Dual-dye optical mapping after myocardial infarction: does the site of ventricular stimulation alter the properties of electrical propagation?
BACKGROUND
Myocardial infarction (MI) disrupts electrical conduction in affected ventricular areas. We investigated the effect of MI on the regional voltage and calcium (Ca) signals and their propagation properties, with special attention to the effect of the site of ventricular pacing on these properties.


METHODS
New Zealand White rabbits were divided into four study groups: sham-operated (C, n = 6), MI with no pacing (MI, n = 7), MI with right ventricular pacing (MI + RV, n = 6), and MI with BIV pacing (MI + BIV, n = 7). At 4 weeks, hearts were excised, perfused, and optically mapped. As previously shown, systolic and diastolic dilation of the LV were prevented by BIV pacing, as was the reduction in LV fractional shortening.


RESULTS
Four weeks after MI, optical mapping revealed markedly reduced action potential amplitudes and conduction velocities (CV) in MI zones, and these increased gradually in the border zone and normal myocardial areas. Also, Ca transients were absent in the infarcted areas and increased gradually 3-5 mm from the border of the normal zone. Neither BIV nor RV pacing affected these findings in any of the MI, border, or normal zones.


CONCLUSIONS
MI has profound effects on the regional electrical and Ca signals and on their propagation properties in this rabbit model. The absence of differences in these parameters by study group suggests that altering the properties of myocardial electrical conduction and Ca signaling are unlikely mechanisms by which BIV pacing confers its benefits. Further studies into the regional, cellular, and molecular benefits of BIV pacing are therefore warranted.
Saba
Samir
S
Cardiovascular Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA. sabas@upmc.edu
Mathier
Michael A
MA
Mehdi
Haider
H
Liu
Tong
T
Choi
Bum-Rak
BR
London
Barry
B
Salama
Guy
G
D000818:Animals; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004396:Coloring Agents; D004562:Electrocardiography / Q000379:methods; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D006329:Heart Conduction System / Q000502:physiology*; D006352:Heart Ventricles / Q000473:pathology; D009203:Myocardial Infarction / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology*; D055095:Optics and Photonics; D011817:Rabbits; D016276:Ventricular Function
D004396:Coloring Agents