REPOLARIZATION DURATION AS A PREDICTOR OF APPROPRIATE ICD INTERVENTIONS IN PATIENTS WITH THE REMOTE MYOCARDIAL INFARCTION, UNTREATED WITH AMIODARONE
The purpose of the study was to assess the usefulness of the repolarization duration in the prediction of the ICD appropriate interventions in the patients with remote myocardial infarction, untreated with amiodarone, with ICD implanted as primary or secondary prevention of SCD.
Early (QTp) and late (TpTe) phases of repolarization were also used.
The study population consisted of 114 patients. All clinical data and Holter recordings were collected before ICD implantation, there were no patients treated with amiodarone. Repolarization duration indices (QTc, QTpc and TpTec- all corrected to the heart rate with Bazett’s formula) were computed from the entire Holter recordings (sinus rhythm, >90% of successive QT intervals suitable for analysis). The study population was followed for at least 2 years. The occurrence of any appropriate ICD delivered therapy was used as the endpoint of the study.
Appropriate ICD intervention (ARYT) occurred in 64 patients (62 males, secondary prevention in 51 pts, LVEF: 39±12%, age: 66±9 years; ARYT+), and 50 patients were free of malignant ventricular arrhythmias during the follow-up (46 males, secondary prevention in 24 pts, LVEF: 35±8%, age: 63±8 years, ARYT-). ARYT+ patients were older (p=0.02), with ICD implanted as secondary prevention more often (p<0.001). All study parameters were found to be higher in ARYT(+) patients: QTc- 466±38 vs 430±26 ms, p=0,001; QTpc- 376±30 vs 348±25 ms, p=0,001 oraz TpTec- 91±13 vs 82±10 ms, p=0,001. Univariate Cox analysis revealed that longer repolarization duration was significantly related to the higher risk of ARYT: QTc 452 ms (HR= 8,21 [95%CI 4,40-15,31], p=0.01), QTpc 368 ms (HR= 4,50 [95%CI 2,53-8,23], p=0.01) and TpTec 85 ms (HR= 2,68 [95%CI 1,55-4,63], p=0.01), respectively.
Indices of repolarization duration were found to be powerful predictors of VT/VF occurrence during the long-term follow-up in patients with remote myocardial infarction, untreated with amiodarone, and with ICD implanted as primary or secondary prevention.