Late Potential in Brugada Syndrome. Introduction: Risk stratification for life-threatening arrhythmic events in Brugada syndrome is not yet established. The aim of the present study was to examine the usefulness of various markers in predicting life-threatening arrhythmic events in the Brugada syndrome. Methods and Results: Forty-six patients with Brugada-type ECGs were categorized into the symptomatic (n = 28) and asymptomatic (n = 18) groups. Statistical analyses were performed with respect to the usefulness of the following markers: SCN5A mutation, pharmacologic challenge, ventricular fibrillation (VF) inducibility by programmed electrical stimulation, and late potential (LP) by signal-averaged ECG (SAECG). Comparison between the two groups revealed a significant difference only in LP positivity (92.6% vs 47.1%, P = 0.0004). The symptomatic group had significantly lower RMS40, longer LAS40, and longer fQRSd compared with the asymptomatic group. A significant difference was noted, especially RMS40. The positive predictive value, negative predictive value, and predictive accuracy when setting a cutoff value of 15 μV were 92.0%, 78.9%, and 86.4%, respectively. Furthermore, patients with an RMS40 value <15 μV (n = 25) showed significantly higher rates of VF recurrence compared with patients with an RMS40 value ≥ 15 μV (n = 19, P = 0.047). Conclusion: Regarding risk stratification for identifying high-risk patients in Brugada syndrome, only LP by SAECG was shown to be useful, suggesting the importance of RMS40 in predicting the history of life-threatening arrhythmic events and the recurrence of VF.

Assessment of markers for identifying patients at risk for life-threatening arrhythmic events in Brugada syndrome.

Late potentials in progressive muscular dystrophy of the Duchenne type

We studied, prospectively, the predictive value of late potentials to cardiac sudden death and sustained ventricular tachycardias in 385 patients with myocardial infarction surviving over 4 weeks. Signal averaged electrocardiogram was performed over a 4 week period from the onset of acute myocardial infarction in all patients. Late potentials were observed in 118 of 385 patients. During the mean follow up period of 24.3 months, 17 patients had cardiac sudden death and 15 patients had symptomatic sustained ventricular tachycardias. In 16 of 17 patients with cardiac sudden death and 14 of 15 patients with sustained ventricular tachycardias, late potentials were observed. Sensitivity, specificity, positive predictive value, negative predictive value, and predictive accuracy of late potentials to cardiac sudden death in these 385 patients were 94.1%, 72.3%, 13.6%, 99.6% and 73.2% respectively. Also, these predictive values of late potentials to sustained ventricular tachycardias in the group of patients were 93.3%, 71.9%, 11.9%, 99.6% and 72.7%, respectively. We concluded that the clinical usefulness of late potentials in patients with myocardial infarction surviving over 4 weeks in the negative predictive value to cardiac sudden death and sustained ventricular tachycardias is superior to that of positive predictive value. Sensitivity of late potentials to these events is also higher.

Prospective study of late potentials to predict cardiac sudden death and ventricular tachycardias in patients with myocardial infarction surviving over 4 weeks

This study examined the age-related criteria of signal-averaged electrocardiographic (SA-ECG) parameters in children. SA-ECGs were obtained in 82 healthy volunteers in six groups depending on age (group 1:1 day to 35 ms, f-QRS duration >110 ms, and LD>35 ms for those age 1 day to 30 ms, f-QRS duration >100 ms, and LD>35 ms for those age 1 month to 40 ms, f-QRS duration >130 ms, and LD>35 ms for those age 1 to 45 ms, f-QRS duration >135 ms, and LD>35 ms for those age 20 to <40 years. RMS and LAS correlated with f-QRS duration (r=−0.78 and 0.76, respectively;p<0.05), suggesting that these parameters are associated with the thickness of the ventricular muscle and the ventricular conduction time. Right atrial pacing had no effect on the measured SA-ECG parameters. The age-related differences in SA-ECG parameters might be due to age-related differences in the thickness of the ventricular muscle and the ventricular conduction time but are not due to differences in the heart rate. The age difference of each parameter on SA-ECG should be considered for ventricular late potentials.

Age-related criteria for signal-averaged electrocardiographic late potentials in children.

Intra-QRS high-frequency ECG changes with ischemia

We investigated the recognition of late potentials in patients with and without organic hear diseases and spontaneous ventricular arrhythmias. None of the normal subjects had late potentials and patients with ventricular arrhythmias but no organic heart diseases, also had no late potentials as well as patients with idiopathic ventricular tachycardias. Late potentials in patients with idiopathic cardiomyopathy were noted more frequently in the dilated type than in the hypertrophic type, especially in those with high grades of ventricular arrhythmias. Patients with old myocardial infarctions had a higher rate of late potentials recognition in cases of sudden death or ventricular tachycardias. On the other hand, we observed lower rates in patients during early stage of acute myocardial infarction in spite of the evidence of a higher rate of ventricular electrical instability. There was no association between ejection fractions, wall motion scores and late potentials. However, a higher recognition of late potentials was found in patients with inferior or posterior myocardial infarction and ventricular aneurysm. We concluded that the late potential must be evaluated in each of the different groups of organic heart diseases in order to estimate the clinical value of ventricular arrhythmias.

The clinical evaluation of the late potentials in patients with ventricular arrhythmias.

The relationship between the time required for reperfusion and the incidence of late potentials was studied in 94 patients who survived a first acute myocardial infarction (AMI) and who showed total occlusion of the infarct-related artery at an initial coronary arteriography. Sixty-three patients who successfully underwent direct percutaneous transluminal coronary angioplasty (PTCA), and 31 who were treated conventionally (controls), underwent signal-averaged electrocardiography. Direct PTCA patients were classified into 5 groups according to the time required for reperfusion: or = 10 h. The incidence of late potentials in these groups was 8%, 12%, 14%, 33%, and 43%, respectively, and 48% in the controls. Late potentials were recorded more frequently as the period until successful reperfusion increased: the incidence of late potentials was significantly lower in the < or = 4 and 4-6 h groups than in the controls (p < 0.005 and p < 0.05, respectively). Therefore, reperfusion achieved within 6 h reduced the incidence of late potentials in AMI patients and may be effective for preventing malignant ventricular arrhythmias.

Effect of reperfusion by direct percutaneous transluminal coronary angioplasty on ventricular late potentials in cases of total coronary occlusion at initial coronary arteriography.

Relationship between ventricular late potentials and left ventricular wall thickness assessed by magnetic resonance imaging in patients with acute myocardial infarction

The occurrence of a systolic sound in hypertrophic obstructive cardiomyopathy (HOCM) has been well known for more than 20 years. This was phonoechocardiographically regarded as the sound coincident with the abrupt halt of the systolic anterior movement (SAM) of the mitral valve echo, and it has been termed the SAM sound. A 58-year-old man with HOCM was admitted with right hemiplegia. He was found to have a SAM sound which waxed and waned in intensity, and at times moved earlier into systole. He was studied by cardiac catheterization, M-mode and two-dimensional Doppler echocardiography (pulsed, continuous wave and color flow Doppler methods). Asymmetric septal hypertrophy (interventricular septal thickness = 25 mm, left ventricular posterior wall thickness = 14 mm), as well as SAM and midsystolic aortic valve closure were demonstrated. The presence and intensity of the sound was not related to rhythm (normal sinus rhythm vs atrial flutter), heart rate, respiration, position, or inhalation of amyl nitrite. Two-dimensional Doppler echocardiography revealed the following: 1. In the left ventricular outflow tract just below the aortic valve, a systolic turbulent flow was always present. 2. In the left ventricular chamber near the apex, a systolic laminar flow was interrupted in those cycles where the SAM sound was present. Otherwise, in cycles lacking the SAM sound, laminar flow in this locality continued throughout systole (even shorter duration than normal). 3. In the left ventricular inflow tract, diastolic flow was unaffected by the presence of the sound. 4. No mitral regurgitation was observed using color flow Doppler echocardiography. In summary, a SAM sound appeared to be associated with sudden deceleration of blood flow from the apex to the mid left ventricle.

SAM sound studied by pulsed Doppler echocardiography

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The clinical evaluation of the late potentials in patients with ventricular arrhythmias.

Effect of reperfusion by direct percutaneous transluminal coronary angioplasty on ventricular late potentials in cases of total coronary occlusion at initial coronary arteriography.

Relationship between ventricular late potentials and left ventricular wall thickness assessed by magnetic resonance imaging in patients with acute myocardial infarction

SAM sound studied by pulsed Doppler echocardiography