Narrow QRS Complex Tachycardia

Dr Vijay AmarnathNIMS,Hyderabad

Narrow QRS Complex Tachycardia

• A narrow QRS complex (<120 msec)- rapid activation of the ventricles via the normal His-Purkinje system,

• above or within the atrioventricular (AV) node (ie, a supraventricular tachycardia).

• origin may be in the sinus node, the atria, the atrioventricular node, the His bundle, or some combination of these sites.

Classification of narrow QRS complex tachycardias by structures required for initiation and maintenance

Atrial tissue only AV junction

Sinus tachycardia AV nodal reentrant tachycardia

Inappropriate sinus tachycardia Atrioventricular reentrant tachycardia

Sinus nodal reentrant tachycardia Junctional tachycardia

Atrial tachycardia Junctional ectopic tachycardia in children

Multifocal atrial tachycardia Nonparoxysmal junctional tachycardia in adults

Atrial fibrillation

Atrial flutter

Paroxysmal SVT

• applied to intermittent SVTs other than AF, atrial flutter, and MAT. PSVT occurs with an incidence of 35 per 100,000 person-years

Physical examination during SVT

• Pulse, BP, S1 : they are regular & constant in regular tachycardia. In AF & A.flutter with variable AV block, pulse, BP & loudness of S1 varies.

• Neck veins :SVT – rapid, regular pulsations (frog sign)A.Flutter – flutter wavesAT & sinus tachycardia – no abnormal pulsations

The Frog sign: in AVNRT or AVRT, the atria contract against closed AV valves rapid, regular, expansive venous pulsations in the neck (that resemble the rhythmic puffing motion of a frog). It is due to simultaneous activation of atria & ventricles.

ASSESSMENT OF REGULARITY OF RHYTHM

• If the rhythm is irregular,scrutinize for discrete atrial activity and for any evidence of a pattern to the irregularity .

• atrial flutter with Mobitz type I second degree AV block (Wenckebach) will exhibit an irregular ventricular rhythm with the pattern of "grouped beating" typical of a Wenckebach rhythm

IDENTIFICATION OF ATRIAL ACTIVITY

• If P waves cannot be clearly identified, the Valsalva maneuver, carotid sinus massage (CSM), or the administration of intravenous adenosine may help to clarify the diagnosis

• Valsalva maneuver• Carotid sinus massage Contraindications • A carotid bruit.• Prior stroke or transient ischemic attack, unless imaging has

shown no significant carotid disease.• A myocardial infarction within the previous six months.• A history of serious cardiac arrhythmias (ventricular

tachycardia or fibrillation).

four possible results

• The slowing of SA nodal activity can cause a temporary decrease in the atrial rate (in patients with sinus tachycardia).

• The slowing of AV nodal conduction can lead to AV nodal block, which may "unmask" atrial electrical activity (ie, reveal P waves or flutter waves) by decreasing the number of QRS complexes that obscure the electrical baseline

• With some narrow QRS complex tachycardias that require AV nodal conduction (especially AVNRT and AVRT), the transient slowing of AV nodal conduction can terminate the arrhythmia by interrupting the reentry circuit. Less commonly, CSM can cause some atrial tachycardias to slow and terminate.

• In some cases, no response is obtained.

Termination of the arrhythmia

• Termination with a P wave after the last QRS complex is most common in AVRT or AVNRT and is rarely seen with AT.

• Termination with a QRS complex can be seen with AVRT, AVNRT, or AT.

• If the tachycardia continues despite successful induction of at least some degree of AV nodal blockade, the rhythm is almost certainly AT or atrial flutter; AVRT is excluded and AVNRT is very unlikely

CHARACTERIZATION OF ATRIAL ACTIVITY

• The atrial rate.• The P wave morphology (ie, identical to normal

sinus rhythm, retrograde, or abnormal).• The position of the P wave in relation to the

preceding and following QRS complexes (ie, the RP relationship).

• The relationship between atrial and ventricular rates (1:1 or otherwise).

Atrial rate

• in isolation is rarely diagnostic • very fast atrial rates (eg >250 beats/minute)-

atrial flutter or atrial tachycardia (AT).

P wave morphology

• Similar to sinus rhythm• Retrograde• Abnormal

• Sinus tachycardia (ST)• Inappropriate sinus tachycardia (IST) — IST is an

unusual condition occurring in patients without apparent heart disease or other cause for sinus tachycardia, such as hyperthyroidism or fever. Affected patients have an elevated resting heart rate and/or an exaggerated heart rate response to exercise; many patients have both. The cause of IST is unknown, but abnormal autonomic control is thought to be important.

• Sinoatrial (SA) nodal reentrant tachycardia (SNRT) — SNRT is uncommon, accounting for fewer than 5 percent of patients referred for electrophysiologic testing. In SNRT, the rate typically ranges from 100 to 150 beats/minute

• Atrial tachycardia (AT), usually originating near the sinus node.

Retrograde P waves

suggest certain diagnoses, specifically AVNRT, AVRT, and less commonly, JET or NPJT.

Abnormal P waves

• most consistent with atrial tachycardias, although some AVRTs have abnormal P waves.

RP relationship

• Short RP tachycardias Abnormal P wave : atrial tachycardia with AV

nodal conduction delay

Slow-fast form of AVNRT

Generation of ECG in common form of AVNRT

Uncommon atrioventricular nodal reentrant tachycardia

AVNRT

• Presence of a narrow complex tachycardia with regular R-R intervals and no visible p waves.

• P waves are retrograde and are inverted in leads II,III,AVF.

• P waves are buried in the QRS complexes –simultaneous activation of atria and ventricles – most common presentation of AVNRT –66%.

• If not synchronous –pseudo s wave in inferior leads ,pseudo r’ wave in lead V1---30% cases .

• P wave may be farther away from QRS complex distorting the ST segment ---AVNRT ,mostly AVRT.

Atrioventricular node reentrant tachycardia (the Jaeggi algorithm),

• pseudo S/R waves,• the RP interval, • the lack of significant ST depression in

multiple leads a correct diagnosis of typical AVNRT can be

made by ECG analysis 76% of the time

Orthodromic AVRT using a rapidly conducting accessory pathway:

Most common type of AVRTInitiated by either an APB or VPBAV conduction is over the AV node & VA conduction over

accessory pathwayActivation of ventricle & atrium follow sequentially P

waves are separated from the QRS complex.Retrograde conduction is rapid P wave closer to the

preceding QRS RP < PR.The QRS may be narrow or if aberrant conduction occurs, a

typical BBB will be present.

The mechanism of QRS alternans during narrow QRS tachycardia is not known. It has been attributed to non-specific intraventricular conduction abnormalities.QRS alternans has been considered to be strongly suggestive of AV re-entrant tachycardia. However, it may also occur during AV nodal re-entrant tachycardia and can also be induced by abrupt rapid atrial pacing

.

ST segment depression

• represent either repolarization changes or a retrograde atrial activation

• more commonly seen in those with an AV reentrant tachycardia associated with an accessory pathway

• aVL notch: any positive deflection at the end of the QRS during tachycardia and its absence during sinus rhythm.

relevant ECG parameters.• Heart rate

– There were no difference in the heart rate during tachycardia between AVNRT and AVRT.

• Pseudo r wave, pseudo Q wave and pseudo S wave.– A pseudo r wave in lead V1 was present more frequently in AVNRT

than in AVRT . – The presence of pseudo S wave or pseudo Q wave in the inferior leads

was exclusively found during AVNRT.

• Retrograde P waves and RP interval-----------.– A retrograde P wave separate from the QRS complex was discernible

more often in AVRT than in AVNRT. – The RP interval was longer in AVRT than in AVNRT.

• ST-segment elevation in aVR lead.– According to the definition, the percentage of patients with aVR ST-

segment elevation was significantly greater in AVRT than in AVNRT

• Cycle length alternans.– Cycle length alternans was present in only four of

the initial 104 patients and all of them were AVRT.

• QRS alternans. – By contrast, QRS alternans was present in both

AVNRT and AVRT, and the difference between the two tachycardias was not statistically significant

A, Patient with a right anteriorpathway: The retrograde P wave is negative in lead V1 and positive inleads II, III and aVF.

Patient with a right posterior pathway: Theretrograde P wave is negative in leads V1, II, III and aVF.

Patient with a right midseptalpathway: The retrograde P wave is biphasic in lead V1 and negative inleads II, III and aVF.

Patient with a right posteroseptal pathway:The retrograde P wave is positive in lead V1, negative in leads II, IIIaVF and biphasic in lead I.

Short and long RP

topograghy

CLASSIFICATION AND MECHANISMS

• European Society ofCardiology and the North American Society of Pacing and Electrophysiology

• Atrial tachycardias were classified as tachycardia arising from the atrium with a regular atrial rate – focal or macroreentrant

• Focal AT-automatic, triggered, or microreentrant mechanisms.– characterized by radial, circular, or centrifugal spread of activation from a single

focus and lack of electrical activation spanning the tachycardia cycle length.

• Macroreentrant atrial tachycardias- reentry through relatively large, potentially well-characterized circuits.– characterized by a repetitive pattern of electrical activation encompassing the

entire cardiac cycle.

• The predominant areas of origin of focal atrial tachycardia– 1.the area along the crista terminalis, – 2.near or aside the four pulmonary veins (superior

veins more commonly), – 3.around or inside the coronary sinus os, – 4.superior vena cava, – 5.atrial septum, and – 6.Koch's triangle.

FOCIRA-

1.CT, 2.the tricuspid annulus (TA) 3. the ostium of the coronary sinus (CS) 4.the perinodal region.

LA- 1.pulmonary vein (PV) ostia 2.mitral annulus (MA) 3.LAA 4.leftsided septum

topography

• Lead V1 is located to the right and anteriorly in relation to the atria, which should be considered as right anterior and left posterior.

• Tachycardias originating from the tricuspid annulus were negative in V1 because of the anterior and rightward location of this structure.

• The P-wave in V1 is universally positive for tachycardias originating at the PVs, because of the posterior location of these structures.

The major limitation in the use of a positive P-wave in lead V1 to predict left atrial origin was in distinguishing foci at the superior CT from the RSPV.

This is an important consideration given the relatively common occurrence of AT from both sites, which are known to be in close anatomic proximity.

Tang et al.made the important observation that RSPV foci showed a change in configuration from biphasic in SR to upright in AT, a change not observed for right-sided tachycardias.

The predictive value of PWM for localizing the atrium of origin was more limited when tachycardia foci arose from the interatrial septum

alogarithm

alogarithm

Atrioventricular node reentrant tachycardia (the Jaeggi algorithm),

• pseudo S/R waves,• the RP interval, • the lack of significant ST depression in

multiple leads a correct diagnosis of typical AVNRT can be

made by ECG analysis 76% of the time

• aVL notch: any positive deflection at the end of the QRS during tachycardia and its absence during sinus rhythm.

relevant ECG parameters.• Heart rate

– There were no difference in the heart rate during tachycardia between AVNRT and AVRT.

• Pseudo r wave, pseudo Q wave and pseudo S wave.– A pseudo r wave in lead V1 was present more frequently in AVNRT

than in AVRT . – The presence of pseudo S wave or pseudo Q wave in the inferior leads

was exclusively found during AVNRT.

• Retrograde P waves and RP interval-----------.– A retrograde P wave separate from the QRS complex was discernible

more often in AVRT than in AVNRT. – The RP interval was longer in AVRT than in AVNRT.

• ST-segment elevation in aVR lead.– According to the definition, the percentage of patients with aVR ST-

segment elevation was significantly greater in AVRT than in AVNRT

• Cycle length alternans.– Cycle length alternans was present in only four of

the initial 104 patients and all of them were AVRT.

• QRS alternans. – By contrast, QRS alternans was present in both

AVNRT and AVRT, and the difference between the two tachycardias was not statistically significant

algorithm

New step

alogarithm

A, Patient with a right anteriorpathway: The retrograde P wave is negative in lead V1 and positive inleads II, III and aVF.

Patient with a right posterior pathway: Theretrograde P wave is negative in leads V1, II, III and aVF.

Patient with a right midseptalpathway: The retrograde P wave is biphasic in lead V1 and negative inleads II, III and aVF.

algorithmPatient with a right posteroseptal pathway:The retrograde P wave is positive in lead V1, negative in leads II, IIIaVF and biphasic in lead I.

Follow P Wave