Focused Bedside Cardiac Ultrasound

Focused bedside cardiac ultrasound (focused cardiac ultrasound, or FoCUS, also called focused echocardiography in emergency and critical care) is a goal directed, limited cardiac examination. It is done by the treating clinician with a handheld or cart based device and a small footprint phased array probe (2 to 5 MHz).

It answers specific questions in real time:

• Is there a pericardial effusion or tamponade?
• Is left ventricular systolic function grossly normal or severely reduced?
• Is the right ventricle dilated (acute strain)?
• Is the patient hypovolaemic or volume overloaded (inferior vena cava size and collapse, left ventricle filling)?
• Are there gross valve abnormalities or large intracardiac masses?

It does not replace formal echocardiography. It complements the clinical examination and answers binary or semi-quantitative questions. The usual views are the parasternal long axis, parasternal short axis (mid-papillary level), apical four chamber, subcostal four chamber and the subcostal inferior vena cava view.

Two dimensional imaging is used, with optional colour Doppler for gross regurgitation, M-mode for inferior vena cava collapse, and tissue measurement such as the E-point septal separation (EPSS) and tricuspid annular plane systolic excursion (TAPSE). The examination takes 3 to 10 minutes.

Focused cardiac ultrasound by trained non-cardiologists (emergency physicians, intensivists, anaesthetists, internists, trauma surgeons) has a high accuracy for the questions it addresses:

• Pericardial effusion: sensitivity 95 to 100%.
• Gross left ventricular dysfunction: sensitivity 85 to 95% for severe dysfunction, with good agreement with a formal study when graded as normal, reduced or severely reduced.
• Right ventricular dilatation: sensitivity 80 to 90% for pulmonary embolism with strain.

Integrated into resuscitation sequences for shock and cardiac arrest, it changes diagnosis and management in a large proportion (30 to 50%) of patients with undifferentiated hypotension or dyspnoea.

Indications.

• Undifferentiated hypotension or shock (hypovolaemic, cardiogenic, obstructive, distributive).
• Cardiac arrest (pulseless electrical activity): to identify reversible causes such as tamponade, massive pulmonary embolism, hypovolaemia, and to confirm cardiac standstill, with brief imaging during pulse checks.
• Acute dyspnoea or chest pain (heart failure, tamponade, pulmonary embolism).
• Trauma (pericardial effusion in the FAST examination).
• Suspected pericardial effusion or ultrasound control of pericardiocentesis.
• Assessment of fluid responsiveness and volume status (inferior vena cava, left ventricular cavity, with dynamic indices).
• Monitoring of response to inotropes or fluid.
• Syncope with cardiac cause.
• Peri-operative assessment of unexplained instability.
• Supporting diagnosis of acute right heart strain.
• Resuscitation of newborns and children in selected settings.

Not for definitive diagnosis of valve disease, cardiomyopathy, endocarditis, or for quantification of ejection fraction.

Contraindications and precautions. None. Examination must not delay compressions or resuscitation (images are acquired during pauses of under 10 seconds in cardiac arrest, with recorded clips for review).

Poor windows (obesity, hyperinflated lungs, chest drains, dressings, mechanical ventilation, positive end expiratory pressure) limit images. The subcostal and apical windows or a left lateral position help. Record findings as limited and interpret them with clinical context. Arrange a formal echocardiogram when findings are abnormal or doubtful.

Preparation and technique. The patient lies supine or in a left lateral position.

The parasternal long axis view (probe in the 3rd to 4th left intercostal space, pointer to the right shoulder) shows the left ventricle, aortic root, left atrium, mitral and aortic valves, right ventricular outflow, and pericardium. The descending aorta lies behind the left atrium. Pericardial effusion lies anterior to the descending aorta, and pleural effusion lies posterior to it.

The parasternal short axis (rotate 90 degrees) shows the left ventricle as a circle for global function and the D-shaped septum in right ventricular pressure overload. The apical four chamber view compares ventricular and atrial sizes. The subcostal view (probe under the xiphoid, aimed at the left shoulder) gives access when other windows fail.

The inferior vena cava is imaged in long axis 2 cm from the right atrium, measuring maximum diameter and the respiratory collapse ("sniff" test or inspiratory change in the ventilated patient). Structured sequences (such as those for shock, cardiac arrest and dyspnoea) combine cardiac, inferior vena cava, lung, abdominal and vascular views.

Normal appearances. The left ventricle is of normal size (end diastolic diameter under 5.5 cm), with the walls thickening and moving inward symmetrically and the cavity reducing by more than 30% in systole (fractional shortening 25 to 45%; E-point septal separation under 7 mm).

The right ventricle is smaller than the left (ratio of right to left ventricular end diastolic area under 0.6, roughly two thirds), triangular, and contracts well (TAPSE 17 mm or more). The septum is flat or bows slightly towards the right ventricle in systole; the left ventricle is circular in short axis.

The valves open and close normally, and there is no pericardial effusion beyond a trivial amount of fluid. The inferior vena cava is under 2.1 cm and collapses by over 50% with inspiration (right atrial pressure 0 to 5 mmHg).

Interpretation.

• Pericardial effusion: anechoic space around the heart (small under 1 cm, moderate 1 to 2 cm, large over 2 cm), best seen in subcostal and parasternal views. Distinguish it from pleural effusion, epicardial fat (echogenic, moves with the heart, anterior), and ascites.
• Tamponade (clinical diagnosis supported by echo): diastolic collapse of the right atrium (late diastole) and right ventricle (early diastole), plethoric inferior vena cava with no collapse, small hyperdynamic ventricles, and exaggerated respiratory variation of mitral and tricuspid inflow. "Swinging heart" occurs in large effusions.
• Left ventricular systolic function (visual estimate, categories): normal or hyperdynamic, mildly or moderately reduced, and severely reduced.
• Hyperdynamic function: cavity almost obliterated in systole, with end systolic cavity obliteration suggesting hypovolaemia or vasodilatation.
• Severely reduced function: minimal wall thickening, a dilated cavity, E-point septal separation over 10 mm, suggests ejection fraction under 30 to 40%.
• Regional wall motion abnormality suggests an acute coronary syndrome but is difficult to assess in a limited examination.
• Right ventricular strain/pulmonary embolism: right ventricle dilated (right to left ratio over 1), D-shaped left ventricle (septal flattening or bowing into the left ventricle in systole and diastole), McConnell sign (hypokinesia of the free wall with a sparing apex), reduced TAPSE (under 16 mm), dilated inferior vena cava, and tricuspid regurgitation.
• In chronic pulmonary hypertension, there is right ventricular hypertrophy.
• Hypovolaemia: small, hyperdynamic left ventricle with end systolic obliteration (the "kissing papillary muscles" sign), small inferior vena cava (under 1.5 cm) with over 50% collapse (in spontaneously breathing patients). In ventilated patients, a distensibility index of over 18% suggests fluid responsiveness.
• Volume overload: dilated, non-collapsing inferior vena cava (over 2.1 cm), with B-lines on lung ultrasound, dilated left atrium, and pleural effusions.
• Distributive/septic shock: hyperdynamic left ventricle (or septic cardiomyopathy with reduced function), normal or small inferior vena cava.
• Cardiogenic shock: dilated hypokinetic left ventricle with dilated inferior vena cava.
• Cardiac arrest: no cardiac activity (standstill) after prolonged resuscitation suggests a poor prognosis. Organised activity in pulseless electrical activity ("pseudo-PEA") identifies patients with low flow states needing volume or vasopressors.
• Cardiac arrest, other findings: reversible causes (tamponade, pulmonary embolism, hypovolaemia, tension pneumothorax) are sought. Ventricular fibrillation appears as quivering without effective contraction.
• Gross valvular disease: large vegetation, flail leaflet, severe regurgitation on colour Doppler (limited accuracy), and severe aortic stenosis (calcified, immobile cusps).
• Aortic root dilatation, dissection flap in the aortic root (limited); abdominal aorta views may be added.
• Intracardiac masses/thrombus: large mobile masses; the right heart thrombus ("clot in transit") is a high risk finding.
• Pleural effusion, pneumothorax and consolidation on lung windows when integrated with lung ultrasound.
• Proximal deep vein thrombosis on compression ultrasound when combined with leg views.

Critical values and findings needing immediate action.

• Pericardial effusion with tamponade physiology: emergency pericardiocentesis under ultrasound control (or surgical drainage in trauma). Give fluid while preparing, and avoid positive pressure ventilation where possible.
• Right ventricular dilatation with shock and suspected massive pulmonary embolism: thrombolysis (or catheter or surgical embolectomy), with anticoagulation.
• Severe left ventricular dysfunction with shock: inotropes, treatment of the cause (acute coronary syndrome, myocarditis), and mechanical support evaluation.
• Hypovolaemia with small hyperdynamic left ventricle: fluid or blood resuscitation, with search for source of bleeding.
• Cardiac arrest with tamponade, pulmonary embolism, or hypovolaemia: targeted treatment during resuscitation.
• Cardiac standstill after prolonged resuscitation: supports a decision to stop resuscitation when combined with clinical factors.
• Large mobile right heart thrombus or vegetation with instability: urgent cardiology and cardiac surgery review.
• Aortic dissection flap or aortic root dilatation with shock: emergency CT angiography or transoesophageal echocardiography and surgery.
• Tension pneumothorax with cardiac compromise: immediate decompression.

Limitations and artefacts.

• It is a limited study: it cannot diagnose or exclude valve disease, cardiomyopathy, diastolic dysfunction, regional wall motion abnormality, or small shunts, and ejection fraction is estimated visually (error of 10 to 15 points). A normal focused study does not exclude significant cardiac disease. Formal echocardiography is needed in most cases with abnormal findings.
• Operator training and competence are key. A minimum number of supervised studies (for example 30 to 50) with image review are needed. Misinterpretation (pericardial fat for effusion, pleural effusion for pericardial effusion, or physiological right ventricular size) leads to errors.
• Poor windows in 10 to 20% of emergency patients (obesity, chronic lung disease, ventilation).
• Inferior vena cava size and collapse are unreliable for right atrial pressure in ventilated patients, in raised intra-abdominal pressure, in athletes, in right heart failure and in tricuspid regurgitation. Fluid responsiveness must be judged by dynamic tests (passive leg raise with velocity time integral change) and the clinical picture.
• Right ventricular dilatation is not specific for pulmonary embolism (chronic lung disease, pulmonary hypertension, right ventricular infarction, arrhythmogenic right ventricular cardiomyopathy). Sensitivity for pulmonary embolism is low (about 50%), so normal right ventricle does not exclude it.
• Hyperdynamic left ventricle may be present with significant mitral regurgitation, or severe sepsis with myocardial depression masks.
• Effusions can be loculated (post-surgery), and tamponade can occur with a small effusion if rapid (haemorrhage) or in the presence of a clot. Localised clot can be echogenic.
• Cardiac arrest imaging prolongs pauses in compressions if poorly timed, so a structured approach and a recorded clip are needed.
• Findings affect decisions only when integrated with clinical data; documentation, storage of images and quality review are required.

Special groups.

• Children and neonates: focused cardiac ultrasound is used for shock, cardiac function, pericardial effusion, and line placement; normal values differ and need paediatric training.
• Pregnancy: safe; used for dyspnoea and peripartum cardiomyopathy; physiological changes (mild chamber dilatation, small effusion) are accounted for.
• Older adults: valve calcification, and chronic heart failure; baseline abnormalities complicate interpretation.
• Trauma patients: pericardial effusion in FAST and serial views; haemorrhagic shock appears as a small hyperdynamic heart.
• Cardiac surgery patients: localised clot and tamponade after surgery are often not visible in transthoracic windows, and transoesophageal echocardiography is needed.
• Critically ill patients: serial examinations to follow response to fluids and drugs, and in combination with lung ultrasound.
• Regions: tuberculous pericardial effusion with tamponade, rheumatic heart disease, peripartum cardiomyopathy, HIV-related cardiomyopathy and pericardial disease, endomyocardial fibrosis, and pulmonary embolism are important.
• Handheld devices with portable training programmes extend echocardiography to rural clinics. Basic focused cardiac ultrasound may be the only cardiac imaging available, but referral for formal echocardiography should be arranged where possible.

Follow up tests. Formal full transthoracic echocardiography, transoesophageal echocardiography, electrocardiogram, troponin, natriuretic peptides, chest radiograph, CT pulmonary angiography, CT angiography of the aorta, lower limb venous duplex, lung ultrasound, FAST examination, blood tests (full blood count, lactate, coagulation, renal function, electrolytes, blood gas),

pericardial fluid analysis (cell count, culture, tuberculosis tests, cytology, adenosine deaminase), repeat focused ultrasound after treatment, coronary angiography, cardiac MR, and referral to cardiology, critical care or cardiac surgery.