Right heart failure

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Rim Halaby, Jad Z Al Danaf, Alberto Castro Molina, M.D.

The right ventricle was previously recognized as a simple conduit between the systemic and the pulmonary circulation, but its importance in maintaining hemodynamic stability and end organ function is now well established.^[1] Right heart function is an important prognostic factor in multiple settings, including congenital heart diseases, pulmonary hypertension, and right heart failure.^[2][3]

Right heart failure can be defined as failure of the right ventricle to pump blood into the lungs adequately. It is a clinical syndrome resulting from functional and structural cardiovascular disorders that impair right ventricular filling and or ejection. In clinical practice, the main physiologic determinants of right ventricular performance mirror those of the left ventricle and include preload, afterload, contractility, and active relaxation (lusitropy).^[1] Right ventricular failure often reflects impaired right ventricle to pulmonary artery coupling and is particularly sensitive to acute increases in pulmonary vascular load.^[4]

Furthermore, isolated right ventricular failure, despite its rarity as compared to left ventricular failure, may carry a worse prognosis in selected settings. Right heart failure is also used interchangeably with cor pulmonale when the pathology is caused by an underlying lung disease.^[2][5]

There are many different ways to categorize right heart failure, which includes whether the abnormality is due to insufficient contraction (systolic dysfunction); or due to insufficient relaxation of the heart (diastolic dysfunction), or to both; whether the problem is primarily increased venous back pressure (preload), or failure to supply adequate arterial perfusion (afterload); whether the abnormality is due to low cardiac output with high systemic vascular resistance or high cardiac output with low vascular resistance (low output heart failure vs. high output heart failure); degree of functional impairment conferred by the abnormality (as reflected in the New York Heart Association Functional Classification^[6]); and the degree of coexisting illness, such as heart failure with systemic hypertension, pulmonary hypertension, diabetes, or chronic renal failure.

A practical approach is to classify right ventricular failure by time course (acute vs chronic) and predominant mechanism, including pressure overload (afterload), volume overload (preload), and primary myocardial dysfunction affecting contractility or lusitropy.^[1][7]

The pathophysiological processes underlying right heart failure can be divided broadly into three: decreased right ventricular contractility, right ventricular pressure overload, and right ventricular volume overload.^[8] The right ventricle tries to adapt acutely by dilatation and chronically by hypertrophy. Whether dilatation or hypertrophy occur, right heart failure gets further exacerbated as a result of these adaptive mechanisms.

Right ventricular performance is tightly linked to ventricular interdependence and pericardial constraint. The right ventricle and left ventricle are anatomically and physiologically integrated through the interventricular septum, and right ventricular pressure or volume overload can impair left ventricular filling and output by shifting the septum and increasing pericardial restraint.^[1] In addition to load dependent mechanisms, cellular and molecular changes such as myocyte hypertrophy, fibrosis, ischemia, neurohormonal activation, and inflammation contribute to progressive right ventricular dysfunction across etiologies.^[9][1]

There are acute and chronic causes of right heart failure. Acute right heart failure is often associated with right ventricular dilation. Chronic right heart failure is often associated with right ventricular hypertrophy.

Common etiologic categories include:

• Acute pressure overload: pulmonary embolism, acute worsening of pulmonary hypertension, severe hypoxemia, and acute respiratory distress with high intrathoracic pressures from mechanical ventilation.^[1][7]
• Chronic pressure overload: pulmonary arterial hypertension and other forms of chronic pulmonary hypertension with progressive right ventricle to pulmonary artery uncoupling.^[3][10]
• Primary myocardial dysfunction: right ventricular myocardial infarction and inflammatory or infiltrative cardiomyopathies affecting the right ventricle.^[11]
• Volume overload: significant tricuspid regurgitation, intracardiac shunts, and chronic right sided valvular lesions.^[7]
• Right ventricular dysfunction secondary to systemic illness and critical illness, including sepsis and severe viral infections; right ventricular dysfunction has also been reported in hospitalized patients with COVID 19 and is associated with adverse outcomes.^[12]

The prevalence of heart failure has been increasing due to the increase in the aging population, early detection, preventive measures, and improvement in therapy. The prevalence of heart failure in the United States was estimated in 2006 to be 5.8 million people of all ages with an estimated incidence of 10 per 1000 for individuals older than 65 years of age.^[13]

Right ventricular failure epidemiology varies by underlying substrate, and is particularly common in advanced pulmonary hypertension, advanced left sided heart failure, and critical illness with acute pulmonary vascular load. Contemporary guidance emphasizes recognizing right ventricular dysfunction as a major determinant of symptoms, exercise limitation, and outcomes across these populations.^[1][7]

Right heart failure, if left undiagnosed and untreated, may lead to impaired quality of life and eventually death. There are several factors that define this natural history depending mainly on the underlying etiology or mechanism of injury, the onset of illness, how early treatment was initiated, and other comorbidities.

Progression is often driven by a cycle of rising right sided filling pressures, impaired forward flow, worsening systemic congestion with hepatic and renal dysfunction, and further neurohormonal activation. In pressure overload states, worsening right ventricle to pulmonary artery uncoupling is a key inflection point associated with clinical deterioration.^[1][4]

In the initial approach to a patient with right heart failure, it is important to determine the underlying etiology, assess functional status, determine the presence of end organ dysfunction (liver and kidney most notably), and identify associated conditions.

Right heart failure is frequently associated with shortness of breath, exercise intolerance and coughing, and in later stages chest discomfort and swelling of the feet or ankles. According to the 2009 Canadian Cardiovascular Society Consensus Conference update on right sided heart failure, right heart failure should be suspected when a patient presents with unexplained exercise intolerance or hypotension with signs of elevated jugular venous pressure (JVP), peripheral edema, hepatomegaly, or a combination of these findings.^[14]

Physical exam should consist of a thorough cardiovascular exam, an abdominal exam, and examination of the extremities. Findings to be aware of are cyanosis, JVD, S2 and S3 heart sounds, ascites, hepatomegaly, and pedal edema.

Laboratory tests are not diagnostic for heart failure, but they are essential to identify precipitating factors of decompensation, assess severity, monitor adverse effects of therapy, and provide prognostic information.^[15] In addition, in patients with right heart failure, an arterial blood gas can be useful in assessing hypoxemia and guiding oxygen therapy.

Right heart failure is often accompanied by right ventricular hypertrophy and right ventricular dilation. General electrocardiographic findings of right ventricular hypertrophy include right axis deviation, an R S ratio greater than 1 in V1, and the presence of P pulmonale.

The plain chest radiograph has limited utility in identifying right heart failure. It might show evidence of underlying causes such as pulmonary embolism or congenital heart disease.

Transthoracic echocardiography plays a key role in the diagnosis of right heart failure by evaluating right ventricular size and function, estimating pulmonary pressures, and assessing tricuspid regurgitation. Recommended measures of right ventricular systolic function include tricuspid annular plane systolic excursion (TAPSE), tissue Doppler S prime, right ventricular fractional area change, and right ventricular longitudinal strain, interpreted in the context of loading conditions and right ventricle to pulmonary artery coupling.^[16][1]

Right heart catheterization can define the hemodynamic profile, quantify pulmonary vascular load, and guide therapy in complex or refractory cases. In acute decompensation, invasive monitoring may help assess response to preload adjustment and afterload targeted therapies, particularly when clinical examination and noninvasive findings are discordant.^[1][7]

Currently, the basis of therapy for right heart failure includes cautious diuresis, rhythm management, and treatment of the underlying cause when feasible. Management can be tailored to etiology specific therapy such as anticoagulation for pulmonary embolism or antibiotics for endocarditis. Management also comprises optimizing right ventricular preload, afterload and contractility.

A contemporary approach emphasizes four parallel goals: optimize preload, reduce right ventricular afterload, augment contractility when needed, and maintain systemic perfusion pressure while treating the precipitating cause.^[1][7]

Optimization of preload includes careful diuresis and management of venous congestion, while avoiding excessive preload reduction that may lower cardiac output. In selected patients, invasive hemodynamic guidance may be useful for titration.^[1][7]

Reduction of afterload depends on etiology and includes reperfusion or anticoagulation for acute pulmonary embolism, correction of hypoxemia and acidosis, minimizing injurious ventilator settings, and targeted pulmonary vasodilator therapy for appropriate forms of pulmonary hypertension.^[1][10]

Augmentation of contractility may be required in shock or low output states. Dobutamine can increase cardiac output and stroke volume in right ventricular myocardial infarction and in pulmonary hypertension, and milrinone may be considered with attention to systemic vasodilation and hypotension.^[1][7]

Since atrial fibrillation and high grade AV block can cause hemodynamic instability in right heart failure, maintaining sinus rhythm and atrioventricular synchrony is important.^[17]

Surgical intervention in right heart failure is mainly indicated for valvular pathologies and congenital heart diseases causing progressive symptoms despite adequate medical interventions. Early correction in selected settings can improve symptoms and outcomes. Treating primary pulmonary hypertension may lead to improved functional capacity, and in selected cases, lung transplant or heart lung transplant can extend survival.^[17][7]

Temporary mechanical circulatory support may be considered for patients with refractory acute right ventricular failure and shock despite optimized pharmacotherapy and correction of reversible causes.^[1][18] Device selection should account for the mechanism of failure and the presence of pulmonary arterial hypertension, since isolated right ventricular assist strategies may be inappropriate when pulmonary vascular resistance is markedly elevated.^[1]

A right ventricular assist device (RVAD) can be a temporary therapy for patients with acute exacerbation of right heart failure. Ongoing research focuses on improved assessment of right ventricle to pulmonary artery coupling and therapies that directly target right ventricular contractility and lusitropy.^[1]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Rim Halaby; Jad Z Al Danaf

There are many different ways to categorize right , which includes whether the abnormality is due to insufficient contraction (systolic dysfunction); or due to insufficient relaxation of the heart (diastolic dysfunction), or to both; whether the problem is primarily increased venous back pressure (preload), or failure to supply adequate arterial perfusion (afterload); whether the abnormality is due to low cardiac output with high systemic vascular resistance or high cardiac output with low vascular resistance (low-output heart failure vs. high output cardiac failure); degree of functional impairment conferred by the abnormality (as reflected in the New York Heart Association Functional Classification^[1]); and the degree of coexisting illness: i.e. heart failure/systemic hypertension, heart failure/pulmonary hypertension, heart failure/diabetes, heart failure/chronic renal failure, etc.

• Right heart failure can be functionally classified according to the New york heart association functional classification – NYHA (I-IV) or structurally according to the American College of Cardiology/ American Heart Association – ACC/AHA (stage A, B, C and D).
• The ACC staging system is useful in that Stage A encompasses “pre-heart failure” — a stage where intervention with treatment can presumably prevent progression to overt symptoms. ACC Stage A does not have a corresponding NYHA class. ACC Stage B would correspond to NYHA Class I. ACC Stage C corresponds to NYHA Class II and III, while ACC Stage D overlaps with NYHA Class IV.

According to the New york heart association functional classification, the classes (I-IV) are:

According to the American College of Cardiology/American Heart Association working group, the stages (A-D) are:^[2]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Rim Halaby; Jad Z Al Danaf

The pathophysiological processes underlying right heart failure can be divided broadly into three: decreased right ventricular contractility, right ventricular pressure overload, right ventricular volume overload ^[1]. Right ventricular hypertrophy or RVH is the predominant change in chronic cor pulmonale although in acute cases dilation dominates. Both hypertrophy and dilatation are the result of increased right ventricular pressure.

• The pathophysiological processes underlying right heart failure can be divided broadly into three:
  • Decreased right ventricular contractility
  • Right ventricular pressure overload
  • Right ventricular volume overload ^[1]

Shown below is an image illustrating the underlying etiologies of heart failure classified according to their pathological basis.

• The right ventricle tries to adapt acutely by dilatation and chronically by hypertrophy. Whether dilatation or hypertrophy occur, right heart failure gets further exacerbated as a result of these adaptive mechanisms.

Shown below is an image illustrating the vicious cycle of right heart failure as a consequence of the acute and chronic compensation of the heart.

• Dilation is essentially a stretching of the ventricles, the immediate result of increasing the pressure in an elastic container.
• When the RV dilates secondary to any injury to the right ventricular myocardium, most notably pressure overload, the tricuspid annulus dilates leading to tricuspid regurgitation and further worsening of RV function thus falling into a vicious cycle of RV dilatation and failure.
• In addition, due to the restrictive effect of an intact pericardium on the RV, the volume overload in the RV is accommodated by a decrease in LV volume caused by bulging of the inter-ventricular septum into the LV cavity thus decreasing its filling capacity. This phenomenon is known as ventricular interdependence. Then as the LV fails, the cardiac output decreases and the systemic and coronary perfusion pressures decrease and further compromise RV function.^[1]
• In severe cases of RV failure, impaired organ perfusion leading to subsequent organ failure will result from increase in venous pressures and decrease in arterial perfusion pressures. Thus, unless the RV is unloaded, the above described vicious cycles will persist leading to worsening of RV function, multiorgan failure and eventually death.

• Ventricular hypertrophy is an adaptive response to a long-term increase in pressure. Additional muscle grows to allow for the increased contractile force required to move the blood against greater resistance.
• Since the RV accommodates a relatively large volume load as a preload, according to the Frank-Starling mechanism, this increase in preload is transmitted into increase in myocardial contractility to maintain stroke volume and eventually in right ventricular hypertrophy. However this occurs on the expense of an increase in RV wall stress that increases oxygen demand. Eventually, these factors will cause a decrease in RV blood supply during the peak times of myocardial oxygen demand leading to ischemia and worsening of RV function.
• Two examples of chronic pressure overload states that are relatively well tolerated by the right ventricle are:
  • Eisenmenger syndrome
  • Congenital pulmonary stenosis^[2]

The following sequence of events lead to right heart failure secondary to left heart failure:

• Increase in pulmonary venous and arterial pressures as a protective mechanism result in pulmonary edema, thus increasing RV afterload.
• Myocardial ischemia involving both ventricles, same as concomitant culprit coronary lesions.
• Left systolic dysfunction will impair coronary blood flow in the right coronary artery, thus compromising blood supply to RV myocardium.
• Similarly, intrinsic myocardial pathology (cardiomyopathy) involves both ventricles.
• Inter-ventricular septal dysfunction secondary to ischemia, hypertrophy or cardiomyopathy leads to ventricular interdependence.
• Dilatation of the LV will cause a decrease in the diastolic filling capacity of the RV, in the setting of an intact pericardium.^[3]

• In order for the right heart failure to be classified as cor pulmonale, its underlying cause must originate in the pulmonary circulation system. In fact, cor pulmonale is a complication of pulmonary hypertension associated with diseases of the:
  • Lungs
    • COPD is the most common cause of cor pulmonale.
  • Pulmonary vasculature.
    • Idiopathic pulmonary hypertension.
  • Upper airway.
    • Obstructive sleep apnea.
  • Abnormality in the ventilatory drive.
  • Chest wall and thoracic cage abnormalities^[4].
• When these diseases are present, hypoxia results. Hypoxic pulmonary vasoconstriction is the major contributor to cor pulmonale. Pulmonary hypertension and subsequent increase in right heart load result from hypoxic vasoconstriction. Hence, the heart tries to adapt by dilatation and/or hypertrophy leading to further right heart failure.^[5]
• Other pathophysiologic mechanisms leading to pulmonary arterial hypertension and cor pulmonale:
  • Hypoxic pulmonary vasoconstriction.
  • Compression of the pulmonary vasculature by lymph nodes or tumors.
  • Anatomic changes in vascularization of the lung.
  • Increased blood viscosity (e.g. polycythemia vera^[6]).
  • Increased volume overload of the right ventricle (e.g. Atrial septal defect).
  • Chronic hypoventialtion of the lung due to mechanical defects (e.g. diaphragmatic paralysis).

• As a result of right ventricular failure, blood backups up into the system venous system, including the hepatic vein. Chronic congestion in the centrilobular region of the liver leads to hypoxia and fatty changes of more peripheral hepatocytes, leading to what’s known as nutmeg liver.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

There are acute and chronic causes of right heart failure. Acute right heart failure is associated with right ventricular dilation. Chronic right heart failure is often associated with right ventricular hypertrophy.

• Acute MI involving the right ventricle
• Massive pulmonary embolization
• Exacerbation of chronic cor pulmonale

• COPD
• Congenital heart disease
• Emphysema
• Loss of lung tissue following trauma or surgery (Pneumonectomy)
• Primary pulmonary hypertension
• Sleep apnea

• Acute MI involving the right ventricle
• Adenopathy
• Adult Respiratory Distress Syndrome (ARDS)
• Alpha-1 Antitrypsin Deficiency
• Alveolar hypoxia in chronic high altitude exposure
• Amyotrophic Lateral Sclerosis (ALS)
• Bilateral diaphragmatic paralysis
• Bronchiectasis
• Bronchopulmonary dysplasia following neonatal respiratory distress syndrome (RDS)
• Chest wall dysfunction
• Chronic bronchitis
• Chronic fungal obstruction
• Chronic Obstructive Pulmonary Disease (COPD)
• Collagen vascular disease
• Congenital heart disease
• Cystic Fibrosis
• Drug-induced lung disease
• Emphysema
• Fibrosing mediastinitis
• Guillain-Barre Syndrome
• Histiocytosis X
• HIV infection
• Hypersensitivity pneumonitis
• Idiopathic pulmonary fibrosis
• Interstitial lung disease
• Kyphoscoliosis
• Left atrial myxoma
• Left ventricular failure
• Mitral regurgitation
• Mitral stenosis
• Myasthenia Gravis
• Myocardial infarction of the right ventricle
• Necrotizing and granulomatous arteritis
• Neuromuscular disease
• Obesity
• Persistent pulmonary hypertension of the newborn
• Pneumoconiosis
• Pneumonectomy
• Poliomyelitis
• Polyradiculitis
• Polycythemia vera ^[3]
• Primary pulmonary hypertension
• Pulmonary hemangiomatosis
• Pulmonary embolism
• Pulmonary emphysema
• Pulmonary fibrosis
• Pulmonary resection
• Right ventricular infarction
• Sarcoidosis
• Schistosomiasis
• Scleroderma
• Sickle Cell Anemia
• Sleep Apnea
• Tuberculosis
• Tumor embolism
• Tumor masses
• Veno-occlusive lung disease

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Jad Z Al Danaf; Rim Halaby

The prevalence of heart failure has been increasing due to the increase in aging population, early detection, preventive measures and improvement in therapy. In 2006, the prevalence of heart failure in the United States was estimated to be 5.8 million people of all ages with an estimated incidence of 10/1000 for individuals older than 65 years of age.^[1]

• According to a 2010 update from the American Heart Association, it has been estimated that there were around 5.8 million people of all ages living with heart failure in the United States in 2006, with an estimated incidence of 10/1000 for individuals older than 65 years of age.^[1]
• Heart failure is also responsible for more hospitalizations than all cancers combined, with an estimated one year mortality of symptomatic heart failure reaching 45%.^[2]
• The prevalence of heart failure has been increasing over the past decade which has been linked to the increase in aging population and improvements in therapeutic innovations in treating cardiac diseases especially myocardial infarction; making early detection in vulnerable patients essential for better outcomes after appropriate preventive interventions.^[3]
• The Framingham Heart study presents proof concerning the increase in the prevalence of heart failure with aging. For example, it has been shown that the prevalence of heart failure increases form 8/1000 in men between 50-59 years of age, to 66/1000 at ages 80-89; with nearly similar values in women (8 and 79/1000 respectively). Hence the prevalence of heart failure approximately doubles with every increase in a decade of age in both men and women ^[3]. The Framingham study also showed that hypertension was the highest prevalent risk factor among the study group in both men and women, and an estimated median survival of 1.7 and 3.2 in men and women respectively.
• Heart failure, a major public health concern, is considered a preventable disease in general. However, no screening methods have been discovered till date to determine this syndrome at an early stage. Despite that, rigorous efforts have been made in the field of heart failure to determine individuals at increased risk of developing heart failure with management of these risk factors (such as hypertension and other vascular diseases). Furthermore, ample efforts were and are still being done in the field of heart failure management that has significantly reduced hospitalizations, mortality and improved functional status. These include the use of angiotensin converting enzyme inhibitors (ACE inhibitors), angiotensin receptor blockers (ARB), beta-blockers, diuretics including spironolactone, biventricular pacing with or without resynchronization therapy, coronary bypass surgery, and the use of multidisciplinary teams to manage a patient with heart failure.^[2]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Jad Z Al Danaf; Rim Halaby

Right heart failure, if left undiagnosed and untreated, may lead to impaired quality of life and eventually death. There are several factors that define this natural history depending mainly on the underlying etiology or mechanism of injury, the onset of illness, how early was treatment initiated and other comorbidities.

The prognosis of right heart failure depends in large part on the underlying cause of the condition. Giving oxygen often improves symptoms, stamina, and survival. Treating primary pulmonary hypertension often leads to greater stamina and a longer life. In some cases, a lung transplant or heart-lung transplant can extend survival.

• Left ventricular failure via ventricular interdependence or same underlying cardiomyopathy
• Tachyarrhythmias (RV tachycardia, RV fibrillation, Atrial fibrillation, Atrial flutter)
• Bradyarrhythmias (sinus node dysfunction, complete heart block)
• Nutmeg or congested liver
  • As result of the right ventricular failure, blood backs up into the system venous system, including the hepatic vein. Chronic congestion in the centrilobular region of the liver leads to hypoxia and fatty changes of more peripheral hepatocytes, leading to what’s known as nutmeg liver.
• Lower extremity venous stasis leading to increased risk of deep venous thrombosis thus pulmonary embolism, which in-turn worsens right ventricular dysfunction
• In severe RHF, decreased pulmonary circulation leads to decreased CO with possible eventual syncope, collapse and sudden death.^[1]

• Of the most common factors that determine the prognosis in right ventricular dysfunction:
  • Tricuspid regurgitation (annular area and velocity)
  • Right ventricular ejection fraction and degree of dilatation, if any.
  • Right atrial size
  • Tissue Doppler of the RV highlighting the level of tissue strain and displacement.
  • Brain natriuretic peptide level
  • Arrhythmia complications^[2]

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