Surface Cardiac Ultrasound.

In this chapter we will be reviewing the cardiac windows in order to perform a focused cardiac ultrasound examination. So we begin by understanding the acoustic windows we need to do a cardiac ultrasound.

Introduction

This is not a full echocardiographic examination. Training in echocardiography is a multilayer process that requires extensive training and certification and not the scope of practice of the Anesthesiologist. Instead, focused cardiac ultrasound, which is a component of POCUS, was borne out of the need to have access to this powerful technology while not overburdening the provider with a detailed understanding of all the capabilities and only with a limited number of views. 

The essence of Focused Cardiac Ultrasound (FoCUS) is mainly for a dichotomous interpretation of findings to answer questions that are crucial to the clinical decision-making process.  It aims to gather sufficient information to assess physiologic status and the reduction of diagnostic uncertainty by narrowing the range of viable diagnosis. The diagnostic approach of FoCUS is qualitative or semiquantitative and the examination is conducted without the requirement of performing specific measurements. Qualitative appreciation of sizes and function (e.g., the right ventricle is dilated or nondilated, normokinetic or hypokinetic) or semiquantification of ranges of function (e.g., the left ventricle is hyperkinetic, normokinetic, hypokinetic, or severely hypokinetic) represents the modus operandi of FoCUS. 

We start by becoming expert sonographers at performing the following 5 FoCUSed views. 

FoCUSed Views

Ideally patients should lie left lateral with left arm extended. It is likely however that you may not be able to change the position of the patient due to hemodynamic instability which may limit one or more of the following views. The phased array transducers used in cardiac imaging (2-8MHz) will be the probe you will be using. The subcostal view can also be obtained using the curved linear probe.

1. Parasternal Short Axis

 
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       RV
                    
           LV       Ant



   Inf
 
                         Lat

 

Parasternal short axis view being interrogated. Indicator to the left shoulder. 3, Apical 4 chamber view; 4 Subcostal View; 5 IVC view.  Mid papillary view seen on the clip on the right. RV, right ventricle; LV, left ventricle; Ant, anterior wall; Lat, lateral wall; Inf, inferior wall. Image adapted from Foresight ultrasound.

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RV

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PV

TV

IAS

AV

Tilting the probe towards the head or feet changes the view you see on the parasternal short axis view. Image adapted from Foresight ultrasound.TV, Tricuspid valve; RV, Right Ventricle; PV, Pulmonic valve; AV, Aortic valve; IAS, Interatrial septum; MV, Mitral valve. Diagram courtesy of foresightultrasound.com

2. Parasternal Long Axis

 
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MV

Left Atrium

LV

AV

LVOT

RV

Turn the indicator towards the right shoulder. 3, Apical 4 chamber view; 4 Subcostal View; 5 IVC view. LV, Left ventricle; RV, Right ventricle; AV, Aortic valve; LVOT, Left ventricle outflow tract; MV, Mitral Valve. Image adapted from Foresight ultrasound

3. Apical 4 chamber

 
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RV

TV

LV

MV

Left Atrium

IAS

Apical 4 chamber view probe position. Arrow indicates orientation of probe marker. 1. Parasternal short axis; 2, Parasternal long axis. 4 Subcostal View; 5 IVC view. LV, Left ventricle; RV, Right ventricle; AV, Aortic valve; IAS, Inter atrial septum; MV, Mitral valve; TV, Tricuspid valve. Image adapted from Foresight ultrasound.

4. Subcostal view

 
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TV

RV

LV

Right Atrium

Liver

Subcostal view on position labeled 4 on the image. Arrow indicates orientation of probe marker. The probe must be almost parallel the patient's skin. 1. Parasternal short axis; 2, Parasternal long axis; 5 IVC view.  ultrasound. RV, Right ventricle; TV, Tricuspid valve. Image adapted from Foresight ultrasound.

5. Inferior Vena Cava view

 
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IVC

RV
 

TV

Right atrium

IVC view. Marker directed towards the sternal notch. RV, Right ventricle; IVC, Inferior vena cava; TV, Tricuspid valve. Image adapted from Foresight ultrasound.

References:

1. Zimmerman JM, Coker BJ. The Nuts and Bolts of Performing Focused Cardiovascular Ultrasound (FoCUS). Anesthesia and analgesia 2017; 124: 753-760.

2. Spencer KT, Kimura BJ, Korcarz CE, Pellikka PA, Rahko PS, Siegel RJ. Focused cardiac ultrasound: recommendations from the American Society of Echocardiography. J Am Soc Echocardiogr. 2013 Jun;26(6):567-81. doi: 10.1016/j.echo.2013.04.001. PMID: 23711341.