radiofrequency ablation of the slow pathway is considered to be the gold standard treatment for patients with atrioventricular nodal reentrant tachycardia ( avnrt ) . pulmonary artery agenesis is a rare anomaly that may occur during embryological development of the heart.1 this agenesis may be accompanied by a complete or partial absence of the lung . in the great majority of the cases , the diagnosis is usually made at or soon after birth and it can be associated with multiple anomalies . an otherwise normal heart may be displaced into the right hemithorax by unilateral pulmonary agenesis.2 catheter ablation of avnrt in the setting of dextrocardia is potentially challenging . there have been a few reports of successful slow pathway ablation in patients with dextrocardia , but usually at the expense of prolonged procedure and fluoroscopy times.37 to our knowledge , slow pathway ablation of a patient with dextrocardia due to pulmonary agenesis has not been described to date . a 35-year - old woman was admitted to our cardiology clinic with complaints of palpitation . she had a 7-year history of paroxysmal palpitations . the tachycardia , at a rate of 170200 bpm , was associated with dyspnea and chest tightness and lasted for up to 60 minutes at a time . her physical examination revealed no breathing sound on the right and a normal breathing sound on the left hemithorax , while the heart s sound was heard from the right hemithorax . the chest radiogram incidentally showed a rudimentary , opacified right hemithorax with mediastinal shift and herniation of the contralateral lung . except for dextroposition of the heart , a 12-lead resting electrocardiogram ( ecg ) showed sinus rhythm at a rate of 64 bpm , a positive qrs complex in avr , a positive p wave in avr and a biphasic p wave in avl , and a prominent r wave in v1 with undetermined horizontal axis ( figure 1 ) . the clinical tachycardia was a regular , narrow qrs tachycardia at a rate of 170 bpm , during which the p wave was indiscernible ( figure 2 ) . computed tomography showed a complete absence of the right lung with dextroposition of the heart ( figure 3 ) . electrophysiological study was performed after obtaining written informed consent and discontinuation of all drugs for five half - lives . the right atrium and the right ventricle were imaged on left lateral and anteroposterior views by contrast injection through inferior vena cava to reveal the cardiac anatomy ( figure 4 ) . then , a 4 mm - tipped ablation catheter ( cordis webster , baldwin park , ca , usa ) was advanced through the 6f sheath into the right atrium and a four - pole fixed - curve diagnostic catheter was placed on the bundle of his . during the electrophysiological study , a narrow qrs tachycardia with a cycle length of 270 ms was reproducibly induced by atrial premature stimulation with an extrastimulus ( figure 5a ) . the ventriculoatrial interval , measured from the onset of ventricular activation on the surface ecg to the earliest deflection of the atrial activation in the his bundle electrogram , was < 60 ms , and the diagnosis of typical slow  fast avnrt was confirmed . his bundle records were taken with an electroanatomi - cal approach . then , slow pathway potentials were recorded ( figure 5b ) . fluoroscopic views of the catheters during the ablation and mapping of the coronary sinus ostium are shown in figures 6 and 7 . during ablation , the radiofrequency energy was adjusted to obtain a catheter tip temperature between 50c and 60c . the current was applied for 60 seconds after junctional tachycardia was observed during ablation ( figure 8) . after the ablation , there was no residual slow pathway conduction and the clinical arrhythmia was not inducible without or with infusion of isoproterenol . the total procedure time was 30 minutes with a total radiofrequency delivery time of 8 minutes and fluoroscopy time of only 6 minutes . no complication occurred after the procedure and the patient was free of symptoms at 1-year follow - up . dextrocardia or complex cardiac anatomy of the heart may be challenging to electrophysiologists during catheter ablation procedures . there have been only a few case reports of catheter ablation of supraventricular tachyarrhythmias in patients with dextrocardia.37 pulmonary agenesis can be localized to a single lobe and it can affect an entire lung or , in rare cases , both lungs.1 although a majority of patients with unilateral agenesis die soon after birth or in early childhood , in some extreme cases , patients can survive up to adulthood , like our patient . the most common and familiar form is the  mirror image of normal  or mirror - image dextrocardia , in which the migration of the apex of the l - bulboventricular loop is into the right hemithorax , as expected . the anterior  posterior relationship of the various parts of the heart is normal , but their right - to - left orientation is reversed . the second most common type is dextroversion , in which the heart appears to be rotated into the right hemithorax relative to its normal position . 3 ) the third type of dextrocardia is dextroposition , in which an otherwise normal heart is displaced or shifted into the right hemithorax by other extracardiac causes such as agenesis or fibrosis of the right lung . our case was a type 3 dextrocardia . to recognize the ecg findings of dextrocardia necessitates a clear understanding of the electrical axis . global negativity in lead i , a positively deflected qrs complex in avr , and right axis deviation and reverse r wave progression in precordial leads are the mean ecg findings in dextrocardia . the finding of a positively deflected qrs complex in avr and a negatively deflected ors complex in lead i may lead to misdiagnosis . the most common cause for this finding is reversed electrode placement of arm leads ( left and right ) . during a standard catheter ablation procedure , the catheter is targeted to the ablation region based on typical local electrogram characteristics ( slow - pathway potentials ) and anatomical landmarks . in contrast to patients with normal anatomy , localization of the slow pathway and stabilization of the catheter are more difficult in patients with dextrocardia . therefore , the time spent in the catheterization laboratory and the fluoroscopy time are markedly longer than in cases with normal hearts . our case illustrates the role of imaging by contrast injection in a patient with dextrocardia . the identification of the accurate anatomy using imaging modalities such as computerized tomography and magnetic resonance imaging and three - dimensional image reconstruction using mapping systems may be useful not only to help the electrophysiologist , enabling a safe and successful catheter ablation procedure , but also to understand the complex anatomical structures and to guide optimal catheter access . however , these modalities are quite expensive and are not easily accessible in every unit . before the ablation procedure , we easily localized the coronary sinus ostium and his bundle position . as such , we did not need an additional catheter in this ablation procedure , but an additional catheter might further facilitate the procedure . we are presenting this pulmonary agenesis case in view of its atypical presentation in adulthood , which is exceptionally rare . as demonstrated in this case , revealing cardiac anatomy by contrast injection or other imaging modalities may shorten the procedure time and decrease the complication rates .
radiofrequency catheter ablation of the slow pathway is considered to be the treatment of choice for patients with atrioventricular nodal reentrant tachycardia . 
 we report a 34-year - old female with mirror image dextrocardia due to unilateral pulmonary agenesis who underwent successful slow pathway ablation for typical atrioventricular nodal reentrant tachycardia . 
 using contrast injection , cardiac anatomy was identified in a short time and successfully ablated .