i am asking in reference to the waves of depolarisation and repolarisation in myocardium. T-vector direction differentiates postpacing from ischemic T-wave inversion in precordial leads.
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Circulation. 2005; 111(8):969-74 (ISSN: 1524-4539)
Shvilkin A; Ho KK; Rosen MR; Josephson ME
Beth Israel Deaconess Medical Center, Boston, Mass 02215, USA.
BACKGROUND: Postpacing precordial T-wave inversion (TWI), known as cardiac memory (CM), mimics ischemic precordial TWI, and there are no established ECG criteria that adequately distinguish between the two. On the basis of CM properties (postpacing sinus rhythm T vector approaching the direction of the paced QRS vector), we hypothesized that CM induced by right ventricular pacing would manifest a TWI pattern different from that of precordial ischemic TWI, thereby discriminating between the two. METHODS AND RESULTS: T-wave axis, polarity, and amplitude on a 12-lead ECG during sinus rhythm were compared between CM and ischemic patients. The CM group incorporated 13 patients who were paced in DDD mode with short atrioventricular delay for 1 week after elective pacemaker implantation. The ischemic group consisted of 47 patients with precordial TWI identified among 228 consecutive patients undergoing percutaneous coronary intervention for an acute coronary syndrome. The combination of (1) positive T(aVL), (2) positive or isoelectric T(I), and (3) maximal precordial TWI>TWI(III) was 92% sensitive and 100% specific for CM, discriminating it from ischemic precordial TWI. CONCLUSIONS: CM induced by right ventricular pacing results in a distinctive T-vector pattern that allows discrimination from ischemic precordial T-wave inversions regardless of the coronary artery involved. It doesn't. The ST-T wave elevates in a myocardial infartion. Postischemic inverted T waves.
This study has followed up the natural history of postischemic inverted T waves and assessed the prognosis. 40 consecutive patients with unstable angina with postischemic precordial inverted T waves in the noninfarcted, previously ischemic area were followed during the persistence (negative T wave period) and after resolution of inverted T waves (positive T wave period). The outcome with frequencies of acute myocardial infarction, acute ischemic syndrome, angina pectoris, positive exercise test, silent myocardial ischemia, anterior wall motion abnormalities on echocardiogram, positive coronary arteriography were determined and compared in the negative versus positive T wave periods. Postischemic inverted T waves showed resolution within the postischemic 3-21 days (at a mean of 10.6 days) in 31 patients on medical treatment alone during the whole study period. Frequencies of parameters/patients determined in negative versus positive T wave periods are as follows: acute myocardial infarction: 5/40 versus 0/31 (non significant), acute ischemic syndrome: 25/40 versus 2/31 (p < 0.001), angina pectoris: 32/40 versus 11/31 (p < 0.001), positive treadmill exercise test: 14/16 versus 14/30 (p < 0.02), silent myocardial ischemia: 14/14 versus 16/31 (p < 0.01), hypokinesis 26/34 versus 4/24 (p < 0.001), positive coronary arteriography: 4/4 versus 11/11 (non significant). In most patients on medical treatment, the postischemic inverted T waves tend to resolve within 3 weeks. Attention has to be paid to the patients with postischemic inverted T waves during the negative T wave period: the high ischemic risk gradually decreases with resolution of negative T waves. Please see the web pages for more details on Myocardial infarction. |
