Hypertrophic cardiomyopathy. Interrelations of clinical manifestations, pathophysiology, and therapy (1)

Analysis of risk factors for complications in echocardiography-guided percutaneous intramyocardial septal radiofrequency ablation

BACKGROUND

The feasibility of percutaneous intramyocardial septal radiofrequency ablation (PIMSRA) for the treatment of hypertrophic obstructive cardiomyopathy (HOCM) has been previously reported. However, limited investigation has been conducted regarding the complications associated with this procedure.

OBJECTIVE

This study aims to analyze the risk factors affecting the occurrence of complications during PIMSRA, such as pericardial effusion, ventricular premature beats, and interventricular septal perforation. In this study, the optimal cut-off values for these risk factors are also explored, and corresponding strategies for prevention are proposed.

METHODS

A total of 101 patients diagnosed with HOCM who underwent the PIMSRA procedure from 2021 to 2022 were included in this retrospective analysis. Patients were classified into subgroups with or without complications based on procedural records. Univariate and multivariate regression analyses were conducted to identify independent risk factors for complications during the PIMSRA procedure.

RESULTS

There were 48 patients with complications and 53 patients without complications. The heart rate at the start of the procedure and the maximum left ventricular outflow tract gradient (LVOTG) were independent risk factors related to PIMSRA complications. The optimal cut-off values for predicting complication occurrence were a heart rate > 49 bpm at the start of the procedure (OR: 3.79, 95% CI: 1.64-8.78, p = 0.002) and a maximum LVOTG > 92 mmHg (OR: 2.57, 95% CI: 1.15-5.75, p = 0.022), respectively.

CONCLUSIONS

The occurrence of PIMSRA complications is primarily associated with the heart rate at the start of the procedure and the maximum LVOTG. It is recommended to establish a comprehensive control plan to minimize the risk of complications during PIMSRA procedures.

The abnormalities of free fatty acid metabolism in patients with hypertrophic cardiomyopathy, a single-center retrospective observational study

BACKGROUND

Previous studies have shown the importance of energy deficiency and malfunctioning mitochondria in the pathophysiology of hypertrophic cardiomyopathy (HCM). There has been a little research into the relationship between plasma free fatty acids (FFA), one of the heart's main energy sources, and HCM. We evaluated its clinical importance in HCM to see if there was a link between plasma FFA metabolism and HCM.

METHODS

In a single-center retrospective observational study, we investigated 420 HCM patients diagnosed at Beijing Anzhen Hospital between January 1, 2018, and December 31, 2022. Meanwhile, 1372 individuals without HCM (non-HCM) were recruited. 391 non-HCM patients were chosen as controls via a propensity score matching (PSM) study with a 1:1 ratio.

RESULTS

FFA in HCM patients showed statistically significant correlations with creatinine (r = 0.115, p = 0.023), estimated GFR (r=-0.130, p = 0.010), BNP (r = 0.152, p = 0.007), LVEF (r=-0.227, p < 0.001), LVFS (r=-0.160, p = 0.002), and LAD (r = 0.112, p = 0.028). Higher FFA levels were found in HCM patients who had atrial fibrillation and NYHY functional classes III or IV (p = 0.015 and p = 0.022, respectively). In HCM patients, multiple linear regression analysis revealed that BNP and LVEF had independent relationships with increasing FFA (Standardized = 0.139, p = 0.013 and =-0.196, p < 0.001, respectively).

CONCLUSIONS

Among HCM patients, the plasma FFA concentration was lower, and those with AF and NYHY functional class III or IV had higher FFA levels, and LVEF and BNP were independently associated with increasing FFA. The findings of the study should help inspire future efforts to better understand how energy deficiency contributes to hypertrophic cardiomyopathy (HCM) development.

Unexpected systolic anterior motion of the mitral valve-related hypoxemia during transurethral resection of the prostate under spinal anesthesia: a case report

BACKGROUND

Dynamic obstruction of the left ventricular outflow tract resulting from systolic anterior motion of the mitral valve can be an unexpected cause of acute and severe perioperative hypotension in noncardiac surgery. We report a patient undergoing spinal anesthesia for transurethral resection of the prostate who experienced sudden hypoxemia caused by systolic anterior motion-induced mitral regurgitation but with a clinically picture simulating fluid overload.

CASE PRESENTATION

An 83-year-old man with a history of hypertension was scheduled for transurethral resection of the prostate. One hour after spinal anesthesia, he developed acute restlessness and dyspnea, with pink frothy sputum and progressive hypoxemia. Slight hypertension was noted, and an electrocardiogram showed atrial fibrillation with a rapid ventricular response. Furosemide and nitroglycerin were thus administered for suspected fluid overload or transurethral resection of the prostate syndrome; however, he then became severely hypotensive. After tracheal intubation, intraoperative transesophageal echocardiography was promptly performed, which revealed an empty hypercontractile left ventricle, significant mitral regurgitation and mosaic flow signal in the left ventricular outflow tract. Following aggressive fluid therapy, his hemodynamic changes stabilized. Repeat echocardiography in intensive care unit confirmed the presence of systolic anterior motion of the anterior mitral leaflet obstructing the left ventricular outflow tract. We speculate that pulmonary edema was induced by systolic anterior motion-associated mitral regurgitation and rapid atrial fibrillation, and the initial management had worsened his hypovolemia and provoked left ventricular outflow tract obstruction and hemodynamic instability.

CONCLUSIONS

Pulmonary edema caused by systolic anterior motion of the mitral valve can be difficult to clinically differentiate from that induced by fluid overload. Therefore, bedside echocardiography is paramount for timely diagnosis and prompt initiation of appropriate therapy in the perioperative care setting.

Exercise stress echocardiography: Where are we now?

Exercise stress echocardiography (ESE) is a widely used diagnostic test in cardiology departments. ESE is mainly used to study patients with coronary artery disease; however, it has increasingly been used in other clinical scenarios including valve pathology, congenital heart disease, hypertrophic and dilated cardiomyopathies, athlete evaluations, diastolic function evaluation, and pulmonary circulation study. In our laboratories, we use an established methodology in which cardiac function is evaluated while exercising on a treadmill. After completing the exercise regimen, patients remain in a standing position or lie down on the left lateral decubitus, depending on the clinical questions to be answered for further evaluation. This method increases the quality and quantity of information obtained. Here, we present the various methods of exercise stress echocardiography and our experience in many clinical arenas in detail. We also present alternatives to ESE that may be used and their advantages and disadvantages. We review recent advances in ESE and future directions for this established method in the study of cardiac patients and underline the advantage of using a diagnostic tool that is radiation-free.

Left Ventricular Remodeling in Hypertrophic Cardiomyopathy: An Overview of Current Knowledge

While most patients with hypertrophic cardiomyopathy (HCM) show a relatively stable morphologic and clinical phenotype, in some others, progressive changes in the left ventricular (LV) wall thickness, cavity size, and function, defined, overall, as “LV remodeling”, may occur. The interplay of multiple pathophysiologic mechanisms, from genetic background to myocardial ischemia and fibrosis, is implicated in this process. Different patterns of LV remodeling have been recognized and are associated with a specific impact on the clinical course and management of the disease. These findings underline the need for and the importance of serial multimodal clinical and instrumental evaluations to identify and further characterize the LV remodeling phenomenon. A more complete definition of the stages of the disease may present a chance to improve the management of HCM patients.

Exercise in hypertrophic cardiomyopathy: restrict or rethink

The detailed physiological consequences of aerobic training, in patients with hypertrophic cardiomyopathy (HCM), are not well understood. In athletes and nonathletes with HCM, there are two hypothetical concerns with respect to exercise: exercise-related worsening of the phenotype (e.g., promoting hypertrophy and fibrosis) and/or triggering of arrhythmia. The former concern is unproven and animal studies suggest an opposite effect, where exercise has been shown to be protective. The main reason for exercise restriction in HCM is fear of exercise-induced arrhythmia. Although the safety of sports in HCM has been reviewed, even more recent data suggest a substantially lower risk for sudden cardiac death (SCD) in HCM than previously thought, and there is an ongoing debate about restrictions of exercise imposed on individuals with HCM. This review outlines the pathophysiology of HCM, the impact of acute and chronic exercise (and variations of exercise intensity, modality, and athletic phenotype) in HCM including changes in autonomic function, blood pressure, cardiac dimensions and function, and cardiac output, and the underlying mechanisms that may trigger exercise-induced lethal arrhythmias. It provides a critical evaluation of the evidence regarding risk of SCD in athletes and the potential benefits of targeted exercise prescription in adults with HCM. Finally, it provides considerations for personalized recommendations for sports participation based on the available data.

Increased heart rate with sleep disordered breathing in hypertrophic cardiomyopathy

BACKGROUND

Current guidelines recommend medications with rate control properties for symptomatic patients with hypertrophic cardiomyopathy (HCM) based on the rationale that lowering heart rate (HR) improves their symptoms. Whether sleep disordered breathing (SDB) is associated with increased HR in HCM patients is not known.

METHOD

We diagnosed uncontrolled SDB (oxygen desaturation index ≥5) in consecutive echocardiographically confirmed HCM patients seen at Mayo Clinic, Rochester, and analyzed their HR as recorded by a 24-h Holter monitor. We compared mean, minimum, maximum HR between those with vs without SDB. In a pilot subanalysis of HCM patients with SDB who also underwent subsequent diagnostic polysomnography (PSG), we analyzed RR interval changes coinciding with obstructive sleep apnea and hypopnea episodes.

RESULTS

Of the 230 HCM patients included in this study (age 54 ± 16 years; 138 male; LVOT pressure gradient at rest 45 ± 39 mmHg), 115 (50%) patients had SDB. HCM patients with SDB were recorded to have higher mean HR (71 vs. 67 bpm; p = .002, adjusted p = .001), and this difference was most pronounced during night hours of 10 PM to 5 AM (61 vs. 67 bpm; p < .001). In the pilot analysis of the available PSG data, the release of obstructive sleep apneas and hypopneas coincided with fluctuation of HR.

CONCLUSIONS

SDB is independently associated with higher mean HR in patients with HCM, and this difference is most significant during sleep. Treatment of SDB, which is readily available, should be tested as a complementary modality to the currently recommended pharmacotherapy aimed at lowering HR in patients with symptomatic HCM.

Long-Term Left Ventricular Remodeling of Patients With Hypertrophic Cardiomyopathy

In hypertrophic cardiomyopathy (HC), a process of left ventricular (LV) remodeling carrying an adverse prognosis has been described. Conversely, a gradual and benign LV wall thinning has been suggested but never investigated. Therefore, we studied a HC cohort over a long period of time to evaluate the occurrence of a LV remodeling with a benign clinical course. Data of HC patients aged 18 to 65 years and without any condition known to influence LV remodeling were analyzed over a mean follow-up of 7.6 ± 5.7 years. Of 231 HC patients (65% males, mean age 46 ± 12 years), 47 (20%) developed LV remodeling, of whom 23 (10%) had a thinning ≥15% of LV maximal wall thickness from baseline without systolic dysfunction (MWT thinning); 13 (6%) progressed to a LV ejection fraction <50% (end-stage HC) and 11 (5%) developed an apical aneurysm. Follow-up length (odds ratio 1.07, 95% confidence interval 1.00 to 1.15, p = 0.06) and maximal LV wall thickness at baseline (odds ratio 1.14, 95% confidence interval 1.04 to 1.25, p = 0.004) were the main predictors of MWT thinning. Compared with patients with end-stage HC and apical aneurysm, those with MWT thinning showed lower HC-related morbidity (92% and 36% vs 22%, p = 0.003) and mortality (31% and 27% vs 4%, p = 0.02). Furthermore, they showed a combined HC-related morbidity and mortality similar to patients without LV remodeling (incidence 29/1000 vs 26/1000 patient-year, p = 0.77). In conclusion, a process of LV wall thinning with a benign outcome can occur over the long term in patients with HC. The prognostic importance of LV remodeling varies in relation to the different changes in LV morphology and function.

Large Q and S waves in lead III on the electrocardiogram distinguish patients with hypertrophic cardiomyopathy from athletes

OBJECTIVE

To identify electrocardiographic findings, especially deep Q and S waves in lead III, that differentiate athletes from patients with hypertrophic cardiomyopathy (HCM).

METHODS

Digital ECGs of athletes and patients with HCM followed at the Stanford Center for Inherited Cardiovascular Disease were studied retrospectively. All patients with HCM had an echocardiogram performed. A multivariable logistic regression model was used to calculate ORs for various demographic and ECG characteristics. Linear regression was used to correlate ECG characteristics with echocardiogram findings.

RESULTS

We studied 1124 athletes and 240 patients with HCM. The average Q+S wave amplitude in lead III (III_Q+S) was significantly higher in patients with HCM compared with athletes (0.71±0.69 mV vs 0.21±0.17 mV, p<0.001). In patients with HCM, III_Q+S directly correlated with interventricular septal (IVS) thickness on echocardiography (ρ=0.45, p<0.001). In a multivariable analysis adjusted for demographic and ECG characteristics, higher III_Q+S values remained independently associated with HCM compared with athletes (OR=4.2 per 0.5 mV, p<0.001). In subgroup analyses of young patients, African-American subjects and subjects without left axis deviation (LAD), III_Q+S remained associated with HCM. The addition of III_Q+S>1.0 mV as an abnormal finding to the International Criteria for athletic ECG interpretation improved sensitivity from 64.2% to 70.4%, with a minimal decrease in specificity.

CONCLUSION

Large Q and S waves in lead III distinguished athletes from patients with HCM, independent of axis and well-known ECG markers associated with HCM. The correlation between IVS thickness in patients with HCM and III_Q+S suggests a partial explanation for this association.

Mixture of Probabilistic Principal Component Analyzers for Shapes from Point Sets

Inferring a probability density function (pdf) for shape from a population of point sets is a challenging problem. The lack of point-to-point correspondences and the non-linearity of the shape spaces undermine the linear models. Methods based on manifolds model the shape variations naturally, however, statistics are often limited to a single geodesic mean and an arbitrary number of variation modes. We relax the manifold assumption and consider a piece-wise linear form, implementing a mixture of distinctive shape classes. The pdf for point sets is defined hierarchically, modeling a mixture of Probabilistic Principal Component Analyzers (PPCA) in higher dimension. A Variational Bayesian approach is designed for unsupervised learning of the posteriors of point set labels, local variation modes, and point correspondences. By maximizing the model evidence, the numbers of clusters, modes of variations, and points on the mean models are automatically selected. Using the predictive distribution, we project a test shape to the spaces spanned by the local PPCA's. The method is applied to point sets from: i) synthetic data, ii) healthy versus pathological heart morphologies, and iii) lumbar vertebrae. The proposed method selects models with expected numbers of clusters and variation modes, achieving lower generalization-specificity errors compared to state-of-the-art.

Fropofol decreases force development in cardiac muscle

Supranormal contractile properties are frequently associated with cardiac diseases. Anesthetic agents, including propofol, can depress myocardial contraction. We tested the hypothesis that fropofol, a propofol derivative, reduces force development in cardiac muscles via inhibition of cross-bridge cycling and may therefore have therapeutic potential. Force and intracellular Ca²⁺ concentration ([Ca²⁺]_i) transients of rat trabecular muscles were determined. Myofilament ATPase, actin-activated myosin ATPase, and velocity of actin filaments propelled by myosin were also measured. Fropofol dose dependently decreased force without altering [Ca²⁺]_i in normal and pressure-induced hypertrophied-hypercontractile muscles. Similarly, fropofol depressed maximum Ca²⁺-activated force ( F_max) and increased the [Ca²⁺]_i required for 50% of F_max (Ca₅₀) at steady state without affecting the Hill coefficient in both intact and skinned cardiac fibers. The drug also depressed cardiac myofibrillar and actin-activated myosin ATPase activity. In vitro actin sliding velocity was significantly reduced when fropofol was introduced during rigor binding of cross-bridges. The data suggest that the depressing effects of fropofol on cardiac contractility are likely to be related to direct targeting of actomyosin interactions. From a clinical standpoint, these findings are particularly significant, given that fropofol is a nonanesthetic small molecule that decreases myocardial contractility specifically and thus may be useful in the treatment of hypercontractile cardiac disorders.-Ren, X., Schmidt, W., Huang, Y., Lu, H., Liu, W., Bu, W., Eckenhoff, R., Cammarato, A., Gao, W. D. Fropofol decreases force development in cardiac muscle.

Left ventricular twist in hypertrophic cardiomyopathy : Predictor of nonsustained ventricular tachycardia

BACKGROUND

We investigated the efficacy of clinical and classic echocardiographic parameters in predicting the occurrence of nonsustained ventricular tachycardia (NsVT) in patients with hypertrophic cardiomyopathy (HCM).

METHODS

The study comprised 59 patients with HCM (47 male, [80%]; mean age, 48.48 ± 14.16 years). Clinical, electrocardiographic, as well as classic two-dimensional and speckle-tracking echocardiography (STE) data were collected. All patients had Holter monitoring within 24-72 h of the echocardiographic examination. NsVT was defined as three or more consecutive premature wide QRS complexes with a heart rate of > 100 bpm. The patient population was categorized into groups based on the occurrence or absence of NsVT on the 24-h Holter recordings.

RESULTS

NsVT was observed in 17 patients (29%). In these patients, higher twist (14.4 ± 3.8 vs.18 ± 7.9; p = 0.02), higher apical rotation (8.7 ± 4.2 vs. 12.2 ± 7; p = 0.02), higher sudden cardiac death risk score (4.4 ± 2.2 vs. 7 ± 3.3; p = 0.007), and decreased global longitudinal peak strain (GLPS; -12.8 ± 3.1 vs. -10.6 ± 2.8; p = 0.014) were observed. In the multivariate logistic regression analysis, including GLPS and twist, GLPS (Odds Ratio [OR]: 1.406; 95% CI: 1.087-1.818; p = 0.009) and twist (OR: 1.236; 95% CI: 1.056-1.446; p = 0.008) were found to be independent predictors of NsVT. In the receiver operating characteristic curve analysis, GLPS < -11.9% predicted NsVT with 82% sensitivity and 60% specificity (area under the curve [AUC]: 0.70; p = 0.014) and twist > 15.2° predicted NsVT with 70% sensitivity and 58% specificity (AUC: 0.69; p = 0.027).

CONCLUSION

Decreased GLPS and increased twist were predictive of NsVT in HCM patients. Parameters that can easily be measured with STE can help detect patients who may develop arrhythmia.

Joint Clustering and Component Analysis of Correspondenceless Point Sets: Application to Cardiac Statistical Modeling

Construction of Statistical Shape Models (SSMs) from arbitrary point sets is a challenging problem due to significant shape variation and lack of explicit point correspondence across the training data set. In medical imaging, point sets can generally represent different shape classes that span healthy and pathological exemplars. In such cases, the constructed SSM may not generalize well, largely because the probability density function (pdf) of the point sets deviates from the underlying assumption of Gaussian statistics. To this end, we propose a generative model for unsupervised learning of the pdf of point sets as a mixture of distinctive classes. A Variational Bayesian (VB) method is proposed for making joint inferences on the labels of point sets, and the principal modes of variations in each cluster. The method provides a flexible framework to handle point sets with no explicit point-to-point correspondences. We also show that by maximizing the marginalized likelihood of the model, the optimal number of clusters of point sets can be determined. We illustrate this work in the context of understanding the anatomical phenotype of the left and right ventricles in heart. To this end, we use a database containing hearts of healthy subjects, patients with Pulmonary Hypertension (PH), and patients with Hypertrophic Cardiomyopathy (HCM). We demonstrate that our method can outperform traditional PCA in both generalization and specificity measures.

Clinical Profile of Athletes With Hypertrophic Cardiomyopathy

BACKGROUND

The phenotype of individuals with hypertrophic cardiomyopathy (HCM) who exercise regularly is unknown. This study characterized the clinical profile of young athletes with HCM.

METHODS AND RESULTS

The electrical, structural, and functional cardiac parameters from 106 young (14-35 years) athletes with HCM were compared with 101 sedentary HCM patients. A subset of athletes with HCM exhibiting morphologically mild (13-16 mm), concentric disease was compared with 55 healthy athletes with mild physiological left ventricular hypertrophy (LVH). Most athletes with HCM (96%) exhibited T-wave inversion and had milder LVH (15.8±3.4 mm versus 19.7±6.5 mm, P<0.001), larger left ventricular cavity dimensions (47.8±6.0 mm versus 44.3±7.7 mm, P<0.001), and superior indices of diastolic function (average E/E' 7.9±2.4 versus 10.7±3.9, P<0.001) compared with sedentary HCM patients. In athletes with HCM, LVH was frequently (36%) confined to the apex and only 15 individuals (14%) exhibited mild concentric LVH mimicking physiological LVH. In these 15 athletes, conventional structural and functional cardiac parameters showed modest sensitivity and specificity for differentiating HCM from physiological LVH: 13% had a left ventricular cavity >54 mm, 87% had a left atrium ≤40, and 100% had an E/E' <12.

CONCLUSIONS

Athletes with HCM exhibit less LVH, larger left ventricular cavities, and normal indices of diastolic function compared with sedentary patients. Only a minority of athletes with HCM constitute the conventional gray zone of mild, concentric LVH. In this minority, conventional echocardiographic parameters alone are insufficient to differentiate HCM from physiological LVH and should be complemented by additional structural and functional assessments to minimize the risk of false reassurance.

Clinical Characteristics and Long-Term Outcomes of Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) has various morphological and clinical features. A decade has passed since the previous survey of the epidemiological and clinical characteristics of Japanese HCM patients. The Aichi Hypertrophic Cardiomyopathy (AHC) Registry is based on a prospective multicenter observational study of HCM patients. The clinical characteristics of 42 ambulant HCM patients followed up for up to 5 years were investigated. The primary endpoint was major adverse cardiac events (MACE), defined as death, non-fatal stroke, admission due to congestive heart failure (CHF), or episodes of sustained ventricular tachycardia/fibrillation. The MACE-free survival during the 5-year follow-up period was 76% according to Kaplan-Meier analysis. HCM-related death occurred in 3 (7%) patients and SCD occurred in 2 (5%) patients. Additionally, 3 (7%) patients were admitted to the hospital due to CHF. Meanwhile, sustained VT was detected in one (2%) of the patients who received ICD implantation and subsequently terminated with antitachycardia pacing using an ICD. The patients with HCM exhibiting left ventricular outflow obstruction (HOCM) had a slightly lower MACE-free survival rate than those with neither HOCM nor dilated-HCM (dHCM) (71% versus 81%, log-rank P = 0.581). Furthermore, the patients with dHCM demonstrated a significantly lower MACE-free survival rate than those with neither HOCM nor dHCM (33% versus 81%, log-rank P = 0.029). In the AHC Registry targeting current Japanese HCM patients, we demonstrated that many HCM patients continue to suffer from MACE despite the development of various treatments for HCM.

Four-Dimensional Speckle Tracking Echocardiography in Patients with Hypertrophic Cardiomyopathy

OBJECTIVE

Abnormal left ventricular (LV) deformational mechanics have been demonstrated in patients with hypertrophic cardiomyopathy (HCM) using two-dimensional (2D) speckle tracking echocardiography, but there is not enough information about the four-dimensional speckle tracking echocardiography (4DSTE) in these patients. The objective of the study was to identify and quantify the left ventricular contractility in patients with HCM using 4DSTE.

METHODS

Thirty patients [age, 54.6 ± 12.1 years; 12 (40%) women] with diagnosis of nonobstructive HCM and 20 healthy controls [age, 47.42 ± 11.43 years; 8 (40%) women] underwent 4DSTE measurement of longitudinal, radial, circumferential, and area strains.

RESULTS

Patients with HCM showed lower longitudinal (-13.5% vs. -20.3%, P < 0.001) and radial (33.4% vs. 43.6%, P < 0.001) strain, but higher circumferential (-22.7% vs. -15.9%, P < 0.001) and area (-30.7% vs. -22.1%, P < 0.001) strain than control subjects. Peak LV twist showed significantly higher values in patients with HCM (13.7 ± 5.3 vs. 11.3 ± 4.8, P < 0.005).

CONCLUSIONS

Patients with HCM have reduced longitudinal and radial strain but increased circumferential and area strain on 4DSTE. These results are found appropriate with previous 2DSTE studies. Thus, 4DSTE is useful to determine LV deformational mechanics.

Sleep-disordered breathing in hypertrophic cardiomyopathy: challenges and opportunities

Sleep-disordered breathing (SDB) may be a treatable risk factor in patients with hypertrophic cardiomyopathy (HCM), the most common inherited cardiomyopathy. Evidence suggests a high prevalence of SDB in HCM. We summarize the pathophysiology of SDB as it relates to hypertension, coronary artery disease, atrial fibrillation, and sudden cardiac death in patients with HCM. The implications regarding the care of patients with HCM and SDB are discussed as well as the knowledge deficits needing further exploration.

Advances in medical treatment of hypertrophic cardiomyopathy

We reviewed the natural history of patients with hypertrophic cardiomyopathy (HCM). The effect of medical treatments on natural history, left ventricular (LV) functions and LV remodeling was also evaluated. Sudden cardiac death and end-stage heart failure are the most serious complications of HCM. Age <30 years and a family history of sudden premature death are risk factors for sudden cardiac death in HCM patients. End-stage heart failure is not a specific additional phenomenon observed in patients with HCM, but is the natural course of the disease in most of those patients. After the occurrence of heart failure, the progression to cardiac death is very rapid. Young age at diagnosis, a family history of HCM, and greater wall thickness are associated with a greater likelihood of developing end-stage heart failure. Neither beta-blockers nor calcium antagonists can prevent this transition. The class Ia antiarrhythmic drugs, disopyramide and cibenzoline are useful for the reduction of LV pressure gradient. Unlike disopyramide, cibenzoline has little anticholinergic activity; therefore, this drug can be easily adapted to long-term use. In addition to the reduction in LV pressure gradient, cibenzoline can improve LV diastolic dysfunction, and induce regression of LV hypertrophy in patients with HCM. A decrease in intracellular Ca(2+) concentration through the activation of the Na(+)/Ca(2+) exchanger associated with cibenzoline therapy is likely to be closely related with the improvement in HCM-related disorders. It is possible that cibenzoline can prevent the progression from typical HCM to end-stage heart failure.

Systolic anterior motion of mitral valve with calcified annulus in octogenarians

Systolic anterior motion of the mitral leaflet causing left ventricular outflow tract obstruction is commonly seen in hypertrophic cardiomyopathy and also in patients with advanced mitral valve disease with excessive anterior leaflet tissue or a reduced aortic-mitral angle. We describe 2 octogenarians who presented with systolic mitral leaflet anterior motion in advanced mitral valve disease with severe mitral annular calcification and associated asymmetrical septal hypertrophy.

Cardiac output response and peripheral oxygen extraction during exercise among symptomatic hypertrophic cardiomyopathy patients with and without left ventricular outflow tract obstruction

OBJECTIVE

Reduction of left ventricular outflow tract obstruction (LVOTO) often improves symptoms in hypertrophic cardiomyopathy (HCM), but the correlation between exercise performance and measured LVOT gradients is weak. We investigated the relationship between LVOTO and cardiorespiratory responses during exercise.

METHODS

The study cohort included 70 patients with HCM (32 with LVOTO, 55 male, age 47±13) attending a dedicated cardiomyopathy clinic and 28 normal volunteers. All underwent cardiopulmonary exercise testing with simultaneous non-invasive haemodynamic assessment using finger plethysmography. Main outcome measures were peak oxygen consumption, cardiac index and arteriovenous oxygen difference.

RESULTS

When compared with controls, patients had reduced peak exercise oxygen consumption (22.4±6.1 vs 34.7±7.7 mL/kg/min, p<0.0001) and cardiac index (5.5±1.9 vs 9.4±2.9 L/min/m(2), p<0.0001). At all workloads, stroke volume index (SVI) was lower and arteriovenous oxygen difference greater in patients. During all stages of exercise, LVOTO in patients was associated with failure to augment SVI and higher oxygen consumption; cardiac reserve (4.4±2.7 vs 6.3±3.6 L/min, p=0.025) and peak mean arterial pressure (104±16 vs 112±16 mm Hg, p=0.033) were lower. Multivariable predictors of cardiac output response were age (β: -0.11; CI -0.162 to -0.057; p<0.0001), peak LVOT gradient (β: -0.018; CI -0.034 to -0.002; p=0.031) and gender (β: -2.286; CI -0.162 to -0.577; p=0.01). Within the obstructive cohort, different patterns of SV response were elicited in patients with similar clinical features.

CONCLUSIONS

Cardiac reserve is reduced in HCM because of failure of SV augmentation. LVOTO exacerbates this abnormal response, but haemodynamic responses vary significantly. Non-invasive exercise haemodynamic assessment may improve understanding of symptoms and help tailor therapy.

Mitochondrial haplogroups modify the risk of developing hypertrophic cardiomyopathy in a Danish population

Hypertrophic cardiomyopathy (HCM) is a genetic disorder caused by mutations in genes coding for proteins involved in sarcomere function. The disease is associated with mitochondrial dysfunction. Evolutionarily developed variation in mitochondrial DNA (mtDNA), defining mtDNA haplogroups and haplogroup clusters, is associated with functional differences in mitochondrial function and susceptibility to various diseases, including ischemic cardiomyopathy. We hypothesized that mtDNA haplogroups, in particular H, J and K, might modify disease susceptibility to HCM. Mitochondrial DNA, isolated from blood, was sequenced and haplogroups identified in 91 probands with HCM. The association with HCM was ascertained using two Danish control populations. Haplogroup H was more prevalent in HCM patients, 60% versus 46% (p = 0.006) and 41% (p = 0.003), in the two control populations. Haplogroup J was less prevalent, 3% vs. 12.4% (p = 0.017) and 9.1%, (p = 0.06). Likewise, the UK haplogroup cluster was less prevalent in HCM, 11% vs. 22.1% (p = 0.02) and 22.8% (p = 0.04). These results indicate that haplogroup H constitutes a susceptibility factor and that haplogroup J and haplogroup cluster UK are protective factors in the development of HCM. Thus, constitutive differences in mitochondrial function may influence the occurrence and clinical presentation of HCM. This could explain some of the phenotypic variability in HCM. The fact that haplogroup H and J are also modifying factors in ischemic cardiomyopathy suggests that mtDNA haplotypes may be of significance in determining whether a physiological hypertrophy develops into myopathy. mtDNA haplotypes may have the potential of becoming significant biomarkers in cardiomyopathy.

Clinical applications of exercise stress echocardiography in the treadmill with upright evaluation during and after exercise

Exercise stress echocardiography is the most frequently used stress test in our laboratory. Exercise echocardiography is used mainly in the study of patients with coronary artery disease. However, the technique is increasingly being used to study other diseases. In our centre, we use an original methodology, published by us in 2000, in which we evaluate heart function during exercise in the treadmill. After the exercise, patients are maintained in orthostatic position when appropriate or lying down in left lateral decubitus for further evaluation. Since this method seems to increase the quality and the quantity of information obtained in so many clinical arenas, we now present a detailed review of this methodology and its applications.

Heart failure in sub-Saharan Africa

The heart failure syndrome has been recognized as a significant contributor to cardiovascular disease burden in sub-Saharan African for many decades. Seminal knowledge regarding heart failure in the region came from case reports and case series of the early 20th century which identified infectious, nutritional and idiopathic causes as the most common. With increasing urbanization, changes in lifestyle habits, and ageing of the population, the spectrum of causes of HF has also expanded resulting in a significant burden of both communicable and non-communicable etiologies. Heart failure in sub-Saharan Africa is notable for the range of etiologies that concurrently exist as well as the healthcare environment marked by limited resources, weak national healthcare systems and a paucity of national level data on disease trends. With the recent publication of the first and largest multinational prospective registry of acute heart failure in sub-Saharan Africa, it is timely to review the state of knowledge to date and describe the myriad forms of heart failure in the region. This review discusses several forms of heart failure that are common in sub-Saharan Africa (e.g., rheumatic heart disease, hypertensive heart disease, pericardial disease, various dilated cardiomyopathies, HIV cardiomyopathy, hypertrophic cardiomyopathy, endomyocardial fibrosis, ischemic heart disease, cor pulmonale) and presents each form with regard to epidemiology, natural history, clinical characteristics, diagnostic considerations and therapies. Areas and approaches to fill the remaining gaps in knowledge are also offered herein highlighting the need for research that is driven by regional disease burden and needs.

MT-CYB mutations in hypertrophic cardiomyopathy

Mitochondrial dysfunction is a characteristic of heart failure. Mutations in mitochondrial DNA, particularly in MT-CYB coding for cytochrome B in complex III (CIII), have been associated with isolated hypertrophic cardiomyopathy (HCM). We hypothesized that MT-CYB mutations might play an important causal or modifying role in HCM. The MT-CYB gene was sequenced from DNA isolated from blood from 91 Danish HCM probands. Nonsynonymous variants were analyzed by bioinformatics, molecular modeling and simulation. Two germline-inherited, putative disease-causing, nonsynonymous variants: m.15024G>A; p.C93Y and m.15482T>C; p.S246P were identified. Modeling showed that the p.C93Y mutation leads to disruption of the tertiary structure of Cytb by helix displacement, interfering with protein–heme interaction. The p.S246P mutation induces a diproline structure, which alters local secondary structure and induces a kink in the protein backbone, interfering with macromolecular interactions. These molecular effects are compatible with a leaky phenotype, that is, limited but progressive mitochondrial dysfunction. In conclusion, we find that rare, putative leaky mtDNA variants in MT-CYB can be identified in a cohort of HCM patients. We propose that further patients with HCM should be examined for mutations in MT-CYB in order to clarify the role of these variants.

Exercise attenuates renal dysfunction with preservation of myocardial function in chronic kidney disease

Previous studies have suggested that exercise improves renal and cardiac functions in patients with chronic kidney disease. The aim of this study was to evaluate the effects of long-term aerobic swimming exercise with overload on renal and cardiac function in rats with 5/6 nefrectomy (5/6Nx). Eight Wistar rats were placed into 4 groups: Control (C), Control+Exercise (E), Sedentary 5/6Nx (NxS) and 5/6Nx+Exercise (NxE). The rats were subjected to swimming exercise sessions with overload for 30 min five days per week for five weeks. Exercise reduced the effect of 5/6Nx on creatinine clearance compared to the NxS group. In addition, exercise minimized the increase in mean proteinuria compared to the NxS group (96.9±10.0 vs. 51.4±9.9 mg/24 h; p<0.05). Blood pressure was higher in the NxS and NxE groups compared to the C and E groups (216±4 and 178±3 vs. 123±2 and 124±2 mm Hg, p<0.05). In the 200 glomeruli that were evaluated, the NxS group had a higher sclerosis index than did the NxE group (16% vs. 2%, p<0.05). Echocardiography demonstrated a higher anterior wall of the left ventricle (LV) in diastole in the NxS group compared with the C, E and NxE groups. The NxS group also had a higher LV posterior wall in diastole and systole compared with the E group. The developed isometric tension in Lmax of the heart papillary muscle was lower in the NxS group compared with the C, E and NxE groups. These results suggested that exercise in 5/6Nx animals might reduce the progression of renal disease and lessen the cardiovascular impact of a reduction in renal mass.

Structural and kinetic effects of hypertrophic cardiomyopathy related mutations R146G/Q and R163W on the regulatory switching activity of rat cardiac troponin I

Mutations in cardiac troponin I (cTnI) that cause hypertrophic cardiomyopathy (HCM) have been reported to change the contractility of cardiac myofilaments, but the underlying molecular mechanism remains elusive. In this study, Förster resonance energy transfer (FRET) was used to investigate the specific structural and kinetic effects that HCM related rat cTnI mutations R146G/Q and R163W exert on Ca(2+) and myosin S1 dependent conformational transitions in rat cTn structure. Ca(2+)-induced changes in interactions between cTnC and cTnI were individually monitored in reconstituted thin filaments using steady state and time resolved FRET, and kinetics were determined using stopped flow. R146G/Q and R163W all changed the FRET distances between cTnC and cTnI in unique and various ways. However, kinetic rates of conformational transitions induced by Ca(2+)-dissociation were universally slowed when R146G/Q and R163W were present. Interestingly, the kinetic rates of changes in the inhibitory region of cTnI were always slower than that of the regulatory region, suggesting that the fly casting mechanism that normally underlies deactivation is preserved in spite of mutation. In situ rat myocardial fiber studies also revealed that FRET distance changes indicating mutation specific disruption of the cTnIIR-actin interaction were consistent with increased passive tension.

Shortening baroreflex delay in hypertrophic cardiomyopathy patients -- an unknown effect of β-blockers

AIMS

Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy and impaired diastolic and systolic function. Abnormal sympathetic-parasympathetic balance is a potential stimulus for left ventricular hypertrophy in HCM patients. β-Blockers are routinely used in HCM for their strong negative inotropic effect; however, these drugs also influence the sympathetic-parasympathetic balance. This study aimed to determine the autonomic control of the cardiovascular system and the autonomic effects of β-blockers in HCM patients treated or untreated with β-blockers.

METHODS

Among 51 HCM outpatients (18-70 years old; 29 men) there were 19 individuals with no medication and 32 subjects treated with a β-blocker. Fourteen age- and gender-matched (23-70 years old; nine men) healthy volunteers were enrolled in the control group. Continuous, non-invasive finger blood pressure was recorded during supine rest for 30 min. Autonomic regulation of the cardiovascular system was measured by heart rate variability and spontaneous baroreflex function (cross-correlation sequence method).

RESULTS

The mean pulse interval, time domain and spectral measures of heart rate variability and baroreflex sensitivity were comparable between HCM patients, treated or not with β-blockers, and the control group. However, the delay of the baroreflex was significantly longer in HCM patients who were not treated with β-blockers [2.0 (1.6-2.3) s] in comparison with HCM patients receiving β-blockers [1.4 (1.1-1.8) s; P = 0.0072] or control subjects [1.2 (0.8-1.8) s; P = 0.0025]. This delay did not differ between HCM patients treated with β-blockers and the control group.

CONCLUSIONS

Hypertrophic cardiomyopathy not treated with β-blockers is accompanied by prolonged baroreflex delay. The use of β-blockers normalizes this delay.

Cardiac and skeletal muscle expression of mutant β-myosin heavy chains, degree of functional impairment and phenotypic heterogeneity in hypertrophic cardiomyopathy

Several mutations in distinct genes, all coding for sarcomeric proteins, have been reported in unrelated kindreds with familial hypertrophic cardiomyopathy (FHC). We have identified nine individuals from three families harboring two distinct mutations in one copy of the β-myosin heavy chain (β-MHC) gene. In this study, the expression of the mutant β-myosin protein isoform, isolated from slow-twitch fibers of skeletal muscle, was demonstrated by Northern and Western blot analysis; this myosin showed a decreased in vitro motility activity and produced a lower actin-activated ATPase activity. Isometric tension, measured in single slow-twitch fibers isolated from the affected individuals, also showed a significant decrease. The degree of impairment of β-myosin function, as well as the loss in isometric tension development, were strictly dependent on the amount of the isoform transcribed from the mutated allele. Interestingly, a strong correlation was also demonstrated between mutant β-myosin content and clinical features of FHC. On the other hand, we were unable to detect any correlation between mutant β-myosin expression and degree of cardiac hypertrophy, thereby strengthening the hypothesis that hypertrophy, one of the hallmarks of FHC, might not necessarily be related to the clinical evolution of this disease. These findings lend support to the notion that additional factors rather than the mutated gene may play a pathogenetic role in cardiac wall thickening, whereas the prognosis appears to be strongly related to the amount of mutant protein.

Hypertrophic cardiomyopathy. Clinical and pathologic correlates

Hypertrophic cardiomyopathy is a primary myocardial disease with a wide range of clinical and morphologic characteristics. It is characterized by increased cardiac mass associated with a non-dilated, hypertrophied left ventricle. Phenotypic variability is substantial and includes both diffuse and segmental forms of left ventricular hypertrophy. Histopathologic features consist of myofiber disorganization, intramural arteriosclerosis, and pathologic fibrosis and matrix connective tissue. Associated functional derangements include dynamic obstruction to left and right ventricular outflow and diastolic dysfunction, including heart failure.

Pacing for drug-refractory or drug-intolerant hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is a genetic disease with an autosomal-dominant inheritance for which negative inotropes are the most widely used initial therapies. Observational studies and small randomised trials have suggested symptomatic and functional benefits using pacing and several theories have been put forward to explain why. Pacing, although not the primary treatment for HCM, could be beneficial to patients with relative or absolute contraindications to surgery or alcohol ablation. Several randomised controlled trials comparing pacing to other therapeutic modalities have been conducted but no Cochrane-style systematic review has been done.

OBJECTIVES

To assess the effects of pacing in drug-refractory or drug-intolerant hypertrophic cardiomyopathy patients.

SEARCH METHODS

We searched the following on the 14/4/2010: CENTRAL (The Cochrane Library 2010, Issue 1), MEDLINE OVID (from 1950 onwards ), EMBASE OVID (from 1980 onwards ), Web of Science with Conference Proceedings (from 1970 onwards). No language restrictions were applied.

SELECTION CRITERIA

Randomised controlled trials of either parallel or crossover design that assess the beneficial and harmful effects of pacing for hypertrophic cardiomyopathy were included. When crossover studies were identified, we considered data only from the first phase.

DATA COLLECTION AND ANALYSIS

Data from included studies were extracted onto a pre-formed data extraction paper by two authors independently. Data was then entered into Review Manager 5.1 for analysis. Risk of bias was assessed using the guidance provided in the Cochrane Handbook. For dichotomous data, relative risk was calculated; and for continuous data, the mean differences were calculated. Where appropriate data were available, meta-analysis was performed. Where meta-analysis was not possible, a narrative synthesis was written. A QUROUM flow chart was provided to show the flow of papers.

MAIN RESULTS

Five studies (reported in 10 papers) were identified. However, three of the five studies provided un-usable data. Thus the data from only two studies (reported in seven papers) with 105 participants were included for this review. There was insufficient data to compare results on all-cause mortality, cost effectiveness, exercise capacity, Quality of life and Peak O2 consumption.When comparing active pacing versus placebo pacing on exercise capacity, one study showed that exercise time decreased from (13.1 ± 4.4) minutes to (12.6 ± 4.3) minutes in the placebo group and increased from (12.1 ± 5.6) minutes to (12.9 ± 4.2) minutes in the treatment group (MD 0.30; 95% CI -1.54 to 2.14). Statistically significant data from the same study showed that left ventricular outflow tract obstruction decreased from (71 ± 32) mm Hg to (52 ± 34) mm Hg in the placebo group and from (70 ± 24) mm Hg to (33 ± 27) mm Hg in the active pacing group (MD -19.00; 95% CI -32.29 to -5.71). This study was also able to show that New York Heart Association (NYHA) functional class decreased from (2.5 ± 0.5) to (2.2 ± 0.6) in the inactive pacing group and decreased from (2.6 ± 0.5) to (1.7 ± 0.7) in the placebo group (MD -0.50; 95% CI -0.78 to -0.22).When comparing active pacing versus trancoronary ablation of septal hypertrophy (TASH), data from one study showed that NYHA functional class decreased from (3.2 ± 0.7) to (1.5 ± 0.5) in the TASH group and decreased from (3.0 ± 0.1) to (1.9 ± 0.6) in the pacemaker group. This study also showed that LV wall thickness remained unchanged in the active pacing group compared to reduction from (22 ± 4) mm to (17 ± 3) mm in the TASH group (MD 0.60; 95% CI -5.65 to 6.85) and that LV outflow tract obstruction decreased from (80 ± 35.5) mm Hg in the TASH group to (49.3 ± 37.7) mm Hg in the pacemaker group.

AUTHORS' CONCLUSIONS

Trials published to date lack information on clinically relevant end-points. Existing data is derived from small trials at high risk of bias, which concentrate on physiological measures. Their results are inconclusive. Further large and high quality trials with more appropriate outcomes are warranted.

Hypertrophic Cardiomyopathy in a Young Adult with RV Aneurysm: Report of a Rare Finding and Review of the Literature

We report a case of a 22-year-old patient with a severe form of hypertrophic cardiomyopathy involving both ventricles, for which he underwent surgical treatment. Echocardiogram and magnetic resonance imaging confirmed the presence of an aneurysm in the inferior-anterior portion of the right ventricle.

MRI classification of asymmetric septal hypertrophic cardiomyopathy and its relation to the presence of risk factors

Asymmetric septal hypertrophic cardiomyopathy (ASH) is the common phenotype of hypertrophic cardiomyopathy (HCM). We sought to classify ASH using magnetic resonance imaging (MRI) and to determine whether the MRI classification of ASH is related to the presence of risk factors for HCM. Ninety-three patients with ASH underwent cine and delayed-enhancement MRI. The ASH was classified morphologically using cine MRI at end-diastole. We evaluated the association between the MRI findings and the presence of risk factors in the ASH. The ASH was classified into three subtypes by MRI: contiguous subtype showing various clinical and MRI features (57%), sigmoid subtype (29%) with fewer risk factors, and reverse-curve subtype (14%) in younger patients with the larger myocardial mass and delayed-enhancement, which were significantly related to the risk factors. MRI was used to classify ASH into three subtypes, which might be related to the presence of risk factors.

Dilated phase of hypertrophic cardiomyopathy caused by two different sarcomere mutations, treated with surgical left ventricular reconstruction and cardiac resynchronization therapy with a defibrillator

We herein report the case of a 61-year-old woman with dilated phase of hypertrophic cardiomyopathy (D-HCM) who had been diagnosed with HCM 17 years previously. On admission, her left ventricle (LV) had marked dilation, dyssynchrony with diffuse severe hypokinesis, and ventricular tachycardia. She had two mutations in the cardiac myosin binding protein-C gene, which were suspected to be the causes of the D-HCM. We performed LV reconstruction surgery and cardiac resynchronization therapy with a defibrillator for her drug-resistant severe heart failure. After surgery, her New York Heart Association class dramatically improved, and she has not been re-hospitalized since these treatments.

Long-term outcomes in hypertrophic cardiomyopathy caused by mutations in the cardiac troponin T gene

BACKGROUND

Hypertrophic cardiomyopathy caused by mutations in the cardiac troponin T gene (TNNT2) has been associated with a high risk of sudden cardiac death (SCD) and mild left ventricular hypertrophy. However, previous studies are limited by sample size, cross-sectional design, and few data in relatives.

METHODS AND RESULTS

Five hundred fifty-two unrelated hypertrophic cardiomyopathy probands were screened for TNNT2 mutations. First-degree relatives were invited for clinical and genetic evaluation. Ninety-two individuals (20 probands and 72 relatives) carried TNNT2 mutations (51 [55%] male; 30±17 years). ECGs and echo were available in 87 (95%) and 88 (96%) individuals, respectively. ECG was normal in 13 (68%) children (<16 years) and 13 (19%) adults. Echo was normal in 18 (90%) children and 16 (24%) adults; 7 (10%) adults had a normal ECG and echo. Thirteen (65%) of 20 families had a history of SCD. Follow-up was available for 75 patients (mean, 9.9±5.2 years); 2 of 16 adults and 2 of 18 children with normal echoes developed left ventricular hypertrophy. Twenty-three (22%) received an implantable cardioverter-defibrillator (20 for primary prophylaxis). One child and 3 adults died of SCD and 2 adults were resuscitated from ventricular fibrillation. One patient had an appropriate implantable cardioverter-defibrillator discharge. The rate of cardiovascular death, transplant, and implantable cardioverter-defibrillator discharge was 1.6% (0.016 person/y; 95% confidence interval, 0.83-2.79%), and SCD 0.93% (0.0093 person/y; 95% confidence interval, 0.37-1.92%).

CONCLUSIONS

Left ventricular hypertrophy is rare in children with TNNT2 mutations. Left ventricular hypertrophy is absent in the minority of adults, but most have an abnormal ECG. Despite adverse family histories, the rate of cardiovascular death during follow-up was similar to that reported in large referral populations.

Cardiomyopathies (hypertrophy and failure): what can offer cardiac magnetic resonance imaging?

In routine, cardiomyopathy, confirmed or not, is a frequent reason for cardiac MRI evaluation. Step by step, by using a wide panel of sequences, cardiac MRI is able to characterize cardiomyopathies by their morphologic and functional phenotype as well as by tissue characterization. Cardiac-MRI is also considered as the most appropriate technique for the follow-up of this disease. The purpose of this article is to browse an overview of the main MRI features of cardiomyopathy, focusing the purpose on hypertrophic forms and myocardial diseases leading to cardiac failure.