[CK] NYHA III vs IIIb

II: ordinary cause SOB
III: less than ordinary cause SOB
IIIb: even minimal activity cause SOB
IV: resting SOB.

IIIb:
 NYHA class III patients who are symptomatic with a recent history of dyspnea at rest

Mozaffarian D, 200440

IIIB or IV

Dyspnea or fatigue at rest or with minimal exertion