Anatomic barriers within the right atrium sustain the macro-reentry circuit. The AV node plays no part in the flutter circuit, so drugs aimed at altering the conduction of the AV node have no effect on the atrial rate.
Note that the inferior leads (II, III and aV F ) of counterclockwise flutter have a characteristic initial, broad “sawtooth” negative deflection followed by a less pronounced positive wave. In contrast, clockwise flutter has predominately upgoing flutter waves in the inferior leads that are typically notched and end with a slightly negative component.
A review of landmarks is helpful, before discussing ablation techniques.
This slide depicts termination of atrial flutter during RF current delivery.
Before the ablation, pacing near the CS os would allow the impulse to travel in both directions, eventually colliding on the lateral wall. After ablation, pacing near the CS os only allows the impulse to travel in one direction, eventually terminating at the line of block.
2011 10 黃金gap detect of afl
How to Identify the Conduction Gaps in the Atrial Flutter using Non-Contact Mapping Jin-Long Huang, MD, Ph D. Cardiovascular Center, Taichung-Veterans General Hospital National Yang-Ming University, Taipei, Taiwan
Right Atrial Flutters (AFL) <ul><li>Typical AFL </li></ul><ul><li>Atypical AFL </li></ul>
Reentry Circuit of Common Atrial Flutter Morady F. N Engl J of Med. 1999;340:534-544.
ECG Comparison Counterclockwise Clockwise Singer: Interventional Electrophysiology. Williams & Wilkins 1997; 356. positive inferiorly and in V6, and negative in lead V1.
A new electrocardiographic algorithm to differentiate upper loop re-entry from reverse typical atrial flutter Yuniadi Y , Tai CT , Huang JL , Chen SA . J Am Coll Cardiol. 2005 Aug 2;46(3):524-8
Oblique View of Right Atrium Crista Terminalis Pectinate Muscle Orifice of Coronary Sinus Superior Vena Cava Fossa Ovalis Eustachian Ridge Inferior Vena Cava Netter F. Atlas of Human Anatomy. 1989;Plate 208.
Catheter Location for Atrial Flutter Ablation Free wall Crista Used with permission of Dr. Brian Olshansky.
Characteristics of Virtual Unipolar Electrograms for Detecting Isthmus Block During RF Ablation of Typical AFL Lin YJ et al. J Am Coll Cardiol 2004;43:2300–4. <ul><li>The 2nd component of unipolar electrograms represents the approaching wavefront in the RA opposite the pacing site. </li></ul><ul><li>We hypothesized that the morphologic characteristics of the second component of double potentials would be useful in detecting complete CTI block. </li></ul>
Group I (n=37):complete bidirectional CTI block During CS pacing, the second component of unipolar electrograms showed an R or Rs pattern.
Group II (n = 12) had incomplete CTI block. The second component of unipolar electrograms showed an rS pattern.
Group III (n= 3) had complete CTI block with transcristal conduction. The second component of unipolar electrograms showed an rSR pattern.
Conclusions <ul><li>A predominant R-wave pattern in the secondcomponent of unipolar double potentials at the ablation line indicates complete CTI block, even in the presence of transcristal conduction. </li></ul>
High Resolution Mapping around the Eustachian Ridge(ER) during Typical Atrial Flutter Huang JL et al J Cardiovasc Electrophysiol. 2006 ;17(11):1187-92. <ul><li>53(M/F= 43/10, 62±14 yrs) with typical AFL. </li></ul><ul><li>The high-resolution mapping of the RA using a noncontact mapping system during AFL and pacing from the CS was performed to evaluate the conduction through the ER. </li></ul>
A (AFL) a b c a b c B (CS Pacing) Type I pattern: ER block
A (AFL) a b c abc B (CS Pacing) abc Type II pattern: Block in AFL and Conduction in CS pacing
A (AFL) a SV b SV c abc SV B (CS Pacing) SV SV SV abc Type III pattern
Results <ul><li>Three types of activation patterns around the ER </li></ul><ul><li>Type I (n=21) exhibited conduction block in the ER during AFL and CS pacing. </li></ul><ul><li>Type II (n=8) exhibited conduction block in the ER during AFL, but conduction through the ER during CS pacing. </li></ul><ul><li>Type III (n=24) exhibited an activation wavefront that passed along the ER, with the sinus venosa as the posterior barrier during AFL. During CS pacing, all cases exhibited conduction through the ER with an rS pattern. </li></ul>
Different ablation strategy in the aged during AFL
RA substrate properties associated with age in patients with typical AFL Huang JL et al. Heart Rhythm. 2008;5(8):1144-51 <ul><li>OBJECTIVE: to characterize the difference in the right atrial (RA) substrate related to aging using noncontact mapping of the right atrium. </li></ul>
Methods <ul><li>A total of 54 patients (23 young [<60 years] and 31 old [≧ 60 years]) with typical AFL who underwent 3-D noncontact mapping of typical AFL were enrolled in the study. </li></ul><ul><li>The atrial substrate was characterized according to </li></ul><ul><li>(1) regional wavefront activation mapping, </li></ul><ul><li>(2) regional conduction velocity </li></ul><ul><li>(3) regional voltage distribution by dynamic substrate mapping. </li></ul>
RESULTS <ul><li>During activation mapping of the crista terminalis, two activation patterns were observed: </li></ul><ul><li>(1) around the upper end of the crista terminalis (67%) </li></ul><ul><li>(2) through a gap in the crista terminalis. </li></ul><ul><li>(3)The presence of a crista terminalis gap was associated </li></ul><ul><li>with a high incidence of induced atypical AFL/atrial </li></ul><ul><li>fibrillation (P <.001). </li></ul><ul><li>More cases with a low-voltage zone (<or=30% peak negative voltage) extending to the medial side of the cavotricuspid isthmus occurred in the old group than in the young group (55% vs 17%, P = .012). </li></ul>
P=0.003 P=0.04 The conduction velocities of the medial CTI were slower in the old group than in the young group.
Locations of the Slowest Conduction during AFL 6% 40% 33% 21% 13% 8% 71% 8% < 60 y/o > 60 y/o P < 0.01 In regional activation mapping of the AFL, the location of the slowest conduction shifted from the lateral cavotricuspid isthmus (71%) in the young group to the medial cavotricuspid isthmus (40%) in the old group.
A: 43 yr male PNV= -4.2 mV B: 79 yr male PNV= -3.9 mV SVC IVC SVC IVC CT SVC IVC SVC IVC CT
Conclusions <ul><li>Three-dimensional mapping showed the different patterns of activation in the Eustachian during AFL. </li></ul><ul><li>Analysis of atrial substrate could show the information of protected isthmus during atypical atrial flutter, which could provide important strategy for ablation. </li></ul><ul><li>Different atrial substrate in the young and old patients with AFL and strategy of ablation should be adjusted in the clinical practice for these two groups. </li></ul>
What else? Besides activation mapping!! Substrate analysis!!
Voltage maps before & after ablation LVZ LVZ IVC IVC SVC 1 cm B. Ablation site <ul><li>Voltage map </li></ul><ul><li>before ablation </li></ul>C. Voltage map after ablation Virtual 10 Virtual 10 11 12 11 12 10 11 12 1 cm 0--5% 5-10% 10-15% 15-20% 20-25% 25-30% 30-35% 35-40% 40-45% 45-50% 50-55% 55-60% 60-65% 65-70% 70-75% 75-80% 80-85% 85-90% 90-100% Ratio to the maximum PNV
A: SR C: LAL pacing B: CSO pacing D: Atypical flutter % of global maximum PNV Septum Lateral wall CT IVC SVC 1 2 3 1 2 3 Voltage map: Normalized to Global Maximal PNV 1.5 mV 2.1 mV 3.4 mV 1.2 mV 0.2 mV 0.8 mV
B C F LVZ LVZ LVZ LVZ LVZ LVZ LVZ LVZ A B C D E F Virtual 10 11 12 13 14 15 H: Virtual electrograms A G: Intracardiac tracing A B C D E F E D LVZ LVZ LVZ LVZ
LVZ LVZ IVC SVC Virtual 1 2 3 1 LVZ Voltage mapping before ablation Voltage mapping after ablation % of global maximum PNV Virtual 1 2 3 1 2 3 IVC 3 2 Pacing from CSO Pacing from CSO
Substrate Mapping to Detect Abnormal Atrial Endocardium with Slow Conduction in Patients with Atypical Right AFL Huang JL et al. J Am Coll Cardiol 2006 ;48(3):492-8 <ul><li>Atypical RA AFL was induced by atrial pacing in 12 patients, </li></ul><ul><li>The protected isthmuses were near the crista terminalis. </li></ul><ul><li>The conduction velocities within these paths were significantly slower than outside the path (0.30±0.18 m/s vs. 1.14±0.41 m/s, respectively, p=0.004). </li></ul>
Ratio to the maximal peak negative voltage Normalized Negative Unipolar Voltage Maximal peak negative voltage of a selected beat
Identify the Protected Isthmus: bordered by the low voltage zones Isthmus LVZ Convergence of voltage lines
LVZ LVZ LVZ LVZ LVZ LVZ LVZ LVZ LVZ LVZ LVZ LVZ % of global maximum PNV Protected Isthmus during RA AFL in 6 pts
Isthmus <ul><li>Mean width: 1.7 ± 0.3 cm 2 (1.2 cm 2 to 2.3 cm 2 ) </li></ul><ul><li>Mean voltage at the isthmus: -0.91 ± 0.39 mV (-0.33 to -1.69 mV) with equivalent to 43 ± 14 % of the maximal PNV (23 to 58%). </li></ul><ul><li>Local Eg were widely fragmented, indicating slow conduction </li></ul><ul><li>The conduction velocities within paths were significantly slower than outside the path (0.30±0.18 m/s vs. 1.14±0.41 m/s, p=0.004). </li></ul>LVZ LVZ Characteristics of the protected isthmus P = 0.01 P = 0.004 PNV Coduction Velocity
Result (I) <ul><ul><li>Prediction of slow conduction of the protected isthmus </li></ul></ul><ul><ul><li>Fixed voltage: -0.54 mV was the best cut-off value by local Eg voltage (sensitivity=61.5% and specificity=85.7%, CI=95%). </li></ul></ul><ul><ul><li>Ratiometric voltage: 37.6% to the maximal PNV was the best cut-off value (sensitivity=92.3% and specificity=85.7%, CI=95%). </li></ul></ul>0 20 40 60 80 100 100-Specificity (%) 100 80 60 40 20 0 Sensitivity (%) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Inside isthmus A: ROC Curve Analysis B: Ratiometric voltage Ratiometric Voltage Outside isthmus
Result (II) <ul><li>Radiofrequency ablation </li></ul><ul><li>Delivery of ablation energy across the path was successful (8.8 ± 2.6 pulses), suggesting it represented the critical isthmus of the reentrant circuit. </li></ul><ul><li>After ablation, voltage mapping showed significant reduction of unipolar negative voltage at the protected isthmus and double potentials appeared, which indicated conduction block. The activation propagated around the upper end of CT, instead of conducted through the protected isthmus. </li></ul>
Conclusions <ul><li>NCM in patients with atypical RA AFL consistently demonstrated slow conduction within LVZ’s in and around the CT. </li></ul><ul><li>Characterization of the RA substrate in terms of unipolar PNV is an effective predictor of the slow conduction path within the critical isthmus of the reentrant circuit. </li></ul><ul><li>A ratiometric threshold, normalized by the maximum PNV, improves the diagnostic accuracy over a fixed amplitude threshold . </li></ul>