Lead Tip Research Articles

The relationship between anatomy and electrical parameters in His bundle pacing

Abstract Background The relationship between anatomy and electrical parameters of His bundle (HB) pacing has not been extensively studied. Purpose To characterize the anatomical location of the HB lead tip and its relationship with acute electrical parameters. Methods Consecutive patients who underwent HB lead implantation, guided by standard fluoroscopy and electrophysiology, were prospectively enrolled. The relationship between HB lead tip and tricuspid valve plane (TVP) was assessed with post-procedure transthoracic echocardiography. Results Twenty-five patients were studied. In 11 patients (44%), the HB lead tip did not cross the TVP (A group): in 7 cases it was screwed in the right atrium at a mean distance of −6.1 mm from the TVP and, in 4 cases, at the level of the tricuspid annulus. In the remaining 14 patients (56%), the lead tip crossed the TVP (V group): it was screwed in the right ventricle at a mean distance of 9.3 mm from the TVP. A and V groups had comparable HB capture thresholds (1.6±1 V vs 1.7±0.7 V, 1 ms pulse-width; p=0.66); selective HB capture was significantly more represented in the A group (91% vs 21%; p=0.001). Significantly higher R-wave amplitudes were seen in the V group (6.7±3 vs 2.5±1.7 mV; p=0.0004), and they positively correlated with the distance from the TVP (p=0.0038). Atrial oversensing was never observed. Conclusion In a consecutive cohort of HBP recipients, the rate of patients who had an effective HB capture in the atrium was substantial and was characterized by different electrophysiological properties than in the ventricle. Funding Acknowledgement Type of funding sources: None.

Angiography-guided mid/high septal implantation of ventricular leads in patients with congenital heart disease.

BackgroundConduction system pacing prevents pacing‐induced cardiomyopathy, but it can be challenging to perform in patients with congenital heart disease (CHD), and mid/high septal lead implantation is an alternative. This study aimed to assess intraprocedural angiography's utility as a guide for mid/high‐septal lead implantation in CHD patients.MethodsThe study subjects were CHD patients with Class I/IIa indications for permanent pacemaker implantation. To guide septal lead implantation, we performed an intraprocedural right ventricular angiogram in anteroposterior, 40° left anterior oblique, and 30° right anterior oblique. The primary endpoint was the lead tip in the mid/high septum on computed tomography (CT). The secondary endpoints were complications and systemic ventricular function on follow‐up.ResultsFrom January 2008 to December 2018, we enrolled 27 patients (mean age: 30 ± 20 years; M:F 17:10) with CHD (unoperated: 20, operated: 7). The mean paced QRS duration was 131.7 ± 5.8 ms, and CT done in 22/27 patients confirmed the lead tip in the mid‐septum in 16, high septum in 5, and apical septum in 1 patient. There were no procedural complications, and during a mean follow‐up of 58 ± 35.2 months, there was no significant change in the systemic ventricular ejection fraction (56.4 ± 8.3% vs 53.9 + 5.9%, P = .08). Two patients with Eisenmenger syndrome died because of refractory heart failure.ConclusionsIntraprocedural angiography is safe and useful to guide mid/high‐septal lead implantation in CHD patients. Mid/high septal lead position preserves systemic ventricular function in patients with CHD during medium‐term follow‐up.

Lead dislodgement after a very long-term period of cardiac implantable electronic device implantation.

A 74‐year‐old man was admitted for a second replacement of a transvenous implantable cardioverter‐defibrillator (ICD) generator at 15 years after implantation. Postoperatively, electrocardiographic monitoring showed atrial lead malfunction. Chest X‐ray revealed that the tip of the active fixation atrial lead was dislocated. We present a case of atrial lead dislodgement after a very long‐term period of an ICD implantation.

Magnetic resonance conditionality of abandoned leads from active implantable medical devices at 1.5 T.

During MR scans, abandoned leads from active implantable medical devices (AIMDs) can experience excessive heating at the lead tip, depending on the type of termination applied to the proximal contacts (proximal end treatment). The influence of different proximal end treatments (ie, [1] freely exposed in the tissue, [2] terminated with metal in contact with the tissue, or [3] capped with plastic, and thereby fully insulated, on the RF-induced lead-tip heating) are studied. A technique to ensure that MR Conditional AIMD leads remain MR Conditional even when abandoned is recommended. Abandoned leads from three MR Conditional AIMDs ([1] a sacral neuromodulation system, [2] a cardiac rhythm management pacemaker system, and [3] a deep brain stimulator system) were investigated in this study. The computational lead models (ie, the transfer functions) for different proximal end treatments were measured and used to assess the in vivo lead-tip heating for four virtual human models (FATS, Duke, Ella, and Billie) and compared with the lead-tip heating of the complete MR Conditional AIMD system. The average and maximum lead-tip heating for abandoned leads proximally capped with metal is always lower than that from the complete AIMD system. Abandoned leads proximally insulated could lead to an average in vivo temperature rise up to 3.5 times higher than that from the complete AIMD system. For the three investigated AIMDs under 1.5T MR scanning, our results indicate that RF-induced lead-tip heating of abandoned leads strongly depends on the proximal lead termination. A metallic cap applied to the proximal termination of the tested leads could significantly reduce the RF-induced lead-tip heating.

B-IN02-04 TRANSHEPATIC ACCESS TO FACILITATE LEAD EXTRACTION IN A PATIENT WITH INTERRUPTED INFERIOR VENA CAVA

Unconventional approaches to achieve transvenous pacing may be required in patients with congenital vascular anomalies and vascular occlusion. We report a case of a patient with congenital interruption of the IVC and multiple venous occlusions requiring transhepatic access for dual chamber pacing system extraction and re-implantation. N/A A 21 year old female with congenital heart disease and a right axillary transvenous pacemaker implanted at age 11 for complete heart block presented with lead fracture. Her history was notable for coarctation repair, bicuspid aortic valve and closure of a large VSD. Vascular access to the heart was limited by a right subclavian vein occlusion extending to the SVC associated with indwelling leads, congenital interruption of the IVC, bilateral IJ occlusions, contralateral L subclavian occlusion and R iliac vein occlusion. A plan was made for lead extraction and placement of new leads. Temporary pacing was achieved with a deflectable decapolar catheter via the left femoral vein to the azygous vein to the SVC. During extraction lead dislodgement occurred before the mechanical extraction sheath could be advanced across the subclavian occlusion. Transhepatic access was obtained to snare the lead tip and apply traction for sheath advancement. With vascular access to the heart achieved, new RA and RV leads were positioned. The transhepatic venotomy was closed with a vascular plug. The patient was discharged without complication. Transhepatic venous access is a safe and effective alternative to more conventional approaches to lead extraction when limited by congenital vascular malformations or occlusion.

The relationship between anatomy and electrical parameters in His bundle pacing: A transthoracic echocardiography evaluation

PurposeThe implantation site of the His bundle (HB) lead may influence pacing parameters. Our aim was to characterize the anatomical location of the HB lead tip and its relationship with acute electrical parameters. MethodsConsecutive patients who underwent HB lead implantation, guided by standard fluoroscopy and electrophysiology, were prospectively enrolled. The relationship between HB lead tip and tricuspid valve plane (TVP) was assessed with post-procedure transthoracic echocardiography. ResultsTwenty-five patients were studied. In 11 patients (44%), the HB lead tip did not cross the TVP (A group): in 7 cases it was screwed in the right atrium at a mean distance of −6.1 mm from the TVP and, in 4 cases, at the level of the tricuspid annulus. In the remaining 14 patients (56%), the lead tip crossed the TVP (V group): it was screwed in the right ventricle at a mean distance of 9.3 mm from the TVP. A and V groups had comparable HB capture thresholds (1.6 ± 1 V vs 1.7 ± 0.7 V, 1 ms pulse-width; p = 0.66); selective HB capture was significantly more represented in the A group (91% vs 21%; p = 0.001). Significantly higher R-wave amplitudes were seen in the V group (6.7 ± 3 vs 2.5 ± 1.7 mV; p = 0.0004), and they positively correlated with the distance from the TVP (p = 0.0038). Atrial oversensing was never observed. ConclusionIn a consecutive cohort of HB pacing recipients, the rate of patients who had an effective HB capture in the atrium was substantial and was characterized by different electrophysiological properties than in the ventricle.

B-PO04-033 THE PACING SITE IS CLOSER TO THE LEFT VENTRICULAR SEPTAL ENDOCARDIUM DURING LEFT BUNDLE BRANCH PACING THAN DURING LEFT VENTRICULAR SEPTAL PACING

Left bundle branch pacing (LBBP) using a transventricular septal method has emerged as an effective approach to physiological pacing. However, differentiating between LBBP and left ventricular (LV) septal pacing (LVSP) remains a challenge because both modalities generate narrow paced QRS complexes, which present with a right bundle branch block (RBBB) electrocardiographic pattern. To compare the distance between the pacing lead tip and LV septal endocardium on echocardiography between patients who underwent successful LBBP and LVSP. Twenty-five consecutive patients (74.2±9.2 y, 60% male) with traditional indications for permanent cardiac pacing were included in this study. Unipolar pacing from final sites generated narrow QRS complexes with a RBBB pattern in all patients. Left bundle branch (LBB) potentials were recorded at the final pacing sites in the 17 patients who constituted the LBBP group. In the 8 patients in the LVSP group, LBB potentials were absent at the final pacing sites and the R-wave peak time in lead V5 was consistent at high and low outputs. Medtronic SelectSecure® 3830 pacing leads were used in all patients. After the procedures, a physician who was blinded to the group selection performed echocardiographic measurements of the distance between the lead tip and LV septal endocardium in all patients. The paced QRS duration was comparable between LBBP and LVSP group (102.4±15.9 ms vs. 113.7±21.1 ms, P=0.264). In the LBBP group, the interval from LBB potential to the onset of the QRS was 31.4±10.0 ms. The distance between the lead tip and LV septal endocardium was 0.4±0.6 mm in the LBBP group and 2.6±2.1mm in the LVSP group during the diastolic phase (P=0.004). During the systolic phase, the distance was 0.6±0.9 mm in the LBBP patients and 4.0±3.6 mm in the LVSP patients (P=0.004). The sensing amplitude identified during follow-up was 16.14±3.83 mV in the LBBP group and 8.98±1.94 mV in the LVSP group (P=0.001). The landing zone of the lead tip was much closer to the LV septal endocardium in patients who underwent LBBP than in those who underwent LVSP. Our study highlights the need for real-time intraprocedural monitoring of the distance between the lead tip and the LV septal endocardium in patients who undergo LBBP.

B-PO02-046 DOUBLE SHEATH-DOUBLE LEAD TECHNIQUE TO OVERCOME DIFFICULT CASES OF HIS BUNDLE LEAD IMPLANTATION

Although His bundle pacing (HBP) can be accomplished in most patients using a single C315His sheath and a single lead (SS-SL) technique, in some patients this approach could be unsuccessful. To develop a double sheath double lead ( DS-DL ) technique to increase success in achieving permanent HBP when facing difficult cases. Single center prospective cohort study that enrolled consecutive patients in whom 3 or more initial HBP attempts using the SS-SL technique have failed in spite of recording and/or capturing the His bundle. Instead of removing the lead from the last inserted site, this lead (L1) was left in place and used as a fixed anatomical radiographic reference. Subsequently, a second Medtronic C315HIS sheath and a second Medtronic SelectSecure™ Model 3830 lead (L2) were introduced to re-initiate the search for a better site around the tip of L1. Depending on the results obtained with L2, either lead can be removed and placed around the tip of other lead (Panels A and B of figure 1). These steps could be repeated in a systematic fashion until achieving adequate thresholds for HBP or declaring the attempts unsuccessful. The lead that was not used for HBP was then placed in the right atrium if indicated (Panel C). The patients had follow-up evaluations at 3, 6, and 12 months post implantation. Eighteen patients were enrolled, mean age 77 ± 10 yrs (10 males). The DS-DL technique was successfully applied to all patients. (See panel D and E of figure 1). This study demonstrated that the DS-DL technique proved to be safe, feasible and highly efficient in achieving permanent HBP in patients in whom the SS-SL technique have failed to achieve a successful implant.

The role of transesophageal echocardiography in predicting technical problems and complications of transvenous lead extractions procedures.

BackgroundTransesophageal echocardiography (TEE) is a useful tool in preoperative evaluation of patients undergoing transvenous lead extraction (TLE).HypothesisEchocardiographic phenomena may determine the difficulty and safety of the procedure.MethodsData from 936 transesophageal examinations (TEE) performed at a high volume center in patients awaiting TLE from 2015 to 2019 were assessed.ResultsTEE revealed a total of 1156 phenomena associated with the implanted leads in 697 (64.85%) patients, including: asymptomatic masses on endocardial leads (AMEL) (58.65%), vegetations (12,73%), fibrous tissue binding the lead to the vein or heart wall (33.76%), lead‐to‐lead binding sites (18.38%), excess lead loops (19.34%), intramural penetration of the lead tip (16.13%) and lead‐dependent tricuspid dysfunction (LDTD) (6.41%). Risk factors for technical difficulties during TLE in multivariate analysis were: fibrous tissue binding the lead to atrial wall (OR = 1.738; p < 0.05), to right ventricular wall (OR = 2.167; p < 0.001), lead‐to‐lead binding sites (OR = 1.628; p < 0.01) and excess lead loops (OR = 1.488; p < 0.05). Lead‐to‐lead binding sites increased probability of major complications (OR = 3.034; p < 0.05). Presence of fibrous tissue binding the lead to the superior vena cava (OR = 0.296; p < 0.05), right atrial wall (OR = 323; p < 0.05) and right ventricular wall (OR = 0.297; p < 0.05) reduced the probability of complete procedural success, whereas fibrous tissue binding the lead to the tricuspid apparatus decreased the probability of clinical success (OR = 0.307; p < 0.05).ConclusionsCareful preoperative TEE evaluation of the consequences of extended lead implant duration (enhanced fibrotic response) increases the probability of predicting the level of difficulty of TLE procedures, their efficacy and risk of major complications.

A New Medical Device Modeling Framework for Predicting the Performance of Indwelling Continence Care Devices and Improving Patient Care

Abstract A computational model of the human torso has been developed to study the stability of implanted leads that are part of a sacral nerve stimulation system. The model was built using presegmented anatomies that were themselves built from imaging of human patients. The sacral leads are represented using beam elements, and their interaction with the tissue is defined using a function that relates frictional force to the amount of slip between the lead and tissue. Displacements to the skin in the sacral region are applied to simulate activities of daily living, and the resulting displacement of the tip of the lead is indicative of its tendency to dislodge in real patients. Validation of the model was performed using experimental results collected in human cadavers. In these experiments, analogous displacements of the skin were applied after implantation of the leads per normal implant procedures. The displacement of the distal tip of the lead was measured using computed tomography (CT) imaging, allowing direct comparison to the predictions of the model. Recognizing that many model inputs were informed by sparse literature values, a novel application of uncertainty quantification methodology was developed wherein all model inputs were treated as uncertain intervals. This allowed an optimization approach to be used for estimating the uncertain interval for the model outputs. The computational model and cadaver results were used to study the performance of a new sacral lead design, relative to a predicate product. The results showed that the reduction in lead axial stiffness in the new design leads to less lead tip displacement, such that the lead is more likely to remain near the therapeutic target in patients.

Subclinical cardiac perforation by cardiac implantable electronic device leads detected by cardiac computed tomography

BackgroundThe relationship between the characteristics of cardiac implantable electronic device (CIED) leads and subclinical cardiac perforations remains unclear. This study aimed to evaluate the incidence of subclinical cardiac perforation among various CIED leads using cardiac computed tomography (CT).MethodsA total of 271 consecutive patients with 463 CIED leads, who underwent cardiac CT after CIED implantation, were included in this retrospective observational study. Cardiac CT images were reviewed by one radiologist and two cardiologists. Subclinical perforation was defined as traversal of the lead tip past the outer myocardial layer without symptoms and signs related to cardiac perforation. We compared the subclinical cardiac perforation rates of the available lead types.ResultsA total of 219, 49, and 3 patients had pacemakers, implantable cardioverter-defibrillators, and cardiac resynchronization therapy, respectively. The total subclinical cardiac perforation rate was 5.6%. Subclinical cardiac perforation by screw-in ventricular leads was significantly more frequent than that caused by tined ventricular leads (13.3% vs 3.3%, respectively, p = 0.002). There were no significant differences in the incidence of cardiac perforation between atrial and ventricular leads, screw-in and tined atrial leads, pacing and defibrillator ventricular leads, nor between magnetic resonance (MR)-conditional and MR-unsafe screw-in ventricular leads. Screw-in ventricular leads were significantly associated with subclinical cardiac perforation [odds ratio, 4.554; 95% confidence interval, 1.587–13.065, p = 0.005]. There was no case subclinical cardiac perforation by septal ventricular leads.ConclusionsSubclinical cardiac perforation by screw-in ventricular leads is not rare. Septal pacing may be helpful in avoiding cardiac perforation.

Computed tomography validated right ventricular mid-septal lead implantation using right ventricular angiography.

BackgroundRight ventricular (RV) mid‐septal pacing has been proposed as an alternative to RV apical pacing. Fluoroscopic and electrocardiogram criteria are unreliable for predicting the RV mid‐septal lead position. This study aimed to define the optimal RV mid‐septal pacing site using RV angiography.MethodsWe randomized patients undergoing pacemaker implantation (PPM) to the RV angiography‐guided group (Group A) or conventional fluoroscopy‐guided group (Group F). In Group A, we performed an angiogram in right anterior oblique (RAO 30°), left anterior oblique (LAO 40°), and left lateral (LL) views. We made a 5‐segment grid in RAO 30° and LL views and a 3‐segment grid in LAO 40° on the angiographic silhouette to define the lead position. Computed tomography (CT) was used to validate the lead tip position in both groups.ResultsWe enrolled 53 patients (Group A: 26, Group F: 27) with a mean age of 55.9 ± 12.2 years. CT images validated the lead position in the mid‐septum (Group A, 23 [88.5%]; Group F, 11 [40.7%], P = .0003) and anteroseptal (Group A, 3 [11.5%]; Group F, 5 [18.5%], P = .24). In Group F, the lead was in the anterior wall in 9 patients (33.3%) and the right ventricular outflow tract in 2 (7.4%) patients and none in these two positions in Group A. The lead tip in segment one on the angiographic 5‐segment grid in RAO 30° and LL views indicated a mid‐septal lead position on CT.ConclusionsRV angiography is safe and may be used to confirm the mid‐septal lead position during PPM.

JCS/JHRS 2019 guideline on non-pharmacotherapy of cardiac arrhythmias.

JCS/JHRS 2019 guideline on non-pharmacotherapy of cardiac arrhythmias.

A novel and practical technique to facilitate lead insertion at the His bundle region.

His bundle (HB) pacing techniques are challenging and time-consuming. This is primarily due to the limitations in locating the relatively small area of the HB body for pacing. Permanent HB pacing was performed in 133 consecutive patients with symptomatic bradycardia. A right atrial septo-gram (RAS) was performed in all patients to locate the HB. Briefly, 8-10cc of contrast was injected through the Medtronic C315HIS delivery sheath while fluoroscopy cine runs were obtained in the RAO 15-20° projection. The images obtained provided the visualization of an approximately 90° angle composed by the medial aspect of the tricuspid valve annulus (TVA) anteriorly and the superior aspect of the interatrial septum superiorly. The apex of this angle coincides with the tip of the triangle of Koch (TK), where the HB body is usually located. A Medtronic SelectSecure™ MRI SureScan™ Model 3830 lead was then advanced and directed towards this area. The HB was mapped using pace mapping and unipolar recordings from the lead tip. Localization of the apex of the TK/HB body with the RAS was successful in all patients. The overall acute success of inserting the lead at the HB was 95%. This study demonstrated that our method of utilizing a RAS to facilitate the localization the HB body proved to be safe and efficient in achieving permanent HB pacing with a success rate higher than previously reported.

Granulomatous abcess on a migrated pacemaker probe.

A 49-year-old patient consulted for abdominal pain and fever, 2 years after treatment of infective endocarditis on a dual-chamber pacemaker (PM) with favourable outcome at this time after treatment by partial surgical removal of the PM and antibiotic therapy. The lead tips were left in the right ventricle (RV) and in the left subclavian vein (thoracic radiography, Panel A, arrows). Abdominal computed tomography (CT) evidenced a thick-walled anterior abdominal fluid collection adjacent to the left liver lobe (Panel B, arrow) communicating with the infero-apical part of the RV on sagittal (Panel C, arrow) and oblique (Panel D, arrow) reconstructions. The residual fragment of the ventricular probe was no more detected within the RV. The collection contained a high-density metallic structure (Panels B and C, arrowhead), suggesting a migration of the RV probe’s fragment through the cardiac wall, the pericardium, and...

Contrast-enhanced image-guided lead deployment for left bundle branch pacing

Left bundle branch pacing (LBBP) is a novel conduction system pacing modality, but pacing lead deployment remains challenging. This study aimed to evaluate the feasibility of visualization-enhanced lead deployment for LBBP implantation and to assess LBBP characteristics on the basis of lead tip location. Successful LBBP with a well-defined lead tip location by visualization of the tricuspid value annulus in 20 patients was retrospectively analyzed to develop an image-guided technique to identify the LBBP target site. This technique was then prospectively tested in 60 patients who were randomized into 2 groups, one using the standard approach (the standard group) and the other using the image-guided technique (the visualization group). The procedural details, electrophysiological characteristics, and short-term follow-up were compared between groups. LBBP was successfully achieved in 28 patients in the standard group and in 29 in the visualization group. The procedural and fluoroscopic durations in the visualization group (66.76 ± 14.62 and 7.83 ± 2.05 minutes) were significantly shorter than those in the standard group (85.46 ± 20.19 and 11.11 ± 3.51 minutes) (P < .01). The number of lead deployment attempts in the visualization group was lower than that in the standard group (2.03 ± 1.18 vs 2.96 ± 1.17; P < .01), and the proportion of left bundle branch potential recorded was higher (79.3% vs 46.4%; P = .01). Using a visualization technique, the procedural and fluoroscopic durations for LBBP implantation were significantly shortened with fewer lead repositioning attempts.

Relationship of paced left bundle branch pacing morphology with anatomic location and physiological outcomes

Left bundle branch pacing (LBBP) is an emerging physiological pacing modality. However, little is known about pacing at different locations on the left bundle branch (LBB). The purpose of this study was to explore pacing and physiological characteristics associated with different LBBP locations. The study included 68 consecutive patients with normal unpaced QRS duration and successful LBBP implantation. Patients were divided into 3 groups according to the paced QRS complex as left bundle branch trunk pacing (LBTP), left posterior fascicular pacing (LPFP), or left anterior fascicular pacing (LAFP). Electrocardiographic (ECG) characteristics, pacing parameters, and fluoroscopic localization were collected and analyzed. There were 17 (25.0%), 35 (51.5%), and 16 (23.5%) patients in the LBTP, LPFP, and LAFP groups, respectively. All subgroups had relatively narrow paced QRS complex (128.6 ± 9.1 ms vs 133.7 ± 11.2 ms vs 134.8 ± 9.6 ms; P = .170), fast left ventricular activation (70.4 ± 9.0 ms vs 70.6 ± 10.2 ms vs 71.0 ± 9.0 ms; P = .986), as well as low and stable pacing thresholds. Delayed right ventricular activation and interventricular dyssynchrony were similar between groups. Fluoroscopic imaging indicated that the lead tip was located most commonly in the basal-middle region of the septum (67.7%), and this was independent of paced QRS morphology group (88.2% vs 57.1% vs 68.8%; P = .106). Pacing at different sites of the LBB resulted in similar intraventricular and interventricular electrical synchrony in patients with an intact conduction system. Fluoroscopic imaging alone could not predict specific LBBP paced ECG morphology.

Cryoneurolysis and Peripheral Nerve Stimulation: Reply.

We would like to thank our colleagues for their thoughtful letter1 regarding the use of percutaneous peripheral nerve stimulation to treat postoperative pain.2 We agree that combining a local anesthetic–based peripheral nerve block with percutaneous peripheral nerve stimulation will most likely prove the optimal management after painful surgical procedures, although we hesitate to describe it as “novel” given this combination was reported in multiple publications previously.3–6 Several feasibility studies found that the acute pain from orthopedic procedures such as rotator cuff repair frequently required the addition of local anesthetic–based nerve block to percutaneous peripheral nerve stimulation in the recovery room.3–6 Therefore, in a recently completed randomized, double-masked, sham-controlled trial (n = 66), we administered a single-injection ropivacaine peripheral nerve block after ultrasound-guided percutaneous lead insertion in all participants (NCT03481725). While the ropivacaine peripheral nerve block did provide effective postoperative analgesia as our colleagues suggest in their letter, the transition to stimulation during block resolution proved very challenging for the majority of participants—it was not a “smooth” transition from one modality to the next. The problem stems from the finding that current intensity requirements can vary dramatically—and unpredictably—preoperatively and postoperatively,3–6 and that percutaneous peripheral nerve stimulation current can induce pain and muscle contractions with an intensity that is too high.3 Therefore, the pulse generator must be set to a relatively low intensity in the recovery room to ensure that the electrical current does not induce pain and/or contractions during block resolution 4 to 12 h postdischarge (and providing suboptimal analgesia until increased by the patient).We agree with our colleagues that the cost of the available percutaneous peripheral nerve stimulation system may discourage its general adoption and that the (off-label) use of existing stimulating perineural catheters is enticing due to their availability and dramatically lower cost. This possibility certainly deserves investigation. However, we are somewhat pessimistic regarding the probability of providing adequate analgesia using a single stimulating catheter to deliver both perineural local anesthetic and, subsequently, electrical current. In general, perineural catheters must be inserted within the same fascial plane as the target nerve/plexus for adequate local anesthetic administration. In contrast—and as described in our review article—for percutaneous peripheral nerve stimulation, “…the optimal distance from the lead tip to epineurium of the target nerve was consistently 1.0 to 1.5 cm… A relatively remote distance theoretically promotes selective stimulation of the desired larger-diameter myelinated sensory neurons without activating motor or smaller-diameter sensory neurons that induce muscle contraction and discomfort, respectively… In addition, leads placed at this distance from the nerve are less sensitive to small changes in positioning due to movement which is critical in avoiding unpleasant sensations with purposeful muscle contraction.”3 Therefore, at more than 1.0 cm from the target nerve and rarely within the same fascial plane, it is improbable that a perineural local anesthetic infusion would provide significant analgesia.The University of California at San Diego has received funding and product for other research projects of Drs. Ilfeld and Finneran from: Epimed (Farmers Branch, Texas); Infutronics (Natick, Massachusetts); and a manufacturer of percutaneous peripheral nerve stimulation devices, SPR Therapeutics (Cleveland, Ohio).

A Case Report of Successful High-Frequency 10-kHz Spinal Cord Stimulator Trial in a Patient with Refractory Thoracic Postherpetic Neuralgia

Background: Spinal cord stimulation can be an effective treatment modality in patients suffering from postherpetic neuralgia who have failed first-line pharmacotherapy and continue to struggle from debilitating pain. Appropriate patient selection and having a wide array of stimulation waveforms can enhance the success of spinal cord stimulator trials. Case Report: In this article, we present a case report of a patient suffering from refractory thoracic postherpetic neuralgia who underwent a successful high-frequency 10-kHz spinal cord stimulator trial. Lead tips were successfully placed at the midline and left paramedial side of the top of T1 vertebral bodies at the source of the pain. The patient was followed up in our clinic 7 days post procedure. At the time of follow-up, our patient reported an 85% to 90% reduction in his pain symptom scores and a significant improvement in his quality of life. Conclusion: Similar successful trials for postherpetic neuralgia have been reported in small studies using traditional low-frequency stimulation waveforms. However, to our knowledge, this is the first report of a successful spinal cord stimulator trial using high-density 10 kHz. Key words: Postherpetic neuralgia, high-frequency spinal cord stimulator, acute herpes zoster

A combined computational and experimental approach to assess the transfer function of real pacemaker leads for MR radiofrequency-induced heating.

To propose and validate a variation of the classic techniques for the estimation of the transfer function (TF) of a real pacemaker (PM) lead. The TF of three commercially available PM leads was measured by combining data from experimental measurements and numerical simulations generated by three sources: a) the experimental local SAR at the tip of the PM lead (single measurement point) exposed to a 64MHz birdcage body coil; b) the experimental current distribution along the PM lead, obtained by directly injecting a 64MHz signal inside the lead; c) the electric field (E-field) simulated with a computational model of the 64MHz birdcage body coil adopted in the experimental measurement performed in a). The effect of the lead trajectory on the estimation of the TF was also estimated. The proposed methodology was validated by comparing the SAR obtained from the PM lead TF with experimental measurements: a maximum difference of 2.2dB was observed. It was also shown that the estimation of the TF cannot be considered independent with the lead trajectory: a variation of the SAR estimation up to 3.4dB was observed. For the three PM lead tested, the error in the SAR estimation is within the uncertainty level of SAR measurements (± 2dB). Additionally, the estimation of the TF using the reciprocity principle is influenced by the particular lead trajectory adopted, even if the consequent variability in the SAR estimation is still close to the uncertainty level of SAR measurements.