Right ventricular function and failure: Methods, models, and mechanisms *

Predictors and prognosis of right ventricular function in pulmonary hypertension due to heart failure with reduced ejection fraction

Aims

Failure of right ventricular (RV) function worsens outcome in pulmonary hypertension (PH). The adaptation of RV contractility to afterload, the RV‐pulmonary artery (PA) coupling, is defined by the ratio of RV end‐systolic to PA elastances (Ees/Ea). Using pressure–volume loop (PV‐L) technique we aimed to identify an Ees/Ea cut‐off predictive for overall survival and to assess hemodynamic and morphologic conditions for adapted RV function in secondary PH due to heart failure with reduced ejection fraction (HFREF).

Methods and results

This post hoc analysis is based on 112 patients of the prospective Magdeburger Resynchronization Responder Trial. All patients underwent right and left heart echocardiography and a baseline PV‐L and RV catheter measurement. A subgroup of patients (n = 50) without a pre‐implanted cardiac device underwent magnetic resonance imaging at baseline. The analysis revealed that 0.68 is an optimal Ees/Ea cut‐off (area under the curve: 0.697, P < 0.001) predictive for overall survival (median follow up = 4.7 years, Ees/Ea ≥ 0.68 vs. <0.68, log‐rank 8.9, P = 0.003). In patients with PH (n = 76, 68%) multivariate Cox regression demonstrated the independent prognostic value of RV‐Ees/Ea in PH patients (hazard ratio 0.2, P < 0.038). Patients without PH (n = 36, 32%) and those with PH but RV‐Ees/Ea ≥ 0.68 showed comparable RV‐Ees/Ea ratios (0.88 vs. 0.9, P = 0.39), RV size/function, and survival. In contrast, secondary PH with RV‐PA coupling ratio Ees/Ea < 0.68 corresponded extremely close to cut‐off values that define RV dilatation/remodelling (RV end‐diastolic volume >160 mL, RV‐mass/volume‐ratio ≤0.37 g/mL) and dysfunction (right ventricular ejection fraction <38%, tricuspid annular plane systolic excursion <16 mm, fractional area change <42%, and stroke‐volume/end‐systolic volume ratio <0.59) and is associated with a dramatically increased short and medium‐term all‐cause mortality. Independent predictors of prognostically unfavourable RV‐PA coupling (Ees/Ea < 0.68) in secondary PH were a pre‐existent dilated RV [end‐diastolic volume >171 mL, odds ratio (OR) 0.96, P = 0.021], high pulsatile load (PA compliance <2.3 mL/mmHg, OR 8.6, P = 0.003), and advanced systolic left heart failure (left ventricular ejection fraction <30%, OR 1.23, P = 0.028).

Conclusions

The RV‐PA coupling ratio Ees/Ea predicts overall survival in PH due to HFREF and is mainly affected by pulsatile load, RV remodelling, and left ventricular dysfunction. Prognostically favourable coupling (RV‐Ees/Ea ≥ 0.68) in PH was associated with preserved RV size/function and mid‐term survival, comparable with HFREF without PH.

Dose-related Effects of Resveratrol in Different Models of Pulmonary Arterial Hypertension: A Systematic Review

BACKGROUND

Pulmonary Arterial Hypertension (PAH) is a severe and progressive disease of pulmonary arterioles. This pathology is characterized by elevation of the pulmonary vascular resistance and pulmonary arterial pressure, leading to right heart failure and death. Studies have demonstrated that resveratrol possesses a protective effect on the mechanisms related to the genesis of the PAH-induced by different models.

OBJECTIVE

This study aimed to investigate the dose-related effects of resveratrol in different models of pulmonary arterial hypertension.

METHODS

To identify eligible papers, we performed a systematic literature search on Scielo, Pub- Med, and Scholar Google. The research was limited to articles written in English in the last 10 years. We used the following descriptors to search: Pulmonary Arterial Hypertension and Resveratrol, OR Resveratrol, and Animal models of Pulmonary Arterial Hypertension, OR Resveratrol, and in vitro models of Pulmonary Arterial Hypertension.

RESULTS

1724 studies were identified through the descriptors used, fifty-five studies with different models of pulmonary arterial hypertension were selected for the full review, forty-four were excluded after application of exclusion and inclusion criteria, totalizing eleven studies included in this systematic review.

CONCLUSION

The results showed that resveratrol, at low and high doses, protects in a dosedependent manner against the development of PAH induced through monocrotaline, normoxia and hypoxia models. In addition to having chemopreventive, anti-inflammatory, antioxidant and antiproliferative properties. In the case of PAH-related myocardial injury, resveratrol protects cells from apoptosis, thus working as an antiapoptotic agent.

Thoracic Epidural Anesthesia Reduces Right Ventricular Systolic Function With Maintained Ventricular-Pulmonary Coupling

Background:

Blockade of cardiac sympathetic fibers by thoracic epidural anesthesia may affect right ventricular function and interfere with the coupling between right ventricular function and right ventricular afterload. Our main objectives were to study the effects of thoracic epidural anesthesia on right ventricular function and ventricular-pulmonary coupling.

Methods:

In 10 patients scheduled for lung resection, right ventricular function and its response to increased afterload, induced by temporary, unilateral clamping of the pulmonary artery, was tested before and after induction of thoracic epidural anesthesia using combined pressure-conductance catheters.

Results:

Thoracic epidural anesthesia resulted in a significant decrease in right ventricular contractility (ΔESV 25 : +25.5 mL, P =0.0003; ΔEes: -0.025 mm Hg/mL, P =0.04). Stroke work, dP/dt MAX , and ejection fraction showed a similar decrease in systolic function (all P <0.05). A concomitant decrease in effective arterial elastance (ΔEa: -0.094 mm Hg/mL, P =0.004) yielded unchanged ventricular-pulmonary coupling. Cardiac output, systemic vascular resistance, and mean arterial blood pressure were unchanged. Clamping of the pulmonary artery significantly increased afterload (ΔEa: +0.226 mm Hg/mL, P <0.001). In response, right ventricular contractility increased (ΔESV 25 : -26.6 mL, P =0.0002; ΔEes: +0.034 mm Hg/mL, P =0.008), but ventricular-pulmonary coupling decreased (Δ(Ees/Ea) = -0.153, P <0.0001). None of the measured indices showed significant interactive effects, indicating that the effects of increased afterload were the same before and after thoracic epidural anesthesia.

Conclusions:

Thoracic epidural anesthesia impairs right ventricular contractility but does not inhibit the native positive inotropic response of the right ventricle to increased afterload. Right ventricular-pulmonary arterial coupling was decreased with increased afterload but not affected by the induction of thoracic epidural anesthesia.

Clinical Trial Registration:

URL: http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=2844 . Unique identifier: NTR2844.

Two-dimensional global longitudinal strain rate is a preload independent index of systemic right ventricular contractility in hypoplastic left heart syndrome patients after Fontan operation

BACKGROUND

Assessment of systemic right ventricular (RV) function in patients with hypoplastic left heart syndrome is important during long-term follow-up after Fontan repair. Traditional echocardiographic parameters to evaluate systolic ventricular function are affected by loading conditions. The only generally accepted load-independent parameter of systolic function, end systolic elastance (Ees), requires invasive catheterization. Therefore, we sought to determine if parameters obtained by 2-dimensional speckle tracking (2DST) were affected by acute changes in preload and correlated with catheterization-derived indices of RV contractility in hypoplastic left heart syndrome patients after Fontan palliation.

METHODS AND RESULTS

Fifty-two patients with hypoplastic left heart syndrome (median age, 6.6; range 2.9-22.2 years) were prospectively enrolled to have echocardiography and conductance catheter studies performed simultaneously. We compared traditional echo, 2-dimensional speckle tracking and catheterization-derived parameters during different states of preload at baseline and during dobutamine infusion. Global longitudinal strain (S) showed a tendency to decrease with preload reduction, whereas global longitudinal strain rate (SR) did not change (S: -17.7 ± 3.4% versus -16.9 ± 3.8%, P=0.08; SR: -1.30 ± 0.29 versus -1.34 ± 0.34 s(-1), P=0.3). S did not change with dobutamine infusion (-17.7 ± 3.4% versus -18.4 ± 3.9%, P=0.24), whereas SR increased significantly (-1.30 ± 0.29 versus -2.26 ± 0.49 s(-1), P<0.001). RV Ees correlated with SR (rs= -0.47, P<0.001), but not with S (rs=0.07, P=0.5) or other echocardiographic parameters.

CONCLUSIONS

In contrast to S, SR was not affected by preload and correlated with Ees of the systemic RV. SR may be a useful noninvasive surrogate of RV contractility and suitable for follow-up of patients with hypoplastic left heart syndrome after Fontan palliation.

Does left ventricular size impact on intrinsic right ventricular function in hypoplastic left heart syndrome?

BACKGROUND

The size of the remnant left ventricle (LV) may influence right ventricular function and thus long-term outcome in palliated hypoplastic left heart syndrome (HLHS). We therefore sought to assess the impact of the size of the hypoplastic LV on intrinsic RV function in HLHS patients after Fontan surgery.

METHODS

Fifty-seven HLHS patients were studied 2.5 (range: 0.8-12.6) years after Fontan-type palliation with the pressure-volume conductance system. The patient cohort was divided into two groups according to the median LV area index (group 1: LV area index ≤ 1.33 cm(2)/m(2), n=29; group 2: LV area index>1.33 cm(2)/m(2), n=28).

RESULTS

The slopes of the end systolic elastance (Ees) and the preload recruitable stroke work relation (Mw) were not different between group 1 and 2 (Ees: 2.70 ± 1.92 vs. 3.68 ± 2.68 mmHg/ml; Mw: 52.75 ± 14.98 vs. 51.09 ± 16.63 mmHg x ml; P=NS for all). Furthermore, the systolic responses to dobutamine were not statistically different between groups. However, the slope of the end diastolic stiffness (Eed) was higher in group 2 and catecholaminergic stimulation resulted in a decrease in Eed in group 2 (group 1: 0.40 ± 0.26 vs. 0.52 ± 0.45; group 2: 0.68 ± 0.44 vs. 0.47 ± 0.38 mmHg/ml, P<0.01). Furthermore Eed was lowest in patients with mitral atresia/aortic atresia, the anatomic subgroup with the smallest LV remnant.

CONCLUSIONS

Intrinsic systolic RV function is not affected by the size of the hypoplastic LV in survivors of surgical palliation of HLHS. Diastolic stiffness, however, was higher in patients with a larger LV remnant.

Diagnosis and treatment of pulmonary hypertension: an update

Over the last five years, knowledge in the field of pulmonary hypertension has grown consistently and significantly. On the basis of various clinical studies showing the usefulness of new diagnostic tools, as well as the efficacy of new medications and drug combinations, new diagnostic and treatment algorithms have been developed. Likewise, in order to simplify the clinical management of patients, the classification of pulmonary hypertension has been changed in an attempt to group the various forms of pulmonary hypertension in which the diagnostic and therapeutic approaches are similar. The objective of this review was to discuss these modifications, based on the 2005 Brazilian guidelines for the management of pulmonary hypertension, emphasizing what has been added to the international guidelines.

Right ventricular dysfunction

PURPOSE OF REVIEW

Until recently the right ventricle's role in myocardial dynamics has not been fully appreciated. This article provides an overview of the pathophysiology, imaging and management of right ventricular dysfunction.

RECENT FINDINGS

That levosimendan may promote right ventricular function opens new avenues for treatment. In addition there are existing therapies such as phosphodiesterase inhibitors and nitric oxide, which offer yet further modalities to improve outcome in right ventricular failure. How these drugs are used, in combination or alone, in conjunction with ventilatory and cardiovascular strategies has not been evaluated in multicentred randomized controlled trials.

SUMMARY

Acute right ventricular dysfunction is relatively common. There is a lack of convincing evidence in favour of any single treatment modality. Imaging methods now permit a more accurate evaluation of the right ventricle and its function. Combining treatments may offer significant advantages and the imaging and monitoring available allows real-time assessment of the response to intervention. This article illustrates how incomplete our knowledge of this condition and its management within the critical care setting is and reinforces previous calls for suitably designed trials to evaluate and develop guidelines for existing strategies and therapeutic agents.

ALTERATION OF RIGHT VENTRICULAR-PULMONARY VASCULAR COUPLING IN A PORCINE MODEL OF PROGRESSIVE PRESSURE OVERLOADING

In acute pulmonary embolism, right ventricular (RV) failure may result from exceeding myocardial contractile resources with respect to the state of vascular afterload. We investigated the adaptation of RV performance in a porcine model of progressive pulmonary embolism. Twelve anesthetized pigs were randomly divided into two groups: gradual pulmonary arterial pressure increases by three injections of autologous blood clot (n=6) or sham-operated controls (n=6). Right ventricular pressure-volume (PV) loops were recorded using a conductance catheter. Right ventricular contractility was estimated by the slope of the end-systolic PV relationship (Ees). After load was referred to as pulmonary arterial elastance (Ea) and assessed using a four-element Windkessel model. Right ventricular-arterial coupling (Ees/Ea) and efficiency of energy transfer (from PV area to external mechanical work [stroke work]) were assessed at baseline and every 30 min for 4 h. Ea increased progressively after embolization, from 0.26+/-0.04 to 2.2+/-0.7 mmHg mL(-1) (P<0.05). Ees increased from 1.01+/-0.07 to 2.35+/-0.27 mmHg mL(-1) (P<0.05) after the first two injections but failed to increase any further. As a result, Ees/Ea initially decreased to values associated with optimal SW, but the last injection was responsible for Ees/Ea values less than 1, decreased stroke volume, and RV dilation. Stroke work/PV area consistently decreased with each injection from 79%+/-3% to 39%+/-11% (P<0.05). In response to gradual increases in afterload, RV contractility reserve was recruited to a point of optimal coupling but submaximal efficiency. Further afterload increases led to RV-vascular uncoupling and failure.

Management strategies for patients with pulmonary hypertension in the intensive care unit

OBJECTIVE

Pulmonary hypertension may be encountered in the intensive care unit in patients with critical illnesses such as acute respiratory distress syndrome, left ventricular dysfunction, and pulmonary embolism, as well as after cardiothoracic surgery. Pulmonary hypertension also may be encountered in patients with preexisting pulmonary vascular, lung, liver, or cardiac diseases. The intensive care unit management of patients can prove extremely challenging, particularly when they become hemodynamically unstable. The objective of this review is to discuss the pathogenesis and physiology of pulmonary hypertension and the utility of various diagnostic tools, and to provide recommendations regarding the use of vasopressors and pulmonary vasodilators in intensive care.

DATA SOURCES AND EXTRACTION

We undertook a comprehensive review of the literature regarding the management of pulmonary hypertension in the setting of critical illness. We performed a MEDLINE search of articles published from January 1970 to March 2007. Medical subject headings and keywords searched and cross-referenced with each other were: pulmonary hypertension, vasopressor agents, therapeutics, critical illness, intensive care, right ventricular failure, mitral stenosis, prostacyclin, nitric oxide, sildenafil, dopamine, dobutamine, phenylephrine, isoproterenol, and vasopressin. Both human and animal studies related to pulmonary hypertension were reviewed.

CONCLUSIONS

Pulmonary hypertension presents a particular challenge in critically ill patients, because typical therapies such as volume resuscitation and mechanical ventilation may worsen hemodynamics in patients with pulmonary hypertension and right ventricular failure. Patients with decompensated pulmonary hypertension, including those with pulmonary hypertension associated with cardiothoracic surgery, require therapy for right ventricular failure. Very few human studies have addressed the use of vasopressors and pulmonary vasodilators in these patients, but the use of dobutamine, milrinone, inhaled nitric oxide, and intravenous prostacyclin have the greatest support in the literature. Treatment of pulmonary hypertension resulting from critical illness or chronic lung diseases should address the primary cause of hemodynamic deterioration, and pulmonary vasodilators usually are not necessary.

Comparison between single-beat and multiple-beat methods for estimation of right ventricular contractility

OBJECTIVE

It was investigated whether pharmacologically induced changes in right ventricular contractility can be detected by a so-called "single-beat" method that does not require preload reduction.

DESIGN

Prospective animal research.

SETTING

Laboratory at a large university medical center.

SUBJECTS

Eight anesthetized pigs.

INTERVENTIONS

End-systolic elastance values obtained by a recently proposed single-beat method (Eessb) were compared with those obtained using the reference multiple-beat method (Eesmb).

MEASUREMENTS AND MAIN RESULTS

Administration of dobutamine increased Eesmb from 1.6 +/- 0.3 to 3.8 +/- 0.5 mm Hg/mL (p =.001), whereas there was only a trend toward an increase in Eessb from 1.5 +/- 0.2 to 1.7 +/- 0.4 mm Hg/mL. Esmolol decreased Eesmb from 1.7 +/- 0.3 to 1.1 +/- 0.2 mm Hg/mL (p =.006), whereas there was only a trend for a decrease in Eessb from 1.5 +/- 0.2 to 1.3 +/- 0.1.

CONCLUSIONS

The present method using single-beat estimation to assess right ventricular contractility does not work as expected, since it failed to detect either increases or decreases in right ventricular contractility induced by pharmacologic interventions.