Contemporary Approach to Aortic and Mitral Regurgitation

Ventricular long-axis contraction as an earlier predictor of outcome in asymptomatic aortic regurgitation

The long-term prognostic significance of left ventricular (LV) long-axis contraction was investigated prospectively in 65 consecutive patients aged 58+/-15 years with asymptomatic aortic regurgitation, normal LV ejection fraction at rest, and no coronary artery or aortic root disease. A complete transthoracic echocardiographic study was performed at baseline and 12 months later. In 24 of 65 patients with peak systolic wave velocity at the lateral mitral annulus (LatS)<9 cm/s, LV diameter (p<0.01), volume (p<or=0.01), mass (p<0.001), and end-systolic wall stress (p<0.001) significantly increased after 12 months, whereas LV shortening and ejection fraction (p=0.001) and tissue Doppler right ventricular peak systolic wave velocity (p<0.05) decreased significantly. In patients with peak systolic wave velocity at the lateral mitral annulus>or=9 cm/s, none of these parameters was significantly affected during follow-up. Aortic valve replacement was performed in 6 of 24 patients (25%) with peak systolic wave velocity at the lateral mitral annulus<9 cm/s and none with peak systolic wave velocity at the lateral mitral annulus>or=9 cm/s. In patients with peak systolic wave velocity at the lateral mitral annulus<9 cm/s, a cut-off value of 6.25 cm/s predicted aortic valve replacement within the next year with 97% sensitivity and 83% specificity. In conclusion, ventricular long-axis contraction seems to be a reliable indicator for outcome prediction in patients with asymptomatic aortic regurgitation.

Left ventricular eccentric remodeling and matrix loss are mediated by bradykinin and precede cardiomyocyte elongation in rats with volume overload

OBJECTIVES

We hypothesized that left ventricular (LV) remodeling and matrix loss in volume overload (VO) are mediated by bradykinin (BK) and exacerbated by chronic angiotensin-converting enzyme (ACE) inhibition.

BACKGROUND

Chronic ACE inhibition increases anti-fibrotic BK and does not attenuate LV remodeling in pure VO. The relative contribution of changes in extracellular matrix versus cardiomyocyte elongation in acute and chronic LV chamber remodeling during VO is unknown.

METHODS

Echocardiography, LV collagen content, and isolated cardiomyocytes were studied in rats after aortocaval fistula (ACF) of 12 h, 2 and 5 days, and 4, 8, and 15 weeks. We also studied ACF rats after BK2 receptor (BK2R) blockade (2 days) or ACE inhibition (4 weeks).

RESULTS

At 2 days after ACF, LV end-diastolic dimension (LVEDD)/wall thickness was increased, and LV interstitial collagen was decreased by 50% without cardiomyocyte elongation. The BK2R blockade prevented collagen loss and normalized LVEDD/wall thickness. From 4 to 15 weeks after ACF, interstitial collagen decreased by 30% and left ventricular end-systolic (LVES) dimension increased despite normal LVES pressure and isolated cardiomyocyte function. The ACE inhibition did not decrease LVEDD/wall thickness, further decreased LV interstitial collagen, and did not improve LV fractional shortening despite decreased LVES pressure.

CONCLUSIONS

Immediately after ACF induction, eccentric LV remodeling is mediated by interstitial collagen loss without cardiomyocyte elongation. Acute BK2R blockade prevents eccentric LV remodeling and improves function. Chronic ACE inhibition does not prevent eccentric LV remodeling or improve function. These findings suggest that ACE inhibitor-mediated increase in LV BK exacerbates matrix loss and explains why ACE inhibition is ineffective in VO.

Genetic Disruption of Angiotensin II Type 1a Receptor Improves Long-Term Survival of Mice With Chronic Severe Aortic Regurgitation

BACKGROUND

Aortic regurgitation (AR) causes left ventricular (LV) volume overload, leading to progressive LV dilatation and dysfunction. In the present study it was examined whether blockade of angiotensin II type 1 receptor (AT1) could improve survival in cases of chronic severe AR.

METHODS AND RESULTS

AR was induced by puncturing the aortic valves of wild-type (WT) and AT1a knockout (KO) mice. Mice that survived for 4 weeks after the operation were deemed to be a model of chronic severe AR and were followed up for 50 weeks (WT, n=29; KO, n=31). Baseline measurements made 4 weeks after surgery showed similar LV cavity and function in both genotypes. These conditions progressively worsened in both genotypes, but 16 weeks after baseline, KO mice showed significantly less LV dilatation, hypertrophy and interstitial fibrosis than WT mice. Cardiac mRNA expression of B-type natriuretic peptide and type I collagen was lower in KO than WT mice. The 50-week mortality rate was significantly lower among KO (45.2%) than WT (86.2%) mice, and postmortem findings indicated that the lower mortality was attributable to a lower incidence of congestive heart failure.

CONCLUSIONS

In cases of chronic severe AR, blockade of AT1 attenuates the progression of LV dilatation, hypertrophy and fibrosis, thereby mitigating heart failure and improving long-term survival.

Preoperative Pulmonary Hypertension Is Associated with Postoperative Left Ventricular Dysfunction in Chronic Organic Mitral Regurgitation: An Echocardiographic and Hemodynamic Study

BACKGROUND

Some degree of pulmonary hypertension (PHTN) is common in patients with chronic mitral regurgitation. The aim of this study was to determine whether preoperative PHTN is associated with postoperative left ventricular (LV) dysfunction.

METHODS

The study included 79 patients with chronic organic mitral regurgitation. Preoperative and postoperative LV function was assessed by echocardiography. Preoperative and postoperative hemodynamics were evaluated by a pulmonary artery catheter.

RESULTS

Pulmonary artery systolic pressure decreased postoperatively (pre 49 +/- 14 vs. post 36 +/- 11 mm Hg, P < .01). Postoperative LV ejection fraction was significantly reduced in patients with preoperative PHTN (pre 61 +/- 11% vs post 49 +/- 12%, P < .01). A stepwise multivariate regression analysis showed that preoperative pulmonary artery systolic pressure and LV end-systolic dimension were independent predictors of postoperative LV ejection fraction (r = -0.53, P < .001, and r = -0.34, P < .05, respectively).

CONCLUSION

Preoperative PHTN is associated with postoperative LV dysfunction in patients with chronic organic mitral regurgitation undergoing mitral valve operation.

Beta1-adrenoceptor blockade mitigates excessive norepinephrine release into cardiac interstitium in mitral regurgitation in dog

Mitral regurgitation (MR) is associated with increased neuronal release of norepinephrine (NE) and epinephrine (EP) into myocardial interstitial fluid (ISF) that may be necessary in sustaining left ventricular (LV) function via activation of cardiomyocyte beta-adrenergic receptors (ARs). However, activation of neuronal beta-ARs on cardiac neurons may lead to further catecholamine release, with an attendant risk of functional deterioration. We hypothesize that a beneficial effect of beta-AR blockade may therefore mitigate excessive catecholamine release from cardiac adrenergic neurons in dogs with MR. We measured the effects of chronic beta-receptor blockade (beta-RB) on ISF NE and EP release using in vivo microdialysis in open-chest anesthetized dogs after 4 wk of MR with or without extended release of metoprolol succinate (100 mg/day) as well as in control dogs. Fractional shortening increased by 30% in both MR and MR + beta-RB dogs after 4 wk of MR. In MR + beta-RB dogs, stellate-stimulated heart rate change was attenuated compared with control and MR dogs, whereas peak change of LV pressure over time (+dP/dt) increased equally in all groups. Stellate-stimulated ISF NE increased fivefold over baseline in MR versus twofold in control dogs (< 0.05), but the NE release was significantly attenuated in MR + beta-RB dogs. In contrast, stellate-stimulated increases in ISF EP did not differ in control, MR, and MR + beta-RB dogs. This study demonstrates that beta-RB attenuates ISF NE release from cardiac neurons and that the LV functional response to MR is not dependent on an excess increase in ISF NE. Thus beta1-RB may exert a beneficial effect by attenuating untoward effects of excessive sympathetic efferent neural NE release while sustaining early LV functional adaptation to MR.

Cardiac surgery in the elderly: indications and management options to optimize outcomes

The elderly have increasingly benefited from the advances in cardiac surgical techniques and perioperative care. Compared to the same procedures in younger patients their operations can be more technically demanding and their level of reserve leaves less margin should complications occur. The importance of using realistic indications for operations with a focus on improving the quality of their lives and of optimal preoperative preparation of patients is emphasized.

Current Perspective on Aortic Valve Repair and Valve-Sparing Aortic Root Replacement

Aortic valve repair and valve-sparing aortic root replacement are attractive concepts because they offer the possibility of valve competence without structural deterioration due to nonviability and they preclude the need for anticoagulation. Enthusiasm for aortic valve repair has waxed and waned over the past 45 years due in part to the inherent technical difficulties and poor mid-term results. Renewed interest in the concept of aortic valve repair has paralleled the development of valve-sparing aortic root replacement over the last 20 years. A current perspective on aortic valve repair and valve-sparing aortic root replacement is presented in the following review. Historical background, indications for repair, technical considerations, and outcomes data are discussed.

Long-Term Outcome of Surgically Treated Aortic Regurgitation

OBJECTIVES

The purpose of this study was to compare postoperative outcome in two groups of patients with chronic severe aortic regurgitation (AR): those operated on early and those operated on late according to the guidelines.

BACKGROUND

The impact of earlier surgery for chronic severe AR as defined in guidelines has not been evaluated.

METHODS

A total of 170 patients with chronic severe AR submitted to aortic valve replacement were prospectively followed up. Patients were divided in two groups depending on the clinical situation at the time of surgery. Group A were 60 patients who were operated on following guidelines advice of earlier surgery, and group B were 110 patients who were operated on late with regard to guideline recommendations.

RESULTS

Follow-up was 10 +/- 6 years (1 to 22 years). During follow-up 44 patients died, 7 patients (12%) from group A and 37 (37%) from group B (p = 0.001). The cause of death was non-cardiac in 11 patients, 2 (3%) in group A and 9 (8%) in group B. Cardiac deaths occurred in 33 patients, 5 (9%) from group A and 28 (28%) from group B (p = 0.002). Causes of death differed between groups A and B: heart failure or sudden death were significantly more frequent in group B (20 patients vs. 1 patient, p = 0.001). Overall survival in groups A and B was 90 +/- 4% vs. 75 +/- 8% at 5 years, 86 +/- 5% vs. 64 +/- 5% at 10 years, and 78 +/- 7% vs. 53 +/- 6% at 15 years, respectively (p = 0.009).

CONCLUSIONS

Early operation as defined in the guidelines improves long-term survival in patients with chronic AR.

Medical and surgical treatment of chronic mitral regurgitation

Chronic severe mitral regurgitation is a progressive disease that can lead to left ventricular dysfunction. New information on the natural history of the disease, along with advances in surgical techniques, has changed the roles of medical and surgical therapies. There is no well-defined role for medical therapy in chronic mitral regurgitation. The goal of the treating physician is therefore to identify the optimal timing for surgical intervention. The timing of surgical intervention depends primarily on two factors: (i) clinical symptoms and (ii) the left ventricular response to volume overload. However, the aetiology of mitral regurgitation, the likelihood of surgical repair, the occurrence of atrial fibrillation and the presence of pulmonary hypertension, together with the haemodynamic response to exercise, are important factors in the optimal surgical timing. New concepts in the understanding of the natural history of the disease coupled with success of mitral repair have recently resulted in a widespread evolution towards earlier surgery.

Quality of life in advanced heart failure: role of mitral regurgitation

BACKGROUND

Quality of life is increasingly used as an important end point in clinical trials of treatments for heart failure; thus, relationships between traditional clinical variables and quality of life need to be understood. Baseline data from an ongoing multi-institutional study of a surgically implanted cardiac support device (CorCap, Acorn Cardiovascular, Inc, St Paul, MN) positioned around the heart to halt progression of remodeling in patients with cardiomyopathy provide an opportunity to study the relationship between mitral regurgitation (MR) and quality of life in a group of relatively young patients.

OBJECTIVE

The objective of this study was to determine whether the degree of MR correlates with quality of life in patients presenting with significant symptoms of heart failure.

METHODS

Baseline MR was assessed by echocardiography and patients were stratified according to whether there was a clinical indication for mitral valve surgery. The effect of heart failure on quality of life was measured by the Minnesota Living with Heart Failure questionnaire (MLHF). The New York Heart Association class, exercise performance measured by peak oxygen consumption and the 6-minute walk test, and the SF-36 physical function measure were analyzed as potential mediating variables.

RESULTS

Mean MR grade was 2 +/- 1.5 on a 0-to-4 (worst) scale (n = 260) and ejection fraction averaged 27% +/- 9%. Most patients (82%) had New York Heart Association class III symptoms. Peak oxygen consumption averaged 14.7 +/- 4.3 mL/kg per minute and average walking distance was 348 +/- 83 m. Median (quartile range) SF-36 physical function was 35 (20-50) on a 0-to-100 (best) scale. Median MLHF score was 61 (47.5-77) on a 0-to-105 (worst) scale. The degree of MR and having an indication for mitral valve repair were not associated with the patients' quality of life. Controlling for symptoms and functional measures, older age was independently associated with better quality of life.

CONCLUSIONS

The degree of MR was not related to MLHF scores, suggesting that surgery to reduce MR might not have predictable effects on quality of life. Further studies are needed to understand why younger patients reported worse quality of life and how this observation could impact therapy.

Effects of angiotensin-converting enzyme inhibition on mitral regurgitation severity, left ventricular size, and functional capacity

BACKGROUND

Mitral regurgitation (MR) is a progressive disorder that leads to left ventricular (LV) dilatation and dysfunction. Previous small studies have shown conflicting results regarding the benefits of afterload reduction for MR.

METHODS

We assessed by serial echocardiography the effects of ramipril on MR severity and LV size by a number of quantitative methods in 26 asymptomatic patients with moderate to severe MR at baseline and again after 6 months of ramipril treatment. We also evaluated exercise capacity, neurohormonal levels, and the Minnesota Living With Heart Failure score.

RESULTS

Despite a significant reduction in blood pressure with ramipril, there was no change in MR severity. MR severity, as assessed by effective regurgitant orifice area, was reduced in individuals with baseline systolic blood pressure (SBP) > or = 140 mm Hg (55.1 +/- 26 vs 37.4 +/- 35.4 mm2, P = .03), but not in individuals with SBP < 140 mm Hg (39.7 +/- 37.7 vs 46.1 +/- 34.1 mm2, P = not significant). Neither LV cavity size, exercise capacity, nor the Minnesota Living With Heart Failure score exhibited a significant change.

CONCLUSIONS

Patients with MR do not experience significant changes in MR severity, LV size, or functional status after 6 months of treatment with angiotensin-converting enzyme inhibition. However, patients with SBP > or = 140 mm Hg represent a subgroup that shows reduction in MR. These data are consistent with current American College of Cardiology/American Heart Association guidelines, which reserve the use of afterload reduction for MR patients with systemic hypertension or LV dysfunction.

Long-term vasodilator therapy in patients with severe aortic regurgitation

BACKGROUND

Vasodilator therapy can reduce the left ventricular volume and mass and improve left ventricular performance in patients with aortic regurgitation. Accordingly, it has been suggested that such therapy may reduce or delay the need for aortic-valve replacement.

METHODS

We randomly assigned 95 patients with asymptomatic severe aortic regurgitation and normal left ventricular function to receive open-label nifedipine (20 mg every 12 hours), open-label enalapril (20 mg per day), or no treatment (control group) to identify the possible beneficial effects of vasodilator therapy on left ventricular function and the need for aortic-valve replacement.

RESULTS

After a mean of seven years of follow-up, the rate of aortic-valve replacement was similar among the groups: 39 percent in the control group, 50 percent in the enalapril group, and 41 percent in the nifedipine group (P=0.62). In addition, there were no significant differences among the groups in aortic regurgitant volume, left ventricular size, left ventricular mass, mean wall stress, or ejection fraction. One year after valve replacement, the left ventricular end-diastolic diameter and end-systolic diameter had decreased to a similar degree among the patients who underwent surgery in each of the three groups, and all the patients had a normal ejection fraction.

CONCLUSIONS

Long-term vasodilator therapy with nifedipine or enalapril did not reduce or delay the need for aortic-valve replacement in patients with asymptomatic severe aortic regurgitation and normal left ventricular systolic function. Furthermore, such therapy did not reduce the aortic regurgitant volume, decrease the size of the left ventricle, or improve left ventricular function.

Development of a new animal model of chronic mitral regurgitation in rats under transesophageal echocardiographic guidance

Large animal models (dog and sheep) are often used for the investigation of the pathophysiology of chronic mitral regurgitation (MR). A major limitation of large animal models is cost. The aim of this study was to develop a new animal model of chronic MR. Left thoracotomy was performed in 34 rats. Under the guidance of transesophageal echocardiography, a fine needle was inserted into the left ventricle (LV) to damage the mitral leaflets and produce MR. Serial transthoracic echocardiography was performed to assess LV remodeling and function. Left atrial and LV diameters were significantly larger, and LV fractional shortening was lower in the MR group than in the sham group. The 150-day survival was 59% in the MR group and 100% in the sham group (P < .01). This new animal model of chronic MR may be used in the study of the pathophysiology of chronic MR and pharmacologic therapies.

Valvular Heart Disease

Aortic regurgitation (AR) is characterized by diastolic reflux of blood from the aorta into the left ventricle (LV). Acute AR typically causes severe pulmonary edema and hypotension and is a surgical emergency. Chronic severe AR causes combined LV volume and pressure overload. It is accompanied by systolic hypertension and wide pulse pressure, which account for peripheral physical findings, such as bounding pulses. The afterload excess caused by systolic hypertension leads to progressive LV dilation and systolic dysfunction. The most important diagnostic test for AR is echocardiography. It provides the ability to determine the cause of AR and to assess the severity of AR and its effect on LV size, function, and hemodynamics. Many patients with chronic severe AR may remain clinically compensated for years with normal LV function and no symptoms. These patients do not require surgery but can be followed carefully for the onset of symptoms or LV dilation/dysfunction. Surgery should be considered before the LV ejection fraction falls below 55% or the LV end-diastolic dimension reaches 55 mm. Symptomatic patients should undergo surgery unless there are excessive comorbidities or other contraindications. The primary role of medical therapy with vasodilators is to delay the need for surgery in asymptomatic patients with normal LV function or to treat patients in whom surgery is not an option. The goal of vasodilator therapy is to achieve a significant decrease in systolic arterial pressure. Future therapies may focus on molecular mechanisms to prevent adverse LV remodeling and fibrosis.

Quantitative determinants of the outcome of asymptomatic mitral regurgitation

BACKGROUND

The clinical outcome of asymptomatic mitral regurgitation is poorly defined, and the treatment is uncertain. We studied the effect on the outcome of quantifying mitral regurgitation according to recent guidelines.

METHODS

We prospectively enrolled 456 patients (mean [+/-SD] age, 63+/-14 years; 63 percent men; ejection fraction, 70+/-8 percent) with asymptomatic organic mitral regurgitation, quantified according to current recommendations (regurgitant volume, 66+/-40 ml per beat; effective regurgitant orifice, 40+/-27 mm2).

RESULTS

The estimated five-year rates (+/-SE) of death from any cause, death from cardiac causes, and cardiac events (death from cardiac causes, heart failure, or new atrial fibrillation) with medical management were 22+/-3 percent, 14+/-3 percent, and 33+/-3 percent, respectively. Independent determinants of survival were increasing age, the presence of diabetes, and increasing effective regurgitant orifice (adjusted risk ratio per 10-mm2 increment, 1.18; 95 percent confidence interval, 1.06 to 1.30; P<0.01), the predictive power of which superseded all other qualitative and quantitative measures of regurgitation. Patients with an effective regurgitant orifice of at least 40 mm2 had a five-year survival rate that was lower than expected on the basis of U.S. Census data (58+/-9 percent vs. 78 percent, P=0.03). As compared with patients with a regurgitant orifice of less than 20 mm2, those with an orifice of at least 40 mm2 had an increased risk of death from any cause (adjusted risk ratio, 2.90; 95 percent confidence interval, 1.33 to 6.32; P<0.01), death from cardiac causes (adjusted risk ratio, 5.21; 95 percent confidence interval, 1.98 to 14.40; P<0.01), and cardiac events (adjusted risk ratio, 5.66; 95 percent confidence interval, 3.07 to 10.56; P<0.01). Cardiac surgery was ultimately performed in 232 patients and was independently associated with improved survival (adjusted risk ratio, 0.28; 95 percent confidence interval, 0.14 to 0.55; P<0.01).

CONCLUSIONS

Quantitative grading of mitral regurgitation is a powerful predictor of the clinical outcome of asymptomatic mitral regurgitation. Patients with an effective regurgitant orifice of at least 40 mm2 should promptly be considered for cardiac surgery.

Impact of left ventricular diastolic function on exercise capacity in patients with chronic mitral regurgitation: an exercise echocardiography study

BACKGROUND

Mitral regurgitation (MR) is known as one of the most frequent causes of heart failure and sudden death. In spite of increasing prevalence of MR, there have been no available data on cardiac determinants of exercise capacity in patients with chronic MR.

HYPOTHESIS

This study aimed to investigate cardiac determinants of exercise capacity in patients with chronic MR.

METHODS

We consecutively enrolled 32 patients (11 men, mean age: 44 +/- 14 years) who had greater than moderate MR with normal left ventricular (LV) systolic function (LV ejection fraction >50%). Conventional echocardiographic indices and parameters measured by Doppler tissue imaging at septal side of mitral annulus were obtained before exercise. Mitral regurgitation fraction, forward stroke volume, pulmonary venous flow velocities, and systolic pulmonary artery pressure (sPAP) were also obtained with standard methods.

RESULTS

Left ventricular ejection fraction was 61 +/- 6% and MR fraction was 48 +/- 13%. All patients finished a symptom-limited treadmill exercise test with a peak heart rate of >85% of predicted maximum heart rate. Mean exercise time was 9.95 +/- 2.17 min, corresponding to 11 +/- 2 metabolic equivalents. Among pre-exercise echocardiographic variables, only early diastolic mitral annulus velocity (E') and pulmonary venous reversal flow velocity (PVa) showed a significant correlation with exercise time (r = 0.44, p = 0.011, and r = -0.40, p = 0.040, respectively), which persisted after multivariate analysis (p = 0.011 and 0.038, respectively). Other parameters such as systolic mitral annulus velocity, resting and postexercise sPAP, forward stroke volume, LV size, LV ejection fraction, left atrial size, and regurgitant fraction showed no significant correlation.

CONCLUSIONS

Left ventricular diastolic function is an important determinant of exercise capacity in patients with chronic MR. Both E' and PVa, accepted surrogate estimates for LV diastolic function, may be useful for identifying patients with chronic MR and with poor exercise capacity.

Mitral regurgitation: Current treatment options and their selection

Mitral regurgitation (MR) is a mechanically complex hemodynamic abnormality of various etiologies that, if untreated, leads to myocardial dysfunction, heart failure, and sudden death. Unless hemodynamically severe, MR is not a major risk factor for debility and death. However, even more modest MR may impact on longevity and may create risk for thromboembolic and infectious sequelae. Currently, therapy for severe MR is surgical valve replacement or repair. When MR is not secondary to ischemic sequelae, generally accepted indications for surgery include any symptoms, left ventricular or right ventricular dysfunction or left ventricular geometric variations that reach defined levels of prognostic concern, or development of atrial fibrillation. However, low perioperative risk of repair causes some to urge surgery for severe MR irrespective of other findings. Similar controversy confounds decisions about mitral valve surgery during coronary artery bypass grafting when MR is a sequel of ischemic disease. Drug treatment has not altered MR outcome, although drugs can mitigate symptoms if surgery is contraindicated by intercurrent disease. There is no basis for prophylactic drug treatment to preserve myocardial function in asymptomatic patients.