P. Michálek, S.B. Hatahet, M. Svetlošák, P. Margitfalvi, I. Waczulíková, S. Trnovec, A. Böhm, O. Beňačka, R. Hatala
Background: Potential of using the T-peak to T-end (TpTe) interval as an electrocardiographic parameter reflecting the transmural dispersion of ventricular repolarization (TDR) to identify patients (pts.) with higher risk of malignant ventricular arrhythmias (MVA) for better selection of candidates for implantable cardioverter-defibrillator (ICD) in primary prevention (PP) of sudden cardiac death (SCD) remains controversial.
Objectives: The primary objective of this study was to investigate the relationship between the TpTe interval on a resting 12-lead electrocardiogram (ECG) and the incidence of MVA resulting in appropriate ICD intervention (AI). The secondary objective was to assess its relationship to overall mortality and analyze other clinical mortality predictors.
Methods: A total of 243 consecutive pts. with severe left ventricular (LV) systolic dysfunction after myocardial infarction (MI) with a single chamber ICD in PP of SCD from one implantation center were included. We excluded all pts. with any other disease that could interfere with the indication of ICD implantation. Primarily investigated intervals were measured manually in accordance with accepted methodology. Data on ICD interventions were acquired from device interrogation during regular outpatient controls. Mortality data were collected from the database of insurance and regulatory authorities.
Results: We did not find a significant relationship between the duration of the TpTe interval and the incidence of MVA (71.5 ms in pts. with MVA vs. 70 ms in pts. without MVA; p=0.408). Similar results were obtained for the corrected TpTe interval (TpTec) and the ratio of TpTe to QT interval (76.3 ms vs. 76.5 ms; p=0.539 and 0.178 vs. 0.181; p=0.547, respectively). There was also no significant difference between the duration of TpTe, TpTec and TpTe/QT ratio in pts. groups by overall mortality (71.5 ms in the deceased group vs. 70 ms in the survivors group; HR 1.01; 95% CI, 0.99 to 1.02; p=0.715, 76.3 ms vs. 76.5 ms; HR 1.01; 95% CI, 0.99 to 1.02; p=0.208 and 0.178 vs. 0.186; p=0.129, respectively). Significant factors affecting mortality included: higher age (HR 1.06; 95% CI, 1.04 to 1.09; p0.001), lower ejection fraction of LV (HR 0.93; 95% CI, 0.89 to 0.97; p=0.001), higher serum creatinine (HR 1.01; 95% CI, 1.01 to 1.02; p .001), lower glomerular filtration rate (HR 0.98; 95% CI, 0.97 to 0.99; p 0.001), higher heart rate (HR 1.02; 95% CI, 1.00 to 1.03; p=0.024) and paradoxically lower BMI (HR 0.94; 95% CI, 0.89 to 0.98; p=0.009). There was a 1.7-fold higher risk of death in pts. with diabetes (HR 1.67; 95% CI, 1.05 to 2.66; p=0.031). No significant difference in survival between smokers and non-smokers was observed (HR 0.84; 95% CI, 0.40 to 1.75; p=0.642). Three-year survival rate was significantly better in the group with AI compared to the non-AI group (92.7% vs. 75.5%; p=0.022, respectively).
Conclusion: This study suggests no significant change in either overall or MVA-free survival associated with ECG parameters reflecting TDR (TpTe, TpTec) in patients with systolic dysfunction after MI and ICD implanted for primary prevention, but differences in some known clinical prognostic factors associated with overall survival were found.