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inappropriate sinus tachycardia ( ist ) is defined as sinus tachycardia at rest [ heart rate ( hr ) 100  bpm ] in sitting position or / and as an average hr    90  bpm during 24-hour holter monitoring .
the most common symptoms are palpitation , dizziness , chest discomfort , orthostatic intolerance , and fatigue .
sometimes , the symptoms can be severe and debilitating , and its etiology is not well understood .
the limitation of these pharmacological approaches is their relatively small effectiveness , intolerance , or side effects of the respective drugs .
several studies with clinical follow - up have suggested that ivabradine administration is a safe and effective second - line therapy in patient affected by ist .
other nonpharmacological interventions such as sinus node ablation are limited by their low efficiency or significant incidence of complications .
sympathetic hyperactivity plays a critical role in the development , maintenance , and aggravation of ventricular arrhythmias .
recently , armaganijan et al reported the relevance of sympathetic activation in patients with vas and suggest a potential role for catheter - based renal sympathetic denervation ( rsd ) in reducing arrhythmic burden .
pokushalov et al reported that rsd reduces systolic and diastolic blood pressure in patients with drug - resistant hypertension and reduces atrial fibrillation recurrences when combined with pulmonary vein isolation .
we hypothesized that rsd could have a salutary effect on ist patterns in patients with poorly controlled of the heart rate by reduction in central sympathetic cardiac stimulation . in this series of cases of ist
, we report 3 cases refractory to conventional pharmacological therapy , in which we were not tempted for ablation of the sinus node .
we , however , use another therapeutic approach , which was rsd , to reduce sympathetic activity in the sinus node . individual baseline features and over time are shown in table 1 .
the patients # 1 and # 2 complained daily of palpitations , tachycardic palpitations , and fatigue , for more than 1 year .
the patient # 3 reported daily palpitations and dizziness , also for more than a year .
three different pharmacological treatment strategies were tested in each patient ( table 1 ) , without achieving an adequate response for symptoms . individual baseline features and
over time all the 3 patients signed the informed consent and the ethics committee ( composed by paola baars gomes moises , luis marcelo rodrigues paz , and humberto cesar tinoco e jonny shogo takahashi ) approved the execution of the case .
the procedures were performed in the catheterization laboratory with direct visualization using fluoroscopy and radiopaque contrast .
paul , mn ) for construction of renal arteries and aorta anatomy , as well as for radiofrequency application in the selected sites .
the patients # 1 and # 3 underwent to catheterization of the right femoral artery by the standard seldinger technique was performed using a 7-fr valved short sheath , after subcutaneous injection of local anesthetic .
unfractionated heparin was administered intravenously , targeting an activated coagulation time between 250 and 350 seconds .
this sheath was advanced to the level of the renal arteries and the ostia were located with nonselective aortography .
the introducer was then carefully deflected to anchor at the ostium of each renal artery to introduce the ablation catheter with open irrigated tip ( st .
the number of ablation spots per artery in each patient , are shown in table 2 .
all procedures were performed without any complications , and the patients remained clinically stable and awoke properly from sedation .
intravenous protamine was infused at the end of the procedure and manual compression of the femoral artery was performed with a mean time of 15 minutes in each patient , followed by compressive dressing .
anatomic reconstruction of renal arteries and abdominal aorta segment with the mapping system ( ensite velocity ) .
( a ) , we used the standard ablation catheter with open irrigated tip and in the bottom panel ( b ) was used the enlightn catheter . notice the red marks , tagged from each ablation spot .
number of ablation spots during renal sympathetic denervation the results were expressed as mean and standard deviation ( mean    sd ) of the mean in this case because of normal distribution .
comparisons between more than 2-paired values were performed by analysis of variance for repeated measures or with kruskal 
all statistical analysis was performed using the program graphpad prism v 6.0 ( graphpad software , la jolla , ca ) .
the results over time , 6 months of follow - up ( including 3 months after the procedure ) , are shown in table 1 .
the 24-hour average hr at baseline was 121.7    2.5  bpm , falling down to 76.0    4.6  bpm 3 months after the ablation procedure ( p  <  0.0001 ) , as shown in figure 2 . a reduction in the mean office blood pressure
was also observed , decreasing from 124.7    11.7/84.0    5.3 to 112.0    10.2/74.7    3.1  mm hg ( p  <  0.0001/p  =  0.0480 ) , as shown in figure 3 .
three months after rsd , all patients were not using any type of medication , and no reported more symptoms . on the contrary , blockade of autonomic nervous system by ablation was defined previously in the other fields of cardiac diseases . for the first time ,
pachon et al in 2004 described in 21 patients , the increase in hr after 
cardioneuroablation ,  considered a new treatment for vasovagal syncope , functional atrioventricular block , and sinus dysfunction , using radiofrequency ( rf ) ablation catheter . in 2011 ,
pachon et al demonstrated in a total of 43 patients with neurocardiogenic or vasovagal syncope with important cardioinhibition ( pauses  =  13.5    13 seconds ) at head - up tilt test , normal electrocardiogram , and normal atropine test that endocardial rf catheter ablation of severe neurally meditated reflex syncope prevented pacemaker implantation and showed excellent long - term results in well - selected patients . despite no action in vasodepression , it seems to cause enough long - term vagal reflex attenuation , eliminating the cardioinhibition , and keeping most patients asymptomatic .
the indication was based on clinical symptoms , reproduction of severe cardioinhibitory syncope , and normal atropine response .
more recently , rivarola et al reported a case of a patient with frequent asymptomatic nocturnal ventricular pauses of 3 to 11 seconds , characteristic of a vagally mediated atrioventricular block , underwent to spectral mapping , used to localize endocardial vagal innervation in the right and left aspects of the interatrial septum , responsible for the sinus node and atrioventricular node modulation , and rf pulses were applied in those sites only .
ablation of the endocardial vagal innervation sites seems to be safe and efficient in reducing the frequency and the length of the ventricular pauses .
it was possible by identifying certain spectral components of the atrial electrogram , resulting in a conservative approach .
average heart rate ( bpm ) during 24-hour holter monitoring at baseline , at months 1 , 2 , and 3 using standard pharmacologic therapy , and postprocedure at the fourth and sixth months of follow - up ( 1 and 3 months after renal sympathetic denervation , respectively ) .
p  <  0.01 , p  <  0.001 , p  <  0.0001 versus baseline values .
values are presented as mean    sd ( n  =  3 ) .
mean office systolic ( closed bars ) and diastolic ( open bars ) blood pressure ( mm hg ) at baseline , at months 1 , 2 , and 3 using standard pharmacologic therapy , and postprocedure at the fourth and sixth months of follow - up ( 1 and 3 months after renal sympathetic denervation , respectively ) .
values are presented as mean    sd ( n  =  3 ) . even trying to map the renal arteries in all their extension , in search of some electric potential of the autonomic nervous system ,
the sympathetic nerves , however , are largely located in the adventitia layer , 1.5 to 2  mm from the lumen of the renal artery , and a greater number of ablated spots already mentioned as a predictor of success , according to the analysis of symplycity htn-3 trial results , may cause more destruction of sympathetic arterial nerves . we know that this is the first report using the rsd for the treatment of ist .
studies with a larger number of patients , a longer time of follow - up , and a control group , however , should be performed .
the success of these 3 consecutive cases makes us think that this may be a promising strategy for treating this disease .
abstractinappropriate sinus tachycardia is defined as sinus tachycardia at rest ( heart rate 100  bpm ) in sitting position or / and as an average heart rate 90  bpm during 24-hour holter monitoring . 
 the most common symptoms are palpitation , dizziness , chest discomfort , orthostatic intolerance , and fatigue . 
 sometimes , the symptoms can be severe and debilitating , and its etiology is not well understood . 
 pharmacological approaches present limitation because of their relatively small effectiveness , intolerance , or side effects.in this series of cases of inappropriate sinus tachycardia , the authors report 3 cases refractory to conventional pharmacological therapy , in which the authors were not tempted for ablation of the sinus node . 
 the authors , however , use another therapeutic approach , which was renal sympathetic denervation , to reduce sympathetic activity in the sinus node , and consequently reduce tachycardia with improvement of symptoms.three months after renal sympathetic denervation , all patients were not using any type of medication , and reported no more symptoms . 
 the authors know that this is the first report using the renal sympathetic denervation for the treatment of inappropriate sinus tachycardia . 
 studies with a larger number of patients , a longer time of follow - up , and a control group , however , should be performed .