Determinants of the degree of functional mitral regurgitation in patients with systolic left ventricular dysfunction: A quantitative clinical study

Leaflet concavity: a rapid visual clue to the presence and mechanism of functional mitral regurgitation

Repairing mitral regurgitation (MR) requires an understanding of its mechanism. Evaluating restricted leaflet closure in functional MR is challenging. Tenting area between leaflets and annulus in long-axis (LAX) views correlates with MR, but is positive even in control subjects; in the 4-chamber view, the incomplete mitral leaflet closure (IMLC) tenting pattern may be subtle and variable. We tested the hypothesis that leaflet concavity toward the left atrium in the LAX view, a rapid visual clue indicating abnormal tethering predominantly by intermediate chords, is a strong indicator of functional MR. We reviewed 90 patients: 40 with inferior myocardial infarction and ejection fraction > or = 50%; 40 with global left ventricular dysfunction and ejection fraction < 50%; and 10 control subjects. We assessed leaflet shape (concave or convex toward the left atrium) and maximum systolic proximal MR jet width in the LAX views. To quantify shape, we measured the leaflet concavity area between the anterior leaflet and a line connecting its ends. Conventional IMLC area was also assessed. Patients with leaflet concavity had significantly greater MR than those without this finding (jet width of 4.6 +/- 0.7 vs 0.5 +/- 0.1 mm, P <.0001), indicating mild-moderate versus trace MR, with differences comparable in those with inferior myocardial infarction and left ventricular dysfunction. Leaflet concavity area most strongly predicted MR by multivariate regression (R(2) = 0.7). Conventional IMLC area did not uniquely distinguish patients with or without MR and correlated more weakly with MR (R(2) = 0.30 vs 0.73). Mitral leaflet concavity in the LAX view provides rapid and reliable recognition of functional MR, with greater reliability than IMLC area. This shape, consistent with tethering by intermediate chords, may have implications for potential intervention.

Determinants of exercise-induced changes in mitral regurgitation in patients with coronary artery disease and left ventricular dysfunction

OBJECTIVES

We sought to examine the determinants of exercise-induced changes in ischemic mitral regurgitation (MR) in patients with left ventricular (LV) dysfunction.

BACKGROUND

In the post-myocardial infarction (MI) phase, ischemic MR contributes to worsening of symptoms and of LV dysfunction.

METHODS

In this study, 70 patients in the chronic, post-MI phase, with LV ejection fraction <45% and at least mild MR, underwent semi-supine exercise Doppler echocardiography. The effective regurgitant orifice (ERO) of MR was quantified at rest and during exercise. Exercise-induced changes in ERO were compared with changes in mitral deformation and in local and global LV remodeling.

RESULTS

The wide range of exercise-induced ERO changes that were observed was unrelated to the degree of MR at rest (r = 0.20). Effective regurgitant orifice changes correlated best with changes in mitral deformation (i.e., differences in systolic mitral tenting area, systolic annular area, and coaptation height) (p < 0.0001). Posterior displacement of the papillary muscles was associated with larger changes in the ERO in both infarct groups. In patients with inferior MI, a decrease in the ERO was related to improvement in wall motion (r = 0.68). The independent predictors of ERO changes during exercise were changes in systolic annular area for all infarct categories, in tenting area and wall motion score in the global population and those with inferior infarction, and in apical displacement of mitral leaflets for patients with anterior MI.

CONCLUSIONS

The degree of MR at rest is unrelated to exercise-induced changes in EROs, which are related to those in local LV remodeling and in mitral deformation but not those in global LV function.

Annuloplasty ring selection for chronic ischemic mitral regurgitation: lessons from the ovine model

BACKGROUND

Chronic ischemic mitral regurgitation (CIMR) is poorly understood and repair operations are often unsatisfactory. This study elucidates the mechanism of CIMR in an ovine model.

METHODS

Sonomicrometry array localization measured the three-dimensional geometry of the mitral annulus and subvalvular apparatus in five sheep before and 8 weeks after a posterior infarction of the left ventricle that produced progressive severe CIMR.

RESULTS

End systolic annular area increased from 647 +/- 44 mm(2) to 1,094 +/- 173 mm(2) (p = 0.01). Annular dilatation occurred equally along the anterior (47.0 +/- 5.6 mm to 60.2 +/- 4.9 mm, p = 0.001) and posterior (53.8 +/- 3.1 mm to 68.5 +/- 8.4 mm, p = 0.005) portions of the annulus. The tip of the anterior papillary muscle moved away from both the anterior and posterior commissures by 5.2 +/- 3.2 mm (p = 0.021) and 7.3 +/- 2.2 mm (p = 0.002), respectively. The distance from the tip of the posterior papillary muscle to the anterior commissure increased by 11.0 +/- 5.7 mm (p = 0.032) while the distance from the tip of the posterior papillary muscle to the posterior commissure remained constant.

CONCLUSIONS

Progressive dilatation of both the anterior and posterior mitral annuli, increased annular area, and asymmetric ventricular dilatation combine to cause CIMR by distortion of mitral valve geometry and tethering of leaflet coaptation. Therefore complete ring annuloplasty may be superior to partial annuloplasty in the treatment of CIMR.

[Physiopathology and etiology of mitral insufficiency]

Mitral regurgitation has a complex pathophysiology. It should be assessed from the study of factors influencing regurgitant volume and the evaluation of hemodynamics effects downstream (impact on left ventricular function) and upstream (level of left atrial compliance and pulmonary pressure). The regurgitant volume is larger when the regurgitation time is longer, the regurgitant orifice is bigger and the magnitude of the left ventrico-atrial systolic gradient higher. The study of left ventricular function is difficult, especially in chronic mitral regurgitation where the apparently normal left ventricular systolic function can hide a significant worsening in myocardiacs fibres contractile abilities. With the increase in life expectancy and with the decrease in the incidence of rheumatic fever, aetiologies of mitral regurgitation have changed in the past 30 years. They are now dominated by dystrophic mitral regurgitation and infective endocarditis while rheumatic fever becomes less frequent.

Left ventricular restoration for ischemic cardiomyopathy--comparison of presence and absence of mitral valve procedure

OBJECTIVE

Association of mitral regurgitation (MR) with ischemic cardiomyopathy (ICM) increases the degree of heart failure and its surgical management remains controversial. The aim of this study was to report the surgical results in patients with or without MR in association with ICM.

PATIENTS AND METHODS

Ninety-two patients with ischemic cardiomyopathy (left ventricular [LV] ejection fraction less than 30% with global akinesis) underwent LV restoration. Pre-operative New York Heart Association (NYHA) functional class was either in class-3 or -4 in all patients. MR was moderate to severe in 38 patients (MR-group) and none or mild in 54 patients (noMR-group). Moderate to severe MR was repaired in addition to the complete coronary artery bypass (CABG) and LV restoration. All patients were followed up and echocardiogram was repeated every 6 months after the surgery.

RESULTS

The procedure of LV restoration was selected pre- and intra-operative examination and endoventricular circular patch plasty was performed in 76, partial left ventricle resection in three, and septal anterior exclusion in 13. CABG was performed in 85 patients with mean 2.4+/-1.1 grafts in MR-group and 3.2+/-0.4 grafts in noMR-group (P<0.0001). In MR-group mitral valve plasty was performed in 24 and replacement in 14. Undersized (26 or 28 mm) circumferential mitral ring was used in 16 patients for mitral plasty. Emergent operation required in 15 patients (13 in MR-group and two in noMR group) and the hospital mortality was 18.4% in MR-group and 3.7% in no MR-group. Mitral regurgitation recurred in two patients with posterior ring annuloplasty and they underwent valve replacement. The post-operative NYHA functional class improved to class-1 or -2 in 65 patients and cumulative survival in 5 years including emergent and hospital deaths was 60.9% in MR-group and 70.1% in noMR-group.

CONCLUSION

In association of MR to ICM, emergent operation required more often and perioperative mortality rate was high. However, the aggressive combined mitral operation in addition to CABG and LV restoration showed the improvement of clinical symptom and quality of life after the surgery.

[Determinants and prognosis of ischemic mitral regurgitation]

Ischemic mitral regurgitation (IMR) is mitral regurgitation (MR) due to complications of coronary artery disease. Two mechanisms can be individualized. Acute MR secondary to ruptured papillary muscle is a rare but often fatal complication of myocardial infarction. We focus on functional MR, much more common, which occurs without any intrinsic valve disease. It was often underrated because of low murmur intensity but is observed between 15 and 20% after a myocardial infarction. The presence and degree of the regurgitation are related to local left ventricular remodeling. The apical and posterior displacement of papillary muscles leads to excess valvular tenting which in turn, in association with loss of systolic annular contraction, determines the severity of the regurgitation. IMR presence is associated with an excess mortality. The mortality risk is directly related to the degree of the regurgitation and a regurgitant volume > or = 30 ml or an effective regurgitant orifice > or = 20 mm2 define a high-risk group. In current clinical practice, IMR is mainly corrected with ring annuloplasty. However, this technique does not correct local alterations of left ventricular remodeling and its benefits on long-term outcome remains to be demonstrated.

[Use of echocardiography in mitral regurgitation for the assessment of its mechanism and etiology for the morphological analysis of the mitral valve]

Echocardiographic assessment of mitral regurgitation allows the diagnosis of its mechanism and cause which are major determinants in the feasibility of mitral valve repair. This assessment is based on a systematic analysis of the different structures of the mitral valve apparatus: mitral annulus (enlargement, calcification), mitral valve morphology (thickening, calcification, floppy valve, vegetations, perforation), mitral valve motion (restriction, identification of the prolapsed leaflets and scallops in patients with mitral valve prolapse or flail leaflets), subvalvular apparatus (ruptured chordae, thickening), papillary muscles, and left ventricular wall. This analysis can diagnose the mechanism of mitral regurgitation according to the Carpentier classification, and can clarify its cause: degenerative lesions (prolapse or flail leaflet with or without ruptured chordae), rheumatic lesions (thickened valves with restricted motion), endocarditis (vegetations, perforation, ruptured chordae), ischemic mitral regurgitation (restricted valve motion with inferior or posterior left ventricular wall asynergy), or functional mitral regurgitation (annular dilatation, displacement of papillary muscles with restricted leaflet motion). Transthoracic echocardiography with harmonic imaging usually allows a comprehensive assessment of functional anatomy of mitral regurgitation. Transesophageal echocardiography is indicated if transthoracic echocardiography is inadequate. It is also indicated just before surgery and as an intraoperative procedure. Real time 3D echocardiography should probably complete the evaluation of mitral regurgitation in the near future.

Acute effects of cardiac resynchronization therapy on functional mitral regurgitation in advanced systolic heart failure

OBJECTIVES

We studied the acute effects of cardiac resynchronization therapy (CRT) on functional mitral regurgitation in heart failure (HF) patients with left bundle branch block (LBBB).

BACKGROUND

Both an decrease [corrected] in left ventricular (LV) closing force and mitral valve tethering have been implicated as mechanisms for functional mitral regurgitation (FMR) in dilated hearts. We hypothesized that an increase in LV closing force achieved by CRT could act to reduce FMR.

METHODS

Twenty-four HF patients with LBBB and FMR were studied after implantation of a biventricular CRT system. Acute changes in FMR severity between intrinsic conduction (OFF) and CRT were quantified according to the proximal isovelocity surface area method by measuring the effective regurgitant orifice area (EROA). Results were compared with the changes in estimated maximal rate of left ventricular systolic pressure rise (LV+dP/dt(max)) and transmitral pressure gradients (TMP), both measured by Doppler echocardiography.

RESULTS

Cardiac resynchronization therapy was associated with a significant reduction in FMR severity. Effective regurgitant orifice area decreased from 25 +/- 19 mm(2) (OFF) to 13 +/- 8 mm(2) (CRT). The change in EROA was directly related to the increase in LV+dP/dt(max) (r = -0.83, p < 0.0001). Compared with OFF, TMP increased more rapidly during CRT, and a higher maximal TMP was observed (OFF 73 +/- 24 mm Hg vs. CRT 85 +/- 26 mm Hg, p < 0.01).

CONCLUSIONS

Functional mitral regurgitation is reduced by CRT in patients with HF and LBBB. This effect is directly related to the increased closing force (LV+dP/dt(max)). The results support the hypothesis that an increase in TMP, mediated by a rise in LV+dP/dt(max) due to more coordinated LV contraction, may facilitate effective mitral valve closure.

Ischemia in three left ventricular regions: Insights into the pathogenesis of acute ischemic mitral regurgitation

BACKGROUND

Acute posterolateral left ventricular ischemia in sheep results in ischemic mitral regurgitation, but the effects of ischemia in other left ventricular regions on ischemic mitral regurgitation is unknown.

METHODS

Six adult sheep had radiopaque markers placed on the left ventricle, mitral annulus, and anterior and posterior mitral leaflets at the valve center and near the anterior and posterior commissures. After 6 to 8 days, animals were studied with biplane videofluoroscopy and transesophageal echocardiography before and during sequential balloon occlusion of the left anterior descending, distal left circumflex, and proximal left circumflex coronary arteries. Time of valve closure was defined as the time when the distance between leaflet edge markers reached its minimum plateau, and systolic leaflet edge separation distance was calculated on the basis of left ventricular ejection.

RESULTS

Only proximal left circumflex coronary artery occlusion resulted in ischemic mitral regurgitation, which was central and holosystolic. Delayed valve closure (anterior commissure, 58 +/- 29 vs 92 +/- 24 ms; valve center, 52 +/- 26 vs 92 +/- 23 ms; posterior commissure, 60 +/- 30 vs 94 +/- 14 ms; all P <.05) and increased leaflet edge separation distance during ejection (mean increase, 2.2 +/- 1.5 mm, 2.1 +/- 1.9 mm, and 2.1 +/- 1.5 mm at the anterior commissure, valve center, and posterior commissure, respectively; P <.05 for all) was seen during proximal left circumflex coronary artery occlusion but not during left anterior descending or distal left circumflex coronary artery occlusion. Ischemic mitral regurgitation was associated with a 19% +/- 10% increase in mitral annular area, and displacement of both papillary muscle tips away from the septal annulus at end systole.

CONCLUSIONS

Acute ischemic mitral regurgitation in sheep occurred only after proximal left circumflex coronary artery occlusion along with delayed valve closure in early systole and increased leaflet edge separation throughout ejection in all 3 leaflet coaptation sites. The degree of left ventricular systolic dysfunction induced did not correlate with ischemic mitral regurgitation, but both altered valvular and subvalvular 3-dimensional geometry were necessary to produce ischemic mitral regurgitation during acute left ventricular ischemia.

Papillary muscle sling: a new functional approach to mitral repair in patients with ischemic left ventricular dysfunction and functional mitral regurgitation

BACKGROUND

In patients with ischemic left ventricular dysfunction (LVD) and functional mitral regurgitation (FMR), restoring a more normal alignment between mitral annulus and laterally displaced papillary muscles (PM) may be beneficial in terms of mitral repair and regional dynamics.

METHODS

Ten patients, 29 to 78 years old, with an ejection fraction of 25% to 45%, pulmonary hypertension greater than 60, and New York Heart Association Class III-IV, had their PMs drawn together by a tightly encircling loop using a 4-mm Gore-Tex tube. Associated mitral annuloplasty rings were only moderately undersized. Efficiency was essentially evaluated on reversal of mitral tenting and control of FMR.

RESULTS

Postoperative echocardioraphy revealed changes in "tenting effect" from 14 +/- 2.8 mm to 4 +/- 1.41 mm. Regurgitation is none to trivial in 9 patients, and mild in 1 patient. The posterior left ventricular wall between the PMs is shortened as a result of the surgical remodeling and may be beneficial on local dynamics.

CONCLUSIONS

Joining the PM side-by-side has an obvious immediate effect on mitral leaflet mobility by suppressing the tethering due to displacement of the PM. An eventual result on local ventricular dynamics needs confirmation.

Trends in the surgical management of ischemic mitral regurgitation

The surgical approach to ischemic mitral regurgitation (IMR) remains a topic of considerable controversy. Will coronary artery bypass alone suffice, or should the valve be intervened upon? The poor late survival of patients with IMR is well recognized, but it remains unknown if this can be altered by addressing the valve directly. And if surgery is undertaken, should the valve be repaired or replaced? The underlying mechanisms of IMR remain incompletely understood, and although current theory focuses on the role of alterations in ventricular geometry in its pathogenesis, IMR is most often addressed by annuloplasty alone. Is this sufficient, or does the ventricle itself require "remodeling?" The debate is confounded by imprecise terminology that fails to distinguish between acute and chronic disease, and active ischemia from completed infarction. Available clinical information is from retrospective studies with all of their inherent limitations and potential for bias. Still, progress is being made as increasing attention is focused on this clinically important entity.

Determinants of the development of mitral regurgitation in pacing-induced heart failure

The pacing-induced heart failure model provides an opportunity to assess the structural and functional determinants of mitral regurgitation (MR) in dilated cardiomyopathy. This study aimed to evaluate MR to better understand the multitude of factors contributing to its development. Heart failure was induced by rapid ventricular pacing (230 beats/min) in 40 mongrel dogs. Left ventricular (LV) size and MR were evaluated echocardiographically. LV contractility was analyzed using a conductance catheter. MR increased to mild in 12 animals (regurgitant orifice area, 0.06+/-0.05 cm(2)), moderate in 15 (0.14+/-0.07 cm(2)), and severe in 13 (0.34+/-0.16 cm(2)). The grade of MR had an inverse relationships with E(max) (the slope of the end-systolic pressure-volume relationship, p<0.01) and dE/dt (the slope of the maximum rate of change of pressure-end-diastolic volume [V(ED)] relationship, p<0.01) and positive relationships with V(ED) and end-diastolic cross-sectional areas and lengths (p<0.05) by univariate analysis. The dE/dt had an independently significant (p<0.01) relationship by multivariable logistic regression. Many factors influence the development of MR and because of its similarity to the clinical situation, this model can be used to investigate MR and heart failure, as well as new surgical therapies.

Mechanism of higher incidence of ischemic mitral regurgitation in patients with inferior myocardial infarction: quantitative analysis of left ventricular and mitral valve geometry in 103 patients with prior myocardial infarction

OBJECTIVE

The mechanism of higher incidence of ischemic mitral regurgitation in patients with inferior compared with anterior myocardial infarction despite less global left ventricular remodeling and dysfunction is controversial. We hypothesized that inferior myocardial infarction causes left ventricular remodeling, which displaces posterior papillary muscle away from its normal position, leading to ischemic mitral regurgitation.

METHODS

In 103 patients with prior myocardial infarction (61 anterior and 42 inferior) and 20 normal control subjects, we evaluated the grade of ischemic mitral regurgitation on the basis of the percentage of Doppler jet area, left ventricular end-diastolic and end-systolic volumes, midsystolic mitral annular area, and midsystolic leaflet-tethering distance between papillary muscle tips and the contralateral anterior mitral annulus, which were determined by means of quantitative echocardiography.

RESULTS

Global left ventricular dilatation and dysfunction were significantly less pronounced in patients with inferior myocardial infarction (left ventricular end-systolic volume: 52 +/- 18 vs 60 +/- 24 mL, inferior vs anterior infarction, P<.05; left ventricular ejection fraction: 51% +/- 9% vs 42% +/- 7%, P <.0001). However, the percentage of mitral regurgitation jet area and the incidence of significant regurgitation (percentage of jet area of 10% or greater) was greater in inferior infarction (percentage of jet area: 10.1% +/- 7.5% vs 4.4% +/- 7.0%, P =.0002; incidence: 16/42 (38%) vs 6/61 (10%), P <.0001). The mitral annulus (area = 8.2 +/- 1.2 cm2 in control subjects) was similarly dilated in both inferior and anterior myocardial infarction (9.7 +/- 1.7 vs. 9.5 +/- 2.3 cm2, no significant difference), and the anterior papillary muscle-tethering distance (33.8 +/- 2.6 mm in control subjects) was also similarly and mildly increased in both groups (35.2 +/- 2.4 vs 35.2 +/- 2.8 mm, no significant difference). However, the posterior papillary muscle-tethering distance (33.3 +/- 2.3 mm in control subjects) was significantly greater in inferior compared with anterior myocardial infarction (38.3 +/- 4.1 vs 34.7 +/- 2.9 mm, P =.0001). Multiple stepwise regression analysis identified the increase in posterior papillary muscle-tethering distance divided by body surface area as an independent contributing factor to the percentage of mitral regurgitation jet area (r2 = 0.70, P <.0001).

CONCLUSIONS

It is suggested that the higher incidence and greater severity of ischemic mitral regurgitation in patients with inferior compared with anterior myocardial infarction can be related to more severe geometric changes in the mitral valve apparatus with greater displacement of posterior papillary muscle caused by localized inferior basal left ventricular remodeling, which results in therapeutic implications for potential benefit of procedures, such as infarct plication and leaflet or chordal elongation, to reduce leaflet tethering.

Ischemic mitral regurgitation: intraventricular papillary muscle imbrication without mitral ring during left ventricular restoration

OBJECTIVES

Functional mitral regurgitation in ischemic cardiomyopathy carries a poor prognosis, and its surgical management remains problematic and controversial. The aim of this study was to report the results of our surgical approach to patients who have had myocardial infarctions and have ventricular dilatation, mitral regurgitation, reduced pump function, pulmonary hypertension and coronary artery disease. This surgical approach consists of endoventricular mitral repair without prosthetic ring, ventricular reconstruction with or without patch, and coronary artery bypass grafting.

PATIENTS

Forty-six patients (aged 64 +/- 10 years) with previous anterior transmural myocardial infarction and mitral regurgitation comprised the study group. Indication for surgery was heart failure in 93% of cases; 25 patients were in New York Heart Association functional class IV and 17 were in class III. Mitral regurgitation was moderate to severe in 32 cases (69%).

RESULTS

All patients underwent coronary artery bypass grafting, with a mean of 3.2 +/- 1.3 grafts. Associated aortic valve replacement was performed in 4 cases. Global operative mortality rate was 15.2%. End-diastolic and end-systolic volumes significantly decreased after surgery (from 140 +/- 40 to 98 +/- 36 mL/m(2) and from 98 +/- 32 to 63 +/- 22 mL/m(2), respectively, P =.001). Systolic pulmonary pressure decreased significantly (from 55 +/- 13 to 43 +/- 16 mm Hg, P =.001). Ejection fraction did not change significantly. Postoperative mitral regurgitation was absent or minimal in 84% of cases; 1 patient had severe mitral regurgitation necessitating valve replacement. New York Heart Association functional class significantly improved. The mean preoperative functional class was 3.4 +/- 0.6 (median 3, range 2-4); after the operation, this decreased to 1.9 +/- 0.7 (median 2, range 1-3, P <.001). Cumulative survival at a 30-month follow-up was 63%.

CONCLUSIONS

Our aggressive, combined surgical approach is aimed at correcting the three components of ischemic cardiomyopathy: relieving ischemia, reducing left ventricular wall tension by decreasing left ventricular volumes, and reducing volume overload and pulmonary hypertension by repairing the mitral valve. Despite a relatively high perioperative mortality rate, surviving patients benefitted from the operation, with improved clinical functional class and thus quality of life.

Isolated annular dilation does not usually cause important functional mitral regurgitation: comparison between patients with lone atrial fibrillation and those with idiopathic or ischemic cardiomyopathy

OBJECTIVES

We sought to test whether isolated mitral annular (MA) dilation can cause important functional mitral regurgitation (MR).

BACKGROUND

Mitral annular dilation has been considered a primary cause of functional MR. Patients with functional MR, however, usually have both MA dilation and left ventricular (LV) dilation and dysfunction. Lone atrial fibrillation (AF) can potentially cause isolated MA dilation, offering a unique opportunity to relate MA dilation to leaflet function.

METHODS

Mid-systolic MA area, MR fraction, LV volumes and papillary muscle (PM) leaflet tethering length were compared by echocardiography among 18 control subjects, 25 patients with lone AF and 24 patients with idiopathic or ischemic cardiomyopathy (ICM).

RESULTS

Patients with lone AF had a normal LV size and function but MA dilation (isolated MA dialtion) significant and comparable to that of patients with ICM (MA AREA: 8.0 +/- 1.2 vs. 11.6 +/- 2.3 vs. 12.5 +/- 2.9 cm(2) [control vs. lone AF vs. ICM]; p < 0.001 for both lone AF and ICM). However, patients with lone AF had only modest MR, compared with that of patients with ICM (MR fraction: -3 +/- 8% vs. 3 +/- 9% vs. 36 +/- 25%; p < 0.001 for patients with ICM). Multivariate analysis identified PM tethering length, not MA dilation, as an independent primary contributor to MR.

CONCLUSIONS

Isolated annular dilation does not usually cause moderate or severe MR. Important functional MR also depends on LV dilation and dysfunction, leading to an altered force balance on the leaflets, which impairs coaptation.

Mechanistic insights into functional mitral regurgitation

Effective valve repair in patients with mitral regurgitation (MR) demands an understanding of its mechanism. In patients with ischemic heart disease and functional MR, which doubles late mortality, normal leaflets are apically displaced. This reflects an altered balance of forces acting on the leaflets: increased tethering forces restricting closure, resulting from an altered geometry of leaflet attachments, and decreased ventricular forces acting to close the leaflets. Extensive evidence confirms a central and predominant role of tethering as the final common pathway inducing functional MR; left ventricular (LV) pressure dynamically modulates the orifice area. Because ischemic MR is a disease of the entire mitral complex, including the remodeling LV, reducing annular size alone is often ineffective. Undersizing rings attempts to compensate for tethering; new and potentially more effective strategies directly address tethering by infarct plication, papillary muscle repositioning with a localized patch, or basal chordal cutting to increase coaptational surface area without prolapse. A comprehensive understanding of the valve in its ventricular context, therefore, provides new opportunities for successful valve repair in patients.

Left ventricular remodeling and functional mitral regurgitation: mechanisms and therapy

Myocardial damage that results in dysfunction and remodeling changes left ventricular shape and size. Mitral competence requires the functional integrity of all components of the mitral apparatus. Progressive remodeling ultimately leads to geometric distortion of multiple elements of the mitral apparatus, resulting in functional mitral regurgitation (MR). In this article, we examine the mechanisms of functional MR in the remodeled ventricle. Surgical treatment should aim to correct all abnormalities of the mitral apparatus. These include (1) revascularization of viable myocardium, (2) reduction of ventricular volume and restoration of shape, (3) realignment of papillary muscles, and (4) reduction of annular orifice size.

Experimental and clinical assessment of mitral annular area and dynamics: what are we actually measuring?

The mitral annulus is an essential, dynamic, and tightly coupled component of the mitral valve/left atrial/left ventricular complex that aids in effective and efficient valve closure and unimpeded left ventricular filling. Although the dynamic nature of mitral annular motion has been studied carefully for more than 30 years, accurate measurement of mitral annular area and motion continues to be a challenge for physiologists and clinicians alike. Roentgenographic ciné imaging of radiopaque markers, sonomicrometry, magnetic resonance imaging, and two-dimensional echocardiography have all been used to evaluate mitral annular area and dynamics, yet widely disparate measurements abound. Paradoxically, newer three-dimensional transesophageal echocardiographic findings may have added to this miasma. To explore the variability of these measurements, we reviewed our experimental data as well as clinical and experimental observations reported in the literature to clarify what we are actually measuring and perhaps explain the reported disagreement. The objective was to shed some light on the possible reasons for these discordant findings.

Evaluation of left ventricular function and mitral regurgitation during left ventricular-based pacing in patients with heart failure

BACKGROUND

Beneficial effects of left ventricular (LV)-based pacing on acute hemodynamic parameters were reported in several series, but only a few studies examined the long-term effects of this new pacing procedure.

AIMS

To assess long-term effects of permanent LV-based pacing on LV function and mitral regurgitation (MR) in patients with refractory congestive heart failure (CHF).

METHODS

A prospective evaluation of LV function and MR was performed in 23 patients with severe but stable CHF and left bundle branch block (mean QRS: 186+/-31 ms) by radionuclide and echocardiographic techniques at baseline and 6 months after implantation of a permanent LV-based (LV alone: 13 patients; biventricular: 10 patients) pacemaker programmed either in a DDD mode (sinus rhythm; n=14) or in a VVIR mode (atrial fibrillation; n=9).

RESULTS

Compared to baseline, the 6 months follow-up visit demonstrated a significant increase in radionuclide derived LV ejection fraction from 23.3+/-7 to 26.2+/-7% (P<0.01) and in echocardiographic LV fractional shortening from 13+/-4 to 16+/-6% (P<0.05), without any change in cardiac index, a significant decrease in LV end-diastolic diameter (from 73.2+/-6 to 71.2+/-7 mm; P<0.05), end-systolic diameter (from 63.6+/-6 to 60.2+/-8 mm; P<0.05) and color Doppler MR jet area (from 11.5+/-6 to 6.6+/-4 cm(1); P<0.001). A comparison of patients with LV pacing alone and patients with biventricular pacing showed similar beneficial effects of pacing on MR severity in the two subgroups and a non-significant trend for a better improvement of LV function during biventricular pacing.

CONCLUSION

Thus, in patients with severe CHF and left bundle branch block, permanent LV-based pacing may significantly improve LV systolic function and decrease MR.

Echocardiographic assessment of mitral regurgitation

Although the natural history of mitral regurgitation (MR) is poorly defined, evidence has been found for excess mortality and morbidity in patients with severe MR who are managed conservatively. With improved mortality and morbidity in the surgical management of this condition, we are becoming increasingly aggressive in offering surgery to patients with severe MR. Surgery may be offered even in the absence of symptoms or left ventricular dysfunction, provided that the valve seems reparable, the patient's MR is severe, and the surgical team is experienced in valve repair. Echocardiography is critically important in determining the feasibility of valve repair and accurately assessing the severity of the patient's MR. It also allows assessment of the effect of MR on the left ventricle and the left atrium.

Echocardiographic evaluation of mitral regurgitation

Accurate evaluation of mitral regurgitation (MR) severity remains a challenging task in clinical cardiology. The importance of proper quantification of regurgitation cannot be underestimated because a delayed decision to replace or repair a defective valve may lead to worsening ventricular function and increased perioperative and long-term mortality. In this review we discuss both recent developments in the quantification of MR as well as new insights into the pathophysiology and progression of this lesion.

Mitral ring annuloplasty: an incomplete correction of functional mitral regurgitation associated with left ventricular remodeling

Functional mitral regurgitation (FMR) occurs commonly in patients undergoing left ventricular (LV) remodeling. It is ubiquitous in patients referred to cardiac transplantation for LV systolic dysfunction and predicts a poor prognosis. The LV remodeling that is responsible for FMR is well understood and involves regional LV dysfunction Mitral annular dilatation is present in patients with idiopathic dilated cardiomyopathy but most often absent in patients with ischemic cardiomyopathy. Nonrandomized observations indicate that implantation of a mitral undersized flexible mitral ring reduces the amount of FMR, reverses LV remodeling, and improves symptoms in patients with end-stage cardiomyopathy and severe FMR. Whether a surgical procedure that does not correct the major LV alterations leading to FMR can have long-lasting effects on the amount of FMR and the reversal of LV remodeling remains to be demonstrated in randomized trials.