SUMMARY To determine the relation between left anterior hemiblock and cardiovascular abnormalities in an ambulatory population, the clinical records and electrocardiograms of 16 600 male applicants for life insurance between 1966 and 1974 were reviewed. There were 413 applicants with left anterior hemiblock; they were compared with an age-matched control group. The subjects with left anterior hemiblock were divided into 2 subgroups based on the direction of the mean frontal place QRS axis: (a) greater than -30°but less than -60°, and (b) between -60°and -90°. The prevalence of left anterior hemiblock increased with age for each decade after the third. Left anterior hemiblock was not associated with cardiovascular abnormalities in 53-4 per cent of subjects age 30 and over and thus occurred as an isolated finding. There was no significant difference in the prevalence of isolated left anterior hemiblock when subjects with a mean QRS axis greater than -30°but less than -60°were compared with those with a mean QRS axis between -60°and -90°.When men of 30 and over with left anterior hemiblock were compared with an age and sex matched control group, there was a significant relation between electrocardiographic abnormalities, hypertension, and cardiac disease. There were no intergroup differences when subjects with a mean QRS axis greater than -30°but less than -600 were compared with subjects with a mean QRS axis between -600 and -90°. However, left anterior hemiblock was not a sensitive marker of clinical cardiac disease in these subjects since this diagnosis was absent in 86 per cent of subjects with left anterior hemiblock. In subjects under 30 a significant relation was present between clinical cardiac disease and left anterior hemiblock because of the high incidence of congenital heart disease in the left anterior hemiblock group.The significance of left anterior hemiblock in the general population remains controversial. Grant (1956) stressed the value of deviation of the mean manifest QRS axis in the frontal plane to the left beyond -30°as a sign of cardiac abnormality and postulated that left axis deviation signifies a conduction disturbance in the anterolateral wall of the left ventricle. On the basis of experimental evidence
Purpose:To determine whether injured myocardium may be identified by simultaneously monitoring contrast-induced T 1 and T 2 * signal intensity time-course changes with an interleaved T 1 -T 2 * imaging sequence. Materials and Methods:Gadolinium-diethylene triamine pentaacetic acid (0.05 mmol/kg) was injected as a bolus into ex vivo pig hearts, and simultaneous T 1 and T 2 * timecourses were obtained during the first pass.Results: Observing contrast-enhanced R 1 or R 2 * rates (1/T 1 or 1/T 2 * times, respectively) early after contrast injection did not fully differentiate viable from nonviable myocardium. T 2 * recovery at maximal T 1 signal intensity, measured using simultaneous T 1 and T 2 * imaging, displayed a significantly different percentage recovery (P Ͻ 0.05) among normal (30.5 Ϯ 2.4% of baseline value), reperfused infarcted (63 Ϯ 7.2%), and low-reflow infarcted (90 Ϯ 2.8%) myocardium. Conclusion:Simultaneously monitoring both T 1 and T 2 * signal intensities may help in the assessment of myocardial injury.
SUMMARY The sensitivity of rest and exercise thallium-201 scintigraphy for the detection of significant coronary artery disease and myocardial ischaemia was compared with rest and exercise electrocardiography in 46 patients with chest pain. Of 26 patients with greater than 70 per cent coronary stenosis, 16 had abnormal rest thallium-201 scintigrams and 13 had Q waves. Myocardial perfusion defects in the resting scintigram correlated very well with evidence of previous myocardial infarction (16 of 17 patients, 94%); significant Q waves were present in 13 of these 17 patients (76%).After exercise, abnormal thallium-201 scintigrams consistent with ischaemia were found in 21 patients (81%). Abnormal exercise electrocardiograms were present in 15 patients (58 %) The combination of abnormal exercise thallium-201 scintigrams or exercise electrocardiograms (23/26, 88%) exceeded abnormal exercise electrocardiograms alone (15/26, 58%). The two procedures were thus complementary. Abnormal rest or exercise thallium-201 scintigrams were obtained in 25/26 patients (96%) compared with abnormal rest or exercise electrocardiograms in 21/26 patients (84%). Twenty patients with less than 50 per cent coronary stenosis had normal rest thallium-201 scintigrams and no Q waves. Two had abnormal exercise thallium-201 scintigrams and 7 had abnormal exercise electrocardiograms. Thus, exercise thallium scintigraphy has higher sensitivity than exercise electrocardiography in detecting exercise induced ischaemia and is more specific. Scintigraphy appears to have a higher sensitivity than electrocardiography in detecting coronary artery disease.While each ofthe patients with triple vessel coronary disease had positive exercise perfusion scintigrams and positive exercise electrocardiograms, the thallium-201 scintigram was more sensitive than the rest or exercise electrocardiogram in patients with single vessel disease.The correlation of thallium perfusion defects at rest and/or exercise with angiographically significant coronary stenosis was higher for the left anterior descending and right coronary arteries than for the circumflex coronary artery.
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