Cardiac output assessment methods in left ventricular assist device patients: A problem of heteroscedasticity.

Equipoise remains about how best to measure cardiac output (CO) in patients with left ventricular assist devices (LVAD). In this study, direct Fick CO was compared with thermodilution (TD) and indirect Fick (iFick) CO in 61 LVAD patients. TD and LaFarge iFick showed moderate correlation with direct Fick (R2 = 0.49 and R2 = 0.38, p < 0.001 for both), while Dehmer and Bergstra iFick showed poor correlation with direct Fick (R2 = 0.29 and R2 = 0.31, p < 0.001 for both). Absolute bias between all CO estimation techniques and direct Fick CO was lowest for TD compared to iFick methods but significant for all methods. All methods tended to overestimate CO compared to direct Fick, with greatest overestimation present in those with the lowest measured direct Fick CO. Bias and frequency of significant discrepancy were least using TD and Lafarge iFick CO estimation methods in this study, with TD CO demonstrating modestly better correlation and less heteroscedasticity compared to Lafarge.

Hemodynamic reserve predicts early right heart failure after LVAD implantation.

BACKGROUND: Early right heart failure (RHF) remains a major source of morbidity and mortality after left ventricular assist device (LVAD) implantation, yet efforts to predict early RHF have proven only modestly successful. Pharmacologic unloading of the left ventricle may be a risk stratification approach allowing for assessment of right ventricular and hemodynamic reserve. METHODS: We performed a multicenter, retrospective analysis of patients who had undergone continuous-flow LVAD implantation from October 2011 to April 2020. Only those who underwent vasodilator testing with nitroprusside during their preimplant right heart catheterization were included (n = 70). Multivariable logistic regression was used to determine independent predictors of early RHF as defined by Mechanical Circulatory Support-Academic Research Consortium. RESULTS: Twenty-seven patients experienced post-LVAD early RHF (39%). Baseline clinical characteristics were similar between patients with and without RHF. Patients without RHF, however, achieved higher peak stroke volume index (SVI) (30.1 ± 8.8 vs 21.7 ± 7.4 mL/m2; p < 0.001; AUC: 0.78; optimal cut-point: 22.1 mL/m2) during nitroprusside administration. Multivariable analysis revealed that peak SVI was significantly associated with early RHF, demonstrating a 16% increase in risk of early RHF per 1 ml/m2 decrease in SVI. A follow up cohort of 10 consecutive patients from July 2020 to October 2021 resulted in all patients being categorized appropriately in regards to early RHF versus no RHF according to peak SVI. CONCLUSION: Peak SVI with nitroprusside administration was independently associated with post-LVAD early RHF while resting hemodynamics were not. Vasodilator testing may prove to be a strong risk stratification tool when assessing LVAD candidacy though additional prospective validation is needed.

Outcomes in Patients With LVADs Undergoing Simultaneous Heart-Kidney Transplantation.

BACKGROUND: Multiple studies have shown better outcomes for simultaneous heart-kidney transplant (sHKT) than for isolated orthotopic heart transplant (iOHT) in recipients with chronic kidney disease (CKD). However, outcomes in patients supported by durable left ventricular assist devices (LVADs) have not been well studied. METHODS: Patients with durable LVADs and stage 3 or higher CKD (eGFR < 60 mL/min/1.73 m2) undergoing iOHT or sHKT between 2008 and 2020 were identified from the United Network for Organ Sharing registry. A Kaplan-Meier survival analysis with associated log-rank test was conducted to compare post-transplant survival rates. Multivariable modeling was used to identify risk-adjusted predictors of 1 year post-transplant mortality. RESULTS: We identified 4375 patients; 366 underwent sHKT, and 4009 underwent iOHT. The frequency of sHKT increased during the study period. The 1-year post-transplant survival rate was worse in patients after sHKT than in patients after iOHT (80.3% vs 88.3%; P < 0.001) and persisted up to 5 years post-transplant (P = 0.001). sHKT recipients were more likely to require dialysis after transplantation and had longer hospital lengths of stay (P < 0.001). Multivariable analysis showed that sHKT remained an independent risk factor for mortality at 1 year (OR 1.58; P = 0.002). CONCLUSIONS: sHKT is becoming more common in patients with durable LVADs. Compared with iOHT, patients with sHKTs have worse short- and long-term survival rates and are more likely to require post-transplant dialysis.

Murine Surgical Model of Topical Elastase Induced Descending Thoracic Aortic Aneurysm.

According to the Center for Disease Control, aortic aneurysms (AAs) were considered a leading cause of death in all races and both sexes from 1999-2016. An aneurysm forms as a result of progressive weakening and eventual dilation of the aorta, which can rupture or tear once it reaches a critical diameter. Aneurysms of the descending aorta in the chest, called descending thoracic aortic aneurysms (dTAA), make up a large proportion of aneurysm cases in the United States. Uncontained dTAA rupture is almost universally lethal, and elective repair has a high rate of morbidity and mortality. The purpose of our model is to study dTAA specifically, to elucidate the pathophysiology of dTAA and to search for molecular targets to halt the growth or reduce the size of dTAA. By having a murine model to study thoracic pathology precisely, targeted therapies can be developed to specifically test dTAA. The method is based on the placement of porcine pancreatic elastase (PPE) directly on the outer murine aortic wall after surgical exposure. This creates a destructive and inflammatory reaction, which weakens the aortic wall and allows for aneurysm formation over weeks to months. Though murine models possess limitations, our dTAA model produces robust aneurysms of predictable size. Furthermore, this model can be used to test genetic and pharmaceutical targets which may arrest dTAA growth or prevent rupture. In human patients, interventions such as these could help avoid aneurysm rupture, and difficult surgical intervention.