Heterocyclic sodium/proton exchange inhibitors and method

Heterocyclic are provided which are sodium/proton exchange (NHE) inhibitors which have the structure ##STR1##

wherein n is 1 to 5; X is N or CR⁵ wherein R⁵ is H, halo, alkenyl, alkynyl, alkoxy, alkyl, aryl or heteroaryl; Z is a heteroaryl gorup, R¹, R², R³ and R⁴ are as defined herein, and where X is N. R¹ is preferably aryl or heteroaryl, and are useful as antianginal and cardioprotective agents. In addition, a method is provided for preventing or treating angina pectoris, cardiac dysfunction, myocardial necrosis, and arrhythmia employing the above heterocyclic derivatives.