Clinical Briefs
Clinical Briefs
By Louis Kuritzky, MD
T axis as an Indicator of Risk of Cardiac Events in Elderly People
T axis on ekg delineates the orientation of ventricular repolarization. Though findings such as ST-T wave segment changes have been used to predict coronary heart disease, evaluation of T axis in the elderly has not.
Since axis is quite simply assessed, such a marker, if consistent, could be of significant clinical use. The population investigated were participants in the Rotterdam Study, which includes 7129 persons aged 55 and older, whose baseline data accrued during the 1990-1993 period. This population-based cohort study seeks to identify the occurrence of risk factors and their effect on chronic disease in the elderly.
Frontal and horizontal T axes were classified into three groups: normal (15-75 degrees), borderline (-15 to 15 degrees, and 75-105 degrees), and abnormal (-180 to -15 degrees and 105-180 degrees).
During follow-up, 165 persons died from cardiac causes, and 192 had nonfatal cardiac events; additionally, 11 persons had a nonfatal cardiac event followed by a fatal event.
The risk of cardiac death was substantially increased for persons with an abnormal frontal T axis (hazard ratio = 3.9) as was sudden cardiac death (hazard ratio = 4.4). In an analysis that examined hazard ratio for cardiac death, abnormal T axis had as great an increased hazard ratio as a history of angina, myocardial infarction, diabetes mellitus, or hypertension.
Kors and colleagues conclude that their data indicate that the T axis is an important independent predictor for cardiac events.
Kors JA, et al. Lancet 1998;352: 601-505.
Effect of Beta- Blockade on Mortality Among High- and Low-Risk Patients After Myocardial Infarction
Even though large trials have indicated that post-myocardial infarction beta blocker (PMIBB) use reduces mortality, up to two-thirds of eligible candidates do not receive them. Even cardiologists omit up to half of potential recipients. Older-age patients is one of the predictors for physician non-use of PMIBB.
The Cooperative Cardiovascular Project is a data base of hospital claims submitted to Medicare for acute myocardial infarction (n = 200,000). In this group, only 34% received PMIBB. Specific subgroups of patients who were even less likely to receive PMIBB included older, sicker, African American, or diabetic patients. Persons with heart failure, C
OPD, or elevated serum creatinine were also less likely to receive this therapy.
During 24-month follow-up, recipients of PMIBB enjoyed a 40% reduction in mortality, even when considering patients with COPD. Even though the percent mortality reductions were a bit less among blacks, older patients, and those with an elevated serum creatinine, their overall higher mortality rates produced an absolute reduction in mortality as substantial as that in the lower risk groups.
Gottlieb and associates conclude that their data suggests a substantial underuse of PMIBB, and that groups who may have been perceived as less likely to benefit (blacks, older patients, patients with renal insufficiency) are instead meritorious groups for consideration of this therapy.
Gottlieb SS, et al. N Engl J Med 1998; 339:489-497.
Sunlight Exposure and Risk of Lens Opacities
Cataract is the most frequent cause of visual loss. The role of sunlight, in particular UV-B, remains controversial. Some information suggests that sunlight is a provocative factor for cataract and is perhaps limited to men—in particular, non-African American men. The methodology for assessing sun exposure in some previous reports has been suboptimal. This report, the Salisbury Eye Evaluation project, quantified ocular UV-B exposure using a UV-B pyranometer. Measurements of ocular sunlight exposure were made through a series of determinations on residents of this community throughout their daily activities.
Overall, women sustained less UV-B exposure than men. Cataract incidence increased with degree of UV-B sun exposure, from the lowest to the highest quartile, and this relationship remained the same for women and African Americans. Since UV-B sun exposure appears to be a risk factor for cataract development, West and associates suggest that simple protective measures are in order. Plastic glasses provide superior UV-B protection to glass, though of course sunglasses are better still. Even wearing a brimmed hat decreases UV-B exposure 30-50% and should be encouraged. Gender and race do not appear to be protective. Public health measures should include addressing attention to public awareness of the ocular toxicity of sun exposure, specifically cataract.
West SK, et al. JAMA. 1998;280:714-718.
Clinical Scenario: The ECG shown in the figure was obtained from a 78-year-old woman who was being evaluated for altered mental status. How would you interpret her 12-lead tracing? What is the most likely etiology for the changes you see?
Interpretation: The rhythm is sinus at a rate of 85 beats/minute. The PR and QRS intervals are normal, but the QT interval is clearly prolonged. The axis is leftward. There is voltage for left ventricular hypertrophy (LVH). However, the most remarkable finding on this tracing is the presence of very deep and symmetric T wave inversion in multiple leads. This is the syndrome of "giant T waves." Although ischemia must clearly be considered as the possible etiology, the point to emphasize is that other entities may also produce this picture of diffusely inverted giant T waves. Among these entities are CNS catastrophes (stroke, hemorrhage, Stokes-Adams attacks); non-Q wave infarction, certain types of hypertrophic cardiomyopathy, and intermittent LBBB (left bundle branch block). The etiology for giant T wave inversion in these different conditions is uncertain. The patient in this case had a recent large stroke, but no evidence of infarction.
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