Muscular subaortic stenosis: the quantitative relationship between systolic anterior motion and the pressure gradient

Obstruction in Hypertrophic Cardiomyopathy: Many Faces

Hypertrophic cardiomyopathy (HCM), the most common inherited cardiomyopathy, exhibits left ventricular hypertrophy not secondary to other causes, with varied phenotypic expression. Enhanced actin-myosin interaction underlies excessive myocardial contraction, frequently resulting in dynamic obstruction within the left ventricle. Left ventricular outflow tract obstruction, occurring at rest or with provocation in 75% of HCM patients, portends adverse prognosis, contributes to symptoms, and is frequently a therapeutic target. Transthoracic echocardiography plays a crucial role in the screening, initial diagnosis, management, and risk stratification of HCM. Herein, we explore echocardiographic evaluation of HCM, emphasizing Doppler assessment for obstruction. Echocardiography informs management strategies through noninvasive hemodynamic assessment, which is frequently obtained with various provocative maneuvers. Recognition of obstructive HCM phenotypes and associated anatomical abnormalities guides therapeutic decision-making. Doppler echocardiography allows monitoring of therapeutic responses, whether it be medical therapies (including cardiac myosin inhibitor therapy) or septal reduction therapies, including surgical myectomy and alcohol septal ablation. This article discusses the hemodynamics of obstruction and practical application of Doppler assessment in HCM. In addition, it provides a visual atlas of obstruction in HCM, including high-quality figures and complementary videos that illustrate the many facets of dynamic obstruction.

Association between Hypertrophic Cardiomyopathy and Variations in Sarcomere Gene and Calcium Channel Gene in Adults

INTRODUCTION

Calcium channel gene variations have been reported to be associated with hypertrophic cardiomyopathy (HCM) in family, but the relationship between calcium channel gene variations and HCM remains undefined in the population.

METHODS

A total of 719 HCM unrelated patients were initially enrolled. Finally, 371 patients were identified based on inclusion and exclusion criteria, including 145 patients with gene negative, 28 patients with a single rare calcium channel gene variation (calcium gene variation), 162 patients with a single pathogenic/likely pathogenic sarcomere gene variation (sarcomere gene variation) and 36 patients with a single pathogenic/likely pathogenic sarcomere gene variation and a single rare calcium channel gene variation (double gene variations). Then the demographic, electrocardiographic, echocardiographic, and follow-up data were collected.

RESULTS

Patients with double gene variations were at an earlier age and had more percent of family history of HCM, and had thicker walls, higher left ventricular outflow tract pressure gradient, more pathological Q waves, and more bundle branch blocks as compared with those with single sarcomere gene variation. During the follow-up period, patients with double gene variations had more primary endpoints than the other three groups (p = 0.0013). Multivariate analysis showed that double gene variations were the independent predictor of primary endpoint events in patients (HR: 4.82, 95% CI: 1.77-13.2; p = 0.002).

CONCLUSION

We found that patients with double gene variations had more severe HCM phenotype and prognosis. The pathogenesis effects of sarcomere gene variation and calcium channel gene variation may be cumulative in HCM populations.

Exaggerated myocardial torsion may contribute to dynamic left ventricular outflow tract obstruction in hypertrophic cardiomyopathy

Aims

Dynamic left ventricular (LV) outflow tract obstruction (LVOTO) is associated with symptoms and increased risk of developing heart failure in hypertrophic cardiomyopathy (HCM). The association of LVOTO and LV twist mechanics has not been well studied in HCM. The aim of the study was to compare the pattern of LV twist in patients with HCM associated with asymmetrical septal hypertrophy with and without LVOTO.

Methods and results

Echocardiography (including speckle tracking) was performed in 212 patients with HCM, divided according to the absence (n = 130) or presence (n = 82) of LVOTO (defined as peak pressure gradient ≥30 mmHg either at rest and/or with Valsalva manoeuvre). Patients with LVOTO were older, had smaller LV dimensions, a higher LV ejection fraction (LVEF), a longer anterior mitral valve leaflet length, and a higher early transmitral pulsed wave to septal tissue Doppler velocity ratio (E/E'). A univariate analysis showed that peak twist was significantly higher in patients with LVOTO compared with patients without LVOTO (19.7 ± 7.3 vs. 15.7 ± 6.0, P = 0.00015). Peak twist was similarly enhanced in patients with LVOTO, manifesting only during Valsalva (19.2 ± 5.6, P = 0.007) and patients with resting LVOTO (19.9 ± 8.0, P = 0.00004) compared with patients without LVOTO (15.7 ± 6.0). A stepwise forward logistic regression analysis showed that LVEF, LV end-systolic dimension indexed to body surface area, anterior mitral valve leaflet length, E/E', and peak twist were all independently associated with LVOTO.

Conclusion

This study demonstrates that increased peak LV twist is independently associated with LVOTO in patients with HCM. Peak twist was similarly exaggerated in patients with only latent LVOTO, suggesting that it may play a contributory role to LVOTO in HCM.

Computational analysis of ventricular mechanics in hypertrophic cardiomyopathy patients

Hypertrophic cardiomyopathy (HCM) is a genetic heart disease that is associated with many pathological features, such as a reduction in global longitudinal strain (GLS), myofiber disarray and hypertrophy. The effects of these features on left ventricle (LV) function are, however, not clear in two phenotypes of HCM, namely, obstructive and non-obstructive. To address this issue, we developed patient-specific computational models of the LV using clinical measurements from 2 female HCM patients and a control subject. Left ventricular mechanics was described using an active stress formulation and myofiber disarray was described using a structural tensor in the constitutive models. Unloaded LV configuration for each subject was first determined from their respective end-diastole LV geometries segmented from the cardiac magnetic resonance images, and an empirical single-beat estimation of the end-diastolic pressure volume relationship. The LV was then connected to a closed-loop circulatory model and calibrated using the clinically measured LV pressure and volume waveforms, peak GLS and blood pressure. Without consideration of myofiber disarray, peak myofiber tension was found to be lowest in the obstructive HCM subject (60 kPa), followed by the non-obstructive subject (242 kPa) and the control subject (375 kPa). With increasing myofiber disarray, we found that peak tension has to increase in the HCM models to match the clinical measurements. In the obstructive HCM patient, however, peak tension was still depressed (cf. normal subject) at the largest degree of myofiber disarray found in the clinic. The computational modeling workflow proposed here can be used in future studies with more HCM patient data.

First-in-man application of Liwen RF™ ablation system in the treatment of drug-resistant hypertrophic obstructive cardiomyopathy

OBJECTIVES

This study sought to evaluate the clinical applicability of the Liwen Liu RF™ ablation system for percutaneous intramyocardial septal radiofrequency ablation (PIMSRA).

BACKGROUND

Data on new cardiac radiofrequency ablation devices for the treatment of hypertrophic obstructive cardiomyopathy (HOCM) are limited.

MATERIALS AND METHODS

From July 2019 to July 2020, a total of 68 patients with drug-resistant HOCM, who underwent PIMSRA with the Liwen RF™ ablation system, which has an ablation electrode of stepless adjustable length, were prospectively enrolled. Safety endpoints included, amongst others, the occurrence of pericardial effusion and/or hemorrhage, cardiac arrhythmias, device failure and procedural death. The reduction in left ventricular outflow tract (LVOT) gradients at 12 months follow-up were used as a surrogate marker for device efficacy.

RESULTS

All procedures were technically successful. The total energy output time of the system was 75.8 (IQR: 30.0) min, and the average power was 43.61 ± 13.34 watts. No ablation system error occurred. The incidence of pericardial effusion or hemorrhage, transient arrhythmia and resuscitation was 8.8, 39.7, and 1.5% during procedure, respectively. None of the patients died. During 30-day follow-up, there were no complications with the exception of a pericardial effusion in one patient (1.5%). No further complications were reported after 30 days. The patients' resting [baseline: 75 (IQR: 48) vs. 12-months: 12 (IQR: 19) mmHg, p < 0.001] and provoked [baseline: 122 (IQR: 53) vs. 12-months: 41 (IQR: 59) mmHg, p < 0.001] LVOT gradients decreased significantly during follow-up.

CONCLUSION

In this study, we demonstrate the safety and feasibility of the Liwen RF™ ablation system to treat HOCM. The system allows for significant and sustainable LVOT gradient reduction during 12-months of follow-up. Hence, the Liwen RF™ ablation system is a promising new device that has the potential to become an alternative to existing septal reduction concepts in HOCM patients.

Systolic anterior motion of the mitral valve in hypertrophic cardiomyopathy: a narrative review

Background and Objective

The prevalence of hypertrophic cardiomyopathy (HCM) is estimated to be 1 in 200 to 500 individuals, with systolic anterior motion (SAM) of the mitral valve (MV) and left ventricular outflow tract (LVOT) obstruction present in 60% to 70%. In this narrative review, we aim to elucidate the pathophysiology of SAM-septal contact and LVOT obstruction in HCM by presenting a detailed review on the anatomy of the MV apparatus in HCM, examining the various existing theories pertaining to the SAM phenomenon as supported by cardiac imaging, and providing a critical assessment of management strategies for SAM in HCM.

Methods

A literature review was performed using PubMed, EMBASE, Ovid, and the Cochrane Library, of all scientific articles published through December 2021. A focus was placed on descriptive studies, reports correlating echocardiographic findings with pathologic diagnosis, and outcomes studies.

Key Content and Findings

The pathophysiology of SAM involves the complex interplay between HCM morphology, MV apparatus anatomic abnormalities, and labile hemodynamic derangements. Echocardiography and cardiac magnetic resonance (CMR) vector flow mapping have identified drag forces, as opposed to the "Venturi effect", as the main hydraulic forces responsible for SAM. The degree of mitral regurgitation with SAM is variable, and its severity is correlated with degree of LVOT obstruction and outcomes. First line therapy for the amelioration of SAM and LVOT obstruction is medical therapy with beta-blockers, non-dihydropyridine calcium-channel blockers, and disopyramide, in conjunction with lifestyle modifications. In refractory cases septal reduction therapy is performed, which may be combined with a 'resect-plicate-release' procedure, anterior mitral leaflet extension, surgical edge-to-edge MV repair, anterior mitral leaflet retention plasty, or secondary chordal cutting.

Conclusions

Recent scientific advances in the field of HCM have allowed for a maturation of our understanding of the SAM phenomenon. Cardiac imaging plays a critical role in its diagnosis, treatment, and surveillance, and in our ability to apply the appropriate therapeutic regimens. The increasing prevalence of HCM places an emphasis on continued basic and clinical research to further improve outcomes for this challenging population.

Left ventricular cavity obliteration: Mechanism of the intracavitary gradient and differentiation from hypertrophic obstructive cardiomyopathy

Background

Controversy surrounds the cause of the pressure gradient in patients with hypertrophic obstructive cardiomyopathy (HOCM). Left ventricular cavity obliteration (LVCO) was first described as the cause of the gradient but subsequently systolic anterior motion (SAM) of the mitral valve has been established as the cause. Nevertheless, the two gradients, though different in origin and significance, share similar characteristics. They both have a similar “dagger” profile, are obtained from the cardiac apex, are associated with a hyperdynamic left ventricle, and the gradients are worsened by Valsalva. The distinction has clinical relevance, because treating the intracavitary gradient (ICG) of LVCO as if it were a SAM‐associated gradient associated with HOCM would be inappropriate and possibly harmful.

Materials and Methods

To clarify the cause and characteristics of the ICG in patients with LVCO in patients without HOCM, we assessed the extent and duration of cavity obliteration, and for differentiation, we compared the spectral profiles with patients with HOCM and severe aortic stenosis (AS).

Results

Higher ICG is associated with a greater extent and more prolonged apposition of LV walls, and smaller left ventricular cavity size.

The spectral profile of patients with AS, HOCM, and LVCO is differentiated by the peak/mean gradient ratios of 2 or less, 2–3, and 3 or greater, respectively, in >90% of patients. Most patients with LVCO without HOCM or severe LVH have an ICG < 36 mm Hg.

Conclusion

The magnitude of ICG is quantitatively associated with the extent and duration of LVCO. Spectral profiles of severe AS, HOCM, and LVCO can be differentiated by the peak/mean gradient ratio.

Left ventricular outflow tract pressure gradient changes after carvedilol-disopyramide cotherapy in a cat with hypertrophic obstructive cardiomyopathy

Disopyramide reduces the left ventricular outflow tract (LVOT) pressure gradient and improves symptoms in humans with hypertrophic obstructive cardiomyopathy (HOCM). However, the efficacy of disopyramide in cats has not been reported. We treated a cat with HOCM with carvedilol and disopyramide cotherapy and monitored the changes in LVOT flow velocity and N-terminal pro B-type natriuretic peptide (NT-proBNP) concentration. A 10-month-old neutered male Norwegian Forest cat was referred with a moderate systolic cardiac murmur. Echocardiography revealed thickening of the left ventricular wall, systolic anterior motion of the mitral valve leaflets, and turbulent aortic flow in the LVOT at systole. The LVOT flow velocity was 5.6 m/s. The plasma NT-proBNP concentration exceeded 1,500 pmol/L. The cat was diagnosed with HOCM and the β-blocker carvedilol was started and gradually increased to 0.30 mg/kg, bid. After 57 days, the LVOT flow velocity (4.8 m/s) and plasma NT-proBNP concentration (870 pmol/L) had decreased but remained elevated. Therefore, disopyramide was added at 5.4 mg/kg po bid and increased to 10.9 mg/kg po bid after 22 days. After 141 days of carvedilol and disopyramide treatment, the systolic anterior motion of the mitral valve leaflets had disappeared and the LVOT flow velocity and plasma NT-proBNP concentration had decreased to 0.7 m/s and 499 pmol/L, respectively. No adverse effect has been observed during the follow-up. Disopyramide might relieve feline LVOT obstruction after only partial response to a beta-blocker. Further large-scale studies are required to investigate the efficacy and safety of disopyramide use in cats with moderate to severe HOCM.

Numerical simulation study on systolic anterior motion of the mitral valve in hypertrophic obstructive cardiomyopathy

BACKGROUND

The hydrodynamic mechanisms of systolic anterior motion (SAM) of the mitral valve in hypertrophic obstructive cardiomyopathy (HOCM) remain unclear.

METHODS

Based on computed tomography (CT) images and clinical data, pre- and post-operative computational models of the left ventricle were constructed for 6 HOCM patients receiving septal myectomy. SAM was abolished in 5 patients and persisted in one after septal myectomy surgery. The obtained simulation results including flow field of the left ventricle and mechanical behaviors of the mitral valve (MV) between pre- and post-operative FSI models were compared.

RESULTS

The pressure difference and shear stress on the mitral valve leaflets (MVL) were relatively high pre-operatively, and decreased significantly after satisfactory surgery, but remained high following failed surgery. The significant increase in coaptation-to-septal distance was found when SAM was abolished.

CONCLUSIONS

Our results indicated that high pressure difference and shear stress on the MVL might directly initiate SAM in HOCM. Successful septal myectomy enlarged the coaptation-to-septal distance sufficiently to keep the MVL away from the ejection flow, thereby eliminating SAM.

Pulsed Doppler Echocardiography: An Historical Perspective

Over the past six decades, echocardiography has evolved into an important technique for not only imaging cardiac structures, but also, by employing the Doppler equation, for assessing cardiac blood flow and tissue velocities. This review focuses on pulsed Doppler echocardiography: its principles, early development, and clinical applications. Important clinical applications include: (1) measurement of flow velocities, stroke volumes, and regurgitant and shunt volumes; (2) assessment of time intervals, e.g., pulmonary artery acceleration time as a measure of pulmonary artery pressure and resistance or the timing of mitral regurgitation in hypertrophic cardiomyopathy; (3) detection of turbulent flow in regurgitation, stenoses, and shunts, enhanced by the implementation of color Doppler; and (4) evaluation of left ventricular diastolic function in conjunction with pulsed tissue Doppler and deformation (strain) measurements.

Echocardiographic Applications of M-Mode Ultrasonography in Anesthesiology and Critical Care

Proficiency in echocardiography and lung ultrasound has become essential for anesthesiologists and critical care physicians. Nonetheless, comprehensive echocardiography measurements often are time-consuming and technically challenging, and conventional 2-dimensional images do not permit evaluation of specific conditions (eg, systolic anterior motion of the mitral valve, pneumothorax), which have important clinical implications in the perioperative setting. M-mode (motion-based) ultrasonographic imaging, however, provides the most reliable temporal resolution in ultrasonography. Hence, M-mode can provide clinically relevant information in echocardiography and lung ultrasound-driven approaches for diagnosis, monitoring, and interventional procedures performed by anesthesiologists and intensivists. Although M-mode is feasible, this imaging modality progressively has been abandoned in echocardiography and is often underutilized in lung ultrasound. This article aims to comprehensively illustrate contemporary applications of M-mode ultrasonography in the anesthesia and critical care medicine practice. Information presented for each clinical application will include image acquisition and interpretation, evidence-based clinical implications in the critically ill and surgical patient, and limitations. The present article focuses on echocardiography and reviews left ventricular function (mitral annular plane systolic excursion, E-point septal separation, fractional shortening, and transmitral propagation velocity); right ventricular function (tricuspid annular plane systolic excursion, subcostal echocardiographic assessment of tricuspid annulus kick, outflow tract fractional shortening, ventricular septal motion, wall thickness, and outflow tract obstruction); volume status and responsiveness (inferior vena cava and superior vena cava diameter and respiratory variability [collapsibility and distensibility indexes]); cardiac tamponade; systolic anterior motion of the mitral valve; and aortic dissection.

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.

The Remarkable 50 Years of Imaging in HCM and How it Has Changed Diagnosis and Management: From M-Mode Echocardiography to CMR

The almost 50-year odyssey of cardiac imaging in hypertrophic cardiomyopathy (HCM), revisited and described here, has been remarkable, particularly when viewed in the timeline of advances that occurred during a single generation of investigators. At each step along the way, from M-mode to 2-dimensional echocardiography to Doppler imaging, and finally over the last 10 years with the emergence of high-resolution tomographic cardiac magnetic resonance (CMR), evolution of the images generated by each new technology constituted a paradigm change over what was previously available. Together, these advances have transformed the noninvasive diagnosis and management of HCM in a number of important clinical respects. These changes include a more complete definition of the phenotype, resulting in more reliable clinical identification of patients and family members, defining mechanisms (and magnitude) of left ventricular outflow obstruction, and novel myocardial tissue characterization (including in vivo detection of fibrosis/scarring); notably, these advances afford more precise recognition of at-risk patients who are potential candidates for life-saving primary prevention defibrillator therapy. This evolution in imaging as applied to HCM has indelibly changed cardiovascular practice for this morphologically and clinically complex genetic disease.

The role of imaging in the diagnosis and management of hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy, affecting approximately 1:500 people. As the yield of genetic testing is only about 35-60%, the diagnosis of HCM is still clinical and based on the demonstration of unexplained and usually asymmetric left ventricular (LV) hypertrophy by imaging modalities. In the past, echocardiography was the sole imaging modality used for the diagnosis and management of HCM. However, in recent years other imaging modalities such as cardiac magnetic resonance have played a major role in the diagnosis, management and risk stratification of HCM, particularly when the location of left ventricular hypertrophy is atypical (apex, lateral wall) and when the echocardiographic imaging is sub-optimal. However, the most unique contribution of cardiac magnetic resonance is the quantification of myocardial fibrosis. Exercise stress echocardiography is the preferred provocative test for the assessment of LV outflow tract obstruction, which is detected only on provocation in one-third of the patients.

M-Mode Ultrasound Applications for the Emergency Medicine Physician

BACKGROUND

M-mode or "motion" mode is a form of ultrasound imaging that is of high clinical utility in the emergency department. It can be used in a variety of situations to evaluate motion and timing, and can document tissue movement in a still image when the recording of a video clip is not feasible.

OBJECTIVES

In this article we describe several straightforward and easily performed applications for the emergency physician to incorporate M-mode into his or her practice, including the evaluation for: 1) pneumothorax, 2) left ventricular systolic function, 3) cardiac tamponade, and 4) hypertrophic cardiomyopathy.

DISCUSSION

The emergency physician and other point-of-care ultrasound providers can use this versatile function in the evaluation of patients for a number of critical cardiopulmonary diagnoses.

CONCLUSION

A great deal of important information may be obtained with M-mode imaging through views and measurements that are relatively easy to obtain.

Basal infarct location but not larger infarct size is associated with a successful outcome after alcohol septal ablation in patients with hypertrophic obstructive cardiomyopathy: a cardiovascular magnetic resonance imaging study

Alcohol septal ablation (ASA) is successful in most but not in all patients with obstructive hypertrophic cardiomyopathy (HCM). We therefore sought to investigate the relation between infarct location versus infarct size with outcome after ASA in patients with obstructive HCM. Baseline characteristics, procedural characteristics, and cardiovascular magnetic resonance findings at baseline and 4-6 month follow-up after ASA were analysed in 47 patients with obstructive HCM in a single-center retrospective study. Infarct size was determined using late gadolinium enhancement. Infarct location was divided into "basal infarction" and "distal infarction" based on an optimal cut-of value of the distance from the basal septum to the beginning of the infarction. A "successful" outcome was defined as 80% reduction of the invasive gradient with a post-procedural gradient of <10 mmHg. Basal infarctions (n = 31) compared to distal infarctions (n = 16) were associated with successful outcome (100 vs. 38%, P < 0.001). Larger infarct size (n = 20) compared to smaller infarct size (n = 27) was not associated with successful outcome (75 vs. 82%, P = 0.72). A more distal location of the infarction, was the only predictor of a less successful outcome (odds ratio 0.76, 95% confidence interval 0.54-0.98, P = 0.03). Basal versus distal infarctions were also associated with a lower provoked gradient at late (2.6 ± 2.2 years) follow-up (11 (6-20) vs. 27 (12-94) mmHg, P = 0.01). Basal infarctions were associated with a successful outcome after ASA. A larger infarct size was not associated with a better outcome.

The role of hemodynamic catheterization in the evaluation of hypertrophic obstructive cardiomyopathy: A case series

Confirmation of the presence and magnitude of left ventricular outflow tract (LVOT) obstruction is a critical component of the evaluation of symptoms in patients with hypertrophic cardiomyopathy (HCM). The presence of LVOT obstruction in patients with severe symptoms refractory to pharmacologic therapy identifies a subgroup of HCM patients who may benefit from septal reduction therapy. Two-dimensional echocardiography with continuous wave Doppler is the main tool for confirming the presence and severity of LVOT obstruction in HCM. However, when uncertainty remains following non-invasive evaluation, invasive hemodynamics studies are required to confirm and quantify LVOT obstruction. In this manuscript we describe a series of 6 cases in which hemodynamic catheterization is instrumental in supplementing non-invasive imaging in the assessment of LVOT obstruction in HCM.

Predictors of outcome after alcohol septal ablation in patients with hypertrophic obstructive cardiomyopathy. Special interest for the septal coronary anatomy

Background

Alcohol septal ablation (ASA) provides symptomatic relief in most but not all patients with hypertrophic obstructive cardiomyopathy (HOCM). Therefore we investigated predictors of outcome after ASA.

Methods

Clinical, echocardiographic, angiographic and procedural characteristics were analysed in 113 consecutive patients. Successful ASA was defined as NYHA ≤ 2 with improvement of at least 1 class combined with a resting gradient < 30 mmHg and provoked gradient < 50 mmHg at 4-month follow-up.

Results

In 37 patients ASA was not successful. In multivariate analysis, baseline gradient (OR 1.06 (1.01–1.11) per 5 mmHg, p = 0.024) and distance to the ablated septal branch (OR 1.09 (1.03–1.16) per mm, p = 0.004) were predictors of unsuccessful outcome. The combined presence of a non-ablated septal branch and a distance ≥ 19 mm to the ablated branch was a predictor of unsuccessful outcome (OR 5.88 (2.06–16.7), p < 0.001).

Conclusions

Baseline gradient and a greater distance from the origin of the left anterior descending artery to the ablated septal branch combined with a non-ablated proximal septal branch are associated with an unsuccessful outcome after ASA.

Predictors of mitral annulus early diastolic velocity: impact of long-axis function, ventricular filling pattern, and relaxation

AIMS

Although left ventricular (LV) relaxation is well recognized as a predictor of mitral annulus (MA) early diastolic (E') velocity, its significance relative to other predictors of E' is less well understood.

METHODS AND RESULTS

We assessed 40 healthy volunteers, 43 patients with acutely decompensated chronic systolic heart failure (HF), and 36 patients with hypertrophic obstructive cardiomyopathy (HOCM) using echocardiography and right or left heart catheterization. Data were obtained at baseline. In addition, in healthy volunteers haemodynamics were varied by graded saline infusion and low body negative pressure, while in HF patients it was varied by vasoactive drug treatment. E- and A-wave velocity (E/A) ratio of the mitral valve inflow, systolic MA velocity integral (s' integral) and E' and late velocity (A') of lateral and septal MA pulsed wave velocities were assessed by echocardiography. Time constant of isovolumic pressure decay τ(0)) was calculated from isovolumic relaxation time/[ln(aortic dicrotic notch pressure) - ln(LV filling pressure)]. In all three groups, s' integral was the strongest predictor of E' (partial r= 0.53-0.79; 0.81 for three groups combined), followed by E/A ratio (partial r= 0.10-0.78; 0.26 for all groups combined) and τ(0) (partial r= -0.1 to 0.023; -0.21 for all groups combined).

CONCLUSION

In healthy adults, patients with systolic HF, or patients with HOCM, E' is related to LV long-axis function and E/A ratio, a global marker of LV filling. E' appears less sensitive to LV relaxation.

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.

Echocardiography in patients with hypertrophic cardiomyopathy: usefulness of old and new techniques in the diagnosis and pathophysiological assessment

Hypertrophic cardiomyopathy (HCM) is one of the most common inherited cardiomyopathy. The identification of patients with HCM is sometimes still a challenge. Moreover, the pathophysiology of the disease is complex because of left ventricular hyper-contractile state, diastolic dysfunction, ischemia and obstruction which can be coexistent in the same patient. In this review, we discuss the current and emerging echocardiographic methodology that can help physicians in the correct diagnostic and pathophysiological assessment of patients with HCM.

The 50-year history, controversy, and clinical implications of left ventricular outflow tract obstruction in hypertrophic cardiomyopathy from idiopathic hypertrophic subaortic stenosis to hypertrophic cardiomyopathy: from idiopathic hypertrophic subaortic stenosis to hypertrophic cardiomyopathy

Dynamic obstruction to left ventricular (LV) outflow was recognized from the earliest (50 years ago) clinical descriptions of hypertrophic cardiomyopathy (HCM) and has proved to be a complex phenomenon unique in many respects, as well as arguably the most visible and well-known pathophysiologic component of this heterogeneous disease. Over the past 5 decades, the clinical significance attributable to dynamic LV outflow tract gradients in HCM has triggered a periodic and instructive debate. Nevertheless, only recently has evidence emerged from observational analyses in large patient cohorts that unequivocally supports subaortic pressure gradients (and obstruction) both as true impedance to LV outflow and independent determinants of disabling exertional symptoms and cardiovascular mortality. Furthermore, abolition of subaortic gradients by surgical myectomy (or percutaneous alcohol septal ablation) results in profound and consistent symptomatic benefit and restoration of quality of life, with myectomy providing a long-term survival similar to that observed in the general population. These findings resolve the long-festering controversy over the existence of obstruction in HCM and whether outflow gradients are clinically important elements of this complex disease. These data also underscore the important principle, particularly relevant to clinical practice, that heart failure due to LV outflow obstruction in HCM is mechanically reversible and amenable to invasive septal reduction therapy. Finally, the recent observation that the vast majority of patients with HCM have the propensity to develop outflow obstruction (either at rest or with exercise) underscores a return to the characterization of HCM in 1960 as a predominantly obstructive disease.

Long-term follow-up after percutaneous septal ablation in hypertrophic obstructive cardiomyopathy

OBJECTIVES

The aim of this study was to evaluate the longterm follow-up results of percutaneous transluminal septal myocardial ablation (PTSMA) in a large patient cohort.

BACKGROUND

PTSMA by alcohol injection into septal branches has shown good acute and short-term results in symptomatic patients with hypertrophic obstructive cardiomyopathy.

METHODS

A total of 100 consecutive symptomatic (NYHA class 2.8 +/- 0.6) patients underwent PTSMA. All patients had clinical and non-invasive follow-up at 3 months, 1 year, and annually up to 8 years.

RESULTS

One patient died at day 2 after intervention due to fulminant pulmonary embolism following deep venous thrombosis, and eight patients required a permanent DDD-pacemaker due to post-interventional complete heart block. Acute reduction of the left ventricular outflow tract gradient was achieved from 76 +/- 37 to 19 +/- 21 mmHg at rest, from 104 +/- 34 to 43 +/- 31 mmHg during Valsalva maneuver, and from 146 +/- 45 to 59 +/- 42 mmHg post extrasystole (p < 0.0001, each). During follow-up (mean follow-up time: 58 +/- 14 months), three additional patients died (sudden death at 48 months, non-cardiac death at 49 months and stroke-related death at 60 months after the index procedure). All living patients showed clinical improvement to NYHA-class 1.4 +/- 0.6 (after 3 months, n = 99), 1.5 +/- 0.6 (after 1 year, n = 99), and 1.6 +/- 0.7 at final follow-up (n = 96; p < 0.0001, each). Non-invasive follow-up studies documented ongoing outflow tract gradient reduction, decrease of septal and left ventricular posterior wall thickness, and improvement of exercise capacity.

CONCLUSIONS

PTSMA is an effective treatment for symptomatic patients with hypertrophic obstructive cardiomyopathy. Follow-up showed ongoing hemodynamic and clinical improvement without increased mortality and morbidity.

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.

Systolic anterior motion (SAM) of the posterior mitral leaflet: Left ventricular outflow tract obstruction in a patient without left ventricular hypertrophy

Systolic anterior motion (SAM) of the anterior mitral leaflet with mitral-septal contact was generally thought to be a major contributor to dynamic left ventricular outflow tract obstruction in patients with hypertrophic cardiomyopathy. We report an interesting case of SAM of the posterior mitral leaflet in a patient without left ventricular hypertrophy, which led to dynamic left ventricular obstruction.

Biphasic left ventricular outflow and its mechanism in hypertrophic obstructive cardiomyopathy

BACKGROUND

Biphasic systolic velocity in the left ventricular (LV) outflow tract (LVOT) occurs in hypertrophic obstructive cardiomyopathy (HOCM). The cause and importance of this observation remain poorly understood.

METHODS

A total of 25 patients with HOCM were matched to 30 control subjects. A function derived from the relation of flow in the proximal descending aorta to that in the LVOT was used to estimate the LVOT systolic flow rate in HOCM. Patients with HOCM were grouped by absence (group I) or presence (group II) of biphasic LVOT velocity.

RESULTS

Biphasic LVOT velocity was associated with biphasic estimated LVOT outflow (P =.002). The LVOT pressure gradient was inversely related to LV outflow rate at the time of the peak gradient (r = -.64, P <.001). Dobutamine increased the gradient and reduced LVOT outflow at the time of the peak gradient. In group II, mitral-septal separation occurred despite a LVOT gradient (36 mm Hg).

CONCLUSION

Biphasic LVOT flow in HOCM occurs and may be caused by "afterload mismatch." The late systolic increase in flow is related to mitral-septal separation. Resolution of systolic anterior motion occurs despite a persistent LVOT pressure gradient, implying a role for forces other than pressure differences.

Echocardiographic assessment of patients with hypertrophic and restrictive cardiomyopathy: imaging and echocardiography

Echocardiography has evolved to be an important tool in the assessment of patients with hypertrophic and restrictive cardiomyopathy. In this article, the authors review the use of echocardiography in diagnosis, differentiation from disease mimics, assessment of prognosis, and the assistance of specific therapies. A pathophysiologic understanding of restrictive cardiomyopathy and constrictive pericarditis will be reviewed along with echocardiographic and Doppler features that help to distinguish these two entities.

Transesophageal echocardiographic (TEE) evaluation of the mitral and tricuspid valves

In skilled hands, multiplane TEE provides a comprehensive assessment of the anatomy and function of the mitral and tricuspid valves. TEE is uniquely effective in the evaluation of the diverse pathophysiologic processes that cause valvular heart disease.

The effect of the atrioventricular interval during atrioventricular sequential pacing on the hemodynamics in dynamic obstruction of the left ventricular outflow tract in dogs

The present study was performed to clarify the mechanism involved in the reduction of the pressure gradient in the left ventricular outflow tract of patients with hypertrophic obstructive cardiomyopathy when treated with atrioventricular (AV) sequential pacing. The effect of AV sequential pacing with variable AV intervals on the hemodynamics and dyssynchronous wall motion was experimentally studied using echocardiography in the dynamic obstruction of the left ventricular outflow tract created by dobutamine infusion in 17 dogs. The pressure gradient of the left ventricular outflow tract decreased with shortening of the AV interval during AV sequential pacing. Also, the dyssynchrony time, defined as the difference in the time between the intraventricular septum and posterior wall during the systolic phase recorded with M-mode echocardiography, increased with shortening of the AV interval during AV sequential pacing. However, very short AV intervals produced a significant decrease in the aortic pressure and increase in the pulmonary capillary wedge pressure. The dyssynchrony time showed a positive liner correlation with the percentage reduction in the pressure gradient of the left ventricular outflow tract (R=0.794, p<0.0001). It was concluded that dyssynchronous wall motion in the left ventricle was produced by pacing from the right ventricular apex and resulted in a reduction in the pressure gradient of the left ventricular outflow tract. Optimization of the AV interval during AV sequential pacing may play an important role in improving the hemodynamics in dynamic obstruction of the left ventricular outflow tract.

Percutaneous transluminal septal myocardial ablation for hypertrophic obstructive cardiomyopathy: long term follow up of the first series of 25 patients

OBJECTIVE

To determine the long term outcome in patients treated with percutaneous transluminal septal myocardial ablation (PTSMA) for hypertrophic obstructive cardiomyopathy (HOCM).

DESIGN AND SETTING

Observational, single centre study.

PATIENTS

25 patients (13 women, 12 men, mean (SD) age 54.7 (15.0) years) with drug treatment resistant New York Heart Association (NYHA) class 2.8 (0. 6) symptoms attributed to a high left ventricular outflow gradient (LVOTG) and a coronary artery anatomy suitable for intervention.

INTERVENTION

PTSMA by injection of 4.1 (2.6) ml of alcohol (96%) into 1.4 (0.6) septal perforator arteries to ablate the hypertrophied interventricular septum.

OUTCOME MEASURES

During in-hospital follow up, enzyme rise, the frequency of atrioventricular conduction lesions requiring permanent DDD pacing, and in-hospital mortality were assessed. Long term follow up (30 (4) months, range 24-36 months) included symptoms, echocardiographic measurements of left atrial and left ventricular dimensions and function, and LVOTG.

RESULTS

Mean postinterventional creatine kinase rise was 780 (436) U/l. During PTSMA 13 patents developed total heart block, permanent pacing being necessary in five of them. One 86 year old patient died from ventricular fibrillation associated with intensive treatment (beta mimetic and theophylline) for coexistent severe obstructive airway disease. After three months, three patients underwent re-PTSMA because of a dissatisfactory primary result, leading to LVOTG elimination in all of them. During long term follow up, LVOTG showed sustained reduction (3 (6) mm Hg at rest and 12 (19) mm Hg with provocation) associated with stable symptomatic improvement (NYHA class 1.2 (1.0)) and without significant global left ventricular dilatation.

CONCLUSIONS

PTSMA is an effective non-surgical technique for reduction of symptoms and LVOTG in HOCM. Prospective, long term observations of larger populations are necessary in order to determine the definitive significance of the procedure.

Percutaneous transluminal septal myocardial ablation

Percutaneous transluminal septal myocardial ablation (PTSMA) is a new, investigational, catheter-based treatment for severely symptomatic, medically refractory hypertrophic obstructive cardiomyopathy. A balloon catheter is used to cannulate and isolate the first or second septal perforator coronary artery. Following balloon inflation and intracoronary myocardial contrast echocardiography, ethyl alcohol is injected through the catheter lumen to cause proximal interventricular septum infarction and relief of outflow tract obstruction with improved patient symptoms. Septal scarring and thinning with reductions in the outflow tract gradients ensues over the following 6 to 12 weeks. Most patients have symptomatic improvement, at least moderate reductions in outflow tract gradients, and possibly improvement in exercise capacity. The most common procedural complication is the development of high-grade atrioventricular block necessitating implantation of a permanent pacemaker in 25% of patients. Compared with surgical myectomy, PTSMA has the advantage of being minimally invasive, easily repeated, and with relatively low major morbidity/mortality risk for patients with comorbid conditions. The findings from recently initiated international registries will be helpful in assessing the overall success and complication rates with PTSMA.

Pacing in hypertrophic cardiomyopathy

Dual chamber pacing has been proposed as an alternative to surgery in the management of hypertrophic cardiomyopathy. Reports have documented hemodynamic and symptomatic benefit from dual chamber pacing, raising the question of whether or not all patients with drug-refractory symptoms should undergo a trial of pacing before consideration of surgery. The enthusiasm for pacing in hypertrophic cardiomyopathy has generated a number of investigations addressing this issue, including several recently concluded clinical trials. This article reviews the recent experience with dual chamber pacing in hypertrophic cardiomyopathy.

An equation to predict the changes in peak left ventricular pressure in hypertrophic obstructive cardiomyopathy after treatment: application to the administration of disopyramide

A theoretical equation was derived based on the time-varying elastance model to predict theoretically the relationship between the delay in the onset of left ventricular outflow obstruction and the reduction in peak left ventricular pressure (LVP) caused by treatment in hypertrophic obstructive cardiomyopathy (HOCM). ECG, LVP, and other hemodynamic parameters were measured during catheterization at a constant heart rate with atrial pacing in 16 patients with HOCM before and after intravenous administration of disopyramide (1 mg/kg). After disopyramide administration, the duration between the R wave of the ECG and the onset of obstruction (T1) was prolonged significantly (from 117 +/- 30 to 155 +/- 32 ms, P < 0.0001), and peak LVP was reduced significantly (from 222 +/- 42 to 177 +/- 39 mmHg, P < 0.0001). The relation between the prolongation of T1 and the percent reduction in peak LVP was predicted well by the theoretical equation (coefficient of determination R2 = 0.926). Our model simplifies the therapeutic strategy for reducing the left ventricular outflow pressure gradient in patients with HOCM, which is to delay the time of onset of obstruction by some methods.

Morbidity outcome in patients with hypertrophic obstructive cardiomyopathy undergoing cardiac septal myectomy: early-extubation anesthesia versus high-dose opioid anesthesia technique

OBJECTIVE

Anesthetic management of patients with hypertrophic obstructive cardiomyopathy (HOCM) undergoing septal myectomy is challenging. The morbidity outcome of early-extubation anesthesia (EEA), or fast tracking, versus high-dose opioid (HDO) anesthesia was studied.

DESIGN

Retrospective study.

SETTING

University teaching hospital.

PARTICIPANTS

One hundred seventy-five cardiac septal myectomy patients (EEA, n = 53; HDO, n = 122).

INTERVENTIONS

EEA technique consisted of low-dose fentanyl, 10 to 15 microg/kg; propofol infusion; midazolam; and inhalation agent. HDO technique consisted of fentanyl, 50 to 100 microg/kg, and benzodiazepines, with or without an inhalation agent. Demographic data, preoperative symptoms, and data on anesthesia management and postoperative complications were recorded.

MEASUREMENTS AND MAIN RESULTS

There were no differences between the groups (EEA v HDO, respectively) regarding age, sex, preoperative symptoms (dyspnea, 89% v 79%; palpitations, 28% v 26%; angina, 47% v 61%; syncope, 47% v 41%), redo surgery, or combined surgery. Mean +/- standard deviation time to tracheal extubation was 7.2 +/- 5.3 hours in EEA versus 19.4 +/- 10.5 hours in HDO patients (p < 0.0001). Intensive care unit (ICU) stay was significantly shorter in EEA versus HDO patients (2.2 v 3.0 days; p < 0.005), with the trend toward earlier hospital discharge (9.7 v 11.3 days; p = 0.09). There was a high requirement for temporary pacing in both groups immediately postoperatively (EEA, 60% v HDO, 48%; p > 0.08). Permanent pacemaker insertion postoperatively was required in 7 of 53 patients (13%) in the EEA group and 11 of 122 patients (9%) in the HDO group (p > 0.25). Atrial arrhythmias occurred postoperatively in 25% of EEA patients versus 34% of HDO patients (p > 0.08).

CONCLUSION

EEA facilitates earlier tracheal extubation by 12 hours in patients with HOCM undergoing septal myectomy, significantly shortening ICU stay by 1 day without increasing perioperative cardiac morbidity or mortality.

Mid-systolic drop in left ventricular ejection velocity in obstructive hypertrophic cardiomyopathy--the lobster claw abnormality

In many patients with obstructive hypertrophic cardiomyopathy, an abrupt mid-systolic drop in left ventricular ejection velocity can be detected. We analyzed 27 patients with obstructive hypertrophic cardiomyopathy who had 43 echocardiographic examinations (mean gradient 53 +/- 6 mm Hg). Exams showing a mid-systolic drop had higher mean outflow tract pressure gradients (90 +/- 6 compared with 29 +/- 4 mm Hg, p < 0.001). After medical elimination of obstruction, the mid-systolic drop was no longer seen. We measured 105 pulsed-wave Doppler tracings in the left ventricular cavity and compared them with 90 continuous-wave tracings through the outflow tract. There was a close temporal correlation between the nadir of the left ventricular velocity drop and the peak continuous-wave left ventricular outflow tract velocity (r = 0.99). There was also a close temporal correlation between the onset of the fall in pulsed velocity and the onset of M-mode mitral-septal contact (r = 0.95).

CONCLUSIONS

The mid-systolic drop in left ventricular velocity is due to impedance to ejection and provides evidence of true obstruction. As left ventricular ejection velocity falls to its mid-systolic nadir because of impedance of ejection, velocity downstream in the left ventricular outflow tract actually rises to its peak. This disparity in the two velocities, deceleration in the left ventricular cavity and acceleration in the left ventricular outflow tract, indicates that the outflow orifice is progressively narrowed over time as the mitral valve is forced into the septum by the rising pressure difference. The obstruction phase is best described as a time-dependent, amplifying feedback loop. The orifice narrows over time because of the rising pressure difference; the pressure difference rises over time because of the narrowing orifice.