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Cardiovascular system diagnostic tests - Coggle Diagram
Cardiovascular system diagnostic tests
Radiography
Thoracic
assess overall heart size, shape, pulmonary vessels and lung parenchyma, as well as surrounding structures.
Cardiomegaly
if mild hard to identify
pericardial fat may mimic appearance of cardiomegaly
cardiac shadow of
puppies
appears slightly large relative to thoracic size compared to that of adult dogs
VERTEBRAL HEART SCORE (VHS)
Measure cardiac long axis from ventral border of left mainstream bronchus to the most ventral aspect of the cardiac apex
this same distance is compared to the thoracic spine beginning at the cranial edge of T4
measure the maximum perpendicular short axis in the central third of the heart shadow
short axis also measured in number of vertebrae beginning with T4
add both measurements to yield the VHS
VHS: 8.5-10.5 vertebrae considered normal for most breeds
breed variations linked to thorax size e.g. dachunds, miniature schnauzer
Microcardia
results from reduced venous return
e.g. shock, hypovolaemia
hypoadrenocorticism
apex appears more pointed and may be elevated from sternum
dorsoventral views
obtain this first in dyspneic patient
detect pleural effusions or pneumothorax
could cause fatal respiratory compromise if animal placed in lateral or dorsal recumbency
heart shape appears more constant than in VD and vessels of the caudal lung lobes are more clearly seen
high kVp and low mA for better resolution among soft tissue structures
exposure ideally made at time of peak inspiration
breed variations
round or barrel chest
cardiac shadow greater sternal contact on lateral view
oval shape cardiac shadow in DV
narrow and deep chested dogs
heart has upright belonged appearance on lateral view
heart has a small, almost circular shape in DV
Indications
evidence of cardiac disease
signs of respiratory compromise
chronic coughing
abnormalities of the thoracic wall
screening for metastases in malignant disease
preceding anaesthesia in animals with evident or suspected thoracic trauma
swallowing disorders or vomiting for which an extra thoracic cause is not apparent
ventrodorsal view
dorsal recumbency with the forelimbs drawn forward
lateral view
forelimbs drawn well forward on lateral view and a foam wedge under the sternum is useful to correct rotation in deep chested breeds
technique
low mAs, high kV exposure factors
broad range of contrast, providing many shades of grey, whilst enabling exposure times to be kept to a minimum and reducing movement unsharpness
use same factor in follow up films
collimate accurately
beam should be collimated from a few cm cranial to the first rib to just beyond the costal arch, to ensure the whole lung field is included
use a grid with large chests and high ma machines
obtain inspiratory films
hard if fast/shallow respiration or if obese
Electrocardiography
Represents electrical depolarisation and repolarisation of the cardiac muscle
provides info on...
heart rate and rhythm
intracardiac conduction
may suggest specific chamber enlargement, myocardial disease, ischaemia, pericardial disease, certain electrolyte imbalances, some drug toxicities
cannot be used to identify the presence of congestive heart failure
Normal cardiac waveforms
P
Activation of atrial muscle
PR interval
Time from onset of atrial muscle activation, through conduction over the AV node, bundle of His, and purkinje fibres
QRS complex
activation of ventricular muscle
normally
narrow and upright
an intraventricular conduction disturbance or ventricular enlargement pattern may cause them to be wide or abnormally shaped
ST segment
period between ventricular depolarisation and repolarisation
T wave
ventricular muscle repolarisation
QT interval
total time of ventricular depolarisation and repolarisation
Sinus rhythms
The sinus rate tends to increase on inspiration and decreased with expiration as a result of fluctuations in vagal tone
may be a cyclic change in P wave configuration (wandering pacemaker), with the P waves becoming taller and spiked during inspiration and flatter during expiration.
common and normal finding in dogs
if pronounced may be associated with chronic pulmonary disease
occurs in resting cats, but not often seen clinically
Sinus arrest
absence of sinus activity lasting at least 2x as long as animal's longest expected QRS to QRS interval
long pauses can cause fainting or weakness
an escape complex usually interrupts the resulting pause if sinus activity does not resume in time
cannot be differentiated with certainty from sinoatrial block by the surface ECG
Ectopic rhythms
Impulses originating from outside the sinus node
Supraventricular premature complexes
supraventricular tachycardias
atrial flutter
atrial fibrillation
ventricular premature complexes
ventricular tachycardia
accelerated ventricular rhythm
ventricular fibrillation
escape complexes
Echocardiography
