Does the progression of myocardial fibrosis lead to atrial fibrillation in patients with hypertrophic cardiomyopathy?

Multimodality Imaging in Patients with Hypertrophic Cardiomyopathy and Atrial Fibrillation

Ventricular hypertrophy is associated with diastolic dysfunction, resulting in increased left atrial (LA) pressure, enlargement, fibrosis, and decreased LA function. Hypertrophic cardiomyopathy (HCM) is characterized by myocyte disarray, myocardial fibrosis, and hypertrophy. Notably, a thickened and noncompliant LV results in the impairment of diastolic function. These conditions promote LA remodeling and enlargement, which contribute to developing and maintaining atrial fibrillation (AF). AF is an atrial arrhythmia that occurs frequently in HCM, and evaluating the morphology and physiology of the atrium and ventricle is important for treatment and prognosis determination in HCM patients with AF. In addition, it provides a clue that can predict the possibility of new AF, even in patients not previously diagnosed with AF. Cardiac magnetic resonance (CMR), which can overcome the limitations of transthoracic echocardiography (TTE), has been widely used traditionally and even enables tissue characterization; moreover, it has emerged as an essential imaging modality for patients with HCM. Here, we review the role of multimodal imaging in patients with HCM and AF.

Automated Quantification of Abnormal QRS Peaks From High-Resolution ECGs Predicts Late Ventricular Arrhythmias in Hypertrophic Cardiomyopathy: A 5-Year Prospective Multicenter Study

Background Patients with hypertrophic cardiomyopathy (HCM) are at risk of ventricular arrhythmia (VA) attributed to abnormal electrical activation arising from myocardial fibrosis and myocyte disarray. We sought to quantify intra-QRS peaks (QRSp) in high-resolution ECGs as a measure of abnormal activation to predict late VA in patients with HCM. Methods and Results Prospectively enrolled patients with HCM (n=143, age 53±14 years) with prophylactic implantable cardioverter-defibrillators had 3-minute, high-resolution (1024 Hz), digital 12-lead ECGs recorded during intrinsic rhythm. For each precordial lead, QRSp was defined as the total number of peaks detected in the QRS complex that deviated from a smoothing filtered version of the QRS. The VA end point was appropriate implantable cardioverter-defibrillator therapy during 5-year prospective follow-up. After 5 years, 21 (16%) patients had VA. Patients who were VA positive had greater QRSp (6.0 [4.0-7.0] versus 4.0 [2.0-5.0]; P<0.01) and lower left ventricular ejection fraction (57±11 versus 62±9; P=0.038) compared with patients who were VA negative, but had similar established HCM risk metrics. Receiver operating characteristic analysis revealed that QRSp discriminated VA (area under the curve=0.76; P<0.001), with a QRSp ≥4 achieving 91% sensitivity and 39% specificity. The annual VA rate was greater in patients with QRSp ≥4 versus QRSp <4 (4.4% versus 0.98%; P=0.012). In multivariable Cox regression, age <50 years (hazard ratio [HR], 2.53; P=0.009) and QRSp (HR per QRS peak, 1.41; P=0.009) predicted VA after adjusting for established HCM risk metrics. In patients aged <50 years, the annual VA rate was 0.0% for QRSp <4 compared with 6.9% for QRSp ≥4 (P=0.012). Conclusions QRSp predicted VA in patients with HCM who were eligible for an implantable cardioverter-defibrillator after adjusting for established HCM risk metrics, such that each additional QRS peak increases VA risk by 40%. QRSp <4 was associated with a <1% annual VA risk in all patients, and no VA risk among those aged <50 years. This novel ECG metric may improve patient selection for prophylactic implantable cardioverter-defibrillator therapy by identifying those with low VA risk. These findings require further validation in a lower risk HCM cohort. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT02560844.

Post-mortem genetic investigation in sudden cardiac death victims: complete exon sequencing of forty genes using next-generation sequencing

Sudden cardiac death (SCD) in young people is predominantly caused by genetic causes as cardiomyopathies. Hypertrophic cardiomyopathy is the most common genetic cardiovascular disease and is responsible for the major proportion of SCD in the young. The purpose of this study was to identify the genetic variants present in young SCD victims with HCM characteristics. From the Portuguese records of autopsies performed at the National Institute of Legal Medicine and Forensic Sciences, North Delegation, 16 young (16-50 years) SCD victims whose death was suspected to be a manifestation of HCM were selected. Using next-generation sequencing, the coding regions of 40 genes associated with HCM, candidates, or strongly related to HCM-phenocopies were investigated. The victims included in this study were all males, with a mean age of 33.4 ± 11.7 years, left ventricle mean thickness of 21.5 ± 6.28 mm, and the majority of deaths occurred during sleep (36%). A pathogenic or likely pathogenic variant was identified in six out of 16 (37.5%) victims, in the most common HCM genes (MYBPC3 and MYH7). Our results indicate that molecular autopsy of SCD victims contributes to a more precise identification of a cause of death, and this can be used in the prevention of SCD cases through family screening of first relatives who may carry the same pathogenic variant.

Machine Learning Methods for Identifying Atrial Fibrillation Cases and Their Predictors in Patients With Hypertrophic Cardiomyopathy: The HCM-AF-Risk Model

Background

Hypertrophic cardiomyopathy (HCM) patients have a high incidence of atrial fibrillation (AF) and increased stroke risk, even with low CHA₂DS₂-VASc (congestive heart failure, hypertension, age diabetes, previous stroke/transient ischemic attack) scores. Hence, there is a need to understand the pathophysiology of AF/stroke in HCM. In this retrospective study, we develop and apply a data-driven, machine learning–based method to identify AF cases, and clinical/imaging features associated with AF, using electronic health record data.

Methods

HCM patients with documented paroxysmal/persistent/permanent AF (n = 191) were considered AF cases, and the remaining patients in sinus rhythm (n = 640) were tagged as No-AF. We evaluated 93 clinical variables; the most informative variables useful for distinguishing AF from No-AF cases were selected based on the 2-sample t test and the information gain criterion.

Results

We identified 18 highly informative variables that are positively (n = 11) and negatively (n = 7) correlated with AF in HCM. Next, patient records were represented via these 18 variables. Data imbalance resulting from the relatively low number of AF cases was addressed via a combination of oversampling and undersampling strategies. We trained and tested multiple classifiers under this sampling approach, showing effective classification. Specifically, an ensemble of logistic regression and naïve Bayes classifiers, trained based on the 18 variables and corrected for data imbalance, proved most effective for separating AF from No-AF cases (sensitivity = 0.74, specificity = 0.70, C-index = 0.80).

Conclusions

Our model (HCM-AF-Risk Model) is the first machine learning–based method for identification of AF cases in HCM. This model demonstrates good performance, addresses data imbalance, and suggests that AF is associated with a more severe cardiac HCM phenotype.

Relation of atrial electromechanical delay to P-wave dispersion on surface ECG using vector velocity imaging in patients with hypertrophic cardiomyopathy

OBJECTIVES

Heterogeneity of structural and electrophysiologic properties of atrial myocardium is common characteristic in hypertrophic cardiomyopathy (HCM). We assessed the dispersion of atrial refractoriness on surface ECG using P-wave dispersion (PWD) and its relation to atrial electromechanical functions using vector velocity imaging (VVI) in HCM population.

METHODS

Seventy-nine HCM patients (mean age: 43.7 ± 13 years, 67% male) were compared with 25 healthy individuals as control. P-wave durations, Pmax and Pmin , P-wave dispersion (PWD), and P terminal force (PTF) were measured from 12-lead ECG. LA segmental delay (TTP-d) and dispersion (TTP-SD) of electromechanical activation were derived from atrial strain rate curves.

RESULTS

HCM patients had longer PR interval, PW duration, higher PWD, PTF, QTc compared to control (p < .001). HCM patients were classified according to presence of PWD into two groups, group I with PWD > 46 ms (n = 25) and group II PWD ≤ 46 ms (n = 54). Group I showed higher prevalence of female gender, higher PTF, QTc interval, left ventricular outflow tract (LVOT) obstruction, p < .01, LVOT gradient (p < .001), LV mass index (p < .01), E/E' (p < .01), and severe mitral regurgitation (p < .001). Moreover, PWD was associated with increased atrial electromechanical delay (TTP-d) and LA mechanical dyssynchrony (TTP-SD), p < .001. LA segmental delay and dispersion of electromechanical activation were distinctly higher among HCM patient.

CONCLUSION

PWD is simple ECG criterion, and it is associated with more severe HCM phenotype and LA electromechanical delay while PTF is linked only to atrial remodeling.

Atrial fibrillation in patients with inherited cardiomyopathies

Atrial fibrillation (AF) often complicates the course of inherited cardiomyopathies and, in some cases, may be the presenting feature. Each inherited cardiomyopathy has its own peculiar pathogenetic characteristics that can contribute to the development and maintenance of AF. Atrial fibrillation may occur as a consequence of disease-specific defects, non-specific cardiac chamber changes secondary to the primary illness, or a combination thereof. The presence of AF can denote a turning point in the progression of the disease, promoting clinical deterioration and increasing morbidity and mortality. Furthermore, the management of AF can be particularly challenging in patients with inherited cardiomyopathies. In this article, we review the current information on the prevalence, pathophysiology, risk factors, and treatment of AF in three different inherited cardiomyopathies: hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia/cardiomyopathy, familial dilated cardiomyopathy, and left ventricular non-compaction cardiomyopathy.

Left ventricular remodeling in hypertrophic cardiomyopathy patients with atrial fibrillation

Background

Atrial fibrillation (AF) is the most common complication in hypertrophic cardiomyopathy (HCM). The mechanisms of AF is associated with left atrial (LA) structural remodeling in HCM patients. However, the impact of left ventricular (LV) remodeling on the presence of AF in HCM patients has not been evaluated yet. We sought to investigate effect of LV remodeling on the presence of AF assessed by cardiovascular magnetic resonance (CMR) in HCM patients.

Methods

A total of 394 HCM patients were enrolled into this study, including HOCM patients (n = 293) and NOHCM patients (n = 101). Patients were divided into HCM with AF (50) and HCM without AF (n = 344). Data were collected from hospital records.

Results

LA diameter and LV remodeling index (LVRI) were significantly higher in HCM patients with AF than that of HCM patients without AF (46.6 ± 7.4 mm versus 39.9 ± 8.0 mm, p < 0.001, and 1.46 ± 0.6 versus 1.2 ± 0.4, p = 0.002, respectively). HCM patients with AF were older than HCM patients without AF (53.6 ± 11.7 years versus 47.7 ± 13.6 years, p = 0.002). Additionally, LVRI positively correlated to LA size (r = 0.12, p = 0.02). In a multivariable logistic regression analysis, when adjusting for age and LV end diastolic mass index, LVRI and LA size remained an independent determinant of AF in HCM patients (OR = 4.7, p = 0.001 and OR = 1.13, P < 0.001).

Conclusion

HCM patients with AF showed significantly more LA diameter, LVRI and age than HCM patients without AF. LVRI and LA size were strong independent predictor of AF in HCM, suggesting LV remodeling may contribute to the occurrence of AF in HCM patients.

Scar Homogenization in Atrial Fibrillation Ablation: Evolution and Practice

Atrial fibrillation (AF) ablation has emerged as the preferred rhythm control strategy for symptomatic paroxysmal AF refractory or intolerant to at least one class I or III antiarrhythmic medication. Since the initial observation by Haissaguerre and colleagues, of pulmonary vein triggers initiating atrial fibrillation (AF), pulmonary vein isolation (PVI) has become the cornerstone for paroxysmal AF ablation therapy.

Right Ventricular and Right Atrial Involvement Can Predict Atrial Fibrillation in Patients with Hypertrophic Cardiomyopathy?

OBJECTIVES AND BACKGROUND

Atrial fibrillation (AF) is associated with clinical deterioration, stroke and disability in patients with hypertrophic cardiomyopathy (HCM). Therefore, the objective of this study was to evaluated cardiac magnetic resonance (CMR)-derived determinants for the occurrence of AF in patients with HCM.

METHODS

98 Patients with HCM and 30 healthy controls underwent CMR and were followed-up for 6 ± 3 years.

RESULTS

19 (19.4%) patients presented with AF at initial diagnosis, 19 (19.4%) developed AF during follow-up and 60 (61.2%) remained in sinus rhythm (SR). Compared to healthy controls, patients with HCM who remained in SR presented with significantly increased left ventricular mass, an elevated left ventricular remodeling index, enlarged left atrial volumes and reduced septal mitral annular plane systolic excursion (MAPSE) compared to healthy controls. Whereas HCM patients who presented with AF at initial diagnosis and those who developed AF during follow-up additionally presented with reduced tricuspid annular plane systolic excursion (TAPSE) and right atrial (RA) dilatation. Receiver-operator curve analysis indicated good predictive performance of TAPSE, RA diameter and septal MAPSE (AUC 0.73, 0.69 and 0.71, respectively) to detect patients at risk of developing AF.

CONCLUSION

Reduced MAPSE measurements and enlarged LA volumes seems to be a common feature in patients with HCM, whereas reduced TAPSE and RA dilatation only seem to be altered in patients with history of AF and those developing AF. Therefore, they could serve as easy determinable markers of AF in patients with HCM.

Inherited Structural Heart Diseases With Potential Atrial Fibrillation Occurrence

Inherited cardiac diseases inducing structural remodeling of the myocardium sometimes develop arrhythmias of various kinds. Among these rhythm disturbances, atrial fibrillation is well known to frequently worsen the prognosis of the primary disorder by increasing morbidity and mortality, especially because of a higher rate of heart failure. In this manuscript, we have reviewed the literature on the most important inherited structural cardiac diseases in whose clinical history atrial fibrillation may occur fairly often.

Atrial and ventricular arrhythmias in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is an autosomal dominant disease caused by mutations in genes coding for cardiac sarcomeres. HCM is the most common inherited heart disease, with a prevalence of 0.2%. There are multiple genetic variants that cause pleomorphic clinical attributes and disease characterized by myocardial disarray and myocardial hypertrophy. Patients are at an increased risk of atrial and ventricular arrhythmias. Management of these arrhythmias is complex. Atrial fibrillation is associated with increased mortality and thromboembolism. Ventricular arrhythmias are life threatening and best treated with an implantable defibrillator.

Predictors of Atrial Fibrillation Risk in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic cardiovascular disease that predisposes individuals to the development of arrhythmias. The most common sustained arrhythmia is atrial fibrillation (AF). Compared with the general population, patients with HCM are more prone to the development of AF. To avoid embolic complications and the clinical deterioration caused by the development of AF in HCM, identifying patients with a tendency toward AF might affect the management of HCM. In this review, we evaluated the predictors of AF development in patients with HCM.

Correlation between myocardial fibrosis and the occurrence of atrial fibrillation in hypertrophic cardiomyopathy: a cardiac magnetic resonance imaging study

Cardiac magnetic resonance imaging (CMR) in hypertrophic cardiomyopathy (HCM) often shows delayed contrast enhancement (DE) representing regions of focal myocardial fibrosis. Atrial fibrillation (AF) is a commonly reported complication of HCM. We determined the relationship between the presence of left ventricular myocardial fibrosis (LVMF) detected by DE-CMR and the occurrence AF in a series of patients with HCM. 67 patients with HCM (47 males; mean age 50.1+/-18.5 years) were studied by CMR measuring mass of LVMF, left ventricular mass, volume and function, and left atrial (LA) area. AF was present in 17 (25%) patients. LVMF was observed in 57% of patients. AF was significantly more frequent in patients who also showed LVMF, compared with the group without LVMF (42.1% vs. 3.4%, respectively; p<0.0001). LA size was larger in patients showing DE (LA area: 37.4+/-11.1 vs. 25.9+/-6.8 cm(2); respectively, p=0.0001). AF in HCM is related with myocardial fibrosis detected by DE-CMR and dilatation of the LA. This fact adds to the proven adverse prognostic value of myocardial fibrosis in HCM, thus, reinforcing the usefulness of this technique in the assessment of these patients.

CMR findings in patients with hypertrophic cardiomyopathy and atrial fibrillation

OBJECTIVES

We sought to evaluate the relation between atrial fibrillation (AF) and the extent of myocardial scarring together with left ventricular (LV) and atrial parameters assessed by late gadolinium-enhancement (LGE) cardiovascular magnetic resonance (CMR) in patients with hypertrophic cardiomyopathy (HCM).

BACKGROUND

AF is the most common arrhythmia in HCM. Myocardial scarring is also identified frequently in HCM. However, the impact of myocardial scarring assessed by LGE CMR on the presence of AF has not been evaluated yet.

METHODS

87 HCM patients underwent LGE CMR, echocardiography and regular ECG recordings. LV function, volumes, myocardial thickness, left atrial (LA) volume and the extent of LGE, were assessed using CMR and correlated to AF. Additionally, the presence of diastolic dysfunction and mitral regurgitation were obtained by echocardiography and also correlated to AF.

RESULTS

Episodes of AF were documented in 37 patients (42%). Indexed LV volumes and mass were comparable between HCM patients with and without AF. However, indexed LA volume was significantly higher in HCM patients with AF than in HCM patients without AF (68 +/- 24 ml.m-2 versus 46 +/- 18 ml.m-2, p = 0.0002, respectively). The mean extent of LGE was higher in HCM patients with AF than those without AF (12.4 +/- 14.5% versus 6.0 +/- 8.6%, p = 0.02). When adjusting for age, gender and LV mass, LGE and indexed LA volume significantly correlated to AF (r = 0.34, p = 0.02 and r = 0.42, p < 0.001 respectively). By echocardiographic examination, LV diastolic dysfunction was evident in 35 (40%) patients. Mitral regurgitation greater than II was observed in 12 patients (14%). Multivariate analysis demonstrated that LA volume and presence of diastolic dysfunction were the only independent determinant of AF in HCM patients (p = 0.006, p = 0.01 respectively). Receiver operating characteristic curve analysis indicated good predictive performance of LA volume and LGE (AUC = 0.74 and 0.64 respectively) with respect to AF.

CONCLUSION

HCM patients with AF display significantly more LGE than HCM patients without AF. However, the extent of LGE is inferior to the LA size for predicting AF prevalence. LA dilation is the strongest determinant of AF in HCM patients, and is related to the extent of LGE in the LV, irrespective of LV mass.

Association of angiotensin-converting enzyme activity and polymorphism with echocardiographic measures in familial and nonfamilial hypertrophic cardiomyopathy

Angiotensin-converting enzyme (ACE) activity and polymorphism contribute significantly to the prognosis of patients with cardiomyopathy. The aim of this study was to determine the activity and type of ACE polymorphism in patients with familial and nonfamilial hypertrophic cardiomyopathy (HCM) and to correlate these with echocardiographic measurements (echo-Doppler). We studied 136 patients (76 males) with HCM (69 familial and 67 nonfamilial cases). Mean age was 41 +/- 17 years. DNA was extracted from blood samples for the polymerase chain reaction and the determination of plasma ACE levels. Left ventricular mass, interventricular septum, and wall thickness were measured. Mean left ventricular mass index, interventricular septum and wall thickness in familial and nonfamilial forms were 154 +/- 63 and 174 +/- 57 g/m(2) (P = 0.008), 19 +/- 5 and 21 +/- 5 mm (P = 0.02), and 10 +/- 2 and 12 +/- 3 mm (P = 0.0001), respectively. ACE genotype frequencies were DD = 35%, ID = 52%, and II = 13%. A positive association was observed between serum ACE activity and left ventricular mass index (P = 0.04). Logistic regression showed that ACE activity was twice as high in patients with familial HCM and left ventricular mass index >or=190 g/m(2) compared with the nonfamilial form (P = 0.02). No other correlation was observed between ACE polymorphisms and the degree of myocardial hypertrophy. In conclusion, ACE activity, but not ACE polymorphisms, was associated with the degree of myocardial hypertrophy in the patients with HCM.

Increased expression of extracellular matrix proteins in rapid atrial pacing-induced atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is characterized by structural remodeling of the extracellular matrix (ECM) in cardiac atrium.

OBJECTIVE

The purpose of this study was to gain further insight into atrial ECM remodeling at the molecular level and to test whether altered expression of ECM proteins was associated with the disease.

METHODS

Sustained AF was induced in nine adult pigs after 3-4 weeks of continuous rapid atrial pacing at a rate of 600 bpm. Histologic studies and immunohistochemical stain were performed to identify the potential pathologic substrate underlying abnormalities in atrial tissues with sustained AF.

RESULTS

In the pathologic findings, the fraction of myocardial ECM (ECM%) was measured, with a significantly greater ECM% found in the AF group compared with the sham operated group (n = 6; i.e., pigs with normal sinus rhythm [SR]). A set of 9,182 genes was screened with cDNA microarray analysis. In AF animals, expression of 121 genes increased and 24 genes decreased by > or =1.75-fold compared with SR animals. Significant up-regulation of fibronectin-1 (4.9-fold), fibrillin-1 (3.1-fold), and fibromodulin (1.9-fold) in the fibrillating atria was confirmed by quantitative real-time reverse transcriptase-polymerase chain reaction. Western blot analysis revealed significantly increased atrial fibronectin-1, fibrillin-1, and fibromodulin in the AF group compared with the SR group (1.5-, 2.7-, and 2.1-fold, respectively). Immunohistochemical staining of AF tissue displayed increased accumulation of fibronectin-1 and fibrillin-1 in the atrial interstitial space.

CONCLUSION

Increased expression of ECM proteins in fibrillating atria supports the hypothesis that ECM metabolism contributes to the development of AF.