Detection And Analysis Of Microvolt T-wave Alternans In Patients With Cardiomyopathy

Objective To investigate the prevalence of TWA in patients with cardiomyopathy and its relation with the cardiac functional parameters including left ventricular end-diastolic dimen-sion (LVEDD) and left ventricle ejection fraction(LVEF),et al as well as with the electrocar-dioindexes,such as QRS duration,QT interval,QT dispersion(QTd) and so on. Methods34patients with cardiomyopathy including33men and1woman aging from40to68(51.53±8.34) years were selected, among which3were patients with ischemic cardiomyopathy,31pa-tients with dilated cardiomyopathy. MTWA was assessed for all the patients with cardiomyopa-thy with spectral method using Cambridge Heart. Heartwave system. The prevalence of MT-WA in patients with cardiomyopathy at rest and during exercise was analyzed in comparation with healthy subjects so as to explore the prevalence of MTWA in patients with cardiomyopa-thy. Physical examination,12-lead surface electrocardiogram and ultrasonic cardiogram were conducted for all the patients with cardiomyopathy. QRS duration, QT interval, QTd, et al were measured by way of12-lead surface electrocardiogram and LVEDD, LVEF, et al were meas-ured by way of ultrasonic cardiogram. The relation of MTWA with LVEDD, LVEF, QRS dura-tion, QT interval, et al was analyzedResults Compared with the MTWA positive rate (2.22%)of healthy subjects which was studied by my tutor, professor Huang Zhichun, the MT-WA positive rate of patients with cardiomyopathy was32.35%and the MTWA positive rate of patients with cardiomyopathy was significantly higher than the healthy subjects (P<0.01). The mean heart rate for patients with cardiomyopathy during exercise was105.71±7.13/min, higher than that at rest which was82.53±9.03/min (P<0.01). The alternans voltage (Valt) during exercise was larger than at rest(P<0.01). Positive MTWA was observed in2patients at rest(5.88%) and in11patients during exercise(32.35%), and the MTWA posi-tive rate during exercise was higher than at rest (P<0.01). There was significant correlation between the heart rate and alternans voltage in vector magnitude(r=0.985, P<0.01), and Valt increased with the increase of heart rate. There were no significant differences in QRS du-ration, QT interval, QTd, et al between positive MTWA and negative MTWA groups of patients with cardiomyopathy (P>0.05). There were no significant differences in the MTWA positive rate between QRS≥120ms and QRS<120ms groups of patients with cardiomyopathy (P>0.05). The LVEDD was larger in positive MTWA than in negative MTWA(P<0.05) and the LVEF in positive MTWA was lower than in negative MTWA (P<0.05) for patients with car-diomyopathy. The MTWA positive rate was higher in patients with LVEDD≥65mm than in pa-tients with LVEDD<65mm(P<0.01) and also higher in patients with LVEF≤40%than in patients with LVEF>40%(P<0.01) for patients with cardiomyopathy. Conclusion The MTWA positive rate of patients with cardiomyopathy is significantly higher than that in healthy subjects. The prevalence of MTWA is positively correlated with heart rate,the alternans volt-age of MTWA and the MTWA positive rate increase with the increase of heart rate and there is significant correlation between the heart rate and alternans voltage in vector magnitude(r=0.985, P<0.01). There are no significant differences in electrocardioindexes including QRS duration, QT interval, QTd and so on between positive MTWA and negative MTWA groups for patients with cardiomyopathy. The LVEDD is larger in positive MTWA than in negative MTWA and the LVEF in positive MTWA is lower than in negative MTWA for patients with cardiomy-opathy. The MTWA positive rate is high in patients with cardiomyopathy with LVEDD≥65mm and/or LVEF≤40%, which sport that TWA is a new prognostic indicator which is worthy of further clinical research.