You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.

Abstract: Some patients converted from ventricular fibrillation to organized rhythms by defibrillation - trained ambulance technicians(EMT - Ds) will refibrillate before hospital arrival.The authors analyzed 271 cases of ventricular fibrillation managed by EMT - Ds working without paramedic back - up.Of 111 patients initially converted to organized rhythms, 19(17 % ) refibrillated, 11(58 % ) of whom were reconverted to perfusing rhythms, including nine of 11(82 % ) who had spontaneous pulses prior to refibrillation.Among patients initially converted to organized rhythms, hospital admission rates were lower for patients who refibrillated than for patients who did not(53 % versus 76 % , P = NS), although discharge rates were virtually identical(37 % and 35 % , respectively).Scene - to - hospital transport times were not predictively associated with either the frequency of refibrillation or patient outcome.Defibrillation - trained EMTs can effectively manage refibrillation with additional shocks and are not at a significant disadvantage when paramedic back - up is not available.
Solution: Ventricular Fibrillation
Why? This term is directly present in the abstract and it is one of the main topic in it. So can be chosen as the medical subject heading.

New input: Abstract: We examined the contributions of dietary protein and mineral to fracture-healing by assessing the mechanical properties of fracture callus in rats that were fed a diet that was deficient in or enriched by these nutrients. In order to isolate the effects of diet on fracture-healing, we developed a method for producing a standard closed femoral fracture with minimum-soft-tissue injury. Three groups of animals were studied. Group I was a control group, in which the rats did not undergo an operation. The rats in Group II underwent intramedullary pinning of the right femur, but no fracture was created. The rats in Group III underwent pinning identical to that used for Group II, after which a closed, transverse femoral fracture was produced. Immediately after surgery, the animals in each group were subdivided into five diet-treatment subgroups. Subgroup A received a regular diet; Subgroup B received a protein-free diet; and Subgroup C received a mineral-free diet that was lacking in calcium, phosphorus, and vitamin D. Subgroup D received a protein-supplemented diet that was composed of three times the calculated requirement of protein, and Subgroup E received a mineral-supplemented diet that was composed of three times the calculated requirements of calcium and phosphorus as well as a therapeutic dose of vitamin D, equivalent to that used in the treatment of osteomalacia. At the end of five weeks, the animals were killed and the right femur of each one was subjected to torsion-testing to failure.(ABSTRACT TRUNCATED AT 250 WORDS)
Solution:
Animal