 Group 1: Sequential nephron blockade SNB Group - 40 patients will receive in addition to the basal therapy, spironolactone 25 mg, spironolactone 25 mg plus furosemide 20 mg, spironolactone 25 mg plus furosemide 40 mg and spironolactone 25 mg plus furosemide 40 mg plus amiloride 5 mg, sequentially. 