Fractional shortening and Teichholz ejection fraction

Clinical background

In the echocardiographic assessment of left ventricular systolic function, ejection fraction (EF) is the dominant measure, but a full volume-based calculation requires apical two- and four-chamber views with careful endocardial border tracing in both systole and diastole. In emergency settings, in the intensive care unit or at point-of-care echocardiography, image quality is often inadequate for this. M-mode linear measurements from the parasternal long axis can then be obtained quickly and with good reproducibility, and from two diameter measurements both fractional shortening (FS) and a volume-based EF can be calculated. The tool therefore has a role when the recommended method is not practically feasible, but it rests on geometric assumptions that must be understood if the result is to be interpreted correctly.

Calculating fractional shortening and the Teichholz ejection fraction

Fractional shortening is calculated as the relative reduction in the internal diameter of the left ventricle from diastole to systole:

$$\text{FS} = \frac{\text{LVIDd} - \text{LVIDs}}{\text{LVIDd}} \times 100$$

where LVIDd is the left ventricular internal diameter in diastole and LVIDs is the left ventricular internal diameter in systole, both measured in millimetres but handled in centimetres in the volume calculation.

The Teichholz method converts these diameter measurements into volumes via an empirically derived formula:

$$V = \frac{7D^3}{2{.}4 + D}$$

where $D$ is the internal diameter in centimetres and $V$ is the chamber volume in millilitres. End-diastolic volume (EDV) is calculated with $D = \text{LVIDd}$ and end-systolic volume (ESV) with $D = \text{LVIDs}$. The ejection fraction is then:

$$\text{EF} = \frac{\text{EDV} - \text{ESV}}{\text{EDV}} \times 100$$

The derivation was performed by Teichholz et al. on the basis of 100 left ventricular angiograms in the right anterior oblique projection [1]. The relationship between the short and long axis of the ventricle was determined across a wide range of volumes and used to formulate a theoretically sound equation for volume calculation from echocardiographic diameter measurements. In 12 patients without asynergy (regional wall motion abnormality), end-diastolic and end-systolic volumes were calculated with good agreement with angiography, irrespective of whether the ventricle was small or large. In 12 patients with left ventricular asynergy, the correlation between echocardiographically and angiographically determined volumes was poor [1].

Interpretation in practice

Fractional shortening is a linear measure and captures only the radial shortening of the basal ventricle. The normal value in adults is given as approximately 25 to 45 per cent, with a lower limit around 25 per cent [3]. A rough classification used in clinical practice:

The Teichholz EF gives a volume-based estimate and may produce values that are more directly comparable with the conventional EF that clinicians are accustomed to. Normal EF in adults is typically above 50 per cent. The same caveat applies to the Teichholz method as to FS, however: the value reflects only the basal ventricle and assumes symmetrical contraction.

A low value (FS below 20 per cent or Teichholz EF below 40 per cent) should prompt further evaluation with a complete echocardiogram including the biplane method of discs, particularly if the patient has clinical signs of heart failure. A normal value does not exclude regional dysfunction, especially not after myocardial infarction with apical or septal asynergy, since the basal segments may retain normal contraction.

Validation and performance

The original validation of the Teichholz method showed good correlation with angiography in patients with symmetrical contraction, but the method's weakness in regional asynergy was demonstrated already in the derivation study [1]. A later comparative study by de Simone et al. tested the Teichholz formula against 2D echocardiography in a cohort of 65 adults with varying chamber sizes [2]. The Teichholz end-diastolic volume correlated with 2D volumes at r = 0.88, but the intercept deviated by minus 23 mL from the line of identity, indicating systematic underestimation of volume. In a second test series of 1,721 participants in the Strong Heart Study, all without segmental wall motion abnormality or mitral regurgitation, the Teichholz stroke volume correlated with the Doppler-derived stroke volume at r = 0.64, with a mean volume close to the Doppler value (72 versus 70 mL) [2]. An alternative Z-based method performed equivalently in terms of correlation but with better calibration, that is, a regression line closer to the line of identity.

In summary: the Teichholz method gives an acceptable rough estimate of chamber volume and EF in patients with symmetrical contraction and normal chamber geometry, but its calibration is inferior to that of more modern methods and it is not validated in patients with regional wall motion abnormality.

Limitations

The most important limitations follow from the fact that both measures sample only the basal ventricle in a single dimension:

Regional wall motion abnormality. In myocardial infarction with asynergy of the apical, septal or lateral segments, the basal segments may contract normally. FS and the Teichholz EF may then show normal values despite manifest systolic dysfunction. This was the principal finding already in Teichholz's original work [1] and is the single most important limitation.

Dilated ventricle. The geometric relationship between short and long axis on which the formula rests holds for a normally shaped ventricle. In marked dilatation, for example in dilated cardiomyopathy or chronic volume overload, this assumption breaks down and the volume calculation becomes unreliable.

Altered chamber geometry. In hypertrophic cardiomyopathy, constrictive pericarditis or marked left ventricular hypertrophy of other cause, the shape of the ventricle may deviate from the assumed prolate ellipsoid, which affects both FS and the Teichholz EF [3].

Load dependence. Both measures are load-dependent, that is, sensitive to changes in preload and afterload. In hypovolaemia, sepsis with vasodilatation or mechanical ventilation, FS and EF may exaggerate contractile function [3].

Right ventricle. The method applies only to the left ventricle. Right ventricular function cannot be assessed with FS or the Teichholz EF.

The biplane method of discs (modified Simpson's) is the method recommended by the ASE and EACVI for echocardiographic determination of EF [4]. Teichholz and FS should be reserved for situations in which image quality or time constraints preclude a complete volume analysis, and the result should always be regarded as a preliminary estimate to be confirmed or replaced by a complete study when circumstances allow.

References

1. Teichholz LE, Kreulen T, Herman MV, Gorlin R. Problems in echocardiographic volume determinations: echocardiographic-angiographic correlations in the presence or absence of asynergy. Am J Cardiol. 1976;37(1):7–11. PMID: 1244736
2. de Simone G, Devereux RB, Ganau A, Hahn RT, Saba PS, Mureddu GF, Roman MJ, Howard BV. Estimation of left ventricular chamber and stroke volume by limited M-mode echocardiography and validation by two-dimensional and Doppler echocardiography. Am J Cardiol. 1996;78(7):801–7. PMID: 8857486
3. Tissot C, Singh Y, Sekarski N. Echocardiographic Evaluation of Ventricular Function, For the Neonatologist and Pediatric Intensivist. Front Pediatr. 2018;6:79. PMID: 29670871
4. Lang RM, Badano LP, Mor-Avi V, et al. Recommendations for cardiac chamber quantification by echocardiography in adults: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. J Am Soc Echocardiogr. 2015;28(1):1–39. PMID: 25559473