Right heart strain (or more precisely right ventricular strain) is a term given to denote the presence of right ventricular dysfunction usually in the absence of an underlying cardiomyopathy. It can manifest as an acute right heart syndrome.
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Pathology
Right heart strain can often occur as a result of pulmonary arterial hypertension (and its underlying causes such as massive pulmonary emboli).
Biomarkers
Patients with right heart strain may have elevated levels of 4:
Radiographic features
CT
The reported sensitivity and specificity of CT in demonstrating right heart dysfunction are around 81% and 47% respectively 5.
Described features include:
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abnormal position of the interventricular septum 1
flattening of the interventricular septum
paradoxical interventricular septal bowing, i.e. towards the left ventricle
right ventricular enlargement (right ventricle bigger than the left ventricle)
pulmonary trunk enlargement (bigger than the aorta)
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features of right heart failure
dilated azygos venous system
dilated hepatic veins +/- with contrast reflux
Echocardiography
The reported sensitivity and specificity of echocardiography in demonstrating right heart dysfunction are around 56% and 42% respectively 5.
Described features include: 9
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dilatation of the right ventricle
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quantified as a basal diameter >4.2 cm, a mid-cavity diameter >3.5 cm, and a length exceeding 8.6 cm
ideally measured in the RV focused apical 4 chamber view
right ventricle/ left ventricle end diastolic basal diameter ratio >1
the right ventricular outflow tract is considered enlarged when the measured diameter in the parasternal long axis exceeds 3.3 cm, or when the measured diameter exceeds 2.7 cm in the distal RVOT, as measured in the basal parasternal short axis view
qualitative features include diffuse rounding and loss of the typical triangular to crescentic morphology
the right ventricle may occupy a portion of the apex, which is in health composed solely of the left ventricle
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interventricular septal flattening
commonly referred to as the "D" sign, a reference to the short axis appearance of the left ventricle in the presence of septal flattening
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an abrupt rise in pulmonary arterial pressures prolong right ventricular contraction
persistence of elevated RV pressures as the LV begins to relax results in reversal of the normal interventricular septal curvature
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leftward bowing of the interatrial septum may be seen, as with the interventricular septum
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free wall thickness >5 mm
excess trabeculation of the myocardium
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right ventricular systolic dysfunction
a pattern of right ventricular free wall hypokinesis with apical sparing is often found, referred to as the McConnell's sign
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elevated right ventricular pressures
right ventricular systolic pressure > 35 mmHg is consistent
the "60/60 sign", putatively indicating an acute cause of elevated right ventricular pressures, with a pulmonary valve acceleration time <60 ms, and a tricuspid regurgitation jet >30 but <60 mmHg
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plethoric inferior vena cava
diameter >2.1 cm as measured in the subcostal long axis view
with loss of its usual phasic variation throughout the respiratory cycle
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often secondary to annular dilation resulting in valvular incompetence
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