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Background Robotics in neurosurgery has demonstrated widening indications and rapid growth in recent years. Robotic precision and reproducibility are especially pertinent to the field of functional neurosurgery. Deep brain stimulation (DBS) requires accurate placement of electrodes in order to maximize efficacy and minimize side effects. In addition, asleep techniques demand clear target visualization and immediate on-table verification of accuracy. Objective To describe the surgical technique of asleep DBS surgery using the Neuro|MateTM Robot (Renishaw plc, Wotton-under-Edge, United Kingdom) and examine the accuracy of DBS lead placement in the subthalamic nucleus (STN) for the treatment of movement disorders. Methods A single-center retrospective review of 113 patients who underwent bilateral STN/Zona Incerta electrode placement was performed. Accuracy of implantation was assessed using 5 measurements, Euclidian distance, radial error, depth error, angular error, and shift error. Results A total of 226 planned vs actual electrode placements were analyzed. The mean 3-dimensional vector error calculated for 226 trajectories was 0.78 +/- 0.37 mm. The mean radial displacement off planned trajectory was 0.6 +/- 0.33 mm. The mean depth error, angular error, and shift error was 0.4 +/- 0.35 mm, 0.4 degrees, and 0.3 mm, respectively. Conclusion This report details our institution's method for DBS lead placement in patients under general anaesthesia using anatomical targeting without microelectrode recordings or intraoperative test stimulation for the treatment of movement disorders. This is the largest reported dataset of accuracy results in DBS surgery performed asleep. This novel robot-assisted operative technique results in sub-millimeter accuracy in DBS electrode placement.

Background Deep brain stimulation (DBS) surgery in patients with pre-existing cochlear implants (CIs) poses various challenges. We previously reported successful magnetic resonance imaging (MRI)-based, microelectrode recording (MER)-guided subthalamic DBS surgery in a patient with a pre-existing CI. Other case reports have described various DBS procedures in patients with pre-existing CIs using different techniques, leading to varying issues to address. A standardized operative technique and workflow for DBS surgery in the setting of pre-existing CIs is much needed. Objective To provide a standardized operative technique and workflow for DBS lead placement in the setting of pre-existing CIs. Methods Our operative technique is MRI-based and MER-guided, following a workflow involving coordination with a neurotology team to remove and re-implant the internal magnets of the CIs in order to safely perform DBS lead placement, altogether within a 24-h time frame. Intraoperative nonverbal communication with the patient is easily possible using a computer monitor. Results A 65-yr old woman with a 10-yr history of craniocervical dystonia and pre-existing bilateral CIs underwent successful bilateral pallidal DBS surgery at our institution. No merging errors or difficulties in targeting globus pallidus internus were experienced. Also, inactivated CIs do not interfere with MER nor with stimulation, and intraoperative communication with the patient using a computer monitor proved feasible and satisfactory. Conclusion DBS procedures are safe and feasible in patients with pre-existing CIs if precautions are taken following our workflow.

International audience; BACKGROUND: Frameless robotic-assisted surgery is an innovative technique for deep brain stimulation (DBS) that has not been assessed in a large cohort of patients.OBJECTIVE: To evaluate accuracy of DBS lead placement using the ROSA$^{(R)}$ robot (Zimmer Biomet) and a frameless registration.METHODS: All patients undergoing DBS surgery in our institution between 2012 and 2016 were prospectively included in an open label single-center study. Accuracy was evaluated by measuring the radial error (RE) of the first stylet implanted on each side and the RE of the final lead position at the target level. RE was measured on intraoperative telemetric X-rays (group 1), on intraoperative O-Arm$^{(R)}$ (Medtronic) computed tomography (CT) scans (group 2), and on postoperative CT scans or magnetic resonance imaging (MRI) in both groups.RESULTS: Of 144 consecutive patients, 119 were eligible for final analysis (123 DBS; 186 stylets; 192 leads). In group 1 (76 patients), the mean RE of the stylet was 0.57 $\pm$ 0.02 mm, 0.72 $\pm$ 0.03 mm for DBS lead measured intraoperatively, and 0.88 $\pm$ 0.04 mm for DBS lead measured postoperatively on CT scans. In group 2 (43 patients), the mean RE of the stylet was 0.68 $\pm$ 0.05 mm, 0.75 $\pm$ 0.04 mm for DBS lead measured intraoperatively; 0.86 $\pm$ 0.05 mm and 1.10 $\pm$ 0.08 mm for lead measured postoperatively on CT scans and on MRI, respectively No statistical difference regarding the RE of the final lead position was found between the different intraoperative imaging modalities and postoperative CT scans in both groups. CONCLUSION: Frameless ROSA (R) robot-assisted technique for DBS reached submillimeter accuracy. Intraoperative CT scans appeared to be reliable and sufficient to evaluatethe final lead position.

INTRODUCTION AND OBJECTIVE:Motor response is recognized as an important guide to sacral neuromodulation (SNM) lead placement as many leads are placed under sedation that alters sensory response. Wh...

We sought to determine the usefulness of motor responses during sacral neuromodulation lead placement by testing the hypothesis that a greater number of motor responses during intraoperative electrode testing would be associated with more durable therapy.We retrospectively reviewed all sacral neuromodulation lead placements at a large academic center from 2010 to 2015. Included in study were all unilateral sacral lead placements for which the presence or absence of a motor response was documented discretely for each electrode. Motor responses were quantified into separate subscores, including bellows and toe response subscores (each range 0 to 4) for a possible maximum total score of 8 when combined. Revision surgery was the primary outcome. Univariate and multivariate analyses were performed for factors associated with lead revision.A total of 176 lead placements qualified for analysis. Mean ± SD cohort age was 58.4 ± 15.9 years, 86.4% of the patients were female and 93.2% had undergone implantation for overactive bladder. Median followup was 10.5 months (range 2 to 36). Overall 34 patients (19%) required lead revision. Revision was negatively associated with the total electrode response score (p = 0.027) and the toe subscore (p = 0.033) but not with the bellows subscore (p = 0.183). Predictors of revision on logistic regression included age less than 59 years at implantation (OR 5.5, 95% CI 2-14) and a total electrode response score less than 4 (OR 4.2, 95% CI 1.4-12.8).Fewer total electrode responses and specifically fewer toe responses were associated with sacral neuromodulation lead revision. These data suggest that placing a lead with more toe responses during testing may result in more durable sacral neuromodulation therapy.

Peripheral nerve stimulators serve as an alternative modality to treat chronic pain conditions; however, long-term complications, specifically lead migration, may occur., Introduction: Peripheral nerve stimulators have emerged as a new generation of advanced modalities to treat chronic pain and avoid opioids. They transmit electrical stimulation through implanted leads and wireless, wearable, external generators. Common complications include infection, nerve damage, and migration of stimulating leads. This article describes 2 cases of complications from lead migration. Methods: Case 1 describes a 61-year-old man with chronic groin pain who underwent an uncomplicated ultrasound-guided ilioinguinal peripheral nerve lead implantation. Case 2 describes a 54-year-old woman with left shoulder pain who underwent an uncomplicated ultrasound-guided percutaneous lead placement near the axillary nerve through a deltoid approach. Both peripheral nerve stimulators were confirmed with fluoroscopy, and each patient was followed up every 2 months for the following 2 years. Results: Both patients experienced lead migration to the skin resulting in erythema and need for lead removal. Initial unsuccessful removal by traction resulted in retained fragments and need for open surgical removal. Discussion: Neurologic complications of peripheral nerve stimulator implantation are rare, but device-associated complications, specifically lead migration, remain a source of long-term problems that can result in decreased coverage of the intended neural target. Conclusion: Thorough patient education, early postimplantation assessment, and extended routine follow-up are necessary to decrease lead-associated complications. If migration does occur, the potential impact of scar tissue on removal should be considered.

Background Microelectrode recording (MER) can be used to map out the target nucleus and identify ideal lead placement. Objective To assess the use of multichannel MER to increase the efficiency of lead placement without compromising patient safety. Methods Analysis of a single center's technique for utilizing multichannel MER with 3 consistent anterior-to-posterior simultaneous passes that include an evaluation of the location of final lead placement, patient diagnosis, target nuclei, and additional work involved for refinement of targeting. Lead revision rates and rate of hemorrhage are also assessed. Results There were a total of 237 lead placements in 123 patients over a 4-yr period. In 4.2% of lead placements, additional planning was required, while only 2.5% required additional MER. The lead placement matched 51.3% of the time in bilateral placements and was consistent regardless of target nuclei. In 84.8% of cases, the final lead placement was within the initial 3 MER passes. An additional 11.3% could be placed without the need for an additional pass. There were 2 lead revisions and no hemorrhage or stroke complications. Conclusion This series demonstrates that our technique of multichannel MER leads to accurate and efficient lead placement maintaining its safety profile.

Background: His bundle pacing (HBP) remains technically challenging and is currently guided by electrograms and 2-dimensional fluoroscopy. Our objective was to describe a new technique for HBP directly guided by electroanatomic mapping (EAM). Methods: Twenty-eight patients were included. The atrioventricular septum was mapped via EAM, and His bundle (HB) electrograms, selective, and nonselective HB capture sites were tagged. Pacing leads were connected to EAM, navigated to tagged HB target sites and deployed. Intracardiac electrograms and pacing parameters were recorded. Lead location was tagged on the cloud of HB sites, which was divided into 3 arbitrary segments. In 5 patients, atrioventricular nodal ablation was performed with direct visualization of the HBP lead by EAM. Results: Reproducible navigation of the pacing lead to predetermined HBP locations guided by EAM was achieved in all patients. The lead was successfully deployed in 25 patients. HB cloud area was 360 (212) mm 2 . There was no correlation between HBP threshold and lead location on the His cloud. The intracardiac electrograms atrial/ventricular ratio at the lead deployment site correlated with its EAM position on the His cloud ( P =0.045). Procedure, fluoroscopy, and mapping times were 116.0 (38.8), 8.6 (6.3), and 9.0 (11.4) minutes, respectively. HBP threshold at implant was 1.5 (2.3) V at 1.5 (1.0) ms. Distance between HB lead and ablation sites was 10.0 (1.3) mm in patients undergoing atrioventricular nodal ablation. Conclusions: Direct guidance of HBP by EAM allows for direct visualization of the pacing lead on the HB cloud and reproducible navigation to predetermined HB capture sites. Intracardiac electrograms atrial/ventricular ratio at the lead deployment site correlates with His cloud location. EAM can be applied during standard HBP procedures or combined with atrioventricular nodal ablation.

Introduction: Pacing of the His bundle and conduction system seems an attractive site for pacing. Lead placement in His-pacing might be technically challenging due to surrounding structures and particular anatomic location. Patient concerns: A 62-years old male patient was admitted for recurrent syncope. Electrocardiographic monitoring revealed periods of complete atrioventricular block with left branch block morphology and a QRS duration of 160 ms. Diagnosis: A diagnosis of intermittent complete atrioventricular block was made with a Class I indication of permanent dual-chamber cardiac pacing. Interventions: A lead delivery system with a C315 His catheter and a Select Secure 3830 69 cm pacing lead was placed at the septal area of the atrioventricular junction with good pacing and sensing thresholds. An important narowing of the QRS was observed. Outcomes: After the procedure, good pacing and sensing parameters were observed. Echocardiography revealed disappearance of the previously recorded ventricular dyssynchronism. Device follow-up at 1 month and 3 months showed stable pacing and sensing parameters. Conclusion: Pacing the distal His bundle normalized the QRS complex, therefore “curing” both the atrioventricular and the left bundle branch conduction abnormalities. As such, the technique can be used as an alternative to cardiac electrical resynchronization therapy with acceptable pacing and detection thresholds and better ventricular activation pattern.

Item does not contain fulltext Dorsal root ganglion stimulation (DRG-S) has shown promise as a treatment for low back pain. The traditional anterograde placement of DRG-S leads can be challenging in patients with anatomical changes from prior back surgery. We describe an "outside-in" placement technique of DRG-S leads in 4 patients with histories of multiple lumbar surgeries, which made the traditional anterograde placement not feasible. At long-term follow-up, the patients experienced substantial pain relief and improvement in quality of life, with no complications. The outside-in lead placement technique may be an efficacious alternative to the traditional techniques in patients with anomalous anatomy from prior surgery.

Here we report a case of severe tricuspid regurgitation related to the pacemaker lead incarcerated in the chordae tendinae, resulting in significantly reduced systolic function of right ventricular and right sided heart failure. The necessity of echocardiography is ignored in the follow-ups after pacemaker implantation, which may be useful for optimal lead placement.

Introduction Symptomatic edema around a deep-brain stimulation (DBS) lead is a rare complication of DBS surgery. Although this phenomenon is not fully understood, clinical presentation of DBS lead edema can be severe enough to prompt treatment. There is a paucity of literature on the clinical course and treatment of DBS lead edema. Case report We present a 65-year-old man with Parkinson disease who developed unilateral DBS lead edema after bilateral subthalamic nucleus lead placement. Infectious, inflammatory, and ischemic causes were thoroughly investigated and ruled out. Clinical symptoms and radiographic changes all returned to normal with supportive care alone. Conclusions Lead edema is a rare complication after DBS surgery. It is important to recognize the benign clinical course of DBS lead edema to counsel patients and avoid unnecessary treatment such as hardware removal.

Background— Cardiac resynchronization therapy is widely used for the treatment of heart failure. Recent data suggest that electric separation during left ventricular pacing varies within the right ventricle (RV). We hypothesized that placement of the RV lead guided by maximal electric separation (MES) would improve response to cardiac resynchronization therapy compared with standard apical placement. Methods and Results— A single-blind, randomized controlled trial was conducted. Patients eligible for cardiac resynchronization therapy-D were enrolled. Left ventricular lead placement was performed at the coronary sinus branch. The RV outflow tract, septum, and apex were mapped during left ventricular pacing and MES recorded. Patients were randomized to receive either apical placement or RV lead placement at the site mapping MES. Left ventricular ejection fraction, 6-minute walk distance, and New York Heart Association functional class were recorded at baseline and 3 months by blinded observers. Response was defined as at least one of the following: 5% absolute increase in ejection fraction, 50 m increase in 6-minute walk distance, or an increase by > 1 functional class. Primary end point was improvement in ejection fraction at 3 months. Fifty patients were randomized (25 MES-guided and 25 apical). Baseline characteristics were similar in the 2 groups. Electric separation was lower in the apex (143±23 versus 168±25 ms in MES group; P =0.01). MES was most commonly septal and rarely apical (4/50 patients). Responders in the MES-guided versus apical group are as follows: Echo 21 versus 13 patients ( P =0.032), 6-minute walk distance 19 versus 12 patients ( P =0.079), and functional class 22 versus 15 patients ( P =0.051). No dislodgment or reposition for suboptimal defibrillation tests was reported. Conclusions— MES-guided placement of the RV lead improves cardiac resynchronization therapy responders compared with standard apical placement.

Introduction: Right ventricular apical (RVA) pacing appears to have detrimental effects on cardiac function and long term outcomes. Right ventricular non-apical (RVNA) pacing, especially in the septal position, has been postulated as an alternative that may lead to less morbidity and mortality. Prior studies have shown conflicting results and been limited by small numbers and short follow-up. We aimed to determine if right ventricular septal lead position was associated with a reduction in long-term mortality compared to RVA lead position. Methods: Patients who underwent dual-chamber pacemaker implantation from 2004 through 2013 were evaluated for right ventricular lead position based on chest radiographs. Lead positions were divided in to apical or non-apical. Non-apical lead positions were subdivided to isolate a septal lead position group. Mortality was compared between these groups. Results: During the study period, 3456 patients underwent dual-chamber pacemaker placement and had images appropriate for lead position evaluation. The group was 53.5% male with a mean age of 74 ± 13 years. RVNA lead position was found in 976 (28.2%) patients, including 243 (7.0%) with a septal position. There was no significant difference in age or prior heart failure diagnosis between groups. Kaplan-Meier survival analysis did not reveal a significant difference in mortality between patients with RVA versus RVNA lead position during 5 year follow-up (p = 0.82). However, septal lead position was associated with a significantly lower mortality compared with RVA position (p = 0.03) (figure). Conclusions: Right ventricular septal lead position is associated with a lower long-term mortality than RVA lead position. This has substantial implications regarding the preferred site for ventricular pacing lead placement.

Background We describe an approach to vagal nerve stimulator (VNS) lead replacement through the posterior cervical triangle. Scar around the structures of the carotid sheath is avoided and new leads are placed on a pristine section of the vagus nerve proximal to the original site. Clinical presentation Skin incision from the implantation surgery is incorporated and extended to allow access to the posterior border of the sternocleidomastoid muscle (SCM). Dissection proceeds along the posterior border of the SCM. The SCM and jugular vein are retracted anterior to expose a fresh segment of the vagal nerve immediately superficial to the carotid artery and proximal to the original electrode site. Once the nerve is adequately exposed, electrode placement proceeds in the standard fashion. Dysfunctional electrodes are left in place, and the lead wire is cut as near the electrodes as can be easily accessed. Three patients have undergone lead revision with this approach. Lead placement was successful and free from complications in all cases. Conclusion The posterior cervical triangle approach provides a virgin dissection plane for VNS revision.

Background Spinal cord stimulation (SCS) is used to treat chronic pain and requires an awake patient for optimized lead positioning to locate paresthesias. Epidural anesthesia may be a suitable anesthetic but has not been evaluated. Methods We performed an open-label, prospective, observational, single-center study to evaluate the safety and efficacy of laminectomy lead placement under epidural anesthesia for the treatment of neuropathic chronic pain. Results The results in our study demonstrate that epidural anesthesia is a suitable technique for SCS lead implant. Conclusions This is the first study using epidural anesthesia for SCS lead implants by laminectomy. The technique seems to be safe and effective.

INTRODUCTION AND OBJECTIVES: Sacral neuromodulation (SNM) is an effective treatment for medically refractory overactive bladder (OAB). The procedure is performed as a 2-stage technique with first stage tined placement (FSTLP) followed by second stage stimulator 4 weeks later. The most significant morbidity for the procedure is infection, reported in up to 12%. We assessed the infection rates in patients who were implanted within a dedicated SNM theatre environment and compared them to those in patients who underwent SNM on mixed operating lists. METHODS: We reviewed the complications in all patients having SNM surgery over a 12 month period within either a dedicated SNM operating theatre, with the same surgeon, advanced nurse practitioner, anaesthetist and radiological team, or on the mixed urological lists. In the mixed theatre lists SNM cases were performed amongst other urological cases by varying theatre teams. Infection rates (requiring lead or device explantation) were recorded, and results compared using Student T-tests. RESULTS: Between Sept 2013-2014, 118 consecutive patients had 2-stage implants performed by each of the two theatre processes (59 in each group). There was no difference in test conversion rates between theatres, but a significant difference in infection rate was observed (p

landmarks add up to the teaching acronym STAR. STAR-technique including a puncture angle of 60 and a gluteal lead exit places 3 to 4 electrode-poles at the nerve. In clinical trial mean operation time for bilateral PNM in STAR was 85min with mean puncture attempts of 3.5 to reach the nerve. Pain decreased statistically significant only in bilateral PNM. CONCLUSIONS: The STAR-approach appears to achieve technical standardisation and optimized reproducibility in pudendal lead placement resulting into an increased feasibility of PNM. The clinical results of pudendal neuromodulation for chronic pelvic pain are promisisng and appear to justify further research in this field.

A persistent left superior vena cava was discovered in a 66-year-old man with heart failure undergoing implantation of a biventricular pacing and defibrillator device. An active fixation right ventricular defibrillator lead was placed through a curved guiding catheter. A sub-selection catheter and a guidewire allowed the engagement of a posterior-lateral branch of the coronary sinus, performance of an angiogram without an occlusive balloon, and optimal lead placement. The right atrial lead was positioned using a standard stylet. Despite the technical challenges, implantation of a biventricular pacing and defibrillator device via a persistent left superior vena cava is safe and feasible.

Implantable cardioverter-defibrillators (ICDs) have revolutionized the treatment of patients at risk for sudden cardiac death. In the nearly 3 decades since the first human ICD implant,1 millions of devices have been implanted worldwide and innumerable lives have been saved. Successful resuscitation of a potentially lethal ventricular arrhythmia by an ICD system depends on successful arrhythmia detection and timely delivery of therapy. Both the ICD generator and the ICD lead are critical components of this system. The lead, in particular, is literally a lifeline whose purpose is to convey critical information about the heart’s rhythm to the ICD generator and, in turn, to deliver life-sustaining therapy when needed. Failure of an ICD lead may result in significant clinical events, including failure to pace, failure to defibrillate, inappropriate shocks, and even death. Article p 2727 ICD leads, like many medical technologies, have undergone a remarkable transformation. Epicardial leads, which necessitated a thoracotomy for lead placement, have given way to transvenous leads, which are easier to implant, less costly, and associated with decreased morbidity and mortality.2 Important advances in transvenous lead technology, such as the development of steroid elution, smaller diameter leads, novel insulations, and multipolar leads, have translated into meaningful clinical benefits for patients. Although modern ICD leads consist primarily of electrodes, conductors, insulation, and a fixation mechanism to attach the lead to the myocardium, lead design and performance vary from model to model. Indeed, monitoring of performance is critical not only to identify products with increased failure rates but also to provide physicians and patients with realistic expectations of device performance. In the current issue of Circulation , Eckstein et al add to our understanding of ICD lead performance.3 The investigators conducted a retrospective analysis of 1317 consecutive patients who received ICD systems (including 38 different ICD lead …

Skeletal muscle is a clinically important body composition component which at present is difficult to quantify in vivo. Previous studies suggest that measured appendicular resistance at 50 kHz can be used to predict extremity skeletal muscle mass, although accurate technician placement of multiple gel electrodes is required. In the present study we developed a new bioimpedance analysis (BIA) electrode stand designed for rapid whole-body and segmental resistance and reactance measurements. The new system incorporates stainless steel hand and foot contact electrodes in place of gel electrodes and employs a previously reported lead placement algorithm for deriving extremity resistances without the need for placing conventional proximal limb gel electrodes. This report describes the new electrode system's design and examines the relationships between contact and gel electrode-measured resistance and between appendicular resistance measured with the recently reported lead placement algorithm and conventionally placed segmental electrodes. Results in healthy adults demonstrate high correlations between contact and gel electrodes (e.g., hand-to-hand, N = 12, r = 0.994, P < 0.001) and between segmental resistance measured by the recently reported approach and conventionally-measured segmental resistance (e.g., right arm, N = 13; r = 0.997, P < 0.001). These results strongly support the validity of the new electrode system's resistance measurements and suggests the feasibility of developing a BIA system for rapidly measuring extremity skeletal muscle mass.

An adult female patient without previous history of pain or psychiatric disorder developed reflex sympathetic dystrophy (RSD) in her left hand and arm after 2 separate injuries, and subsequent arthroscopy and arthroscopic surgery. Traditional management with systemic medications, nerve blocks, and behavioral pain management were unsuccessful. With subsequent development of depression and suicide attempt, electroconvulsive therapy (ECT) was administered using bilateral lead placement. Total resolution of her pain occurred for several hours after the first treatment. Over the course of the full ECT series the pain, vasculature changes of RSD, and depression resolved completely. Prominent psychiatric disturbances were complications arising after ECT and the resolution of the RSD, and during long-term follow-up. A review of the literature from the 1940s revealed numerous cases of chronic, intractable pain treated successfully by ECT, although none of the case series were controlled studies. More recent literature questions if 'modified' ECT, using unilateral lead placement, is less effective than bilateral lead placement, in treating pain syndromes. Resolution of the vascular changes of RSD after ECT raises questions of possible cerebral contributions to the pathophysiology of RSD.

Eranti et al1 report an interesting correlation between an underappreciated electrocardiogram parameter, that is, P terminal force (PTF), and mortality. Indeed, PTF magnitude ≥0.04 mm·ms, if present along with an interatrial block (P-wave duration >110 ms), is considered highly specific and reasonably sensitive for diagnosing left atrial enlargement.2 The determination of PTF is restricted to lead V1, wherein lead placement error has a significant potential …

An 82-year-old man complained of lassitude, sweating, and fever for &5 weeks. On physical examination, a new 3/6 diastolic murmur was heard at the left sternal border, and the patient was admitted with suspected endocarditis. The patient’s history revealed a VVI pacemaker implantation 9 months earlier for unspecified bradycardia at another institution and a transient ischemic attack 2 months before admission. On admission, C-reactive protein was elevated at 68.6 mg/L, and Staphylococcus epidermidis was isolated in several blood cultures. The frontal and lateral views (Figure 1A and 1B) of a chest radiograph showed inadvertent pacemaker lead malpositioning into the left ventricle. Additionally, the right bundle-branch block-like pattern of a paced ECG (Figure 2) gave concern of lead malpositioning. Transthoracic echocardiography confirmed the malpositioning of the pacemaker lead into the left ventricle and …

Spatial vectorcardiograms of a group of normal young adults, recorded with two systems of electrode placement, have been studied. Those recorded with the equilateral tetrahedron as the reference system were similar to records previously described and had QRS-loops of two configurations. Those recorded with a method of lead placement designed to reduce the errors inherent in the commonly used reference frames had greater uniformity of form and orientation of both the QRS and T-loops.