Cardiac magnetic resonance assessment of dyssynchrony and myocardial scar predicts function class improvement following cardiac resynchronization therapy.
OBJECTIVE
We tested a circumferential mechanical dyssynchrony index (circumferential uniformity ratio estimate [CURE]; 0 to 1, 1 = synchrony) derived from magnetic resonance-myocardial tagging (MR-MT) for predicting clinical function class improvement following cardiac resynchronization therapy (CRT).


BACKGROUND
There remains a significant nonresponse rate to CRT. MR-MT provides high quality mechanical activation data throughout the heart, and delayed enhancement cardiac magnetic resonance (DE-CMR) offers precise characterization of myocardial scar.


METHODS
MR-MT was performed in 2 cohorts of heart failure patients with: 1) a CRT heart failure cohort (n = 20; left ventricular ejection fraction of 0.23 +/- 0.057) to evaluate the role of MR-MT and DE-CMR prior to CRT; and 2) a multimodality cohort (n = 27; ejection fraction of 0.20 +/- 0.066) to compare MR-MT and tissue Doppler imaging septal-lateral delay for assessment of mechanical dyssynchrony. MR-MT was also performed in 9 healthy control subjects.


RESULTS
MR-MT showed that control subjects had highly synchronous contraction (CURE 0.96 +/- 0.01), but tissue Doppler imaging indicated dyssynchrony in 44%. Using a cutoff of <0.75 for CURE based on receiver-operator characteristic analysis (area under the curve: 0.889), 56% of patients tested positive for mechanical dyssynchrony, and the MR-MT CURE predicted improved function class with 90% accuracy (positive and predictive values: 87%, 100%); adding DE-CMR (% total scar <15%) data improved accuracy further to 95% (positive and negative predictive values: 93%, 100%). The correlation between CURE and QRS duration was modest in all cardiomyopathy subjects (r = 0.58, p < 0.001). The multimodality cohort showed a 30% discordance rate between CURE and tissue Doppler imaging septal-lateral delay.


CONCLUSIONS
The MR-MT assessment of circumferential mechanical dyssynchrony predicts improvement in function class after CRT. The addition of scar imaging by DE-CMR further improves this predictive value.
Department of Medicine, Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Kenneth C
KC
Bilchick
Veronica
V
Dimaano
Katherine C
KC
Wu
Robert H
RH
Helm
Robert G
RG
Weiss
Joao A
JA
Lima
Ronald D
RD
Berger
Gordon F
GF
Tomaselli
David A
DA
Bluemke
Henry R
HR
Halperin
Theodore
T
Abraham
David A
DA
Kass
Albert C
AC
Lardo
D000328:Adult; D000368:Aged; D002921:Cicatrix / Q000473:pathology; D015331:Cohort Studies; D017147:Defibrillators, Implantable; D015150:Echocardiography, Doppler; D005260:Female; D005583:Fourier Analysis; D006333:Heart Failure / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D009206:Myocardium / Q000473:pathology*; D011237:Predictive Value of Tests; D012372:ROC Curve; D020127:Recovery of Function; D012189:Retrospective Studies; D013314:Stress, Mechanical; D013318:Stroke Volume; D016896:Treatment Outcome; D016277:Ventricular Function, Left