Myelopreservation with the CDK4/6 inhibitor trilaciclib in patients with small-cell lung cancer receiving first-line chemotherapy: a phase Ib/randomized phase II trial.

BACKGROUND: Chemotherapy-induced damage of hematopoietic stem and progenitor cells (HSPC) causes multi-lineage myelosuppression. Trilaciclib is an intravenous CDK4/6 inhibitor in development to proactively preserve HSPC and immune system function during chemotherapy (myelopreservation). Preclinically, trilaciclib transiently maintains HSPC in G1 arrest and protects them from chemotherapy damage, leading to faster hematopoietic recovery and enhanced antitumor immunity. PATIENTS AND METHODS: This was a phase Ib (open-label, dose-finding) and phase II (randomized, double-blind placebo-controlled) study of the safety, efficacy and PK of trilaciclib in combination with etoposide/carboplatin (E/P) therapy for treatment-naive extensive-stage small-cell lung cancer patients. Patients received trilaciclib or placebo before E/P on days 1-3 of each cycle. Select end points were prespecified to assess the effect of trilaciclib on myelosuppression and antitumor efficacy. RESULTS: A total of 122 patients were enrolled, with 19 patients in part 1 and 75 patients in part 2 receiving study drug. Improvements were seen with trilaciclib in neutrophil, RBC (red blood cell) and lymphocyte measures. Safety on trilaciclib+E/P was improved with fewer ≥G3 adverse events (AEs) in trilaciclib (50%) versus placebo (83.8%), primarily due to less hematological toxicity. No trilaciclib-related ≥G3 AEs occurred. Antitumor efficacy assessment for trilaciclib versus placebo, respectively, showed: ORR (66.7% versus 56.8%, P = 0.3831); median PFS [6.2 versus 5.0 m; hazard ratio (HR) 0.71; P = 0.1695]; and OS (10.9 versus 10.6 m; HR 0.87; P = 0.6107). CONCLUSION: Trilaciclib demonstrated an improvement in the patient's tolerability of chemotherapy as shown by myelopreservation across multiple hematopoietic lineages resulting in fewer supportive care interventions and dose reductions, improved safety profile, and no detriment to antitumor efficacy. These data demonstrate strong proof-of-concept for trilaciclib's myelopreservation benefits. CLINICAL TRAIL NUMBER: NCT02499770.

The actin binding protein scinderin acts in PC12 cells to tether dense-core vesicles prior to secretion.

Mechanistic understanding of the control of vesicle motion from within a secretory cell to the site of exocytosis remains incomplete. In this work, we have used total internal reflection (TIRF) microscopy to examine the mobility of secretory vesicles at the plasma membrane. Under resting conditions, we found vesicles showed little lateral mobility. Anchoring of vesicles in this membrane proximal compartment could be disrupted with latrunculin A, indicating an apparent actin dependent process. A candidate intermediary between vesicles and the actin skeleton is the actin binding protein scinderin. Co-transfection of an shRNA construct against scinderin blocked secretion, and also increased the mobility of vesicles in the membrane-proximal section of the cell, indicating a dual role for scinderin in secretion; tethering vesicles to the cytoskeleton, as well as liberating them following stimulation through the previously described calcium dependent actin severing activity. Analysis of lipid dependence indicates that scinderin exhibits calcium dependent binding to phosphatidyl-inositol monophosphate, providing a possible mechanism for vesicle binding.

Docetaxel plus oxaliplatin with or without fluorouracil or capecitabine in metastatic or locally recurrent gastric cancer: a randomized phase II study.

BACKGROUND: Docetaxel/cisplatin/infusional 5-fluorouracil (5-FU; DCF) is a standard chemotherapy regimen for patients with advanced gastric cancer (GC). This phase II study evaluated docetaxel/oxaliplatin (TE), docetaxel/oxaliplatin/5-FU (TEF), and docetaxel/oxaliplatin/capecitabine (TEX) in patients with advanced GC. PATIENTS AND METHODS: Patients with metastatic or locally recurrent gastric adenocarcinoma (including carcinoma of the gastro-oesophageal junction) were randomly assigned (1 : 1 : 1) to TE, TEF, or TEX. Each regimen was tested at two doses before full evaluation at optimized dose levels. The primary end point was progression-free survival (PFS). Overall survival (OS), tumour response, and safety were also assessed. A therapeutic index (median PFS relative to the incidence of febrile neutropenia) was calculated for each regimen and compared with DCF (historical data). RESULTS: Overall, 248 patients were randomly assigned to receive optimized dose treatment. Median PFS was longer with TEF (7.66 [95% confidence interval (CI): 6.97-9.40] months) versus TE (4.50 [3.68-5.32] months) and TEX (5.55 [4.30-6.37] months). Median OS was 14.59 (95% CI: 11.70-21.78) months for TEF versus 8.97 (7.79-10.87) months for TE and 11.30 (8.08-14.03) months for TEX. The rate of tumour response (complete or partial) was 46.6% (95% CI 35.9-57.5) for TEF versus 23.1% (14.3-34.0) for TE and 25.6% (16.6-36.4) for TEX. The frequency and type of adverse events (AEs) were similar across the three arms. Common grade 3/4 AEs were fatigue (21%), sensory neuropathy (14%), and diarrhoea (13%). Febrile neutropenia was reported in 2% (TEF), 14% (TE), and 9% (TEX) of patients. The therapeutic index was improved with TEF versus TEX, TE, or DCF. CONCLUSION: These results suggest that TEF is worthy of evaluation as an arm in a phase III trial or as a backbone regimen for new targeted agents in advanced GC. CLINICALTRIALS.GOV: Identifier Trial registration number: NCT00382720.

Stepped care treatment delivery for depression: a systematic review and meta-analysis.

BACKGROUND: In stepped care models patients typically start with a low-intensity evidence-based treatment. Progress is monitored systematically and those patients who do not respond adequately step up to a subsequent treatment of higher intensity. Despite the fact that many guidelines have endorsed this stepped care principle it is not clear if stepped care really delivers similar or better patient outcomes against lower costs compared with other systems. We performed a systematic review and meta-analysis of all randomized trials on stepped care for depression. METHOD: We carried out a comprehensive literature search. Selection of studies, evaluation of study quality and extraction of data were performed independently by two authors. RESULTS: A total of 14 studies were included and 10 were used in the meta-analyses (4580 patients). All studies used screening to identify possible patients and care as usual as a comparator. Study quality was relatively high. Stepped care had a moderate effect on depression (pooled 6-month between-group effect size Cohen's d was 0.34; 95% confidence interval 0.20-0.48). The stepped care interventions varied greatly in number and duration of treatment steps, treatments offered, professionals involved, and criteria to step up. CONCLUSIONS: There is currently only limited evidence to suggest that stepped care should be the dominant model of treatment organization. Evidence on (cost-) effectiveness compared with high-intensity psychological therapy alone, as well as with matched care, is required.

Comparison of energy metabolism in liver grafts from donors after circulatory death and donors after brain death during cold storage and reperfusion.

BACKGROUND: Donation after circulatory death (DCD) liver grafts have supplemented the donor organ pool, but certain adverse outcomes have prevented exploration of the full potential of such organs. The aim of this study was to determine key differences in basic energy metabolism between DCD and donation after brainstem death (DBD) grafts. METHODS: Microdialysis samples from DCD and DBD allograft parenchyma from cold storage to 48 h after reperfusion were analysed by colorimetric methods. Interstitial lactate, pyruvate and glycerol levels were measured and the lactate/pyruvate ratio was calculated to estimate energy depletion of the grafts. Histological features of ischaemia and reperfusion injury were assessed. RESULTS: Donor age, extent of steatosis and cold ischaemia time were comparable between ten DCD and 20 DBD organs. DCD grafts had higher levels of interstitial lactate (median 11.6 versus 1.2 mmol/l; P = 0.015) and increased lactate/pyruvate ratio (792 versus 38; P = 0.001) during cold storage. There was no significant difference in glycerol levels between DCD and DBD grafts (225.1 versus 127.5 µmol/l respectively; P = 0.700). Rapid restoration of energy levels with lactate clearance, increased pyruvate levels and reduced lactate/pyruvate ratio was seen following reperfusion of functioning DCD grafts, parallel with levels in DBD grafts. Histology revealed more pronounced glycogen depletion in DCD grafts. Three allografts that failed owing to primary non-function showed energy exhaustion with severe glycogen depletion. CONCLUSION: Liver grafts from DCD donors exhibited depletion of intracellular energy reserves during cold storage. Failed allografts showed severe energy depletion. Modified organ preservation techniques to minimize organ injury related to altered energy metabolism may enable better utilization of donor organs after circulatory death.

Netmums: a phase II randomized controlled trial of a guided Internet behavioural activation treatment for postpartum depression.

BACKGROUND: Despite the high prevalence of postnatal depression (PND), few women seek help. Internet interventions may overcome many of the barriers to PND treatment use. We report a phase II evaluation of a 12-session, modular, guided Internet behavioural activation (BA) treatment modified to address postnatal-specific concerns [Netmums Helping With Depression (NetmumsHWD)]. METHOD: To assess feasibility, we measured recruitment and attrition to the trial and examined telephone session support and treatment adherence. We investigated sociodemographic and psychological predictors of treatment adherence. Effectiveness outcomes were estimated with the Edinburgh Postnatal Depression Scale (EPDS), Generalized Anxiety Disorder-7, Work and Social Adjustment Scale, Postnatal Bonding Questionnaire, and Social Provisions Scale. RESULTS: A total of 249 women were recruited via a UK parenting site, Netmums.com. A total of 83 women meeting DSM-IV criteria for major depressive disorder were randomized to NetmumsHWD (n = 41) or treatment-as-usual (TAU; n = 42). Of the 83 women, 71 (86%) completed the EPDS at post-treatment, and 71% (59/83) at the 6-month follow-up. Women completed an average of eight out of 12 telephone support sessions and five out of 12 modules. Working women and those with less support completed fewer modules. There was a large effect size favouring women who received NetmumsHWD on depression, work and social impairment, and anxiety scores at post-treatment compared with women in the TAU group, and a large effect size on depression at 6 months post-treatment. There were small effect sizes for postnatal bonding and perceived social support. CONCLUSIONS: A supported, modular, Internet BA programme can be feasibly delivered to postpartum women, offering promise to improve depression, anxiety and functioning.

A randomized, placebo-controlled phase 2 study of ganitumab (AMG 479) or conatumumab (AMG 655) in combination with gemcitabine in patients with metastatic pancreatic cancer.

BACKGROUND: We evaluated the efficacy and safety of ganitumab (a mAb antagonist of insulin-like growth factor 1 receptor) or conatumumab (a mAb agonist of human death receptor 5) combined with gemcitabine in a randomized phase 2 trial in patients with metastatic pancreatic cancer. PATIENTS AND METHODS: Patients with a previously untreated metastatic pancreatic adenocarcinoma and an Eastern Cooperative Oncology Group (ECOG) performance status ≤1 were randomized 1 : 1 : 1 to i.v. gemcitabine 1000 mg/m(2) (days 1, 8, and 15 of each 28-day cycle) combined with open-label ganitumab (12 mg/kg every 2 weeks [Q2W]), double-blind conatumumab (10 mg/kg Q2W), or double-blind placebo Q2W. The primary end point was 6-month survival rate. Results In total, 125 patients were randomized. The 6-month survival rates were 57% (95% CI 41-70) in the ganitumab arm, 59% (42-73) in the conatumumab arm, and 50% (33-64) in the placebo arm. The grade ≥3 adverse events in the ganitumab, conatumumab, and placebo arms, respectively, included neutropenia (18/22/13%), thrombocytopenia (15/17/8%), fatigue (13/12/5%), alanine aminotransferase increase (15/5/8%), and hyperglycemia (18/2/3%). CONCLUSIONS: Ganitumab combined with gemcitabine had tolerable toxicity and showed trends toward an improved 6-month survival rate and overall survival. Additional investigation into this combination is warranted. Conatumumab combined with gemcitabine showed some evidence of activity as assessed by the 6-month survival rate.

Extremely large variations of atmospheric 14C concentration during the last glacial period.

A long record of atmospheric 14C concentration, from 45 to 11 thousand years ago (ka), was obtained from a stalagmite with thermal-ionization mass-spectrometric 230Th and accelerator mass-spectrometric 14C measurements. This record reveals highly elevated Delta14C between 45 and 33 ka, portions of which may correlate with peaks in cosmogenic 36Cl and 10Be isotopes observed in polar ice cores. Superimposed on this broad peak of Delta14C are several rapid excursions, the largest of which occurs between 44.3 and 43.3 ka. Between 26 and 11 ka, atmospheric Delta14C decreased from approximately 700 to approximately 100 per mil, modulated by numerous minor excursions. Carbon cycle models suggest that the major features of this record cannot be produced with solar or terrestrial magnetic field modulation alone but also require substantial fluctuations in the carbon cycle.

Two endocytic recycling routes selectively fill two vesicle pools in frog motor nerve terminals.

We have identified and characterized two vesicle recycling pathways in frog motor nerve terminals. We exploited the differential staining properties of FM dyes of varying hydrophobicity to label selectively two different vesicle pools, using optical imaging and electron microscopy of photoconverted dyes. During a 1 min tetanus, a rapidly recycling route places vesicles selectively into a small readily releasable pool comprising about 20% of vesicles. After the tetanus, a much slower pathway (from which FM2-10 but not FM1-43 can be rinsed) delivers vesicles via infoldings and cisternae selectively to a reserve pool with a halftime of about 8 min. Mixing between the two pools is slow. During stimulation at 30 Hz, 10-15 s is required to mobilize and release dye from the reserve pool.

Extracellular amino acid levels in the human liver during transplantation: a microdialysis study from donor to recipient.

Using microdialysis, we have monitored extracellular levels of amino acids and related amines in the human liver at three stages of the transplantation procedure: donor retrieval, back table preparation and during 48 h post-implantation. By comparing the ratio of mean levels at the donor and back table stages, with the ratio between early (2-6 h) and late (43-48 h) post-reperfusion, these amines were classified into one of three groups. In one group, back table levels were markedly higher than during the donor stage, with levels declining over time post-reperfusion. A second group had much lower levels in the back table than during the donor phase, and post-reperfusion levels were either stable or increased over time. Concentrations of amino acids in the final group remained relatively constant at all stages. This study illustrates the value of microdialysis in providing organ-specific metabolic data that may indicate specific mechanisms of poor graft function.

Monolithic column-based reversed-phase liquid chromatography separation for amino acid assay in microdialysates and cerebral spinal fluid.

The development of a HPLC method using a monolithic C18 column is described using fluorescence detection for the assay of 21 amino acids and related substances with derivatisation using ortho-phthaldialdehyde (OPA) in the presence of 3-mercaptopropionic acid (3-MPA). The method employs a tertiary gradient and has a run time of 24 min. Linearity (r2) for each amino acid was found to be greater than 0.99 up to a 10 microM concentration; reproducibility across all analyses (relative standard deviation (R.S.D.)) was between 0.97 and 6.7% and limit of detection (LOD) between 30 and 300 fmol on column. This method has been applied to the analysis of amino acids in both spinal microdialysis and cerebral spinal fluid samples.

Low altitude unmanned aerial vehicle for characterising remediation effectiveness following the FDNPP accident.

On the 12th of March 2011, The Great Tohoku Earthquake occurred 70 km off the eastern coast of Japan, generating a large 14 m high tsunami. The ensuing catalogue of events over the succeeding 12 d resulted in the release of considerable quantities of radioactive material into the environment. Important to the large-scale remediation of the affected areas is the accurate and high spatial resolution characterisation of contamination, including the verification of decontaminated areas. To enable this, a low altitude unmanned aerial vehicle equipped with a lightweight gamma-spectrometer and height normalisation system was used to produce sub-meter resolution maps of contamination. This system provided a valuable method to examine both contaminated and remediated areas rapidly, whilst greatly reducing the dose received by the operator, typically in localities formerly inaccessible to ground-based survey methods. The characterisation of three sites within Fukushima Prefecture is presented; one remediated (and a site of much previous attention), one un-remediated and a third having been subjected to an alternative method to reduce emitted radiation dose.

High-resolution radiation mapping to investigate FDNPP derived contaminant migration.

As of March 2016, five years will have passed since the earthquake and ensuing tsunami that crippled the Fukushima Daiichi Nuclear Power Plant on Japan's eastern coast, resulting in the explosive release of significant quantities of radioactive material. Over this period, significant time and resource has been expended on both the study of the contamination as well as its remediation from the affected environments. Presented in this work is a high-spatial resolution foot-based radiation mapping study using gamma-spectrometry at a site in the contaminated Iitate Village; conducted at different times, seventeen months apart. The specific site selected for this work was one in which consistent uniform agriculture was observed across its entire extent. From these surveys, obtained from along the main northwest trending line of the fallout plume, it was possible to determine the rate of reduction in the levels of contamination around the site attributable to the natural decay of the radiocesium, remediation efforts or material transport. Results from the work suggest that neither the natural decay of radiocesium nor its downward migration through the soil horizons were responsible for the decline in measured activity levels across the site, with the mobilisation of contaminant species likely adhered to soil particulate and the subsequent fluvial transport responsible for the measurable reduction in activity. This transport of contaminant via fluvial methods has already well studied implications for the input of contaminant material entering the neighbouring Pacific Ocean, as well as the deposition of material along rivers within previously decontaminated areas.

Reduction in incidence of inducible ventricular tachycardia after myocardial infarction by treatment with streptokinase during infarct evolution.

The aim of this study was to determine whether intravenous streptokinase administered with or without oral aspirin to patients with evolving myocardial infarction reduces the inducibility of ventricular tachycardia at electrophysiologic study and thus the risk of sudden death in infarct survivors. Of 159 patients randomized at Westmead Hospital to the multicenter Second International Study of Infarct Survival (ISIS-2) after streptokinase and aspirin in acute myocardial infarction, 87 underwent electrophysiologic testing 6 to 28 days after infarction to determine their risk of subsequent ventricular arrhythmias (streptokinase 20 patients; aspirin 25 patients; streptokinase and aspirin 21 patients; both placebos 21 patients). Patients who underwent electrophysiologic testing had similar clinical characteristics to those of patients who did not. The stimulation protocol comprised up to and including four extrastimuli applied to the right ventricular apex at twice diastolic threshold. An abnormal result was defined as ventricular tachycardia with a cycle length greater than or equal to 230 ms lasting greater than or equal to 10 s. Ventricular tachycardia was inducible at electrophysiologic study in 8 patients who received placebo streptokinase, but in no patient who received active streptokinase (8 of 46 versus 0 of 41; p = 0.005, Fischer's exact test). Ventricular tachycardia was inducible in 4 patients who received aspirin therapy and 4 who did not (4 of 41 versus 4 of 46; p = NS). During a mean follow-up period of 39 +/- 9 months, there were no spontaneous episodes of ventricular tachycardia, ventricular fibrillation or witnessed sudden death in the streptokinase-treated group compared with three such events in the placebo-treated group (p = 0.13). When compared with placebo therapy, intravenous streptokinase substantially reduced the incidence of inducible ventricular tachycardia in infarct survivors. No similar benefit was attributable to aspirin therapy.

Simultaneous 60-electrode mapping of ventricular tachycardia using percutaneous catheters.

OBJECTIVES: We developed a new approach for mapping ventricular tachycardia at electrophysiologic study using simultaneous recordings from up to 60 catheter electrodes. BACKGROUND: Good results for surgical or catheter ablation of ventricular tachycardia are limited by the ability to detect and completely map all of the underlying arrhythmogenic areas. Currently, catheter mapping of all configurations of ventricular tachycardia is impossible or unsatisfactory in at least 60% of patients because of poorly tolerated rapid rates, nonsustained ventricular tachycardia or multiple configurations. METHODS: Twenty-four patients with recurrent ventricular tachycardia refractory to antiarrhythmic drugs were studied using up to six percutaneous decapolar catheters introduced into the ventricles. Left ventricular maps of ventricular tachycardia were achieved by two to three transseptal catheters, two to three transaortic catheters, a coronary sinus catheter and right ventricular catheters. Simultaneous endocardial maps of either right or left ventricles were possible with a resolution of approximately 1 to 2 cm. Up to 60 electrograms were digitized and recorded simultaneously using a custom-computerized mapping system. RESULTS: Successful maps of 73 ventricular tachycardia configurations were obtained in 22 patients. The mapping procedure failed in two patients because of inability to catheterize the left ventricle in one and inability to induce monomorphic ventricular tachycardia in the other. The mean (+/- SD) ventricular tachycardia cycle length was 285 +/- 53 ms (range 215 to 470). A total of 39 separate arrhythmogenic areas (median 1, interquartile [25% to 75%] range 1 to 3/patient) were detected, of which 21 (54%) were in the left ventricular free wall, 17 (44%) were in the ventricular septum, and 1 (2%) was in the right ventricular outflow tract. Ten patients (45%) had at least two arrhythmogenic areas. Thirteen patients subsequently underwent operation. All but one of the arrhythmogenic areas found at surgical mapping had been identified at preoperative catheter mapping. Complications of the preoperative mapping procedure occurred in four patients, with complete resolution in three and minor long-term sequelae in the other. CONCLUSIONS: This technique permits detailed catheter mapping of all types of monomorphic ventricular tachycardias, including those leading to hemodynamic collapse, and should enable better choice and direction of surgical or catheter ablation.

Behavior of late potentials on the body surface during programmed ventricular stimulation.

OBJECTIVES: This study sought to evaluate the behavior of late potentials on the body surface by signal averaging during programmed stimulation and to correlate the findings with the cycle length of induced ventricular tachycardia. BACKGROUND: Clinically relevant late potentials may be concealed within the QRS complex and may be missed by the conventional signal-averaged electrocardiogram (SAECG). In contrast, some late potentials may arise from dead-end pathways or pathways not capable of supporting sustained ventricular tachycardia (VT). It has been shown that durations of late potentials in sinus rhythm correlate poorly with VT cycle length. METHODS: Signal-averaged electrocardiography during sinus rhythm, right ventricular pacing (S1) and introduction of a right ventricular extrastimulus (S2) was performed in 95 patients: 11 patients with a structurally normal heart and no inducible VT (Group I); 44 with a previous myocardial infarction (MI) and no inducible monomorphic VT (Group II); and 40 with a previous MI and inducible monomorphic VT (Group III). RESULTS: The best subset of SAECG variables and the best cut points for each variable to differentiate between patients with and without VT were first established for each rhythm studied. Total duration of the filtered QRS complex (QRSD) was found to be the only independent predictor of inducibility of VT. When late potentials were defined for these criteria (QRSD > OR = 113, > or = 178 and > or = 168 ms for the SAECG during sinus rhythm, S1 and S2, respectively), there was no difference in the incidence of false positive (16% vs. 18%) or false negative (30% vs. 26%) late potentials between sinus rhythm and S1. During S2, there were significantly fewer false positive late potentials (11% vs. 16%) and fewer false negative late potentials (17% vs. 30%) than with sinus rhythm. Compared with sinus rhythm, 31% of the false positive late potentials detected during sinus rhythm were lost, whereas 43% of the false negative late potentials became detectable after S2, resulting in improved sensitivity (83% vs. 70%), specificity (89% vs. 84%) and predictive accuracy (86% vs. 77%, p < 0.05). Among the patients with VT, QRSD during S2 achieved the best correlation with VT cycle length (r = 0.74) and was the only independent predictor of VT cycle length when all SAECG variables were considered. CONCLUSIONS: Late potentials revealed by ventricular extrastimuli but concealed during sinus rhythm may be clinically relevant and may explain some of the false negative late potentials and reduced sensitivity of the conventional SAECG in predicting VT. In contrast, those late potentials that are detected during sinus rhythm but lost after ventricular extrastimuli are often clinically irrelevant and may account for the false positive late potentials and reduced specificity of the conventional SAECG.

Extrastimulus-related shortening of the first postpacing interval in digitalis-induced ventricular tachycardia: observations during programmed electrical stimulation in the conscious dog.

The effect of different modes of pacing on interval and configuration of the first postpacing QRS complex was studied during digitalis-induced ventricular tachycardia in the conscious dog. The effect of overdrive pacing was related to pacing rate; the longest pacing intervals resulted in prolongation of the first postpacing interval, while increasing the rate of overdrive pacing led to a progressive shortening of the first postpacing interval. When extrastimuli were introduced during fixed rate pacing, the duration of the first postpacing interval was found to be predominantly effected by the extrastimulus coupling interval. The importance of the last paced interval to the duration of the first postpacing cycle length was also observed when only a single or two extrastimuli were given. The duration of the first postpacing interval was found to be independent of the site site of stimulation. In contrast, the configuration of the first postpacing QRS complex was found to be related to the site of pacing; the first postpacing QRS complex originated close to the site of stimulation independent of the configuration of the tachycardia. In conclusion, it was found that during digitalis-induced ventricular tachycardia 1) the first postpacing interval is mainly, dependent on the interval of the last paced beat, 2) the length of the first postpacing interval is independent of the site of stimulation, but 3) the configuration of the first postpacing QRS complex is related to the site of stimulation. These findings may facilitate the understanding of complex ventricular arrhythmias observed during severe digitalis intoxication in human beings.

Effect of repetition of extrastimuli on sensitivity and reproducibility of mode of induction of ventricular tachycardia by programmed stimulation.

This study examined the effect of repeating the delivery of a programmed extrastimulus that previously failed to induce ventricular tachycardia, without the usual practice of concurrently altering other stimulation variables such as pacing site or basic cycle length. The impact of such repetition on both sensitivity and day to day variability in mode of arrhythmia induction was assessed in 24 patients with documented sustained ventricular tachycardia or fibrillation. Programmed stimulation in the absence of drugs was performed in each patient on 3 separate days. In the first 12 patients, each extrastimulus was scanned through diastole to refractoriness four times if no ventricular tachyarrhythmia was induced (longitudinal repetition); in the second 12 patients, each extrastimulus was delivered four times at a particular coupling interval before the interval was decreased in 10 ms steps to a closer coupling interval (lateral repetition). Day to day reproducibility of the mode of arrhythmia induction was compared with reproducibility in a control group of 18 similar patients studied previously on 3 separate days without repetition. A sustained ventricular tachyarrhythmia was inducible in all studies with four or fewer extrastimuli. In the group studied with longitudinal repetition, there was a 25% increased yield of induced ventricular tachycardia due solely to repetition of each extrastimulus scan, and the 95% confidence limit for tachycardia induction with any extrastimulus was achieved by delivering that extrastimulus three times. In the group studied with lateral repetition, there was also an increased yield of induced ventricular tachycardia at any extrastimulus coupling interval achieved by repetitive delivery of that coupling interval.(ABSTRACT TRUNCATED AT 250 WORDS)

Differences between patients with ventricular tachycardia and ventricular fibrillation as assessed by signal-averaged electrocardiogram, radionuclide ventriculography and cardiac mapping.

This study examined 65 patients with ventricular tachycardia or fibrillation late after myocardial infarction to determine whether they differed with respect to duration of ventricular activation in sinus rhythm and left ventricular ejection fraction. Patients with spontaneous ventricular tachycardia had a longer ventricular activation time in sinus rhythm than did patients with spontaneous ventricular fibrillation. This difference was detected with the signal-averaged electrocardiogram (ECG) (tachycardia 181 +/- 33 ms, fibrillation 152 +/- 23 ms, p less than 0.001) and at epicardial mapping (tachycardia 210 +/- 17 ms, fibrillation 192 +/- 17 ms, p less than 0.02). Left ventricular ejection fraction was lower in patients with spontaneous ventricular tachycardia (0.22 +/- 0.09) than in patients with spontaneous ventricular fibrillation (0.27 +/- 0.09) (p less than 0.05). The patients with both spontaneous and inducible ventricular fibrillation had a shorter ventricular activation time on the signal-averaged ECG (129 +/- 17 ms) and a higher ejection fraction (0.36 +/- 0.05) than did either patients with spontaneous ventricular fibrillation and inducible ventricular tachycardia (158 +/- 21 ms and 0.25 +/- 0.08, respectively, each p less than 0.01) or patients with both spontaneous and inducible ventricular tachycardia (181 +/- 33 ms and 0.22 +/- 0.09, respectively, each p less than 0.001). Of the patients with inducible ventricular tachycardia, presentation with tachycardia rather than fibrillation was associated with a longer ventricular activation time on the signal-averaged ECG (181 +/- 33 versus 158 +/- 21 ms, p less than 0.02) and a longer cycle length of inducible ventricular tachycardia (290 +/- 61 versus 259 +/- 44 ms, p = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitation of day to day variability in mode of induction of ventricular tachyarrhythmias by programmed stimulation.

Spontaneous day to day variability in the mode of induction of ventricular tachycardia at programmed stimulation in the drug-free state has been described but not quantitated. To quantitate this variability, this study employed a new protocol of programmed stimulation in which the number of extrastimuli required for tachycardia induction was the only major stimulation variable. This protocol was applied to 18 consecutive patients with previously documented sustained ventricular tachyarrhythmia due to coronary artery disease. One to seven extrastimuli were available for arrhythmia induction if required. Each patient underwent programmed stimulation in the absence of antiarrhythmic drugs on 3 separate days with a mean interval of 5 +/- 2.7 days between studies. A sustained ventricular tachyarrhythmia was inducible in all studies with less than or equal to 4 extrastimuli; the mean number of extrastimuli required was 2.4 +/- 0.8. Day to day variability in the number of extrastimuli required for tachycardia induction was observed in the majority of patients (72%). Eleven patients (61%) varied by one extrastimulus over the three control studies, and two patients (11%) varied by two extrastimuli. At analysis of variance, the 95% confidence interval for the degree of day to day variability was +/- 1 extrastimulus from the mean number required in the three studies. Multiple configurations of induced ventricular tachycardia were frequently observed at repeat studies and occurred in 15 patients (83%). In conclusion, spontaneous day to day variability in mode of induction of ventricular tachycardia in the absence of drugs is common.(ABSTRACT TRUNCATED AT 250 WORDS)