Dr. Marta Sitges
Reversal of left ventricular dyssynchrony has recently been addressed as a therapeutic goal in heart failure patients with the advent of cardiac resynchronization therapy (CRT). Its evaluation requires first knowing the normal mechanics of the heart and how pathology changes it.
Dr Derumeaux elegantly summarized the physiology of the normal left ventricular mechanical sequence with electric and mechanical activation starting at the apical subendocardial region with a delay in the timing of electric and mechanical events, larger in the basal than in the apical region. This pattern changes in patients with cardiomyopathy and can be studied with cardiac imaging techniques. Doppler Tissue Imaging (DTI) echocardiography has been widely used to assess dyssynchrony predicting response to CRT when using time differences in peak or onset of myocardial systolic velocity. However, there are still some technical limitations such as the signal noise and the presence of multiple systolic peaks that may limit the reproducibility and clinical application in daily clinical practice as Dr Abraham wisely pointed out. Another way to overcome limitations of DTI velocity analysis is to look at myocardial deformation as proposed by Dr Breithardt either with simple M-mode, DTI derived strain or the newer speckle tracking techniques. He acknowledged that the use of velocity may yield a faster and easier identification of dyssynchrony, but if sequence of activation needs to be analyzed, strain analysis would be more reliable. Dr Voigt gave another stimulating and brilliant insight into the left ventricular complex mechanics, demonstrating that we can measure left ventricular rotation with MRI and echocardiography, the latter being more feasible for CRT patients. Although techniques such as DTI or speckle tracking still have technical limitations, he underscored that left ventricular torsion is a sensitive measure of global dysfunction Finally, left ventricular dyssynchrony may be also assessed during exercise as proposed by Dr Lancellotti since in up to 30% of patients, exercise induces dyssynchrony, while in another 30% it is normalized, maybe helping to select candidates for CRT.
Great efforts have been made to improve knowledge of the complex mechanics of the left ventricle. A complex phenomenon might not be easily simplified in one single parameter. Consequently, assessment of left ventricular dyssynchrony may need a global and comprehensive evaluation, probably including myocardial segmental motion analysis and ventricular rotation at rest and maybe during exercise.
Assessment of left ventricular dysynchrony in cardiac resynchronisation therapy candidates Symposium
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