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

Hipertrofik kardiyomiyopati hastalarında atriyal fibrilasyon gelişimini öngörmede kardiyak manyetik rezonans görüntülemenin rolü

Amaç:, Bu çalışmada Hipertrofik kardiyomiyopati (HKMP) hastalarında geç kontrast tututulmu (GKT), toplam sol ventrikül kütlesi (TSVK), mitral yetersizlik ve sol atriyum (SA) hacmi dahil olmak üzere Kardiyak manyetik rezonans (KMR) görüntüleme parametreleri ile atriyal fibrilasyon (AF) arasındaki ilişkiyi araştırmayı amaçladık. Gereç ve Yöntem: Bu çalışmaya HKMP tanısı alan, KMR çekimi yapılmış ve 48 saatlik Holter monitorizasyonu olan ardışık 122 hasta dahil edilmiştir. KMR tecrübesine sahip Radyoloji ve Kardiyoloji uzman hekimleri tarafından KMR görüntüleri değerlendirilmiştir. TSVK, SA hacmi, GKT varlığı ve yaygınlığı, mitral yetersizliği ve maksimum sol ventrikül kalınlığını içeren KMR parametreleri ile AF arasındaki korelasyon değerlendirilmiştir. Bulgular: SA hacmi ve AF arasında anlamlı bir korelasyon gözlendi. Ek olarak TSVK, AF ile ilişkili bulundu. TSVK, SA hacmi ve GKT'nin kapsamını değerlendiren lojistik çok değişkenli analiz, yalnızca sol atriyal hacmin bağımsız öngörücü olduğunu ortaya koydu. GKT, TSVK, mitral yetersizlik ve SA hacminin varlığı ve yaygınlığı arasında anlamlı korelasyonlar gözlendi. Sonuç: GKT'nin varlığı, SA hacmi ile pozitif korelasyon gösterdi. SA hacmi, HKMP hastalarında AF'nin en önemli bağımsız belirleyicisi gibi görünmektedir.

Electrophysiological and Structural Remodeling of the Atria in a Mouse Model of Troponin-I Mutation Linked Hypertrophic Cardiomyopathy: Implications for Atrial Fibrillation

Hypertrophic cardiomyopathy (HCM) is an inherited cardiac disorder affecting one in 500 of the general population. Atrial fibrillation (AF) is the most common arrhythmia in patients with HCM. We sought to characterize the atrial electrophysiological and structural substrate in young and aging Gly203Ser cardiac troponin-I transgenic (HCM) mice. At 30 weeks and 50 weeks of age (n = 6 per strain each group), the left atrium was excised and placed on a multi-electrode array (MEA) for electrophysiological study; subsequent histological analyses and plasma samples were analyzed for biomarkers of extracellular matrix remodeling and cell adhesion and inflammation. Wild-type mice of matched ages were included as controls. Young HCM mice demonstrated significantly shortened atrial action potential duration (APD), increased conduction heterogeneity index (CHI), increased myocyte size, and increased interstitial fibrosis without changes in effective refractory periods (ERP), conduction velocity (CV), inflammatory infiltrates, or circulating markers of extracellular matrix remodeling and inflammation. Aging HCM mice demonstrated aggravated changes in atria electrophysiology and structural remodeling as well as increased circulating matrix metalloproteinases (MMP)-2, MMP-3, and VCAM-1 levels. This model of HCM demonstrates an underlying atrial substrate that progresses with age and may in part be responsible for the greater propensity for AF in HCM.

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.

Predictors and Mechanisms of Atrial Fibrillation in Patients With Hypertrophic Cardiomyopathy

Atrial fibrillation (AF) in hypertrophic cardiomyopathy (HC) is associated with significant symptomatic deterioration, heart failure, and thromboembolic disease. There is a need for better mechanistic insight and improved identification of at risk patients. We used cardiovascular magnetic resonance (CMR) to assess predictors of AF in HC, in particular the role of myocardial fibrosis. Consecutive patients with HC referred for CMR 2003 to 2013 were prospectively enrolled. CMR parameters including left ventricular volumes, presence and percentage of late gadolinium enhancement in the left ventricle (%LGE) and left atrial volume index (LAVi) were measured. Overall, 377 patients were recruited (age 62 ± 14 years, 73% men). Sixty-two patients (16%) developed new-onset AF during a median follow up of 4.5 (interquartile range 2.9 to 6.0) years. Multivariable analysis revealed %LGE (hazard ratio [HR] 1.3 per 10% (confidence interval: 1.0 to 1.5; p = 0.02), LAVi (HR 1.4 per 10 mL/m²[1.2 to 1.5; p < 0.001]), age at HC diagnosis, nonsustained ventricular tachycardia and diabetes to be independent predictors of AF. We constructed a simple risk prediction score for future AF based on the multivariable model with a Harrell's C-statistic of 0.73. In conclusion, the extent of ventricular fibrosis and LA volume independently predicted AF in patients with HC. This finding suggests a mechanistic relation between fibrosis and future AF in HC. CMR with quantification of fibrosis has incremental value over LV and LA measurements in risk stratification for AF. A risk prediction score may be used to identify patients at high risk of future AF who may benefit from more intensive rhythm monitoring and a lower threshold for oral anticoagulation.

Atrial matrix remodeling in atrial fibrillation patients with aortic stenosis

BACKGROUND

This study aimed to evaluate atrium extracellular matrix remodeling in atrial fibrillation (AF) patients with severe aortic stenosis, through histological fibrosis quantification and extracellular matrix gene expression analysis, as well as serum quantification of selected protein targets.

METHODS

A posthoc analysis of a prospective study was performed in a cohort of aortic stenosis patients. Between 2014 and 2019, 56 patients with severe aortic stenosis submitted to aortic valve replacement surgery in a tertiary hospital were selected.

RESULTS

Fibrosis was significantly increased in the AF group when compared to sinus rhythm (SR) patients (p = 0.024). Moreover, cardiomyocyte area was significantly higher in AF patients versus SR patients (p = 0.008). Conversely, collagen III gene expression was increased in AF patients (p = 0.038). TIMP1 was less expressed in the atria of AF patients. MMP16/TIMP4 ratio was significantly decreased in AF patients (p = 0.006). TIMP1 (p = 0.004) and TIMP2 (p = 0.012) were significantly increased in the serum of AF patients. Aortic valve maximum (p = 0.0159) and mean (p = 0.031) gradients demonstrated a negative association with serum TIMP1.

CONCLUSIONS

Atrial fibrillation patients with severe aortic stenosis present increased atrial fibrosis and collagen type III synthesis, with extracellular matrix remodelling demonstrated by a decrease in the MMP16/TIMP4 ratio, along with an increased serum TIMP1 and TIMP2 proteins.

Prognostic and functional implications of left atrial late gadolinium enhancement cardiovascular magnetic resonance

BACKGROUND

Left atrial (LA) late gadolinium enhancement (LGE) on cardiovascular magnetic resonance (CMR) imaging is indicative of fibrosis, and has been correlated with reduced LA function, increased LA volume, and poor procedural outcomes in cohorts with atrial fibrillation (AF). However, the role of LGE as a prognostic biomarker for arrhythmia in cardiac disease has not been examined.

METHODS

In this study, we assessed LA LGE using a 3D LGE CMR sequence to examine its relationships with new onset atrial arrhythmia, and LA and left ventricular (LV) mechanical function.

RESULTS

LA LGE images were acquired in 111 patients undergoing CMR imaging, including 66 patients with no prior history of an atrial arrhythmia. During the median follow-up of 2.7 years (interquartile range (IQR) 1.8-3.7 years), 15/66 (23%) of patients developed a new atrial arrhythmia. LA LGE ≥10% of LA myocardial volume was significantly associated with an increased rate of new-onset atrial arrhythmia, with a hazard ratio of 3.16 (95% CI 1.14-8.72), p = 0.026. There were significant relationships between LA LGE and both LA ejection fraction (r = - 0.39, p < 0.0005) and echocardiographic LV septal e' (r = - 0.24, p = 0.04) and septal E/e' (r = 0.31, p = 0.007).

CONCLUSIONS

Elevated LA LGE is associated with reduced LA function and reduced LV diastolic function. LA LGE is associated with new onset atrial arrhythmia during follow-up.

Modulation of Human Cardiac TRPM7 Current by Extracellular Acidic pH Depends upon Extracellular Concentrations of Divalent Cations

TRPM7 channels participate in a variety of physiological/pathological processes. TRPM7 currents are modulated by protons but opposing effects of external pH (pH_o) (potentiation vs inhibition) have been reported. TRPM7 has been less studied in human cardiomyocytes than in heart-derived non-cardiomyocyte cells. We used the whole-cell patch-clamp technique on isolated human atrial cardiomyocytes to investigate the impact of an acidic pH_o on the TRPM7 current. With voltage-dependent and other ion channels inhibited, cardiomyocytes were challenged with external acidification in either the presence or the absence of extracellular divalent cations. TRPM7 outward and inward currents were increased by acidic pH_o in extracellular medium containing Ca²⁺ and Mg²⁺, but suppressed by acidic pH_o in the absence of extracellular Ca²⁺ and Mg²⁺. The potentiating effect in the presence of extracellular divalents occurred at pH_o below 6 and was voltage-dependent. The inhibitory effect in the absence of extracellular divalents was already marked at pH_o of 6 and was practically voltage-independent. TRPM7 current density was higher in cardiomyocytes from patients with history of coronary vascular disease and the difference compared to cardiomyocytes from patients without history of myocardial ischemia increased with acidic pH_o. We demonstrate that proton-induced modification of TRPM7 currents depends on the presence of extracellular Ca²⁺ and Mg²⁺. Variability of the TRPM7 current density in human cardiomyocytes is related to the clinical history, being higher in atrial fibrillation and in ischemic cardiomyopathy.

Comparison of Long-Term Outcome between Apical and Asymmetric Septal Hypertrophic Cardiomyopathy

Objectives: As reported, diagnostic age, gender and presence of outflow tract obstruction have an impact on prognosis in patients with hypertrophic cardiomyopathy. The aim of this study was to compare the long-term outcome between apical hypertrophic cardiomyopathy (ApHCM) and asymmetric septal hypertrophic cardiomyopathy (ASHCM) after the exclusion of these factors. Methods: A total of 540 patients (270 with ApHCM and 270 with ASHCM) identified in a consecutive single-center cohort were retrospectively studied. The two groups were matched by diagnostic age, gender and the presence of outflow tract obstruction. Clinical characteristics and long-term outcomes were compared. Results: The mean follow-up duration in ASHCM and ApHCM were 6.6 ± 5.5 and 7.6 ± 4.1 years, respectively. During follow-up, 16 patients experienced cardiovascular death in the ASHCM group, while 2 patients experienced cardiovascular death in the ApHCM group (6.3 vs. 0.7%, p < 0.01). Cardiovascular morbidity in the ASHCM and ApHCM groups were 39.9 and 18.5% (p < 0.01). In the multivariate Cox regression analysis late gadolinium enhancement (LGE; HR 4.81, 95% CI 1.28-78.0, p = 0.03) and unexplained syncope (HR 9.68, 95% CI 1.9-17.2, p < 0.01) were independent predictors for cardiovascular mortality. Unexplained syncope was independently associated with a higher risk for sudden cardiac death (HR 4.3, 95% CI 1.2-15.3, p = 0.02). Conclusions: After eliminating the interference of diagnostic age, gender and outflow tract obstruction, ASHCM represented a worse prognosis with a higher incidence of cardiovascular mortality and morbidity than ApHCM. LGE was a strong predictor for cardiovascular death.

Single-dose gadobutrol in comparison with single-dose gadobenate dimeglumine for magnetic resonance imaging of chronic myocardial infarction at 3 T

OBJECTIVES

The aim of this study was to compare the contrast-to-noise ratio (CNR) values of infarct and remote myocardium as well as infarct and blood after application of 0.1 mmol/kg gadobutrol and 0.1 mmol/kg gadobenate dimeglumine on late gadolinium enhancement magnetic resonance (MR) images.

MATERIAL AND METHODS

The study was a prospective randomized controlled clinical study. After informed consent was obtained, 20 patients (12 men, 8 women; mean age, 67 ± 11 years) with known chronic myocardial infarction were included for an intraindividual comparison of a single-dose gadobutrol and a single-dose gadobenate dimeglumine. Two MR imaging examinations were performed within a period of 28 days in a crossover design. Late gadolinium enhancement imaging was performed 10 minutes after gadolinium administration using a 2-dimensional phase-sensitive inversion recovery gradient echo sequence at 3 T. Infarct size, signal intensities (SIs), signal-to-noise ratio, and CNR were determined on phase-sensitive MR images. Values for CNR were calculated as CNRinfarct/myocardium = (SIinfarct - SImyocardium)/SDnoise and CNRinfarct/blood = (SIinfarct - SIblood)/SDnoise. In addition, the areas of myocardial infarction were determined on single slices. The entire infarct volumes were calculated by adding the areas with hyperenhancement multiplied by the slice thickness.

RESULTS

Late gadolinium enhancement was present in all patients. Median values of the infarct area, infarct volume, and transmurality for gadobutrol and gadobenate dimeglumine showed good to excellent concordance (rc = 0.85, rc = 0.95, and rc = 0.71, respectively). The mean signal-to-noise ratio values for infarct, remote myocardium, and ventricular blood were 18.6 ± 6.5, 4.1 ± 3.7, and 14.6 ± 7.5, respectively, for gadobutrol and 18.8 ± 8.9, 4.9 ± 4.5, and 17.8 ± 10.1, respectively, for gadobenate dimeglumine (P = 0.93, P = 0.48, and P = 0.149, respectively). The mean values of CNRinfarct/myocardium and CNRinfarct/blood were 14.5 ± 5.9 and 4.0 ± 4.6, respectively, for gadobutrol and 13.9 ± 6.1 and 0.9 ± 4.5, respectively, for gadobenate dimeglumine (P = 0.69 and P = 0.02, respectively).

CONCLUSION

Both gadobutrol and gadobenate dimeglumine allow for successful late gadolinium enhancement imaging of chronic myocardial infarction after a single-dose application (0.1 mmol/kg) at 3 T. Gadobutrol provides a higher CNR between infarct and blood. The CNRs between infarct and normal myocardium, infarct size, and transmural extent were similar for both contrast agents.

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.

Sex-dependent pathophysiological mechanisms in hypertrophic cardiomyopathy: implications for rhythm disorders

Differences in cardiac physiology are seen between men and women in terms of health and disease. Sex differences start to develop at puberty and are maintained during aging. The prevalence of almost all cardiovascular diseases is found to be higher in men than in women, and disease progression tends to be more rapid in male than in female patients. In cohorts of patients with hypertrophic cardiomyopathy (HCM), the most common autosomal inherited cardiac disease, men are overrepresented, suggesting increased penetrance of HCM-causing mutations in male patients. Cardiac remodeling in patients with HCM is higher in men than in women, the same is seen in HCM animal models. Patients with HCM are at increased risk of sudden cardiac death (SCD) and developing rhythm disorders. There seems to be no sex effect on the risk of SCD or arrhythmias in patients with HCM; however, animal studies suggest that certain mutations predispose men to SCD.

The incidence, pattern, and prognostic value of left ventricular myocardial scar by late gadolinium enhancement in patients with atrial fibrillation

OBJECTIVES

This study sought to identify the frequency, pattern, and prognostic significance of left ventricular (LV) late gadolinium enhancement (LGE) in patients with atrial fibrillation (AF).

BACKGROUND

There are limited data on the presence, pattern, and prognostic significance of LV myocardial fibrosis in patients with AF. LGE during cardiac magnetic resonance imaging is a marker for myocardial fibrosis.

METHODS

A group of 664 consecutive patients without known prior myocardial infarction who were referred for radiofrequency ablation of AF were studied. Cardiac magnetic resonance imaging was requested to assess pulmonary venous anatomy.

RESULTS

Overall, 73% were men, with a mean age of 56 years and a mean LV ejection fraction of 56 ± 10%. LV LGE was found in 88 patients (13%). The endpoint was all-cause mortality, and in this cohort, 68 deaths were observed over a median follow-up period of 42 months. On univariate analysis, age (hazard ratio [HR]: 1.05; 95% confidence interval [CI]: 1.03 to 1.08; chi-square likelihood ratio [LRχ(2)]: 15.2; p = 0.0001), diabetes (HR: 2.39; 95% CI: 1.41 to 4.09; LRχ(2): 10.3; p = 0.001), a history of heart failure (HR: 1.78; 95% CI: 1.09 to 2.91; LRχ(2): 5.37; p = 0.02), left atrial dimension (HR: 1.04; 95% CI: 1.01 to 1.08; LRχ(2): 6.47; p = 0.01), presence of LGE (HR: 5.08; 95% CI: 3.08 to 8.36; LRχ(2): 28.8; p < 0.0001), and LGE extent (HR: 1.15; 95% CI: 1.10 to 1.21; LRχ(2): 35.6; p < 0.0001) provided the strongest associations with mortality. The mortality rate was 8.1% per patient-year in patients with LGE compared with 2.3% patients without LGE. In the best overall multivariate model for mortality, age and the extent of LGE were independent predictors of mortality. Indeed, each 1% increase in the extent of LGE was associated with a 15% increased risk for death.

CONCLUSIONS

In patients with AF, LV LGE is a frequent finding and is a powerful predictor of mortality.

The role of cardiac magnetic resonance imaging in the assessment of non-ischemic cardiomyopathy

Cardiovascular magnetic resonance imaging (CMR) plays an increasing role in the assessment of patients with various cardiovascular disorders. Given its enhanced spatial resolution, improved tissue characterization, and lack of ionizing radiation, it has become the test of choice in the evaluation of patients with new-onset cardiomyopathy of unknown etiology. In this paper, we will review the role of CMR in the evaluation of patients with various types of non-ischemic cardiomyopathy.