Acute Right Heart Failure

“The right ventricle is not important until it is, and once it is important it is everything.  The way you die is from right heart failure” – Professor Michael Pinsky.1

This learning session focuses on the understanding, recognition and management of acute right heart failure (RHF).  Chronic right heart dysfunction and pulmonary hypertension are outside the scope of this session, yet there is an excellent RCEMLearning session on pulmonary hypertension here.2

RHF has historically been an underappreciated and under-recognised syndrome and heart failure education has traditionally focused on left heart failure (LHF).  However, right ventricular (RV) dysfunction is an independent predictor of mortality across a range of pathologies, including primary respiratory disease, biventricular failure and pulmonary embolism (PE).3, 4  As treatment of LHF has improved, RHF is increasingly the pathophysiological mechanism through which these patients die and is often referred to as the “final common pathway”.1, 5

The right ventricle is complex and less forgiving of insults than the left ventricle (LV).  RHF can develop into a vicious cycle of compounding physiological insults resulting in multi-organ failure and cardiac arrest. Crucially, common treatments for critically unwell patients such as intravenous (IV) fluids and intubation, often exacerbate this vicious cycle.  As such, prompt recognition and management of RHF is essential in the Emergency Department (ED).  

Definition 

The European Society of Cardiology (ESC) distinguishes the following3:

• Right heart dysfunction: when “a measure of RV function falls outside the recommended range of normal”, usually seen on echocardiography
• Right heart failure: “a clinical diagnosis with signs and symptoms of systemic congestion in combination with structural and/or functional abnormalities of the right heart”

A diagnosis of RHF requires evidence of both systemic congestion & right heart dysfunction.  Early echocardiography and a thorough clinical assessment should be performed in all patients with suspected RHF. 

The adult RV is complex in shape, appearing triangular longitudinally, and crescenteric when viewed in cross section, wrapping around the LV.6 It is important to recall this anatomy when considering the mechanisms of RV dysfunction - see later sections on contractility and volume overload.

Figure 1 - ‘Triangular’ longitudinal section of RV (Apical 4 chamber view on cardiac ultrasound)6

Figure 2 - ‘Crescenteric’ cross-section of RV (Parasternal short axis on cardiac ultrasound)6

Figure 3 - RV wrapping around the ‘Bullet shaped LV’ (3D model)6

Cardiac Output

Avoiding the pitfalls in the management of RHF requires a good understanding of the pathophysiology.

The RV determines cardiac output(CO) by delivering the venous return to the left heart.  The LV is then responsible for generating a sufficiently high blood pressure with which individual organs can autoregulate their perfusion pressure – the LV “charges the capacitor” (1).   The RV is therefore the flow-limiting factor, as the LV can only utilise volume delivered to it by the RV.  

To increase CO (e.g. during exercise) there must be a matched increase in both left and right CO.  Since cardiac output is the product of heart rate (HR) and stroke volume (SV) i.e. CO = HR × SV, increasing CO can only occur through:

• Increasing HR (positive chronotropy)
• Increasing SV:
  • Increasing contractility
  • Reducing afterload
  • Optimising preload (the Frank-Starling mechanism).  

Failure in one of the above mechanisms leads initially to compensation via other mechanisms (e.g. RV hypertrophy in chronic pulmonary hypertension).  When compensatory mechanisms are overwhelmed or in a significant acute insult (e.g. high-risk PE), CO can no longer be maintained, causing rapid decompensation and cardiovascular collapse.  

The equations below illustrate the relationships between pressure, vascular resistance and cardiac output for both the right and left ventricles.  

The equations below illustrate the relationships between pressure, vascular resistance and cardiac output for both the right and left ventricles.  

Learning Bite 

• The RV determines cardiac output
• Increasing RV CO requires:
  • an increase in contractility - increased mean pulmonary arterial pressure (mPAP)
  • or a decrease in afterload - decreased pulmonary vascular resistance (PVR) or left atrial pressure (LAP)
  • or optimising preload

Mechanisms of RV Dysfunction

The three principal mechanisms behind RV dysfunction are impaired contractility, pressure overload, volume overload.  Understanding these is key to approaching treatment considerations.

Figure 4 - Mechanisms of RV Dysfunction

1. Impaired contractility

RV contraction occurs via three mechanisms: (7) 

1. Longitudinal base-to-apex contraction, the largest contributor to RV systolic output, and measured with ‘TAPSE’ on echocardiography (3, 8, 9)
2. Synergistic LV contraction, thickening the septum and pulling the RV against the LV, accounting for 20-40% of RV systolic output
3. Inward movement of the RV free-wall in a ‘bellows-like’ effect

Figure 5 - RV contraction mechanisms. Adapted from wikimedia

Impaired LV function therefore has the potential to reduce RV output by 20-40%.  Longitudinal contraction can be compromised by RV ischaemia. 

RV perfusion occurs predominantly via the right coronary artery (RCA).  The RCA perfusion pressure gradient (ΔP) is determined by the difference between aortic and RV pressure.  In contrast to the LV, RV perfusion occurs during both diastole & systole in healthy individuals.  

RV diastolic perfusion pressure = ΔPdiastolic = (DBP – RVEDP)

*RVEDP = RV End Diastolic Pressure

RV systolic perfusion pressure = ΔPsystolic = (SBP – RVESP)

*RVESP = RV End Systolic Pressure

Figure 6 - Coronary perfusion pressures (21)

A rise in RV pressures (e.g. acute PE) and/or drop in aortic blood pressure (hypotension) reduces RV perfusion and risks RV ischaemia.  A high-risk (previously termed “massive”) PE causes life-threatening RV ischaemia through both mechanisms.

Poor cardiac perfusion leads to ischaemia, reducing ventricular compliance and contractility.  Therefore, in order to optimise RV perfusion, we must reduce RV pressures by reducing pulmonary vascular resistance (PVR), and increase systemic blood pressure i.e. increase SVR.  We call this afavourable PVR:SVR ratio.  

Learning Bite

• Hypotension reduces RV perfusion and impairs contractility.  It should be treated aggressively with vasopressors to prevent RV ischaemia
• Once adequate perfusion is restored, impaired RV contractility can be augmented with inotropes

2. Pressure Overload

RV afterload is mainly influenced by PVR (pulmonary vascular resistance) and left atrial pressure (LAP).   A normal RV is thin walled and weak and cannot generate significantly increased pressures (unlike the LV).  Decreasing afterload is therefore an essential mechanism through which RV CO increases. 

mPAP = mean Pulmonary Arterial Pressure, LAP = Left Atrial Pressure, PVR = Pulmonary Vascular Resistance

Learning Bite

• Acutely elevated RV afterload is poorly tolerated (e.g. PE)
• Treat hypoxia, hypercapnia & acidosis and avoid intubation if possible

3. Volume Overload

The LV & RV share the same space within the pericardium, divided by the interventricular septum (IVS). Overfilling (dilation) of one chamber, causes a shift in the IVS, decreasing filling of the other.  This is known as ‘ventricular interdependence.’  

Volume overload and IV fluid administration can be detrimental in RV failure in two main ways:

• Increasing central venous pressure (CVP) and worsening systemic congestion
• RV dilatation, which impairs LV filling as a result of ventricular interdependence, reduces the LV stroke volume

Figure 7 - Normal RV:LV in parasternal short axis view on ultrasound (6)

Figure 8 - RV volume overload causes a shift of the IVS into the LV cavity, significantly reducing LV volume.  This is easily seen on echocardiography as ‘septal shift’ or the ‘D-sign’ in the parasternal short axis view (9)

This is an important phenomenon to recognise, as clinicians are often reluctant to diurese hypotensive patients.  In RV volume overload diuresis may reduce RV pressures, which will improve RV perfusion / contractility and increase output from both ventricles (9).  

An important exception to remember is the case of RV infarction.  Here a hypotensive patient may benefit from fluid resuscitation as they are preload dependent due to poor contractility.

Learning Bite

• RV volume overload reduces LV filling (preload) & hence CO.  Fluid resuscitation may therefore worsen hypotension in RHF and diuretics are often beneficial

Systemic congestion

The backpressure for the systemic circulation is the CVP*, normally 0-5mmHg. Backpressure increases as the pump ahead fails. Systemic congestion due to elevated CVP may manifest as cardiorenal syndrome, acute liver injury, bowel wall oedema or peripheral oedema. Signs may be subtle and not easily recognised. A low/normal CVP can therefore rule out a diagnosis of RHF.

NB CVP is a surrogate for right atrial pressure (RAP) and these terms are used interchangeably

In LV failure, we are all too aware that giving IV fluids risks pulmonary oedema as the backpressure (LAP) increases.

Similarly, in RV failure, giving IV fluids risks systemic congestion as RAP/CVP increases.

Learning Bite

• A normal/low CVP makes a diagnosis of RHF extremely unlikely
• Treating systemic congestion requires diuresis and/or improving RV function

The RV ‘Spiral of Death’

We have seen that the RV copes poorly with the following:

• Impaired contractility (due to poor perfusion)
• Pressure overload
• Volume overload

Unfortunately, any of the above may deleteriously affect the others, leading to a vicious cycle of decompensation culminating ultimately in multi-organ failure and death.  This is depicted in the following diagram with the principal mechanisms highlighted in red:

Figure 9 - pathophysiology of acute RV failure, adapted from ESC(4). TR = Tricuspid regurgitation

Learning Bite

The pathophysiology of RHF involves self-perpetuating vicious cycles that can lead to rapid cardiovascular collapse. Recognition of the precipitant is paramount to avoiding or escaping said cycles.

History

RHF is a syndrome rather than a diagnosis, and may therefore present with signs or symptoms of:

• the primary cause, e.g. chest pain in PE, fever in viral myocarditis, painful limb in DVT
• poor cardiac output, e.g. exertional dyspnoea
• systemic congestion, e.g. RUQ pain in hepatic congestion or ankle swelling from peripheral oedema

The history should include a chronology of presenting symptoms, specifically the presence of syncope/presyncope which carries a worse prognosis. 

PMH: focus on pulmonary disease (COPD, ILD, smoking history), VTE risk factors, cardiac history (IHD, previous MI) and history of pulmonary hypertension.  

Physical Examination

Examination may be very non-specific.  Chronic RV dysfunction will usually show signs of systemic congestion – peripheral oedema, elevated JVP, tender hepatomegaly, ascites.  Acute RHF (e.g. PE, RVMI, myocarditis) may not demonstrate these features.  Signs of poor perfusion (including mottled/cool extremities, slow CRT, delirium or reduced urine output) are concerning, and overt hypotension is extremely concerning.  Observations may demonstrate tachycardia, low or inappropriately normal blood pressure (BP), reduced GCS or hypoxia.  

Diagnosis requires evidence of systemic congestion + RV dysfunction.  Having suspected RHF from the history/examination, investigations should be performed to confirm the diagnosis, rule out other causes of shock (e.g. sepsis, hypovolaemia) and establish the precipitating cause (e.g. CTPA for PE, US for DVT).  The presence of DVT has a positive likelihood ratio of +14 for PE and can be rapidly ruled-in at the bedside with point-of-care ultrasound (POCUS).

RV dysfunction:

• Echocardiography – the investigation of choice.  See below. 
• ECG – may show AF, RVH, RV strain patterns or acute RV myocardial infarction 
• CTPA – rule in/out PE and/or RV dilatation 

Figure 11 – RVMI. Note ST elevation in III > II10

Figure 12 - RVMI in same patient (right sided leads)10

Reduced end-organ perfusion (from low CO or systemic congestion):

• VBG – raised lactate suggesting systemic malperfusion, pH, pCO2
• FBC, U&E, LFTs, INR – AKI suggesting “cardiorenal syndrome” or deranged LFTs/INR suggesting “shocked liver”
• Urine output - reduced suggesting cardiorenal syndrome
• POCUS:
  • Causes: DVTs, pulmonary oedema from LHF, pneumonia
  • Sequelae: ascites, pleural or pericardial effusions

Outpatient investigations of chronic RV dysfunction (e.g. pulmonary function tests, right heart catheterisation) are beyond the scope of this article.

Whilst a comprehensive echocardiogram including quantitative measurements is ideal, bedside point of care echo (POCUS) is usually sufficient to identify RV dysfunction.  A full description of echocardiographic assessments is outside the scope of this article.  The methods mentioned below are accessible to EM Physicians with basic echo training, demonstrate good interobserver reliability and correlate well with mortality/morbidity (8,12).

POCUS in combination with clinical judgement should be used to guide initial diagnosis and management, with a comprehensive study performed as soon as feasible.  A previous echo is helpful as it can be difficult to establish acute vs chronic right heart dysfunction on bedside echo alone.  Remember, RV dysfunction can be acute or chronic, and none of the signs below are specific for a certain pathology – not all RV dilation is PE!

Plethoric IVC 

(Systemic Congestion) 

The IVC is a surrogate for CVP/RAP.  In systemic congestion this would be expected to be dilated > 2.1cm and not collapsing.  A flat/collapsing IVC indicates low RV filling pressures and appropriate ‘forward flow’ and should make one reconsider a diagnosis of RHF.  

A dilated IVC is sensitive but not specific as it may also be seen in other conditions e.g. cardiac tamponade.

RV dilation & septal flattening 

(Volume & Pressure Overload)

RV dilatation (an RV/LV ratio > 1.0) is an independent marker of increased mortality (13).  Dilatation is usually associated with shift of the interventricular septum into the LV (‘septal flattening’ or the ‘D-sign’) and timing can give clues to volume vs pressure overload.  

• Diastolic septal flattening – volume overload
• Systolic & diastolic septal flattening – volume & pressure overload

Video 1 - Normal RV/LV ratio seen in parasternal short axis view on cardiac ultrasound   (6)

Video 2 - Septal flattening (“D-sign") seen in parasternal short axis view on cardiac ultrasound (6)

TAPSE 

(Impaired Contractility) 

‘Tricuspid Annular Plane Systolic Excursion’ (TAPSE) measures RV longitudinal systolic function (see Figure 1, blue arrow).  It correlates well with mortality/morbidity (3,8). 

Figure 13 - Normal TAPSE (14)

Figure 14 - Impaired TAPSE (9)

RV Hypertrophy

(Chronic adaptation)

RV diastolic free wall thickness > 5mm is considered RV hypertrophy (RVH).  This is a marker of RV adaptation to elevated afterload seen in chronic pulmonary hypertension.

Learning Bite

• A normal or flat IVC makes a diagnosis of RV failure extremely unlikely
• Impaired TAPSE is highly predictive of increased mortality

Specific Management:

General Management:

Figure 15 - Management principles by mechanism

Supportive management is critical to avoid/reverse the vicious cycle of RHF: 

• Improve contractility 
  • Optimise RV perfusion – correct hypotension with vasopressors
  • Stop negative chronotropes/inotropes (e.g. beta-blockers/calcium-channel blockers)
  • Consider positive inotropes – adrenaline/milrinone/dobutamine

• Reduce pressure overload
  • Correct hypoxia, hypercapnia and acidosis.  (NB Oxygen is a pulmonary vasodilator)
  • Avoid positive pressure ventilation – do not intubate these patients unless absolutely necessary.  If intubated use low PEEP, low pressure ventilation, and aim for normoxia and normocarbia
  • Inhaled/IV pulmonary vasodilators – see section below

• Optimise volume status
  • Assess RV & LV chamber sizes with echo
  • If volume overloaded or septal shift present, diuresis may cause rapid improvement (4, 9) 
  • Cautious fluids in RV myocardial infarction may be helpful

Introduction

Vasopressors & inotropesmay be required in the haemodynamically unstable RHF patient and early Intensive Care and cardiology review is recommended.

Vasopressors

Vasopressors should be instigated immediately in the hypotensive RHF patient to support RV perfusion.  However, vasopressor choice is paramount as a rise in SVR must be greater than any rise in PVR, otherwise therapy may be counterproductive.

Vasopressin – Increases SVR through V1R agonism and reduces PVR through activating endothelial nitric oxide (15, 16).  In theory this has the best PVR:SVR profile (15, 17)

Adrenaline – Good choice at low doses as it has a favourable increase in SVR and contractility with minimal change in PVR (9, 15, 17)

Noradrenaline – Response is dose-dependent.  At low doses Noradrenaline increases SVR more than PVR (favourable PVR:SVR ratio), but at higher doses PVR increases more creating an unfavourable ratio (8, 13, 15)

Phenylephrine – A bad choice.  Phenylephrine is a pure alpha agonist, increasing SVR and PVR.  It does not have a favourable PVR:SVR ratio and should be avoided (15, 16, 18)

IV pulmonary vasodilators (sildenafil, epoprostenol) – Used in chronic pulmonary hypertension and should not be initiated/titrated without specialist consultation.

Inotropes

Inotropic support may be required to increase RV contractility after optimising perfusion. 

Milrinone/Dobutamine – Inodilators.  Increase contractility but ↓SVR so usually combined with a suitable vasopressor e.g. vasopressin/noradrenaline (4, 15)

Adrenaline – As above (15, 16)

Table 1 – Vasoactive agents & their effects on PVR/SVR. Modified from Olsson et al.17

Learning bite

• Start appropriate vasopressors early in the hypotensive RHF patient
• Low-dose adrenaline is a good first choice

Inhaled pulmonary vasodilators

Inhaled pulmonary vasodilators are an option in the ICU and not typically available in the ED.  Common agents are inhaled Nitric Oxide (iNO) and inhaled prostacyclins (e.g. epoprostenol).

A number of studies support the use of nebulised milrinone or GTN as potent inhaled pulmonary vasodilators (19).  Nebulised, these act locally in the pulmonary vasculature and have minimal effect on SVR.  They are cheap, widely available and easy to setup, although their use is not incorporated into guidelines at present.

Mechanical Support & Transplant

For appropriate patients with severe RHF, referral for ECMO or mechanical right ventricular assist devices (RVADs) should be considered.  These treatments act as a bridge either to recovery (e.g. in high-risk PE), or to heart transplant in select candidates.

Figure 16 - Causes & management principles of RHF

RHF = Right heart dysfunction + signs or symptoms of systemic congestion

• RHF is under-recognised and carries a high mortality and morbidity
• RHF occurs through impaired contractility, pressure overload and volume overload
• RV perfusion occurs throughout diastole & systole; preventing hypotension is key to supporting perfusion
• RHF consists of compounding mechanisms causing vicious cycles of decompensation
• Diagnosis  should include early echocardiography to demonstrate RV dysfunction

• RV-friendly resuscitation includes:
  • Supporting contractility
    • Optimise RV perfusion (reduce RV pressure, avoid hypotension)
    • Inotropes
  • Optimise volume status
    • Carefully consider diuretics vs. fluids (which are often detrimental) 
  • Reduce pressure overload
    • Reduce PVR (avoid intubation as much as possible)
• Treat the cause
• Consider early referral for ECMO or mechanical support

Pitfalls

• Not keeping a high clinical suspicion for acute right heart dysfunction
• Assuming RV dysfunction on bedside echo is always PE
• Giving fluids to treat hypotension, then more fluids as it worsens
• Being afraid to diurese due to hypotension
• Delaying early treatment with vasopressors
• Reflexively intubating patients in RHF

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