Systolic anterior motion of the mitral chordae tendineae: prevalence and clinical and Doppler-echocardiographic features

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.

Mavacamten, a Novel Therapeutic Strategy for Obstructive Hypertrophic Cardiomyopathy

PURPOSE OF REVIEW

Pharmacological treatment options for hypertrophic cardiomyopathy (HCM) are currently limited and comprise non-disease specific therapies such as β-blockers, non-dihydropyridine calcium channel blockers, and disopyramide. These agents that offer a variable degree of symptomatic relief, often suboptimal, are often limited by side-effects and fail to address the key molecular abnormalities of the disease.

RECENT FINDINGS

Mavacamten is a novel, first-in-class, allosteric inhibitor of cardiac myosin ATPase, which reduces actin-myosin cross-bridge formation, thereby reducing myocardial contractility and improving myocardial energetic consumption in experimental HCM models. Following a successful Phase 2 study, the recently published phase III, placebo-controlled, randomized EXPLORER-HCM trial demonstrated the efficacy and safety of mavacamten in reducing left ventricular outflow tract obstruction and ameliorating exercise capacity, New York Heart Association functional class and health status in patients with obstructive HCM. Mavacamten represents the first agent specifically developed for HCM successfully tested in a Phase III trial, to be registered soon for clinical use, representing a radical change of paradigm in the pharmacological treatment of HCM.

Systolic anterior motion of mitral chordae tendineae: prevalence and clinical implications in liver transplantation

Background

Although systolic anterior motion (SAM) of the mitral valve anterior leaflet is well-known to cause hemodynamic perturbation in many anesthetic situations, the prevalence and clinical implication of SAM of mitral chordae tendineae (chordal SAM) in liver transplantation (LT) has not been evaluated. We aimed to assess the impact of chordal SAM on intraoperative postreperfusion syndrome and short and long-term all-cause mortality.

Methods

We retrospectively evaluated 1751 LT recipients from January 2011 to June 2017 who had preoperative echocardiography. Echocardiography-derived parameters and the prevalence of post-reperfusion syndrome between those with chordal SAM and without chordal SAM were compared. The cumulative mortality rate according to the presence of chordal SAM was evaluated by the Kaplan-Meier survival curve.

Results

Of the enrolled recipients, 21 (1.2%) had chordal SAM in preoperative echocardiography. Compared to those without chordal SAM, patients with chordal SAM had a smaller end-systolic volume index (median 18 ml/m² vs. 22 ml/m², P = 0.015) and end-diastolic volume index (median 52 ml/m² vs. 63 ml/m², P = 0.011). However, there was no difference in systolic and diastolic function in echocardiography. The prevalence of intraoperative post-reperfusion syndrome did not show any difference (42.9% vs. 45.3%, P = 1.000). Over the mean 4.8-year follow-up, cumulative 90-day and overall mortality also did not show a difference (Log rank P > 0.05, both).

Conclusions

Preoperative screening of echocardiography in LT recipients detects 1.2% of chordal SAM. It is found with small left ventricular volume, but is not related with intraoperative post-reperfusion syndrome and short- and long-term postoperative all-cause mortality in LT.

The Disappearing Murmur: Systolic Anterior Motion of the Mitral Valve Leaflet in a Non-hypertrophic Cardiomyopathy Patient

Systolic anterior motion (SAM) of the mitral valve is a well-known phenomenon associated with left ventricular outflow tract obstruction and hemodynamic compromise. This finding may occur in patients with or without hypertrophic cardiomyopathy. In this report, a patient with no prior medical history presented to the hospital with left-sided chest pain and high-risk echocardiogram (ECG) findings. Left heart catheterization with coronary angiography was negative for coronary artery disease. His initial examination was significant for a systolic murmur due to the underlying SAM, as demonstrated by transthoracic echocardiogram. During his hospitalization, he developed acute heart failure syndrome as a result of dynamic outflow tract obstruction. He was treated with fluid resuscitation with a resolution of his hemodynamic compromise. On a follow-up examination, there was no murmur and SAM was no longer present on echocardiogram. This case demonstrates the importance of recognizing the clinical manifestations of SAM as well as its role in maintaining an appropriate hemodynamic status.

Normal Variants in Echocardiography

Echocardiography is a powerful and convenient tool used routinely in the cardiac evaluation of many patients. Improved resolution and visualization of cardiac anatomy has led to the discovery of many normal variant structures that have no known pathologic consequence. Importantly, these findings may masquerade as pathology prompting unnecessary further evaluation at the expense of anxiety, cost, or potential harm. This review provides an updated and comprehensive collection of normal anatomic variants on both transthoracic and transesophageal imaging.

Diverse geometric changes related to dynamic left ventricular outflow tract obstruction without overt hypertrophic cardiomyopathy

BACKGROUND

Dynamic left ventricular (LV) outflow tract (LVOT) obstruction (DLVOTO) is not infrequently observed in older individuals without overt hypertrophic cardiomyopathy (HCM). We sought to investigate associated geometric changes and then evaluate their clinical characteristics.

METHODS

A total of 168 patients with DLVOTO, which was defined as a trans-LVOT peak pressure gradient (PG) higher than 30 mmHg at rest or provoked by Valsalva maneuver (latent LVOTO) without fixed stenosis, were studied. Patients with classical HCM, acute myocardial infarction, stress induced cardiomyopathy or unstable hemodynamics which potentially induce transient-DLVOTO were excluded.

RESULTS

Their mean age was 71 ± 11 years and 98 (58%) patients were women. Patients were classified as pure sigmoid septum (n = 14) if they have basal septal bulging but diastolic thickness less than 15 mm, sigmoid septum with basal septal hypertrophy for a thickness ≥15 mm (n = 85), prominent papillary muscle (PM) (n = 20) defined by visually large PMs which occluded the LV cavity during systole or 1/2 LVESD, or as having a small LV cavity with concentric remodelling or hypertrophy (n = 49). The prominent PM group was younger, had a higher S' and lower E/e' than other groups. In all groups, a higher peak trans-LVOT PG was related (p < 0.10) to higher E/e', systolic blood pressure, relative wall thickness, and pulmonary arterial systolic pressure. In multivariate analysis, resting trans-LVOT PG correlated to pulmonary arterial pressure (ß = 0.226, p = 0.019) after adjustment for systolic blood pressure, relative wall thickness, and E/e'.

CONCLUSIONS

DLVOTO develops from various reasons, and patients with prominent PMs have distinct characteristics. We suggest to use DLVOTO-relieving medication might reduce pulmonary pressure in this group of patients.

Relation of immediate decrease in ventricular septal strain after alcohol septal ablation for obstructive hypertrophic cardiomyopathy to long-term reduction in left ventricular outflow tract pressure gradient

Alcohol septal ablation (ASA) aims to decrease left ventricular outflow tract (LVOT) obstruction in patients with obstructive hypertrophic cardiomyopathy (HC). To date, no diagnostic variables at baseline are available to predict long-term success of the procedure. We hypothesized that an immediate decrease in septal longitudinal strain after ASA would be associated with sustained LVOT gradient decrease after 6 months. ASA was performed in 22 patients with HC and severe drug-refractory symptoms. Clinical evaluation and 2-dimensional echocardiography were performed before, 1 day after, and 6 months after ASA. During 6-month follow-up, New York Heart Association class improved (2.7 +/- 0.5 vs 1.4 +/- 0.6, p <0.01) and LVOT gradient decreased (68 +/- 31 vs 21 +/- 21 mm Hg, p <0.01). Strain evaluation showed considerable decreases in basal septal strain (-12 +/- 3% vs -8 +/- 2%, p <0.01) and midseptal strain (-13 +/- 4% vs -8 +/- 3%, p <0.01) 1 day after ASA. Decreases in basal septal and midseptal strain 1 day after ASA were strongly related to the decrease in LVOT gradient during 6-month follow-up (r = 0.70, p <0.01, and r = 0.65, p <0.01, respectively). In conclusion, in patients with HC and severe drug-refractory symptoms, immediate decrease in septal strain after ASA is strongly related to a decrease in LVOT gradient after 6 months and might therefore serve as an early determinant for long-term success of the ASA procedure.