Current of injury amplitude during left bundle branch area pacing implantation: impact of filter settings, ventricular pacing, and lead type.

AIMS: Monitoring current of injury (COI) during left bundle branch area pacing (LBBAP) implantation is useful to evaluate lead depth. Technical aspects for recording COI amplitude have not been well studied. Our aims were to evaluate the impact of high-pass filter settings on electrogram recordings during LBBAP implantation. METHODS AND RESULTS: Consecutive patients with successful LBBAP implantation had unipolar recordings of COI at final lead position at different high-pass filter settings (0.01-1 Hz) from the tip electrode during sensing and pacing, and from the ring electrode during sensing. Duration of saturation-induced signal loss was also measured at each filter setting. COI amplitudes were compared between lumenless and stylet-driven leads. A total of 156 patients (96 males, aged 81.4 ± 9.6 years) were included. Higher filter settings led to significantly lower COI amplitudes. In 50 patients with COI amplitude < 10 mV, the magnitude of the drop was on average 1-1.5 mV (and up to 4 mV) between 0.05 and 0.5 Hz, meaning that cut-offs may not be used interchangeably. Saturation-induced signal loss was on average 10 s at 0.05 Hz and only 2 s with 0.5 Hz. When pacing was interrupted, the sensed COI amplitude varied (either higher or lower) by up to 4 mV, implying that it is advisable to periodically interrupt pacing to evaluate the sensed COI when reaching levels of ∼10 mV. Lead type did not impact COI amplitude. CONCLUSION: High-pass filters have a significant impact on electrogram characteristics at LBBAP implantation, with the 0.5 Hz settings having the most favourable profile.

Optimizing transseptal puncture guided by three-dimensional mapping: the role of a unipolar electrogram in a needle tip.

AIMS: A three-dimensional electroanatomic mapping system-guided transseptal puncture (3D-TSP), without fluoroscopy or echocardiography, has been only minimally reported. Indications for 3D-TSP remain unclear. Against this background, this study aims to establish a precise technique and create a workflow for validating and selecting eligible patients for fluoroless 3D-TSP. METHODS AND RESULTS: We developed a new methodology for 3D-TSP based on a unipolar electrogram derived from a transseptal needle tip (UEGM tip) in 102 patients (the derivation cohort) with intracardiac echocardiography (ICE) from March 2018 to February 2019. The apparent current of injury (COI) was recorded at the muscular limbus of the foramen ovalis (FO) on the UEGM tip (sinus rhythm: 2.57 ± 0.95 mV, atrial fibrillation: 1.92 ± 0.77 mV), which then disappeared or significantly reduced at the central FO. Changes in the COI, serving as a major criterion to establish a 3D-TSP workflow, proved to be the most valuable indicator for identifying the FO in 99% (101/102) of patients compared with three previous techniques (three minor criteria) of reduction in atrial unipolar or bipolar potential and FO protrusion. A total of 99.9% (1042/1043) patients in the validation cohort underwent successful 3D-TSP through the workflow from March 2019 to July 2023. Intracardiac echocardiography guidance was required for 6.6% (69/1042) of patients. All four criteria were met in 740 patients, resulting in a 100% pure fluoroless 3D-TSP success rate. CONCLUSION: In most patients, fluoroless 3D-TSP was successfully achieved using changes in the COI on the UEGM tip. Patients who met all four criteria were considered suitable for 3D-TSP, while those who met none required ICE guidance.

Change in left bundle branch potential-ventricular interval during lead implantation: what is the mechanism?

A 75-year-old male with sick sinus syndrome (SSS) underwent left bundle branch (LBB) pacing (LBBP) implantation. Intraoperative recordings showed that the LBB potential-ventricular (LBB-V) interval gradually decreased from 47 to 19 ms (ms). Two-year follow-up indicated stable pacing parameters and consistent electrocardiogram (ECG) results. Despite potential conduction delays caused by lead implantation, a watchful waiting strategy demonstrated recovery potential without impacting long-term prognosis or pacing parameters.

Gradual development of left bundle branch current of injury during left bundle branch pacing lead implantation.

A larger left bundle branch (LBB) potential or LBB current of injury (COI) indicates a low LBB capture threshold in LBB pacing. During LBB pacing in an 85-year-old woman, achieving a low LBB capture threshold did not initially present with a larger LBB potential or LBB COI, but rather with a new initial negative deflection in a ventricular electrogram. LBB COI gradually developed over 7 min thereafter, which suggested that the lead tip had reached the left ventricular subendocardium. Therefore, this negative deflection may be the first sign to avoid further lead rotation.

Genesis of ischemic ST segment changes: A study using precordial bipolar leads and regional vectorcardiograms.

BACKGROUND: Precordial Bipolar Leads (PBLs), Weighted Unipolar Leads (WUL), and Regional Vectorcardiograms (RVCGs) are constructed using the same data recorded by a standard 12­lead ECG, but they provide additional information not visible in the standard 12­lead ECG (ECG) tracings. OBJECTIVES: In previous studies during balloon occlusion of the LAD and RCA, we observed a complete ischemic inversion of the QRS waves, with folding of the loop and ST segment shift. In the present study, we aim to investigate this abnormality using new ECG methods. We hypothesize that utilizing PBL, WUL, and RVCG in patients with ischemia caused by total acute coronary artery occlusion enables the detection of specific abnormalities-such as changes in waveform time/amplitude, the presence of the omega sign, distortion and folding of RVCG loops, and alterations in loop direction in both the transverse and frontal planes-that are not easily discernible with a standard 12­lead ECG. This enhanced detection aids in understanding the mechanisms underlying electrocardiographic changes and may assist in managing patients when diagnostic uncertainties arise. METHODS: Thirty-three patients undergoing elective PTCA were studied before and after acute LAD (16 patients) or RCA (17 patients) occlusion, and their data were processed with new methods based on PBLs, WULs, and RVCGs. RESULTS: 1. In acute ischemia due to occlusion of the LAD and RCA, the most important current of injury occurs in the right to left axis. This axis is underestimated by the standard 12­lead ECG and only partially complemented by leads V3R and V4R. 2. The two-dimensional presentation detects a new sign (the omega sign), not detectable in the classic ECG, but almost always present in ischemia. It also allows for an accurate identification of the J point. 3. Ischemic R wave peak delay results in distortion and folding of the RVCG loop and causes displacement of the J point and the ST segment. 4. Wave inversion changes the loop direction in the transverse and frontal plane. CONCLUSIONS: Precordial bipolar leads, weighted unipolar leads, and regional vectorcardiograms provide essential information omitted by the standard 12­lead ECG.

Ventricular injury in acute left circumflex occlusion: Exploration using precordial bipolar leads and regional vectorcardiograms.

BACKGROUND: Precordial Bipolar Leads (PBLs) provide new electrocardiographic information derived from standard 12­lead ECG recordings. OBJECTIVES: To explore the usefulness of PBLs in patients with acute circumflex coronary artery (CxCA) occlusion. METHODS: Twelve patients undergoing elective percutaneous transluminal coronary angioplasty (PTCA) were studied before and after acute CxCA occlusion and their data were processed with new methods based on PBLs. RESULTS: The findings were: 1. In right PBL V2-V1, a strong systolic current of injury moving in the left-to-right direction coexists with a strong right-to-left current of injury displayed in left standard unipolar precordial leads (V4, V5 and V6). 2. Ischemic changes lead to a significant increase (approximately 10 ms) in the QRS duration in different leads, although changes in the QRS loop rotation and folding were absent. 3. In the transverse, sagittal, and frontal planes, superimposing two PBLs and the corresponding Regional VCG facilitates the location of the J-point. 4. In the Regional VCGs of this group of patients, J-point and ST segment shifts produced an image that reminds the Greek letter omega (Ω). 5. The currents of injury flowing in opposite directions could result in electrical cancellation that minimizes ECG changes in the standard 12­lead recordings. CONCLUSIONS: Computerized processing of digital, standard 12­lead ECG recordings, provides new valuable diagnostic data in patients with acute CxCA occlusion. The loops revealed important information related to systolic currents of injury. Because these methods use routine 12­lead ECG data, the procedure is based only in software applications. CONDENSED ABSTRACT: Twelve patients undergoing PTCA were studied before and after acute CxCA occlusion and their data were processed with the new methods based on Precordial Bipolar Leads (PBLs) to explore their usefulness. The results showed strong systolic currents of injury in different and sometimes opposite directions in the right-to-left axis and ischemic alterations in the time and amplitude of the QRS waves. The superimposition of two-dimensional coordinates planes (x-y, x-z or z-y) helped to locate the J-point and to display the Regional VCG omega sign (Ω) of myocardial injury. In conclusion, computerized processing of digital ECG data provides new diagnostic information in patients with acute CxCA occlusion.

Right ventricle injury in RCA occlusion: Exploration using precordial bipolar leads and surrogate vectorcardiograms.

BACKGROUND: Precordial Bipolar Leads (PBL) provide new electrocardiographic information derived from standard 12­lead ECG recordings. OBJECTIVES: To explore the usefulness of PBL in patients with acute right coronary artery (RCA) occlusion. METHODS: Sixteen patients undergoing elective percutaneous transluminal coronary angioplasty (PTCA) were studied before and after RCA occlusion and their data were processed with new methods based on PBL. RESULTS: The findings were: 1. In PBL V2-V1, strong systolic currents of injury moving in the left to right direction coexist with those directed towards leads II, III and aVF. 2. Changes in the time of the peaks of the QRS waves do not alter the duration of the QRS. 3. The QRS loops of the surrogate VCG generated show that, during ischemia, the time changes in the peak of the QRS waves displayed in one axis are the consequence of an increase in the amplitude of the waves observed in the perpendicular axis. 4. The use of two simultaneous dimensions (transverse and frontal planes) facilitates the location of the J-point. 5. In the surrogate VCGs of this group of patients, J-point and ST segment shifts produced an image that reminded the Greek letter omega (Ω). 6. The QRS wave changes, in time and amplitude, explained the rotational changes and the ischemic distortions of the surrogate VCG loops. CONCLUSIONS: Computerized processing of ECG data appears to provide new and valuable diagnostic data in patients with acute RCA occlusion. The loops revealed important information related to systolic currents of injury. Because these methods use routine 12­lead ECG data, the procedure is based only in software applications.

Incremental benefit of a novel signal recording system during mapping and ablation.

AIMS: Current electrophysiology signal recording and mapping systems have limited dynamic range (DR) and bandwidth, which causes loss of valuable information during acquisition of cardiac signals. We evaluated a novel advanced signal processing platform with the objective to obtain and assess additional information of clinical importance. METHODS AND RESULTS: Over 10 canines, we compared intracardiac recordings within all cardiac chambers, in various rhythms, in pacing and during radiofrequency (RF) ablation across two platforms; a conventional system and the PURE EP™ [(PEP); Bio Sig Technologies, Inc., Los Angeles, CA, USA]. Recording cardiac signals with varying amplitudes were consistently and reproducibly observed, without loss of detail or introduction of artefact. Further the amplitude of current of injury (COI) on the unipolar signals correlated with the instantaneous contact force (CF) recorded on the sensing catheter in all the animals (r2 = 0.94 in ventricle). The maximum change in the unipolar COI correlated with the change in local electrogram amplitude during non-irrigated RF ablation (r2 = 0.61 in atrium). Reduction in artefact attributable to pacing (20 sites) and noise during ablation (48 sites) was present on the PEP system. Within the PEP system, simultaneous display of identical signals, filtered differently, aided the visualization of discrete conduction tissue signals. CONCLUSION: Compared to current system, the PEP system provided incremental information including identifying conduction tissue signals, estimates of CF and a surrogate for lesion formation. This novel signal processing platform with increased DR and minimal front-end filtering may be useful in clinical practice.

Electrophysiological characteristics and clinical values of left bundle branch current of injury in left bundle branch pacing.

BACKGROUND: Left bundle branch pacing (LBBP) is emerging as a novel option for physiological ventricular pacing. The impact of current of injury (COI) at left bundle branch (LBB) has not been previously evaluated. METHODS: Consecutive patients with QRS duration less than 120 milliseconds referred for LBBP in whom LBB potentials were recorded were included from August 2018 to March 2019. We recorded LBB COI during LBBP and assessed its impact on the pacing parameters and complications during implantation and at short term follow-up. RESULTS: A total of 115 patients with an identifiable LBB potential at implant were included. LBB COI was confirmed in 77 (67.0%) of these patients. Three types of LBB COI were observed. LBB was captured in all patients at a pacing threshold less than 1.5 V/0.5 ms in COI(+) patients, while present in only 29 patients without an LBB COI(-) (100% vs 76.3%; P < .001). There was no significant difference between COI(+) and COI(-) patients in LBB bundle capture threshold (0.64 ± 0.24 vs 0.74 ± 0.26 V/0.5 ms). Selective LBBP was more common in COI(+) group than COI(-) group (54.5% vs 0%; P < .001). Pacing parameters were stable and no lead perforation or dislodgements were observed during follow-up. CONCLUSIONS: LBB COI is commonly observed during LBBP in cases with an identifiable LBB potential and can be associated with a low LBB capture threshold and demonstrable selective capture of the LBB acutely and during follow-up. A COI does not preclude safe and stable LBBP pacing.

Efficacy of the current of injury in envisaging the dislodgement of leads implanted in the right atrial septum or the right ventricular septum.

BACKGROUND: The implantation of leads in the right atrial septum (RAS) or the right ventricular septum (RVS) is technically challenging, and dislodgement occurs occasionally. This study aims to determine a predictor for the dislodgement of leads implanted in the RAS or RVS. METHODS: This retrospective cohort study enrolled 137 consecutive patients who underwent the cardiac implantable electronic devices implantation, using active fixation leads in the RAS and RVS. We compared the pacing threshold, R- or P-wave amplitude, slew rate, and presence of the current of injury (COI) between dislodged and nondislodged leads. RESULTS: We performed lead fixation for 74 and 125 times in the RAS and RVS, respectively. Atrial lead dislodgement occurred five times (6.8%) intraoperatively and five times (6.8%) postoperatively, whereas ventricular lead dislodgement occurred eight times (6.4%) intraoperatively and three times (2.4%) postoperatively. Although there were no lead parameters that showed a significant difference common to RAS lead and RVS lead, the presence of the COI was significantly different between nondislodged and dislodged leads in both the RAS and RVS (atrial leads: 57.8% vs 0%, P < 0.001; ventricular leads: 67.5% vs 9.1%, P < 0.001). The positive predictive value of COI presence for predicting no lead dislodgement was 100% and 98.7% in the RAS and RVS, respectively. CONCLUSION: Lead dislodgement is more likely when the COI is absent; documentation of COI should be pursued during lead implantation in challenging sites as the RAS and RVS.

Prediction of midterm performance of active-fixation leads using current of injury.

BACKGROUND: There are only limited prospective data on the clinical relevance of current of injury (COI) as a predictor of the midterm performance of active-fixation leads. This study sought to investigate whether it is possible to predict the midterm performance of active-fixation leads using COI recorded at the time of implantation. METHODS AND RESULTS: One hundred fifty patients (78 men; mean age, 63 ± 19 years) who received active-fixation pacing (n = 201) and defibrillator (n = 51) leads were studied. COI was measured from the intracardiac bipolar electrogram recorded at the time of lead implantation. The study outcome was good lead performance at 6 months, defined as P wave ≥ 1.5 mV, threshold <1.5 V for atrial lead, R-wave ≥ 5 mV, and threshold <1 V for ventricular lead. A total of 102 active-fixation atrial and 150 ventricular leads were implanted. During a 6-month follow-up, invasive intervention was required for seven atrial and seven ventricular leads. In multivariate analysis, COI was the only independent predictor of good outcome for the active-fixation atrial (odds ratio [OR]: 5.67, 95% confidence interval [CI]: 2.18-14.76, P = 0.001) and ventricular leads (OR: 3.99, 95% CI: 1.08-21.26, P = 0.002). Receiver-operating characteristic analysis identified ST-segment elevation ≥2.0 mV for the atrial leads (sensitivity, 75%; specificity, 89%) and ≥10.0 mV for the ventricular leads (sensitivity, 70%; specificity, 87%) as optimal cutoffs for good midterm performance. CONCLUSIONS: Midterm performance of active-fixation leads is predictable using COI recorded at the time of lead implantation. A ST-segment elevation ≥2.0 mV in the atrial leads and ≥10.0 mV in the ventricular leads are recommended to improve the lead performance at 6 months.

Making Sense of Electrical Stimulation: A Meta-analysis for Wound Healing.

Electrical stimulation as a mode of external enhancement factor in wound healing has been explored widely. It has proven to have multidimensional effects in wound healing including antibacterial, galvanotaxis, growth factor secretion, proliferation, transdifferentiation, angiogenesis, etc. Despite such vast exploration, this modality has not yet been established as an accepted method for treatment. This article reviews and analyzes the approaches of using electrical stimulation to modulate wound healing and discusses the incoherence in approaches towards reporting the effect of stimulation on the healing process. The analysis starts by discussing various processes adapted in in vitro, in vivo, and clinical practices. Later it is focused on in vitro approaches directed to various stages of wound healing. Based on the analysis, a protocol is put forward for reporting in vitro works in such a way that the outcomes of the experiment are replicable and scalable in other setups. This work proposes a ground of unification for all the in vitro approaches in a more sensible manner, which can be further explored for translating in vitro approaches to complex tissue stimulation to establish electrical stimulation as a controlled clinical method for modulating wound healing.

Transseptal Transition Patterns During Left Bundle Branch Area Lead Implantation.

BACKGROUND: Continuous deep septal pacing and signal recording during implantation of left bundle branch pacing (LBBP) lead enables to monitor beat-to-beat changes of electrocardiogram (ECG) and myocardial current of injury (COI) as the lead crosses the septum. OBJECTIVES: This study aimed to characterize patterns of continuous QRS, ST-T, and COI change for monitoring of the lead depth and instantaneous determination of the obtained capture type (LBBP vs left ventricular septal pacing [LVSP]). METHODS: The ECG and COI during lead implantation were scrutinized for sudden changes of V6 R-wave peak time, V1 initial and terminal R-wave amplitude, V3-V6 R-wave amplitude, repolarization pattern and S-wave amplitude in I, V5-V6, and COI drop. The sudden and gradual transition patterns were diagnosed depending on the presence or absence of the above beat-to-beat ECG phenomena, respectively. RESULTS: A total of 212 pacemaker recipients were analyzed; LBBP and LVSP were obtained in 77.4% and 22.6%, respectively. There were 4.7 ± 2.1 and 0.2 ± 0.6 beat-to-beat phenomena in LBBP and LVSP patients, respectively. The sudden transition pattern, recognized in 80.7%, had sensitivity and specificity for LBBP diagnosis of 98.8% and 81.2%, respectively. A sudden drop of COI (29.4 ± 8.5 mV to 12.8 ± 4.9 mV) was observed in 53.9% patients (LBBP was simultaneously obtained in 92.7%). CONCLUSIONS: Capture of left bundle branch during lead penetration is a beat-to-beat phenomenon. Two transseptal transition patterns were identified: 1) sudden, which is typical for obtaining LBBP; and 2) gradual, which is typical for obtaining LVSP. A sudden COI drop, a very observable phenomenon, also identified reaching the left subendocardial area.

Electrophysiological characteristics of septal perforation during left bundle branch pacing.

BACKGROUND: Left bundle branch pacing (LBBP) provides a low and stable threshold by direct capture of left bundle fibers on the left ventricular subendocardium. As the procedure involves the deployment of the pacing lead deep inside the septum, septal perforation is a potential complication. OBJECTIVES: The purpose of this study was to analyze the morphology of intracardiac electrograms and unipolar pacing parameters to identify septal perforation in patients undergoing LBBP. METHODS: Patients who had undergone successful LBBP between January 2020 to November 2021 were retrospectively included in the study. RESULTS: LBBP was attempted in 219 patients and was successful in 212 (96.8% success rate). Septal perforation during lead deployment was identified in 30 patients (14.1%). Peak troponin release was 188 ± 162 pg/mL. Mean unipolar impedance during septal perforation was 404.6 ± 19.9 Ω (400-450 Ω in 16 patients [53.3%]; <400 Ω in 14 patients [46.7%]). A cutoff <450 Ω for diagnosing septal perforation had high sensitivity (100%) and specificity (96.6%). Current of injury amplitude reduced from 15.4 ± 11.6 mV just before perforation to 0.9 ± 0.6 mV after perforation. Based on morphology, unfiltered unipolar electrograms were classified into 2 patterns: (1) type I (QS) seen in 20 patients (67%) due to complete perforation (mean unipolar impedance 402.5 ± 20.4 Ω); and (2) type II (RS/rS) seen in 10 patients (33%) due to partial perforation, with 80% showing capture (mean impedance 411 ± 21.3 Ω). All 30 patients underwent successful reimplantation at a new site. No patient developed lead dislodgment during mean follow-up of 9.9 ± 6.7 months. CONCLUSION: Although considered one of the concerns of LBBP, septal perforation, when recognized promptly during implantation by unipolar parameters and treated by reimplantation, would be benign and not associated with an unfavorable outcome.

Case report: Left bundle branch pacing guided by real-time monitoring of current of injury and electrocardiography.

Background: Left bundle branch (LBB) pacing (LBBP) has recently emerged as a physiological pacing mode. Current of injury (COI) can be used as the basis for electrode fixation position and detection of perforation. However, because the intermittent pacing method cannot monitor the changes in COI in real time, it cannot obtain information about the entire COI change process during implantation. Case summary: Left bundle branch pacing was achieved for treatment of atrioventricular block in a 76-year-old female. Uninterrupted electrocardiogram and electrogram were recorded on an electrophysiology system. In contrast to the interrupted pacing method, this continuous pacing and recording technique enables real-time monitoring of the change in ventricular COI and the paced QRS complex as the lead advances into the interventricular septum. During the entire screw-in process, the COI amplitude increased and then decreased gradually after reaching the peak, followed by a small but significant, rather than dramatic, decrease. Conclusion: This case report aims to demonstrate the clinical significance of changes in COI and QRS morphology for LBBP using real-time electrocardiographic monitoring and filtered and unfiltered electrograms when the lead is deployed using a continuous pacing technique. The technique could be used to confirm LBB capture and avoid perforation.

Current of injury is an indicator of lead depth and performance during left bundle branch pacing lead implantation.

BACKGROUND: Monitoring of lead depth is crucial to achieve left bundle branch pacing (LBBP) with a low capture threshold and avoid septal perforation, but lacks informative approach. OBJECTIVE: We aimed to prospectively assess the predictive value of current of injury on the occurrence of inadequate left bundle branch (LBB) capture threshold and acute septal perforation. METHODS: Consecutive patients who received LBBP were enrolled. ST-segment elevation ≥ 25% of intrinsic R-wave amplitude on the unipolar intracardiac electrogram was defined as a sign of distinct current of injury. An LBB capture threshold of <1.5 V/0.5 ms was considered acceptable. RESULTS: LBBP was attempted 513 times in 212 patients. The LBB capture threshold was more likely to improve to an acceptable level after 10 minutes in leads with initial (33 of 47 vs 0 of 8, with vs without) and residual (29 of 33 vs 4 of 14, with vs without) current of injury recorded on the tip electrode (P < .0001). Lead perforation during the procedure has occurred in 11 patients who had no current of injury noted on the tip electrode. The ratio of current of injury recorded on the tip electrode to that on the ring electrode was correlated to the lead depth determined by sheath angiography (Spearman correlation coefficient -0.624; P < .0001), and microperforation is highly possible when the ratio is decreased to <1 (sensitivity 100%; specificity 96.6%). CONCLUSION: Current of injury is a useful tool in forecasting LBBP lead depth and septal perforation, and it could facilitate the decision-making process when the initial LBB capture threshold is undesirable.

Wireless microcurrent stimulation improves blood flow in burn wounds.

RATIONALE: Skin breakdown, as in wounds, leads to an electric potential, defined as current of injury with the intent of wound closure. Burn wounds are defined by different zones of perfusion having a direct influence on further therapy (e.g. conservative management or skin grafting). We studied immediate, quantifiable effects of electric stimulation on skin perfusion in burn wounds. METHOD: Wireless Microcurrent Stimulation (WMCS) was utilised as an adjunct therapeutic modality in 10 patients with partial thickness burn wounds. Microcirculation in the skin was quantified with a Laser Doppler (LDI) before and after WMCS treatment. We included a control group of 10 healthy individuals. RESULTS: A single application of WMCS significantly increased mean flow, velocity and subsequently, haemoglobin and oxygen saturation in partial thickness burn wounds. In healthy skin these parameters increased, but were far less pronounced than in thermally injured skin. CONCLUSION: This study revealed, for the first time that non-contact WMCS improves blood flow in critically perfused partial thickness burn wounds without disturbing the wound or systemically affecting the patient and may represent a promising adjunct tool in burn treatment, with the potential of faster healing by enhanced perfusion of burn wounds and reduction of the zone of stasis. LEVEL OF EVIDENCE: III.