid leaflets to the papillary muscles.
What is the main pulmonary artery responsible for?
Curving cranially over the aortic root and ascending aorta, then branching into left and right pulmonary arteries.
Where is the coronary sinus located?
On the floor of the right atrium, just inside the entrance of the caudal vena cava.
What is the intervenous tubercle?
A ridge of muscular tissue on the posterior right atrial wall that serves to stream blood flow from the cranial vena cava towards the tricuspid orifice.
What is the fossa ovalis?
A region of thin, fibrous inter-atrial septum representing the site of the embryologic foramen ovale.
How does reduced cardiac output lead to activation of neurohormonal mechanisms in heart disease?
Reduced cardiac output triggers activation of neurohormonal mechanisms as a compensatory mechanism.
What are the irreversible changes in anatomy and physiology seen in patients with heart disease?
Patients with heart disease exhibit cardiac and vascular fibrosis, enlarged cardiac chambers, and a higher baroreceptor set-point.
What are the causes of reduced cardiac output in specific cardiac disorders?
Mitral valve disease, dilated cardiomyopathy, hypertrophic cardiomyopathy, patent ductus arteriosus, aortic/pulmonic stenosis, and tachycardiac-induced cardiomyopathy.
How does mitral valve disease lead to reduced cardiac output?
A leak in the mitral valve causes a percentage of stroke volume to be returned to the left atrium instead of being pushed forward into the arterial system.
What is the mechanism of reduced cardiac output in dilated cardiomyopathy?
Muscular weakness of the left ventricle leads to reduced stroke volume and drop in cardiac output.
How does hypertrophic cardiomyopathy result in reduced cardiac output?
Myocardial fibrosis and abnormal force transduction lead to muscular thickening, diastolic dysfunction, and reduced stroke volume.
What effect does patent ductus arteriosus have on cardiac output?
Diastolic run-off of blood through the PDA reduces mean arterial pressure, unloads baroreceptors, and decreases cardiac output.
What is meant by ‘high output heart failure’?
It refers to the reduced cardiac output caused by a large ventricular septal defect (VSD) or arteriovenous shunt.
How does aortic or pulmonic stenosis contribute to RAAS activation?
Severe reduction in outflow from either side of the heart activates RAAS by unloading baroreceptors.
How do chronic tachyarrhythmias lead to cardiomyopathy and CHF?
Tachyarrhythmias reduce cardiac output by impairing ventricular filling and causing myocardial dysfunction, triggering the baroreflex and RAAS activation.
What are the consequences of chronic RAAS activation on the heart?
Myocardial fibrosis, reduced diastolic function, increased risk of arrhythmias, reduced myocardial perfusion, and potential for infarction.
What is pressure overload and how does it contribute to cardiac remodeling?
Pressure overload occurs when the heart faces increased afterload, leading to concentric hypertrophy and thickening of the myocardium.
What is volume overload and how does it contribute to cardiac remodeling?
Volume overload occurs when the heart receives excessive blood volume, causing eccentric hypertrophy and dilation of cardiac chambers.
What is the role of myocardial fibrosis in cardiac remodeling?
Myocardial fibrosis contributes to reduced diastolic function, arrhythmias, and can lead to ischemia and potential infarction.
What adaptations does the heart undergo in response to the primary deficit affecting it?
The heart undergoes additional remodeling to compensate for the primary deficit and maintain cardiac function.
What are T-tubules in cardiomyocytes?
Long invaginations of the cell surface membrane.
What is the function of T-tubules?
To facilitate rapid depolarisation of the cell and reduce the distance calcium ions have to travel.
What is the sarcoplasmic reticulum?
A highly folded series of membranous sacs.
What is the function of the sarcoplasmic reticulum?
To store calcium ions and release them during systole.
How many types of calcium channel/pump exist in the cardiomyocyte?
Four.
What is the function of the L-type calcium channel?
To allow an influx of calcium into the cytosol.
What is the calcium-induced calcium release channel?
A large protein that opens up when activated and allows calcium ions to leave the sarcoplasmic reticulum.
What is the SERCA2a pump?
An ATP dependent pump that pumps calcium ions from the cytosol into the sarcoplasmic reticulum.
What is the sodium-calcium exchanger?
A passive, two-way channel that exchanges sodium ions for calcium.
What happens when the action potential arrives in a cardiomyocyte?
L-type calcium channels open and allow an influx of calcium ions into the cytosol.
What causes contraction of the cardiomyocyte?
Binding of calcium ions to the sarcomere.
How is the intracellular calcium concentration normalized at end-systole?
Through re-uptake into the sarcoplasmic reticulum and facilitated diffusion out of the cell surface membrane.
What are the three factors that lead to contraction of the sarcomere?
Protein structure of the sarcomere, influx of calcium to the cytosol, and ATP release.
What are actin and myosin?
The two crucial proteins of the sarcomere that interact via binding sites.
What is the state of the sarcomere during diastole?
Relaxed, with myosin heads prevented from activity by troponin proteins.
What happens when there is an increased intracellular calcium ion concentration?
A change in the sarcomere leading to contraction.
Who is the Module Developer of Small Animal Medicine Distance Learning Module 12?
Dr Kieran Borgeat
Who are the Module Tutors of Small Animal Medicine Distance Learning Module 12?
Dr Brad Gavaghan and Dr Fiona Meyers
What are the learning objectives of Week 1 of Small Animal Medicine Distance Learning Module 12?
- Describe and recognise the anatomy of the left side of the heart and its relationship to the great vessels
- Describe and recognise the anatomy of the right side of the heart and its relationship to the great vessels
- Integrate this information of the heart as a 2-dimensional structure into 3-d anatomy
- Understand the basic anatomy of the conduction system of the heart
- Identify the difference between the atrial and ventricular action potential, and describe how pacemaker cells are different
- Describe calcium cycling within the cardiomyocyte and the role of various transporters and receptors in excitation-contraction coupling
- Describe the ultrastructure of the sarcomere and how contraction of the myocyte is initiated
- Relate blood pressure, heart rate, stroke volume, vascular resistance and cardiac output through two basic equations and predict how these variables will change in states of exercise and haemorrhage
- Describe the renin-angiotensin-aldosterone system and how it contributes to clinical signs of congestive heart failure
- Contextualise the primary problem in three commonly acquired heart diseases and how they lead to RAAS activation
- Appreciate the basic principles of cardiac remodelling and integrate this with clinical conditions in order to predict what sort of cardiac remodelling will occur
What is the structure and function of the ascending aorta?
It is a large, elastic vessel centrally located within the heart that recoils after filling to generate arterial flow.
What is the function of the brachiocephalic trunk?
It is the first aortic branch that gives rise to the left and right carotid arteries and the right subclavian artery.
What is the role of the pulmonary veins?
They drain oxygenated blood from the lungs back to the left heart.
Describe the left atrium. What is its function?
The left atrium is a low-pressure receiving chamber from the pulmonary circulation.
What is the purpose of the left auricle?
It is a blind-ending pouch on the cranio-lateral aspect of the left atrium, representing the embryologic left atrium.
What is the primary function of the left ventricle?
It is the heart’s primary pump responsible for driving blood into the arterial system.
Why is the aortic valve of critical importance?
It maintains systemic arterial pressure and tissue perfusion.
What is the mitral valve? What is its role?
The mitral valve is a bicuspid atrioventricular valve that prevents significant back-flow of blood into the left atrium during ventricular systole.
What is the purpose of the conduction system in the heart?
To generate coordinated contraction that maximizes stroke volume.
Where is the sino-atrial node located?
In the high right atrium wall.
What structures join the sino-atrial node and pass electrical impulses into the left atrium?
Inter-nodal pathways.
Where is the atrioventricular (AV) node located?
On the floor of the right atrium.
What is the function of the fibrous AV annulus?
To electrically isolate the atria from the ventricles, except at the AV node.
Which structure descends the basilar interventricular septum from the AV node?
Bundle of His.
What divides off the bundle of His and carries impulses to each ventricle separately?
Left and right bundle branches.
Where are the tiny, terminal branches of the conduction pathways located?
Purkinje fibres.
What happens to the electrical impulses after leaving Purkinje fibres?
They travel on a slower pathway via gap junctions between cell membranes.
Why is the conduction in the AV node naturally slow?
To allow the atria to contract and prime the ventricles before they contract.
What is the purpose of the atrial-ventricular relationship and timing?
To maximize cardiac output by synchronizing atrial and ventricular contractions.
Which ventricle finishes ejection slightly earlier, following depolarization?
The left ventricle.
What do deep S waves in lead II suggest?
Right ventricular enlargement.
What is the resting membrane potential of a cardiomyocyte?
Around -80 mV.
What happens if the cardiomyocyte is depolarized to a threshold potential?
A coordinated sequence of ion channel opening and closing is initiated.
How does the atrial action potential differ from the ventricular action potential?
The atrial action potential has little sodium channel involvement and does not have a calcium-induced plateau.
Where are pacemaker cells located?
Throughout the conduction system, but primarily in the sinoatrial node.
What is the function of lower order pacemakers in the heart?
To act as backup pacemakers in cases of sinoatrial node dysfunction or atrioventricular block.
What is the process that links electrical impulses to contraction in the heart?
Excitation-contraction coupling.
Which ion is crucial for maintaining excitation-contraction coupling in cardiomyocytes?
Calcium.
What are the two structural features of cardiomyocytes that assist in rapid calcium ion cycling?
Specialized channels and receptors, and calcium ion flow within the cytosol.
What does the troponin complex shape look like?
The troponin complex has a specific shape.
What happens when calcium ions bind to troponin C?
Calcium ions bind to troponin C and remove the inhibitory troponin subunit.
What happens when myosin heads bond to actin?
Myosin heads induce a conformational change, shortening the sarcomere.
What is the process called when myosin heads bond to actin?
The process is called cross-bridge formation.
What is the role of calcium ions and ATP molecules in sarcomere shortening?
They contribute to the ratchet-like action that pulls the molecules over one another.
What happens after calcium dissociates from troponin C?
The troponin complex reverts to its inactive state and the binding site is covered.
What are the basic functional equations in cardiovascular physiology?
The equations are blood pressure = (cardiac output) x (systemic vascular resistance) and cardiac output = (stroke volume) x (heart rate).
What are the cornerstones of survival for reduced cardiac output?
The activation of baroreceptors and the renin-angiotensin-aldosterone system (RAAS).
Why do compensatory mechanisms in heart failure become maladaptive?
They increase myocardial workload in a hypofunctional heart and accelerate the disease process.
What is the role of the baroreceptor reflex?
It prevents loss of consciousness when standing up or experiencing changes in vascular resistances and cardiac output.
What triggers the renin-angiotensin-aldosterone system?
Detection of reduced renal blood flow by the nephron triggers the system.
What are the negative results for cardiac patients from the renin-angiotensin-aldosterone system?
Increased blood volume, increased afterload, reduced vagal tone, sympathetic activation, and cardiac remodelling and fibrosis.
Do the compensatory mechanisms in cardiac patients remain activated chronically?
Yes, unless treated surgically or with a heart transplant.
Are the compensatory mechanisms meant for chronic activation in the heart?
No, they are not meant for chronic activation.
What does chronic activation of the compensatory mechanisms lead to in heart failure?
Clinical signs of volume overload and fluid accumulation, known as congestive heart failure (CHF).
What is the term used to describe thickening of the myocardium?
Myocardial hypertrophy
What type of hypertrophy is seen with increased circulating blood volume?
Eccentric hypertrophy
What is the term used to describe the increased chamber diameter and reduced wall thickness to chamber size ratio?
Dilation
Why is it not common to see atrial hypertrophy in cases of volume overload?
Low pressures in diastole require minimal hypertrophy
What changes can be predicted using basic principles to make a diagnosis of a particular disease?
Changes in heart structure and function
If patients with a particular disease live without treatment, which side of the heart is more likely to fail?
The side of the heart associated with the particular disease
How can you calculate heart rate in beats per minute if the paper speed is 25mm/second?
Multiply the number of complexes in 15cm by 10.
How can you calculate heart rate in beats per minute if the paper speed is 50mm/second?
Multiply the number of complexes in 15cm by 20.
What should be the relationship between P wave and QRS complex in a sinus rhythm?
A sinus rhythm will always have a P wave followed by a QRS complex.
What does a P wave followed by no QRS complex indicate?
P waves may not be followed by a QRS in an AV block.
How can you check if the relationship between the P wave and QRS wave is normal?
Measure the P-Q interval using the ECG ruler and compare it against the reference interval times.
What do upright and narrow complexes in lead II indicate?
Upright and narrow complexes in lead II indicate supraventricular impulses.
Which part of the heart has the highest intrinsic rate and acts as the dominant pacemaker?
The sinoatrial node (SAN) has the highest intrinsic rate and acts as the dominant pacemaker.
What can hypoxic or damaged cells in the heart do?
Hypoxic or damaged cells can create abnormal pacemakers.
What is the significance of pacemaker hierarchy in clinical settings?
Pacemaker hierarchy helps determine the conduction system disorder when the heart rate is low in specific regions.
Which lead is typically used to read ECGs?
ECGs are typically read using Lead II.
What does the P wave represent in an ECG?
The P wave represents the depolarization of the right and left atrium.
What does the P-Q interval represent in an ECG?
The P-Q interval represents the depolarization of the atrioventricular node (AVN).
What does the QRS complex represent in an ECG?
The QRS complex represents the depolarization of the ventricles, including the septum, left ventricle, and right ventricle.
What does the T wave represent in an ECG?
The T wave represents the repolarization of the ventricles.
How can electrolyte imbalances affect the T wave in an ECG?
Prominent T waves may indicate electrolyte imbalances, such as hyperkalemia.
What differentiates supraventricular beats from ventricular beats?
Supraventricular beats originate from the sinoatrial node (SAN), have positive P waves in Lead II, and narrow upright QRS-T complexes. Ventricular beats are wider and bizarre in appearance, lack P waves, and are the result of an abnormal pacemaker.
What are some clinical signs associated with left-sided congestive heart failure?
Inappetence, lethargy/depression, weakness, exercise intolerance, tachypnea.
What is often the first clinical sign in cats with heart disease?
Sudden onset dyspnea.
What can cause sudden onset dyspnea in cats with heart disease?
Congestive heart failure or acute pain and paresis/paralysis caused by an arterial thromboembolism.
What are some early clinical signs of heart disease in cats?
Lethargy, reduced exercise capability.
Do cats with cardiac disease have seizures?
No, but some cats with arrhythmias may develop hypoxic neurological activity that mimics a partial seizure.
What should be palpated during a physical examination for cardiac evaluation?
The whole thorax, including high up under the triceps muscles.
What does an apical impulse on the right-hand side suggest during palpation?
Cardiac hypertrophy or remodeling, leading to potential diagnostic tests in a patient without a murmur.
What pulses should be checked during a physical examination?
Both femoral pulses.
What type of pulses may be found in a patient with a patent ductus arteriosus (PDA)?
Hyperkinetic pulses, characterized by a wider pulse and referred to as ‘snappy’ or ‘water hammer’ pulses.
What should be checked regarding mucous membranes during a physical examination?
Mucous membrane color and capillary refill time (CRT).
What is considered a normal capillary refill time (CRT)?
<2 seconds.
What should be checked for regarding jugular veins during a physical examination?
Jugular pulsation/distension in the thoracic inlet region.
What type of stethoscope is best for auscultating small animal patients?
Stethoscope with a pediatric diaphragm.
What should be auscultated first during a cardiac evaluation?
The apical impulse on the left-hand side.
What should be assessed during auscultation to identify systole and diastole?
The pulse at the same time as listening.
What is the point of maximal intensity of a PDA murmur?
Very high up behind the triceps muscle.
Where is the point of maximal intensity of a mitral murmur?
In the left apical region.
What could a murmur with a point of maximal intensity at the left heart base indicate?
Pulmonic or aortic stenosis.
What should be auscultated over the right heart base?
Some aortic murmurs that may radiate around and across to the right-hand side.
What is examined during abdominal ballottement and jugular venous distension?
Evidence of ascites in a dog with right-sided congestive heart failure.
What can be mistaken for a large abdomen in dogs with right-sided congestive heart failure?
Evidence of ascites.
How is abdominal ballottement performed?
Place palm on one side of abdomen, tap on opposite side to feel for fluid wave.
What can be detected by checking for jugular venous distension?
Presence of high pressure in jugular vein is diagnostic of right-sided congestive heart failure.
What are the four types of breathing patterns?
- Restrictive 2. Obstructive 3. Inspiratory 4. Paradoxical
Which respiratory pattern indicates a disorder in the pleural space or pulmonary interstitium/alveoli?
Restrictive pattern
What does obstructive breathing pattern indicate?
Disease in the lower airways such as chronic bronchitis or asthma (in cats).
Which respiratory pattern localizes the problem to the extra-thoracic airways?
Inspiratory pattern
What causes paradoxical breathing pattern?
Respiratory fatigue of the diaphragm and intercostal muscles, seen in pleural space disease.
How is an ECG generated?
Electrodes are attached to the limbs which detect electrical activity of the heart.
What is the purpose of True Leads in an ECG?
They provide three perspectives on the heart’s electrical activity.
How many electrodes are used to generate a 6-lead ECG?
Four electrodes are used.
How are augmented leads created in an ECG?
An imaginary electrode is created by averaging two signals from different electrode pairs.
What does the RF-LF lead represent in a 6-lead ECG?
The positive electrode is at the right forelimb.
How many augmented leads are there in a 6-lead ECG?
There are three augmented leads.
What is the positive electrode position in the LF-LH lead of a 6-lead ECG?
At the left foot (hindlimb).
On a DV view, where do veins lie?
Veins lie centrally.
On a lateral view, where do veins lie?
Veins lie ventrally.
What is the size of the artery and vein expected to be?
They should be of a similar size.
What is the maximum width of vessels that should be allowed when they cross the 9th rib?
They should not be wider than the 9th rib.
On a lateral view, what part of the artery and vein should have a similar size?
The proximal third of the 4th rib.
What should be assessed in the lung fields?
The contrast between the lung fields and the vessels.
What does good contrast between the lung fields and vessels indicate?
No lung patterns are present.
What does increased radiodensity of the lung fields with a loss of vessel contrast indicate?
Alveolar lung pattern.
What can be seen in the normal patient regarding central bronchial markings?
Central bronchial markings can be seen.
What do left atrial dilation, pulmonary venous distension, and an alveolar/interstitial lung pattern on radiography imply?
Left-sided congestive heart failure.
How can the vertebral heart score be measured?
Using the long and short axis of the heart and counting the vertebrae lengths.
What is the first step in measuring the vertebral heart score?
Measure the long axis of the heart on the x-ray.
What is the second step in measuring the vertebral heart score?
Measure the short axis of the heart on the x-ray.
What should be done with the measurement of the long axis of the heart?
Compare it against the spinal column and count the vertebrae lengths.
What should be done with the measurement of the short axis of the heart?
Compare it against the spinal column and count the vertebrae lengths.
What is the final step in calculating the vertebral heart score?
Add the two vertebrae lengths together.
How can dogs with isolated atrial fibrillation be converted?
Dogs with isolated atrial fibrillation can be converted using pharmaceuticals or by performing electrical cardioversion.
What sedation method is not advised for potential cardiac patients during thoracic radiography?
Deep sedation using dexmedetomidine is not advised for potential cardiac patients during thoracic radiography.
What is the preferred timing of radiographs for conscious or partially sedated cardiac patients?
Radiographs for conscious or partially sedated cardiac patients should be timed with peak inspiration.
What can complicate the review of radiographs in equivocal cases of airway disease or congestive heart failure in cardiac patients?
A mild interstitial pattern may be present in radiographs of cardiac patients, which can complicate the review in equivocal cases.
What are the recommended settings for exposure when taking thoracic radiographs?
A high kV and low mAs should be used for short exposure time and minimal blurring of moving intrathoracic structures.
How can image blur be reduced in thoracic radiographs?
Using a shorter exposure time can help reduce image blur in thoracic radiographs.
What is an indicator of x-ray intensity in radiography?
mAs (milliamperes over time) is an indicator of x-ray intensity in radiography.
Why should the mAs be reduced and the kV be increased in thoracic radiography?
Reducing mAs and increasing kV helps to expose x-rays for a short duration while maintaining natural contrast in the thoracic cavity.
What is a tip for reviewing chest radiographs using a traditional light box?
Use the hot light function to highlight specific areas of the film after reviewing under bright light.
What is the recommended distance between the x-ray generator and the plate/cassette during radiography?
The recommended distance is around 1 meter between the x-ray generator and the plate/cassette.
How can image quality be improved for larger chests during thoracic radiography?
Using a grid may help improve image quality for larger chests (e.g., dogs over 12kg).
What view should be taken first in three-view chest radiography?
The dorsoventral view (DV) should be taken first in three-view chest radiography.
What should be included in the collimation for the dorsoventral view in chest radiography?
The collimation should include the thoracic inlet cranially and the last rib caudally.
Why is a three-view chest radiography desirable?
In each lateral view, one lung will undergo atelectasis and not be imaged well.
What should be included in the lateral collimation in chest radiography?
The lateral collimation should include the lateral aspects of the ribs.
What breed of dogs are commonly affected by dilated cardiomyopathy (DCM)?
Bulldogs, Great Danes, Irish Wolfhounds, Deerhounds, Newfoundland, Boxers
What is the prevalence of DCM in dogs above three years old?
It seems to increase dramatically
What other heart disease is often confused with DCM in dogs?
Arrhythmogenic right ventricular cardiomyopathy (ARVC)
What is the most commonly affected heart disease in cats?
Hypertrophic cardiomyopathy (HCM)
What is the prevalence of HCM in cats in large prevalence studies?
1 in 7 cats in a shelter population, but can rise to 1 in 2.5 cats in older age
Which cat breed is often affected by HCM?
Maine Coon, Ragdoll, Sphynx, Bengal, British Shorthair, Norwegian Forest, Persian and Birman
What genetic marker has been identified for HCM in Maine Coons and Ragdolls?
Myosin-binding protein C3
What heart diseases are commonly seen in Dogue de Bordeaux?
Right-sided cardiomyopathy, atrial fibrillation (AF), subaortic stenosis, tricuspid dysplasia
What heart condition is French Bulldogs more likely to present with?
Pulmonic stenosis
What clinical signs may be associated with heart disease without congestive heart failure in dogs?
Lethargy/depression, syncope, weakness, exercise intolerance, and coughing
What clinical signs may be associated with left-sided congestive heart failure in dogs?
Inappetence, lethargy/depression, weakness, exercise intolerance, tachypnoea, and polyuria/polydipsia
What clinical signs may be associated with heart disease without congestive heart failure in cats?
Lethargy/depression, syncope, weakness, and exercise intolerance
What is the heritability of most cardiac diseases?
Most cardiac diseases, acquired and congenital, are considered to be genetic and therefore heritable.
