Left ventricular outflow tract obstruction as a risk factor for sudden cardiac death in hypertrophic cardiomyopathy

Incidence, risk assessment and prevention of sudden cardiac death in cardiomyopathies

Cardiomyopathies are a significant contributor to cardiovascular morbidity and mortality, mainly due to the development of heart failure and increased risk of sudden cardiac death (SCD). Despite improvement in survival with contemporary treatment, SCD remains an important cause of mortality in cardiomyopathies. It occurs at a rate ranging between 0.15% and 0.7% per year (depending on the cardiomyopathy), which significantly surpasses SCD incidence in the age- and sex-matched general population. The risk of SCD is affected by multiple factors including the aetiology, genetic basis, age, sex, physical exertion, the extent of myocardial disease severity, conduction system abnormalities, and electrical instability, as measured by various metrics. Over the past decades, the knowledge on the mechanisms and risk factors for SCD has substantially improved, allowing for a better-informed risk stratification. However, unresolved issues still challenge the guidance of SCD prevention in patients with cardiomyopathies. In this review, we aim to provide an in-depth discussion of the contemporary concepts pertinent to understanding the burden, risk assessment and prevention of SCD in cardiomyopathies (dilated, non-dilated left ventricular, hypertrophic, arrhythmogenic right ventricular, and restrictive). The review first focuses on SCD incidence in cardiomyopathies and then summarizes established and emerging risk factors for life-threatening arrhythmias/SCD. Finally, it discusses validated approaches to the risk assessment and evidence-based measures for SCD prevention in cardiomyopathies, pointing to the gaps in evidence and areas of uncertainties that merit future clarification.

Validation of the Risk Stratification for Sudden Cardiac Death in Chinese Patients With Hypertrophic Cardiomyopathy

Accurate identification of hypertrophic cardiomyopathy (HCM) patients at high risk of sudden cardiac death (SCD) event is challenging. The objective of this study was to validate the three SCD risk stratifications recommended by the 2014 European Society of Cardiology (ESC) guideline, the 2020 American Heart Association /American College of Cardiology (AHA/ACC) guideline, and the 2022 ESC guideline in Chinese patients with HCM. Our study population are made up of a cohort of 856 HCM patients without prior SCD events. The endpoint was defined as SCD or equivalent events (successful resuscitation after cardiac arrest or appropriate ICD shock for ventricular tachycardia or ventricular fibrillation). During a median follow-up of 43 months, SCD endpoints occurred in 44 (5.1%) patients. A total of 34 (77.3%) patients suffering from SCD events were classified correctly into high-risk groups by the 2020 AHA/ACC guideline, 27(61.4%) by the 2022 ESC guideline, and 13 (29.6%) by the 2014 ESC guideline. The C-statistic of the 2020 AHA/ACC guideline was 0.68 (95% CI, 0.60-0.76), which performed better than the 2022 ESC guideline (0.65: 95% CI, 0.56-0.73), and the 2014 ESC guideline (0.58: 95% CI, 0.48-0.67). The 2020 AHA/ACC guideline displayed better discrimination for SCD risk stratification in Chinese HCM patients than the other two guidelines, with a higher sensitivity but lower specificity.

Clinical profile and outcomes of pediatric hypertrophic cardiomyopathy in a South Indian tertiary care cardiac center: a three decade experience

INTRODUCTION

Although much research has been done on adult hypertrophic cardiomyopathy, data on pediatric hypertrophic cardiomyopathy is still limited.

METHODS AND RESULTS

The study enrolled all patients with cardiomyopathy who presented to us between 1990 to 2020 and were younger than 18 yrs. During the thirty-year study period, we identified 233 cases of pediatric cardiomyopathy. Sixty-three cases (27%) had hypertrophic cardiomyopathy. Out of the 63 HCM cases, 12% presented in the neonatal period and 37% presented in the first year of life. The median age of presentation was 7 yrs (Range 0.1-18 yrs). Sixteen patients had proven syndromic, metabolic, or genetic disease (25%). LV outflow obstruction was present in 30 patients (47%). Noonan syndrome was present in 9 of the 63 patients (14%). Dyspnea on exertion was the most common mode of presentation. Cardiac MRI was done in 28 patients, out of which 17 had late gadolinium enhancement (LGE). Mid myocardial enhancement was the most common pattern. Four patients had LGE of more than 15%. Over a mean follow-up period of 5.6 years (0.1-30 years), twenty-one were lost to follow-up (33%). Among the patients whose outcome was known, eleven died (26%), and thirty-one (73%) were alive. The 5-year survival rate of HCM patients was 82%, and the 10-year survival rate was 78%. Seven died of sudden cardiac death, three from heart failure, and one from ventricular arrhythmias. Sustained ventricular arrhythmias were seen in three patients and atrial arrhythmias in two. First-degree AV block was seen in 10 patients (15%) and bundle branch blocks (BBB) in five (8%). Eight patients required ICD or transplant (12.7%). Two patients underwent ICD for primary prevention, and one underwent PPI for distal AV conduction disease. Among the various clinical, echocardiographic, and radiological risk factors studied, only consanguinity showed a trend towards higher events of death or ventricular arrhythmias (P-value 0.08).

CONCLUSION

More than one-third of our HCM cohort presented in infancy. LV outflow tract obstruction is common (47%). Mid myocardial enhancement was the most common pattern of late gadolinium enhancement. SCD was the most common cause of death. The outcome in our HCM cohort is good and similar to other population cohorts. Only Consanguinity showed a trend towards higher events of death or ventricular arrhythmias.

Arrhythmic Risk Stratification among Patients with Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a cardiac muscle disorder characterized by generally asymmetric abnormal hypertrophy of the left ventricle without abnormal loading conditions (such as hypertension or valvular heart disease) accounting for the left ventricular wall thickness or mass. The incidence of sudden cardiac death (SCD) in HCM patients is about 1% yearly in adults, but it is far higher in adolescence. HCM is the most frequent cause of death in athletes in the Unites States of America. HCM is an autosomal-dominant genetic cardiomyopathy, and mutations in the genes encoding sarcomeric proteins are identified in 30-60% of cases. The presence of this genetic mutation carries more than 2-fold increased risk for all outcomes, including ventricular arrhythmias. Genetic and myocardial substrate, including fibrosis and intraventricular dispersion of conduction, ventricular hypertrophy and microvascular ischemia, increased myofilament calcium sensitivity and abnormal calcium handling, all play a role as arrhythmogenic determinants. Cardiac imaging studies provide important information for risk stratification. Transthoracic echocardiography can be helpful to evaluate left ventricular (LV) wall thickness, LV outflow-tract gradient and left atrial size. Additionally, cardiac magnetic resonance can evaluate the prevalence of late gadolinium enhancement, which when higher than 15% of LV mass is a prognostic maker of SCD. Age, family history of SCD, syncope and non-sustained ventricular tachycardia at Holter ECG have also been validated as independent prognostic markers of SCD. Arrhythmic risk stratification in HCM requires careful evaluation of several clinical aspects. Symptoms combined with electrocardiogram, cardiac imaging tools and genetic counselling are the modern cornerstone for proper risk stratification.

Risk factors of sudden cardiac death in hypertrophic cardiomyopathy

PURPOSE OF REVIEW

Hypertrophic cardiomyopathy (HCM) is one of the leading causes of sudden cardiac death (SCD) in younger people and athletes. It is crucial to identify the risk factors for SCD in individuals with HCM. This review, based on recent systematic literature studies, will focus on the risk factors for SCD in patients with HCM.

RECENT FINDINGS

An increasing number of studies have further explored the risk factors for SCD in patients with HCM, and new risk markers have emerged accordingly. In addition, more accurate SCD risk estimation and stratification methods have been proposed and continuously improved.

SUMMARY

The identification of independent risk factors for HCM-related SCD would likely contribute to risk stratification. However, it is difficult to predict SCD with absolute certainty, as the annual incidence of SCD in adult patients with HCM is approximately 1%. The review discusses the established risk factors, such as a family history of SCD, unexplained syncope and some new risk factors. Taken together, the findings of this review demonstrate that there is a need for further research on individual risk factors and that SCD risk stratification in HCM patients remains a clinical challenge.

Penetrance of Hypertrophic Cardiomyopathy in Sarcomere Protein Mutation Carriers

Background

Predictive genetic screening of relatives of patients with hypertrophic cardiomyopathy (HCM) caused by sarcomere protein (SP) gene mutations is current standard of care, but there are few data on long-term outcomes in mutation carriers without HCM.

Objectives

The aim of this study was to determine the incidence of new HCM diagnosis in SP mutation carriers.

Methods

This was a retrospective analysis of adult and pediatric SP mutation carriers identified during family screening who did not fulfill diagnostic criteria for HCM at first evaluation.

Results

The authors evaluated 285 individuals from 156 families (median age 14.2 years [interquartile range: 6.8 to 31.6 years], 141 [49.5%] male individuals); 145 (50.9%) underwent cardiac magnetic resonance (CMR). Frequency of causal genes was as follows: MYBPC3 n = 123 (43.2%), MYH7 n = 69 (24.2%), TNNI3 n = 39 (13.7%), TNNT2 n = 34 (11.9%), TPM1 n = 9 (3.2%), MYL2 n = 6 (2.1%), ACTC1 n = 1 (0.4%), multiple mutations n = 4 (1.4%). Median follow-up was 8.0 years (interquartile range: 4.0 to 13.3 years) and 86 (30.2%) patients developed HCM; 16 of 50 (32.0%) fulfilled diagnostic criteria on CMR but not echocardiography. Estimated HCM penetrance at 15 years of follow-up was 46% (95% confidence interval [CI]: 38% to 54%). In a multivariable model adjusted for age and stratified for CMR, independent predictors of HCM development were male sex (hazard ratio [HR]: 2.91; 95% CI: 1.82 to 4.65) and abnormal electrocardiogram (ECG) (HR: 4.02; 95% CI: 2.51 to 6.44); TNNI3 variants had the lowest risk (HR: 0.19; 95% CI: 0.07 to 0.55, compared to MYBPC3).

Conclusions

Following a first negative screening, approximately 50% of SP mutation carriers develop HCM over 15 years of follow-up. Male sex and an abnormal ECG are associated with a higher risk of developing HCM. Regular CMR should be considered in long-term screening.

Mortality Among Referral Patients With Hypertrophic Cardiomyopathy vs the General European Population

Importance

It is unclear whether hypertrophic cardiomyopathy (HCM) conveys excess mortality when compared with the general population.

Objective

To compare the survival of patients with HCM with that of the general European population.

Design, Setting, and Participants

Retrospective cohort study of 4893 consecutive adult patients with HCM presenting at 7 European referral centers between 1980 and 2013. The data were analyzed between April 2018 and August 2019.

Main Outcomes and Measures

Survival was compared using standardized mortality ratios (SMRs) calculated with data from Eurostat, stratified by study period, country, sex, and age, and using a composite end point in the HCM cohort of all-cause mortality, aborted sudden cardiac death, and heart transplant.

Results

Of 4893 patients with HCM, 3126 (63.9%) were male, and the mean (SD) age at presentation was 49.2 (16.4) years. During a median follow-up of 6.2 years (interquartile range, 3.1-9.8 years), 721 patients (14.7%) reached the composite end point. Compared with the general population, patients with HCM had excess mortality throughout the age spectrum (SMR, 2.0, 95% CI, 1.48-2.63). Excess mortality was highest among patients presenting prior to the year 2000 but persisted in the cohort presenting between 2006 and 2013 (SMR, 1.84; 95% CI, 1.55-2.18). Women had higher excess mortality than men (SMR, 2.66; 95% CI, 2.38-2.97; vs SMR, 1.68; 95% CI, 1.52-1.85; P < .001).

Conclusions and Relevance

Among patients referred to European specialty centers, HCM was associated with significant excess mortality through the life course. Although there have been improvements in survival with time, potentially reflecting improved treatments for HCM, these findings highlight the need for more research into the causes of excess mortality among patients with HCM and for better risk stratification.

Risk stratification in hypertrophic cardiomyopathy

Sudden cardiac death (SCD) is the most devastating complication of hypertrophic cardiomyopathy (HCM). The greatest challenge in the management of HCM is identifying those at increased risk, since an implantable cardioverter-defibrillator (ICD) is a potentially life-saving therapy. We sought to summarize the available data on SCD in HCM and provide a clinical perspective on the current differing and somewhat conflicting data on risk stratification, with balanced guidance regarding rational clinical decision-making. Additionally, we sought to determine the status of the current implementation of guidelines compiled by HCM experts worldwide. The HCM Risk-SCD model helps improve the risk stratification of HCM patients for primary prevention of SCD by calculating an individual risk estimate that contributes to the clinical decision-making process. Improved risk stratification is important for decision-making before ICD implantation for the primary prevention of SCD.

Hypertrophic cardiomyopathy: genetics and clinical perspectives

Hypertrophic cardiomyopathy (HCM) is the most common inherited heart disease and defined by unexplained isolated progressive myocardial hypertrophy, systolic and diastolic ventricular dysfunction, arrhythmias, sudden cardiac death and histopathologic changes, such as myocyte disarray and myocardial fibrosis. Mutations in genes encoding for proteins of the contractile apparatus of the cardiomyocyte, such as β-myosin heavy chain and myosin binding protein C, have been identified as cause of the disease. Disease is caused by altered biophysical properties of the cardiomyocyte, disturbed calcium handling, and abnormal cellular metabolism. Mutations in sarcomere genes can also activate other signaling pathways via transcriptional activation and can influence non-cardiac cells, such as fibroblasts. Additional environmental, genetic and epigenetic factors result in heterogeneous disease expression. The clinical course of the disease varies greatly with some patients presenting during childhood while others remain asymptomatic until late in life. Patients can present with either heart failure symptoms or the first symptom can be sudden death due to malignant ventricular arrhythmias. The morphological and pathological heterogeneity results in prognosis uncertainty and makes patient management challenging. Current standard therapeutic measures include the prevention of sudden death by prohibition of competitive sport participation and the implantation of cardioverter-defibrillators if indicated, as well as symptomatic heart failure therapies or cardiac transplantation. There exists no causal therapy for this monogenic autosomal-dominant inherited disorder, so that the focus of current management is on early identification of asymptomatic patients at risk through molecular diagnostic and clinical cascade screening of family members, optimal sudden death risk stratification, and timely initiation of preventative therapies to avoid disease progression to the irreversible adverse myocardial remodeling stage. Genetic diagnosis allowing identification of asymptomatic affected patients prior to clinical disease onset, new imaging technologies, and the establishment of international guidelines have optimized treatment and sudden death risk stratification lowering mortality dramatically within the last decade. However, a thorough understanding of underlying disease pathogenesis, regular clinical follow-up, family counseling, and preventative treatment is required to minimize morbidity and mortality of affected patients. This review summarizes current knowledge about molecular genetics and pathogenesis of HCM secondary to mutations in the sarcomere and provides an overview about current evidence and guidelines in clinical patient management. The overview will focus on clinical staging based on disease mechanism allowing timely initiation of preventative measures. An outlook about so far experimental treatments and potential for future therapies will be provided.

Sudden death related cardiomyopathies - Hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a form of inherited cardiomyopathy. Most individuals with HCM experience minimal symptoms throughout their lifetime. However, those with HCM are at risk of ventricular arrhythmias and sudden cardiac death (SCD), the most feared complication of HCM. Implantable cardioverter defibrillator (ICD) implantation has played a large role in transforming this disease from one with an ominous prognosis to one with mortality rates that are on par with the general public. Since the early 2000s, balance between SCD prevention and unnecessary ICD placement has been sought, this is reflected in the evolution of SCD risk stratification models for patients with HCM. This review discusses key concepts pertaining to HCM, with emphasis on prevention of SCD, and summarizes and compares the recommendations for ICD implantation in current guidelines.

Sudden Cardiac Death Risk Stratification and the Role of the Implantable Cardiac Defibrillator

Hypertrophic cardiomyopathy (HCM) is associated with an increased risk of sudden cardiac death (SCD), although perhaps not as significantly as previously believed. Given the heterogeneous nature of this disease entity, risk stratification of individuals with HCM remains challenging. The recent HCM risk-SCD prediction model seems to perform well in assessing individual SCD risk. Even though implantable cardiac defibrillators (ICDs) are effective in preventing SCD in patients at increased risk, the importance of shared decision making in deciding whether or not to undergo ICD implantation cannot be understated.

Prevention of Sudden Cardiac Death in Hypertrophic Cardiomyopathy: What has Changed in The Guidelines?

Background

The new European Society of Cardiology guidelines for hypertrophic cardiomyopathy (HCM) define the estimation of sudden cardiac death (SCD) risk as an integral part of clinical management. An implantable cardioverter defibrillator (ICD) is recommended (class IIa) when the risk is ≥ 6%.

Objectives

To compare the SCD risk stratification according to the 2011 and 2014 recommendations for ICD implantation in patients with HCM.

Methods

Retrospective study including 105 patients diagnosed with HCM. The indication for ICD was assessed using the 2011 and 2014 guidelines. Statistical analysis was performed using SPSS software version 19.0.0.2®. The tests performed were bilateral, considering the significance level of 5% (p < 0.05).

Results

Regarding primary prevention, according to the 2011 ACCF/AHA recommendations, 39.0% of the patients had indication for ICD implantation (level of evidence IIa). Using the 2014 guidelines, only 12.4% of the patients had an indication for ICD implantation. Comparing the two risk stratification models for patients with HCM, we detected a significant reduction in the number of indications for ICD implantation (p < 0.001). Of the 41 patients classified as IIa according to the 2011 recommendations, 68.3% received a different classification according to the 2014 guidelines.

Conclusion

Significant differences were found when comparing the SCD risk stratification for ICD implantation in the two guidelines. The current SCD risk score seems to identify many low-risk patients who are not candidates for ICD implantation. The use of this new score results in a significant reduction in the number of ICD implanted.

Galectin-3: A Novel Biomarker Predicts Sudden Cardiac Death in Hypertrophic Cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy is a primary cardiac disease characterized by left ventricular hypertrophy, myocyte hypertrophy and irregularities and interstitial fibrosis in the absence of any cardiac or systemic diseases and may lead to sudden cardiac death (SCD). Galectin-3 is a β-galactoside-binding lectin that has been associated with cardiac fibrosis and inflammation. In this study, we aimed to investigate the relationship between serum galectin-3 levels and the criteria for 5-year sudden death risk, recently defined in the European Society of Cardiology guidelines (2014), in patients with hypertrophic cardiomyopathy.

MATERIALS AND METHODS

A total of 52 hypertrophic cardiomyopathy patients were enrolled in the study. Patients were questioned for sudden death risk predictors as outlined in the 2014 European Society of Cardiology guideline. A standardized clinical evaluation was carried out on the basis of previously described prognostic variables to calculate the 5-year risk of SCD. Blood samples were taken from all patients to measure serum galectin-3 levels. A statistical significance level of P < 0.05 was accepted in all tests.

RESULTS

We found that there was a significant correlation between the estimated 5-year risk of SCD and serum levels of galectin-3.

CONCLUSIONS

Galectin-3 may be an inexpensive and easily accessible parameter to predict arrhythmia risk. In addition, it can be used to determine antiarrhythmic prophylaxis as a predictor of an arrhythmia storm in implantable cardioverter defibrillator-implanted patients who are not available for magnetic resonance imaging.

International External Validation Study of the 2014 European Society of Cardiology Guidelines on Sudden Cardiac Death Prevention in Hypertrophic Cardiomyopathy (EVIDENCE-HCM)

Background:

Identification of people with hypertrophic cardiomyopathy (HCM) who are at risk of sudden cardiac death (SCD) and require a prophylactic implantable cardioverter defibrillator is challenging. In 2014, the European Society of Cardiology proposed a new risk stratification method based on a risk prediction model (HCM Risk-SCD) that estimates the 5-year risk of SCD. The aim was to externally validate the 2014 European Society of Cardiology recommendations in a geographically diverse cohort of patients recruited from the United States, Europe, the Middle East, and Asia.

Methods:

This was an observational, retrospective, longitudinal cohort study.

Results:

The cohort consisted of 3703 patients. Seventy three (2%) patients reached the SCD end point within 5 years of follow-up (5-year incidence, 2.4% [95% confidence interval {CI}, 1.9–3.0]). The validation study revealed a calibration slope of 1.02 (95% CI, 0.93–1.12), C-index of 0.70 (95% CI, 0.68–0.72), and D-statistic of 1.17 (95% CI, 1.05–1.29). In a complete case analysis (n= 2147; 44 SCD end points at 5 years), patients with a predicted 5-year risk of <4% (n=1524; 71%) had an observed 5-year SCD incidence of 1.4% (95% CI, 0.8–2.2); patients with a predicted risk of ≥6% (n=297; 14%) had an observed SCD incidence of 8.9% (95% CI, 5.96–13.1) at 5 years. For every 13 (297/23) implantable cardioverter defibrillator implantations in patients with an estimated 5-year SCD risk ≥6%, 1 patient can potentially be saved from SCD.

Conclusions:

This study confirms that the HCM Risk-SCD model provides accurate prognostic information that can be used to target implantable cardioverter defibrillator therapy in patients at the highest risk of SCD.

Ventricular Arrhythmias and Sudden Cardiac Death

Ventricular arrhythmias remain a significant cause of sudden cardiac death (SCD), and knowledge of their cause and high-risk features is important. SCD occurs when the interaction between vulnerable substrates and acute triggers results in sustained ventricular tachycardia progressing to ventricular fibrillation. Here, the authors aim to review the role of ventricular arrhythmias in SCD, first by approaching the substrates that support ventricular arrhythmias, and then by exploring features of these substrates and the acute triggers that may lead to SCD.

Implantable cardioverter defibrillators for primary prevention of sudden death in hypertrophic cardiomyopathy

AIMS

Sudden cardiac death (SCD) may complicate hypertrophic cardiomyopathy (HCM) natural course. Patient selection for implantable cardioverter defibrillator (ICD) therapy in the primary prevention setting is still a challenge.

METHODS

Thirty-seven HCM patients with a primary prevention ICD were included. All patients underwent preimplantation SCD risk assessment and semi-annual device interrogation during follow-up. Primary end point was the time to first appropriate ICD intervention including antitachycardia pacing or shock. Inappropriately delivered ICD therapies served as secondary end point.

RESULTS

During a median follow-up of 3.1 years, 10 (27%) patients received one or more appropriate ICD therapies. First appropriate ICD intervention rate was 7.2%/year (95% CI: 3.4-13.2) with a 5-year cumulative probability of 29.2 ± 7.4%. No SCD risk marker was significantly associated with the primary end point, whereas event rates were comparable among patients with one, two or three or more SCD risk markers (log-rank P = 0.58). Patients with a history of SCD in first-degree relatives with HCM were at 3.8 times higher risk of experiencing an ICD intervention compared with those with no family history of SCD (HR: 3.8; 95% CI: 1.0-14.1, P = 0.05). Seven (18.9%) patients experienced one or more inappropriate ICD therapies; beta-blocker therapy was associated with 75% fewer inappropriate ICD interventions (HR: 0.15; 95% CI: 0.03-0.89).

CONCLUSION

Current criteria identify a subgroup of patients with HCM at increased risk of major arrhythmic events as indicated by high ICD intervention rates. However, no individual risk marker demonstrated superior predictive ability over the others, whereas simple arithmetic summing of risk markers was not associated with increased ICD intervention rates.

Validation of the 2014 European Society of Cardiology Sudden Cardiac Death Risk Prediction Model in Hypertrophic Cardiomyopathy in a Reference Center in South America

Sudden cardiac death (SCD) is a common cause of death in hypertrophic cardiomyopathy (HC). Our aim was to conduct an external and independent validation in South America of the 2014 European Society of Cardiology (ESC) SCD risk prediction model to identify patients requiring an implantable cardioverter defibrillator. This study included 502 consecutive patients with HC followed from March, 1993 to December, 2014. A combined end point of SCD or appropriate implantable cardioverter defibrillator therapy was assessed. For the quantitative estimation of individual 5-year SCD risk, we used the formula: 1 - 0.998(exp(Prognostic index)). Our database also included the abnormal blood pressure response to exercise as a risk marker. We analyzed the 3 categories of 5-year risk proposed by the ESC: low risk (LR) <4%; intermediate risk (IR) ≥4% to <6%, and high risk (HR) ≥6%. The LR group included 387 patients (77%); the IR group 39 (8%); and the HR group 76 (15%). Fourteen patients (3%) had SCD/appropriate implantable cardioverter defibrillator therapy (LR: 0%; IR: 2 of 39 [5%]; and HR: 12 of 76 [16%]). In a receiver-operating characteristic curve, the new model proved to be an excellent predictor because the area under the curve for the estimated risk is 0.925 (statistical C: 0.925; 95% CI 0.8884 to 0.9539, p <0.0001). In conclusion, the SCD risk prediction model in HC proposed by the 2014 ESC guidelines was validated in our population and represents an improvement compared with previous approaches. A larger multicenter, independent and external validation of the model with long-term follow-up would be advisable.

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

Background—

Hypertrophic cardiomyopathy is associated with sudden cardiac death (SCD). Some studies have shown an association between risk of sudden death and left ventricular maximal wall thickness (MWT), but there are few data in patients with extreme hypertrophy. The aim of this study was to determine the relation between MWT and the risk of SCD.

Methods and Results—

This is a multicenter, retrospective, longitudinal cohort study of 3673 adult (≥16 years) patients, previously used to develop and validate a risk prediction model for SCD (HCM Risk-SCD [hypertrophic cardiomyopathy risk-SCD]). There was an inverted U-shaped relation between MWT and the estimated 5-year risk of SCD. In patients with MWT≥35 mm (n=47; mean age, 33 years; 81% men), there was a single SCD end point (annual rate, 0.2%; 95% confidence interval, 0.03–1.60) and 3 additional cardiovascular events during a median follow-up of 9.5 years. Compared with patients with MWT≤14 mm, those with MWT≥35 mm did not have a higher risk for SCD (hazard ratio, 0.22; 95% confidence interval, 0.03–1.65), cardiovascular death (hazard ratio, 0.66; 95% confidence interval, 0.26–1.67), or all-cause mortality (hazard ratio, 0.73; 95% confidence interval, 0.32–1.69).

Conclusions—

The risk of SCD has a complex, nonlinear relationship to MWT. The pathophysiological mechanisms behind this observation require further study but implantable cardioverter defibrillator implantation should not be guided solely on the severity of left ventricular hypertrophy.

Contemporary strategies for risk stratification and prevention of sudden death with the implantable defibrillator in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is regarded as the most common nontraumatic cause of sudden death (SD) in young people (including trained athletes). Introduction of implantable cardioverter-defibrillators (ICD) to HCM 15 years ago represented a new paradigm for clinical practice and probably the most significant advance in management of this disease. ICDs offer protection against SD by terminating potentially lethal ventricular tachyarrhythmias (11%/year secondary and 4%/year primary prevention), although implant decisions are weighed against the possibility of device-related complications (5%/year). ICDs have altered the natural history of HCM, creating the opportunity for extended or normal longevity for many patients. However, assessing SD risk and targeting appropriate candidates for prophylactic device therapy can be compounded by unpredictability of the underlying arrhythmogenic substrate, evident by delays ≥10 years between implant and first ICD intervention. Multiple or a single strong risk marker within the clinical profile of an individual HCM patient can justify consideration for a primary-prevention ICD when combined with physician judgment and shared decision making. The role of the mathematical SD risk score proposed by the European Society of Cardiology to identify patients who benefit from ICD therapy is incompletely resolved. Contemporary treatment interventions and advanced risk stratification using ≥1 conventional markers have served the HCM patient population well, with reduced disease-related mortality rates across all age groups to <1%/year, due largely to the penetration of ICDs into HCM practice. Prevention of SD has now become an integral, albeit challenging, component of HCM management, contributing importantly to its emergence as a contemporary treatable cardiac disease.

Independent Assessment of the European Society of Cardiology Sudden Death Risk Model for Hypertrophic Cardiomyopathy

Risk stratification for sudden death (SD) is an essential component of hypertrophic cardiomyopathy (HC) management, given the proven effectiveness of implantable cardioverter-defibrillators (ICD) for preventing SD. Although highly effective in identifying high-risk patients, current stratification algorithms remain incomplete and novel strategies are encouraged. In this regard, reliability of the statistical model to predict SD risk in HC, as recommended by the recent European Society of Cardiology (ESC) guidelines, was retrospectively tested in an independent cohort of 1,629 consecutive patients with HC aged ≥16 years. Of the 1,629 patients, 35 incurred SD events, but only 4 of these (11%) had high predictive risk scores >6%/5 years consistent with an ICD recommendation, and most (60%; n = 21) had scores <4%/5 years that would not justify ICDs. Of 46 high-risk patients with appropriate ICD interventions for ventricular fibrillation/tachycardia, 27 (59%) had low SD risk scores of <4%/5 years, regarded by ESC as insufficient to recommend ICDs, and only 12 (26%) had scores >6%/5 years, considered an ICD indication; 11 of these 12 had already met conventional criteria warranting implantation with 2 to 3 risk markers. Of 414 patients with ICDs but without appropriate interventions, 258 (62%) had low risk scores (<4%/5 years) that would argue against implant. In conclusion, primary risk stratification using the ESC prognostic score applied retrospectively to a large independent HC cohort proved unreliable for prediction of future SD events. Most patients with HC with SD or appropriate ICD interventions were misclassified with low risk scores and therefore would have remained unprotected from arrhythmic SD without ICDs.

Validation of the 2014 European Society of Cardiology guidelines risk prediction model for the primary prevention of sudden cardiac death in hypertrophic cardiomyopathy

BACKGROUND

The recently released 2014 European Society of Cardiology guidelines of hypertrophic cardiomyopathy (HCM) use a new clinical risk prediction model for sudden cardiac death (SCD), based on the HCM Risk-SCD study. Our study is the first external and independent validation of this new risk prediction model.

METHODS AND RESULTS

The study population consisted of a consecutive cohort of 706 patients with HCM without prior SCD event, from 2 tertiary referral centers. The primary end point was a composite of SCD and appropriate implantable cardioverter-defibrillator therapy, identical to the HCM Risk-SCD end point. The 5-year SCD risk was calculated using the HCM Risk-SCD formula. Receiver operating characteristic curves and C-statistics were calculated for the 2014 European Society of Cardiology guidelines, and risk stratification methods of the 2003 American College of Cardiology/European Society of Cardiology guidelines and 2011 American College of Cardiology Foundation/American Heart Association guidelines. During follow-up of 7.7±5.3 years, SCD occurred in 42 (5.9%) of 706 patients (ages 49±16 years; 34% women). The C-statistic of the new model was 0.69 (95% CI, 0.57-0.82; P=0.008), which performed significantly better than the conventional risk factor models based on the 2003 guidelines (C-statistic of 0.55: 95% CI, 0.47-0.63; P=0.3), and 2011 guidelines (C-statistic of 0.60: 95% CI, 0.50-0.70; P=0.07).

CONCLUSIONS

The HCM Risk-SCD model improves the risk stratification of patients with HCM for primary prevention of SCD, and calculating an individual risk estimate contributes to the clinical decision-making process. Improved risk stratification is important for the decision making before implantable cardioverter-defibrillator implantation for the primary prevention of SCD.

Hypertrophic cardiomyopathy in 2013: Current speculations and future perspectives

Hypertrophic cardiomyopathy (HCM), the most variable cardiac disease in terms of phenotypic presentation and clinical outcome, represents the most common inherited cardiomyopathic process with an autosomal dominant trait of inheritance. To date, more than 1400 mutations of myofilament proteins associated with the disease have been identified, most of them “private” ones. This striking allelic and locus heterogeneity of the disease certainly complicates the establishment of phenotype-genotype correlations. Additionally, topics pertaining to patients’ everyday lives, such as sudden cardiac death (SCD) risk stratification and prevention, along with disease prognosis, are grossly related to the genetic variation of HCM. This review incorporates contemporary research findings and addresses major aspects of HCM, including preclinical diagnosis, genetic analysis, left ventricular outflow tract obstruction and SCD. More specifically, the spectrum of genetic analysis, the selection of the best method for obstruction alleviation and the need for a unique and accurate factor for SCD risk stratification are only some of the controversial HCM issues discussed. Additionally, future perspectives concerning HCM and myocardial ischemia, as well as atrial fibrillation, are discussed. Rather than enumerating clinical studies and guidelines, challenging problems concerning the disease are critically appraised by this review, highlighting current speculations and recommending future directions.

A novel clinical risk prediction model for sudden cardiac death in hypertrophic cardiomyopathy (HCM risk-SCD)

AIMS

Hypertrophic cardiomyopathy (HCM) is a leading cause of sudden cardiac death (SCD) in young adults. Current risk algorithms provide only a crude estimate of risk and fail to account for the different effect size of individual risk factors. The aim of this study was to develop and validate a new SCD risk prediction model that provides individualized risk estimates.

METHODS AND RESULTS

The prognostic model was derived from a retrospective, multi-centre longitudinal cohort study. The model was developed from the entire data set using the Cox proportional hazards model and internally validated using bootstrapping. The cohort consisted of 3675 consecutive patients from six centres. During a follow-up period of 24 313 patient-years (median 5.7 years), 198 patients (5%) died suddenly or had an appropriate implantable cardioverter defibrillator (ICD) shock. Of eight pre-specified predictors, age, maximal left ventricular wall thickness, left atrial diameter, left ventricular outflow tract gradient, family history of SCD, non-sustained ventricular tachycardia, and unexplained syncope were associated with SCD/appropriate ICD shock at the 15% significance level. These predictors were included in the final model to estimate individual probabilities of SCD at 5 years. The calibration slope was 0.91 (95% CI: 0.74, 1.08), C-index was 0.70 (95% CI: 0.68, 0.72), and D-statistic was 1.07 (95% CI: 0.81, 1.32). For every 16 ICDs implanted in patients with ≥4% 5-year SCD risk, potentially 1 patient will be saved from SCD at 5 years. A second model with the data set split into independent development and validation cohorts had very similar estimates of coefficients and performance when externally validated.

CONCLUSION

This is the first validated SCD risk prediction model for patients with HCM and provides accurate individualized estimates for the probability of SCD using readily collected clinical parameters.

Fragmented QRS as a predictor of arrhythmic events in patients with hypertrophic obstructive cardiomyopathy

OBJECTIVES

This study aims to determine whether fragmented QRS (fQRS) in the surface electrocardiogram (ECG) at implantable cardioverter defibrillator (ICD) implant can predict arrhythmic events using appropriate therapy delivered by the ICD as a surrogate.

BACKGROUND

Hypertrophic obstructive cardiomyopathy (HOCM) is a genetic disorder associated with life-threatening arrhythmias frequently requiring an ICD. Seeking a noninvasive method of risk stratification remains a challenge.

METHODS

This paper is a retrospective, multicenter study of patients with HOCM and ICD. Surface 12-lead ECGs were analyzed. Appropriate therapy was validated by a blinded Core Lab. Univariate and multivariate analyses were performed. A p value of <0.05 was considered significant.

RESULTS

We included 102 patients from 13 centers. Mean age at implant was 41.16 ± 18.25 years, 52% were male. Mean left ventricular ejection fraction was 61.56 ± 9.46% and two thirds had heart failure according to the New York Heart Association class I. Secondary prophylaxis ICD implantation was the indication for implant in 40.2% of cases. About half received a single-chamber ICD. fQRS was present at the time of diagnosis in 21 and in 54% at ICD implant. At a mean follow-up of 47.8 ± 39.3 months, 41 patients (40.2%) presented with appropriate therapy. In a multivariate logistic regression, predictors of appropriate therapy included fQRS at implant (odds ratio [OR], 16.4; 95% confidence interval [CI], 3.6-74.0; p = 0.0003), history of combined ventricular tachycardia/fibrillation/sudden death (OR, 14.3; 95% CI, 3.2-69.3; p = 0.001) and history of syncope (OR, 5.5; 95% CI, 1.5-20.4; p = 0.009). Ten deaths (9.8%) occurred during the follow-up. fQRS in the lateral location increased the risk of appropriate therapy (p < 0.0001).

CONCLUSIONS

fQRS predicts arrhythmic events in patients with HOCM and should be considered in a model of risk stratification.

Hypertrophic cardiomyopathy in childhood

Hypertrophic cardiomyopathy has important differences in children compared with adults, particularly with regard to the range of causes and the outcomes in infants. Survival is highly dependent on etiology, particularly in the youngest patients, and pursuit of the specific cause is therefore necessary. The clinical utility of defining the genotype in children with familial hypertrophic cardiomyopathy exceeds that at other ages and has a highly favorable cost/benefit ratio. Although most of the available information concerning treatment and prevention of sudden death is derived in adults, management of children requires consideration of the differences in age-specific risk/benefit ratios.