Normal sinus rhythm (Fig. 10.1)

Heart rate remains within range.

R-R intervals remain almost the same.

There is a P wave for every QRS complex.

P-R interval is almost constant.

The variations in P-P interval are <0.12 s.

Sinus arrhythmia (Fig. 10.2)

Heart rate remains within range.

Pauses are shorter than twice the normal R-R interval.

There is a P wave for every QRS complex.

P-R interval is almost constant.

There are variations in R-R interval.

Sinus rhythm is more irregular with more P-P variations.

Sinus arrest (Fig. 10.3)

Pauses are equal to or greater than twice the normal R-R interval.

Sinoatrial block (Fig. 10.4)

Pauses are exactly twice or <twice of normal R-R interval.

Wandering pace maker (Fig. 10.5)

There are wide variations in the amplitude of “P” waves.

P-R interval may vary from normal to short in duration.

Sinus tachycardia (Fig. 10.6)

There is marked increase in heart rate as compared to normal heart rate.

Heart rhythm is regular.

R-R intervals are normal or may vary slightly.

There is “P” wave for every QRS complex.

P-R interval is almost constant.

Severe tachycardia may be associated with P wave hidden in preceding T wave.

Configuration of both “P” and “QRS” is normal.

Sinus bradycardia (Fig. 10.7)

There is marked decrease in heart rate as compared to normal heart rate.

Heart rhythm is almost regular.

There is a “P” wave for every QRS.

P-R interval is prolonged.

“P” wave amplitude may vary (wandering pace maker).

All “QRS” complexes are alike.

Supraventricular premature complex

Heart rate may be normal.

Impulses originate above the AV node (either in the atrium or the AV junction).

Rhythm is irregular and is broken by a premature beat followed by pause.

P-R interval is either slightly shorter or longer.

There is a P wave for every QRS complex.

P wave of premature beat may be hidden in preceding “T” wave.

Premature “P” may be altered.

In case of junctional (nodal) premature beat, “P” is inverted, i.e., negative.

In case of atrial premature beat, “P” wave is positive but different from normal P.

Atrial premature contractions (Figs. 10.8 and 10.9)

Configuration of premature (P′ wave) P′ is different.

QRS-T complex is normal for normal P wave.

QRS-T complex is absent for premature (P′) wave.

P-R interval of APC may be prolonged with altered morphology of QRS.

Atrial tachycardia or paroxysmal atrial tachycardia (Figs. 10.10 and 10.11)

Tachycardia may be intermittent or continuous.

Tachycardia may be regular (R-R interval same).

Premature (P′) wave is positive in lead II.

There is a P wave for every QRS in a normal complex.

Configuration of P′ wave is different.

P′ wave may be hidden in preceding T wave.

P′ wave during tachycardia is positive but different from P wave when heartbeat is normal.

Atrial fibrillation (Fig. 10.12)

Heartbeat is exceeding the normal limit.

Heart rhythm is irregular but may not be apparently visible when heart rate is rapid.

There are no P waves or P-R intervals.

P wave is replaced by fine baseline undulations (“f” wave).

QRS is normal without P wave.

Atrial flutter (Fig. 10.13)

Heart rate is normal or rapid.

Rhythm is regular or irregular.

There are no P-R intervals.

Ventricles respond in a periodic manner (2:1, 3:1, or 4:1).

Normal P wave is replaced by coarse sawtooth oscillations.

Sino atrial standstill (Fig. 10.14)

Sometimes heart rate is low.

Rhythm is regular or irregular.

P wave is absent.

QRS is without P wave.

There are no P-R intervals.

QRS is normal if it arises near the bundle of His or bizarre if it arises in ventricular muscle mass.

Junctional (nodal) escape rhythm (Fig. 10.15)

Hear rate is normal or slow.

Rhythm is irregular with long pauses in isolated escape beat.

Rhythm is regular when junctional rhythm persists.

There is a P wave for every QRS complex.

P wave occurs before, during, or just after QRS complex.

P wave is negative.

P-R interval is slightly shorter when present.

QRS complexes are normal.

AV junctional tachycardia (Figs. 10.16 and 10.17)

Hear rate is normal or rapid.

Rhythm is usually normal.

Tachycardia may be in bursts.

There is a P wave for every QRS complex.

P wave may be hidden in preceding T wave.

P-R interval may be constant.

P waves are negative, while QRS complexes are normal.

AV junctional beats occurring in high numbers (more than 60 bpm) are termed as AV junctional tachycardia.

Ventricular premature beat (Fig. 10.18)

Heart rate is generally normal.

Normal rhythm is broken by premature beats followed by pause.

There is no P wave for premature beats.

QRS is related to P wave in normal beats.

Abnormal beats do not have consistent P-R interval.

QRS complex of premature beat is bizarre.

If there is one VPC, it is called single.

Two VPCs in succession are called pair.

Three VPCs in succession are called run.

If all VPCs are similar, they are from a unifocal origin.

When VPCs vary in conformation, they are of multifocal origin.

If VPC is alternating (i.e., one beat sinus and other VPC), it is called ventricular bigeminy.

When two beats are sinus and third beat is VPC or one beat is sinus and two beats are VPC, it is called trigeminy.

When major deflection of VPC is negative in lead II, the focus of ectopic beat is considered in the left ventricle.

When major deflection of VPC is positive in lead II, the focus of ectopic beat is considered in the right ventricle.

Ventricular fibrillations/flutters (Figs. 10.19 and 10.20)

There is no coordinated heartbeat.

Specific P waves and QRS complexes are absent.

There is a series of baseline undulations.

Coarse undulations are called flutters.

Fine undulations are called fibrillations.

Ventricular escape beat (Fig. 10.21)

Heart rate is within range or slow.

Heart rhythm is irregular when there is isolated ventricular escape beat.

Idioventricular rhythm is regular.

P wave may or may not occur.

There is no P wave for escape beats.

P wave may be normal but QRS complex is bizarre.

R-on-T phenomenon (Fig. 10.22)

Reported first in humans by Smirk (1949).

A VPC is occurring on T.

It has been reported in dogs also (Engel et al. 1978).

There is a superimposition of an ectopic beat (R) on

T wave of preceding beat.

Ventricular tachycardia (Fig. 10.23)

Four or more VPCs in a row are called ventricular tachycardia.

Enhanced ventricular rhythm (60–100 bpm).

HR is usually slow than sinus tachycardia.

Ventricular asystole (Figs. 10.24 and 10.25)

There is no ventricular rhythm (QRS).

Configuration of P is normal with severe third-degree AV block.

No atrial and ventricular rhythm.

Atrioventricular heart block (AV blocks)

 First-degree AV blocks (Fig. 10.26)

Heart rate is usually normal.

Heart rhythm is sinus.

There is a P wave for every QRS complex.

P-R interval is consistent but increased (more than 0.13 s).

P wave and QRS complex is normal.

 Second-degree AV blocks

Heart rate is normal or slow.

Rhythm is broken by absence of one or several QRS complexes.

There is a P wave for every QRS complexes, but some P waves are without QRS complex.

Normal complexes have consistent P-R interval.

Normal P wave and QRS complexes are of normal configuration.

Second-degree AV blocks are of two types (Mobitz types I and II).

 Second-degree AV blocks (Mobitz type I) (Fig. 10.27)

There is a progressive prolongation of the P-R interval until a non-conducted P′ wave.

 Second-degree AV blocks (Mobitz type II) (Fig. 10.28)

Atrial rate is higher than ventricular rate.

Rhythm is irregular owing to absence of one or more QRS complexes.

P wave is usually normal.

P-R interval is constant and may be normal or prolonged.

 Third-degree AV blocks (Fig. 10.29)

Ventricular heart rate is slow.

Heart rhythm is regular.

There are more P waves than QRS complexes.

P-R interval is varying.

There is no consistent relationship between atrial and ventricular beats.

Configuration of P waves is normal.

QRS complexes near normal or bizarre.

Sick sinus syndrome (Fig. 10.30)

It is due to abnormalities of SA node.

It is also called bradycardia-tachycardia syndrome.

Tachycardia and bradycardia are alternating.

T-on-P phenomenon

There is sinus tachycardia.

QT interval is prolonged (mainly due to ST segment).

T is closely followed by next P or P is buried in the downstroke of preceding T.

Ventricular preexcitation

Heart rate is usually normal.

Rhythm may be sinus or arrhythmic.

There is a P wave for every QRS complex.

P-R interval is constant but short.

P wave is normal.

QRS complexes may be wide and aberrant.

Upstroke of the R wave (delta wave) is slurred (Fig. 10.31).

Wolff-Parkinson-White syndrome

Heart rate is extremely high.

P wave is unrecognizable.

QRS may be normal, wide with delta wave.

Lown-Ganong-Levine preexcitation

P-Q interval is shortened.

QRS complex is normal.

Atrioventricular accessory pathway arrhythmia

It is an uncommon but fatal arrhythmia.

Labrador and Golden Retrievers are predisposed.

Electrical impulse travels in reverse direction.

Congestive heart failure is due to tachycardia.

Heart rate is very high exceeding 240.

When rhythm is sinus, ECG is normal.