A 46-year-old male patient otherwise healthy, presented with repetitive short bouts of AT occurring constantly while speaking and at mid inspiration. The arrhythmia was provoked even by social talking, and was not associated with stress or physical activity. Electrocardiography (ECG) during the tachycardia revealed a P wave biphasic in V1, positive in the inferior leads and isoelectric in L1, suggesting origination from the SVC or the RSPV. A tall P wave in L2 favored an SVC origin4figure 1A
Holter monitoring revealed 50-700 premature atrial contractions (PACs) per hour and more than 3000 short episodes of AT lasting 3-16 beats. Beta-blockers and class 1C antiarrhythmic drugs (AAD) were ineffective. The patient underwent an electrophysiological study (EPS) under deep sedation. Body surface ECG and endocardial electrograms were monitored continuously with a computerized multichannel recording system (EP Tracer, CardioTek B.V. , Maastricht, The Netherlands) at a sample setting of up to 1000 Hz. The arrhythmia could not be induced by programmed electrical stimulation in the RA or the CS, nor by isoproterenol infusion and withdrawal, given alone or with concomitant pacing. The only mode of induction of the tachycardia was by waking the patient and asking him to speak. While awake, AT started with talking and ceased even between sentences. AT following the respiratory rate could also be demonstrated. Interestingly, the arrhythmia was not uniform and other morphologies of the P wave during tachycardia could be documented. A tri-dimensional map of the RA was performed using a nonfluoroscopic electro-anatomic mapping system (NavX, St. Jude Medical, St. Paul, Minnesota). The clinical arrhythmia was mapped to the postero-medial aspect of the SVC figure 2A
. Using a radio-frequency (RF) generator (IBI-1500, St Jude Medical), focal RF delivery to that region eliminated the AT and significantly decreased the frequency of ectopic activity. Several weeks later, the patient reported that symptoms reoccurred. ECG during the tachycardia revealed a positive P wave in V1 and a broad notched P wave in L2, favoring an RSPV origin4figure 1B
. A second attempt was made to ablate the tachycardia. The patient was kept awake and talking. Frequent short bouts of AT were demonstrated during the whole study, concomitant with speaking or following the respiration rate. As in the first study, AT was not uniform and had several morphologies. The left atrium (LA) was accessed through a previously unknown PFO. The site of earliest activation of the second clinical tachycardia was mapped to the antero-lateral aspect of the RSPV (figure 2B
, video 1). Focal RF energy applied to sites with early and fractionated electrograms failed to terminate the tachycardia. Prolongation of the sinus cycle length by 20-30% and frequentsinus pauses were observed during RF delivery. Thereafter, a 28 mm diameter cryo-balloon (Arctic front, Medtronic, Minneapolis, Minnesota) was advanced into the LA through the PFO, using a 15F outer diameter deflectable sheath (FlexCath, Medtronic), over a 20 mm circular mapping catheter (Achieve, Medtronic) placed through its central lumen. Cryo-ablation of the RSPV orifice and antrum was performed as published5 figure 3
. The arrhythmia disappeared a few seconds after the temperature measured at the balloon's base dropped below freezing. The patient tolerated the procedure well, including right phrenic stimulation during cryo-ablation to avoid nerve injury, albeit while awake. During the next 24 hours of continuous monitoring, sinus tachycardia up to 100 beats per minutes was observed. It persisted for a few months, very gradually subsiding. The patient remained arrhythmia free.
Three-dimensional mapping with NavX of the RA and SVC (A), and the LA and pulmonary veins (B).
The site of earliest activation, white colored, is postero-medial in the SVC and antero-lateral in the RSPV (see torso, right upper corner). These two regions are across each other, the RSPV lines behind the SVC. CS - coronary sinus, LIPV - left inferior pulmonary vein, LSPV - left superior pulmonary vein, RIPV - right inferior pulmonary vein, RSPV - right superior pulmonary vein, SVC – superior vena cava.