Small annulus or small patient? It's the aortic complex that matters for TAVR

Proper valve sizing has become critical to insuring success and reducing complications of transcatheter aortic valve replacement (TAVR). The limited availability of valve sizes has raised questions about the safety and outcomes of TAVR in patients with annular sizes at the small and large ends of the spectrum. Watanabe et al. present the outcomes patients with small body surface areas (BSA< 1.75) m compared to those with BSA> 1.75 m in a small series of patients. Although they claim to show that the clinical outcomes for TAVR are similar between the two groups, their data tell a much different story—a cautionary tale about the risks of using the currently available transcatheter valves in small patients. The authors use the median BSA to subdivide their patients, but it is doubtful that this provides the most interesting comparison since we would expect to see the highest number of complications among the extremely small patients, so evaluating the lowest quartile or tertile would provide a more meaningful analysis than using the lower half. In light of this, their “small” patients had relatively normal sized aortic valve diameters (23.3 6 1.9 cm, derived from CT), iliacs (8.26 6 1.3 cm), and coronary ostia heights (13.5 6 2.9 cm on the left and 14.4 6 2.8 on the right). Even though these values were slightly smaller than their comparison group, they would not be considered particularly small. Most importantly, the ratio of the TAVR-valve to the CT-annulus diameter was exactly the same 1.11 6 0.06 for the small and large body size cohorts. Given this, it is not surprising that the overall clinical results between the two groups were similar. Although not statistically significant, the 2.3% rate of annular rupture was more than five times that seen in the comparator group. Had it not been for the single annular rupture seen in the large body cohort, the rate of annular rupture in the small BSA cohort would have been statistically higher. This is an extremely distressing finding since the observation of annulus rupture in five of these 96 patients, far exceeds what would be expected, given that there were no annular ruptures observed in the 806 patients who underwent TAVR in the PARTNER cohort A and B studies [1,2], or the 876 patients who underwent TAVR in the extreme [3] and high risk [4] CoreValve studies. This high rate of annular ruptures reported in this cohort is an important signal that should not be ignored. Despite the overall average valve oversizing of only 11%, the annulus rupture likely occurred among patients with the most extreme oversizing (i.e., those >1 to 2 SD from the mean). The authors’ dichotomization of BSA along the median likely diluted the relationship of annular oversizing and annular rupture within the aggregate data—a finding that may be revealed by evaluating quartiles of size, or by considering annulus size and BSA as continuous, rather than dichotomous variables. We have reported increased rate of complications among patients with small LV chamber size undergoing aortic valve procedures, as they have an increased risk for annular rupture, dynamic outflow track obstruction once the aortic stenosis is relieved by TAVR, and pulmonary congestion due to impaired diastolic filling. Our study showed that small chamber size, not small BSA was independently associated with increased risk [5]. This is consistent with the numerous studies showing that annular rupture is associated with valve-annulus oversizing—which occur more frequently among patients with small annulus sizes due the lack of availability of valve sizes <23 mm. There are theoretical benefits of TAVR among patients with small outflow tracks. As the authors point out, TAVR valves offer a superior hemodynamic profile