23. Macroreentrant Atrial Tachycardia
(MRT)
MRT (Flutter) is conventionally defined as a circuit with a
diameter of greater than 2 cm in diameter and frequently occurs
around a central obstacle.
24. Typical Atrial Flutter
• The first description of Typical Atrial Flutter was
presented by Sir Thomas Lewis in 1912.
• The ECG was characteristic of this arrhythmia showing
a ‘saw tooth’ pattern in leads II, III, and/or aVF .
• In lead V1 a positive deflection is usually seen but a
biphasic deflection may also be detected.
25. Typical Atrial Flutter
• Puech in the early sixties, showed the mechanism of this
arrhythmia is a large re-entrant right atrial circuit bounded
anteriorly by the tricuspid annulus and posteriorly by orifices of
the IVC and SVC and the Eustachian ridge and the crista
terminalis.
• Activation is usually counterclockwise, descending the anterior
and lateral walls and ascending the septal and posterior wall of
the right atrium.
• Activation is dependent on the cavotricuspid isthmus (CTI).
29. Mechanisms of Atrial Flutters
• Some tachycardias show a typical ECG pattern of
Flutters may not be CTI dependent and conversely an
atypical ECG can be CT dependent.
• Term Typical Flutters refers to CTI dependent
regardless of the ECG pattern.
• Term Atypical Flutters refers to a non-CTI
dependent Flutters.
30. Typical Flutters with Unusual
ECG Pattern
• Reverse Typical Atrial Flutter:
– In 10% of the cases, a reverse direction of rotation
(clockwise re-entry) has been observed.
– Reverse Typical Atrial Flutter can be induced in the EP
lab in about 50% of the patients presenting only clinically
counterclockwise Flutter.
Europace, Vol. 4, July 2002
37. Upper loop re-entry tachycardia
(ULR)
• Upper loop re-entry tachycardia (ULR) is a non-CTI
dependent tachycardia involving the upper portion of
the RA and a clockwise rotation, isthmus was
identified between the superior vena cava and the
fossa ovalis.
Europace, Vol. 4, July 2002
39. Lower loop re-entry tachycardia
(LLR)
• LLR can alternate with Typical Flutter, passing
through the CTI the activation goes up towards the
IAS, short circuits the crista terminalis and
descends along the lower part of the right lateral
wall while simultaneously activating the rest of the
lateral wall in an ascending direction.
• The mean cycle length is usually from 170 to 250
ms, positive forces in inferior leads and V1
Europace, Vol. 4, July 2002
41. Left Atrial Flutter
• The most frequent left Atrial Flutters are
perimitral, peripulmonary veins, septal, roof
and posterior wall,
• Usually seen after AF ablation.
Europace, Vol. 4, July 2002
43. Post AF Ablation AT
• It is common to need more than one ablation
procedure
• ATs (ERAT) account for up to 50%
of arrhythmias post AF ablation
• Most will be left atrial in origin
• Often less well tolerated than AF
• Rhythm control usually difficult with AADs
HRS/EHRA/ECAS Expert Consensus on Catheter and Surgical Ablation of AF Heart Rhythm Vol 9 No 4 April2012
44. Mechanisms
• Focal
• Micro-reentry
• Macro-reentry (Flutter) Larger circuit
-‐cavo-tricuspid isthmus dependent
-‐roof dependent
-‐mitral isthmus dependent (peri-mitral)
• Maps to a single area of early activation
45. Focal or Micro Re-‐entry
Maps to a single area of
early activation
More common:
Post PVI
Post CAFEs
Heck, Rosso & Kistler JCE 2011; 22: 832-‐8
52. A: AT with a left
lateral origin and no
pre-existing lines of
block
B: AT with a left lateral
origin and pre-existing
CTI block resulting in a
high-to-low RA
activation
C: Simultaneous LA and
RA activation in case
of a roof-dependent LA
AT the RA, being
activation via the
Bachmann bundle
Heart Rhythm, Vol 7, No 5, May 2010
53. A: AT with
CTI-dependant RA
flutter
B: Septal/roof-
dependant AT without
pre-existing lines of
block in the atria
C: AT with the same
origin but pre-existing
CTI block resulting in a
high-to-low RA
activation
D: AT with a
left lateral origin and a
pre-existing conduction
block in the lateral mitral
isthmus
Heart Rhythm, Vol 7, No 5, May 2010
68. Scar – Related or
Incisional Atrial Tachycardia
• Incisional Flutters which includes those
where the circuit uses previous surgery
related scars.
• Frequently seen in patients with history of
surgical correction of CHD.
Europace, Vol. 4, July 2002
69. Incisional Atrial Tachycardia
• Ablation is often more difficult
– multiple circuits are common
– difficult to define critical isthmus
– difficult to achieve block across an isthmus
• Mapping is facilitated by an advanced
mapping system
• Successful ablation: 50 – 88%
Akar, et al.2001,Chan, et al.2000,Delacretaz, et al.2001, Nakagawa, et al.2001,Triedman, et al.1997 Jais, et al.2000,Saoudi, et al.2001,Tai, et
al.2001,Thomas, et al.2000
85. Conclusion
• Atypical atrial flutter represents a large variety of
supraventricular tachycardias and refers to any non-
CTI dependent tachycardia.
• Ablation of non–CTI-dependent flutter can be
substantially more difficult than for CTI-dependent
ones.
• The underlying circuit(s) can be located in either the
right or left atrium.
Akar JG, Kok LC, Haines DE, DiMarco JP, Mounsey JP. J Am Coll Cardiol 2001;38:377-84.
86. Conclusion
• Recurrence and complications vary depending on the
underlying substrate, location of the tachycardia circuit
and extent of ablation.
• The most notable complications are diaphragmatic
paralysis caused by phrenic nerve injury and
thromboembolism after conversion from atrial flutter.
Nakagawa H, Shah N, Matsudaira K, et al. Circulation 2001;103:699-709.
87. Where is the target ?
• Localizing the circuit and creating a line of
block that includes an electrically inert
anatomic structure
Conclusion