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Use of a Novel Pacing Lead with a 1.1 mm Tip-to-Ring Spacing Aids in Patient Management
Case History A 70-year-old female presented with fatigue, chest pain and heart palpitations. She had a history of hypertension and paroxysmal atrial fibrillation (AF); in the preceding two years, she had been treated for hypertension and paroxysmal AF, including a recent episode of persistent AF requiring cardioversion. Following the cardioversion, she was maintained on warfarin, propafenone and metoprolol. The metoprolol was discontinued due to ongoing fatigue despite restoration of sinus rhythm. Her electrocardiogram demonstrated sinus bradycardia at 50 bpm as well as a first-degree heart block. An echocardiogram revealed left atrial dimension of 4.5 cm. She also had left ventricular hypertrophy with an ejection fraction of 60 percent. A stress test showed a markedly reduced exercise tolerance, requiring termination of the test at the beginning of stage 2 of a modified Bruce protocol due to fatigue. She reached a peak heart rate of 98 bpm (65 percent of maximal predicted heart rate). She underwent an electrophysiology (EP) study, which confirmed sinus node dysfunction with a sinus node recovery time of 1,950 ms and corrected sinus node recovery time of 1,200 ms; her PR interval was 257 ms. Other EP testing was normal. Because of her ongoing fatigue symptoms, it was determined that a pacemaker would be necessary to manage both her atrial fibrillation and sinus nodal dysfunction. She was enrolled in the FSR OptiSense Atrial Lead Clinical Trial and was randomized to receive the novel atrial pacing lead (OptiSense lead, Model 1699T, St. Jude Medical, St. Paul, Minnesota) with 1.1 mm inter-electrode spacing along with a DDDR pacemaker (Victory ® XL DR, Model 5816, St. Jude Medical) and a standard right ventricular lead (Tendril ® SDX lead, Model 1688T, St. Jude Medical).1Comparing the Pacing Leads In the FSR OptiSense Clinical Trial, the two leads evaluated were the Tendril SDX 1688T lead and the OptiSense 1699T atrial pacing lead (Figure 1). Both leads offer good maneuverability and fluoroscopic visibility, as well as a slender body diameter and 7 French (Fr) introducer. The Tendril SDX lead has a standard inter-electrode spacing of 10 mm and has been widely used for atrial and ventricular pacing applications. The OptiSense pacing lead, however, is designed to reduce far-field R-wave signals and mitigate oversensing. It is available with a 1.1 mm tip-to-ring spacing, which allows the lead to be set to a greater sensitivity setting, as well as reduced sensing of inappropriate R-wave signals. This allows for greater sensing of low amplitude atrial fibrillation waves, while reducing inappropriate far-field signals, which in turn reduces inappropriate mode switching. In addition, clinical studies have demonstrated that the reduced tip-to-ring spacing did not negatively affect P-wave sensing, capture thresholds or lead impedances.1,2Implantation of the Lead Implantation of the OptiSense 1699T pacing lead is very similar to placement of other leading pacing leads such as the Tendril SDX 1688T lead. It has similar steerability and utilizes the same implant tools as the 1688T. In general, this was a routine right atrial lead placement. The procedure was conducted under moderate conscious sedation using 2 milligrams Versed and 100 micrograms Fentanyl. The vascular access point for the procedure was the axillary vein, using a standard 7 Fr sheath. The lead was placed in the right atrial appendage, which is a common location used for most atrial leads. During the procedure, the PSA measurements for the right atrial lead demonstrated P-waves at 2.6 mV, capture threshold of 0.7 V at 0.5 ms, and an atrial lead impedance of 569 ohms. There were no far-field R-waves evident at progressively increased atrial sensitivities of 0.5 mV, 0.25 mV or 0.1 mV. The right ventricular lead and pulse generator were added in standard fashion, and the system was placed in a left prepectoral pocket. The pulse generator was programmed to an atrial lead sensitivity of 0.25 mV at the completion of the procedure. Except for the more sensitive atrial sensitivity setting, the implant procedure using the OptiSense lead was no different than the procedure used with traditional active-fixation atrial leads. Follow-up and Results Testing conducted after the procedure and prior to discharge indicated acute pacing system stability. Prior to discharge, the patient’s atrial capture threshold was less than 0.25 V and her P-wave was 4 mV. At three-month follow-up, her atrial capture threshold was 0.5 V and her P-wave was greater than 5 mV. At six-month follow-up, the capture threshold remained at 0.5 V and the P-wave was 4 mV. There were no far-field R-waves evident during follow-up testing (Figure 2). Overall, the OptiSense atrial lead demonstrated chronic stability. In the weeks following pacemaker implantation, the patient reported that her initial symptoms of heart palpitations and fatigue had been reduced or eliminated. She was able to be more active and was no longer limited by shortness of breath. She also had not felt any atrial fibrillation, although the diagnostics reported that two episodes of AF had in fact occurred. The stored intracardiac electrogram (EGM) tracings are shown in Figures 3 and 4. The stored EGMs showed that the device correctly identified atrial fibrillation and atrial flutter with appropriate mode switch behavior. There was no far-field R-wave sensing observed. Discussion The OptiSense pacing lead was successfully implanted, improving the management of paroxysmal AF by reducing the oversensing of far-field R-wave signals (Figure 5). This reduced the amount of inappropriate mode switching, allowing for improved A-V synchrony and the ability to set a more sensitive atrial sensing for detection of arrhythmias.3–7 The patient case study presented here also demonstrated the typical electrical measurement observations seen in the St. Jude Medical OptiSense IDE trial. In the OptiSense trial, 122 patients were enrolled (mean age: 73 years), of which 47 percent were female and 73 percent had a history of hypertension. At three months, electrical data showed a mean bipolar p-wave amplitude of 2.64 ± 1.4 mV and a mean atrial capture threshold of 0.59 ± 0.16 V. Overall, the trial demonstrated a significant reduction (p = 0.03) in the percentage of patients with inappropriate mode switching when comparing the treatment (1.1 mm electrode spacing) to the control group (10 mm electrode spacing). It also demonstrated that the occurrence of oversensed far-field R-waves was higher during paced ventricular beats than with intrinsic conduction events. The issue with detection of far-field R-waves was significantly reduced using this lead design, which should allow more sensitive and reliable atrial programmed settings for patients with paroxysmal atrial fibrillation. This will allow appropriate sensing of small amplitude atrial fibrillation signals and qualify episodes more appropriately as true sustained events rather than the in/out mode switch phenomena frequently seen during atrial fibrillation. During the clinical investigation, when the device was at its most sensitive setting (0.1 mV), 91 percent of the OptiSense lead patients exhibited no oversensing of paced far-field R-wave signals.8,9 This indicated that the OptiSense lead may improve overall pacemaker performance and reliability of automatic mode switching. Also, the inappropriate mode-switch from far-field R-waves was essentially eliminated at programmed sensitivity level of 0.2 mV or more. In addition, while not exemplified in this case, the OptiSense lead could be placed in the atrial septal region to further improve the pacing benefits in atrial fibrillation.10,11Conclusion In summary, this case study demonstrated that atrial arrhythmia signals to the pacemaker were reliably detected, and the result was an improvement in the management of the patient’s paroxysmal AF. The patient’s symptoms of palpitations and fatigue were well-controlled with a combination of anti-arrhythmic drug therapy and appropriate DDDR pacing. Over time, there was no noticeable loss of signal amplitude. Additionally, detection of atrial arrhythmia was achieved without signal dropout. The OptiSense lead also provided reliable automatic mode switch feedback without inappropriate mode switching due to far-field R-wave signals despite programming to a highly sensitive setting. The medical profile of patients who would benefit from this lead design include those with sick sinus syndrome and paroxysmal AF who will be receiving a pacemaker, as well as patients requiring a lead revision that demonstrated numerous inappropriate mode switch episodes. Editor’s Note: This article was peer reviewed by one or more members of EP Lab Digest’s editorial board.
