Baseline visit and initiation of spironolactone therapy
After the second investigation, patients attended for measurements of all clinical and biochemical parameters for which a response to treatment would assess the accuracy of the MTO and AVS. Obtaining the baseline measurements at this point in the study allowed a maximum interval between the discontinuation of any interfering medicines being taken at screening and the opportunity for the blood pressure response to initiation of spironolactone to be assessed as a predictor of response to surgery.After 4 d of home blood pressure recordings (three readings twice daily; 24 in total), blood was drawn for electrolytes, renin activity and/or renin mass, aldosterone, NT-pro-BNP and troponin. On the rare occasion that the minimum number of home blood pressure recordings was not available, office blood pressure recordings (an average of three sequential readings) were used instead. Participants also performed a 24-h urine collection for urine steroid profiles. Participants then commenced spironolactone 50 mg once daily for 2 weeks, increasing to 100 mg once daily depending on side effects and any concerns about renal function or potassium homeostasis. The response to spironolactone was recorded at 2 and 4 weeks after initiation of spironolactone with both home and office blood pressure recordings. Patients unable to tolerate spironolactone were treated with 25 mg eplerenone twice daily for 2 weeks, increasing to 50 mg twice daily.