Circadian variation of the QT interval in patients with sudden cardiac death after myocardial infarction. 1998

G Yi, and X H Guo, and M Reardon, and M M Gallagher, and K Hnatkova, and A J Camm, and M Malik
Department of Cardiological Sciences, St. George's Hospital Medical School, London, United Kingdom.

To evaluate the potential prognostic value of the circadian variation of QT intervals in predicting sudden cardiac death (SCD) in patients after myocardial infarction (MI), 15 pairs of post-MI patients (15 died suddenly within 1 year after MI [SCD victims] and 15 remained event-free [MI survivors]) were studied (mean age 60 +/- 8 years; 24 men and 6 women). The pairs were matched for age, gender, infarct site, presence of Q wave, left ventricular ejection fraction, thrombolytic and beta-blocker therapy. Fourteen normal subjects served as controls (mean age 55 +/- 9 years; 12 men). A 24-hour Holter electrocardiographic (ECG) recording was obtained from each subject. All recordings were analyzed using a Holter ECG analyser. QT, RR, and heart rate-corrected QT intervals (QTc) were automatically calculated by the analyzer, and hourly and 24-hour mean values of each measurement were derived from each recording. There was a pronounced circadian variation in the QT interval in parallel with the trend in the RR interval in normal subjects and in MI survivors. Circadian variation in both indexes was blunted in SCD victims. The QT interval was significantly longer at night than during the day in normal subjects (388 +/- 28 vs 355 +/- 21 ms, p = 0.001) and in MI survivors (358 +/- 25 vs 346 +/- 15 ms, p = 0.008), but not in SCD victims (357 +/- 32 vs 350 +/- 31 ms, p = 0.6). The 24-hour mean value of the QT interval in SCD victims did not differ significantly from that in normal subjects or MI survivors. The QT interval at night was significantly shorter in SCD victims than in normal subjects (357 +/- 32 vs 388 +/- 28 ms, p = 0.02), but daytime values were similar. The QT interval in SCD victims did not differ significantly from that of MI survivors at any time. The QTc interval exhibited a small circadian variation in normal subjects. This variation was abolished in SCD victims and MI survivors. The 24-hour mean value of QTc was significantly longer in SCD victims than in normal subjects (424 +/- 25 vs 402 +/- 21 ms, p = 0.02), and in MI survivors (424 +/- 25 vs 404 +/- 32 ms, p < 0.05). The QTc interval of SCD victims differed from that of normal subjects during both the day (421 +/- 25 vs 400 +/- 17 ms, p = 0.02) and night (424 +/- 26 vs 403 +/- 23 ms, p = 0.03). Thus, blunted circadian variation in QT intervals, abolished circadian variation in QTc intervals, and prolonged QTc intervals may suggest an increased risk of SCD in patients after MI.

UI MeSH Term Description Entries
D008297 Male Males
D008875 Middle Aged An adult aged 45 - 64 years. Middle Age
D009203 Myocardial Infarction NECROSIS of the MYOCARDIUM caused by an obstruction of the blood supply to the heart (CORONARY CIRCULATION). Cardiovascular Stroke,Heart Attack,Myocardial Infarct,Cardiovascular Strokes,Heart Attacks,Infarct, Myocardial,Infarction, Myocardial,Infarctions, Myocardial,Infarcts, Myocardial,Myocardial Infarctions,Myocardial Infarcts,Stroke, Cardiovascular,Strokes, Cardiovascular
D011237 Predictive Value of Tests In screening and diagnostic tests, the probability that a person with a positive test is a true positive (i.e., has the disease), is referred to as the predictive value of a positive test; whereas, the predictive value of a negative test is the probability that the person with a negative test does not have the disease. Predictive value is related to the sensitivity and specificity of the test. Negative Predictive Value,Positive Predictive Value,Predictive Value Of Test,Predictive Values Of Tests,Negative Predictive Values,Positive Predictive Values,Predictive Value, Negative,Predictive Value, Positive
D002940 Circadian Rhythm The regular recurrence, in cycles of about 24 hours, of biological processes or activities, such as sensitivity to drugs or environmental and physiological stimuli. Diurnal Rhythm,Nyctohemeral Rhythm,Twenty-Four Hour Rhythm,Nycthemeral Rhythm,Circadian Rhythms,Diurnal Rhythms,Nycthemeral Rhythms,Nyctohemeral Rhythms,Rhythm, Circadian,Rhythm, Diurnal,Rhythm, Nycthemeral,Rhythm, Nyctohemeral,Rhythm, Twenty-Four Hour,Rhythms, Circadian,Rhythms, Diurnal,Rhythms, Nycthemeral,Rhythms, Nyctohemeral,Rhythms, Twenty-Four Hour,Twenty Four Hour Rhythm,Twenty-Four Hour Rhythms
D005260 Female Females
D005500 Follow-Up Studies Studies in which individuals or populations are followed to assess the outcome of exposures, procedures, or effects of a characteristic, e.g., occurrence of disease. Followup Studies,Follow Up Studies,Follow-Up Study,Followup Study,Studies, Follow-Up,Studies, Followup,Study, Follow-Up,Study, Followup
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D012189 Retrospective Studies Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons. Retrospective Study,Studies, Retrospective,Study, Retrospective
D013318 Stroke Volume The amount of BLOOD pumped out of the HEART per beat, not to be confused with cardiac output (volume/time). It is calculated as the difference between the end-diastolic volume and the end-systolic volume. Ventricular Ejection Fraction,Ventricular End-Diastolic Volume,Ventricular End-Systolic Volume,Ejection Fraction, Ventricular,Ejection Fractions, Ventricular,End-Diastolic Volume, Ventricular,End-Diastolic Volumes, Ventricular,End-Systolic Volume, Ventricular,End-Systolic Volumes, Ventricular,Fraction, Ventricular Ejection,Fractions, Ventricular Ejection,Stroke Volumes,Ventricular Ejection Fractions,Ventricular End Diastolic Volume,Ventricular End Systolic Volume,Ventricular End-Diastolic Volumes,Ventricular End-Systolic Volumes,Volume, Stroke,Volume, Ventricular End-Diastolic,Volume, Ventricular End-Systolic,Volumes, Stroke,Volumes, Ventricular End-Diastolic,Volumes, Ventricular End-Systolic

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