Identification of patients with hypertrophic cardiomyopathy at high risk for sudden death

The prevalence and the prognostic value of microvolt T-wave alternans in patients with hypertrophic cardiomyopathy

BACKGROUND

Nonsustained ventricular tachycardia (nVT) may have ominous implications for patients with hypertrophic cardiomyopathy (HCM). The microvolt T-wave alternans (TWA) has been proposed as a noninvasive tool-identifying patients at risk of sudden cardiac death and ventricular tachycardia/fibrillation (VT/VF). The aim of the study was to determine the significance of TWA in predicting nVT episodes and compare how other electrocardiographic parameters can predict the occurrence of nVT.

METHODS

The study group consisted of 88 patients with HCM. TWA was assessed during exercise test using the CH2000 system. All patients underwent Holter monitoring (HM) within 2-4 weeks before TWA test (preexercise HM1) and immediately after (postexercise HM2). During HM, we analyzed: arrhythmias, QT intervals, the presence of late ventricular potentials (LP), heart rate variability, heart rate turbulence.

RESULTS

Depending on TWA results, the patients were divided into two groups: TWA+; 46 patients (52.3%) with positive/indeterminate results, and TWA-; 42 patients (47.7%) with negative results. The nVT episodes were more frequent among TWA(+) both in HM1 and HM2. The presence of TWA increases the risk of postexercise nVT over twenty times (OR = 21.03). Moreover, in HM1, QTc and LP, and in HM2, again QTc and N-terminal precursor of brain natriuretic peptide proved to be significant predictors of nVT. The addition of TWA to the models did not improve the arrhythmia risk assessment.

CONCLUSIONS

Repolarization abnormality plays an important role in generating nVT in patients with HCM, but TWA does not specifically predict the risk of arrhythmic end point.

Role of invasive and noninvasive testing in risk stratification of sudden cardiac death in children and young adults: an electrophysiologic perspective

Sudden cardiac death is a rare, but devastating, event in the young population. Arrhythmia is the mechanism of death in many cases. In addition to clinical history, noninvasive and invasive tests can be used to identify patients who are at risk. Although these tools are not perfect, they can prove valuable if used in proper clinical circumstances. An overview of these tests is presented.

Utility of genetic screening in hypertrophic cardiomyopathy: prevalence and significance of novel and double (homozygous and heterozygous) beta-myosin mutations

Genetic screening of the beta-myosin heavy chain gene (MYH7) was evaluated in 100 consecutive unrelated patients with hypertrophic cardiomyopathy (HCM) and 200 normal unrelated subjects. Seventeen beta-myosin mutations were identified in 19 patients. Notably, 13, or 76%, were novel. Mutations were detected in both alleles in two patients: homozygous for Lys207Gln in one, and heterozygous for Pro211 Leu and Arg663His in another. No mutation was detected in the controls. MYH7-associated HCM was associated with more marked left atrial enlargement and syncope than non-MYH7-related HCM. Our findings indicate that: (1) screening methods should allow identification of novel mutations; and (2) more than one sarcomeric mutation may be present in a patient more commonly than is appreciated. Further studies are necessary to ascertain the clinical consequences of the novel and compound gene abnormalities, and to determine whether correlating functional domain to phenotype provides more useful information about the clinical significance of the molecular defects.

Electrophysiological phenotyping in genetically engineered mice

Advances in transgene and gene targeting technology have enabled sophisticated manipulation of the mouse genome, providing important insights into the molecular mechanisms underlying cardiac conduction, arrhythmogenesis, and sudden cardiac death. The mouse is currently the principal mammalian model for studying biological processes, particularly related to cardiac pathophysiology. Murine models have been engineered harboring gene mutations leading to inherited structural and electrical disorders of the heart due to transcription factor mutations, connexin protein defects, and G protein and ion channelopathies. These mutations lead to phenotypes reminiscent of human clinical disease states including congenital heart defects, cardiomyopathies, and long-QT syndrome, creating models of human electrophysiological disease. Functional analyses of the underlying molecular mechanisms of resultant phenotypes require appropriate and sophisticated experimental methodology. This paper reviews current in vivo murine electrophysiology study techniques and genetic mouse models pertinent to human arrhythmia disorders.

Clinical significance of T-wave alternans in hypertrophic cardiomyopathy

The clinical significance of T-wave alternans (TWA) in hypertrophic cardiomyopathy (HCM) is unclear, so SV1+RV5 and QT dispersion on 12-lead electrocardiograms (ECG), the parameters of the left ventricle on echocardiography and the family history of HCM and sudden death were investigated in 53 patients with HCM who experienced TWA. The maximal numbers of successive ventricular ectopic beats (max VE) and nonsustained ventricular tachycardia (NSVT) were measured by Holter monitoring. In 13 patients, genetic abnormalities were examined. In 22 patients, the hypertrophy of myocytes, disarray and fibrosis were histopathologically examined using a scoring method. TWA was positive in 27 patients (TWA+ group), negative in 14 (TWA- group) and indeterminate in 12. The ECG and echocardiographic parameters, family history and genetic abnormalities did not significantly differ between the TWA+ and TWA- groups. Max VE, the percentage of patients with NSVT and disarray score in the TWA+ group were significantly higher than those in the TWA- group (3.6+/-3.6 vs 1.3+/-0.7, 37% vs 0%, 1.9+/-1.1 vs 0.7+/-0.5; p<0.05). TWA in HCM correlates with histopathological changes, especially disarray and ventricular tachyarrhythmia, and measuring it may be a noninvasive means of detecting high-risk patients with HCM.

Cardiac electrophysiology in genetically engineered mice

The mouse has become the principal animal model for studying biologic processes in mammals. Major advances in transgene and gene targeting technology enabled manipulation of the mouse genome in a predictable fashion. Mutant mouse strains provide important insights into the molecular mechanisms underlying normal and disordered cardiac conduction and sudden cardiac death. A variety of mouse strains harboring gene mutations leading to inherited developmental disorders have been designed. Structural protein abnormalities, connexin protein defects, and ion channelopathies associated with human clinical phenotypes, including congenital heart disease, cardiomyopathies, long QT syndrome, and muscular dystrophy, have been engineered into the mouse genome, creating models of human electrophysiologic disease. Functional analyses of the underlying molecular mechanisms of resultant phenotypes require appropriate and sophisticated experimental methodology. In this review, genetic mouse models pertinent to human arrhythmogenic disorders and their application to present-day ex vivo and in vivo murine electrophysiologic technology at the whole organ and animal levels are discussed.

Sudden cardiac death in the young athlete

Sudden cardiac death in athletes is usually due to underlying cardiovascular disease. In the young less than 30 years of age, the most common abnormality is hypertrophic cardiomyopathy, followed by congenital coronary artery anomalies. The final common pathway is usually ventricular fibrillation. Sudden cardiac death in the young is rare but remains a source of concern. A careful screening history and physical examination, especially for potential athletes, should identify the majority of young people at risk.

[Sudden death in hypertrophic myocardiopathy]

Hypertrophic cardiomyopathy is the most common cause of sudden death in young individuals who are otherwise healthy. Risk of sudden death is highest in patients who are between 14 and 35 years old. Several mechanisms are involved in sudden death: ventricular arrhythmias, supraventricular arrhythmias leading to cardiac collapse, bradycardias and severe ischemia. Many studies have analyzed how to identify high risk patients. The factors that best identify high risk patients are: previous history of sudden death or syncope, induction in adults of sustained ventricular arrhythmias, the presence of non-sustained ventricular tachycardia in symptomatic patients, the presence of ischemia associated with hypotension in children, the presence of mutations in the beta-myosin heavy chain together with a family history of sudden death and a poor left ventricular ejection fraction. Risk stratification should be done on an individualized basis. In those patients in whom a high risk for sudden arrhythmic death is suspected, the only current effective treatment is the implantable defibrillator.

Simultaneous percutaneous treatment in hypertrophic obstructive cardiomyopathy and coronary artery disease: a case report

Percutaneous transluminal coronary angioplasty (PTCA) is an established therapy for coronary artery disease (CAD), whereas percutaneous transluminal septal myocardial ablation (PTSMA) is becoming increasingly significant in the therapy of symptomatic patients with hypertrophic obstructive cardiomyopathy (HOCM). We report the first ever simultaneous treatment, in a 62-yr-old patient, of significant HOCM and a 75% LAD stenosis from which the septal branch to be occluded stemmed. Using a double wire technique, first the septal branch was occluded through a fractional injection of 4 ml absolute alcohol, thus ablating the hypertrophied septal myocardium with reduction of the left ventricular outflow tract (LVOT) gradient at rest from 80 to 9 mmHg. Following this, the LAD stenosis was dilated and stented. Complications, in particular a trifascicular block or ventricular dysrhythmia, did not occur during the hospital stay. To conclude, combined PTSMA and PTCA may be considered as a therapeutic alternative to a combined surgical intervention in individual cases of symptomatic HOCM and CAD, provided that the potential complications are taken into account.

[Clinical picture and therapy of hypertrophic cardiomyopathy]

Hypertrophic cardiomyopathy is defined as a primary, sometimes familial and genetically fixed myocardial hypertrophy. In the obstructive form of the disease (HOCM) a dynamic outflow tract obstruction of the left, occasionally also the right ventricle can be found. HOCM is the most frequent cause of stress-induced syncope or sudden cardiac death in younger patients. An individual estimation of prognosis is difficult although several risk factors have been identified. In addition to standard therapy of symptomatic patients (medical treatment with betablockers and calcium-antagonists of verapamil-type as well as surgical myotomy/myectomy) DDD-pacemaker implantation and percutaneous transluminal septal myocardial ablation (PTSMA) by alcohol-induced septal branch occlusion have been introduced. After PTSMA significant outflow tract gradient reduction can be achieved in > 90% of patients. Due to remodeling after circumscribed myocardial necrosis further gradient reduction has been observed during follow-up. Optimization of ablated septal area by echocardiographic monitoring resulted in reduction of the most important complication (trifascicular block with need of permanent pacemaker implantation) and improvement of acute and follow-up results. Long-term follow-up and comparison with established treatment options are necessary to evaluate the definitive importance of the promising new treatment.

Percutaneous transluminal septal myocardial ablation in hypertrophic obstructive cardiomyopathy: acute results and 3-month follow-up in 25 patients

OBJECTIVES

We report the acute results and midterm clinical course after percutaneous transluminal septal myocardial ablation (PTSMA) in symptomatic patients with hypertrophic obstructive cardiomyopathy (HOCM).

BACKGROUND

In the treatment of HOCM, surgical myectomy and DDD pacemaker therapy are considered the standard procedural extensions to drug therapy with negatively inotropic drugs. As an alternative nonsurgical procedure for reducing the left ventricular outflow tract (LVOT) gradient, PTSMA by alcohol-induced septal branch occlusion was introduced. However, clinical follow-up has not been sufficiently described.

METHODS

In 25 patients (13 women, 12 men; mean [+/- SD] age 54.7 +/- 15.0 years) who were symptomatic despite sufficient drug therapy, 1.4 +/- 0.6 septal branches were occluded with an injection of 4.1 +/- 2.6 ml of alcohol (96%) to ablate the hypertrophied interventricular septum. After 3-months, follow-up results of LVOT gradients and clinical course were determined.

RESULTS

The invasively determined LVOT gradients could be reduced in 22 patients (88%), with a mean reduction from 61.8 +/- 29.8 mm Hg (range 4 to 152) to 19.4 +/- 20.8 mm Hg (range 0 to 74) at rest (p < 0.0001) and from 141.4 +/- 45.3 mm Hg (range 76 to 240) to 61.1 +/- 40.1 mm Hg (range 0 to 135) after extrasystole. All patients had angina pectoris for 24 h. The maximal creatine kinase increase was 780 +/- 436 U/liter (range 305 to 1,810) after 11.1 +/- 6.0 h (range 4 to 24). Thirteen patients (52%) developed a trifascicular block for 5 min to 8 days requiring temporary (n = 8 [32%]) or permanent (DDD) pacemaker implantation (n = 5 [20%]). An 86-year old woman died 8 days after successful intervention of uncontrollable ventricular fibrillation in conjunction with beta-sympathomimetics in chronically obstructive pulmonary disease. The remaining patients were discharged after 11.3 +/- 5.4 days (range 5 to 24), after an uncomplicated hospital course. Clinical and echocardiographic follow-up was achieved in all 24 surviving patients after 3 months. No cardiac complications occurred. Twenty-one patients (88%) showed clinical improvement, with a New York Heart Association functional class of 1.4 +/- 1.1. A further reduction in LVOT gradient was shown in 14 patients (58%).

CONCLUSIONS

PTSMA of HOCM is a promising nonsurgical technique for septal myocardial reduction, with a consecutive reduction in LVOT gradient. Possible complications are trifascicular blocks, requiring permanent pacemaker implantation, and tachycardiac rhythm disturbances. Clinical long-term observations of larger patient series and a comparison with conventional forms of therapy are necessary to determine the conclusive therapeutic significance.

Dispersion of ventricular repolarization in hypertrophic cardiomyopathy

On an averaged QRS-T cycle from a 15-lead record (12-lead electrocardiogram + XYZ leads) and through interactive editing, four electrocardiographic indices of the dispersion of ventricular repolarization (DVR) are automatically computed and represent the maximal interlead difference of QT and JTend and QT and JTapex. The values of these indices were then examined in three clinical groups matched for age and sex: normal subjects (control), patients with left ventricular hypertrophy (LVH group), and patients with hypertrophic cardiomyopathy (HCM group) without ventricular arrhythmias and without interacting drugs. The mean values of all four DVR indices were significantly increased in the HCM group compared with the control group and the LVH group of another origin (ie, for the QTe dispersion index, the mean values and the 97.5th percentiles were, respectively, 65 +/- 18 ms and 97 ms in the HCM group, 41 +/- 25 ms and 79 ms in the LVH group, and 31 +/- 15 ms and 58 ms in the control group). The maximal QT interval was also significantly longer in the HCM group (464 +/- 30 ms) than in the LVH group (436 +/- 32 ms) and the control group (428 +/- 25 ms).