Predictive Power of f99 Repolarization Index for the Occurrence of Ventricular Arrhythmias
Corrado Giuliani1, Cees A Swenne2, Sumche Man2
1Department of Information Engineering, Polytechnic University of Marche, Ancona, Italy.
Insights
The f99 index, a new measure of cardiac repolarization, shows promise in predicting dangerous ventricular arrhythmias. Maximizing this index over orthogonal leads offers the best predictive power for sudden cardiac death risk.
Area of Science:
- Cardiology
- Biomedical Engineering
- Medical Diagnostics
Background:
- Cardiac repolarization defects, detectable via ECG, are linked to sudden cardiac death.
- Current repolarization-based indices lack sufficient sensitivity and specificity for clinical use.
- A novel f99 index was developed to assess repolarization dynamics.
Purpose of the Study:
- To evaluate the predictive capability of the f99 index for ventricular arrhythmias.
- To determine if the f99 index can identify patients at higher risk of sudden cardiac death.
- To compare the performance of the f99 index across different ECG lead configurations.
Main Methods:
- The study included 170 patients with implantable cardioverter-defibrillators (ICDs).
- The f99 index was calculated from 15 ECG leads and maximized over precordial, standard 12-lead, and orthogonal XYZ leads.
- Predictive power was assessed using the area under the receiver operating characteristic curve (AUC).
Main Results:
- Patients who developed ventricular arrhythmias (ICD_Cases) had significantly higher median f99 index values compared to controls.
- The f99 index maximized over orthogonal leads (f99_MaxXYZ) showed the highest AUC (0.68).
- Higher f99 values indicate more fragmented cardiac repolarization.
Conclusions:
- The f99 index is a promising tool for assessing the risk of ventricular arrhythmias.
- Maximizing the f99 index over orthogonal leads enhances its predictive accuracy.
- This index may aid in identifying individuals at risk for sudden cardiac death.
Background:
Defects of cardiac repolarization, noninvasively identifiable by analyzing the electrocardiographic (ECG) ST segment and T wave, are among the major causes of sudden cardiac death. Still, no repolarization-based index has so far shown sufficient sensitivity and specificity to justify preventive treatments. Thus, the aim of this work was to evaluate the predictive power of our recently proposed f99 index for the occurrence of ventricular arrhythmias.
Methods:
Our study populations included 170 patients with implanted cardiac defibrillator (ICD), 44 of which developed ventricular tachycardia and/or fibrillation during the 4-year follow-up (ICD_Cases) and 126 did not (ICD_Controls). The f99 index, defined as the frequency at which the repolarization normalized cumulative energy reaches 99%, was computed in each of the 15 (I to III, aVl, aVr, aVf, V1 -V6 , X, Y, Z) available ECG leads independently, and then maximized over the 6 precordial leads (f99_MaxV1 -V6 ), 12 standard leads (f99_Max12STD) and three orthogonal leads (f99_MaxXYZ) to avoid dispersion-related issues. Each index predictive power was quantified as the area under the receiving operating characteristic curve (AUC).
Results:
Median f99_MaxV1 -V6 , f99_Max12STD and f99_MaxXYZ values were significantly higher in the ICD_Cases than in the ICD_Controls (48 Hz vs. 35 Hz, P<0.05; 51 Hz vs. 43 Hz, P<0.05; 45 Hz vs. 31 Hz, P<10(-3) ; respectively), indicating a more fragmented repolarization in the former group. The AUC values were 0.62, 0.63 and 0.68, respectively.
Conclusions:
The f99 represents a promising risk index for the occurrence of ventricular arrhythmias, especially when maximized over the three orthogonal leads.
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