Device implantation in patients with a persistent left superior vena cava (PLSVC) is often difficult due to abnormal venous anatomy. In patients with a PLSVC, venous drainage from the left arm typically flows into the right atrium through a dilated coronary sinus (CS). As a result, implantation of CS pacing leads can be challenging due to lack of appropriate target vessels in the enlarged CS. In this article, we describe the use of an active fixation CS lead in a patient with a PLSVC. Case Presentation The patient is a 71-year-old male with a history of non-ischemic cardiomyopathy and NYHA class III congestive heart failure symptoms. He also had chronic atrial fibrillation with persistently slow ventricular response (heart rates in the 40-60 bpm range). He had previously failed cardioversion with and without antiarrhythmic therapy. He had had repeated hospital admissions for pulmonary edema and fluid overload in spite of treatment with carvedilol, lisinopril and daily oral diuretics. On examination, he had an elevated blood pressure of 168/86 and a pulse of 60 bpm. He had a jugular venous pressure of 8 cm H20 and bibasilar rales. His point of maximal impulse was diffuse, and he had a II/VI mid-peaking systolic murmur along the left sternal border. There were no gallops. His extremities had 1-2+ bilateral pitting edema to the knees. His electrocardiogram demonstrated atrial fibrillation with a left bundle branch block (QRS duration of 170 ms). Echocardiography revealed a moderately to severely dilated left ventricle (LVID of 70 mm), ejection fraction of 20%, and severe biatrial enlargement. Based on his symptoms and refractoriness to optimal medical therapy, the decision was made to implant a biventricular cardioverter defibrillator. Procedure After giving informed consent, the patient was brought to the electrophysiology laboratory in the usual fasting state. He was prepped and draped in a sterile manner. Lidocaine (1% with epinephrine) was infiltrated 2 cm caudal to the left clavicle for local anesthesia. A 4-cm incision was used to access the prepectoral fascia, and a defibrillator pocket was made. Using the modified Seldinger technique, a medial axillary venipuncture was performed under fluoroscopic guidance. A J-tipped guidewire was passed into the vein and almost immediately passed caudally on the left side of the spine. A 4-Fr SafeSheath® dilator (Pressure Products, Inc., San Pedro, CA) was passed over the wire, and a venogram was performed using 10 cc of Isovue® (Bracco Diagnostics, Inc., Princeton, NJ), a nonionic contrast agent. This demonstrated the presence of a PLSVC (Figure 1). Following this, one more medial axillary venipuncture was made, and a guidewire was also placed in the vein. Over the first guidewire, a 7-Fr SafeSheath® introducer (Pressure Products, Inc.) was placed. Through this, a 70-cm Durata® lead (St. Jude Medical, Sylmar, CA) was advanced fluoroscopically. This lead was passed down the PLSVC through the coronary sinus and into the low right atrium. The lead stylet was removed and manually shaped in a spiral configuration. The lead was then prolapsed past the tricuspid valve into the right ventricular apex. The active fixation helix was deployed and the lead proved stable (Figure 2). All pacing numbers were within normal limits. The sheath was peeled away and the lead was secured to the pocket floor. Following this, a 9-Fr SafeSheath® introducer (Pressure Products, Inc.) was placed over the remaining guidewire. An attempt to visualize the CS with a 20-cc contrast venogram was performed. There were no lateral branches visualized. Therefore, a CPS Direct® SL Right-Sided (OC-R) (model 410116; St. Jude Medical) coronary sinus sheath was passed. A 5-French Rosch Inferior Mesenteric (RIM) catheter (Cook Inc., Bloomington, IN) was advanced through the CS sheath. A Whisper View guidewire (Boston Scientific, Natick, MA) was then advanced through the RIM catheter. In the LAO 20º position, the wire was used to blindly cannulate lateral branches off the CS. Ultimately, a mid-lateral branch was cannulated and the RIM catheter was subselected into the branch (Figure 2). A total of 5 cc of contrast was used to opacify this branch. It was laterally directed, but small and without significant length. The RIM catheter was withdrawn and the wire left in place. A QuickFlex™ Model 1156T CS lead (St. Jude Medical) was advanced over the wire into the vein. Immediately upon withdrawing the wire, the lead fell back into the main CS. The branch was then re-cannulated with the wire. An Attain StarFix® Model 4195 lead (Medtronic, Inc., Minneapolis, MN) was then advanced over the wire into a lateral position in this branch. The active fixation lobes were deployed and the lead proved stable (Figures 3 and 4). Lead interrogation numbers were within normal limits, and high output pacing did not capture the phrenic nerve. The outer sheath was then cut away and the lead was secured to the pocket floor. The leads were inserted into a Promote™ RF biventricular ICD (model 3207-36; St. Jude Medical). All testing through the device was acceptable and stepdown defibrillation testing was performed after induction of ventricular fibrillation. The patient’s defibrillation threshold was ≤ 10J and there was no significant loss of R-wave sensing at the lowest sensitivity. The pocket was then closed, and the patient was brought to the recovery area. Discussion In this case report, we describe the use of an active fixation coronary sinus lead successfully implanted in a patient with a PLSVC. The prevalence of this condition has been reported to be 0.3–0.5%. It is the most common thoracic venous anomaly.1 It is an embryological remnant of a vessel that is normally the counterpart of the normal right-sided SVC. Historically, implantation of a CS or RV pacing lead in the left side of these patients has been difficult.2-4 In this particular patient, the main body of the CS was very large with relatively rapid blood flow. The subselected venous branch was short and a passive fixation CS lead immediately became dislodged. Given this anatomy, it was unlikely that a lead without active fixation would have been stable. The Medtronic Attain StarFix CS lead was only recently introduced into the U.S. market. This unipolar lead, which can be positioned with the aid of a guidewire or with a stylet, is the first active fixation left heart lead. By distally advancing the outer, blue, polyurethane push tubing of this lead, three sets of lobes can be deployed once the lead is positioned in the desired cardiac vein. Each set of these lobes is separated by radiopaque indicator rings, which, when viewed fluoroscopically during the implant procedure, move closer together as the lobes are deployed (Figure 5). Furthermore, the lobes can be undeployed by withdrawing the push tubing if there is a need for repositioning this lead. The push tubing also has a unique hydrophilic coating on the inner diameter surface that, when exposed to body fluids, hydrates the coating. Therefore, this coating reduces friction between the inner surface of the push tubing and the outer surface of the lead insulation to allow easier deployment of the lobes.5 Conclusion Over the next several weeks, the patient slowly improved. His two-month post-procedure echocardiogram demonstrated improved systolic function with an ejection fraction of 35-40%. His functional status improved significantly as well (he is now NYHA class II). The Medtronic Attain StarFix lead measurement data remained unchanged from the implant procedure.