Right Ventricular Perfusion

Perspectives on the History of Coronary Physiology: Discovery of Major Principles and Their Clinical Correlates

Coronary circulation plays an essential role in delivering oxygen and metabolic substrates to satisfy the considerable energy demand of the heart. This article reviews the history that led to the current understanding of coronary physiology, beginning with William Harvey's revolutionary discovery of systemic blood circulation in the 17th century, and extending through the 20th century when the major mechanisms regulating coronary blood flow (CBF) were elucidated: extravascular compressive forces, metabolic control, pressure-flow autoregulation, and neural pathways. Pivotal research studies providing evidence for each of these mechanisms are described, along with their clinical correlates. The authors describe the major role played by researchers in the 19th century, who formulated basic principles of hemodynamics, such as Poiseuille's law, which provided the conceptual foundation for experimental studies of CBF regulation. Targeted research studies in coronary physiology began in earnest around the turn of the 20th century. Despite reliance on crude experimental techniques, the pioneers in coronary physiology made groundbreaking discoveries upon which our current knowledge is predicated. Further advances in coronary physiology were facilitated by technological developments, including methods to measure phasic CBF and its regional distribution, and by biochemical discoveries, including endothelial vasoactive molecules and adrenergic receptor subtypes. The authors recognize the invaluable contribution made by basic scientists toward the understanding of CBF regulation, and the enormous impact that this fundamental information has had on improving clinical diagnosis, decision-making, and patient care.

A young woman presenting with dyspnoea and diffuse T-wave inversions: a case report

Background

T-wave inversions on electrocardiograms (ECGs) indicate a variety of conditions, such as coronary artery disease, myocarditis, and cardiomyopathy. Pulmonary artery stenosis (PAS) and pulmonary hypertension (PH) may cause right ventricular enlargement and ischaemia, which are reflected as T-wave inversions on ECGs. Continuous ECG monitoring is crucial for detecting dynamic changes indicative of PAS progression and reversal in right heart remodelling.

Case summary

This report presents the case of a young woman who experienced exertional dyspnoea for 5 years with ECG findings showing T-wave inversions across multiple leads. The patient was diagnosed with PAS and PH caused by Takayasu arteritis (TA). Following three successful balloon pulmonary angioplasty sessions, the patient exhibited significant clinical improvement, including the remission of PAS and PH. Throughout a 59-month cumulative follow-up period, the sustained effectiveness of the treatment was evidenced by the regression of right heart remodelling, as manifested in the normalization of the initially inverted T-waves on the ECG.

Discussion

Electrocardiogram changes, including right axis deviation, right bundle branch block, a deep S wave in lead I (R/S < 1), and a prominent R wave in lead aVR (R/Q > 1), have been termed PAS syndrome, often linked to TA-associated PAS, especially in young East Asian females. Early diagnosis is crucial but challenging due to atypical symptoms. The non-invasive ECG is vital for detection, with balloon pulmonary angioplasty serving as an effective treatment for TA-induced PAS when surgery is not an option, improving outcomes and potentially reversing right heart remodelling.

Personalized coronary and myocardial blood flow models incorporating CT perfusion imaging and synthetic vascular trees

Computational simulations of coronary artery blood flow, using anatomical models based on clinical imaging, are an emerging non-invasive tool for personalized treatment planning. However, current simulations contend with two related challenges - incomplete anatomies in image-based models due to the exclusion of arteries smaller than the imaging resolution, and the lack of personalized flow distributions informed by patient-specific imaging. We introduce a data-enabled, personalized and multi-scale flow simulation framework spanning large coronary arteries to myocardial microvasculature. It includes image-based coronary anatomies combined with synthetic vasculature for arteries below the imaging resolution, myocardial blood flow simulated using Darcy models, and systemic circulation represented as lumped-parameter networks. We propose an optimization-based method to personalize multiscale coronary flow simulations by assimilating clinical CT myocardial perfusion imaging and cardiac function measurements to yield patient-specific flow distributions and model parameters. Using this proof-of-concept study on a cohort of six patients, we reveal substantial differences in flow distributions and clinical diagnosis metrics between the proposed personalized framework and empirical methods based purely on anatomy; these errors cannot be predicted a priori. This suggests virtual treatment planning tools would benefit from increased personalization informed by emerging imaging methods.

Essential right heart physiology for the perioperative practitioner POQI IX: current perspectives on the right heart in the perioperative period

As patients continue to live longer from diseases that predispose them to right ventricular (RV) dysfunction or failure, many more patients will require surgery for acute or chronic health issues. Because RV dysfunction results in significant perioperative morbidity if not adequately assessed or managed, understanding appropriate assessment and treatments is important in preventing subsequent morbidity and mortality in the perioperative period. In light of the epidemiology of right heart disease, a working knowledge of right heart anatomy and physiology and an understanding of the implications of right-sided heart function for perioperative care are essential for perioperative practitioners. However, a significant knowledge gap exists concerning this topic. This manuscript is one part of a collection of papers from the PeriOperative Quality Initiative (POQI) IX Conference focusing on "Current Perspectives on the Right Heart in the Perioperative Period." This review aims to provide perioperative clinicians with an essential understanding of right heart physiology by answering five key questions on this topic and providing an explanation of seven fundamental concepts concerning right heart physiology.

How Would I Treat My Own Chronic Thromboembolic Pulmonary Hypertension in the Perioperative Period?

Chronic thromboembolic pulmonary hypertension (CTEPH) results from an incomplete resolution of acute pulmonary embolism, leading to occlusive organized thrombi, vascular remodeling, and associated microvasculopathy with pulmonary hypertension (PH). A definitive CTEPH diagnosis requires PH confirmation by right-heart catheterization and evidence of chronic thromboembolic pulmonary disease on imaging studies. Surgical removal of the organized fibrotic material by pulmonary endarterectomy (PEA) under deep hypothermic circulatory arrest represents the treatment of choice. One-third of patients with CTEPH are not deemed suitable for surgical treatment, and medical therapy or interventional balloon pulmonary angioplasty presents alternative treatment options. Pulmonary endarterectomy in patients with technically operable disease significantly improves symptoms, functional capacity, hemodynamics, and quality of life. Perioperative mortality is <2.5% in expert centers where a CTEPH multidisciplinary team optimizes patient selection and ensures the best preoperative optimization according to individualized risk assessment. Despite adequate pulmonary artery clearance, patients might be prone to perioperative complications, such as right ventricular maladaptation, airway bleeding, or pulmonary reperfusion injury. These complications can be treated conventionally, but extracorporeal membrane oxygenation has been included in their management recently. Patients with residual PH post-PEA should be considered for medical or percutaneous interventional therapy.

Pulmonary Hypertension Induces Serotonin Hyperreactivity and Metabolic Reprogramming in Coronary Arteries via NOX1/4-TRPM2 Signaling Pathway

BACKGROUND

Clinical evidence revealed abnormal prevalence of coronary artery (CA) disease in patients with pulmonary hypertension (PH). The mechanistic connection between PH and CA disease is unclear. Serotonin (5-hydroxytryptamine), reactive oxygen species, and Ca2+ signaling have been implicated in both PH and CA disease. Our recent study indicates that NOXs (NADPH [nicotinamide adenine dinucleotide phosphate] oxidases) and TRPM2 (transient receptor potential cation channel subfamily M member 2) are key components of their interplay. We hypothesize that activation of the NOX-TRPM2 pathway facilitates the remodeling of CA in PH.

METHODS

Left and right CAs from chronic hypoxia and monocrotaline-induced PH rats were collected to study vascular reactivity, gene expression, metabolism, and mitochondrial function. Inhibitors or specific siRNA were used to examine the pathological functions of NOX1/4-TRPM2 in CA smooth muscle cells.

RESULTS

Significant CA remodeling and 5-hydroxytryptamine hyperreactivity in the right CA were observed in PH rats. NOX1/4-mediated reactive oxygen species production coupled with TRPM2-mediated Ca2+ influx contributed to 5-hydroxytryptamine hyperresponsiveness. CA smooth muscle cells from chronic hypoxia-PH rats exhibited increased proliferation, migration, apoptosis, and metabolic reprogramming in an NOX1/4-TRPM2-dependent manner. Furthermore, the NOX1/4-TRPM2 pathway participated in mitochondrial dysfunction, involving mitochondrial DNA damage, reactive oxygen species production, elevated mitochondrial membrane potential, mitochondrial Ca2+ accumulation, and mitochondrial fission. In vivo knockdown of NOX1/4 alleviated PH and suppressed CA remodeling in chronic hypoxia rats.

CONCLUSIONS

PH triggers an increase in 5-hydroxytryptamine reactivity in the right CA and provokes metabolic reprogramming and mitochondrial disruption in CA smooth muscle cells via NOX1/4-TRPM2 activation. This signaling pathway may play an important role in CA remodeling and CA disease in PH.

Anesthetic management in patients having catheter-based thrombectomy for acute pulmonary embolism: A narrative review

Pulmonary embolism is the third leading cause of cardiovascular death. Novel percutaneous catheter-based thrombectomy techniques are rapidly becoming popular in high-risk pulmonary embolism - especially in the presence of contraindications to thrombolysis. The interventional nature of these procedures and the risk of sudden cardiorespiratory compromise requires the presence of an anesthesiologist. Facilitating catheter-based thrombectomy can be challenging since qualifying patients are often critically ill. The purpose of this narrative review is to provide guidance to anesthesiologists for the assessment and management of patients having catheter-based thrombectomy for acute pulmonary embolism. First, available techniques for catheter-based thrombectomy are reviewed. Then, we discuss definitions and application of common risk stratification tools for pulmonary embolism, and how to assess patients prior to the procedure. An adjudication of risks and benefits of anesthetic strategies for catheter-based thrombectomy follows. Specifically, we give guidance and rationale for use monitored anesthesia care and general anesthesia for these procedures. For both, we review strategies for assessing and mitigating hemodynamic perturbations and right ventricular dysfunction, ranging from basic monitoring to advanced inodilator therapy. Finally, considerations for management of right ventricular failure with mechanical circulatory support are discussed.

Role of Oxygen Starvation in Right Ventricular Decompensation and Failure in Pulmonary Arterial Hypertension

Right ventricular (RV) function and eventually failure determine outcome in patients with pulmonary arterial hypertension (PAH). Initially, RV responds to an increased load caused by PAH with adaptive hypertrophy; however, eventually RV failure ensues. Unfortunately, it is unclear what causes the transition from compensated RV hypertrophy to decompensated RV failure. Moreover, at present, there are no therapies for RV failure; those for left ventricular (LV) failure are ineffective, and no therapies specifically targeting RV are available. Thus there is a clear need for understanding the biology of RV failure and differences in physiology and pathophysiology between RV and LV that can ultimately lead to development of such therapies. In this paper, we discuss RV adaptation and maladaptation in PAH, with a particular focus of oxygen delivery and hypoxia as the principal drivers of RV hypertrophy and failure, and attempt to pinpoint potential sites for therapy.

Perioperative Management in Pulmonary Endarterectomy

Pulmonary endarterectomy (PEA) is the treatment of choice for patients with chronic thromboembolic pulmonary hypertension (PH), provided lesions are proximal enough in the pulmonary vasculature to be surgically accessible and the patient is well enough to benefit from the operation in the longer term. It is a major cardiothoracic operation, requiring specialized techniques and instruments developed over several decades to access and dissect out the intra-arterial fibrotic material. While in-hospital operative mortality is low (<5%), particularly in high-volume centers, careful perioperative management in the operating theater and intensive care is mandatory to balance ventricular performance, fluid balance, ventilation, and coagulation to avoid or treat complications. Reperfusion pulmonary edema, airway hemorrhage, and right ventricular failure are the most problematic complications, often requiring the use of extracorporeal membrane oxygenation to bridge to recovery. Successful PEA has been shown to improve both morbidity and mortality in large registries, with survival >70% at 10 years. For patients not suitable for PEA or with residual PH after PEA, balloon pulmonary angioplasty and/or PH medical therapy may prove beneficial. Here, we describe the indications for PEA, specific surgical and perioperative strategies, postoperative monitoring and management, and approaches for managing residual PH in the long term.

Perioperative Right Ventricular Dysfunction and Abnormalities of the Tricuspid Valve Apparatus in Patients Undergoing Cardiac Surgery

Right ventricular (RV) dysfunction frequently occurs after cardiac surgery and is linked to adverse postoperative outcomes, including mortality, reintubation, stroke, and prolonged ICU stays. While various criteria using echocardiography and hemodynamic parameters have been proposed, a consensus remains elusive. Distinctive RV anatomical features include its thin wall, which presents a triangular shape in a lateral view and a crescent shape in a cross-sectional view. Principal causes of RV dysfunction after cardiac surgery encompass ischemic reperfusion injury, prolonged ischemic time, choice of cardioplegia and its administration, cardiopulmonary bypass weaning characteristics, and preoperative risk factors. Post-left ventricular assist device (LVAD) implantation RV dysfunction is common but often transient, with a favorable prognosis upon resolution. There is an ongoing debate regarding the benefits of concomitant surgical repair of the RV in the presence of regurgitation. According to the literature, the gold standard techniques for assessing RV function are cardiac magnetic resonance imaging and hemodynamic assessment using thermodilution. Echocardiography is widely favored for perioperative RV function evaluation due to its accessibility, reproducibility, non-invasiveness, and cost-effectiveness. Although other techniques exist for RV function assessment, they are less common in clinical practice. Clinical management strategies focus on early detection and include intravenous drugs (inotropes and vasodilators), inhalation drugs (pulmonary vasodilators), ventilator strategies, volume management, and mechanical support. Bridging research gaps in this field is crucial to improving clinical outcomes associated with RV dysfunction in the near future.

What echocardiographic findings differentiate acute pulmonary embolism and chronic pulmonary hypertension?

BACKGROUND

Pulmonary embolism (PE) and pulmonary hypertension (PH) are potentially fatal disease states. Early diagnosis and goal-directed management improve outcomes and survival. Both conditions share several echocardiographic findings of right ventricular dysfunction. This can inadvertently lead to incorrect diagnosis, inappropriate and potentially harmful management, and delay in time-sensitive therapies. Fortunately, bedside echocardiography imparts a few critical distinctions.

OBJECTIVE

This narrative review describes eight physiologically interdependent echocardiographic parameters that help distinguish acute PE and chronic PH. The manuscript details each finding along with associated pathophysiology and summarization of the literature evaluating diagnostic utility. This guide then provides pearls and pitfalls with high-quality media for the bedside evaluation.

DISCUSSION

The echocardiographic parameters suggesting acute or chronic right ventricular dysfunction (best used in combination) are: 1. Right heart thrombus (acute PE) 2. Right ventricular free wall thickness (acute ≤ 5 mm, chronic > 5 mm) 3. Tricuspid regurgitation pressure gradient (acute ≤ 46 mmHg, chronic > 46 mmHg, corresponding to tricuspid regurgitation maximal velocity ≤ 3.4 m/sec and > 3.4 m/sec, respectively) 4. Pulmonary artery acceleration time (acute ≤ 60-80 msec, chronic < 105 msec) 5. 60/60 sign (acute) 6. Pulmonary artery early-systolic notching (proximally-located, higher-risk PE) 7. McConnell's sign (acute) 8. Right atrial enlargement (equal to left atrial size suggests acute, greater than left atrial size suggests chronic).

CONCLUSIONS

Emergency physicians must appreciate the echocardiographic findings and associated pathophysiology that help distinguish acute and chronic right ventricular dysfunction. In the proper clinical context, these findings can point towards PE or PH, thereby leading to earlier goal-directed management.

Myocardial perfusion and flow reserve in the asynchronous heart: mechanistic insight from a computational model

The tight coupling between myocardial oxygen demand and supply has been recognized for decades, but it remains controversial whether this coupling persists under asynchronous activation, such as during left bundle branch block (LBBB). Furthermore, it is unclear whether the amount of local cardiac wall growth, following longer-lasting asynchronous activation, can explain differences in myocardial perfusion distribution between subjects. For a better understanding of these matters, we built upon our existing modeling framework for cardiac mechanics-to-perfusion coupling by incorporating coronary autoregulation. Regional coronary flow was regulated with a vasodilator signal based on regional demand, as estimated from regional fiber stress-strain area. Volume of left ventricular wall segments was adapted with chronic asynchronous activation toward a homogeneous distribution of myocardial oxygen demand per tissue weight. Modeling results show that 1) both myocardial oxygen demand and supply are decreased in early activated regions and increased in late-activated regions; 2) but that regional hyperemic flow remains unaffected; while 3) regional myocardial flow reserve (the ratio of hyperemic to resting myocardial flow) decreases with increases in absolute regional myocardial oxygen demand as well as with decreases in wall thickness. These findings suggest that septal hypoperfusion in LBBB represents an autoregulatory response to reduced myocardial oxygen demand. Furthermore, oxygen demand-driven remodeling of wall mass can explain asymmetric hypertrophy and the related homogenization of myocardial perfusion and flow reserve. Finally, the inconsistent observations of myocardial perfusion distribution can primarily be explained by the degree of dyssynchrony, the degree of asymmetric hypertrophy, and the imaging modality used.NEW & NOTEWORTHY This versatile modeling framework couples myocardial oxygen demand to oxygen supply and myocardial growth, enabling simulation of resting and hyperemic myocardial flow during acute and chronic asynchronous ventricular activation. Model-based findings suggest that reported inconsistencies in myocardial perfusion and flow reserve responses with asynchronous ventricular activation between patients can primarily be explained by the degree of dyssynchrony and wall mass remodeling, which together determine the heterogeneity in regional oxygen demand and, hence, supply with autoregulation.

Assessment of Right Ventricle Function and Tricuspid Regurgitation in Heart Failure: Current Advances in Diagnosis and Imaging

Right ventricular (RV) systolic dysfunction increases mortality among heart failure patients, and therefore, accurate diagnosis and monitoring is paramount. RV anatomy and function are complex, usually requiring a combination of imaging modalities to completely quantitate volumes and function. Tricuspid regurgitation usually occurs with RV dysfunction, and quantifying this valvular lesion also may require multiple imaging modalities. Echocardiography is the first-line imaging tool for identifying RV dysfunction, with cardiac MRI and cardiac computed tomography adding valuable additional information.

Consensus guidelines for the perioperative management of patients undergoing endoscopic retrograde cholangiopancreatography

Deep sedation without tracheal intubation (monitored anaesthesia care) and general anaesthesia with tracheal intubation are commonly used anaesthesia techniques for endoscopic retrograde cholangiopancreatography (ERCP). There are distinct pathophysiological differences between monitored anaesthesia care and general anaesthesia that need to be considered depending on the nature and severity of the patient's underlying disease, comorbidities, and procedural risks. An international group of expert anaesthesiologists and gastroenterologists created clinically relevant questions regarding the merits and risks of monitored anaesthesia care vs general anaesthesia in specific clinical scenarios for planning optimal anaesthetic approaches for ERCP. Using a modified Delphi approach, the group created practical recommendations for anaesthesiologists, with the aim of reducing the incidence of perioperative adverse outcomes while maximising healthcare resource utilisation. In the majority of clinical scenarios analysed, our expert recommendations favour monitored anaesthesia care over general anaesthesia. Patients with increased risk of pulmonary aspiration and those undergoing prolonged procedures of high complexity were thought to benefit from general anaesthesia with tracheal intubation. Patient age and ASA physical status were not considered to be factors for choosing between monitored anaesthesia care and general anaesthesia. Monitored anaesthesia care is the favoured anaesthesia plan for ERCP. An individual risk-benefit analysis that takes into account provider and institutional experience, patient comorbidities, and procedural risks is also needed.

Management of Acute Right Ventricular Failure

PURPOSE OF REVIEW

Acute right ventricular failure (RVF) is a frequent condition associated with high morbidity and mortality. This review aims to provide a current overview of the pathophysiology, presentation, and comprehensive management of acute RVF.

RECENT FINDINGS

Acute RVF is a common disease with a pathophysiology that is not completely understood. There is renewed interest in the right ventricle (RV). Some advances have been principally made in chronic right ventricular failure (e.g., pulmonary hypertension). Due to a lack of precise definition and diagnostic tools, acute RVF is poorly studied. Few advances have been made in this field. Acute RVF is a complex, frequent, and life-threatening condition with several etiologies. Transthoracic echocardiography (TTE) is the key diagnostic tool in search of the etiology. Management includes transfer to an expert center and admission to the intensive care unit (ICU) in most severe cases, etiological treatment, and general measures for RVF.

Heart failure in systemic right ventricle: Mechanisms and therapeutic options

d-loop transposition of the great arteries (d-TGA) and congenitally corrected transposition of the great arteries (cc-TGA) feature a right ventricle attempting to sustain the systemic circulation. A systemic right ventricle (sRV) cannot support cardiac output in the long run, eventually decompensating and causing heart failure. The burden of d-TGA patients with previous atrial switch repair and cc-TGA patients with heart failure will only increase in the coming years due to the aging adult congenital heart disease population and improvements in the management of advanced heart failure. Clinical data still lags behind in developing evidence-based guidelines for risk stratification and management of sRV patients, and clinical trials for heart failure in these patients are underrepresented. Recent studies have provided foundational data for the commencement of robust clinical trials in d-TGA and cc-TGA patients. Further insights into the multifactorial nature of sRV failure can only be provided by the results of such studies. This review discusses the mechanisms of heart failure in sRV patients with biventricular circulation and how these mediators may be targeted clinically to alleviate sRV failure.

Pulmonary Artery Banding for Dilated Cardiomyopathy in Children: Returning to the Bench from Bedside

Current treatment paradigms for end-stage dilated cardiomyopathy (DCM) in children include heart transplantation and mechanical support devices. However, waitlist mortality, shortage of smaller donors, time-limited durability of grafts, and thrombo-hemorrhagic events affect long-term outcomes. Moreover, both these options are noncurative and cannot preserve the native heart function. Pulmonary artery banding (PAB) has been reinvented as a possible “regenerative surgery” to retrain the decompensated left ventricle in children with DCM. The rationale is to promote positive ventricular–ventricular interactions that result in recovery of left ventricular function in one out of two children, allowing transplantation delisting. Although promising, global experience with this technique is still limited, and several surgical centers are reluctant to adopt PAB since its exact biological bases remain unknown. In the present review, we summarize the clinical, functional, and molecular known and supposed working mechanisms of PAB in children with DCM. From its proven efficacy in the clinical setting, we described the macroscopic geometrical and functional changes in biventricular performance promoted by PAB. We finally speculated on the possible underlying molecular pathways recruited by PAB. An evidence-based explanation of the working mechanisms of PAB is still awaited to support wider adoption of this surgical option for pediatric heart failure.

Correlations among noninvasive right ventricular myocardial work indices and the main parameters of systolic and diastolic functions

BACKGROUND

Right ventricular (RV) myocardial work (RVMW) is the latest method used to assess RV function. To date, correlations among RVMW indices and RV systolic and diastolic functions have not been studied.

METHODS

A total of 106 healthy volunteers (median age, 34 years; 46% male) were prospectively enrolled. RVMW indices were measured using the RV pressure-strain loop using specific software. The correlations among RVMW indices and other RV functions were analyzed.

RESULTS

During the multivariate analysis, the RV global work index (RVGWI) was significantly correlated with RV global longitudinal strain (RV GLS) (p < .0001), pulmonary systolic artery pressure (PASP) (p < .0001), and tricuspid annular (TA) plane systolic excursion (TAPSE) (p = .036). RV global constructive work (RVGCW) was correlated with RV GLS (p < .0001) and PASP (p < .0001). RV global wasted work (RVGWW) was correlated with RV GLS (p = .008) and TA isovolumetric acceleration (TA IVA) (p = .008). RV global work efficiency (RVGWE) was correlated with RV GLS (p < .0001) and tissue Doppler (TD) RV myocardial performance index (TD RMPI) (p = .043).

CONCLUSION

RVMW indices showed good correlations with RV myocardial systolic function.

RIGHT VENTRICLE FUNCTION IN PATIENTS WITH ANTERIOR MYOCARDIAL INFARCTION: ARE WE SURE IT IS NOT INVOLVED?

The right and left ventricle of heart are intimately connected by anatomical and functional links. Hence, acute changes in cardiac geometry and function can modify the performance and physiology of both sides of the heart, influencing each other. After a brief overview of the anatomy and related imaging techniques for the study of right ventricular function, we report a review on the interesting correlation of acute anterior myocardial infarction and right ventricular function, very often underestimated.

Right ventricular myocardial energetic model for evaluating right heart function in pulmonary arterial hypertension

Background

Pulmonary arterial hypertension (PAH) increases right ventricular (RV) workload and decreases myocardial oxygen reserve, eventually leading to poor cardiac output. This study created and assessed a novel model of RV work output based on RV hemodynamics and oxygen supply, allowing new insight into causal mechanisms of RV dysfunction.

Methods

The RV function model was built upon an earlier, left ventricular model and further adjusted for more accurate clinical use. The model assumes that RV total power output (1) is the sum of isovolumic and stroke power and (2) is linearly related to its right coronary artery oxygen supply. Thus, when right coronary artery flow is limited or isovolumic power is elevated, less energy is available for producing cardiac output. The original and adjusted models were validated via data from patients with idiopathic PAH (n = 14) and large animals (n = 6) that underwent acute pulmonary banding with or without hypoxia.

Results

Both models demonstrated strong, significant correlations between RV oxygen consumption rate and RV total power output for PAH patients (original model, R² = 0.66; adjusted model, R² = 0.78) and sheep (original, R² = 0.85; adjusted, R² = 0.86). Furthermore, the models demonstrate a significant inverse relationship between required oxygen consumption and RV efficiency (stroke power/total power) (p < 0.001). Lastly, higher NYHA class was indicative of lower RV efficiency and higher oxygen consumption (p = 0.013).

Conclusion

Right ventricular total power output can be accurately estimated directly from pulmonary hemodynamics and right coronary perfusion during PAH. This model highlights the increased vulnerability of PAH patients with compromised right coronary flow coupled with high afterload.

Low-Dose Propranolol Prevents Functional Decline in Catecholamine-Induced Acute Heart Failure in Rats

Severe hyper-catecholaminergic states likely cause heart failure and cardiac fibrosis. While previous studies demonstrated the effects of beta-blockade in experimental models of single-catecholamine excess states, the detailed benefits of beta-blockade in more realistic models of hyper-adrenergic states are less clearly understood. In this study, we examined different therapeutic dosages and the effects of propranolol in rats with hyper-acute catecholamine-induced heart failure, and subsequent cardiopulmonary changes. Rats (n = 41) underwent a 6 h infusion of epinephrine and norepinephrine alone, with additional low-dose (1 mg/kg) or high-dose propranolol (10 mg/kg) at hour 1. Cardiac and pulmonary tissues were examined after 6 h. Catecholamine-only groups had the lowest survival rate. Higher doses of propranolol (15 mg/kg) caused similarly low survival rates and were not further analyzed. All low-dose propranolol rats survived, with a modest survival improvement in the high-dose propranolol groups. Left ventricular (LV) systolic pressure and LV end-diastolic pressure improved maximally with low-dose propranolol. Cardiac immunohistochemistry revealed an LV upregulation of FGF-23 in the catecholamine groups, and this improved in low-dose propranolol groups. These results suggest catecholamine-induced heart failure initiates early pre-fibrotic pathways through FGF-23 upregulation. Low-dose propranolol exerted cardio-preventative effects through FGF-23 downregulation and hemodynamic-parameter improvement in our model of hyper-acute catecholamine-induced heart failure.

Cardiovascular subphenotypes in patients with COVID-19 pneumonitis whose lungs are mechanically ventilated: a single-centre retrospective observational study

Unsupervised clustering methods of transthoracic echocardiography variables have not been used to characterise circulatory failure mechanisms in patients with COVID‐19 pneumonitis. We conducted a retrospective, single‐centre cohort study in ICU patients with COVID‐19 pneumonitis whose lungs were mechanically ventilated and who underwent transthoracic echocardiography between March 2020 and May 2021. We performed latent class analysis of echocardiographic and haemodynamic variables. We characterised the identified subphenotypes by comparing their clinical parameters, treatment responses and 90‐day mortality rates. We included 305 patients with a median (IQR [range]) age 59 (49–66 [16–83]) y. Of these, 219 (72%) were male, 199 (65%) had moderate acute respiratory distress syndrome and 113 (37%) did not survive more than 90 days. Latent class analysis identified three cardiovascular subphenotypes: class 1 (52%; normal right ventricular function); class 2 (31%; right ventricular dilation with mostly preserved systolic function); and class 3 (17%; right ventricular dilation with systolic impairment). The three subphenotypes differed in their clinical characteristics and response to prone ventilation and outcomes, with 90‐day mortality rates of 22%, 42% and 73%, respectively (p < 0.001). We conclude that the identified subphenotypes aligned with right ventricular pathophysiology rather than the accepted definitions of right ventricular dysfunction, and these identified classifications were associated with clinical outcomes.

Coronary blood flow in heart failure: cause, consequence and bystander

Heart failure is a clinical syndrome where cardiac output is not sufficient to sustain adequate perfusion and normal bodily functions, initially during exercise and in more severe forms also at rest. The two most frequent forms are heart failure of ischemic origin and of non-ischemic origin. In heart failure of ischemic origin, reduced coronary blood flow is causal to cardiac contractile dysfunction, and this is true for stunned and hibernating myocardium, coronary microembolization, myocardial infarction and post-infarct remodeling, possibly also for the takotsubo syndrome. The most frequent form of non-ischemic heart failure is dilated cardiomyopathy, caused by genetic mutations, myocarditis, toxic agents or sustained tachyarrhythmias, where alterations in coronary blood flow result from and contribute to cardiac contractile dysfunction. Hypertrophic cardiomyopathy is caused by genetic mutations but can also result from increased pressure and volume overload (hypertension, valve disease). Heart failure with preserved ejection fraction is characterized by pronounced coronary microvascular dysfunction, the causal contribution of which is however not clear. The present review characterizes the alterations of coronary blood flow which are causes or consequences of heart failure in its different manifestations. Apart from any potentially accompanying coronary atherosclerosis, all heart failure entities share common features of impaired coronary blood flow, but to a different extent: enhanced extravascular compression, impaired nitric oxide-mediated, endothelium-dependent vasodilation and enhanced vasoconstriction to mediators of neurohumoral activation. Impaired coronary blood flow contributes to the progression of heart failure and is thus a valid target for established and novel treatment regimens.

Assessment of Myocardial Function During Blood Pressure Manipulations Using Feature Tracking Cardiovascular Magnetic Resonance

Background: Coronary autoregulation is a feedback system, which maintains near-constant myocardial blood flow over a range of mean arterial pressure (MAP). Yet in emergency or peri-operative situations, hypotensive or hypertensive episodes may quickly arise. It is not yet established how rapid blood pressure changes outside of the autoregulation zone (ARZ) impact left (LV) and right ventricular (RV) function. Using cardiovascular magnetic resonance (CMR) imaging, measurements of myocardial tissue oxygenation and ventricular systolic and diastolic function can comprehensively assess the heart throughout a range of changing blood pressures.

Design and methods: In 10 anesthetized swine, MAP was varied in steps of 10–15 mmHg from 29 to 196 mmHg using phenylephrine and urapidil inside a 3-Tesla MRI scanner. At each MAP level, oxygenation-sensitive (OS) cine images along with arterial and coronary sinus blood gas samples were obtained and blood flow was measured from a surgically implanted flow probe on the left anterior descending coronary artery. Using CMR feature tracking-software, LV and RV circumferential systolic and diastolic strain parameters were measured from the myocardial oxygenation cines.

Results: LV and RV peak strain are compromised both below the lower limit (LV: Δ1.2 ± 0.4%, RV: Δ4.4 ± 1.2%, p < 0.001) and above the upper limit (LV: Δ2.1 ± 0.4, RV: Δ5.4 ± 1.4, p < 0.001) of the ARZ in comparison to a baseline of 70 mmHg. LV strain demonstrates a non-linear relationship with invasive and non-invasive measures of oxygenation. Specifically for the LV at hypotensive levels below the ARZ, systolic dysfunction is related to myocardial deoxygenation (β = −0.216, p = 0.036) in OS-CMR and both systolic and diastolic dysfunction are linked to reduced coronary blood flow (peak strain: β = −0.028, p = 0.047, early diastolic strain rate: β = 0.026, p = 0.002). These relationships were not observed at hypertensive levels.

Conclusion: In an animal model, biventricular function is compromised outside the coronary autoregulatory zone. Dysfunction at pressures below the lower limit is likely caused by insufficient blood flow and tissue deoxygenation. Conversely, hypertension-induced systolic and diastolic dysfunction points to high afterload as a cause. These findings from an experimental model are translatable to the clinical peri-operative environment in which myocardial deformation may have the potential to guide blood pressure management, in particular at varying individual autoregulation thresholds.

How We Would Treat Our Own Pulmonary Hypertension if We Needed to Undergo Cardiac Surgery

Pulmonary hypertension (PH) is a disease that has many etiologies and is particularly prevalent in patients presenting for cardiac surgery, with which it is linked to poor outcomes. This manuscript is intended to provide a comprehensive review of the impact of PH on the perioperative management of patients who are undergoing cardiac surgery. The diagnosis of PH often involves a combination of noninvasive and invasive testing, whereas preoperative optimization frequently necessitates the use of specific medications that affect anesthetic management of these patients. The authors postulate that a thoughtful, multidisciplinary approach is required to deliver excellent perioperative care. Furthermore, they use an index case to illustrate the implications of managing a patient with pulmonary hypertension who presents for cardiac surgery with cardiopulmonary bypass.

Exploring Functional Differences between the Right and Left Ventricles to Better Understand Right Ventricular Dysfunction

The right and left ventricles have traditionally been studied as individual entities. Furthermore, modifications found in diseased left ventricles are assumed to influence on right ventricle alterations, but the connection is poorly understood. In this review, we describe the differences between ventricles under physiological and pathological conditions. Understanding the mechanisms that differentiate both ventricles would facilitate a more effective use of therapeutics and broaden our knowledge of right ventricle (RV) dysfunction. RV failure is the strongest predictor of mortality in pulmonary arterial hypertension, but at present, there are no definitive therapies directly targeting RV failure. We further explore the current state of drugs and molecules that improve RV failure in experimental therapeutics and clinical trials to treat pulmonary arterial hypertension and provide evidence of their potential benefits in heart failure.

Pulmonary Hypertension in 2021: Part I-Definition, Classification, Pathophysiology, and Presentation

The World Symposium on Pulmonary Hypertension (WSPH) was organized by the World Health Organization in 1973 in response to an increase in pulmonary arterial hypertension in Europe caused by aminorex, an appetite suppressant. The mandate of this meeting was to review the latest clinical and scientific research and to formulate recommendations to improve the diagnosis and management of pulmonary hypertension (PH).¹ Since 1998, the WSPH has met every five years and in 2018, the sixth annual WSPH revised the hemodynamic definition of PH. This two-part series will review the updated definition, classification, pathophysiology, presentation, diagnosis, management, and perioperative management of patients with PH. In the first part of this series, the definition, classification, pathophysiology, and presentation will be reviewed.

[Vasopressors: Physiology, Pharmacology and Clinical Applications]

Vasopressors are widely used in anaesthesiology and critical care medicine, to treat harmless (e.g. anaesthesia-induced hypotension) as well as life-threatening conditions (e.g. septic shock). Some clinically used vasopressors resemble endogenous substances - such as norepinephrine - while others have been artificially synthesized (e.g. phenylephrine). Most of the substances used in different clinical scenarios have various effects except for vasoconstriction alone. Therefore, a thorough understanding of the pharmacology and clinical profile of every single substance is of highest importance prior to practical usage. Furthermore, the fundamentals of vascular physiology and vasotonic regulation are mandatory to safely provide vasopressor-based therapies. This article covers the essentials of physiology and pharmacology of vasopressors, and the clinical settings they are used in (e.g. septic shock, vasoplegic shock after cardiac surgery, trauma-induced hypotension).

Derivation and validation of Pd/Pa in the assessment of residual ischemia post-intervention: A prospective all-comer registry

BACKGROUND

Measurement of post-percutaneous coronary intervention (PCI) fractional flow reserve (FFR) demonstrates residual ischemia in a large percentage of cases deemed angiographically successful which, in turn, has been associated with worse long-term outcomes. It has recently been shown that a resting pressure index, Pd/Pa, has prognostic value post stenting, however, its diagnostic value relative to FFR post-PCI has not been evaluated.

METHODS

The diagnostic accuracy of Pd/Pa in identifying ischemia (FFR≤0.80) pre- and post-PCI was evaluated. Three patient subsets were analyzed. A reference pre-PCI cohort of 1,255 patients (1,560 vessels) was used to measure the accuracy of pre-PCI Pd/Pa vs. FFR. A derivation post-PCI group of 574 patient (664 vessels) was then used to calculate the diagnostic accuracy of post-PCI Pd/Pa vs. FFR. A final prospective validation cohort of 230 patients (255 vessels) was used to test and validate the diagnostic performance of post-PCI Pd/Pa.

RESULTS

Median Pd/Pa and FFR were 0.90 (IQR 0.90-0.98) and 0.80 (IQR 0.71-0.88) in the reference pre-PCI model, 0.96 (IQR 0.93-1.00) and 0.87 (IQR 0.77-0.90) in the post-PCI derivation model, and 0.94 (IQR 0.89-0.97) and 0.84 (IQR 0.77-0.90) in the post-PCI validation model respectively. There was a strong linear correlation between Pd/Pa and FFR in all three models (p < 0.0001). Using ROC analysis, the optimal Pd/Pa cutoff value to predict a FFR ≤ 0.80 was ≤0.92 (AUC 0.87) in the pre-PCI model, ≤0.93 (AUC 0.85) in the post-PCI derivation model, and ≤ 0.90 (AUC 0.91) in the post-PCI validation model. Using a hybrid strategy of post-PCI Pd/Pa and post-PCI FFR when necessary (25% patients), overall diagnostic accuracy was improved to 95%.

CONCLUSIONS

Pd/Pa has excellent diagnostic accuracy for identifying ischemia post-intervention. Using a hybrid strategy of post-PCI Pd/Pa first, and FFR afterwards, if required, adenosine administration can be avoided in over 75% of physiologic assessments post intervention.

Right Ventricular Dysfunction in Patients With COVID-19: A Systematic Review and Meta-analysis

OBJECTIVE

This systematic review and meta-analysis aimed to describe the features of right ventricular impairment and pulmonary hypertension in coronavirus disease (COVID-19) and assess their effect on mortality.

DESIGN

The authors carried out a systematic review and meta-analysis of observational studies.

SETTING

The authors performed a search through PubMed, the International Clinical Trials Registry Platform, and the Cochrane Library for studies reporting right ventricular dysfunction in patients with COVID-19 and outcomes.

PARTICIPANTS

The search yielded nine studies in which the appropriate data were available.

INTERVENTIONS

Pooled odds ratios were calculated according to the random-effects model.

MEASUREMENTS AND MAIN RESULTS

Overall, 1,450 patients were analyzed, and half of them were invasively ventilated. Primary outcome was mortality at the longest follow-up available. Mortality was 48.5% versus 24.7% in patients with or without right ventricular impairment (n = 7; OR = 3.10; 95% confidence interval [CI] 1.72-5.58; p = 0.0002), 56.3% versus 30.6% in patients with or without right ventricular dilatation (n = 6; OR = 2.43; 95% CI 1.41-4.18; p = 0.001), and 52.9% versus 14.8% in patients with or without pulmonary hypertension (n = 3; OR = 5.75; 95% CI 2.67-12.38; p < 0.001).

CONCLUSION

Mortality in patients with COVID-19 requiring respiratory support and with a diagnosis of right ventricular dysfunction, dilatation, or pulmonary hypertension is high. Future studies should highlight the mechanisms of right ventricular derangement in COVID-19, and early detection of right ventricular impairment using ultrasound might be important to individualize therapies and improve outcomes.

Perioperative Management of Pulmonary Hypertension. a Review

Pulmonary hypertension is a rare and progressive pathology defined by abnormally high pulmonary artery pressure mediated by a diverse range of aetiologies. It affects up to twenty-six individuals per one million patients currently living in the United Kingdom (UK), with a median life expectancy of 2.8 years in idiopathic pulmonary hypertension. The diagnosis of pulmonary hypertension is often delayed due to the presentation of non-specific symptoms, leading to a delay in referral to specialists services. The complexity of treatment necessitates a multidisciplinary approach, underpinned by a diverse disease aetiology from managing the underlying disease process to novel specialist treatments. This has led to the formation of dedicated specialist treatment centres within centralised UK cities. The article aimed to provide a concise overview of pulmonary hypertension's clinical perioperative management, including key definitions, epidemiology, pathophysiology, and risk stratification.

Physiology of the Right Ventricle Across the Lifespan

The most common cause of heart failure in the United States is ischemic left heart disease; accordingly, a vast amount of work has been done to elucidate the molecular mechanisms underlying pathologies of the left ventricle (LV) as a general model of heart failure. Until recently, little attention has been paid to the right ventricle (RV) and it has commonly been thought that the mechanical and biochemical properties of the RV are similar to those of the LV. However, therapies used to treat LV failure often fail to improve ventricular function in RV failure underscoring, the need to better understand the unique physiologic and pathophysiologic properties of the RV. Importantly, hemodynamic stresses (such as pressure overload) often underlie right heart failure further differentiating RV failure as unique from LV failure. There are significant structural, mechanical, and biochemical properties distinctive to the RV that influences its function and it is likely that adaptations of the RV occur uniquely across the lifespan. We have previously reviewed the adult RV compared to the LV but there is little known about differences in the pediatric or aged RV. Accordingly, in this mini-review, we will examine the subtle distinctions between the RV and LV that are maintained physiologically across the lifespan and will highlight significant knowledge gaps in our understanding of pediatric and aging RV. Consideration of how RV function is altered in different disease states in an age-specific manner may enable us to define RV function in health and importantly, in response to pathology.

High Versus Normal Blood Pressure Targets in Relation to Right Ventricular Dysfunction After Cardiac Surgery: A Randomized Controlled Trial

OBJECTIVE

Management of right ventricular (RV) dysfunction is challenging. Current practice predominantly is based on data from experimental and small uncontrolled studies and includes augmentation of blood pressure. However, whether such intervention is effective in the clinical setting of cardiac surgery is unknown.

DESIGN

Randomized controlled trial.

SETTING

Single-center study in a tertiary teaching hospital.

PARTICIPANTS

The study comprised 78 patients equipped with a pulmonary artery catheter (PAC), classified according to PAC-derived RV ejection fraction (RVEF); 44 patients had an RVEF of <20%, and 34 patients had an RVEF between ≥20% and <30%.

INTERVENTIONS

Patients randomly were assigned to either a normal target group (mean arterial pressure 65 mmHg) or a high target group [mean arterial pressure 85 mmHg]). The primary end- point was the change in RVEF over a one-hour study period.

MEASUREMENTS AND MAIN RESULTS

There was no significant between-group difference in change of RVEF <20% (-1% [-3.3 to 1.8] in the normal-target group v 0.5% [-1 to 4] in the high-target group; p = 0.159). There was no significant between-group difference in change in RVEF 20%-to-30% (-1% [-3 to 0] in the normal-target group v 1% [-1 to 3] in the high-target group; p = 0.074). These results were in line with the simultaneous observation that echocardiographic variables of RV and left ventricular function also remained unaltered over time, irrespective of either baseline RVEF or treatment protocol.

CONCLUSION

In a mixed cardiac surgery population with RV dysfunction, norepinephrine-mediated high blood pressure targets did not result in an increase in PAC-derived RVEF compared with normal blood pressure targets.

Perioperative management of patients with pulmonary hypertension undergoing non-cardiothoracic, non-obstetric surgery: a systematic review and expert consensus statement

BACKGROUND

The risk of complications, including death, is substantially increased in patients with pulmonary hypertension (PH) undergoing anaesthesia for surgical procedures, especially in those with pulmonary arterial hypertension (PAH) and chronic thromboembolic PH (CTEPH). Sedation also poses a risk to patients with PH. Physiological changes including tachycardia, hypotension, fluid shifts, and an increase in pulmonary vascular resistance (PH crisis) can precipitate acute right ventricular decompensation and death.

METHODS

A systematic literature review was performed of studies in patients with PH undergoing non-cardiac and non-obstetric surgery. The management of patients with PH requiring sedation for endoscopy was also reviewed. Using a framework of relevant clinical questions, we review the available evidence guiding operative risk, risk assessment, preoperative optimisation, and perioperative management, and identifying areas for future research.

RESULTS

Reported 30 day mortality after non-cardiac and non-obstetric surgery ranges between 2% and 18% in patients with PH undergoing elective procedures, and increases to 15-50% for emergency surgery, with complications and death usually relating to acute right ventricular failure. Risk factors for mortality include procedure-specific and patient-related factors, especially markers of PH severity (e.g. pulmonary haemodynamics, poor exercise performance, and right ventricular dysfunction). Most studies highlight the importance of individualised preoperative risk assessment and optimisation and advanced perioperative planning.

CONCLUSIONS

With an increasing number of patients requiring surgery in specialist and non-specialist PH centres, a systematic, evidence-based, multidisciplinary approach is required to minimise complications. Adequate risk stratification and a tailored-individualised perioperative plan is paramount.

Quantitative assessment of the entire right ventricle from one acoustic window: An attractive approach in patients with congenital heart disease in daily practice

BACKGROUND

Right ventricular (RV) function is recognized as an important prognostic factor in adult congenital heart disease (ACHD). The accuracy of established parameters including tricuspid annular plane systolic excursion (TAPSE), RV fractional area change (RVFAC) and tissue Doppler imaging (TDI S') is limited as only a small RV region is reflected. We previously introduced a novel four-view approach with different RV walls visualized from one apical view using electronic plane rotation, also known as iRotate.

AIM

To evaluate the entire RV function using electronic plane rotation echocardiography within the spectrum of ACHD compared with healthy subjects.

METHODS AND RESULTS

One hundred and forty-two ACHD patients were recruited from the outpatient clinic and 89 healthy subjects. All subjects underwent a transthoracic echocardiogram with evaluation of TAPSE, TDI S' and peak systolic longitudinal RV strain (RV-LS) from all RV walls using the four-view electronic plane rotation model. With exception of TDI S' in inferior coronal view, all parameters were lower in ACHD vs healthy subjects (p < 0.001). Within the ACHD patients, RV strain was lower in anterior (-15.9 ± 4.9) and inferior coronal view (-15.1 ± 4.5) versus lateral (-17.6 ± 5.0) and inferior wall (-17.2 ± 4.7) (p < 0.05). RV-LS values of systemic RV were lower (p < 0.05), but no difference was observed between subpulmonic RV loading conditions.

CONCLUSION

The four-view electronic plane rotation model represents a reproducible, easily applicable and complete RV assessment in daily practice. RV function is significantly decreased in the ACHD group using both regional and global assessment parameters. Complete RV strain analysis reveals regional differences.

Right Atrial Volume Index as a Predictor of Persistent Right Ventricular Dysfunction in Patients with Acute Inferior Myocardial Infarction and Proximal Right Coronary Artery Occlusion Treated with Primary Percutaneous Coronary Intervention

Objectives

Patients with right ventricular (RV) infarctions associated with inferior infarctions have higher rates of adverse events than isolated inferior infarctions. Right atrial volume index (RAVI) has recently been described as a predictor of clinical outcome in patients with chronic systolic heart failure and pulmonary hypertension. The aim of this study is to assess the ability of RAVI to predict the persistent RV dysfunction after acute inferior STEMI due to occlusion of proximal RCA. To the best of our knowledge, this is the first study to investigate the relation between RAVI and persistent RV dysfunction in such group of patients.

Patients and methods

Sixty-five consecutive patients with recent first acute inferior STEMI who underwent primary percutaneous coronary intervention (PPCI) were prospectively included in the study. Echocardiographic evaluation was performed at the time of discharge and at 3 months. All the patients underwent standard echocardiographic assessment using conventional 2D and tissue Doppler imaging (TDI).

Results

Patients were divided into two groups according to right ventricular function (RVF) 3 months after acute myocardial infarction (AMI). The normal RVF group included 41 (63%) patients and the impaired RVF group included 24 (37%) patients. RAVI was significantly higher in patients with impaired RVF (p=<0.001). RAVI was a predictor of persistently impaired RV function (odds ratio = 1.786, 95% confidence interval, 1.367–2.335, p value= <0.001) and (odds ratio = 1.829, 95% confidence interval, 1.358–2.462, p value= <0.001) in univariate and multivariable logistic regression analyses respectively. In receiving operator characteristics (ROC) curve analysis, RAVI with a cutoff value ≥ 30 ml/m² had a 87.5% sensitivity, a 92.24% specificity area under Receiving operator characteristics (ROC) curve = 0.964 for predicting persistently impaired RVF.

Conclusion

In patients with inferior STEMI with proximal RCA occlusion, RAVI is an independent predictor of persistently impaired RVF with a cut-off value ≥ 30 ml/m².

Prognostic Implications of Increased Right Ventricular Wall Tension in Secondary Tricuspid Regurgitation

Secondary tricuspid regurgitation (TR) imposes a chronic volume overload on the right ventricle (RV) which can increase RV wall tension (RVWT). The aim of this study was to investigate the prognostic implications of increased RVWT in patients with significant secondary TR. A total of 1,142 patients with moderate-to-severe secondary TR were included. Based on the simplified Laplace-Young's law, RVWT was defined as the product between pulmonary artery systolic pressure (PASP) and RV base-to-apex length. The association between RVWT and risk of all-cause death was identified with spline curve analysis and patients were divided according to the cut-off of RVWT beyond which the hazard ratio (HR) and 95% confidence interval for all-cause mortality were above 1. Four hundred sixty-five (41%) patients had RVWT >3,300 mm Hg x mm and formed the group with increased RVWT. Patients with increased RVWT were more likely male, had more frequent heart failure symptoms and presented with more co-morbidities, larger RV and left ventricular (LV) dimensions, worse LV function, more severe secondary TR and higher PASP compared with patients with nonincreased RVWT. During a median follow-up of 51 (17 to 86) months, 586 (51%) patients died. The cumulative 5-year survival rate was significantly worse in patients with increased RVWT as compared with patients with nonincreased RVWT (38% vs 63% p <0.001). After correcting for potential confounders, increased RVWT retained an independent association with all-cause mortality (HR 1.555; 95% CI 1.268 to 1.907; p <0.001). In conclusion, increased RVWT is independently associated with worse prognosis and its evaluation may improve risk stratification in patients with significant secondary TR.

Myocardial Perfusion Simulation for Coronary Artery Disease: A Coupled Patient-Specific Multiscale Model

Patient-specific models of blood flow are being used clinically to diagnose and plan treatment for coronary artery disease. A remaining challenge is bridging scales from flow in arteries to the micro-circulation supplying the myocardium. Previously proposed models are descriptive rather than predictive and have not been applied to human data. The goal here is to develop a multiscale patient-specific model enabling blood flow simulation from large coronary arteries to myocardial tissue. Patient vasculatures are segmented from coronary computed tomography angiography data and extended from the image-based model down to the arteriole level using a space-filling forest of synthetic trees. Blood flow is modeled by coupling a 1D model of the coronary arteries to a single-compartment Darcy myocardium model. Simulated results on five patients with non-obstructive coronary artery disease compare overall well to [\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{15}$$\end{document}15O]\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {H}_{{2}}$$\end{document}H2O PET exam data for both resting and hyperemic conditions. Results on a patient with severe obstructive disease link coronary artery narrowing with impaired myocardial blood flow, demonstrating the model’s ability to predict myocardial regions with perfusion deficit. This is the first report of a computational model for simulating blood flow from the epicardial coronary arteries to the left ventricle myocardium applied to and validated on human data.

Treatment Targets for Right Ventricular Dysfunction in Pulmonary Arterial Hypertension

Right ventricle (RV) dysfunction is the strongest predictor of mortality in pulmonary arterial hypertension (PAH), but, at present, there are no therapies directly targeting the failing RV. Although there are shared molecular mechanisms in both RV and left ventricle (LV) dysfunction, there are important differences between the 2 ventricles that may allow for the development of RV-enhancing or RV-directed therapies. In this review, we discuss the current understandings of the dysregulated pathways that promote RV dysfunction, highlight RV-enriched or RV-specific pathways that may be of particular therapeutic value, and summarize recent and ongoing clinical trials that are investigating RV function in PAH. It is hoped that development of RV-targeted therapies will improve quality of life and enhance survival for this deadly disease.

The right ventricle

The healthy right ventricle (RV) has a thin-walled structure compared to the thick-walled left ventricle (LV). It has a complex shape that appears crescentic when viewed in cross section and triangular when viewed from the side.

Automating Model Generation for Image-Based Cardiac Flow Simulation

Computational fluid dynamics (CFD) modeling of left ventricle (LV) flow combined with patient medical imaging data has shown great potential in obtaining patient-specific hemodynamics information for functional assessment of the heart. A typical model construction pipeline usually starts with segmentation of the LV by manual delineation followed by mesh generation and registration techniques using separate software tools. However, such approaches usually require significant time and human efforts in the model generation process, limiting large-scale analysis. In this study, we propose an approach toward fully automating the model generation process for CFD simulation of LV flow to significantly reduce LV CFD model generation time. Our modeling framework leverages a novel combination of techniques including deep-learning based segmentation, geometry processing, and image registration to reliably reconstruct CFD-suitable LV models with little-to-no user intervention.1 We utilized an ensemble of two-dimensional (2D) convolutional neural networks (CNNs) for automatic segmentation of cardiac structures from three-dimensional (3D) patient images and our segmentation approach outperformed recent state-of-the-art segmentation techniques when evaluated on benchmark data containing both magnetic resonance (MR) and computed tomography(CT) cardiac scans. We demonstrate that through a combination of segmentation and geometry processing, we were able to robustly create CFD-suitable LV meshes from segmentations for 78 out of 80 test cases. Although the focus on this study is on image-to-mesh generation, we demonstrate the feasibility of this framework in supporting LV hemodynamics modeling by performing CFD simulations from two representative time-resolved patient-specific image datasets.

Clinical relevance of adding intravascular ultrasound to coronary angiography for the diagnosis of extrinsic left main coronary artery compression by a pulmonary artery aneurysm in pulmonary hypertension

OBJECTIVES

We sought to assess the clinical value of adding intravascular ultrasound (IVUS) evaluation to coronary angiography (CA) to guide extrinsic left main coronary artery (LMCA) compression diagnosis and treatment in pulmonary hypertension (PH).

BACKGROUND

LMCA compression due to a pulmonary artery aneurysm (PAA) is a severe complication of PH. Although guidelines encourage the use of IVUS for LMCA disease evaluation, it has hardly been used in this scenario.

METHODS

We analyzed morbimortality of type 1 and 4 PH patients with clinically suspected LMCA compression by a PAA between 2010 and 2018 in a reference unit. LMCA compression was prospectively assessed with CA ± IVUS. Angiographic-LMCA compression was considered conclusive when LMCA stenosis>50% was present in four predetermined projections; inconclusive, when LMCA stenosis>50% was present in <4 projections and negative if no stenosis>50% was present. Patients with conclusive and inconclusive CA underwent IVUS. IVUS-LMCA compression was defined as systolic minimum lumen area < 6 mm² .

RESULTS

LMCA compression was suspected in 23/796 patients (3%). CA was conclusive for compression in 7(30.5%), inconclusive in 9(39%), and negative in 7(30.5%). IVUS confirmed LMCA compression in 6/7(86%) patients with conclusive CA and in 2/9(22%) with inconclusive CA. Patients fulfilling IVUS criteria for LMCA compression underwent stent implantation. At 20 months follow-up a composite end-point of death, stent restenosis/thrombosis, or lung transplant was reported in three patients (13%).

CONCLUSIONS

CA can misdiagnose LMCA extrinsic compression. IVUS discriminates better whether significant compression by a PAA exists or not, avoiding unnecessary LMCA stenting. Patients treated following this strategy show a low rate of major clinical events at 20 months follow-up.

Supra-coronary aortic banding improves right ventricular function in experimental pulmonary arterial hypertension in rats by increasing systolic right coronary artery perfusion

AIM

Pulmonary arterial hypertension (PAH) results in right ventricular (RV) dysfunction owing, in part, to RV ischemia. The relative contribution of RV microvascular rarefaction vs reduced right coronary artery perfusion pressure (RCA-PP) to RV ischemia remains unknown. We hypothesize that increasing RCA-PP improves RV function in PAH by increasing RV systolic perfusion.

METHODS

Supra-coronary aortic banding (SAB) or sham surgery was performed on male Sprague-Dawley rats. Seven to ten days later, rats received either monocrotaline (MCT; 60 mg/kg) or saline. After 1 month, echocardiography, cardiac catheterization, ^99m Tc-sestamibi single-photon emission computed tomography (SPECT) and microsphere infusion studies were performed. The RV was harvested for measurement of hypertrophy (RVH), fibrosis and immunoblotting, and the lung was harvested for pulmonary artery (PA) histology.

RESULTS

Supra-coronary aortic banding increased systolic pressures in proximal aorta and systolic RCA-PP in SAB + MCT vs MCT rats (114 ± 12 vs 5 ± 9 mm Hg), without altering diastolic RCA-PP. SAB + MCT rats had improved RV function vs MCT rats, evident from their significantly increased cardiac output (CO), RV free wall (RVFW) thickening, tricuspid annular plane systolic excursion (TAPSE) and RV-PA coupling indices. RV-PA coupling indices and CO correlated directly with systolic RCA-PP. RV perfusion was increased in SAB + MCT vs MCT rats and correlated well with CO; whereas microvascular rarefaction was unaltered. SAB + MCT rats had less RVH and fibrosis and lower PA pressures vs MCT rats. SAB + MCT rats had significantly lower RV pyruvate kinase muscle isoform 2/1 ratios than MCT rats, consistent with restoration of oxidative metabolism.

CONCLUSION

A SAB-induced increase in systolic RCA-PP improves RV perfusion and function in MCT rats. Maintaining systolic RCA perfusion can preserve RV function in PAH.

COPD and acute myocardial infarction

COPD is strongly associated with cardiovascular disease, in particular acute myocardial infarction (AMI). Besides shared risk factors, COPD-related factors, such as systemic inflammation and hypoxia, underlie the pathophysiological interaction between COPD and AMI. The prevalence of COPD amongst AMI populations ranges from 7% to 30%, which is possibly even an underestimation due to underdiagnoses of COPD in general. Following the acute event, patients with COPD have an increased risk of mortality, heart failure and arrhythmias during follow-up. Adequate risk stratification can be performed using various imaging techniques, evaluating cardiac size and function after AMI. Conventional imaging techniques such as echocardiography and cardiac magnetic resonance imaging have already indicated impaired cardiac function in patients with COPD without known cardiovascular disease. Advanced imaging techniques such as speckle-tracking echocardiography and T1 mapping could provide more insight into cardiac structure and function after AMI and have proven to be of prognostic value. Future research is required to better understand the impact of AMI on patients with COPD in order to provide effective secondary prevention. The present article summarises the current knowledge on the pathophysiologic factors involved in the interaction between COPD and AMI, the prevalence and outcomes of AMI in patients with COPD and the role of imaging in the acute phase and risk stratification after AMI in patients with COPD.

Computed tomographic myocardial mass compared with invasive myocardial perfusion measurement

Objective

The prognostic importance of a coronary stenosis depends on its functional severity and its depending myocardial mass. Functional severity can be assessed by fractional flow reserve (FFR), estimated non-invasively by a specific validated CT algorithm (FFR_CT). Calculation of myocardial mass at risk by that same set of CT data (CTmass), however, has not been prospectively validated so far. The aim of the present study was to compare relative territorial-based CTmass assessment with relative flow distribution, which is closely linked to true myocardial mass.

Methods

In this exploratory study, 35 patients with (near) normal coronary arteries underwent CT scanning for computed flow-based CTmass assessment and underwent invasive myocardial perfusion measurement in all 3 major coronary arteries by continuous thermodilution. Next, the mass and flows were calculated as relative percentages of total mass and perfusion.

Results

The mean difference between CTmass per territory and invasively measured myocardial perfusion, both expressed as percentage of total mass and perfusion, was 5.3±6.2% for the left anterior descending territory, −2.0±7.4% for the left circumflex territory and −3.2±3.4% for the right coronary artery territory. The intraclass correlation between the two techniques was 0.90.

Conclusions

Our study shows a close relationship between the relative mass of the perfusion territory calculated by the specific CT algorithm and invasively measured myocardial perfusion. As such, these data support the use of CTmass to estimate territorial myocardium-at-risk in proximal coronary arteries.