الفهرس 
Cardiac MemoryOnly 14 pages are availabe for public view
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Abstract
Cardiac memory is defined as an altered T wave on electrocardiogram recorded during sinus rhythm,having been induced by a preceding period of abnormal ventricular activation. Cardiac memory may often be unrecognized,but it has potentially important clinical implications, such as alteration in the action of anti-arrhythmic drugs, with reduced efficacy or potential proarrhythmic effects. the activation patterns initiated by epicardial pacing may increase transmural dispersion of repolarization and prolongation of the QT interval.
Because cardiac memory can mimic T wave inversion(TwI) in myocardial ischemia, differentiation between these 2 events is important.
The objective of this study was to investigate the value of T wave inversion after resumption of sinus rhythm in patients revealing repetitive uniform premature ventricular complexes(PVCs) (detected by 24 hour Holter monitoring) and chest pain for the the differentiation between cardiac memory and myocardial ischaemia.
The study included fifty patients who presented with chest pain and repetitive uniform premature ventricular complexes( PVCs)
detected by 24 hour Holter monitoring.
According to the shape of T wave after resumption of sinus rhythm,patients were divided into two groups:
Group Ι(25 patients):included patients who revealed symmetrical T wave inversion following resumption of sinus rhythm as detected by 24 hour Holter monitoring. Group ΙΙ(25 patients) : included patients who revealed upright T wave following resumption of sinus rhythm as detected by 24 hour Holter monitoring.
Our study showed that drug intake (including angiotensin receptor blockers,angiotensin converting enzyme inhibitors and Calcium channel blockers which prevent repolarization abnormalities after PVCs) was significantly higher in Group II in comparison with Group I.
Incidence of Diastolic dysfunction(as assessed by measurement of E/A ratio which detected by transthoracic Echocardiography)was found to be significantly higher in Group I than Group II.
Also the study showed that the incidence Non sustained ventricular tachycardia Was significantly higher in Group I in comparison with Group II.
All patients underwent Myocardial Perfusion imaging using Technetium 99m sestamibi for detection of myocardial ischaemia. ischaemic patients were found to be significantly higher in group I(18 patients) than group II(8 patients).
Duration of T wave inversion was calculated in Group I patients and was found to be significantly longer in ischaemic(12─40 minutes) than non ischaemic(7─24 minutes) Group I patients.
Our study concluded that the ideal cutoff value of the duration of T wave inversion (after repetitive uniform PVCs, in patients presenting with chest pain) for prediction of Coronary artery disease is 20 minutes at 77.8% sensitivity and 85.7% Specificity.
Voltage of T wave inversion was calculated in Group I patients and was found to be significantly larger in ischaemic(0.2─0.6 mV) than non ischaemic(0.2─0.4 mV) group I patients.
Our study found that the ideal cutoff value of the voltage of T wave inversion (after repetitive uniform PVCs, in patients presenting with chest pain) for prediction of Coronary artery disease is 0.3 mV at.83.3% sensitivity and 85.7% Specificity.