The present invention relates to methods for the treatment of conditions characterised by abnormalities of myocardial cell ion levels, such as Na.sup.+, K.sup.+ and Ca.sup.2+ ions. The present invention also relates to methods of treatment of heart failure and myocardial hypertrophy. The invention also relates to compounds and compositions, such as .beta..sub.3 adrenoceptor agonists, useful in the treatment of mammals, particularly humans, having a condition characterised by abnormalities of myocardial cell ion levels, such as Na.sup.+, K.sup.+ and Ca.sup.2+ ions, including heart failure and myocardial hypertrophy.