Left bundle branch area pacing: How to prevent a coronary venous fistula

In patients with decreased left ventricular ejection fraction (LVEF) and the need of cardiac pacing for an advanced AV block, the left bundle branch area pacing (LBBAP) has emerged as an effective tool to promote the physiological pacing of conduction system in order to prevent the detrimental effects of a permanent right ventricular pacing. Although coronary vein fistulas seem to be rare and harmless, literature is sparse about this complication. The first two cases describe the occurrence of coronary vein fistulas; in the last case, we show a simple method which can be helpful to avoid the breach of septal veins during LBBAP implantation. Following a successful transcatheter aortic valve implantation (TAVI), an 83yearold male experienced a complete AV block. As the patient had a moderate reduction of LVEF, he was implanted with a LBBAP. After positioning the lead via the designed 3D pacingtool system which included a specific delivery sheath (Selectra 3D, Biotronik) and an extandableretractable active screw, styletdriven pacing lead (Solia S60, Biotronik), left bundle capture was achieved and proven by the expected QR morphology in lead V1 (pacing at higher output), narrowing of the QRS and reasonable left ventricular activation time. As our common clinical practice for LBBAP implantation, the contrast injection was used to assess the lead depth through the interventricular septum. The angiography— performed in right anterior oblique projection (Figure 1A)— showed that the contrast dye filled a septal vein which went upward and posteriorly and then joined the coronary sinus. No symptoms, no EKG changes, and no pericardial effusion were detected immediately and after the procedure. As the parameters of amplitude and threshold were optimal, the lead was not retracted. All the electric parameters remained stable at the end of the procedure and the day after. The patient never experienced chest pain and the troponin test showed no myocardial impairment. The second case deals with an 84yearold patient who was admitted for advanced AV block associated with moderate depression of the LVEF due to ischemic heart disease. Based on the basal QRS of 130 ms and the presumptive high percentage of pacing in a left ventricular dysfunction, the LBBAP was attempted. The lead was placed using the abovementioned 3D pacingtool system and a capture of the left bundle branch area was achieved (Figure 1B). From the right ventricle, the lead was inserted through the septum with 7– 8 clockwise turns. After penetration of the lead, contrast was injected through the sheath, filling the perforator branch vein and reaching the great cardiac vein of the coronary sinus (Figure 1B, in left anterior oblique projection). The electronic parameters were fine (sensed Rwave 11.5 mV, capture threshold 0.6 V@0.4 ms, impedance 730 Ω), no symptoms and no EKG changes occurred, no signs of pericardial effusion were detected. As the parameters of amplitude and threshold were optimal, the lead was not retracted. All the electric parameters remained stable at the end of the procedure and the day after. The following hospital stay was unremarkable. Finally, a 76yearold patient was referred for pace and ablate strategy because of atrial fibrillation with high ventricular rates and mildly depressed left ventricular ejection fraction. Before placing

In patients with decreased left ventricular ejection fraction (LVEF) and the need of cardiac pacing for an advanced AV block, the left bundle branch area pacing (LBBAP) has emerged as an effective tool to promote the physiological pacing of conduction system in order to prevent the detrimental effects of a permanent right ventricular pacing. Although coronary vein fistulas seem to be rare and harmless, literature is sparse about this complication. The first two cases describe the occurrence of coronary vein fistulas; in the last case, we show a simple method which can be helpful to avoid the breach of septal veins during LBBAP implantation.
Following a successful transcatheter aortic valve implantation (TAVI), an 83-year-old male experienced a complete AV block. As the patient had a moderate reduction of LVEF, he was implanted with a LBBAP. After positioning the lead via the designed 3D pacingtool system which included a specific delivery sheath (Selectra 3D, Biotronik) and an extandable-retractable active screw, stylet-driven pacing lead (Solia S60, Biotronik), left bundle capture was achieved and proven by the expected QR morphology in lead V 1 (pacing at higher output), narrowing of the QRS and reasonable left ventricular activation time. As our common clinical practice for LBBAP implantation, the contrast injection was used to assess the lead depth through the interventricular septum. The angiography-performed in right anterior oblique projection ( Figure 1A)-showed that the contrast dye filled a septal vein which went upward and posteriorly and then joined the coronary sinus. No symptoms, no EKG changes, and no pericardial effusion were detected immediately and after the procedure. As the parameters of amplitude and threshold were optimal, the lead was not retracted. All the electric parameters remained stable at the end of the procedure and the day after. The patient never experienced chest pain and the troponin test showed no myocardial impairment.
The second case deals with an 84-year-old patient who was admitted for advanced AV block associated with moderate depression of the LVEF due to ischemic heart disease. Based on the basal QRS of 130 ms and the presumptive high percentage of pacing in a left ventricular dysfunction, the LBBAP was attempted. The lead was placed using the abovementioned 3D pacing-tool system and a capture of the left bundle branch area was achieved ( Figure 1B). From the right ventricle, the lead was inserted through the septum with 7-8 clockwise turns. After penetration of the lead, contrast was injected through the sheath, filling the perforator branch vein and reaching the great cardiac vein of the coronary sinus ( Figure 1B, in left anterior oblique projection). The electronic parameters were fine (sensed R-wave 11.5 mV, capture threshold 0.6 V@0.4 ms, impedance 730 Ω), no symptoms and no EKG changes occurred, no signs of pericardial effusion were detected. As the parameters of amplitude and threshold were optimal, the lead was not retracted. All the electric parameters remained stable at the end of the procedure and the day after.
The following hospital stay was unremarkable.  Figure 2A and Video S1). In this case, the contrast injected through the sheath was able to visualize a septal vein which joined to coronary sinus (Figure 2A and Video S1). Later on, the lead was implanted in the LBBAP avoiding the region of septal branch which was previously identified ( Figure 2B).
Breaching a septal vein during the catheter positioning is a rare-but probably underdiagnosed-complication of the LBBAP implantation, unlikely to be harmful according to the few cases described. 1-3 A recent large registry-based observational multicenter study reported 7 cases of coronary vein fistulas out of 2533 LBBAP procedures (0.28%). 1 In addition, two case reports had previously described this complication. 2,3 In all these reported cases, no serious consequences followed. In all the cases, given the small size and asymptomatic nature of the fistula, no Although all the reports of coronary vein fistulas describe a benign course without serious harms for the patient, 1-3 the last case emphasizes a possible role of the contrast agents before LBBAP, in order to assess possible routes of small perforator veins through the septum helping to avoid them during lead implantation.

CO N FLI C T O F I NTER E S T S TATEM ENT
The authors declare no conflicts of interest.

E TH I C S A PPROVA L S TATEM ENT
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PATI ENT CO N S ENT S TATEM ENT
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