The direction of these investigations now has two motives: a) identification of the subject at risk for sudden death; and b) development of methodologic approaches for assessing efficacy of preventive measures. Our essential hypotheses relate two factors as crucial for the emergence of ventricular fibrillation (VF); namely, electrical instability of the myocardium and transient risk factors. The latter primarily derive from higher nervous activity. We continue in our overall objectives to define the significance of electrical instability. Our specific goals include: 1) to improve methods for assessing ventricular vulnerability in the fully conscious animal; 2) to determine effect on ventricular fibrillation threshold of a number of newer agents; and 3) to assess the possible role of central nervous system drugs on susceptibility to VF. In human studies we shall continue to define the proper use of antiarrhythmics for protecting patients resuscitated from ventricular fibrillation. An additional goal will be to implement the community cardiology program within the framework of the YMCA. BIBLIOGRAPHIC REFERENCES: Lown, B. and Cohen, B.H.: Ventricular premature beats: To treat or not to treat? Prim. Cardiol. 3 (1): 16-20, 1977. Lown, B., Graboys, T.B., Podrid, P.J., Cohen, B.H., Stockman, M.B., and Gaughan, C.E.: Effect of a digitalis drug on ventricular premature beats (VPBs). New Eng. J. Med. 296: 301-306, 1977.