Slow wall motion rather than electrical conduction delay underlies mechanical dyssynchrony in postinfarction patients with narrow QRS complex.
BACKGROUND
The mechanism of mechanical dyssynchrony in postinfarction patients with a narrow QRS complex is not defined but essential for cardiac resynchronization therapy (CRT).


RESULTS
Left ventricular electrical activation and subsequent wall motion were recorded for 16 patients with ischemic cardiomyopathy during intrinsic rhythm using a modified NOGA electromechanical mapping system. Ten patients presented mechanical dyssynchrony on tissue Doppler imaging, while 6 patients served as control subjects. The local activation time (LAT) was set by the maximum downslope of the unipolar electrogram. Local wall motion time (LMT) was defined as the time needed for the catheter tip to traverse half of its maximum inward deflection during systole. LAT and LMT were measured relative to the onset of the QRS complex. Electrical activation showed a septal-to-lateral pattern in all patients with a mean endocardial activation time of 65 +/- 13 ms. Control subjects exhibited 97.5% of all LMTs <290 +/- 17 ms. Delayed motion areas (cut-off LMT > 300 ms) showed no slowing of conduction. Wall motion time corrected for differences in electrical activation (LMT-LAT) was significantly longer in delayed (289 +/- 34 ms) than in regular (204 +/- 24 ms) motion areas (P = 0.002). Delayed motion segments were hypokinetic on echocardiography and presented a lower maximum inward motion (9.9 +/- 1.1 mm) compared to regular segments (10.9 +/- 1.2 mm) on electromechanical maps (P = 0.004). Viability, however, was preserved with unipolar and bipolar voltage amplitude >7 mV and >1.5 mV for 79% of all delayed motion areas.


CONCLUSIONS
Dyssynchronous segments of an ischemic myocardium show unimpaired local activation but slow wall motion, thereby limiting the benefit of ventricular preexcitation via CRT.
Klemm
Hanno U
HU
Department of Cardiology, University Heart Center Hamburg, Hamburg, Germany. h.klemm@uke.uni-hamburg.de
Krause
Korff T
KT
Ventura
Rodolfo
R
Schneider
Carsten
C
Aydin
Muhammat A
MA
Johnsen
Christin
C
Boczor
Sigrid
S
Meinertz
Thomas
T
Morillo
Carlos A
CA
Kuck
Karl-Heinz
KH
D001145:Arrhythmias, Cardiac / Q000150:complications / Q000175:diagnosis; D018780:Body Surface Potential Mapping / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications* / Q000175:diagnosis*; D015203:Reproducibility of Results; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis* / Q000209:etiology*