Sildenafil for Pulmonary Hypertension in the Early Postoperative Period After Mitral Valve Surgery

Inhaled NO at a crossroads in cardiac surgery: current need to improve mechanistic understanding, clinical trial design and scientific evidence

Inhaled nitric oxide (NO) has been used in pediatric and adult perioperative cardiac intensive care for over three decades. NO is a cellular signaling molecule that induces smooth muscle relaxation in the mammalian vasculature. Inhaled NO has the unique ability to exert its vasodilatory effects in the pulmonary vasculature without any hypotensive side-effects in the systemic circulation. In patients undergoing cardiac surgery, NO has been reported in numerous studies to exert beneficial effects on acutely lowering pulmonary artery pressure and reversing right ventricular dysfunction and/or failure. Yet, various investigations failed to demonstrate significant differences in long-term clinical outcomes. The authors, serving as an advisory board of international experts in the field of inhaled NO within pediatric and adult cardiac surgery, will discuss how the existing scientific evidence can be further improved. We will summarize the basic mechanisms underlying the clinical applications of inhaled NO and how this translates into the mandate for inhaled NO in cardiac surgery. We will move on to the popular use of inhaled NO and will talk about the evidence base of the use of this selective pulmonary vasodilator. This review will elucidate what kind of clinical and biological barriers and gaps in knowledge need to be solved and how this has impacted in the development of clinical trials. The authors will elaborate on how the optimization of inhaled NO therapy, the development of biomarkers to identify the target population and the definition of response can improve the design of future large clinical trials. We will explain why it is mandatory to gain an international consensus for the state of the art of NO therapy far beyond this expert advisory board by including the different major players in the field, such as the different medical societies and the pharma industry to improve our understanding of the real-life effects of inhaled NO in large scale observational studies. The design for future innovative randomized controlled trials on inhaled NO therapy in cardiac surgery, adequately powered and based on enhanced biological phenotyping, will be crucial to eventually provide scientific evidence of its clinical efficacy beyond its beneficial hemodynamic properties.

Pulmonary hypertension secondary to valvular heart disease: a state-of-the-art review

Pulmonary hypertension (PH) is a common disease affecting up to 1% of the population and at least 50% of patients diagnosed with heart failure (HF) (Hoeper et al. in Lancet Respir Med 4(4):306-322, 2016). It is estimated that PH is present in 15% to 60% of patients with valvular heart disease (VHD) which can result from an increase in pulmonary blood flow and subsequently in pulmonary venous congestion and pulmonary vascular resistance (PVR). It is important to identify the severity of PH in patients with VHD to appropriately risk stratify and manage these patients (Magne et al. in JACC Cardiovasc Imaging 8(1):83-99, 2015). In this review, we examine the diagnostic criteria for PH and its pathophysiology. We also focus on the growing evidence supporting the presence of PH secondary to VHD and describe the contemporary surgical and medical therapeutic interventions in this patient population (Fig. 1).

Pulmonary Vasodilator and Inodilator Drugs in Cardiac Surgery: A Systematic Review With Bayesian Network Meta-Analysis

OBJECTIVE

The authors performed a systematic review to evaluate the effect of pharmacologic therapy on pulmonary hypertension in the perioperative setting of elective cardiac surgery (PROSPERO CRD42023321041).

DESIGN

Systematic review of randomized controlled trials with a Bayesian network meta-analysis.

SETTING

The authors searched biomedical databases for randomized controlled trials on the perioperative use of inodilators and pulmonary vasodilators in adult cardiac surgery, with in-hospital mortality as the primary outcome and duration of ventilation, length of stay in the intensive care unit, stage 3 acute kidney injury, cardiogenic shock requiring mechanical support, and change in mean pulmonary artery pressure as secondary outcomes.

PARTICIPANTS

Twenty-eight studies randomizing 1,879 patients were included.

INTERVENTIONS

Catecholamines and noncatecholamine inodilators, arterial pulmonary vasodilators, vasodilators, or their combination were considered eligible interventions compared with placebo or standard care.

MEASUREMENTS AND MAIN RESULTS

Ten studies reported in-hospital mortality and assigned 855 patients to 12 interventions. Only inhaled prostacyclin use was supported by a statistically discernible improvement in mortality, with a number-needed-to-treat estimate of at least 3.3, but a wide credible interval (relative risk 1.26 × 10-17 - 0.7). Inhaled prostacyclin and nitric oxide were associated with a reduction in intensive care unit stay, and none of the included interventions reached a statistically evident difference compared to usual care or placebo in the other secondary clinical outcomes.

CONCLUSIONS

Inhaled prostacyclin was the only pharmacologic intervention whose use is supported by a statistically discernible improvement in mortality in the perioperative cardiac surgery setting as treatment of pulmonary hypertension. However, available evidence has significant limitations, mainly the low number of events and imprecision.

Microvascular dysfunction following cardiopulmonary bypass plays a central role in postoperative organ dysfunction

Despite significant advances in surgical technique and strategies for tissue/organ protection, cardiac surgery involving cardiopulmonary bypass is a profound stressor on the human body and is associated with numerous intraoperative and postoperative collateral effects across different tissues and organ systems. Of note, cardiopulmonary bypass has been shown to induce significant alterations in microvascular reactivity. This involves altered myogenic tone, altered microvascular responsiveness to many endogenous vasoactive agonists, and generalized endothelial dysfunction across multiple vascular beds. This review begins with a survey of in vitro studies that examine the cellular mechanisms of microvascular dysfunction following cardiac surgery involving cardiopulmonary bypass, with a focus on endothelial activation, weakened barrier integrity, altered cell surface receptor expression, and changes in the balance between vasoconstrictive and vasodilatory mediators. Microvascular dysfunction in turn influences postoperative organ dysfunction in complex, poorly understood ways. Hence the second part of this review will highlight in vivo studies examining the effects of cardiac surgery on critical organ systems, notably the heart, brain, renal system, and skin/peripheral tissue vasculature. Clinical implications and possible areas for intervention will be discussed throughout the review.

Pulmonary hypertension associated with cardiopulmonary bypass and cardiac surgery

BACKGROUND AND AIM

Pulmonary hypertension (PH) is frequently associated with cardiovascular surgery and is a common complication that has been observed after surgery utilizing cardiopulmonary bypass (CPB). The purpose of this review is to explain the characteristics of PH, the mechanisms of PH induced by cardiac surgery and CPB, treatments for postoperative PH, and future directions in treating PH induced by cardiac surgery and CPB using up-to-date findings.

METHODS

The PubMed database was utilized to find published articles.

RESULTS

There are many mechanisms that contribute to PH after cardiac surgery and CPB which involve pulmonary vasomotor dysfunction, cyclooxygenase, the thromboxane A2 and prostacyclin pathway, the nitric oxide pathway, inflammation, and oxidative stress. Furthermore, there are several effective treatments for postoperative PH within different types of cardiac surgery.

CONCLUSIONS

By possessing a deep understanding of the mechanisms that contribute to PH after cardiac surgery and CPB, researchers can develop treatments for clinicians to use which target the mechanisms of PH and ultimately reduce and/or eliminate postoperative PH. Additionally, learning about the most up-to-date studies regarding treatments can allow clinicians to choose the best treatments for patients who are undergoing cardiac surgery and CPB.

Post-operative Right Ventricular Failure After Cardiac Surgery: A Cohort Study

Introduction: Right ventricular failure (RVF) after cardiac surgery is an important risk factor for morbidity and mortality. Its diagnosis is challenging, and thus, its incidence and predictors are not well-established. We investigated the incidence, complications, and variables associated with clinically relevant post-operative RVF.

Methods: We included all patients who underwent cardiac surgery with cardiopulmonary bypass between 2016 and 2019 in a cardiac surgery center with standardized diagnostic and therapeutic management of RVF. RVF was considered only if clinically relevant: associated with hemodynamic instability requiring catecholamine support and inhaled nitric oxide relayed by sildenafil.

Results: Overall, 3,826 patients were included, of whom, 110 (2.9%) developed post-operative RVF. Mortality was not different among patients who developed post-operative RVF, compared with the rest of the cohort (1.8 vs. 0.7%, p = 0.17). Using a composite outcome that combined death, reintubation, stroke, and prolonged intensive care unit stay (more than 14 days) yielded an incidence of 6.6%, and RVF was associated with this composite outcome with an odds ratio of 3.6 (2.2–5.8), p < 0.001. In a multivariable model, pre-operative variables independently associated with post-operative RVF were pre-operative atrial fibrillation (AF) {adjusted odds ratio (adjOR) 3.22 [95% confidence interval (95%CI) = 1.94–5.36], p < 0.001}, left ventricle ejection fraction below 50% [adjOR = 2.55 (95%CI = 1.52–4.33), p < 0.001], systolic pulmonary artery pressure above 55 mmHg [adjOR = 8.64 (95%CI = 5.27–14.1); p < 0.001], mitral valve surgery [adjOR = 2.17 CI (95%CI = 1.28–3.66), p = 0.004], and tricuspid valve surgery [adjOR = 10.33 (95%CI = 6.14–17.4), p < 0.001]. In patients who developed post-operative RVF requiring treatment, 32 (29.1%) showed RV dysfunction before surgery.

Conclusion: In this cohort study, 2.9% of patients developed clinically significant post-operative RVF. Moreover, RVF was associated with severe adverse outcomes, including death, strokes, reintubation, and prolonged intensive care unit stay.