The Impella microaxial-flow pump can directly unload left ventricle (LV) in cases of acute heart failure. Extracorporeal membrane oxygenation (ECMO) is widely used for circulatory support. Although the clinical effectiveness of ECMO has been demonstrated, insufficient LV loading reduction may not be advantageous for myocardial recovery. The objective was to compare ventricular loading reduction and reversibility of ventricular fibrillation (VF) with either Impella or ECMO. Six dogs were used. Extracorporeal membrane oxygenation was established by the femoral artery and right atrium. The Impella LD was inserted in LV by the ascending aorta. An acute failing heart was created by sequential coronary artery ligations. Pressure-volume (PV) relationships were acquired without a device and with ECMO or Impella. When VF occurred, direct cardioversion was performed while supported by either ECMO or Impella. The PV area, which is a measure of ventricular unloading and is correlated with myocardial oxygen consumption, decreased more with Impella than with ECMO. Successful defibrillation was achieved more effectively while under Impella support. Superior ventricular unloading with the Impella device may provide higher recovery potential to damaged hearts than ECMO and may have a significant impact not only on intensive care of patients with heart failure but also on resuscitation.
Background
Progressive left ventricular (LV) dysfunction can be a major late complication in patients with chronic right ventricular (RV) pressure overload (e.g., tetralogy of Fallot). We therefore examined LV function (serial echocardiography and ex vivo Langendorff) and histology in a model of infant pressure-load RV hypertrophy (RVH).
Methods and Results
Ten-day-old rabbits (N=6 per time point, total = 48) that underwent pulmonary artery banding (PAB) were sacrificed at 2–8 weeks after PAB, and comparisons were made with age-matched sham controls. LV performance (myocardial performance index, MPI) decreased during the progression of RVH although the LV ejection fraction (EF) was maintained. In addition, RVH caused significant septal displacement, reduced septal contractility, and decreased LV end-systolic (LVDs) and diastolic (LVDd) dimensions, resulting in LV diastolic dysfunction with the appearance of preserved EF. Significant septal and LV free wall apoptosis (myocyte-specific TUNEL and activated caspase-3), fibrosis (Masson’s trichrome stain), and reduced capillary density (CD31 immunostaining) occurred in the PAB group after 6–8 wks (all p<0.05).
Conclusion
This is the first study showing that pressure overload of the RV resulting in RVH causes LV diastolic dysfunction while preserving EF through mechanical and molecular effects upon the septum and LV myocardium. In particular, the development of RVH is associated with septal and LV apoptosis and reduced LV capillary density.
Beating-heart perventricular muscular ventricular septal defect closure without cardiopulmonary bypass can be successfully achieved by using a catheter-based patch delivery and fixation system under real-time three-dimensional echocardiographic guidance. This approach might be a better alternative to cardiac surgery or transcatheter device closure.
Objectives: In patients with high-risk hypoplastic left heart syndrome (HLHS), the Norwood operation (NW) in the neonatal period still results in high mortality compared with other cardiac surgery. Bilateral pulmonary artery banding (bPAB), a very effective initial procedure for HLHS, for which the specific evaluation is as yet unsatisfactory, was performed, and we report our findings in the present study.
Methods:We have performed bPAB since 2006. A total of 17 patients with HLHS or a variant underwent bPAB before the NW. Echocardiography was performed between bPAB and the NW, and the flow acceleration just after bPAB and before NW was evaluated. Before the NW, a catheter examination was also performed.Results: bPAB was performed at 6.6 AE 0.6 days of age, and the NW at 130 AE 88 days. The patients' mean body weight (BW) was 2.5 AE 0.4 kg at bPAB and 4.0 AE 1.1 kg at the NW. The length of the tape for bPAB was 9.9 AE 0.6 mm in the right pulmonary artery (RPA) and 9.4 AE 0.6 mm in the left (LPA) because the RPA was usually wider than the LPA. The tape width was 2 mm in all cases. The catheter examination was performed at 95 AE 85 days after bPAB. The arterial oxygen saturation (SaO 2 ) was 71% AE 8.6%. Multivariate regression analysis revealed that SaO 2 was estimated well using 4 factors: the banding size of the RPA, BW at bPAB, BW at NW, and BW in the period between bPAB and catheter examination (R 2 ¼ 0.79). Echocardiography just after bPAB showed that the blood flow at the bPAB had accelerated to 3.0 AE 0.8 m/s in the RPA and 3.3 AE 0.8 m/s in the LPA (P ¼ .004). The estimated pressure gradient was 39.2 AE 17.6 mm Hg in the RPA and 46.1 AE 23.0 mm Hg in the LPA (P ¼ .006). The blood flow at bPAB was accelerated to 3.7 AE 0.7 m/s in the RPA and 4.0 AE 0.6 m/s in the LPA before NW (P ¼ .013). The estimated pressure gradient was 62.6 AE 27.6 mm Hg in the RPA and 56.1 AE 19.6 mm Hg in the LPA before NW (P ¼ .014). The catheter examination revealed mean wedge pressures of 18.0 AE 7.2 mm Hg for the RPA and 16.2 AE 4.3 mm Hg for the LPA. The operative mortality rate was 0%. One patient required a repeat operation to adjust the bPAB, and prolonged pleural effusion was observed in 1 case.
Conclusions:The postoperative SaO 2 after bPAB correlated closely with the banding size and BW at bPAB, NW and during the period after bPAB. Because the mean PA pressure before NW was low enough for single ventricular circulation, the bPAB in this study was an effective option for high-risk patients undergoing HLHS or a variant. We believe the bPAB sizes used were suitable and were determined as follows: BW plus 7 mm for the LPA and BW plus 7.5 mm for the RPA.
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