Chordal geometry determines the shape and extent of systolic anterior mitral motion: in vitro studies

Changes in left ventricular-aortic angulation are associated with the development of obstruction in hypertrophic cardiomyopathy

OBJECTIVE

To characterize changes in ventricular morphology in patients with hypertrophic cardiomyopathy who develop left ventricular (LV) outflow tract obstruction.

METHODS

We reviewed patients with hypertrophic cardiomyopathy with LV outflow tract obstruction who underwent septal myectomy from May 2012 to June 2023. Among 68 patients initially without obstruction documented up to 7.6 years (interquartile range, 6.3-9.4 years) before the operation, a comparison was made with 78 patients with nonobstructive hypertrophic cardiomyopathy over a similar period. Patients who did not develop obstruction were matched with those who did on sex, age, and maximum septal wall thickness during the initial echocardiography, identifying 41 matched pairs. Echocardiographic data, including 5 measures of angulation, were compared between the groups.

RESULTS

The median interval between echocardiographic assessments was 7.5 years (interquartile range, 6.3-8.1 years) among patients with obstruction versus 7.3 years (interquartile range, 6.2-9.0 years) in patients without nonobstruction. Patients with obstruction were more likely to have hypertension at both times. The maximum septal wall thickness increased within both groups (both P values < .001), but the magnitude of increase was not different between groups (P = .130). Patients with obstruction exhibited a greater increase in LV mass (P < .001) compared with patients without obstruction (P = .004). Aortic angulation significantly increased in 4 of the 5 measurements (all P values < .001) in patients with obstruction, whereas patients with no obstruction showed no change. Anterior and posterior mitral valve leaflet lengths and coaptation lengths remained similar in both groups over time.

CONCLUSIONS

The development of LV outflow tract obstruction in patients with hypertrophic cardiomyopathy was associated with progressive LV outflow tract angulation and increased LV hypertrophy, as reflected by LV mass. Progression to obstruction was not related to changes in the mitral valve leaflet morphology.

Surgery for Hypertrophic Obstructive Cardiomyopathy: Comprehensive LVOT Management beyond Septal Myectomy

Hypertrophic cardiomyopathy (HCM) is a complex, underestimated, multifaceted disease frequently associated with left ventricular outflow tract (LVOT) obstruction. It is clearly demonstrated that this is due not only to septal hypertrophy but also to systolic anterior motion (SAM) of mitral valve leaflets secondary to mitral valve/subvalvular apparatus abnormalities. Surgical treatment involves performing an extended septal myectomy, eventually followed by ancillary procedures to those structures responsible for maintaining LVOT obstruction, if necessary. In this review, we describe the spectrum of possible surgical techniques beyond septal myectomy and their pathophysiologic rationale.

Three-Dimensional Imaging and Dynamic Modeling of Systolic Anterior Motion of the Mitral Valve

Left ventricular outflow tract (LVOT) obstruction in hypertrophic cardiomyopathy (HCM) is often caused by systolic anterior motion (SAM) of the mitral valve caused by the interplay between increased left ventricular (LV) wall thickness and an abnormal mitral valve anatomy and geometry. Three-dimensional (3D) echocardiographic imaging of the mitral valve has revolutionized the practice of cardiology, paving the way for new methods to see and treat valvular heart disease. Here we present the novel and incremental value of 3D transesophageal echocardiography (TEE) of SAM visualization. This review first provides step-by-step instructions on acquiring and optimizing 3D TEE imaging of SAM. It then describes the unique and novel findings using standard 3D TEE rendering as well as dynamic mitral valve modeling of SAM from 3D data sets, which can provide a more detailed visualization of SAM features. The findings include double-orifice LVOT caused by the residual leaflet, the dolphin smile phenomenon, and delineation of SAM width. Finally, the review discusses the essential role of 3D TEE imaging for preprocedural assessment and intraprocedural guidance of surgical and novel percutaneous treatments of SAM.

Analysis of three-chamber view conventional and tagged cine MRI in patients with suspected hypertrophic cardiomyopathy

OBJECTIVES

To investigate the potential value of adding a tagged three-chamber (3Ch) cine to clinical hypertrophic cardiomyopathy (HCM) magnetic resonance imaging (MRI) protocols, including to help distinguish HCM patients with regionally impaired cardiac function.

METHODS

Forty-eight HCM patients, five patients with "septal knuckle" (SK), and 20 healthy volunteers underwent MRI at 1.5T; a tagged 3Ch cine was added to the protocol. Regional strain, myocardial wall thickness, and mitral valve leaflet lengths were measured in the 3Ch view.

RESULTS

In HCM, we found a reduced tangential strain with decreased diastolic relaxation in both hypertrophied (p = 0.003) and remote segments (p = 0.035). Strain in the basal septum correlated with the length of the coaptation zone + residual leaflet (r = 0.48, p < 0.001). In the basal free wall, patients with SK had faster relaxation compared to HCM patients with septal hypertrophy.

DISCUSSION

The 3Ch tagged MRI sequence provides useful information for the examination of suspected HCM patients, with minimal additional time cost. Local wall function is closely associated with morphological changes of the mitral apparatus measured in the same plane and may provide insights into mechanisms of obstruction. The additional strain information may be helpful when analyzing local myocardial wall motion patterns in the presence of SK.

Evaluation of N-terminal prohormone of brain natriuretic peptide and cardiac troponin-I levels in cats with systolic anterior motion of the mitral valve in the absence of left ventricular hypertrophy

OBJECTIVES

To identify the prevalence of systolic anterior motion of the mitral valve (SAM) in apparently healthy cats in the absence of left ventricular hypertrophy (LVH) and examine the relationship between specific cardiac biomarker concentrations and echocardiographic parameters in these individuals.

ANIMALS

eighty client-owned cats.

MATERIALS AND METHODS

retrospective study; inclusion criteria were the presence of SAM on conscious echocardiography and concurrent measurement of plasma N-terminal prohormone of brain natriuretic peptide (NT-proBNP) and serum cardiac troponin-I (cTnI). Cats were excluded if they had LVH, left atrial enlargement or systemic disease. The percentages of cats with NT-proBNP and cTnI concentrations above the normal reference range were calculated. The correlation between each biomarker concentration and left ventricular myocardial wall thickness, left atrial size and maximum left ventricular outflow tract velocity was evaluated.

RESULTS

Thirty-four of 80 patients with SAM showed no evidence of cardiac remodelling (LVH or left atrial enlargement). Of these patients, 30 of 34 had elevated NT-proBNP, and cTnI was elevated in 13 of 27 (48.1%) cats where this biomarker was measured in association with the NT-proBNP assay. A positive correlation was observed between concentration of plasma NT-proBNP and maximum left ventricular outflow tract velocity (rs = 0.67, p<0.0001). No significant correlations were found between the concentration of biomarkers and the remaining echocardiographic parameters.

CONCLUSIONS

SAM is frequently observed in cats even in the absence of cardiac remodelling, and these individuals often demonstrate elevated plasma NT-proBNP and serum cTnI concentrations. Plasma NT-proBNP elevation is correlated with the severity of the left ventricular outflow obstruction caused by SAM.

Transcatheter Mitral Valve Planning and the Neo-LVOT: Utilization of Virtual Simulation Models and 3D Printing

PURPOSE OF REVIEW

Transcatheter mitral valve replacement (TMVR) is an emerging alternative for patients with severe mitral valve regurgitation who are considered at high risk for conventional surgical options. The early clinical experience with TMVR has shown that pre-procedural planning with computed tomography (CT) is needed to mitigate the risk of potentially lethal procedural complications such as left ventricular outflow tract (LVOT) obstruction. The goal of this review is to provide an overview of key concepts relating to TMVR pre-procedural planning, with particular emphasis on imaging-based methods for predicting TMVR-related LVOT obstruction.

RECENT FINDINGS

Risk of LVOT obstruction can be assessed with CT-based pre-procedural planning by using virtual device simulations to estimate the residual 'neo-LVOT' cross-sectional area which remains after device implantation. A neo-LVOT area of less than 2 cm² is currently thought to increase the risk of obstruction; however, additional studies are needed to further validate this cutoff value. Three-dimensional printing and personalized computational simulations are also emerging as valuable tools which may offer insights not readily confered by conventional two-dimensional image analysis. The simulated neo-LVOT should be routinely assessed on pre-procedural CT when evaluating anatomical suitability for TMVR.

Emerging pharmacologic and structural therapies for hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy is the most common inherited heart disease. Although it was first described over 50 years ago, there has been little in the way of novel disease-specific therapeutic development for these patients. Current treatment practice largely aims at symptomatic control using old drugs made for other diseases and does little to modify the disease course. Septal reduction by surgical myectomy or percutaneous alcohol septal ablation are well-established treatments for pharmacologic-refractory left ventricular outflow tract obstruction in hypertrophic cardiomyopathy patients. In recent years, there has been a relative surge in the development of innovative therapeutics, which aim to target the complex molecular pathophysiology and resulting hemodynamics that underlie hypertrophic cardiomyopathy. Herein, we review the new and emerging therapeutics for hypertrophic cardiomyopathy, which include pharmacologic attenuation of sarcomeric calcium sensitivity, allosteric inhibition of cardiac myosin, myocardial metabolic modulation, and renin-angiotensin-aldosterone system inhibition, as well as structural intervention by percutaneous mitral valve plication and endocardial radiofrequency ablation of septal hypertrophy. In conclusion, while further development of these therapeutic strategies is ongoing, they each mark a significant and promising advancement in treatment for hypertrophic cardiomyopathy patients.

Routine Papillary Muscle Realignment and Septal Myectomy for Obstructive Hypertrophic Cardiomyopathy

BACKGROUND

Septal myectomy has been the mainstay of the surgical treatment of obstructive hypertrophic cardiomyopathy (HCM); however, recently there is growing appreciation for associated mitral valve abnormalities that contribute to left ventricular outflow tract (LVOT) obstruction. In this study, we describe our experience with combined papillary muscle realignment (PMR) and septal myectomy for the treatment of obstructive HCM.

METHODS

We identified 44 patients undergoing surgery for obstructive HCM whose anatomy was amenable to combined PMR and septal myectomy at our institution over a 20-month period. All patients underwent resting and stress echocardiography preoperatively and postoperatively. Demographic, clinical, and imaging data were prospectively collected in a cardiac surgery database.

RESULTS

Patient age ranged broadly, with mean age of 54 (range, 18 to 76) years. Preoperatively, 70% of patients were New York Heart Association functional class III or IV, the mean stress LVOT gradient was 144 mm Hg, and severe mitral regurgitation (MR) with stress was seen in 81%. Additional procedures included division of myocardial bands (50%) and chordae (43%) and resection of accessory papillary muscles (25%). Following the procedure, mean resting and stress gradients were reduced to normal (12 and 27 mm Hg, respectively; p < 0.0001). No patient had severe MR and only 3 (6.8%) had moderate MR (p < 0.0001). Mean length of stay was 6 days and there were no mortalities.

CONCLUSIONS

Septal myectomy combined with PMR is a safe, highly effective, and reproducible procedure that reliably relieves LVOT obstruction and corrects MR without the need for mitral valve repair or replacement.

Management of systolic anterior motion of the mitral valve: a mechanism-based approach

Although the mechanism of systolic anterior motion (SAM) of the mitral valve is unknown, it is known to have a multifactorial pathophysiology. Echocardiographic analysis of the mitral leaflet revealed the step-wise progression of SAM, and intraventricular flow analysis revealed the contribution of drag force generated by the misled flow below the posterior leaflet. Although several diverse clinical features of SAM are already known, some key features need to be abstracted from among them to understand the regulation of SAM establishment. This paper reviews past articles that have investigated the mechanism of SAM and proposes a mechanism-based concept to provide insights for better comprehension of SAM recognition.

Long-term outcomes for different surgical strategies to treat left ventricular outflow tract obstruction in hypertrophic cardiomyopathy

AIMS

Surgical intervention is used to treat dynamic left ventricular outflow tract obstruction (LVOTO) in hypertrophic cardiomyopathy. This study assesses the effect of different surgical strategies on long-term mortality and morbidity.

METHODS AND RESULTS

In total, 347 patients underwent surgical intervention for LVOTO (1988-2015). Group A (n = 272) underwent septal myectomy; Group B (n = 33), septal myectomy and mitral valve (MV) repair; Group C (n = 22), myectomy and MV replacement; and Group D (n = 20), MV replacement alone. Median follow-up was 5.2 years (interquartile range 1.9-7.9). The mean resting LVOT gradient improved post-operatively from 71.9 ± 39.6 mmHg to 13.4 ± 18.5 mmHg (P < 0.05). Overall, 72.4% of patients improved by >1 New York Heart Association (NYHA) class; 58.9% of patients undergoing MV replacement alone did not improve their NYHA class. There were 5 perioperative deaths and 20 late deaths (>30 days). Survival rates at 1, 5 and 10 years respectively were 98.4, 96.9, 91.9% in Group A; 97.0, 92.4, 61.6% in Group B; 100.0, 100.0, 55.6% in Group C; and 94.7, 85.3, 85.3% in Group D (log-rank, P < 0.05). Long-term (>30 days) complications included atrial fibrillation (29.6%), transient ischaemic attack/stroke (2.4%) and heart failure hospitalisation (3.2%). There were 16 repeat surgical interventions at 3.0 years.

CONCLUSION

Septal myectomy is a safe procedure resulting in symptomatic improvement in the majority of patients. The annual incidence of non-fatal disease-related complications after surgical treatment of LVOTO is relatively high. Patients who underwent MV replacements had poorer outcomes with less symptomatic benefit in spite of a similar reduction in LVOT gradients.

Hypertrophic obstructive cardiomyopathy: the Mayo Clinic experience

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is a primary myocardial disease characterized by left ventricular hypertrophy in the absence of other etiologies. Clinical presentation may vary from asymptomatic to sudden cardiac death. Medical treatment is the first-line therapy for symptomatic patients. Extended left ventricular septal myectomy is the procedure of choice if medical treatment is unsuccessful or intolerable.

MAYO CLINIC EXPERIENCE

More than 3,000 patients have had septal myectomy for HCM at the Mayo Clinic (MN, USA) from 1993 to 2016. Risk of hospital death after isolated septal myectomy for obstructive HCM is <1% and is similar to the risk of operation for elective mitral valve repair. Complications, such as complete heart block requiring permanent pacemaker, are uncommon (2%), although partial or complete left bundle branch block is a frequent finding on the postoperative ECG. Relief of left ventricular outflow tract (LVOT) obstruction with septal myectomy dramatically improves symptoms and exercise capacity in symptomatic patients with obstructive HCM. More than 90% of severely symptomatic patients have improvement by at least two functional classes, and reduction of outflow gradients by myectomy decreases or eliminates symptoms of dyspnea, angina and/or syncope. Basal obstruction with systolic anterior motion (SAM) is treated by transaortic myectomy. The transapical approach was applied in 115 patients with obstructive midventricular and apical variants of HCM between 1993 and 2012. All patients with midventricular obstruction had gradient relief and none developed an apical aneurysm or ventricular septal defect. Recurrent obstruction after satisfactory myectomy was rare.

CONCLUSIONS

Septal myectomy effectively and definitively relieves LVOT obstruction and cardiac symptoms in patients with obstructive HCM. In experienced centers, early mortality for isolated septal myectomy is less than 1%, and overall results are excellent and continue to improve in the current era.

Dynamic obstruction in hypertrophic cardiomyopathy

PURPOSE OF REVIEW

The present article reviews the recent advances in the echocardiographic assessment of left ventricular outflow tract (LVOT) obstruction in hypertrophic cardiomyopathy (HCM). In particular, it highlights the role of novel imaging techniques in promoting our understanding of the pathophysiology of obstruction and discusses the prognostic value of information obtained from exercise echocardiography and the emerging role of image-guidance technologies for interventional relief of obstruction.

RECENT FINDINGS

The advent of novel echocardiography technologies, such as vector flow mapping, continues to expand our understanding of the exact mechanism of systolic anterior motion leading to dynamic LVOT obstruction by providing new insights into the interaction between pathologic mitral geometry and the left ventricular flow field. New studies provide evidence for the prognostic value of exercise echocardiography in the assessment of patients with HCM. Myocardial contrast perfusion imaging can delineate the anatomy of septal perforator arteries and identify the downstream septal perfusion bed, which is critical for safely guiding the procedure of alcohol septal ablation.

SUMMARY

Echocardiography represents a versatile, continuously evolving, and easily repeatable technique, allowing truly dynamic imaging studies, and is therefore most appropriate to evaluate a dynamic disease condition such as LVOT obstruction in HCM. It provides profound insights into the pathophysiology of LVOT obstruction, information on its clinical impact, and guidance for its relief by interventional strategies.

Mitral valve disease--morphology and mechanisms

Mitral valve disease is a frequent cause of heart failure and death. Emerging evidence indicates that the mitral valve is not a passive structure, but--even in adult life--remains dynamic and accessible for treatment. This concept motivates efforts to reduce the clinical progression of mitral valve disease through early detection and modification of underlying mechanisms. Discoveries of genetic mutations causing mitral valve elongation and prolapse have revealed that growth factor signalling and cell migration pathways are regulated by structural molecules in ways that can be modified to limit progression from developmental defects to valve degeneration with clinical complications. Mitral valve enlargement can determine left ventricular outflow tract obstruction in hypertrophic cardiomyopathy, and might be stimulated by potentially modifiable biological valvular-ventricular interactions. Mitral valve plasticity also allows adaptive growth in response to ventricular remodelling. However, adverse cellular and mechanobiological processes create relative leaflet deficiency in the ischaemic setting, leading to mitral regurgitation with increased heart failure and mortality. Our approach, which bridges clinicians and basic scientists, enables the correlation of observed disease with cellular and molecular mechanisms, leading to the discovery of new opportunities for improving the natural history of mitral valve disease.

Acute effects of ivabradine on dynamic obstruction of the left ventricular outflow tract in cats with preclinical hypertrophic cardiomyopathy

Background

Ivabradine is a negative chronotropic drug with minimal effects on central hemodynamics. Its effect on dynamic obstruction of the left ventricular outflow tract (LVOT) in cats with hypertrophic cardiomyopathy (HCM) remains unknown.

Hypothesis/Objectives

Ivabradine reduces dynamic obstruction of the LVOT in cats with HCM.

Animals

Twenty‐eight client‐owned cats with preclinical HCM and dynamic LVOT obstruction.

Methods

Randomized, double‐blind, active‐control single dose study. Cats received a single dose of either ivabradine (0.3 mg/kg PO) or atenolol (2 mg/kg PO). Heart rate, echocardiographic variables, and systolic blood pressure (SBP) were recorded before and 3 hours after drug administration. Statistical comparisons were made using ANCOVA.

Results

Peak velocity in the LVOT was significantly decreased compared to baseline for both drugs; however, the effect was more prominent with atenolol (mean reduction 2.53 m/s; 95% CI 2.07–3.13 m/s) compared to ivabradine (mean reduction 0.32 m/s; 95% CI −0.04 to 0.71 m/s; P < .0001). Echocardiographic indices of systolic function were largely unchanged by ivabradine, but significantly reduced by atenolol.

Conclusions and Clinical Importance

A single dose of ivabradine decreases dynamic LVOT obstruction in cats with HCM, but the clinical effect is negligible and inferior compared to that achieved by atenolol.

Preoperative morphological analysis by transesophageal echocardiography and predictive value of plasma landiolol concentration during systolic anterior motion mitral valve repair : a report of three cases

We report three cases with systolic anterior motion (SAM) after mitral valve plasty. Preoperative mitral valve morphology is a risk factor for SAM. The morphological characteristics of SAM have been revealed in several studies. We found a small distance between coaptation and the interventricular septum in all cases, and cases 2, and 3 had a low AL/PL ratio, whereas case 3 had a large PML, which was revealed by transesophageal echocardiography. With the use of 3D transesophageal echocardiography, when mitral valve prolapse was investigated, in all three cases, it was easy to specify lesions. The issue for the future is 3D analysis when SAM is occurring.

In vivo measurement of mitral leaflet surface area and subvalvular geometry in patients with asymmetrical septal hypertrophy: insights into the mechanism of outflow tract obstruction

BACKGROUND

Analyzing the determinants of systolic anterior motion of the mitral valve and consequent left ventricular outflow tract (LVOT) obstruction in patients with asymmetrical septal hypertrophy requires a comprehensive 3-dimensional analysis of mitral leaflet (ML) area, papillary muscle (PM) geometry, and the distribution of left ventricular hypertrophy.

METHODS AND RESULTS

Real-time 3-dimensional echocardiography was performed in 47 patients with asymmetrical septal hypertrophy and 32 normal controls. Patients included 20 with resting LVOT obstruction (group I) and 27 without (group II). Customized software (Omni 4D) provided a validated measure of ML surface area, LVOT area, mitral annular area and nonplanarity, LVOT hypertrophy index by topography (percent area with wall thickness >16 mm), and 3-dimensional PM positions relative to annulus. ML area was more than twice as large in group I than normal and 1.4 times normal in group II (P<0.001). Group I patients were also characterized by higher LVOT hypertrophy index and medial and anterior displacements of both PMs, resulting in a shorter inter-PM distance. Independent determinants of LVOT obstruction were indexed total ML area (adjusted odds ratio, 5.651; 95% confidence interval, 1.573 to 20.304; P=0.008) and inter-PM distance (adjusted odds ratio, 0.416; 95% confidence interval, 0.203 to 0.854; P=0.0169). Minimal LVOT area during systole correlated well with peak LVOT pressure gradient (R(2)=0.83, P<0.001); its independent determinants were left ventricular end-systolic volume (P=0.0183), indexed total ML area (P=0.0108), inter-PM distance (P=0.0378), annular height (P=0.0047), and LVOT hypertrophy index (P=0.0098).

CONCLUSIONS

Myocardium is not the only tissue affected in patients with asymmetrical septal hypertrophy, and primary changes of the mitral apparatus, including ML area increase and PM displacement, are independent determinants of LVOT obstruction and provide a comprehensive mechanism that determines leaflet slack and anteriorly directed motion. Abnormal PM-mitral valve geometry assessed by real-time 3-dimensional echocardiography can provide reasonable new targets for individualized intervention.

Echocardiographic assessment of left ventricular geometry and the mitral valve apparatus in cats with hypertrophic cardiomyopathy

OBJECTIVES

This retrospective study addressed the general hypothesis that abnormalities of the mitral valve apparatus are common in cats with idiopathic hypertrophic cardiomyopathy (HCM) and contribute to dynamic obstruction of the left ventricular outflow tract (LVOT).

ANIMALS, MATERIALS AND METHODS

106 cats (28 controls and 78 with HCM) had transthoracic two-dimensional and Doppler echocardiography performed with quantification of 33 variables. Three groups of cats (control [Group-1], HCM without obstruction [Group-2], and HCM with obstruction [Group-3]) were identified and compared by analysis of variance, chi(2) analysis, and correlation analysis.

RESULTS

Cats in Group-3 had more LV and papillary muscle hypertrophy, increased length of the anterior mitral valve leaflet, and a higher prevalence of false tendons in the LVOT compared to cats in Group-2 (P < or = 0.05). The length of the anterior mitral valve leaflet was correlated to the severity of dynamic obstruction (P < or = 0.05) and the magnitude of LV hypertrophy (P < or = 0.001). Systolic anterior motion of chordae tendineae (CAM) was observed in 16% of control cats and >50% of cats with HCM (P < or = 0.05).

CONCLUSIONS

Abnormalities of the mitral valve are common in cats with HCM suggesting a possible role in the pathogenesis of dynamic outflow tract obstruction.

Pathophysiology and Treatment of Hypertrophic Cardiomyopathy

All patients with hypertrophic cardiomyopathy (HCM) should have five aspects of care addressed. An attempt should be made to detect the presence or absence of risk factors for sudden arrhythmic death. If the patient appears to be at high risk, discussion of the benefits and risks of ICD are indicated, and many such patients will be implanted. Symptoms are appraised and treated. Bacterial endocarditis prophylaxis is recommended. Patients are advised to avoid athletic competition and extremes of physical exertion. First degree family members should be screened with echocardiography and ECG.

Asymmetry of Systolic Anterior Motion of the Mitral Valve in Patients with Hypertrophic Obstructive Cardiomyopathy: A Real-time Three-dimensional Echocardiographic Study

By geometric analysis of real-time 3-dimensional echocardiography performed in 39 patients with hypertrophic obstructive cardiomyopathy and definite systolic anterior motion of the mitral valve, we found that the angle between the mitral annular plane and basal portion of the anterior mitral valve leaflet, and the angle between the basal portion of the anterior leaflet and its tip portion measured in the medial and central anteroposterior planes, were significantly smaller than those in the lateral plane. The distance between the interventricular septum and the anterior mitral valve tip in the medial and central plane was also significantly smaller than that in the lateral plane. The lateral distance between the interventricular septum and the anterior mitral valve tip was the only independent determinant of left ventricular outflow tract pressure gradient by multiple stepwise regression analysis. In conclusion, systolic anterior motion of the mitral valve develops predominantly in the medial side, resulting in laterally located narrow left ventricular outflow tract opening in patients with hypertrophic obstructive cardiomyopathy.

Percutaneous Versus Surgical Treatment for Patients With Hypertrophic Obstructive Cardiomyopathy and Enlarged Anterior Mitral Valve Leaflets

Background— The purpose of this study was to compare percutaneous transluminal septal myocardial ablation (PTSMA) and septal myectomy combined with mitral leaflet extension (MLE) in symptomatic hypertrophic obstructive cardiomyopathy patients with an enlarged anterior mitral valve leaflet (AMVL). Both PTSMA and myectomy reduce septal thickness and left ventricular outflow tract (LVOT) gradient; however, an uncorrected enlarged AMVL may predispose to residual systolic anterior motion (SAM) after successful standard myectomy or PTSMA. Myectomy with MLE previously demonstrated superior hemodynamic results compared with standard myectomy, but its value relative to PTSMA is unknown.

Methods and Results— Twenty-nine patients (aged 44±12 years) underwent myectomy with MLE, and 43 patients (aged 52±17 years) underwent PTSMA. Mitral leaflet area was similar in both groups (16.7±3.4 versus 15.9±2.7 cm 2 , respectively). After PTSMA, 2 patients died, 4 needed a reintervention, and 4 required a permanent pacemaker for complete heart block. After surgery, only 1 patient needed a reintervention. At 1-year follow-up, LVOT gradients did not differ between surgical and PTSMA patients (17±14 versus 23±19 mm Hg, respectively). Preinterventional mitral regurgitation grade was more severe in the surgical group, but with myectomy combined with MLE, the residual grade was similar to that of PTSMA. Mean SAM grade decreased significantly more after surgery (from 2.9±0.3 to 0.5±0.7 mm Hg versus from 2.8±0.5 to 1.3±0.9 mm Hg, P <0.05).

Conclusions— PTSMA in these selected patients with hypertrophic obstructive cardiomyopathy had more periprocedural complications and resulted in more reinterventions. Hemodynamic results (SAM grade and reduction in mitral regurgitation) were better in surgical patients.

Septal myectomy for obstructive hypertrophic cardiomyopathy

Septal myectomy effectively relieves left ventricular outflow tract obstruction (LVOTO) and cardiac symptoms in both adults and children with obstructive hypertrophic cardiomyopathy (HCM). Abnormal attachments of the papillary muscles and chordae and other cardiac lesions can be repaired at the same time. Early mortality for isolated septal myectomy in both children and adults is low (0% to 2.5%). Median echocardiographic LVOT gradients at rest on late follow-up have been as low as 0 to 5 mm Hg. Symptomatic improvements after myectomy occurs in the majority; 90% of patients improve by at least one functional class, and most remain improved on late follow-up. Late survivorship compares very favorably with the natural history of nonoperated patients with symptomatic obstructive HCM. These results serve as a basis for comparison with newer nonsurgical alternatives.

Extended septal myectomy for hypertrophic obstructive cardiomyopathy with anomalous mitral papillary muscles or chordae

OBJECTIVES

Transaortic left ventricular septal myectomy yields excellent results for most severely symptomatic patients with hypertrophic obstructive cardiomyopathy. However, associated anomalies of the mitral subvalvular apparatus may prevent complete relief of obstruction, and mitral valve replacement has been advocated. We reviewed our results of procedures designed to relieve obstruction with preservation of the mitral valve.

METHODS

Among 291 patients undergoing septal myectomy from 1975 to 2002, 56 (ages 2-77 years) had anomalous mitral subvalvular apparatus including anomalous chordae (n = 28) and papillary muscles with direct insertion into mitral leaflets (n = 13) or fusion to septum (n = 31) or free wall (n = 12); 82% of patients were in New York Heart Association class III or IV. Operation included resection of anomalous chordae (28 patients), relief of papillary muscle fusion (36 patients), and extended septal myectomy, wider at the apex than the base.

RESULTS

There were no early deaths and no patients required mitral valve replacement. Mean peak pressure gradients decreased from 70 +/- 28 to 4.9 +/- 8.4 mm Hg and mean mitral regurgitation grade decreased from 2.3 to 1.0 (P <.001). Mean follow-up was 2.8 +/- 2.6 years. Freedom from reoperation at 4 years was 95%. There were 3 late noncardiac deaths; 98% of patients were in New York Heart Association class I or II.

CONCLUSIONS

Hypertrophic obstructive cardiomyopathy associated with anomalous mitral papillary muscles or chordae can be successfully treated without mitral valve replacement by surgical relief of the anomalies and an extended septal myectomy; early mortality is low, obstruction and mitral regurgitation are significantly reduced, and late results are excellent.

Sustained Improvement After Combined Anterior Mitral Leaflet Extension and Myectomy in Hypertrophic Obstructive Cardiomyopathy

Background— Mitral leaflet extension (MLE) combined with septal myectomy is a new surgical approach to treat hypertrophic obstructive cardiomyopathy (HOCM) and an enlarged mitral leaflet area. The study presents the long-term clinical results and outcome of this technique.

Methods and Results— MLE entails grafting a glutaraldehyde-preserved autologous pericardial patch onto the center portion of the anterior mitral valve leaflet. Twenty-nine patients with HOCM were studied. Mean follow-up (±SD) was 3.4±2.1 years (range 3 months to 7.7 years). The preoperative calculated mitral leaflet area was 16.7±3.4 cm 2 . New York Heart Association functional class improved significantly from 2.8±0.4 to 1.3±0.4 ( P <0.05), width of the interventricular septum decreased from 23±4 to 17±2 mm ( P <0.05), left ventricular outflow tract gradient decreased from 100±20 to 17±14 mm Hg ( P <0.01), severity of mitral regurgitation graded on a scale from 0 to 4+ decreased from 2.5±0.9 to 0.5±0.6 ( P <0.01), and severity of the systolic anterior motion of the mitral valve graded on a scale from 0 to 3+ decreased from 2.9±0.3 to 0.5±0.7 ( P <0.01) postoperatively. There were no deaths associated with surgery.

Conclusions— Long-term follow-up shows sustained improvement in functional status, reduction of outflow tract obstruction, and attenuation of mitral regurgitation and systolic anterior motion of the mitral valve. In this respect, the new technique widens the surgical applications in HOCM.

Obstructive hypertrophic cardiomyopathy: echocardiography, pathophysiology, and the continuing evolution of surgery for obstruction

Our understanding of the pathophysiology of obstruction in hypertrophic cardiomyopathy has evolved since initial descriptions in the late 1950s. This review addresses the cause of obstruction, from early ideas that a muscular outflow tract sphincter was the cause, through the discovery of systolic anterior motion (SAM) of the mitral valve, to current understanding that flow drag, the pushing force of flow, is the dominant hydrodynamic mechanism for SAM. The continuing redesign and modification of surgical procedures to relieve outflow obstruction have corresponded to ideas about the cause of this condition. In this review we discuss the evolution of surgical procedures to relieve obstruction and review modern surgical approaches. Medical and nonsurgical methods for reducing obstruction are reviewed, as well as efforts to prevent sudden arrhythmic cardiac death. Echocardiography has become central to understanding this complex phenomenon, and for clinical diagnosis, operative planning and intraoperative management.

Systolic anterior motion begins at low left ventricular outflow tract velocity in obstructive hypertrophic cardiomyopathy

OBJECTIVES

The purpose of this study was to determine whether the dynamic cause for mitral systolic anterior motion (SAM) is a Venturi or a flow drag (pushing) mechanism.

BACKGROUND

In obstructive hypertrophic cardiomyopathy (HCM), if SAM were caused by the Venturi mechanism, high flow velocity in the left ventricular outflow tract (LVOT) should be found at the time of SAM onset. However, if the velocity was found to be normal, this would support an alternative mechanism.

METHODS

We studied with echocardiography 25 patients with obstructive HCM who had a mean outflow tract gradient of 82 +/- 6 mm Hg. We compared mitral valve M-mode echocardiogram tracings with continuous wave (CW) and pulsed wave (PW) Doppler tracings recorded on the same study. A total of 98 M-mode, 159 CW, and 151 PW Doppler tracings were digitized and analyzed. For each patient we determined the LVOT CW velocity at the time of SAM onset. This was done by first determining the mean time interval from Q-wave to SAM onset from multiple M-mode tracings. Then, CW velocity in the outflow tract was measured at that same time interval following the Qwave.

RESULTS

Systolic anterior motion began mean 71 +/- 5 ms after Q-wave onset. Mean CW Doppler velocity in the LVOT at SAM onset was 89 +/- 8 cm/s. In 68% of cases SAM began before onset of CW and PW Doppler LV ejection.

CONCLUSIONS

Systolic anterior motion begins at normal LVOT velocity. At SAM onset, though Venturi forces are present in the outflow tract, their magnitude is much smaller than previously assumed; the Venturi mechanism cannot explain SAM. These velocity data, along with shape, orientation and temporal observations in patients, indicate that drag, the pushing force of flow, is the dominant hydrodynamic force that causes SAM.

Echocardiographic predictors of left ventricular outflow tract obstruction and systolic anterior motion of the mitral valve after mitral valve reconstruction for myxomatous valve disease

OBJECTIVE

To determine predictors of systolic anterior motion and left ventricular outflow tract obstruction (SAM/LVOTO) after mitral valve repair (MVRep) in patients with myxomatous mitral valve disease.

BACKGROUND

Mechanisms for the development of SAM/LVOTO after MVRep have been described; however, predictors of this complication have not been explored. We hypothesize that pre-MVRep transesophageal echocardiography (TEE) can predict postrepair SAM/ LVOTO.

METHODS

Using TEE, the lengths of the coapted anterior (AL) and posterior (PL) leaflets and the distance from the coaptation point to the septum (C-Sept) were measured before and after MVRep in 33 patients, including 11 who developed SAM/LVOTO (Group 1) and 22 who did not (Group 2).

RESULTS

Group 1 patients had smaller AL/PL ratios (0.99 vs. 1.95, p < 0.0001) and C-Sept distances (2.53 vs. 3.01 cm, p = 0.012) prior to MVRep than those in Group 2. Resolution of SAM/LVOTO was associated with increases in AL/PL ratio and C-Sept distance. This reflects a more anterior position of the coaptation point in those who developed SAM/ LVOTO.

CONCLUSIONS

These data suggest that TEE analysis of the mitral apparatus can identify patients likely to develop SAM/LVOTO after MVRep for myxomatous valve disease. The findings are consistent with the concept that SAM of mitral leaflets is due to anterior malposition of slack mitral leaflet portions into the LVOT. The position of the coaptation point of the mitral leaflets is dynamic and a potential target and end point for surgical designs to prevent SAM/LVOTO post MVRep.

Visualization of flow patterns from stents and stent-grafts in an in vitro flow-model

RATIONALE AND OBJECTIVES

The authors determine flow characteristics and pressure gradients of different stents and stent grafts in an in vitro flow-model.

METHODS

Five vascular stents (Memotherm, Cragg, two Palmaz P308, Strecker, and Wall) and one stent graft (Cragg EndoPro System 1), equal in length (60 mm) and diameter (10 mm), were deployed in a closed flow-model. The inner diameter of the tube measured 9 mm. Flow at 1.5 L/min, 6 L/min, and 10 L/min was simulated. Flow patterns were visualized by anionic particles illuminated with two Helium-Neon lasers. Laminary flow characteristics and pre-/poststent pressure gradients were determined in either expanded stent, 25% stenosis, or 50% stenosis.

RESULTS

Stent implantation induced a decrease of laminary flow compared with an unstented tube with and without concentric 25% stenosis (P < 0.01) at all flow rates and an increase of pressure gradients compared with an unstented tube for flow rates greater than 1.5 L/min (P < 0.01) (except for Cragg EndoPro System 1 stent, which revealed an increase of the pressure gradient at a flow rate of 1.5 L/min [P < 0.01]). Memotherm stent permitted maximum of laminary flow at all flow rates and stenoses (expanded: 79.50% at 1.5 L/min to 69.90% at 10 L/min; P < 0.01). Memotherm and Palmaz permitted lowest pressure gradients (P < 0.01). All of the endoprostheses demonstrated laminary flow at 50% stenosis.

CONCLUSIONS

The investigated stents and stent grafts showed different severity of flow disturbances and pressure gradients at different graded stenoses. Inadequate stent depolyment bears the risk of creating less laminary flow and pathologic pressure gradients. Because flow disturbances and pressure gradients may influence neointimal hyperplasia, stent design and completeness of stent unfolding are important regarding the appearance of postinterventional restenoses.

Mechanism of benefit of negative inotropes in obstructive hypertrophic cardiomyopathy

BACKGROUND

Drugs with negative inotropic effect are widely used to decrease obstruction in hypertrophic cardiomyopathy (HCM). However, the mechanism of therapeutic benefit has not been studied.

METHODS AND RESULTS

We used M-mode, two-dimensional, and pulsed Doppler echocardiography to study 11 patients with obstructive HCM before and after medical elimination of left ventricular outflow tract obstruction. We measured 148 digitized pulsed Doppler tracings recorded in the left ventricular cavity 2.5 cm apical of the mitral valve. Successful treatment slowed average acceleration of left ventricular ejection by 34% (P=.001). Mean time to peak velocity in the left ventricle was prolonged 31% (P=.001). Mean time to an ejection velocity of 60 cm/s was prolonged 91% (P=.001). Before treatment, left ventricular ejection velocity peaked in the first half of systole; after successful treatment, it peaked in the second half (P=.001). In contrast, after treatment, we found no change in peak left ventricular ejection velocity. We also found no change in the distance between the mitral coaptation point and the septum, as measured in two planes, indicating no treatment-induced alteration of this anatomic relationship.

CONCLUSIONS

Medical treatment eliminates mitral-septal contact and obstruction by decreasing left ventricular ejection acceleration. By slowing acceleration, treatment reduces the hydrodynamic force on the protruding mitral leaflet and delays mitral-septal contact. This, in turn, results in a lower final pressure gradient.

Resting echocardiographic features of latent left ventricular outflow obstruction in hypertrophic cardiomyopathy

We determined resting echocardiographic features predictive of latent left ventricular (LV) outflow obstruction in 50 consecutive patients with nonobstructive hypertrophic cardiomyopathy (26 provocable, 24 nonprovocable with amyl nitrite inhalation) to have a better understanding of the pathophysiology of this condition and to identify such patients without pharmacologic provocation. Measurements included wall thickness, type of hypertrophy, LV outflow tract diameter, degree of mitral systolic anterior motion, outflow pressure gradient, and ventricular volume. The direction of the ejection streamline was measured to assess the magnitude of the drag force acting on the mitral valve. Thirteen of 16 patients (81%) with proximal septal bulge were provocable, whereas only 3 of 8 patients (38%) with asymmetric septal hypertrophy and 10 of 26 (38%) with concentric hypertrophy were provocable (p < 0.05). LV outflow tract was significantly narrower and the angle between the ejection flow and the mitral valve was larger in provocable patients. The sensitivity for predicting provocable patients by a combination of a narrow outflow tract (< or = 2 cm) and a large angle (> or = 35 degrees) was 65%, with a specificity of 80% and a positive predictive value of 79%. When these criteria were combined with the presence of septal bulge, the sensitivity was 35%, but the specificity and the positive predictive value were both 100%. Patients with nonobstructive hypertrophic cardiomyopathy with proximal septal bulge, a narrow LV outflow tract, and an oblique angle between the ejection flow and the mitral valve appeared to be predisposed for latent outflow obstruction. These features are consistent with the presence of the large Venturi and drag forces. Thus, the left ventricle, which is capable of increasing both the Venturi and the drog forces on the basis of the morphologic change, contributes to the development of outflow obstruction with amyl nitrite inhalation.

Initial results of combined anterior mitral leaflet extension and myectomy in patients with obstructive hypertrophic cardiomyopathy

OBJECTIVES

The purpose of this study was to describe the clinical and functional results of combined anterior mitral leaflet extension and myectomy in patients with hypertrophic obstructive cardiomyopathy.

BACKGROUND

Septal myectomy is the most commonly performed surgical procedure in patients with hypertrophic cardiomyopathy and left ventricular outflow tract obstruction. Because of the role of the mitral valve in creating the outflow tract gradient, mitral valve replacement or plication is performed in selected cases in combination with myectomy, often with better hemodynamic results than those of myectomy alone. Mitral valve leaflet extension, in which a glutaraldehyde-preserved autologous pericardial patch is used to enlarge the mitral valve along its horizontal axis, is a novel surgical approach in patients with hypertrophic obstructive cardiomyopathy.

METHODS

Eight patients with hypertrophic obstructive cardiomyopathy were treated with mitral leaflet extension and myectomy. Preoperative and postoperative data (New York Heart Association functional class, number of drugs prescribed, width of the interventricular septum, severity of mitral valve regurgitation severity of systolic anterior motion of the mitral valve and outflow tract gradient) were compared with those of 12 patients undergoing myectomy alone.

RESULTS

Preoperative evaluation demonstrated that mitral regurgitation and systolic anterior motion of the mitral valve were more severe in the group undergoing mitral valve extension (p < 0.001 and p < 0.05, respectively). There were no deaths associated with either surgical procedure. Two patients, both treated by myectomy alone, died during the follow-up period. Postoperatively, patients treated with mitral valve extension had less mitral regurgitation (p < 0.005), less residual systolic anterior motion (p < 0.001), greater improvement in functional class (p = 0.05) and greater reduction in the number of drugs (p < 0.005) and in septal thickness (p < 0.05).

CONCLUSIONS

Mitral leaflet extension in combination with myectomy is a promising new surgical approach that may provide superior results to those of myectomy alone. Further studies are needed to determine the clinical value of this procedure.

New insights into the reduction of mitral valve systolic anterior motion after ventricular septal myectomy in hypertrophic obstructive cardiomyopathy

To determine the mechanism of reduction of mitral valve systolic anterior motion by myectomy, we examined 33 patients with hypertrophic obstructive cardiomyopathy echocardiographically before and after myectomy. Measurements included outflow tract diameter, the direction of ejection streamline (the angle between the ejection flow and the mitral valve), midventricular fractional area change, and papillary muscle inward excursion in the short-axis image. After myectomy, the outflow tract was enlarged (from 1.2 +/- 0.3 cm to 2.1 +/- 0.4 cm; p < 0.001), and the ejection flow became more parallel to mitral leaflets (from 51 +/- 10 degrees to 28 +/- 8 degrees; p < 0.001), whereas hyperdynamic midventricular fractional area change was reduced (81% +/- 14% to 62% +/- 14%; p < 0.001), and papillary muscle excursion decreased (1.3 +/- 0.3 cm to 0.8 +/- 0.3 cm; p < 0.001). Outflow enlargement and reduced ventricular contraction would decrease the Venturi force. Change of ejection streamline and reduced contraction would decrease the drag force onto the mitral leaflets. Blunted papillary motion would increase the mitral leaflet tension and decrease the effect of drag force on both leaflets. Thus myectomy decreases Venturi and drag forces and appears to reduce systolic anterior motion of the mitral valve.

Papillary muscle displacement causes systolic anterior motion of the mitral valve. Experimental validation and insights into the mechanism of subaortic obstruction

BACKGROUND

Systolic anterior motion (SAM) of the mitral valve in hypertrophic cardiomyopathy (HCM) has generally been explained by a Venturi effect related to septal hypertrophy, causing outflow tract narrowing and high velocities. Patients with HCM, however, also have primary abnormalities of the mitral apparatus, including anterior and inward or central displacement of the papillary muscles, and leaflet elongation. These findings have led to the hypothesis that changes in the mitral apparatus can be a primary cause of SAM by altering the forces acting on the mitral valve and its ability to move in response to them. Despite suggestive observations, however, it has never been prospectively demonstrated that such changes can actually cause SAM.

METHODS AND RESULTS

To test this hypothesis in vivo, anterior papillary muscle displacement was created in 7 dogs studied by echocardiography, with controlled cardiac output and heart rate. In all 7 dogs, papillary muscle displacement caused SAM, with an outflow tract gradient (33 +/- 19 mm Hg) and mitral regurgitation in 6. As in patients with HCM, the mitral valve was displaced anteriorly and the coaptation point shifted toward the insertion of the leaflets, creating longer distal residual leaflets that moved anteriorly.

CONCLUSIONS

Primary changes in the mitral apparatus can cause SAM without septal hypertrophy. In this model, SAM appears to be determined by the ability of the leaflets to move anteriorly (papillary muscle displacement causing slack and increased residual leaflet length) and their interposition into the outflow stream by anterior displacement, determining the direction of this motion. Geometric factors observed in HCM and in patients with SAM without HCM can therefore play a primary role in causing SAM.