2 Echocardiographic Assessment of Patients with Systolic Heart Failure
Definition, Staging, and Etiology of Systolic Heart Failure
• Heart failure (HF): abnormality of cardiac function responsible for inability of the heart to provide blood flow at rates commensurate with tissue requirement, or to do so only at increased filling pressures.
• The single most useful diagnostic test in the evaluation of patients with HF is the comprehensive two-dimensional (2D) echocardiogram coupled with Doppler flow studies.1 The goals of echocardiography in systolic HF are:
• Define etiology and in particular determine if systolic HF is due to a primary myocardial disease (including consequences of coronary disease) or a primary valve disease.
Dimension/Volumes | Use/Advantages | Limitations |
---|---|---|
Linear | ||
M-mode | Reproducible | Beam frequently off-axis |
High frame rates | Single dimension not representative in distorted ventricles | |
2D-guided | Assures orientation perpendicular to LV axis | Lower frame rates than in M-mode |
Single dimension only | ||
Volumetric | ||
Biplane Simpson’s method | Corrects for shape distortions | Apex frequently foreshortened |
Minimizes mathematic assumptions | Endocardial dropout | |
Relies on only two planes | ||
Area-length method | Partial correction for shape distortion | Based on mathematic assumptions |
3D echocardiography | Best correlation with MRI | Endocardial definition |
Further enhanced by contrast use |
Echocardiographic Methods for Assessment of Left Ventricular Systolic Function
Image Acquisition and Interpretation
• Various imaging modalities can be used for assessment of left ventricular systolic function (see Table 2-1).
Indexes of Global Left Ventricular Systolic Function
• Left ventricular size
• EF by visual assessment
• This value is an estimation based on appreciation of ventricular area change in systole from multiple views.
• EF by linear measurements (Figure 2-1)
• EF by volumetric measurements (Figure 2-2)
• Stroke volume and cardiac output (Figure 2-3)
Assessment of Regional Left Ventricular Function
• RWMA due to ischemia does not occur at rest until epicardial coronary artery stenosis is greater than 85%.
• Echocardiography overestimates the area of ischemic or infarcted myocardium as adjacent regions are affected by tethering, regional loading conditions, and stunning.
• The presence of regional left ventricular dysfunction not respecting coronary distribution can be seen in various diseases, such as post–coronary artery bypass grafting, infiltrative cardiomyopathies (sarcoidosis), cardiac tumors, myocarditis, etc.
• Other tools are gaining momentum in assessing regional wall motion, particularly segmental left ventricular strain or strain rate (see Figure 2-4).
Assessment of LV Diastolic Function
Assessment of Hemodynamic Consequences
• Estimate right atrial pressure using inferior vena cava size and variation, and right ventricular pressure using tricuspid regurgitation velocity.
Key Points
• Left ventricular internal diameter and EF are key parameters in the diagnosis and follow-up assessment of systolic dysfunction.
• The ASE recommends use of biplane method of disks (modified Simpson’s method) for EF calculations.
Echocardiographic Assessment of Specific Causes of Systolic Heart Failure
Ischemic LV Dysfunction
• The presence of resting RWMAs in a coronary artery distribution pattern and/or evidence of old myocardial infarction (thinned, scarred myocardial wall; LV aneurysm) are key echocardiographic findings.
• Resting RWMAs can also be seen with stunned/hibernating myocardium and occasionally in non-ischemic disease.
• Intravenous contrast should be used whenever endocardial border definition is suboptimal in two or more contiguous segments.
• Stress echocardiography is an established method of assessment of myocardial ischemia.
• Exercise (treadmill or stationary bike) is the preferred stress method. It can be combined with oxygen consumption for better quantification of exercise ability. Dobutamine is the most commonly used pharmacologic stress agent.
• MR can be associated with ischemic left ventricular dysfunction, and is most commonly due to tethering of the posterior mitral leaflet (Figure 2-7); an effective regurgitant orifice (ERO) greater than 0.20 cm2 and a regurgitant volume greater than 30 mL are associated with poor prognosis.
• Always assess for intraventricular thrombus in patients with low EF and aneurysmal changes (Figure 2-8). This is best done by administration of intravenous contrast.
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