Numbers needed to detect a significant change in myocardial strain and left ventricular twist measured by complementary spatial modulation of magnetization (CSPAMM).

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POSTER PRESENTATIONOpen Access
Numbers needed to detect a significant change
in myocardial strain and left ventricular twist
measured by complementary spatial modulation
of magnetization (CSPAMM)
Peter Swoboda1*, Abdulghani M Larghat2, Timothy Fairbairn2, Manish Motwani2, John P Greenwood2, Sven Plein2
From 15th Annual SCMR Scientific Sessions
Orlando, FL, USA. 2-5 February 2012
Summary
We have calculated the inter-study reproducibility of
myocardial strain and twist measured by CSPAMM and
calculated the number of subjects required to detect a
significant change in these parameters.
Background
The inter-study reproducibility of parameters measured
by CSPAMM such as circumferential strain, radial strain
and left ventricular (LV) twist have not been described
in detail and it is not known how many subjects are
required to detect a significant change.
Methods
12 healthy volunteers (6 male, mean age 33±15 years)
underwent CMR studies on two separate occasions
(mean interval of 8±3 days) using an identical CSPAMM
pulse sequence with images acquired in 3 short axis
slices at the apex, mid-ventricle and base. Data were
analysed using harmonic phase analysis (Tag Track,
Gyrotools, Zurich, CH). Circumferential Lagrangian
strain, radial Lagrangian strain and rotation were calcu-
lated for the three short axis slices. Left ventricular (LV)
twist was calculated by subtracting the basal rotation
from the apical rotation. The mean difference between
paired measurements, the standard deviation (SD) of the
differences and the coefficient of variability (CoV) were
calculated.
The sample sizes required by CMR to show a clinical
change with a power of 90% and an a error of 0.05
were calculated using the formula n = f (a, P) x s 2 x
2/ δ 2 , where n is the sample size, a the significance
level, P the study power required and f the value of the
factor for different values of a and P (f = 10.5 for
a=0.05 and p = 0.90), with s the inter-study standard
deviation of differences between visits and δ the desired
difference to be detected.
Results
Inter-study reproducibility of circumferential strain
(CoV 3.7% to 5.5%) and LV twist (CoV of 9.6%) were
good (Table 1). Radial strain showed poorer inter-study
reproducibility (CoV of 13.8 - 23.4%).
Sample size calculations suggested that 20 or fewer
subjects are needed to detect a 10% change in circumfer-
ential strain with a power of 90% and an a error of 0.05.
For LV twist, 66 subjects would be required (Table 2).
Conclusions
CSPAMM tagged CMR with HARP analysis provides
reproducible measurements of circumferential strain and
twist with small numbers required to detect differences
in serial studies. The method may provide powerful sur-
rogate data for clinical studies.
Funding
This research has partly been supported by a grant from
the British Heart Foundation. This funding body was
not involved in the study design, data collection, data
analysis or writing of the manuscript.
1Department of Cardiology, Leeds General Infirmary, Leeds, UK
Full list of author information is available at the end of the article
Swoboda et al. Journal of Cardiovascular Magnetic Resonance 2012, 14(Suppl 1):P259
http://www.jcmr-online.com/content/14/S1/P259
© 2012 Swoboda et al; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.

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Author details
1Department of Cardiology, Leeds General Infirmary, Leeds, UK.
2Multidisciplinary Cardiovascular Research Centre & Leeds Institute of
Genetics, Health and Therapeutics, University of Leeds, Leeds, UK.
Published: 1 February 2012
doi:10.1186/1532-429X-14-S1-P259
Cite this article as: Swoboda et al.: Numbers needed to detect a
significant change in myocardial strain and left ventricular twist
measured by complementary spatial modulation of magnetization
(CSPAMM). Journal of Cardiovascular Magnetic Resonance 2012 14(Suppl 1):
P259.
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Table 1 Inter-study reproducibility as the percentage difference between the two scans and the equivalent Coefficient
of Variation(%)
EndocardiumMidlineEpicardium
Mean diff % SDCoV (%) Mean diff % SDCoV (%)Mean diff % SDCoV (%)
Circumferential strainApex
Mid LV
Base
7.27
7.41
6.44
5.74
4.02
4.21
5.45
5.50
4.77
5.75
5.32
7.14
3.41
2.64
4.43
4.23
3.89
5.31
5.02
6.09
6.50
4.29
4.15
4.56
3.71
4.50
4.83
Radial StrainApex
Mid LV
Base
17.17
17.10
24.98
15.17
11.53
23.40
14.33
13.78
23.40
LV twist 13.4710.71 10.68 12.519.589.8015.20 11.1712.15
Table 2 Mean values of circumferential strain, radial strain and LV twist from 12 healthy volunteers and the sample
size required to detect a 10% change in each absolute value.
EndocardiumMidline Epicardium
Mean Sample SizeMeanSample Size Mean Sample Size
Circumferential strainApex
Mid LV
Base
-0.38
-0.33
-0.29
20
15
14
-0.29
-0.24
-0.23
9
8
16
-0.21
-0.19
-0.18
10
11
14
Radial Strain Apex
Mid LV
Base
0.22
0.21
0.21
153
172
436
LV twist (degrees) 12.25 7210.44 66 8.60 112
Swoboda et al. Journal of Cardiovascular Magnetic Resonance 2012, 14(Suppl 1):P259
http://www.jcmr-online.com/content/14/S1/P259
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