Common criteria for implant of a cardioverter defibrillator include verification of a 2:1 energy safety margin or a fixed safety margin of 10 joules. These criteria have been established empirically. We present a statistically model based on defibrillation efficacy curves which may be used to establish a criterion which would meet a predetermined target. As an example, an implant criterion is derived based on a goal of 1-year sudden cardiac death survival of at least 99% by selecting an expected first-shock efficacy to meet that target. Logistic regression was performed on data from over 1,500 defibrillator implants including successful epicardial and transvenous electrode system implants as well as data from unsuccessful implants. A random sample from these curves was used to generate a representative sample of 1,000 potential implant candidates. By assuming successful defibrillation using a series of shocks at specified energies, i.e., choosing an implant criterion, the probability of successful defibrillation of the patient by a single shock at a predetermined maximum output can be established. Independent data are used to validate the model's accuracy in predicting defibrillation efficacy within the derived example.

for advisory boards and speaking for Medtronic and Abbott. Support for meta-analysis of Medtronic trials of CRT.• Anne B. Curtis, MD --Medtronic, Inc.: honoraria for speaking, data monitoring board for clinical trial; Abbott: medical advisory board; honoraria for speaking; data monitoring board for clinical trial; Novartis: medical advisory board; honoraria for speaking; Janssen

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Summary 1.The major aim of this paper was to explore the mechanistic basis of induced defensive ant response in myrmecophytic Piper species and their ant-partner Pheidole bicornis by combining experimental trials and chemical analysis. 2.In field experiments, the response of Pheidole ants to simulated stem-damage of their host plant was documented. Their reaction to other myrmecophytic and non-myrmecophytic Piper species was explored by fixing respective stem sections onto inhabited Piper fimbriulatum individuals. After artificial damage to stems of P. fimbriulatum and stem sections from other myrmecophytic Piper , the number of ants increased to a maximum of 63 individuals on the damaged internode within the first 10 min. By contrast, no or only a poor reaction was elicited by stem sections from the selected non-myrmecophytic Piper species. 3. Solid-phase microextraction/gas chromatography-mass spectrometry identified 68 volatile organic compounds (VOCs) which were emitted from wounded stem bark of three myrmecophytic ( P. fimbriulatum , P. obliquum , P. sagittifolium ) and two non-myrmecophytic ( P. hispidum , P. riparense ) Piper species, comprising monoterpenes, sesquiterpenes, simple aromatic compounds, and green leaf volatiles (GLVs, oxylipins). Despite considerable variation in the VOC profiles, an analysis of similarities ( anosim ) classified the accumulation of the sesquiterpenes β -caryophyllene, germacrene D and emission of the oxylipin reactive electrophilic species (RES) compounds hexanal, cis -3-hexene-1-ol, 2-hexenal, 2-undecanone and 1-hexanol as characteristic of the myrmecophytic species. 4. Synthesis . Field experiments showed that mechanical disturbance of myrmecophytic Piper stems is not sufficient to elicit recruitment and alertness of the ant-partner Ph. bicornis , but that specific volatiles released from the host plant are responsible. Analyses of the VOCs identified after simulated stem damage of three myrmecophytic and two non-myrmecophytic Piper species revealed differences in their VOC emission profiles: Only in the myrmecophytic species were induced stress compounds found, such as various oxylipin RES or the sesquiterpene β -caryophyllene, which are typically emitted after plant damage for interplant signalling. Some of these compounds (e.g. hexanal, 1-hexanol) are known to induce alerting and alarm behaviours in several ant species. Our study provides evidence that the VOCs of the Piper host plant may signal stem damage and induce recruitment and alert behaviour of associated Pheidole ants.