Features of the trials	MDC (1993)	MERIT-HF (1999)
Number of patients	383	3,991
Mean age	49 years	64 years
Gender	Men: 73 percent	Men: 78 percent
	Women: 25 percent	Women: 22 percent
Race	Not reported	White: 94 percent
		Black: 5 percent
Ejection fraction	Less than 40 percent	Less than 40 percent
New York Heart Association classification	Class II: 47 percent	Class II: 41 percent
	Class III: 47 percent	Class III: 55 percent
	Class IV: 4 percent	Class IV: 4 percent
Etiology of heart failure	Idiopathic	Ischemic and nonischemic
Starting dosage	Metoprolol tartrate, 10 mg per day	Metoprolol succinate, 12.5 to 25 mg per day
Target dosage	100 to 150 mg per day in divided doses twice daily	200 mg per day
Average duration of study	12 to 18 months	12 months
Primary end point	Mortality plus need for transplantation	Mortality
Results	Risk of reaching end point: placebo, 20.1 percent; metoprolol tartrate, 12.9 percent	Absolute mortality: placebo, 11.0 percent per patient-year of follow-up; metoprolol succinate, 7.2 percent per patient-year of follow-up
Comments	Treatment improved clinical status, reduced the need for heart transplantation and was safe.	Study was stopped early. Treatment reduced sudden deaths and deaths from progressive pump failure.
	No improvement in mortality.