Indications
Diagnosis of Cardiogenic Shock (see Cardiogenic Shock, [[Cardiogenic Shock]])
Clinical Features
- Left Ventricular Failure
- Global: severely diminished contraction of all left ventricular walls
- Focal: hypokinesis (decreased contraction) or akinesis (no contraction) of specific LV segments
- Right Ventricular Failure
- Decreased RV Contraction in Longitudinal Aspect
- Decreased Movement of Tricuspid Valve Toward Apex
Diagnosis of Pulmonary Hypertension (see Pulmonary Hypertension, [[Pulmonary Hypertension]])
- Clinical Efficacy
- Study of Echocardiogram Compared to Swan-Ganz Catheterization in the Diagnosis of Pulmonary Hypertension (J Am Soc Echocardiogr, 2016) [MEDLINE]
- Echocardiogram Reliably Estimates Right Ventricular Systolic Pressure, Assuming Attention is Given to Simple Quality Metrics
Diagnosis of Ventricular Assist Device (VAD) Pump Thrombosis (see Ventricular Assist Device, [[Ventricular Assist Device]])
Evaluation of Acute Pulmonary Embolism (PE) (see Acute Pulmonary Embolism, [[Acute Pulmonary Embolism]])
Clinical Features
- Direct Signs
- Clot in Transit
- Clot in Main PA: seen primarily on transesophageal echocardiogram (TEE)
- Indirect Signs
- Dilated RV
- Impaired RV Free Wall Function (with/without Intact Apical Function)
- Systolic Septal Flattening (with “D-Shape” of LV)
Evaluation of Hypovolemic Shock (see Hypovolemic Shock, [[Hypovolemic Shock]])
Clinical Features
- Small LV End-Diastolic and End-Systolic Area
- Small, Collapsible IVC
- Greater than 50% Inspiratory Collapse: suggests that CVP is <8
- LV Cavity Obliteration (“Kissing” Papillary Muscles)
Evaluation for Pericardial Tamponade (see Tamponade, [[Tamponade]])
Clinical Features
- Pericardial Effusion (see Pericardial Effusion, [[Pericardial Effusion]])
- Chamber Collapse
- Diastolic RV and LV Collapse
- Systolic RA and LA Collapse
- Inflow Velocity Variablity
- Increased Variability in Mitral (>25%) Inflow Velocity
- Increased Variability in Tricuspid (>40%) Inflow Velocity
Evaluation of Volume Status in Septic Shock (see Sepsis, [[Sepsis]])
- Physiology
- Mechanical Ventilation in the Passive Patient
- Inspiration -> Increases Intrathoracic Pressure and RA Pressure, Resulting in IVC Distention
- Expiration -> Decreases Intrathoracic Pressure and RA Pressure, Resulting in IVC Collapse
- Rationale
- A Fluid-Responsive Circulation Will Demonstrate Significant Cyclic Respiratory Variation in IVC Volume and Left Ventricular Stroke Volume
- In Contrast, if Circulation is Not Fluid-Responsive, Only Small Respirophasic Changes Will Be Seen in the IVC or Left Ventricular Stroke Volume
- Caveats
- Lung Distention Increases the Pressure Around Pulmonary Capillaries, Increasing RV Afterload
- Normally, this Doesn’t Have Significant Consequence for the Circulation
- However, in the Setting of RV Failure, this will Result in Fluid-Unresponsiveness Despite Significant Respiratory Variation in the Left Ventricular Stroke Volume
- Technique of IVC Diameter Measurement
- IVC is Imaged in a Subxiphoid, Long-Axis View (Either off the Frozen Image with Caliper Function or with M-Mode Imaging)
- IVC Diameter is Measured 2-3 cm Below the Right Atrium or Just Caudad to the Inlet of the Hepatic Veins: allows an estimation of right atrial pressure
- IVC Diameter Should Be Measured at End-Expiration
- Clinical Efficacy
- Minimal/Maximal IVC Diameter as a Guide to Fluid Responsiveness in Sedated, Mechanically-Ventilated Patients (Intensive Care Med, 2004) [MEDLINE]
- Correlations: r = 0.58 (minimal IVC diameter) and r = 0.44 (maximal IVC diameter)
- Variation in IVC Diameter = Max Diameter-Min Diameter/Mean Diameter
- Respiratory Variation in IVC Diameter was Greater in Fluid Responders than in Fluid Non-Responders
- Threshold Variation in IVC Diameter of 12% (Max Diameter-Min Diameter/Mean Diameter) or 18% (Max Diameter-Min Diameter/Min Diameter) Separated Fluid Responders (Positive Predictive Value: 93%) from Fluid Non-Responders (Positive Predictive Value: 92%)
- In Spontaneously Breathing Patient, A Dilated IVC (>2 cm) without a >50% Decrease in IVC Diameter with Gentle Sniffing Usually Indicates an Elevated Right Atrial Pressure (Chest, 2005) [MEDLINE]
- However, this is Less Specific in Mechanically-Ventilated Patients, Since there is a High Prevalence of IVC Dilation in These Patients
- General Features of Echocardiogram Which Predict Fluid Responsiveness (Chest, 2012) [MEDLINE]
- Assumptions: patient is either on mechanical ventilation with respiratory efforts or is breathing spontaneously
- If the Left Ventricle is Hyperdynamic with End-Systolic Effacement, There is a High Probability of Fluid Responsiveness
- If the IVC is <1 cm in Diameter, There is a High Probability of Fluid Responsiveness
- If the IVC is Between 1-2.5 cm, There is an Indeterminate Probability of Fluid Responsiveness
- If the IVC is >2.5 cm in Diameter, There is a Low Probability of Fluid Responsiveness
Technique
Background-Normal Echocardiogram
Assessment of RV Size
- RV is normally 60% of the LV size at end-diastole (best seen in apical 4-chamber view)
- End-Diastolic RV Cavity Size >60% of the End-Diastolic LV Cavity Size Indicates Moderate-Severe RV Enlargement
Assessment of RV Wall Thickness
- RV wall is normally <4 mm thick
- RV Wall Thickness >5 mm is Abnormal
Assessment of Septal Kinetics
- Rationale: the septum normally moves toward the LV during ventricular systole
- Interpretation
- Pressure overload of the right ventricle causes a straightening of the interventricular septum during systole: results in a D-shape of the LV during LV during systole
- Volume overload of the RV causes a straightening of the septum during diastole: results in a D-shape of the LV during LV during diastole
Assessment of RV Systolic Function
- Rationale: the RV has more longitudinal rather than transverse motion during systole, so the degree of longitudinal systolic movement of the tricuspid annulus correlates with overall RV systolic function
- Technique
- Tricuspid annular plane systolic excursion (TAPSE): M-mode interrogation in apical 4-chamber view using a line through the tricuspid annulus
- Interpretation
- Normal TAPSE: >17 mm (values below this indicate decreased RV systolic function)
Estimation of Pulmonary Artery Systolic Pressure
- Technique: pulmonary artery systolic pressure assessment requires the presence of a tricuspid regurgitation (TR) jet
- Continuous wave Doppler interrogation line is placed along the main axis of the TR jet to measure the blood flow velocity of the regurgitant jet
- With use of the modified Bernoulli equation, the pressure gradient across the valve is calculated
- Once the pressure gradient is known, adding the RA pressure to this gradient yields an estimate of pulmonary artery systolic pressure
- The RA pressure may be measured directly if a central venous catheter is in place or estimated from the size and respiratory variation of the inferior vena cava (IVC
Assessment of Preload Sensitivity
- Clinical Efficacy
- Change in Stroke Volume After Passive Leg Raising Identifies Preload Sensitivity (Intensive Care Med, 2007) [MEDLINE]
References
- The respiratory variation in inferior vena cava diameter as a guide to fluid therapy. Intensive Care Med. 2004;30(9):1834-1837 [MEDLINE]
- Bedside ultrasonography in the ICU: part 1. Chest. 2005 Aug;128(2):881-95 [MEDLINE]
- Passive leg raising predicts fluid responsiveness in the critically ill. Crit Care Med. 2006;34(5):1402-1407 [MEDLINE]
- Diagnosis of central hypovolemia by using passive leg raising. Intensive Care Med. 2007;33(7):1133-1138 [MEDLINE]
- Shock: Ultrasound to guide diagnosis and therapy. Chest 2012; 142(4):1042-1048. Doi:10.1378/chest.12-1297 [MEDLINE]
- Focused critical care echocardiography. Crit Care Med. 2013;41:2618–2626 [MEDLINE]
- Advanced echocardiography for the critical care physician: Part 1. Chest. 2014;145:129–134 [MEDLINE]
- Advanced echocardiography for the critical care physician: Part 2. Chest. 2014;145:135–142 [MEDLINE]
- Bedside ultrasonography for the intensivist. Crit Care Clin. 2015 Jan;31(1):43-66. doi: 10.1016/j.ccc.2014.08.003. Epub 2014 Oct 3 [MEDLINE]
- Addressing the Controversy of Estimating Pulmonary Arterial Pressure by Echocardiography. J Am Soc Echocardiogr. 2016 Feb;29(2):93-102. Epub 2015 Dec 11 [MEDLINE]