Table 7.2 Summary: Recognition of arrhythmias

Arrhythmia Clinical examination ECG findings
Supraventricular arrhymias
Sinus arrest/block
Fairly common, usually physiological
slow/normal rate
regular under lying rhythm with pauses
regular underlying rhythm with intermittent pauses >/=2 P-P intervals with no P wave
Sinus bradycardia
Rare, usually pathological
slow regular rhythm long R-R intercal, normal P-QRS-T
Sinus arrhythmia
Uncommon at rest, common after light exercise, physiological
slow/normal rate
variable S1-S1 interval
variable R-R intercal
+/- wandering pacemaker
(variable P wave morphology)
First degree AV block
Fairly common, usually physiological
slow/normal rate
long A sound - S1 interval
prolonged R-R interval (>0.5 sec)
Second degree AV block
Nearly always physiological, abolished by increased sympatectic/decreased vagal tone, very common
regularly irregular rhythm or occasional pauses (dropped beats)
A sound not followed by S1 + S2
pulse deficit
isolated jugular A wave may be palpable
P wave blocked and not followed by QRS
double R-R interval at block
Mobitz type 1 = variable P-R interval prior to block
Mobitz type 2 = constant P-R interval
Third degree AV block
Pathological, may cause collapse or death, rare
slow rate
regular rhythm
A sounds have no relation to S1 + S2
no relationship between P waves and QRS regular juctional ventricular escapes
Atrial premature complexes (APCs)
Farily common, abnormal, variable significance, may be associated with poor performance
normal/fast rate
irregular rhythm
premature beat usually follwed by non-compensatory pause
+/- pulse deficit
premature P wave
P wave pay be different configuration
P-R interval may change
P wave may be buried in previous T wave
Atrial tachycardia
Uncommon, pathological, significant, may need treatment, box rest advisable
fast rate
regular or irregular
may be abolished by vagal manoeuvre
+/- signs of cardiovascular compromise
irregular if short bursts
regular if sustained
P waves often obscured
P waves may be abnormal
normal QRS
Junctional tachycardia
Uncommon, pathological, significany, may need treatment, box rest advisable
fast rate
regular or irregular
+/- signs of cardiovascular compromise
+/- signs of systemic disease
irregular if short bursts
regular if sustained
P waves unrelated to QRS but can be retrograde
normal QRS
Atrial fibrillation (AF)
Most common arrhytmia affecting athletic performance.
Careful case selection essential prior to treatment
normal or fast rate
irregularly irregular rhythm
may have long diastolic intervals followed by a flurry of beats
no A sound
variable intesity heart sounds
variable pulse quality
+/- signs of underlying heart disease
irregular R-R interval
no P waves
f waves usually seen
normal QRS
occasionally slight variation in QRS amplitude
Atrial flutter
Rare, definitions vary, can be thought of as a similar condition to AF
fast rate
irregular or regular rhythm
no A sound
sawtooth f waves
+/- fixed F-QRS relationship
Pre-excitation syndromes
Rare, may or may not be significant, can be a mechanism for re-entry supraventricular tachydysrhythmias
normal or fast rate
regular ehythm
may sound normal
+/- clinical signs
short P-R interval
delta wave at beginning or QRS complex
Accelerated idiojunctional rhythm
Sometimes found in very sick animals, e.g. those recovering from colic surgery
Antidysrhymic treatment not required
Treat underlying condition
slightly rasied rate (40-50)
regular rhythm
A sounds may not be heard, but if detected have no relationship to S1+S2
normal QRS
no relationship between QRS and P waves
junctional rate slightly faster than sinus rate
Ventricular rhythms
Premature ventricular complexes (VPCs)
Variable significance
Investigation for underlying myocardial or systemic disease required
May be induced or abolished by exercise
premature S1 + S2
loud S1, quiet S2
usually followed by compensatory pause
+/- pulse deficit
premature QRS not preceded by P wave
QRS morphology differs cf normal
QRS may be wide (>0.14 sec), but can be normal
T wave orientation opposite to QRS
Ventricular tachycardia
Uncommon, significant
Box rest required, +/- antidysrhythmic drugs
Treat underlying disease
fast regular rhythm
may have burst of rapid beats
usually signs of CV compromise
+/- signs of underlying diesease
More than four consecutuve VPC's
sustained or paroxysmal
QRS different morpholohy cf normal
P waves may ben seen occasionally and bear no relationship to QRS
Capture +/- fusion beats may be seen
Accelerated idiocentricular rhythm
Uncommon, similar mechanism to idiojunctional rhythm
Antidysrhythmic treatment not required, treat underlying condition
slightly raised rate (40-50)
regular rhythm
A sounds may not be hears, if detected have no relationship to S1 + S2
abnormal QRS (may be wide, different morphology)
no relationship between QRS and P waves ventricular rate slightly faster than sinus rate capture and fusion beats may be seen
Ventricular fibrillation
Almost invariably fatal
Institute emergency treatment
no pulse
no clear heart sounds
no palapable cardiac impulse
no clear complexes
bizarre undulating baseline