New approach to the estimation of the extent of myocardial fibrosis in patients with dilated cardiomyopathy: use of signal-averaged electrocardiography

[Left bundle branch block - dilated cardiomyopathy - heart failure: common links in the closed pathogenetic chain]

This review summarizes the available information on the epidemiology and prognosis of patients with left bundle branch block (LBBB), morphological alterations of the myocardium both resulting in and ensuing LBBB, cardiac biomechanics in LBBB, and possibilities of its correction.

Efficacy of antitachycardia pacing for electrical storms in patients with implantable defibrillators

INTRODUCTION

Although antitachycardia pacing (ATP) is effective in terminating ventricular tachyarrhythmias in patients with implantable cardioverter defibrillators (ICDs), the efficacy of ATP during an electrical storm (ES) and the positive impact on all-cause mortality have not been fully elucidated.

METHODS AND RESULTS

From 2010 to 2012, 1570 patients who underwent ICD implantation in 48 ICD centers in Japan were enrolled in the study and prospectively followed up. Patients with long QT syndrome, Brugada syndrome, and idiopathic ventricular fibrillation were excluded. The prevalence of shocks during ESs and impact on the all-cause mortality were evaluated. During a median follow-up of 28 months, there were 127 ESs in 84 patients. Of those 127 ESs, 80 ESs (63%) in 37 patients were treated by only ATP and the remaining 47 ESs in 47 patients required at least one shock. The lower ventricular rate of the initial arrhythmia during ES (odds ratio [OR]: 1.02 per unit; 95% confidence interval [CI]: 1.00-1.04; p = .02) and narrower QRS complex (OR: 1.03 per unit; 95% CI: 1.01-1.06; p < .01) were the independent predictors of ATP success during the ES. The patients treated with ATP alone tended to have lower all-cause mortality compared to those that required shocks during the ES (log-rank p = .10).

CONCLUSIONS

ATP was effective in patients suffering from ESs as it avoided painful shocks in more than half of the cases. Patients who received only ATP during ES tended to have lower mortality compared to those who received the shock.

Determinants and prognostic implications of left ventricular mechanical dispersion in aortic stenosis

AIMS

The present study aimed at investigating the association between left ventricular (LV) mechanical dispersion measured with speckle tracking echocardiography and severity of aortic stenosis (AS) and its impact on prognosis.

METHODS AND RESULTS

This retrospective study included 630 patients [age 72 (62-78) years, 61.4% men] with various grades of AS (mild AS, 19.8%; moderate AS, 37.0%; severe AS, 43.2%). LV mechanical dispersion (defined as standard deviation of time from Q/R on electrocardiogram to peak longitudinal strain in 17 LV segments) was assessed by speckle tracking echocardiography. Clinical, electrocardiographic, and echocardiographic determinants of increased LV mechanical dispersion were evaluated. During a follow-up of 107 (43-133) months, the independent association between LV mechanical dispersion and all-cause mortality (n = 302, 48%) was evaluated including aortic valve replacement as time-dependent co-variate. LV mechanical dispersion increased significantly with increasing severity of AS (mild AS, 54.5 ± 17.2 ms; moderate AS, 56.7 ± 19.3 ms; severe AS, 70.9 ± 24.3 ms; P < 0.001). Independent determinants of increased mechanical dispersion included older age (β = 0.28; P = 0.003), lower LV ejection fraction (β = -0.24; P = 0.020), smaller aortic valve area (β = -8.55; P = 0.001), larger LV mass index (β = 0.20; P < 0.001), and longer QRS duration (β = 1.12 per each 10 ms increase; P = 0.012). LV mechanical dispersion showed incremental prognostic value for all-cause mortality (hazard ratio 1.10 per each 10 ms increase, 95% confidence interval 1.04-1.15; P < 0.001).

CONCLUSION

LV mechanical dispersion assessed by speckle tracking echocardiography increases significantly with severity of AS and is significantly associated with all-cause mortality.

Fragmentation of the paced QRS complex: a marker of antitachycardia pacing effectiveness among ICD patients

INTRODUCTION

The presence of notches in the paced QRS complex (P-QRS) from the right ventricular apex (RVA) reflects delays in the activation of the left ventricle and may therefore be associated with longer times of stimulus conduction. Our objective was to determine prospectively the relationship between the duration of a notch ≥0.1 mV in the P-QRS (DN) and the effectiveness of antitachycardia pacing (ATP).

METHODS AND RESULTS

We followed 286 implantable cardioverter-defibrillator (ICD) patients with left ventricular dysfunction (pacing site: RVA) for 41 ± 27 months. ICD programming was standardized. P-QRS (100 bpm) was obtained at implant (50 mm/s). A total of 955 monomorphic ventricular tachycardias (VTs) with a cycle length of 335 ± 32 milliseconds occurred consecutively in 108 patients. ATP was successful in 84% of VTs. DN correlated with the probability of ineffective ATP (C = 0.67; P < 0.001), the cutoff point with the best sensitivity and specificity being 50 milliseconds. The adjusted mean ATP effectiveness per patient was 76% (95% CI: 72-85). Patients with a DN ≥ 50 milliseconds had a lower ATP efficiency: 67% (56-77) versus 92% (87-97) and a higher proportion of VTs terminated with shocks (SH): 31% (21-42) versus 8% (2-14); P < 0.001 for both. Although the occurrence of VT was similar (41% vs. 40%), the incidence of VT-related SH was higher in patients with a DN ≥ 50 (25% vs. 14%; P = 0.01) in the overall study population (n = 286).

CONCLUSIONS

When ATP is applied to the RVA, a DN ≥ 50 milliseconds is associated with a lower ATP effectiveness and a higher risk of SH due to VT.

QRS prolongation in the prediction of clinical cardiac events in patients with acute heart failure: analysis of data from the Korean Acute Heart Failure Registry

OBJECTIVES

A prolonged QRS duration has been associated with an unfavorable prognosis in chronic compensated heart failure (HF). However, its predictive value during an admission for acute HF is limited, even in HF with a preserved ejection fraction (EF). The purpose of this study was to evaluate the prognostic utility of the QRS duration in acute HF.

METHODS

Analyses were performed using data from 1,489 patients with a 2-year follow-up. The patients were selected from the Korean Acute Heart Failure Registry and were divided into three groups according to QRS duration (≤80, 81-119 or ≥120 ms). The all-cause mortality and readmission for HF were assessed.

RESULTS

During the study period, 774 primary events occurred (359 deaths and 415 HF). The event frequencies were higher in patients with a prolonged QRS duration. The increased risk associated with the QRS duration was also demonstrated after adjustment for cardiac outcome variables. The prognostic significance of the QRS duration was demonstrated in patients with reduced EF but not in those with a preserved EF.

CONCLUSIONS

A prolonged QRS duration could be a significant predictor of the 2-year cardiac outcome in patients with acute HF, particularly in those with a reduced EF.

QRS duration is associated with atrial fibrillation in patients with left ventricular dysfunction

BACKGROUND

QRSduration (QRSd) is associated with higher mortality and morbidity in patients with left ventricular (LV) dysfunction. The association between QRSd and atrial fibrillation (AF) has not been studied in this patient population.

OBJECTIVES

To investigate the association between QRSd and AF in patients with LV dysfunction.

METHODS

Data were obtained from the National Registry to Advance Heart Health (ADVANCENT) registry, a prospective multicenter registry of patients with left ventricular ejection fraction (LVEF) < or = 40%. A total of 25 268 patients from 106 centers in the United States, were enrolled between June 2003 and November 2004. Demographic and clinical characteristics of patients were collected from interviews and medical records.

RESULTS

: Mean age was 66.3+/-13 years, 71.5% were males, and 81.9% were white. A total of 14 452 (57.8%) patients had a QRSd < 120 ms, 5304 (21.2%) had a QRSd between 120 and 150 ms, and 5269 (21%) had a QRSd > 150 ms. Atrial fibrillation occurred in 20.9%, 27.5%, and 35.5% of patients in the QRS groups, respectively (P < 0.0001). After adjusting for potential AF risk factors (age, gender, race, body mass index, hypertension, diabetes, renal failure, cancer, lung disease, New York Heart Association [NYHA] class, ejection fraction, etiology of cardiomyopathy) and the use of angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers, and lipid lowering drugs, QRS duration remained independently associated with AF (odds ratio: 1.20, 95% confidence interval: 1.14-1.25).

CONCLUSION

In this large cohort of patients, QRSd was strongly associated with AF and therefore may predict the occurrence of this arrhythmia in patients with LV dysfunction. This association persisted after adjusting for disease severity, comorbid conditions, and the use of medications known to be protective against AF.

Noninvasive time and frequency predictors of long-standing atrial fibrillation early recurrence after electrical cardioversion

BACKGROUND

Several clinical factors have been studied to predict atrial fibrillation (AF) recurrence after electrical cardioversion (ECV) with limited predictive value.

METHODS

 A method able to predict robustly long-standing AF early recurrence by characterizing noninvasively the electrical atrial activity (AA) with parameters related to its time course and spectral features is presented. To this respect, 63 patients (20 men and 43 women; mean age 73.4 ± 9.0 years; under antiarrhythmic drug treatment with amiodarone) who were referred for ECV of persistent AF were studied. During a 4-week follow-up, AF recurrence was observed in 41 patients (65.1%).

RESULTS

 RR variability and the studied AA spectral features, including dominant atrial frequency (DAF), its first harmonic and their amplitude, provided poor statistical differences between groups. On the contrary, f waves power (fWP) and Sample Entropy (SampEn) of the AA behaved as very good predictors. Patients who relapsed to AF presented lower fWP (0.036 ± 0.019 vs 0.081 ± 0.029 n.u.(2) , P < 0.001) and higher SampEn (0.107 ± 0.022 vs 0.086 ± 0.033, P < 0.01). Furthermore, fWP presented the highest predictive accuracy of 82.5%, whereas SampEn provided a 79.4%. The remaining features revealed accuracies lower than 70%. A stepwise discriminant analysis (SDA) provided a model based on fWP and SampEn with 90.5% of accuracy.

CONCLUSIONS

 The fWP has proved to predict long-standing AF early recurrence after ECV and can be combined with SampEn to improve its diagnostic ability. Furthermore, a thorough analysis of the results allowed outlining possible associations between these two features and the concomitant status of atrial remodeling.

Relationship between mechanical and electrical remodelling in patients with cardiac resynchronization implanted defibrillators

AIMS

Cardiac resynchronization therapy (CRT) is associated with reverse left ventricular (LV) remodelling. However, the effects of CRT-induced mechanical remodelling on electrical remodelling, and the occurrence of ventricular arrhythmias have not been clearly established. We studied the relationship between mechanical remodelling, electrical remodelling, and the occurrence of appropriate implantable cardioverter-defibrillator (ICD) therapy 1 year after CRT.

METHODS AND RESULTS

We analysed data from 45 patients who underwent ICD-CRT implantation at our centre. Significant LV reverse remodelling was defined by a minimum 10% decrease in the LV end-diastolic diameter (LVEDd) at 1 year of follow-up. Electrocardiographic indices of dispersion of repolarization [QTc, Tpeak-Tend (Tp-e) and their dispersion] were measured immediately and 1 year post-CRT implantation. The occurrence of appropriate ICD therapy was noted for each patient. Patients with (n= 21) and without (n= 24) significant LV reverse remodelling had similar baseline characteristics. At 1 year of follow-up, patients with mechanical reverse LV remodelling exhibited a significant decrease in QTc (505 ± 42 vs. 485 ± 52 ms, P < 0.05) and Tp-e (107 ± 26 vs. 92 ± 22 ms, P < 0.0001). However, patients without mechanical LV reverse remodelling exhibited a significant increase in QT dispersion (29 ± 43 vs. 98 ± 47 ms, P = 0.002) and Tp-e dispersion (22 ± 21 vs. 54 ± 36 ms, P = 0.0001). Finally patients with mechanical LV reverse remodelling experienced a lower rate of ICD therapy (P = 0.0025) after a mean follow-up of 19 months.

CONCLUSION

Reverse LV mechanical remodelling is associated with reversal of electrical remodelling and a lower rate of appropriate ICD therapy following CRT.

Prediction of Cardiac Resynchronization Therapy Response

Background— Left ventricular (LV) fibrosis is important for the response to cardiac resynchronization therapy (CRT). Calibrated integrated backscatter derived by 2D echocardiography quantifies myocardial ultrasound reflectivity, which may provide a surrogate of LV fibrosis. The aim of the study was first, to investigate the relation of myocardial ultrasound reflectivity assessed with calibrated integrated backscatter on CRT response, and second, to explore the “myocardial ultrasound reflectivity–CRT response” relation in patients with ischemic and nonischemic heart failure (HF).

Methods and Results— One hundred fifty-nine patients with HF referred for CRT underwent an extensive echocardiographic evaluation at baseline and at 6-month follow-up. LV dyssynchrony was derived from speckle-tracking analysis. Calibrated integrated backscatter was obtained from the parasternal long-axis view. The mean value of calibrated integrated backscatter of the anteroseptal and posterior wall was used to estimate myocardial ultrasound reflectivity. CRT response was defined as reduction ≥15% of LV end-systolic volume. At baseline, LV dyssynchrony was significantly larger in responders as compared with nonresponders (188�96 ms versus 115�68 ms, P <0.001), and CRT responders showed less myocardial ultrasound reflectivity as compared with nonresponders (−20.8�3.0 dB versus −17.0�3.0 dB, P <0.001). In multivariable logistic regression analysis, independent predictors for CRT response were LV dyssynchrony, renal function, and myocardial ultrasound reflectivity. Importantly, myocardial ultrasound reflectivity provided an incremental value to CRT response (χ 2 change=40, P <0.001). Considering patients with ischemic HF, the only independent predictor of CRT response was myocardial ultrasound reflectivity, whereas in patients with nonischemic HF, independent predictors of LV reverse remodeling were myocardial ultrasound reflectivity, LV dyssynchrony, and renal function.

Conclusions— Assessment of myocardial ultrasound reflectivity is important in the prediction of CRT response in ischemic and nonischemic patients.

Cardiac iodine-123 metaiodobenzylguanidine imaging predicts sudden cardiac death independently of left ventricular ejection fraction in patients with chronic heart failure and left ventricular systolic dysfunction: results from a comparative study with signal-averaged electrocardiogram, heart rate variability, and QT dispersion

OBJECTIVES

We prospectively compared the predictive value of cardiac iodine-123 metaiodobenzylguanidine (MIBG) imaging for sudden cardiac death (SCD) with that of the signal-averaged electrocardiogram (SAECG), heart rate variability (HRV), and QT dispersion in patients with chronic heart failure (CHF).

BACKGROUND

Cardiac MIBG imaging predicts prognosis of CHF patients. However, the long-term predictive value of MIBG imaging for SCD in this population remains to be elucidated.

METHODS

At entry, cardiac MIBG imaging, SAECG, 24-h Holter monitoring, and standard 12-lead electrocardiography (ECG) were performed in 106 consecutive stable CHF outpatients with a radionuclide left ventricular ejection fraction (LVEF) <40%. The cardiac MIBG washout rate (WR) was obtained from MIBG imaging. Furthermore, the time and frequency domain HRV parameters were calculated from 24-h Holter recordings, and QT dispersion was measured from the 12-lead ECG.

RESULTS

During a follow-up period of 65 +/- 31 months, 18 of 106 patients died suddenly. A multivariate Cox analysis revealed that WR and LVEF were significantly and independently associated with SCD, whereas the SAECG, HRV parameters, or QT dispersion were not. Patients with an abnormal WR (>27%) had a significantly higher risk of SCD (adjusted hazard ratio: 4.79, 95% confidence interval: 1.55 to 14.76). Even when confined to the patients with LVEF >35%, SCD was significantly more frequently observed in the patients with than without an abnormal WR (p = 0.02).

CONCLUSIONS

Cardiac MIBG WR, but not SAECG, HRV, or QT dispersion, is a powerful predictor of SCD in patients with mild-to-moderate CHF, independently of LVEF.

Relationship between QRS duration and prognosis in non-ST-segment elevation acute coronary syndrome

BACKGROUND

Previous studies have shown that prolonged QRS duration increases the risk of death in patients with heart failure and after an ST-segment elevation acute myocardial infarction. Very little data exist about the prognostic implications of QRS duration in the non-ST-segment elevation acute coronary syndrome (NST-ACS): unstable angina and non-ST elevation acute myocardial infarction (non-STEMI).

METHODS

This is a prospective and observational study in which we included 502 patients (age 71+/-10 years, 68% males, 29% diabetes) consecutively admitted for NST-ACS. QRS duration was manually measured from the 12-lead electrocardiogram. Our aim is to assess the relation between the QRS duration on admission (QRSd) and the risk of cardiovascular death (CvD) in the long-term.

RESULTS

Mean QRSd was: 93+/-19 ms. After a median follow-up of 450 days, the cumulative incidence of CvD was: 17.8%. QRSd correlated with the incidence of CvD during the follow-up period: c=0.72 (p<0.001). The best cut-off point was 90 ms (sensitivity, specificity and negative predictive value of QRSd>or=90 ms for CvD: 82, 68 and 93%). According to the Kaplan-Meier analysis, QRSd>or=90 ms was associated with an increase in the risk of CvD: 26.6% versus 7.2% (log rank: 28.6; p<0.001). Cumulative incidence of CvD was higher in QRSd>or=90 ms in patients with unstable angina: 15.5% versus 4% (p=0.02), and in those with non-STEMI: 30.5% versus 8.9% (p<0.001). After adjusting for other significant variables (Cox-regression analysis), QRSd>or=90 ms persisted as an independent predictor for overall CvD (Hazard Ratio: 2.62; 95% Confidence Interval: 1.44-4.74; p<0.001).

CONCLUSION

In NST-ACS, the QRSd, even in the normal range, has prognostic implications. QRSd>or=90 ms is independently associated with an increased risk of CvD in the long-term.

Left bundle branch block as a risk factor for progression to heart failure

The prevalence of conduction disturbances, particularly left bundle branch block (LBBB), is strongly correlated with age and with the presence of cardiovascular disease. LBBB has been reported to affect approximately 25% of the heart failure (HF) population and it is likely that the deleterious role of such conduction disorders in the progression to HF has been underestimated. The purpose of this article is to review the data from the literature indicating that LBBB may have a causative role, mediated through the resulting intra-ventricular asynchrony, in the deterioration of cardiac function and the development of cardiac remodelling and HF. It also aims to address the potential for future clinical therapies for this conduction disorder.

Association of QRS duration and outcomes after myocardial infarction: the VALIANT trial

BACKGROUND

Prolongation of the QRS duration has been shown to be associated with adverse outcomes among heart failure (HF) patients. The association of QRS duration with clinical outcomes in the post-myocardial infarction (MI) setting is less well defined.

OBJECTIVES

To assess the prognostic significance of QRS duration prolongation on initial electrocardiogram after acute MI.

METHODS

QRS duration was measured in 403 patients with MI complicated by left ventricular dysfunction, signs or symptoms of HF, or both, who were enrolled in the Valsartan in Acute Myocardial Infarction (VALIANT) echo study. The cohort was divided into quartiles of QRS duration (<75 ms, 75-88 ms, 89-108 ms, >108 ms). The number of clinical events were determined and compared across the groups.

RESULTS

Increasing QRS duration is associated with a higher incidence of HF, sudden death (SD), and cardiovascular (CV) death (P-trend <0.05) but not with stroke or recurrent MI. The univariate relative risks for HF, SD, and CV death with increasing QRS duration quartiles were 1.31 (95% CI, 1.06-1.64), 1.57 (95% CI, 1.03-2.40), and 1.31 (95% CI, 1.03-1.66), respectively, but QRS duration did not remain independently predictive of adverse outcome after adjusting for the 10 most predictive baseline covariates. Baseline end-diastolic and end-systolic volumes were larger and ejection fraction was lower in the higher QRS quartile groups.

CONCLUSIONS

Prolonged QRS duration, even within the normal range, is associated with larger ventricular volumes, reduced systolic function, and an increased risk for development of HF, SD, and CV death after MI but appears to be a marker, rather than an independent predictor, for increased risk.

Usefulness of spatial dispersion of QRS duration in predicting mortality in patients with mild to moderate chronic heart failure

To prospectively evaluate the prognostic significance of spatial dispersion of QRS duration (S-QRSd) on a signal-averaged electrocardiogram in patients with chronic heart failure (CHF), we studied 114 consecutive stable outpatients with radionuclide left ventricular ejection fraction <40%. Cardiac and sudden deaths were significantly more often observed in patients with than without abnormal S-QRSd. S-QRSd is a powerful prognostic marker of the mortality in patients with mild to moderate CHF.

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.

Idiopathic dilated cardiomyopathy in an Omani population of the Arabian Peninsula: prevalence, clinical profile and natural history

We have analysed prospectively the prevalence and clinical profile of idiopathic dilated cardiomyopathy (IDC) in a circumscribed native population of the Sultanate of Oman over 3 years (1992-1994). Identified patients were followed up for a period ranging from 1 to 8 years (median 4 years) and the variables related to outcome determined. IDC was diagnosed in 97 patients, giving a prevalence of 43.2/100,000 population during the study period. 84.5% of patients were aged over 35 years and males outnumbered females (M/F=1.4:1). Factors related to poor outcome were an initial left ventricular ejection fraction </=30% (P=0.01), severe symptoms, i.e. NYHA functional class III or IV at presentation (P=0.04), and significant ventricular tachycardia during follow up (P=0.02). However, multivariate regression analysis yielded only low LVEF as the predictor of poor outcome (P=0.01). When analysed from age of onset of symptoms, survival figures were 94% at 1 year (95% CI 88 to 99%), 76% at 5 years (95% CI 67 to 86%) and 68% at 8 years (95% CI 54 to 82%). Mean survival was 6.5 years (95% CI 6 to 7 years). Patients were still at risk of fatal ventricular arrhythmia even when haemodynamically stable and had left ventricular ejection fraction >30%.

An animal model of arrhythmogenesis in congestive heart failure

Background: Patients with congestive heart failure (CHF) frequently die from arrhythmias, but models to study arrhythmogenic mechanisms during progressive CHF are lacking. Consequently we examined the feasibility of using dogs with an ischemic insult followed by rapid pacing to study ventricular arrhythmias in CHF. Methods: Eighteen chronically instrumented dogs had ischemic damage induced by inflating a balloon tipped catheter in a coronary artery for 90 min. After 2 weeks recovery, electrophysiologic studies were performed on no drugs, during esmolol infusion, and during isoproterenol infusion. The pacer was turned on at 250 bpm in 12 dogs, but not in six controls, and studies repeated bi-weekly for up to 6 weeks. Results: Serial echocardiograms documented progressive CHF, and serial signal averaged electrocardiograms demonstrated prolongation of total QRS, increased duration of terminal QRS<40 mv, and decreased RMS voltage of the terminal 20 ms of QRS in paced dogs. Arrhythmia severity increased as CHF progressed, but responses were quite variable, unaffected by esmolol, and minimally altered by isoproterenol. Conclusions: Ischemic left ventricular damage followed by rapid ventricular pacing in dogs produces a model that closely mimics patients with CHF and ventricular arrhythmias, including a heterogeneous pathophysiologic response to intervention.

Evolution of QRS duration after myocardial infarction: clinical consequences

The natural history of late potentials after acute myocardial infarction (AMI) has been studied in the first 2 years following myocardial infarction (MI). The purpose of the study was to assess the influence of some time delays since MI, including a time delay longer than 2 years on signal-averaged ECG (SAECG). SAECG was recorded at 40-Hz high pass filtering in 40 patients 10 days after acute MI (SAECG 1), then repeated 6-12 months later (mean 9 +/- 3 months) (SAECG 2), and then, 2-4 years later (mean 3 +/- 2 years) (SAECG 3). QRS duration, root mean square voltage of the last 40 ms of QRS (RMS 40), and low amplitude signal duration (LAS) were measured at the first (1), second (2), and third recording (3).

RESULTS

(***P < 0.001) [table: see text] The analysis of individual results showed a lengthening QRS duration at the third recording only in patients who had a decreased left ventricular ejection fraction (LVEF) at the third recording. In 12 patients with LVEF > 40%, QRS duration did not change at the first and third recording (104 +/- 15 vs 101 +/- 12 ms). In all 28 patients, but one with LVEF < 40%, QRS duration increased from 107 +/- 12 to 128 +/- 18 ms***. There was no correlation between QRS duration and LVEF at the second recording and no correlation between QRS duration increase at the third recording and the presence or not of late potentials at the first recording. QRS duration lengthening at the third recording was significantly correlated with a left ventricular (LV) dilatation occurrence at the two-dimensional echocardiogram. All arrhythmic events, but two, occurred in patients who developed a QRS duration prolongation and were significantly correlated (P < 0.01) to a mean longer QRS duration (132 +/- 20 ms) than in patients without arrhythmic events (113 +/- 17 ms). In conclusion, the patients with a LV impairment, and who developed a LV dilatation several months after AMI, presented a delayed lengthening of QRS duration noted only at least 2 years after infarction. These patients are at risk of arrhythmic events.

Familial dilated cardiomyopathy: cardiac abnormalities are common in asymptomatic relatives and may represent early disease

OBJECTIVES

This study sought to determine whether early disease is identifiable in asymptomatic relatives of patients with dilated cardiomyopathy (DCM) by means of noninvasive cardiologic assessment.

BACKGROUND

DCM is diagnosed on the basis of advanced heart failure, where cardiac dilation and impaired contractility are recognized in the absence of a recognized etiology (World Health Organization criteria). However, initial clinical presentation may be with severe complications: thromboembolism, arrhythmia or sudden death. DCM has recently been recognized to be familial, with autosomal dominant inheritance in many cases. Familial disease is present in 9% to 20% of patients with DCM, and the ability to identify early disease in such people may improve patient management and aid in the understanding of pathogenesis.

METHOD

We prospectively assessed 408 asymptomatic relatives (mean [+/-SD] age 35 +/- 15 years, 193 men) of 110 consecutive patients with DCM by means of history and physical examination, two-dimensional echocardiography, 12-lead and signal-averaged electrocardiography and metabolic exercise testing. We hypothesized that signs of lesser cardiac dysfunction in such relatives might indicate early disease.

RESULTS

Twenty-nine percent of relatives had abnormal results on the echocardiogram. Twenty percent (n = 45) had left ventricular enlargement (LVE), defined as LV end-diastolic diameter (LVEDD) > or = 112% predicted; 6% (n = 13) had depressed fractional shortening (dFS), defined as FS < or = 25%; and 3% (n = 7) had frank DCM, defined as LV dilation, impaired contractile performance and LVEDD > or = 112% plus FS < or = 25%. Other abnormalities of cardiac function were identified in relatives with LVE or dFS: A greater number with LVE had an abnormal metabolic exercise test result than normal relatives (9% vs. 1%, p < 0.05). Relatives with LVE and abnormal maximal oxygen consumption (VO2max) (defined as VO2max < 80% predicted) had a lower absolute VO2max than normal relatives (30 +/- 8 vs. 43 +/- 9 ml/min per kg, p = 0.01). The QRS duration (at the 25-Hz filter) on the signal-averaged electrocardiogram was prolonged in relatives with LVE (103 +/- 13 ms) and dFS (102 +/- 12 ms) compared with that of normal relatives (97 +/- 12 ms, p < 0.05). Over a mean 39-month follow-up period, 12 relatives with LVE (27%) and none with dFS developed symptomatic DCM (p < 0.0001). One relative with LVE died suddenly, and another underwent heart transplantation.

CONCLUSIONS

Nearly one-third of asymptomatic relatives (29%) have echocardiographic abnormalities, and 27% of such relatives progress to development of overt DCM. Early identification of such people would permit appropriate intervention that might influence the serious complications and mortality of this disease.

Arrhythmias and sudden death in heart failure

Survival of patients with heart failure has improved over the past decade due to advances in medical therapy. Sudden death continues to cause 20 to 50% of deaths. Ventricular arrhythmias are common in patients with heart failure. Ventricular hypertrophy, scars from prior myocardial infarction, sympathetic activation, and electrolyte abnormalities contribute. Some sudden deaths are due to bradyarrhythmias and electromechanical dissociation rather than ventricular arrhythmias. The risks and benefits of antiarrhythmic therapies continue to be defined. Class I antiarrhythmic drugs should be avoided due to proarrhythmic and negative inotropic effects that may increase mortality. For patients resuscitated from sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) amiodarone or an implantable cardioverter defibrillator (ICD) should be considered. ICDs markedly reduce sudden death in VT/VF survivors, but in advanced heart failure, this may not markedly extend survival. Catheter or surgical ablation can be considered for selected patients with bundle branch reentry VT or difficult to control monomorphic VT. For patients who have not had sustained VT/VF antiarrhythmic therapy should generally be avoided, but may benefit some high risk patients. Amiodarone may be beneficial in patients with advanced heart failure and rapid resting heart rates. ICDs may improve survival in selected survivors of myocardial infarction who have inducible VT.

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

Family studies have confirmed that familial dilated cardiomyopathy is common and that a large proportion of relatives have mild left ventricular enlargement and therefore potentially early disease. Previous studies have shown that patients with idiopathic dilated cardiomyopathy have abnormalities of the signal-averaged electrocardiogram (ECG). We assessed the usefulness of analysis of the signal-averaged ECG in the evaluation of familial dilated cardiomyopathy. Signal-averaged electrocardiographic recordings were obtained from 58 patients with idiopathic dilated cardiomyopathy, from 161 of their relatives (35 of whom had left ventricular enlargement), and from 59 healthy subjects. Signal-averaged ECGs were analyzed using both time domain and spectral turbulence analysis techniques. The time domain and spectral turbulence analysis variables were markedly abnormal in patients with idiopathic dilated cardiomyopathy compared with relatives considered normal and healthy controls (p <0.05). Late potentials were more common in patients with idiopathic dilated cardiomyopathy (17%) and in relatives with left ventricular enlargement (20%) than in normal relatives (5%) or healthy controls (5%) (p = 0.003). Spectral turbulence analysis was abnormal in 24% of patients with idiopathic dilated cardiomyopathy, 14% of relatives with left ventricular enlargement, 6% of normal relatives, and 5% of healthy controls (p = 0.0006). The sensitivity, specificity, and positive predictive accuracy for identification of relatives with left ventricular enlargement were 20%, 95%, and 54% for time domain analysis and 14%, 94%, and 42% for spectral turbulence analysis. Similar positive predictive accuracy was achievable with spectral turbulence analysis and with time domain analysis. In conclusion, the signal-averaged ECG is frequently abnormal in patients with idiopathic dilated cardiomyopathy and relatives with left ventricular enlargement.

An approach to the detection of autonomic neuropathy by use of signal-averaged electrocardiography

The beat-to-beat variation of PR interval, which is thought to be a reflection of autonomic nervous system, is difficult to measure with accuracy because the variation is too subtle. However, R wave amplitude in the P wave triggered SAECG is easily attenuated in comparison to that in the R wave triggered SAECG, which might be due to PR interval fluctuation. To determine whether autonomic neuropathy could be detected by use of SAECG, two types of SAECGs triggered by P and R waves were recorded in 23 diabetics with autonomic neuropathy and 41 age matched controls. The peak voltage of filtered QRS complex was measured in the R wave and P wave triggered SAECGs. Percent attenuation of the filtered QRS voltage was calculated by dividing the difference between the voltages in the R wave and P wave triggered SAECGs by the voltage in R wave triggered SAECG. The percent attenuation of filtered QRS voltage was significantly smaller in diabetics with autonomic neuropathy than controls (4.6% +/- 4.9% vs 16.3% +/- 15.0%; P < 0.001). These results suggest that the degree of attenuation of filtered QRS voltage in the P wave triggered SAECG would be useful for the detection of autonomic neuropathy.

The signal-averaged electrocardiogram: update on clinical applications

The signal-averaged electrocardiogram (SAECG) facilitates noninvasive recording of low-amplitude cardiac signals such as ventricular late potentials. The SAECG has been used to accurately predict life-threatening ventricular tachyarrhythmias in patients after acute myocardial infarction and with nonischemic dilated cardiomyopathy, and to screen for inducible ventricular tachycardia in patients with unexplained syncope and with nonsustained ventricular tachycardia. This review focuses on currently accepted methodology and clinical and research applications of the SAECG.

Comparison of time domain and spectral turbulence analysis of the signal-averaged electrocardiogram for the prediction of prognosis in idiopathic dilated cardiomyopathy

BACKGROUND

Despite significant advances in the treatment of heart failure, the prognosis of patients with idiopathic dilated cardiomyopathy remains poor. Although several of prognostic variables have been shown to be useful in risk stratification of patients with idiopathic dilated cardiomyopathy, their predictive accuracy is low and clinical usefulness uncertain.

HYPOTHESIS

This study was undertaken to assess the signal-averaged electrocardiogram (SAECG) in patients with idiopathic dilated cardiomyopathy and to compare the ability of time domain and spectral turbulence analytic techniques to predict clinical outcome.

METHODS

SAECG analysis was performed in 80 patients with idiopathic dilated cardiomyopathy. Nineteen patients had left bundle-branch block and eight were taking low-dose amiodarone for life-threatening arrhythmias. Conventional time domain and spectral turbulence analyses of the SAECG were performed using Del Mar 183 software.

RESULTS

During a follow-up of 27 +/- 19 months, 24 patients developed progressive heart failure, while the others remained clinically stable. Late potentials were detected in 28% of patients and were equally frequent in patients with and without progressive heart failure (38 vs. 23%, p = 0.20). Spectral turbulence analysis was abnormal in 34% of patients, and patients with abnormal results developed progressive heart failure more frequently than those with normal results (50 vs. 17%, p = 0.01). All spectral turbulence analysis parameters were significantly different in patients with progressive heart failure compared with those who remained clinically stable (p < or = 0.01). Furthermore, progressive heart failure-free survival at 2 years was significantly lower in patients with abnormal compared with normal results (63 vs. 87%; p < 0.05), but was similar in patients with and without late potentials (72 vs. 83%; p = 0.30). The relative risk for developing progressive heart failure using spectral turbulence analysis was 3.4 (95% confidence interval 1.2-9.7) and 2.8 (95% confidence interval 1.1-8.7) using time domain analysis. The sensitivity, specificity, and the positive and negative predictive accuracy for identifying patients who developed progressive heart failure were 50, 83, 50, and 83%, respectively, (p = 0.01) for spectral turbulence analysis, and 36, 85, 45 and 80%, respectively, (p = 0.09) for time domain analysis.

CONCLUSION

Abnormalities in the SAECG of patients with idiopathic dilated cardiomyopathy are common and appear to provide a noninvasive marker for development of progressive heart failure.

Time-domain signal-averaged electrocardiogram in nonischemic ventricular tachycardia

The prevalence of late ventricular potentials (LVPs) detected by signal averaged ECG (SAECG) is variable in nonischemic heart diseases. In idiopathic dilated cardiomyopathy, the prevalence increases from about 25% to 70%-90% in cases of spontaneous sustained ventricular tachycardia (VT), is not significantly correlated with hemodynamic and Holter data, and has a good positive predictive value for induced and spontaneous sustained VT. However, its predictive value for cardiac death has not been established. In primary hypertrophic cardiomyopathy, LVPs are rare (about 10%), not correlated to hemodynamic data, enhanced in cases of spontaneous sustained VT (up to 77%), and have a good predictive value of induced VT. LVP-SAECG are frequent in arrhythmogenic right ventricular dysplasia (ARVD) (70%-80%). They can identify patients with VT and an unapparent or limited form of this disease, or ARVD with few ventricular arrhythmias. The prevalence (26%-37%) of LVPs in mitral valve prolapse is clearly higher than in normal individuals or in other valvular diseases and is enhanced in cases of spontaneous and induced VT. Its significance remains speculative. After surgical repair of tetralogy of Fallot, LVPs can identify a group of patients with higher probability of induced and spontaneous risk of VT. The usefulness and significance of LVPs in other nonischemic cardiac diseases have not to date been established. In "true" idiopathic VT, without proved structural cardiac disease, the prevalence of LVPs does not exceed that observed in normal individuals (0%-5%), but in "apparent" idiopathic VT the prevalence of LVPs rises to 20%-40%. In these latter cases more invasive techniques must be used to discover a limited form of myocardiopathy.

Prevalence of late potentials in adult aortic stenosis

Sudden death and syncope are well-recognized clinical manifestations of valvular aortic stenosis (AS). Furthermore, patients with left ventricular hypertrophy due to hypertension have a greater prevalence of late potentials (LP) compared with normal subjects. Chronic pressure overload in AS is frequently characterized by development of left ventricular hypertrophy. The aims of this study were (1) to determine the prevalence of LP in patients with moderate to severe AS, and (2) to investigate the relationship between LP and left ventricular hypertrophy. Signal-averaged electrocardiograms (SAECG) were recorded using a 40 Hz high pass filter in 32 patients (19 M and 13 F), aged 69 +/- 11 years with AS, and in 25 age- and sex-matched controls. QRS duration (QRSD) < 114 ms, low amplitude signal of last 40 ms (LAS40) < 38 ms and root mean square voltage of last 40 ms (RMS40) > 20 microV were considered normal. LP were considered to be present if at least two of the above criteria were abnormal. Each patient underwent a complete echo-Doppler examination and the following parameters were measured; aortic valve area, fractional shortening, left ventricular end-diastolic diameter and mass index. Coronary arteriography was performed in 17 (53%) patients. LP were present in 8 out of 32 (25%) AS patients and in 1 out of 25 controls (4%); this difference was statistically significant (P < 0.006). No difference with regard to age, sex, presence of congestive heart failure, angina, syncope, complex ventricular arrhythmias and coronary artery disease was found in AS patients with and without LP. No correlation was found between indices of left ventricular structure and function and each SAECG parameter. In conclusion, the prevalence of LP in patients with AS is higher than in controls and the presence of LP in AS might be related to factors other than coronary artery disease and left ventricular mass and/or function.

Incidence and prediction of induced ventricular tachyarrhythmias in idiopathic dilated cardiomyopathy

The value of time-domain and spectral turbulence analyses of the signal-averaged electrocardiogram (SAECG) for predicting induction of sustained monomorphic ventricular tachycardia (VT) was prospectively investigated in 70 patients with idiopathic dilated cardiomyopathy. Sustained VT was induced in 9 patients (13%). The prevalence of abnormal time-domain and spectral analyses was 16 and 37%, respectively. The total predictive accuracy of time-domain and spectral analyses for VT induction was 86 and 67%, respectively (p < 0.01). The predictive accuracy of time-domain and spectral analysis was similar in patients without an intraventricular conduction defect (94 and 84%, respectively). However, the predictive accuracy of time-domain was higher than that of spectral analysis in patients with an intraventricular conduction defect (65 vs 25%; p < 0.05). The poor concordance between spectral analysis and programmed stimulation results was mainly due to the high number of false-positive recordings in the presence of an intraventricular conduction defect (9 of 20 cases). With the use of stepwise discriminant function analysis, an abnormal time-domain SAECG was the only variable predicting the induction of sustained VT (p < 0.0003). In dilated cardiomyopathy, an abnormal time-domain SAECG and induced sustained VT are rare, both time-domain signal-averaged electrocardiography and spectral analysis have a high predictive accuracy for VT induction in patients without an intraventricular conduction defect, and spectral analysis does not improve VT prediction in those with a conduction defect.

Time-domain and frequency-domain analyses of the signal-averaged ECG in patients with ventricular tachycardia and ischemic versus nonischemic dilated cardiomyopathy

The value of time-domain and frequency-domain (spectral turbulence) analyses of the signal-averaged electrocardiogram was investigated to predict induced sustained monomorphic ventricular tachycardia (VT). Two groups of patients with spontaneous nonsustained VT and left ventricular ejection fraction less than 50% were enrolled: 70 patients with idiopathic dilated cardiomyopathy (group 1) and 70 patients with ischemic heart disease (group 2). Sustained VT was induced in 9 cases (13%) in group 1 and 16 (23%) in group 2. The prevalence of abnormal time-domain and spectral turbulence analysis was 16 and 37%, respectively, in group 1 and 27 and 51%, respectively, in group 2 (NS). In group 1, the predictive accuracy of time-domain and spectral turbulence analysis for induced VT was 86 and 67%, respectively (P < .01). In group 2, the predictive accuracy of the two techniques for induced VT was, respectively, 79 and 66% (NS). In both groups, the predictive accuracy of time-domain analysis was higher than that of spectral turbulence analysis in patients with intraventricular conduction defect (IVCD): 65 versus 25%, respectively, in group 1 (P < .01), and 81 versus 44%, respectively, in group 2 (P < .05). However, the predictive accuracy of time-domain and spectral analyses was similar in patients without IVCD: 94 versus 84%, respectively, in group 1, and 77 versus 74%, respectively, in group 2. Thus, in patients with dilated cardiomyopathy, (1) the etiology does not affect the predictive accuracy of time and frequency domain and frequency-domain analyses have high predictive accuracy in patients without IVCD; and (3) spectral turbulence analysis does not improve VT prediction in patients with IVCD.