Exercise-Induced Repolarization Alternans Heterogeneity in Patients with an Implanted Cardiac Defibrillator

Abstract Repolarization alternans (RA

The Power of Exercise-Induced T-wave Alternans to Predict Ventricular Arrhythmias in Patients with Implanted Cardiac Defibrillator

ABSTRACT The power of exercise-induced T-wave alternans (TWA) to predict the occurrence of ventricular arrhythmias was evaluated in 67 patients with an implanted cardiac defibrillator (ICD). During the 4-year follow-up, electrocardiographic (ECG) tracings were recorded in a bicycle ergometer test with increasing workload ranging from zero (NoWL) to the patient's maximal capacity (MaxWL). After the follow-up, patients were classified as either ICD_Cases (n = 29), if developed ventricular tachycardia/fibrillation, or ICD_Controls (n = 38). TWA was quantified using our heart-rate adaptive match filter. Compared to NoWL, MaxWL was characterized by faster heart rates and higher TWA in both ICD_Cases (12−18 µ V vs. 20−39 µ V; P < 0.05) and ICD_Controls (9-15 µ V vs. 20−32 µ V; P < 0.05 ). Still, TWA was able to discriminate the two ICD groups during NoWL (sensitivity = 59−83%, specificity = 53−84%) but not MaxWL (sensitivity = 55−69%, specificity = 39−74%). Thus, this retrospective observational case-control study suggests that TWA's predictive power for the occurrence of ventricular arrhythmias could increase at low heart rates

Dependency of T-Wave Alternans Predictive Power for the Occurrence of Ventricular Arrhythmias on Heart Rate

Abstract T-wave alternans (TWA), a promising index of cardiac electrical instability, is known to increase its amplitud

The power of exercise-induced T-wave alternans to predict ventricular arrhythmias in patients with implanted cardiac defibrillator

none3siExercise-induced T-wave alternans (TWA) predictive power for the occurrence of ventricular arrhythmias was evaluated in 67 patients with an implanted cardiac defibrillator (ICD). During the 4-year follow-up, electrocardiographic (ECG) tracings were recorded while performing a bicycle ergometer test with increasing workload ranging from zero (NoWL) to the patient’s maximal capacity (MaxWL). After the follow-up, patients were classified as either ICD_Cases (n=29), if developed ventricular tachycardia/fibrillation, or ICD_Controls (n=38). TWA was quantified using our heart-rate adaptive match filter. Compared to NoWL, MaxWL was characterized by faster heart rates and higher TWA in both ICD_Cases (12-18 µV vs. 20-39 µV; P<0.05) and ICD_Controls (9-15 µV vs. 20-32 µV; P<0.05 ). Still, TWA was able to discriminate the two ICD groups during NoWL (sensitivity=59-83%, specificity=53-84%) but not MaxWL (sensitivity =55-69%, specificity=39-74%). Thus, this retrospective observational case-control study suggests that TWA predictive power for the occurrence of ventricular arrhythmias could increase at low heart rates.L Burattini; S Man; CA SwenneBurattini, Laura; S., Man; Ca, Swenn

T-Wave Alternans Identification in Routine Exercise ECG Tracings: Comparison of Methods

Abstract T-wave alternans (TWA) is often measured in special exercise than the latter (MinHR: 22 µV, MaxHR: 38 µV

Dependency of Exercise-Induced T-Wave Alternans Predictive Power for the Occurrence of Ventricular Arrhythmias from Heart Rate

T-wave alternans (TWA) is a noninvasive index of risk for the occurrence of ventricular arrhythmias. It is known that TWA amplitude (TWAA) increases with heart rate (HR) but how the TWA predictive power varies with HR remains unknown. Thus, the aim of this study was to evaluate the dependency of exercise-induced TWA predictive power for the occurrence of ventricular arrhythmias from HR

The Olson method for detection of acute myocardial ischemia in patients with coronary occlusion

An automated ECG-based method may provide diagnostic support in the management of patients with acute coronary syndrome. The Olson method has previously proved to accurately identify the culprit artery in patients with acute coronary occlusion. Methods The Olson method was applied to 360 patients without acute myocardial ischemia and 52 patients with acute coronary occlusion. Results This study establishes the normal variation of the Olson wall scores in patients without acute myocardial ischemia, which provides the basis for implementation of the Olson method for triage of patients with acute coronary syndrome. All patients with acute occlusion had Olson wall scores above the upper limit of normal. Conclusion The Olson method can be used for ischemia detection with very high sensitivity. Future studies are needed to explore specificity in patients with non-ischemic ST elevation

T-Wave Alternans Hysteresis on Heart Rate

Microvolt T-wave alternans (TWA) increases with heart rate (HR). Thus, TWA is usually analyzed during exercise. However, since TWA during recovery is usually not analyzed, it is not clear if TWA and HR are linked by a one-to-one correspondence, or if it does exist a TWA hysteresis on HR. To investigate such issue TWA was identified in ECG recordings of 266 patients with implanted cardio-defibrillator acquired during a bicycle ergometer test, which included a HR-increasing exercise and a HR-decreasing recovery, both characterized by a HR from 80 to 125 bpm. TWA was always found to have a positive association with HR but, at each HR, exercise TWA was typically different from recovery TWA. Specifically, TWA increased exponentially during exercise (fitting-exponential-curve correlation: ρ=0.99, P<10-7) while decreased linearly during recovery (fittingline correlation: ρ=0.94, P<10-4). The two fitting curves crossed at about 115 bpm, so that for lower HRs (80-110 bpm) exercise TWA was significantly lower than recovery TWA (16-21 µV vs. 22-27 µV; P<0.01), while for higher HRs (120-125 bpm) exercise TWA was significantly higher than recovery TWA (41-51µV vs. 28 µV; P<10-6). Thus, it does exist a TWA hysteresis on HR since TWA does not depend only on the actual value of HR but also on such value being reached during exercise or recovery

Logistic Regression to Enhance Risk Assessment by Left Ventricular Ejection Fraction and f99

Sudden cardiac death remains one of the leading causes of death in developed countries. Left ventricular ejection fraction (LVEF) and f99 are two noninvasive indexes of cardiovascular risk (traditional the former and innovative the latter) which, taken singularly, have not shown sufficiently high SCD predictive power to justify preventive actions. Thus, the aim of the present study was to investigate if their combination improves predictability of ventricular arrhythmias. To this aim, ECG recordings from 266 ICD patients, of which 76 developed ventricular tachycardia or fibrillation during the 4-year follow-up (ICD_Cases), and 190 did not (ICD_Controls). The ECGs of each patient was used to compute the f99, a repolarization index defined as the frequency at which the cumulative power energy reaches 99%. Eventually, a logistic regression between LVEF and f99 was performed in order to derive a combined predictor (CP) of ventricular arrhythmia. Goodness of each index was evaluated in terms of the area under the receiver operator curve (AUC). When used singularly, LVEF and f99 respectively provided an AUC of 0.67 and 0.64. When combined to get CP=-0.15-0.05·LVEF+0.03·f99, this provided an AUC of 0.71. In conclusion, use of logistic regression improves LVEF and f99 predictability of ventricular arrhythmias

Intra-Individual Comparison of Sinus and Ectopic Beats Probing the Ventricular Gradient’s Activation Dependence

Wilson assumed that the ventricular gradient (VG) is independent of the ventricular activation order. This paradigm has often been refuted and was never convincingly corroborated. We sought to validate Wilson’s concept by intra-individual comparison of the VG of sinus beats and ectopic beats, thus assessing the effects of both altered ventricular conduction (caused by the ectopic focus) and restitution (caused by ectopic prematurity). We studied standard diagnostic ECGs of 118 patients with accidental extrasystoles: normally conducted supraventricular ectopic beats (SN, N = 6) and aberrantly conducted supraventricular ectopic beats (SA, N = 20) or ventricular ectopic beats (V, N = 92). In each patient, we computed the VG vectors of the predominant beat, VGp→, of the ectopic beat, VGe→, and of the VG difference vector, ΔVGep→, and compared their sizes. VGe→ of the SA and V ectopic beats were significantly larger than VGp→ (53.7 ± 25.0 vs. 47.8 ± 24.6 mV∙ms, respectively; p ΔVGep→ were three times larger than the difference of VGe→ and VGp→ (19.94 ± 9.76 vs. 5.94 mV∙ms, respectively), demonstrating differences in the VGp→ and VGe→ spatial directions. The amount of ectopic prematurity was not correlated with ΔVGep→, although the larger VG difference vectors were observed for the more premature (<80%) extrasystoles. Electrical restitution properties and electrotonic interactions likely explain our findings. We conclude that the concept of a conduction-independent VG should be tested at equal heart rates and without including premature extrasystoles