Left ventricular shape: A factor in the etiology of functional mitral regurgitation in heart failure The relationship between left ventricular (LV) shape and functional mitral regurgitation (MR) was examined in 18 dogs with long-standing heart failure produced by multiple sequential intracoronary microembolirations. Global LV shape changes were evaluated from angiographic silhouettes obtained at baseline (before embolization) and during heart failure. LV shape changes at end systole and end diastole were quantitated based upon the ratio of the major-to-minor axis and the sphericity index. Among the 18 dogs studied, 11 developed 1 + to 3+ MR during heart failure and seven did not. There was no difference among the two groups with respect to hemodynamics, LV ejection fraction, chamber volume, and regional wall motion. A significant difference, however, was observed between the two groups with respect to the global indexes of LV shape. In dogs with MR, the end-systolic major-to-minor axis ratio decreased 29 + 3% between baseline and heart failure compared with only a 18 + 3% decrease in dogs without MR (p < 0.01). In dogs with MR, the end-systolic sphericity index increased 72 r 11% between baseline and heart failure compared with an increase of only 30 t 5% in dogs without MR (p < 0.02). Significant and directionally similar differences were observed during end diastole. These data indicate that in heart failure functional MR is associated with a more spherical LV and is not the result of simple LV chamber enlargement. Shape changes of the LV that occur in heart failure may be an important determinant of functional MR. (AM HEARTJ 1992;123:981.)

Hani N. Sabbah, PhD, Tatsuji Kono, MD, Howard Rosman, MD, Syed Jafri, MD, Paul D. Stein, MD, and Sidney Goldstein, MD, Detroit, Mich.

Functional mitral regurgitation (MR) is frequently observed in patients with congestive heart failure. The mechanisms responsible for this valvular incompetence are not fully understood. Functional MR is often attributed to the presence of left ventricular (LV) dilatation. Ventricular chamber enlargement is thought to induce a retraction of the mitral valve leaflets by the chordae tendineae and the papillary muscles, leading to incomplete coaptation of the valvular leaflets and the development of MR.l Ventricular dilatation, however, can cause alterations in many of the anatomic elements that make up the mitral valve complex, any one of which can lead to regurgitation. In addition to an increase of LV chamber size, the functional integrity of the mitral apparatus can be influenced by the derangement of any one of several anatomic components of the mitral valve apparatus including left atria1 enlargement, dilatation of the mitral anulus, elongation of the From the Henry cular Medicine. Received Reprint Grand

Ford

for publication

Heart May

and Vascular 9, 1991;

requests: Hani N. Sabbah, Blvd., Detroit, MI 48202.

4/l/35359

PhD,

Institute, accepted Henry

Division Sept. Ford

of Cardiovas-

16, 1991. Hospital,

2799

West

chordae tendineae, and dysfunction of the papillary muscle and the free wall of the LV.2 Echocardiographic studies by Boltwood et a1.3 in patients with dilated cardiomyopathy have focused attention on the dilatation of the mitral valve anulus as a primary mechanism of functional MR. In their study, patients with auscultatory evidence of MR showed a marked increase in mitral valve area, mitral annular area, and left atria1 volume compared with patients without auscultatory evidence of mitral incompetence.3 Other studies,4-6 however, have failed to show a good correlation between the presence of functional MR and mitral annular dilatation. Bulkley and Robert@ suggested that mitral annular dilatation is a rare cause of functional MR. A cross-sectional echocardiographic study by Chandraratna and Aronow6 showed that dilatation of the mitral valve annular ring can occur in patients with dilated cardiomyopathy but does not correlate with the presence of functional MR. Perloff and Roberts2 proposed a different mechanism to explain the means by which LV enlargement can lead to mitral valve incompetence. These investigators speculated that alterations in the shape of the LV may be important determinants of functional MR. The present study expands on this concept by providing data that support 961

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962

Sabbah et al.

Table I. Hemodynamic, angiographic, with and without mitral regurgitation

and neurohormonal

measurements Baseline

Dogs without

MR

MR

Mitral

*p = probability

regurgitation; relative

heart failure

failure

in dogs

P

61 63

+ 2 f 5

25 Z!I 3 6+1 3.0 k 0.4 2300 + 200 350

i

14

21 i 101 t 79 t

5 10 9

21 * 2.2 -t2800 t 674 +

4 0.2 170 144