Background—
Late potentials (LP) detected with signal-averaged ECGs are known to be useful in identifying patients at risk of Brugada syndrome (BS) and arrhythmogenic right ventricular cardiomyopathy (ARVC). Because the pathophysiology is clearly different between these disorders, we clarified the LP characteristics of these disorders.
Methods and Results—
This study included 15 BS and 12 ARVC patients and 20 healthy controls. All BS patients had characteristic ECG changes and symptomatic episodes. All ARVC patients had findings that were consistent with recent criteria. Three LP parameters (filtered QRS duration, root mean square voltage of the terminal 40 ms of the filtered QRS complex, and duration of low-amplitude signals [<40 µV] in the terminal, filtered QRS complex) were continuously measured for 24 hours using a novel Holter-based signal-averaged ECG system. The incidences of LP determination in BS (80%) and ARVC (91%) patients were higher than in healthy controls (5%;
P
<0.0001 in both) but did not differ between BS and ARVC patients. In BS patients, the dynamic changes of all LP parameters were observed, and they were pronounced at nighttime. On the contrary, these findings were not observed in ARVC patients. When the SD values of the 3 LP parameters (filtered QRS duration, root mean square voltage of the terminal 40 ms of the filtered QRS complex, and duration of low-amplitude signals [<40 µV] in the terminal, filtered QRS complex) over 24 hours were compared for the 2 patient groups, those values in BS patients were significantly greater than those in ARVC patients (
P
<0.0001 in all).
Conclusions—
LP characteristics detected by the Holter-based signal-averaged ECG system over 24 hours differ between BS and ARVC patients. Dynamic daily variations of LPs were seen only in BS patients. This may imply that mechanisms of lethal ventricular arrhythmia in BS may be more correlated with autonomic abnormality than that of ARVC.
Nifekalant (NF), a pure K(+) channel blocker developed in Japan, has been reported to be effective in the treatment of life-threatening ventricular arrhythmias. We studied its efficacy in 18 men and 4 women with out-of-hospital ventricular fibrillation (VF) admitted to our emergency department between August 2001 and March 2004. The number of DC shocks delivered for out-of-hospital VF, serum Na(+) and K(+), arterial blood pH, and base excess were compared in 8 patients treated with NF, 0.3 mg/kg i.v. followed by a continuous intravenous (group N) versus 14 patients treated with lidocaine, 2 mg/kg, i.v. (group C). The two groups were similar with respect to their baseline characteristics. Sinus rhythm returned in 5 of 8 patients in group N versus 2 of 14 patients in group C (P < 0.05). These seven patients were admitted to the intensive care unit, though all died within 1 month. The results of this study suggest that NF may be effective in defibrillation of out-of-hospital VF, though controlled studies are needed to confirm our observations.
Inter-fascicular VT could be misdiagnosed as idiopathic left VT due to the limitations of the conventional EP study. Failed RFCA in presumptive idiopathic left VT cases has to be carefully investigated by further analysis, and a tailored RFCA strategy targeting the requisite portions of the left fascicles in the inter-fascicular VT reentrant circuit will be required for the successful elimination of the inter-fascicular VT.
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