Altered mitral valve kinematics with atrioventricular and ventricular pacing.
OBJECTIVE
Pacing-induced mitral regurgitation contributes to the 'pacemaker syndrome', which usually is observed with ventricular (V) pacing, but has also been reported with atrioventricular (AV) sequential pacing. Effects of different pacing modes on 3-D kinematics of the mitral apparatus are incompletely understood.


METHODS
Radio-opaque markers were placed on the left ventricular (LV) and mitral apparatus including the annulus, leaflets and papillary muscles of eight sheep. Hemodynamic and 3-D dynamic marker geometry were obtained one week later with biplane videofluoroscopy (60 Hz) during atrial (pacing site = left atrium), AV-sequential (140 ms interval) and (anterolateral LV epicardial) ventricular pacing.


RESULTS
Compared with A-pacing (*p <0.05): 1) The regurgitant fraction increased with both AV- and V-pacing (A: 6 +/- 3%, AV: 13 +/- 3%*, V: 15 +/- 2%*); 2) AV and V-pacing delayed closure at the leaflet center (A: 21 +/- 10 ms, AV: 52 + 5 ms*, V: 92 +/- 6 ms*) and posterior commissure (A: 17 +/- 10 ms, AV: 46 +/- 8 ms*, V: 94 +/- 6 ms*). V-pacing delayed valve closure at the anterior commissure (A: 27 +/- 9 ms, V: 94 +/- 6 ms*); 3) The end-diastolic leaflet opening angle was greater with AV- and V-pacing (anterior mitral leaflet (AML): A: 32 +/- 2 degrees, AV: 41 +/- 4 degrees*, V: 46 +/- 4 degrees*; posterior mitral leaflet (PML): A: 56 +/- 4 degrees, AV: 62 +/- 3 degrees*, V: 68 +/- 3 degrees*); 4) 'Effective' end-diastolic PML midline length was reduced with AV- and V-pacing (A: 11.2 +/- 0.7 mm, AV: 10.0 +/- 0.4 mm*, V: 10.2 +/- 0.3 mm*), as was the distance from each papillary muscle (PM) tip to the AML edge ('effective' chordal length) close to the commissures (anterior PM-AML: A: 31.5 +/-1.8 mm, AV: 30.5 +/- 1.9 mm*, V: 29.7 +/- 1.8 mm*; posterior PM-AML: A: 33.7 +/- 1.8 mm, AV: 33.1 +/- 1.9 mm*, V: 32.8 +/- 1.9 mm*).


CONCLUSIONS
Both ventricular and AV-sequential-pacing resulted in a more widely opened valve at end-diastole and leaflet dyssynchrony with delayed mitral valve closure and early systolic mitral regurgitation. These alterations which result in pacing-induced mitral regurgitation may be clinically important in patients with impaired LV function.
Department of Cardiovascular and Thoracic Surgery, Stanford University School of Medicine, Stanford, California 94305-5247, USA.
Frank
F
Langer
Frederick A
FA
Tibayan
Filiberto
F
Rodriguez
Tomasz
T
Timek
Mary K
MK
Zasio
David
D
Liang
George T
GT
Daughters
Neil B
NB
Ingels
D Craig
DC
Miller
D000818:Animals; D001283:Atrioventricular Node / Q000503:physiopathology; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects / Q000379:methods*; D002306:Cardiac Volume / Q000502:physiology; D002815:Chordae Tendineae / Q000503:physiopathology; D002933:Cineradiography / Q000379:methods; D003971:Diastole; D006339:Heart Rate / Q000502:physiology; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D008943:Mitral Valve / Q000503:physiopathology*; D008944:Mitral Valve Insufficiency / Q000209:etiology; D010210:Papillary Muscles / Q000503:physiopathology; D012756:Sheep; D013318:Stroke Volume / Q000502:physiology; D013577:Syndrome; D016277:Ventricular Function, Left / Q000502:physiology; D017725:Ventricular Pressure / Q000502:physiology