What's New in EP

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    WHATS NEW IN EPSection Editor: Peng-Sheng Chen, M.D.

    DEBUT Trial

    Sudden unexplained death syndrome(SUDS) is the leading cause of deathin young, healthy, southeast Asian men.The DEBUT (Defibrillator Versus -Blockers for Unexplained Death inThailand) trial is a randomized clin-ical trial to compare the annual all-cause mortality rates among SUDSpatients treated with -blockers ver-sus that among patients treated withan implantable cardioverter defibrillator(ICD). The trial (Nademanee et al., Cir-culation 2003;107:2221) enrolled a to-tal of 86 patients who were either SUDSsurvivors or probable SUDS survivors.The patients were randomized to re-ceive an ICD or propranolol. During the3-year follow-up period of the maintrial, there were 4 deaths; all occurredin the -blocker group (P = 0.02).Seven subjects in the ICD arm had re-current ventricular fibrillation (VF), andall were effectively treated by the ICD.When the results of the main trial and thepilot study were combined, there were7 deaths (18%) in the -blocker groupand no deaths in the ICD group. In addi-tion, there were a total of 12 ICD patientsreceiving ICD discharges due to recur-rent VF. The authors concluded that ICDtreatment provides full protection fromdeath related to primary VF in a SUDSpopulation and is superior to -blockadetreatment.

    Cardiac ResynchronizationTherapy in Heart Failure

    The MIRACLE (Multicenter InSyncRandomized Clinical Evaluation) trialshowed that cardiac resynchronizationtherapy (CRT) improves the clinicalsymptoms among patients with severeheart failure and intraventricular con-duction delay (Abraham et al., N EnglJ Med 2002;346:1845). St. John Suttonet al. (Circulation 2003;107:1985) usedDoppler echocardiography to test thehypothesis that CRT results in improvedleft ventricular (LV) size and func-tion. Doppler echocardiography wasperformed in a total of 323 patientsin the MIRACLE trial at baseline and3 and 6 months after therapy. At 6

    months, CRT was associated with re-duced end-diastolic and end-systolicvolumes, reduced LV mass, increasedejection fraction, reduced mitral regur-gitation, and improved myocardial per-formance index compared with control.Improvements with CRT were greater inpatients with a nonischemic versus is-chemic cause of heart failure. The au-thors concluded that CRT in patientswith moderate-to-severe heart failureis associated with reversed LV remod-eling, improved LV function, and de-creased mitral regurgitation.

    Quality of Life and Heart RateVariability in the MUSTIC Study

    The MUltisite STimulation In Car-diomyopathy (MUSTIC) study demon-strated that atriobiventricular pacingsignificantly improves exercise toler-ance and quality of life in patients withchronic heart failure and intraventric-ular conduction delay (N Engl J Med2001;12:873). To test the hypothesis thatthe beneficial effects of biventricularpacing persist for at least 1 year, Lindeet al. (Am J Cardiol 2003;91:1090) per-formed a quality-of-life assessment in76 patients in the MUSTIC trial. Theresults showed that biventricular pacingimproved quality of life in patients withheart failure and intraventricular con-duction delays. The benefits were sus-tained over 12-month follow-up. Alonsoet al. (Am J Cardiol 2003;91:1144) per-formed a study on heart rate variabil-ity in MUSTIC patients using 24-hourambulatory ECG recordings at base-line and during longitudinal follow-up(912 months). The standard deviationof normal-to-normal (SDNN) intervalsover the recording period increased sig-nificantly during biventricular pacingcompared with baseline. This improve-ment also was observed beyond 1-yearfollow-up.

    Imaging Studies of thePulmonary Vein

    Kato et al. (Circulation 2003;107:2004) used magnetic resonance imaging(MRI) to define pulmonary vein (PV)

    anatomy before and after catheter abla-tion of atrial fibrillation (AF). Twenty-eight patients underwent gadolinium-enhanced MRI before and 6 weeksafter their procedures. Results showedthat AF patients had larger PV diame-ters than control subjects. The left PVshad a longer neck than the right PVs.Detectable PV narrowing was observedin 24% of veins. Among them, 2 veinshad moderate-to-severe narrowing and15 veins had mild narrowing. All pa-tients were asymptomatic, and none re-quired treatment. The authors concludedthat AF patients have larger PVs thancontrol subjects. The benefits of prepro-cedural MRI of PVs include the abilityto evaluate the number, size, and shapeof the PVs. MRI also provides assess-ment of the severity of PV stenosis.

    Schwartzman et al. (J Am Coll Car-diol 2003;41:1349) used multidetectorhelical computed tomography (MDCT)to study the left atrium (LA) and PV.The study included 70 subjects with and47 subjects without AF. They found thatthe LA and PV dimensions were sig-nificantly larger in AF versus non-AFsubjects, men versus women, and sub-jects with persistent versus paroxysmalAF. The authors concluded that MDCTimages of the LA and PVs are accurateand provide detailed anatomic informa-tion. There were significant differencesin the sizes of LA and PV between AFand non-AF patients.

    Thyrotoxic Periodic Paralysisand Ventricular Fibrillation

    Boccalandro et al. (Lancet 2003;361:1432) reported a 24-year-old manwho presented with weakness of bothlegs, 3-kg weight loss, and 12-lead ECGshowing sinus tachycardia and long QTintervals. Soon after the ECG was taken,the patient went into VF and had to beresuscitated. Thyroid-stimulating hor-mone was