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Background: Despite the positive impact of implantable cardioverter defibrillators (ICDs) and wearable cardioverter defibrillators (WCDs) on prognosis, their implantation is often withheld especially in Japanese heart failure patients with reduced left ventricular ejection fraction (HFrEF) who have not experienced ventricular tachycardia (VT) or ventricular fibrillation (VF) for uncertain reasons. Recent advancements in heart failure (HF) medications have significantly improved the prognosis for HFrEF. Given this context, a critical reassessment of the treatment and prognosis of ICDs and WCDs is essential, as it has the potential to reshape awareness and treatment strategies for these patients. Methods: We are initiating a prospective multicenter observational study for HFrEF patients eligible for ICD in primary and secondary prevention, and WCD, regardless of device use, including all consenting patients. Study subjects are to be enrolled from 31 participant hospitals located throughout Japan from April 1, 2023, to December 31, 2024, and each will be followed up for 1 year or more. The planned sample size is 651 cases. The primary endpoint is the rate of cardiac implantable electronic device implementation. Other endpoints include the incidence of VT/VF and sudden death, all-cause mortality, and HF hospitalization, other events. We will collect clinical background information plus each patient's symptoms, Clinical Frailty Scale score, laboratory test results, echocardiographic and electrocardiographic parameters, and serial changes will also be secondary endpoints. Results: Not applicable. Conclusion: This study offers invaluable insights into understanding the role of ICD/WCD in Japanese HF patients in the new era of HF medication.
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INTRODUCTION: Transvenous lead extractions (TLEs) for cardiac implantable electronic device complications often encounter difficulties with strong adhesions to the myocardium or vessels. In this report, we introduce a novel "Four-Stage Rocket" technique for effective TLE in cases where conventional methods fail. METHODS AND RESULTS: Two challenging cases where conventional TLE methods failed were treated using a combination of four devices: Needle's Eye Snare, Agilis NxT Steerable Introducer, GlideLight Laser sheath, and GORE® DrySeal Flex Introducer sheath, employed via the inferior vena cava. The "Four-Stage Rocket" technique successfully detached firmly adhered leads near the tricuspid valve annulus, where the traditional superior vena cava approach was inadequate. CONCLUSION: The "Four-Stage Rocket" technique offers a potential alternative in complex TLE cases, aligning the laser direction with the adhesion detachment and reducing the tissue damage risk.
Subject(s)
Defibrillators, Implantable , Device Removal , Femoral Vein , Lasers , Pacemaker, Artificial , Humans , Device Removal/instrumentation , Device Removal/methods , Male , Aged , Treatment Outcome , Female , Middle Aged , Catheterization, Peripheral/instrumentationABSTRACT
Objective: Postoperative pain is a major issue with subcutaneous implantable cardioverter defibrillators (S-ICD). In 2020, we introduced intravenous patient-controlled analgesia (IV-PCA) in addition to the conventional, request-based analgesia for postoperative pain control in S-ICD. To determine the effect and safety, we quantitatively assessed the effect of IV-PCA after S-ICD surgery over conventional methods. Methods: During the study period, a total of 113 consecutive patients (age, 50.1 ± 15.5 years: males, 101) underwent a de novo S-ICD implantation under general anesthesia. While the postoperative pain was addressed with either request-based analgesia (by nonsteroid anti-inflammatory drugs, N = 68, dubbed as "PCA absent") or fentanyl-based IV-PCA in addition to the standard care (N = 45, dubbed as "PCA present"). The degree of postoperative pain from immediately after surgery to 1 week were retrospectively investigated by the numerical rating scale (NRS) divided into four groups at rest and during activity (0: no pain, 1-3: mild pain, 4-6: moderate pain, 7-10: severe pain). Results: Although IV-PCA was removed on Day 1, it was associated with continued better pain control compared to PCA absent group. At rest, the proportion of patients expressing pain (mild or more) was significantly lower in the PCA present group from Day 0 to Day 4. In contrast to at rest, a better pain control continued through the entire study period of 7 days. No serious adverse events were observed. A few patients experienced nausea in both groups and the inter-group difference was not found significant. Conclusion: IV-PCA suppresses postoperative pain in S-ICD without major safety concerns.
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[This corrects the article DOI: 10.1007/s12070-022-03257-0.].
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BACKGROUND: The lesion index (LSI) helps predict the lesion size and is widely used in ablation of various types of arrhythmias. However, the influence of the ablation settings on the lesion formation and incidence of steam pops under the same LSI value remains unclear. METHODS: Using a contact force (CF) sensing catheter (TactiCath™) in an ex vivo swine left ventricle model, RF lesions were created with a combination of various power steps (30 W, 40 W, 50 W) and CFs (10 g, 20 g, 30 g, 40 g, 50 g) under the same LSI values (5.2 and 7.0). The correlation between the lesion formation and ablation parameters was evaluated. RESULTS: Ninety RF lesions were created under a target LSI value of 5.2, and eighty-four were developed under a target LSI value of 7.0. In the LSI 5.2 group, the resultant lesion size widely varied according to the ablation power, and a multiple regression analysis indicated that the ablation energy delivered was the best predictor of the lesion formation. To create a lesion depth > 4 mm, an ablation energy of 393 J is the best cutoff value, suggesting a possibility that ablation energy may be used as a supplemental marker that better monitors the progress of the lesion formation in an LSI 5.2 ablation. In contrast, such inconsistency was not obvious in the LSI 7.0 group. Compared with 30 W, the 50-W ablation exhibited a higher incidence of steam pops in both the LSI 5.2 and 7.0 groups. CONCLUSIONS: The LSI-lesion size relationship was not necessarily consistent, especially for an LSI of 5.2. To avoid any unintentional, weak ablation, the ablation energy may be a useful supportive parameter (393 J as a cutoff value for a 4-mm depth) during ablation with an LSI around 5.2. Thanks to a prolonged ablation time, the LSI-lesion size relationship is consistent for an LSI of 7.0. However, it is accompanied by a high incidence of steam pops. Care should be given to the ablation settings even when the same LSI value is used.
Subject(s)
Catheter Ablation , Swine , Animals , Steam , Heart Ventricles/surgery , Arrhythmias, Cardiac/surgeryABSTRACT
Average beat interval (BI) and beat interval variability (BIV) are primarily determined by mutual entrainment between the autonomic-nervous system (ANS) and intrinsic mechanisms that govern sinoatrial node (SAN) cell function. While basal heart rate is not affected by age in humans, age-dependent reductions in intrinsic heart rate have been documented even in so-called healthy individuals. The relative contributions of the ANS and intrinsic mechanisms to age-dependent deterioration of SAN function in humans are not clear. We recorded ECG on patients (n = 16 < 21 years and n = 23 41-78 years) in the basal state and after ANS blockade (propranolol and atropine) in the presence of propofol and dexmedetomidine anesthesia. Average BI and BIV were analyzed. A set of BIV features were tested to designated the "signatures" of the ANS and intrinsic mechanisms and also the anesthesia "signature". In young patients, the intrinsic mechanisms and ANS mainly contributed to long- and short-term BIV, respectively. In adults, both ANS and intrinsic mechanisms contributed to short-term BIV, while the latter also contributed to long-term BIV. Furthermore, anesthesia affected ANS function in young patients and both mechanisms in adult. The work also showed that intrinsic mechanism features can be calculated from BIs, without intervention.
Subject(s)
Atropine , Sinoatrial Node , Adult , Humans , Propranolol , Heart Rate/physiology , Autonomic Nervous System/physiology , ElectrocardiographyABSTRACT
There is a host of research on the structure of working memory (WM) and its relationship with intelligence in adults, but only a few studies have involved children. In this paper, several different WM models were tested on 170 Japanese school children (from 7 years and 5 months to 11 years and 6 months). Results showed that a model distinguishing between modalities (i.e., verbal and spatial WM) fitted the data well and was therefore selected. Notably, a bi-factor model distinguishing between modalities, but also including a common WM factor, presented with a very good fit, but was less parsimonious. Subsequently, we tested the predictive power of the verbal and spatial WM factors on fluid and crystallized intelligence. Results indicated that the shared contribution of WM explained the largest portion of variance of fluid intelligence, with verbal and spatial WM independently explaining a residual portion of the variance. Concerning crystallized intelligence, however, verbal WM explained the largest portion of the variance, with the joint contribution of verbal and spatial WM explaining the residual part. The distinction between verbal and spatial WM could be important in clinical settings (e.g., children with atypical development might struggle selectively on some WM components) and in school settings (e.g., verbal and spatial WM might be differently implicated in mathematical achievement).
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Background: The upper extremity siding cardiac implantable electrical device tends to have a limited range of motion during the perioperative period; however, the underlying reason lacks scientific evidence. This study aimed to investigate the safety of the two methods (stepwise or early) of postoperative early upper extremity rehabilitation. Methods: We retrospectively investigated 650 consecutive patients with a new implantable pacemaker (PM), implantable cardioverter-defibrillator (ICD), cardiac resynchronization therapy (CRT), or generator exchange between March 2017 and December 2020.The limitation program was conducted from March 2017 to March 2018. The intervention program started as a stepwise protocol in April 2018 and was switched to an early protocol in December 2019. Results: This study analyzed 591 patients, excluding 59 who met the exclusion criteria. The mean age was 76.0 (69.0-82.0) years; 412 (69.7%) patients had a PM, 79 (13.4%) had an ICD, and 100 (16.9%) utilized CRT. There were 155 patients in the limitation protocol, 251 in the stepwise protocol, and 185 patients in the early protocol groups. Postoperative complications occurred in 53 (9.0%) patients. There was no significant difference in the incidence of all complications between the three groups (16 patients [10.3%] vs. 26 patients [10.4%] vs. 11 patients [5.9%]). Shoulder exercise-related complications were defined as hematoma (p = .94), lead dislodgement (p = .16), and increased pacing threshold (p = .23). General complications included wound infection (p = .51), pneumothorax (p = .27), tamponade (p = .07), and deep venous thrombosis (p = .26). Conclusion: Raising of the upper extremity siding cardiac implantable electrical devices above the head did not compromise postoperative safety.
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Total endoscopic thyroidectomy (TET) using low CO2 insufflation provides cosmetic advantage, excellent working space and visibility. On the contrary, suctioning blood or mist/smoke produced by energy device application causes narrowing of working space especially in neck surgery. In this regard, AirSeal intelligent flow system would be particularly suitable in TET. However, the benefit of AirSeal is unknown in TET unlike abdominal surgery. Therefore, the impact of AirSeal was evaluated in TET in this study. Twenty patients who underwent total endoscopic hemithyroidectomy were retrospectively analyzed. Insufflation was conducted by either conventional or AirSeal system according to the surgeon's preference. Short-term surgical outcomes including operation time, bleeding, frequency of scope cleaning, and disappearance of subcutaneous emphysema were compared as well as actual visibility. AirSeal application dramatically reduced obstacle smoke/mist and prevented narrowing working space by suctioning. Frequency of scope cleaning was significantly less in AirSeal group than that in conventional group (p = 0.016). In patients with nodule < 5 cm, intraoperative hemorrhage was less in AirSeal group than that in the counterpart (p = 0.077) regardless of larger nodule size in AirSeal group (p = 0.058). Notably, subcutaneous emphysema around surgical cavity disappeared significantly earlier in AirSeal group than in the counter parts (p = 0.019). On the contrary, AirSeal application did not shorten operation time in the current study. AirSeal provided excellent visibility and seamless operation. AirSeal has great potential to decrease not only surgeon's stress but surgical invasion on patients. The results in this study give rational to AirSeal application to TET. Supplementary Information: The online version contains supplementary material available at 10.1007/s12070-022-03257-0.
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Background: Recently, a novel contact force (CF) sensing catheter with mesh-shaped irrigation tip (TactiFlex SE, Abbott) was invented and is expected to be useful for safe and effective radiofrequency ablation. However, this catheter's detailed characteristics of the lesion formation are unknown. Methods: With an in vitro model, TactiFlex SE and its predecessor, FlexAbility SE, were used. A cross-sectional analysis of 60 s lesions (combination of various energy power settings [30, 40, and 50 W], and CFs [10, 30, and 50 g]) and longitudinal analysis (combination of various powers [40 or 50 W], CFs [10, 30, and 50 g] and ablation times [10, 20, 30, 40, 50, and 60 s]) of both catheters were analyzed and compared. Results: One hundred eighty RF lesions were created in protocol 1 and 300 in protocol 2. The lesion formation, impedance changes, and steam pops characteristics were similar between the two catheters. Higher CFs were related to higher incidences of steam pops. A nonlinear, time-dependent increase in the lesion depth and diameter was observed for all power and CF settings, and linear, positive correlations between the RF delivery time and lesion volume were observed for all power settings. Compared with 40 W, a 50 W ablation created greater lesions. Longer durations with higher CF settings had a higher steam pop incidence. Conclusions: The lesion formation and incidence of steam pops with TactiFlex SE and FlexAbility SE were similar. A 40 or 50 W ablation with careful CF control not to exceed 30 g in addition to monitoring impedance drops was required to safely create transmural lesions.
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BACKGROUND: A novel Diamond Temp™ (DT; Medtronic, Minneapolis, MN, USA) catheter has enabled performing a surface temperature-controlled ablation. The chemical vapor deposition diamond of the ablation catheter acts as a thermal radiator and is useful for effective cooling of the ablation catheter tip. However, a detailed analysis of the lesion formation with this catheter remains unknown. METHODS: DT catheters were used in an excised swine heart experimental model. A cross-sectional analysis of 60-s lesions [a combination of various energy power settings (30, 40, and 50â¯W), and various contact forces (CF) (10, 30, and 50â¯g)] and a longitudinal analysis [a combination of various powers (40â¯W or 50â¯W), various CFs (10, 30, and 50â¯g), and various ablation times (5â¯s, 10â¯s, 15â¯s, 20â¯s, 25â¯s, 30â¯s, and 60â¯s)] of the DT catheter were analyzed. RESULTS: The maximum lesion depth, maximum diameter, and lesion volume with a 10â¯g ablation were significantly lower than those with a 30â¯g or 50â¯g ablation. There were no significant differences in the lesion formation between the 30â¯g ablation and 50â¯g ablation under each radiofrequency (RF) power setting. The impedance drops with steam pops were significantly greater than those without steam pops (pop (+) vs. pop (-), 26.2⯱â¯6.6 Ohm vs. 18.4⯱â¯7.1 Ohm, pâ¯=â¯0.0001). A non-linear, time-dependent increase in the lesion depth and diameter was observed for all power and CF settings. Comparing the lesion depth and diameter between 40â¯W and 50â¯W under the same CF setting and same ablation time, most of the settings had no significant difference. CONCLUSION: Ablation lesions created with the DT catheter were similar to other catheters. Similar ablation lesions were created with the 40â¯W or 50â¯W ablation under the same CF setting and same ablation time. Regardless of the ablation power, monitoring the general impedance during the RF application was indispensable for a safe procedure.
Subject(s)
Catheter Ablation , Steam , Animals , Swine , Cross-Sectional Studies , Catheters , Heart , Heart Ventricles/pathology , Catheter Ablation/methods , Equipment DesignABSTRACT
INTRODUCTION: Local impedance (LI) parameters of IntellaNav STABLEPOINT for successful pulmonary vein isolation (PVI) of atrial fibrillation (AF) remain unclear. The purpose of this study was to seek LI data achieving successful PVI. METHODS: Consecutive AF patients who underwent catheter ablation with STABLEPOINT were prospectively enrolled in two centers. PVI was performed under a constant 35-or 40-watt power, 20-s duration, and >5-g contact force. The operators were blinded to the LI data. The characteristics of all ablation points with/without conduction gaps (Unsuccess or Success tags) after the first-attempt PVI were evaluated for the right/left PVs and anterior/posterior wall (RPV/LPV and AW/PW, respectively), and cutoff values of LI data were calculated for successful lesion formation. RESULTS: A total of 5257 ablation points in 102 patients (65 [58-72] years old, 65.7% male) were evaluated. The LI drop values were higher in the Success tags than Unsuccess tags on the LPV-AW and RPV-AW/PW (p < .001), except for the LPV-PW (p = .105). The %LI drop values (LI drop/initial LI) were higher for the Success tags in all areas (15.8 [12.2%-19.6%] vs. 11.6 [9.7%-15.6%] in LPV-AW: p < .001, 15.0 [11.5%-19.3%] vs. 11.4 [8.7%-17.3%] in LPV-PW: p = .035, 15.3 [11.5%-19.4%] vs. 9.9 [8.1%-13.7%] in RPV-AW: p < .001, and 13.3 [10.1%-17.4%] vs. 8.1 [6.3%-9.5%] in RPV-PW, p < .001). The LI drop and %LI drop cutoff values were 20.0 ohms and 11.6%, respectively. CONCLUSIONS: An insufficient LI drop with STABLEPOINT was associated with a gap formation during PVI, and the best cutoff values for the LI drop and %LI drop were 20.0 ohms and 11.6%, respectively.
Subject(s)
Atrial Fibrillation , Catheter Ablation , Pulmonary Veins , Humans , Male , Middle Aged , Aged , Female , Atrial Fibrillation/diagnosis , Atrial Fibrillation/surgery , Pulmonary Veins/surgery , Electric Impedance , Treatment Outcome , Heart Rate , Catheter Ablation/adverse effects , RecurrenceABSTRACT
BACKGROUND: In adult patients, subcutaneous implantable cardioverter defibrillators (S-ICDs) have been reported to be non-inferior to transvenous ICDs with respect to the incidence of device-related complications and inappropriate shocks. Only a few reports have investigated the efficacy of S-ICDs in the pediatric field. This study aimed to investigate the utility and safety of S-ICDs in patients ≤18 years old. METHODS: This study was a multicenter, observational, retrospective study on S-ICD implantations. Patients <18 years old who underwent S-ICD implantations were enrolled. The detailed data on the device implantations and eligibility tests, incidence of appropriate- and inappropriate shocks, and follow-up data were assessed. RESULTS: A total of 62 patients were enrolled from 30 centers. The patients ranged in age from 3 to 18 (median 14 years old [IQR 11.0-16.0 years]). During a median follow up of 27 months (13.3-35.8), a total of 16 patients (26.2%) received appropriate shocks and 13 (21.3%) received inappropriate shocks. The common causes of the inappropriate shocks were sinus tachycardia (n = 4, 30.8%) and T-wave oversensing (n = 4, 30.8%). In spite of the physical growth, the number of suitable sensing vectors did not change during the follow up. No one had any lead fractures or device infections in the chronic phase. CONCLUSIONS: Our study suggested that S-ICDs can prevent sudden cardiac death in the pediatric population with a low incidence of lead complications or device infections. The number of suitable sensing vectors did not change during the patients' growth.
Subject(s)
Defibrillators, Implantable , Adult , Humans , Child , Adolescent , Retrospective Studies , Treatment Outcome , Defibrillators, Implantable/adverse effects , Death, Sudden, Cardiac/epidemiology , Death, Sudden, Cardiac/prevention & control , Arrhythmias, CardiacABSTRACT
Sub-optimal atrioventricular delay (AVD) is one of the main causes of non-responder for cardiac resynchronization therapy (CRT). Recently, device-based algorithms (DBAs) that provide optimal AVD based on intracardiac electrograms, have been developed. However, their long-term effectiveness is still unknown. This study aims to investigate the effect of optimizing AVD using DBAs over a long period, on the prognosis of patients undergoing CRT. A total of 118 patients who underwent CRT at our hospital between April 2008 and March 2018, were retrospectively reviewed; 61 of them with optimizing AVD using DBAs were classified into the treated group (group 1), and the remaining 57 were classified into the control group (group 2). The median follow-up period was 46.0 months. The responder and survival rate in group 1 were significantly better than those in group 2 (group 1 vs. group 2: responder rate = 64% vs. 46%, p = 0.046; survival rate: 85.2% vs. 64.9%, p = 0.02). Moreover, investigating only the non-responder population showed that group 1 had an improved survival rate compared to group 2 (group 1 vs. group 2 = 72.7% vs. 45.1%, p = 0.02). Optimizing AVD using DBAs was a significant contributor to the improved survival rate in CRT non-responders in multivariate analysis (HR 3.6, p = 0.01). In conclusion, the long-term optimizing AVD using DBAs improved the survival rate in CRT and the prognosis of CRT non-responders, as well.
Subject(s)
Cardiac Resynchronization Therapy , Heart Failure , Humans , Retrospective Studies , Heart Failure/diagnosis , Heart Failure/therapy , Prognosis , Algorithms , Treatment OutcomeABSTRACT
Background: The local impedance (LI) is an emerging technology that monitors tissue-catheter coupling during radiofrequency (RF) ablation. The relationships between the LI, RF delivery time, and lesion formation remain unclear. Methods: Using an LI-enabled RF catheter in an ex vivo experimental model, RF lesions were created combined with various steps in the power (40 and 50 W), CF (10 g, 30 g, and 50 g), and time (10s, 20s, 30s, 40s, 50s, and 60s at 40 W and 5 s, 10s, 20s, 30s, 40s, 50s, and 60s at 50 W). The correlations between the LI drop, lesion size, and RF delivery time were evaluated. The rate of change in the time-dependent gain in the LI, depth, and diameter and the time to reach 90% decay of the peak dY/dT (time to 90% decay) were assessed. Results: The correlation between the LI drop and ablation time revealed non-linear changes. The time to a 90% decay in the LI drop differed depending on the RF ablation setting and was always shorter with the 50 W setting than 40 W setting. The LI drop always correlated with the lesion formation under all ablation power settings. Deeper or wider lesions were predominantly created within the time to 90% decay of the LI drop. Conclusion: The LI drop was useful for predicting lesion sizes. Deeper or wider lesions cannot be obtained with a longer ablation than the 90% decay time of the LI drop. A shorter ablation than the 90% decay time of the LI drop would be preferable for an effective ablation.
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Swallowed rice cake (mochi) without chewing retained in the stomach intactly. We successfully treated the hardened mochi without surgery. Eye-catching images showed as many as 10 intact mochi in the stomach and endoscopic crushing procedure.
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Cardiac implantable electrical devices (CIED) such as pacemakers, implantable cardioverter defibrillators, and cardiac resynchronization therapies are generally recommended for older patients and those with severe heart failure (HF). However, there is currently a lack of evidence on the relationship between frailty and readmission rates among patients with CIED. This study investigated whether preoperative frailty influenced readmission rates among patients with CIED over a one-year period following implantation. The study retrospectively analyzed 101 patients who underwent CIED implantations. To compare frailty-based differences in their characteristics and readmission rates, these participants were categorized into frailty and non-frailty groups via the modified frailty index (mFI). The frailty group had a significantly higher readmission rate than the non-frailty group (non-frailty group vs. frailty group = 1 vs. 8 patients: P < 0.05). Further, a multivariate analysis showed that frailty was a significant readmission factor. Based on individual analyses with/without histories of HF, the readmission rate also tended to be higher among individuals considered frail via the mFI (readmission rate in HF patients: non-frailty group vs. frailty group = 1 vs. 5 patients: P = 0.65; non-HF patients: non-frailty group vs. frailty group = 0 vs. 3 patients: P = 0.01). Participants with preoperative frailty showed higher readmission rates within a one-year period following implantation compared to those without preoperative frailty. This tendency was consistent regardless of HF history. The mFI may thus help predict readmission among patients with CIED.
Subject(s)
Cardiac Resynchronization Therapy , Defibrillators, Implantable , Frailty , Heart Failure , Humans , Patient Readmission , Retrospective Studies , Risk Factors , Frailty/therapy , Heart Failure/surgeryABSTRACT
BACKGROUND: A novel irrigation catheter (QDOT MICRO™) has been introduced, which enables a surface temperature-controlled ablation combined with tip cooling. However, the detailed description of its complex behavior and effect on the incidence of pops and lesion formation remains elusive. This study aimed to systematically investigate the ablation characteristics, feedback behavior, and incidence of steam pops in a simplified ex vivo swine model. METHODS: Using swine ventricular tissue perfused with saline at 37°C, we systematically created lesions with 4×3 combinations of the wattage (20, 30, 40, and 50 W) and contact force (CF, 10, 30, and 50 g). Ablation was continued for either 120 s or until a steam pop occurred and repeated 10 times with each setting. The lesion geometry, ablation index, feedback dynamics, and conditions underlying the steam pops were measured and analyzed. RESULTS: Steam pops occurred particularly frequently in combinations of a low CF and high power (10 g vs. 30 g+50 g [p < .0001]; 40 W+50 W vs. 20 W+30 W [p < .0001]). Failure to activate a feedback process was associated with a 5.1 times higher incidence of steam pops (21/109 vs.11/11, [95% CI 3.499-7.716], p < .0001). The wattage feedback was particularly evident with a high CF (30 and 50 g) and high initial wattage (40 and 50 W). The average delivered wattage at 27 W predicted the occurrence of steam pops. CONCLUSION: The temperature-controlled ablation with the QDOT MICRO™ demonstrated a complex feedback behavior, which contributed to a reduced incidence of steam pops and prolonged lead time to the pops.