Heart disease investigation Flashcards
What is the cause for gallops rythm? What is its clinical significance
Gallops are caused by audible low frequency”third” and “fourth” heart sounds
- these diastolic sounds are associated with the termination of rapid ventricular filling (S3) and atrial contraction against a stiff ventricle (S4) (which is the most common in cats)
Gallops rhythm usually indicate diastolic disease in cats
- the incidence of the gallop sound may vary with the sympathetic tone in individual patients
What is the cause of heart murmurs in cats with cardiomyopathy
In cats with cardiomyopathy, most heart murmurs are due to either mitral regurgitation and/or dynamic left ventricular outflow tract obstruction due to anterior motion of the anterior leaflet of the mitral valve
What are the main causes for functional murmurs
Functional (=physiologic) murmurs may occur in animals with reduced blood viscosity (e.g., anemia) or high sympathetic tone (e.g., excitement, fever, thyrotoxicosis)
What are the two causes of heart murmur that need to be differentiated from heart murmur associated with heart disease in older cats
Older cats may have systolic murumurs which are related to:
- blood flow into a dilated aorta (aortic redudency)
- or dynamic right ventricular outflow obstruction
These are generallyy not clinically significant but they cannot be distinguished from more sinister heart conditions by auscultation alone
What is consider a normal vertebral heart score in cats? Why isn’t it the same value as in dogs?
The vertebral heart score system has been validated in cats
- normal is considered to be < 8.1 in the cat
The values are smaller for cats than for dogs because they have comparatively longer thoracic vertebrae
What is the size of artery and vein in a same lung lobe
Normally, the artery and vein of the same lung lobe are approximately of the same size in both lateral and DV/VD views
Describe the modified VHS system to evaluate the LA on the radiographic lateral view
A line between the cardiac apex and the ventral border of the left mainstem bronchus is drawn
The distance between that line and the caudal contour of the left atrial wall just dorsal to the border of the caudal vena cava is measured
This value is projected on the thoracic vertebrae beginning with the cranial edge of T4 to measure the modified VHS system
- normal < 1
What are the main differentials for cardiomegaly on a thoracic X-ray
Heart disease
Severely anemic cats
primary respiratory disorders
thyrotoxicosis
What are the radiographic signs suggestive of right heart enlargement
Radiographic signs suggestive of right heart enlargement include:
- increased convexity or bulging of the cranial and right border of the cardiac silhouette in the lateral and DV/VD view
- elevation of the cardiac apex from the sternum and a shift of the apex cranially and to the left in the lateral and DV/VD view
- slight elongation of the cardiac silhouette with tracheal elevation in the lateral view
What is the cause for valentine shape in the DV or VD view in a cat with heart disease
The valentine shape is a strong indicator of cardiac disease in the cat, particularly non-dilated cardiomyopathy
This radiographic feature is primarily due to left atrium enlargement alone rather than right atrial or biatrial enlargement and may occasionally be seen in cats without true cardiomegaly
What are the typical radiographic signs of cardiogenic pulmonary edema
Typical radiographic signs of cardiogenic pulmonary edema include, but are not limited to:
- unstructured interstitial pulmonary opacities (i.e., the borders of the pulmonary vessels often become indistinct) that progress to an alveolar pattern depending on edema severity
- the distribution of cardiogenic pulmonary edema in cats is predominantly diffuse/non-uniform
What are the most frequent diagnoses for significant enlargement of the entire cardiac silhouette
Pericardial space disease (e.g., effusions, pericardioperitoneal hernias)
Advanced dilated cardiomyopathy
Explain why left-sided heart disease in cats causes pleural effusion rather than pulmonary edema such as in dogs
Left-sided heart disease in cats causes pleural effusion because the visceral pleura is drained by the pulmonary veins
- elevated pulmonary venous pressures decrease this drainage and an effusion ensues
What are the characteristics of cardiogenic pleural effusions
Cardiogenic pleural effusions can have the characteristics of:
- a transudate (TP<25g/l, TNCC<1000/µl)
- a modified transudate (TP 25-35 g/l, TNCC 500-10000/µL
- a chyle
What can you conclude when you notice an increased inspiratory component and no obvious upper respiratory tract difficulty in a cat
If there is an increased inspiratory component and no obvious upper respiratory tract difficulty, then the cat likely has a pleural effusion and thoracocentesis may be appropriate
Explain why is it important to measure LA size at the level of the aortic root
It is measured on a right parasternal short-axis view at the level of the root of the aorta during diastole
This gives an indication of relative LA enlargement
- a left atrium to aortic root ratio > 1.5 indicates left atrial dilation
If LA size is normal, then it is highly unlikely that congestive heart failure is the cause of the clinical signs in a dyspneic cat
- exceptions:
- constrictive pericarditis
- cranial vena cava obstruction
What is the purpose of the left sided view in heart ultrasonography
The left-sided views are useful for obtaining views of the valves so that they can be investigated via Doppler
- this is important when looking for valvular stenosis or insufficiency
What is the difference between pulsed wave Doppler and continuous wave Doppler
Pulsed wave Doppler
- the transducer alternates between sending and receiving an ultrasound signal
- it is useful for investigating low-velocity blood flow from a selected point along the ultrasound beam
Continuous wave Doppler:
- it involves the constant generation of ultrasound and concurrent transducer reception of the reflected signal
- it can measure high blood flow velocities with accuracy
- it cannot tell the exact anatomical point from which this high-velocity signal is emanating
- there is no capacity for concurrent 2D imaging
What are the components of the electrical pathway of the heart
The conduction system of the heart comprises five parts:
- sinoatrial node
- atrioventricular node
- bundle of His
- right and left bundle branches
- Purkinje fibers
How is obtained the lead II in the ECG graph
The information for Lead II is derived from the electrical diagonal produced by placing:
- a negative pole on the right forelimb
- a positive pole on the left hind limb
When the overall direction of the electrical impulse is traveling towards the positive pole, the ECG cursor will move in a positive direction above the baseline
When the overall direction of the electrical impulse is away from the positive pole, the cursor will move below the baseline in a negative direction
What are the key features associated with the sinoatrial node
It is located in the right atrium
It tends to be the pacemaker of the heart
- The rate at which the SA node fires is directly influenced by the sympathetic nervous system (to increase the heart rate) or the parasympathtetic nervous system (to decrease it)
Once the SA node fires, the impulse then spreads from myocyte to myocyte within the atria until it hits the refractory tissue between the atria and the ventricles (AV junction) where it is then directed through the AV node
- as this impulse spreads through the atria, it is recorded as a positive wave on the ECG (the P wave)
What are the key features associated with the atrioventricular node
The AV node tissue is more refractory than the preceeding myocytes
- there is a delay in the propagation of the impulse and thus a pause in the ECG trace
- the time taken for conduction of the impulse through the atria and thence the AV node is known as the P-R interval
The P-R interval (measured in seconds) gives an indication of how “easy” or “difficult” the impulse finds it to move through the AV nodal tissue
The level of AV node refractoriness may be influenced by:
- external factors (e.g., vagal tone, digoxin)
- disease of the AV nodal tissue itself
- delays or cessation of atrial to ventricular conduction is known as “AV block”
What are the key features associated with bundle of His, bundle branches and Purkinje fibers
Once the impulse passes through the AV node, it is then propagated rapidly through the bundle of His and then the right and left bundle branches to the apex of the heart
- this is so that contraction of the ventricular myocardium squeezes the blood upwards towards the right and left ventricular outflow tracts
The spread of the electrical impulse through the ventricular conduction system is represented by the QRS complex
What is represented by the T wave? What is its diagnostic value
The T wave represents the potential difference created by repolarization of the ventricular myocytes in readiness for the next heart beat
The T wave is variable in cats which makes its diagnostic value when changed negligible
- apart from a tall, spiked T wave with hyperkalemia
