Acute Left Ventricular Failure (LVF)
You will come across acute left ventricular failure often during your medical jobs. This occurs when the left ventricle is unable to adequately move blood through the left side of the heart and out into the body. This causes a backlog of blood (like too many buses waiting to pick up people at a bus stop) that increases the amount of blood stuck in the left atrium, pulmonary veins and lungs. As the vessels in these areas are engorged with blood due to the increased volume and pressure they leak fluid and are unable to reabsorb fluid from the surrounding tissues. This causes pulmonary oedema, which is where the lung tissues and alveoli become full of interstitial fluid. This interferes with the normal gas exchange in the lungs, causing shortness of breath, oxygen desaturation and the other signs and symptoms.
- Iatrogenic (e.g. aggressive IV fluids in frail elderly patient with impaired left ventricular function)
- Myocardial Infarction
Acute LVF typical presents as a rapid onset breathlessness. This is exacerbated by lying flat and improves on sitting up. Acute LVF causes a type 1 respiratory failure (low oxygen without an increase in carbon dioxide in the blood).
- Shortness of breath
- Looking and feeling unwell
- Cough (frothy white/pink sputum)
- Increase respiratory rate
- Reduced oxygen saturations
- 3rd Heart Sound
- Bilateral basal crackles (sounding “wet”) on auscultation
- Hypotension in severe cases (cardiogenic shock)
There may also be signs and symptoms related to underlying cause, for example:
- Chest pain in ACS
- Fever in sepsis
- Palpitations in arrhythmias
If they also have right sided heart failure you could find:
- Raised Jugular Venous Pressure (JVP) (a backlog on the right side of the heart leading to an engorged jugular vein in the neck)
- Peripheral oedema (ankles, legs, sacrum)
TOM TIP: When you are on the wards and a nurse asks you to review a patient that has just started desaturating ask yourself how much fluid that patient has been given and whether they might not be able to process that much. For example, an 85 year old lady with chronic kidney disease and aortic stenosis is prescribed 2 litres of fluid over 4 hours and then starts to drop her oxygen saturations. This is a common scenario and a dose of IV furosemide can often work like magic to clear some fluid and ease their breathing.
- Clinical Examination
- ECG (to look for ischaemia and arrhythmias)
- Arterial Blood Gas (ABG)
- Chest Xray
- Bloods (routine bloods for infection, kidney function, BNP and consider troponin if suspecting MI)
If the clinical presentation is acute LVF then treat before having the diagnosis confirmed by BNP or echo. Without treatment they can deteriorate before getting the investigations.
B-type Natriuretic Peptide (BNP) Blood Test
B-type Natriuretic Peptide (BNP) is a hormone that is released from the heart ventricles when the cardiac muscle (myocardium) is stretched beyond the normal range. Finding a high result indicates the heart is overloaded (with blood) beyond its normal capacity to pump effectively.
The action of BNP is to relax the smooth muscle in blood vessels. This reduces the systemic vascular resistance making it easier for the heart to pump blood through the system. BNP also acts on the kidneys as a diuretic to promote the excretion of more water in the urine. This reduces the circulating volume helping to improve the function of the heart.
Testing for BNP is sensitive but not specific. This means that when negative it is useful in ruling out heart failure, but when positive result can have other causes. Other causes of a raised BNP include:
- Pulmonary embolism
- Renal impairment
This is useful in assessing the function of the left ventricle and any structural abnormalities in the heart. The main measure of the left ventricular function is the ejection fraction. This is the percentage of the blood in the left ventricle is squeezed out with each ventricular contraction. An ejection fraction above 50% is considered normal.
Chest Xray Findings
Cardiomegaly on a chest xray is defined as a cardiothoracic ratio of more than 0.5. This is when the diameter of the widest part of the heart (the wides part of the cardiac silhouette) is more than half the diameter of the widest part of the lung fields.
Upper lobe venous diversion. Usually when standing erect the lower lobe veins contain more blood and the upper lobe veins remain relatively small. In LVF there is such a back-pressure that the upper lobe veins also fill with blood and become engorged (referred to as upper lobe diversion). This is visible as increased prominence and diameter of the upper lobe vessels on a chest xray.
Fluid leaking from oedematous lung tissue causes additional xray findings of:
- Bilateral pleural effusions
- Fluid in interlobar fissures
- Fluid in the septal lines (Kerley lines)
Use the simple mnemonic Pour SOD for acute LVF:
- Pour away (stop) their IV fluids
- Sit up
Sit the patient upright. When lying flat the fluid in the lungs spreads to a larger area. When upright gravity takes it to the bases leaving the upper lungs clear for better gas exchange.
Oxygen if their oxygen saturations are falling (<95%). As always be cautious in patients with COPD.
Diuretics (e.g. IV furosemide 40mg stat). This reduces the circulating volume and means the heart is less overloaded allowing it to pump more effectively. This is like taking your backpack off when on a hike – it allows you to walk more easily.
Monitor fluid balance. Measuring fluid intake, urine output, U&E bloods and daily body weight is essential to balance their fluid input and output.
Other options to consider in severe acute pulmonary oedema or cardiogenic shock (not routinely used) include:
Intravenous opiates (opiates such as morphine act as vasodilators but are not routinely recommended).
Non-Invasive Ventilation (NIV). Continuous Positive Airway Pressure (CPAP) involves using a tight fitting mask to forcefully blow air into their lungs. This helps to open the airways and alveoli to improve gas exchange. If NIV does not work they may need full intubation and ventilation.
“Inotropes”, for example an infusion of noradrenalin. Inotropes strengthen the force of heart contractions and improve heart failure, however they need close titration and monitoring, so by this point you would need to send the patient to the local coronary care unit / high dependency unit / intensive care unit.
Last updated October 2018