Paradoxic decrease in ischemic mitral regurgitation with papillary muscle dysfunction: Insights from three-dimensional and contrast echocardiography with strain rate measurement

Ischemic mitral regurgitation (MR) was first ascribed to papillary muscle (PM) contractile dysfunction. Current theories include apical leaflet tethering caused by left ventricular (LV) distortion, but PM dysfunction is still postulated and commonly diagnosed. PM contraction, however, parallels apic...

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Published in:Circulation (New York, N.Y.) N.Y.), 2001-10, Vol.104 (16), p.1952-1957
Main Authors: MESSAS, Emmanuel, GUERRERO, J. Luis, HANDSCHUMACHER, Mark D, CHOW, Chi-Ming, SULLIVAN, Suzanne, SCHWAMMENTHAL, Ehud, LEVINE, Robert A
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Cardiology. Vascular system
Coronary heart disease
Disease Models, Animal
Echocardiography - methods
Echocardiography, Doppler
Echocardiography, Three-Dimensional
Heart
Heart Conduction System - physiopathology
Hemodynamics
Internet
Medical sciences
Mitral Valve Insufficiency - complications
Mitral Valve Insufficiency - physiopathology
Myocardial Contraction - physiology
Myocardial Ischemia - complications
Myocardial Ischemia - physiopathology
Papillary Muscles - physiopathology
Sheep
Stress, Mechanical
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Summary:Ischemic mitral regurgitation (MR) was first ascribed to papillary muscle (PM) contractile dysfunction. Current theories include apical leaflet tethering caused by left ventricular (LV) distortion, but PM dysfunction is still postulated and commonly diagnosed. PM contraction, however, parallels apical tethering, suggesting the hypothesis that PM contractile dysfunction can actually diminish MR due to ischemic distortion of the inferior base alone. We therefore occluded the proximal circumflex circulation in 7 sheep while maintaining PM perfusion, confirmed by contrast echocardiography. By 3D echocardiography, we measured the tethering distance between the ischemic medial PM tip and anterior annulus and LV ejection volume to give MR (by subtracting flowmeter LV outflow). In 6 sheep without initial MR, inferior ischemia alone produced PM tip retraction with restricted leaflet closure and mild-to-moderate MR (regurgitant fraction, 25.2+/-2.8%). Adding PM ischemia consistently decreased MR and tethering distance (5.2+/-0.3 to 1.4+/-0.3 mL; +3.8+/-0.5 mm to -2.2+/-0.7 mm axially relative to baseline; P
ISSN:0009-7322
1524-4539
DOI:10.1161/hc4101.097112