Myocardial ischemia detected by thallium scintigraphy is frequently related to cardiac arrest and syncope in young patients with hypertrophic cardiomyopathy

Myocardial perfusion improvement and mechanism after percutaneous intramyocardial septal radiofrequency ablation in obstructive hypertrophic cardiomyopathy: a study of myocardial contrast echocardiography

The data on myocardial perfusion of the percutaneous intramyocardial septal radiofrequency ablation (PIMSRA) for obstructive hypertrophic cardiomyopathy (HOCM) are still lacking, although PIMSRA have been proved to be of great safety and efficacy. The aim of this study was to quantitatively analyze the changes in myocardial perfusion after PIMSRA using myocardial contrast echocardiography (MCE). 27 HOCM patients treated with PIMSRA were retrospectively analyzed, and their echocardiographic parameters and perfusion parameters of MCE were collected before and 12 months after PIMSRA. A reperfusion curve was used to quantify microvascular blood volume (A), microvascular flux rate (β), and microvascular blood flow (MBF) of each segment. Then the value difference (Δ) of parameters between post- and pre-operation were calculated. Finally, the correlation between the changes in MBF and in each echocardiographic parameter was analyzed. (1) Compared with baseline, the global A, β and MBF were significantly increased in HOCM patients after PIMSRA (all P < 0.001). The β, MBF were increased in the interventricular septum (P < 0.001, respectively), and the A, β, MBF were increased in the left ventricular wall (all P < 0.001). (2) Correlation analysis showed that the ΔMBF of interventricular septum was mainly negatively correlated with the maximum interventricular septum thickness (ΔIVSTmax, r=-0.670, P < 0.001), mean interventricular septum thickness (ΔIVSTmean, r=-0.690, P < 0.001), and left ventricular mass index (ΔLVMI, r=-0.774, P < 0.001), while the ΔMBF of left ventricular wall was positively correlated with left ventricular end-diastolic volume index (ΔLVEDVI, r = 0.621, P = 0.001) and stroke volume index (ΔSVI, r = 0.810, P < 0.001). Myocardial perfusion was improved at both interventricular septum and ventricular wall in HOCM patients after PIMSRA. MCE can provide a new dimension for the efficacy evaluation to PIMSRA procedure.

Effect of beta-blockers and exercise restriction on the prevention of sudden cardiac death in pediatric hypertrophic cardiomyopathy

BACKGROUND

Risk assessment tools and effective prevention strategies for sudden cardiac death (SCD) in pediatric patients with hypertrophic cardiomyopathy (HCM) have not been established. This study aimed to evaluate the efficacy of beta-blockers and exercise restriction for SCD prevention in this population.

METHODS

We retrospectively reviewed the medical records of patients aged <18 years who were diagnosed with HCM at our center between January 1996 and December 2021. SCD and aborted SCD were defined as SCD equivalents. We divided patients based on whether they were prescribed beta-blockers or exercise restriction and compared the outcomes among the groups. The primary outcome was the overall survival (OS), and the secondary outcome was the cumulative SCD equivalent rate. Outcomes were analyzed using Kaplan-Meier curves and Cox proportional hazard analysis. We also compared patients according to the occurrence of SCD equivalents to identify SCD risk predictors.

RESULTS

Among the 43 included patients [mean age, 7.7 (1.6-12.1) years; 23 male individuals], SCD equivalents occurred in 13 patients over 11.2 (4.5-15.6) years of follow-up, among whom 12 were resuscitated and 1 died. The OS rate was significantly higher in the beta-blocker and exercise restriction groups than in the non-beta-blocker and non-exercise restriction groups (81.3 % vs. 19.1 %, p < 0.01 and 57.4 % vs. 12.7 %, p < 0.01, respectively). Among the 13 patients with SCD equivalents, 5 had 9 recurrent SCD equivalents. A significant difference was observed between the SCD equivalent and non-SCD equivalent groups in the history of suspected arrhythmogenic syncope (p < 0.01) in the univariable but not in the multivariable analysis.

CONCLUSIONS

Beta-blockers and exercise restriction may decrease the risk of SCD in pediatric patients with HCM and should be considered for SCD prevention in this population, particularly because predicting SCD in these patients remains challenging.

Advances in Multi-Modality Imaging in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is characterized by abnormal growth of the myocardium with myofilament disarray and myocardial hyper-contractility, leading to left ventricular hypertrophy and fibrosis. Where culprit genes are identified, they typically relate to cardiomyocyte sarcomere structure and function. Multi-modality imaging plays a crucial role in the diagnosis, monitoring, and risk stratification of HCM, as well as in screening those at risk. Following the recent publication of the first European Society of Cardiology (ESC) cardiomyopathy guidelines, we build on previous reviews and explore the roles of electrocardiography, echocardiography, cardiac magnetic resonance (CMR), cardiac computed tomography (CT), and nuclear imaging. We examine each modality's strengths along with their limitations in turn, and discuss how they can be used in isolation, or in combination, to facilitate a personalized approach to patient care, as well as providing key information and robust safety and efficacy evidence within new areas of research.

Mechanisms and prognostic impact of myocardial ischaemia in hypertrophic cardiomyopathy

Despite the progress made in risk stratification, sudden cardiac death and heart failure remain dreaded complications for hypertrophic cardiomyopathy (HCM) patients. Myocardial ischaemia is widely acknowledged as a contributor to cardiovascular events, but the assessment of ischaemia is not yet included in HCM clinical guidelines. This review aims to evaluate the HCM-specific pro-ischaemic mechanisms and the potential prognostic value of imaging for myocardial ischaemia in HCM. A literature review was performed using PubMed to identify studies with non-invasive imaging of ischaemia (cardiovascular magnetic resonance, echocardiography, and nuclear imaging) in HCM, prioritising studies published after the last major review in 2009. Other studies, including invasive ischaemia assessment and post-mortem histology, were also considered for mechanistic or prognostic relevance. Pro-ischaemic mechanisms in HCM reviewed included the effects of sarcomeric mutations, microvascular remodelling, hypertrophy, extravascular compressive forces and left ventricular outflow tract obstruction. The relationship between ischaemia and fibrosis was re-appraised by considering segment-wise analyses in multimodal imaging studies. The prognostic significance of myocardial ischaemia in HCM was evaluated using longitudinal studies with composite endpoints, and reports of ischaemia-arrhythmia associations were further considered. The high prevalence of ischaemia in HCM is explained by several micro- and macrostructural pathological features, alongside mutation-associated energetic impairment. Ischaemia on imaging identifies a subgroup of HCM patients at higher risk of adverse cardiovascular outcomes. Ischaemic HCM phenotypes are a high-risk subgroup associated with more advanced left ventricular remodelling, but further studies are required to evaluate the independent prognostic value of non-invasive imaging for ischaemia.

Coronary microvascular disease in hypertrophic and infiltrative cardiomyopathies

Pathologic hypertrophy of the cardiac muscle is a commonly encountered phenotype in clinical practice, associated with a variety of structural and non-structural diseases. Coronary microvascular disease is considered to play an important role in the natural history of this pathological phenotype. Non-invasive imaging modalities, most prominently positron emission tomography and cardiac magnetic resonance, have provided insights into the pathophysiological mechanisms of the interplay between hypertrophy and the coronary microvasculature. This article summarizes the current knowledge on coronary microvascular dysfunction in the most frequently encountered forms of pathologic hypertrophy.

Efficacy of Catheter Ablation for Atrial Fibrillation in Hypertrophic Cardiomyopathy: A Systematic Review and Meta-Analysis

Atrial fibrillation (AF) is the most common arrhythmia in patients with hypertrophic cardiomyopathy (HCM). Catheter ablation (CA) has emerged as an effective therapy for AF. We conducted a meta-analysis to update the current clinical evidence on the efficacy of CA for AF in patients with HCM. We searched PubMed, Embase, Cochrane and Clinicaltrials.gov for interventional and observational studies assessing single and multiple procedure success rate of CA in HCM patients. Our meta-analysis included 25 studies involving 1817 patients. Success rate following single procedure was 40.4% (95% CI 33.1 to 48.0%) at latest follow-up. The pooled success rate following multiple procedures was 51.4% (95% CI 42.9% to 60.0%) at latest follow-up. In the subgroup analysis for AF subtype, TCA was more successful for paroxysmal AF compared to non-paroxysmal AF. For the subset of studies reporting drug-free success rate, single and multiple procedures had a success rate of 33.4% (95% CI 19.3 to 49.1%) and 51.8% (95% CI 41.3 to 62.2%) at latest follow-up, respectively. CA is a suitable option for AF in patients with HCM. Success rate is greater in paroxysmal AF, after multiple procedures and with antiarrhythmic drugs.

Myocardial bridging in adult with hypertrophic cardiomyopathy: Imaging findings with coronary computed tomography angiography

Myocardial bridgin in an adult with hypertrophic cardiomyopathy is a rare congenital coronary artery anomaly. It is often detected incidentally, and its true incidence in the general population is not known. Myocardial bridging may cause compression of a coronary artery, and it has been suggested that myocardial ischemia may result. Symptoms of myocardial bridging in the adult with hypertrophic cardiomyopathy are syncope, palpitations, dyspnea, and chest pain. Also, arrhythmia and myocardial infarction can be seen; these can cause sudden death, especially in athletes and young people. We present a case of a 48-year-old male with hypertrophic cardiomyopathy and myocardial bridging detected by coronary computed tomography angiography who complained of chest pain.

Microvascular Dysfunction in Hypertrophic Cardiomyopathy

Myocardial ischemia is an established pathophysiological feature of hypertrophic cardiomyopathy (HCM) that impacts various clinical features, including heart failure (HF) and sudden cardiac death (SCD). The major determinant of myocardial ischemia in HCM is coronary microvascular dysfunction (CMD) in the absence of epicardial coronary artery abnormalities. Despite the impossibility to directly visualize microcirculation in vivo, a multimodality approach can allow a detailed assessment of microvascular dysfunction and ischemia. Accordingly, the non-invasive assessment of CMD using transthoracic Doppler echocardiography, positron emission tomography, and cardiac magnetic resonance should now be considered mandatory in any HCM patient. Noteworthy, a complete diagnostic work-up for myocardial ischemia plays a major role in the approach of the patients with HCM and their risk stratification. Chronic and recurrent episodes of ischemia can contribute to fibrosis, culminating in LV remodeling and HF. Ischemia can potentially constitute an arrhythmic substrate and might prove to have an added value in risk stratification for SCD. Accordingly, strategies for the early diagnosis of CMD should now be considered an important challenge for the scientific community.

Syncope in hypertrophic cardiomyopathy (part I): An updated systematic review and meta-analysis

AIMS

To describe the proportion of patients with syncope among those affected by hypertrophic cardiomyopathy (HCM) and the relevance of syncope as risk factor for sudden cardiac death and life-threatening arrhythmic events.

METHOD AND RESULTS

Systematic review of original articles that assessed syncope in HCM patients. Literature search of PubMed including all English publications from 1973 to 2021.We found 57 articles for a total of 21.791 patients; of these, 14 studies reported on arrhythmic events in the follow-up. Syncope was reported in 15.8% (3.452 of 21.791) patients. It was considered unexplained in 91% of cases. Life-threatening arrhythmic events occurred in 3.6% of non-syncopal patients and in 7.7% of syncopal patients during a mean follow-up of 5.6 years. A relative risk of 1.99 (95%CI 1.39 to 2.86) was estimated for syncope patients by the random effect model using Haldane continuity correction for 0 events.

CONCLUSIONS

In the current practice, the cause of syncope remained unexplained in most patients affected by HCM. The management of patients seems mainly driven by risk stratification rather than identification of the aetiology of syncope. There is a need of precise instructions how to apply the recommendations of current guidelines to this disease, which tests are indicated and how to interpret their findings. The protocol was registered in Prospero (ID: 275963).

Recommendations for Multimodality Cardiovascular Imaging of Patients with Hypertrophic Cardiomyopathy: An Update from the American Society of Echocardiography, in Collaboration with the American Society of Nuclear Cardiology, the Society for Cardiovascular Magnetic Resonance, and the Society of Cardiovascular Computed Tomography

Hypertrophic cardiomyopathy (HCM) is defined by the presence of left ventricular hypertrophy in the absence of other potentially causative cardiac, systemic, syndromic, or metabolic diseases. Symptoms can be related to a range of pathophysiologic mechanisms including left ventricular outflow tract obstruction with or without significant mitral regurgitation, diastolic dysfunction with heart failure with preserved and heart failure with reduced ejection fraction, autonomic dysfunction, ischemia, and arrhythmias. Appropriate understanding and utilization of multimodality imaging is fundamental to accurate diagnosis as well as longitudinal care of patients with HCM. Resting and stress imaging provide comprehensive and complementary information to help clarify mechanism(s) responsible for symptoms such that appropriate and timely treatment strategies may be implemented. Advanced imaging is relied upon to guide certain treatment options including septal reduction therapy and mitral valve repair. Using both clinical and imaging parameters, enhanced algorithms for sudden cardiac death risk stratification facilitate selection of HCM patients most likely to benefit from implantable cardioverter-defibrillators.

Effect of cilobradine in cats with a first episode of congestive heart failure due to primary cardiomyopathy

INTRODUCTION

Heart rate (HR) is often elevated in cats with cardiomyopathies (CMPs). Pharmacologic modulation of HR may reduce cardiac morbidity and mortality.

OBJECTIVES

To investigate the effects of cilobradine vs. placebo, regarding time to cardiac mortality or morbidity in cats with first episode of congestive heart failure (CHF) due to primary CMP.

ANIMALS

Three hundred and sixty-seven client-owned cats with primary CMP that had presented with a first episode of CHF at 50 centers in Europe. Per-protocol population comprised 193 cats (n = 89 cilobradine, n = 104 placebo). An interim analysis for futility was planned.

METHODS

Prospective, randomized, placebo-controlled, double-blinded, multicenter clinical trial. Primary outcome variable was the time to a composite of cardiac mortality or cardiac morbidity.

RESULTS

Median time to primary outcome was 84 days (95% confidence interval [CI]: 63-219 days) in the cilobradine group (CG) and 203 days in the placebo group (95% CI: 145-377 days) with observed hazard ratio of 1.44, indicating a higher hazard for the CG (P = 0.057). Mean HR was 28 beats per minute (bpm) lower at Day 7 (P < 0.0001) and remained 29 bpm lower at Day 360 (P = 0.026) in the CG than that in the placebo group. Although the number of adverse events did not differ, there were more serious adverse events in the CG.

CONCLUSIONS

Heart rate reduction by cilobradine in cats with a first episode of CHF due to primary CMP did not reduce cardiac mortality and morbidity.

Prognostic Significance of Myocardial Ischemia Detected by Single-Photon Emission Computed Tomography in Children with Hypertrophic Cardiomyopathy

Myocardial ischemia caused by microvascular dysfunction is an important pathophysiologic component of hypertrophic cardiomyopathy (HCM), promoting myocardial fibrosis, adverse left ventricular remodeling, and impacting on clinical course and outcome in HCM patients. The aim of study was to assess the prevalence and clinical significance of myocardial ischemia in children with HCM using 99mTc-MIBI single-photon emission computed tomography (SPECT). Ninety-one children with HCM, median age 13.6 years, underwent SPECT evaluation from 2006 to 2017. Imaging was performed at rest and after maximal exercise. Myocardial perfusion defects were identified in 70 children (76.9%; group I), median age 13.8 years. Fixed perfusion defects were evident in 22 of them, while reversible at rest in 48. In 21 children (23.1%; group II), median age 11 years, myocardial perfusion defects were not detected. Patient demographics, echocardiography, resting electrocardiogram (ECG), 24-h Holter ECG, myocardial fibrosis in cardiovascular magnetic resonance imaging, and cardiovascular events were analyzed and compared between the groups. During follow-up at a median of 8.3 years in children with myocardial ischemia, clinical endpoints occurred more often (47 vs. 5; p = 0.02) and more patients reached a clinical endpoint (28 [40%] vs. 3 [14.3%]; p = 0.036). In children with myocardial ischemia, myocardial fibrosis was observed with greater frequency. Myocardial perfusion defects may reflect an ischemic process which (1) affects the clinical manifestations and (2) is an important predictor of adverse clinical events and risk of death in children with HCM. Myocardial ischemia in HCM patients frequently correlates with myocardial fibrosis.

Coronary microvascular dysfunction in stable ischaemic heart disease (non-obstructive coronary artery disease and obstructive coronary artery disease)

Diffuse and focal epicardial coronary disease and coronary microvascular abnormalities may exist side-by-side. Identifying the contributions of each of these three players in the coronary circulation is a difficult task. Yet identifying coronary microvascular dysfunction (CMD) as an additional player in patients with coronary artery disease (CAD) may provide explanations of why symptoms may persist frequently following and why global coronary flow reserve may be more prognostically important than fractional flow reserve measured in a single vessel before percutaneous coronary intervention. This review focuses on the challenges of identifying the presence of CMD in the context of diffuse non-obstructive CAD and obstructive CAD. Furthermore, it is going to discuss the pathophysiology in this complex situation, examine the clinical context in which the interaction of the three components of disease takes place and finally look at non-invasive diagnostic methods relevant for addressing this question.

Coronary microvascular dysfunction in hypertrophic cardiomyopathy: Pathophysiology, assessment, and clinical impact

Myocardial ischemia constitutes one of the most important pathophysiological features in hypertrophic cardiomyopathy. Chronic and recurrent myocardial ischemia leads to fibrosis, which may culminate in myocardial dysfunction. Since the direct visualization of coronary microcirculation in vivo is not possible, its function must be studied indirectly. Invasive and noninvasive techniques allow microcirculatory dysfunction to be evaluated, including echocardiography, magnetic resonance, positron emission tomography, and cardiac catheterization. Blunted myocardial blood flow and coronary flow reserve have been suggested to associate with unfavorable prognosis. Microcirculatory dysfunction may be one additional important parameter to take into account for risk stratification beyond the conventional risk factors.

Hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease. The disease is characterized by marked variability in morphological expression and natural history, ranging from asymptomatic to heart failure or sudden cardiac death. Left ventricular hypertrophy and abnormal ventricular configuration result in dynamic left ventricular outflow obstruction in most patients. The goal of pharmacological therapy in HCM is to alleviate the symptoms, and it includes pharmacotherapies and septal reduction therapies. In this review, we summarize the relevant clinical issues and treatment options of HCM.

Metabolic Alterations in Inherited Cardiomyopathies

The normal function of the heart relies on a series of complex metabolic processes orchestrating the proper generation and use of energy. In this context, mitochondria serve a crucial role as a platform for energy transduction by supplying ATP to the varying demand of cardiomyocytes, involving an intricate network of pathways regulating the metabolic flux of substrates. The failure of these processes results in structural and functional deficiencies of the cardiac muscle, including inherited cardiomyopathies. These genetic diseases are characterized by cardiac structural and functional anomalies in the absence of abnormal conditions that can explain the observed myocardial abnormality, and are frequently associated with heart failure. Since their original description, major advances have been achieved in the genetic and phenotype knowledge, highlighting the involvement of metabolic abnormalities in their pathogenesis. This review provides a brief overview of the role of mitochondria in the energy metabolism in the heart and focuses on metabolic abnormalities, mitochondrial dysfunction, and storage diseases associated with inherited cardiomyopathies.

Hypertrophic Cardiomyopathy: A Vicious Cycle Triggered by Sarcomere Mutations and Secondary Disease Hits

Significance: Hypertrophic cardiomyopathy (HCM) is a cardiac genetic disease characterized by left ventricular hypertrophy, diastolic dysfunction, and myocardial disarray. Disease onset occurs between 20 and 50 years of age, thus affecting patients in the prime of their life. HCM is caused by mutations in sarcomere proteins, the contractile building blocks of the heart. Despite increased knowledge of causal mutations, the exact path from genetic defect leading to cardiomyopathy is complex and involves additional disease hits. Recent Advances: Laboratory-based studies indicate that HCM development not only depends on the primary sarcomere impairment caused by the mutation but also on secondary disease-related alterations in the heart. Here we propose a vicious mutation-induced disease cycle, in which a mutation-induced energy depletion alters cellular metabolism with increased mitochondrial work, which triggers secondary disease modifiers that will worsen disease and ultimately lead to end-stage HCM. Critical Issues: Evidence shows excessive cellular reactive oxygen species (ROS) in HCM patients and HCM animal models. Oxidative stress markers are increased in the heart (oxidized proteins, DNA, and lipids) and serum of HCM patients. In addition, increased mitochondrial ROS production and changes in endogenous antioxidants are reported in HCM. Mutant sarcomeric protein may drive excessive levels of cardiac ROS via changes in cardiac efficiency and metabolism, mitochondrial activation and/or dysfunction, impaired protein quality control, and microvascular dysfunction. Future Directions: Interventions restoring metabolism, mitochondrial function, and improved ROS balance may be promising therapeutic approaches. We discuss the effects of current HCM pharmacological therapies and potential future therapies to prevent and reverse HCM. Antioxid. Redox Signal. 31, 318-358.

Is there a role for cardiac positron emission tomography in hypertrophic cardiomyopathy?

Coronary microvascular dysfunction and, its functional consequence, myocardial ischemia are common pathologic features in patients with hypertrophic cardiomyopathy (HCM). Both have been commonly invoked as potential triggers of and/or contributors to the underlying pathophysiological processes leading to heart failure, and malignant ventricular arrhythmias. Positron emission tomography (PET) with myocardial blood flow quantification provides a unique opportunity to evaluate the integrity and function of the coronary microcirculation in HCM. The purpose of the present review is to summarize all the pertinent literature and future perspectives of the role of PET in the evaluation and risk stratification of patients with HCM.

Energetic drain driving hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common form of hereditary cardiomyopathy and is mainly caused by mutations of genes encoding cardiac sarcomeric proteins. HCM is characterized by hypertrophy of the left ventricle, frequently involving the septum, that is not explained solely by loading conditions. HCM has a heterogeneous clinical profile, but diastolic dysfunction and ventricular arrhythmias represent two dominant features of the disease. Preclinical evidence indicates that the enhanced Calcium (Ca²⁺ ) sensitivity of the myofilaments plays a key role in the pathophysiology of HCM. Notably, this is not always a direct consequence of sarcomeric mutations, but can also result from secondary mutation-driven alterations. Here, we review experimental and clinical evidence indicating that increased myofilament Ca²⁺ sensitivity lies upstream of numerous cellular derangements which potentially contribute to the progression of HCM toward heart failure and sudden cardiac death.

Automated Quantitative Stress Perfusion in a Clinical Routine

Cardiovascular magnetic resonance (CMR) perfusion imaging is a robust noninvasive technique to evaluate ischemia in patients with coronary artery disease (CAD). Although qualitative and semiquantitative methods have shown that CMR has high accuracy in diagnosing flow-obstructing lesions in CAD, quantitative ischemic burden is an important variable used in clinical practice for treatment decisions. Quantitative CMR perfusion techniques have evolved significantly, with accuracy comparable with both PET and microsphere evaluation. Routine clinical use of these quantitative techniques has been facilitated by the introduction of automated methods that accelerate the work flow and rapidly generate pixel-based myocardial blood flow maps.

Coronary Microvascular Dysfunction: Clinical Considerations and Noninvasive Diagnosis

Chest pain in patients without obstructive coronary artery disease has been realized as a frequent problem encountered in clinical practice. Invasive flow investigations have suggested that up to two-thirds of patients with nonobstructive coronary atherosclerosis may have microvascular dysfunction (MVD). Positron emission tomography myocardial perfusion imaging in conjunction with tracer-kinetic modeling enables the concurrent quantification of myocardial blood flow (MBF) in milliliters per minute per gram of tissue. This allows the assessment of hyperemic MBFs and myocardial flow reserve for the noninvasive identification and characterization of MVD as an important functional substrate for angina symptoms amenable to intensified and individualized medical intervention with nitrates, calcium-channel blockers, statins, angiotensin-converting enzyme inhibitors, and/or angiotensin II type 1 receptor blockers. Recent investigations suggest that cardiac magnetic resonance and computed tomography may also be suitable for the noninvasive detection of MVD. Whether intensified and individualized treatment related improvement or even normalization of hyperemic MBF and/or myocardial flow reserve may lead to a persistent reduction in angina symptoms and/or improved cardiovascular outcome as compared to standard care, deserves further testing in large-scale randomized clinical trials.

Cardiovascular magnetic resonance T2* mapping for structural alterations in hypertrophic cardiomyopathy

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HCM patients exhibited significantly decreased T2* values compared to controls.

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Within HCM patients, those with myocardial fibrosis presented with decreased T2* values.

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T2* provided good diagnostic accuracy to diagnose HCM with fibrosis.

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T2* may add information for identifying a higher risk sub-group of HCM patients.

Purpose

Hypertrophic cardiomyopathy (HCM) is characterized by a heterogeneous morphology and variable prognosis. A mismatch between left ventricular mass (LVM) and microvascular circulation with corresponding relative ischemia has been implicated to cause myocardial replacement fibrosis that deteriorates prognosis. Besides parametric T1 mapping, Cardiovascular Magnetic Resonance (CMR) T2* mapping is able to identify ischemia as well as fibrosis in cardiac and extracardiac diseases. Therefore, we aimed to investigate the value of T2* mapping to characterize structural alterations in patients with HCM.

Methods

CMR was performed on a 1.5 T MR imaging system (Achieva, Philips, Best, Netherlands) using a 5-channel coil in patients with HCM (n = 103, 50.6 ± 16.4 years) and in age- and gender-matched controls (n = 20, 44.8 ± 16.9 years). T2* mapping (1 midventricular short axis slice) was acquired in addition to late gadolinium enhancement (LGE). T2* values were compared between patients with HCM and controls as well as between HCM patients with- and without fibrosis.

Results

HCM patients showed significantly decreased T2* values compared to controls (26.2 ± 4.6 vs. 31.3 ± 4.3 ms, p < 0.001). Especially patients with myocardial fibrosis presented with decreased T2* values in comparison to those without fibrosis (25.2 ± 4.0 vs. 28.7 ± 5.3 ms, p = 0.003). A regression model including maximum wall thickness, LVM and T2* values provided good overall diagnostic accuracy of 80% to diagnose HCM with and without fibrosis.

Conclusion

In this study, parametric mapping identified lower T2* values in HCM patients compared to controls, especially in a sub-group of patients with myocardial fibrosis. As myocardial fibrosis has been suggested to influence prognosis of patients with HCM, T2* mapping may add information for identifying a higher risk sub-group of HCM patients.

Coronary Microvascular Disease Pathogenic Mechanisms and Therapeutic Options: JACC State-of-the-Art Review

Coronary microvascular disease (CMD) refers to the subset of disorders affecting the structure and function of the coronary microcirculation, is prevalent in patients across a broad spectrum of cardiovascular risk factors, and is associated with an increased risk of adverse events. Contemporary evidence supports that most patients with CMD also have macrovessel atherosclerosis, which has important implications for their prognosis and management. In this state-of-the-art review, the authors summarize the pathophysiology of CMD, provide an update of diagnostic testing strategies, and classify CMD into phenotypes according to severity and coexistence with atherosclerosis. They examine emerging data highlighting the significance of CMD in specific populations, including obesity and insulin resistance, myocardial injury and heart failure with preserved ejection fraction, and nonobstructive and obstructive coronary artery disease. Finally, they discuss the role of CMD as a potential target for novel interventions beyond conventional approaches, representing a new frontier in cardiovascular disease reduction.

Sudden Cardiac Death in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a heart disease characterized by hypertrophy of the left ventricular myocardium and is most often caused by mutations in sarcomere genes. The structural and functional abnormalities are not explained by flow-limiting coronary artery disease or loading conditions. The disease affects at least 0.2% of the population worldwide and is the most common cause of sudden cardiac death in young people and competitive athletes because of fatal ventricular arrhythmia. In some patients, however, HCM has a benign course. Therefore, it is of utmost importance to properly evaluate patients and single out those who would benefit from an implanted cardioverter defibrillator. In this article, we review and summarize the sudden cardiac death risk stratification algorithms, methods of preventing death due to HCM, and novel factors that may improve the existing prediction models.

Stress Myocardial Blood Flow Heterogeneity Is a Positron Emission Tomography Biomarker of Ventricular Arrhythmias in Patients With Hypertrophic Cardiomyopathy

Patients with hypertrophic cardiomyopathy (HC) are at increased risk of sudden cardiac death. Abnormalities in myocardial blood flow (MBF) detected by positron emission tomography (PET) are common in HC, but a PET marker that identifies patients at risk of sudden cardiac death is lacking. We hypothesized that disparities in regional myocardial perfusion detected by PET would identify patients with HC at risk of ventricular arrhythmias. To test this hypothesis, we quantified global and regional MBFs by ¹³NH₃-PET at rest and at stress, and developed a heterogeneity index to assess MBF heterogeneity in 133 symptomatic patients with HC. The MBF heterogeneity index was computed by dividing the highest by the lowest regional MBF value, at rest and after vasodilator stress, in each patient. High stress MBF heterogeneity was defined as an index of ≧1.85. Patients with HC were stratified by the presence or the absence of ventricular arrhythmias, defined as sustained ventricular tachycardia (VT) and/or nonsustained VT, during follow-up. We found that global and regional MBFs at rest and stress were similar in patients with HC with or without ventricular arrhythmias. Variability in regional stress MBF was observed in both groups, but the stress MBF heterogeneity index was significantly higher in patients with HC who developed ventricular arrhythmias (1.82 ± 0.77 vs 1.49 ± 0.25, p <0.001). A stress MBF heterogeneity index of ≧1.85 was an independent predictor of both sustained VT (hazard ratio 16.1, 95% confidence interval 3.2 to 80.3) and all-VT (sustained-VT + nonsustained VT: hazard ratio 3.7, 95% confidence interval 1.4 to 9.7). High heterogeneity of stress MBF, reflected by an MBF heterogeneity index of ≥1.85, is a PET biomarker for ventricular arrhythmias in symptomatic patients with HC.

Clinical Outcomes of Myocardial Bridging versus No Myocardial Bridging in Patients with Apical Hypertrophic Cardiomyopathy

Objective: To determine the prevalence and clinical effects of myocardial bridging (MB) in patients with apical hypertrophic cardiomyopathy (AHCM). Methods: Angiograms from 212 AHCM patients were reviewed to identify MB. The patients were classified into 2 groups: AHCM with and AHCM without MB. We reviewed patient records on cardiovascular (CV) risk factors, symptoms, CV events, and CV mortality. Results: In all, 60 patients with MB and 100 without MB were included. Rates of angina (61.7 vs. 40%; p = 0.008), mimicking non-ST-segment elevation myocardial infarction (15 vs. 3%, p = 0.013), and Canadian Cardiovascular Society class III/IV angina (18.3 vs. 4%; p = 0.003) were higher in patients with MB than in those without. Mean follow-up periods (65.5 ± 50.5 vs. 64.4 ± 43.6 months, p = 0.378) and CV mortality (3.3 vs. 1%; p = 0.652) were similar in the 2 groups. Kaplan-Meier estimates demonstrated that CV event-free survival rates were lower in patients with MB than in those without (71.7 vs. 88%; p = 0.022). MB, late gadolinium enhancement, and female sex were independent risk factors for CV events in a multivariate Cox regression analysis adjusted for other risk factors. Conclusion: More serious symptoms and a higher risk of CV events were observed in AHCM patients with MB than in those without MB. CV mortality was similar in these 2 groups.

Role of PET to evaluate coronary microvascular dysfunction in non-ischemic cardiomyopathies

Coronary microvascular dysfunction (CMD) can result from structural and functional abnormalities at the intramural and small coronary vessel level affecting coronary blood flow autoregulation and consequently leading to impaired coronary flow reserve. CMD often co-exists with epicardial coronary artery disease but is also commonly seen in patients with various forms of heart disease, including dilated, hypertrophic, and infiltrative cardiomyopathies. CMD can go unnoticed without any symptoms, or manifest as angina, and/or dyspnea, and contribute to the development of heart failure, and even sudden death especially when co-existing with myocardial fibrosis. However, whether CMD in non-ischemic cardiomyopathy is a cause or an effect of the underlying cardiomyopathic process, or whether it can be potentially modifiable with specific therapies, remains incompletely understood.

Hypertrophic obstructive cardiomyopathy

Hypertrophic obstructive cardiomyopathy is an inherited myocardial disease defined by cardiac hypertrophy (wall thickness ≥15 mm) that is not explained by abnormal loading conditions, and left ventricular obstruction greater than or equal to 30 mm Hg. Typical symptoms include dyspnoea, chest pain, palpitations, and syncope. The diagnosis is usually suspected on clinical examination and confirmed by imaging. Some patients are at increased risk of sudden cardiac death, heart failure, and atrial fibrillation. Patients with an increased risk of sudden cardiac death undergo cardioverter-defibrillator implantation; in patients with severe symptoms related to ventricular obstruction, septal reduction therapy (myectomy or alcohol septal ablation) is recommended. Life-long anticoagulation is indicated after the first episode of atrial fibrillation.

Integrated Imaging in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HC) has a very heterogeneous clinical spectrum and lends itself to multimodality imaging for evaluation and management. This review addresses clinical applications of cardiac imaging in patients with HC. Integrating various techniques of echocardiography and cardiac magnetic resonance (CMR) is discussed in the clinical context such as diagnosis, evaluation, management, risk stratification, and family screening of patients with HC. The utility of periprocedural imaging techniques is highlighted for guiding surgical and transcatheter septal reduction procedures. More limited roles of invasive or computed tomography coronary angiography are discussed for patients with HC with chest pain and risk factors for coronary artery disease. Nuclear techniques although available for decades play a more limited role in contemporary routine management but may assist in risk assessment. Newer CMR and echo imaging techniques are discussed in their emerging roles for further characterization of patients with HC and family members with prospects of preclinical diagnosis. The strengths of the different imaging modalities are presented as well as a flow diagram summarizing integrated imaging in this disease. In conclusion, integrated imaging using the various imaging techniques predominantly echocardiography and CMR based on the clinical picture plays an essential role in the management of patients with HC.

Prognostic role of stress echocardiography in hypertrophic cardiomyopathy: The International Stress Echo Registry

BACKGROUND

Stress echo (SE) may have a role in the outcome in patients with hypertrophic cardiomyopathy (HCM).

OBJECTIVES

The aim was to assess the prognostic value of SE in a retrospective multicenter study in HCM.

METHODS

We enrolled 706 HCM patients. The employed stress was exercise (n=608) and/or vasodilator (n=146, dipyridamole in 98 and adenosine in 48). We defined SE positivity according to clinical/hemodynamic criteria including: symptoms (all stress modalities), exercise-induced hypotension (failure to increase or fall >20mmHg, exercise) and exercise-induced left ventricular outflow tract obstruction (left ventricular outflow tract obstruction >50mmHg); and ischemic criteria, such as new wall motion abnormalities (new wall motion abnormality) and/or reduction of coronary flow reserve velocity (CFVR≤2.0) on left anterior descending coronary artery with vasodilator stress assessed in 116 patients. All patients completed the clinical follow-up.

RESULTS

Positive SE showed more frequently CFVR reduction, exercise-induced hypotension, left ventricular outflow tract obstruction, and symptoms (38, 23, 20 and 15% respectively), but new wall motion abnormality only in 6%. During a median follow-up of 49months 180 events were observed, including 40 deaths. Clinical/hemodynamic criteria did not predict outcome (X2 0.599, p=0.598), whereas ischemia-related SE criteria (X2: 111.120, p<0.0001) was significantly related to outcome. Similarly, mortality was predicted with SE ischemic-criteria (X2 16.645, p<0.0001).

CONCLUSIONS

SE has an important prognostic significance in HCM patients, with ischemia-related end-points showing greater predictive accuracy than hemodynamic endpoints. New wall motion abnormalities and impairment of CFVR should be specifically included in SE protocols for HCM.

Catheter ablation for atrial fibrillation in hypertrophic cardiomyopathy patients: a systematic review

PURPOSE

The primary aim of this systematic review was to assess the efficacy of catheter ablation of atrial fibrillation (AF) in patients with hypertrophic cardiomyopathy (HCM). Differentiation based off catheter ablation modalities was not considered due to the limited scope of the current field. Studies that employed alcohol septal ablation for the treatment of AF in HCM patients were excluded as were abstracts, case reports, conference presentations, editorials, reviews, and expert opinions

METHODS

Electronic searches were performed in six databases from their inception until January 2014. Relevant studies regarding catheter ablation for AF in HCM populations were identified. Data was extracted and analyzed according to pre-defined clinical endpoints

RESULTS

A review was undertaken of eight studies in which 241 HCM patients underwent catheter ablation for AF. Overall AF-free survival at last follow-up ranged from 47 to 77% (64-67%). Sinus rhythm was maintained at last follow-up in 47-82% (median 64-67%). AF recurrence ranged from 0 to 66% (median 35-40%).

CONCLUSION

A review of the current evidence suggests that catheter ablation of AF in HCM patients is effective with suitable efficacy and is justified in select patients. Future adequately powered randomized studies should be undertaken aimed at addressing long-term efficacy and complications associated with procedural outcomes.

Clinical topic: Nuclear imaging in hypertrophic cardiomyopathy

Non-invasive cardiac imaging plays a central role in the diagnosis and management of patients with hypertrophic cardiomyopathy. Transthoracic echocardiography is the imaging technique of first choice to evaluate wall thickness, left ventricular systolic and diastolic function, presence of left ventricular outflow tract obstruction, and abnormal mitral anatomy, whereas cardiac magnetic resonance provides additional information on tissue characterization (replacement fibrosis) using late gadolinium enhancement. Nuclear imaging techniques permit also the assessment of left ventricular systolic and diastolic function in patients with hypertrophic cardiomyopathy but are more frequently used to evaluate myocardial ischemia (particularly assessment of microvascular dysfunction using positron emission tomography) and abnormal sympathetic myocardial innervation. This review article provides an overview of the use of nuclear imaging techniques to refine the phenotyping and risk stratification of patients with hypertrophic cardiomyopathy with particular focus on prediction of progression to overt heart failure, detection of myocardial ischemia, and evaluation of the arrhythmogenic substrate and risk of sudden cardiac death.

Role of multimodality cardiac imaging in the management of patients with hypertrophic cardiomyopathy: an expert consensus of the European Association of Cardiovascular Imaging Endorsed by the Saudi Heart Association

Taking into account the complexity and limitations of clinical assessment in hypertrophic cardiomyopathy (HCM), imaging techniques play an essential role in the evaluation of patients with this disease. Thus, in HCM patients, imaging provides solutions for most clinical needs, from diagnosis to prognosis and risk stratification, from anatomical and functional assessment to ischaemia detection, from metabolic evaluation to monitoring of treatment modalities, from staging and clinical profiles to follow-up, and from family screening and preclinical diagnosis to differential diagnosis. Accordingly, a multimodality imaging (MMI) approach (including echocardiography, cardiac magnetic resonance, cardiac computed tomography, and cardiac nuclear imaging) is encouraged in the assessment of these patients. The choice of which technique to use should be based on a broad perspective and expert knowledge of what each technique has to offer, including its specific advantages and disadvantages. Experts in different imaging techniques should collaborate and the different methods should be seen as complementary, not as competitors. Each test must be selected in an integrated and rational way in order to provide clear answers to specific clinical questions and problems, trying to avoid redundant and duplicated information, taking into account its availability, benefits, risks, and cost.