Circulatory support for right ventricular dysfunction

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.

Can the temporary use of right ventricular assist devices bridge patients with acute right ventricular failure after cardiac surgery to recovery?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was: Can the temporary use of right ventricular assist devices (RVADs) bridge patients to recovery who suffer acute right ventricular failure after cardiac surgery? More than 183 papers were found using the reported search, of which 13 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. Indications for surgical intervention included coronary artery bypass surgery, valve replacement, post-heart transplant and left ventricular assist device insertion. Significant reductions in central venous pressure (P = 0.005) and mean pulmonary artery pressures (P < 0.01) were reported during and after RVAD support. Furthermore, increases in right ventricular cardiac output (P < 0.05), right ventricular ejection fraction (P < 0.05), right ventricular stroke work (P < 0.05) and pulmonary artery oxygen saturations (P < 0.05) were also seen. Assessment by one study showed that on Day 7 after RVAD removal, the right ventricular ejection fraction had increased by up to 40%. Dynamic echocardiography studies performed before, during and after RVAD placement demonstrated that after RVAD implantation, right ventricular end-diastolic dimensions (P < 0.05) and right atrial dimensions decreased (P < 0.05) and right ventricular ejection fraction (P < 0.05) increased. Although several studies successfully weaned patients from an RVAD, there were several complications, including bleeding requiring surgical intervention. However, this may be reduced by using percutaneous implantation (bleeding incidence: 4 of 9 patients) rather than by a surgically implanted RVAD (bleeding incidence: 5 of 5 patients). However, mortality is higher in percutaneous RVAD patients rather than in surgical RVAD (80-44%) patients. Causes of death cited for patients on an RVAD included multiorgan failure, sepsis, thromboembolic events, reoccurring right heart failure and failure to wean due to persistent right ventricular failure. We conclude that RVADs have been successfully used to bridge patients to recovery after cardiac surgery; however, RVADs carry numerous risks and a high mortality rate.

Anesthetic considerations for patients with advanced valvular heart disease undergoing noncardiac surgery

Patients with valvular heart disease represent a growing segment of the population and can present major challenges to clinical anesthesiologists. This review focuses on patients with advanced left-sided valvular disease undergoing noncardiac surgery. The pathophysiology and anesthetic implications of aortic stenosis and insufficiency and mitral stenosis and insufficiency are discussed, with a focus on optimizing perioperative management and decision making for patients with these conditions.

Decreased left ventricular function, myocarditis, and coronary arteriolar medial thickening following monocrotaline administration in adult rats

Decreased right as well as left ventricular function can be associated with pulmonary hypertension (PH). Numerous investigations have examined cardiac function following induction of pulmonary hypertension with monocrotaline (MCT) assuming that MCT has no direct cardiac effect. We tested this assumption by examining left ventricular function and histology of isolated and perfused hearts from MCT-treated rats. Experiments were performed on 50 male Sprague-Dawley rats [348 +/- 6 g (SD)]. Thirty-seven rats received MCT (50 mg/kg sc; MCT group) while the remainder did not (Control group). Three weeks later, pulmonary artery pressure was assessed echocardiographically in 20 MCT and 8 Control rats. The hearts were then excised and perfused in the constant pressure Langendorff mode to determine peak left ventricular pressure (LVP), the peak instantaneous rate of pressure increase (+dP/dtmax) and decrease (-dP/dtmax), as well as the rate pressure product (RPP). Histological sections were subsequently examined. Pulmonary artery pressure was higher in the MCT-treated group compared with the Control group [12.9 +/- 6 vs. 51 +/- 35.3 mmHg (P < 0.01)]. Left ventricular systolic function and diastolic relaxation were decreased in the MCT group compared with the Control group (+dP/dtmax 4,178 +/- 388 vs. 2,801 +/- 503 mmHg/s, LVP 115 +/- 11 vs. 83 +/- 14 mmHg, RPP 33,688 +/- 1,910 vs. 23,541 +/- 3,858 beats x min(-1) x mmHg(-1), -dP/dtmax -3,036 +/- 247 vs. -2,091 +/- 389 mmHg/s; P < 0.0001). The impairment of cardiac function was associated with myocarditis and coronary arteriolar medial thickening. Similarly depressed ventricular function and inflammatory infiltration was seen in 12 rats 7 days after MCT administration. Our findings appear unrelated to the degree of PH and indicate a direct cardiotoxic effect of MCT.

Successful weaning from cardiopulmonary bypass with central venous prostaglandin E1 and left atrial norepinephrine infusion in patients with acute pulmonary hypertension

OBJECTIVE

Postoperative pulmonary hypertension increases the mortality risk in cardiac surgery. We have used central venous prostaglandin E1 (PGE1) and left atrial norepinephrine (NE) infusion to wean from cardiopulmonary bypass (CPB) patients with refractory postoperative pulmonary hypertension.

DESIGN

Observational, nonrandomized study.

SETTING

Department of Cardiac Surgery in a university hospital.

PATIENTS

We studied 10 nonconsecutive American Society of Anesthesiologists III and New York Heart Association class III-IV patients with postoperative pulmonary hypertension and low cardiac output syndrome preventing separation from CPB.

INTERVENTIONS

Patients received right atrial PGE1 (31.5 +/- 6.26 ng/kg/min) and left atrial NE (0.11 +/- 0.02 microg/kg/min) infusion. Hemodynamic data were obtained before CPB (T0), after CPB under maximal inotropes and vasodilator infusion (T1), 10 mins (T2) and 12 hrs (T3) after PGE1 and NE infusion, and 48 hrs after withdrawal of PGE1 and NE (T4).

MEASUREMENTS AND MAIN RESULTS

All patients were successfully weaned from CPB and survived. The biatrial infusion of PGE1 and NE caused a dramatic reduction in mean pulmonary artery pressure (from 42.8 +/- 5.1 mm Hg at T1 to 28.5 +/- 2.6 mm Hg at T2 and 20.5 +/- 2.0 mm Hg at T4), pulmonary vascular resistance index (from 1158 +/- 269 dyne x sec/cm5 x m2 at T1 to 501 +/- 99 dyne x sec/cm5 x m2 at T2 and 246 +/- 50 dyne x sec/cm5 x m2 at T4), and pulmonary-to-systemic vascular resistance index ratio (from 0.61 +/- 0.17 at T1 to 0.20 +/- 0.04 at T2 and 0.11 +/- 0.03 at T4). Cardiac index increased from 1.7 +/- 0.2 L/min/m2 at T1 to 2.3 +/- 0.2 L/min/m2 at T2 and 2.9 +/- 0.1 L/min/m2 at T4.

CONCLUSIONS

In patients with refractory postoperative pulmonary hypertension, the combined administration of low-dose PGE1 in the right atrium and NE in the left atrium is an effective means to wean patients from cardiopulmonary bypass.

Evaluation of a pulsatile pediatric ventricular assist device in an acute right heart failure model

BACKGROUND

The development of pulsatile ventricular assist devices for children has been limited mainly by size constraints. The purpose of this study was to evaluate the MEDOS trileaflet-valved, pulsatile, pediatric right ventricular assist device (stroke volume = 9 mL) in a neonatal lamb model of acute right ventricular failure.

METHODS

Right ventricular failure was induced in ten 3-week-old lambs (8.6 kg) by right ventriculotomy and disruption of the tricuspid valve. Control group 1 (n = 5) had no mechanical support whereas experimental group 2 (n = 5) had right ventricular assist device support for 6 hours. The following hemodynamic parameters were measured in all animals: heart rate and right atrial, pulmonary arterial, left atrial, and systemic arterial pressures. Cardiac output was measured by an electromagnetic flow probe placed on the pulmonary artery.

RESULTS

All results are expressed as mean +/- standard deviation and analyzed by Student's t test. A p value less than 0.05 was considered statistically significant. Base-line measurements were not significantly different between groups and included systemic arterial pressure, 80.6 +/- 12.7 mm Hg; right atrial pressure, 4.6 +/- 1.6 mm Hg; mean pulmonary arterial pressure, 15.6 +/- 4.2 mm Hg; left atrial pressure, 4.8 +/- 0.8 mm Hg; and cardiac output, 1.4 +/- 0.2 L/min. Right ventricular injury produced hemodynamics compatible with right ventricular failure in both groups: mean systemic arterial pressure, 38.8 +/- 10.4 mm Hg; right atrial pressure, 16.8 +/- 2.3 mm Hg; left atrial pressure, 1.4 +/- 0.5 mm Hg; and cardiac output, 0.6 +/- 0.1 L/min. All group 1 animals died at a mean of 71.4 +/- 9.4 minutes after the operation. All group 2 animals survived the duration of study. Hemodynamic parameters were recorded at 2, 4, and 6 hours on and off pump, and were significantly improved at all time points: mean systemic arterial pressure, 68.0 +/- 13.0 mm Hg; right atrial pressure, 8.2 +/- 2.3 mm Hg; left atrial pressure, 6.4 +/- 2.1 mm Hg; and cardiac output, 1.0 +/- 0.2 L/min.

CONCLUSIONS

The results demonstrate the successful creation of a right ventricular failure model and its salvage by a miniaturized, pulsatile right ventricular assist device. The small size of this device makes its use possible even in small neonates.

Mechanical circulatory assistance in paediatric patients with cardiac failure

Extracorporeal membrane oxygenation (ECMO) was initially developed for respiratory failure. Its use, however, has evolved into an excellent method of preoperative and postoperative support in the treatment of infants and children with acquired and congenital heart disease. Along with ECMO, the left ventricular assist device (LVAD) and the intraaortic balloon pump (IABP) have also found a place in the management of paediatric patients with heart failure. This report documents 15 patients who were treated with one or a combination of these mechanical devices, either preoperatively or postoperatively. There is a 74% survival rate and the long-term outcome has been excellent in most cases. The use of heparin-coated devices and tight regulation of heparin has allowed the transfer of infants and children from standard cardiopulmonary bypass to assist devices in the operating room. Mechanical devices are an essential adjunct for the preoperative and postoperative treatment of infants and children with cardiac disease.

Extracorporeal membrane oxygenation for cardiac support in children

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) support for cardiac failure has been used in children since 1981 at the Children's Hospital in Pittsburgh. Most children required support after cardiac operations. Recently, however, a larger number of patients with decompensated cardiomyopathy or myocarditis have been supported with ECMO, which was used as a bridge to transplantation in most.

METHODS

From 1981 to 1994, 68 children were placed on ECMO for cardiac support.

RESULTS

The overall survival for the entire time period was 38%, with the more recent experience survival increased to 47%. In 14 children, ECMO was used as a bridge to transplantation, with 9 children receiving a heart transplant and 7 long-term survivors. Extracorporeal membrane oxygenation has also been used to resuscitate 11 children after sudden cardiac arrest, with a long-term survival of 53%.

CONCLUSIONS

We conclude that ECMO support for severe cardiac failure is effective. Patient selection and the use of heart transplantation for intractable heart failure have improved the overall survival.

Efficacy of a skeletal muscle-powered dynamic patch: Part 2. Right ventricular assistance

The purpose of this study was to assess the feasibility of using a skeletal muscle-powered dynamic patch to assist the failing right ventricle. Seven adult mongrel dogs were used in the study. The proximal portion of the left latissimus dorsi muscle was harvested and reattached to the actuator to serve as a skeletal muscle energy convertor. The right ventricular free wall was fully excised and the dynamic patch was implanted under cardiopulmonary bypass. After weaning from cardiopulmonary bypass, the latissimus dorsi muscle was stimulated using a burst frequency of 33 Hz, a burst duration of 200 ms, and 1:2 synchronous mode stimulation with the native R wave. Latissimus dorsi muscle stimulation increased systolic aortic pressure (78 versus 91 mm Hg; p < 0.01), mean aortic pressure (56 versus 62 mm Hg; p < 0.05), aortic blood flow (0.73 versus 0.97 mL; p < 0.01), and systolic right ventricular pressure (41 versus 56 mm Hg; p < 0.01). The mean right atrial pressure decreased from 14 to 9.6 mm Hg (p < 0.01). Our results demonstrate that the use of a right ventricular dynamic patch powered by a skeletal muscle linear-type actuator can not only function as a right ventricular free wall substitute but also lead to the augmentation of right ventricular and global cardiac function.

Pulmonary artery balloon counterpulsation: safe after peripheral placement

Pulmonary artery balloon counterpulsation is a promising experimental technique for treatment of right ventricular failure. However, clinical application has been limited in that the only device presently available (the large-volume intraaortic balloon) must be placed within a synthetic graft. Because a balloon with a smaller volume (which could be placed through a peripheral vein and be contained entirely within the pulmonary artery) would make the technique feasible on a wider scale, we tested an 8-mL pulmonary artery balloon placed through the femoral vein in 12 dogs. Two groups of animals were compared. One group had the pulmonary artery balloon in place but not counterpulsating; the other had the pulmonary artery balloon in place and counterpulsating. Each group was studied for 12 hours. A variety of hemodynamic parameters were measured. Effective diastolic augmentation and systolic unloading were noted in all 6 dogs that underwent counterpulsation (5.0 +/- 1.1 mm Hg of diastolic augmentation and 9.5 +/- 1.6 mm Hg of systolic unloading). Pulmonary function, as measured by arterial blood gas sampling and pulmonary vascular resistance, was not impaired. Examination of the heart and lungs showed no detrimental pathologic effects of pulmonary artery balloon counterpulsation. Placement of the balloon through a peripheral vein with a guidewire was easy and uncomplicated. We conclude that pulmonary artery balloon counterpulsation is safe over an extended period of 12 hours in the canine model and that diastolic augmentation and systolic unloading can be produced.

Pulmonary artery balloon counterpulsation for intraoperative right ventricular failure

Two cases of severe low cardiac output and right ventricular failure after coronary artery bypass grafting necessitated pulmonary artery balloon counterpulsation after intraaortic balloon pumping and maximal inotropic/pressor support were unsuccessful in maintaining a satisfactory cardiac output. Hemodynamic improvement was sufficient to allow removal of the device 2 and 3 days postoperatively, with survival in 1 patient. Pulmonary artery counterpulsation is less morbid in comparison with other mechanical methods of right ventricular support and is applicable in right ventricular failure of intermediate severity.

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.