Usefulness of signal-averaged electrocardiography in evaluation of idiopathic-dilated cardiomyopathy in families

Cardiomyopathy, familial dilated

Dilated cardiomyopathy (DCM) is a heart muscle disease characterized by ventricular dilatation and impaired systolic function. Patients with DCM suffer from heart failure, arrhythmia, and are at risk of premature death. DCM has a prevalence of one case out of 2500 individuals with an incidence of 7/100,000/year (but may be under diagnosed). In many cases the disease is inherited and is termed familial DCM (FDC). FDC may account for 20–48% of DCM. FDC is principally caused by genetic mutations in FDC genes that encode for cytoskeletal and sarcomeric proteins in the cardiac myocyte. Family history analysis is an important tool for identifying families affected by FDC. Standard criteria for evaluating FDC families have been published and the use of such criteria is increasing. Clinical genetic testing has been developed for some FDC genes and will be increasingly utilized for evaluating FDC families. Through the use of family screening by pedigree analysis and/or genetic testing, it is possible to identify patients at earlier, or even presymptomatic stages of their disease. This presents an opportunity to invoke lifestyle changes and to provide pharmacological therapy earlier in the course of disease. Genetic counseling is used to identify additional asymptomatic family members who are at risk of developing symptoms, allowing for regular screening of these individuals. The management of FDC focuses on limiting the progression of heart failure and controlling arrhythmia, and is based on currently accepted treatment guidelines for DCM. It includes general measures (salt and fluid restriction, treatment of hypertension, limitation of alcohol intake, control of body weight, moderate exercise) and pharmacotherapy. Cardiac resynchronization, implantable cardioverter defibrillators and left ventricular assist devices have progressively expanding usage. Patients with severe heart failure, severe reduction of the functional capacity and depressed left ventricular ejection fraction have a low survival rate and may require heart transplant.

Prognostic value of an abnormal signal-averaged electrocardiogram in patients with nonischemic dilated cardiomyopathy

The usefulness of an abnormal signal-averaged ECG (SAECG) for the risk stratification of patients with dilated cardiomyopathy was studied prospectively in 76 patients. Multiple analysis showed that an abnormal SAECG predicted cardiac mortality (p = 0.0046), sudden cardiac death, and the need for resuscitation (p = 0.003); however, it did not predict death from heart failure and heart transplantation.

Increased left ventricular dimensions in patients with frequent nonsustained ventricular arrhythmia and no evidence of underlying heart disease

INTRODUCTION

To test the hypothesis that frequent nonsustained ventricular premature beats (VPBs) in patients without underlying heart disease are the first marker of mild systolic dysfunction of the left ventricle, we evaluated whether a subclinical abnormality of left ventricular function and/or an intraventricular conduction defect was present at the first clinical documentation of the arrhythmia.

METHODS AND RESULTS

We compared 57 patients (mean age 46 +/- 14 years) with > 30 VPBs/hour and no heart disease (A) to 32 healthy volunteers (mean age 42 +/- 12 years) without arrhythmia (B). Left ventricular echocardiographic parameters and signal-averaged ECG were evaluated. Filtered QRS duration (98 +/- 10 msec in A vs 98 +/- 7 msec in B) was similar in the two groups. End-diastolic left ventricular diameter (EDLVD) was 50 +/- 6 mm in A versus 47 +/- 3 mm in B (P < 0.005); 15 patients (26%) and none of the controls had EDLVD > or = 55 mm (P < 0.005). Filtered QRS interval was longer in the subgroup of patients (n = 15) with increased EDLVD (> or = 55 mm) compared with the subgroup (n = 42) with EDLVD < 55 mm (106 +/- 9 msec vs 95 +/- 9 msec; P < 0.001) and was related to greater left ventricular mass.

CONCLUSION

We documented a subclinical but significant increase of left ventricular dimensions that suggests that frequent VPBs may be an initial marker of mild systolic dysfunction of the left ventricle. However, an effect of VPBs per se in modifying left ventricular dimensions cannot be excluded.