The prognostic significance of nonsustained ventricular tachycardia in hypertrophic cardiomyopathy

Left ventricular twist in hypertrophic cardiomyopathy : Predictor of nonsustained ventricular tachycardia

BACKGROUND

We investigated the efficacy of clinical and classic echocardiographic parameters in predicting the occurrence of nonsustained ventricular tachycardia (NsVT) in patients with hypertrophic cardiomyopathy (HCM).

METHODS

The study comprised 59 patients with HCM (47 male, [80%]; mean age, 48.48 ± 14.16 years). Clinical, electrocardiographic, as well as classic two-dimensional and speckle-tracking echocardiography (STE) data were collected. All patients had Holter monitoring within 24-72 h of the echocardiographic examination. NsVT was defined as three or more consecutive premature wide QRS complexes with a heart rate of > 100 bpm. The patient population was categorized into groups based on the occurrence or absence of NsVT on the 24-h Holter recordings.

RESULTS

NsVT was observed in 17 patients (29%). In these patients, higher twist (14.4 ± 3.8 vs.18 ± 7.9; p = 0.02), higher apical rotation (8.7 ± 4.2 vs. 12.2 ± 7; p = 0.02), higher sudden cardiac death risk score (4.4 ± 2.2 vs. 7 ± 3.3; p = 0.007), and decreased global longitudinal peak strain (GLPS; -12.8 ± 3.1 vs. -10.6 ± 2.8; p = 0.014) were observed. In the multivariate logistic regression analysis, including GLPS and twist, GLPS (Odds Ratio [OR]: 1.406; 95% CI: 1.087-1.818; p = 0.009) and twist (OR: 1.236; 95% CI: 1.056-1.446; p = 0.008) were found to be independent predictors of NsVT. In the receiver operating characteristic curve analysis, GLPS < -11.9% predicted NsVT with 82% sensitivity and 60% specificity (area under the curve [AUC]: 0.70; p = 0.014) and twist > 15.2° predicted NsVT with 70% sensitivity and 58% specificity (AUC: 0.69; p = 0.027).

CONCLUSION

Decreased GLPS and increased twist were predictive of NsVT in HCM patients. Parameters that can easily be measured with STE can help detect patients who may develop arrhythmia.

Risk stratification for sudden cardiac death

Sudden cardiac death (SCD) is a leading cause of mortality in industrialized countries, and ventricular fibrillation and sustained ventricular tachycardia are the major causes of SCD. Although there are now effective devices and medications that can prevent such serious arrhythmias, it is crucial to have methods of identifying patients at risk. Numerous studies suggest that most patients dying of SCD have coronary artery disease or cardiomyopathy. Functional or electrophysiological measurements are effective in risk stratification. Left ventricular ejection fraction measured by echocardiography or cardiac imaging techniques is the gold standard to detect high-risk patients. Electrophysiological studies have also been used for risk stratification. Noninvasive techniques and measurements, such as T-wave alternans, signal-averaged electrocardiography, nonsustained ventricular tachycardia, heart rate variability, and heart rate turbulence, have been proposed as useful tools in identifying patients at risk for SCD. This article reviews the epidemiology, mechanisms, substrates, and current status of risk stratification of SCD.

Late hyperenhancement in gadolinium-enhanced magnetic resonance imaging: comparison of hypertrophic cardiomyopathy patients with and without nonsustained ventricular tachycardia

AIM

To assess the extent of hyperenhancement in hypertrophic cardiomyopathy (HCM) patients with nonsustained ventricular tachycardia (NSVT) in comparison to patients without NSVT.

DESIGN

In HCM patients, NSVT in Holter monitoring is a risk factor for sudden cardiac death; however, its positive predictive value is low. Varying risk of sudden death related to NSVT may be dependent on the heterogeneous extent of the arrhythmogenic substrate, which seems to be visible as hyperenhancement in gadolinium-enhanced magnetic resonance imaging (MRI).

METHODS

Hyperenhancement was assessed in 47 HCM patients (30 males and 17 females, mean age 42 +/- 12 years): 32 patients had NSVT, 15 patients had no NSVT. The extent of hyperenhancement was calculated by software and expressed as a mass.

RESULTS

In HCM patients with NSVT 97% had some extent of hyperenhancement on MRI, ranging from 1 to 76 g. The mean mass of hyperenhanced myocardium was 19 +/- 18 g (8.1 +/- 7.6% of total left ventricular mass). In HCM patients without NSVT, a significantly lower percentage of patients (60%) had hyperenhancement (P < 0.05). However, the amount of hyperenhanced myocardium was not significantly different (13 +/- 19 g, 6.3 +/- 9.1% of total left ventricular mass; P < 0.05).

CONCLUSIONS

Hyperenhancement was visible in almost all HCM patients with NSVT (97%) and in a significantly lower percentage of patients without NSVT (60%). Whether this finding explains the increased risk of sudden death in case of NSVT is not clear, since the extent of hyperenhancement was not significantly different between the two groups.

Autonomic cardiac control in animal models of cardiovascular diseases II. Variability analysis in transgenic rats with α-tropomyosin mutations Asp175Asn and Glu180Gly

Animal models of cardiovascular diseases allow to investigate relevant pathogenetic mechanisms in detail. In the present study, the mutations Asp175Asn and Glu180Gly in alpha-tropomyosin (TPM1), known cause familiar hypertrophic cardiomyopathy (FHC) were studied for changes in hemodynamic parameters and spontaneous baroreflex regulation in transgenic rats in comparison to transgenic and non-transgenic controls by telemetry. Heart rate variability (HRV) and blood pressure variability (BPV) were analyzed using time- and frequency domain, as well as non-linear measures. The dual sequence method was used for the estimation of the baroreflex regulation. In transgenic rats harboring mutated TPM1, changes in HRV were detected during exercise, but not at rest. Both mutations, Asp175Asn and Glu180Gly, caused increased low frequency power. In addition, in animals with mutation Asp175Asn a reduced total HRV was observed. BPV did not show any differences between all transgenic animal lines. During exercise, a strong increase in the number of bradycardic and tachycardic fluctuations accompanied with decreased baroreflex sensitivity (BRS) was detected in animals with either TPM1 mutation, Asp175Asn or Glu180Gly. These data suggest, that the analysis of cardiac autonomic control, particularly of baroreflex regulation, represents a powerful non-invasive approach to investigate the effects of subtle changes in sarcomeric architecture on cardiac physiology in vivo. In case of mutations Asp175Asn or Glu180Gly in TPM1, early detection of alterations in autonomic cardiac control could help to prevent sudden cardiac death in affected persons.

Left ventricular outflow tract obstruction and sudden death risk in patients with hypertrophic cardiomyopathy

AIMS

Left ventricular outflow tract obstruction (LVOTO) is associated with reduced survival in patients with hypertrophic cardiomyopathy (HCM). The influence of LVOTO on survival from SD in relation to other recognized clinical risk markers is unknown.

METHODS AND RESULTS

A total of 917 patients with HCM (554 males, 43+/-15 years) were studied; 288 (31.4%) had LVOTO at rest (> or =30 mmHg). During follow-up [median 61 (30;99) months], 54 (5.9%) patients died suddenly (SD), survived ventricular fibrillation, or had an appropriate ICD discharge; 25 (2.7%) died from heart failure or were transplanted; 17 (1.8%) died from other cardiovascular causes. Five-year survival from all-cause death or cardiac transplantation was lower in patients with LVOTO [86.5% (95% CI: 81.7-91.2) vs. 90.1% (95% CI: 87.3-92.8), P=0.006], with a trend towards higher all-cause death and transplantation with increasing LVOTO [(RR per 20 mmHg=1.24 (95% CI: 1.08-1.42), P=0.003)]. In patients with obstruction, there was a significant relation between 5-year survival from all-cause death and functional limitation (NYHA class I: 91.0%; NYHA class II: 83.3%; NYHA class III/IV: 82.6%, P=0.002). LVOTO was associated with reduced survival from SD and ICD discharge (SD/ICD) [91.4% (95% CI: 87.4-95.3) vs. 95.7% (95% CI: 93.8-97.6), P=0.0004]. Magnitude of LVOTO was related to a higher occurrence of SD/ICD [RR per 20 mmHg=1.36 (95% CI: 1.12-1.65), P=0.001]. There was no relation between survival from SD/ICD, LVOTO, and NYHA class. The annual rate of SD/ICD in patients with LVOTO and no risk factors was 0.37% (95%CI: 0.05-1.35). There was a trend towards lower survival from SD/ICD, with increasing numbers of risk factors in patients with and without LVOTO (P=0.002 and P=0.002, respectively). Multivariable analysis demonstrated that LVOTO was an independent predictor of SD/ICD, with a 2.4-fold (P=0.003) increase in the risk of SD/ICD.

CONCLUSION

LVOTO is associated with an increased risk of SD/ICD that is related to the severity of obstruction and the presence of other recognized risk factors for SD. The low sudden death mortality in asymptomatic patients with LVOTO and no other SD risk markers suggests that aggressive interventions to reduce LVOTO are unwarranted in this group. Further studies are required to determine the most appropriate treatment strategies (ICD or gradient reduction) in patients with additional risk factors.

Ambulatory monitoring of aborted sudden cardiac death related to hypertrophic cardiomyopathy

BACKGROUND

A 47-year-old woman with obstructive hypertrophic cardiomyopathy presented with chest pain that had persisted despite treatment with verapamil and alpha-receptor antagonists. The patient had no other significant cardiac symptoms, no history of hypertension, and no familial predisposition to hypertrophic cardiomyopathy or sudden cardiac death. A loud (grade III/VI), dynamic, systolic ejection murmur was noted that could be heard diffusely over the precordium.

INVESTIGATIONS

Radionuclide perfusion imaging, coronary angiography, intracoronary Doppler flow measurements, and ambulatory electrocardiographic monitoring.

DIAGNOSIS

Obstructive hypertrophic cardiomyopathy, myocardial ischemia and sudden cardiac arrest.

MANAGEMENT

Surgical myectomy and cardioverter-defibrillator implantation.

Non-sustained ventricular tachycardia in hypertrophic cardiomyopathy: an independent marker of sudden death risk in young patients

OBJECTIVES

The aim of this study was to examine the characteristics of non-sustained ventricular tachycardia (NSVT) episodes during Holter monitoring and to determine their relationship to age and prognosis.

BACKGROUND

It has been suggested that NSVT is only of prognostic importance in patients with hypertrophic cardiomyopathy (HCM) when repetitive, prolonged, or associated with symptoms.

METHODS

We studied 531 patients with HCM (323 male, 39 +/- 15 years). All underwent ambulatory electrocardiogram monitoring (41 +/- 11 h).

RESULTS

A total of 104 patients (19.6%) had NSVT. The proportion of patients with NSVT increased with age (p = 0.008). Maximum left ventricular wall thickness and left atrial size were greater in patients with NSVT. Mean follow-up was 70 +/- 40 months. Sixty-eight patients died, 32 from sudden cardiac death (SCD). Twenty-one patients received an implantable cardioverter defibrillator (ICD). There were four appropriate ICD discharges. In patients < or =30 years (but not >30), five-year freedom from sudden death was lower in those with NSVT (77.6% [95% confidence interval (CI): 59.8 to 95.4] vs. 94.1% [95% CI: 90.2 to 98.0]; p = 0.003). There was no relation between the duration, frequency, or rate of NSVT runs and prognosis at any age. The odds ratio of sudden death in patients < or =30 years of age with NSVT was 4.35 (95% CI: 1.54 to 12.28; p = 0.006) compared with 2.16 (95% CI: 0.82 to 5.69; p = 0.1) in patients >30 years of age.

CONCLUSIONS

Non-sustained ventricular tachycardia is associated with a substantial increase in sudden death risk in young patients with HCM. A relation between the frequency, duration, and rate of NSVT episodes could not be demonstrated.

Ventricular arrhythmias in the athlete

Life-threatening ventricular arrhythmias in the athlete nearly always occur in the presence of structural heart disease. In the last few years, 2 new causes of life-threatening arrhythmias have been described in patients with normal hearts-that of the Brugada syndrome and that of commotio cordis. Non-life-threatening premature ventricular beats and even nonsustained ventricular tachycardia are not rare, and although usually benign, can be secondary to cardiomyopathies. Athletes with symptoms of syncope, especially if exertional, warrant a complete evaluation. The treatment of athletes and other individuals with life-threatening ventricular arrhythmias has been revolutionized by the implantable cardioverter defibrillator, a device that affords excellent protection from sudden death. Defining those athletes who would benefit from the implantable defibrillator is not always clear. Furthermore, participation in competitive athletics for athletes with life-threatening arrhythmias or structural heart disease known to put the athlete at risk for life-threatening arrhythmias is usually prohibited.

Electrophysiological abnormalities and arrhythmias in alpha MHC mutant familial hypertrophic cardiomyopathy mice

A new mouse cardiac electrophysiology method was used to study mice harboring an alpha-myosin heavy chain Arg403Gln missense mutation (alpha-MHC403/+), which results in histological and hemodynamic abnormalities characteristic of familial hypertrophic cardiomyopathy (FHC) and sudden death of uncertain etiology during exercise. Wild-type animals had completely normal cardiac electrophysiology. In contrast, FHC mice demonstrated (a) electrocardiographic abnormalities including prolonged repolarization intervals and rightward axis; (b) electrophysiological abnormalities including heterogeneous ventricular conduction properties and prolonged sinus node recovery time; and (c) inducible ventricular ectopy. These data identify distinct electrophysiologic abnormalities in FHC mice with a specific alpha-myosin mutation, and also validate a novel method to explore in vivo the relationship between specific genotypes and their electrophysiologic phenotypes.