- Inability to tolerate beta blockers Atrio-ventricular block (grade II-III), prolonged QT interval or sick sinus syndrome Renal insufficiency (creatinine ≥ 1.6 and/or, GFR < 60 ml/min) or renal failure requiring dialysis Atrial fibrillation or other markedly irregular rhythm CCTA performed within a week prior to the index catheterization.