Relationship between outflow obstruction and left ventricular functional impairment in hypertrophic cardiomyopathy: a Doppler echocardiographic study

Exploring the Continuum of Hypertrophic Cardiomyopathy-From DNA to Clinical Expression

The concepts underlying hypertrophic cardiomyopathy (HCM) pathogenesis have evolved greatly over the last 60 years since the pioneering work of the British pathologist Donald Teare, presenting the autopsy findings of “asymmetric hypertrophy of the heart in young adults”. Advances in human genome analysis and cardiac imaging techniques have enriched our understanding of the complex architecture of the malady and shaped the way we perceive the illness continuum. Presently, HCM is acknowledged as “a disease of the sarcomere”, where the relationship between genotype and phenotype is not straightforward but subject to various genetic and nongenetic influences. The focus of this review is to discuss key aspects related to molecular mechanisms and imaging aspects that have prompted genotype–phenotype correlations, which will hopefully empower patient-tailored health interventions.

Left atrial remodeling postseptal myectomy for severe obstructive hypertrophic cardiomyopathy: Analysis by two-dimensional speckle-tracking echocardiography

BACKGROUND

Septal myectomy relieves left ventricular outflow obstruction (LVOTO) and is associated with excellent long-term outcomes. LVOTO is associated with diastolic dysfunction and increased left atrial (LA) size. We sought to investigate the changes in LA volumes and function postmyectomy and the association between these changes with clinical outcomes postmyectomy.

METHODS

Sixty-six hypertrophic cardiomyopathy patients undergoing myectomy were retrospectively studied. Preprocedural and 6- to 18-month postmyectomy follow-up transthoracic echocardiographic images were obtained. LA volumes and strain were assessed by two-dimensional speckle-tracking echocardiography.

RESULTS

Left atrial volumes, that is, indexed maximal, minimal, and pre-A volumes reduced postmyectomy, yet remained increased compared to controls (105.6 ± 34.5 mL vs 84.9 ± 26.7 mL, 45.2 ± 25.7 mL vs 35.4 ± 22.6 mL, 70.1 ± 31.4 mL vs 35.4 ± 22.6 mL, respectively, P < 0.05). The total emptying index did not improve postmyectomy and remained lower than controls (58.6 ± 12.4 vs 59.9 ± 12.8, P = NS) whereas atrial contraction improved, yet did not normalize (active emptying index 36.1 ± 14.9 vs 41.1 ± 16.2, P < 0.05). The conduit volume remained reduced postmyectomy (18.6 ± 13.3 mL vs 16.6 ± 15.1 mL, P = NS). LA strain also did not improve postmyectomy (26.8 ± 7.3 vs 28.5 ± 8.8, P = NS). A multivariable logistic regression identified preprocedural E/e' ratio and indexed maximal LA volume, as independent predictors for LA volume reduction ≥20% postmyectomy. During a mean follow-up of 4.9 ± 2.3 years postmyectomy, 24.2% of the patients developed atrial fibrillation and <5% of patients were severely symptomatic. We found no associations between LA volumes/function and atrial fibrillation or symptoms postmyectomy.

CONCLUSION

Postmyectomy LA volumes decreased, and the contractile function improved. There was no association between LA volumes/function and clinical outcomes postmyectomy. Notably, the LA remained enlarged (though to a lesser degree) with reduced strain and emptying fraction, suggesting possible atrial myopathy.

Modeling Cardiac Hemodynamic Response During Exercise in Health and Hypertrophic Cardiomyopathy

INTRODUCTION

Hypertrophic cardiomyopathy (HCM) is associated with altered hemodynamics in the left ventricular outflow tract and tissue abnormalities. Exercise testing has become an integral and powerful tool for the noninvasive evaluation of HCM and, in some patients, it could define a treatment strategy. Obiective: To model the hemodynamic alterations during exercise in healthy and HCM patients, obtained by noninvasive methods.

METHODS

Cardiac output (CO), heart rate (HR), arterial blood pressure (ABP) and Total Peripheral Resistance (TPR) were assessed during exercise. The evaluation included a curve-fitting approach (sigmoidal model) that allowed a quantitative comparison of CO profiles.

RESULTS

When compared to controls, patients with HCM showed reduced peak exercise cardiac output and demonstrated high peripheral resistance during exercise. Analysis of modeled it CO curves revealed a higher maximum rate of recovery in healthy individuals than in HCM patients.

CONCLUSION

The application of the sigmoidal model showed to be efficient in the characterization of CO dynamics for the different studied groups.

Disease Stage-Dependent Changes in Cardiac Contractile Performance and Oxygen Utilization Underlie Reduced Myocardial Efficiency in Human Inherited Hypertrophic Cardiomyopathy

BACKGROUND

Reduced myocardial efficiency represents a target for therapy in hypertrophic cardiomyopathy although therapeutic benefit may depend on disease stage. Here, we determined disease stage-dependent changes in myocardial efficiency and effects of myectomy surgery.

METHODS AND RESULTS

Myocardial external efficiency (MEE) was determined in 27 asymptomatic mutation carriers (genotype positive/phenotype negative), 10 patients with hypertrophic obstructive cardiomyopathy (HOCM), 10 patients with aortic valve stenosis, and 14 healthy individuals using [¹¹C]-acetate positron emission tomography and cardiovascular magnetic resonance imaging. Follow-up measurements were performed in HOCM and aortic valve stenosis patients 4 months after surgery. External work did not differ in HOCM compared with controls, whereas myocardial oxygen consumption was lower in HOCM. Because of a higher cardiac mass, total cardiac oxygen consumption was significantly higher in HOCM than in controls and genotype positive/phenotype negative. MEE was significantly lower in genotype positive/phenotype negative than in controls (28±6% versus 42±6%) and was further decreased in HOCM (22±5%). In contrast to patients with aortic valve stenosis, MEE was not improved in patients with HOCM after surgery, which was explained by opposite changes in the septum (decrease) and lateral (increase) wall.

CONCLUSIONS

Different mechanisms underlie reduced MEE at the early and advanced stage of hypertrophic cardiomyopathy. The initial increase and subsequent reduction in myocardial oxygen consumption during disease progression indicates that energy deficiency is a primary mutation-related event, whereas mechanisms secondary to disease remodeling underlie low MEE in HOCM. Our data highlight that the benefit of therapies to improve energetic status of the heart may vary depending on the disease stage and that treatment should be initiated before cardiac remodeling.

4D flow MRI and T1 -Mapping: Assessment of altered cardiac hemodynamics and extracellular volume fraction in hypertrophic cardiomyopathy

PURPOSE

Hypertrophic cardiomyopathy (HCM) is associated with altered hemodynamics in the left ventricular outflow tract (LVOT) and myocardial tissue abnormalities such as fibrosis. The aim of this study was to quantify changes in LVOT 3D hemodynamics and myocardial extracellular volume fraction (ECV, measure of fibrosis) and to investigate relationships between elevated flow metrics and left ventricular (LV) tissue abnormalities.

MATERIALS AND METHODS

Cardiac magnetic resonance imaging (MRI) including 4D flow (field strength = 1.5T, resolution = 2.1-4.0 × 2.1-4.0 × 2.5-3.2 mm(3) ; venc = 150-250 cm/s; TE/TR/FA = 2.2-2.5msec/4.6-4.9msec/15°) for the in vivo assessment of 3D blood flow velocities with full coverage of the LVOT was applied in 35 patients with HCM (54 ± 15 years) and 10 age-matched healthy controls (45 ± 14 years). In addition, pre- and postcontrast myocardial T1 -mapping (resolution = 2.3 × 1.8 mm, slice thickness = 8 mm, TE/TR-FA = 1.0-1.1msec/2.0-2.2msec/35°) of the LV (basal, mid-ventricular, apical short axis) was performed in a subgroup of 23 HCM patients. Analysis included the segmentation of the LVOT and quantification of peak systolic LVOT pressure gradients and rate of viscous energy loss EL ' as well as left ventricular ECV.

RESULTS

HCM patients demonstrated significantly elevated peak systolic LVOT pressure gradients (21 ± 16 mmHg vs. 9 ± 2 mmHg) and energy loss EL ' (3.8 ± 2.5 mW vs. 1.5 ± 0.7 mW, P < 0.005) compared to controls. There was a significant relationship between increased LV fibrosis (ECV) with both elevated pressure gradients (R(2) = 0.44, P < 0.001) and energy loss EL ' (R(2) = 0.46, P < 0.001).

CONCLUSIONS

The integration of 4D-flow and T1 -mapping-MRI allowed for the evaluation of tissue and flow abnormalities in HCM patients. Our findings suggest a mechanistic link between abnormal LVOT flow, increased LV loading, and adverse myocardial remodeling in HCM.

Effects of alcohol septal ablation on left ventricular diastolic filling patterns in obstructive hypertrophic cardiomyopathy

Alcohol septal ablation (ASA) has been shown to improve left ventricular (LV) diastolic function in patients with obstructive hypertrophic cardiomyopathy (HCM). However, its beneficial effect on diastolic function assessed by cardiac magnetic resonance (CMR) has not been reported. We investigated the mid-term changes of diastolic function by CMR combined with echocardiography in HCM patients after ASA at a median of 14-month follow-up. CMR parameters of diastolic function including peak filling rate (PFR), and time to peak filling rate (TPFR) were evaluated in 43 patients (aged 48 ± 9 years). LV diastolic function improved significantly measured by echocardiography with the decrease in ratio of transmitral early LV filling velocity (E) to early diastolic mitral lateral annular velocity (E') (14.20 ± 1.17 to 11.58 ± 1.16, p < 0.001) and E-wave deceleration time (194.04 ± 19.30 to 168.45 ± 12.58 ms, p < 0.001). PFR increased significantly with associated decrease in TPFR after ASA (both p < 0.001) at follow-up. Furthermore, patients with larger decrease in LVOT gradients had a greater improvement of LV diastolic function, as measured by the reduction of E/E' (p < 0.001) and increase of PFR (p < 0.001). In conclusion, this study demonstrated that successful ASA results in both echocardiographic and CMR indices of diastolic function improvement after ASA at 14-month follow-up. ASA therapy can significantly reduce LVOT gradient and mitral regurgitation, both of which may contribute to the improvement of diastolic function.

Effects of septal myectomy on left ventricular diastolic function and left atrial volume in patients with hypertrophic cardiomyopathy

Ventricular septal myectomy in patients with obstructive hypertrophic cardiomyopathy (HC) has been shown to reduce left ventricular (LV) outflow tract (LVOT) gradient and improve symptoms, although little data exist regarding changes in left atrial (LA) volume and LV diastolic function after myectomy. We investigated changes in LA size and LV diastolic function in patients with HC after septal myectomy from 2004 to 2011. We studied 25 patients (age 49.2 ± 13.1 years, 48% women) followed for a mean of 527 days after surgery who had serial echocardiography at baseline and at most recent follow-up, at least 6 months after myectomy. In addition to myectomy, 3 patients (12%) underwent Maze surgery and 13 (52%) underwent mitral valve surgery, of whom 5 had a mitral valve replacement or mitral annuloplasty. Patients with mitral valve replacement or mitral annuloplasty were excluded from LV diastolic function analysis. LA volume index decreased (from 47.2 ± 17.6 to 35.9 ± 17.0 ml/m(2), p = 0.001) and LV diastolic function improved with an increase in lateral e' velocity (from 7.3 ± 2.9 to 9.8 ± 3.1 cm/sec, p = 0.01) and a decrease in E/e' (from 14.8 ± 6.3 to 11.7 ± 5.5, p = 0.051). Ventricular septal thickness and LVOT gradient decreased, and symptoms of dyspnea and heart failure improved, with reduction in the New York Heart Association functional class III/IV symptoms from 21 (84%) to 1 (4%). In conclusion, relief of LVOT obstruction in HC by septal myectomy results in improved LV diastolic function and reduction in LA volume with improved symptoms.

Understanding changes in cardiovascular pathophysiology

Cardiovascular pathophysiological changes, such as hypertension and enlarged ventricles, reflect the altered functions of the heart and its circulation during ill-health. This article examines the normal and altered anatomy of the cardiac valves, the contractile elements and enzymes of the myocardium, the significance of the different factors associated with cardiac output, and the role of the autonomic nervous system in the heart beat. It also explores how certain diseases alter these functions and result in cardiac symptoms. Nurses can benefit from knowledge of these specific changes, for example, by being able to ask relevant questions in order to ascertain the nature of a patients condition, by being able to take an effective patient history and by being able to read diagnostic results, such as electrocardiograms and cardiac enzyme results. All this will help nurses to promote sound cardiac care based on a physiological rationale.

Echocardiography in hypertrophic cardiomyopathy: the role of conventional and emerging technologies

Hypertrophic cardiomyopathy is a relatively common inherited cardiomyopathy that is occasionally challenging to differentiate from hypertensive heart disease and athlete hearts on the basis of morphologic or functional abnormalities alone. Echocardiography has traditionally played a preeminent role in the diagnosis, formulation of management strategies, and the prognostication of this complex disease. In this review, we briefly profile the utility and pitfalls of established echocardiographic modalities and discuss the evolving role of novel echocardiographic imaging modalities such as tissue Doppler, Doppler-based strain, 2-dimensional strain (speckle tracking imaging), and 3-dimensional imaging in the assessment of hypertrophic cardiomyopathy.

Simultaneous imaging of myocardial motion and chamber blood flow with SPAMM n' EGGS (Spatial Modulation of Magnetization With Encoded Gradients for Gauging Speed)

PURPOSE

To provide simultaneous measurements of one-dimensional (1-D) myocardial displacement and 1-D chamber blood flow in a single breath-held acquisition using an MR imaging technique, SPAMM n' EGGS (Spatial Modulation of Magnetization With Encoded Gradients for Gauging Speed).

MATERIALS AND METHODS

Velocity encoding bipolar gradients sensitive to chamber blood flow were played out before the readout gradient in a 1-1 SPAMM-tagged MR imaging pulse sequence. For any given motion-flow encoded direction, the acquired image sequence was later postprocessed to separate the tag motion and blood flow terms. Experiments were performed on seven normal volunteers, and two pigs with moderate ischemic mitral regurgitation. Left-ventricular motion and trans-valvular flow obtained using the SPAMM n' EGGS pulse sequence was compared against measurements obtained using standard tagging and phase-contrast pulse sequences, respectively.

RESULTS

Results in normal volunteers and diseased pigs demonstrate multiphase correlated measurements of myocardial motion and chamber blood flow using SPAMM n' EGGS. A close correspondence in these measurements to conventional tagging and phase-contrast sequences is confirmed.

CONCLUSION

We have demonstrated that simultaneous acquisition of myocardial motion and chamber blood flow is possible within a single breath-hold. The data obtained using the SPAMM n' EGGS pulse sequence may be useful in the planning and evaluation of mitral-valve repair procedures.

Importance of transesophageal echocardiography in the critically ill and injured patient

Echocardiography, particularly transesophageal echocardiography (TEE), is a vital diagnostic and monitoring imaging modality for the intensivist. The field of echocardiography spans different venues and pathologies, ranging from surface transthoracic echocardiography and portable hand-held echocardiography, to contrast echocardiography, stress echocardiography, and TEE, among others. Numerous investigations have proven the worth of echocardiography, especially TEE, in the critically ill and injured patient, changing lives with the identification of obvious and subtle cardiothoracic diseases. Because this powerful imaging tool is immediately available and portable, crucial delays in diagnosis are not commonplace; rather than echocardiography, TEE, specifically, should be (and is in some institutions) the standard of care and management in assisting the intensivist in diagnosis of a variety of maladies. The effect of TEE technology is quite formidable, and numerous investigations have borne this out. The therapeutic effect of TEE ranges from 10% to 69%, with the majority of investigations falling into the 60% to 65% range. The diagnostic yield of TEE is far greater, approaching 78%. This article will detail the importance of echocardiography, its efficacy, and its high-yield imaging capability, particularly when compared with other imaging modalities, even transthoracic echocardiography.