Based On Time-domain Method Of Dynamic Electrocardiogram In Healthy People And Patients With Hypertrophic Cardiomyopathy, T-wave Alternans Analysis

Part I Analysis of Ambulatory Electrocardiogram-BasedTracking of T-wave Alternans by Time-domain Method inHealthy Chinese【Objective】To investigate a feasible approach for analysis of ambulatoryelectrocardiogram-based(AECG) tracking of T-wave alterna ns(TWA) by time-doma inmethod in healthy Chinese and try to find whether there are dynamic changes of TWAin daily life.【Methods】Sixty-five healthy Chinese were recruited as norma l volunteers. All of themunderwent ambulatory ECGs test for at least 20 hours. Digital ECGs were recordedby modified lead V1, V5 and avF. TWA was detected continuously using modifiedmoving avera ge (MMA) method in three predetermined periods: 2-4 a.m, 5-7 a.m, 8-10 a.m. The nomal range of TWA was studied and the voltage of TWA in differentperiods and leads were compared.【Results】The value of Valt had a positive skewed distribution. The 75th percentilevalue of Valt in three predetermined periods and three leads is no more tha n 5μV. Thema ximum and minimum ma gnitude of TWA occurs at 8-10 a.m and 2-4 a.m,respectively; There is significa nt difference in the voltage value of TWA among threeleads (P<<0.01). The value of Valt in lead avF is higher tha n that in other leads.There are interactions between leads and periods (P=0.0108). The ma gnitude of TWAin modified lead V1 in three predetermined periods was shown difference (P<0.05),while the difference of TWA value in modified lead V5 is not significa nt (P>0.05).【Conclusion】TWA level in healthy Chinese changes dynamica lly in daily life.These changes, to some extent, are consistent with the accommoda tion of autonomicnerve and release of related hormones. Ambulatory electrocardiogram-based tracking of T-wave alterna ns by time-doma in method is, just in time, capable of capture thesechanges. Moreover, it is important to choose appropriate periods to collection TWAsamples and leads for recording. PartⅡAnalysis of T-wave Alternans in Patients withHypertrophic Cardiomyopathy by Time-domain Method【Objective】To analyze T-wave Alternans(TWA) in patients of different clinicalfeatures with hypertrophic cardiomyopathy(HCM) by time-doma in method.【Methods】Thirty patients with HCM and 39 normal volunteers were enrolled.Patients were divided into subgroups according to clinical features, i.e., nonsusta inedventricular tachycardia, unexpla ined syncope, family history of premature suddendeath, obstructive left ventricular outflow tract, the specific region of left ventricularhypertrophy and the ma ximum wall thick ness of left ventricula r. Ambulatoryelectrocardiogram (AECG) test were performed for at least 20 hours, using threemodified precordial leads. Time-doma in TWA were detected automa tically usingmodified moving avera ge technology. The ma ximum of the individ ual ma xTWA inthreee leads were recorded when the onset heart rate < 125 b.p.m. Compare thevoltage of TWA between HCM patients and normal volunteers, and compare thevoltage of TWA among patients in subgroups.【Results】The voltage of TWA in HCM group and normal volunteer group was 33(23, 67)μV and 38 (25, 52)μV, respectively. There was no significa nt differencebetween two groups (P=0.52). TWA voltage was significa ntly higher in patients withunexpla ined syncope, comparing to patients without syncope (P=0.02). However, nodifference was shown in the comparisons among other subgroups. There wasdifferences when comparing the voltage of patients with unexpla ined syncope to thatof normal volunteers (P=0.02). And the same result was found in the comparisonbetween patients who had family history of premature sudden death and normalvolunteers (P=0.04). 【ConclusiConclusion】The level of T-wave alterna ns in hypertrophic cardiomyopathy isreleva nt to clinical features of the disease. The reason for higher risk of sudden deathin patients with unexpla ined syncope or family history of premature sudden deathprobablely was that increased TWA, ma nifestation of electrical instablility, is prone toproduce reentry, which may induce ma ligna nt arrhythmias. Therefore, using TWA testtogether with other risk factors may improve the accuracy of risk stratification inHCM patients.