The below are some classifications with IV, bot II related to paired/coupled VES; hence the exact classification remains unknown but we the word is here.

Градация желудочковых экстрасистол по Лауну — Вольфу
I — до 30 экстрасистол за любой час мониторирования
II — свыше 30 экстрасистол за любой час мониторирования
III — полиморфные экстрасистолы
IVa — парные экстрасистолы
IVb — групповые экстрасистолы, триплеты и более, короткие пробежки желудочковой тахикардии
V — ранние желудочковые экстрасистолы типа R на T
— http://ru.wikipedia.org/wiki/Экстрасистолия

Ventricular arrhythmias were categorized according to the Lown-Wolf classification38 : grade 0, no premature ventricular complexes; grade 1, <30 premature ventricular complexes per hour; grade 2, >30 premature ventricular complexes per hour; grade 3, multiform; grade 4A, couplets; grade 4B, salvos (>3 consecutive premature ventricular complexes at a rate >110 beats per minute); and grade 5, R-on-T phenomenon.
— http://circ.ahajournals.org/content/91/5/1450.long

Based on Holter monitoring, Lown proposed the following classification of ventricular extrasystoles:

Class 0: absence ventricular extrsistoles at least 3 hours;
Class I: premature ventricular extrasistoles, monomorphic and occasional, the occurrence is less than one ventricular extrasistole per minute or less than 30 ventricular extrasystoles per hour.
Class II: frequent monomorphic ventricular extrasystoles, more than one ventricular extrasistole per minute or more than 30 ventricular extrasystoles per hour.
Class IIIa: polymorphic ventricular extrasystoles (multifocal).
Class IIIb: systematized ventricular extrasystoles (bigeminy, trigeminy).
Class IVa: coupled repetitive ventricular extrasystoles (2 ventricular extrasystoles)
— http://www.doctortipster.com/3744-ventricular-extrasystoles-...

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Note added at 2 hrs (2013-04-25 05:19:54 GMT)
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Grading (which, as such, is not typing) is assumed based on paired VES occuring both in the context and the classifications cited.