Page 172 - Problem-Based Feline Medicine

164 PART 3 CAT WITH SIGNS OF HEART DISEASE

VENTRICULAR TACHYCARDIA*** Diagnosis
The heat rate is above 220 bpm (Figure 10.3).
Classical signs
There is no association between P waves and the QRS
● Fast and regular heart rate above 220 beats complex (P waves may be seen anywhere in the cardiac
per minute. cycle).
● Strong precordial impulse.
The QRS morphology is aberrant.
● Loud S1 heart sound.
● Weakness/collapse (rare). This arrhythmia is usually regular, but some degree of
variability of the cardiac rhythm may be present.
This arrhythmia may be sustained or occur in parox-
Pathogenesis ysms.

The arrhythmia originates from the ventricles. Changes in heart rate are abrupt.
Ventricular tachycardias most commonly result from
Differential diagnosis
primary cardiac disease.
Supraventricular tachycardia (supraventricular tachy-
Most often, it is the result of myocardial fibrosis asso-
cardia with aberrant ventricular conduction, or atrial
ciated with a cardiomyopathy.
flutter without variable conduction but with aberrant
Sustained ventricular tachycardia may be caused by ventricular conduction) may appear similar to ventricular
myocardial infarction. tachycardia on the ECG. Supraventricular tachycardia
may have P waves preceding the QRS complex.
Other causes of ventricular tachycardia include meta-
bolic acidosis and drug-induced (digitalis). Motion or electrical artifact can usually be resolved
by improved ECG recording technique: repositioning
the electrodes, moistening the skin with alcohol, posi-
tioning the cat on a non-metal table isolated from other
Clinical signs electrical devices.
In the majority of patients, clinical signs are related to
the underlying disease. Treatment
Some patients do not show clinical signs from the If the patient is symptomatic (hypotension, cardio-
tachycardia. genic shock, collapse), or sustained heart rate greater
than 220 bpm, then immediate therapy is recom-
Clinical signs related to a fast heart rate (> 280 bpm)
mended.
include restlessness, tachypnea, open-mouth breath-
ing, poor pulse quality and delayed capillary refill Correct any metabolic, electrolyte or acid–base abnor-
time. malities.

Lead II 25 mm/s 1cm/mV
V V V V V V V V V
F F

Figure 10.3. Ventricular tachycardia. “V” marks VPCs. Fusion beats are marked “F”.