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.

Example input: 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.
Example output: Ventricular Fibrillation
Example explanation: 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.
Q: Abstract: The cutaneous application of antiviral agents was studied by iontophoresis, a process that increases penetration of most drugs 20- to 60-fold. Twenty-seven subjects with vesicular orolabial herpes were treated one time in a double-blind, placebo-controlled clinical study: nine received vidarabine monophosphate (ara-AMP), nine received acyclovir (ACV), and nine received NaCl. Ara-AMP-treated lesions yielded lower titers of virus after 24 hr compared with lesions treated with NaCl or ACV (P less than .05). Ara-AMP significantly decreased the duration of shedding of virus (P less than .05) and time to dry crust (P less than .05) compared with the other two agents. There was a trend toward decreased healing time after ara-AMP treatment.
A:
Acyclovir