the vein of marshall ( vom ) is an embryonic remnant of the left superior vena cava.1 ) the ligament of marshall ( lom ) , which contains nerves , fibrous tissues , and muscle bundles ( marshall bundle ) , is adjacent to the vom.2 ) the lom is a trigger of ectopic beats initiating paroxysmal atrial fibrillation ( af)3 ) and is innervated by the arrhythmogenic autonomic nerve.4 ) moreover , the lom is connected to the neighboring left atrium ( la ) including the perimitral area and lateral ridge , and may be a part of the re - entrant circuit .
therefore , the lom may play a role in the initiation and maintenance of af or atrial tachycardia ( at ) .
recently , the feasibility of injection of pure ethanol into the vom was demonstrated ; the adjunctive effect to pulmonary vein isolation ( pvi ) was indicated.5 ) in addition , vom ethanol infusion assists in consisting achieving bidirectional perimitral isthmus ( pmi ) block.6 ) however , the effectiveness of the infusion in persistent atrial fibrillation ( peaf ) , which is an extensive substrate in the la , is unclear . in the present case ,
af was terminated by ethanol infusion adjunctive to complex fractionated atrial electrogram ( cfae ) guided ablation in a patient with peaf .
a 64-year - old male presented with a 6-month history of symptomatic drug refractory peaf . the patient was admitted for catheter ablation of af .
transthoracic echocardiogram revealed normal ejection fraction of 55 - 60% with mildly enlarged la of 43.8 mm in the anterior - posterior diameter .
cardiac magnetic resonance ( cmr ) imaging revealed late gadolinium enhancement ( lge ) in 20% of the la surface including the anterior and posterior wall .
cfaes in the la were mapped for 6 seconds using ensite navx system three - dimensional automated software ( endocardial solutions , st .
the cfaes were predominantly located at perimitral , septal area and left atrial appendage base ( fig .
activation pattern at the high clustering of cfae was mapped using high density 20-pole catheters ( afocus ii ; st .
the activation patterns obtained from three af beats of unipolar recordings at each cfae site were classified into four categories : 1)complete reentry , 2 ) incomplete reentry , 3 ) wave collision , and 4 ) wave breakup with conduction block .
we preferentially targeted cfae areas with complete or incomplete reentry pattern because these sites might play an important role as rotor . in this case , only the perimitral area had re - entrant , rotor - like electrical activity ( fig .
, we assumed that the perimitral area could be the critical site for af perpetuation .
therefore , we decided to infuse ethanol into the vom as an add - on to radiofrequency ablation . at first , cannulation into coronary sinus was performed by ablation catheter ( therapy coolflex ; st .
paul , mn , usa ) and 8 fr sheath ( sl1 sheath ; st .
paul , mn , usa ) . to confirm the existence and feasibility of vom ,
( 7 fr ; cordis , miami , fl , usa ) was subselectively engaged into the vom and then a hi - torque floppy ii angioplastic guidewire 0.014 ( abbott , santa clara , ca , usa ) was advanced into the vom as far as possible .
a ryujin plus otw 2.020 mm angioplasty balloon catheter ( terumo , tokyo , japan ) was advanced into the vom over the angioplastic wire and inflated at the ostium of vom .
engagement of the balloon catheter into the vom was confirmed by injecting contrast medium into the vom ( fig .
2b ) , and 1 cc of 100% ethanol was injected into the vom three times ( fig .
each injection was delivered over 1 minute through a balloon lumen and flushed with normal saline . within 30 seconds after the first ethanol injection
la local activation time mapping demonstrated macro - reentrant at , the circuit of which involved reentry around the mitral annulus in a counterclockwise fashion ( fig .
bidirectional block of pmi line was achieved after ablation within cs adjunct to pmi ablation ( fig .
this case report demonstrates that ethanol infusion into the vom can effectively eliminate cfaes at pmi .
in addition , we suggest that activation mapping at cfaes area during af can identify the critical cfaes that maintain the peaf . even though the underlying etiology of cfae has not been fully elucidated , cfaes are considered as slow conduction or pivot sites , which represent continuous reentry of the fibrillatory waves.7 ) based on these theories , cfae guided ablation is widely used for modifying the extensive substrate of the la and/or right atrium in patients with peaf . however , whether cfae reflects slow conduction or pivot site , or only wave collision that overlaps different wavelets at the same area is contentious . moreover
, 90% of continuous cfae sites do not overlap over lge on cmr and occur at non - lge and patchy lge sites.8 ) therefore , identification of the critical pivot site perpetuating af among the continuous fractionated electrogram is necessary . in the present case , we performed unipolar activation mapping at the cfae areas using a high density circular catheter to identify critical pivots and preferentially targeted the sites with complete or incomplete reentry pattern because these areas might be crucial for the perpetuation of af . among three cfaes sites , only the pmi area had complete reentry pattern and ablation at this site easily lead to termination of af
. therefore , this case suggests the usefulness of unipolar mapping to identify the true cfae sites which is related to the persistence of af . however , there is limitation of unipolar mapping , which includes difficulty in positioning the lasso catheter at the la septum , la lateral ridge and below the la appendage .
the present case highlights that peaf can be terminated and organized to at by ethanol infusion into the vom .
valderrbano et al.5 ) demonstrated the feasibility of ethanol infusion into vom adjunct to pvi ; ethanol infusion decreased voltage around pmi and the la lateral ridge .
in addition , ethanol infusion in the vom has an adjunctive effect in perimitral flutter ablation.6 ) the proximal portion of lom has complex muscle fiber connections to cs adjacent to pmi.1 ) the mid - portion of lom is directly connected to the la lateral ridge and pulmonary veins.1 ) these muscle fiber connections can act as an anchor of re - entry .
therefore , ethanol infusion into the vom can lead to substrate modification at pmi and la lateral ridge .
moreover , the pmi area and la lateral ridge are too thick to achieve transmural lesion only by endocardial ablation . therefore , ethanol infusion in the vom can be an effective intervention for achieving transmural scar and facilitating durable conduction block at this area .
however , in this case , bidirectional block of pmi was not achieved by only ethanol infusion , but required endocardial pmi and intra - cs ablation adjunct to ethanol infusion .
the transmurality and bidirectional block could be achieved by pmi ablation in only 15% of patients.9 )
this finding suggests that ablation of pmi concurrent with endocardial or epicardial lateral ridge may be needed to achieve transmural lesion in most cases .
therefore , ethanol infusion into vom can be applied to the patients with peaf , especially when cfaes clusters at pmi area and the la lateral ridge .
 we report the case of a 64-year - old male with persistent atrial fibrillation ( af ) terminated by ethanol infusion into vein of marshall as add - on therapy . 
 three - dimensional automated complex fractionated atrial electrogram ( cfae ) during af revealed clustering of cfae at perimitral isthmus ( pmi ) and its unipolar mapping showed rotor - like activation , which was suggested to be critical in the perpetuation of af . 
 af was organized to atrial tachycardia ( at ) by 100% ethanol infusion in the vein of marshall . 
 adjunctive radiofrequency ablation at pmi successfully terminated at and led to bidirectional block of pmi . 
Introduction
Case
Discussion