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The threshold voltage and current necessary for ventricular defibrillation was measured in dogs using capacitor-discharge and half-sinusoidal pulses of current of various durations. From these quantities the electrical strength required for defibrillation was determined and expressed as energy, peak current, and charge per gram of heart. The optimum current duration depends on the criterion selected. It was found that with half-sinusoidal current, less energy, current, and charge were required; this type of waveform approximates that delivered by capacitor-inductor defibrillators. For minimum energy with this waveform, the optimum duration range is 1.25 to 8.3 msec and the energy required is approximately 7 mw-sec per gram of heart. For minimum current, the optimum duration is 8.3 msec; with this duration the peak half-sinusoidal current is about 30 mamp per gram of heart. There is no clearly defined duration for minimum charge for capacitor-discharge or half-sinusoidal current.

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Objectives: To identify associations between MRI-detected skin thickening and enhancement and metastasis-free-survival (MFS) given recent reports of skin thickening on ultrasound being a poorer prognostic indicator. Methods: Interrogation of a prospectively collected database of ultrasound-visible breast lesions showed 214 lesions with pre-treatment MRIs available for analysis in a single centre. Data on metastasis-free-survival (MFS) was prospectively collected. Retrospective MRI review was performed blinded to outcome. Imaging factors recorded were presence of skin thickening and enhancement, non-mass-enhancement (NME) and abnormal nodes, mass characteristics, perilesional oedema and background parenchymal enhancement. Statistical analysis used Chi-squared test, Kaplan-Meier survival curves, the Log-rank test and Receiver-Operator-Characteristic (ROC) curves. Results: During a median follow-up period of 5.6 years, 21 (10%) of 212 patients developed distant metastases. Skin thickening [24 of 30 (80%) vs 169 of 184 (92%), p = 0.043] and skin enhancement [15 of 20 (75%) vs 178 of 194 (92%), p = 0.016] were associated with poorer MFS. Large index lesion size [p < 0.001, AUC 0.823], large sum of masses [p < 0.001, AUC 0.813], increasing total lesion extent including NME [p < 0.001, AUC 0.749] and abnormal axillary nodes [55 of 66 (83%) vs 138 of 148 (93%), p = 0.024] were also associated with poorer MFS. Conclusions: Skin thickening and enhancement on breast MRI are associated with poorer MFS. These findings should be taken into account when managing patients with invasive breast cancer. Advances in knowledge: Skin enhancement on breast MRI at diagnosis is associated with metastases development. Skin thickening on breast MRI is associated with future metastatic disease.

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