Risk stratification for sudden cardiac death in hypertrophic cardiomyopathy: systematic review of clinical risk markers

Distinct ECG Phenotypes Identified in Hypertrophic Cardiomyopathy Using Machine Learning Associate With Arrhythmic Risk Markers

Aims: Ventricular arrhythmia triggers sudden cardiac death (SCD) in hypertrophic cardiomyopathy (HCM), yet electrophysiological biomarkers are not used for risk stratification. Our aim was to identify distinct HCM phenotypes based on ECG computational analysis, and characterize differences in clinical risk factors and anatomical differences using cardiac magnetic resonance (CMR) imaging.

Methods: High-fidelity 12-lead Holter ECGs from 85 HCM patients and 38 healthy volunteers were analyzed using mathematical modeling and computational clustering to identify phenotypic subgroups. Clinical features and the extent and distribution of hypertrophy assessed by CMR were evaluated in the subgroups.

Results: QRS morphology alone was crucial to identify three HCM phenotypes with very distinct QRS patterns. Group 1 (n = 44) showed normal QRS morphology, Group 2 (n = 19) showed short R and deep S waves in V4, and Group 3 (n = 22) exhibited short R and long S waves in V4-6, and left QRS axis deviation. However, no differences in arrhythmic risk or distribution of hypertrophy were observed between these groups. Including T wave biomarkers in the clustering, four HCM phenotypes were identified: Group 1A (n = 20), with primary repolarization abnormalities showing normal QRS yet inverted T waves, Group 1B (n = 24), with normal QRS morphology and upright T waves, and Group 2 and Group 3 remaining as before, with upright T waves. Group 1A patients, with normal QRS and inverted T wave, showed increased HCM Risk-SCD scores (1A: 4.0%, 1B: 1.8%, 2: 2.1%, 3: 2.5%, p = 0.0001), and a predominance of coexisting septal and apical hypertrophy (p < 0.0001). HCM patients in Groups 2 and 3 exhibited predominantly septal hypertrophy (85 and 90%, respectively).

Conclusion: HCM patients were classified in four subgroups with distinct ECG features. Patients with primary T wave inversion not secondary to QRS abnormalities had increased HCM Risk-SCD scores and coexisting septal and apical hypertrophy, suggesting that primary T wave inversion may increase SCD risk in HCM, rather than T wave inversion secondary to depolarization abnormalities. Computational ECG phenotyping provides insight into the underlying processes captured by the ECG and has the potential to be a novel and independent factor for risk stratification.

Mid-term outcomes of biventricular obstruction and left ventricular outflow tract obstruction after surgery correction in child and adolescent patients with hypertrophic cardiomyopathy

BACKGROUND

Data on the outcomes of hypertrophic cardiomyopathy (HCM) with biventricular obstruction are limited.

OBJECTIVE

Our aim is to compare mid-term outcomes of biventricular outflow tract obstruction (BVOTO) HCM, left ventricular outflow tract obstruction (LVOTO) HCM and nonobstructive hypertrophic cardiomyopathy (NO-HCM) in children and adolescents who were treated with standard medication or surgical resection.

METHODS

This retrospective study identified 21 BVOTO patients and recruited 27 LVOTO and 24 NO-HCM patients younger than 18 years presenting at our institution. The primary endpoint was all-cause death, and secondary endpoints were cardiovascular events.

RESULTS

More BVOTO patients (61.9%) than LVOTO (19.2%) and NO-HCM patients (25%) exhibited New York Heart Association (NYHA) III/IV status (p < 0.01). Fourteen BVOTO and 16 LVOTO patients obtained a significant reduction of outflow tract pressure gradients after surgery (vs. preoperative baseline, p < 0.001). One of the 14 BVOTO patients died, whereas no deaths occurred among LVOTO patients. Three of 14 BVOTO surgery patients had complete heart block (CHB) and 4 had new right bundle branch block (RBBB), while no CHB or RBBB occurred in the LVOTO surgery patients. The BVOTO patients had a longer duration of aortic cross-clamping and postoperative hospital days than the LVOTO patients (p < 0.05). During a median 42-month follow-up, no deaths occurred among the remaining patients. The primary and secondary endpoint-free survival rates of the BVOTO group were comparable to those of the LVOTO and NO-HCM groups.

CONCLUSIONS

In children and adolescents, BVOTO patients were associated with more severe symptoms than LVOTO and NO-HCM patients; however, good mid-term outcomes similar to those of the LVOTO and NO-HCM groups can be achieved with the application of contemporary cardiovascular treatment strategies. Notably, BVOTO surgery was associated with an increased risk of CHB and RBBB compared to LVOTO surgery.

Interaction of Adverse Disease Related Pathways in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HC) has been characterized as a generally progressive genetic heart disease, creating an ominous perspective for patients and managing cardiologists. We explored the HC disease burden and interaction of adverse clinical pathways to clarify patient expectations over long time periods in the contemporary therapeutic era. We studied 1,000 consecutive HC patients (52 ± 17 years) at Tufts Medical Center, followed 9.3 ± 8 years from diagnosis, employing a novel disease pathway model: 46% experienced a benign course free of adverse pathways, but 42% of patients progressed along 1 major pathway, most commonly refractory heart failure to New York Heart Association class III or IV requiring surgical myectomy (or alcohol ablation) or heart transplant; repetitive or permanent atrial fibrillation; and least commonly arrhythmic sudden death events. Eleven percent experienced 2 of these therapeutic end points at different times in their clinical course, most frequently the combination of advanced heart failure and atrial fibrillation, whereas only 1% incurred all 3 pathways. Freedom of progression from 1 to 2 disease pathways, or from 2 to 3 was 80% and 93% at 5 years, respectively. Annual HC-related mortality did not differ according to the number of pathways: 1 (0.8%), 2 (0.8%), or 3 (2.4%) (p = 0.56), and 93% of patients were in New York Heart Association classes I or II at follow-up. In conclusion, it is uncommon for HC patients to experience multiple adverse (but treatable) disease pathways, underscoring the principle that HC is not a uniformly progressive disease. These observations provide a measure of clarity and/or reassurance to patients regarding the true long-term disease burden of HC.

Predictors of risk for sudden death in childhood hypertrophic cardiomyopathy: the importance of the ECG risk score

Objective

To establish which risk factors are predictive for sudden death in hypertrophic cardiomyopathy (HCM) diagnosed in childhood.

Methods

A Swedish national cohort of patients with HCM diagnosed <19 years of age was collected between 1972 and 2014, consisting of 155 patients with available ECGs, with average follow-up of 10.9±(SD 9.0) years, out of whom 32 had suffered sudden death or cardiac arrest (SD/CA group). Previously proposed risk factors and clinical features, ECG and ultrasound measures were compared between SD/CA group and patients surviving >2 years (n=100), and features significantly more common in SD/CA group were further analysed with univariate and multivariate Cox hazard regression in the total cohort.

Results

Ranked according to relative risk (RR) the ECG risk score >5 points had an RR of 46.5 (95% CI 6.6 to 331), sensitivity of 97% (83% to 100%) and specificity of 80% (71% to 88%) (p<0.0001), and was the best ECG predictor, predicting a 5-year risk of SD/CA of 30.6%. The following are other features with importantly raised RR: Detroit wall thickness Z-score >4.5: 9.9 (3.1 to 31.2); septal thickness ≥190% of upper limit of normal for age (septum in % of 95th centile for age (SEPPER) ≥190%): 7.9 (3.2 to 19.4); ventricular tachycardia: 9.1 (3.6 to 22.8); ventricular ectopics on exercise testing: 7.4 (2.7 to 20.2); and left ventricular outflow gradient (left ventricular outflow tract obstruction (LVOTO)) >50 mm Hg: 6.6 (4.0 to 11.0). Family history was non-significant. Multivariate Cox hazard analysis gives the following as early predictors: limb-lead QRS amplitude sum (p=0.020), SEPPER ≥190% (p<0.001) and LVOTO at rest (p=0.054); and for late predictors: last ECG risk score (p=0.002) and last Detroit Z-score (p=0.001). Both early (p=0.028) and late (p=0.037) beta-blocker doses reduced risk in the models.

Conclusions

ECG phenotype as assessed by ECG risk score is important for risk of sudden death and should be considered for inclusion in risk stratification of paediatric patients with HCM.

Hypertrophic Cardiomyopathy: Genetics, Pathogenesis, Clinical Manifestations, Diagnosis, and Therapy

Hypertrophic cardiomyopathy (HCM) is a genetic disorder that is characterized by left ventricular hypertrophy unexplained by secondary causes and a nondilated left ventricle with preserved or increased ejection fraction. It is commonly asymmetrical with the most severe hypertrophy involving the basal interventricular septum. Left ventricular outflow tract obstruction is present at rest in about one third of the patients and can be provoked in another third. The histological features of HCM include myocyte hypertrophy and disarray, as well as interstitial fibrosis. The hypertrophy is also frequently associated with left ventricular diastolic dysfunction. In the majority of patients, HCM has a relatively benign course. However, HCM is also an important cause of sudden cardiac death, particularly in adolescents and young adults. Nonsustained ventricular tachycardia, syncope, a family history of sudden cardiac death, and severe cardiac hypertrophy are major risk factors for sudden cardiac death. This complication can usually be averted by implantation of a cardioverter-defibrillator in appropriate high-risk patients. Atrial fibrillation is also a common complication and is not well tolerated. Mutations in over a dozen genes encoding sarcomere-associated proteins cause HCM. MYH7 and MYBPC3, encoding β-myosin heavy chain and myosin-binding protein C, respectively, are the 2 most common genes involved, together accounting for ≈50% of the HCM families. In ≈40% of HCM patients, the causal genes remain to be identified. Mutations in genes responsible for storage diseases also cause a phenotype resembling HCM (genocopy or phenocopy). The routine applications of genetic testing and preclinical identification of family members represents an important advance. The genetic discoveries have enhanced understanding of the molecular pathogenesis of HCM and have stimulated efforts designed to identify new therapeutic agents.

Abnormal sodium channel mRNA splicing in hypertrophic cardiomyopathy

BACKGROUND

Our previous studies showed that in ischemic and nonischemic heart failure (HF), the voltage-gated cardiac Na⁺ channel α subunit (SCN5A) mRNA is abnormally spliced to produce two truncated transcript variants (E28C and D) that activate the unfolded protein response (UPR). We tested whether SCN5A post-transcriptional regulation was abnormal in hypertrophic cardiomyopathy (HCM).

MATERIAL AND METHODS

Human heart tissue was obtained from HCM patients. The changes in relative abundances of SCN5A, its variants, splicing factors RBM25 and LUC7A, and PERK, a major effector of the UPR, were analyzed by real time RT-PCR and the expression changes were confirmed by Western Blot.

RESULTS

We found reduced full-length transcript, increased SCN5A truncation variants and activation of UPR in HCM when compared to control hearts. In these patients, real time RT-PCR revealed that HCM patients had decreased SCN5A mRNA to 27.8±4.07% of control (P<0.01) and an increased abundance of E28C and E28D (3.4±0.3 and 2.8±0.3-fold, respectively, P<0.05). PERK mRNA increased 8.2±3.1 fold (P<0.01) in HCM patients. Western blot confirmed a significant increase of PERK.

CONCLUSIONS

These data suggested that the full-length SCN5A was reduced in patients with HCM. This reduction was accompanied by abnormal SCN5A pre-mRNA splicing and UPR activation. These changes may contribute to the arrhythmic risk in HCM.

Genetics and Genomics of Single-Gene Cardiovascular Diseases: Common Hereditary Cardiomyopathies as Prototypes of Single-Gene Disorders

This is the first of 2 review papers on genetics and genomics appearing as part of the series on "omics." Genomics pertains to all components of an organism's genes, whereas genetics involves analysis of a specific gene or genes in the context of heredity. The paper provides introductory comments, describes the basis of human genetic diversity, and addresses the phenotypic consequences of genetic variants. Rare variants with large effect sizes are responsible for single-gene disorders, whereas complex polygenic diseases are typically due to multiple genetic variants, each exerting a modest effect size. To illustrate the clinical implications of genetic variants with large effect sizes, 3 common forms of hereditary cardiomyopathies are discussed as prototypic examples of single-gene disorders, including their genetics, clinical manifestations, pathogenesis, and treatment. The genetic basis of complex traits is discussed in a separate paper.

Usefulness of 14-Day Holter for Detection of Nonsustained Ventricular Tachycardia in Patients With Hypertrophic Cardiomyopathy

Nonsustained ventricular tachycardia (NSVT), defined as ≥3 consecutive ventricular beats at ≥120 beats/min lasting <30 seconds, is an independent predictor of sudden cardiac death (SCD) in hypertrophic cardiomyopathy (HC). Current guidelines recommend 24- to 48-hour Holter monitoring as part of SCD risk stratification. We sought to assess the difference in diagnostic yield of 14-day Holter monitoring compared to 24-48 hours for the detection of NSVT and to assess the prevalence and characteristics of NSVT in patients with HC with prolonged monitoring. We retrospectively analyzed the 14-day Holter monitors of 77 patients with HC from May 2014 to March 2016. Number of episodes and maximal length and rate on each day were recorded. NSVT was detected in 75.3% of patients during 14-day Holter monitoring. The median number of runs was 2 (range 0 to 26 runs). The median number of beats of the longest run was 10.5 (range 3 to 68 beats) with a mean maximum rate of 159.5 ± 20.8.4 beats/min (range 102 to 203 beats/min). First episodes of NSVT were detected throughout the 14 days, with only 22.5% and 44.8% of the episodes captured within the first 24 and 48 hours of monitoring, respectively. In conclusion, prolonged Holter monitoring revealed ≥1 episode of NSVT in 75% of patients with HC of which <50% were detected within the first 48 hours. Hence, prolonged Holter monitoring may be superior for SCD risk stratification in HC. However, the high prevalence of NSVT in this population may limit its utility in evaluating the risk for SCD of the individual patient.

Rapid Device-Detected Nonsustained Ventricular Tachycardia in the Risk Stratification of Hypertrophic Cardiomyopathy

BACKGROUND

Nonsustained ventricular tachycardia (NSVT) detected by ambulatory Holter (Holter NSVT) is a major risk factor for sudden cardiac death in hypertrophic cardiomyopathy (HCM). We hypothesized that the prognostic utility of Holter NSVT in HCM would improve with prolonged monitoring and a higher heart rate cut-off for detection.

METHODS

We enrolled 60 patients (44 ± 14 years) with HCM, who had a prophylactic implantable cardioverter defibrillator (ICD). Positive Holter NSVT (prior to implant) was defined as ≥3 beats at ≥120 beats per minute (bpm). We assessed the prevalence of rapid NSVT (RNSVT) detected by their ICD within 12 months of its implant, defined as 4-16 beats at ≥150-200 bpm. The primary outcome was appropriate ICD therapy (antitachycardia pacing and shocks) for sustained ventricular arrhythmia (VA).

RESULTS

Holter NSVT was detected in 34 patients. RNSVT occurred in 21 (35%) patients of whom five did not have Holter NSVT. Over a median follow-up of 61 (interquartile range 29, 129) months after ICD implant, nine patients had VA. RNSVT, but not Holter NSVT, was significantly associated with VA (hazard ratio 6.2, 95% confidence interval [1.3-30], P = 0.01) by multivariable Cox regression analysis that included conventional risk factors. Receiver operating characteristic analysis for RNSVT (area under curve 0.80, P = 0.005) showed that the occurrence of ≥2 episodes of RNSVT discriminated patients for VA optimally (sensitivity 78%, specificity 84%, positive predictive value 47%, negative predictive value 96%).

CONCLUSIONS

In this pilot study, RNSVT detected by continuous monitoring independently predicted VA in HCM and offered superior discrimination of VA risk compared to conventional risk factors, including Holter NSVT. Future studies are needed to validate these findings in a larger, unselected HCM cohort.

Distribution and Clinical Significance of High Signal Intensity of the Myocardium on T2-Weighted Images in 2 Phenotypes of Hypertrophic Cardiomyopathy

OBJECTIVE

The aim of this study was to evaluate distribution and clinical significance of high signal intensity of the myocardium on T2-weighted images (T2-HI) in 2 phenotypes of hypertrophic cardiomyopathy (HCM).

METHODS

Thirty-six patients with asymmetrical septal HCM (ASH) and 18 patients with apical HCM (APH) and their 864 myocardial segments were investigated. The distribution of T2-HI was compared with that of late gadolinium enhancement (LGE), and the relationships between T2-HI and clinical risk markers were evaluated. T2 values of the T2-HI were estimated with T2 mapping.

RESULTS

The T2-HI was observed in 18 segments (3.1%) in 13 patients with ASH (36.1%) and in 12 segments (4.2%) in 8 patients with APH (44.4%). It was often localized outside LGE. The presence of T2-HI was related to syncope in ASH (P = 0.016). Furthermore, it had higher T2 values (61.1 milliseconds) than the reference myocardium (47.3 milliseconds).

CONCLUSIONS

High signal intensity of the myocardium on T2-weighted images often locates outside LGE and reflects myocardial damage, which is related to syncope in ASH.

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.

Hypertrophic Cardiomyopathy in Adulthood Associated With Low Cardiovascular Mortality With Contemporary Management Strategies

BACKGROUND

Hypertrophic cardiomyopathy (HCM) has been prominently associated with adverse disease complications, including sudden death or heart failure death and a generally adverse prognosis, with annual mortality rates of up to 6%.

OBJECTIVES

This study determined whether recent advances in management strategy, including implantable cardioverter-defibrillators (ICDs), heart transplantation, or other therapeutic measures have significantly improved survival and the clinical course of adult HCM patients.

METHODS

We addressed long-term outcomes in 1,000 consecutive adult HCM patients presenting at 30 to 59 years of age (mean 45±8 years) over 7.2±5.2 years of follow-up.

RESULTS

Of 1,000 patients, 918 (92%) survived to 53±9.2 years of age (range 32 to 80 years) with 91% experiencing no or only mild symptoms at last evaluation. HCM-related death occurred in 40 patients (4% [0.53%/year]) at 50±10 years from the following events: progressive heart failure (n=17); arrhythmic sudden death (SD) (n=17); and embolic stroke (n=2). In contrast, 56 other high-risk patients (5.6%) survived life-threatening events, most commonly with ICD interventions for ventricular tachyarrhythmias (n=33) or heart transplantation for advanced heart failure (n=18 [0.79%/year]). SD occurred in patients who declined ICD recommendations, had evaluations before application of prophylactic ICDs to HCM, or were without conventional risk factors. The 5- and 10-year survival rates (confined to HCM deaths) were 98% and 94%, respectively, not different from the expected all-cause mortality in the general U.S. population (p=0.25). Multivariate independent predictors of adverse outcome were younger age at diagnosis, female sex, and increased left atrial dimension.

CONCLUSIONS

In a large longitudinally assessed adult HCM cohort, we have demonstrated that contemporary management strategies and treatment interventions, including ICDs for SD prevention, have significantly altered the clinical course, now resulting in a low disease-related mortality rate of 0.5%/year and an opportunity for extended longevity.

Genotype-phenotype Correlations of Hypertrophic Cardiomyopathy When Diagnosed in Children, Adolescents, and Young Adults

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is the most common heritable cardiovascular disease and a leading cause of identifiable sudden cardiac death (SCD) in the young. Herein, we sought to determine the genotype-phenotype correlations in a cohort of unrelated, genotyped patients diagnosed with HCM at a young age, as well as to characterize the differences between HCM diagnosed in adulthood and HCM diagnosed at a young age.

METHODS AND RESULTS

From 1999 to 2011, 1053 unrelated patients diagnosed with HCM were enrolled in research-based genetic testing. The electronic medical record was reviewed to identify those with HCM diagnosed at ≤21 years (N = 137, mean age at diagnosis 13.2 ± 6 years, 64% male). From this cohort of patients recruited from a tertiary care referral center, the genetic test was positive in 71 (52%), which was significantly higher than patients diagnosed >21 years (31%; P < .001). Genotype-positive patients had increased maximum left ventricular wall thickness (24.9 ± 8.0 vs. 21.6 ± 7.4 mm, P = .01) and higher incidence of reverse-curve ventricular septal morphology (71% vs. 40%, P < .001). Unrelated to genotype status, 26/137 patients (19%) experienced significant HCM-related morbidity/mortality including progressive heart failure symptoms in 12, transplantation in 4, and death in 10.

CONCLUSIONS

Among patients diagnosed with HCM during the first two decades of life, the yield of genetic testing is significantly higher than when diagnosed at later age. While the phenotype of young HCM patients is worse than patients whose HCM is diagnosed at later age, the phenotypes of genotype-positive and genotype-negative young patients were similar. Independent of genotype, nearly 30% of the patients with follow-up in this study had symptom progression, transplant, or death.

Implantable Cardioverter-defibrillator Therapy for Hypertrophic Cardiomyopathy: Usefulness in Primary and Secondary Prevention

INTRODUCTION AND OBJECTIVES

Hypertrophic cardiomyopathy is a frequent cause of sudden death. Clinical practice guidelines indicate defibrillator implantation for primary prevention in patients with 1 or more risk factors and for secondary prevention in patients with a history of aborted sudden death or sustained ventricular arrhythmias. The aim of the present study was to analyze the follow-up of patients who received an implantable defibrillator following the current guidelines in nonreferral centers for this disease.

METHODS

This retrospective observational study included all patients who underwent defibrillator implantation between January 1996 and December 2012 in 3 centers in the province of Barcelona.

RESULTS

The study included 69 patients (mean age [standard deviation], 44.8 [17] years; 79.3% men), 48 in primary prevention and 21 in secondary prevention. The mean number of risk factors per patient was 1.8 in the primary prevention group and 0.5 in the secondary prevention group (P=.029). The median follow-up duration was 40.5 months. The appropriate therapy rate was 32.7/100 patient-years in secondary prevention and 1.7/100 patient-years in primary prevention (P<.001). Overall mortality was 10.1%. Implant-related complications were experienced by 8.7% of patients, and 13% had inappropriate defibrillator discharges.

CONCLUSIONS

In patients with a defibrillator for primary prevention, the appropriate therapy rate is extremely low, indicating the low predictive power of the current risk stratification criteria.

Family History of Sudden Death Should Be a Primary Indication for Implantable Cardioverter Defibrillator in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the leading cause of sudden death in young patients. A number of noninvasive clinical markers, including family history, have formed the basis for a risk stratification strategy aimed at identifying high-risk patients with HCM. The observation that sudden death can occur in multiple relatives of the same family, and clinical studies in which a family history of HCM-related sudden death emerges as an independent predictor of sudden death, support the principle that family history should be considered a risk factor which, in the appropriate clinical scenario, can form the basis for recommending prophylactic implantable cardioverter defibrillator therapy.

Historical perspectives on the implantable cardioverter-defibrillator and prevention of sudden death in hypertrophic cardiomyopathy

The implantable cardioverter-defibrillator (ICD) was not originally envisioned as a treatment to prevent sudden death (SD) in young people with genetic heart diseases. In the case of hypertrophic cardiomyopathy (HCM), initially it was not known whether the ICD would be effective in patients with a disease very different morphologically and functionally from coronary artery disease. Nevertheless, several observational clinical studies have shown that the ICD reliably terminates life-threatening ventricular tachyarrhythmias in HCM, and is largely responsible for reducing HCM mortality to 0.5% per year, by preventing SD and changing the natural course of the disease.

Comparison of the new risk prediction model (HCM Risk-SCD) and classic risk factors for sudden death in patients with hypertrophic cardiomyopathy and defibrillator

AIMS

Hypertrophic cardiomyopathy is one of the main causes of sudden death in young people. Recent clinical practice guidelines include a risk prediction model for sudden death (HCM Risk-SCD), which facilitates the decision of whether to implant a defibrillator. The aim of our study was to ascertain the percentage of events in our series of primary prevention implantable cardioverter-defibrillator recipients with hypertrophic cardiomyopathy and whether HCM Risk-SCD predicts the onset of arrhythmic events.

METHODS AND RESULTS

This was an observational, retrospective cohort study, which included 48 primary prevention defibrillator recipient patients with HCM. We compiled their demographic and clinical characteristics, estimated 5-year risk using HCM Risk-SCD, and collected the documentation on arrhythmias during follow-up. The majority was male (66.7%) and mean age at implantation was 44.44 ± 14.46 years. Non-sustained ventricular tachycardia was the most prevalent risk factor (66.67%), followed by a family history of sudden death (47.92%). Mean HCM Risk-SCD was 6.15 ± 5.01%. HCM Risk-SCD was the only factor independently associated with the onset of ventricular tachyarrhythmia, above any other classic risk factor or association [odds ratio = 1.46 (95% confidence interval 1.051-2.013); P = 0.02]. None of the 11 patients estimated as low risk using HCM Risk-SCD suffered any appropriate events (P < 0.05).

CONCLUSIONS

During an average follow-up of 4 years, 16.67% presented appropriate events (4.16%/year). HCM Risk-SCD predicted the onset of events more suitably than classic risk factors.

Improved robust T-wave alternans detectors

New statistical and spectral detectors, the modified matched pairs t test, the extended spectral method and the modified spectral method, were proposed for T-wave alternans (TWA) detection gaining robustness according to trend and single-frequency interferences. They were compared to classic detectors such as matched pairs t test, unpaired t test, spectral method, generalized likelihood ratio test and estimated TWA amplitude within a simulation framework and applied to real data. The optimal detection threshold was selected by using a full Monte-Carlo simulation where signals, with and without alternans episodes, were corrupted by Gaussian noise with different power and single-frequency interferences with different tones. All the combinations of noise and frequency were selected and repeated 500 times in order to compute probability of detection ([Formula: see text]) and the false alarm probability ([Formula: see text]), providing ROC curves. The study group consisted of 50 patients with implantable cardioverter-defibrillator (age: [Formula: see text]; LVEF: [Formula: see text]), who were paced (ventricular pacing) at 100 bpm. Two-minute recordings were analyzed. The XYZ orthogonal lead system was used. The best performance was reached by using the modified matched pairs t test (in comparison with the spectral method and other reference methods).

Risk Stratification in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a hereditary primary myocardial disease that is most commonly due to mutations within genes encoding sarcomeric contractile proteins and is characterised by left ventricular hypertrophy in the absence of a cardiac or systemic cause. Although the overall prognosis is relatively good with an annual mortality rate <1 %, the propensity to potentially fatal ventricular arrhythmias is the most feared complication. The identification of patients at risk of arrhythmogenic sudden cardiac death (SCD) is an essential component in disease management. Aborted SCD and malignant ventricular arrhythmias are the most powerful risk factors for SCD and ICD implantation is recommended in such circumstances. The selection of patients who may benefit from ICD therapy for primary prevention purposes is more challenging. The heterogeneous nature of the disease and the variation in trigger factors provides an adequate explanation for the low predictive accuracy of most conventional risk factors in isolation. A new risk model for risk stratification proposed by the European Society of Cardiology HCM outcome group shows promise but requires validation in different cohorts. The ICD is the only effective therapy in preventing SCD for the disease with a relatively low adverse event rate, but most deaths occur in relatively young patients. However, it is also difficult to ignore the complications with the ICD, therefore, the strive to perfect risk stratification in HCM should continue to ensure that only the most high-risk patients receive an ICD.

Hypertrophic cardiomyopathy: present and future, with translation into contemporary cardiovascular medicine

Hypertrophic cardiomyopathy (HCM) is a common inherited heart disease with diverse phenotypic and genetic expression, clinical presentation, and natural history. HCM has been recognized for 55 years, but recently substantial advances in diagnosis and treatment options have evolved, as well as increased recognition of the disease in clinical practice. Nevertheless, most genetically and clinically affected individuals probably remain undiagnosed, largely free from disease-related complications, although HCM may progress along 1 or more of its major disease pathways (i.e., arrhythmic sudden death risk; progressive heart failure [HF] due to dynamic left ventricular [LV] outflow obstruction or due to systolic dysfunction in the absence of obstruction; or atrial fibrillation with risk of stroke). Effective treatments are available for each adverse HCM complication, including implantable cardioverter-defibrillators (ICDs) for sudden death prevention, heart transplantation for end-stage failure, surgical myectomy (or selectively, alcohol septal ablation) to alleviate HF symptoms by abolishing outflow obstruction, and catheter-based procedures to control atrial fibrillation. These and other strategies have now resulted in a low disease-related mortality rate of <1%/year. Therefore, HCM has emerged from an era of misunderstanding, stigma, and pessimism, experiencing vast changes in its clinical profile, and acquiring an effective and diverse management armamentarium. These advances have changed its natural history, with prevention of sudden death and reversal of HF, thereby restoring quality of life with extended (if not normal) longevity for most patients, and transforming HCM into a contemporary treatable cardiovascular disease.

Female sex is associated with worse prognosis in patients with hypertrophic cardiomyopathy in China

Background

Sex plays an important role in the clinical expression and prognosis of various cardiovascular diseases. This study was designed to observe the effects of sex on hypertrophic cardiomyopathy (HCM).

Methods and Results

A total of 621 unrelated patients with HCM without heart failure (460 males) were enrolled from 1999 to 2011. Compared to male patients, at baseline female patients were older at diagnosis (49.6±17.2 years vs. 46.7±14.4 years, P = 0.033), and had greater frequency of left ventricular outflow tract obstruction (72/161, 44.7% vs. 149/460, 32.4%, P = 0.005). During the average four year follow-up period (range 2–7 years), survival analysis showed that the incidences of mortality from all causes, cardiovascular death and progression to chronic heart failure were greater in women than in men (P = 0.031, 0.040 and 0.012, respectively). After adjustment for multiple factors that may confound survival and cardiac function, female sex remained an independent risk factor for all-cause mortality, cardiovascular death, and chronic heart failure [hazard ratio (HR) 2.19, 95% confidence interval (CI) 1.21–3.95, P = 0.010; HR 2.19, 95% CI 1.17–4.09, P = 0.014; HR 1.73, 95% CI 1.12–2.69, P = 0.014, respectively] in HCM patients. Subgroup analysis revealed that female sex as a risk factor was identified only in patients younger than 50 years old (P = 0.011, 0.011 and 0.009, respectively), but not for those 50 years or older.

Conclusion

Our results suggest that female sex is associated with worse survival and heart failure in HCM patients. Further studies are required to determine whether female hormones modify the clinical expression and prognosis of HCM.

Heart rate recovery in patients with hypertrophic cardiomyopathy

Recovery in heart rate (HR) after exercise is a measure of autonomic function and a prognostic indicator in cardiovascular disease. The aim of this study was to characterize heart rate recovery (HRR) and to determine its relation to cardiac function and morphology in patients with hypertrophic cardiomyopathy (HC). We studied 18 healthy volunteers and 41 individuals with HC. All patients underwent clinical assessment and transthoracic echocardiography. Continuous beat-by-beat assessment of HR was obtained during and after cardiopulmonary exercise testing using finger plethysmography. HRR and power spectral densities were calculated on 3 minutes of continuous RR recordings. Absolute HRR was lower in patients than that in controls at 1, 2, and 3 minutes (25.7 ± 8.4 vs 35.3 ± 11.0 beats/min, p <0.001; 36.8 ± 9.4 vs 53.6 ± 13.2 beats/min, p <0.001; 41.2 ± 12.2 vs 62.1 ± 14.5 beats/min, p <0.001, respectively). HRR remained lower in patients at 2 and 3 minutes after normalization to peak HR. After normalization to the difference in HR between peak exercise and rest, HRR was significantly impaired in individuals with obstructive HC at 3 minutes compared with controls. HR at 3 minutes correlated with peak left ventricular outflow tract gradient (B 0.154 beats/min/mm Hg, confidence interval 0.010 to 0.299, p = 0.037) and remained a significant predictor of HRR after multivariable analysis. Spectral analysis showed a trend toward an increased low-frequency to high-frequency ratio in patients (p = 0.08) suggesting sympathetic predominance. In conclusion, HRR is impaired in HC and correlates with the severity of left ventricular outflow tract gradient. Prospective studies of the prognostic implications of impaired HRR in HC are warranted.

Almanac 2014: cardiomyopathies

Cardiomyopathies are myocardial disorders that are not explained by abnormal loading conditions and coronary artery disease. They are classified into a number of morphological and functional phenotypes that can be caused by genetic and non-genetic mechanisms. The dominant themes in papers published in 2012-2013 are similar to those reported in Almanac 2011, namely, the use (and interpretation) of genetic testing, development and application of novel non-invasive imaging techniques and use of serum biomarkers for diagnosis and prognosis. An important innovation since the last Almanac is the development of more sophisticated models for predicting adverse clinical events.

Risk stratification in hypertrophic cardiomyopathy: time for renewal?

Systematic clinical assessment and careful monitoring of patients with hypertrophic cardiomyopathy (HCM) can be used to identify a cohort of patients that benefit from medical intervention and almost certainly improve long-term outcomes. One of the major limitations of the current approach is a lack of predictive power of individual risk factors, which means that many patients receive therapy. The aim of this review is to highlight other aspects of the disease, assessed using old and new medical technologies, that appear to provide new prognostic information. The hope for the future is that their incorporation in new risk algorithms will improve treatment for all HCM patients with the disease, irrespective of their vulnerability to adverse complications.

Risk stratification at diagnosis for children with hypertrophic cardiomyopathy: an analysis of data from the Pediatric Cardiomyopathy Registry

BACKGROUND

Treatment of children with hypertrophic cardiomyopathy might be improved if the risk of death or heart transplantation could be predicted by risk factors present at the time of diagnosis.

METHODS

We analysed data from the Pediatric Cardiomyopathy Registry, which collected longitudinal data for 1085 children with hypertrophic cardiomyopathy from 1990 to 2009. Our goal was to understand how patient factors measured at diagnosis predicted the subsequent risk of the primary outcome of death or heart transplantation. The Kaplan-Meier method was used to calculate time-to-event rates from time of diagnosis to the earlier of heart transplantation or death for children in each subgroup. Cox proportional-hazards regression was used to identify univariable and multivariable predictors of death or heart transplantation within each causal subgroup.

FINDINGS

The poorest outcomes were recorded for the 69 children with pure hypertrophic cardiomyopathy with inborn errors of metabolism, for whom the estimated rate of death or heart transplantation was 57% (95% CI 44-69) at 2 years. Children with mixed functional phenotypes also did poorly, with rates of death or heart transplantation of 45% (95% CI 32-58) at 2 years for the 69 children with mixed hypertrophic and dilated cardiomyopathy and 38% (95% CI 25-51) at 2 years for the 58 children with mixed hypertrophic and restrictive cardiomyopathy. For children diagnosed with hypertrophic cardiomyopathy at younger than 1 year, the rate of death or transplantation was 21% (95% CI 16-27) at 2 years. For children diagnosed with hypertrophic cardiomyopathy and a malformation syndrome, the rate of death or transplantation was 23% (95% CI 12-34) at 2 years. Excellent outcomes were reported for the 407 children who were diagnosed with idiopathic hypertrophic cardiomyopathy at age 1 year or older, with a rate of death or heart transplantation of 3% (95% CI 1-5) at 2 years. The risk factors for poor outcomes varied according to hypertrophic cardiomyopathy subgroup, but they generally included young age, low weight, presence of congestive heart failure, lower left ventricular fractional shortening, or higher left ventricular end-diastolic posterior wall thickness or end-diastolic ventricular septal thickness at the time of cardiomyopathy diagnosis. For all hypertrophic cardiomyopathy subgroups, the risk of death or heart transplantation was significantly increased when two or more risk factors were present and also as the number of risk factors increased.

INTERPRETATION

In children with hypertrophic cardiomyopathy, the risk of death or heart transplantation was greatest for those who presented as infants or with inborn errors of metabolism or with mixed hypertrophic and dilated or restrictive cardiomyopathy. Risk stratification by subgroup of cardiomyopathy, by characteristics such as low weight, congestive heart failure, or abnormal echocardiographic findings, and by the presence of multiple risk factors allows for more informed clinical decision making and prognosis at the time of diagnosis.

FUNDING

US National Institutes of Health and Children's Cardiomyopathy Foundation.

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.

Comparison of 3D phase-sensitive inversion-recovery and 2D inversion-recovery MRI at 3.0 T for the assessment of late gadolinium enhancement in patients with hypertrophic cardiomyopathy

RATIONALE AND OBJECTIVES

To compare free-breathing three-dimensional (3D) phase-sensitive inversion recovery (PSIR) with breath-holding two-dimensional (2D) IR sequences to determine which is better for detecting and characterizing myocardial late gadolinium enhancement (LGE) in hypertrophic cardiomyopathy (HCM) patients.

MATERIALS AND METHODS

Thirty HCM patients clinically underwent 3.0 T cardiac magnetic resonance imaging that included 3D-PSIR and 2D-IR. The amount of LGE lesions was calculated and expressed as %LGE of the myocardial mass, and the average of the %LGE value reported by two observers was recorded as the final %LGE. We also counted the number of LGE lesions and recorded their location. The myocardium-LGE contrast, margin sharpness, artifacts, and overall image quality were graded on a 4-point grading scale (1 = poor, 2 = fair, 3 = good, 4 = excellent).

RESULTS

The mean %LGE on 2D-IR was 24.7 ± 0.6, 17.5 ± 0.6, and 8.5 ± 0.3, respectively, for the basal, mid-, and apical myocardium; the corresponding values were 24.2 ± 0.4, 20.0 ± 0.4, and 7.7 ± 0.3 on 3D-PSIR (2D-IR versus 3D-PSIR, P = .87). On 2D IR and 3D-PSIR images, 13, 52, and 53, and 9, 74, and 33 LGE lesions were detected in the subendocardial, midwall, subepicardial area, respectively. The myocardium-LGE contrast and overall image quality were significantly higher on 3D-PSIR than 2D-IR images (P < .001); the sequences did not differ significantly with respect to margin sharpness and artifact.

CONCLUSION

Three-dimensional PSIR sequence yields higher image contrast, better image quality, and greater detection ability for LGE lesions than 2D-IR sequence.

Sudden cardiac arrest in a young patient with hypertrophic cardiomyopathy and zero canonical risk factors: the inherent limitations of risk stratification in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy is the most common heritable cardiovascular disease and a common cause of sudden cardiac death (SCD) in young adolescents and athletes. Clinical risk stratification for SCD is predicated on the presence of established risk factors; however, this assessment is far from perfect. Herein, we present a 16-year-old male who was resuscitated successfully from his sentinel event of out-of-hospital cardiac arrest. Prior to this event, he was asymptomatic and lacked all traditional SCD-predisposing risk factors for hypertrophic cardiomyopathy.

Surface fragmented QRS in a patient with hypertrophic cardiomyopathy and malignant arrhythmias: Is there an association?

An 18- year old woman with hypertrophic cardiomyopathy, aborted sudden cardiac death and implanted with an implantable cardioverter defibrillator (ICD), developed progressive fragmentation of her surface 12-lead electrocardiogram (ECG). During the follow-up, she presented with multiple appropriate ICD discharges. Here, we discuss the possible association between surface fragmented ECG and the risk of ventricular arrhythmias in patients with hypertrophic cardiomyopathy.

Ventricular arrhythmias complicating hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy is the most common genetic cardiovascular disorder and the leading cause of sudden cardiac death in the young. This article reviews the ventricular arrhythmias associated with hypertrophic cardiomyopathy, the difficulties in risk stratification, and current and future therapeutic strategies.

The role of renin-angiotensin-aldosterone system polymorphisms in phenotypic expression of MYBPC3-related hypertrophic cardiomyopathy

The phenotypic variability of hypertrophic cardiomyopathy (HCM) in patients with identical pathogenic mutations suggests additional modifiers. In view of the regulatory role in cardiac function, blood pressure, and electrolyte homeostasis, polymorphisms in the renin-angiotensin-aldosterone system (RAAS) are candidates for modifying phenotypic expression. In order to investigate whether RAAS polymorphisms modulate HCM phenotype, we selected a large cohort of carriers of one of the three functionally equivalent truncating mutations in the MYBPC3 gene. Family-based association analysis was performed to analyze the effects of five candidate RAAS polymorphisms (ACE, rs4646994; AGTR1, rs5186; CMA, rs1800875; AGT, rs699; CYP11B2, rs1799998) in 368 subjects carrying one of the three mutations in the MYBPC3 gene. Interventricular septum (IVS) thickness and Wigle score were assessed by 2D-echocardiography. SNPs in the RAAS system were analyzed separately and combined as a pro-left ventricular hypertrophy (LVH) score for effects on the HCM phenotype. Analyzing the five polymorphisms separately for effects on IVS thickness and Wigle score detected two modest associations. Carriers of the CC genotype in the AGT gene had less pronounced IVS thickness compared with CT and TT genotype carriers. The DD polymorphism in the ACE gene was associated with a high Wigle score (P=0.01). No association was detected between the pro-LVH score and IVS thickness or Wigle score. In conclusion, in contrast to previous studies, in our large study population of HCM patients with functionally equivalent mutations in the MYBPC3 gene we did not find major effects of genetic variation within the genes of the RAAS system on phenotypic expression of HCM.

Cardiac MRI evaluation of hypertrophic cardiomyopathy: left ventricular outflow tract/aortic valve diameter ratio predicts severity of LVOT obstruction

PURPOSE

To evaluate if left ventricular outflow tract/aortic valve (LVOT/AO) diameter ratio measured by cardiac magnetic resonance (CMR) imaging is an accurate marker for LVOT obstruction in patients with hypertrophic cardiomyopathy (HCM) compared to Doppler echocardiography.

MATERIALS AND METHODS

In all, 92 patients with HCM were divided into three groups based on their resting echocardiographic LVOT pressure gradient (PG): <30 mmHg at rest (nonobstructive, n = 31), <30 mmHg at rest, >30 mmHg after provocation (latent, n = 29), and >30 mmHg at rest (obstructive, n = 32). The end-systolic dimension of the LVOT on 3-chamber steady-state free precession (SSFP) CMR was divided by the end diastolic aortic valve diameter to calculate the LVOT/AO diameter ratio.

RESULTS

There were significant differences in the LVOT/AO diameter ratio among the three subgroups (nonobstructive 0.60 ± 0.13, latent 0.41 ± 0.16, obstructive 0.24 ± 0.09, P < 0.001). There was a strong linear inverse correlation between the LVOT/AO diameter ratio and the log of the LVOT pressure gradient (r = -0.84, P < 0.001). For detection of a resting gradient >30 mmHg, the LVOT/AO diameter ratio the area under the receiver operating characteristic (ROC) curve was 0.91 (95% confidence interval [CI] 0.85-0.97). For detection of a resting and/or provoked gradient >30 mmHg, the LVOT/AO diameter ratio area under the ROC curve was 0.90 (95% CI 0.84-0.96).

CONCLUSION

The LVOT/AO diameter ratio is an accurate, reproducible, noninvasive, and easy to use CMR marker to assess LVOT pressure gradients in patients with HCM.