Pulmonary circulatory support

Successful Use of Intra-aortic Balloon Counterpulsation for Systemic Ventricular Failure Following Total Pericardiectomy for Calcific Chronic Constrictive Pericarditis

We report two male patients aged 18 and 19 years, respectively, undergoing total pericardiectomy for chronic calcific constrictive pericarditis who developed systemic ventricular failure unresponsive to medical management following surgery. The failing circulation was successfully reestablished using intra-aortic balloon counterpulsation. Aortic counterpulsation facilitates recovery of ventricular function and appears to be a reasonable alternative in select instances of refractory cardiac failure following pericardiectomy.

Intracardiac Right-to-Left Shunt Complicating Right Ventricular Failure

Three cases of intracardiac right-to-left shunt at the atrial level complicating right ventricular failure (RV) are described. Severe hypoxemia resulted in 2 patients and stroke in the third. This was a consequence of right ventricular infarction causing right-sided heart failure resulting in high right-sided pressures. Echocardiography demonstrated the shunts. A review of the literature on this uncommon problem suggested management strategies based on the limited experience with this condition.

Pulmonary Bleeding During Right Ventricular Support After Left Ventricular Assist Device Implantation

OBJECTIVES

Right heart failure still occurs in up to 20% of patients after implantation of a left ventricular assist device (LVAD). One treatment option for these patients is the implantation of a temporary right ventricular assist device (RVAD). Experimental data suggest that non-pulsatile perfusion of the lungs is associated with an increased rate of pulmonary hemorrhage. The aim of this study was to determine the incidence of pulmonary bleeding complications in these patients.

DESIGN

Observational study.

SETTING

Single center, university hospital.

PARTICIPANTS

This study included patients undergoing LVAD implantation for end-stage heart failure and subsequent implantation of a temporary right ventricular support system.

INTERVENTIONS

In this study, 25 patients who underwent LVAD and additional temporary RVAD implantation were screened for pulmonary bleeding complications.

MEASUREMENTS AND MAIN RESULTS

The mean Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) level at the time of LVAD implantation was 2.84. All patients experienced severe right ventricular failure (tricuspid annular plane systolic excursion [TAPSE], 10.16±26.3 mm) and severe pulmonary hypertension (right atrial [RA] pressure, 56.21±15.58 mmHg). Average duration of right ventricular support was 11.12±7.20 days, with right ventricular support being administered to 14 patients for more than 7 days. Seventeen patients were weaned successfully from right ventricular support after a mean support duration of 5 days. Five patients developed pulmonary bleeding complications, diagnosed using computed tomography scan and bronchoscopy. All bleeding occurred after postoperative day 7 and was associated with RVAD flow of more than 4 L/min within 24 hours before bleeding occurred.

CONCLUSIONS

The data presented in this study suggested that right ventricular support for more than 7 days and a blood flow greater than 4 L/min were associated with pulmonary bleeding complications. This should be taken into consideration when temporary right ventricular support after LVAD implantation is planned.

Use of Intra-Aortic Balloon Counterpulsation in an Adult Patient With Left Ventricular Failure following Repair of Tetralogy of Fallot: A Case Report

We report the case of a 26-year-old male patient who developed primary left ventricular failure with subsequent biventricular failure early following intracardiac repair of tetralogy of Fallot. The failing biventricular circulation was successfully supported using intra-aortic balloon counterpulsation. Aortic counterpulsation facilitates recovery of biventricular function and appears to be a reasonable alternative in select instances of systemic ventricular failure following repair of tetralogy of Fallot.

Intra-aortic balloon counterpulsation in a patient with the failing Fontan circulation

We report a 23-year-old patient undergoing functionally univentricular repair who developed cardiac failure due primarily to systemic ventricular dysfunction. The failing Fontan circulation was successfully re-established using intra-aortic balloon counterpulsation. Aortic counterpulsation facilitates recovery of systemic ventricular function, and appears to be a reasonable alternative in select instances of cardiac failure in patients with the Fontan circulation.

A chronic heart failure model by coronary artery ligation in the goat

The availability of a reliable heart failure model in large animals is important. We report upon our efforts to develop a chronic heart failure model in seven goats using sequential ligation of the left anterior descending (LAD) coronary artery and its diagonal branch. After anesthesia and left thoracotomy, the LAD artery was ligated, and the diagonal vessel at the same level was ligated one hour later. Cardiac measurements were performed with a thermodilution catheter and by ultrasonography. Two months after the operation, the same measurements were made and animals were sacrificed for postmortem examinations of their hearts. Hemodynamic measurements, except cardiac output, showed no significant changes immediately after the coronary artery ligation. Echocardiographic measurements showed significant changes in the ejection fraction and fractional shortening without changes in left ventricular dimensions. Wall motion analyses demonstrated variable degrees of anteroseptal dyskinesia and akinesia in all animals immediately after coronary artery ligation. Five animals have undergone hemodynamic and ultrasonographic studies 2 months after coronary artery ligation. The results obtained from these animals showed significant increases in central venous pressure, right ventricular pressure, pulmonary artery pressure, and pulmonary artery capillary wedge pressure, and a significant decrease in cardiac output. Increases in left ventricular dimensions and decreases in ejection fraction with fractional shortening in ultrasonographic studies were also observed. Pathologically, well-demarcated thin-walled anteroseptal infarcts, with chamber enlargement, were clearly seen with dilatation of the heart chambers in all specimens. Based on this study, we conclude that goats, like sheep, can provide a reliable model of chronic heart failure by coronary artery ligation and in view of the many advantages offered by goats, we believe that this animal model will be useful for cardiac experimentation.

Cavopulmonary assist: circulatory support for the univentricular Fontan circulation

BACKGROUND

Following Fontan palliation, the univentricular circulation is notable for coexisting systemic venous hypertension and pulmonary arterial hypotension. Assisted cavopulmonary blood flow to overcome this pressure gradient would restore the circulation to one more closely resembling normal two-ventricle physiology. We hypothesized that mechanical augmentation of cavopulmonary blood flow would provide physiologic stability in a model of cavopulmonary diversion and univentricular circulation.

METHODS

Yearling sheep (n = 13, mean weight 56.5 kg) underwent total cavopulmonary diversion on cardiopulmonary bypass. The superior and inferior vena cavae were anastomosed directly to the right pulmonary artery. Axial flow pumps were positioned within both vena cavae to assist blood flow from the systemic venous circulation into the pulmonary vasculature. Baseline ventilation was resumed, cardiopulmonary bypass was weaned, and pump support was titrated to obtain normal physiologic measurement. Cardiopulmonary data were collected for 6 hours.

RESULTS

All animals demonstrated hemodynamic stability without need for volume loading, inotropic support, or pulmonary vasodilator therapy. Cardiac output, pulmonary vascular resistance, pulmonary arterial pressure, inferior vena caval pressure, and arterial pCO(2) and pO(2) values 6 hours after intervention were similar to baseline values. Arterial lactate levels steadily decreased throughout the cavopulmonary assist period.

CONCLUSIONS

Cavopulmonary assist with a percutaneous pump provides physiologic stability in a model of total cavopulmonary diversion and univentricular Fontan circulation without altering regional volume distribution or cardiac output. This mode of circulatory support may have potential to benefit patients with marginal Fontan hemodynamics in both the early and late time periods.

A one-way valved atrial septal patch: a new surgical technique and its clinical application

Patients who undergo surgical repair of congenital heart defects, characterized by a hypoplastic right ventricle or high pulmonary vascular resistance, are at high risk for the development of postoperative right heart failure. This risk may discourage the surgical team from carrying out a biventricular or complete repair in such patients. To reduce the risk for right heart failure, we developed a one-way, valved, atrial septal patch to serve as an artificial one-way foramen ovale and tested it in an animal model. By permitting right-to-left shunt, this device decompresses the failing right ventricle and maintains systemic cardiac output. The device has been used in 15 patients divided into three different groups: group 1 (n = 8), patients with a hypoplastic right ventricle and pulmonic stenosis or atresia, seven of whom underwent a biventricular repair; group 2 (n = 5), patients with evidence of pulmonary disease after longstanding left-to-right shunt caused by a correctable atrial or ventricular septal defect, all of whom had a complete repair; group 3, two patients with acute right heart failure in whom the device was used as a last option of treatment to wean them from cardiopulmonary bypass. This article presents our data in regard to the use of the one-way, valved, atrial septal patch and the indications for its clinical use.

Right-to-left flow through a patent foramen ovale in acute right ventricular infarction. Two case reports and a proposal for management

Right-to-left shunting through a foramen ovale complicating acute right ventricular infarction and resulting in severe arterial hypoxemia has been described eight times before. Treatment strategies have often aimed at reducing the shunt. Four patients died. Less attention has been paid to attempts at revascularization and, despite a high incidence of atrioventricular conduction disturbances, to temporary dual-chamber pacing. We describe herein two patients with postcardiac surgical right ventricular infarction complicated by severe right-to-left interatrial shunting. Treatment strategy was aimed at improving right ventricular function, and right-to-left shunting ceased. All efforts should be directed at treating right ventricular dysfunction, which is the cause of the clinical picture, and not at reducing the shunt, which is a secondary phenomenon.

Skeletal muscle ventricles in the pulmonary circulation: up to 16 weeks' experience

Skeletal muscle ventricles (SMVs) were constructed from the right latissimus dorsi muscle of 8 mongrel dogs. After a 3-week vascular delay period, each SMV was electrically preconditioned with 2-Hz continuous stimulation of the thoracodorsal nerve for 6 weeks. A porcine-valved conduit was then anastomosed between the right ventricle and the SMV, with a second valved conduit connecting the SMV to the main pulmonary artery. The pulmonary artery was then ligated proximal to the conduit. The SMVs were stimulated to contract in 1:2 diastolic mode with a 33-Hz burst frequency. Effective right ventricular assist was achieved in all dogs. Cardiac output increased by 22.6% (1,799 +/- 97 versus 1,467 +/- 84 mL/min; p less than 0.001), systemic systolic arterial pressure by 9.3% (90.1 +/- 3.5 versus 82.4 +/- 3.9 mm Hg; p less than 0.005), and peak pulmonary artery pressure by 31.8% (27.8 +/- 2.0 versus 21.1 +/- 1.7 mm Hg; p less than 0.001) at the initiation of this study. In 6 dogs, effective right heart assist was sustained for periods of between 1 week and 12 weeks. Two dogs survived for longer than 3 months, though with evidence of deteriorating SMV function. These results demonstrate the feasibility of providing sustained right ventricular assist using this modified "Rastelli-SMV" configuration, which obviates the limitations imposed by low right atrial preload.

Pulmonary artery counterpulsation to improve right ventricular function after heart transplantation

The effectiveness of pulmonary artery counterpulsation in improving right ventricular function after heart transplantation was evaluated in a pig model. The balloon catheter was introduced through the anterior wall of the pulmonary artery distal to the pulmonary valve. A Millar catheter with a distal high-fidelity pressure transducer was placed in the right ventricle, where the peak rate of pressure rise, dP/dT, was measured. Pulmonary artery counterpulsation significantly improved right ventricular function, increasing both dP/dT and systolic pressure. A diastolic dip in pulmonary artery pressure and a fall in the early portion of the right ventricular pressure curve were seen. Inflation of the balloon caused a second (suprasystolic) wave in that curve. Improved right ventricular function was also seen when normal pig hearts were counterpulsated after occlusion of the right coronary artery and following increased afterload due to occlusion of a main pulmonary artery. There were no changes in central venous or systemic pressure. The results indicate that pulmonary artery counterpulsation may be valuable when the transplanted heart has a poorly functioning right ventricle.

A rapid method for determining the need for mechanical support of the right ventricle

Right ventricular failure following cardiac surgery must be rapidly diagnosed and treated to minimize injury to the heart. Switching from aortic to pulmonary artery perfusion during cardiopulmonary bypass is a method of rapidly testing the adequacy of right ventricular function and supporting the ventricle if necessary. A centrifugal pump has been used for long-term support for two cases managed in this manner.

Pulmonary complications of a roller pump right ventricular assist device

The pulmonary effects of a right ventricular assist device (RVAD) were evaluated in a model of ischemic right ventricular (RV) failure. The right coronary artery (RCA) was ligated for 240 min in 12 mongrel dogs. Group 1 (n = 5) was supported medically (iv fluids, epinephrine); Group 2 (n = 7) had an RVAD instituted 30 mins after RCA ligation, but no inotropic support was given. The RVAD was a standard roller pump providing right atrial to pulmonary artery flow which unloaded the RV. The ratio of area of infarction (AI) to area at risk (AR) of the RV was determined by vital dye staining. Total lung water (TLW) was determined by gravimetric analysis and expressed as milliliters per kilogram body weight. Throughout the experiment animals in Group 1 had significantly higher RV systolic pressures. Pulmonary vascular resistance was increased significantly in Group 2 at 4 hr (318% of baseline vs 33%). Mean pulmonary artery pressure increased significantly in Group 2 from 9.4 +/- 0.9 mm Hg at baseline to 21.0 +/- 5.0 mm Hg at 4 hr. Group 2 animals had a decreased AI/AR ratio (19 +/- 3 vs 57 +/- 9) and increased TLW (20 +/- 3 vs 9 +/- 1). Lung biopsies in Group 2 revealed perivascular, peribronchial, and intraalveolar hemorrhages that were not present in Group 1. In conclusion, a roller pump RVAD limits RV infarction but produces pulmonary hypertension, increases pulmonary vascular resistance, and creates pulmonary edema and hemorrhage in the process.

Efficacy of intra-aortic balloon pumping for failing Fontan circulation

The Fontan circulation occasionally cannot be sustained by currently available medical treatment. In these circumstances, mechanical assistance to the Fontan circulation should be considered. We have experienced three cases where Fontan circulation was assisted by intra-aortic balloon pumping (IABP). The hemodynamic improvement and weaning from IABP were successfully achieved in all cases. One patient survived the serious postoperative course with the aid of IAPB, and two patients died following multiorgan failure, though the circulation had eventually been re-established. By studying the postoperative hemodynamics assisted by IABP, it is concluded that IABP is a reasonable, efficacious strategy to support and to re-establish the failing Fontan circulation, though the changes in hemodynamic variables will not immediately coincide with IABP application.

Successful use of a right ventricular assist device

Right ventricular failure caused by myocardial infarction may be refractory to treatment designed to support the systemic ventricle. A new type of right ventricular assist device driven by an impeller pump was successfully used for 79 hours after emergency revascularisation after right coronary occlusion. Despite renal failure requiring haemofiltration the patient has now fully recovered.

A rational approach to the selection of an assist device for the failing right ventricle

Assist devices have become available for the treatment of right ventricular (RV) failure. The present study assesses the efficacy of pulmonary artery balloon counterpulsation (PABC) in restoring RV output to normal levels. In a porcine model of RV failure during left heart bypass, PABC restored RV output to normal, provided that the RV output was not depressed to less than 50% of baseline values. When RV failure was more severe, PABC was not effective in restoring RV output to base line. This study suggests that a rational approach should be developed for the use of right heart assist devices. In moderately severe RV failure, PABC may be successful in restoring cardiac output to normal. However, in extreme failure a right heart bypass is necessary.

The current status of mechanical circulatory support

In summary, techniques for support of a failing circulation have advanced steadily over the past thirty years. Just as the use of the intra-aortic balloon pump has permitted successful treatment of certain groups of high-risk patients, so increasing application of more invasive techniques of mechanical circulatory support has extended the range of surgical endeavour. Nevertheless, it is evident that further advances in the design and construction of mechanical circulatory support devices are most likely to occur in conjunction with developments in bioengineering technology. These advances will in turn demand analysis by means of careful animal and clinical investigations. Although the general clinical use of an off-the-shelf mechanical ventricular support will give rise to major financial and ethical problems it is likely that application of these devices may herald a new era in the field of artificial organ replacement.

Evaluation of right ventricular function during right ventricular bypass

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Right ventricular failure. Pathophysiology and treatment

The cardiac surgeon is faced with RV failure in two main situations: in isolation or in patients with left-sided cardiac assist. Adequate volume loading, correction of acidosis and oxygenation, cardiac pacing, pharmacologic agents, and systemic intra-aortic balloon pumping allow stabilization in most of these patients. When these measures fail, some form of mechanical assistance of the right ventricle becomes necessary. Balloon counterpulsation in the pulmonary artery improves RV output but does not restore the systemic perfusion if the right ventricle is profoundly depressed. When the right ventricle is profoundly depressed, a mechanical assist pump is the only device capable of restoring systemic perfusion. Like the left ventricle, the right ventricle, given time and support, can recover enough function to allow weaning from the assist device and survival.