_____________________________Sorin Pescariu et al 45

orIgInal arTIClES

abstract

Received for publication: Apr. 13, 2008. Revised: Jun. 26, 2008.

rEZUMat

2nd Cardiology Clinic, Institute of Cardiovascular Disease, Victor Babes University of Medicine and Pharmacy, Timisoara

Correspondence to:Sorin Pescariu, Institute of Cardiovascular Disease, 13A G. Adam Str., Timisoara, Tel. +40-256-207355Email: sorinpescariu@yahoo.com

VEntricUlar arrhythMias risk EValUation by MicroVolt t-waVE altErnans VErsUs PrograMMEd VEntricUlar stiMUlation in Post-Myocardial infarction PatiEnts with PrEsErVEd EjEction fraction and no VEntricUlar arrhythMias

Sorin Pescariu, Daniel Brie, Dana Maximov, Dana Popa, Milovan Slovenski, adina Ionac, Cristian Mornos, andreea Dumitrescu, Stefan Iosif Dragulescu

Objective: The study objective is to determine the feasibility of Microvolt T-wave alternans (MTWA) for ventricular arrhythmia risk evaluation in patients with complete interventional revascularization after myocardial infarction, preserved left ventricular ejection fraction (LVEF) and no prior malignant ventricular arrhythmias. Material and methods: Study population included 74 patients (13 women - 18%, mean age 56 11 years) with LVEF 45% (mean LVEF 59 13%) and no prior sustained ventricular arrhythmias underwent successfully interventional revascularization with stent implantation for acute or recent myocardial infarction (1 or 2 coronary vessel disease). At 30 days after interventional revascularization all patients underwent MTWA exercise test (Heartwave system, Cambridge Heart Inc. 2000) followed by electrophysiological study with standard programmed ventricular stimulation-PVS (including 1 to 3 extrastimuli). Results: Sixteen patients (22%) were found positive at MTWA test, 52 patients (70%) had a negative test, and 6 patients (8%) had an indeterminate test. At PVS positive response- sustained ventricular arrhythmias were induced in only two patients with previous positive MTWA (one patient with ventricular monomorphic tachycardia, one patient with ventricular polymorphic tachycardia). They were implanted with an implantable cardioverter defibrillator. In 12 patients with negative response at PVS, 9 with previous positive MTWA and 3 with previous negative MTWA, nonsustained (between 10-25 seconds) ventricular tachycardia was induced. Two cases with positive MTVA refused the PVS. The sensitivity of MTWA test for ventricular arrhythmias was 90%, with 81% specificity. The negative predictive value of MTWA for ventricular arrhythmic events was 97% and the positive predictive value was 14.3%. The average follow-up was 14 months without major arrhythmic events for all cases, including those implanted with ICD. Conclusions: The MTWA test has a good negative predictive value for arrhythmic events in this category of patients and can be used for risk stratification. We consider that in patients with positive MTWA, further invasive evaluation, respectively PVS, is necessary.Key Words: electrophysiological study, Microvolt T-wave alternans, ventricular arrhythmia, programmed ventricular stimulation, myocardial infarction

Obiectiv: Determinarea fezabilit\]ii MTWA (Microvolt T-wave alternans) pentru evaluarea riscului de aritmie ventricular\ la pacien]ii cu interven]ie de revascularizare complet\ dup\ infarct miocardic, frac]ie de ejec]ie a ventriculului stng (FEVS) p\strat\ [i f\r\ aritmii ventriculare maligne n antecedente. Material [i metode: Lotul de studiu a fost format din 74 pacien]i (13 femei - 18%, vrst\ medie 56 11 ani), cu FEVS 45% (FEVS mediu 59 13%) [i f\r\ aritmii ventriculare sus]inute n antecedente, care au fost supu[i interven]iei de revascularizare cu implantare de stent pentru infarct miocardic acut sau recent (boala coronarian\ mono sau bi-vascular\). Dup\ 30 de zile de la interven]ia de revascularizare to]i pacien]ii au efectuat un test de efort MTWA (Heartwave system, Cambridge Heart Inc. 2000) urmat de un studiu electrofiziologic cu stimulare ventricular\ programat\ standard (SVP) (ce a inclus ntre 1 [i 3 stimuli). Rezultate: {aisprezece pacien]i (22%) au fost pozitivi la testul MTWA, 52 pacien]i (70%) au avut un test negativ, iar 6 (8%) un test nedeterminat. La SVP, r\spuns pozitiv - aritmie ventricular\ sus]inut\ - au prezentat doar doi pacien]i cu teste MTWA pozitiv (un pacient a prezentat tahicardie ventricular\ monomorfic\, iar altul tahicardie ventricular\ polimorfic\). La ace[tia a fost implantat un dispozitiv cardioverter - defibrilator. La al]i 12 pacien]i cu r\spuns negativ la SVP, nou\ cu MTWA anterior pozitiv, iar trei cu MTWA negativ, a fost indus\ tahicardie ventricular\ nesus]inut\ (ntre 10 [i 25 de secunde). Doi pacien]i cu test MTWA pozitiv au refuzat SVP. Sensibilitatea MTWA n detectarea aritmiilor ventriculare a fost de 90%, cu o specificitate de 81%. Valoarea predictiv\ negativ\ a MTWA pentru evenimente aritmice ventriculare a fost de 97%, iar cea pozitiv\ a fost de 14.3%. Urm\rirea medie a fost de 14 luni, f\r\ evenimente aritmice majore n toate cazurile, inclusiv la cei cu cardioverter-defibrilator implantabil. Concluzii: Testul MTWA are o valoare predictiv\ negativ\ bun\ pentru evenimentele aritmice la aceast\ categorie de pacien]i [i poate fi utilizat\ pentru stratificarea riscului. Consider\m c\ la pacien]ii cu MTWA pozitiv este necesar\ investigarea ulterioar\ invaziv\, respectiv SVP. Cuvinte cheie: studiu electrofiziologic, Microvolt T-wave alternans, aritmie ventricular\, stimulare ventricular\ programat\, infarct miocardic

introdUction

Patients with reduced left ventricular ejection fraction (LVEF) after myocardial infarction (MI) are at risk of ventricular arrhythmias and many reports regarding risk stratification in these patients have been published.1-3 Few studies evaluated the risk stratification markers in post-MI patients with preserved LVEF. Risk

_____________________________46 TMJ 2008, Vol. 58, No. 1 - 2

stratification is important in patients with preserved LVEF despite the better prognosis of these patients.4 Microvolt T-wave alternans (MTWA) is a useful marker for identification of high-risk patients post-MI patients with reduced LVEF 30%, or 110 beats/min. Sustained alternans is defined as lasting at least one minute

with alternans voltage (Valt) 1.9 V and alternans ratio 3.0 in any orthogonal lead or two consecutive precordial leads during exercise. The test was defined as negative when the positive criteria were not met and artifact-free data were available showing a heart rate maintained at a level >105 beats/min for at least one min. The test was defined as indeterminate when the results did not meet either the positive or negative criteria.

Standard programmed ventricular stimulation After local anesthesia using lidocaine 1%, three

6-Fr quadripolar electrode catheters were inserted percutaneously through the femoral vein and advanced to the high lateral right atrium, across the tricuspid valve, recoded the His bundle electrogram, and to the right apex in all patients.

Programmed ventricular stimulation was performed using stimulus duration of 2-ms at amplitude of two to three times the diastolic threshold, with up to three extrastimuli at basic drive cycle lengths, 600 ms and 400 ms respectively, starting at apex, then at outflow tract. Coupling intervals of extrastimuli were decreased in 10-ms interval until coupling interval of 180 ms was reached or refractoriness of all extrastimuli was reached.

The endpoint of electrophysiology was the induction of sustained ventricular tachycardia (>30 s in duration or associated with hemodynamic compromise requiring earlier intervention) or the completion of stimulation protocol. The induction of ventricular fibrillation was defined prospectively as an indeterminate result.

Follow-upAll patients were followed for an average of 14

months. Clinical follow-up was obtained as regular interval. Arrhythmic events during follow-up were defined as:

1. Sustained ventricular tachycardia or ventricular fibrillation;

2. Appropriate ICD therapy for ventricular tachyarrhythmia with documentation of the rhythm leading to the shock by stored electrograms by the device;

3. Sudden cardiac death

Statistical analysisAll results are expressed as mean standard

deviation. Sensivity, specificity, positive and negative predictive value, and the predictive accuracy of event-free prediction were evaluated.

_____________________________Sorin Pescariu et al 47

rEsUlts

A number of 74 patients (61 men, 82%) evaluated in this study. (Table 1) The mean age of this cohort was 56 11 years, and the mean left ventricular ejection fraction 59 13%. All patients had acute or recent myocardial infraction (one or two coronary vessel disease) that underwent successfully interventional revascularization with stent implantation. At 30 days after interventional revascularization all patients underwent MTWA exercise test followed by electrophysiological study with standard programmed ventricular stimulation as describe earlier.

Table 1. Patients characteristics.

Figure 1. T-wave alternas positive test. Alternas precordial trend summary.

The microvolt TWA test was positive in 16 patients (22%), negative in 52 patients (70%), while 6 patients (8%) had an indeterminate test. (Fig. 1,2)

Figure 2. T-wave alternas positive test. Alternans vector trend summary.

Indeterminate test was primarily due to frequent ectopic beats or the inability to achieve the target heart rate of >105 beats/min. Previous report in the MI population with reduced LV function has combined positive and indeterminate microvolt TWA into one abnormal group. In our study we separated patients with a positive microvolt TWA test from pat