Patients were randomized to placebo or 40 mg/day of extended-release isosorbide mononitrate added to standard therapy and titrated to 60 mg/day at week 6 if blood pressure exceeded 140/90 mmHg.The primary objective was to assess the effect on clinical pulse pressure of extended-release isosorbide mononitrate added to standard therapy in patients aged over 65 years with refractory isolated systolic hypertension after 3 months of treatment.The secondary objectives were as follows : to quantify the effect of adding the study drug on central blood pressure and vascular compliance using the augmentation index and pulse wave velocity ; to evaluate the safety profile by recording adverse effects ( frequency , type , severity ) and the percentage of patients who had to withdraw from the trial because of adverse events ; to quantify the percentage of patients who reach a clinical systolic blood pressure < 140 mmHg or < 130 mmHg measured by ambulatory blood pressure monitoring ; and to quantify the change in pulse pressure measured by ambulatory blood pressure monitoring .