Effectiveness of a low contrast load CT angiography protocol in octogenarians and nonagenarians being evaluated for transcatheter aortic valve replacement

IntroductionTranscatheter aortic valve replacement (TAVR) typically requires computed tomographic angiography (CTA) for aortoiliofemoral assessment to determine feasibility of a transfemoral approach, although many candidates being considered for TAVR are at increased risk of contrast-induced nephropathy (CIN).ObjectiveTo determine the feasibility and safety of a load contrast load CTA protocol in octogenarians and nonagenarians at risk of CIN.ApproachWe evaluated 54 consecutive octogenarians and nonagenarians considered for TAVR who underwent CTA using a standard contrast protocol (n= 21) versus a protocol incorporating low-dose contrast in patients at risk of CIN (n= 33). We compared clinical characteristics, CTA image quality (score 1–4) and interpretability, and clinical outcomes, including CIN and vascular complications.ResultsThe mean age was 88.5±4.0 years, 37% were male, and chronic renal insufficiency was common in both the standard and low-dose contrast cohorts (57% vs. 70%, P= .39). The low-dose contrast protocol was associated with a significantly less contrast volume compared to standard contrast protocol (127±18 ml vs 76±55 ml, P< .001). Individuals imaged using low-dose (n= 16) versus standard (n= 17) contrast protocols received 80% less contrast volume (23±10 vs. 125±23 ml, P< .001). There was similar graded image quality (3.8±0.4 vs. 3.9±0.3, P= .76) and interpretability (100% for each, P= 1.0) between standard and low-dose contrast protocol groups. There was no significant difference in rates of CIN after CTA between standard and low-dose contrast protocol groups (10% vs. 3%, P= .55), with no CIN events in those imaged by low-dose CTA. There were no major vascular injuries associated with TAVR or pigtail insertion, no major bleeding for CTA, and no noninterpretable studies in all patients.ConclusionIn this proof-of-principle study, a low-dose contrast protocol appears feasible and safe in octogenarians and nonagenarians undergoing screening for TAVR, and results in significant reduction in contrast load as compared to a standard contrast protocol without observed differences in image quality or safety.