Reversible pulmonary trunk banding with a balloon catheter: assessment of rapid pulmonary ventricular hypertrophy

Von Willebrand factor as a biological sensor of blood flow to monitor percutaneous aortic valve interventions

RATIONALE

Percutaneous aortic valve procedures are a major breakthrough in the management of patients with aortic stenosis. Residual gradient and residual aortic regurgitation are major predictors of midterm and long-term outcome after percutaneous aortic valve procedures. We hypothesized that (1) induction/recovery of high molecular weight (HMW) multimers of von Willebrand factor defect could be instantaneous after acute changes in blood flow, (2) a bedside point-of-care assay (platelet function analyzer-closure time adenine DI-phosphate [PFA-CADP]), reflecting HMW multimers changes, could be used to monitor in real-time percutaneous aortic valve procedures.

OBJECTIVE

To investigate the time course of HMW multimers changes in models and patients with instantaneous induction/reversal of pathological high shear and its related bedside assessment.

METHODS AND RESULTS

We investigated the time course of the induction/recovery of HMW multimers defects under instantaneous changes in shear stress in an aortic stenosis rabbit model and in patients undergoing implantation of a continuous flow left ventricular assist device. We further investigated the recovery of HMW multimers and monitored these changes with PFA-CADP in aortic stenosis patients undergoing transcatheter aortic valve implantation or balloon valvuloplasty. Experiments in the aortic stenosis rabbit model and in left ventricular assist device patients demonstrated that induction/recovery of HMW multimers occurs within 5 minutes. Transcatheter aortic valve implantation patients experienced an acute decrease in shear stress and a recovery of HMW multimers within minutes of implantation which was sustained overtime. In patients with residual high shear or with residual aortic regurgitation, no recovery of HMW multimers was observed. PFA-CADP profiles mimicked HMW multimers recovery both in transcatheter aortic valve implantation patients without aortic regurgitation (correction) and transcatheter aortic valve implantation patients with aortic regurgitation or balloon valvuloplasty patients (no correction).

CONCLUSIONS

These results demonstrate that variations in von Willebrand factor multimeric pattern are highly dynamic, occurring within minutes after changes in blood flow. It also demonstrates that PFA-CADP can evaluate in real time the results of transcatheter aortic valve procedures.

Chronic treatment with anabolic steroids induces ventricular repolarization disturbances: cellular, ionic and molecular mechanism

The illicit use of supraphysiological doses of androgenic steroids (AAS) has been suggested as a cause of arrhythmia in athletes. The objectives of the present study were to investigate the time-course and the cellular, ionic and molecular processes underlying ventricular repolarization in rats chronically treated with AAS. Male Wistar rats were treated weekly for 8 weeks with 10mg/kg of nandrolone decanoate (DECA n=21) or vehicle (control n=20). ECG was recorded weekly. Action potential (AP) and transient outward potassium current (I(to)) were recorded in rat hearts. Expression of KChIP2, Kv1.4, Kv4.2, and Kv4.3 was assessed by real-time PCR. Hematoxylin/eosin and Picrosirius red staining were used for histological analysis. QTc was greater in the DECA group. After DECA treatment the left, but not right, ventricle showed a longer AP duration than did the control. I(to) current densities were 47.5% lower in the left but not in the right ventricle after DECA. In the right ventricle the I(to) inactivation time-course was slower than in the control group. After DECA the left ventricle showed lower KChIP2 ( approximately 26%), Kv1.4 ( approximately 23%) and 4.3 ( approximately 70%) expression while the Kv 4.2 increased in 4 ( approximately 250%) and diminished in 3 ( approximately 30%) animals of this group. In the right ventricle the expression of I(to) subunits was similar between the treatment and control groups. DECA-treated hearts had 25% fewer nuclei and greater nuclei diameters in both ventricles. Our results strongly suggest that supraphysiological doses of AAS induce morphological remodeling in both ventricles. However, the electrical remodeling was mainly observed in the left ventricle.

Pulmonary Artery Banding

Proponents of a telemetrically adjustable pulmonary artery band (PAB) device have cited simplified postoperative management and shortened length of stay as advantages associated with that technology. This report concerns a recent experience with both conventional pulmonary artery banding (conv-PAB) and the telemetrically adjustable PAB FloWatch (FW-PAB). From January 2005 through December 2008, 19 consecutive infants underwent either conv-PAB (8 patients, mean age 3.5 months, mean weight 4.1 kg) or FW-PAB (11 patients, mean age 2.6 months, mean weight 3.1 kg). Indications for PAB were left ventricular retraining (1 patient in FW-PAB), palliation prior to biventricular repair (7 patients in conv-PAB and 10 in FW-PAB group), and staged univentricular repair (1 patient in conv-PAB). In-hospital mortality was 0%. In the FW-PAB group, 1 FloWatch device was removed because of hemodynamic compromise related to the bulk of the device. There were no major complications in the conv-PAB group and no differences between groups with respect to postoperative ventilation time or length of stay in the intensive care unit or in hospital. In the FW-PAB group, a mean of 3.1 ± 1.7 regulations per patient were undertaken. Of the regulations, 85% (29/34) were adjustments to tighten the device, and 15% (5/34) were to loosen it. During follow-up, 8 patients underwent intracardiac repair and pulmonary artery debanding: 4 in the conv-PAB group and 4 in the FW-PAB group. The course of patients in both groups after PAB were similar. Major differences in length of stay and resource utilization were not apparent.

Reversible pulmonary trunk banding III: Assessment of myocardial adaptive mechanisms—contribution of cell proliferation

OBJECTIVES

Rapid ventricular conditioning induced by pulmonary artery banding has been recommended for patients with transposition of the great arteries who have lost the chance for the arterial switch operation or whose systemic (right) ventricle failed after the atrial switch. The present study was designed to experimentally evaluate 2 types of pulmonary artery banding (continuous and intermittent) and verify histologically the changes (hypertrophy or hyperplasia or both) of cardiomyocytes and vascular and interstitial cells from the stimulated ventricle beyond the neonatal period.

METHODS

Twenty-one goats, 30 to 60 days old, were divided into 3 groups, each comprising 7 animals, as follows: control group (no surgical procedure); continuously stimulated group (systolic overload maintained for 96 hours); and intermittently stimulated group (4 periods of 12-hour systolic overload, alternated with a resting period of 12 hours). The animals were then killed for histologic and immunohistochemical analysis of the hearts. Murine monoclonal antibody Ki-67 was used as a proliferation cell marker. Myocardial collagen area fraction was determined by Sirius red staining.

RESULTS

For both stimulated groups, a significant increase occurred in right ventricular cardiomyocytes and respective nuclei diameters compared with the controls (P < .05). The number of Ki-67-positive cardiomyocytes and interstitial/vessel cells from the right ventricle was augmented in both trained groups in relation to the left ventricle (P < .05). There was no significant difference in the right ventricular collagen area fraction from both trained groups compared with controls.

CONCLUSIONS

Irrespective of the shorter training time (periods of overload intercalated with resting), the intermittent stimulation regimen was able to produce a similar training of the subpulmonary ventricle compared with the continuous stimulation regarding mass acquisition, cell hypertrophy, and hyperplasia.

Early Clinical Results of the Telemetric Adjustable Pulmonary Artery Banding FloWatch-PAB

Background— Adjustment of pulmonary artery banding (PAB) may be a challenging procedure in complex congenital heart defects. Whatever the technique used, subsequent re-operations are frequently needed to control the pulmonary blood flow or pressures.

Objective— To report the efficacy of a new telemetric adjustable PAB (FloWatch-PAB) operated with the help of an external control unit that transmits to the implant energy and commands to further narrow or release the pulmonary artery using radiofrequency waves.

Methods and Results— In a multicenter, prospective, nonrandomized, single-arm clinical investigation, 13 children (median age, 4.5 months; range, 6 days to 11 years; median weight, 4.2 kg; range, 3.1 to 27kg) underwent implantation of the FloWatch-PAB through median sternotomy in 8 and left thoracotomy in 5. The diagnosis was multiple ventricular septal (VSD) defects with complex anatomy in 3, single ventricle without pulmonary stenosis in 2, VSD with elevated pulmonary vascular resistance (PVR) in 2, atrio-ventricular canal (AVC) with elevated pulmonary vascular resistance in 1, AVC with diminutive right ventricle in 1, complex transposition of the great arteries in 3, and pulmonary atresia with complex pulmonary arteries anatomy in 1. All patients had normosystemic systolic pulmonary artery pressure. Additional procedures were performed in 7: atrial septectomy in 2, double aortic arch division in 1, patent ductus arteriosus ligation in 2, and coarctation repair in 2. There were no early or late deaths or device-related complications in a mean follow-up of 24 weeks (range, 18 to 42 weeks). A mean of 5.8 telemetric regulations per patient using the FloWatch-PAB were required to adjust the tightening of the PAB to the clinical needs (narrowing 74%, releasing 26%). At last follow-up, systolic pulmonary artery pressure was within normal range in all patients but 1. Systemic oxygen saturation demonstrated optimal regulation of the pulmonary blood flow in all according to each specific defect. Four patients were successfully corrected (VSD closure, AVSD repair, and 2 arterial switches with VSD closure). The device was easily removed and the pulmonary artery re-expanded spontaneously.

Conclusion— This new device is safe and allows optimal adjustment of PAB in complex heart defects. In children requiring PAB, the use of this technology can obviate the need for early re-operations and appears to be a valuable option in the panel of surgical alternatives for selected infants.

Biventricular Support With the Jarvik 2000 Ventricular Assist Device in a Calf Model of Pulmonary Hypertension

The Jarvik 2000 ventricular assist device (VAD) is clinically efficacious for treating end-stage left ventricular failure. Because simultaneous right ventricular support is also occasionally necessary, we developed a biventricular Jarvik 2000 technique and tested it in a calf model. One VAD was implanted in the left ventricle with outflow-graft anastomosis to the descending aorta. The other VAD was implanted in the right ventricle with outflow-graft anastomosis to the pulmonary artery. Throughout the 30 day study, hemodynamic values were continuously monitored. On day 30, both pumps were evaluated at different speeds, under various hemodynamic conditions. By gradually occluding the pulmonary artery proximally or distally, we simulated varying degrees of high pulmonary vascular resistance, right ventricular hypertension, global heart failure, or ventricular fibrillation. The two VADs maintained biventricular support even during pulmonary artery occlusion and ventricular fibrillation, yielding a cardiac output of 3-11 L/min, left ventricular end-diastolic pressure of 11-24 mm Hg, and central venous pressure of 9-25 mm Hg. End-organ function was unimpaired, and no major adverse events occurred. The dual VADs offered safe, effective biventricular assistance in the calf. Additional studies are needed to assess the effects of lowered pulse pressure upon the pulmonary circulation and to develop a single pump speed controller.

Remote control of pulmonary blood flow: initial clinical experience

OBJECTIVE

After positive experimental results were obtained with the FloWatch-R-PAB (EndoArt S.A., Lausanne, Switzerland), an implantable device for pulmonary artery banding with telemetric control, it was tested in a prospective, multicenter clinical trial.

METHODS

From June to September 2002, 6 patients with a mean age of 10.6 months (1-31 months) and a mean weight of 6.5 kg (3.5-11 kg) underwent pulmonary artery banding with the implantation of the FloWatch-R-PAB device through median sternotomy (4 patients) or left thoracotomy (2 patients). The diagnoses were the following: univentricular heart (2 patients), complete atrioventricular septal defect (2 patients), ventricular septal defect (1 patient), and multiple ventricular septal defects with double aortic arch (1 patient). The associated procedures were atrioseptostomy with cardiopulmonary bypass (2 patients), closure of patent ductus arteriosus (2 patients), and division of double aortic arch (1 patient).

RESULTS

In a mean follow-up of 7 months (6-9 months), there were no early or late deaths, reoperations, or device-related complications. A mean of 5 regulations per patient (range 2-14) were required to adjust the tightening of the pulmonary artery banding, 50% (15/30) within the first postoperative week, 20% (6/30) during the second week, and 30% (9/30) within 8 months after surgery. In 70% (21/30) of the cases, the regulation was required to further narrow the pulmonary artery, and in 30% (9/30) of the cases, the regulation was required to release the pulmonary artery.

CONCLUSIONS

The initial trial confirmed the adequate functioning of the FloWatch-R-PAB device as telemetrically adjustable pulmonary artery banding. Repeated pulmonary artery banding adjustments, dictated by the clinical need in all patients even weeks after surgery, were accomplished without need for reoperation or invasive procedures. In children requiring pulmonary artery banding, the therapeutic strategies can be expanded by this promising technology. This device should be particularly indicated in patients with transposition of the great arteries requiring left ventricular retraining.

Reversible pulmonary trunk banding. II. An experimental model for rapid pulmonary ventricular hypertrophy

OBJECTIVE

An experimental model with a reversible pulmonary trunk banding device was developed with the aim of inducing rapid ventricular hypertrophy. The device consists of an insufflatable cuff connected to a self-sealing button.

METHODS

The right ventricles of 7 young goats (average weight, 8.7 kg) were submitted to systolic overload and evaluated according to the hemodynamic, echocardiographic, and morphologic aspects. Baseline biopsy specimens were taken from the myocardium for microscopic analysis. The device was implanted on the pulmonary trunk and inflated so that a 0.7 right ventricular/left ventricular pressure ratio was achieved. Echocardiographic and hemodynamic evaluations were performed every 24 hours. Systolic overload was maintained for 96 hours. The animals were then killed for morphologic study. Another 9 goats (average weight, 7.7 kg) were used for control right ventricular weight.

RESULTS

The systolic right ventricular/pulmonary trunk pressure gradient varied from 10.1 +/- 4.3 mm Hg (baseline) to 60.0 +/- 11.0 mm Hg (final). Consequently, the right ventricular/left ventricular pressure ratio increased from 0.29 +/- 0.06 to 1.04 +/- 0.14. The protocol group showed a 74% increase in right ventricular mass when compared with the control group. Serial 2-dimensional echocardiography showed a 66% increase in right ventricular wall thickness. There was a 24% increase in the mean myocyte perimeter, and the myocyte area increased 61%.

CONCLUSIONS

The device is easily adjustable percutaneously, enabling right ventricular hypertrophy in 96 hours of gradual systolic overload. This study suggests that the adjustable pulmonary trunk banding might provide better results for the 2-stage Jatene operation and for the failed atrial switch operations to convert to the double-switch operation.