Methods and compositions for the detection, diagnosis, and prevention of cardiac conditions are provided. Polymorphisms of .beta..sub.1-adrenergic receptor are provided. The Gly389 .beta..sub.1-adrenergic receptor variants are not as responsive to treatment .beta. blockers such as carvedilol, metoprolol or bisoprol. Thus, genotyping .beta..sub.1-adrenergic receptor polymorphisms is useful for predicting relative responsiveness to treatment with beta blockers. The Gly389 polymorphism also may be used, alone or in conjunction with other adrenergic receptor polymorphisms, to predict relative risk of developing cardiovascular diseases such as heart failure or to predict relative survival rate in patients with heart failure or other cardiovascular diseases. Also provided are transgenic mice and transgenic cells expressing the .beta..sub.1-adrenergic receptor polymorphisms, and their use in identifying therapeutic agents.