Inverted U-Shaped Relation Between the Risk of Sudden Cardiac Death and Maximal Left Ventricular Wall Thickness in Hypertrophic Cardiomyopathy

Performance of 2020 AHA/ACC HCM Guidelines and Incremental Value of Myocardial Strain for Predicting SCD

Background

The 2020 American Heart Association (AHA)/American College of Cardiology (ACC) guidelines for sudden cardiac death (SCD) risk stratification in hypertrophic cardiomyopathy (HCM) need further international validation.

Objectives

Performance of the guidelines and the incremental value of myocardial strain for predicting SCD in HCM were investigated.

Methods

In 1,416 HCM patients, SCD risk was stratified according to the 2020 AHA/ACC and 2014 European Society of Cardiology (ESC) guidelines. Left ventricular (LV) global longitudinal strain (GLS) and left atrial reservoir strain (LARS) were measured. The main outcome consisted of SCD events.

Results

Overall, 29.1% had major risk factors (RFs), and 14.7% had nonmajor RFs in the absence of major RFs; estimated 5-year SCD event rates were 6.8% and 2.3%, respectively. SCD risk was significantly increased in the former group but not in the latter. When stratified by the number of RFs, 5-year SCD event rates were 1.9%, 3.0%, 4.9%, and 18.4% for patients with 0, 1, 2, and 3 or more RFs, respectively. SCD risk was elevated in patients with multiple RFs but not in those with a single RF. Performance of the AHA/ACC and ESC guidelines did not differ significantly over 10 years (5-year time-dependent area under the curve: 0.677 vs 0.724; P = 0.235). Decreased LV GLS and LARS were independently associated with SCD events with optimal cutoffs of LV GLS <13% and LARS <21%. Adding LV GLS and LARS to the guidelines had incremental predictive value.

Conclusions

The 2020 AHA/ACC guidelines were predictive of SCD events with modest power in a large Asian HCM cohort. Implantable cardioverter-defibrillators are reasonable in patients with multiple RFs, and consideration of myocardial strain can improve SCD prediction.

Identification of fibrosis in hypertrophic cardiomyopathy: a radiomic study on cardiac magnetic resonance cine imaging

OBJECTIVES

Hypertrophic cardiomyopathy (HCM) often requires repeated enhanced cardiac magnetic resonance (CMR) imaging to detect fibrosis. We aimed to develop a practical model based on cine imaging to help identify patients with high risk of fibrosis and screen out patients without fibrosis to avoid unnecessary injection of contrast.

METHODS

A total of 273 patients with HCM were divided into training and test sets at a ratio of 7:3. Logistic regression analysis was used to find predictive image features to construct CMR model. Radiomic features were derived from the maximal wall thickness (MWT) slice and entire left ventricular (LV) myocardium. Extreme gradient boosting was used to build radiomic models. Integrated models were established by fusing image features and radiomic models. The model performance was validated in the test set and assessed by ROC and calibration curve and decision curve analysis (DCA).

RESULTS

We established five prediction models, including CMR, R1 (based on the MWT slice), R2 (based on the entire LV myocardium), and two integrated models (I_CMR+R1 and I_CMR+R2). In the test set, I_CMR+R2 model had an excellent AUC value (0.898), diagnostic accuracy (89.02%), sensitivity (92.54%), and F1 score (93.23%) in identifying patients with positive late gadolinium enhancement. The calibration plots and DCA indicated that I_CMR+R2 model was well-calibrated and presented a better net benefit than other models.

CONCLUSIONS

A predictive model that fused image and radiomic features from the entire LV myocardium had good diagnostic performance, robustness, and clinical utility.

KEY POINTS

• Hypertrophic cardiomyopathy is prone to fibrosis, requiring patients to undergo repeated enhanced cardiac magnetic resonance imaging to detect fibrosis over their lifetime follow-up. • A predictive model based on the entire left ventricular myocardium outperformed a model based on a slice of the maximal wall thickness. • A predictive model that fused image and radiomic features from the entire left ventricular myocardium had excellent diagnostic performance, robustness, and clinical utility.

Relationship Between Maximal Left Ventricular Wall Thickness and Sudden Cardiac Death in Childhood Onset Hypertrophic Cardiomyopathy

BACKGROUND

Maximal left ventricular wall thickness (MLVWT) is a risk factor for sudden cardiac death (SCD) in hypertrophic cardiomyopathy (HCM). In adults, the severity of left ventricular hypertrophy has a nonlinear relationship with SCD, but it is not known whether the same complex relationship is seen in childhood. The aim of this study was to describe the relationship between left ventricular hypertrophy and SCD risk in a large international pediatric HCM cohort.

METHODS

The study cohort comprised 1075 children (mean age, 10.2 years [±4.4]) diagnosed with HCM (1-16 years) from the International Paediatric Hypertrophic Cardiomyopathy Consortium. Anonymized, noninvasive clinical data were collected from baseline evaluation and follow-up, and 5-year estimated SCD risk was calculated (HCM Risk-Kids).

RESULTS

MLVWT Z score was <10 in 598 (58.1%), ≥10 to <20 in 334 (31.1%), and ≥20 in 143 (13.3%). Higher MLVWT Z scores were associated with heart failure symptoms, unexplained syncope, left ventricular outflow tract obstruction, left atrial dilatation, and nonsustained ventricular tachycardia. One hundred twenty-two patients (71.3%) with MLVWT Z score ≥20 had coexisting risk factors for SCD. Over a median follow-up of 4.9 years (interquartile range, 2.3-9.3), 115 (10.7%) had an SCD event. Freedom from SCD event at 5 years for those with MLVWT Z scores <10, ≥10 to <20, and ≥20 was 95.6%, 87.4%, and 86.0, respectively. The estimated SCD risk at 5 years had a nonlinear, inverted U-shaped relationship with MLVWT Z score, peaking at Z score +23. The presence of coexisting risk factors had a summative effect on risk.

CONCLUSIONS

In children with HCM, an inverted U-shaped relationship exists between left ventricular hypertrophy and estimated SCD risk. The presence of additional risk factors has a summative effect on risk. While MLVWT is important for risk stratification, it should not be used either as a binary variable or in isolation to guide implantable cardioverter defibrillator implantation decisions in children with HCM.

Risk Prediction Models and Scores in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) has historically been linked with sudden cardiac death (SCD). Currently, it is well established that only a subset of patients is at the highest risk stratum for such a catastrophic event. Detection of patients belonging to this high-risk category can allow for timely defibrillator implantation, changing the natural history of HCM. Inversely, device implantation in patients deemed at low risk leads to an unnecessary burden of device complications with no apparent protective benefit. Previous studies have identified a series of markers, now considered established risk factors, with genetic testing and newer imaging allowing for the detection of novel, highly promising indices of increased risk for SCD. Despite the identification of a number of risk factors, there is noticeable discrepancy in the utility of such factors for risk stratification between the current American and European guidelines. We sought to systematically review the data available on these two approaches, presenting their rationale and respective predictive capacity, also discussing the potential of novel markers to augment the precision of currently used risk stratification models for SCD in HCM.

Childhood Hypertrophic Cardiomyopathy: A Disease of the Cardiac Sarcomere

Hypertrophic cardiomyopathy is the second most common cause of cardiomyopathy presenting during childhood and whilst its underlying aetiology is variable, the majority of disease is caused by sarcomeric protein gene variants. Sarcomeric disease can present at any age with highly variable disease phenotype, progression and outcomes. The majority have good childhood-outcomes with reported 5-year survival rates above 80%. However, childhood onset disease is associated with considerable life-long morbidity and mortality, including a higher SCD rate during childhood than seen in adults. Management is currently focused on relieving symptoms and preventing disease-related complications, but the possibility of future disease-modifying therapies offers an exciting opportunity to modulate disease expression and outcomes in these young patients.

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.