Atrial TachycardiaAtrial Tachycardia

Dr Mohamed Salih AzizDr Mohamed Salih AzizKing Abdualaziz Medical City RiyadhKing Abdualaziz Medical City Riyadh

definitiondefinition

Atrial tachycardia is defined as a Atrial tachycardia is defined as a supraventricular tachycardia (SVT) supraventricular tachycardia (SVT) that does not require the that does not require the atrioventricular (AV) junction, atrioventricular (AV) junction, accessory pathways, or ventricular accessory pathways, or ventricular tissue for initiation and maintenance tissue for initiation and maintenance of the tachycardia of the tachycardia

The ECG typically shows a narrow QRS complex The ECG typically shows a narrow QRS complex tachycardia (unless bundle branch block tachycardia (unless bundle branch block aberration occursaberration occursHeart rates during atrial tachycardia are highly Heart rates during atrial tachycardia are highly variable, with a range of variable, with a range of 100-250100-250 beats per beats per minuteminuteThe atrial rhythm is usually The atrial rhythm is usually regularregularThe conducted ventricular rhythm is also usually The conducted ventricular rhythm is also usually regularregular but may become but may become irregularirregular, often at , often at higher atrial rates because of variable higher atrial rates because of variable conduction through the AV node, thus producing conduction through the AV node, thus producing conduction patterns such as 2:1, 3:1, and conduction patterns such as 2:1, 3:1, and

Wenckebach AV block.Wenckebach AV block.

The The P waveP wave morphology may give clues to morphology may give clues to the site of origin and mechanism of the atrial the site of origin and mechanism of the atrial tachycardia.tachycardia.In the case of a focal tachycardia, the P wave In the case of a focal tachycardia, the P wave morphology and axis depend on the location morphology and axis depend on the location in the atrium from which the tachycardia in the atrium from which the tachycardia originates. In the case of macroreentrant originates. In the case of macroreentrant circuits, the P wave morphology and axis circuits, the P wave morphology and axis depend on activation patterns.depend on activation patterns.

Types of Atrial TachycardiaTypes of Atrial Tachycardia

A-Based on endocardial activation:A-Based on endocardial activation:

1)1) focal atrial tachycardiafocal atrial tachycardia

arises from a localized area in the atria arises from a localized area in the atria such as the crista terminalis, pulmonary such as the crista terminalis, pulmonary veins, ostium of the coronary sinus, or atrial veins, ostium of the coronary sinus, or atrial septum. Focal atrial tachycardia that septum. Focal atrial tachycardia that originates from the pulmonary veins may originates from the pulmonary veins may trigger atrial fibrillation trigger atrial fibrillation

2) reentrant atrial tachycardias2) reentrant atrial tachycardias..

most commonly occur in persons with most commonly occur in persons with structural heart disease, complex heart structural heart disease, complex heart disease, and particularly after surgery disease, and particularly after surgery involving incisions or scarring in the atria. involving incisions or scarring in the atria. these atrial tachycardias are similar to the these atrial tachycardias are similar to the typical atrial flutterstypical atrial flutters

3)Sinoatrial reentrant tachycardia3)Sinoatrial reentrant tachycardia is a subset of focal atrial tachycardia due to is a subset of focal atrial tachycardia due to reentry arising within the sinus node situated reentry arising within the sinus node situated at the superior aspect of the crista terminalis. at the superior aspect of the crista terminalis. The P wave morphology and atrial activation The P wave morphology and atrial activation sequence are similar to those of sinus sequence are similar to those of sinus tachycardiatachycardia

MAT MAT

is a unique type of atrial tachycardia in which atrial is a unique type of atrial tachycardia in which atrial activation originates from multiple atrial foci. activation originates from multiple atrial foci. MAT often occurs in patients experiencing an MAT often occurs in patients experiencing an exacerbation of chronic obstructive pulmonary exacerbation of chronic obstructive pulmonary disease, a pulmonary thromboembolism, an disease, a pulmonary thromboembolism, an exacerbation of congestive heart failure, or exacerbation of congestive heart failure, or severe illness especially under critical care severe illness especially under critical care with inotropic infusion. with inotropic infusion. It is often associated with hypoxia and It is often associated with hypoxia and sympathetic stimulation. sympathetic stimulation. Digitalis toxicity also may be present in Digitalis toxicity also may be present in persons with MAT, with triggered activity as persons with MAT, with triggered activity as the mechanismthe mechanism

Pathophysiologic mechanisms

Several pathophysiologic mechanisms have been Several pathophysiologic mechanisms have been ascribed to atrial tachycardia. These mechanisms ascribed to atrial tachycardia. These mechanisms can be differentiated based on the pattern of can be differentiated based on the pattern of onset and termination and response to drugs and onset and termination and response to drugs and

atrial pacingatrial pacing..

Automatic atrial tachycardia Automatic atrial tachycardia (enhanced automaticity(enhanced automaticity))

is observed both in patients with normal heart is observed both in patients with normal heart structure and in those with organic heart disease. structure and in those with organic heart disease.

The tachycardia typically exhibits a warm-up The tachycardia typically exhibits a warm-up phenomenon, during which the atrial rate gradually phenomenon, during which the atrial rate gradually accelerates after its initiation and slows prior to its accelerates after its initiation and slows prior to its termination. termination.

It is rarely initiated or terminated by single atrial It is rarely initiated or terminated by single atrial stimulation or rapid atrial pacing, but it may be stimulation or rapid atrial pacing, but it may be transiently suppressed by overdrive pacing.transiently suppressed by overdrive pacing.

Carotid sinus massage and adenosine do not Carotid sinus massage and adenosine do not terminate the tachycardia even if they produce a terminate the tachycardia even if they produce a transient AV nodal block. transient AV nodal block.

Electrical cardioversion is ineffective (being Electrical cardioversion is ineffective (being equivalent to attempting electrical cardioversion in equivalent to attempting electrical cardioversion in a sinus tachycardiaa sinus tachycardia

Triggered activityTriggered activity

is due to delayed after-depolarizationsis due to delayed after-depolarizations

occurs in patients with digitalis intoxication or conditions occurs in patients with digitalis intoxication or conditions associated with excess catecholamines. associated with excess catecholamines.

the arrhythmia can be initiated, accelerated, and the arrhythmia can be initiated, accelerated, and terminated by rapid atrial pacing.terminated by rapid atrial pacing.

It may be sensitive to physiologic and pharmacologic It may be sensitive to physiologic and pharmacologic maneuvers such as adenosine, verapamil, and beta-maneuvers such as adenosine, verapamil, and beta-blockers, which all can terminate the tachycardia. blockers, which all can terminate the tachycardia. Occasionally, this atrial tachycardia may arise from Occasionally, this atrial tachycardia may arise from multiple different sites in the atria, producing a multiple different sites in the atria, producing a multifocal or multiform atrial tachycardia. This may be multifocal or multiform atrial tachycardia. This may be recognized by varying P wave morphology and recognized by varying P wave morphology and irregularity in the atrial rhythm.irregularity in the atrial rhythm.

Reentrant tachycardiaReentrant tachycardia

Intra-atrial reentry tachycardias may have either a Intra-atrial reentry tachycardias may have either a macroreentrant or a microreentrant circuit. macroreentrant or a microreentrant circuit.

Macroreentry is the usual mechanism in atrial flutter Macroreentry is the usual mechanism in atrial flutter and in scar- and incision-related (postsurgical) atrial and in scar- and incision-related (postsurgical) atrial tachycardia.tachycardia.

Microreentry can arise in a small focal area such as in Microreentry can arise in a small focal area such as in sinus node reentrant tachycardia. sinus node reentrant tachycardia.

Typically, reentrant atrial tachycardia arises suddenly, Typically, reentrant atrial tachycardia arises suddenly, terminates suddenly, and is paroxysmal.terminates suddenly, and is paroxysmal.

Carotid sinus massage and adenosine are ineffective Carotid sinus massage and adenosine are ineffective in terminating the tachycardia even if they produce a in terminating the tachycardia even if they produce a transient AV nodal block. On electrophysiologic study,transient AV nodal block. On electrophysiologic study,

it can be induced and terminated by programmed it can be induced and terminated by programmed extrastimulation. As is typical in other reentry extrastimulation. As is typical in other reentry tachycardias, electrical cardioversion terminates this tachycardias, electrical cardioversion terminates this type of atrial tachycardia.type of atrial tachycardia.

HistoryHistory

Typically, atrial tachycardia manifests as a Typically, atrial tachycardia manifests as a sudden onset of palpitations. sudden onset of palpitations.

If atrial tachycardia is due to enhanced If atrial tachycardia is due to enhanced automaticity, it may be nonsustained but automaticity, it may be nonsustained but repetitive or continuous or sustained, as in repetitive or continuous or sustained, as in reentrant forms of atrial tachycardia. reentrant forms of atrial tachycardia.

Patients may present with a tachycardia that Patients may present with a tachycardia that gradually speeds up soon after its onset gradually speeds up soon after its onset (warm-up phenomenon). The patient may be (warm-up phenomenon). The patient may be unaware of this. This finding during ECG unaware of this. This finding during ECG monitoring, as with a Holter, is suggestive that monitoring, as with a Holter, is suggestive that the supraventricular tachycardia is atrial the supraventricular tachycardia is atrial tachycardiatachycardia. .

•If accompanied by palpitations, patients also may If accompanied by palpitations, patients also may report dyspnea, dizziness, lightheadedness, fatigue, report dyspnea, dizziness, lightheadedness, fatigue, or chest pressure. One should recognize the early or chest pressure. One should recognize the early manifestations of tachycardia-induced manifestations of tachycardia-induced cardiomyopathy, ie, a decline in effort tolerance and cardiomyopathy, ie, a decline in effort tolerance and symptoms of heart failure, in patients with frequent symptoms of heart failure, in patients with frequent or incessant tachycardias. or incessant tachycardias.

* Lightheadedness may result from relative * Lightheadedness may result from relative hypotension, depending on the heart rate and other hypotension, depending on the heart rate and other factors such as the state of hydration and factors such as the state of hydration and particularly the presence of structural heart particularly the presence of structural heart disease. The faster the heart rate, the more likely a disease. The faster the heart rate, the more likely a patient is to feel lightheaded. If the patient has a patient is to feel lightheaded. If the patient has a rapid rate and severe hypotension, syncoperapid rate and severe hypotension, syncope may may occuroccur..

PhysicalPhysical

The primary abnormality noted upon physical The primary abnormality noted upon physical examination is a rapid pulse rate. In most atrial examination is a rapid pulse rate. In most atrial tachycardias this is regular. However, in rapid tachycardias this is regular. However, in rapid atrial tachycardias with variable AV conduction atrial tachycardias with variable AV conduction and in multifocal atrial tachycardia (MAT), the and in multifocal atrial tachycardia (MAT), the pulse may be irregular. pulse may be irregular. Blood pressure may be low in those patients Blood pressure may be low in those patients with fatigue, lightheadedness, or presyncope. with fatigue, lightheadedness, or presyncope. The cardiovascular examination should be The cardiovascular examination should be aimed at excluding underlying structural heart aimed at excluding underlying structural heart diseases such as valvular abnormalities and diseases such as valvular abnormalities and evidence of heart failure. evidence of heart failure. Abnormal thyroid function should also be in the Abnormal thyroid function should also be in the differential diagnosis differential diagnosis

Atrial Tachycardia With 3:2 and 2:1 AV Block-KHAtrial Tachycardia With 3:2 and 2:1 AV Block-KH The ectopic atrial rate is 150 bpm. Some of the

ectopic P waves are easily seen and indicated by the arrows. Other P waves are burried in the T waves and not so easily identified. Atrial tachycardia with AV block is often a sign of digitalis intoxication. 3:2 and 2:1 AV block is seen in this example.

The ectopic P waves, easily seen in this example, The ectopic P waves, easily seen in this example, occur in groups, separated by short pauses. This occur in groups, separated by short pauses. This is likely due to an exit block just distal to the atrial is likely due to an exit block just distal to the atrial pacemaker. Because not all of the P waves make pacemaker. Because not all of the P waves make it to the ventricles, there is also 2nd degree AV it to the ventricles, there is also 2nd degree AV block. Therefore, two levels of block are present: block. Therefore, two levels of block are present: one in the atria and one at the level of the AV one in the atria and one at the level of the AV junction.junction.

Very Subtle Atrial Tachycardia With 2:1 Block-KHVery Subtle Atrial Tachycardia With 2:1 Block-KHFrank Yanowitz Copyright 1996 Frank Yanowitz Copyright 1996

Although at first glance this looks like normal sinus Although at first glance this looks like normal sinus rhythm at 95 bpm. On closer look, there are 2 'P' rhythm at 95 bpm. On closer look, there are 2 'P' waves for every QRS; the atrial rate is 190 bpm. waves for every QRS; the atrial rate is 190 bpm. Note the hidden 'P' in the T waves. This rhythm is Note the hidden 'P' in the T waves. This rhythm is likely due to digitalis intoxication, as are the GI likely due to digitalis intoxication, as are the GI symptoms.symptoms.

Atrial tachycardia With 3:2 AV BlockAtrial tachycardia With 3:2 AV Block

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