Acute right ventricular failure--from pathophysiology to new treatments

Levosimendan improves right ventriculovascular coupling in a porcine model of right ventricular dysfunction*

OBJECTIVE

Experimental data suggest that levosimendan has pulmonary vasodilatory properties which, in combination with its positive inotropic effects, would render it particularly attractive for the treatment of right ventricular dysfunction. To test this hypothesis, we developed an experimental model of right ventricular failure and analyzed the effects of levosimendan on ventriculovascular coupling between the right ventricle and pulmonary artery (PA).

DESIGN

Prospective, randomized, placebo-controlled animal study.

SETTING

University hospital laboratory.

SUBJECTS

Fourteen pigs (mean weight 36 +/- 1 kg).

INTERVENTIONS

Pigs were instrumented with biventricular conductance catheters, a PA and right coronary artery flow probe, and a high-fidelity pulmonary pressure catheter. Right ventricular dysfunction was induced by repetitive episodes of ischemia/reperfusion in the presence of temporary PA constriction. Pigs were randomly assigned to receive levosimendan (120 mg/kg/hr [corrected] for 10 mins followed by continuous infusion of 60 mg/kg/hr [corrected] for 45 mins) or the placebo (control).

MEASUREMENTS AND MAIN RESULTS

Induction of right ventricular dysfunction resulted in a 42% decrease in contractility (reduction in slope of preload recruitable stroke work [Mw] from 2.5 +/- 0.4 to 1.8 +/- 0.5 mW x sec x mL(-1); p = .02) and a 60% increase in right ventricular afterload (effective pulmonary arterial elastance [PA-Ea] from 0.6 +/- 0.1 to 1.0 +/- 0.3 mm Hg x mL(-1); p < .01). Right ventriculovascular coupling, as assessed by the quotient of right ventricular end-systolic elastance (E(max)) over PA-Ea, decreased from 1.23 +/- 0.38 to 0.64 +/- 0.21 (p = .03). Treatment with levosimendan improved right ventricular contractility (Mw from 1.9 +/- 0.4 to 2.9 +/- 0.5 mW x sec x mL(-1); p < .01), lowered right ventricular afterload (PA-Ea from 1.1 +/- 0.3 to 0.8 +/- 0.3 mm Hg x mL(-1); p = .02), and restored right ventriculovascular coupling to normal values (E(max)/PA-Ea = 1.54 +/- 0.51). Levosimendan also significantly increased coronary blood flow and left ventricular contractility (Mw from 7.2 +/- 3.3 to 9.5 +/- 2.9 mW x sec x mL(-1); p = .01) but did not affect biventricular diastolic function.

CONCLUSIONS

In an experimental model of acute right ventricular dysfunction, levosimendan improved global hemodynamics and optimized right ventriculovascular coupling via a moderate increase in right ventricular contractility and a mild reduction of right ventricular afterload.

Effects of levosimendan versus dobutamine on pressure load-induced right ventricular failure*

OBJECTIVE

A transient increase in pulmonary arterial (PA) pressure can persistently depress right ventricular (RV) contractility. We investigated the effects of dobutamine and levosimendan on RV-PA coupling in this model of RV failure.

DESIGN

Prospective, controlled, randomized animal study.

SETTING

University research laboratory.

SUBJECTS

Fifteen anesthetized dogs.

INTERVENTIONS

Transient (90-min) PA constriction to induce persistent RV failure. Random assignment to dobutamine 5 and 10 microg/kg/min or levosimendan 12 microg/kg for 10 mins followed by 0.1 and 0.2 microg/kg/min.

MEASUREMENTS AND MAIN RESULTS

We measured PA distal resistance and proximal elastance by pressure-flow relationships and vascular impedance. We measured RV contractility by the end-systolic pressure-volume relationship (Ees), PA effective elastance by the end-diastolic to end-systolic relationship (Ea), and RV-PA coupling efficiency by the Ees/Ea ratio. PA constriction persistently increased PA resistance and elastance, increased Ea from 0.95 +/- 0.07 to 3.01 +/- 0.28 mm Hg/mL, decreased Ees from 1.17 +/- 0.09 to 0.58 +/- 0.07 mm Hg/mL, and decreased Ees/Ea from 1.26 +/- 0.09 to 0.22 +/- 0.03 (p < .05). Dobutamine did not affect pulmonary hemodynamics, markedly increased RV contractility, and improved RV-PA coupling. Levosimendan decreased PA resistance and elastance, increased RV contractility, and restored RV-PA coupling. Compared with dobutamine, levosimendan decreased RV afterload and therefore better restored RV-PA coupling at similar inotropic state.

CONCLUSIONS

A transient increase in PA pressure persistently worsens PA hemodynamics, RV contractility, RV-PA coupling, and cardiac output. Levosimendan restores RV-PA coupling better than dobutamine because of similar inotropic effects and additional pulmonary vasodilatory effects.

Do calcium sensitizers affect right ventricular functions in patients with chronic heart failure?

Calcium sensitizers also improve cardiac function by increasing the contraction of the myocardium without significantly increasing intracellular calcium levels. Although right ventricular function is an important role for better cardiac global function, there is no study about effects of levosimendan on right ventricular function measured by tissue Doppler imaging. The aim of the present study was to evaluate changes of myocardial properties in patients with idiopathic dilated cardiomyopathy using tissue Doppler imaging after levosimendan infusion. This tissue Doppler study shows that levosimendan also affects myocardial especially systolic waves of right ventricle and those of left ventricle.

Adaptation of the right ventricle to an increased afterload in the chronically volume overloaded heart

BACKGROUND

Increased right ventricular afterload is a common problem after correction of various heart diseases with chronic volume overload. We determined the effects of an acute increase of right ventricular afterload in normal and chronically volume overloaded hearts.

METHODS

In 6 dogs, volume overload was induced by chronic arteriovenous shunts for 3 months. Six sham-operated animals served as controls. After closing the shunts, right ventricular systolic and end-diastolic pressure as well as end-diastolic volume were measured by conductance catheter. In addition, pressure-volume loops were recorded. Myocardial contractility was described by the slope of the end-systolic pressure-volume relationship. Afterload was increased to right ventricular systolic pressure to 35 mm Hg and to 50 mm Hg by pulmonary banding.

RESULTS

Chronic volume overload resulted in a significant increase of right ventricular systolic pressure (34 +/- 2 versus 25 +/- 2 mm Hg, p < 0.05), end-diastolic pressure (10.4 +/- 1.7 versus 6.8 +/- 0.4 mm Hg, p < 0.05), and end-diastolic volume (39 +/- 2 versus 33 +/- 3 mL, p < 0.05). Baseline contractility (1.47 +/- 0.24 versus 1.53 +/- 0.32 mm Hg/mL) did not differ. While afterload increase to 35 and 50 mm Hg led to stepwise increase in contractility (2.73 +/- 0.30 mm Hg/mL and 4.15 +/- 0.30 mm Hg/mL, p < 0.05 versus baseline, respectively) at unchanged end-diastolic pressure and volume in controls, it showed only a slight increase (2.11 +/- 0.38 mm Hg/mL and 2.99 +/- 0.29 mm Hg/mL, p < 0.05 versus sham) with concomitant increase in end-diastolic pressure (12.4 +/- 2.2 mm Hg/mL and 16.3 +/- 1.9 mm Hg, p < 0.05) and volume (42 +/- 4 mL and 48 +/- 8 mL, p < 0.05) in the chronically volume overloaded group.

CONCLUSIONS

Chronic volume overload per se does not impair right ventricular contractility. However, the inotropic adaptation (homeometric autoregulation) to an increased afterload is limited, which is partly compensated by the Frank-Starling mechanism (heterometric autoregulation).

Non-invasive assessment of pulmonary hypertension: Doppler-echocardiography

Pulmonary hypertension (PH) is a clinical condition characterised by elevated pulmonary artery pressure (PAP) and vascular resistances. At the onset of the disease, symptoms are frequently atypical so that PH diagnosis is usually made when the disease is advanced, which often is too late for efficacious treatment. As a consequence the prognosis is poor. Echo-Doppler evaluation allows: (a) an early identification of patients with PH, (b) to establish a patient's prognosis and (c) to evaluate a proper patient's follow-up. In patients with PH echocardiography provides information about right heart dimensions, pulmonary artery pressures, right ventricle systolic and diastolic function and left and right ventricle interdependence. Most importantly Echo-Doppler evaluation has became a major diagnostic tool for PH allowing evaluation of changes with time and with different treatments which are aimed at reducing pulmonary artery pressure and right heart dimensions and at improving right heart function.

Acute perioperative heart failure

PURPOSE OF REVIEW

Changes in epidemiology and advances in the treatment of coronary artery disease, hypertension and diabetes mellitus have increased the prevalence of heart failure in the general population, and also the number of patients with heart failure presenting for surgery. Particularly in the perioperative period, patients with chronic heart failure are faced with numerous triggers of acute decompensation that can partly be avoided or treated. Patients without preexisting myocardial contractile dysfunction may sustain severe perioperative complications, e.g. myocardial infarction, with subsequent acute heart failure as a consequence. Approaches for diagnosis and treatment in these situations may vary considerably.

RECENT FINDINGS

Patients with preexisting heart failure undergoing non-cardiac surgery suffer substantial morbidity and mortality despite advances in perioperative care. The importance of heart failure as an independent risk factor is underlined by the fact that patients with coronary artery disease but without heart failure have a similar 30-day mortality rate to the general population. B-type natriuretic peptide testing is an attractive and non-invasive tool in non-surgical patients for the diagnosis of heart failure, but its role in the perioperative period for the diagnosis of myocardial contractile dysfunction is less clear. For inotropic support, levosimendan, a myofilament calcium sensitizer, has become available in several European countries, and encouraging positive reports have recently been published in this area.

SUMMARY

The role of B-type natriuretic peptide testing in the perioperative period is confounded by several variables that limit its use in that setting. New developments in positive inotropic therapy are challenging older and potentially harmful treatment strategies.

Right Ventricular Function After Coronary Surgery with or Without Bypass

BACKGROUND AND OBJECTIVE

Myocardial protection during aortic clamp period may sometimes be inadequate, especially for the right. The aim of this study was to compare right ventricle function after cardiac surgery with or without bypass.

METHODS

Patients undergoing multivessel coronary surgery with proximal severe right coronary lesion were included in a prospective observational cohort study including 29 patients undergoing coronary surgery with or without bypass. All patients were monitored with a pulmonary artery catheter with continuous right ventricular function. Right ventricular ejection fraction was measured at the arrival in ICU, 1, 3, 6, and 18 hours later.

RESULTS

The number of grafts that was higher in the bypass group (4.0 +/- 1.3) than in the off-pump group (2.6 +/- 0.6, p = 0.001). In the on-pump group, the right ventricular ejection fraction significantly decreased from 32.9 +/- 2.8 at arrival in ICU to 26.1 +/- 2.4, 6 hours later whereas in the off-pump group, it did not significantly change (32.4 +/- 1.8 to 31.9 +/- 2.3). Meanwhile, at the same time intervals, CVP was significantly lower in the off-pump group.

CONCLUSIONS

In patients with severe right coronary stenosis, off-pump cardiac surgery seemed to provide better right ventricular protection.

Initial experience with bosentan (Tracleer) as treatment for pulmonary arterial hypertension (PAH) due to congenital heart disease in infants and young children

INTRODUCTION

Bosentan, a dual endothelin-receptor antagonist, has been shown to be an effective treatment option in patients with the idiopathic form of pulmonary arterial hypertension (PAH). We used bosentan as compassionate treatment in infants and young children with congenital heart disease (CHD) who had a) PAH preoperatively representing a contraindication to corrective surgery or b) persisting PAH after corrective surgery causing right heart failure and reduced exercise tolerance.

METHODS

Seven children with PAH due to CHD (median age 3.8 years; range 1.5 to 6.4 years) received 3 mg/kg/d bosentan (Tracleer) orally. Clinical, echocardiographic and hemodynamic parameters were measured and laboratory tests performed before treatment and during steady state while on treatment. Routine liver function parameters were monitored monthly.

RESULTS

Mean bosentan treatment time was 8.6+/-5 months. During bosentan therapy there were no significant adverse events. The clinical status remained stable or improved in all patients: NYHA class decreased from 2.6+/-0.6 to 1.7+/-0.6 (p<0.05). This was associated with a mean reduction of the right ventricular systolic pressure (RVSP) from 96+/-11 mmHg to 71+/-26 mmHg (p<0.05).

CONCLUSIONS

Treatment with bosentan in infants and young children with PAH due to congenital heart disease was tolerated without significant side effects and resulted in stabilization of clinical status. A significant reduction in right ventricular systolic pressure (RVSP) could be demonstrated. These results suggest that the dose regimen used is appropriate and safe for the treatment of infants and children with PAH, resulting in a reduction of pathologically increased pulmonary vascular resistance.

The acutely decompensated right ventricle: pathways for diagnosis and management

Decompensated right ventricular (RV) failure is becoming increasingly common as the prevalence of predisposing conditions grows. Advances in diagnosis and management have granted insights into the following pathophysiologic mechanisms of RV dysfunction: impaired RV contractility, RV pressure overload, and RV volume overload. Emerging imaging modalities, such as cardiac MRI, and new therapeutic agents, such as pulmonary selective vasodilators, have expanded our options for evaluation and management, respectively. An improved understanding of pathophysiology and technologic progress provides us with new pathways in the diagnosis and hemodynamic support of these often critically ill patients.

Clinical review: Positive end-expiratory pressure and cardiac output

In patients with acute lung injury, high levels of positive end-expiratory pressure (PEEP) may be necessary to maintain or restore oxygenation, despite the fact that 'aggressive' mechanical ventilation can markedly affect cardiac function in a complex and often unpredictable fashion. As heart rate usually does not change with PEEP, the entire fall in cardiac output is a consequence of a reduction in left ventricular stroke volume (SV). PEEP-induced changes in cardiac output are analyzed, therefore, in terms of changes in SV and its determinants (preload, afterload, contractility and ventricular compliance). Mechanical ventilation with PEEP, like any other active or passive ventilatory maneuver, primarily affects cardiac function by changing lung volume and intrathoracic pressure. In order to describe the direct cardiocirculatory consequences of respiratory failure necessitating mechanical ventilation and PEEP, this review will focus on the effects of changes in lung volume, factors controlling venous return, the diastolic interactions between the ventricles and the effects of intrathoracic pressure on cardiac function, specifically left ventricular function. Finally, the hemodynamic consequences of PEEP in patients with heart failure, chronic obstructive pulmonary disease and acute respiratory distress syndrome are discussed.

An emerging role for calcium sensitisation in the treatment of heart failure

Heart failure occurs in 2 - 3% of the adult population in the developed world. With decompensation of cardiac function, haemodynamic stability can be achieved by using intravenous vasodilators, diuretics and inotropes. Unlike traditional inotropes, Ca2+ sensitisers enhance cardiac function without significantly increasing cardiac oxygen consumption, promoting arrhythmia or impairing lusitropy. The most promising drug in this new class is levosimendan, which has a unique dual mechanism; it enhances cardiac output through a Ca(2+)-dependent stabilisation of cardiac myofilaments and exhibits vasodilatory effects by opening ATP-dependent K(+) channels. Clinical trials have demonstrated the beneficial haemodynamic effects of levosimendan, and prospective trials are currently underway to confirm its potential benefits on long-term prognosis. Updated guidelines from the European Society of Cardiology advise on how to incorporate levosimendan into care for patients who have acute heart failure.

Lack of alteration of endogenous nitric oxide pathway during prolonged nitric oxide inhalation in intensive care unit patients

OBJECTIVE

To compare hemodynamic and gasometric variables and the plasma concentrations of nitric oxide metabolites (cyclic guanosine monophosphate and nitrate and nitrite), endothelin-1, and renin-angiotensin metabolites before and after the start of nitric oxide inhalation, after prolonged nitric oxide inhalation, and before and after nitric oxide withdrawal.

DESIGN

Prospective study.

SETTING

Surgical intensive care unit, university hospital.

SUBJECTS

Patients with acute lung injury and right ventricular failure.

INTERVENTIONS

Nitric oxide inhalation (10-12 ppm) during a median of 2.9 days (12 hrs to 6.5 days).

MEASUREMENTS AND MAIN RESULTS

The pulmonary vasodilator effects of inhaled nitric oxide improved arterial oxygenation in patients with acute lung injury (p < .05) and reduced right atrial pressure in patients with right ventricular dysfunction (p < .01). These beneficial effects lasted the whole period of prolonged inhaled nitric oxide therapy up to 6.5 days. However, when inhaled nitric oxide was withdrawn, pulmonary vasodilator effects rapidly disappeared, and Pao2/Fio2 ratio markedly deteriorated in all studied patients to return to pre-inhaled nitric oxide levels. Changes in plasma cyclic guanosine monophosphate and nitrate and nitrite paralleled those of pulmonary vasodilatory effects. An immediate increase in plasma cyclic guanosine monophosphate with a slightly delayed increase in plasma nitrate and nitrite was observed at inhaled nitric oxide start with no attenuation during the prolonged inhaled nitric oxide therapy. A marked decrease toward pre-inhaled nitric oxide levels was seen within hours of inhaled nitric oxide withdrawal. In addition, no alteration of plasma endothelin-1 or renin-angiotensin mediators was observed during or after inhaled nitric oxide therapy.

CONCLUSIONS

Our study showed a lack of attenuation in the beneficial effects of inhaled nitric oxide and a lack of alteration of endogenous nitric oxide, endothelin-1, and renin-angiotensin pathways during prolonged nitric oxide inhalation.

Hypertension artérielle pulmonaire en anesthésie–réanimation

OBJECTIVE

To review the perioperative anaesthetic management of pulmonary arterial hypertension.

DATA SOURCES

Extraction from Pubmed database of French and English articles on the perioperative anaesthetic management of pulmonary hypertension for 9 years.

DATA SELECTION

The collected articles were reviewed and selected according their quality and originality. The more recent data were selected.

DATA SYNTHESIS

Pulmonary arterial hypertension is classically divided in primary and secondary. Primary pulmonary hypertension (familial and sporadic) is relatively severe and rare. Muscularization of the terminal portion of the pulmonary vascular arterial tree, caused by smooth muscle cell hyperplasia is the first change. Pulmonary arterial hypertension linked with disorders of the respiratory system and hypoxemia or pulmonary venous hypertension including mitral valve disease and chronic left ventricular dysfunction are often associated with high morbidity and mortality. The main consequence of pulmonary hypertension development is the occurrence of right-sided circulatory failure. A better understanding of disease pathophysiology will contribute to the development of new therapies increasing then the prognosis of these patients. The management of primary pulmonary hypertension or secondary pulmonary arterial hypertension is a challenge for the anaesthesiologist because the risk of right ventricular failure is markedly increased.