Radiofrequency ablation for atrial fibrillation (AF) has emerged as a valuable therapy option; however, high rates of AF recurrence after ablation remain a limitation of this procedure. The recent Substrate Modification with Aggressive Blood Pressure Control (SMAC-AF) randomized controlled trial enrolled hypertensive patients, defined as BP>130/80mmHg, who had either persistent or paroxysmal AF, resistant or intolerant to at least one class I or III antiarrhythmic drug, who were scheduled for catheter ablation. 173 patients were randomly assigned to standard-of-care blood pressure target, 140/90mmHg or aggressive target, 120/80mmHg; there was no reduction in recurrence (HR 0.94, 95% CI 0.65-1.38 for aggressive control). This post-hoc analysis of the SMAC-AF population aimed to compare the risk factors for AF recurrence in each of the two cohorts. Using the SMAC-AF cohorts, we investigated how baseline characteristics and serum NT-pro-brain-natriuretic-peptide measured after AF ablation were associated with AF recurrence, defined as >30s of AF, more than 3 months post-ablation. Univariate Cox regression analysis was used to determine association between variables and AF recurrence. Of the 173 patients, 88 were randomized to the aggressive cohort, and 85 into the standard group. 106 (61.3%) patients had AF recurrence and 67 (38.7%) patients did not. Table 1 shows variables associated with AF recurrence. In the standard group, age (HR 1.03, p=0.04), number of antihypertensive medications (HR 1.31, p=0.048), and use of a calcium channel blocker (HR 1.81, p=0.03) were associated with recurrence. Twelve month NT-proBNP ≥300pg/ml was associated with higher AF recurrence as well. In the aggressive cohort, baseline systolic blood pressure (SBP) (HR 1.03, p=0.02), baseline SBP ≥ 140mmHg (HR 2.14, p=0.01), complex ablation during initial procedure (HR 3.11, p=0.01) were associated with recurrence, while use of diuretic (HR 0.44, p=0.01) was associated with reduced recurrence. There was a trend towards a reduction in occurrence with more anti-hypertensive agents (HR 0.81, p=0.08). An elevated baseline NT-proBNP had a trend towards association with recurrent AF; there were too few patients with an NT-proBNP ≥300pg/ml at 12 months (n=7 in the aggressive group) to determine significance in this group. In this post-hoc analysis, variables associated with recurrent AF differed between the aggressive and standard groups. Although aggressive blood pressure lowering was not associated with an improvement in AF recurrence in the entire cohort, there may be benefit in patients with higher baseline NT-proBNP, and older age. These associations need to be further clarified in ongoing clinical studies.