Force generation and shortening capabilities of left ventricular myocardium in primary and secondary forms of mitral regurgitation

Secondary mitral regurgitation (part 2): deliberations on mitral surgery and transcatheter repair

Secondary mitral regurgitation (MR) develops as a consequence of postinfarction remodelling of the ventricle or other causes of left ventricular (LV) dilatation and dysfunction. The presence of MR amplifies the poor prognosis of the failing ventricle, but it has not been established whether the adverse outcomes stem from the MR or whether the MR is simply a marker of progressive LV dysfunction. In this article, an attempt will be made to clarify the clinical impact of mitral surgery and transcatheter repair in patients with secondary MR. Observational studies indicate symptomatic improvement, but the results of randomised trials are mixed. Furthermore, neither mitral surgery nor transcatheter repair consistently leads to reversal of the adverse LV remodelling. There is, however, general agreement that these procedures do not have a salutary effect on survival. Certainly mitral surgery and transcatheter repair can substantially reduce the mitral regurgitant flow, but inconsistencies and uncertainties regarding clinical outcomes persist in the published literature. Some such problems could be resolved by utilisation of more accurate and reproducible imaging modalities in randomised studies of patients who are most likely to benefit from a reduction in the regurgitant volume—namely those with the most severe MR.

Secondary mitral regurgitation (part 1): volumetric quantification and analysis

Secondary mitral regurgitation (MR) develops as a consequence of left ventricular (LV) dilatation and dysfunction, which complicates its evaluation and management. The goal of this article is to review the assessment of secondary MR with special emphasis on quantification and analysis of LV volume data. At the present time, the optimal method for making these measurements appears to be cardiac MRI. In severe MR (both primary and secondary), the regurgitant fraction (RF) exceeds 50%, and as a result, the LV end diastolic volume (EDV) is increased. In secondary MR, the ejection fraction is depressed (generally <40%) and despite an RF >50%, the regurgitant volume (RegV) rarely meets the current published criteria for severe MR (>60 mL). The ratio of the RegV to EDV, which is very low in secondary MR, reflects the effect of the RegV on the ventricle and it may be predictive of the fractional change in LV size that can be expected after correction of MR. Accurate measurement of the volumetric parameters is essential to proper management of patients with secondary MR.

Tei-index in symptomatic patients with primary and secondary mitral regurgitation

Significant mitral regurgitation (MR) may result from primary valve dysfunction or develop secondary to ischemic or dilated cardiomyopathy. The index 'isovolumic contraction time and isovolumic relaxation time divided by ejection time' (ICT + IRT/ET, 'Tei-index') is a well established measure of global cardiac function in patients with dilated cardiomyopathy and cardiac amyloidosis. We sought to define the diagnostic value of the Tei-index in patients with significant MR of various origin. Sixteen asymptomatic control subjects (8 male (m)/8 female (f), age 62+/-8 years, control group), 12 patients with primary MR (PMR) (mean grade 3.1+/-0.3, due to rupture of the chordae tendineae (n = 2), flail leaflet (n = 1), valve prolapse (n = 6) or rheumatic degeneration (n = 3), 6 m/6 f, age 58+/-18 years, NYHA class 2.5+/-0.3, PMR group) and 25 patients with secondary MR (SMR) (mean grade 3.1+/-0.3; due to ischemic (n = 14) or dilated cardiomyopathy (n = 10), 19 m/6 f, age 60+/-11 years, NYHA class 3.1+/-0.5, SMR group) underwent conventional two-dimensional (2D) and Doppler echocardiographic examination including measurement of the Tei-index. In the SMR group, left ventricular ejection fraction was reduced compared to the control and the PMR group (29+/-13% vs. 59+/-8% and 59+/-8%, p < 0.001 for both comparisons). The E/A ratio was elevated in PMR and SMR groups in comparison to the control group (1.74+/-0.44 and 1.70+/-0.45 vs. 1.09+/-0.28, p < 0.05). The Tei-index was easily and reproducibly measured in all study subjects. The mean value of the index was significantly elevated in the SMR group compared to control and PMR groups (0.87+/-0.3 vs. 0.42+/-0.07 and 0.38+/-0.05, p < 0.001). The difference between the control group and the PMR group did not reach statistical significance. In MR patients, receiver operating characteristic curve analysis for the Tei-index yielded an area under the curve of 0.96+/-0.03 for separating the PMR and the SMR group. Using a Tei-index > 0.51 as a cutpoint, SMR was identified with a sensitivity of 92% and a specificity of 88%. In MR patients, a significant correlation between left ventricular end-systolic volume and the Tei-index was observed (r = 0.71, p < 0.01). The Tei-index is a feasible and sensitive indicator of overall cardiac dysfunction in severely symptomatic patients with significant MR secondary to ischemic or dilated cardiomyopathy. The index is in the normal range in symptomatic patients with PMR and preserved systolic function. The Tei-index differentiates between patients with SMR and PMR and may be useful in the work-up of such patients.

Left ventricular function in chronic mitral regurgitation: preoperative and postoperative comparison

OBJECTIVES

The present study was designed to evaluate the effects of surgical procedure on left ventricular systolic and diastolic function in patients with mitral regurgitation.

BACKGROUND

Left ventricular systolic function has been shown to decline after operation in patients with chronic mitral regurgitation.

METHODS

Using simultaneous cineangiography and left ventricular micromanometry, we evaluated left ventricular systolic and diastolic function in 14 patients with chronic mitral regurgitation both preoperatively and at an average of 22 months after operation. Eight patients underwent mitral valve reconstruction, and six had a valve replacement with interruption of the chordae tendineae. We compared these patients with 10 control subjects.

RESULTS

Preoperatively, patients with mitral regurgitation demonstrated normal global and regional left ventricular systolic function. Peak rate of diastolic filling was increased (p < 0.01), and passive chamber stiffness was decreased, compared with that in control subjects (p < 0.01), and there was normal myocardial stiffness. Postoperatively, systolic and diastolic function returned to normal in patients undergoing mitral valve reconstruction. In contrast, global systolic function was depressed in patients after valve replacement (p < 0.05), with regional dysfunction in the area of papillary muscle attachment (p < 0.01). Diastolic function was depressed in this group, with a prolonged time constant of pressure decay (p < 0.01) and a depressed rate of early diastolic filling and strain rate (p < 0.05). Passive elastic stiffness was within the normal range in all postoperative patients.

CONCLUSIONS

The type of operation performed to correct chronic mitral regurgitation has an important effect on postoperative left ventricular function. Systolic and diastolic function are preserved after mitral valve reconstruction. Mitral valve replacement with chordal interruption is associated with global and regional systolic dysfunction and early diastolic filling and relaxation abnormalities.

The relationship of afterload to ejection performance in chronic mitral regurgitation

Simultaneous left ventricular micromanometry and biplane cineangiography were performed in nine control subjects (group 1), 14 patients with chronic mitral regurgitation and an ejection fraction of 57% or greater (group 2), and 13 patients with mitral regurgitation and an ejection fraction of less than 57% (group 3). End-diastolic volume index was increased in both groups with mitral regurgitation (p less than .001) compared with the control group. Left ventricular end-diastolic wall thickness did not differ among the three groups, but the left ventricular muscle mass index was greater in both groups with mitral regurgitation than in controls (p less than .001). End-diastolic pressure was elevated in both groups 2 and 3 compared with group 1 (p less than .05), but peak systolic, mean systolic, and incisural pressure were not different among the three groups. End-diastolic stress was larger in groups 2 and 3 than in group 1 (p less than .05). Muscle fiber stretch was greater in group 2 than in the control group (p less than .05) but was not different between the controls and group 3. End-systolic stress, determined as the circumferential stress at aortic valve closure, at the maximal pressure/volume ratio, or using a nonsimultaneous method, was larger in group 3 than in groups 1 and 2. Mean systolic stress was evaluated from aortic valve opening to aortic valve closure in all patients; mean stress from end-diastole to aortic valve closure and from end-diastole to minimum volume was assessed in mitral regurgitation alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiographic evaluation of responses to left ventricular volume loading by principal components and nomographic analysis

Changes in performance of left ventricles (LV) with volume overloads are difficult to determine by conventional clinical methods. This information, however, is important for the proper timing of therapeutic interventions to preserve LV function. Seven size-adjusted (by regression with end-diastolic diameter, EDD) LV performance parameters from 100 normal echocardiograms (echos) were entered into a principal component analysis (PCA). Two factors (linear combination of the 7 parameters) were obtained from the analysis. Prediction limits (95%) about these two factors used in combination, correctly classified 92% of the normal echos. More detailed analysis of the two PCA factors revealed that the majority of the variability within the factors was explained by size-adjusted parameters resultant from the EDD posterior wall (factor 1) and EDD septal excursion (factor 2) regressions, respectively. Plots of the 95% prediction limits about these two regression lines provided nomograms. These nomograms used in combination, correctly classified 95% of the normal echos. When the performance parameters of 64 volume loaded ventricles were evaluated by PCA, four groups were identified. Ten ventricles (16%) were hypokinetic, 29 (45%) were hyperkinetic, 23 (36%) were nomokinetic, and 2 (3%) could not be classified. These classifications were supported by significant between group differences of shortening fraction, velocity of circumferential shortening, and velocity of circumferential expansion. Nomographic classification of the same volume loaded hearts was in excellent (94%) agreement with PCA classification. Nomographic analysis (derived from the PCA) is offered as a less complex, more clinically applicable echo method for evaluating LV performance of volume loaded hearts.

Regional left ventricular wall motion abnormalities in chronic volume overload

Computer-assisted analysis of left ventricular (LV) wall motion has been performed in 12 patients (pts) with chronic volume overload and in seven normal subjects. All pts were in sinus rhythm, without congestive heart failure and without coronary artery disease at selective coronary angiography; 30 degrees right anterior oblique ventriculograms were employed in each case. Thirty-six radiants were automatically traced and the percent shortening of each radiant was calculated using two different reference methods (fix and floating methods). In valvular heart disease (VHD) pts LV volumes were significantly increased, and ejection fraction and LV eccentricity were significantly reduced. LV eccentricity inversely correlated with LV volumes. VHD pts showed regional LV abnormalities. Inferoapical and anterior wall motion was significantly reduced (two-sample t-test P less than 0.05) using the fix method. With this method a significant inverse correlation between percent shortening of the radiants correspondent to the inferoapical region and end-diastolic and end-systolic volumes was found; a significant direct correlation was found with LV systolic eccentricity. Ejection fraction directly correlated with the percent shortening of radiants correspondent to both the anterior and inferior regions. The role of LV "dynamic geometry" alterations as a possible cause for the observed regional LV wall motion abnormalities is emphasized.

Left ventricular regional wall motion and velocity of shortening in chronic mitral and aortic regurgitation

Left ventricular regional wall motion (percent systolic shortening) and velocity of shortening were studied in patients with heart failure due to chronic volume overloads of mitral and aortic regurgitation. Biplane left ventriculograms were analyzed by computer and divided into four regions: anterior, inferior, posterolateral and septal. The study patients included 12 normal subjects; 21 patients with aortic regurgitation (10 asymptomatic and 11 with congestive heart failure); and 11 patients with mitral regurgitation (4 asymptomatic and 7 with congestive heart failure). No patient had coronary artery disease. With heart failure, ejection fraction was decreased (p less than 0.05) in both aortic and mitral regurgitation (normal 62 +/- 3 percent [mean +/- standard error of the mean], aortic regurgitation 48 +/- 3 and mitral regurgitation 51 +/- 5). In mitral regurgitation with heart failure, the percent segment shortening in anterior (normal 42 +/- 2, mitral regurgitation 27 +/- 5) and posterolateral (normal 23 +/- 3, mitral regurgitation 16 +/- 4) regions was significantly decreased (p less than 0.05), whereas this value in the inferior (normal 32 +/- 2, mitral regurgitation 28 +/- 6) and septal (normal 46 +/- 4, mitral regurgitation 47 +/- 5) regions was normal. In aortic regurgitation with heart failure, anterior (27 +/- 2), inferior (17 +/- 3) and septal (5 +/- 1) segment shortening was significantly decreased, whereas posterolateral segment shortening was significantly decreased, whereas posterolateral segment shortening was normal (24 +/- 3). In both groups with heart failure, mean shortening velocity showed regional variations similar to those of percent shortening, whereas peak instantaneous shortening velocity was not reduced in mitral regurgitation compared with normal values. In the asymptomatic group, shortening and mean shortening velocity were normal, whereas peak instantaneous shortening velocity was increased in mitral regurgitation. In aortic and mitral regurgitation with decreased left ventricular function demonstrated by a reduced ejection fraction, there are regional wall motion abnormalities that are not caused by coronary disease.

Current status of radionuclide imaging in valvular heart disease

In valvular heart disease, there is a different radionuclide angiographic pattern in each of three left-sided valve abnormalities: pressure overload (aortic stenosis), volume overload (aortic or mitral regurgitation) and inflow obstruction (mitral stenosis). In pressure overload, the left ventricle is usually normal in size or minimally dilated. The ejection fraction may be normal, increased or decreased. In volume overload, there is left ventricular dilatation with a normal or reduced ejection fraction at rest. Scans may be performed during exercise to unmask abnormalities of ventricular function not evident at rest. In inflow obstruction, left ventricular function is usually normal but may be depressed. Right ventricular function may be abnormal secondary to pulmonary hypertension. Radionuclide angiography in valvular heart disease evaluates the impact of the valve abnormality on cardiac chamber size and function, which is useful in managing the patient, in determining the prognosis and in evaluating the success of valve surgery. Thallium-2-1 imaging evaluates regional myocardial blood flow and cell integrity and can be used to assess associated coronary artery disease.

Echocardiographic findings in different types of mitral regurgitation

Forty-eight patients with mitral regurgitation were studied by echocardiography to establish differential diagnostic features. Six patients with rheumatic mitral insufficiency manifested broad and bright echoes from the anterior mitral leaflets and slowed EF slopes. In the majority of patients with prolapse of the mitral valve leaflets due to rupture or redundancy of the chordae tendineae, a posterior sagging of the CD portion of the thin mitral leaflet echoes was evident. Cases with anterior leaflet rupture revealed increased rate and amplitude of anterior cusp opening with a spiked E point. Eight patients with posterior ruptured chordae tendineae were noted to have a paradoxical diastolic anterior motion of the posterior mitral leaflet. Eight instances of mitral insufficiency due to papillary muscle dysfunction manifested a flat CD segment and characteristic double diamond-shaped pattern of the leaflets, lying within an enlarged left ventricular cavity. In two patients with mitral insufficiency associated with calcification of the mitral annulus, a thickened, intense echo was seen posterior to the leaflets. Echocardiograms taken in the patients with severe mitral insufficiency also demonstrated enlarged left ventricular end-diastolic dimensions, increased stroke volume, and increased amplitude of septal motion. The ejection fraction was usually normal, but in 11 it was reduced, suggesting impaired left ventricular function. Echocardiography is an extremely useful technique in evaluating patients with mitral insufficiency, delineating the etiology and severity of the disease, and aiding in grossly assessing left ventricular function.

Mechanics of left ventricular contraction in chronic severe mitral regurgitation

The mechanics of left ventricular contraction were studied during diagnostic cardiac catheterization using high-speed cineangiography in 11 patients with severe chronic mitral regurgitation. Compared with a group of previously studied normal subjects, most of the patients with mitral regurgitation demonstrated a reduced velocity of shortening (V cf ) during ejection at maximum wall stress, average = 1.01 circumferences/sec (circ/sec) (range 0.64-1.47 circ/sec). Maximum and mean V cf values also were reduced in these patients, averaging 1.40 and 0.94 circ/sec, respectively. These findings are in contrast to those in acute experimental mitral regurgitation, and to observations of normal shortening velocities in chronic experimental volume overloading, in which left ventricular contraction velocity is augmented. Compared with normal subjects, patients with mitral regurgitation had significantly larger left ventricular end-diastolic circumferences and volumes, and higher total left ventricular stroke volumes. The mean regurgitant volume was 41% of the total stroke volume, of which an average of 46% was ejected into the left atrium prior to aortic valve opening. The ejection fraction and extent of fiber shortening were normal in all but two patients despite depressed shortening velocities in most. It is concluded that analysis of velocity in the ejecting phase of left ventricular contraction is useful in detecting apparent alterations in inotropic state in the face of the altered loading conditions accompanying chronic mitral regurgitation. Further, favorable unloading conditions early during systole in patients with mitral regurgitation appear to mask the effects of a depressed inotropic state on the pumping function of the heart.