Small Left Ventricle and Clinical Outcomes After Transcatheter Aortic Valve Replacement

Case Report: Mechanical hemolysis resulting from left ventricular outflow tract obstruction after aortic valve replacement relieved by transapical beating-heart septal myectomy

Background

Aortic stenosis (AS) in combination with left ventricular outflow tract obstruction (LVOTO) has occasionally been reported. However, making a precise diagnosis and successfully treating this combination is challenging due to the hemodynamic interaction between the two conditions.

Case summary

A 56-year-old male patient who had been diagnosed with severe AS and asymmetric left ventricular hypertrophy underwent aortic valve replacement (AVR) and a conventional septal myectomy. Immediately after the procedure, significant systolic anterior motion and mitral regurgitation developed, necessitating a surgical mitral edge-to-edge repair. Ten days after the procedure, the patient developed hematuria and LVOTO, which was confirmed by echocardiography. Because the LVOTO might have been the cause of the hematuria, the patient underwent alcohol septal ablation, but this had little effect. Three months later, a transapical beating-heart septal myectomy (TA-BSM) was performed in our hospital. Postoperatively, the LVOTO had been significantly ameliorated and the hematuria had resolved.

Conclusion

For patients with AS and LVOTO due to a hypertrophic interventricular septum, inadequate amelioration of the LVOTO after AVR may lead to severe hemolytic hematuria. TA-BSM is a minimally invasive, safe, and effective surgical procedure for ameliorating LVOTO in patients with aortic valve prostheses.

Global Sensitivity Analysis of Four Chamber Heart Hemodynamics Using Surrogate Models

Computational Fluid Dynamics (CFD) is used to assist in designing artificial valves and planning procedures, focusing on local flow features. However, assessing the impact on overall cardiovascular function or predicting longer-term outcomes may requires more comprehensive whole heart CFD models. Fitting such models to patient data requires numerous computationally expensive simulations, and depends on specific clinical measurements to constrain model parameters, hampering clinical adoption. Surrogate models can help to accelerate the fitting process while accounting for the added uncertainty. We create a validated patient-specific four-chamber heart CFD model based on the Navier-Stokes-Brinkman (NSB) equations and test Gaussian Process Emulators (GPEs) as a surrogate model for performing a variance-based global sensitivity analysis (GSA). GSA identified preload as the dominant driver of flow in both the right and left side of the heart, respectively. Left-right differences were seen in terms of vascular outflow resistances, with pulmonary artery resistance having a much larger impact on flow than aortic resistance. Our results suggest that GPEs can be used to identify parameters in personalized whole heart CFD models, and highlight the importance of accurate preload measurements.

Small Left Ventricle and Clinical Outcomes After Transcatheter Aortic Valve Replacement

Background

In patients undergoing transcatheter aortic valve replacement (TAVR), those with small left ventricle (LV) may have an increased risk of poor outcomes, because small LV is associated with low‐flow (LF), left ventricular hypertrophy. However, the impact of small LV on patients undergoing TAVR remains unknown.

Methods and Results

We examined 2584 patients who underwent TAVR between October 2013 and May 2017 using data from the Japanese multicenter registry. On the basis of the American Society of Echocardiography guidelines, small LV was defined as left ventricular end‐diastolic dimension <42.0 mm for men or <37.8 mm for women. The 2‐year clinical outcomes were compared between patients with and without small LV using multivariable Cox regression analyses and propensity score matching. Subgroup analyses by LF, left ventricular hypertrophy were performed. Of 2584 patients who underwent TAVR, 466 (18.0%) had small LV. Patients with small LV had smaller body size and less comorbidity, and were more likely to have LF status compared with those without. Small LV was associated with a higher 2‐year all‐cause (20.8% versus 14.3%; adjusted hazard ratio [HR],1.58 [95% CI, 1.20–2.09]; P=0.0013) and cardiovascular mortality (8.8% versus 5.5%; adjusted HR, 1.93 [95% CI, 1.25–2.98]; P=0.0028). Propensity score matching analysis showed consistent findings. In subgroup analyses, LF, left ventricular hypertrophy did not interact with small LV.

Conclusions

Small LV, determined by a simple echocardiographic parameter, was associated with poorer clinical outcomes after TAVR regardless of LF, left ventricular hypertrophy. LV size may be useful for assessing clinical outcomes after TAVR.

Registration

URL: https://www.umin.ac.jp/ctr/index.htm; Unique identifier: UMIN000020423.