Identification of Caries Risk Determinants in Toddlers: Results of the GUSTO Birth Cohort Study.

The aim of this study was to identify risk determinants leading to early childhood caries (ECC) and visible plaque (VP) in toddlers. Data for mother-child pairs participating in the Growing Up in Singapore towards Healthy Outcomes (GUSTO) birth cohort were collected from pregnancy to toddlerhood. Oral examinations were performed in 543 children during their clinic visit at 24 months to detect ECC and VP. Following logistic regression, ECC and VP were jointly regressed as primary and secondary outcomes, respectively, using the bivariate probit model. The ECC prevalence was 17.8% at 2 years of age, with 7.3% of children having a VP score >1. ECC was associated with nighttime breastfeeding (3 weeks) and biological factors, including Indian ethnicity (lower ECC rate), higher maternal childbearing age and existing health conditions, maternal plasma folate <6 ng/mL, child BMI, and the plaque index, while VP was associated with psychobehavioral factors, including the frequency of dental visits, brushing frequency, lower parental perceived importance of baby teeth, and weaning onto solids. Interestingly, although a higher frequency of dental visits and toothbrushing were associated with lower plaque accumulation, they were associated with increased ECC risk, suggesting that these established caries-risk factors may be a consequence rather than the cause of ECC. In conclusion, Indian toddlers may be less susceptible to ECC, compared to Chinese and Malay toddlers. The study also highlights a problem-driven utilization pattern of dental services (care sought for treatment) in Singapore, in contrast to the prevention-driven approach (care sought to prevent disease) in Western countries.

What the child "SAID" to the dentist: A UK randomized controlled trial.

BACKGROUND: The electronic Survey of Anxiety and Information for Dentists (eSAID) allows children to tell dentists about their feelings and coping preferences. It is a computer "quiz" with 26 questions and free-text responses that produces a report for the children that they can then hand to their dentist. This is the first study to report the use of eSAID in a hospital paediatric dental clinic. METHODS: This was a randomized controlled trial to evaluate whether children thought that eSAID benefitted them, made them less anxious, and improved cooperation and their treatment satisfaction. Fifty-one children aged 8-13 years were randomized to complete either eSAID or a control version in the waiting room before their scheduled dental appointment. The study group had a 26-item questionnaire; the control had only two items. Both groups scored their anxiety on a 7-point anxiety scale at the start and again at the end of the quiz. All subjects handed the resultant eSAID report as a printout to their dentist. Dental treatment proceeded as planned. After treatment, each child reported how they thought the eSAID quiz had benefitted them by scoring on a 10 cm Visual Analogue Scale and their satisfaction on the Modified Treatment Evaluation Inventory. The operating dentists scored the children's cooperation using a 10 cm Visual Analogue Scale. RESULTS: Overall, the baseline anxiety levels were low (study: mean 1.2; control: mean 1.5). The study group's post-survey anxiety reduced by 0.4, whereas controls' increased by 0.2; this difference is statistically significant (p = .04). However, it made no difference to the children's self-reported benefit (p = .30), satisfaction (p > .05), or cooperation (p = .34). CONCLUSIONS: eSAID reduced pre-treatment anxiety but made no difference to children's perceived benefit, satisfaction, or cooperation. Future study should include known anxious children.

Limit on Tensor Currents from

In the standard model, the weak interaction is formulated with a purely vector-axial-vector (V-A) structure. Without restriction on the chirality of the neutrino, the most general limits on tensor currents from nuclear ß decay are dominated by a single measurement of the ß-ν[over ¯] correlation in ^{6}He ß decay dating back over a half century. In the present work, the ß-ν[over ¯]-α correlation in the ß decay of ^{8}Li and subsequent α-particle breakup of the ^{8}Be^{*} daughter was measured. The results are consistent with a purely V-A interaction and in the case of couplings to right-handed neutrinos (C_{T}=-C_{T}^{'}) limits the tensor fraction to |C_{T}/C_{A}|^{2}<0.011 (95.5% C.L.). The measurement confirms the ^{6}He result using a different nuclear system and employing modern ion-trapping techniques subject to different systematic uncertainties.

ß-delayed neutron spectroscopy using trapped radioactive ions.

A novel technique for ß-delayed neutron spectroscopy has been demonstrated using trapped ions. The neutron-energy spectrum is reconstructed by measuring the time of flight of the nuclear recoil following neutron emission, thereby avoiding all the challenges associated with neutron detection, such as backgrounds from scattered neutrons and γ rays and complicated detector-response functions. (137)I(+) ions delivered from a (252)Cf source were confined in a linear Paul trap surrounded by radiation detectors, and the ß-delayed neutron-energy spectrum and branching ratio were determined by detecting the ß(-) and recoil ions in coincidence. Systematic effects were explored by determining the branching ratio three ways. Improvements to achieve higher detection efficiency, better energy resolution, and a lower neutron-energy threshold are proposed.

Tensor interaction limit derived from the α-ß-ν[over ¯] correlation in trapped 8Li ions.

A measurement of the α-ß-ν[over ¯] angular correlation in the Gamow-Teller decay (8)Li→(8)Be(*)+ν[over ¯]+ß, (8)Be(*)→α+α has been performed using ions confined in a linear Paul trap surrounded by silicon detectors. The energy difference spectrum of the α particles emitted along and opposite the direction of the ß particle is consistent with the standard model prediction and places a limit of 3.1% (95.5% confidence level) on any tensor contribution to the decay. From this result, the amplitude of any tensor component C(T) relative to that of the dominant axial-vector component C(A) of the electroweak interaction is limited to |C(T)/C(A)|<0.18 (95.5% confidence level). This experimental approach is facilitated by several favorable features of the (8)Li ß decay and has different systematic effects than the previous ß-ν[over ¯] correlation results for a pure Gamow-Teller transition obtained from studying (6)He ß decay.

Cenicriviroc, a dual CCR2 and CCR5 antagonist leads to a reduction in plasma fibrotic biomarkers in persons living with HIV on antiretroviral therapy.

Background: Chronic HIV is associated with increased inflammation and tissue fibrosis despite suppressive antiretroviral therapy (ART). Monocytes and macrophages have been implicated in the pathogenesis of fibrosis, facilitated by chemokine receptor interactions.Methods: We assessed systemic fibrotic biomarkers (transforming growth factor beta-1 [TGF-ß1], thrombospondin-1 [TSP-1], C-terminal pro-peptide of collagen type I [CICP], and IL-11) in banked plasma from a previously published 24-week open-label trial of cenicriviroc (CVC), a dual CCR2/CCR5 antagonist, among persons living with HIV (PLWH) on stable ART with undetectable plasma HIV RNA (<50 copies/mL). Fibrotic markers were assessed by ELISA and Luminex. Untreated HIV-seronegative individuals (n = 6) of similar age and demographics served as a comparator group.Results: Median age of PLWH was 55 years. At baseline, PLWH had higher median TGF-ß1 (2.11 vs 1.62 ng/mL, p = 0.01), TSP-1 (236.74 vs 83.29 ng/mL, p < 0.0001), and CICP (200.46 vs 111.28 ng/mL, p = 0.01), but lower IL-11 (36.00 vs 53.74 pg/mL, p = 0.01) compared to HIV-uninfected individuals. Over 24 weeks, median TGF-ß1 (-0.74 ng/mL, p = 0.006), TSP-1 (-52.12 ng/mL, p < 0.0001), and CICP (-28.12 ng/mL, p < 0.0001) decreased and IL-11 (28.98 pg/mL, p < 0.0001) increased in PLWH. At week 24, TGF-ß1, CICP, and IL-11 were similar between the two groups (p > 0.05), while TSP-1 remained elevated in PLWH (p = 0.009) compared to controls.Conclusions: PLWH had higher levels of the plasma fibrotic markers TGF-ß1, TSP-1, and CICP. After 24 weeks of CVC, fibrotic markers generally returned to levels comparable to HIV-uninfected controls. Dual CCR2 and CCR5 blockade may ameliorate the detrimental fibrotic events that persist in treated HIV.

Relationship between ionic perturbations and electrophysiologic changes in a canine Purkinje fiber model of ischemia and reperfusion.

Standard and ion-sensitive microelectrodes were used to identify the basis of electrophysiologic changes that occur in canine cardiac Purkinje fibers superfused with "ischemic" solution (40 min) and then returned to standard Tyrode's solution. Maximum diastolic potential (EMDP) decreased (-92.6 +/- 2.4 to -86.0 +/- 4.0 mV; n = 19; P less than 0.001) during exposure to "ischemia," and after reperfusion, rapidly hyperpolarized to -90.0 +/- 4.7 (2 min) and then depolarized to -47.0 +/- 7.5 mV (10 min; P less than 0.001). No significant change in intracellular K activity (alpha ik) was noted throughout. Extracellular K activity (alpha ek) changed only during reperfusion, reaching a nadir at 5 min (3.5 +/- 0.4 to 2.6 +/- 0.5 mM, P less than 0.03), and thus can not account for the decrease in EMDP during reperfusion. Mean alpha iNa increased (8.7 +/- 1.3 to 10.9 +/- 1.9 mM; n = 10; P less than 0.01) during ischemia, but rapidly declined during reperfusion to 5.1 +/- 2.2 mM (10 min; P less than 0.01). Exposure to acetylstrophanthidin (4-5 x 10(-7) M) during the final 10 min of ischemia increased alpha iNa to 19.9 +/- 3.8 mM (n = 5), which was unchanged at 5 min of reperfusion. This suggests that Na-K pump inhibition during ischemia was minimal and that the pump was stimulated early during reperfusion, accounting for the initial transient hyperpolarization. Resting tension did not change significantly during exposure to ischemia; however, return to control Tyrode's solution caused a marked rise to 11.3 +/- 9.9 mg/mm2 (n = 13, P less than 0.001). This is consistent with a calcium overload state during reperfusion. The depolarization seen during reperfusion may result from activation of a Ca-activated, nonselective cation channel or enhanced electrogenic Na/Ca exchange.

Oral cleanliness of 12-13-year-old and 15-year-old school children of Sunsari District, Nepal.

The aim of the study was to evaluate the oral cleanliness of school children in the District of Sunsari, Nepal. A multi-stage random sampling oral epidemiological survey was conducted in private and government, urban, rural town and rural village schools in 15 illakas of Sunsari District, Eastern Nepal. A total of 600, 12-13-year-old and 600 15-year-old school children were examined by trained examiners using the simplified oral hygiene index (OHI-S). The average age-group, debris and calculus index scores were combined to obtain the simplified oral hygiene index (OHI-S). The mean OHI-S scores were compared and evaluated using the parametric t-test for two independent samples. The mean OHI-S for urban 12-13-year-old school children was 0.98 compared to 1.34 for school children of rural towns and 1.44 for school children of rural villages and these differences in mean OHI-S were statistically significant (P < 0.005). In the 15-year-old age group, urban school children had a mean OHI-S score of 1.00 compared to 1.37 for rural towns and 1.43 for rural villages. The variance in the mean OHI-S scores were statistically significant (P < 0.005). The overall level of cleanliness in the school children surveyed was good. Children of urban schools had the lowest scores followed by school children from rural towns and then rural villages. When the mean OHI-S scores were compared with the DMFT scores, there was an inverse relationship between oral cleanliness and dental caries. Frequency of sugar consumption and the availability and affordability of fluoridated toothpaste may be important factors in the development of dental caries than oral cleanliness.

Health-related quality of life relative to clinical outcomes in patients with atrial fibrillation treated with ventricular rate stabilisation pacing.

AIMS: It is uncertain whether patient perception of atrial fibrillation (AF) is based on the fast ventricular rate as such or the irregularity of the ventricular responses. This trial was designed to confirm the effectiveness of a ventricular rate stabilisation (VRS) algorithm in reducing ventricular irregularity during permanent pacing in patients with AF and to assess the patient preference and effect on quality of life (QoL). METHODS: In this multicentre single-blind randomised crossover trial, 184 patients with drug-refractory permanent (n=91) or paroxysmal (n=93) AF received a VVI(R) or DDD(R) pacemaker respectively and were paced in a randomised sequence with VRS on or off for two months. Clinical assessments (QoL, New York Heart Association (NYHA) classification, echocardiography, six-minute walk test and Holter recording) were carried out at baseline, at randomisation and after each crossover period. QoL assessment was performed using Aquarel, a new disease-specific QoL questionnaire for pacemaker patients, the Short Form 36 survey (SF-36), the Duke Activity Status Index (DASI) and the Symptom Checklist frequency and severity scores. At the end of the study patients preferences for VRS-on or VRS-off were recorded. RESULTS: VRS pacing reduced ventricular irregularity without increasing the mean ventricular rate. VRS-on was preferred by 65.8% of patients with paroxysmal AF; patients with permanent AF had no preference. QoL did not show improvement during VRS pacing on any of the instruments. CONCLUSION: VRS pacing is effective in reducing ventricular rhythm irregularity. QoL does not improve during VRS pacing but preference for VRS pacing appears particularly outspoken for patients with paroxysmal AF.

Randomized assessment of syncope trial: conventional diagnostic testing versus a prolonged monitoring strategy.

BACKGROUND: Establishing a diagnosis in patients with unexplained syncope is complicated by infrequent and unpredictable events. Prolonged monitoring may be an alternative strategy to conventional testing with short-term monitoring and provocative tilt and electrophysiological testing. METHODS AND RESULTS: Sixty patients (aged 66+/-14 years, 33 male) with unexplained syncope were randomized to "conventional" testing with an external loop recorder and tilt and electrophysiological testing or to prolonged monitoring with an implantable loop recorder with 1 year of monitoring. If patients remained undiagnosed after their assigned strategy, they were offered crossover to the alternate strategy. A diagnosis was obtained in 14 of 27 patients randomized to prolonged monitoring compared with 6 of 30 patients undergoing conventional testing (52% versus 20%, P=0.012). Crossover was associated with a diagnosis in 1 of 6 patients undergoing conventional testing compared with 8 of 13 patients who completed monitoring (17% versus 62%, P=0.069). Overall, prolonged monitoring was more likely to result in a diagnosis than was conventional testing (55% versus 19%, P=0.0014). Bradycardia was detected in 14 patients undergoing monitoring compared with 3 patients undergoing conventional testing (40% versus 8%, P=0.005). CONCLUSIONS: A prolonged monitoring strategy is more likely to provide a diagnosis than conventional testing in patients with unexplained syncope. Consideration should be given to earlier implementation of a monitoring strategy.

Cost-effectiveness of the implantable cardioverter-defibrillator: results from the Canadian Implantable Defibrillator Study (CIDS).

BACKGROUND: In the Canadian Implantable Defibrillator Study (CIDS), we assessed the cost-effectiveness of the implantable cardioverter-defibrillator (ICD) in reducing the risk of death in survivors of previous ventricular tachycardia (VT) or fibrillation (VF). METHODS AND RESULTS: Healthcare resource use was collected prospectively on the first 430 patients enrolled in CIDS (n=212 ICD, n=218 amiodarone). Mean cost per patient, adjusted for censoring, was computed for each group based on initial therapy assignment. Incremental cost-effectiveness of ICD therapy was computed as the ratio of the difference in cost (ICD minus amiodarone) to the difference in life expectancy (both discounted at 3% per year). All costs are in 1999 Canadian dollars (C$1 approximately US$0.65). Over 6.3 years, mean cost per patient in the ICD group was C$87 715 versus C$38 600 in the amiodarone group (difference C$49 115; 95% CI C$25 502 to C$69 508). Life expectancy for the ICD group was 4.58 years versus 4.35 years for amiodarone (difference 0.23, 95% CI -0.09 to 0.55), for incremental cost-effectiveness of ICD therapy of C$213 543 per life-year gained. ICD benefit was greater in patients with low left ventricular ejection fraction (<35%), and cost-effectiveness in this group was more attractive (C$108 484). Alternative extrapolations of survival benefit and costs to 12 years indicated cost-effectiveness in the range of C$100 000 to C$150 000 per life-year gained. CONCLUSIONS: At C$213 543, the value for the money offered by ICD therapy is not attractive by currently accepted standards. Further research is warranted to identify the indications and patient subgroups for whom ICDs are a cost-effective use of resources.

Cryothermal ablation of the slow pathway for the elimination of atrioventricular nodal reentrant tachycardia.

BACKGROUND: We report the first successful slow pathway ablation using a novel catheter-based cryothermal technology for the elimination of atrioventricular nodal reentrant tachycardia (AVNRT). METHODS AND RESULTS: Eighteen patients with typical AVNRT underwent cryoablation. Reversible loss of slow pathway (SP) conduction during cryothermy (ice mapping) was demonstrated in 11 of 12 patients. Because of time constraints, only 2 sites were ice mapped in 1 patient. Seventeen of 18 patients had successful cryoablation of the SP. One patient had successful ice mapping of the SP, but inability to cool beyond -38 degrees C prevented successful cryoablation. A single radiofrequency lesion at this site eliminated SP conduction. No patient has had recurrent AVNRT over 4.9+/-1.7 months of follow-up. During cryoablation, accelerated junctional tachycardia was not seen and was therefore not available to guide lesion delivery. Adherence of the catheter tip during cryothermy (cryoadherence) allowed atrial pacing to test for SP conduction. Cryoablation in the anterior septum produced inadvertent transient PR prolongation consistent with loss of fast pathway conduction in 1 patient and transient (6.5 seconds) 2:1 AV block in another. On rewarming, the PR interval returned to normal, and the AV nodal effective refractory period was unchanged in both. Accelerated junctional tachycardia was seen on rewarming in both but not during cryothermy. CONCLUSIONS: Cryothermal ablation of the SP was achieved in patients with this novel technique. Successful ice mapping of both the SP and fast pathway was demonstrated. The ability to test the functionality of specific ablation sites before production of a permanent lesion may eliminate inadvertent AV block.

Randomized crossover comparison of DDDR versus VDD pacing after atrioventricular junction ablation for prevention of atrial fibrillation. The atrial pacing peri-ablation for paroxysmal atrial fibrillation (PA (3)) study investigators.

BACKGROUND: Some clinical data suggest that atrial-based pacing prevents paroxysmal atrial fibrillation (AF). This study tested the hypothesis that DDDR pacing compared with VDD pacing prevents AF after atrioventricular (AV) junction ablation. METHODS AND RESULTS: Patients were randomized to DDDR pacing (n=33) or to VDD pacing (n=34) after AV junction ablation and followed every 2 months for 6 months. Patients then crossed over to the alternate pacing mode and were followed for an additional 6 months. Primary analysis included the time to first recurrence of sustained AF (duration >5 minutes), total AF burden, and the development of permanent AF. The time to first episode of AF was similar in the DDDR group (0.37 days, 95% CI 0.1 to 1.3 days) and the VDD pacing group (0.5 days, 95% CI 0.2 to 1.7 days, P=NS). AF burden increased over time in both groups (P<0.01). At the 6-month follow-up, AF burden was 6.93 h/d (95% CI 4. 37 to 10.96 h/d) in the DDDR group and 6.30 h/d (95% CI 3.99 to 9.94 h/d) in the VDD group (P=NS). Twelve (35%) patients in the DDDR group and 11 (32%) patients in the VDD group had permanent AF within 6 months of ablation. Within 1 year of follow-up, 43% of patients had permanent AF. CONCLUSIONS: DDDR pacing compared with VDD pacing does not prevent paroxysmal AF over the long term in patients in the absence of antiarrhythmic drug therapy after total AV junction ablation. Many patients have permanent AF within the first year after ablation.

Tumor-associated antigen TA90 immune complex assay predicts recurrence and survival after surgical treatment of stage I-III melanoma.

PURPOSE: Immune complexes (IC) containing the tumor-associated antigen TA90 can be identified in the sera of melanoma patients. We have shown that an enzyme-linked immunosorbent assay for TA90-IC can detect subclinical metastasis before surgical treatment of early-stage melanoma. We assayed the TA90-IC levels of postoperative sera from patients with melanoma and evaluated their relationship to recurrence and survival. PATIENTS AND METHODS: Multiple archival serum samples prospectively collected during postoperative surveillance of 166 patients with American Joint Committee on Cancer stage I, II, or III melanoma were analyzed for TA90-IC in a blinded fashion. Results were correlated with disease recurrence and survival determined by database and chart review. RESULTS: TA90-IC status in the early postoperative period was strongly correlated with survival. Five-year overall survival rates were 84% for TA90-IC-negative patients and 36% for TA90-IC-positive patients (P =.0001). Respective 5-year disease-free survival rates were 74% and 24% (P =.0001). The TA90-IC assay was a significant predictor of survival for both stage II and III patients. Multivariate analysis identified TA90-IC status as the strongest independent prognostic factor for both overall and disease-free survival. The TA90-IC assay was elevated in 54 (77%) of 78 patients who developed recurrent disease, becoming positive 19 +/- 7 months before clinical evidence of recurrence. Overall, the assay detected recurrence with a sensitivity of 78% and specificity of 77%. Exclusion of patients receiving postoperative immunotherapy with a polyvalent melanoma cell vaccine increased sensitivity and specificity to 92% and 86%, respectively. CONCLUSION: The TA90-IC assay can accurately predict survival and detect the presence of subclinical disease after surgery for melanoma, which should be useful in selecting patients for adjuvant therapy. Because the TA90-IC assay detected recurrence on an average of 19 months sooner than did routine clinical and radiographic evaluation, it may allow more timely therapeutic interventions.

A prospective evaluation of 5-fluorouracil plus cisplatin in advanced squamous-cell cancer of the head and neck.

Recent studies have shown improved efficacy of chemotherapy in patients with advanced squamous-cell cancer of the head and neck. Our purpose was to evaluate prospectively the activity of cisplatin plus 5-fluorouracil (5FU) in 37 patients with advanced stage IV squamous-cell cancer of the head and neck. There were two groups. Group 1 consisted of 19 previously untreated patients with either T4 or N3 disease. They received 100 mg/m2 cisplatin (days 1 and 28) and 120-hour infusion of 1,000 mg/m2/24 hours 5FU (days 1 to 5 and 28 to 32). They subsequently were offered preoperative radiotherapy (RT) and surgery. Group 2 consisted of 18 previously treated patients. They received 5FU and cisplatin in the same dosage every 28 days for either recurrent or metastatic disease. It was found that in group 1 there was an 84% response rate (five complete responses (CR) and 11 partial responses (PR) ). Three of those with PR achieved a CR after RT. Seven patients have had RT plus surgery and are disease free at 8 to 27 month follow-up. Six patients (one CR, five PR) refused surgery and progressed within 4 months. In group 2 there was an 11% response rate after two cycles (two PR), three patients had a minimal response (MR, less than 50% response) and received a mean of four cycles of treatment. Three patients with stable disease received a mean of four cycles of chemotherapy until progression. Two of 11 patients who had received previous chemotherapy plus RT showed an MR; nine of these patients had shown a response to their previous chemotherapy. Only one of 14 patients who had RT plus chemotherapy had a PR, and three had MR. Of five patients who had previous surgery, only one had a PR. All five had received chemotherapy as well. It was concluded that 5FU plus cisplatin is an effective combination in previously untreated patients. In previously treated patients with recurrent disease, there is a substantially lower response rate.

Predictors of defibrillation efficacy in patients undergoing epicardial defibrillator implantation. The Multicenter Pacemaker-Cardioverter-Defibrillator (PCD) Investigators Group.

OBJECTIVES: The objective of this study was to identify predictors of defibrillation threshold in patients undergoing epicardial defibrillator implantation. BACKGROUND: Factors that predict epicardial defibrillation efficacy are poorly defined. METHODS: The data from 375 consecutive adult patients were reviewed. After exclusion of 137 patients in whom defibrillation threshold was not obtained, 238 patients (32 women and 206 men) with a mean age of 58.9 +/- 13.3 years formed the study group. Coronary heart disease was present in 175 patients and the mean left ventricular ejection fraction was 35.8 +/- 15.4%. At device implantation, three epicardial patch sizes were available and shocks could be delivered over one current pathway (two patches) or over two current pathways (three patches with simultaneous or sequential shocks). Defibrillation threshold was defined as the lowest programmed energy that successfully defibrillated the heart, provided there had been an unsuccessful shock at a lower energy level or successful defibrillation at < or = 5 J. RESULTS: The mean defibrillation threshold was 8.6 +/- 5.3 J. With univariate analysis, female gender, sequential shocks with three patches, higher left ventricular ejection fraction and lower New York Heart Association functional class predicted a lower defibrillation threshold. In the multivariate analysis, female gender (coefficient -3.9; 95% confidence interval [CI] -1.9 to -5.0 J), ejection fraction (coefficient -0.6; CI -0.1 to -1.0 J/decile) and sequential shocks (coefficient -2.5; CI -1.0 to -4.0 J) were independently associated with a lower defibrillation threshold. Total epicardial patch conductive surface area normalized to body surface area reached borderline significance (coefficient 0.004; CI 0 to 0.01; p = 0.10). Antiarrhythmic drug use, including amiodarone, did not predict defibrillation threshold. CONCLUSIONS: Female gender, high left ventricular ejection fraction and the use of sequential pulse shocks were important determinants of improved defibrillation efficacy.

Multicenter experience with a pectoral unipolar implantable cardioverter-defibrillator. Active Can Investigators.

OBJECTIVES: The purpose of this study was to prospectively examine in a multicenter study the methods of use, efficacy and complications of a unipolar cardioverter-defibrillator in patients at risk for sudden cardiac death. BACKGROUND: Implantation of cardioverter-defibrillators in the pectoral region offers a significant opportunity to improve the management of patients with life-threatening arrhythmias. Unipolar, single-lead, pectoral implantable cardioverter-defibrillators might decrease related mortality, morbidity and costs in the care of such patients. METHODS: From November 3, 1993 to May 8, 1995, a unipolar defibrillator (Medtronic model 7219C) was selected for use in 473 patients from 74 centers (386 [82%] men, 87 [18%] women; mean [+/- SD] age 59 +/- 13 years, range 16 to 88). The clinical indication for use was ventricular fibrillation in 157 patients, sustained ventricular tachycardia in 236, both ventricular tachycardia and ventricular fibrillation in 53 and syncope or inducible ventricular tachycardia/ventricular fibrillation in 27. Coronary artery disease was present in 323 patients (68%). The mean left ventricular ejection fraction was 0.36 +/- 0.15 (range 0.10 to 0.85). The distribution of New York Heart Association congestive heart failure was class I = 34%; class II = 45%; class III = 17%; and class IV = 2%. RESULTS: The unipolar cardioverter-defibrillator was inserted successfully in 464 (98%) of 473 candidates. Effective defibrillation occurred with the first shock polarity tested in 88% of patients, after a polarity switch in 8% and after lead or generator repositioning in 2%. The stored energy defibrillation threshold was obtained at implantation in 339 patients (72%) and was 11.5 +/- 6.1 J, with 72% of patients having a defibrillation threshold < or = 12 J. The mean "skin-to-skin" implantation time was 96 +/- 45 min (range 25 to 335 min). Complications occurred in 29 patients (6%). Device therapy for 2,160 spontaneous ventricular tachycardia or fibrillation episodes occurred in 128 patients (27%) over a 2,732 device-month experience (range 0 to 17.2) and was effective in 98.7% of episodes. There were 14 deaths (10 nonsudden cardiac, 3 sudden cardiac, 1 noncardiac). Cumulative survival, on an intention-to-treat basis from all causes of death at 17.2 months, was 94.4%. CONCLUSIONS: Unipolar pectoral implantable cardioverter-defibrillators can be inserted with a high likelihood of success in a relatively brief procedure. Defibrillation thresholds are low, morbidity is modest, and survival rates are good with this new type of implantable cardioverter-defibrillator.

Junctional tachycardia: a useful marker during radiofrequency ablation for atrioventricular node reentrant tachycardia.

OBJECTIVES: The aim of this study was to evaluate junctional tachycardia as a useful marker during radiofrequency ablation for atrioventricular (AV) node reentrant tachycardia. BACKGROUND: Junctional tachycardia appears to be a response of the atrioventricular node to injury and is seen during both radiofrequency AV node ablation and slow and fast pathway ablation for AV node reentrant tachycardia. We hypothesized that junctional tachycardia heralding AV node block and that associated with slow or fast pathway ablation may have different characteristics that could be useful in preventing inadvertent AV block. METHODS: Characteristics of junctional tachycardia were examined after 59 radiofrequency ablation sessions in 53 consecutive patients with a mean age (+/- SD) of 41.6 +/- 16.5 years. Type 1 junctional tachycardia was followed by transient second- or third-degree AV block (n = 5) or permanent third-degree AV block (n = 1). Type 2 junctional tachycardia was followed by normal AV conduction (n = 53). RESULTS: Fifty-one patients had typical AV node reentrant tachycardia, and two patients had atypical tachycardia. Fast pathway ablation was attempted during 6 sessions and slow pathway ablation during 53 sessions. Patients underwent 15.3 +/- 10 radiofrequency applications, with a mean duration of 24 +/- 9.7 s. Junctional tachycardia was observed an average of 2.8 +/- 1.8 times per ablation session. Type 1 junctional tachycardia had a significantly faster rate than that of type 2 (cycle length 363 +/- 44 vs. 558 +/- 116, p < 0.001). In addition, type 1 junctional tachycardia was associated with predominantly ventriculoatrial block whereas type 2 was associated with predominantly 1:1 ventriculoatrial conduction (2 of 6 vs. 47 of 53 episodes, p < 0.05). CONCLUSIONS: We conclude that junctional tachycardia leading to AV block can be recognized by a faster junctional rate and ventriculoatrial block. This is a useful marker of impending AV block during slow and fast pathway ablation.

Defibrillation shocks produce different effects on Purkinje fibers and ventricular muscle: implications for successful defibrillation, refibrillation and postshock arrhythmia.

OBJECTIVES: To understand the mechanisms of postdefibrillation arrhythmias and failed defibrillation, we studied the cellular effects of high voltage shocks on different cardiomyocytes in the dog. BACKGROUND: The causes of postdefibrillation arrhythmias and unsuccessful defibrillation are not clear. METHODS: High voltage shocks with voltage differentials of 9.3 to 97.6 V/cm were delivered to isolated canine papillary muscles with attached Purkinje fibers. Transmembrane potentials were recorded simultaneously from the Purkinje fiber and the ventricular muscle using standard microelectrode techniques. RESULTS: After delivery of high voltage shocks, significant depolarization and rapid firing were observed in Purkinje fibers. The maximal rate of the rapid firing in the Purkinje fibers correlated with shock intensity (r = 0.69, p < 0.05). In contrast, in ventricular muscle, only slight depolarization and a transient refractory state were observed after the shock. The incidence of the refractory state was correlated with both the shock intensity and the rate of the rapid firing in the Purkinje fiber (r = 0.89 and 0.74, p < 0.01 and 0.05, respectively). Propranolol at a concentration sufficient for complete beta-blockade (1 mg/liter) did not change the tissue response to shocks but suppressed or abolished the shock-induced rapid firing of Purkinje fibers at a higher concentration (3 mg/liter). Blockade of the slow calcium channel with verapamil (400 micrograms/dl) did not alter the responsiveness of the preparation to shocks. CONCLUSION: These results indicate that high voltage shocks induce different responses in Purkinje fibers and ventricular muscle. The shock-induced rapid firing in the Purkinje fiber may contribute to postshock arrhythmias and possibly refibrillation in some cases. The shock-induced transient refractory state in the ventricular muscle may prevent the ventricle from responding to the rapid firing and thus may decrease the incidence of postshock arrhythmias.

Sinus node-atrioventricular node isolation: long-term results with the "corridor" operation for atrial fibrillation.

The "corridor" operation is designed to restore sinus rhythm to patients with atrial fibrillation by electrically isolating the sinus node, a band of atrial tissue and the atrioventricular (AV) node from the remaining atrial tissue. Nine patients with drug-refractory atrial fibrillation underwent this operation; four patients had chronic atrial fibrillation and five had paroxysmal atrial fibrillation; the mean duration of symptoms was 12 +/- 8 years. Patient ages ranged from 25 to 68 years (mean 48 +/- 12). At preoperative electrophysiologic study, no patient had evidence of an accessory AV pathway or AV node reentry. Sinus node recovery time could not be determined in five patients because of recurrent atrial fibrillation during or before programmed stimulation. At operation the corridor of atrial tissue connecting the sinus and AV nodes was successfully isolated from the remaining left and right atrial tissue in all patients. One patient required early reoperation for recurrent atrial fibrillation before hospital discharge. At the predischarge electrophysiologic study, the corridor remained isolated in all patients except for one patient who had intermittent conduction between the corridor and excluded right atrium. One patient had nonsustained atrial fibrillation and one had atrial tachycardia evident in the corridor. Atypical AV node reentry of uncertain significance was induced in one other patient. Over a total follow-up of 191 patient months (mean 21 +/- 20), seven patients remained free of atrial fibrillation. Two patients had recurrent atrial fibrillation, which in one patient was effectively controlled by a single antiarrhythmic agent. A permanent pacemaker was implanted in four patients for sinus node dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)